Handbook Of
RTHODONTICS 4th Edition
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ROBERT E. MOYERS
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FOURTH EDITION
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lIandbook of Orthodontics
ROBERT
D.Se.
E.
MOYERS,
(HON.)
D.D.S., PH.D.,
Professor of Dentistry (Orthodontics) SchooL of Dentistry FeLLow, Center for Human Growth and DeveLopment The University of Michigan Ann Arbor, Michigan
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YEAR BOOK MEDICAL PUBLISHERS,.INC. CHICAGO·
LONDON·
BOCA RATON
Copyright Q 1958, 1963, 1973, 1988 by Year Book Medical Publishers, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any meanselectronic, mechanical, photocopying, recording, or otherwise-without prior written permission from the publisher. Printed in the United States of America. 2
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Library of Congress Cataloging-in-Publication
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Data
Moyers, Robert E. Handbook of orthodontics / Robert E. Moyers. - 4th ed. p. cm. Rev. ed. of: Handbook of orthodontics for the student and general practition~r. 3rd ed. 1973, cl 972. Includes bibliographies and index. ISBN 0-8151-6003-8 l. Orthodontics.
I. Moyers,
Robert E. Handbook of orthodontics
for the student and general practitioner. II. Title. [DNLM: 1. Orthodontics. WU 400 M938h] RK52l.M6 1988 617.6'43-dcl9 DNLMlDLC For Library of Congress
Sponsoring Editor: David K. MarshalllMark-Christopher
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87-34075 CIP Mitera
Assistant Director, Manuscript Services: Frances M. Perveiler Production Manager, Text and Reference/Periodicals: Etta Worthington Proofroom Supervisor: Shirley E. Taylor
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To my parents, whose many sacrifices made possible my education
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CONTRIBUTORS
JAMES K. AVERV, D.D.S., PH.D. Director, Dental Research 'Institute and Professor of Dentistry, School of Dentistry; Professor of Anatomy, The University of Michigan Medical School, Ann Arbor, Michigan FRED L. BOOKSTEIN, PH.D. Research Scientist, The Center for Human Growth and Development; Research Scientist, Biostatistics, School of Public Health; Research Scientist, Developmental and Reproductive Biology; Associate Professor of Geological Sciences, College of Literature, Science, and the Arts, The University of Michigan, Ann Arbor, Michigan ALPHONSE R. BURDI, M.S., PH.D. Professor of Anatomy, Director, Inteflex Program, The University of Michigan Medical School; Research Scientist, Center for Human Growth and Development, The University of Michigan, Ann Arbor, Michigan KATHERINE W. L. DRVLAND VIG, B.D.S.,
M.S.
Associate Professor of Dentistry (Orthodontics), School of Dentistry, The University of Michigan, Ann Arbor, Michigan DONALD H. ENLOW, PH.D. Professor and Chairman, Orthodontics, Assistant Dean for Graduate Studies and Research, Thomas Hill Distinguished Professor of Oral Biology, Case Western Reserve University, Cleveland, Ohio
RAVMOND J. FONSECA, B.A., D.M.D. Professor of Dentistry (Oral Surgery), School of Dentistry; Associate Professor (Oral Surgery), Department of General Surgery, The University of Michigan Medical School, Ann Arbor, Michigan
W. STUART HUNTER, D.D.S,
ROBERT E. MOVERS, D.D.S.,
PH.D.,
University of
D.Sc.
(HON.)
Professor of Dentistry (Orthodontics), School of Dentistry; Fellow, Center for Human Growth and Development, The University of Michigan, Ann Arbor, Michigan MICHAEL L. RIOLO, D.D.S.,
M.S.
Research Investigator, Center for Human Growth and Development, The University of Michigan, Ann Arbor, Michigan ' PER RVGH, DR. ODONT. Chairman, Department of Orthodontics and Facial Orthopedics, Faculty of Dentistry, University of Bergen, Bergen, Norway ARTHUR
T.
STOREY, D.D.S.,
PH.D.
Professor and Head, Department of Orthodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, San Antonio, Texas
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PH.D.
Professor of Orthodontics, Faculty of Dentistry, Western Ontario, London, Ontario, Canada
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PREFACE TO THE FOURTH EDITION
He that publishes a book runs a very great hazard, since nothing can be more impossible than to compose one that may secure the approbation of every reader.-MIGUEL DE CERVANTESSAAVEDRA,DON QUIXOTE
The favorable reception of previous editions of this book, the appearance of Spanish, Japanese, and Portuguese editions, * and important recent changes in the field of orthodontics have encouraged me to undertake this fourth edition. The nature of dental practice in these years has been remarkably altered by fluoridation of communal water supplies, the proliferation of govemmentally sponsored dental programs and dental insurance, a literal revolution in dental materials and instrumentation, and a large increase in the number of practicing dentists. These factors have altered the public's desires and awareness of dental services and have forever changed the previous primary preoccupation of dentists with restorative and prosthetic procedures, thus forcing a broader perception of our profession. Unfortunately, dentists and patients change their views more readily than dental school curricula are modified. So there persists a need for further information about orthodontics for both student and practitioner alike. Sources of sound orthodontic knowledge are often not as available as in other dental fields, and dentists usually have far less orthodontic background; therein lies a major problem for both dentists and the public. Dentists who wish to improve their skills and knowledge in orthodontics now may choose from many available short courses, yet often such offerings are not sponsored by dental schools or societie~ but are private entrepreneurial efforts. Many such courses in the United States are taught by clinicians with little or no formal training in orthodontics, and emphasis is frequently on one favored appliance. Courses for general dentists on the basic subjects of diagnosis and growth and development are more rare, but might be more practical and rewarding. The present enthusiasm to integrate orthodontics into general practice poses difficulties for lay people, too, since few are aware of the divergences of training provided dental students in the several clinical fields. They know their family dentist is a skillful
restorative dentist and may logically assume him/her to 'be equally well trained in orthodontics, but that is rarely so. Orthodontics is not only one of the most difficult clinical fields in dentistry, it is also one of the most rapidly changing. It is hard to learn and hard to keep abreast of current best practice. This book is written to provide the dental student with a firm foundation in the basics of growth and development and to provide a healthy approach to orthodontic diagnostic and treatment procedures. It is NOT a compendium of all orthodontic information, nor can reading it serve as a substitute for direct instruction or supervised clinical experience. It is written, too, to provide the family dentist with modem, fair perspectives of orthodontics and its place in general practice. The book is widely read by specialists in orthodontics and seems to have been especially useful for beginning graduate students and residents. This fourth edition, as in previous editions, has three sections: Growth and Development, Diagnosis, and Treatment. Each section IS introduced by a "mini-essay" written to define the scope and purpose of the section and to provide a foretaste of problems and challenges of that particular section's chaptFs. Growth is the business of the orthodontist, variations in' growth and morphology provide the need and basis for a diagnosis, and growth is the raw lT1ilterialfrom which treatment changes are wrought. The difficult intrtcacies of growth, more thanflny other factor, separate orthodontics from the rest of dentistry. Several dental specialties are defined by their particular techniques; orthodontics is defined by the clinical problems created by developmental variability. The section on growth is enlarged, particularly by a splendid chapter *There have also been unauthorized versions of the third English edition in three different countries, although I am not sure whether they are due to the worthiness of the book or the laxity of international copyright conventions.
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Preface to the Fourth Edition
by Professor Storey, and purposefully occupies a major portion of the book. The secti~n on diagnosis has been written to sharpen discriminatory insights and to enhance the ability to recognize subtle deviations in growth and morphology. Ear more serious mistakes are due to the failure to discern significant clinical differences between similar appearing malocclusions than are due to inappropriate selection of an appliance. The section on treatment has been expanded to include separate chapters on early, adoles-
cent, and adult treatments. Improved techniques and the availability of prefabricated appliances have permitted shortening the chapter on orthodontic techniques. This fourth edition is more than a revision of the third: it is a new book written to address the theoretical and practical needs of the most rapidly changing field in a changing profession. ROBERT E. MOYERS, D.D.S.,
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PHD.
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ACKNOWLEDGMENTS
... because if 1'd a known what a trouble it was to make a book I wouldn't a tackled it .... -MARK TWAIN, HUCKLEBERRY FINN, CHAPTERXlm
Making a book is a trouble, as Mark Twain said, but it is made much easier by those who aid in its production, for no one really writes a book, such as this, alone, I am most indebted to my co-authors, Professors James K, Avery, Donald H. Enlow, Arthur T, Storey, Alphonse R, Burdi, Fred L. Bookstein, W, Stuart Hunter, Per Rygh, Michael L. Riolo, Katherine W, L. Dryland Vig, and Raymond J, Fonseca. All are close associates and friends, some for over 30 years, and I note with pride that three are former students, Their knowledge of orthodontics and allied fields brings authority to their writing and completeness to this book, The craniofacial group at The Center for Human Growth and Development has, since the last edition, become one of the most active and well known in craniofacial biology, We collaborate to sponsor symposia, secure research funds, train young colleagues, publish monographs, give courses, etc" but one important activity, not well known, must be acknowledged here, viz" the critical reading of one another's writing. Katherine Ribbens, editor for The Center for Human Growth and Development, has been a: constant help as this new edition progressed, Stanley Gam, David Carlson, Jim McNamara, Fred L. Bookstein, Peter Vig, and Michael L. Riolo have each read several parts of this book and have responded with criticism, comments, and suggestions in the most detailed and supportive manner. I am especially grateful for their candor, perseverance of correctness, and willingness to help with this writing: I am indeed lucky to be a part of such a group, Since the first edition, Year Book Medical Publishers, Inc, has given counsel, support, and much patience, all of which is valued and noted with gratitude, New drawings and charts have been prepared by the talented
group at Technical Illustration, Division of Research Development and Administration, University of Michigan (Dale Austin, Eugene Leppanen, and David Oliver), and Terryl Lynn, Tom TenHave, biostatistician at The Center for Human Growth and Dovelopment, has provided most of the statistics and tables, and he and Richard Miller, also of The Center for Human Growth and Development, have generated all computer plots used herein, Pamela Dietrich and Gail Sonnett have typed most of the manuscript with its many revisions. A very special mention must be made of the role a writer's family plays when a book is being written, especially when the gestation is prolonged as was this. Through the past years my wife, Barbara, and daughters, Mary and Martha, have made sketches, read drafts critically, checked references, and even served as photographer's models. Those efforts, while helpful, are not their principal contribution, which is the continual support and tolerance they have given to the selfish, time-consuming, isolating madness called writing. They know I am grateful, but readers should know, too, lest when they are tempted to begin such an undertaking, they think they can do it alone. " I am pleased to acknowledge my gratitude to all these people, but errors and omissions that may have occurred are solely my responsibility. In the past, friendly critical readers have helped rectify such problems and have made many useful suggestions. I invite you to do so, too, and assure you that comments sent to me at The Center for Huml!~ Growth and Development, The Univeriril}' of Michigan, 300 N: Ingalls SI., Ann Arbor, Michigan 48109, Will be received with gratitude and appreciation. ROBERT E. MOYERS, D.D.S., PHD.
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CONTENTS
Preface to the Fourth Edition
ix
C. Changing Concepts and Hypotheses of Craniofacial Growth 48 D. Controlling Factors in Craniofacial Growth 51
SECTION I GROWTH AND DEVELOPMENT 1
E. Regional Development 53 F. Overall Pattern of Craniofacial Growth 67 G. Racial and Ethnic Differences H. "Adult" Craniofacial Growth
I / Introduction to the Study and Practice of Orthodontics 2 by Robert E. Moyers
A. Problems in Studying Orthodontics B. What is Orthodontics? 3 C. The Purpose of This Book D. How to Use This Book Summary
2 5 / Maturation of the Orofacial Musculature A. Orofacial Muscles
2 / Basic Concepts of Growth and Development
B. Methods of Study 76 C. Basic Concepts of Orofacial Neuromuscular Physiology 79 D. Reflex Determinants of Mandibular
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Registration Positions 84 E. Growth and Adaptation of Orofacial Muscles 89 F. Interaction of Orofacial Muscles With
A. Classes of Alterations in Biologic Activities 7 B. Principles and Themes of Development C. Some Definitions 8 D. Divisions of Developmental Science E. Methods of Studying Growth and 10 Development F. Variables Affecting Physical Growth G. Pattern 12
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11
Development of the Craniofacial Skeleton and the Dentition 94
6 / Development of the Dentition and the Occlusion
99
by Alphonse R. Surdi and Robert E. Moyers
H. Variability 13 I. Timing 16 J. The Evaluation of Physical Growth Summary 17
16
18
by lames K. Avery
4 / Growth of the Craniofacial Skeleton
74
6
by Robert E. Moyers
A. Period of Organization of the Face B. Development of Oral Structures C. Differentiation of Supporting Structures 31 D. The Fetal Period-Third to Ninth Month 34 Summary 35
73
by Arthur T. Storey
4 5
5
3 / Prenatal Facial Growth
67 67
19 26
A. B. C. D. E.
Prenatal Dental Development 100 The Mouth of the Neonate 105 The Primary Teeth and Occlusion Development of the Permanent Teeth The Permanent Dentition 119
7 / Etiology of Malocclusion 37
A. The Role of Craniofacial Skeleton Growth in Orthodontics 38 B. Rudiments of Bone Growth 39
111
F. Dimensional Changes in the Dental Arches 121 126 G. The Mixed Dentition Period H. Dentitional and Occlusal Development 140 Young Adult I. Clinical Implications 142
by Robert E. Moyers and Donald H. Enlow
106
in the
147
by Robert E. Moyers
A. B. C. D.
148 The Orthodontic Equation 149 Primary Etiologic Sites Time 151 151 Causes and Clinical Entities
Summary
162 xiii
xiv
Contents
SECTION 11
DIAGNOSIS
165
E. Techniques of Tracing Cephalograms 255 F. Geometric Methods 255 G. Understanding and Using the CephalogramCephalometric Analyses 263 H. Some Problems and Limitations of
167
8 / The Cursory Orthodontic Examination by Robert E. Moyers
169 169
A. Before the Examination B. The Cursory Examination Summary 182 9 / Classification Malocclusion
and Terminology 183
Cephalometries 281 I. The Future of Cephalometries Appendix: A Brief Cephalometric Atlas 283 A. Overall Facial Dimensions
of
by Robert E. Moyers
A. B. C. D. E. F. G. H.
SECTION III
A. Evaluation of Sensory and Motor Abilities 197 B. Muscle Groups 198 C. Examination of Specific Neuromuscular Functions 206 Joint
221
226
Cephalogram
251
A. Selection of Orthodontic Cases in General Practice 333
C. Treatment Planning in the Transitional Dentition 340 D. Treatment Planning in the Permanent 340 Dentition E. Limiting Factors in Orthodontic 340 Therapy F. Some Common Mistakes 342 15 / Early Treatment
12 / Analysis of the Craniofacial Skeleton: Cephalometries 247
Purposes of Cephalometries History 250 Obtaining the Cephalogram Anatomic Structures in the
332
B. Treatment Planning in the Primary 340 Dentition
Relationships 241 F. Registration of Jaw Relationships 242 G. The Temporomandibular Joints 244 H. Relationships of the Teeth to Their Skeletal Support 245 Summary 245
A. B. C. D.
14 / Planning Orthodontic Trea!ment by Robert E. Moyers
Diagnostic Data 222 Analysis of Tooth Development Size of Teeth 228 240 Arch Dimensions Prediction of Future Occlusal
by Robert E. Moyers. Fred L. Bookstein. Hunter
A. Forces Within the Masticatory System 307 B. Force Systems in Orthodontic and Functional Jaw Orthopedic Appliances 308 C. Periodontal and Other Tissue Responses to Orthodontic Forces 313 D. Controlled Alteration of Craniofacial Growth 322 E. Other Effects of Orthodontic Treatment 324 F. Retention, Relapse, and Occlusal Stabilization 326
by Robert E. Moyers
A. B. C. D. E.
303
by Per Rygh and Robert E. Moyers
195
by Robert E. Moyers
11 / Analysis of the Dentition and Occlusion
TREATMENT
296
13 / Force Systems and Tissue Responses to Forces in Orthodontics and Facial Orthopedics 306
la / Analysis of the Orofacial and Jaw Musculature 196
D. Analysis of Temporomandibular Dysfunction 216 Summary 218
284
B. Regional Anatomic Dimensions C. Craniofacial Constants 296
184
What is a Classification System? Purposes of Classifying 184 When to Classify 184 Systems of Classification and Terminology 186 Class I Syndrome 191 Class 11 Syndrome 191 Class III Syndrome 194 Limitations of Classification Systems
283
343
by Robert E; Moyers and Michael L. Riolo and W. Stuart
249 250
A. Understanding Early Treatment B. Defining Goals in Early Treatment C. Assessment of the Results of Early Treatment 347 D. Clinical Problems and Procedures
345 . 347
348
Contents
16 / Adolescent Treatment
432
18 / Orthodontic Techniques
by Robert E. Moyers
A. Understanding Adolescent Treatment B. Defining Goals in Adolescent Treatment 434' C. Assessment of Results of Adolescent Treatment 435 440 D. Clinical Problems 17/
Adult Treatment
511
by Robert E. Moyers
434
A. B. C. D. E.
Basic Laboratory Techniques 512 Basic Clinical Techniques 513 Fixed Appliances 518 Attached Removable Appliances 524 Loose Removable Appliances (Functional Appliances, Functional Jaw Orthopedic Appliances, Etc.) 531 F. Myotherapeutic Exercises 542 G. Correction of Deleterious Oral Habits 543 H. Occlusal Equilibration (Occlusal Adjustment) 551
472
by Robert E. Moyers, Katherine W. L. Dryland Vig, and Raymond J. Fonseca
A. Orthodontic Treatment for Adults With Good Oral Health 473 B. Orthodontic Treatment of Malocclusions Complicated by Periodontal Disease and Loss of Teeth 475 C. Orthodontic Treatment Combined With Orthognathic Surgery 494
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Index
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561
xv
SECTION I
Growth and Development Robert E. Moyers, D.D.S.,
Ph.D.
GROWTH
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Growth, in common English usage, is a word with several different meanings. Cities, crystals, crops, and cancers "grow." Habits "grow" on a person, stocks "grow" in value, a face "grows" pale when one is frightened, and one "grows" in wisdom as one ages. Such varied usages tend to reduce the import of a particular meaning. In biology, growth is the increase in size or mass accompanying normal development; however, in orthodontics growth, and the verb grow, are used quite loosely in several ways, which can present real and unfortunate semantic traps for the unwary. The following quotations (all gathered in one day from conversations with colleagues, notations in case histories, and articles in the orthodontic literature) illustrate the broad and imprecise common usages of the words. They also reveal misconceptions about the biologic processes involved, misunderstandings of the specifics of craniofacial development, admixtures of wishful thinking and facts, and just plain nonsense. • "The mandibular length grew 6 mm." (description of a specific dimensional increase). • "This face grew bigger." (description of a general increase in size). • "The mandible grows downward and forward." (description of a population vector). • "Marie's mandible exhibits 'clockwise' rotation in growth." (description of a specific vector). • "He grew rapidly during adolescence." (comment on an increase in rate of general growth).
• • • • •
"1 expect the mandible to show a 'spurt' in growth within the next 18 months." (prediction of a specific increase in timing and rate of growth). "She had a typical Class III growth pattern." (assumption of group vectors of change). "1 feel this patient has very little growth left." (estimate of future amounts of size change). "He is a bad grower." (qualitative description of growth). ''I'm going to do a 'growth prediction'." (assumption of ability to estimate practically future growth). "1 think I'll wait for some growth before 1 start treatment." (expectation of an increase in rate of growth, which will presumably aid therapy).
When this important word-growth-is used casually or imprecisely in orthodontics it not only reflects a person's carelessness bot also reveals how much must yet be learned and applied in practice. Students may justifiably ask how they can ever comprehend a subject so important, so complicated"and so misunderstood, but they must try, for growth is the raw material of orthodontic treatments. Without the biologic dynamics of natural and contrived chal}ges in craniofacial morphology no occlusion can be improved, no fate made more esthetic. The first chapters of this book contain fair summaries of our knowledge of craniofacial developmental biology at this time, but the field is an active area of much research, so orthodontists follow the literature carefully to keep up with current ideas. Nothing typifies orthodontics better than its dependence for clinical progress on advances in craniofacial biology.
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CHAPTER
1 Introduction to the Study and Practice of Orthodontics Robert E. Moyers, D.D.S., Ph.D.
Nothing is known in our profession by guess; and I do not believe, that from the first dawn of medical science to the present moment, a single correct idea has ever emanated from conjecture: it is right, therefore; that those who are studying their profession should be aware that there is no short road to knowledge.-SIR ASTLEY PASTONCOOPER, in A Treatise on Dislocations and Fractures of the Joints
OUTLINE
A. PROBLEMS IN STUDYING ORTHODONTICS
A.
B.
Problems in studying orthodontics I.
For the dental student
1. For the Dental Student
2.
For the dentist in practice
Many undergraduate orthodontic courses consist of a few hours of instruction late in the curriculum, with very little clinical experience. When orthodontic teaching begins, the student's attitudes toward dentistry may have been set by good teaching in other courses in which success is based on other concepts or diffen~nt clinical goals. For example, good restorative dentistry traditionally has required a higher proportion of technical skills than of biologic knowledge. Orthodontics', perhaps more than any other field of dentistry, is dependent on a thorough working knowledge of the developmental biology of the face. Unwittingly, the dental students may have acquired the idea that dental problems are solved by t~chniques alone. The student l1}ay think that the only thing separating the several clinical branches of dentistry is variation in technical procedures. Much of clinical dentistry is related to repair or restoration, but orthodontics is carried out primarily by guidance of growth. The strategies and tactics of growth and development are conceptually quite different from replacing lost parts. Most dentists (including teachers) are frank to admit that they know less about orthodontics than any' other branch of clinical dentistry. The teaching of undergraduate orthodontics is difficult, since usually there is little time in the curriculum. Teachers in
What is orthodontics? I. 2.
C. D.
History Scope
The purpose of this book How to use this book
The complicated nature of dental occlusion, including its development, maintenance, and correction, is the primary reason for the existence of dentistry as a separate healing arts profession. However, we have tended to emphasize in the past the restorative aspects of occlusion rather than its development and correction. The problems of occlusal development and correction are just as much the responsibility and concern of the general practitioner as of the orthodontist; therefore, basic knowledge concerning occlusal development, facial growth, and the correction of malocclusion should be part of the training of every dentist. It is ilot the tradition in many dental schools to spend mU,ch time on growth and development or training in the diagnosis and treatment of malocclusion; therefore, some problems arise for the dental student or practicing dentist who wishes to study orthodontics.
2
Introduction
to the Study and Practice of Orthodontics
3
other departments may have little understanding of orthodontics; consequently, orthodontic concepts are not reenforced and integrated well into general clinical teaching. Finally, the subject does not lend itself well to the semester or quarter module, nor to class rotations through the orthodontic department for periods of a few weeks. To be effective, orthodontic teaching must be spread over months or years while cases are being treated or the child is maturing to the moment when treatment can be begun. Growth changes take time and cannot be compressed to fit into a single term to suit the schedule.
2. For the Dentist in Practice The dentist in practice who has had an inadequate undergraduate orthodontics course, and seeks further training, may be surprised to learn the kind of courses offered in orthodontics for the generalist. Scarcely any short course can include clinical experience because of the time necessary to treat a malocclusion. Most orthodontic books are written for the specialist. Finally, the attitudes finely developed to ensure success in the other branches of dentistry may handicap the generalist as he or she begins to study orthodontics; for example, a fine clinical sense (If compromise in treatment goals (see Chapter 14, in which the limiting factors in orthodontic treatment are discussed). The dentist in practice who would learn orthodontics may have to overcome a lack of basic undergraduate training and may have difficulty in obtaining extensive postgraduate training of a practical clinical nature. This book was written specifically to help the general dentist and dental student start to overcome these difficulties.
B. WHAT IS ORTHODONTICS? Orthodontics is that branch of dentistry concerned with the study of the growth of the craniofacial complex, the development of occlusion, and the treatment of dentofacial abnormalities.
1. History Hippocrates' was among the first to comment about craniofacial deformity:
"Ol
IpO~OL ot
OUTEOlUlV. U'TTEPli>m
J.LEV KlYpLEplYVXEVE<;,
tUXVpL
KlYL T&AAlY KlYL
ot OE KElplYAlYA-yEE<; KlYL wmppvTol. KOLAm
KlYL 606vTE<;
TOVTEOlUlV
'TTlYPTjAAlYl'J.LEVOl."
(Among those individuals with long shaped heads, some have thick necks, strong parts and bones. Others have strongly arched palates, their teeth are irregularly arrayed, crowding one another, and they are bothered by headaches and otorrhea.) Adamandios,! writing in the fifth century A.D., noted that "those persons whose lips are pushed out because of cuspid displacement are ill tempered, abusive shouters and defamers:"
"OUOl
KlYTa
KlYK08vJ.LOl,
TaU<;
K1JVOOOVTlY<; KOPV
U~plUTlYL,
(
1JUlOI'VWJ.LlKOL<;). "
KpaKTm.
Ta
XELATj,
E'TTEU~OAOl.
"
FIG 1-1. Ancient Greek skull (circa 300 B.c.) shows use of gold wires to align and stabilize mandibular incisors in an adult whose malocclusion has been complicated Vasili Haralabakis.
by periodontal disease. (Courtesy of Professor Aristotelean University of Thessaloniki. Greece.)
Crude appliances that seemingly were designed to regulate the teeth have been found as archaeologic artifacts in tombs of ancient Egypt, Greece, and the Mayans of Mexico (Fig Orthodontics, as we think of it today, however, probably has its roots in France in the eighteenth century, when Pierre Fauchard, that most famous of all dentists, described an orthodontic appliance easily recognized as such by any modern dentist. Other articles concerning the development of the dentition and facial growth were written in the same period, but certainly John Hunter's (17281793) natural history of the human teeth is of the most interest to orthodontists.
I-I).
In the United States of America in the latter part of the nineteenth century, Kingsley, Farrar, Talbot, and Guilford presented pioneer writings on the treatment of malocclusion. Most North Americans maintain that orthodontics, however, really had its origin at the turn of the century, when Edward H. Angle published A System of Appliances for Correcting Irregularities of the Teeth and established a school for the training of dentists as orthodontic specialists. " The field developed differently in North America than in Europe. Angle was an intellectual and mechanical genius who dominated the orthodontic scene.in the New World more than any one person in Europe. Further, he improvised clever appliances for the precise positioning of the individual teeth, since, from the start, he emphasized the,)mportance of correct occlusion. In Eur6pe" on the other hand', early leaders in the field studied more the role of the craniofacial skeleton in dentofacial anomalies and malocclusion. Perhaps this is the reason that in the United States the field is called orthodontics (from the Greek orthos, meaning straight, and odontos, meaning tooth), whereas in Europe such terms as dental orthopedics, orthopedie dentofaciale, and Gebissund Kieferorthopedie are used. Although the terms generally are interchangeable, they reflect differences in emphasis during historical development and they betray differences in the aims of appliance therapy among various countries. In recent years the
4
Growth and Development
terms "orthodontics" and "dentofacial orthopedics" have sometimes come to be used almost interchangeably throughout the world, a reflection of the increased exchange of ideas and concepts. Most dental specialities developed within the profession, gradually evolving their own literature, specialized skills, and advanced training programs but maintaining strong ties to the mother profession. In the United States of America, orthodontic concepts, techniques, and specialized training, on the other hand, developed largely from within the specialty. Orthodontics in North America from the time of Angle has been a bit more apart from dentistry than any other dental specialty. Therefore, North American concepts of orthodontics, as well as mechanics, have been oriented differently from European concepts. The specialty of orthodontics has .flourished intellectually, clinically, and scientifically and has attracted some of the finest teachers, scientists, and clinicians in dentistry, yet orthodontic training in the undergraduate curriculum still is generally superficial. As a result, most dentists really are not well trained in orthodontics. On the other hand, graduate training programs have been strengthened, their scientific base has been broadened, and the numbers enrolled have increased until today a high percentage of all graduating dentists go on to orthodontic specialty training. Indeed, the number of orthodontics in the United States has increased so greatly in recent years that many areas where there once was a shortage are now well supplied, and the family dentist in these regions feels less obligation to treat severe mal occlusions than he or she did when orthodontic colleagues were not available. The extensive adoption of insurance and third party payment plans has had as much impact on orthodontics as other branches of dentistry. Such plans make good dental care possible at low cost for a large percentage of American families. Good dental care which includes orthodontics and malocclusion treatment is now more available and feasible than at any other time. National health schemes in other countries include orthodontics. Therefore, there continues to be an increasingly important role for orthodontics the practice of dentistry throughout the world.
in
2. Scope Orthodontic therapy is directed to malocclusion, abnormal growth of the complex of craniofacial bones, and malfunction of the orofacial neuromusculature, which alone or in combination may cause any of the following: a) Impaired mastication. b) Unfortunate facial esthetics.
c) Dysfunction of the temporomandibular articulation. d) Susceptibility to periodontal disease. e) Susceptibility to dental caries. f) Impaired speech due to mal positions of the teeth. Orthodontic therapy involves the three primary tissue systems concerned in dentofacial development, namely, the dentition, the craniofacial skeleton, and the facial and jaw musculature. By means of suitable appliances, muscle function is improved and teeth are positioned more favorably to provide better esthetics, occlusal function, oral health, and speech. Correction of the craniofacial
skeleton, however, is a different matter, since it is more difficult to alter the craniofacial skeleton than it is to position teeth. It is possible, however, to direct and alter favorably the growth of the craniofacial skeleton in young children. In older patients, whose facial growth is mostly completed, the teeth are positioned to camouflage disharmonies of the facial skeletal pattern. In the most extreme cases orthognathic surgery is utilized in conjunction with orthodontics. Finally, the neuromusculature, an important part of improved function and esthetics, is used in orthodontic treatment to modify the growth of the craniofacial skeleton. Orthodontic treatment may utilize many procedures, although perhaps the most frequent is the precise positioning of the individual teeth with orthodontic appliances. However, appliances for orthopedic correction of the craniofacial skeleton, surgery, myotherapy, and even psychotherapy are all used in modem orthodontic practice. Dentists interested in providing high-quality orthodontic service for their patients have the obligation to gain as much knowledge as possible in order to serve well the patients they treat themselves and refer others to a specialist for cooperative treatment. The next section provides additional perspectives on this matter.
C. THE PURPOSE OF THIS BOOK Most books in orthodontics
are written for the orthodontic
specialist and intended for practitioners with considerable knowledge of the subject. This volume presupposes very little orthodontic background on the part of the reader. It reaily has two purposes: to serve as an introductory text for dental students and to supply basic orthodontic knowledge for the dentist who does not specialize in orthodontics. Orthodontics traditionally has never occupied a large place in the dental curriculum; therefore, the teacher of orthodontics has the difficult job of presenting a complicated and exciting clinical field in just a few hours. Additionally, the basic science underlying orthodontics--craniofacial growth and d~velopment-usually must also be taught in the same orthodontic course. The new dental graduate soon learns that he or she is more poorly prepared in orthodontics than in any other clinical field, yet sees malocclusions every' day. Which should be treated? How? Which should be referred? When? Which should be observed for later action? Why? In brief, every dental student and practitioner needs a source of fa~ts concerning growth and orthodontics (I) to augment formal lectures, (2) to extend knowledge, and (3) to provide a readyreference manual when confronted with clinical problems. Orthodontics is a part of dentistry; therefore, all dentists need some orthodontic knowledge if for no other reason than that most malocclusions are diagnosed first by the family dentist, not the orthoflontist.' ~. Some see two ways in orthodontics: a high road and a low road. High-road treatment is comprehensive, precise, well done, and limited by expense to but a few-the way of the specialist. Low-road treatment is thought to be clumsy, utilizing simpler appliances and compromised goals but providing some service for a large proportion of the population-the way of family dentists. This myth of two quality levels in orthodontics is perpetuated by those who make extravagant or ill-founded claims, for example, "If you use this appliance, you never need to extract teeth"; "The
Introduction periodontal response is different with this appliance"; "A cephalometric analysis is not necessary with this system"; "This is a general practitioner's appliance," Of course, there is only one way in orthodontics-a way open to all dentists. Some, because of more training and experience, can travel farther along the same road-that is all. Modern dentists dedicated to the highest standards in all other branches of dentistry do not accept the invitation to lower their standards. They prefer to provide their patients with the best possible care, to travel the high road as far as their knowledge and skills will permit. The purpose of this book is to help each dentist do all the orthodontics possible of the highest quality.
D. HOW TO USE THIS BOOK Since this volume is intended to be a handbook rather than an exhaustive text, its plan differs from that of many dental books. It is suggested that one first read the entire book in sequence, studying those portions of most interest. There should be no difficulty in using the book for consultation concerning clinical problems if the arrangement of the subject matter is understood. The book is divided into three sections, Growth and Development, Diagnosis, and Treatment, the outlines of which can be seen in the Table of Contents. In addition, each chapter's contents are outlined again at the beginning of the chapter. A list of "Key Points" is provided at the beginning of most chapters as is a brief summary at the end. In addition to the References, a list of Suggested Readings are included at the end of chapters. The latter are intended to aid the reader interested in pursuing further the subject under discussion. Although it is quite true that one cannot move teeth without some sort of appliance, it is equally true that orthodontic treatment cannot be successful without a thorough knowledge of the underlying theory. More malocculsions are mismanaged because of ignorance of the facts of growth and diagnosis than by lack of knowledge of appliances. Gadgetry is so much fun, but in orthodontics it is useless without basic knowledge. Section III will be of little use to the clinician who does not understand Sections I and 11on Growth and Development and Diagnosis. When aid with a specific clinical problem is desired, the following procedure is suggested: (I) Locate that section where the problem is discussed. (2) While reading, compare the photographs and drawings with your problem. (3) Each section of Chapters 15, 16, and 17 generally follows this order: (a) introduction to the problem, including a discussion of etiology; (b) differential diagnosis; (c) specific steps in treatment; (d) general discussion. As you read, make comparisons with the facts you have gathered concerning your case. (4) Refer back to earlier chapters, when it is indicated, for a more detailed discussion of the predisposing conditions of the case. As familiarity with the chapters on Growth
to the Study and Practice of Orthodontics
5
and Development and Diagnosis is gained, such references will be less necessary. (5) During the discussion of steps in treatment, reference will be made to techniques described in Chapter 18. The conditions that underlie a satisfactory plan of treatment are presented, but no attempt is made to describe all the possible methods of therapy for a given problem. Only one procedure, which will give adequate results in the hands of the nonspecialist doing orthodontic work, is usually described. It will be easy for most readers to think of other satisfactory methods of treatment, and any orthodontist who chances on these pages will know many ways of achieving similar results. Many problems are beyond the scope of this book as far as treatment details are concerned, but the principles are given. No attempt is made to provide details of appliance construction or manipulation, but the principal methods are introduced. No book is a substitute for experience or good training, nor can any set of rules take the place of good judgment or spare one from thinking. Orthodontics, more than any other branch of dentistry, defies distillation to an ever-applicable axiom or procedure. Ortega y Gasset' wrote about the economy of good teaching, that is, the presentation of the least amount of information that will provide the student with an understanding of the subject. Some books are written to impress the reader, some to provide an exhaustive source of material for reference; this book was written to further the role of orthodontics
in the daily practice of dentistry.
SUMMARY Orthodontics presents special problems for the dental student because the course is traditionally brief and often late in the curriculum. Furthermore, success in orthodontics is more dependent on a working knowledge of craniofacial growth and development than in other clinical fields. It is difficult to provide good postgraduate clinical training in orthodontics for the general dentist because of the time involved for growth and treatment. Orthodontics has a lengthy history and today includes the study of craniofacial growth, the development of occlusion, and the·treatment of dentofacial abnormalities. Orthodontic knowledge is needed by all dentists, not just by orthodontists. This book serves as a text for dental students and as a reference manual for general dentists in practice .
.,.
REFERENCES I. Adamandios: Quoted by Haralabakis HN: Presidential address. Trans Eur Orthod Soc 1964; 46-47. 2, .Hippocrates: Epidemics VI, 1,2. 3. Ortega y Gasset J: Mission of the University, London, Routledge & Kegan Paul, Ltd, 1946.
2
CHAPTER
Basic Concepts of Growth and Development Robert E. Moyers, D.D.S., Ph.D.
Life is change; for when you are through changing, you are through.-BRucE
KEY POINTS
status of the patient, recognize any pathologic deviations, and plan treatment.
1. Growth and development are different from shortterm biologic alterations and long-term evolutionary change. 2. Development includes all of the undirectional, normal changes in life from fertilization to death. 3. Development translocation.
=
growth
OUTLINE A.
Classes of alterations in biologic activities I. , 2. 3.
+ differentiation +
4. Development is characterized by changes in complexity, a shift to fixation of function, and more independence, all of which is under genetic control, yet modified by the environment.
B. "
6. The methods of gathering and analyzing growth data affect greatly one's ability to use them. 7. Physical growth is varied by many factors, both genetic and environmental. 8. There is great variability in the expression of growth and development within a given population. 9. "Normal" refers to the expected or typical but is misused as a goal of treatment or when confused with the ideal. 10. Growth is evaluated in clinical practice to assess the
C"
I. 2.
Principles Major themes in development a) Changing complexity b) Shifts from competent to fixation c) Shifts from dependent t6 independent d) Modulation by environment
Some definitions ,.-. • :'.1. 2. 3. 4. 5.
D.
Short-term physiologic or morphologic alterations Long-term genetic and evolutionary changes Developmental events
Principles and themes of development
5. Developmental science includes many fields of study, basic and clinical, biological as well as behavioral.
6
BARTON
Growth Development Differentiation Translocation Maturation
Divisions of developmental science I. 2. 3. 4.
Molecular biology Developmental biology Physical growth Behavioral development
Basic Concepts of Growth and Development E.
Methods of studying physical growth and development I.
Types of growth data a) Opinion b) Observations
older. Biologic scientists study all the various types of alterations in biologic activity.
c) d)
2.
3.
F.
G.
H.
Advantages method
2)
Disadvantages method
of the cross-sectional of the cross-sectional
c) Overlapping or semilongitudinal Evaluation of growth data
I. 2. 3. 4.
Heredity Nutrition Illness Race
5. 6. 7. 8.
Climate and seasonal effects on growth Adult physique Socioeconomic factors Exercise
9. 10.
Family size and birth order Secular trends
data
11.
Psychological
disturbance
Pattern 1.
Definition
2. 3.
Contributions to pattern Clinical implications
Variability
2. 3.
J.
I)
Variables affecting physical growth
I.
I.
Ratings and rankings Quantitative measurements I) Direct data 2) Indirect growth measurements 3) Derived data Methods of gathering growth data a) Longitudinal I) Advantages of the longitudinal method 2) Disadvantages of the longitudinal method b) Cross-sectional
7
Concepts of normality a) Statistical b) Evolutionary c) Functional d) Esthetic e) Clinical Age equivalence Significance of variability
Timing The evaluation of physical growth I. 2. 3.
Why assess? Questions to be asked General growth standards
All of us have been aware since early childhood that a basic characteristic of life is change. We have watched the short-term biologic activities of animals as they gather food, protect themselves, play, and reproduce. We have noticed the slower changes in plants and animals that occur in response to the changing seasons. We have watched ourselves and friends change as we get
A. CLASSES OF ALTERATIONS IN BIOLOGIC ACTIVITIES 1. Short-term Physiologic or Morphologic Alterations The skin may develop a bruise after trauma, the adrenalin titre of our blood rises and falls with changes in our emotions, our body temperature varies according to the time of day and general bodily activities, and animal pelts show variations in color and texture with the seasons. All such alterations are sporadic biologic adjustments to changing environmental stimuli. The changes usually are reversible, the organism returning to a state not very different from what it was originally. Such short-term alterations in biologic activity are not part of the systematic changes of development. There are two kinds of development occurring simultaneously: evolutionary development and life cycle development. Life cycle developments are connected to one another by a single-celled stage, the fertilized egg. When we look at a whole series of life cycles changing over a long time, we are studying evolutionary development.
2. Long-term Genetic and Evolutionary Changes Basic alterations in the genetic make up of an organism-mutations-may be inherited by offspring. If the mutation changes the organism in such a way that it cannot compete as well in its environment, it may not survive. On the other hand, the mutant may be better fitted for survival than its unchanged neighbors and thus the mutation contribut~s to the process of natural selection. The summation of the surviving mutations contributes to the evolution of many species. Long-term genetic and evolutionary changes are quite different from the short-term changes mentioned above. Much more time is needed for the new variety to be obvious in its population. Interest in the changes centers not on the individual but on the alterations in the genetic pool within the. population. In order to understand the significance of genetic ~volutionary changes, population biologists must study large populations within which genetic changes are occurring.
3. Developmental Events There are changing biologic activities that occur in a progt~sive fashion in the 'life history of every organism and that can~ot be considered under the two preceding classifications. Consider the life cycle of a typical mammal (Fig 2-1). The pace of the changes is too slow to be considered a short-term alteration and far too fast to reflect changes in the gene pool or evolutionary trends. There are other important differences: all of the changes are progressive, sequential, and irreversible, leaving the organism unalterably changed from its former state. Single cells develop as do unorganized populations of cells, specific organs, and individuals. Developmental scientists are concerned with all of the changes of an organism from conception to death.
8
Growth and Development
DEATH
FIG 2-1. Developmental events in a single life cycle. (After Sussman M: Growth ed 2. Foundations of Modern Biology Series. En-
glewood Cliffs, NJ, Prentice-Hall, 1964. Reproduced by permission.)
B. PRINCIPLES AND THEMES OF DEVELOPMENT
the chance to be a physician, engineer, philosopher, or dentist. However, advanced standing usually "fixes" one's career and it is more difficult to change.
and Development,
1. Principles No principles or mechanisms of development are unique to embryos, the face, man, or even mammals. For this reason principles and mechanisms of development are best understood through use of a generalized model system. As a model of himself, man can be used only descriptively, not experimentally. Much that we have learned about human development has been learned by the formulation of such general models during studies of species other than man.
2. Major Themes in Development a) Changing Complexity Changes in complexity take place at all levels of organization from the sub-cellular to the whole organism. Ordinarily complexity increases with development, as in the nervous system, but the most complex period of the developing dentition occurs when the primary teeth are erupted and functioning while the permanent teeth are developing in the jaws. The system is thus simplified with the loss of the primary teeth and the complete eruption of the permanent teeth.
c) Shifts From Dependent to Independent Development brings greater independence at most levels of organization. The totally dependent fetus becomes the somewhat 'less dependent child who finally develops into the totally independent adult.
d) Ubiquity of Genetic Control Modulated by Environment At all levels the genetic control of development is constantly being modified by environmental interactions which persist through life,
C. SOME DEFINITIONS' Semantic difficulties are present when the words growth and devetopment are considered. Each term carries concepts not present in~the other and yet there is ove)"lap in their usage. Sometimes they are synonyms, sometimes they are not. Practice varies with the user and the fields of science. The definitions which follow are in common use in developmental throughout the rest of this book.
biology and will be used
b) Shifts From Competent to Fixation Undifferentiated cells are capable of becoming any of several cell types through development, but after they are fully differentiated they become fixed and cannot ordinarily become another type. This is like the student entering the university who still has
1. Growth Growth may be defined as the normal changes in amount of living substance. Growth is the quantitative aspect of biologic
Basic Concepts of Growth and Development
FIG
~ ~"~,~
development and is measured in units of increase per units of time, for instance, inches per year or grams per day. Growth .is the result of biologic processes by means of which living matter normally gets larger. It may be the direct result of cell division or the indirect product of biologic activity (e.g., bones and teeth). Typically, we equate growth with enlargement, but there are instances in which growth results in a normal decrease in size, for example, the thymus gland after puberty. Growth emphasizes the normal dimensional changes during development. Growth may result in increases or decreases in size, change in form or proportion, complexity, texture, and so forth. Growth is change in quantity.
2. Development Development refers to all the naturally occurring unidirectional changes in the life of an individual from its existence as a single cell to its elaboration as a multi functional unit terminating in death. It encompasses the normal sequential events between fertilization and death. Note that development to the biologist refers to the individual in contradistinction to species. Life of the individual does not start as gametes or zygote, but as primordial germ cells which give rise to gametes. In some invertebrates and in plants life starts from almost any cell which is properly stimulated and maintained. The term "multifunctional unit" emphasizes the elaboration of multiple functions rather than multiple cellularity. Unidirectional changes continue until death. Thus, development = growth + differentiation + translocation: These terms are not synonymous.
3. Differentiation Differentiation is the change from generalized cells or tissues to more specialized kinds during development. Differentiation is change in quality or kind.
9
2-2.
A bone may move by two means: It can grow (cortical drift) by selective deposition and resorption (A) or it can become displaced from one position to another (translocation) (B). (From Enlow OH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced by permission.)
example, of the ripening of the ovum and we think of pubescence as a period of rapid maturation as well as accelerated physical growth.
D. DIVISIONS OF DEVELOPMENTAL SCIENCE Growth and developmental studies do not exist apart from other biologic disciplines or their techniques. Studies of developmental events require the knowledge and methods of gross and microscopic anatomy, psychology, biochemistry, physiology, genetics, anthropology, and other disciplines. There are, however, four large divisions within the broad field of growth and development.
1. Molecular Biology During the 1920s and 1930s, physical scientists developed a fantastic array of exciting concepts and very precise new instrumentation, for example, the electron microscope. During the same time, in the field of biochemistry, equally important advances were being made in concepts and in precision of methods. When it became possible to elucidate the detailed roles of specific molecules in 1iving systems by means of these new tools of biochemistry and biophysics (the study of physical phenomena in living processes), an exciting new era in biology began. We are in the midst of a biologic revolution that is as important for man as the atomic revolution. The discovery of RNA and DNA and deciphering the -genetic code are among the most exciting events in the history of science. Molecular biology includes such fast-developing new disciplines as molecular genetics, biophysics, and genetic engineering.
4. Translocation Translocation is change in position. The chin point is translocated (moved) downward and forward far more than any growth at the chin itself. Indeed, most of the growth is taking place at the condyle and ramus while the entire mandible is translocated ventrally (Fig 2-2).
5. Maturation The term maturation is sometimes used to express the qualitative changes which occur with ripening or aging. We speak, for
i: l?evelopmental
Biol~gy
Because a fertilized egg starts as a single microscopic cell and eventually, by development, becomes an adult comprising millions of cells, the biologists who study this fascinating series of events represent several areas of speciality. The fieid of developmental biology includes workers from cellular biology, embryology, teratology, reproductive biology, perinatal biology, and other disciplines. Developmental oral biology is the area of research and teaching concerned with craniofacial growth and development.
10
Growth and Development
3. Physical Growth The field of physical growth is really the study of organ and body growth and includes analysis of such problems as morphogenesis, height and weight, growth rates, retarded growth, metabolic disturbances in growth, developmental 'physical fitness, pubescence, and morphometrics. Developmental scientists working in physical growth include pediatricians, anthropologists, endocrinologists, nutritionists, and dentists. Dentistry can take pride in the fact that research orthodontists probably have contributed more to the knowledge of the postnatal growth of the head and face than any other single discipline. Clinical orthodontics has often been described as the applied study of the physical growth of the head and face.
4. Behavioral
Development
As the child grows physically, patterns of interaction develop with the env'ironment (i.e., behavior). Behavior appears in typical sequences during development just as the physical attributes of the body appear in an expected pattern. Scientists studying behavioral development include embryologists, developmental psychologists, psychiatrists, physiologists, physiologic psychologists, and geneticists. Previously these large divisions of growth and development were viewed as a linear spectrum from the molecule to the behaving adult individual, but the exciting new breakthroughs in molecular biology cause us to view these divisions in a more circular pattern. The molecular aspects of brain activity, for example, may provide the answers to how we think, reason, remember, and forget.
b) Observations Observations are useful for studying all-or"none phenomena, for example, congenital absence of teeth. Observations also are used in a limited way when more quantitative data are not possible, for example, "In cursory visual examination of 67 Eskimo children ranging between 6 and 11 years, not one case of Class II malocclusion was observed."
c) Ratings and Rankings Certain data are difficult to quantify and thus may be compared to conventional rating scales. Such scales may be based on developmental stages, on typical forms or patterns, or on standard color charts. The method is used for the evaluation of breast development, pubic and axillary hair patterns, ear shape, eye col or, and fingerprints. Tooth shape (square, tapering, and ovoid), facial form, and tooth development are common examples of the use of ratings or rankings. Whereas ratings make use of comparisons with conventional accepted scales or classifications, rankings array data in ordered sequences according to value. Thus, one reads such statements in the literature as "When the ten tallest boys werecompared with the ten shortest boys in the sample it was found .... "
d) Quantitative Measurements Science is concerned with quantitation. Indeed, if one cannot express an idea or a fact as a meaningful quantity, one has scarc.ely begun to think about it in a scientific way. Quantitation minimizes misunderstanding and permits the testing of hypotheses by other workers. Any scientist has the right to be skeptical of another's opinion, no matter how renowned the holder of that opinion, until it can be reduced to numbers for testing and further study.
E. METHODS OF STUDYING GROWTH AND DEVELOPMENT How do we study man's development? Not always by studying man himself. It is useful that the basic principles of development are common to many living organisms since all of man's development is not accessible to ready study by experimentation. Irrespective of the source of the growth data, the way the data are analyzed is important.
1. Types of Growth Data a) Opinion When Aunt Tillie says "My, how Johnny has grown. I do believe he's going to be taller than his father, " no one really takes her seriously, for this is but a friendly lay opinion of growth prediction based on no quantitative data and intended primarily as flattery. However, opinion does creep into our textbooks and scientific journals, where it is not so easily labeled as opinion, since one expects substantiated facts in such places. Opinion is, at best, a clever guess based on experience. Much scientific knowledge began as an intuitive hunch made by a careful observer, so opinions are not to be derided. However, they are the crudest form of scientific knowledge and are not to be accepted' when better data are available. They should always be designated for what they are~ne person's biased guess .
1) Direct Data.-Direct
data are derived from measurements
taken on the living person or cadaver by means of calipers, scales, measuring tapes, and other measuring devices. Measuring the size . of the teeth with a Boley gauge in the mouth of a patient produces direct data. 2) Indirect Growth Measurements.-Indirect growth measurements are those taken from images or reproductions of the actual person, for example, measurements made from photographs, dental casts, or cephalograms. ',.
3) Derived Data.-Derived data are obtained by comparing at least two other measurements. "When we say that a person's mandible grew 2 mm between ages 7 and 8, the 2 mm have not actually been measured; rather, the mandibular length at 7 years has been subtracted from)he mandibular length at 8 years and the inc;einent thus derived is assumed.,to represent growth. 2. Methods
of Gathering
Growth
Data
a) Longitudinal Measurement made of the same person or group at regular intervals through time are longitudinal measurements.
•
1) Advantages of the Longitudinal Method.Variability in development among individuals within the
Basic Concepts of Growth and Development
• •
•
•
••
•
group is put in proper perspective. The specific developmental pattern of an individual can be studied, permitting serial comparisons. Temporary temporal problems in sampling are smoothed out with time, and an unusual event or -a mistake in measuring is more easily seen and corrections made. 2) Disadvantages of the Longitudinal Method.Time. If one wishes to study the growth of the human face from birth to adulthood by means of longitudinal data, it will take a lifetime to gather the data. Expense. Longitudinal studies necessitate the maintenance of laboratories, research personnel, and data storage for a long time and thus are costly. Attrition. The parents of children in longitudinal studies change their places of residence or lose interest in the study, and some children die. The result is a gradual diminution in sample size. The attrition in a typical longitudinal study often reaches 50% in 15 years.
Averaging. The changes in average size of a group of individuals do not adequately indicate the sequence of events that is followed by any single individual.
11
may go from 3 to 6 years of age, subs ample B from 4 to 7, subsample C from 5 to 8, and so forth. 3. Evaluation
of Growth
Data
The evaluation of growth data is one of the most complicated and fascinating branches of statistics. Many facts of growth lie hidden in clinicians' or scientists' crude hunches and can be bared for further study only by careful and imaginative statistical dissection. Those who deride statistical studies of growth and clinical data usually are totally ignorant of the possibilities of modem statistical methods. Although the statistical treatment of biologic data is beyond the scope of this book, in my opinion, an introductory working knowledge of statistics is a necessity for every physician and dentist; otherwise, one has no way of evaluating the significance of the findings regularly presented in clinical and research journals. Orthodontists and other craniofacial growth scientists have developed the field of cephalometrics in order to study grov.::th, quantify morphology, and assess the progress of treatment (see Chapter 12). There is no better example of the evaluation of growth data than the day-to-day use of cephalometrics in research and practice.
b) Cross-Sectional Measurement made of different individuals or different samples and studied at different periods are cross-sectional measure" ments. Thus, one may measure a group of 7-year-old boys and on the same day, at the same school, measure a group of 8-yearold boys. Changes between 7 and 8 years of age in boys at that school are thus assumed after study of the data obtained.
F. VARIABLES AFFECTING PHYSICAL GROWTH Variability may be seen in the rate, timing, or character of growth as well as the achieved or ultimate size.
1. Heredity 1) Advantages
of the Cross-Sectional
Method.-
• •
It is quicker. It is less costly.
•
Because it is simpler to get large samples by the cross-sectional method, statistical treatment of the data sometimes is made easier.
• •
The method allows repeating of studies more readily. The method is used for cadavers, skeletons, and archaeologic data.
2) Disadvantages of the Cross-Sectional Method.-It must always be assumed that the groups being measured and compared are similar. Cross-sectional group averages tend to obscure individual variations. This is particularly obfuscating when studying the timing of developmental ev~~ts, for example, the onset of pubescence or the adolescent growth spurt.
c) Overlapping or Semilongitudinal Data. Longitudinal and cross-sectional methods are combined by some workers to seek the advantages of each. In this way, one might compress 15 years of study into 3 years of gathering data, each subs ample including children studied for the same number of years but started at different ages. For example, subsample A
Genetic studies of physical growth make use of twin and family data. Differences between monozygotic and dizygotic twins are assumed to be differences due to environment. There is genetic control of the size of parts to a great extent, of the rate of growth, and of the onset of growth events, for example, menarche, dental classification, the eruption of teeth, ossification of bones, and the start of the adolescent growth spurt. Not all the genes are active at birth. Some only express themselves in the surroundings made possible by the physiologic growth of later years; such effects are . called "age limited." An important point for orthodontics: there is a considerable degree of independence between growth before and growth during adolescence. 2. Nutrition ':' '. Malnutrition delays' growth and may affect size of parts, body prbportions, body chemistry, and the quality and texture of some tissues (e.g., teeth and bones). Malnutrition may also delay growth and the adolescent growth spurt, but children have fine recuperative powers provided the adverse conditions have not been too extreme. During rather short periods of malnutrition growth slows up and waits for better times. With the return of good nutrition growth takes place unusually fast until the genetically determined curve is neared once more and subsequently followed. Though "catchup growth" is seen in both sexes, girls seem to be better buffered against the effects of malnutrition and illness.
12
Growth and Development
3. Illness Systemic disease has an effect on child growth, but the plasticity of the human organism during growth is so great that the clinician must differentiate between minor illnesses and major illnesses. The usual minor childhood illnesses ordinarily cannot be shown to have much effect on physical growth. On the other hand, serious prolonged and debilitating illnesses have a marked effect on growth. The pediatrician is concerned not only with the diseases that may kill or maim the child but also with those that affect the growth process as well. Some of the effects of disease on facial growth are discussed later in this book (Chapter 12).
4. Race Anthropologists studying the racial aspects of growth have a problem in the definition of race. Some so-called racial differences are clearly due to climatic, nutritional, or socioeconomic differences. However, gene pool differences account for the fact that North American blacks are ahead of whites in skeletal maturity at birth and for at least the first 2 years of life. This progress is associated with advanced motor behavior and earlier ability to crawl and sit up. North American blacks also calcify and erupt their teeth about I year earlier than whites.
S. Climate and Seasonal Effects on Growth There is a general tendency for those living in cold climates to have a greater proportion of adipose tissue, and much has been made of the skeletal variations associated with variations in climate. There are seasonal variations in the growth rates of children and in the weights of newborn babies. Contrary to popular belief, climate has little direct effect on rate of growth.
6. Adult Physique There are correlations between the adult physique and earlier development events. For example, tall women tend to mature later and there are variations in the rate of growth associated with differing somatotypes.
be useful for the development of motor skills, for increase in the muscle mass, for fitness, and for general well-being, those children who exercise strenuously and regularly have not been shown to grow more favorably.
9. Family Size and Birth Order There are differences in the sizes of individuals, in their maturational levels of achievement, and in their intelligence that can be correlated with the size of the family from which they came. First-born children tend to weigh less at birth and ultimately achieve less stature and a higher I.Q.
10. Secular Trends Size and maturational changes in large populations can be shown to be occurring with time that, as yet, have not been well explained. Fifteen-year-old boys are approximately 5 inches taller than l5-year-old boys were 50 years ago. The average age at onset of menarche has steadily become earlier throughout the entire world. Both of these facts seem to be true when race, socioeconomic level, nutrition, climate, and other differences have been carefully controlled in the samples. Such changes are called secular trends in growth and, although thoroughly and meticulously studied, have yielded no really satisfactory and generally accepted explanation for such interesting findings.
11. Psychological Disturbance It has been shown that children experiencing stressful conditions display an inhibition of growth hormone. When the emotional stress is removed they begin again to secrete growth hormone normally, and "catch-up" groWlh is seen. It is suspected that the same thing may happen under less extreme conditions and thus account for lesser variations in individuals' growth, but the evidence is scanty.
G.PATTERN 1. Definition
7. Socioeconomic Factors Socioeconomic aspects obviously include some growth factors mentioned previously (e.g., nutrition); yet, there are discrete differences. Children living in favorable socioeconomic conditions tend to be larger, display different types of growth (e. g., heightweight ratios), and show variation in the timing of growth, when compared with disadvantaged children. Some of the causes of these differences are obvious and some of the implications are puzzling. As our society becomes more affluent, how long will we get bigger and mature earlier? Are such changes really improvements? It is interesting to note that many of the positive relationships are associated with socioeconomic "class" and not with family income.
8. Exercise A strong case for the effects of exercise on linear growth has not been made in a quantitative fashion. Although exercise may
In biology the word "pattern" has many meanings and uses: arrangement of parts, values, or events; arbitrary lists of statistics; or relations among measurements. All include the concept of persistence or invariance, in contrast to the word growth, which conveys the idea of change in size. The biologic usage applicable in craniofacial growth is that which defines pattern as a set of constrai!lts operating to preserye the integration of parts under varying conditions or through time (see Ch~pters 4 and 12).
2. Contributions to Pattern The fundamental plan of growth is laid down very early within the safety of the uterus where bones show their well-defined shapes before function and interaction with the environment begins. Therefore, genetic factors are important, but the interactions throughout life between heredity and the environment are clearly what determines the expression of pattern. However, it is very
Basic Concepts of Growth and Development difficult to determine quantitatively each.
the relative contributions
of
13
normality varies and is often a source of misunderstanding.
a) Statistical
3. Clinical Implications In orthodontics, use of the word pattem..has both a morphologic and a developmental application (see Chapter 4). "That child has a Class 11facial pattern" may be a typical morphologic statement of pattern, while "Susie has a vertical growth pattern" is a statement applying the definition to development.
H. VARIABILITY
In statistics, there are specific mathematical ways for portraying the central tendency of a group or population, for example, the mean (an average of values), the median (that value midway between the greatest and smallest measurement, i.e., an average of position), the mode (the most frequent measurement, i.e., an average of popularity or frequency), and the standard deviation (SD, a mathematical expression of the distribution of individuals around the mean) (Fig 2-3).
b) Evolutionary . Variability is the law of nature. Because of the infinite number of genetic possibilities, no two individuals (except possibly monozygotic twins) are ever exactly alike. Variations in response to environment cause increasing differences among similar individuals with'time. Variability may be demonstrated in many ways. In physical growth, variability is demonstrated by the use of statistics, which express quantitatively the range of differences found in a large population of individuals of similar age, sex, socioeconomic background, and race. Such comparisons evoke the logical question "What is normal?"
1. Concepts of Normality Normal refers to that which is usually expected, is ordinarily seen, or is typical, but usage of the word normal and the concept
A
X
I
All forms of life today have passed the critical test of survival. Bizarre and abnormal forms, unable to cope, have been lost.
c) Functional It is normal for most biologic forms to establish effective homeostasis with the environment in order to adapt and survive.
d) Esthetic Often we forget the role that culture plays in determining what within a given group is considered normal. The feet of baby girls have been bound to produce warped, distorted growth; wooden plates have been inserted into the lips of women; scarring of the face has been practiced, etc. What one would consider normal for the feet, the lips, or the facial musculature would, of course, be affected, in these instances, by the particular culture.
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A, measures of central tendency. The standard deviation is a way of depicting the spread of values around the mean (X). Given a normal curve, ± 1 SO = 67% in all cases, ± 2 SO = approximately 95%, ± 3 SO = approximately 98%. B, an array of a sample of severe malocclusions will likely not reveal a normal distribution but may, depending on the utility of the measures, show the presence of "types" (see subgroups superimposed on the distribution). C, severe malocclusions, > ± 1 SO, occur in less than one-third of the population, while those ± 2 SO from the population mean, are so rare it is difficult to accumulate a number sufficient for meaningful statistical analysis. 0, distribution of molar relationship in a sample of dental casts from 7-year-old children. 0-1, left-side (SO = 1.5 mm). 0-2, right-side (SO = 1.7 mm). Note left-right differences in
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501
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14
Growth and Development e) Clinical
necessarily
In dentistry
Almost ,every textbook of dentistry includes a picture of "normal occlusion," showing a perfect intercuspation of 32 permanent teeth. The probabilities individual
of such an intercuspation.appearing
in an
are very, very small and thus, from a statistical
stand-
normality.
illogical
central
tendency
for the group.
Normal
measurements
difficulties
must not interfere
needed for understanding
ment (see Chapter
treatment
it should be thought of as the
of the group.
among these various concepts of
14). Misuse
growth
in planning
treatment.
of normality
in clinical
the
treatand
orthodontics,
To use the normal values for a
group as the best goal of treatment and irrational;
with
or planning
of the concept
the term normal has led to many problems particularly
Rather,
individual
conflicts
The semantic
clear thinking
point, quite abnormal. The concept of normality must not be equated with the ideal or the desired, nor is it appropriate as a goal of for an individual.
found in' anyone
There are obvious
we have often equated the term normal with ideal.
for an individual
is not only
it may indeed be harmful.
are not
82 PLOT OF MALE AND FEMALE MEANS FOR ANNUAL CHANGE IN MANDIBULAR LENGTH ACROSS AGE
PLOT OF MALE AND FEMALE MEANS FOR MANDIBULAR LENGTH ACROSS AGE 80
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FIG 2-4. Growth plotted in different ways. A, stature. A-1, note effect of adolescence on population differences in sexual dimorphism. A-2, stature velocity curves. Note early appearance of effects of pubescence on rates of stature increase in girls. B, mandibular length (condylionpogonion) plotted against chronological age. B-1, accumulated length. B-2, velocity (incremental) plot. Note population differences between stature and mandibular length. C, mandibular length and stature plotted against "dental age." (Zero is not the time of birth, as in
chronologic age, but time of arrival of the first permanent incisor.) C-1, accumulated mandibular length. C-2, mandibular increments/ year (velocity). C-3, stature. C-4, stature increments. D, comparison of mandibular and stature changes in two individuals. Note differences in timing and percent annual change. (Data from University of Michigan Growth Study, Center for Human Growth and Development, University of Michigan, Ann Arbor. ~
15
Basic Concepts of Growth and DeveLopment
c, PLOT OF MALE CHANGE
5' I I-
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16
Growth and Development
2. Age Equivalence Because individuals develop in different patterns, producing variability, all individuals of a given chronologic age are neither necessarily of the same size nor the same stage of maturation and development. A problem is thus posed for the clinician and the developmental scientist, namely, how does one compare individuals of the same chronologic age but varying stages of biologic development? A number of "developmental ages" have been suggested as a method of meeting this problem. Thus, one hears of skeletal age (SA), usually based on the carpal calcification; dental age (DA), based on the number of teeth calcified or erupted; chronologic age (CA), expressed as years and months from birth; mental age (MA), and so forth. It often is better to compare individuals at the same stage of biologic development rather than at the same chronologic age.
J. THE EVALUATION
OF PHYSICAL
GROWTH 1. Why Assess? The clinician is interested in assessing physical growth for the following reasons: a) The identification of grossly abnormal pathologic growth. b) The recognition and diagnosis of significant deviations from normal growth. c) The planning of therapy. d) The determination of the efficacy of therapy. Unless the clinician has a clear and quantitative assessment of growth at the start of treatment, it will be impossible to evaluate later how well any treatment has progressed.
2. Questions to Be Asked
3. Significance of Variability The significance of variation from the norm for the group in which an individual is found can be understood only if the individual's present status is thought of in terms of progress toward his or her own goal rather than rigidily comparing this person's progress to the group's progress toward its goal. It thus becomes necessary to appraise the growth of the individual and to compare this pattern in the light of his or her familial tendency and the larger group to which he or she belongs (see Section J, The Evaluation of Physical Growth). Gross variation from the central tendency may also be indicative of a pathologic condition or a grossly abnormal pattern of growth that will markedly affect treatment.
I. TIMING The timing of developmental events is largely under geneticcontrol, yet altered by the environment. The developmental scientist is interested in when growth processes are" turned on," for example, pubescence, or when they cease. The age of maximum growth increments during puberty-the adolescent spurt-is not only of developmental interest but is used as a marker for timing other growth events (Fig 2-4). There are sex-related differences in the timing of many growth phenomena. Usually, girls precede boys, for example, in pubescence, dental calcification, and ossification of carpal bones. Further, there are differences related to physique, for example, taller children tend to reach the adolescent spurt later than short-legged, stocky types. Such severe environmental effects as disease and malnutrition not only affect the quality of the growth but may alter the timing of development as well. Nowhere is timing more critical than in the fusion of facial parts in early prenatal growth (see Chapter 3). Cleft lip and/or cleft palate is a well-known example of a gross craniofacial deformity resulting from a failure of facial parts to fuse at a critical time. When dental and facial skeletal growth are not synchronized, some malocclusions are produced and others aggravated. Much of this book deals with the problem of mal-timed developmental events in the face.
a) What is the status of the patient at the moment? Most of the time, the clinician must base judgments on a single examination and therefore must determine status of the individual by crosssectional evaluation alone. b) What is the progress of growth to date? When serial records are available longitudinal comparisons to the patient's own pattern of development can be made. c) How does he/she compare with others? Comparison with others of the same age, sex, and race is done with derived growth standards, but the abuse of growth standards is a sad and unfortunate story. Most of the mistakes in the use of growth standards are the result of two problems in understanding: (I) the choice of the appropriate standard; and (2) the nature of biologic variability. Unless the standards have been derived from a population applicable to the problem at hand, it is better not to use standards at all. Indeed, for many problems in facial growth, as it relates to clinical practice, few appropriate standards are available. Furthermore, to choose one or two mean values from a biased sample and apply them rigidily to all individuals with no understanding of the entire craniofacial complex and the adaptations and reasons for the variations from the mean is naive and ridiculous and handicaps-one in planning the treatment. d) How does he/she fit the family pattern? Only recently have quantitative studies of familial tendency in facial growth appeared in the literature, yet much can be learned by studying records of siblings and parents. Most orthodontists believe that the second child in a family can be treated better because of what was learned from treating the first. e) What will he/she do in the future? The prediction of craniofacial growth is one of the liveliest topics in the literature today (se\; Chapter 12). The most. popular methods predict coarsely the growth of an individual from data d,erived from populations. Much can be learned, but the estimates are more qualitative description than precise prognostication, more clinical art than science. However, no one should begin orthodontic treatment without estimating as well as possible what can be expected in the future. The direction, amount, site, and timing of growth affect the treatment and the retention of the results of treatment. It would be ideal if one could, by data derived from a single cephalogram, make quantitative predictions of the details of growth and form change for that individual even during the modifying effects of treatment.
Basic Concepts of Growth and Development Such predictive methods are now under development and may some day have a significant impact on orthodontic treatment planning. The new methods are based on sophisticated computer manipulation of large data bases and the use of strikingly original approaches to mathematical modeling of craniofacial form and growth.
3. General Growth Standards The evaluation of the physical growth of the total child is a large field of science in itself. Many methods have been devised to appraise height, weight, skeletal development, muscle strength, the onset of pubescence, and other factors. Ingenious and complicated formulae of growth have resulted in many clever graphic methods of portraying growth standards so that the individual may be compared to norms. Such evaluations of physical growth are done daily in pediatric and dental practice, but there is always danger of oversimplification of the complexity of growth by assuming that anyone or two measurements truly reveal the progress of physical growth.
SUMMARY To the biologist growth and development are the normal changes from birth to death in an individual organism. Growth and development are therefore different from random, short-term biologic alterations and long-term evolutionary trends. Growth is size change. Differentiation is specialization. Translocation is change in position. Development = growth + differentiation +
17
translocation. Developmental science includes many fields of interdisciplinary study and highly specialized methods of research and clinical application. Growth and development show wide variability of expression within a population. This variability is the source of many clinical problems. The expected average or norm is not a good expression of the wide variability seen and the normal is, unfortunately, often misused as a goal of treatment or is confused with ideal development. The evaluation of the growth and development of the individual patient is an important part of orthodontics as a basis of comparison with the normal, as a means of discovering and diagnosing maldevelopment (malocclusion), and as the foundation for planning orthodontic treatment.
SUGGESTED
READINGS
Baer M: Growth and Maturation, An Introduction to Physical Development. Cambridge, Mass, Howard A. Doyle Publishing Co, 1973. Falkner F: Human Development. Philadelphia, WB Saunders, Co, 1966. Falkner F, and Tanner JM: Human Growth, New York, Plenum Publishing Corp, vol I, Developmental Biology and Prenatal Growth; vol 2, Postnatal Growth and Neurobiology; vol 3, Methodology, Genetics, and Nutritional Effects on Growth, 1986. Harrison GA, Weiner JS, Tanner JM, et al. Human Biology, 2nd ed. Oxford, Oxford University Press, 1977. Lowrey GH: Growth and Development of Children, ed 8. Chicago, Year Book Medical Publishers, 1986. Young JZ: An Introduction to the Study of Man. Oxford, Oxford University Press, 1971.
CHAPTER
3 Prenatal Facial Growth lames K. Avery, D.D.S.,
Ph.D.
The history of man for the nine months preceding his birth would, probably, be far more interesting and contain events of greater moment than all the three score and ten years that follow it.-SAMuEL TAYLORCOLERIDGE, Miscellanies, Aesthetic and Literary ...
KEY POINTS 1. Critical events leading to normal facial growth occur in the first 4 weeks of life. 2. Precursor cells migrate into the facial region as the architects of the individual characteristics of facial growth.
9. The bony skeleton of the medial face develops from cartilage, while the lateral face develops from connective tissue or membrane. 10. The hyoid (2nd) arch muscles migrate over the face during formation, whereas the muscles of mastication develop only within the mandibular (first) arch.
3. Environmental factors play a significant role in developmental malformations. 4. Cleft lip/palate is one of the more common congenital malformations, appearing in one of every 800 births. 5. In the early stages of development the face is segmented by branchial arches which, if they do not disappear, can result in branchial clefts and related lateral facial malformations. 6. The face is closely related to brain development, and defects of the anterior brain usually result in facial deformations. 7. The palate initially develops as shelves formed beside and below the tongue. These then elevate above the tongue. This complex developmental process may result in cleft palate.
8. The blood supply of the face shifts from the internal to external carotid arteries at the time the palatal shelves are maximally developing.
18
OUTLlNE A.
Period of organization of the face I. The branchial arches ~ 2. Development of the perioral region 3. Changes in facial proportions 4. Origin of facial malformations B. Development of oral structures Development of the tongue 2. Formation alld elevation of the palatal shelves ".3. Factors in ~ormal palatal development 4. Fusion of the palatat shelves 5. Tooth development 6. Salivary gland development C .. Differentiation of supporting structures Development of the chondrocranium 2. Development of the maxillary complex 3. Development of the bony palate 4. Mandible and temporomandibular joint
I.
I.
Prenatal Facial Growth 5. 6. D.
Facial muscles Muscles of mastication
The fetal period-third I. 2.
19
A. PERIOD OF ORGANIZATION OF THE FACE
to ninth months
Craniofacial changes Radiographic changes
1. The Branchial Arches An understanding of the events leading to the organization of the face in its normal form is critical to the understanding of various factors responsible for abnormal development in that area. These events take place during the first 4 weeks in prenatal life as the fundamental plan for an individual's face unfolds. The first sign of growth is in the expansion of the forebrain. The tissues ov.erlying the forebrain will differentiate into the nasal areas and forehead. Other tissues develop soon after, and will migrate and form the maxillary processes and mandibular arch. All these tissues will differentiate into the specific facial characteristics of that individual. The minute proportional differences that occur in each human face are what make each of us a distinctly recognizable individual. Each of us is unique (identical twins are a partial exception). Environmental factors will play a role in this differentiation. Prior to the beginning of heartbeats and establishment of the umbilical circulation, in the fourth prenatal week, the embryo is isolated from the extrenal environment, utilizing its yolk sac for nourishment and growth. This period is one of rapid enlargement of the embryo. The increase in cellular proliferation enhances the potential for teratogenic (adverse environmental) factors to alter development. This chapter describes the events leading to maturation of the human face and evaluates the role of normal and adverse factors that affect the delicate balance of growth.
Differentiation of the human face takes place early in prenatal life, specifically between the fifth and seventh weeks after fertilization occurs.]4 During this short period, a number of important events occur that determine the formation of the human face. In the fourth week after conception, the future face and neck region located under the fore brain of the human embryo becomes segmented (Fig 3-I,A). Five branchial arches are formed, appearing as rounded, tubular enlargements, and are bounded by clefts and grooves that help define each arch. They are numbered beginning anteriorly. The mid and lower facial regions develop, in part, from the first two, named the mandibular and hyoid arches. The third also contributes to the base of the tongue. Within each of these branchial arches arise skeletal, muscular, vascular, connective tissue, epithelial, and neural elements that develop into the systems supplying the face and neck. Most of the structures of the adult face thus develop from the first and second branchial arches and from tissues surrounding the forebrain. In the early period of development (i.e., the fourth week), it is difficult to distinguish the primary craniofacial features of the human embryo from those of other mammales (Fig 3-1 ,A and B). The human face is first characterized by an invagination or dimple in the surface ectoderm layer appearing just below the forebrain. As this pit deepens, it forms the outline of the oral cavity (Figs 3-1 ,A and 3-2,A). The tissue masses immediately surrounding this oral pit will form the human face. In the fourth week, the posterior boundary of the oral pit comes into contact with the developing foregut. As the ectodermal oral plate meets
Branchial Arches
Oral Cavity
.
Heart
i.
A FIG 3-1. Sketches of human embryos at 5 (A) and 7 weeks (B) illustrate appearance of human face during the 2-week time period in which the face develops.
20
Growth and Development are the flexures that occur during the fourth week in the region of the future neck. The brain flexes ventrally, then dorsally and, as a result, the head becomes more erect.
the entodermal lining of the gut, the membranes disintegrate, and continuity between the oral cavity and the gastrointestinal tract is first gained. At 5 weeks (Fig 3 - I ,A), the "face" appears crowded between the rapidly growing forebrain and the heart, which occupies much of the chest cavity at this stage. The nonfunctioning, developing lungs are still quite small, composed mainly of conducting bronchi until the respiratory bronchioles begin to form in the fourth month.17 As the lungs do not function in respiration until after birth, the oxygen needs are supplied from the placenta through the umbilical veins to the heart. The heart, however, must function very early. It becomes conspicuous by its size in the third week and initiates a beat in the fourth week of embryonic life.'9 During the prenatal period, the heart not only pumps blood thr~ughout the body of the embryo but also conducts blood to, through, and from the placental system back to the heart. The heart is proportionately much larger at this time than it will be in the adult body and, therefore, requires much space for its proper development. The growth of the heart affects the development of the face, not only because of the importance of the blood supply to its development but also because the face during its early period of rapid growth and organization is crowded between the enlarging forebrain and the pulsating heart. Even at this early stage, the growth pattern of the face is downward and forward as it grows out from between these two organs. Important related occurrences
2. Development The "face"
Anterior view of the developing face in the human embryo from the fourth to the eighth prenatal weeks. (Remainder of body was removed to reveal face.) At 4 weeks (A), the future face is indicated by the bulging forebrain and the first branchial arch immediately below it. By 6 weeks (B), the oral slit is noted, with nasal pits appearing above it. The eyes appear on the sides of the head. The mandibular arch bounds the oral slit below. At 6'/2 weeks (C), the eyes are nearer the front of the face. The nose is defined, and the developing ears appear at the corners of the mouth. At 8 weeks (D), the masses comprising the face have fused together to bound the oral cavity, and the forebrain has begun its forward growth, leaving the ears behind.
at the fifth week is about as thick as the sheet
of paper from which you are reading, and the whole face is only about I 1/2 mm wide. At this time, the oral pit is bounded above by the frontal area and below by the mandibular arch, which appears shovel shaped (Fig 3-2, A and B). A midline groove is apparent, disappearing during the sixth week. At this time, two small, oval, raised areas appear just above the lateral aspects of the future mouth. In the next 48 hours, the centers of these raised areas become depressions as the tissues around them continue to grow anteriorly (Fig 3-2,B and C). The depressions deepen into pits that will become the future nostrils and the masses surrounding them-the bridge and the sides of the external nose. The tissue between the nasal pits is termed the medial nasal process and those lateral to the pits are called lateral nasal processes. These tissues originate from the superficial epithelial and connective tissues of the frontal area as they all grow downward and forward together (Fig 3-2,C). Figure 3-2,D shows fusion taking place between the median nasal processes and the lateral nasal processes, which
A
FIG 3-2.
of the Perioral Region
Prenatal Facial Growth
21
FIG 3-3. Development of the upper lip. The maxillary processes (MP) fuse with the medial nasal processes (MN) to form the floor of the nostril. The lateral nasal processes (LN) enlarge to form the sides of the nose. The slit below the nostrils is the nasal fin (NF), which is the potential site of cleft lip. The mandible (MD) is below the oral pit. NP = nasal pit.
FIG 3-4. Frontal section of upper face in fetus shows the nasal pits (NP) and forming nasal fins (NF). LN = lateral nasal process; MN = medial nasal process; MP maxillary processes; MD = mandible.
will be described later. Before this fusion occurs, however, the nasal pits undergo further elongation. The raised anterior edges of these pits form the shape of minute horseshoes, with the open sides below (Fig 3-3). As they grow forward, the inferior ends of the horseshoes come into contact with each other (Fig 3-4). The distance between these two nasal pits does not increase during this important period of facial development, although the pits themselves increase in both height and length.24 Since the tissue underlying each nostril represents the first separation of the nasal cavity from the oral cavity, it has been designated as the primary palate by some authors.]9 The mode of formation of these pits is important, since a failure in any of the steps in their development may result in a cleft lip. The steps in
fusion of the upper lip are illustrated in Figure 3 - 5. Step I can be defined as the contact between the epithelium covering the medial border of the maxillary process and the lateral border of the medial nasal process. These two epithelial-covered processes together form a lamina termed the "nasal fin" (Fig 3-5). Upon contact, adhesion of two epithelial sheets occurs; they become fused into a single sheet. Then, degeneration of this sheet occurs, resulting in connective tissue penetration through it (Fig 3-5,B and C). This area of penetration expands rapidly and the nasal fin is eliminated except at its anterior and posterior limits. In this way, the lip is unified anteriorly, and separation of the floor of the pits in' the form of a cleft is prevented. The tissue underlying and 'between the two nasal pits is termed the primary palate since it
FIG
3-5~
Development of the floor of the nostril and the nasal fin below it. A and B, ·as the nostril elongates,
A
the epithe-
lium of the, maxillary and medial nasal processes fuse together and an opening appears through which connective tissue of the lip grows. C, as the tissue
B
of the lip is unified, it forms the primary palate, which is a small mass of tissue bounded by the oral cavity below and the nostril above. D, posteriorly, the nasal pit opens into the roof of the oral cavity by splitting of the two sheets of epithelium.
-.
22
Growth and Development
forms a separation between the primitive nasal cavity and the oral cavity. At the posterior limits of the epithelial fin, the same two epithelial sheets split apart, producing an opening between the nasal pits and the roof of the oral cavity (personal communication; H.C. Srivasta and A. Barry) (Fig 3-5,D). This p0sterior opening of the nasal pit is termed the internal nares and is the posterior limit of the primary palate. Later, the nasal cavities enlarge posteriorly to form a space overlying the entire oral cavity. The oral and nasal cavities are then separated by the secondary palatal shelves. These shelves are termed the "secondary palate," as they are secondary to the primary palate. The nasal cavity then opens posteriorly in the nasopharynx (see Fig 3-22). The failure of any of these rather complex developmental steps to occur in sequence and a.t the approximate interval of time may result in congenital defects. This is the reason such defects are most common today. One in every 800 births results in either cleft lip, cleft palate, or the combined defect. In summary, lip development is a three-stage process, the first being contact of the two epithelial sheets covering the adjacent processes; the second, fusion of the epithelium into a single sheet; and, finally, degeneration of this sheet, followed by invasion by connective tissue of the lip growing through it. The developing eyelids are an example of two epithelial laminae that come into tight contact but do not fuse or undergo connective tissue penetration. They simply remain closed, with their surfaces fused, until the seventh prenatal month, at which time they open, exposing the eyes. In the sixth week, the upper face appears flat and broad, with the nasal pits positioned on the lateral corners of the face. The distance between the nasal pits represents approximately 90% of the width of the face. Lateral to this region are the maxillary processes, which appear at this stage as triangular or wedge-shaped masses located at the superior lateral aspects of the oral cavity (see Fig 3-3). At 6 weeks, the mandibular arch appears broad and flat and comprises the lower border of the oral cavity. In the midline, a slight constriction still can be seen, and laterally the auricle of the ear will arise from six small hillocks of tissue that appear to circumscribe the branchial cleft positioned between the mandibular and hyoid arches (see Fig 3-1 ,A and B). Three of the hillocks arise from the mandibular arch and the three below the cleft arise from the hyoid arch. The first branchial slit later will become the external auditory canal (see Fig 3-2,C and D).
3. Changes in Facial Proportions Three or 4 days later, at 6 '/2 weeks, the facial proportions appear to have changed greatly, due to an increase in dimension laterally to the nasal pits. There has been, in this short span of time, an expansion of the anterior region of the brain, causing the lateral maxillary regions to move to the front of the face. Thus, the eyes and adjacent cheek tissues are rotated 90 degrees from the sides to the front of the face because of this differential growth. The medial nasal area now makes up only the relatively small medial segment of the upper lip. The medial nasal tissue interposes between the maxillary wedges at this stage and will become the site of the future philtrum of the upper lip* (see Fig 3-2,D). Early in the seventh week, the face appears recognizably human as a result of the frontal location of the eyes, differentiation of the nose, and enlargement of the mandible (see Fig 3-2,D). Later, as the face increases in height, the nostrils will no longer be on the same horizontal plane as the eyes. At the seventh week, the furrows separating the mandibular, maxillary, and nasal areas are less marked. The external ears are now visible, having differentiated from the auricular hillocks. It is of interest that such complex structures as our external ears can arise from six small and initially uniform enlargements. The ear will appear well differentiated by the sixteenth prenatal week. 19
4. Origin of Facial Malformations During the period of organization of the face, the mandibular processes and maxillae emerge from the first branchial arch while the forehead and nasal area arise from tissues overlying the forebrain. These different origins, each with its own very precise set of activities and timetables, create the primary cause of facial variability, both within and outside normal limits of growth. During the fourth to sixth week the forebrain undergoes lateral expansion as the prosencephalon forms the lateral ventricles. As
*The medial nasal process does not occur in the rabbit, which has a shallow cleft at the midline, hence the term "harelip." It is a misnomer, however, to define the human cleft as a "harelip," since a cleft rarely occurs in the midline; rather, it appears laterally between the medial nasal and maxillary processes. The rare midline cleft occurs when the globular or medial nasal processes do not merge properly (see Fig
3-4) ..
MP MA
A 3-6.
E
BeD
FIG The period of maximal facial development occurs from the fifth to the seventh weeks. The frontonasal process (FNP), maxillary process (MP), mandibular (MA), and hyoid arch (HY) contribute tissues to facial growth. Observe the changes in facial proportions as nasal
".
F
pits (NP) appear in (B). The space between them then remains constant while growth lateral to them causes the nose to appear smaller. The maxillary (MP) and medial nasal process (MNP) fuse to form the upper lip. LNP = lateral nasal process; AH = auricular block.
Prenatal Facial Growth
23
is thus shaped by the forebrain, and the tissues that overlay it contain the neural crest cells which migrate from their origin in the dorsal neural tube down into the prospective face. A deficiency in crest cells, for example, may cause a lack of olfactory nerve development and in turn a lack of nasal placode formation. An absence of nasal pit and ethmoidal sense capsule follows (Fig 37). The resulting anterior medial facial defect may be classified as ethmocephaly, which by name indicates both brain tissue and nasal deficiency (Fig 3-8). The severe forms of these facial malformations clearly reveal the relationship of neural facial development. Lack of anterior brain development usually leads to neural crest and olfactory nerve deficiency and lack of induction of the nasal field. A partial deficiency will lead to ethmocephaly simplex, which may result in a median cleft lip and/or nose (Fig 3-9).
FIG 3-7. The neural crest cells arise from the neural folds and migrate onto the face. During migration they lie under the skin, then proliferate and contribute to all facial structures. a result the face broadens and the eyes appear to migrate from their position on the lateral head to the front of the face. This change is a result of the general widening of the face with growth of the tissues behind and underlying the eyes (Fig 3-6). The face
A unilateral or bilateral cleft lip is a more common deficiency of the lip than the midline cleft. These clefts are the result of a localized growth fault in the floor of the nostril. This may be due to a lack of development of the nasal fin in which the two halves may not fuse, which results in an oronasal cleft (Fig 3-5), or there may be a lack of penetration of the epithelial fin by connective tissue, which could allow the fin to split apart after initial closure and a cleft to appear (Figs 3-10 and 3-11). Other defects of the anterior face may rise from the lack of "merging" along facial grooves. Merging is defined as the filling in of grooves by tissue growth underlying the groove (Fig 3-6). Grooves appear between the nose and eye, (naso-optic) or at the angles of the mouth (macrostomia) (see Fig 3-14). The sixth to seventh prenatal week is an important period in development of these types of defects because these grooves are most apparent at that time, as seen in
Fig 3-2,C. Defects of the lateral face are usually associated with the branchial arches. These defects may again arise from neural crest cell deficiencies as these cells migrate into the branchial arches in early development when the anterior neuropore is closing, similar to the way they do anteriorly in the face (Figs 3-7 and 3-8). Alteration of the external ear is the most common defect found in
FIG 3-9. FIG 3-8. Ethmocephalic complex with lack of development of anterior brain, nasal, and midlip tissue.
Ethmocephaly simplex showing a median cleft lip and nose. This is an example of a "harelip" and is rare compared with a common cleft of the lip and nostril.
24
Growth and Development
FIG 3-10. Views of nasal pits at 6 and 6'/2 weeks.
Initially they are a blind
pocket connected to the oral cavity anteriorly by a slit-like opening. The covering of the maxillary (MP) and medial nasal process (MNP) form these epithelial sheets which later fuse and are penetrated by connective tissue, as seen on the right. Meanwhile the posterior aspect of the pit opens into the roof of the mouth. The lateral nasal process (LNP) supports the lateral aspect of the nostril.
the branchial
arch syndrome
(Fig
3-12),
but it also includes
terations of the facial skeleton and/or muscular development, defects, and clefts of the branchial
grooves (Fig
3-13).
al-
tongue
Branchial
clefts or cysts appear most often along the anterior border of the sternocleidomastoid
muscle (Fig
Col/ins (mandibulofacial of the branchial
3-13). Pierre Robin
dysostosis)
arches. The former
syndromes condition
and Treacher
are both defects
is characterized
by
FIG 3-12. Lack of improper auricular development. One or several of the original auricular hillocks did not merge together (refer to Fig 3-2,C. In addition to a lack of auricle development, there is also a lack of a functional external auditory canal; thus, the first branchial groove did not develop properly and, likely, middle ear development affected.
a short mandible,
3-14).
Those
development
enlarged
with
tongue,
Treacher
Midline
of the malar arches, a shortened
midline
They result from
of the first branchial
soft-tissue
deficiency
persistence
at that site. Thryoglossal
of the cord of epithelial
gland developed
(Fig
lack of
mandible,
although
a lack of development
arch, resulting
tulas are also seen in the midline
exhibit curved
which results in loss of hearing
defects also occur in the mandible,
3-16).
rare (Fig
and possible cleft palate (Fig
Coli ins syndrome
and lack of middle ear development (Fig 3-15).
was also
they are of the
in both skeletal and duct cysts and fis-
of the neck, which cells from which
are due to the thyroid
3-17) .
.
..
FIG 3-11. Bilateral isolated shaped process
complete cleft lip. The philtrum or medial nasal process is as a mass suspended from the nose. Observe the wedgemaxillary processes which did not contact the medial nasal at the proper time to effect closure.
FIG 3-13. Failure of complete obliteration of the cervical sinus results in a cervical cyst and branchial fistula. They may be found on the neck along the anterior border of the sternocleidomastoid muscle.
Prenatal Facial Growth
25
FIG 3-14. A case of Pierre Robin syndrome with malformed ear, macrostomia, and short lower jaw. Note the auricular tag on the right side of the face.
Treacher Collins Syndrome (mandibulofacial dysostosis)
f7r" I
:~
--: coloboma of lower Iid
,
...
"\
1'; ... '... .2;f~ '~ ...
"
"
rr~1:,> "
/
;.
/
~~-,1",< ..,
cilia absent
med ial to coloboma
ptosis of upper eyelid
abnormal hair growth on cheek micrognathism
hypoplastic
zygomatic arches
.
malformed
ear
;;.
FIG 3-15. Diagram of Treacher
Collins syndrome
shows the facial features of
this condition. Most usual is the lack of zygoma development, antimongoloid slant of the eyes, and short lower jaw. (Courtesy of AI-
phonse R. Burdi, Department Medical School, Ann Arbor.)
of Anatomy,
University
of Michigan
26
Growth and Development
FIG 3-17. This thryoglossal cyst and fistula developed from the epithelial cord, which descends down the anterior neck to form the thyroid gland.
FIG 3-16. A mandibular cleft. This defect stems from the fifth prenatal week when a midline constriction in the mandibular arch is apparent. Lack of unity of the mandibular processes at the midline results in loss of soft-tissue and bony union. There is also a lack of development of mandibular anterior teeth.
B. DEVELOPMENT
OF ORAL STRUCTURES
1. Development of the Tongue The tongue musculature originates from the occipital myotomes at the beginning of the fourth week.' As it grows anteriorly into the floor of the mouth, it carries forward its nerve and blood supply from more posterior regions and develops into an oral part (the body) and into a pharyngeal part (the base). The body arises, in part, from contributions of the first branchial arch, and the base arises from the second, third, and fourth arches. The body of the tongue is indicated by three primodia, the paired lateral lingual swellings, and a centrally located tuberculum impar (Fig 3-18,A).
At the fifth week, the base of the tongue is indicated by a median elevation, the copula. Between the copula and the tuberculum impar a small pit appears, termed the foramen caecum, which gives origin to the thyroid gland tissue. During the sixth and seventh weeks, the lateral lingual swellings enlarge and relatively reduce the size of the tuberculum impar. A furrow appears along the lateral borders of the tongue, separating it from the developing alveolar ridges (Fig 3-18,B). The two lateral lingual swellings then merge, and the body of the tongue appears as a more unified structure (Fig 3-18,C). The tongue grows so rapidly that it pushes into the nasal cavity above and between the two palatine shelves (Fig 3-19,B), and by 8 '/2 or 9 weeks the muscles of the body of the tongue appear clearly differentiated (Fig 3-19,C). Thus, the oral and nasal cavities originate from the single stomodeal cavity and become separated as the palatal shelves elevate and grow between them. "
A
B
lateral lingual swellings tuberculum impor
c
D body of tongue fungiform papilla
foremen caecum
filiform papillo
copulo
vallate popillo
glottis
sulcus terminalis lingual ton;ii bose of tong ue epiglottis
FIG 3-18. Diagram of the developing tongue. A, 5th; B, sixth; and C, seventh prenatal week; D, adult.
Prenatal Facial Growth
27
FIG 3-19. A, removal of the front of the face reveals the relationship of the developing tongue to the palate. At 6 weeks (B), the tongue is a small mass of undifferentiated tissue. NC = nasal cavity; NS = nasal septum; QC = oral cavity. At 7 weeks (C), the enlarged and differentiated tongue extends up into the nasal cavities. The palatal
shelves (PS) are beside the tongue. At 8'/2 weeks (D), the palatal shelves appear above the tongue. At 10 weeks (E), the palatal shelves fuse together to delimit the nasal and oral cavities. P = palate. (From Shapiro M (ed): The Scientific Bases of Dentistry. Philadelphia, WB Saunders ,.
Reproduced Co, 1966, p TT.; -# -
by permission.)
t ;.
2. Formation and Elevation of the Palatal Shelves As the enlarging
tongue pushes dorsally
the palatal shelves develop
in a wedge shape and, because of the
presence of the tongue, grow downward along either side of the tongue step in palatal development shelves from a vertical position
overlying
sition probably
into the nasal cavity,
(Fig
into the floor of the mouth 3-19,C).
The next critical
results in the movement
position
of the palatal
beside the tongue to a horizontal
the tongue (Fig 3-19,D).
This change in po-
involves
shelves (Fig 3-20).26 oanteriorly,
movement
of both the tongue and palatal
As the shelves roll over the tongl!e poster-
the tongue may glide anteriorly
to the shelf movement. 25 Closure
tongue separates the oral and nasal cavities The tongue may press upward
shelves over the
(Fig 3-19,C
and D).
against the palatal shelves, helping
to bring them into closer approximation in the midline.
to offer less resistance
of the palatal
These movements
to facilitate
their contact
of palatal closure may be quite
28
Growth and Development
FIG 3-20. Movements of the palatal shelves and tongue during palate closure. The tongue moves anteriorly (C), depressing downward (D) and laterally (E) as the palatal shelves slide from B to A over the tongue.
rapid, possibly occurring with about the same speed as when one swallows (Fig 3-20). This process occurs between the eighth and ninth weeks after conception in the human, when, as investigators have shown, the paraoral structures of the human respond to stimulation.'2 It is possible that the nerve supply to the tongue and cheeks is thus sufficiently developed to provide some neuromuscular guidance to the intricate activity of palatal closure.
mandible become attached and confluent with the adjacent facial branches of the external carotid (Fig 3-21,B and C). If, for any reason, this important shift of the blood supply of the face and palate from the internal to the external carotid is delayed, the effect on the developing tissues undoubtedly would be notable. It is a coincidence that this important shift occurs at this critical time in the palatofacial development.
3. Factors in Normal Palatal Development
4. Fusion of the Palatal Shelves
Other activities, such as bringing the head to an erect position, may be related to the elevation of the palatal shelves26 As the head elevates, the neck becomes recognizable and the face is no longer pressed against the thoracic cavity, due partially to settling of the heart more inferiorly in the thorax. At this time, spontaneous movements of the head, elevation of the lower jaw, opening of the mouth, and movement of the tongue occur for the first time]2 (see Chapter 5). Deficiencies of oxygen, various foodstuffs, or vitamins have been reported experimentally to cause cleft lip and palate and other types of facial defects in mice and rats.6.27 On the other hand, excesses of certain endocrine substances, a number of drugs, and irradiation will have teratogenic effects on the developing face and palate, as shown in the embryos of experimental animals.22·27 In regard to vascularity, which, of course, controls the amount of oxygen and nutritional elements, the face and palate seem unique in development. There is a most important shift in circulation in this region during the critical time period of the seventh and eighth weeks.18 The vessels of the branchial arches give rise to the external and internal carotid arteries, which provide the vascular supply to the face and palate when the first and second branchial arch vessels begin to disappear. During the sixth week, the stapedial artery arising from the internal carotid supplies most of the midfacial region (Fig 3-21,A and B). Then, during the seventh week, the stapedial artery severs its contact with the internal carotid. At the same time, its branches to the maxilla and
By 8]/2 prenatal weeks, the palatal shelves appear above the tongue and in near contact with each other (see Fig 3-19 ,C). Then, during the ninth and tenth weeks, they come into contact and fusion begins (Figs 3-19,D and 3-22,C). First, the epithelial coverings of the shelves join to form a single layer of cells. Next, degeneration occurs as the connective tissue of the shelves penetrates this midline epithelial barrier and intermingles across the area (see Fig 3-19,D). Thus, the process is similar to that occurring in the lip (see Fig 3-10). In a few cases, the two shelves have been repdrted to separate after initial fusion, with resulting epithelially covered connective tissue bands stretching across the palate between the shelves.]O As bone forms· in the p~late, the area along the midline anteroposteriorly will become a suture where important expansive growth of the palate occurs. The entire palate does not contllct and fuse at the same time. Initial contact occurs in the centrarregion of the secondary palaty just posterior to the anterior or primary palatine process (Fig 3-22,B) and closure continues both anteriorly and posteriorly from this point (Fig 3-22,C). After initial contact and fusion, further closure occurs by a process of "merging," which results in the medial space between the two processes being eliminated (Fig 3-22,D). The anterior palatine foramen and a suture between the premaxilla and the palatal processes of the maxilla remain in the postnatal period as evidence of the early existence of the primary and secondary palate (Fig 322,C and D).
Prenatal Facial Growth
29
\
A
Stapedial a. Int. carotid a. Exl. carotid a. Corn. carotid a. Aortic Arch
I
FIG 3-21. Three stages of shift in blood supply from the internal to the external carotid arteries in the fetus. At Max. Mand. div. of Stapedial Max. a. Int. Carotid a. Ext. Carotid a. lingual a. Facial a. Corn. Carotid Aortic Arch
c degenerating Stop. a. Max. a. 1nl. Carotid a. Ext. Carotid a. lingual a. Facial '0. Corn. Carotid a. Aortic Arch
\
\ '"
r·
-,
;.
6 weeks (A), the blood supply to the face is from a.
the stapedial branch of the internal carotid. At weeks (B), the stapedial has expanded into maxillary and mandibular divisions. At 7 weeks the stapedial detaches from the internal carotid
6'/2 the (C), and
its terminal branches join the maxillary artery of the external carotid. This shift occurs during the vital stages of development of the face and palate. (After Padget OH: The development of the cranial arteries in the human embryo. Contrib Embryo/1948; 32:212. Reproduced with permission.)
30
Growth and Development
FIG 3-22. View of the roof of the mouth showing closure and fusion of the palate. Bony development is shown on the right side of the palate. At 8 weeks (A), the shelves are horizontal and grow toward the midline. At 9 weeks (B), the shelves are in near contact and the premaxillary-maxillary ossification centers appear. At 10 weeks (C), the soft tissue of the palate has fused and ossification centers of the premaxilla-maxilla grow medially. At 14 weeks (D), the premaxillary bone supports the incisors and the maxillary bone supports the cuspids and first molars. The palatine bone supports the second molars.
5. Tooth Development
6. Salivary Gland Development
By the seventh week, the epithelial labial lamina becomes apparent along the perimeter of the maxillary and mandibular processes (Fig 3-23). This wedge of epithelial cells penetrates the underlying connective tissue to separate the tissue of the future alveolar ridge from the lip. At the same time, a second lamina, lingual to the labial lamina, appears and grows into the alveolar ridge. This is the dental lamina, which, at regular intervals, will give rise to the epithelial enamel organs (Fig 3-23). These organs, along with adjacent dental papillae of connective tissue origin, rapidly differentiate to form the enamel and dentin of the teeth. As the developing crowns enlarge and the roots elongate, the jaws increase in anterior and lateral dimension, as well as height, to provide space for the teeth and growing alveolar processes.
The parotid and submandibular salivary glands appear in the connective tissue of the developing cheek in the sixth week. The third set of major salivary glands, the sublingual, appears in the eighth week. All of the major, as well as minor, salivary glands follow the same pattern of development in which proliferation of epithelial cells initially occurs from the oral mucosa, followed by growth of a solid cord of cells into the underlying connective tissue. This cord of cells then continues to proliferate, growing toward the region of future gland location. At this site, the epithelial cords branch repeatedly and the twig-like ends of the cords form berrylike secretory acini. Gradually, the entire system of epithelial cords becomes hollow and forms the duct system of the gland.24 The site of origin of each major gland, as revealed by the initial epi-
alveolar ridge FIG 3-23. Diagram of the developing right side of the mandibular arch illlustrating the division of the tissue of the lip and jaw by the developing labial lamina. The dental lamina, tooth germs, and Meckel's cartilage are shown. (From Steele P: Dimensions of Dental Hygiene. Philadelphia, Lea & Febiger, 1966, p 280. Reproduced by permission.)
dental lamina labial lamina developing mandible
enamel organs Meckel's cartilage
Prenatal Facial Growth
31
ST
FIG 3-24.
FM
Sagitttal view of the cartilaginous cranial base at 9 weeks. The bar of cartilage extends uninterrupted posteriorly from the foramen magnum (FM) anteriorly to the tip of the nasal septum on the left. The location of the sella turcica (ST) is seen.
FIG 3-25. Sagittal view of the cartilaginous cranial base showing the positional relationship of the ethmoid (E), the vomer (V), the sphenoid (SP), and the basioccipital (Ba) bones. The dotted lines containing (SE) and (SO) indicate the sites of the future sphenoethmoidal and spheno-occipital synchondrosis. S = nasal septum.
thelial growth, thus later will be the orifice of the main duct of the gland, ejecting its secretion to the oral cavity. The connective tissue adjacent to the developing glands grows around them, encapsulates them, and grows into the glands to subdivide them into lobules (see Fig 3-27). This organization is complete by the third month, and the differentiation of the terminally located acinar cells and canalization of the ducts occurs at about the sixth prenatal month. The acini of the mucous glands become functional during the sixth month, whereas the serous glands become functional by birth.8
C. DIFFERENTIATION STRUCTURES
OF SUPPORTING
1. Development of the Chondrocranium The skeletal elements that form the skull develop initially in support of the brain, yet others appear very early in the rapidly developing face as well. The brain is given support by cartilages forming along its base, the chondrocranial elements, whereas the . flat bones of the skull, the neurocranial elements, surround the brain. The chondrocranium also is important to the growing face and supports both areas through the development of a bar of cartilage extending uninterrupted along the midline from the anterior nasal region ot the foramen magnum (Fig 3-24). The cartilaginous septum may function in anterior facial growth as well as in support. Its early fibrous attachment to the premaxilla has been demonstrated.]5 According to Scott,z] it doubles its length from the tenth to the fourteenth prenatal week, trebles it by 17 weeks, and is six times as large by 36 weeks. Anteriorly, this cartilage forms a
capsule related to the olfactory nerve endings-the nasal capsule. More posteriorly, the cartilage supports the pituitary; laterally, the otic capsules develop around the middle and internal ear structures; and most posteriorly, it forms the occipital cartilages around the foramen magnum. These cartilages establish the cranial base as early as the eighth week and will be transformed mostly into bone, with the future ethmoid bone arising from the nasal capsule, al)d parts of the sphenoid, temporal, and occipital from the more po'sterior cartilage. As each of these bones develops, cartilagenous centers remain between them, forming the cranial base synchondroses (Fig 3-25). These centers will provide for further growth and expansion of the cranial base. The anteriorly located nasal capsule is a large and important cartilage to the developing face and consists of a medial septum component, the mesethmoid, and two lateral cartilaginous wings (Fig 3-26,A).
2. Development
of the Maxillary ComIilex
Until bone formation occurs, the nasal capsule is the only ske.letal support of the upper face. Lateral and inferior to the cranial base cartilages, ossification centers appear in support of these parts of the face as it begins to develop in width during the prenatal period15 (Fig 3-26,B and C). The nasal, premaxillary, maxillary, lacrimal, zygomatic, palatine, and temporal ossification centers appear and expand until they appear as bones separated only by sutures (Fig 3-26,D).
3. Development
of the Bony Palate
The bones of the palate arise from several ossification centers.
32
Growth and Development
A R
\ FIG
3-26.
A, diagram of cartilaginous skeleton of the face at 9 weeks. The nasal capsule represents the maxillary skeleton, and Meckel's cartilage represents the mandibular skeleton at this age. B, diagram of the mandible at 16 weeks, illustrating the developing body of the mandible and condyle. Meckel's cartilage still persists. C, diagram of the mandible at 24 weeks. The coronoid process is evident, as is the appearance of the temporomandibular joint. 0, diagram of the skeleton of the face at 30 weeks. The membrane bones of the nasomaxillary complex develop externally to the endochondral bones, replacing the cartilages of the middle of the face.
In the eighth week, bilaterally located bony centers in the anterior palate give rise to the premaxilla and maxilla; they may arise in common but then develop medially in an independent fashion (see Fig 3-22,B and C). The premaxillary bone supports the maxillary incisor teeth, whereas the maxillary bone supports the cuspid and molar teeth. 28 PosteriorIy, the horizontal plates of the palatine bone grow medially from single bilateral ossification centers (see Fig 3-22,C). By the fourteenth week, the bony palate is well established, with a midline suture extending its length between the premaxillary, maxillary, and palatine bones. A bilateral suture also appears between the palatal aspects of the premaxilla and the maxilla (see Fig 3-22,D).
4. Mandible and Temporomandibular
Joint
The lower part of the face is supported by a rod-shaped bar known as Meckel's cartilage (Fig 3-26,A). This bar extends from near the midline of the mandibular arch posteriorIy into the otic capsule, where the two posterior elements later become the malleus and incus bones of the middle ear (Fig 3-26,A). These two bones function in the articulation of the mandible in lower animals and are known as the articular and quadrate.9 There is some evidence in man that the malleus and incus function to provide a movable joint until the mandibular condyle develops in relation to the glenoid fossa of the temporal bone (Fig 3-27). Thus, from approximately the eighth to the eighteenth week, this joint may function in jaw movement until an anterior shift in temporomandibular articulation occurs. Then, these two cartilages ossify and function as middle ear bones. The bony mandible develops laterally to Meckel's cartilage as a thin, flat, rectangular bar, except for a small region near its anterior extremity, where the cartilage ossifies and is fused to the mandible. Since the body of the mandible is attached to Meckel's cartilage, it could function and be carried
forward in growth until regression of this cartilage, at which time the condyle becomes functional. The condyle arises independently initially as a carrot-shaped cartilage and is enclosed by the developing bone of the posterior part of the mandible (see Fig 326,B). The condylar cartilage is transformed rapidly into bone except at its proximal end, where it forms an articulation with the temporal bone in the glenoid fossa (see Fig 3-26,C). This cartilaginous head of the condyle, enveloped in a fibrous covering that is continuous with the joint capsule, persists and functions as a growth center until about the twenty-fifth year of postnatal life. The two condylar heads function similarly to the epiphyses of long bones. The cartilage of the condylar head gradually is replaced by bone (Fig 3-28). The condylar head is separated from the temporal bone by a thin disk of connective tissue, which appears as a result of two clefts in the fibrous tissue that form the upper and lower compartments of the joint cavity. Gradually, this collagenous disk thickens, as does the bone forming the joint cavity, until the complete jojnt is developed (Fig 3-28). Bone forms rapidly along the superior surface of the body of the mandible between the developing teeth. As the bony mandible continues to grow during the prenatal·period, fibrous connective tissue and what is known as symphyseal cartilage unite the two halves of the mandible, and serve as a growth site until the first year after birth, by which ti,me it is calcified. The angle of the mandible by birth is about 130 degrees with the condyle, thus nearly in a line with the body, wherea~ the large coronoid process projects above the head of the condyle (see Fig 3-26,D).
S. Facial Muscles The facial muscle mass, termed the subcutaneous colli, appears in the fourth week in the ventral lateral portion of the hyoid arch just beneath the surface of the skin. Gradually, in the fifth week, it spreads out, unfolding liS the head elevates from the chest
Prenatal Facial Growth
33
FIG 3-27. Sagittal section through the developing temporomandibular joint and middle ear at 16 weeks. Note the forming upper and lower compartments of the joint and the ossifying condyle, middle ear bones, developing muscles, and salivary glands. C = condyle; I = incus; SG = salivary glands .
~
..
~'~
..
.,
~~~~,.
...•._--.,
FIG 3-28. "-...
.external auditory
,~~~)
i,
W
f
1
lateral pterygoid muscle
"'.&
Iower
synovial
." cavit/
f
canal
Diagram of the postnatal temporomandibular joint, illustrating the dense, fibrous articular disk with the adjacent superior and inferior articular spaces. Underlying the fibrous covering of the condyle is a band of hyaline cartilage, below which is the developing bone of the condyle. (From Steele P: Dimensions of Dental Hygiene. Philadelphia, Lea & Febiger, 1966, p 316. Reproduced by permission.)
head ofco~
wall.? This muscle mass fans out and stylohyoid, digastric, and stapedial muscle masses appear. The seventh nerve travels along with the facial muscle,8 which now migrates up the side of the neck and over the face and cranium to meet the sheet of muscle from the opposite side. During the fifth to ninth weeks, the muscles of the human face differentiate and become functional to some extent, since stimulation of the perioral region in this latter period may result in reflexogenic responses, such as neck flexion and head turning. 11 The ear causes the muscle to split into the anterior and posterior auricular parts. The advancing sheet then separates into a superficial and a deep layer in the seventh week. I The superficial fibers form the spread of the platysma muscle over the mandible to the cheek, forehead, and temporal region (Fig 3-29). The sphincter colli is the deep layer and gives rise to several muscles, including the occipitalis. Degeneration of intermediate
parts gives rise to the anterior, superior, and postauricular frontalis and occipitalis muscles. Between the seventh and ninth weeks, the superficial and deeper muscles differentiate rapidly. The sphincter colli also forms the orbicularis, the caninus, and the incisivus labii superioris muscles as the fibers of the more superficial platysma fac~i attach to the mandible. The quadratus labii inferioris and mentalis muscles of the lower face appear in the eighth to ninth week but are not well defined until the thirteenth week. At this time, the orbicularis oculi and the buccinator muscles appear from the deep fibers of the sphincter colli, whereas the triangularis and platysma arise from the superficial facei. Overlying the buccinator muscle, the buccal fat pad develops (Fig 3-30). It enlarges significantly during prenatal life, extending deep between the masseter and temporalis muscles. It functions in sucking and causes the cheek to appear plump in the newborn. By the fourteenth week,
34
Growth and Development
FIG 3-29 (left). Diagram of the developing facial muscles at 9 weeks. This sheet of muscle grows cranially from the hyoid arch and splits at the ear into the anterior and posterior auricular parts. Deep and superficial facial muscles arise from this mass.
FIG 3-30 (right). Diagram of the developing masticatory muscles at 9 weeks. These muscles develop in the mandibular arch before the skeletal elements on which they insert.
all the facial muscles are in their definitive positions and the young muscle fibers are differentiating.
6. Muscles of Mastication At this same time, the muscles of mastication are developing in the mesenchyme of the mandibular arch. These muscles begin differentiation in the seventh week, and nerve fibers are apparent in them by the eighth week. Although the muscles of mastication develop at first in close relationship to Meckel's cartilage and the cranial base cartilages, they are independent and only later attach to the bony skeleton (Fig 3-30). The temporal is muscle begins lateral development in the eighth week, occupying the space anterior to the otic capsule. As the temporal bone begins to ossify in the thirteenth week, the muscle attaches along a broad front. At about this time, the masseter muscle begins attachment to the zygomatic arch as it undergoes lateral growth, providing space for muscle development. 19 The pterygoid muscles differentiate in the seventh week and early are related to the cartilages of the cranial base and the condyle (see Fig 3-27). Later, as the bony skull appears and increases in width and length, these muscles expand rapidly. Typically the fetal histologic structure of the muscles of mastication appears by the twenty-second week.
D. THE FETAL PERIOD-THIRD MONTH
TO NINTH
1. Craniofacial Changes By the third month, the face assumes a more human appearance. The eyes are now directed forward and the eyelids have grown together and are fused. The head is erect and the bridge of the nose becomes somewhat more prominent. As the face grows downward and forward, the ears appear on a horizontal plane with the eyes instead of at the lower corners of the face, as in the embryonic period. During the fetal period, from the twelfth to the thirty-sixth week, the head increases in length from approximately 18 mm to 120 mm, in width from about 12 mm to 74 mm, and in height from 20 mm to 100 mm, thus maintaining a fairly constant ratio of width to length but not to height. Prior to the fifth month, the height increase is greatest, whereas width and length increases are proportional. At birth, the cranial vault is proportionally about
eight times larger than the face. In the embryonic period, the cranium-to-face ratio may be as high as 40: I ,dropping at 4 months to 5: I because of the differentially more rapid facial growth during the period. The cranium then grows faster in the late prenatal months to attain the 8: I ratio at birth. Postnatal facial growth will reduce the adult ratio to approximately 2: I.
2. Radiographic Changes The radiographic appearance of the mandible at the beginning of the fetal period is that of a slightly curved bone, but, by the fifteenth week, the condyle, coronoid process, and the angle bethe incisor teeth in the lower come evident. 9 Radiographically, jaw make their appearance in the fifth month and the molar crypts are evident in the sixth month. During the fetal period, the mandible increases in length five times, whereas the intercondylar width increases six times. The gonial angle, which was virtually nonexistent at the beginning of this period, increases to about 130 degrees at birth. Although these increases follow closely the overall growth of the face, the lower jaw appears retrognathic at birth. The palate increases in length fourfold and the maxillary region about fivefold (Fig 3-31). At the beginning of the fetal period, the frontal bones are apparent. The nasal bones appear at 3 months and the first signs of cranial base bone appear at 10 1/2 weeks. The sella turcica is clearly visible at 4 1/2 months and attains its characteristic shape at 5 months. The sphenoethmoidal and sphenooccipital synchondroses are evident at 6 months (Fig 3-31). , At birth, the intervening connective tissue that separates the bones of the cranial vault is still wide. At six sites located at each corner of the parietal bones they form the fontanelles (Fig 3-32). Synchondroses between the ethmoid, sphenoid, and occiptal bones are still actively growing at birth. The skull contains 45 separate bom;s.at birth, which will be-reduced by fusions and consolidations to 22 in the adult. For example, th~ frontal bones at birth are still paired and separated by the metopic suture. Similarly, the paired halves of the mandible are separated by the symphyseal suture. The occipital is in four parts, with synchondroses between them, and the tympanic annulus is still separate from the temporal'bone. Some of these sutures, such as the midline mandibular suture, disappear shortly after birth. The maxillary midpalatal suture, however, does not close until the sixth to seventh year, although it may be orthopedically activated until the late teens (see Chapter 15).
35
Prenatal Facial Growth
Premaxillary
Maxillary
Palatine
FIG 3-31. Cleared human specimen illustrating the bones of the cranial base at 21 weeks. The synchondroses of the cranial base are indicated
by arrows. Premaxillary, maxillary, and palatine processes be seen forming the palate.
can
Anh~piop fontanel
FIG 3-32. The cranium at birth. Note the fontanelles, one at each corner of the parietal bones (From Caffey J: Pediatric X-ray Diagnosis, ed 6. Chicago, Year Book Medical Publishers, 1972. Reproduced by permission.)
Postet'iop latet'al fontanel A
SUMMARY A. Organization
·'B. Development of Oral Structures of the Face
The face develops from four tissue masses which surround the oral pit. Above it is the frontal area, laterally binding it to the maxillary processes, and below it the mandibular and hyoid masses. In the neck, tubular branchial arches add further complexity to development. The face is complex because of the numbers of masses that fuse and merge to develop it. It is no wonder that the face and the associated roof of the mouth are two of the most common areas of congenital defects in the body. Also, the face develops very early in prenatal life, during the fifth to seventh weeks, and in the short span of time of 2 weeks. Facial proportions change rapidly as the eyes move from a lateral position to the front of the face. The brain and face are closely allied, and anterior brain deficiencies usually result in facial defects.
The tongue undergoes a growth spurt during the fourth to seventh embryonic weeks and is so large it fills the combined oronasal cavity. At this same time this cavity proceeds to divide into two, the nasal and. oral, by growth of three tissue wedges: 6rre. anterior and two lateral. As they enlarge, the lateral wedges grow down on either side of the tongue. As the shelves continue to grow they depress the tongue, sliding over it to form a roof to the oral cavity. They finally contact in the midline by the eighth week, by which time other oral tissues such as teeth and salivary glands are apparent.
C. Differentiation
of Supporting
Structures
The facial skeleton is initially comprised of two types of tissue: cartilage and bone. The cartilage develops in the midline
36
Growth and Development
to form the chondrocranium. It gradually transforms into bone. In the lateral face, bones originate in the connective tissue (membrane) to develop the bony skeleton of the maxilla and mandible. The bones of the midline form the cranial base and soon merge with the lateral bones in support of the brain and faCe. The mandible is a complex bone, developing its condyle in cartilage and its body in membrane. The facial muscles grow from the neck (hyoid arch) and spread over the front, sides, and back of the head. The muscles of mastication (mandibular) develop within the first arch.
D. The Fetal Period-Third
to Ninth Months
During the third to ninth months the embryo increases in size and develops body proportions. The head lengthens and increases in width by about six times and in height by five times. The cranium-to-face ratio decreases from 40: I during the first 12 weeks to 5: I at 4 months and increases slightly at term to 8: I. The cranium-face size ratio again decreases after birth to 2: I. At the same time the number of skull bones is reduced from 45 separate bones at birth to 22 in the adult.
REFERENCES I. Bates MN: Early hypoglossae musculature. Am J Anat 1948; 83:329. 2. Burdi AR: Sagittal growth of the naso-maxillary complex during the second trimester of human prenatal development. J Dent Res; 1965; 112-125. 3. Burdi AR: Section I. Epidemiology, etiology, and pathogenesis of cleft lip and palate. Cleft Palate J 1977; 14(4):262-269. 4. Dickson DR, Grant JCB, Sicher Het al: Status of research in cleft palate anatomy and physiology: July, 1973-Part I. Cleft Palate J 1974; 11(4):471-492, 1974. 5. Eisbach KJ, Bardach J, Klausner EC: The influence of primary unilateral cleft lip repair on facial growth. Part II: Direct cephalometry of the skull. Cleft Palate J 1978; 15(2):109-117. 6. Fraser FC, Walker BE, Trasler DG: Experimental production of congenital cleft palate, genetic and environment factors. Pediatrics 19(4): 1957. 7. Gasser RF: The development of the facial muscles in man. Am J Anat 1967; 120:257. 8. Gasser RF: The development of the facial nerve in man. Ann Otol Rhinol Laryngol 1967; 76:37.
9. Gerrie J: The phylogeny of the mammalian tympanic cavity and auditory ossicles. J Laryngol Otol 1948; 62:339. 10. Hayward JR, Avery JK: A variation in cleft palate. J Oral Surg 1957; 15:320. 11. Hooker D: The Prenatal Origin of Behavior. Porter Lecture Series XVIII, March 12-13, 1951. Lawrence, University of Kansas Press, 1952, 136 pp. 12. Humphrey T: The development of mouth opening and related reflexes involving the oral area of human fetuses. Ala J Med Sci 1968; 5: 126. 13. Iregbulem FRCS: Median cleft of the lower lip. Plast Reconstr Surg 1978; 61(5):777-789. 14. Langman J: Medical Embryology, 4th ed. Baltimore, Williams & Wilkins Co, 1981, pp 268-306. 15. Latham DA: Maxillary development and growth: The septo premaxillary ligament, J Anat 1970; 107:471. 16. Lowry RB, Trimble BK: Incidence rates for cleft lip and palate in British Columbia 1952-1971 for North American Indian, Japanese, Chinese and total populations: Secular trends over twenty years. Teratology 1977; 16(3):277-283. 17. Moore KL: The Developing Human, 2nd ed, Philadelphia, WB Saunders Co, 1977. 18. Pad get DH: The development of the cranial arteries in the human embryo. Contrib Embryol 1948; 32:212. 19. Patten BM: Human Embryology, 3rd ed. New York, Blakiston Division, McGraw-Hill Book Co, 1968. 20. Ross RB, Johnston MC: Cleft Lip and Palate. Baltimore, Williams & Wilkins Co, 1972. 21. Scott JH: Dento-facial Development and Growth: Facial Growth during the Foetal Life. New York, Pergamon Press, 1967, P 79. 22. Spriestersbach DC, Dickson DR, Fraser FC, et al: Clinical research in cleft lip and cleft palate: The state of the art. Cleft Palate J 1973; 10(2):113-165. 23. Steele P: Dimensions of Dental Hygiene. Philadelphia, Lea & Febiger, 1966. 24. Streeter GL: Developmental horizons in human embryos: Age groups XI to XXII. Contrib Embryol 1951; 2: 197, 191. 25. Trasler DG, and Fraser FC: Role of the tongue in producing cleft palate in mice with spontaneous cleft lip. Dev Bioi 1963; 6:45. 26. Verrusio AC: A mechanism for closure of the secondary palate. Teratology 1970; 3:17. 27. Warkany J, Kalter H: Congenital malformations. N Engl J Med 1961; 265:993, 1046. 28.'Woo JK: Ossification and growth of human maxilla, premaxilla, and palate bone. Anat Rec 1949; 105:737-761.
CHAPTER
4 Growth of the Craniofacial Skeleton Robert E. Moyers, D.D.S., Donald H. Enlow, Ph.D.
Ph.D.
Those who are enamoured of practice without science are like a pilot who goes into a ship without rudder or compass and never has any certainty where he is going. Practice should always be based upon a sound knowledge of theory. -LEONARDO
DA VINeI. The Notebooks of Leonardo da Vinci,
Vol 11, Chapter XXIX (translated by Edward MacCurdy)
KEY POINTS 1. Variations in cranofacial morphology are a primary source of serious malocclusions. 2. Planned changes of bone growth and morphology are a fundamental basis of orthodontic treatment. 3. Bone forms in two basic modes, endochondral and intramembranous, named after the site of appearance. 4. All bone growth is a mixture of two basic processes, deposition and resorption, which are carried out by investing growth fields. Shape changes are produced by remodeling, and enlargement may result in growth movements. 5. The assumption of tight genetic control of craniofacial bone growth has yielded to a structuralfunctional approach, largely in response to Moss' "functional matrix" hypothesis. 6. Natural controlling factors of craniofacial bone growth include genetics, "function," general bodily growth, and neurotrophism. 7. Disruptive factors of facial bone growth may be elective (e.g., orthodontic treatment), environmental (e.g., altered nasorespiratory function), or congenital (e. g., gross craniofacial anomalies).
8. Growth of the cranial vault is paced largely by growth of the enclosed brain. 9. Basicranium growth is effected by a complex combination of synchondrosal elongation, sutural growth, and extensive cortical drift and remodeling. 10.' Nasomaxillary growth mechanisms involve the sutures, endosteal and periosteal surfaces, and alveolar processes. Alveolar remodeling contributes " significantly to height, width, and length increases correlated with eruption.
11. Mandibular growth modes and mechanisms are much argued but it is agreed that a greater part is intramembranously rather than endochondrally determined. Areas, of muscle and tooth attachment " ;'.ilre important parts of growth and shape change. The condylar region plays a special role in mandibular growth and translation.
12. Mandibular growth coincides roughly with growth in stature and may display coincident periods of . accelerated growth.
13. An important clinical issue is the extent to which clinicians can alter mandibular growth. 14. The temporal component of the temporomandibular joint.is less studied but it grows significantly by both
37
38
Growth and Development
intramembranous
and endochondral
mechanisms.
15. There are important sexual differences in overall craniofacial growth-boys grow more, over a longer time, and are more apt to show "spurts" in growth. 16. Racial and ethnic differences in craniofacial morphology are well documented but little is known about growth differences among racial, ethnic, or national groups.
2.
a) b)
OUTLINE A. B.,
/ 2.
~'
3.
C.
4.
bone formation
. b) Intramembranous bone formation Methods of studying bone growth a) Vital staining b) Radioisotopes c) Implants d) Comparative anatomy e) Roentgenographic cephalometrics f) Natural markers Mechanisms of bone growth a) Deposition and resorption b) Growth fields c) Remodeling d) Growth movements I) Drift 2) Displacement
4.
The genetic concept The functional concept Hypotheses of craniofacial growth a) The genetic "theory" b) Sicher's hypothesis (sutural dominance) c) Scott's hypothesis (nasal septum) d) Moss' hypothesis (functional matrix) e) Petrovic's hypothesis (cybernetics) Current concepts
5.
Controlling factors in craniofacial growth I.
2.
E.
Osteogenesis a) Endochondral
Changing concepts and hypotheses of craniofacial growth I. 2. 3.
D.
3.
The role of craniofacial skeletal growth in orthodontics Rudiments of bone growth I.
Natural a) Genetics b) "Function" c) General body growth d) Neurotrophism Disruptive factors a) Orthodontic forces b) Surgery c) Malnutrition d) Malfunctions e) Gross craniofacial anomalies
Regional development I.
Cranial vault a) b)
Functions Growth I) Mechanisms
and sites
2) Timing 3) Compensatory mechanisms c) Theoretical and clinical issues Basicranium
F. G.
Functions Growth I) Mechanisms and sites 2) Timing 3) Compensatory mechanisms c) Theoretical and clinical issues Nasomaxillary complex a) Functions b) Growth I) Mechanisms and sites 2) Amounts and directions (a) Maxillary height (b) Maxillary width (c) Maxillary length 3) Timing 4) Compensatory mechanisms 5) Effects on dentition and occlusion c) Theoretical problems d) Clinical issues Mandible a) Functions b) Growth I) Mechanisms and sites (a) Role of the condylar cartilage (b) Ramus and corpus (c) Alveolar process 2) Amounts and directions (a) Height (b) Width (c) Length (d) "Rotation" 3) Timing 4) Compensating mechanisms 5) Effects on dentition and occlusion c) Theoretical problems d) Clinical issues Temporomandibular joint a) Functions and growth b) Mechanisms and sites c) Effects on dentition and occlusion d) Clinical and theoretic ab issues
Overall pattern of craniofacial growth Racial and ethnic differences
Ut ". "Adult"
craniofa'tial growth
A. THE ROLE OF CRANIOFACIAL SKELET AL GROWTH IN ORTHODONTICS In orthodontics skeletal growth is emphasized more than other aspects of craniofacial development, perhaps because the methods for its study were developed earlier. Knowledge of skeletal morphology and growth is routinely applied in clinical practice; these can be visualized easily in the cephalogram: but there are problems.
Growth of the Craniofacial Measurements in the cephalogram show the results of growth of something, somewhere, at some time, but of what? Why? And in response to which biologic stimuli or energies? The craniofacial bony skeleton is a composite structure which supports and protects a series of vital functions-but it is more the place of the action than the action itself. We may measure a football stadium, carefully noting its external dimensions, seating capacity, location of principal components (i.e., playing field, spectators' seats, press box, entrances, aisles, restrooms, and so forth, even observing remodeled additions of parts and enlargement of stadium size), but from this information we may deduce only secondary information about the game of football itself. The stadium tells us nothing of the rules, purpose, or strategies of the ga!TIe, its tactical development, skills required of the players, its impact on those who watch, or how the game is won or lost. In fact, we cannot even be sure which of several particular football games are played in the stadium. This chapter deals with changes in the structures of the craniofacial skeleton, where much of the action of craniofacial growth takes place. Craniofacial growth differs from the football stadium analogy in an important respect-there are significant interactions constantly between the game of growth and the structure where it takes place. Further, there is a mutual biologic dependency of growth, function, and structure on one another. Football can be played without a stadium but craniofacial growth and its structure, the skull, are inseparable. But like the analogy of the stadium, study of skeletal dimensions alone doesn't tell us much about growth itself, only the results of that growth. Study of the craniofacial skeleton tells us what has happened, not why, and only from inference and deduction can we predict what may happen later. Nonetheless, craniofacial skeletal growth is very important in orthodontics, since variations in craniofacial morphology are the source of most serious malocclusions, and clinical changes of bony growth and morphology are a fundamental basis of orthodontic treatment.
B. RUDIMENTS OF BONE GROWTH* 1. Osteogenesis Bone forms in two basic modes named after the site of appearance: cartilage or membranous connective tissue. a) Endochondral Bone Formation During endochondral bone formation, the original mesenchymal tissue first becomes cartilage. Endochondral bone formation is a morphogenetic adaptation providing continued production of bone in special regions that involve relatively high levels of compression. Thus, it is found in the bones associated *In sections Band E we have drawn heavily on the classic work of my colleague and collaborator for this chapter, Professor Donald H. Enlow. It is impossible to note every sentence herein which might be cited as an Enlow reference. The reader is urged to read Suggested Readings at the end of this chapter for more detailed study of his writings and those of other principal workers in the field. Note, too, that Enlow's methods provide vivid descriptions of what has taken place during bony growth. Why it takes place is another matter for the theoreticians (see Section C)-R.E.M.
Skeleton
39
with movable joints and some parts of the basicranium. Cartilage cells hypertrophy, their matrix becomes calcified, the cells degenerate, and osteogenic tissues invade the dying and disintegrating cartilage and replace it (Fig 4-1). Endochondral bone is not formed directly from cartilage; it invades cartilage and replaces it. The "epiphyseal mechanism" of bone growth (or its equivalent) does not exert a direct regulatory influence over the growth changes that occur in all of the other portions of an enlarging bone. Rather, it is concerned essentially with its own local production of bone tissue in particular areas served by the specialized cartilaginous plate. Growth in all other regions of a bone, however, proceeds in a closely interrelated manner, although the control and coordinating mechanisms are poorly understood at present. At least four fundamental ideas summarize the importance of the cartilage-bone interface seen in endochondral bone formation. Cartilage is rigid and firm, but not ordinarily calcified, thus providing three basic growth functions: (I) flexibility yet support for appropriate structures (e.g., the nose); (2) pressure tolerance in specific sites where compression occurs (e.g., the articular cartilages and epiphyseal growth in long bones); and (3) a growth site in conjunction with enlarging bones (e.g., the synchondroses of the cranial base and the condylar cartilage). Cartilage grows both appositionally, by the activity of its chondrogenic membrane, and interstitially, by cell divisions of chondrocytes and by additions to its intercellular matrix. Interstitial growth of bone with its calcified matrix is, of course, impossible. Bone, unlike cartilage, is tension adapted and cannot grow directly in heavy-pressure areas because its growth is dependent upon its vascular osteogenic covering membrane. "Growth cartilages" appear where linear growth is necessary toward the direction of pressure, allowing the bone to lengthen toward the force area and yet grow elsewhere by membranous ossification in conjunction with all periosteal and endosteal surfaces. b) Intramembranous Bone Formation In intramembranous bone formation, the undifferentiated mesenchymal cells of the membranous connective tissue change to osteoblasts and elaborate osteoid matrix. The matrix or intercellular substance becomes calcified, and bone results. Bone tissues laid down by tbe periosteum, endosteum, sutures, and the periodontal membrane (ligament)* are all intramembranous in formation (Fig 4-2). Intramembranous ossification " *The term periodontal-"-ligament" is used in other chapters. However.::'it i.s felt by one of this chapter's authors (D.E.) that "membrane" is much more appropriate for the subject of facial growth since this word emphasizes the important processes of "membranous" and endochondral bone growth and the role of the various osteogenic membranes (periosteum, endosteum, sutures, periodontal membrane) in carrying out growth and remodeling. "Ligament" implies a primary binding or attaching function. "Membrane," however, better connotes the multiple and dynamic functions during childhood craniofacial growth of one of the most remarkable connective tissue membranes anywhere in the body. In addition to its ligamentous role, it contributes directly to (I) tooth formation, (2) tooth eruption, (3) drifting of teech, (4) sensory nerve reception, (5) vascular pathways, (6) growth of alveolar bone, and (7) extensive alveolar remodeling associated with orthodontic tooth movements.
40
Growth and Development
A
B
==c::> oQGC) 000 000 000 000 000 o c:::> c:::>
FIG 4-1. Endochondral bone growth. In A, the zones of the growth cartilage are schematized. Zone a, the reserve cartilage, feeds new cells into b, the zone of cell division. The cells in zone b undergo rapid division, forming columns of flattened chondrocytes. This growth process is responsible for elongation of the bone. In succession, the daughter cells undergo hypertrophy (zone c), the matrix calcifies (zone d), and this calcified matrix becomes partially resorbed and invaded by vessels (zone e). Undifferentiated cells carried in by vascular sprouts provide osteoblasts, which in turn deposit a thin crust of bone on the remnants of the calcified cartilage matrix (zone f). The entire process is continuous and repetitive, one zone transferring into the next. Note that zone b becomes changed directly into zone c (arrow 1), zone d into zone e (arrow 2), and zone e into zone f (arrow 3). As the entire
cartilage grows in a linear direction toward the top of the illustration, bone replacement follows. In B, the growth of a cranial synchondrosis is schematized. Note that proliferation in bone formation occurs on both sides of the plate, in contrast to the epiphyseal plate pictured in D. C represents the growth cartilage of the mandibular condyle. A zone of prechondrocyte proliferation occurs just beneath a covering lay'er;.of fibrous capsule. Note that columns of prechondrocytes are poorly' represented. A trypical longobone epiphysis showing a secondary center, articular cartilage, epiphyseal (growth) plate, and medullary endochondral bone is represented in D. (From Enlow DH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced by permission.)
Growth of the Craniofacial
Skeleton
41
D
FIG 4-2.
f
Intramembranous bone formation. In a center of ossification (A), the cells and matrix of the undifferentiated connective tissue (late mes-
E}arly bone spicule (5) is shown in the enlarged trabeculae for reference. Blood vessels (3) have now become enclosed in the fine,
enchyme) undergo a series of changes that produce small spicules of bone. Some cells (1) remain relatively undifferentiated, but others (2) develop into osteoblasts that lay down the first fibrous bone matrix (osteoid), which subsequently becomes mineralized, as in stage B. Original blood vessels are retained in close proximity to the formative bony trabeculae (3). As bone deposition by osteoblasts continues, some of these cells are enclosed by their own deposits and become osteocytes (4). Some undifferentiated cells develop into new osteoblasts (6), and other remaining osteoblasts undergo cell division to accommodate enlargement of the trabeculae. The outline of an
cancellous spaces (C). These spaces also contain a scattering of fibers, undifferentiated connective tissue cells, and osteoblasts. At lower magnification (D), the characteristic fine, cancellous nature of the cortex is seen. This bone tissue type is widely distributed
in the
p(e~§Ital as well as the young postnatal skeleton. It is a particularly fast-growing variety of bone tissue. Note that the periosteum (also formed from undifferentiated cells in the ossification center) has become arranged into inner (cellular) and outer (fibrous) layers. (From Enlow OH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced
by permission.)
42
Growth and Development
is the predominant mode of growth in the skull, even in composite "endochondral" elements, such as the sphenoid and mandible, where endochondral and intramembranous growth occur in the same bone. The basic modes of formation (or resorption) are similar, regardless of the kind of membrane involved. Bone tissue sometimes is classified as "periosteal" or "endosteal" according to its site of formation. Periosteal bone always is of intramembranous origin, but endosteal bone may be either intramembranous or endochondral in origin, depending on the site and mode of formation. Intramembranous bone growth may be summarized by means of several basic ideas: , Intramembranous bone growth occurs in areas of tension. The membranes (periosteum, sutures, periodontium) have their own internal deposition and remodeling processes. The membrane grows outward rather than just backing off as bone is laid down behind it. As it does so it undergoes extensive fibrous changes in order to maintain continuity among the periosteum, muscle insertions, and the bone itself. Therefore, there is constant deposition and resorption on the bone surfaces as part of membranous remodeling and relinking processes. The periodontal membrane converts the pressures exerted against the teeth during occlusal functions into tension on the collagenous fibers attaching the tooth to the alveolar bone. The positions of teeth within the alveolar process are altered during eruption, during mesial drifting, and as they adapt to facial growth or orthodontic forces. These changes are made possible by constant remodeling and relinkage processes of the fibrous attachments between the tooth and the bone.
Alizarin, the essential dye of the madder plant, has subsequently been identified and synthesized, and this and other vital dyes (e.g., procion and tetracycline) are used extensively in bone research. The primary value of such vital dyes lies in depicting the pattern of postnatal bone deposition over an extended period in one animal. A series of injections will leave layers of dyed bone alternating with unstained bone (Fig 4-3). The method reveals the manner in which bone is laid down, the sites of growth, the direction and amounts of growth, and the timing and relative duration of growth at different sites. It does not, however, provide direct evidence of bone resorption; resorptive activity must be inferred. b) Radioisotopes Radioisotopes of certain elements or compounds often are used as in vivo markers for studying bone growth. Such labeled material is injected and, after a time, located within the growing bones by means of Geiger counters or autoradiographic techniques. In the latter method, the bones or sections of bones are placed
2. Methods of Studying Bone Growth The face always has intrigued man, and there is a rich and lengthy heritage of exciting cooperative research among archaeologists, physical anthropologists, anatomists, and orthodontic scientists. Often the only human remains found by the archaeologist are fragments of the craniofacial skeleton and a few teeth. From these slender clues the anthropologist has constructed workable hypotheses concerning the evolution of the human face. In few fields are there so many and varied workers from human biology because of the importance of the face's developmental complexities to clinicians. Knowledge of facial growth is absolutely necessary to clinical orthodontic practice. Each field brings its own methods of study, goals, biases, and traditions. The reader is cautioned to remember that no one method is sufficient, and conclusions based on one approach must be balanced by the findings derived from other techniques to provide a synthesis of understanding. a) Vital Staining* In 1736, BeIchier' reported that the bones of animals who had eaten the madder plant were stained a red color. The bones contained a band of red stain followed by an unstained band. *For a good survey of in vivo staining and marking methods, see the article by Baer and Gavan.1
FIG 4-3. The use of tetracycline HCI as a vital bone marker in monkeys. A, cutaneous resorption: external resorption in nuchal region (a); deposition peripheral to nuchal region (b). Two fluorescent tetracycline HCllabels are visible. B, meningeal depository surface of the anterior cranial floor with contralateral Riolo.)
resorption.
(B courtesy of Or. Mi(;hael
Growth of the Craniofacial against photographic emulsions that are then exposed by emission of radiation from the radioactive substance. c) Implants Bjork7 devised an ingenious
method of Implanting tiny bits of tantalum or biologically inert alloys into growing bone. These serve as radiographic reference markers for serial cephalometric analysis. The method allows precise orientation of serial cephalograms and information on the amount and sites of bone growth (Fig 4-4). This method is useful because bone does not grow interstitially and therefore implants placed inside a bone are stable. d) Comparative Anatomy Significant contributions to our knowledge of human facial growth have been provided through comparisons with other species. Not only can experimental work be done more readily on animals but often basic principles common to growth in all species are first recognized and defined by studies in comparative anatomy. Much of our knowledge of the phylogeny of the anatomic com-
Skeleton
43
ponents comprising the head has been derived from comparative studies of fossil and present-day species. e) Roentgenographic Cephalometry Physical anthropologists and anatomists have measured the head with calipers to provide standards of both living and dry skulls (craniometry). From these methods evolved a branch of anthropometry, roentgenographic cephalometry. The joining of craniometry and radiology made possible standardized serial studies of the living, growing craniofacial skeleton and associated features. Cephalometry has contributed significantly to our knowledge of human craniofacial skeletal growth, and cephalometric methods are used routinely, not only for the study of facial growth but also for orthodontic diagnosis, treatment planning, and the assessment of therapeutic results (see Chapter 12). f) Natural Markers The persistence of certain developmental features of bone has led to their use as natural markers. By means of serial radiography,
FIG 4-4.
B
Use of implants to study craniofacial growth. A, cephalogram of a rhesus monkey showing the use of implants.68 Note specifically the use of implants in the cranial base region. B, studying mandibular growth in a rhesus monkey by superimposition over the mandibular implants. Note the change of the landmarks (e.g., c to c', pc to pc') with growth.
44
Growth and Development
trabeculae, nutrient canals, and lines of arrested growth can be used for reference to study deposition, resorption, and remodeling. Erilow23-25 has developed and used extensively methods for studying bone deposition, resorption, and remodeling in decalcified and ground sections (Fig 4-5). By relating the findings to other methods, for example, cephalometrics or vital dyes, our knowledge of bone growth has been extended greatly. Many of the illustrations in this chapter are based on information derived by these methods of study. Certain natural markers are also used as cephalometric landmarks,o-12 (see Chapter 12).
3. Mechanisms of Bone Growth Although the reader has studied the histology of bone, the practical aspects of such study are often not appreciated until the need arises to understand what can be expected from bone growth and how it might be altered to the patient's advantage. What follows in this section is a simple presentation of a complicated subject of much important current research: Many factors are still unknown; many issues are still unresolved. More detailed information can be gained from the Suggested Readings listed at the end of the chapter. All bone growth is a complicated mixture of two basic processes, deposition and resorption, which are carried out by growth fields comprised of the soft tissues investing the bone. 59. 60 Because the fields grow and function differently on different parts of the bone, the bone undergoes remodeling (i.e, shape change). When the amount of deposition is greater than the resorption, enlargement of the bone necessitates its displacement (i.e., its physical relocation) in concert with other bone displacement.
a) Deposition and Resorption On one side of a bony cortex new bone is added, on the other side, bone is taken away. Deposition occurs on the surface facing the direction of growth, while resorption is seen on the surface facing away (see Fig 4-5). The result is a process termed cortical drift. a gradual movement of the growing area of the bone. Bone does not add even accretions on its outside surfaces as in the concentric rings of a tree (see Fig 4-7 A). The complex morphologies of facial bones make uniform enlargement impossible and differential growth a necessity; thus, some areas grow more rapidly and some outside surfaces show resorption (see Fig
4-5). Enlow's "V" principle is useful in understanding deposition and resorption in complicated remodeling during growth in length (e.g .• the ends of long bones or the neck of the mandible) (Fig 4_6).23
o FIG 4-5. Enlow's method of studying ground bone sections. The sequence of remodeling changes that produced the cortical arrangement seen in photomicrograph A is shown schematically in S, C, and D. Prior to the lateral drift, stage S, the cortex is composed of inner (endosteal) and outer (periosteal) zones. Simultaneously, new bone is added at surface 1, removed from side 2, added to surface 3, and resorbed on side 4 as shown in C. The composite result is drift of this entire region of the bone in the direction indicated by the arrows in C. The final stage schematized in D is comparable with the actual photomicrograph shown in A. (From Enlow DH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced by permission. )
b) Growth Fields All surfaces, inside and outside, of every bone are covered by an irregular pattern of "growth fields" comprised of various soft-tissue osteogenic membranes or cartilages. Bone does not grow itself, it is grown by this environment of soft-tissue growth fields. The genetic program for bone growth is not contained within the hard bone tissue; rather, the determinants of bone growth reside in the bone's investing soft tissues~muscles, integument, mucosa, -owod vessels, nerves, connective tissue, the brain, etc63 Any bone has both resorptiye and depository fields over all its inside and out~jde cortical surfaces~ The varying activities and rates of growth of these fields are the basis for the differential growth processes that produce bones of irregular shapes. The irregularity is a response to the varied functions imposed on the bone by attachments of muscle, sutural articulations with other bones, insertions of teeth, and other processes. About one-half the total amount of cortical bone is periosteal in origin (from the covering membrane)' and half is endosteal (formed by the lining membrane). Approximately half of both periosteal and endosteal surfaces are resorptive and half are depository.
Growth of the Craniofacial
45
Skeleton
A
B B
C
\
o
A
-0-
B B
C
o
+ FIG 4-6. The "V" principle have a "V" shape. and resorption ( overall dimension
(top left). Many facial bones or parts of bones Note that deposition ( + ) occurs on the inner side ) on the outer. The "V" moves from A to B as the increases (Le., movement is toward the wide end
of the "V"). Thus, simultaneous growth movement and enlargement occur. (Bottom left) note that the diameter at A is reduced as the broad part of the bone is relocated to B. Wider parts become narrower by periosteal resorption and endosteal deposition. (Right) a transverse section at A shows why the periosteal surface is resorptive. The section at B shows new endosteal bone added onto the inner
surface of the cortex. At C, endosteal new bone produces an inward growth phase. A section at 0 shows a cortex composed entirely of periosteal bone following outward reversal as this part of the bone now increases its diameter. Now the outer surface is depository and the endosteal resorptive. If markers were placed at X, Y, and Z, note that X will eventually be freed, Y moves from periosteal cortex to endosteal, and Z is also released, by endosteal resorption. (From ,Enlow DH: Handbook of Facial Growth, 2nd ed. Philadelphia, WB Saunders Co, 1982. Reproduced by permission.)
t Some growth
fields
having
special
roles in the growth
bones are called growth sites (Fig 4-7B).
particular
the mandibular
condyle,
droses of the basicranium, These special growth
the maxillary
of
These include.
tuberosity,
the synchon-
the sutures, and the alveolar processes.
sites do not cause all of the growth
in their
one considers their growth
the epiphyseal
against the large forces of gravity,
·.tLons, etc. By and large, craniofacial
region
argued whether
droses in the cranial
bone, for all other inside and outside
gional
ticipate
as well in the overall
growth
growth centers,"
that a special
controls
growth
implies
area somehow
of the bone. The term "growth
the "force,"
"energy,"
or solely within
or "motor"
seems less·,important base are growth
muscle contrac-
of growth now, condyle
centers in the
although
it is still
and the synchon-
centers (see Section E, Re-
Development).
process.
Some growth sites have been called" which
par-
the concept
or not the mandib\llar
bone, or carry out even most of the growth process of a particular surfaces must actively
plates of long bones which continue
center"
a term
the overall
also implies
that
for a bone resides primarily
its growth center. This concept finds support when
c) Remodeling Facial bones are not enlarged by generalized that merely
follows
get bigger
as a balloon
required
differential
existing
contours
enlarges,
growth
activity
surface accretion
(see Fig 4-7 A): they do not
for their shape changes.
The
necessary for bone shaping,
46
Growth and Development
termed remodeling,
involves
simultaneous
deposition
and resorp-'
tion on all inner and outer surfaces of the entire bone. Remodeling, a basic 'part of the growth
process,
changes in shape, dimensions, regional
adjustments
biochemical moval
are four
provides
regional
it also produces
that adapt to the developing-function
bone and its various growing There
not only
and proportions,
kinds
remodeling,
mineral
the constant replacement
Haversian
remodeling,
struction
in bone tissues:27 (I)
continuous
deposition
homeostasis;
and re-
(2) growth
re-
as primary
or trauma,
Growth
involves
of bone during childhood;
the secondary
vascular
eration and reconstruction growth
soft tissues, of remodeling
involving
of ions to maintain
of the
modeling,
process of cortical
bone is replaced;
and (4) the regen-
of bone during and following
remodeling
the formation
during
childhood
of a highly
of the rapid rates of deposition.
vascular
This original
(3)
recon-
pathology
and adolescent bone because
bone is gradually
replaced, as the child matures, with slower growing types of bone which are less vascular and even nonvascular in some areas. Thus,
••• v=
/,-~p--,/,1.-
--
--x
FIG 4-7. Diagrammatic representation of the principles of craniofacial growth, Explanations of craniofacial growth have often been oversimplified in the literature. The various bones of the craniofacial skeleton do not enlarge by a process of generalized surface accretion following 'existing contours, as in A. Facial growth has been presented as a process occurring largely in facial sutures (1, 2, 3, and 4 in B) and by additions to the alveolar margin and maxillary tuberosity (5). This oversimplification does not take into account the extensive remodeling growth that occurs in virtually all parts of craniofacial bones, A bone may move by two means: it can grow (cortical drift) by selective deposition and resorption (C) or it can become displaced (D) from one position to another. Relocation is shown by schematized segments (E), In E, the black segment at the left occupies the number
.1 position, As longitudinal
growth (addition
of neW segments)
con-
tinue,Sc however, the black segment becomes relocated in a position to number 2, 3, 4, etc. Although its r~lative position with respect to the other segment constantly changes, note that it does not move; rather, it becomes relocated because of growth taking place in other areas, Relocation (F) underlies most .of the remodeling that takes place during growth in the mandible. For example, portions of the condyle become converted into the neck. In these superimposed growth stages, sections of a and b show the local changes that occur as the bone enlarges. Remodeling is a process of reshaping and resizing as a consequence of progressive continuous relocation, (From Enlow OH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968, Reproduced
by permission,)
Growth of the Craniofacial the rate of remodeling
is intensive
during
cence and slows down considerably extent during adulthood.
adapts to the changing
functional
parts of the bone producing,
d) Growth Movements
and adoles-
but persists to a much lesser
To summarize, growth remodeling and functions of the soft tissues which these soft tissues grow and function
childhood
Two kinds of growth
is paced by the growth surround the bones. As
a progressively adjustments
continuous fitting together of the separate bones within ing soft ·tissue environment.
are seen during the enlarge-
bones: cortical drift and displacement
4-7
is growth
and 4-8).
Drift
movement
(relocation
of a bone by the remodeling
osteogenic tissues, while displacement the whole bone as it remodels.
actions exerted on it; (2) relocate
as a result,
movements
ment of craniofacial
of an enlarging portion
they (I) shape the bone, which
whole bone; and (3) carry out regional
47
Skeleton
is a physical
(Figs
or shifting) action of its movement
of
larger
to maintain
1) Drift.-Combinations
their grow-
in growth 4-7C).
movement
of deposition
toward the depository
Drift is seen with remodeling
z
and resorption
surface-drift
enlargement
result
(see Fig
and is produced
x
m \\ -.......•
o ."
z ,.
••• 1.
x
FIG 4-8. Cortical drift and displacement. In A, the model has been positioned from Pto P'. It may do this b.y either of two basic processes: direct cortical growth (drift) (B) or displacement (C). These two processes frequently produce movement in divergent directions simultaneously. In D, for example, the model itself is growing to the right (arrow) but is being carried to the left at the same time. In E, the model drifts (deposition in conjunction with resorption on contralateral surfaces) from Pto P' for a distance designated as d'. The carrier moves in an opposite course from X to Z for the distance
d2.
In F, the original
",
relationship prior to these movements is indicated by X and I. The relative position of the model if drift alone occurred would be at m. The carrier, however, has moved from X to Z. If displacement alone occurred, the relative position of the model would be at j. The combination of both drift and displacement, however, results in the final positional relationship seen between Z and k. (From Enlow OH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced by permission.)
48
Growth and Development
by the deposition of the new bone on one side of the cortical plate, while resorption occurs on the opposite side. If an implant is placed on the surface of the depository side of a bony cortex, it becomes gradually embedded in the cortex as new bone .continues to form over that surface and as resorption occurs on the opposite surface. In time the implant becomes relocated from one side of the cortex to the other, not because of its own movement (the implant is immobile), but because of the drift of the bone around it (see Fig 4-7E). 2) Displacement.-Displacement, on the other hand, is movement of the whole bone as a unit (see Fig 4-7D). As a bone is carried away from its articulation with other bones, growth remodeling simultaneously maintains relationships of the bones to each other. For example, as the entire mandible is displaced from its articulation in the glenoid fossa, it is necessary for the condyle and ramus to grow upward and backward to maintain relationships. As the condylar neck, coronoid process, and ramus remodel to accommodate the displacement, they also grow in size and sustain basic shape (see Fig 4-7F). This entire process is called primary displacement, that is, displacement associated with the bone's own enlargement. Secondary displacement is movement of a bone related to enlargement of other bones. Drift and displacement occur together and complement each other (i .e., they move in the same direction) or they may take place in contrasting directions (see Fig 4-8), making it difficult . to determine the separate contributions of remodeling and displacement during cephalometric analyses (see Chapter 12); however, they are separate processes.
C. CHANGING CONCEPTS AND HYPOTHESES OF CRANIOFACIAL
GROWTH
Anyone beginning study in a field wrestles first with the current conventional wisdom but often has difficulty understanding how colleagues arrived at the understanding they hold. Kuhn45 has written wisely about what he terms "scientific revolutions," and Carlsonl7 has applied Kuhn's concepts to the field of craniofacial
biology. Kuhn45 defines "normal science" as the research findings generally agreed to be basic to a scientific field. Therefore, a normal science is that which new students must grasp if they are to understand the basic concepts of their new discipline. Kuhn45 invents a new term (by distorting the meaning of a classic Greek word)-"paradigm"-by which he means the current conceptual framework of a scientific field. Kuhn's "paradigm" is closely related to his ideas of "normal science," but paradigms change, new paradigms are suggested, and paradigms may be out of step with the normal science of the time. The result is conflict within a field-Kuhn's "scientific revolution." Gradually, a new paradigm assumes dominance, and a new normal science for the field emerges (Fig 4-9). For some time there have been attempts to provide an overriding conceptual framework for all craniofacial growth or, failing that, a neat synthesis of several "theories." These efforts have generally not yet been successful because of the varied aspects and complicated nature of craniofacial growth. It is, however, useful for us to review the evolution of the governing concepts in the field of facial growth through the years. Kuhn45 and Carlsonl7 would call these "paradigms."
1. The Genetic Concept For many years craniofacial growth research was dominated by interest in skeletal morphology, an interest which began in archaeology, physical anthropology, and anatomy. The tempo increased when the craniostat was converted into the radiographic cephalometer and the field of cephalometrics emerged, making possible serial study of the growing human craniofacial skeleton. Brodie,15. 16noting the persistent pattern of facial configuration, assumed it was under tight genetic control. Research focused on the growth sites for this control: the sutures, craniofacial cartilages, and periosteum. The assumption was made that the cartilages and facial sutures were under genetic control and that the brain determined the vault dimensions (which meant vault sutures were passive while facial sutures were actively forcing bones apart). Wendell Wylie termed this thinking "Orthodontic Calvinism" (see Section D-l-a, Controlling Factors in Craniofacial Growth, Genetics). Since
PARADIGM 1
I SC'ENTIFIC
iY PARADIGM
1
~
2
.-.
I .-. REVOLUTION PARADIGM
NORMAL PARADIGM SCIENC~
J>I ;,ARADIGM2
I!)I__________
NORMAL
SCIENCE
FIG 4-9. Representation of how changes in "normal science" are wrought by the introduction of new paradigms during scientific revolution. (From Carlson DS: Craniofacial biology as normal science, in Johnson LE Jr (ed): New Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1985. Reproduced by permission.)
Growth of the Craniofacial Skeleton the concept was one of an invariant, predetermined pattern of craniofacial growth, there began an interest in prediction, which was assumed to be easy (see Chapter 12). In the 1940s two events reflected changing ideas about the dominant genetic concepts: (l) a marked ilfcrease in the use of animals in craniofacial research; and (2) the introduction of jaw and facial electromyography. 65.66 Moss' 1960 formulation of the functional matrix hypothesis later provided a logical framework for an emerging new concept. 64Through the distance of time, it may be thought that each of these events precipitated new thinking. We believe the reverse is true. Just as it was the need to quantify and study the head serially which prompted the development of the cephalometer, so the desire to see beyond the craniofacial ~keleton heightened interest in the experimental model and neuromuscular function. One of us (R.E.M.) began the first work in craniofacial electromyography in 1946 (just 5 years after the publication of Brodie's classic paper in 1941) and within a year supervised 'a thesis research project involving the effects on skeletal growth of extirpation of the temporal muscle in neonate rats.82 Scientific historians dependent alone on the literature of a period are always some years out of phase with the origin and development of the ideas which resulted in that literature.
watershed paper whose importance was difficult to appreciate at that time.59 He called this new concept the "functional matrix hypothesis. "
2. The Functional Concept It was some time after Moss' first paper before the functional matrix concept came to influence thinking in craniofacial growth (Fig 4-10).64 The concept gradually was clarified by several rephrasings, but perhaps its best statement appeared in 1981: " ... in summary form, the functional matrix hypothesis explicitly claims that the origin, growth and maintenance of all skeletal tissue and organs are always secondary, compensatory, and obligatory responses to temporally and operationally prior events for processes that occur in specifically related non-skeletal tissues, organs for functioning spaces (functional matrices)."63 Some have misunderstood and misstated or misapplied Moss' ideas. His own writing is more conservative and careful than some others on the same topic. It is a theory difficult to prove or disprove, but it has been provocatively useful and probably has done more in modern times than any other single new idea to alter the thinking of those interested in craniofacial growth.
Moss,59. 60.64 adopting van der Klaauw's93 concepts, suggested that skeletal tissues were passive and under the control of functional components to which the craniofacial skeleton adapted. First he demonstrated that the sutures of the cranial vault were
3. Hypotheses of Craniofacial Growth Through the years, a number of hypotheses of craniofacial development have been formulated which are often encountered in textbooks and the periodical literature, where they are sometimes
passive. 58 Then his ideas, which obviously had been fermenting in his mind for some time, were somewhat inprecisely stated in a
1950
1940
1970
1960
NASAL
SEPTU'-4,
'-4ANOIBULAR
CRANIAL CONDYLE
1900 GENETIC PREDETERMINATION
GENETIC PREDETERMINATION
GENETIC PREDETERMINATION
49
BASE,
NASAL
SEPTU'-4,
CRANIAL
'-4ANOIBULAR
CONDYLE
BASE, \71
ANTHROPOLOGICAL CRANIOLOGY
CRANIOFACIAL
STRUCTURO-
a
APPROACH
PHYLOGENETICALLY
'FUNCTIONAL
,-----------~-_._---~
I
l
i--1
COMPARATIVE
WNCTlONAL
ANATOMY, EMBRYOLOGY
CLASSICAL (EP/GENETlCS),
:
L FIG
PALEONTOLOGY
I
COMPLEX
AS HIGHLY ADAPTABLE, ONTOGENETICALLY
FUNCTIONAL
MATfm( HYPOTHESIS
EPIGENESIS (SENSU
STRICTOJ
:
f7'11j :-If :
l
4-10.
Changing concepts of craniofacial growth acting as paradigms to alter the normal science of craniofacial biology. (From Carlson DS: Craniofacial biology as normal science, in Johnson LE Jr (ed): New Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1985. Reproduced by permission.)
I
50
Growth and Development
called "theories." Theory requires a basis of sound evidence; while hypothesis is thoughtful conjecture of the meaning of incomplete evidence. In the long run the most useful hypotheses are those which can be rigorously tested. It is interesting to place them in the historical evolution of overriding conceptS' ("paradigms") discussed earlier (Fig 4-10).
a) The Genetic "Theory" The genetic theory simply said that genes determine all. Although called a theory it was more assumed than proven. A brief summary of its current pertinency follows in Section 0-1. After the general assumptions were found to be flawed, some said "perhaps this part is genetically controlled while that is not," or "this part,is more controlled by heredity than that." Such statements showed uneasiness with the all-embracing aspects of the' 'theory. "
b) Sicher's Hypothesis (Sutural Dominance) Sicher'9' deduced from the many studies using vital dyes that the sutures were causing most of the growth; in fact, he said" ... the primary event in sutural growth is the proliferation of the connective tissue between the two bones. If the sutural connective tissue proliferates il creates the space for oppositional growth at the borders of the two bones." Replacement of the proliferating connective tissue was necessary for functional maintenance of the bones. He felt that the connective tissue in sutures of both the nasomaxillary complex and vault produced forces which separated the bones, just as the synchondroses expanded the cranial base and the epiphyseal plates lengthened long bones. Sicher'8 viewed the cartilage of the mandible somewhat differently, stating that it grew both interstitially, as epiphyseal plates, and appositionally, as bone grows under periosteum. His ideas came to be called the "sutural dominance theory," but it would seem he held sutures, cartilage, and periosteum all responsible for facial growth and assumed all were under tight intrinsic genetic control. c) Scott's Hypothesis (Nasal Septum) Scott,85-87 noting the prenatal importance of cartilaginous portions of the head, nasal capsule, mandible, and cranial base, and feeling that this development was under intrinsic genetic control, held that they continued to dominate facial growth postnatally. He specifically emphasized how the cartilage of the nasal septum during its growth paced the growth of the maxilla.85 Sutural growth, Scott felt, came in response to the growth of other structures including cartilaginous elements, brain, the eyes, and so forth87 Latham46 elaborated on Scott's ideas about the nasal septum and maxillary growth, emphasizing the role of the septo-premaxillary ligament beginning in the later part of the fetal period. He felt the maxillary sutures began as sliding joints adapting to initiating growth forces elsewhere, but later manifest increasing osteogenesis, contributing to the main displacing force at the free surfaces. Thus, he combines ideas of Scott, Sicher, and Moss.
d) Moss' Hypothesis (Functional Matrix) As noted elsewhere, Moss feels that bone and cartilage lack growth determination and grow in response to intrinsic growth of associated tissues, noting that the genetic coding for craniofacial skeletal growth is outside the bony skeleton.63 He terms the associated tissues "functional matrices. "59 Each component of a
functional matrix performs a necessary service-such as respiration, mastication, speech-while the skeletal tissues support and protect the associated functional matrices. Moss divides the skull into a series of discrete functional components each comprised of a functional matrix and an associated skeletal unit, c(esignating functional matrices as either periosteal or capsular.60 A periosteal functional matrix affects deposition and resorption of adjacent bony tissue; therefore, the matrix controls remodeling and the size and shape of a bone (e. g., the interaction between the temporal muscle and the coronoid process of the mandible). Moss identifies two large, enveloping capsular matrices: the cerebral and the facial.60 Each contains specific tissues and structures and spaces, spaces which must remain open to fulfill their functions. As each capsular matrix and its associated elements expand, all of the bones, endochondral and intramembranous, grow to maintain the physiologic spaces. Thus, Moss argues, the skeletal tissues grow only in response to soft-tissue growth. The effect is a passive translation of skeletal components in space.
e) Petrovic's Hypothesis (Servosystem) Using the language of cybernetics, Petrovic73 reasoned that it is the interaction of a series of causal change and feedback mechanisms which determines the growth of the variouscraniofacial regions. According to this servosystem theory of facial growth, control of primary (see E-4, Mandible, later in this chapter) cartilages takes a cybernetic form of a "command" whereas, in contrast, control of secondary cartilage (e.g., the mandibular condyle) is comprised not only of a direct effect of cell multiplication but also of indirect effects.76 In his experiments Petrovic detected no genetically predetermined final length for the mandible79 Rather, the direction and magnitude of condylar growth variation are perceived as quantitative responses to the lengthening of the maxilla.75. 77.78 Petrovic's provocative ideasc are ~specially useful in understanding the role of functional appliances in mandibular growth. 74.80For a more detailed study see Suggested Readings and, especially, his 1984 paper.74 4. Current Concepts Where are we now? What do we do now? What is true (now)? We have been, in Kuhnian terms, in the midst of a scientific revolution. Carlson17 calls it moving from the genetic paradigm to th€ structural-functional approach (see Fig 4-10). Everything is not yet known and much research is yet to be done, but clinicians must treat patients with working hypothes1s of growth in mind while issues are being resolved by craniofacial biologists in their minds and laboratories. ':. While we may no longer seek a synthesizing single theory for aft. of craniofacial growth, w~ may now have, because of Petrovic's work, a convenient model and a "language" by which to describe and relate growth activities to one another, thus obviating any need for another "paradigm." It is very important to remember that old ideas persist in the literature, in the thinking of some teachers, and the treatment planning of some clinicians long after they have been disproven and abandoned by craniofacial research biologists. It is also essential to realize that while fresh, exciting, new ideas may be revealing and useful, only time can attest to their truth and their
Growth of the Craniofacial
Skeleton
51
place in understanding the complicated mosaic of craniofacial growth. " What follows in the rest of this chapter is as clear and direct a statement of conventional wisdom as we can write at this time.
greater than has been thought in recent years. Primary genetic control determines certain initial features (e.g., tooth buds calcify in the jaws, and mandibles form in faces, not legs). Secondarily, there are inductive local feedback and inner communication mech-
Others would write it differently, and scientific reports regularly will alter parts of the overall picture of craniofacial development as new concepts, hypotheses, and theories emerge and are applied.
anisms between cells and tissues-the teeth "talk to" the bone, the muscles "talk to" the bone, and the bone "talks back" to the
D. CONTROLLING FACTORS IN CRANIOFACIAL GROWTH 1. Natural Van Limborgh94~96 has divided the factors controlling skeletal morphogenesis into five groups, namely, intrinsic genetic factors, local and general epigenetic factors, and local and general environmental influences. It is the proportional importance of these various groups of factors in the control of later craniofacial skeletal development that we must try to understand.
a) Genetics* One can often conclude immediately that all resemblances in families are genetic and structural. But such similarities as facial expressions, mode of laughter, and way of speaking may be learned as a result of living together. Garn et al. 28 report similarities in fatness in families as a cohabit:ltional effect, suggesting that living together and consuming the same food result in measurable similarities in some structural dimensions. What we sometimes assume to be genetic may be acquired and superimposed on a genetic foundation common to parents and progeny. The old argument about heredity versus environment has changed from the question of which is more important to how, when, and in what way does environment alter the original form laid down by heredity. When we think of inheritance, we remember such things as the fact that by examination of the parents we can predict precisely the ABO blood types of the progeny, for blood types are distributed discontinuously (i.e., in any sample, everyone falls into one of the four blood types). Such a discontinuous distribution is evidence for simple Mendelian inheritance. A continuous distribution of a variable, with most values grouped around a mean, is evidence for inheritance from several or many genes. There are no craniofacial skeletal measures which are discontinuous in their distribution. In ,addition to multiple genes there are the effects of the environment on the product of the genetic contro~ during formation. Undoubtedly there are primary controls for initiation and formation of facial structures. Van Limborgh96 reports experimental studies on chick embryos indicating that the intrinsic genetic information necessary for the differentiation of cranial cartilages and bones is supplied by neural crest cells. He feels that the importance o! intrinsic genetic factors for control of craniofaci~] differentiation, perhaps even intramembranous bone growth, is considerably
*In writing this section on genetics we have borrowed heavily from a splendid summarizing paper by Professor W. S. Hunter. 37 Because he is a geneticist, an active research worker, and an orthodontist, he is able to place these matters in sound, useful perspective.
-.
muscles. As a result, the genes for muscles have a modifying effect on the products of bony initiation and formation. Although it is argued whether or not there is simple gene control of formation of facial bones, the end result after tooth formation and muscle development appears to be polygenic or multifactorial. What is environment to the bone is genetic to the muscles and the teeth: van Limbourgh's "epigenetic factors." There is also some kind of an overriding sizing mechanism, far more precisely seen in the dentition than the bones. Although the upper and lower teeth are never perfectly matched, all of the teeth in an individual tend to be proportionately large or small (see Chapter 6). If the face were under rigid genetic control, it would be possible to predict features of children from cephalometric data of the parents. A number of studies illuminate this particular point: the best involve parents whose children have achieved maturity, so that little growth is yet expected from them.38 Given multifactorial controls, it can be shown that the highest correlation between parents and progeny can only be a correlation of r = .5. This can be compared to the correlation for blood type, namely, r = 1.0 between parents and progeny. Squaring the correlation coefficient enables one to arrive at the amount of variation explained or predicted for one variable in the correlation by the other. Thus a correlation of 0.5 enables one to predict only 25% of a child's mandibular size from knowledge about the parents' mandibular sizes. Since the usual correlation between parents' and children's dimensions is about 0.3, something less than 15% of children's dimensions are predictable or explained by parents' dimensions. If we wish to apply genetics clinically, we must ask what other alternatives than predicting size are available to us. Johnston noted that 30% to 54% of the variability of a patient's Class II malocclusion features can be explained by using data from the patient himself or herself. 42Hunter et al. 38 obtained a slightly higher amount, 60%. These facts are utilized in the cephalometric diagnoses detaileq in Chapter 12, particularly in "prediction"; however, the examination of parents for the purpose of forecasting size in children is not likely to be clinically very useful. , Some investigators, feeling that heritability in the face is not entirely polygenic, have undertaken investigations to study the matter. However, from the investigations thus far, two conclusions seen inescapable: (I) inheritance of facial dimensions is polygenic84 and (2) no more than one-fourth of the variability of any dimension in .~hildren can be explained by consideration of that dimension in parentS . 37 To summarize, it is highly unlikely that any component of the facial skeleton is inherited in the Mendelian fashion. Rather, the evidence strongly supports polygenic inheritance, greatly limiting our ability to explain facial dimensions from study of parents. Even if the size of facial bones were inherited in a Mendelian fashion, that inherited pattern is altered by environmental influences, some epigenetic and some general, to such an extent that in the patient the underlying genetic features cannot be easily detected.
52
Growth and Development
FIG 4-11. Relationship of times of emergence of certaif} teeth and the onset and end of peak height velocity (PHV). (From Hagg U, Taranger J: Dental development assessed by tooth counts and its correlation to somatic development during puberty. Eur J Orthod 1984; 6:55-64. Reproduced by permission.)
l
PHV
ONSET
GIRLS 1 2
2
1l,;.,
2.z; 2
11 2
3 :z
END
(
{'..
3
~ ~~
8
9
10
!
,............,
T
T
7
11
12
5
PHV
ONSET
BOYS
6
5
~
13
14
15
END
!
T
16
17
18
,............,
19
20
YEARS
DESv
b) "Function" Normal function plays a role in skeletal growth, for its absence, as in temporomandibular ankylosis, aglossia, and neuromuscular disorders, results in gross distortion of bony morphology. The role of ftmction as the primary factor in control of craniofacial growth is the essence of Moss' "functional matrix hypothesis" (see Section C). The role of malfunction in causing compensatory abnormal growth is appreciated (see D-2-d. Disruptive Factors, Malfunction, later in this section). Read carefully the sections on compensatory mechanisms for each region in Section E, Regional Development, for an understanding of the sites of compensatory growth and their adaptive responses to altered function.
c) General Body Growth Biological maturity plays a general role in all aspects of maturation of the individual.44 All maturational events are influenced in individuals by a combination of factors including genetic, climatic, racial, nutritional, and socioeconomic. For this reason there has been considerable interest in the relationship between the maturation and timing of somatic growth and dimensional growth in the craniofacial complex'"' 9. 11.14.21.72.97.98The most obvious dimension in growth of the child's body, and that studied most frequently, is height, which is measured easily and reliably. The· velocity curve for height diminishes continuously from birth except for two spurts, the first a small and inconsistent one at about 6 or 7 years of age and the second at the time of puberty (Fig 4_11).29 During the pubertal spurt in stature, the velocity of growth is apt to be greater than at any other time when orthodontic treatment is ordinarily undertaken. Therefore it would seem to be of great benefit if aspects of orthodontic treatment depending on growth could be undertaken during this time. It would be especially beneficial if one could predict any craniofacial spurts from earlier developmental events. All facial dimensions do not undergo a spurt, nor is the rate of increased velocity, the onset, the duration, or the cessation similar in all people. Generally, however, those facial dimensions which do spurt do so at about the same time as stature. On the average, the peak of the growth spurt in stature is about 12 years in girls and 14 years in boys, but the standard deviation is nearly I year for each sex."7 It would be most advantageous to predict the onset of spurts in facial growth. However, this is exceedingly difficult and it is hard to identify the growth spurt until it is well under way. Therefore, most studies have concentrated on the Maximum Height Velocity (also known as Peak Height Velocity). It is well known that several other maturational events are related to
DES
M'"
the overall height growth curve; for example, skeletal age, derived from hand-wrist radiographs, is an established method of estimating physical maturity and has value in predicting adult height. Orthodontists, however, have tried to use the hand-wrist radiograph not to predict ultimate adult height or even facial dimension but, rather, the time of the Peak Height Velocity in growth. Many have attempted to derive clinical precision from this general biologic relationship, however. Houston,'6 in one of the most thorough and best designed studies, concludes that' 'the practical difficulties of timing ossification events and the need for serial observations before an estimate of age at Peak Height Velocity can be made, . will preclude their use in most clinical situations." Lewis et al.:7 after studying mandibular spurts, flatly stated: "It can be desirable to determine whether a spurt has occurred in an individual patient. For this purpose, skeletal age, as determined from carpal radiographs, may be only slightly more meaningful than chronological age, and neither is sufficiently precise for many clinical applications. " The use of population means to predict developmental events in the individual provides very little help because of the extent of normal variation. Even if one were able to predict the Peak Height Velocity, approximately one-half of the advantage would be lost since it occurs before the peak. Dental development has also been tried as an indicator of the timing of the pubertal growth spurt, but it too has not been very helpful. 22.30 To summarize, somatic growth and craniofacial growth are generally related, but that relationship is difficult to utilize in precise, practical prediction of facial dimensional change. This is not to say that the general information is not useful clinically, it is;'but its practical, quantified application has sometimes been overstated.
d) Neurotrophism It is known that neural activity controls muscle activity and gro}V~h. Nervous controL of skeletal growth, assumedly by transmissibn of a substance through th~ axons of the nerves, has been hypothesized for years and is called neurotrophism. The history of this idea, the arguments for and against it, and its relationships to current theories of craniofacial growth have been reviewed in articles by Behrents3 and by Moss.62 Theoretically, a direct neurotrophic effect on osteogenesis is possible, but, logical as it seems, it has not been demonstrated experimentally. Neurotrophism could act indirectly by the nerves inducing and affecting soft-tissue growth and function, which in turn would control or modify skeletal growth and morphology-the
Growth of the Craniofacial basic idea in Moss' functional matrix hypothesis, which holds bone growth to be mostly in response to the surrounding soft tissues. But'neurotrophism, even within Moss' view, 6' has an element of primary cause and control. Such evidence as we have (Behrents,' Piminides,"' and others) seems to say that neurotrophic mechanisms exist and may have some primary impact, but the overall effect is slight. Nor can we yet, by this evidence, separate clearly any direct neurotrophic effects on bone from neurotrophic effects on muscle or their varying functions.
2. Disruptive Factors Disruptive factors in facial growth are those which do not rQutinely contribute to normal variation but when they appear in the individual may be important. They may be elective, environmental, or congenital in origin.
a) Orthodontic Forces Orthodontic forces are utilized to affect growth and alter tooth positions. The general biologic responses to orthodontic forces are discussed in Chapter 13, and specific local effects of orthodontic force systems on growth are discussed in Section E. Regional Development.
b) Surgery Orthognathic or plastic surgery is undertaken for two reasons: to correct a craniofacial anamoly (e.g., cleft palate) or to improve craniofacial esthetics in non anomalous faces deviating significantly from the norm (see Chapter 17). Modem surgical techniques have improved the surgeon's ability to reposition parts of the face, but there remain two problems much studied yet still not thoroughly understood: (1) relapse of the surgical result, even in "nongrowing adults;" and (2) the effects of surgery on subsequent growth. The latter problem is particularly important when the surgery has been performed on young patients. Carlson et al. 's point out that these two factors are closely interrelated since growth itself is largely a process of adaptation of parts. Data on the effects of surgery on "normal," healthy children and adults are quite incomplete (see Suggested Readings). The effects of surgery on craniofacial anamolies and their subsequent growth is even less understood because of the magnitude of the necessary surgical correction and lack of understanding of the basic abnormal growth which created and maintains the syndromal anomaly.
c) Malnutrition Although it is presumed that gross malnutrition affects craniofacial growth in humans (it has been studied some in animals), there is little specific information available.
d) Malfunctions That altered malfunction can play a role in craniofacial morphology is well documented in the experimental laboratory by the classic research of Harvold, 31-34Petrovic,73-so McNamara,5'-55 and Carlson.1s-2o Clinical studies of the effects of altered nasorespiratory function on growth and morphology (Linder-Aronson)4S-50 and posture (Solow and Tallgren)9" 92support the long-held biases of orthodontists and physicians that craniofacial growth is determined to some extent by the functional environment of the cran-
Skeleton
53
iofacial skeleton. The enunciation of the functional matrix theory by Moss59 and the well-documented research noted above give solid support to the idea that function helps determine morphology during normal growth and that altered function can produce altered morphology. The role of nasorespiratory malfunction (e.g., "mouthbreathing") is discussed in Chapter 7, as is altered occlusal function-the so-called "functional mal occlusions . " The idea that function plays a controlling factor in craniofacial morphology not only has a theoretical base and etiologic credibility but is clinically attractive, for if the environment plays an important role in controlling morphology, surely then the orthodontist can find therapeutic help in contriving ways to alter that environment. This latter point, of course, is the basis for the entire concept of functional appliance therapy. The Suggested Readings at the end of this chapter include several items on the role of nasorespiratory function and craniofacial growth, muscle adaptation in the craniofacial region, determinants of mandibular form and growth, and clinical alteration of the growing face. This will be an exciting and active area for research for some time in the future. The clinician who wishes to apply the principles being clarified by this research must guard against the overly enthusiastic advocacy by some clinical colleagues, tempering their optimism with the sound findings from basic and clinical research.
e) Gross Craniofacial Anomalies Patients with a gross craniofacial anomaly present a head and face markedly altered during early organogenesis in ways hard to discern postnatally. It is difficult to note all of the primary sites and the nature and extent of the dysmorphogenesis except in the crudest of terms (e.g., what is seen in the radiograph). Further, it is nearly impossible to separate original dysplasia from later adaptive growth. We attempt to understand this grossly dysplastic growth from our knowledge of variable normative growth, which is not very helpful since there is more variation within a single syndrome (e.g., Apert's) than in the random nonaffected population. Our knowledge of postnatal growth of some of the more common syndromes (e.g., cleft palate) has become better in recent years, but much fundamental work is still needed. Fortunately a number of fine research centers are dedicated to the understanding and treatment of these problems. Detailed discussion of anomalous craniofacial growth is impossible in a volume of this type; therefore, readers interested in broadening their knowledge should see the Suggested Readings at the end of this chapter. A few references are listed which give overviews of this important area. "
,.,c.
E. REGIONAL DEVELOPMENT The same outline will be used in each of the regions to be discussed in this section. Note the four subsections titled "Compensatory Mechanisms," for therein are described those areas best able to compensate and adapt when usual growth has failed or is in any way abnormal. The regions most able to adapt and compensate naturally are also those most able to respond to clinically imposed forces (see Chapter 13).
54
Growth and Development
FIG
4-12.
Distribution of resorptive and depository periosteal surfaces in the cranial vault, cranial base, and nasomaxillary complex as seen in a lateral internal view. Resorptive regions are shown in black and depository regions in light gray.
1. Cranial
Vauft
a) Functions The primary function of the bony cranial vault is protection of the brain. The vault's growth is paced by the growth of the brain itself.
b) Growth 1) Mechanisms and Sites.- The growth of the bones of the calvaria utilizes a suture system plus relatively small surface de-· posits on both the ectocranial and endocranial sides. Remodeling adjustments are minor, primarily adjacent to sutures. Extensive remodeling changes do not take place. The calvaria encloses the brain; all major arteries, veins, nerves and the spinal cord enter or leave by way of the cranial floor. The continued positioning of the foramina associated with them thus is not a factor in the growth of the skull roof. The bones of the cranial vault are joined with one another by sutures, and the bones of the nasomaxillary complex are linked together and to the cranial vault by a system of sutural junctions providing sites for growth and adjustment (Fig 4-12). 2) Timing.The growth of the skull roof is provided by sutural responses to the expansion of the enclosed brain; thus, vault growth is paced by brain growth. Since brain growth is largely completed in early childhood, the cranial vault is one of the first regions of the craniofacial skeleton to achieve full size, though the vault sutures are patent for some time after growth is mostly over. 3) Compensatory Mechanisms.The sutural system of the cranial vault provides extensive adaptive capability for such path-
ologies as hydrocephalus or cultural practices as head binding. However, when cranial stenosis occurs almost all of the adaptive compensatory possibilities are lost and a very serious clinical problem prevails.
c. Theoretical and Clinical Issues There is general agreement on the mechanisms and methods of vault growth, but there is little understanding of the control of cessation of sutural growth potential. What determines when a suture closes? Why do some close before others? Why do they not all close approximately togetheras brain growth is diminished? The principal clinical issues are those seen with grossly abnormal and anomalous growth (e.g., cranial stenosis, hydrocephaly). In almost every serious instance the clinical problem requires surgical rather than orthodontic intervention. 2. Basicranium
a) Functions The human cranial floor and calvaria are adapted to upright boQ,y.posture and the development of relatively large cerebral hemispheres. These factors are assoc(ated with a midventrally positioned foramen magnum and a marked flexure of the cranial base because of the huge forward expansion of the frontal lobes in man and the backward and downward enlargement of the occipital and cerebellar lobes (see Fig 4-12). Cranial base flexure places the foramen magnum directly over the vertical spinal cord and achieves a forward alignment of the face and orbits because of human bipedal posture. The basicranium not only supports and protects the brain and spinal cord but also articulates the skull with the vertebral column,
Growth of the Craniofacial
Skeleton
55
FIG 4-13. Growth sites in the cranial base. The sphenoid bone is at b. The left arrow points to the sphenoethmoidal synchondrosis; the right arrow, to the spheno-occipital synchondrosis.
mandible: and maxillary region. One of its important functions is as an adaptive or buffer zone between the brain, face, and pharyngeal region, whose growths are paced differently. b) Growth 1) Mechanisms
and Sites.-Growth
of the basicranium
is
carried out by a complex balance among sutural growth, elongation
at synchondroses,
and extensive cortical drift and remodeling (Figs combination provides (I) differential growth enlargement between the cranial floor and the calvaria, (2) expansion of confined contours in the various endocranial fossae, and (3) maintenance of passages and housing for vessels and nerves and such appendages as the hypophysis. Elongation of the cranial . base is provided by growth at the synchondroses and direct cortical
4-13 and 4-14). This
FIG 4-14. The distribution of resorptive and depository periosteal surfaces in the cranial floor. Resorptive regions are shown in black and depository areas in gray.
-.
56
Growth and Development
growth (see Fig floor
produces
4-13).
The process of cortical
regionally
variable
growth
drift in the cranial
movements
in a gen-
cranial base growth are buffered by the complicated of cranial base structures with other bones.83
articulations
erally ectocranial direction by surface resorption (see Fig 4-14) from the endocranial site, with proportionate deposition on external surfaces. -
erally considered
Growth of the cranial floor has a direct effect on placement of the midface and mandible. As the anterior cranial fossae and
iofacial skeleton and the least affected by such external influences as altered neuromuscular function or orthodontic treatment. There-
cranial
fore, the cranial floor displays less compensatory growth relative to the viscerocranium than is seen in other craniofacial structures.
floor
elongate,
larging nasomaxillary respondingly.
the underlying complex,
The spheno-occipital
the entire middle face anteriorly, pharyngeal mandible
region.
displacement
of the maxilla.
the basicranium mandibular
anteriorly
complex
of the
the ramus enlarges
as the
with the forward
Thus, the anteroposterior
growth
role in both nasomaxillary
of and
growth.
The various
hypotheses
mode ling with the completion chondroses, however, to grow somewhat though
fossae show reduced rates of reof brain growth.
are paced differently,
in length for an extended
they must be under
similar
control
growth cartilages in the body, pubescent'
The cranial
syn-
and the fossae continue period of time. Alto that of the other
'spurts"
in endochondral
about craniofacial
clear in explaining
neurocranial
much basicranium
change, for example,
the functioning potential
The cranial
The basicranium
is gen-
of the cran-
c) Theoretical and Clinical Issues
residing
cephalometric nificant
within
analysis,
contribution
the orthodontist's itself.
maxillary
growth
are less
than any other part. How is due to the influence
of
the cartilages?
for the orthodontist that neurocranial
to the malocclusion.
of course, affects the midfacial floor
growth
growth fields, and how much to the inherent growth
It is frustrating 2) Timing.-
Mechanisms.-
to be the most stable of all portions
elongates, displacing an enlargement
in conjunction
has an important
by the en-
and ramus increases cor-
producing
Correspondingly,
is displaced
space occupied
pharynx,
3) Compensatory
during.the
structures
make a sig-
Skeletal base dysplasia,
and mandibular
nor surgeon's
Treatment
to discover,
regions, but neither
efforts ordinarily
alter the cranial
must consist of compensatory
and mandibular
growth
alteration
of
of form and tooth positioning.
FIG 4-15. The sutural and periosteal membranes. In the upper diagram, the edges of two adjacent bones (A) are joined by the connective tissue
arrows). Note the changed positions of the markers (x). The fibers of the former zone B have now become embedded in the new bone
of the suture. Note the position of markers (x). The border zone (B) inserts directly into the surface of the bone. At its other end, each
(A'). A new border zone has formed from the old intermediate
fiber of zone B continues into the labile linkage fibrils of the intermediate zone (C). These fibrils are more delicate than the heavy, coarse fibers of the capsular zone (0). This layer contains the vessels (b) and may become
regionally subdivided into separate capsular zones for each side of the suture junction. The periosteum is similarly composed of a border zone (B), an intermediate zone (C), and a dense outer fibrous zone (0). In the lower diagram, an arbitrary increment of new zone has been added (+ arrows) to each sutural bone surface (A'). The old bones (A) have become displaced away from each other (oISPL
zone (C). As its fibrils lengthen in a direction away from bone surfaces, they undergo differentiation into coarse, mature collaganous fibers. The bone simultaneously increases in thickness by subperiosteal (and also endosteal) deposition (+ arrows). The coarse fibers of the border zone become embedded attachment fibers as the linkage fibrils of the continuous intermediate zone differentiate into the fibers of a new border zone. As the entire periosteum "drifts" in an outward course, the linkage fibrils lengthen in a direction toward zone 0 and increase in number to accommodate the expanded coverage. (From Enlow OH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced
by permission.)
Growth of the Craniofacial Several of the craniofacial syndromes involve gross dysplasia of the basicranium with resultant imposed abnormal adaptive growth else'where in the face and cranial vault.
3. Nasomaxillary
Complex
a) Functions Dentists appreciate the important role of the nasomaxillary region in mastication (attachment of teeth and muscles), but it has other important functions as well. The nasomaxillary complex provides a significant portion of the airway, contains the physiologically important nasal mucosae with their glands and temperature-adjusting vascular components, separates nasal from oral cavities, houses the olfactory nerve endings, encloses the eyes, and adds resonance to the voice because of the sinuses contained within the region. Its growth must adapt to that of the basicranium to which it is attached and to the mandible with which it functions
Skeleton
57
in mastication, speech, facial expression, respiration, etc. Its functions are as complex as its growth and adaptations. b) Growth 1) Mechanisms and Sites.- The mechanisms for growth in the nasomaxillary complex are the sutures, the nasal septum, the periosteal and endosteal surfaces, and the alveolar processes. As Mills56 points out, the maxilla is increased in size by subperiosteal activity during postnatal growth, although the periosteum has different names in different sites. Over most surfaces it is simply periosteum; in some areas, mucoperiosteum; where the periosteum of one bone meets another, it is termed a suture; and where the two bones become one bone (alveolar process) and interface with the modified bone of the tooth's root (cementum), the periosteum is called the periodontal membrane. Despite the different names on different body surfaces, all carry out the essential role of remodeling (Figs 4-15 and 4-16). The entire nasomaxillary complex
FIG 4-16.
"
Sections of the nasofrontal suture from a young, rapidly growing kitten prepared according to the differential polychrome procedure. All three zones in both A and B can be seen. The coarse fibers of the border zone (a) and the delicate linkage fibrils of trhe intermediate zone (b) are indicated in photomicrograph B. The heavy, coarse fiber bundles of the capsular zone (c) are labeled in photomicrograph A. (From Enlow DH: The Human Face. New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced by permission.)
;;.
58
Growth and Development
FIG
4-17.
Regional depository and resorptive periosteal surfaces in the nasomaxillary complex. The resorptive surfaces are shown in black and depository surfaces in light gray. The white zones (t) are areas in which normal variation occurs in the reversal line between resorptive and depository
surfaces.
is joined together and to the cranial vault and cranial base by the most complicated sutural system of all, a primary mechanism for the region's growth and adaptation (see Figs 4-14 and 4-15). An endochondral mechanism for bone growth, as is seen in long bones, the mandible, and the cranial base, is not widespread in the midface, although the midfacial extensions of the ethmoid are of endochondrial origin. The embryonic nasal capsule does not simply ossify to become the bones of the nasomaxillary complex: The growth of the cartilaginous part of the nasal septum, however, has been regarded as a souce of the force that displaces the maxilla anteroinferiorly, although this theory has been largely modified by many researchers. Growth and remodeling of most of the midfacial complex accompanies and follows this displacement by the familiar intramembranous bone process. Sometimes too much emphasis is still placed on the nasal septum in midface growth, suggesting almost a dominant role. It must be remembered that virtually all of the inner and outer surfaces of each bone within the midface complex are actively involved in the total growth remode!ing process (see Figs 4-14, 415, 4-17, 4-18, and 4-19). All the endosteal and periosteal sur- . faces are blanketed by localized growth fields which operate essentially independently but somehow harmoniously with one another. Thus, surface growth remodeling is very active, providing much regional increase and remodeling which accompany and
FIG
4-18.
Growth and displacement
in the nasomaxil-
lary complex. Left, the resorption and deposition necessary to produce the adult nasomaxillary complex are clearly shown. Right, the displacement necessary to accompany the adult nasomaxillary remodeling configuration is depicted.
adapt to the additions taking place in sutures, synchondroses, condyles, and so forth. The variety of growth processes is nowhere more elaborate or complicated in the head and face than in the nasomaxillary region.
2) Amounts and Directions.(a) Maxillary Height.-The classic implant studies of Bjork al)d Skiellerlo confirm that maxillary height increases because .of sutural growth toward the frontal and zygomatic bones and appositional growth in the alveolar process. Apposition also occurs on the floor of the orbits with resorptive modeling of the lower surfaces. Simultaneously the nasal floor is lowered by resorption while apposition occurs on the hard palate. The relative portions of vertical increases at different growth sites is important. The orbits do not increase in height in childhood through adolescence to the same degree as does the nasal cavity, so that the sutural lowering of the maxillary corpus is compensated for some\Vhat by apposition of the floor of the orbit. The lowering of the floor pf the orbit from the age of four onward is somewhat less· than half the sutural lowering of the maxillary corpus .. Growth at the median suture produces more millimeters of width increase than appositional remodeling, but surface remodeling must everywhere accompany sutural additions.lo Alveolar remodeling contributing to significant early vertical growth is also
Growth of the Craniofacial
+
B
Skeleton
59
+
+
+
FIG 4-19. Vertical growth and displacement in the nasomaxillary complex. The palate grows in an inferior direction by subperiosteal bone deposition on its entire oral surface, with corresponding resorptive removal from its opposite surface (A and B). At the same time, the nasomaxillary complex is increasing its overall size (C) while being displaced inferiorly by growth of parts above and behind it (D).
c
important in the attainment of width because of the divergence of the alveolar processes. As they grow vertically, their divergence increases the width. Up to the time that the mandibular condyles have ceased their most active growth (late adolescence), maxillary alveolar process increases constitute nearly 40% of the total maxillary height increases. IQ , (b) Maxillary Width.-Growth in the median suture is more important thJln appositional remodeling in the development of maxillary width.'O Growth increases at the median suture mimic the general growth. curve for body height, and maximum pubertal .growth in the median suture coincides with the time for maximum growth iri the facil\J sutures as seen in the profile radiograph.'o :; - How~ver, there is 'not a correlation between growth in width at .: the mt;?ian suture and the sutural growth contributing to height of , the maxilla. Mutual transverse rotation of the two maxillae'results . in separation of the halves more posteriorly than anteriorly. (c) Maxillary Length.-Length increases in the maxilla after about the second year occur by apposition on the maxillary tuberosity and by sutural growth toward the palatine bone. Surface resorption occurs anteriorly on the bony maxillary arch. Bjork and Skieller's implant studies show th'is anterior surface to be rather stable sagittally, IQ but the maxillary arch is remodeling as it grows downward, which is why the anterior region is resorptive.27 Its labial surface moves away from the largely inferior direction of growth. The maxilla rotates forward in relation to the anterior cranial base.
3) Timing.-Alveolar process increases are closely correlated with the eruption of teeth. Increases in' overall maxillary height coincide nicely with vertical growth in the mandible. There
is some general pacing of overall maxillary and mandibular growth, for both are roughly coincident with general bodily growth. 4) Compensatory Mechanisms.-All mechanisms of nasomaxillary growth are well designed for adaptive and compensatory growth, but adaptation is most dramatically seen in the alveolar process. When the palate is narrow, for example, the alveolar process compensates in both height and width. The plane of occlusion is coordinated during growth with the overall morphologic pattern, alveolar process deposition and resorption compensating nicely for palatal displacement. Thus, in skeletal deep bite, where the gonial angle is more nearly orthogonal, the occlusal plane (established by alveolar process growth) is nearly parallel to the mandibular plane. On the other hand, when anterior face height is disproportibnately long, anterior alveolar growth com~nsates and the occlusal plane is steep . Because of the adaptive and compensatory nature of alveolar growth the occlusion is sometimes at variance with the skeletal relationship and one finds a CIllss I mollIT relationship, for example, in a retrognathic(Class II) skeleton. Predicting skeletal growth does not predict precisely the future occlusal relationship.70 Orthodontic treatment, >irrespective of the appliance, depends, to a g;eat extent, on the adaptive capacity of alveolar process growth and remodeling. 5) Effects on Dentition and OccIusion* .-Bimolar width in the first molar region correlates nicely with vertical growth of the maxilla, growth in the midpalatal suture, and growth in height. The dental arch in the maxilla drifts forward on an average of 5 mm by late adolescence in the molar region and 2.5 mm in the *See also Chapter 6.
60
Growth and Development
incisors. 10 The dental arch perimeter is thus shortened (see Chapter 6). The important point to note here, however, is that crowding is not due simply to the differences in tooth size between the primary and permanent dentition, or even to mesial drifting, for Bjork and Skieller showed that the lateral segments, though drifting mesially, were unchanged in length while the incisor segments were shortened. 10 The shortening of the maxillary dental arch perimeter continues at least through the termination of growth in the mandibular condyles, and its greatest association is with the eruption of the maxillary second molar, not the third as is commonly assumed. Further, the root development of the third molars, and thus the initiation of eruption, occurs after the greatest shortening of length in the maxillary dental arch. The crowding in the frontal segments In the maxilla, therefore, seems to be due to mesial drifting of all the teeth and to shortening of the anterior segments, probably the result of the convergence of the dental arch anteriorly as the sagittal shift of the teeth is directed inward over a narrowing bone base. c) Theoretical
Problems
Previously the principal theoretical problem seemed to be whether or not the expanding nasal septum is the principal energizing force in nasomaxillary. growth movements, or whether' it operates in conjunction with other soft tissue displacing forces. Most authorities now hold the latter view. d) Clinical Issues Whether the clinican can alter nasomaxillary morphology and growth is no longer seriously argued, for the documentation is overwhelming (see Chapter 15). The biologic principles of such adaptations to orthodontic forces are discussed in Chapter 13. The sutural system adapts to posterior forces (extraoral, cranial, and cervical traction), anterior traction (face masks), and transverse forces (lingual archwires and rapid palatal expansion devices).
A
Variations in maxillary growth and morphology may play important roles in some skeletal malocclusions, for example, Class 11 (excessive midface growth) and Class III (decreased midface growth). Altered nasorespiratory function and nasomaxillary growth are other important clinical issues (see Chapter 7). The region is the site of the single most common gross craniofacial anomaly, namely, cleft palate.
4. Mandible a) Functions The mandible, the most highly mobile of the craniofacial bones, is singularly important, for it is involved in the vital functions of mastication, maintenance of the airway, speech, and facial expression. b) Growth The modes, mechanisms, and sites of mandibular growth are complicated and much argued in the literature. Some of the problems in interpretation of mandibular growth data are shown i:J Figure 4-20. Note that the mandible basically is a slender, Ushaped bone with an endochondral growth mechanism at each end and intramembranous growth between-just as in long bones. To it are attached muscles and teeth. Both prenatally and postnatally only a small percentage of mandibular growth is "endochondrally" developed; a far greater portion is intramembrously determined. Growth and shape changes of the areas of muscle attachment and teeth insertion are controlled more by muscle function and eruption of the teeth than by intrinsic cartilaginous or osteogenic factors. The cephalometrist, on whose research we depend greatly, locates handy landmarks around this odd-shaped bone in sites of easy visualization (Fig 4-20B), but they are insufficient in number and imprecise in location, and thus we are unable to segregate cleanly developmental and adaptive changes of the different regions to
B
o
Growth from intrinsic factors associated
•
Growth from remodeling associated
c muscle attachments
CD
Growth from remodeling associated
c eruptions
.
c condylar cartilage
;;.
Me
FIG 4-20. A, endochondrial bone growth in the mandible. One may visualize the mandible as the central portion of a tubular long bone that has
been bent so that half of each epiphyseal plate is in either condylar position. This bent tube constitutes the corpus mandibularis, to which are attached areas of bone for muscle insertion and areas for holding the teeth. (A adapted from Symons NBB: Dental Record 1951; 71 :41.) 8, ultimate portions of the mandible associated with different aspects of growth on cephalometric landmarks (see Chapter 12). (See Fig 4-15 for explanation of Part 8 elements.)
Growth of the Craniofacial their own controlling mechanisms. It is neat consider the mandible as a single unit, but its be understood only by studying enlargement separately in the regions identified in Figure 1) Mechanisms
and
Skeleton
61
and handy for us to adaptive growth can and change in form
4-20.
Sites.-
(a) Role of the Condylar Cartilage.The condyle is of special interest because it is a major site of growth, it is involved in one of the most complicated articulations in the body, and there have been so many opinions about its role in mandibular growth. The mandible is really a membrane bone remodeling over all surfaces, though one part develops in response to a phylogenetically altered developmental situation and becomes the condylar region. The condylar cartilage is a secondary cartilage (meaning that it did not develop by differentiation from embryonic primary cartilages) which makes an important contribution to the overall length of the mandible. Regional adaptive growth in the condylar area is important because the corpus of the mandible must be maintained in functioning juxtaposition with the base of the skull where it articulates. The condylar region and the ramus must adapt to the numerous functional demands placedon it, yet allow the growth displ,!cement of the mandible away from the skull. The many arguments about condylar growth focus mostly on one question: Is the condylar cartilage the principal force that produces the forward and downward displacement of the mandible? For many years it was considered the primary "growth center" of the bone, controlling and pacing its entire growth. Proponents of the functional matrix· theory, however, claimed that some mandibles function adequately and seem to be positioned rather normally when condyles are absent, so perhaps the condyle did not play the role of the master growth control center or cause mandibular displacement. (For a dissenting view see 10hnston42) They concluded that soft-tissue development carries the mandible forward and downward while condylar growth fills in the resultant space to maintain contact with the basicranium. The growth mechanism of the condylar area is fairly clear (Fig 4-21), the main factor being t~e mesenchymal cells (i.e., the periosteum) above the cartilage itself, how they grow, and what influences them. A significant fact about condylar cartilage is.that, compared with other cartilages, it reacts faster with a lower threshold to outside mechanical factors. The condyle does not determine how the mandible grows, rather it is the mandible which determines how the condyle grows. Articular function determines condylar growth, and articular function is dependent on how the mandible grows. Mandibular growth is determined by factors outside the mandible-muscles, maxillary growth, etc. Cartilage is present because variable levels of surface pressure occur in the joint at the articular contacts. An endochondral growth mechanism is required because the condyle grows in the direction of the articulation in the face of pressure, a situation which pure intramembranous bone growth could not tolerate. Cartilage of the mandibular condyle is not like that of an epiphyseal plate or synchondrosis, for it is, as noted earlier, different in origin and structure. Primary cartilages have some degree of intrinsic growth potential; but the condylar cartilage is a secondary cartilage and is presumed not to have such potential, although Petrovic et al80 have noted the role of hormones in condylar cartilage growth. This
FIG 4-21. A, hyalinization in the intermaxillary suture of the palate of the Rhesus monkey after experimental compression. 8, heavy, rapid expansion of the intermaxillary suture of the palate in the Rhesus monkey. (From Linge L: Tissue Changes in Facial Sutures Incident to Mechanical Influences. An Experimental Study in Macaca mulatta, thesis. University of Oslo, 1973. Reproduced by permission, courtesy of L. Linge.) assumption fits neatly with the functional matrix theory. Transplantation experiments with the condyles and adjacent tissues also ,shed light on this problem. When the condyle is transplanted alone, it does not flourish, but when it is transplanted with adjacent bones, it does.26 Other experiments hav.e shown that if the condylar head is transplanted in situations which providejtwith function, it grows normally. 10hnston42 and colleagues carried out experiments in which the condyles of guinea pigs were detached from the body Of-!he mandible. The diiached condyles continued to grow downward while the ramal portion collapsed upwards because of the influence of the muscles. After the two parts were reunited, normal growth continued. In experimental animals, if the condyle is removed, the region is diminished in size but the rest of the mandible continues to grow through periosteal remodeling. Experimental injection of papain, which interferes with chondrogenesis, produces quite similar results. Koski43 and colleagues conclude from several well-designed studies that periosteal tension in the condylar neck provides a built-in control for growth of the ramus by way of the cartilage and that other local factors, such as the lateral
62
Growth and Development
FIG 4-22. A, comparison of a child's mandible with an adult's. This frequently used orientation is very misleading. The child's mandible simply could not become the adult mandible by general overall growth as this orientation indicates. B, by orienting differently, the effects of growth displacement, remodeling, and resorption are better visualized. On the left, a child's mandible has been superposed to show areas of resorption and deposition. Note the"extensive remodeling, deposition, and cortical drift necessary to produce the outline of the adult mandible. On the right, the orienta\ion and registration on the condylar region dramatizes the displacement of the mandible with growth.
pterygoid muscle, may introduce outside control. They indicate that periosteal integrity is important for normal proliferative activity of the connective tissue cells of the condyle apart from the role of the lateral pterygoid muscle. Their work clarifies the roles of ramal remodeling and condylar growth, reducing a conflict of theories to understandable integration. Clear-cut, all-or-none conclusions are hard to make, but the following seem logical in the face of the evidence. The condylar region plays an important role in mandibular growth because of the articular site and because of the extensive regional remodeling necessary. Though the condylar cartilage is a secondary cartilage, it probably plays some role in the translation of the mandible. At the same time animal experimentation and human clinical studies have shown that the condylar cartilage is highly responsive when the mandible is repositioned purposefully during growth (see D, Clinical Issues). In our efforts to find which single theory of mandibular growth is correct, we may have missed an important point, namely, that several growth mechanisms may be operating together and it is simply the proportionate contribution of each that is at question. Perhaps both the condylar cartilage and the functioning muscles translate the mandible, and, in the absence of one, the other does its best to compensate. In either event the integrity of the periosteum of the condylar neck region is important. When the environment is radically changed, as during the insertion of a functional appliance, the compensatory contributions of both are enhanced.
(b) Ramus and Corpus.- The additions of new bone provided by the condyle produce a dominant growth movement (translation) of the mandible as a whole (Fig 4-22). The posterior border of the ramus, in conjunction with the condyle, also undergoes a major growth movement (cortical drift) that follows a posterior and somewhat lateral course (Fig 4-23). The combination of condylar and ramus growth brings about (I) a backward transposition
of the entire ramus (the anterior border is resorptive), thereby simultaneously elongating the mandibular body; (2) a displacement of the mandibular corpus in an anterior direction; (3) a vertical lengthening of the ramus as the mandible is displaced; and (4) movable articulation during these various growth changes (see Fig 4-22). As the ramus grows and becomes relocated in a posterior direction, the lingual tuberosity correspondingly grows and moves posteriorly in a manner comparable to the maxillary tuberosity. Studies of remodeling, animal experimentation, and the use of implants have provided the information in the previous paragraph. It is easy to perceive how difficult it is to study mandibular growth with cephalometric natural landmarks alone (see Fig 420). For example, corpus length cephalometric ally is usually defined as the distance from gonion to such anterior landmarks as pogonion, yet gonion is being carried along by ramal changes in one direction while pogonion moves forward nearly oppositely. Further, cephalometric definitions of corpus and ramus result in changes in the ramal-corpal angle (the so-called "gonial" angle) yet the relationship between the corpus of the mandible and the posterior cranial base is one of great angular constancy. 71 (See discussion of "rotation" later.) The growth movements of the mandible, in general, are complemented by corresponding changes occurring in the maxilla. A primary function of corpus displacement is the continuous positionipg of the mandibular arch relative to the complementary growth moveibents of the maxilla. As the lJIaxilla becomes displaced anteriorly and inferiorly, a simultaneous displacement of the mandible in equivalent directions and approximate extent occurs. Muscle attachment areas of the ramus play an important role in localized remodeling and cortical drift accompanying the downward and forward mandibular displacement. Areas of muscle attahment at the coronoid processes and the gonial regions become fully differentiated only in response to the development and functioning of the muscles that insert there. It has been shown exper-
Growth of the Craniofacial
Skeleton
63
FIG 4-23. The distribution of resorptive and depository periosteal surfaces in the human mandible is mapped in these drawings, Periosteal surfaces that undergo progressive removal during growth are indicated in black; outer surfaces that are depository gray,
imentally that these regions do not develop well if the muscles are removed'very early or if the nerves and vessels serving these muscles are severed (see Sections C and D), The mandible appears to "grow" in a forward and downward manner when visualized in superimposed serial cephalometric tracings registered on the cranial base, causing an important problem in the analysis of treatment effects (Chapter 12) (Fig 4-24), Actual growth, however, takes place in a wide variety of regional directions, The predominant trend of growth generally is superior and posterior, but simultaneous displacement of the whole mandible occurs in an opposite (i ,e" anterior and inferior) course, regardless of the many varying regional directions of growth, remodeling, and local drift.
(c) Alveolar Process.- The alveolar process is not present when teeth are absent. Its formation is controlled by dental eruption and it resorbs when teeth are exfoliated or extracted, The teeth, in either arch, are not carried forward and downward exactly as the mandible and maxilla are by growth and displacement, for intercuspation restrains the teeth somewhat. Thus the alveolar processes serve as important buffer zones helping to maintain occlusal relationships during differential mandibular and midface growth,
in nature are indicated in light
Alveolar process growth is most active during eruption, plays an important and unappreciated role during emergence and initial intercuspation (see Chapter 6), and continues to maintain the occlusal relationships during vertical growth of the mandible and maxilla, When corpus growth is essentially over, vertical alveolar growth persists as the occlusal surfaces wear; thus occlusal height is maintained even in adulthood. Adaptive remodeling of the alveolar process makes orthodontic tooth movements possible. 2)
Amounts and Directions*-
(a)Height.-Ramus
height increases correlate well with corpus length and overall mandibular length, and periods of accelerated growth roughly coincide with those in stature.47 Alveolar process height increases are highly correlated with eruption, Anterior mandibular height (e.g., mandibular line to incisal edge) is related to dental development and overall mandibular growth downward and forward. Therefore, mandibular anterior height is related to facial type and is quite different in, for example, a skeletal deep bite and a long anterior face height. *Tables of mandibular of Chapter 12,
dimensional
change will be found at the end
FIG 4-24. Serial cephalograms superposed on the cranial base. '. The changes seen adtie chin are the summation of all growth between the chin and the cranial base, not just mandibular growth and displacement alone: Compare with Fig 4-22.
64
Growth and Development
FIG 4-25. Three types of rotation of the mandible during growth. A, forward rotation with the center at the incisal edges of the lower incisors. B, forward rotation with the center at the premolars. C, backward rotation with the center at the occluding molars. (From Bj6rk A: Prediction of mandibular growth rotation. Am J Orthod 1969; 55:585599. Reproduced by permission.)
metallic implants and other methods. However, the nature and the amount of "rotation" are sometimes misinterpreted through the use of conventional cephalometric landmarks. Some of the confusion is eliminated by the use of implants or carefully chosen natural markers in the mandible, for example, the mandibular canal, the lower rim of the crypt for molars, and the inner contour of the cortical plate of the lower portion of the symphysis (see Chapter 12). Bj6rkl2 also makes a clear distinction between what he terms "matrix rotation" and "intramatrix rotation" (Fig 426). "Matrix rotation" often goes in the form of a pendulum movement with the rotation point in the condyle." "Intramatrix rotation" is the "rotation" of the mandibular corpus' inner half of its matrix within the mandibular corpus and not in the condyle (Fig 4-26,B). It is important to note that Skieller, Bj6rk et al90 show that the total so-called "rotation" is made up of the sum of both "matrix" and "intramatrix" rotations (Fig 4-27).12 Apparently in most instances the "intramatrix rotation" accounts for most of the total, though there is great variability. , 'Rotation" is an unfortunate choice of terms to explain what are essentially complex remodeling shape changes difficult to depict and quantify with conventional cephalometric techniques (see Chapter 12). The mathematics of rotation is appropriate when studying the kinematics of jaw opening and closing, for the shape of the mandible does not change during brief periods of time. During growth over time, as Bj6rkl2 has emphasized and others studyihg "mandibular rotation" often have not, all parts undergo
(b) Width.-Bigonial and bicondylar diameter increases are a function of growth in overall mandibular length and the natural divergence of the mandible. Most width increases occur simply because the mandible grows longer, though some periosteal deposition occurs (see Fig 4-23). Mandibular width increases are generally more evenly acquired than those of overall length or· height.
a ~
(c) Length.-Mandibular
length is measured two ways (I) overall length (e.g., condylion-gnathion) and (2) corpus length (e.g., pogonion-gonion). Both dimensions show increases correlated with ramus height increases, and "spurts" in mandibular length occur about the same time as "spurts" in stature.
(d) "Rotation".-Serial cephalometric studies, using cranial base registrations, imply that normally the mandible is carried away from the posterior cranial base in a downward and forward direction. When the mandibular corpus is steeply related to the posterior cranial base, and anterior face height increases are significantly greater than those posteriorly, the mandible is sometimes said to "rotate" posteriorly (Fig 4-25). A significant amount of the excessive anterior face height in such instances is contributed by mandibular anterior height. Thus, the alveolar process in the mandible under such circumstances is significantly higher anteriorly than in the molar region. Obversely, when posterior face height is greater than normal, the bite tends to be deeper and the mandible Bj6rk8 and others2.41 have is said to display anterior "rotation." studied this so-called "mandibular growth rotation" by the use of
APPOSition
Resorptlon
82
.
0,,"
;;.
-,
~
APPOSition
_
Resorptlon
FIG 4-26. A, matrix rotation. In both forwards and backwards matrix rotation the mandible moves as a pendulum with the center of rotation in the condyles. B, intramatrix rotation. The areas of apposition and resorption change with forward and backward intramatrix rotation: B1, forward; B-2, backward intramatrix rotation. (From Bj6rk A, Skieller V: Normales und anomales Wachstum des Unterkiefers: Einer Synthese longitudinaler kephalometrischer Implantstudien wahrend eines Zeitraums van 25 Tahren. Inf Orthod Kieferorthop 1984; 16:954. Reproduced by permission.)
Growth of the Craniofacial
A1
A2
~
-
\J\
Unterkleferrotatlon
....
'y \
65
Skeleton
~
+ 8°
l
Behandlung R
7176'4'
He
71769 12" g6 306
B
I
/" H,
OOL/
6 106
Total 100% _
MatriX 71%
uu_
----
I /~
+ 2°
I
u
+ 6°l. + 4°l.
Retention
I
I
ruckwarts
Intramatrlx
146
12
166
186
206
24 6
29%
306
Jahre
- 14,0°
FIG 4-27. A, mandibular rotation backwards. Treatment took place from approximately age 17 to 19'/2 years. Note that of the total "rotation" "11% is accounted for by "matrix rotation" and 29% by "intrarTiatrix rotation." This pattern is typical of patients with disproportionate anterior face height growth. 8, serial tracings of a mandible rotating forwards. Registration is on implants. Note the extensive apposition and remodeling in the corpus. In such cases "intramatrix rotation" accounts for the preponderance of the total "rotation," quite the reverse of that shown in A. (From Bj6rk A, Skieller V: Normales und anomales Wachstum des Unterkiefers: Einer Synthese longitudinaler kephalometrischer Implantstudien wahrend eines Zeitraums von 25 Tahren. Inf Orthod Kieferorthop 1984; 16:9-54. Reproduced by permission.)
shape changes, altering landmark positions and relationships of parts, which makes true rotational analysis a staggeringly difficult procedure both conceptually and mathematically. We agree with Bookstein 13 that tensor analysis is a better way to study craniofacial shape change. Much that is reported as mandibular "rotation" is mostly regional compensatory remodeling (' 'intramatrix rotation") to corpus translation. 3) Timing.-Spurts in mandibular dimensions are common but not universal and are more frequently seen in boys than girls, occurring approximately 1'/2 years earlier in girls.47 The most important spurt in mandibular growth is that related to puberty; it usually occurs before Peak Height Velocity, but there is remarkable variation in this relationship.47. 97 Almost all first pubertal spurts occur after ulnar sesamoid ossification and before menarchy-two developmental events which have been used to predict skeletal growth spurts. The prediction of the timing of mandibular growth spurts, and whether or not they will occur at all, would be of some
clinical import. However, most research shows that such prediction's are not sufficiently precise for practical clinical application.47 "
4) Compensating Mechanisms.-As noted above, the areas of muscle attachment and the alv'eolar process are the most adaptive, and hence variable, regions in the mandible. In extremes of facial type these regions show great morphologic variance. For e~ample, the shape of the'coronoid process, the amount and placemelit of the alveolar process, ansl the condylar angle are greatly different in a skeletal open bite than a skeletal deep bite (see Figs 4-26 and 4-27). Maximal differences in these regions are also seen between Class II and Class III cases and in skeletal asymmetry. Precision-bracketed orthodontic appliances mostly take advantage of the adaptive capacity of the alveolar process as it responds to tooth movements. Functional appliances change the way that muscle contractions shape the areas of attachment and guide the eruption of teeth and hence the shape of the alveolar process. In addition, repositioning of the mandible with a functional appliance
66
Growth and Development
may change the amounts and directions of growth in the condylar region.51
5) Effects on Dentition and Occlusion.-Variation in mandibular morphology and size contributes more sigllificantly to most malocclusions than does maxillary variability. The mandible, for example, is more apt to be at fault in both Class II and Class III malocclusions than is the maxilla. When there are significant variations in mandibular morphology, both the upper and lower dentitions must adapt during development. 68 Typical. tooth displacements in a skeletal Class II or III malocclusion noted early in life help to predict the ultimate molar and incisor relationship which will obtain with subsequent growth.
c) Theoretical problems Currently the two theoretical issues of most interest are (I) the role of the condylar cartilage in mandibular growth and (2) the source of the mandibular displacement which occurs during mandibular growth. Functional matrix theorists hold that it is the surrounding soft tissues which displace the mandible, while others feel that the endochondral mechanisms in the condyle push the mandible downward and forward.
d) Clinical Issues The principal clinical issue in mandibular growth is the extent to which the clinician can alter mandibular morphology. 57 The work of Petrovic, McNamara, and Carlson, particularly, reveals the mandible as much more amenable to clinical control than previously thought. Their work provides a theoretical framework for understanding and planning control of mandibular growth, and their animal experiments demonstrate the timing of such possibilities and the maturationallimitations. Clinical studies generally are much more difficult to design and, hence, clinical reports of altered mandibular growth are less clear in their conclusions. It seems significant that the more extensive and thoroughly designed clinical studies are quite consonant with the experimental studies,oB while many of those which conclude that one cannot alter mandibular growth are flawed in their mensurational methodology or design. This important issue is not fully understood as yet, and clinicians, while awaiting more detailed and critical reports, must protect themselves against both the overly enthusiastic claims of some and the denial of any clinical effects on the mandible by others, for we are undoubtedly able to affect mandibular growth and form much more than previously thought, but we have much to learn about this important clinical advantage.
5. Temporomandibular
Joint
The condylar component of the temporomandibular joint is much studied (see E-4, Mandible), but the temporal component (eminentia articularis and fossa) is much less so, hence our knowledge about it is quite incomplete. The embryologic development of the region has received attention (see Chapter 3) but postnatal changes are less well known.
the development of the primary dentition, fossa depth increases appreciably and the eminence becomes clearly identified. Later the articular disc, which at birth is completely vascularized, becomes clearly avascular in the mid region. The vascularization of the superior surface of the condyle disappears at about the same time. Probably the definition of the joint contours is a result of the stimulation of beginning masticatory function since both the form and position of the fossae are different with congenital absence of a ramus or unilateral condylectomy. During childhood the mandibular fossa becomes deeper and the slope of the eminentia steeper as a result of differential deposition and resorption, mostly deposition on the eminence. The literature contains arguments about the duration of growth of the articular eminence. Sparse data and logic both indicate that the region grows and remodels continuously but in a decelerated fashion as bone growth and remodeling occur elsewhere in the body.
b) Mechanisms and Sites Although the region is clearly one growing by intramembranous ossification, a number of researchers have drawn attention to the role of an endochondral-like mechanism in eminetia growth in humans and monkeys analogous to the growth mechanisms in the condyle (e.g., see the works by Hinton in Suggested Readings). This is not surprising since, as discussed earlier, cartilage appears in areas where pressure exists but bone growth must proceed. Studies of altered mandibular function in growing animals clearly indicate that the temporal portion of the joint is responsive in concert with the condyle and that maturation plays a similar role in the duration and extent of the effects of altered function of the temporomandibular joint (the article by Hinton and McNamara in Suggested Readings provides a good summary).
c) Effects on Dentition and Occlusion Much of the research on temporomandibular kinematics and the relationship of occlusion to joint morphology has been done on adults needing occlusal rehabilitation. It almost seems that some believe the joint incapable of adaptation and remodeling. Certainly, modern occlusal rehabilitation practice involves carefully fitting the occlusion to some features of the joint morphology, for example, the slope of the eminence. Developmentalists studying occlusion note the interrelationships of occlusion and the joint with overall craniofacial morphology during growth and emphasize the interrelationships rather than the dependence of occlusal relationships on unchanging joint morphology. Indeed it can be expected, as the animal experimental evidence shows, that definitive studies of orthodontic correction during growth should be expected to show There is an concomitant changes in temporal joint remodeling.35 ext~nsive literature evalu(!ting the relationships of mandibular fossa deptJt -to dental stress factors such as tooth wear, loss of teeth, periodontal disease, and fractures.' Since some force probably is delivered to the joints during function, 30. 40 reported adaptative and compensatory changes are not surprising and provide the rationale for the establishment of proper occlusal function to promote reasonably normal joint growth and physiologic function.
d) Clinical and Theoretical Issues
a) Functions and Growth In the neonate the temporal articular surfaces are almost flat since the eminence and fossa are not well differentiated, lacking the familiar S-shaped profile characteristic of adult joints. During
-.
While the theoretical issues of the growth and remodeling of the temporal component of the joint are not much argued, the clinical aspects are. For example, it is not fully known how tem-
Growth of the Craniofacial poromandibular growth and adaptation vary with different craniofacial types. Further, there is the question about the "proper" position of the condyle within the fossa and whether or not slight variance in condylar positioning affects changes in growth amounts or directions. We are in a period of intensive study of temporomandibular joint growth and the developmental aspects of temporomandibular joint dysfunction67 It is suggested that the reader study carefully the Selected Readings at the end of this chapter (e.g., the monograph by Carlson, McNamara and Ribbens), and read the new literature carefully as this complicated and fascinating area of regional craniofacial growth becomes better understood.
The gross effects of summarized craniofacial growth are usually depicted cephalometrically by registration of successive tracings on common cranial base landmarks (see Fig 4-24). The additive result of displacement, growth, and remodeling appears to be downward and forward despite local change in many different directions (see Fig 4-24). As noted in Chapter 12, such orientations and registrations can be misleading. The usual simplistic presentations of overall pattern of growth thus often conceal rather than reveal important regional and sexual differences of great clinical import. There are sexual differences in overall growth (men grow more, grow actively over a longer time span, display more "spurts", and so forth) but such differences are better understood by studying regional sexual dimorphisms (see Section E). From a clinical standpoint the most significant overall sexual differences are seen in the achievement of facial height (see Chapter 12). Total facial height and some components of it show remarkable sexual dimorphisms in amount, timing, and pattern of growth, necessitating sexually different treatment strategies for certain types of open bite and deep bite (see Chapters 15 and 16).
G. RACIAL AND ETHNIC DIFFERENCES Morphologic differences among the various human races and ethnic groups have long been studied. Indeed craniofacial features are probably used more than any others to typify group characteristics and diversities. There are a very large number of cephalometric studies of craniofacial morphology of widely varying racial and ethnic groups ranging from Australian aborigines to Bantu, Lapps, North American whites, Japanese, Swedes, several North American Indian tribes, Mexicans, Brazilians, French, Italians, Greeks, Finns, North American blacks, and others. * The literature on racial morphologic craniofacial diversity is detailed and extensive but there are few studies on growth differences among racial, ethnic, and national groups (see, e.g., the article by Moyers and Miura69). Most extensively reported on are North American whites and Europeans. Serial cephalometric data of North American blacks exist but are not yet fully analyzed. *This is not to suggest that these studies are available in a handy form for clinical diagnostic use; they are not. It will require an extensive research project in itself to standardize and normalize the various data sets for practical comparisons.
-.
67
It is a great pity we know much about morphologic variation among ethnic groups and little about the developmental differences which produce it.69 Even casual reading of the international orthodontic clinical literature suggests different distribution of malocclusions among, to name obvious examples, Japanese, Italians, Swedes, British, and North American whites. Since radiation hygiene regulations now restrict serial cephalometric growth studies in most countries, it will likely be some time before detailed knowledge of growth differences among races is known.
H. " ADULT" CRANIOFACIAL F,. OVERALL PATTERN OF CRANIOFACIAL GROWTH
Skeleton
GROWTH
There exists a general viewpoint that craniofacial growth decelerates after pubescence, ceasing sometime in the third decade of life--earlier in women than in men. The perception that there is very little adult growth appears as assumptive in many articles and is reiterated in almost all textbooks, including earlier editions of The Handbook of Orthodontics! Studies have existed for many years which present contrary evidence. Though one can criticize almost any of the reports (e.g., for small sample size, lack of sufficiently long series, flawed research design, or inappropriate methods of measurement), when they are taken in toto, the findings undeniably affirm the presence of continuing changes in craniofacial morphology throughout life. It is true that there has not been a complete consensus among researchers themselves, but the' contrary evidence is less abundant and less sound. Part of our failure to appreciate the extent of adult skeletal growth may be due to the restricted use of the word "growth" in cephalometrics to mean size increase alone (and size frequently "measured" by changes in an angle whose apex is far removed from the bone or region under study [e.g., LANB to measure mandibular length or growth]). A recent monograph by Behrents4 forces us to abandon the old views of minimal adult craniofacial growth. Behrents4 did an extensive adult follow-up research of subjects in the original Bolton study, analyzing 163 individuals ranging in age from 17 to 83 years, all of whom had previous extraordinarily complete serial growth data, including cephalograms, obtained during childhood and adolescence. His findings provide good evidence of surprising extensive craniofacial changes throughout life. " Behrent's results4 may be briefly summarized as follows: a) Craniofacial
.
b) ..
c)
d)
e)
size and shape changes continue past 17 years to the oldest ages studied. Significant sexual dimorphism exists: men are larger at all ages, they gi6w more, and their adult growth is more apt to persist along the same vectors of adolescent growth. Women showed periods of increased rates of craniofacial growth, apparently related to the time of pregnancies. Skeletal changes resulted from continuous localized remodeling, producing differential alterations in size and shape. The amounts of growth were not sufficient to serve as a basis for practical adult orthopedic or functional appliance therapy.
68
Growth and Development f)
The amounts of growth were sufficient, however, to cause significant adaptations in mandibular orientation 'and occlusal relations.
The implications for clinical dentistry of this important work are not yet fully realized, but it is obvious that treatments (orthodontic, restorative, prosthetic) based on a presumptive "stability" of occlusion if treated "properly" are challenged, for all occlusions obviously change. Our treatment goals should not be based on hoping for static relationships but rather on achieving favorable adaptations to the inevitable changes of aging.
REFERENCES I. Baer MJ, Gavan JA: Symposium on bone growth as revealed by in vivo markers. Am J Phys Anthropoll968; 29: 155. 2. Baumrind S, Korn EL, West EE: Prediction of mandibular rotation: An empirical test of clinical performance. Am J Orthod 1984; 86:371-385. 3. Behrents RG: Deja vu: Neurotrophism and the regulation of craniofacial growth, in: McNamara JA Jr (ed): Factors Affecting the Growth of the Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. 4. Behrents RG: Growth in the Aging Craniofacial Skeleton, monograph 17. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. 5. Belchier, J: An account of the bones of animals being changed to a red color by ailment only. Philos Trans 1736; 39:286. 6. Bergersen EO: The male adolescent facial growth spurt: Its prediction and relation to skeletal maturation. Angle Orthod 1972; 42:319-336. 7. Bjork A: Facial growth in man. Studies with the aid of me- . tallic implants. Acta Odontol Scand 1955; 13:9. 8. Bjork A: Prediction of mandibular growth rotation. Am J Orthod 1969; 55:585-599. 9. Bjork A, Helm S: Prediction of the age of maximum pubertal growth in body height. Angle Orthod 1967; 37:134-143. 10. Bjork A, Skieller V: Postnatal growth and development of the maxillary compolex, in McNamara JA Jr (ed): Factors Affecting the Growth of the Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976, pp 61-99. 11. Bjork A, Skieller V: Normal and abnormal growth of the mandible: A synthesis of longitudinal cephalometric implant studies over a period of 25 years. Eur J Orthod 1983; 5: 146. 12. Bjork A, Skieller V: Normales und anomales Wachstum des Unterkiefers: Einer Synthese longitudinaler kephalometrischer Implantstudien wahrend eines Zeitrams von 25 Jahren. InfOrthod Kieferorthop 1984; 16:9-54. 13. Bookstein FL: Measuring treatment effects on craniofacial growth, in McNamara JA Jr, Ribbens KA, Hose RP (eds): Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983.
14. Bowden BD: Epiphyseal changes in the hand/wrist area as indicators of adolescent stage. Aust Orthod J 1976; 4:87104. 15. Brodie AG: Behavior of normal and abnormal facial growth patterns. Am J Orthod Oral Surg 1941; 27:633-647. 16. Brodie AG: On the growth pattern of the human head. Am J Anat 1941; 68:209-262. 17. Carlson DS: Craniofacial biology as normal science, in Johnston LE Jr (ed): New Vistas in Orthodontics. Lea & Febiger, Philadelphia, 1985. 18. Carlson DS, Ellis E Ill, Schneiderman ED et al: Experimental models of surgical intervention in the growing face: Cephalometric analysis of facial growth and relapse, in McNamara JA Jr, Carlson DS, Ribbens KA (eds): The Effect of Surgical Intervention on Craniofacial Growth, monograph 12. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1982. 19. Carlson DS, McNamara JA Jr, Graber LW et al.: Experimental studies of the growth and adaptation of the temporomandibular joint, in Irby WG (ed): Current Concepts in Oral Surgery. St Louis, CV Mosby, 1980. 20. Carlson DS, Maxwell LC: Adaptation of the muscles of mastication to altered mandibular function. Am J Phys Anthropol 1980; 52:212. 21. Cohen AM: The timing of orthodontic treatment in relation to growth. Br J Orthod 1980; 7:69-74. 22. Demirjian A: Dentition, in Falkner F, Tanner JM (eds): Human Growth. London, Bailliere Tindall, 1978, vol 2, pp 413-414. 23. Enlow DH: Principles of Bone Remodeling. Springfield, Ill, Charles C Thomas, 1963. 24. Enlow DH: The Human Face: An Account of the Postnatal Growth and Development of the Craniofacial Skeleton. New York, Hoeber Medical Division, Harper & Row, 1968. 25. Enlow DH: The remodeling of bone, in Buettne-Janusch J (ed): Yearbook of Physical Anthropology Series, Vol 20. Washington DC, 1976. 26. Enlow DH: Role of the TMJ in facial growth and development, in Laskin D, Greenfield W, Gale J, et al. (eds): The President's Conference on the Examination, Diagnosis and Management of Temporomandibular Disorders. Chicago, American Dental Association, 1982. 27. Enlow DH: Handbook of Facial Growth, 2nd ed. Philadel. phia, WB Saunders Co, 1982. 28~ Garn SM, LaVelle M, Pilkington 11: Obesity and living together. Marriage Fam Rev 1984; 7:33-47. 29. Hagg U, Taranger J: Skeletal 'stages of the hand and wrist as indicators of the pubertal growth spurt. Acta Odontol Scand 1980; 38:187-200. 30. Hagg U, Taranger J: pen tal development assessed by tooth " OQunts and its correlation to somatic development during puberty. Eur J Orthod 1984; 0:55-64. 31. Harvold EP: Neuromuscular and morphological adaptations in experimentally induced oral respiration, in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 32. Harvold EP: Altering craniofacial growth: Force application and neuromuscular-bone interaction, in McNamara JA Jr, Ribbens KA, Howe RP (eds): Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series.
Growth of the Craniofacial
33.
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Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. Harvold EP, Chierici G, Vargervik K: Experiments on the development of dental malocclusions. Am J Orthod 1972; 61:38-44 .• Harvold EP, Vargervik K, Chierici G: Primate experiments on oral sensation and dental malocclusion. Am J Orthod 1973; 63:494-508. Hinton RJ, McNamara JA Jr: Temporal bone adaptations in response to protrusive function in juvenile and growing adult Rhesus monkeys (Macaca mulatta). Eur J Orthod 1984; 6:155-174. Houston WJB: Relationships between skeletal maturity estimated from hand-wrist radiographs and the timing of the adolescent growth spurt. Eur J Orthod 1980; 2:81-93. Hunter WS: Genetics and forecasting. Lecture presented at the Canadian Association of Orthodontists Meeting, Toronto, Ontario, 1981. Hunter WS, Balbach DR, Lamphier DE: The heritability of attained growth in the human face. Am J Orthod 1970; 58:128-134. Hylander WL: Patterns of stress and strain in the Macaque mandible, in Carlson DS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981. Hylander WL, Crompton A W: Loading patterns and jaw movement during the masticatory power stroke in macaques. Am J Phys Anthropol 1980; 52:239. Isaacson RJ, Erdman AG, Hultgren GW: Facial and dental effects of mandibular rotation, in Carlson DS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1980. Johnston LE Jr: The functional matrix hypothesis: Reflections in a jaundiced eye, in McNamara JA Jr (ed): Factors Affecting the Growth of the Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. Koski K, Ronning 0: Condyle neck periostomy and the mitotic activity in the condylar tissues of young rats. Swed Dent J (suppl 15) 1982; 109-113; Part n. Proc Finn Dent Soc 1983; 79: 147-150. Krogman WM: Maturation age of the growing chiid in relation to the timing of statural and facial growth at puberty. Trans Stud Coll Physicians Phila 1979; 1:33-42. Kuhn TS: The Structure of Scientific Revolutions, 2nd ed. Chicago, University of Chicago Press, 1970. Latham RA: An appraisal of the early maxillary growth mechanism, in McNamara JA Jr (ed): Factors Affecting the Growth of the Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. Lewis A, Roche AF, Wagner B: Growth of the mandible during pubescence. Angle Orthod 1982; 52:325-342. Linder-Aronson S: Adenoids-their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition. Acta Otolaryngol (suppl) 1970; 265. Linder-Aronson S: Effects of adenoidectomy on the dentition and facial skeleton over a period of five years. Transactions of the Third International Orthodontic Congress 1973,p85.
...•
Skeleton
69
50. Linder-Aronson S: Naso-respiratory function and craniofacial growth, in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 51. McNamara JA Jr: Neuromuscular and skeletal adaptations to altered function in the orofacial region. Am J Orthod 1973; 64:578-606. 52. McNamara JA Jr: Functional determinants of craniofacial size and shape, in Carlson DS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981. 53. McNamara JA Jr, Bookstein FL, Shaughnessy TG: Skeletal and dental adaptations during functional regulation therapy. Am J Orthod 1985; 88:91-110. 54. McNamara JA Jr, Carlson DS: Quantitative analysis of temporomandibular joint adaptations to protrusive function. Am J Orthod 1979; 76:593-611. 55. McNamara JA Jr, Connelly TG, Mc Bride MC: Histological studies of temporomandibular joint adaptations, in McNamara JA Jr (ed): Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. 56. Mills JRE: A clinician looks at facial growth. Br J Orthod 1983; 10:58-72. 57. Mills JRE: Clinical control of craniofacial growth: A skeptic's viewpoint, in McNamara JA Jr, Ribbens KA, Howe RP (eds): Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. 58. Moss MD: Extrinsic determination of sutural area morphology. Acta Anat 1961; 44:263-272. 59. Moss ML: The functional matrix, in Kraus BS, Riedel R (eds): Vistas in Orthodontics, Philadelphia, Lea & Febiger, 1962; pp 85-98. 60. Moss ML: The primary role of functional matrices in facial growth. Am J Orthod 1969; 55:566. 61, Moss ML: An introduction to the neurobiology of orofacial growth. Acta Biotheratica 1972; 22:236-259. 62. Moss ML: Neurotrophic regulation of craniofacial growth, in McNamara JA Jr (ed): Control Mechanisms in Craniofacial Growth, monograph 3. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. 63. Moss ML: Genetics, epigenetics and causation. Am J Orthod 1981; 80:366-375. 64. Moss ML, Young R: A functional approach to craniology. " Am J Phys Anthropol 1960; 18:281-292. 65;, Moyers RE: Temporomandibular muscle contraction patterns in Angle class n, divfsion I, malocclusions: An electromyographic analysis. Am J Orthod 1949; 35:837-857. 66. Moyers RE: An electromyographic analysis of certain muscles involved in temporomandibular movement. Am J Orthod 1950; 36:481-515. 67. Moyers RE: The development of occlusion and temporomandibular disorders, in Carlson DS, McNamara JA Jr, Ribbens KA (eds): Developmental Aspects of Temporomandibular Joint Disorders, monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985 .
70
Growth and Development
68. Moyers RE, Elgoyhen JC, Riolo ML, et al: Experimental production of Class 1II in Rhesus monkeys. Trans Eur Orthod Soc 1970; 46:61. 69. Moyers RE, Miura F: The use of serial cephalograms to study racial differences in development. Presented at the VII International Congress on Anthropoligic and Ethnologic Sciences, Tokyo, Japan, 1968. 70. Moyers RE, Wainright RL: Skeletal contributions to occlusal development, in McNamara JA Jr (ed): The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977. 71. Moyers RE, Wainright RL, Primack VP: Craniofacial constants: Their use in cephalometries (unpublished data). 72. ,Nanda RS: The rates of growth of several facial components measured from serial cephalometric roentgenograms. Am J Orthod 1955; 41:658-673. 73. Petrovic A: Control of postnatal growth of secondary cartilages of the mandible by mechanisms regulating occlusion. Trans Eur Orthod Soc 1974; 50:69-75. 74. Petrovic A: Experimental and cybernetic approaches to the mechanisms of action of functional appliances on mandibular growth, in McNamara JA Jr, Ribbens KA (eds): Malocclusion and the Periodontium, monograph 15. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984. 75. Petrovic A, Oudet C, Stutzmann J: Behandlungsergebnisse hinsichtlich der Dauer der iibertriebenen posturalen Vorschubstellung des Unterkiefers. Tierexperimentelle Untersuchungen uber den Mechanismus des Ruckfalls. Forschr Kieferorthop 1976; 37:40-51. 76. Petrovic A, Stutzmann J: Le muscle pterygoidien externe et la croissance du condyle mandibulaire. Recherches experimentales chez le jeune rat. Orthod Fr 1972; 43:271-285. 77. Petrovic A, Stutzmann J: Further investigations into the functioning of the "comparator" of the servosystem (respective positions of the upper and lower dental arches) in the control of the condylar cartilage growth rate and of the lengthening of the jaw, in McNamara JA Jr (ed): The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977. 78. Petrovic A, Stutzmann J: Tierexperimentelle Untersuchungen iiber das Gesichtsschadelwachstum und seine Beeinflussung. Eine biologische Erklarung der sogenannte Wachstumsrotation des Unterkiefers. Fortsch Kieferorthop 1979; 40:1-24. 79. Petrovic AG, Stutzmann 11, Gasson N: The final length of the mandible: Is it genetically predetermined? in Carlson DS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981. 80. Petrovic AJ, Stutzmann J, Oudet C: Control process in the postnatal growth of the condylar cartilage, in McNamara JA Jr (ed): Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. 81. Piminidis MZ: The Mandibular Trigeminal Nerve of the Rat: An Autoradiographic Study of Its Sensory Nerve Endings and a Morphological and Histological Study of OralFacial Motor and Growth Changes Following Early Lesion of Trigeminal Ganglion, Ph.D. thesis. Boston University, School of Dentistry, 1975.
82. Rampton FR: Temporal Muscle Dysfunction as a Basis for Etiology in Malocclusion, master's thesis. College of Dentistry, University of Iowa, Iowa City, 1949. 83. Roche AF, Lewis AB: Sex differences in the elongation of the cranial base during pubescence. Angle Orthod 1974; 44:279-294, 84. Saunders SR, Popovich F, Thompson G: A family study of craniofacial dimensions in the Burlington Growth Centre sample. Am J Orthod 1980; 78:394-403. 85. Scott JH: Studies in the growth of the upper jaw. Dent Rec 1948; 68:277-291. 86. Scott JH: The growth of the human face. Proc R Soc Med 1954; 47:91. 87. Scott JH: Craniofacial regions: Contributions to the study of facial growth. Dent Pract 1955; 5:208. 88. Sicher H: The growth of the mandible. Am J Orthod Oral Surg 1947; 33:30-35. 89. Sicher H, Dubrul EL: Oral Anatomy, 5th ed. St Louis, CV Mosby Co, 1970. 90. Skieller V, Bjork A, Linde-Hansen T: Prediction mandibular rotation evaluated from a longitudinal implant sample. Am J Orthod 1984; 86:359-370. 91. Solow B, Tallgren A: Head posture and craniofacial morphology. Am J Phys Anthropol 1976; 44:417 -436. 92. Solow B, Tallgren A: Dentoalveolar morphology in relation to craniocervical posture. Angle Orthod 1977; 47:157-164. 93. van der Klaauw CJ: Size and position of functional components of the skull. Arch Neerl Zool 1948-1952; 9: I. 94. van Limborgh J: A new view on the control of the morphogenesis of the skull. Acta Morphol Neerl Scand 1970; 8:143. 95. van Limborgh J: Factors controlling skeletal morphogenesis in Dixon AD, Sarnat BG (eds): The International Conference on Factors and Mechanisms Influencing Bone Growth. New York, Alan R. Liss, 1982. 96. van Limborgh J: Morphologic control of craniofacial growth, in McNamara JA Jr, Ribbens KA, Howe RP (eds): Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. 97. Woodside DG: Distance, Velocity and Relative Growth Rate Standards for Mandibular Growth for Canadian Males and Females, Aged Three to Twenty Years. M.Sc. thesis, University of Toronto, 1969. Wood side D: Some effects of activator treatment on the growth rate of the mandible and the position of the midface. Transactions of the Third International Orthodontic Congress, London, 1975.
SUGGESTED
READINGS
B,'''R.UDIMENTS OF BONE GROWTH Baer 11, Gavan JA: Symposium on bone growth as revealed by in vivo markers. Am J Phys Anthropol 1968; 29:155. Dixon AD, Sarnat BG (eds): The International Conference on Factors and Mechanisms Influencing Bone Growth. New York, Alan R. Liss, 1982. Enlow DH: Principles of Bone Remodeling. Springfield, Ill, Charles C Thomas, 1969. Enlow DH: The remodeling of bone, in Buettner-James J (ed): Yearbook of Physical Anthropology Series, Vol 20. Washington DC, 1976.
Growlh of the Craniofacial Enlow OH: Handbook of Facial Growth, WB Saunders Co, 1982.
2nd ed. Philadelphia,
C. CHANGING CONCEPTS AND" HYPOTHESES OF CRANIOFACIAL GROWTH Carlson os: Craniofacial biology as normal science, in lohnston LE lr (ed): New Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1985. Moss ML: The functional matrix,in Kraus, BS, Riedel R (eds): Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1962; pp 85-98. Moss ML: The primary role of functional matrices in facial growth. Am J Orthod 1969; 55:566. Moss ML: Genetics, epigenetics and causation. Am J Orthod 1981; 80:366-375. Petrovic AG: Experimental and cybernetic approaches to the mechanisms of action of functional appliances on mandibular growth, in McNamara lA lr, Ribbens KA (eds): Malocclusion and Ihe Periodonlium, monograph 15. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984, pp 213-268.
D. CONTROLLING CRANIOFACIAL
FACTORS IN GROWTH
Skelelon
71
a jaundiced eye, in McNamara lA lr (ed): Faclors Affecling Ihe Growth oflhe Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. McNamara lA lr: Functional determinants of craniofacial size and shape, in Carlson OS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981. Moss ML: The functional matrix, in Kraus BS, Riedel R (eds): Vistas in Orlhodontics. Philadelphia, Lea & Febiger, ]962; pp 85-98. Moss ML: The primary role of functional matrices in facial growth. Am J Orthod 1969; 55:566. Moss ML: An introduction to the neurobiology of orofacial growth, ACIa Biomelrica ]972; 21:236-259. Moss ML: Neurotrophic regulation of craniofacial growth, in McNamara lA lr (ed): Control Mechanisms in .Craniofacial Growlh, monograph 3. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. Moss ML: Genetics, epigenetics and causation. Am J Orthod ]981; 80:366-375. Carlson OS, McNamara lA lr (eds): Muscle Adaplalion in Ihe Craniofacial Region, monograph 8. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1978.
Disruptive Factors Orthodontic Forces
Behrents RG: Deja vu: Neurotrophism and the regulation of craniofacial growth, in McNamara lA lr (ed): Faclors Affecling Ihe Growlh of Ihe Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. Behrents RG, lohnston LE lr. The influence of the trigeminal nerve on facial growth and development. Am J Orlhod 1984; 85:199-206. McNamara lA lr (ed): Conlrol Mechanisms in Craniofacial Growlh, monograph 3. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. McNamara lA lr (ed): Delerminants of Mandibular Form and Growlh, monograph 4. Craniofacial Growth Series. Arln Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1974. Dixon AD, Sarnat BG (eds): The Inlernalional Conference on Faclors and Mechanisms Influencing Bone Growlh. New York, Alan R. Liss, 1982. Hagg U, Taranger l: Dental development assessed by tooth counts and its correlation to somatic development during puberty. Eur J Orthod 1984; 6:55-64. Hinton Rl: Form and function in the temporomandib\llar joint, in Carlson OS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981. Houston WlB: Relationships between skeletal maturity estimated from hand-wrist radiographs and the timing of the adolescent growth spurt. EurJ Orthod 1980; 2:81-93. lohnston LE lr: The functional matrix hypothesis: Reflections in
-..
McNamara lA lr, Ribbens KA, Howe RP (eds): Clinical Alleralion of Ihe Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983.
Surgery McNamara lA lr, Carlson OS, Ribbens KA (eds): The EffecI of Surgical Intervention on Craniofacial Growlh, monograph 12. Craniofacial Growth Series. An'n Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1982. Malfunction ¥cNamara lA lr (ed): Naso-Respiralory FunClion and Craniofacial Growlh, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979."
Gross Craniofacial Anomalies
0
B;r~sma (ed): Birth Defecls AIlas and Compendium. Baltimore, Williams & Wilkins, ]973. Bergsma 0, Langman l, Paul NW: Morphogenesis and Malformation of Face and Brain. The National Foundation 1975; XI:7. Converse lM, McCarthy lG, Wood-Smith 0 (eds): Symposium on Diagnosis and Trealmenl of Craniofacial Anomalies. St Louis, CV Mosby Co, 1979. Grabb WC, Rosenstein SW, Bzoch KR (eds): Clefl Lip and Palale. Boston, Little, Brown Co, 1971.
72
Growth and Development
E. REGIONAL DEVELOPMENT Cranial Vault Enlow OH: Handbook of Facial Growth, 2nd ed. Philadelphia, WB Saunders Co, 1982. Basicranium Bosma JF (ed): Development of the Basicranium, publ NIH 76989. US Department of Health, Education and Welfare, .Public Health Service, National Institutes of Health, Bethesda, Maryland, 1976. Enlow OH: Handbook of Facial Growth, 2nd ed. Philadelphia, WB Saunders Co, 1982.
Nasomaxillary
joint, in lrby WG (ed): Current Concepts in Oral Surgery. St Louis, CV Mosby, 1980. Carlson OS, McNamara JA Jr, Ribbens KA (eds): Developmental Aspects of Temporomandibular Joint Disorders, monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. Hinton RJ: Form and function in the temporomandibular joint, in Carlson OS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981. Hinton RJ, McNamara JA Jr: Temporal bone adaptations in response to protrusive function in juvenile and growing adult Rhesus monkeys (Macaca mulatta). Eur J Orthod 1984; 6: 155174. Moffett BC: The morphogenesis of the temporomandibular joint. AmJ Orthod 1966; 52:401-415.
Complex
Enlow OH: Handbook of Facial Growth, 2nd ed. Philadelphia, WB Saunders Co, 1982. McNamara JA Jr (ed): Factors Affecting the Growth of the Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. Mandible McNamara JA Jr (ed): Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. Enlow OH: Handbook of Facial Growth, 2nd ed. Philadelphia, WB Saunders Co, 1982. Kantomaa T: The Role of the Mandibular Condyle in the Facial Growth. Proc Finn Dent Soc 1984; 80:(suppl IX) I-57.
Temporomandibular
Joint
Carlson OS, McNamara JA Jr, Graber LW, et al. Experimantal studies of the growth and adaptation of the temporomandibular
F. OVERALL PATTERN OF CRANIOFACIAL GROWTH Enlow OH: Handbook of Facial Growth, 2nd ed. Philadelphia, WB Saunders, 1982. Solow B: Factor analysis of craniofacial variables, in Moyers RE, Krogman WM (eds): Craniofacial Growth in Man. Oxford, Pergamon Press, 1971.
H. " ADULT" CRANIOFACIAL
Behrents RG: Growth in the Aging Craniofacial Skeleton, monograph 17. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. Behrents RG: An atlas of Growth in the Aging Craniofacial Skeleton, monograph 18. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985.
~" ,'.
,.
GROWTH
"
:.. ..
CHAPTER
5 Maturation of the Orofacial Musculature Arthur T. Storey, D.D.S.,
Ph.D.
It is not easy to blow and swallow at the same time.PLAUTUS (Mostellaria, Act Ill, Scene ii)
KEY POINTS 1. The facial muscles not only provide expression but also contribute to the maintenance of facial and mandibular posture. 2. Posture of the head, mandible, tongue, and hyoid is interactive. 3. Mandibular movement is best perceived as movement of a free body manipulated in an intricate web of orofacial muscles with the teeth and joints acting as stops and guides . 4. Reflexes of the upper airway and alimentary tract are interactive. Protective reflexes preempt supportive reflexes. 5. Sophisticated instruments are available by which to study movement, force, and pressure resulting from orofacial muscle activity. 6. Forces exerted by orofacial muscles may arise from active tension, passive tension, or a combination of both. 7. The relative contribution of active tension to total tension in jaw muscles is different while one is awake or asleep. The ratios differ in facial muscles, which have no muscle spindles. 8. Reflexes of facial muscles appear to be initiated and modulated by cutaneous receptors, while reflexes of
jaw muscles originate in receptors around the teeth and in muscles and joints. 9. Closure into full intercuspation may be actively or passively guided. Long-standing active guidances may lead to alterations in jaw growth or to dysfunction. 10. Protrusion of the tongue in posture, a reflex response . to encroachment on the pharyngeal airway, can lead to altered tooth positions. 11. Forces in mastication normally do not move teeth; . indeed, vertical forces stabilize the teeth.
,
12. Swallowing, serving both an alimentary and an airway function, involves some muscles (obligate) which are tightly regulated in the~synergy; others (facultative) may be recruited. Obligate muscles are insensitive to fee
73
74
Growth and Development reflexes, position
but intercuspal position and retruded are in part actively determined.
contact
16. Retruded contact position is passively determined actively attained. This makes it the most reliable the registration positions if all passive stops are attained.
but of
17. There are no longitudinal studies on orofacial muscle growth. Limited studies on adaptation suggest that changes in functional length and adaptation in tendon and in muscle attachment to bone occur in the growing animal but not in the adult.
18.
Ontogenetic in sights into orofacial behavior patterns, although not well documented, provide useful clues in assessing normal development.
OUTLINE A.
Orofacial Muscles I. 2. 3.
B.
C.
I. 2.
Anatomic Functional
3.
a) Movement b) Force and pressure c) Electromyography Behavioral
Basic Concepts of Orofacial Neuromuscular Physiology
3.
4.
3.
Postural position Intercuspal position (usual occlusal position, centric occlusion) Retruded contact position
Growth and adaptation of orofacial muscles I. 2.
F.
Active and passive tension Simple orofacial reflexes a) Facial reflexes b) Jaw reflexes c) Tongue reflexes Complex orofacial reflexes a) Mastication b) Bruxism c) Swallowing d) Gagging e) Speech Learned and unlearned reflexes
·Reflexdeterminants of mandibular registration positions I. 2.
E.
Facial muscles Jaw muscles Portal muscles
Methods of Study
I. _ 2.
D.
muscles are often dIscussed by region, a somewhat artificial designation since orofacial behavior recognizes no regional boundaries. For exarnple, swallowing entails muscle activities in the facial, jaw, and portal regions: at both the sensory and motor level there is much interaction among regions.21 The facial musculature innervated by the seventh cranial nerve has as a major function that of expression. The jaw musculature innervated by the fifth cranial nerve is exemplified by masticatory function. Oral and pharyngeal muscles innervated by the fifth, ninth, and tenth cranial nerves collectively serve such important functions as respiration and alimentation. The standard anatomic description of a muscle includes its location, origin and insertion, action, innervation and blood supply, an approach appropriate for surgery, but in orthodontics, it is necessary to view the orofacial musculature in a different context to understand its effects on growth of the face and the effects of mal relation of jaws and facial structures on muscle activity. The emphasis in this section will be on the function of the orofacial musculature.
Structural Functional and behavioral
Interaction of orofacial muscles with development of the craniofacial skeleton and the dentition
A. OROFACIAL MUSCLES The orofacial muscles may be classified according to region, cranial nerve innervation, or function. Functions of the various
1. Facial Muscles The primary function of the facial muscles is expression of the emotions. Duchenne22 electrically stimulated these muscles in the human in an attempt to find the role of the individual muscle in the display of emotions. The expression of emotions in man and animals fascinated Charles Darwin,'8 who wrote one of the first books contending that behavioral patterns are as characteristic of a species as are its structural forms. The capacity for expressing affective states is highest developed in the human. Coleman17 contends the human is capable of 7,000 possible facial expressions. There is considerable racial and individual variability in the development of these muscles in the human, affording an anatomic basis for variability in facial expression.37 In addition to expression of emotions, these muscles are important in maintenance of posture of facial structures. Paresis of the orbicularis oculi leads to drooping of the lower eyelid and drying of the conjunctiva with subsequent inflammation. Paralysis of the orbicularis oris or muscles inserting into the corner of the mouth will lead to drooling and angular cheilosis. According to Proffitn the lip and buccinator muscles opposed by the tongue contribute to a postural equilibrium of the teeth. The facial muscles also contribute to stabilization of the mandible during infantile s~allowing and in chewing and swallowing in the edentulous and occlusally compromised adult. It is quite possible that postural alterations in the facial muscles may· contribute to structural changes in the jaws, as has been documented for alterations in postural activity of the mandibular muscles (see Section E). ., frankeF8 has speculated that the buccinator muscles exert a constraining force on the maxillary, alveolar process as well as the teeth. The demonstrated increase in arch width with the appliance bearing his name (see Chapter 18) is attributed to the buccal shields which hold the cheeks from the alveolar process and teeth. 54 Form also dictates function: patients with short upper lips or excessively proclined maxillary incisors compensate by elevation of the lower lip, through action of the mentalis muscle, to establish an anterior seal during swallowing (see Fig 10-3). Facial muscles also play an important role in both visual and spoken communication: a smile or frown is part of a universal language. Lip contact with
Maturation
of the Orofacial Musculature
75
opposing lip or teeth provides one-quarter of the articulations of the English language. Lips and cheeks are essential as well for bolus control in mastication; patients with facial palsies have problems with food accumulation in the labial and buccal vestibule of the affected side.
2. Jaw Muscles Jaw muscles are often designated as levators and depressors or protractors and retractors, but this classification of muscles acting as synergists or antagonists can be a handicap to a better understanding of their roles in posture and jaw muscle synergies. The simplest concept of neural control of mandibular posture is of the mandible maintained against gravity by the stretch reflex in tfie mandibular elevators. Electromyographic (EMG) studies of postural position have shown that the inframandibular group of muscles are more active than the levator muscles.58 (This can be interpreted as depressors opposing levators in the determination of posture of the mandible or as an indicator of muscle activity regulating the posture of the tongue and hyoid.) As will be shown later, it is wrong to think of posture of the mandible without thinking of posture of the tongue, hyoid complex, and other structures because all are intimately related. This concept of posture of the mandible involving posture of other structures can be extended to the head. Brodie'o conceived of head posture as determined by a chain of muscles ventral to the vertebral column opposed by another chain dorsal to the cervical' vertebrae. (The ventral chain would include the mandibular levators, the muscles connecting the mandible to the hyoid bone, and the muscles connecting the hyoid to the sternum.) Extension of the head results in an increase in freeway space, while flex ion results in a decrease'" Changes in head posture also affect the anteroposterior position of the mandible in postural position'" While the mandible is capable of a pure rotational movement early in opening and late in closure, studies have shown that normal opening and closing are never purely rotational.66. 88. 91The actual rotation centers are dorsal to the mandibular ramus and shift during opening and closing. This means that the opening and closing of the mandible can no longer be conceived as largely an interplay between levators and depressors. Mandibular movement is more accurately perceived as that of a free body manipull,lted in an intricate muscular web, with the teeth and joints acting as stops and guides. If it were not this way, patients with bilateral condylectomies could never chew. This concept of the jaw suspended in a web of muscles is helpful in understanding the mechanisms which bring about stabilization of the mandible in both chewing and swallowing. If there are marked deflective contacts in the teeth (e.g., "slides in centric" and "functional malocclusions"), the mandible is shifted to the position of maximal intercuspation, displacing one or both condyles from their ideal position. Such a displacement can only be accomplished by a complex interaction of all the muscles inserting onto the mandible. Before teeth arrive in the infant, mandibular stabilization is affected by synergistic activity of both levator and depressor muscles, and the facial muscles may be called upon to assist in the stabilization, for example, during swallowing. In this interactive web, muscles serve various functions: but the superior head of the lateral pterygoid muscle is illustrative of
-..
FIG 5-1. Moments for the two heads of the lateral pterygoid muscle at rest (postural position) and open positions computed about the instantaneous centers of rotation of the mandible. At postural position (R) the superior head (5) has a closing moment ( + 176) while the inferior head (J) has an opening moment ( - 756). At the open position (0) both heads have opening moments. (From Grant PG: Lateral pterygoid: Two muscles. AmJAnat 1973; 138:1-10. Used by permission.)
a muscle's multiple functions. CaJculationsofthis muscle's vector about the instantaneous center of rotation (see Fig 5-1) suggest that its action early in opening and late in closure is to stabilize the joint. 32 This hypothesis is further supported by EMG st~dies in both monkey'6. 8' and human (reference 42 and Williamson EI1, personal communication, March 1980). Through the remainder of, the mandible's range of motion, the muscle functions to distract the disc or check its return.'o Thus, the same muscle can act in two very different ways in a particular synergy. Probably the most important application of this field concept of muscle action relates to its effect on development of the jaws. The effect of postural activity is likely to be, more important than that of synergies such as mastication and swallowing.72 The alteration of mandibular, tongue, and hyoid position in mouth breathing changes the environment of both the mandible and maxilla and alters the way they grow. The" "long fa,ce syndrome," which Linder-Aronson45 associates with mouth-breathing, is a good example. Early treatment of functional posterior and anterior crossbites is advised to preveht eventual perpetuation in bone, yet the fdnhional protraction of the mandible in posture in Class II malocclusions,39 the so-called "Sunday bites," does not lead to skeletal correction. What is the difference in adaptive stimulus between a naturally occurring protrusive posture and that resulting from a functional appliance? We do not know, but finding out would have great clinical consequence. Perhaps it is the frequent return of the mandible to a more dorsal position during mastication and swallowing which cancels the biologic signals to joint structures to adapt. Perhaps this is why the functional appliances which are worn the most hours per day seem to work best. These are tan-
76
Growth and Development
TABLE 5-1. Effector Sites Giving Rise to Supportive and Protective Reflexes of
A fi'"
SITE
EFFECTOR the Upper Airway and AlimentarySUPPORTIVE Tract SITES
REFLEXES
PROTECTIVE'>"'" REFLEXES
Upper airway
Nose Pharynx
Sniffing Airway maintenance Airway maintenance
Apnea, sneezing Sniffling
Suckling Mastication Swallowing Swallowing
Spitting
Larynx
Alimentary tract
Mouth Pharynx Esophagus
Apnea Glottic closure Swallowing Coughing
8 GENIOGLOSSus
MASSETER
I
. ,•
Mass
ORIS ORBiCuLARIS
00
Gagging Vomiting
•
8
talizing questions for the investigator condylar growth.
of control mechanisms
B
on
B
3. Portal Muscles The term "portal area" was coined by Bosma7 to denote the upper alimentary and respiratory tracts. The muscles of the portal area serve the multiple functions of posture, respiration, and feeding. Portal muscles include the muscles of the tongue (both intrinsic and extrinsic), the soft palate, the pharyngeal pillars, the pharynx proper, and the larynx. It is the crossing of these tracts in the pharynx that requires special reflex controls for maintenance and protection. Complex neural controls are necessary to allow only the most important reflex to occupy the portal area at one time. Reflexes of the oropharynx must support a patent airway during respiration and provide a pressure gradient during swallowing. If foreign substances gain accidental access to either the alimentary· or the respiratory tract, protective reflexes must be called into play, for example, retching and coughing. A more complete listing of portal reflexes if given in Table 5- I. Each effector site is capable of giving rise to several reflexes-with some reflexes, such as swallowing, engaging more than one site. The two portal.reflexes of greatest significance to orthodontics are pharyngeal airway maintenance and swallowing. (A discussion of swallowing is found in Section C.) An important anatomic feature of the respiratory pharynx is its ventral wall, which is formed by the base of the tongue. If the tongue is large for the space enclosing it, the tongue might be expected to spill into the pharynx. Only in the infantile syndrome of Robin and in sleep apneas does this happen, with great risJc for the patient. Otherwise the tongue is postured forWard or bucplly, leading to anterior or posterior open bites. (It is posture of the tongue rather than thrusting in swallowing which accounts for this kind of open bite when it occurs. See Section C-4). Anterior open bites have also been shown to be associated with large tongue-totongue space ratios. S2 Subjects with anterior open bites have very active tongue protraction reflexes4s (see Fig 5-2). This finding explains well the role of the tongue in open bites associated with a history of thumb-sucking. The thumb-sucking may create an
B
FIG 5-2. Histograms of muscle activity in normal (A) and open bite (B) subjects on opening to maximum (vertical line B-B). GG, Mass, and 00 indicate threshold increase in electrical activity (20% of baseline). Note that in the subject with normal occlusion the increase in genioglossus activity begins late and is small while in the subject with the open bite the increased activity occurs early in opening and is very large. Vertical calibration, 250 mV; horizontal calibration, 1.0 second. (From Lowe AA, Johnston WO: Tongue and jaw muscle activity in response to mandibular rotations in a sample of normal and anterior open-bite subjects. Am J Orthod 1979; 76:565-576. Used by permission.)
open bite, while the tongue activity maintains it (Chapters 7 and
10).;'·
B.METHODSOFSTUDY 1. Anatomic The oldest method of studying muscle is gross dissection. The shape, boundaries, origin, and insertion provide insight into the possible force vectors of the muscle; but estimated force vectors for the whole muscle have limited value in predicting the real force
Maturation vl
studies
it has been found
(Eriksson25) that the temporalis, the masseter, the anterior medial pterygoid, and the lateral pterygoid muscles are 75% composed of type I fibers (based on cross-sectional areas). While this suggests that these muscles are primarily responsible for posture of the mandible, it is quite likely that these fibers also perform most of the modest work entailed in mastication of a modem soft diet.
Type IIA fibers are found in significant proportions (30%) only in the digastric muscle. Type lIB fibers, which are found in all jaw muscles, are present in the highest proportion (45%) in the superior posterior temporalis, posterior medial pterygoid, and anterior digastric muscles. The mix of fiber types is quite different between the digastric and lateral pterygoid muscles, both of which are jaw depressors, but not between the two heads of the lateral pterygoid (Eriksson25). These and other studies on the jaw muscles of man have shown that the size and proportions of the different types are not the same as in limb muscles. The jaw muscles display a broad spectrum of types which are highly adaptive to the functional demands placed on them. While type 11 fibers are significantly larger in human subjects with high biting forces (RingqvisC9), there appears to be no significant adaptation in fiber size or distribution
of the Orofacial Musculature
77
to the state of the occlusion assessed by numbers of opposing contacts (Ringqvist8o). The specification of fiber types is not solely determined by function since differentiation into the two major fiber types occurs at 20 to 23 weeks gestation (Ringqvist et al."). One wonders about the effects of functional orthodontic treatment on fiber types, but this is impossible to state because of the heterogenous character of jaw muscles and the obvious technical difficulties in making such a determination.
2. Functional a) Movement The study of movement resulting from muscle action is an old and respected field designated kinesiology. This scientific discipline is not to be confused with the chiropractic fad which, sadly, has adopted the same name but which has as a major goal the optimizing of muscle performance through various muscle, dental, and skull manipulations. Movement of facial structures has been a favorite subject since the invention of recording on moving film. The technology of topographic mapping can be adapted to the study of the face in repose. Observing the movement of a shadow grid projected onto the face during activity of the facial musculature is an old technique which has been updated using Moire fringe and computer tech· nologies.23 Movement of facial structures can also be explored in three dimensions by holography. One of the first techniques for movement studies of the mandible was to record on moving film the movement of a small ball or a light projecting from the mandibular incisors. This principle has been updated so that a small 'magnet attached to the lower incisors is tracked by three magnetometers and movement displayed in three planes of space on a storage cathode ray oscilloscope or x-y recorder. 36 Another system uses clutches on both the jaws and displacement transducers to simulate movement of models of the teeth.97 Still another uses light-emitting diodes affixed to the teeth and tracked by two special cameras with coordinate sensors to display three-dimensional movement of any point of the mandible, including the condyle.4I Movement of the mandible and the portal structures can be visualized in cineradiographs, landmarks can be digitized, and alterations in position or shape quantified. This tool has been most helpful in understanding the movements associated with swallowing. 16 b) Force and Pressure Other parameters which can be used to assess the activities of orofacial muscles are those of force and pressure. Pressures of the lips, cheeks, and tongue against the teeth have been measured by a number of investig';l.tors using strain gauges (e.g., ProffiC3). Mas!icatory, swallowing, and maximal biting forces have been recorded on the teeth, for exampl'e by Graf and coworkers.3I Pressure transducers are an important tool in studying pressure gradients in the upper alimentary tract during swallowing. Warren96 has developed an instrument which permits simultaneous recording of air flow through both the nose and the mouth. c) Electromyography The instrument most often used for evaluating the activity of orofacial muscles is the electromyograph. Although it is possible
78
Growth and Development
to measure other parameters of muscle activity (e.g., change in tension, heat production), the electrical activity is the easiest to record .. Electrodes may be placed on the skin over the muscle or inserted into the body of the muscle. Electrode type can be selected so as to study a large portion of the muscle or a few motor units in a specific region. Surface electrodes record from a larger population of muscle fibers than do needle electrodes. Both types of electrodes record the membrane action potentials from the several to many fibers in a single motor unit which arrive at the electrode at different times, giving a unique signature to that unit as long as the electrode is not moved. This permits the investigator to study the behavior of individual units and how the units are recruited. Figure 5-3 illustrates the manner in which force is increased by an increase in frequency of firing units (temporal summation) and by the addition of other units (quantal summation). As more and more units are added and units fire at greater frequencies, the action potentials from the various units merge together and' produce the typical electromyogram. At high force levels, the interaction of both negatively and positively going action potentials (the "interference pattern") leads to a leveling off of the electromyogram so that the linear relationship between force generated and EMG amplitude in isometric contraction no longer
holds. The electromyogram can be quantified by measuring either the height of the action potentials or the frequency of the individual action potentials. At high levels of activity, when action potential spikes are superimposed, frequency counts become inaccurate. Although electromyography can give useful information on whether a muscle is active and define when the activity begins and ends in the muscle fibers sampled, it is impossible to know how much activity in the muscle is being missed. Movement cannot be inferred from the electromyograph alone for reasons already discussed: antagonistic muscles may be working synergistically to control the movement or provide stabilization. Other instruments monitoring force, pressure, or position must be used in conjuction with the electromyograph to correlate muscle activity with effect. The author of this text was one of the first to use the electromyogram in the study of the orofacial muscles,63 opening up a field in which much work has been done and continues. Our growing knowledge of the role of the orofacial muscles in posture and movement, of reflexes regulating these muscles, and of muscle pattern changes in dysfunction becomes increasingly useful to the clinician. The study by Lowe and 'lohnston48 in which a high correlation was shown beween early EMG activity in the genioglossus muscle and open bite is an example of clinical insights to be gained from electromyography.
3. Behavioral
FIG 5-3.
Whi1e the experimental methods of anatomy and physiology provide rigorous procedures for studying orofacial muscle function, there are obvious limitations in applications to humans. Disciplined observation of behavior can be very useful; it is noninvasive and examines total muscle activity in the natural state. The acquisition of complex patterns of behavior may be looked upon by analogy to a tree. According to the concepts of Windle, 100 discrete reflexes become aggregated into increasingly complicated patterns of behavior. The branches and twigs are consolidated into the trunk. An alternative concept is suggested by the development of behavior in human fetuses, where gross behavior such as head flexure or jaw opening precedes more discrete behavior such as tongue and eyelid reflexes38 To the trunk of the tree are added the branches and the twigs, Mastication can be visualized as a consolidation of simple elements such as jaw opening, jaw closing, ja-Y' translation, tongue protraction, and tongue retraction into a more elaborate synergy according to the model of Windle. Other behavior, such as swallowing, appears to emerge as a fully developed reflex to which other elements are aldded. As is often the case, orofacial behavior cannot be forced into a single mold, and
A diagrammatic representation of the mechanism whereby tension (dotted line) is increased in striated muscle, The upper three traces (Units A, B, and C) represent the action potentials recorded separately from three motor units of different thresholds with a needle electrode in the muscle, At minimal tension, only Unit A fires (at far left of trace). As activation increases to produce an increase in tension, Unit A fires at an increasing frequency (temporal summation) and Unit B, and later Unit C, begin to fire (quantal summation). Units Band C also demonstrate temporal summation. The bottom trace illustrates how the three units would appear as usually seen in an electromyogram recorded from the skin overlying these motor units,
may fit either concept or ,~ combination of both. '. In all animals, it appears that some behavior is predetermined and u~learned. Nest building of birtls is predetermined while singing is learned from birds of the same species. Life-sustaining behavior such as ventilation and swallowing are usually considered predetermined, yet the exclusive cortical control of respiration in sea mammals and the early "respiratory" movements of the fetus in utero suggest that ventilation may indeed be learned, The boluspropelling component of swallowing appears to be predetermined while the anterior seal and stabilization components are learned.
Unit
B
Units
I
A,B&C
~~
I
,
... ...•...
Maturation
of the Orofacial Musculature
79
Those elements of behavior which are congenital are less easily alteredt by training than are those which are learned during develqpment or through life. Attempts to alter the bolus-propelling components of swallowing by training will be unsuccessful whereas the anterior seal and stabilization components can be changed by training as well as by altering the sensory feedback from the structures modified by orthodontic treatment (see Chapters IQ and 18). Myofunctional therapy directed at the role of the tongue in bolus handling is likely to be unsuccessful. There are no adequately controlled, reliably measured clinical studies of success of such therapy.
C. BASIC CONCEPTS OF OROF ACIAL NEUROMUSCULAR PHYSIOLOGY 1. Active and Passive Tension ~ When a muscle is stretched, the tension in that muscle increases. This increase in tension may be the result of reflex contraction of the muscle. If the muscle contains sensory organs called muscle spindles, the elongation of the spindle excites the spindle afferents, which synapse on motor neurons innervating the gross muscle (extnifusal fibers), resulting in their contraction. This is the classic stretch reflex. The spindle afferents can be segregated into at least two types (nuclear bag or primary and nuclear chain or secondary endings) which are preferentially sensitive to a sudden (phasic) stretch or a prolonged (tonic) stretch. Since all the mandibular levator muscles possess spindles,21 this mechanism can occur with stretch of these muscles. This tension resulting from ~ contraction of muscle tissue is called active tension. In this example it is the result of reflex activity, but can also be increased by willed contraction of the muscles as in volitional clenching of the teeth. Since the facial muscles possess I;lospindles,21 stretching of facial muscles will not elicit a stretcfi" re"flex. Nevertheless, the tension .in these muscles will increase with elongation because of the elastic properties of muscle and its investing tissues. Tension which results from the physical properties alone of the tissue is called passive tension. In many muscles, elongation will result in an increase in both active and passive tension. The sum of both tensions is appropriately called total tension. The curves for all three tensions, as the length of the muscle is increased, is illustrated in Figure 5-4 for an innervated limb muscle. Below a specific length, all the tensions are zero. As the muscle is stretched, the active tension increases. In a muscle containing spindles, this has been attributed to the stretch reflex. Initially, there is no passive tension, so that total tension is equal to active tension. As the stretching increases, the muscle begins to behave elastically: passive tension now begins to add to total tension. As the muscle is elongated further, active tension is inhibited while passive tension continues to increase. On further stretching, active tension is suppressed as passive tension rises exponentially. At this length, total tension is the same as passive tension. The active tension curve may be due In part to the extent to which the actin and myosin filaments overlap. The generation of active tension falls off if the overlap is excessive or inadequate. In Figure 5-5 this relationship between the degree of filament overlap and tension development is depicted .
;;; ;
z o ;;; z ~ .. --Total Tension •...••.••.•..•••.. Active Tension ._. Passive Tension
",II'Ii I .I.,,, I •
..,. ~ ,.'
'f
..... ·1 MUSClE
,,
~
LENGTH
FIG 5-4. The relationship of tension to muscle length in innervated skeletal muscle. Total tension which increases with length is the sum of active and passive tensions. Active tension is due to the contraction of muscle (stretch reflex in the example 'given in the text) while passive tension is due to the viscoelastic properties of the muscle and its investing tissues. Note that at short muscle lengths the tension is all active while at long lengths it is all passive. Vertical dashed line is optimal length of muscle for generation of maximal active tension. For the innervated limb in Figure 5-4, the decline in active tension with increasing muscle length is due to initiate inhibitory reflexes suppressing the contraction brought about by excitation of spindle afferents. In limb muscle, this inhibitory reflex may be the result of excitation of Golgi tendon organs giving rise to the inverse stretch reflex. Many treatment procedures in orthodontics result in elongation of jaw and facial muscles. Expansion of the dental arches stretches the cheeks or lips and increases tension in the buccinator and orbicularis oris muscles. Increasing the occlusal vertical di-
1.0
oz (f) Z
•••.0.5
I&l
~ LENGTH ACTI
N
z
FIG 5-5. Diagram to illustrate the'mechanism whereby maximal active tension is generated at an optimal length, (vertical dashed line). The length tension curve at the top of the figure is the same as the active tension curve in Figure 5-4. At this length the active filament in the bottom of the figure optimally overlaps the myosin filament within a sarcomere muscle segment between Z lines. If the muscle is lengthened the active filament overlaps less of the myosin filament and force generation is reduced. Ifthe muscle is shortened the active fiber can be visualized as buckling so that the interface between the filaments is unable to generate maximal tension. (From Elftman H: Biomechanics of muscle with particular application to studies of gait. J Bone Joint Surg 1966; 48A:363-377. Used by permission.)
•
80
Growth and Development
mension in closed-bite
malocclusions
will stretch in the levator
muscles. Appliances such as bite planes and activators which increase vertical dimension and/or advance the mandible increase tensions in both levator and retractor muscles. Habits such as mouth-breathing, which increase the postural vertical dimension, increase tension in levator muscles, Surgical procedures which set back or advance the mandible or impact the maxilla profoundly affect muscle length and increase or decrease tensions in muscles of the face, mandible, and the hyoid complex. Why are treatment procedures which change muscle length successful in some malocclusions and not in others? Why does increasing vertical face height in faces with acute gonial angles tend to cause relapse as does surgical advancement of the mandible with a closing rotation? Why can contact and postural vertical dimension be increased with impunity in growing patients but not in adults? Are the length tension curves different for the levator muscles in a Iong face compared with those in a short face? Tabary and coworkers92 have shown that the passive tension curve of limb muscle does not change following immobilization in a lengthened position. Following immobilization in a shortened position, extensibility is decreased, that is, shortened muscles are less elastic. Only a beginning has been made in characterizing the active/passive tension curves for levator muscles in mammals. Exploratory work on the combined jaw levators in humans confirms that the active tension rises then falls with increase in length as with limb muscle, but no data on differences between subjects with skeletal malrelationships have been reported. Since the stretch reflex is attenuated or abolished in jaw muscles during sleep, passive tension is the major motor force generated in these muscles by functional appliances at night. On a theoretical basis, it would seem reasonable to expect that the contribution of active tension to total tension in facial muscles would be different from that in jaw muscles since facial muscles contain no spindles. Characterization of the active and passive tension curves in lips and cheeks might be indicative of the extent to which expansion could be used in treatment.
2. Simple Orofacial Reflexes No attempt will be made here to review the basic physiology of those reflexes which are arbitrarily designated as simple. Only those aspects of clinical relevance will be discussed. a) Facial Reflexes Reference was made in the previous section to the question of the extent to which passive and active tensions contribute to the total tension exerted by the lips on the teeth. A perioral reflex, which can be elicited by brief mechanical or electric~1 stimu'lation of the lips, has been postulated as playing a role in voluntary lip motor control in speech.53 This reflex is probably initiated from cutaneous receptors in the lips. Sustained stretching produces no reflex response,6' which is not surprising as there are no muscle spindles in the orbicularis oris muscle. In a study (M0ller, unpublished data) of upper and lower lip postural activity and facial form, the only sig!1ificant correlation was between lower lip EMG and lower face height. This reflex activity is undoubtedly due to the mentalis muscle acting to effect an anterior lip seal. Baril and Moyers' demonstrated that the men-
talis reflex is suppressed by contact of the lower lip with an acrylic projection added to an oral shield at the level of the mandibular alveolar process (see Fig 18-40). Reflexes of both the orbicularis oris and the mentalis muscles appear to be largely determined by excitation of cutaneous receptors.
b) Jaw Reflexes Simple jaw reflexes can be conveniently divided into vertical (jaw closing and opening) and horizontal (anteroposterior and lateral) categories. Because of the occlusal consequences, the jaw closing and lateral reflexes are particularly relevant to orthodontic treatment. Although it has been known for a long time that receptors in and around the teeth protect the teeth from excessive loading (negative feedback), it can be shown that the same receptors may increase occlusal loading (positive feedback).49 EMG studies 101 and occlusal force studies'o have shown that jaw position determines whether the jaw closing reflex will be enhanced or suppressed. Contact on anterior teeth alone suppresses biting force while contact alone on posterior teeth increases biting force. Contact of teeth on the balancing (nonworking) side suppresses biting force while contact on the working side enhances biting force. The forces are attenuated on the side (or sides) where condylar translation occurs (i.e., heavy biting force is avoided when the joint has to be stabilized by muscle activity). These jaw position determinants of closing forces have been suggested as a rationale for cuspid-guided or mutually protected occlusal schemes: the forces on the "guiding" or "protecting" teeth are less if in the anterior rather than posterior segments. Williamson and Lundqvist98 have shown that anterior guidance which discludes posterior teeth suppresses levator contractions. Mechanical stimulation of orofacial as well as other body sites leads briefly to a cessation of ongoing muscle activity in jaw levators as well as depressors."" 101 If the stimulus is non-noxious, the duration of this silent period is about 20 msec. If the stimulus is painful, the duration is prolonged. Patients suffering from orofacial pain frequently have prolonged silent periods but these silent periods are not unique to one pain syndrome.'2 The prolonged silent period may be indicative of a depressed pain threshold. Useful insight into lateral jaw reflexes comes from studies in which occlusal interferences are removed from or artificially introduced into the occlusal scheme. When an occlusal interference is incorporated into the dentition so that it occurs on the working side, reflex responses to the interference rarely occur."' Closure from initial contact on the working side during chewing is usually passively or nonreflexly guided by the tooth inclines. That is, the occlusal guidance is passive (see Fig 5-6,A). On the other hand, when a balancing occlusal interference is incorporated into the demi.tion, nearly half of the closures are actively or reflexly guided into loll intercuspation. On initial, contact of the balancing interference, the levator muscles fall silent briefly (silent period), then asymmetrically contract to shift the mandible laterally to avoid the interference. That is, the occlusal guidance is active (see Fig 56,B). This lateral reflex initially is unlearned or unconditioned. Following multiple contacts on the interference, the offending contact may be avoided through conditioning (Fig 5-6,C). When the lateral shift on closure from retruded contact position into intercuspal position is small it is sometimes referred to asa "slide in centric"; when larger, as a functional posterior crossbite. Some-
Maturation A
PASSIVE
B
GUIDANCE
ACTIVE
GUIDANCE
C
a) unconditioned
FIG
ACTIVE
5-6.
inclines. B, a balancing side contact elicits a reflex response (zigzag arrow). On initial contact muscle activity ceases (silent period) followed by a lateral jaw reflex avoiding further cuspal contact on closure into intercuspal position. C, in time the balancing contact may become avoided on closure into intercuspal position. (From Storey AT: The neurobiology of occlusion, in Johnston LE Jr (ed): New Vistas Philadelphia,
Lea & Febiger,
1985.
Used
81
has a significant effect on digestion in the human. Studies have shown that masticatory efficiency makes little difference to the degree of digestion except for poorly digestible foods such as fried meat and legumes. 26 What appears of significance to orthodontic treatment are the magnitude and direction of the occlusal forces in mastication and the extent to which these forces contribute to
GUIDANCE
b) conditioned
Occlusal guidances may be active or passive. A, a working side contact between opposing buccal cusps elicits no reflex response (straight arrow). The closure to intercuspal position is along cuspal
in Orthodontics, permission.)
of the Orofacial Musculature
by
times the conditioning seems to affect the postural position, since the path of closure from postural position to intercuspal position may demonstrate no lateral deviation. Examples of EMG studies before and after occlusal equilibration are shown in Figures 1866 and 18-67, where procedures for equilibrating functional crossbites in the primary and early mixed dentition are also discussed. Lateral jaw reflexes may lead to skeletal asymmetries in the growing child or to temporomandibular disorders in susceptible patients.
c) Tongue Reflexes Of the simple tongue reflexes, that of most significance to orthodontic diagnosis and treatment is tongue posture. Reflex control of tongue posture is essential for maintenance of the pharyngeal airway and plays an important role in the position of the teeth. It is not surprising that the demands of the airway may reflexly alter tongue po:>ture and consequently tooth positions. The base of the tongue forms the anterior wall of the pharynx which serves as the portal for both the alimentary tra):t and the airway (see Section A-3). Maintenance of the pharyngeal airway demands that the tongue base not be allowed to intrude into this airway. This vital function is performed by the genioglossus muscle. EMG studies of this muscle show a small activity in synchrony with respiration. The genioglossus reflex may be initiated by a large tongue or large tonsils or it may also be initiated by jaw opening.48 Sustained jaw opening, as in mouth-breathing, leads to sustained tongue protraction. Such forward posturing of the tongue may force incisor teeth labially or prevent eruption of mandibular incisors if the tongue rests over the incisal edges. Large tongues may spill over the buccal teeth, preventing their eruption, and may produce a posterior open bite or a deep overbite.
tooth movement or tooth stability .. That the teeth make contact during chewing has been unequivocally proven21 even though claims to the contrary still appear in the dental literature. Position of the teeth is thought to be determined by forces of occlusion as well as lip or tongue pressures and eruption.72 Since the teeth are apart most of the time and yet possess the capability of eruption through life, occlusal contacts, intermittent though they are, must account for the vertical stability of tooth position. Continuing vertical movement of a tooth ("passive eruption") following loss of antagonists is a clinical observation supporting this hypothesis. Use of a functional appliance or a maxillary appliance with a flat anterior bite plane to permit eruption of posterior teeth offers further validation. One may ask whether masticatory occlusal forces can move teeth. If so, orthodontic treatment need only approximate the correct position of a cusp in a fossa and occlusal forces will' cause the teeth to settle into the best occlusal relationship possible. The few experimental studies in animals and man fail to answer this question because the forces are either interrupted' continuous forces or have a significant continuous component. 89 Unpublished studies by the writer of this chapter and coinvestigators in Bern, Switzerland, suggest that if the occlusal force on the tooth with an occlusal interference does not elicit either a lateral jaw refleX or suppression of the jaw-closing reflex, the intermittent forces of mastication and swallowing will cause the tooth to move if there are no constraints on that tooth's ability to move. If the occlusal force is such that simple jaw reflexes are evoked, the interfering tooth is avoided and tooth movement does not occur. Since teeth normally are stable, masticatory occlusal forces ordinarily do not move teeth, but in some parafunctions, such as bruxism, occlusal forces may produce tooth mobility and movement. The question why the protective simple jaw reflexes are inactive in parafunctions is a tantalizing one.
b) Bruxism Tooth clenching and grinding (bruxism) are usually considered parafunctions of the adult and are thought to result from physiological stress with or without occlusal interferences. Bruxism, however, is also found in children and has alleged associations with allergies, asthma, ")digestive upsets," "nervousness," and other conditipns (see Chapters 7 and 10). Its signs and symptoms ci;ln be artificially induced by sustained tooth clenching. 15 While the"pain is initially of muscle origin, the hyperactivity responsible for the pain may have a variety of etiologies.21 Genetic factors have been shown to be important in the genesis and pattern of bruxism in children46 (see Chapter 6). The relationships, if any, between bruxism in childhood and later life are not known, nor are longitudinal studies available.
3. Complex Orofacial Reflexes a) Mastication
c) Swallowing
There is little evidence to indicate that the extent of chewing
As in the case of mastication,
the features of swallowing of
82
Growth and Development
TABLE 5-2. Requirements of Swallowing Pressure Gradient ongue piS on ac Ion Stab,ilzatton of tongue base T . t l'
Genioglossus Facial muscles L eva tor musc Ies {MUSCles in floor of mouth
Pharyngeal constrictors: stripping action Esophagus: peristalsis Prevention of Reflux Incisors
Anterior oral seal
Orbicularis
Oris
Temporalis
fLipS Tongue palate apposition Hypopharyngeal sphincter Gastroesophageal sphincter Protection of Airway Palate/Pharyngeal wall opposition Elevation of larynx Adduction 'of vocal folds Apnea
l Tongue Masseter
Mylohyoid
Geniohyoid
most significance to orthodontic treatment are the role of occlusal and tongue forces in establishing tooth position. Occlusal forces in swallowing have received less attention than those in mastication but appear to be of the same magnitude as those in chewing2. 30 (The implications for tooth position are the same as in chewing.) As seen in Table 5-1, swallowing is both an alimentary and a protective reflex. It can be initiated reflexly by mechanical stimulation by a bolus in the pharynx and by chemical stimulation. by water in the larynx. The swallow evoked in the larynx also protects the airway against further penetration. Abnormalities of swallowing can be differentiated into vagaries of either the alimentary or airway reflex. Because swallowing serves an airway protective role, it is not surprising that it is rigorously programmed. There are three essential features of swallowing (Table 5-2): (I) establishment of a pressure gradient, (2) prevention of reflux, and (3) protection of the airway. The muscles responsible for these essential features are characterized by an al!-or-none participation and rigid sequencing of contractions insensitive to feedback-the obligate muscles. 2\ Once the swallow has begun, all the muscles participate in their stereotyped way (see Fig 10-15). ' In contrast to the obligate muscles of swallowing are muscles which participate more loosely in the synergy-the facultative muscles (see Fig 10-15). Facultative muscles serve the function of stabilizing the tongue base and establishing an anterior oral seal. They mayor may not participate in swallowing, and if they do so, may participate in varying degrees. They are very sensitive to feedback, especially from the teeth. The extent to which the facultative muscles participate depends on the need for stabilization of the tongue base and the adequacy of lips and teeth to effect an anterior oral seal. When one is swallowing liquids or saliva, the tongue requires less stabilization than when one is swallowing solid boluses; there may be little or no contraction of facial and mandibular levator muscles. When one is swallowing a solid bolus, stabilization of the mandible as well as the tongue base may be required. When teeth are present and in acceptable occlusion, the levator muscles will
Posterior
Tongue
Palatopharyngeus.
Superior
Constrictor
FIG 5-7. Schematic summary of electromyographic activity in obligate (dark silhouettes) and facultative (stippled silhouettes) muscles during swallowing. The obligate muscles participate rigidly in the synergy whereas the facultative muscles' participation is variable. Classification of the genioglossus muscle (open silhouette) has yet to be determined. (From Dubner R, Sessle BJ, Storey AT: The Neural Basis of Oral and Facial Function. New York, Plenum Press, 1978. Used by permission.) bring the teeth together in swallowing. When teeth are absent or create occlusal disharmonies in intercuspation, the facial muscles will stabilize the mandible.63 (See Chapter 10 for the clinical signifjcance of these variants of swallowing.) While the obligate muscles are programmed prior to birth and incapable of conditioning, the facultative muscles adapt to naturally occurring stimuli (e.g., bolus consistency, occlusal interferences) and to training procedures. The action pattern of..the genioglossus, the protractor of the ton~u.~, is left unfilled in Figure 5-7 because it is not yet clear whether it is obligate or facultative: It may even vary from patient to patient. Should the muscle be obligate, training programs to correct tongue-thrust swallows would not be indicated; should the muscle be facultative, the rationale for tongue training to correct a tongue-thrust would seem more logical (but see Section C-4). d) Gagging Gagging is a reflex initiated from the oropharynx and may be regarded as protective of either the upper alimentary tract or
Maturation the airway. The afferent arm of the reflex is not exclusively in .the glossopharyngeal nerve4: the trigeminal nerve would appear also be to involved in troublesome gaggers. The reflexogenic sites (e.g., faucial pillars, base of tongue, soft palate, and posterior pharyngeal wall) are normally in contact with each other .ilnd the food bolus but do not give rise to gagging under these conditions. An explanation for this refractoriness might suggest new strategies for suppression of gagging. Since central vagal stimulation has been shown to suppress pharyngeal motor activity in dogs thought to be gagging,13 maneuvers increasing central vagal discharge, for example, holding the breath in deep inspiration, might be expected to suppress gagging during the taking of dental impres·sions. Gagging is readily conditioned: a previously neutral stimulus, such as the sight of a loaded dental impression tray approaching the mouth, can lead to gagging in the problem gagger.
e) Speech Speech problems which may be improved by orthodontics are those of faulty articulation. The articulatory valves most likely to be drawn to the attention of the dentist for correction are the velopharyngeal valve and the labiodental, linguodental, and linguoalveolar valves. Velopharyngeal incompetence may be due to absence of structure (e.g., cleft palate), disproportion of structure (e.g., short palate, deep nasopharynx, short functional palate), or neurologic defects (e.g., muscle or central nervous system) (see Fig 5-8).
SHORT
SOFT
of the Orofacial Musculature
83
The velopharyngeal valve not only closes to protect the nasal passages from bolus entry during swallowing but also during all voiced sounds in the English language except for rn, nand ng. With velopharyngeal incompetence, speech is hypemasal. Treatment of velopharyngeal incompetence may involve the dentist along with the plastic surgeon and speech therapist. The dentist may be required to construct a speech bulb (in case of cleft palate, short palate) or palatal lift appliance (in cases of neuromuscular defect). In patients with short palates, tonsillectomy and adenoidectomy should be avoided if at all possible to minimize the risk of velopharyngeal incompetence. The articulatory valves involving dental and alveolar structures represent about one-third of the articulations in the English and v, the linguodental th language. These are the labiodentals (both voiced and unvoiced), and the linguoalveolar sounds t, d, s, sh, and I. Dentists may be requested by speech therapists to treat malposed teeth or provide replacements for missing teeth in order to improve articulation. While this may be helpful, especially during the years when speaking skills are being learned, Travis has pointed out that "abnormalities of orofacial structures cannot of themselves along be considered as prime causes of defective articulation. "94 There is evidence of considerable adaptability in the use of the lips and tongue in compensating for dental malformations. For example, a subject with missing maxillary incisors may articulate the sound using upper lip and mandibular incisors instead of the usual apposition of the lower lip and maxillary
f
f
PALATE
DEEP
PHARYNX
~ .0 .•
~.'t-
'IlL..
t'"
.;Co ., i~••"
NEUROMUSCULAR
DEFICITS
FIG 5-8. Velopharyngeal incompetency may be due to structural or functional deficiencies. The soft palate may be short (A) or the pharynx deep (8). Valving may also be jeopardized by varying degrees of muscle dysfunction (C and D). (From Warren DW: Aerodynamic studies of upper airway: Implications for growth, breathing, and speech, in
SHORT
FUNCTIONAL
PALATE
McNamara JA Jr (ed): Naso-respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1979. Used by permission.)
84
Growth and Development
incisors. While certain skeletal malocclusions are more likely to impair speech, it is not inevitable: one micrognathic may be unintelligible, another may be a radio announcer. While lisping is often associated with tongue-thrust swallowing, Fletcher et al. 27 found it in only one-third of their sample of abnormal swallowers aged 6 to 18 years. As with tongue-thrusting, sibilant distortion spontaneously improves with age.
4. Learned and Unlearned Reflexes In previous sections, examples have been given .of learned and unlearned reflexes of the orofacial region. Swallowing, encompassing the obligate muscles, is an unlearned reflex. The basis for ~o designating the reflex is as follows: a) The reflex is fully functional early in fetal life. b) The muscles are insensitive to feedback. c) The 'reflex is all-or-none. Since the reflex necessitates a precise regulation of a number of muscles, it must be programmed in a rigid sequence. It is not surprising that the reflex is unlearned. On the other hand, the facultative muscles, which play a role in forming an anterior oral seal and stabilizing the tongue base, are more varied in their participation. They also contribute to jaw stabilization prior to eruption of the teeth. This portion of the reflex can be said to be learned. Anterior open bites, short upper lips, and marked overjets can lead to varying learned or conditioned muscle responses. The genioglossus reflex, which protects the pharyngeal airway from obstruction, would be expected to fit into the classification of unlearned reflexes. Posture of the tongue, as has been pointed out earlier, is tightly tied to posture of the mandible. Jaw opening (a change in posture) initiates tongue protrusion through excitation of temporomandibular jaw receptors. Local anesthetic injected into the joint capsules bilaterally in the cat and monkey abolishes the genioglossus reflex.4? Since the reflex is much more active in subjects with relatively large tongues, it may be that the jaw-opening reflex is unlearned and that tongue protrusion is learned. If this is so, tongue posturing should be amenable to conditioning. Current treatment with this objective includes the use of cribs and myofunctional therapy (see Chapter 18). ' Cribs and myofunctional therapy, in the past, have been primarily directed at tongue-thrusting and swallowing. Since swallowing occurs, on average, 600 times per day44 (higher frequencies are extrapolations and erroneous), and the oropharyngeal duration of swallowing is about I second, tongue-thrusting forces act for only 10 minutes per day. It is highly unlikely that forces of this duration, irrespective of magnitude, will move teeth. Therapy directed at posture is now receiving"greater emphasis?O and has a better rationale. Treatment directed at changing tongue posture should not be undertaken, however, without consideration of the reason for the abnormal posture. Treatment should take into consideration the cause of the abnormal posture and not aggravate the conditions giving rise to the reflex response. (See also Chapters 10 and 18).
TABLE
5-3.
Learning Sequence Interference CONDITIONED STIMULUS (CS)
for Avoidance
UNCONDITIONED STIMULUS (US)
Balancing interference Position of + Balancing interference mandible Position of mandible -------------
of a Balancing-Side UNCONDITIONED RESPONSE (UR)
---?
---?
Occlusal CONDITIONED RESPONSE (CR)
Mandibular deviation Mandibular deviation Mandibular .....••. deviation
The reflex responses elicited by occlusal interferences were discussed earlier in this section. When the threshold for a reflex altering jaw movement was not exceeded, closure into full intercuspation was guided by the inclines of the teeth (and the constraints of the joints). When the threshold for reflexes altering jaw movement was exceeded, an unconditioned reflex was initiated avoiding the occlusal interference. In time, the occlusal interference may be avoided through conditioning (see Fig 5-6C). Avoidance of the interference will be "reinforced" by sporadic contact on the interference. Elimination of the interference by grinding or tooth movement will "extinguish" the active guidance. This sequence of events is summarized in Table 5-3. A balancing-side interference (US) gives rise to mandibular deviation (UR), an unlearned reflex. Mandibular position near tooth contact, probably detected by mandibular joint and/or muscle receptors (CS), coupled with balancing-side contact (US), results in continued mandibular deviation. Eventually, mandibular position near tooth contact (CS) gives rise to mandibular deviation (CR) without striking the occlusal interference. Gagging at the sight or smell of the loaded impression tray is another example of conditioning. In this case, the unconditioned stimulus is excitation of oropharyngeal receptors in the mucosa. Visual or olfactory stimuli, on repeated association with the unconditioned stimuli, give rise on their own to conditioned gagging. Extinguishing this reflex by the principle of disassociation suggests strategies for control alternative to those cited earlier. Disassociation strategies might include the use of topical anesthetics.
D. REFLEX DETERMINANTS OF MANDIBULAR REGISTRATION POSITIONS An active (i.e., reflex) muscle contribution in the determination of the three major registration positions of the mandible has been asserted by some and denied by others. The extent to which pos.tural position, intercuspal position, and retruded contact positioIi;.are actively or pa;sively determined affects their reliability as registration positions.'
1. Postural Position Postural position is used in orthodontics in diagnosis and in taking the bite for functional appliances. Postural position may be
r
Maturation FREEW AY
CONTROL
FIG
SPACE
AFTER No THIOPENTAL
AFTER CHOLINE
SUCCINYl
5-9.
Mean freeway space in a sample of 27 healthy subjects measured with Frankfort plane horizontal prior to and after intravenous injection of an anesthetic dose of sodium thiopental and a paralytic dose of succinyl choline. Vertical lines indicate one standard deviation. The increases in freeway in the two test procedures compared to the control are highly significant. Freeway space is unequivocally.determined by reflex mechanisms. used in the differential diagnosis of functional malocclusions from dental/skeletal malocclusions. Deviations in the path of closure from postural position to intercuspal position are useful in diagnosing retrusively occluded mandibles (see Chapters 10 and 15). Postural position is also used in the differential diagnosis of deepbite cases: the freeway space will be larger than normal in cases with inadequate vertical development of the buccal segments and normal in cases of over-eruption of the incisor teeth. The extent to which a bite for a functional appliance is taken ahead of and beyond postural position depends on the rationale for the therapy (see Chapters 15 and 18). Since all the registration positions are three-dimensional, the question as to whether determination is active or passive must be asked in the vertical, anteroposterior, and mediolateral directions. Arguments are still advanced for the passive, vertical determination of postural position. The presence of electrical adivity in the levator and depressor muscles of the mandible in posutral position has been attributed to experimental artifact. Irrefutable evidence that the vertical component of postural position is actively determined comes from studies in which freeway space is measured under general anesthetic and neuromuscular blockade. In one such study,20 freeway space was measured on two separate occasions in relaxed, awake subjects sitting upright with the Frankfurt plane horizontal. The mean freeway space in 27 cases was 2.3 mm. Following anesthesia with intravenous sodium thiopental, the mean freeway space increased to 8.6 mm and to 10.2 mm on the addition of a paralytic dose of succinyl choline-chloride. These data are illustrated in Figure 5-9. Although there is no doubt that the vertical component of postural position is reflexly determined, the contributory muscles and reflexes have yet to be specified. In subjects with normal occlusions, postural position is on the opening-closing path of the mandible below the intercuspal position in the same sagittal and transverse planes (Fig 5-10). It
of the Or(jfacial Musculature
85
is not clear whether the normal anteroposterior and mediolateral location of the postural position is actively or passively determined. Malocclusions can effect an anterior or lateral displacement of postural position. Children with Class 11 mal occlusions due to a deficient mandible have been observed to posture the mandible forward. Ingervall,39 in a series of studies in children, found the mean anteroposterior difference between the postural position and the intercuspal position to be 1.37 mm and 0.83 mm in Angle Class 11, Division I and Division 2 cases, respectively. The mean position of postural position in Class 11cases compared with Class I occlusions is illustrated in Figure 5-10. It is obvious that postural position in Class 11 malocclusions is actively positioned forward of the expected position. This anterior positioning in postural position has been termed a "Sunday bite." It would be more appropriate to call it a "Sunday posture. " Teleologic thinking attributes it to a conscious attempt on the part of the patient to improve his or her profile. Since the child never or rarely sees his or her profile, it is more likely a reflex regulation, perhaps to maintain an adequate airway. Children with Class 11 malocclusion, on closure into intercuspal position from postural position, therefore translate the mandible dorsally. Postural position may also be displaced in a mediolateral direction (as in the case of functional posterior crossbites) to the side of the crossbite. In order to diagnose a "functional crossbite," it is necessary to observe the closure pattern from postural position or from retruded contact position (see Chapters 8 and 10). Closure from postural position to intercuspal position will show no lateral deviation in skeletal crossbites. Since postural position is clearly determined by muscular contraction, it becomes important to specify the reflexes accounting for that muscle contraction in order to identify the active reflexes and manipulate them when appropriate. The usual reflex
® CLASS
NORMAL
11,div.l.
,&
CLASS
11,div.2.··
FIG 5-10. Mean position of postur5!1 in the mid sagittal plane of children with eli-l~S 11malocclusions projected onto the border envelope of motion of the mandible for both division l' and 2 types. The uppermost circle represents intercuspal position. The solid line circle with dot represents retruded contact position in the division 1 sample of 32 children and the broken line circle with dot retruded contact position in the division 2 sample of 22 children. The square with cross represents the mean position in a Class I sample referenced to an intercuspal position common with both Class 1Isamples. Postural position is 1.37 mm ahead of intercuspal position in the division 1 sample and 0.83 ahead in the division 2 sample. (From Ingervall B: Studies of mandibular positions in children. Odontol Rev 1968; 19(suppl 15):1-53. Used by permission.)
86
Growth and Development
cited as the basis for postural position of the mandible is the tonic stretch reflex of the mandibular levators (i.e., the myotatic reflex). (The original designation was myostatic reflex but a perpetuated typographic error dictates the present spelling.) Since the stretch reflex and its gamma biasing mechanisms are taught in all physiology courses, the spindle mechanism will not be discussed here. Because the levator muscles of the mandible are richly supplied with muscle spindles and since the monosynaptic reflex arc has been demonstrated both anatomically and physiologically, there seems little doubt that the tonic stretch reflex plays a role in postural position. Although one of the earliest concepts of spindle function was that of a length-sensitive, negative feedback system returning the muscle to its original length (in the case of the mandible, to its original position), other roles have been postulated for the spindle. These include an error detector role in identifying mismatches between execution of a movement and the central com-
5
10
min
5
10
min
o
2
mm
B o
mand for the movement and a load-compensator role whereby the gain on the contracting muscle is increased in order to execute the motor task when the load is increased.21 One problem with the concept of the muscle spindle as a position receptor is the extent to which it can be biased by the gamma efferents (the motor nerves innervating the intrafusal muscle of the spindle) and thereby change the sensitivity of the receptor. The gamma efferent system can be likened to a child changing the sensitivity of a bathroom scale unknown to the parent being weighed. Although the spindles would appear to be unlikely candidates for monitoring jaw position, psychophysical experiRements clearly implicate them in that function (Morimot059). ceptors in the temporomandible joint are also well suited for monitoring position of the mandible (Kawamura and Abe43). A number of investigators have recorded from tonically firing, position-sensitive units in the temporomandibular joints of experimental animals. These receptors probably serve as the unconditioned stimulus for reflexes initiated in the joint and as a conditioned stimulus for reflexes initiated elsewhere. An example of temporomandibular joint determination of mandibular position is seen. in patients in which the mandible is postured away from a painful joint. Postural position of the mandible is also determined by the A Benavioral
stale
AlerT Orowsy DU,iet Sleep
AClM: sleep
. B MasseteriC reflex
100-
'/075501.5-
0120 observations/min
f'
~
FIG 5-11. The effects of states of wakefulness on the stretch reflex of the jaw. Behavioral state was assessed from the electroencephalogram and the masseteric reflex from the electromyogram in eight cats. Note the extent to which the amplitude of the stretch reflex is dependent on the state of wakefulness. When the cat is fully awake the reflex appears without attenuation. When in active sleep (rapid eye movement) the reflex is completely abolished. (From Chase MH, McGinty OJ, Sterman MB: Cyclic variation in the amplitude of a brain stem Experimentia 1968; reflex during sleep and wakefulness. 24(specialia):47-48. Used by permission.)
-..
mm FIG 5-12 The effects of affective state or emotion on postural position. Freeway space was recorded with an intraoral electromechanical device in a subject watching a suspense film in (A) and a ballet in (B) for 15 minutes. Note the smaller freeway and frequent tooth contacts While watching the film with more emotional content. on the vertical scale represents intercuspal position. (From Schwindling R, Stark, W: Physiology of mandibular positions. Front Oral Physio/1974; 1:199237. Used by permission.)
0
demands for a patent upper airway. Where nasal breathing is impossible and the patient is forced to breathe through the mouth, the posture of the mandible changes along with posture of the tongue and hyoid complex. Where the pharyngeal tonsils are enlarged so that the pharyngeal airway is partially obstructed, the postures of the mandible, the tongue, and the hyoid complex are reflexly repositioned to establish an adequate airway. Although the initial reflex is probably the result of stimulation of receptors monitoring adequacy of ventilation (e.g., peripheral and c.entral chemoreceptors), the reflexes may become conditioned so that receptors monitoring the position of the mandible, tongue, and hyoid ·complex assume the regulatory role. , Experimental studies demonstrating the effects of general anesthetic on postural position of the mandible demonstrate the important effects of the state of wakefulness on the reflex control of postural position. Chase and.coworkersl4 have shown that the masseteric reflex in the cat parallels perfectly the state of wakefulness as fPo.nitored by the electroencephalogram. In Figure 5-11 is illustrated the lively nature of the n;flex when the animal is fully awake and its complete absence when the animal is in deep sleep. This means the control of postural position of the mandible, tongue, and hyoid complex must be under different reflex control when the subject is sleeping than when the subject is awake. The myotatic reflex cannot be responsible for postural position of the mandible in the sleeping state. Not only is the postural position of the mandible under dramatic control by the reticular formation of the brain but also by the limbic brain which is the seat of the emotions. 9 Figure 5-12 illustrates changes in postural position as a result of emotional state.
Maturation TABLE 5-4 .. Determinants of Postural Position PAS'SIVE
ACTIVE
Inactive levator muscles
Stretch reflex of levator muscles Temporomandibular joint reflexes Airway supportive reflexes
Negative intraoral pressure
The hypothesized and experimentally verified determinants of postural position are summarized in Table 5-4. The postulated passive determinants (left column) have been invalidated.
2. Intercuspal Position (Usual Occlusal Position, Centric Occlusion) The' intercuspal registration position is used for the classification of mal occlusions according to Angle. It is the position in which the relationships of the teeth are described prior to and after orthodontic treatment. Since the intercuspal position can usually be identified in hand-articulated casts, the natural assumption is that the position is passively determined by occlusal anatomy and positions of the teeth. In some cases such as extreme skeletal open bites and unilateral hyperplasia of one condyle, the temporomandibular joints may function as a passive determinant. lntercuspal position may be actively determined in functional mal occlusions such as crossbites (both posterior and anterior) and dual bites (cases in which intercuspal position is more than an arbitrary 3 mm ahead of retruded contact position) and in cases with steep incisal guidance where lingually inclined incisors may reflexly cause retraction of the mandible on closure into full intercuspation. When the intercuspal position is actively determined, its use in diagnosis alone can lead to errors. For example, a patient with a pseudo Class III malocclusion might be misdiagnosed as having a skeletal Class III malocclusion. Active guidance may be initiated from the dentition, from the temporomandibular joints, and from receptors monitoring adequacy of the pharyngeal airway. The conditions under which occlusal factors initiate active guidance were discussed in Section C-2 (see Fig 5-6). Some of the determining factors are as follows.89,90 The magnitude of the occlusal force is an obvious determinant. A strong force is more likely to elicit a response than a weak one. The speed of closing may be a variable. The direction of the force is likely to play a role based on the known greater sensitivity of the receptors around the teeth to forces applied at right angles to the crown rather than along the long axis. Direction of the force will be affected by the closing patterns and anatomy and arrangement of the teeth. Since the loading of teeth is more axial on the working side and more likely to be tangential on the balancing side, the direction of force favors feedback from balancing interferences. The threshold of the receptors surrounding the teeth will also determine whether feedback will occur. Receptors in inflamed tissues are much more sensitive than those in normal tissues. The frequency and duration of occlusal contacts will determine whether feedback occurs immediately or is delayed. Avoidance of occlusal interferences may be delayed for several days. The discharges from the receptors are ignored for a period
of the Orofacial Musculature
87
of time ("habituation") if the forces are not immediately threatening to the integrity of the supporting tissues. Perhaps repeated trauma to the tooth results in periodontal inflammation, lowering of the receptor threshold, and then avoidance of the interference. The extent of root development would also appear to be a factor. The tactile thresholds of maxillary incisor teeth are significantly lower in incisors with incompletely formed roots compared to those with fully formed roots. 33 Occlusal feedback may be affected by the position of the mandible. The jaw-jerk reflex is abolished on the working side while enhanced in the muscles on the balancing side.29 Feedback from the levator muscles is suppressed on the working side but facilitated on the balancing side. This also holds for feedback from the dentition. Axial forces are increased on the working side but decreased on the balancing side foIlowing an artificial increase in mandibular first molar crown height. 30 Levator muscle activity is increased on the working side and decreased on the balancing side with4 or without98 premature tooth contact. Other studies have demonstrated that mandibular levator activity is increased when occlusal forces are borne only by the posterior teeth and decreased when they are borne exclusively by the anterior teeth.99 These studies demonstrate that occlusal feedback is also determined by the segment of the dental arch bearing the occlusal load. Computer modeling of jaw mechanics by Smith87 suggests that the muscle forces and vectors are determined by a prerequisite for minimal loading of the temporomandibular joints. There are numerous possibilities for active guidance to be enhanced by central effects originating in various parts of the brain. 21, 89 Those parts of the brain associated with state of wakefulness, with pain modulation, and with affective state or emotion are known to exert powerful effects along with basal ganglia and cerebral cortex. It may weIl be that these central effects override the other determinants of active guidance in dysfunctional or parafunctional states. The intercuspal position may be also reflexly determined as a result of reflexes arising in the temporomandibular joint. Normally the best intercuspation of the teeth dictates the positions of the joints. However, in cases of inflammation within the joint the hierarchy may be reversed: the joints may dictate intercuspal position. An example of such a condition would be that in which a joint had been traumatized, for example as a consequence of dislocation and damage to the capsule and ligaments during a difficult 'extraction. The resultant inflammation lowers the threshold of receptors in the capsule of the joint and initiates protective reflexes guarding against further damage to the j~ints. As discussed in the previous section, postural position under these circumstances is also altered. In cases in which the pharyngeal airway is jeopardjz~d, for example, by.enlarged pharyngeal tonsils, the intercuspal position may be affected as well, as the postural position. Ricketts78 has documented cases in which Class I occlusions have reverted in Class 11, Division 1, mal occlusions subsequent to the removal of pharyngeal tonsils. Reflexes responsible for active guidance are essential for protection of the teeth, the temporomandibular joints, and the airway. These reflexes guard against trauma to the teeth or joint and assure an adequate airway. Since this additional reflex burden diminishes motor efficiency and may lead to altered posture and subsequent abnormal development of the jaws in the growing child, the goal
88
Growth and Development
TABLE 5-5. Determinants of Intercuspal Position
I
Posselt, 1968 1952 ngervall.,
ACTIVE
Anatomy of teeth Position of teeth
Occlusal reflexes Temporomanditiular joint reflexes Airway supportive reflexes
of all occlusal therapy, including orthodontic treatment, should be to eliminate perpetual reflex guidances. This is the basis for the early treatment of all functional malocclusions. The passive and active determinants of intercuspal position are outlined in Table 5-5. There are semantic problems with the use ot the term centric occlusion, sometimes used as a synonymous term for intercuspal position. For, some clinicians centric occlusion is the same as intercuspal position; for others, it is the same as centric relation occlusion (the tooth contact position when the mandible is centric relation).
3. Retruded Contact Position The retruded contact position, like the postural position, is used in the diagnosis of functional malocclusions and dual bites. The mandible is manipulated into retruded contact position and the patient is asked to close into the intercuspal position. Excessive slides in either the mediolateral or anteroposterior direction are cause for concern. A small anteroposterior separation between the retruded contact position and usual occlusal position is normal. Some clinicians consider coincidence of these positions desirable in the adult. Ingervall reported that in children with Class I occlusions anteroposterior distance between retruded contact position and intercuspal position is 0.85 mm39 (Table 5-6). In Class 11 malocclusions this anteroposterior separation is slightly larger. When the separation exceeds 3 mm the occlusion is referred to as a "dual bite." Coincident intercuspal position and retruded contact position has been claimed to predispose to temporomandibular disorders.6. 34.68.75-77 Reproducibility of the retruded contact position makes it the most reliable reference position. This reproducibility suggests that the retruded contact position is passively determined, presumably by the anatomic structures making up the temporomandibular joint complex, including the disc. However, there are dental clinicians who believe that the retruded contact position is at least partly
CHILDREN
Class
Fa I NT
& Jacoby,
~'
1961
Boucher
'I'. ~
/PANTOGR:( McMillen,
1972
concious anaesthetized
and nm.
block
FIG 5-13. Diagrammatic representation of changes in retruded contact position recorded with various instruments in conscious patients and in the same patients under general anesthesia and neuromuscular blockade. Ingervall's study40 was carried out on children; all others in adults. (Adapted from Posselt,71 Ingervall,40Boucher,9 and McMillenS5) determined9 The controversy continues because of disparate results in studies registering this position under general anesthesia and neuromuscular blockade. The registration devices which have been used in these studies include the gothic arch tracer, the needle point tracer, and the mandibular pantograph. In studies using the gothic arch tracer in both adults and children, retruded contact position was found to be coincident in both the conscious and the blockaded subjects40·7I (see Fig 5-13). Retruded contact position would appear to be passively determined. However, in another study using the needle point device, the retruded contact position was found to be more retrusive under neuromuscular blockade (Boucher and Jacoby8). The investigators concluded that retruded contact position was a "muscular" position (i.e., it was actively determined). In a study by McMillen,55 using the pantograph, the investi'gator was surprised to find the condyles dropped vertically when the muscles were paralyzed. These surprising and somewhat confusing data can be interpre\ed as follows. Like the articulator, which simulates the passive determinants of mandibular position and movement, the temporomandibular joint assembly can beconsidered to have stops limiting the condylar movement any further in the dorsal, superior,
TABLE 5-6. Anteroposterior Differences Between Retruded Contact and IntetCj.J.spalPositions*t
OCCLUSION
NEEDLE
ARCH
;A"
~,
PASSIVE
Anatomy of temporomandibular joints
GOTHIC
".
y ..•
ADULTS
n29 SD n RANGE M ±0.34 SD 0.55 1.25 ±elm 0.07 0.7-2.1 35 22 0.89 1.20 0.35 0040 0.06 0.10 0.2-3.1 0.1-1.7 0.3-2.0 32 0.85
11
*Adapted from Ingervall B: Studies of mandibular positions in children. Odontol Rev 1968; 19(suppI15):1-3. tM = means; elm = standard error of the means.
l
Maturation
FIG 5-14. Passive and active guidances of the temporomandibular joint as visualized in the sagittal plane. Anatomical determinants and passive guidances illustrated on the left are represented schematically to the right as hatched superior and posterior "stops." Reflexes (solid zigzag arrows) are necessary for the condyle to attain the superior (A) and posterior (B) "stops." Protective reflexes originating in the dentition or the joint may cause unilateral or bilateral protraction (C, dotted zig-zag arrow) of the condyle and disc. and medial directions (Fig 5-14). These stops are structural (bones and ligaments) and therefore passive, and with suitable registration techniques can be duplicated. Reflexes, however, are involved in reaching these stops, especially the dorsal and superior stops. EMG studies have shown that retractor muscles are more active in the retruded contact position than in the intercuspal position.]]' 62. 74 This can be demonstrated readily by palpation of the posterior temporal and digastric muscles on voluntary retrusion into the retruded contact position. Retruded contact position is a "strained" position. In the vertical direction, a levator reflex normally holds the condyle in a superiorly seated position. However, when the levator muscles are fatigued, as in lengthy pantographing sessions, the condyle can be observed to drop. Normally this does not occur. In summary, retruded contact position is passively determined but attained by reflex action. This is also true for the medial stops. These determinants of retruded contact position are summarized in Table 5-7. The protractor muscle reflex distracts the mandible from its dorsal stop: it is not a determinant of this registration position. Just as there is a semantic problem with centric occlusion, there is a s~mantic problem with centric relation. While the tra-
TABLE 5-7. Determinants of Retruded Contact Position PASSIVE
ACTIVE
Anatomy of temporomandibular joints
Protractor muscle reflex Levator muscle reflex Retractor muscle reflex
of the Orofacial Musculature
89
ditional view of centric relation is the jaw position when the condyles are in their "uppermost, rearmost, median" position (i.e., synonymous with the retruded contact position), the view that the condyle should be in an "uppermost foremost position" is becoming more widely accepted (Dawson,]9 and Celenza and Nasedkin]2). These two views account for real controversies (e.g., should centric relation ideally be in the rearmost position) and fancied controversies (e.g., the desirability of a "long centric"). In the healthy joint, the condyle and disc assembly attain the passive dorsal stop through retractor muscle activity when intercuspal position is in the usual anterior relationship to retruded contact position. In patients with occlusal interferences giving rise to protective reflexes, protractor muscles may prevent the mandible from attaining its most retrusive position. In the patient with the traumatized temporomandibular joint referred to earlier in this section, protective reflexes originating in the joint will not allow reliable registration of retruded contact position since manipulation of the mandible for recording is difficult. Muscle resistance to manipulation of the mandible is a sign that the registration position will not be recorded accurately until the protective reflexes have been eliminated.
E. GROWTH AND ADAPT AnON OF OROF ACIAL MUSCLES A number of concepts regarding the growth of muscles affect the rationales for orthodontic treatment and should be recognized, since concepts sometimes are conflicting or paradoxical. A fundamental concept at issue is whether the growth of muscles is secondary to growth of the bones of the face or whether the growth of the muscles determines growth of these bones. The idea that muscles determine growth of the bones of the face is much in vogue, having been popularized by Moss"" (see Chapter 4). In his concept, the "functional matrix" dictates the development of the bones of the jaws, face, and cranium. The functional matrix concept has defied rigorous testing and so the question of whether the muscle is primary or secondary in growth of the jaws and face is still unsettled. Another concept that prevails in dentistry is that of a predetermined resting length for each muscle and a "memory" of ,resting length which causes the muscle to return to that length should it be changed. This concept is familiar in the dictum that the bite should not be increased beyond the freeway in prosthodontic treatment and the dictum that "counterclockwise" surgical advancements of the mandible will relapse because of stretching of the pterygomasseteric muscle sling of muscles. Increasing the "o
90
Growth and Development
rigorously in the growing child where the levator muscles seem to be more adaptive and where bite openings beyond postural position are readily accepted by the young patient. This concept of fixity of muscle length appears to be implicitly held for facial muscles as well since short upper lips are not expected to elongate with any form of current orthodontic correction (see Chapter 10).
160
150
-
T- T, tendon to tendon
........T-M, tendon - - - M-M, fTXISc/e
10 ffXJscle
10 muscle
140 130 120
1. Structural While the growth of facial bones has been extensively studied by radiologic measurement (with and without implants) there are few studies on muscle (organ) growth in either experimental animals or humans. The problem is one of finding a suitable marker for 11lUscle.Short lengths of barbed broaches have been inserted into the masseter and digastric muscles of experimental animals, and their movements relative to each other or to other markers in bone or ligament examined radiographically. 57.64 Interpretation of results may be complicated by adaptations occurring in muscle beyond the implants, in the tendon and at the insertion. Silver dust suspended in gelatin and implanted into the masseter muscle of growing pigs has been used as a marker. 55 Although muscle implants are not as stable as bone implants, studies using these techniques indicate that jaw muscles do adapt to changes in length in the growing animal64 but are less likely to do so in the adult57 Petrovic and coworkers69 have shown that functional shortening of the lateral pterygoid in the rat by means of a functional appliance (active protraction) results in a reduction in the number of sarcomeres (Table 5-8). Anterior traction of the mandible with elastics (passive protraction) has no effect. While growth of the muscle organ would intuitively be thought to be in the muscle tissue, the role of the investing tissues and ligaments must also be examined. Some insight into the adaptive response of jaw muscle tendon comes from the study by Muhl and Grimm.64 Two markers were placed in the tendon and two markers in the muscle belly of the digastric muscle of growing rabbits and changes in distances between markers measured by three- . dimensional radiography following surgical shortening of the tendon (Fig 5- IS). All long-term adaptation in this experiment took place in the tendon.
\
110
\
··1',
100
90
Y·- •••
-
..;::.::.:;~~
1\
\ •...
80
'..--- - ,------.
\
.... .....
70 -40 -30 -20
-10
0 .•.10 +20 +30 +40 +50 DAYS
FIG 5-15. Mean percentage changes in marker distances before and after surgical shortening of the tendon of the digastric muscle of the growing rabbit. Note that following the length changes due to the surgery the tendon markedly elongated while the muscle and the junction of the tendon to muscle shortened. (From Muhl ZF, Grimm AF: Adaptability of rabbit digastric muscle to an abrupt change in length: A radiographic study. Arch Oral Bioi 1974; 19:829-833. Used by permission.) the masseter muscle did not keep pace with the mandible-which slipped forward under the muscle. This tantalizing piece of information suggests that jaw muscle growth may be secondary to mandibular growth. The form-function controversy is not dead. Another possible site of adaptation is at the interface between muscle and bone. The nature of the interface with bone changes from an insertion into the periosteum in the growing animal to an inserti'on into the bone in the adult. The muscle origin and insertion must be considered as sites of adaptation to changes in muscle length imposed by orthodontic treatment (e.g., functional apR}iances, combined orthodontic-surgical correction, bite planes) as well as normal growth. These limited data have obvious implications for planning ortho~ontic treatment alone or in conjunction with surgery where functional muscle length is changed. Where adaptation cannot be' expected, relapse is likely to occur. Besides the structural changes associated with growth and adapUition are those of chang·es in muscle type. The limited literature on fiber types in orofacial muscles of humans indicates that differentiation of type I and II fibers occurs at about 20 to 23 week's gestation8' The proportions of different fiber types during growth are likely to be determined in large measure by functional demand. 1
These few implant studies have looked at short-term adaptations in jaw muscles to lengthening. Only the single study using silver dust as a marker35 examined adaptation during normal growth (no studies have been done on the human). According to these authors
TABLE 5-8. Effects of Active and Passive Protraction of the Mandible on Length of Lateral Pterygoid in the Rat' LATERAL (NUMBER
PTERYGOID
OF SARCOMERES;
CONTROUTEST)
Protraction of mandible (active) Protraction of mandible (passive)
2401/2132 (P>0.01) 2417/2334 (N.S.)
'Adapted from Petrovic AG, Stutzmann JJ, Oudet CL: Control processes in the postnatal growth of the condylar cartilage of the mandible, in McNamara JA Jr (ed): Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development. University of Michigan, 1975, pp 101-153.
2. Functional and Behavioral There are no longitudinal studies on the development orofacial musculature similar to those on the development
of the of the
Maturation
of the Orofacial Musculature
91
FIG 5-16. Tongue posture in the neonate. Note that while the mandible is in its postural position, the tongue is postured forward and touches the lips while the gum pads are held slightly apart.
facial skeleton. A large literature, mostly of an anecdotal nature, catalogs the development of orofacial function (see Peiper"7). The pediatric and neurologic literature documents the ontogony of ~ number of orofacial reflexes such as the rooting reflex, suckling, and other feeding activity. Speech pathologists have timetables for normal development of speech similar to those used by dentists for tooth eruption. These descriptions, after Gesell and Piaget, are of a behavioral type and have associated with them the concept of attaining particular behaviors in sequence and by a "normal" chronologic age."6 Orofacial behavior whose development is pertinent to orthodontics includes mandibular and tongue posture, swallowing, and mastication. The reflexes and associated biasing mechanisms accounting for mandibular posture (described earlier in Section D) are functioning at birth though they become sequentially more complex with normal developmental events (e.g., eruption of teeth, establishment of occlusion, beginning of mastication) and unpredictably so with occurrences such as loss of teeth, pain, temporomandibular disorders, and so forth. In the neonate the postural position is likely the starting orientation for such activities as suckling, respiration, and swallowing. Tongue posture in the neonate is more forward than later since the tongue is part of a very active sensory perceptual system (Fig 5-16). Many oral functions in the neonate are guided primarily by tactile stimuli from the lips and tongue. Later when the incisors erupt the tongue posture changes to the mature position. Mandibular growth downward and forward increases the intraoral volume, and alveolar process growth vertically during eruption aids in the normal change in the tongue's posture during the first year of life.63 A retention of the infantile tongue posture is sometimes seen, creating a difficult and persistent open bite (see Chapter 18).62
The infantile swallow, an essential function in the neonate, is closely associated with suckling, and both are well developed
by about the thirty-second week of intrauterine life.38 During the infantile swallow the tongue is between the gum pads in' close apposition the with lips, and its contraction plus those of the facial muscles help to stabilize the mandible. The mandibular elevators, which play a prominent role in normal mature swallows, show minimal activity (Fig 5-17 ,A).63 All occlusal functions are learned in stages as the nervous system and the orofacial and jaw musculature mature concomitantly with the development of the dentition. During the latter half of the first year of life, several maturational events occur that alter markedly the functioning of the orofacial musculature. The arrival of the incisors cues the more precise opening and closing movements of the mandible, compels a more retracted tongue posture, and initiates the learning of mastication. As soon as bilateral poster-ior occlusion is established (usually with the eruption of the first primary molars), true chewing motions are seen to start, and the learning of the mature swallow begins. Gradually, the fifth _cranial nerve muscles assume the role of mandibular stabilization "' during the swallow, and the muscles of facial expression abandon suckling and the infantile swall()w and begin to learn the delicate and complicated functions of speech and' facial expressions. The transition from infantile to mature swallow takes place over several months, aided by maturation of neuromuscular elements, the appe~ance of upright heAd posture, and, hence, a change in the direction of gravitational forces'on the mandible, the instinctive desire to chew, the necessity to handle textured food, dentitional development, and so forth. Most children achieve most features of the mature swallow at 12 to 15 months of age. Characteristic features of the rriature swallow are (I) the teeth are together (although they may be apart with a liquid bolus), (2) the mandible is stabilized by contractions of the fifth cranial nerve, (3) the tongue tip is held against the palate above and behind the incisors, and (4) minimal contractions of the lips are seen during the swallow (Fig 5-17) 62
92
Growth and Development Left Anterior- 1'"mporal Left. Orb1culii'ris Oris-Buccinator
r
i 100
'"V
1 second
FIG 5-17 A, an infantile swallow. In this instance, the baby fell asleep at the mother's breast. The swallow recorded is an unconscious swallow of saliva during sleep. Note the dominance of the facial muscles and the minimal activity in the only mandibular elevator sampled. (A from Moyers RE: The infantile swallow. Trans Europ Orthod Society 1964;
...•
S'i.'ALLOli
40:1£Q. Used by permissiO'ri:) 8, mature swallows. A comparison of the teeth-together and teeth-apart swallow. The record at the bottom (R.G.) is that of a typical mature swallow. Note the strong contractions in the temporal muscle. The record at the top (E.B.) is of a child of the same age. Note, however, that this child has a teeth-apart swallow, since there is far greater activity of the facial muscles than there
Maturation
Left
Anterior
Left
Middle
of the Orofacial Musculature
93
Temporal
1~~N1l~ Temporal
~
.
I'WML,~,.......: ..••• .J~•..Ill ~~:,\:.~'~~~ . {, •..,.~"'TT'1'~ I • ')i i: ' \
Left
Posterior
Left
Masseter
R' 19ht Anterior
Temporal
~.... ,~
1 Right Middle .••.•.•• Tempora -..:.:......""""'-..,.. iIN'-J.JJ-w~~~"l,. Right
Posterior Q4
••• rr-
Temporal
!••
(,~II~~ L...• IIl~,\Jv....;.....u.......JJ.! "I' 'TfI~ ~i 7~~•.... '-n T··;II; l.Ji:'~/I'\!~:~I~~rf"""" ,'II'..· I I
Temporal, Dw
__ . ~_:"-''''1".'~~I, I •
, '~~~""~If"" '" ...•
I sr<:.
I',.
"1
,
I
'
,•.••.•.
FIG 5-17 (cont.). is of the mandibular elevators. An unconscious swallow (C) and a volitional swallow (D) of water are compared. These records were taken from the same person during the same experimental period.
(C and 0 from Eggleston WB Jr, Ekleberry JW: An Electromyographic EvaluatiQ[1 of Treated Orthodontic Cases, thesis. Scll~ol of Dentistry, University of Michigan, Ann Arbor, 1961. and Functional
94
Growth and Development
F. INTERACTION OF OROFACIAL MUSCLES WITH DEVELOPMENT OF THE CRANIOF ACIAL SKELETON AND THE DENTITION Sections A-2, A-3, C-I, C-2, C-3, ,and E-I in this chapter and sections in Chapters 4, 6, 7, and 10 contain discussions of these crucial interactions and their implications in the etiology of malocclusion and in planning orthodontic treatment. A recurring theme is that posture dictates the form appropriate to that posture. Phasic activities such as mastication, swallowing, and speech are less likely to cause structural adaptations unless tl)e forces, are heavy and/or act over long periods of time. Bruxism is an example of a, phasic activity which can cause structural changes in the muscles, teeth, periodontal ligaments, and alveolar bone" This function-structure interaction, however, works both ways: structure can also influence function, Some dentists see the forwardpostured tongue in faces with excessive anterior face height (the so-called "long face syndrome" or "steep angle case") as an adaptation to the bony morphology. Other dentists see the altered facial morphology as the consequence of altered tongue posture, Tongue protraction in cases of anterior open bites secondary to digital habits is a good example of an interaction existing in both directions. Some anterior open bites result from abnormal function while others cause an adaptation in function (see Chapters 7 and 10).
Much has yet to be learned about the relationships between neuromuscular growth and function and growth of the craniofacial skeleton and occlusion. Many of the leading oral biology laboratories in the world concentrate on this important theme. Perhaps no single advancing area has caused more changes in this ,edition of this book, both in theory and practice, than the constantly appearing new knowledge about the old theme of form and function. The reader is urged to make a serious effort to correlate similar sections in Chapter 4, Growth of the Craniofacial Skeleton, and Chapter 6, The Development of the Dentition and Occlusion, with the ideas in this chapter. Textbooks neatly segregate subjects for ease in writing and presentation of ideas; the clinician has no such luxury, and the important concepts of form versus function presented in Chapters 4 through 6 may often be combined in the patient. Treatment of such functional aspects of malocclusion is presented in three chapters on treatment, namely, Chapters 15 through 17.
SUMMARY The orofacial musculature serves vital functions of respiration and alimentation as well as expression and communication. Functions in one region are tightly linked to functions in another: posture of the head, mandible, tongue, and hyoid and supportive and protective reflexes of the portal area are highly interactive. These functions are also interactive with the structures they serve: function may dictate the form or form dictate the function. Posture would appear to be more important as a determinant of mandibular form and tooth position than synergies of relatively short duration such as speech, mastication, and swallowing. The reflexes which form the basis of orofacial function and
behavior may be unlearned, learned, or a mixture. Learned patterns are more amenable to change by alteration in form or training than are unlearned patterns. The three registration positions (postural position, intercuspal position, and retruded contact position) are under variable degrees of reflex regulation. The mix is determined by the position and the conditions under which it is recorded. The extent to which the position is reflexly regulated determines its reliability as a registration position. The forces exerted by the orofacial muscles vary with the muscle and the conditions. These forces are a combination of active (reflex) and passive (nonreflex) components. Facial muscles do not possess spindles and therefore lack a stretch reflex. Jaw muscles are rich in spindles: the contribution of reflex to total tension is highly variable. In contrast to growth of the bones of the face, little is known about the growth of the muscles. Short-term adaptation to changes in length has been documented as occurring in the muscle, in the tendon, and at the muscle insertion in growing animals. These adaptations are much smaller in the adult.
REFERENCES I. Ahlgren J: An electromyographic analysis of the response to activator (Andresen-Haupl) therapy. Odontol Rev 1960; 11:125-151. 2. Amprino R, Cattaneo R: Il substrato isotologico delle varie modalita di inserzioni tendinee alle ossa nell'uomo. Ricerche su individui di varia eta. Z Anat Entwicklungsgesch 1937; 107:680-705. 3. Anderson DJ: Measurements of stress in mastication. IJ Dent Res 1956; 35:664-670. 4. Bakke M, Moller E: Distortion of maximal elevator activity by unilateral premature tooth contact. Scand J Dent Res 1980; 88:67-75. 5. Ballantine HT Jr, Talbert R, Currens JH, et al: Studies of sensation, circulation and respiration after bilateral glossopharyngeal rhyzotomy. Trans Am Neurol Assac 1954; 79:69-72. 6. Baril 0, Moyers EE: Electromyographic analysis of the iemporalis muscle and certain facial muscles in thumb and finger sucking patients. J Dent Res 1960; 39:536-553. 7. Berry DC, Watkinson AC: Mandibular dysfunction and incisor relationship. Br Dent J 1978; 144:74-77. 8. Bosma JF: Introduction to the symposium, in Bosma JF, Showacre J (eds): Development of Upper Respiratory Anatomy and Function. Implications for Sudden Infant Syndrome. Washington DC, US Government Printing Office, 1975. 9. Boucher L, Jacoby J: Posterior border movements of the '''llUman mandible. rP~osthet Dent 1961; 11:836-841. 10. Brill N, Tryde G: Physiology' of mandibular positions. Front Oral Physiol 1974; 1: 199-237. 11. Buxbaum JD, Parente FJ, Ramsey WO, et al: A comparison of centric relation with maximum intercuspation based on quantitative electromyography. J Oral Rehabil 1982; 9:45-51. 12. Celenza FY, Nesedkin IN: Occlusion-The State afthe Art. Chicago, Quintessence, 1978. 13. Chaffee RB, Zabara J, Tansy MF: Suppression of the gag reflex by exaggerated respiratory movements. J Dent Res 1970; 49:572-575.
Maturation 14. Chase MH, McGinty DJ, Sterman MB: Cyclic variation in the amplitude of a brain stem reflex during sleep and . wakefulness. Experimentia 1968; 24(specialia): 47-48. 15.' Christensen LV: Some subjective-experimental parameters of experimental tooth clenching in children. J Oral Rehabi11980; 7:205-213. 16. Cleall IF: Deglutition: a study of form and function. Am J Orthod 1965; 51:566-594. 17. Coleman D: Facial action coding system: 7,000 possible facial expressions, Psychol Today 1981; 15:42-49. 18. Darwin D: The Expression of the Emotions in Man and Animals (1872). Chicago, University of Chicago Press, 1965. 19. Dawson PE: Evaluation, Diagnosis and Treatment of Occlusal Problems. St Louis, CV Mosby, 1974. 20. Disney TV: The Effects of Succinylcholine Chloride and Sodium Thiopental on the Rest Position of the Mandible, M.Sc. thesis. Dalhousie University, 1978. 21. Dubner R, Sessle Bl, Storey AT: The Neural Basis of Oral'and Facial Function. New York, Plenum Press, 1978. 22. Duchenne GB A: Physiologie des Mouvements (1867); Philadelphia, WB Saunders Co, 1959. 23. Duncan lP, Vickers GM, Forsyth DG: Replication of anatomical and other irregular surfaces. Proceedings of the Fourth North American Metalworkers Research Conference, 1976; 295-301. 24. Elftman H: Biomechanics of muscle with particularapplication to studies of gait. J Bone Joint Surg 1966; 48A:363-377 . 25. Eriksson P-O: Muscle-fibre composition of the human mandibular locomotor system. Swed Dent J 1982; 12(suppl): 1-44. 26. Farrell lH: The effect of mastication on the digestion of food. Br Dent J 1956; 100:149-155. 27. Fletcher SG, Casteel RL, Bradley DP: Tongue-thrust swallow, speech articulation and age. J Speech Hear Disord 1961; 26:201-208. 28. Frankel R: Technik und Handhabung der Funktionsregler, Berlin, Veb Verlag Yolk u Gesundheit, 1976 .. 29. Goldberg U: The effect of jaw position on the excitability of two reflexes involving the masseter muscle in man. Arch Oral Bioi 1972; 17:565-576. 30. Graf H: Occlusal forces during function, in Rowe NH (ed): Occlusion: Research in Form and Function, Proceedings of the Symposium, Ann Arbor, University of Michigan, 1975, pp 90-111. 31. Graf H, Grassl H, Aeberhard Hl: A method for measurement of occlusal forces in three dimensions. Helv Odontol Acta 1974; 18:7-11. 32. Grant PG: Lateral pterygoid: two muscles? Am J Anat 1973; 138:1-10. 33. Greenberger RS: A Study of Pressoreceptive Thresholds of Teeth in Children, M.Sc. th~sis. Ann Arbor, University of Michigan, 1966. 34. Grewcock R1G, Ballard CF: Clinical aspects and physiological mechanism of abnormal paths of closure. Trans Eur Orthod Soc 1954; pp 273-294. 35. Grimm AF, Katele KV: Silver dust-a tool to study growth interrelationships between bone, periosteum and muscle. Anat Rec 1979; 194:539-555. 36. Hannam AG, De Cou RD, Scatt lD, et al: The kinesiographic measurement of jaw displacement. 1 Prosthet Dent 1980; 44:88-93.
-.
of the Orofacial Musculature
95
37. Huber E: Evolution of Facial Musculature and Facial Expression. Baltimore, lohns Hopkins University, 1931 . 38. Humphrey T: The development of mouth opening and related reflexes involving the oral area of human fetuses. Ala J Med Sci 1968; 5:126-157. 39. Ingervall B: Studies of mandibular positions in children. Odontol Rev 19(suppl 15) 1968; I-53. 40. Ingervall B: Recording of retruded positions of mandible in children. A comparison between registrations in general anaesthesia and with children awake.Odontol Rev 1968; 19:413-421. 41. loss A, Graff H: A method for analysis of human mandibular occlusal movements. Schweiz Monatsschr Zahnheilk 1979; 89:1211-1220. 42. Kamiyama T: An electromyographic study on the function of the external pterygoid muscle (Japanese). Kokubyo Z 1958; 25:576-595. 43. Kawamura Y, Abe K: Role of sensory information from temporomandibular joint. Bull Tokyo Med Dent Univ 1974; 21 (suppl): 78-82. 44. Lear CSC, Flanagan lB, Moorrees CFA: The frequency of deglutition in man. Arch Oral Bioi 1965; 10:83-99. 45. Linder-Aronson S: Adenoids. Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition. Acta Otolaryngol 1970; 265:(suppl) 1-132. 46. Lindqvist B: Bruxism in twins. Acta Odontol Scand 1974; 32: 177-187. 47. Lowe AA: Mandibular joint control of genioglossus muscle activity in the cat (Felis domesticus) and monkey (Macaca irus), Arch Oral Bioi ]978; 23:787-793. 48. Lowe AA, lohnston WD: Tongue and jaw muscle activity in response .to mandibular rotations in a sample of normal and anterior open-bite subjects. Am J Orthod 1979; 76:565-576. 49. Lund lP, Lamarre Y: The importance of positive feedback from periodontal pressoreceptors during voluntary isometric contraction of jaw closing muscles in man. J Bioi Buccale 1973; 1:345-351. 50. Mahan PE, Wilkinson TM, Gibbs CH, et al: Superior and inferior bellies of the lateral pterygoid muscle: EMG activity at basic jaw positions. J Prosth Dent] 983; 50:710718. 51. Maxwell LC, Carlson DS, Brangwyn CE: Lack of 'acid reversal' of myofibrillar adenosine triphosphatase in masticatory muscle fibres of rhesus monkeys. Histochem J " 1980; 12:209-219. 52. McCall WD: Other diagnostic techniques (EMG, thermography, laboratory). American Dental Association President's Conference on the Etiology, Diagnosis and Management of TMl Disorder, Chicago, lune 1-4, 1982. 53. McClean MD, Folklins lW, Larson CR: The role of the ':'" perioral reflex in I.ip motor control for speech. Brain Lang "'-1979; 7:42-61. 54. McDougall PD, McNamara lA lr, Dierkes lM: Arch width development in Class II patients treated with the Frankel appliance. Am J Orthod 1982; 82: 10-22. 55. McMillen LB: Border movements of the human mandible. J Prosthet Dent 1972; 27:524-532. 56. McNamara lA: The independent functions of the two heads of the lateral pterygoid muscle. Am J Anat 1973; 138:197-205. 57. McNamara lA, Carlson DS, Yellich GM, et al: Musculoskeletal adaptation following orthognathic surgery, in Carl-
96
Growth and Development
son DS, McNamara JA Jr (eds): Muscle Adaptation in the Craniofacial Region, monograph 8. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1978, pp 91-155. 58. M~ller E: The chewing apparatus: An electromyographic study of the action of the muscles of mastication and its correlation to facial morphology. Acta Physiol Scand 1966; 69(suppl 280): 1-229. 59. Morimoto T: Mandibular position sense in man. Front Oral Physioll983; 4:80-101. 60. Moss ML: The functional matrix, in Kraus BS, Riedel RA (eds): Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1962. 61. Moyers RE: An electromyographic analysis of certain muscles involved in temporomandibular movement. Am J 'Orthod 1950; 36:481-516. 62. Moyers RE: The role of musculature in orthodontic diagnosis and treatment planning, in Kraus BS, Riedel RA (eds): Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1962. 63. Moyers RE: The infantile swallow. Trans Eur Orthod Soc 1964; 40: 180-187. 64. Muhl ZF, Grimm AF: Adaptability of rabbit digastric muscle to an abrupt change in length: A radiographic study. Arch Oral Biol1974; 19:829-833. 65. Neilson PD, Andrews G, Guitar BE, et al: Tonic stretch reflexes in lip, tongue and jaw muscles. Brain Res 1979; 178:311-327. 66. Nevakari K: An analysis of the mandibular movement from rest to occlusal position. Acta Odontol Scand 1956; 14(suppl 19) 1-129. 67. Peiper A: Cerebral Function in Infancy and Childhood Nagler B, Nagler H (trans). New York, Consultants Bureau, 1963. 68. Perry HT: Relation of occlusion to temporomandibular joint dysfunction: The orthodontic viewpoint. J Am Dent Assoc 1960; 79: 137 -141. 69. Petrovic AG, Stutzmann 11, Oudet CL: Control processes in the postnatal growth of the condylar cartilage of the mandible, in McNamara JA Jr (ed): Determinants of Man- . dibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975, 101-153. 70. Pierce RB: Tongue Thrust: A Look at Oral Myofunctional Disorders. Lincoln, Nebraska, Cliffs Notes, 1978. 71. Posselt V: Studies in the mobility of the human mandible. Acta Odontol Scand lO(suppl 10) 1952; 1-160. 72. Proffit WR: Equilibrium theory re-examined: To what extent do tongue and lip pressures influence tooth position (and thereby occlusion?), in Perry man JH (ed): Oral Physiology and Occlusion. New York, Pergamon Press, 1978. 73. Proffit WR: The facial musculature in its relation to the dental occlusion, in Carlson DS, McNamara JA Jr (eds): Muscle Adaptation in the Craniofacial Region, monograph 8. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1978. 74. Pruzansky S: Applicability of electromyographic procedures as a clinical aid in the detection of occlusal disharmony. DentClinNorthAm 1960; 117-130. 75. Rakoski Von Th: Funktionelle Kiefergelenkst6rungen bei Kindem. Fortschr Kieferorthop 1971; 32:37-57. 76. Ricketts RM: Laminagraphy in the diagnosis of temporo-
77.
78. 79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92. " 93.
mandibular joint disorders. J Am Dent Assoc 1953; 45:620-648. Ricketts RM: Facial and denature changes during orthodontic treatment as analyzed from the temporomandibular joint. Am J Orthod 1955; 41: 162-179. Ricketts RM: Respiratory obstruction syndrome. Am J Orthod 1968; 54:495-514. Ringqvist M: Fiber types in human masticatory muscles. Relating to function. Scand J Dent Res 1974; 82:333355. Ringqvist M: Size and distribution of histochemical fibre types in masseter muscle of adults with different states of occlusion. J Neurol Sci 1974; 22:429-438. Ringqvist M, Ringqvist I, Thornell L-E: Differentiation of fibres in human masseter temporal and biceps brachii muscles. J Neurol Sci 1977; 32:265-273. Roehm EG: Computed tomographic measurement of tongue volume relative to its surrounding space, M.Sc. thesis. University of Manitoba, 1981. Schaerer P, Stallard RE, Zander HA: Occlusal interferences and mastication: An electromyographic study. J Prosthet Dent 1967; 17:438-449. Schwindling R, Stark W: As adapted by Brill N, Tryde G: Physiology of mandibular positions. Front Oral Physiol 1974; 1:199-237. Sessle BJ, Gurza SC: Jaw movement-related activity and reflexly induced changes in the lateral pterygoid muscle of the monkey Macaca fascicularis. Arch Oral Biol 1982; 27: 167-173. Shriberg L, Kwiatkowski J: Natural Process Analysis. A Procedure for Phonological Analysis of Continuous Speech Samples. New York, John Wiley & Sons, 1980. Smith DM: A Numerical Model of Temporomandibular Joint Loading, M.S. thesis. State University of New York at Buffalo, 1984. Stone AC:Cinefluorographic study of mandibular movements in Class 11, division 2 malocclusion, M.Sc. thesis. University of Manitoba, 1971. Storey AT: The neurobiology of occlusion, in Johnston LE (ed): New Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1985. Storey AT: The neurobiology of temporomandibular disorders, in Carlson DS, McNamara JA Jr, Ribbens KA (eds): Developmental Aspects of Temporomandibular Joint Disorders, monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. Superstine M: Mandibular movement in children as revealed by the use of rapid serial cephalograms, M.Sc. thesis. University of Michigan,""1957. Tabary JC, Tabary C, Tardieu C, et al: Physiological and structural changes in the cat's soleus muscle due to immobilization at differept.lengths by ptaster casts. J Physiol ;fLond) 1972; 224:231-144. Thexton AJ, Hiiemae KM: The twitch contraction characteristics of opossum jaw musculature. Arch Oral Bioi 1975; 20:743-748.
94. Travis LE: Handbood of Speech Pathology and Audiology, Englewood, NJ, Prentice-Hall, 1971. 95. Vanoucek HL: An electromyographic and cephalometric radiographic investigation of variations in mandibular position in relation to head position, M.Sc. thesis. Northwestern University, 1961. 96. Warren DW: Aerodynamic studies of upper airway: impli-
Maturation
97.
98. 99.
100.
1'01.
cations for growth, breathing, and speech, in McNamara JA Jr (ed): Naso-respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. Wickwire NA, Gibbs CH, Jacobson AP, et al: Chewing patterns in normal children. Angle Orthod 1981; 51:4860. Williamson EH: Occlusion and TMJ dysfunction. J Clin Orthod 1981; 15:333-350. Williamson EH, Lundqvist DO: Anterior guidance: Its effect on electromyographic activity of the temporal and masseter mug;les. J Prosthet Dent 1983; 49:816-823. Windle WF: Correlation between the development of local reflexes and reflex arcs in the spinal cord of cat embryos. J Comp Neurol 1934; .59:487-503. Yu S-K, Schmitt J, Sessle BJ: Inhibitory effects on jaw muscle activity of innocuous and noxious stimulation of facial and intraoral sites in man. Arch Oral Bioi 1973; 18:861-870.
SUGGESTED READINGS Anderson DJ, Matthews B (eds): Mastication. Bristol, England, J Wright and Sons, 1976. Bosma J: Oral and pharyngeal development and function. J Dent Res 1963; 42:375-380. Carlson OS, McNarnara JA Jr (eds): Muscle Adaptation in the Craniofacial Region, monograph 8. Craniofacial Growth Se- . ries. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975.
of the Orofacial Musculature
97
Dubner R, Sessle BJ, Storey AT: The Neural Basis of Oral and Facial Function. New York, Plenum Press, 1978. Johnston LE (ed): New Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1985. Kawamura Y, Dubner R (eds): Oral-Facial Sensory and Motor Functions. Chicago, Quintessence, 1981. Kraus BS, Riedel RA (eds): Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1962. McNamara JA Jr, Ribbens KA (eds): Naso-respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. McNamara JA Jr (ed): Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. McNamara JA Jr (ed): Factors Affecting the Growth of the Midface, monograph 6. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. Marimoto T: Mandibular position sense in man. Front Oral Physiol1983; 4:80-101. Peiper A: Cerebral Function in Infancy and Childhood, Nagler B, Nagler H (trans). New York, Consultants Bureau, 1963. Perry man HH (ed): Oral Physiology and Occlusion. New York, Pergamon Press, 1978. Sessle BJ, Hannan AG (eds): Mastication and Swallowing: Biological and Clinical Correlates. Toronto, University of Toronto Press, 1976. Wood WW: A review of masticatory function. J Prosthet Dent 1987; 57:222-232.
CHAPTER
6 Development of the Dentition and the Occlusion Alphonse R. Burdi, M.S., Ph.D. Robert E. Moyers, D.D.S., Ph.D.
Adam and Eve had many advantages, but the principal one was that they escaped teething.-MARK TWAIN.The Tragedy of Pudd'nhead Wilson. Chapter 4, "Pudd'nhead Wilson's Calendar"
KEY POINTS 11. Variation in eruption of permanent teeth may be produced by racial differences, sexual dimorphisms, economic status, localized pathosis, extraction of the primary predecessor, and injury.
1. Embryonic development of both dentitions proceeds through four stages: initiation, bud, cap, and bell. 2. Variations in tooth size, position, sequence of development, and sexual dimorphisms are also apparent during prenatal development. 3. The neonate's mouth has no teeth. 4. The relationship of the neonatal gum pads is a poor indicator of future dental occlusal relations . 5. Calcification of the primary teeth begins about the fourteenth intrauterine week. 6. Primary teeth emerge in typical sequences beginning around the seventh month (mandibular incisor) and ending about the twenty-sixth month (maxillary second primary molar). ,. 7. The primary occlusion shows less variability than the permanent and is established by the functional muscle matrix as the teeth erupt. 8. The primary occlusion changes as an adaptation to skeletal growth and occlusal wear. 9. Girls are generally more advanced than boys at all stages of dental calcification. 10. Teeth do not begin to move occlusally until crown formation is completed.
12. Tooth size is largely determined genetically. 13. There are relationships among dental agenesis, delayed development, and diminished size of teeth. ."
14. Supernumerary teeth are rarer than congenitally missing teeth and occur more frequently in males. 15. Dental arch width changes are timed more closely to dental development than to overall skeletal growth. 16. Dental arch circumference reduces during the late transitional and early permanent dentition.
J7. The distal surfaces of the second primary molars are •., determinant factors in tIJe initial permanent molar occlusion. 18. Subsequent occlusal changes occur as a result of differential craniofacial skeletal growth, caries, loss of primary teeth, muscle habits, and other factors. 19. Third molars show more variability in development than any other teeth. 20. The adaptive mechanisms permitting occlusal homeostasis vary greatly with the stage of development. 99
100
Growth and Development
OUTLINE A.
Prenatal Dental Development (ARB) 1.
2.
B.
C.
I. 2.
The gum pads Neonatal jaw relationships
3.
Precociously
I.
Calcification
2.
Eruption a) Interrelationships between calcification and eruption b) Factors regulating and affecting eruption c) Timing and variability of eruption d) Sex differences e) Sequence of eruption f) Eruption and bodily growth g) Ectopic development h) Factors determining the tooth's position during eruption
The Permanent Dentition (REM) Size of teeth Number of teeth a) b)
G.
5.
6.
H.
Missing teeth Supernumerary
teeth
Dimensional Changes in the Dental Arches (REM) I.
Width
2. 3. 4. 5.
Length or depth Circumference or perimeter Dimensional changes during orthodontic therapy Overbite and overjet
The Mixed Dentition Period (REM) I. 2.
Uses of the dental arch perimeter Occlusal changes in the mixed dentition
-.
First molar eruption a) Mandible b) Maxilla Incisor eruption a) Mandible b) Maxilla Cuspid and bicuspid eruption a) Mandible b) Maxilla Second molar eruption
DentitionaI and Occlusal Development in the Young Adult (REM) I. 2. 3. 4. 5.
I.
Development of the primary teeth a) Calcification b) Eruption c) Teething and systemic disturbances d) Size and shape of primary teeth e) Anomalies f) Primary tooth resorption g) Ankylosis of primary teeth Development of the primary occlusion a) Neuromuscular considerations b) Primary dental arches c) Occlusal relations d) Disorders of the primary occlusion
Development of the Permanent Teeth (REM)
I. 2.
F.
4.
erupted primary teeth
The Primary Teeth and Occlusion
2.
E.
The prenatal beginnings of the dentitions a) Initiation of odontogenesis I) Bud stage 2) Cap stage 3) Bell stage b) Sequence patterns Spatial patterns a) Arch shape b) Spacing c) Fields
The Mouth of the Neonate (REM)
I.
D.
3.
Third molar development Dimensional changes Occlusal changes Resorption of permanent teeth Arrangement of the teeth in the jaws
Clinical Implications (REM) I. 2.
Normal versus ideal occlusion Models of occlusion
3.
Occlusal adaptive mechanisms
A. PRENATAL DENTAL DEVELOPMENT Seeing things from their beginnings is most advantageous; thus, the concern with morphogenic patterns from their embryonic inception looks to the future of these patterns in the growing child. Although the tooth might be regarded clinically as an isolated unit, its biology (and that of the surrounding tissues) is best understood in the context of the total life cycle of these structures. The length of the morphogenic period, from the first appearance of the tooth bud to eruption and functional occlusion, should not be underestimated. Both the orthodontist and the general practitioner should understand the prenatal origins of typical and atypical spatial arrangements of developing teeth within the jaws. 73 The evaluation of a given tooth within its dental arch is best carried out in reference to past developmental timing, present spatial patterning, and future functional demands.
1. The Prenatal Beginnings of the Dentitions ',.
The embryonic development of both deciduous and permanent teeth proceeds in four stages which are named for the characteristic features of the stage: initiation, bud, cap, and bell (Fig 6-1). a) Initiation of Odontogenesis '.•The first sign of tootIY'development appears late in the third embryonic week when the epitheliaUining of the oral cavity begins to thicken in broad zones. This thickening is brought about from deep within the specialized connective tissue beneath the oral lining by a combination of cell-cell cytoplasmic contacts and movement of transmissible proteins. The interacting connective tissue. had its origins in neural crest material. The epithelial thickenings occur on the inferolateral borders of the maxillary and on the superolateral borders of the mandibular arches where the two join to form the lateral margins of the mouth. By the sixth week, two additional maxillary odontogenic tissues have arisen more anteriorly. At 6
Development '''~oral
~
101
epithelium dental
A
of the Dentition and Occlusion
jaw dental
lamina mesenchyme bud
dental
permanent dental
lamina
reticulum
c ~l'~~
enamel dentin dental
root
FIG
pulp
sheath
6-1.
Early stages of tooth formation (A-F) followed by initiations of eruption and emergence (G-H). Approximate ages are 8 weeks (A), 10 weeks (B), 11 weeks (C), 12 weeks (D), 4 months (E), 6 months (F), 8 months (G), and into the postnatal eruption periods. (Modified from
Burdi AR: The develoPrT1ent and eruptions of the human dentitions, in"Ferrester DJ, Wagner ML, Fleming J (eds): Pediatric Dental Medicine. Philadelphia, Lea & Febiger: 1981.)
102
Growth and Development
weeks, the four maxillary odontogenic zones coalesce to form a continuous dental lamina, and the two mandibular odontogenic zones fuse at the midline. These upper and lower dental fields now form C-shaped epithelial arches. The teeth begin with invagination of the dental lamina into the underlying mesenchyme at specific locations along the free border of each arch. Morphologic changes in the dental lamina begin at about 6 weeks in utero and continue beyond birth to the fourth or fifth year. This occurs in three main phases: a) Initiation of the entire deciduous dentition occurs during the second month in utero. b) Initiation of the permanent teeth that will be the successors of the deciduous teeth occurs by the growth into surrounding connective tissues of the free distal end of the dental lamina, giving rise to the successional lamina. Its continuing growth lingual to the enamel organ of each deciduous tooth occurs from about the fifth month in utero (second premolars). c) The dental lamina elongates distal to the second deciduous molar and gives rise to the permanent molar tooth germs. The time of initiation of the first permanent molar is about 4 months in utero; for the second permanent molar, 1 year; and for the third permanent molar, 4 to 5 years.
A
B
Cervical
loop
c
D
Epithelial
1) Bud Stage.-Soon
after dental lamina formation, a vestibular furrow divides the cheeks and lips from the dental arches. Subsequently, the dental lamina shows specific sites of increased mitotic activity which produce knob-like tooth buds corresponding to the ten deciduous teeth in each jaw. The first buds to form (at about the seventh week) are of the mandibular anterior teeth. By the eighth week, all mandibular and maxillary deciduous tooth buds are present. 2) Cap Stage.- The growth rate throughout the bud is not uniform, being more active peripherally. By the end of the eighth week, there appears a concavity on the deep surface of the bud. The tooth is now in its cap stage. As the epithelium of the capshaped tooth organ enlarges and proliferates into deeper specialized connective tissues (ectomesenchyme), there is increased activity in cells contiguous with the ectodermal tooth bud. Areas of increased cellular density eventually give rise to the nonenamel portions of the tooth and its periodontal matrix. At this time the essential parts of the tooth-enamel organ, dental papilla, and dental follicle-are identifiable. Collectively they are called the tooth germ. 3) Bell Stage.- The bell stage represents enlargement of the overall size of the tooth germ and deepening of its undersurface. Cells at the center secrete an acid mucopolysaccharide into the extracellular space between the epithelial cells covering the germ, which results in a drawing in of the water and an enlargement of the germ. A zone of stretched but interconnected cells, the stellate reticulum, is produced at the center of the germ. Epithelial cells next to the papilla develop into an enamel-producing layer of cells, the inner dental epithelium; epithelial cells along the leading edge of the germ form the outer dental epithelium, which eventually gives rise to the dental cuticle. The transition zone between outer and inner dental epithelia forms the cervical loop.
membrane
FIG 6-2. A-D, arrangement of enamel and dentin forming tissues with the key tissues involved in root development. (Modified from Orban BJ: Oral Histology and Embryology. St Louis, CV Mosby Co, 1976.)
The differentiation of dentin-producing odontoblasts in the dental papilla is initiated by the neigh boring cells of the inner dental epithelium. Enamel formation cannot occur until the proper amount of dentin is laid down. This same reciprocal interaction between the inner and outer enamel epithelia also occurs in tooth formation. In the cervical loop area, neighboring cells of the two epithelia progressively constrict around the dental papilla to leave onJy a small opening, which will become the apical foramen. At this time, the dentin which forms the tooth root is first laid down (Fig 6 - 2). The germ loses its connection with the oral epithelium, and the inner enamel epithelium begins to fold, making it possible to recognize the crown shape of specific morphologic classes of teeth. By this process of J:1istodifferentiation, a mass of ectoderman;: derived epithelial cells progressively differentiates into the comp6nents of the tooth which determine crown shape, initiate dentin formation, and form enamel. b) Sequence Patterns The 20 deciduous tooth buds differentiate through the cap and bell stages at rates that manifest recognizable sequence patterns, or polymorphisms. 11 In the main there is a mesiodistal gradient of embryonic tooth development, dil-di2-c-dml-dm2, but other developmental sequences are seen in 25% of the cases studied. These embryonic sequence variations may be the prenatal
Development
0r 8~ I,8 I « IIr Ir 0A
L 46 I 10 ,, (/) ....J II0 W -- ,6 ~14 Q J: 12 W Z 01 ~ c:: 4 2 15 10 CHANGING E 25wks
2
E
16
r
of the Dentition and Occlusion
103
B ARCH SHAPE PATTERNS
CHANGING ARCH SHAPE PATTERNS 16
MAXILLA
MANDIBLE
E
.s
14
25wks
J:
I~ Z
W
12
....J
J: U
Ir
« Ir 8 Q Ir W
t;
o
6
0-
I
Ir o Ir ~
Z
2
« o ARCH
WIDTH
(mm)
o
4
2 ARCH
6
WIDTH
8
10
(mm)
FIG 6-3. Graphic reconstructions of prenatal dental arch quadrants of the upper (A) and lower (B) jaws. Note the catenary shape of the aligned dental arch at 12.5 weeks. The shadowed areas show a reshaping
of the arch by progressive
lingual drifting of the lateral incisor tooth
germ. Midline length is shown on the vertical axis and arch width on the horizontal axis.
B MLP
di 1
,.
v
c
~
.~~--------------------------dm2
baseline
DlP
FIG 6-4. A, photomicrograph of a 10 f.l. frontal section through face of 24week human fetus showing the linear distances from the midline to points on the tooth germ which are subsequently transferred onto grids for graphic reconstructions. The inset shows transverse cuts through the body and head of a prenate with marked cervical flexure. producing a frontal section through the face. B, two-dimensional reconstruction made from measurements from projected histologic
sections through the prenatal face. This dental arch quadrant shows the arrangement of tooth germs in the aligned arch (solid lines) and where the catenary-shaped aligned arch is reshaped by the lingual drifting of the lateral incisor tooth germ (dashed lines). The horizontal lines show how data taken from each histologic section is "stacked" to produce the reconstruction.
104
Growth and Development
antecedents of polymorphisms of sequence tions.22 Here are three examples:
in postnatal
50
denti-
a) Postnatally, mandibular incisors tend to erupt earlier than their maxillary opponents, while maxillary precedence predominates in the posterior teeth.46 In the embryo, opponent deciduous tooth germs are usually at the same maturational stage9; but such inter-jaw differences as occur show mandibular advancement for the incisor tooth germs and a maxillary precedence for the maxillary molars. b) In postnatal tooth development there is a distance gradient of crown size correlations; teeth closer together within a jaw quadrant show higher correlations in crown size than widely separated teeth. 29.31.36Observations in a series of human embryos paralleled the postnatal observations for maxillary and mandibular tooth germs in both male and female embryos.24. 2R c) In the calcification and eruption of permanent teeth, except the third molar,6s girls are advanced; in that of deciduous teeth, boys are somewhat advanced. Prenatally, male tooth germ development is consistently ahead of female. 10 As with palatal closure, which occurs at a faster rate in male embryos than in female," one might explain the sexual dimorphism as a possible delayed influence of the second X chromosome at the embryonic tissue level. 71
2. Spatial Patterns a) Arch Shape The postnatal human dental arch is generally described by a catenary curve.62 Scott reported that the catenary pattern also held for both the embryonic dental lamina and the arrangement of tooth germs. This has been shown to be an overgeneralization7 The prenatal dental arch progressively changes shape; at 6 to 8 weeks it is anteroposteriorly flattened, not a catenary curve at all. By the bell stage of the tooth germs, the anterior segment of the dental arch has elongated and approaches the catenary by th~ beginning of the fourth month. A bilateral cleft lip and palate arrests this development; with surgical correction of the cleft and continued facial growth, the maxillary dental arch may proceed toward the expected catenary shape.3R Figures 6-3,A and 6-3,BR4 show the general run of arch form change from 3 months to 6 months prenatal development. Note the lingual drift of the deciduous lateral incisors and the increase in the dental spacing in the molar region. Figures 6-4,A and 6-4,B show how.these data were derived from thinly sectioned human prenatal heads by. graphic reconstructions. R4 b) Spacing There have been many studies on the development of tooth spacing postnatally, among them the classic contributions of LundstromSR and Moorrees, 67but less work has been reported about the prenatal period. The deciduous anterior teeth, especially the lateral incisor, often appear crowded and out {)f alignment within the total dental arch before birth (cf. Fig 6-3), but usually erupt in good alignment. RRThe sum of the mesiodistal diameters of the five deciduous tooth germs in each jaw quadrant increases over
Summed Crown Diameters
~ (f)
z Q 30 (f)
Z W ~
(5 ....J
~ Z W
o
ow ~
~
10
Summed Inferdentol
::::l
~-
(f)
50
lOO
...... ~_-&.°oo--a--__ ~_-o_ o 0
150
CROWN-RUMP
FIG
\
tr- ....• o
o
Space
200
LENGTH
250
300
(in mm)
6-5.
Changing relationship between summed crown sizes of di 1-di2-cdm1-dm2 and summed interdental spaces in prenates during 10 to 28 weeks of development. Summed crown sizes increase eightfold, whereas summed interdental spacing shows little correlation with increasing body size.
time until at about 23 weeks it exceeds the length of the aligned dental arch (Fig 6-5). Interdental spacing is relatively constant during this period.26 Most tooth germs show significant increase in mesiodistal crown size related to linear growth phases from II to 14 and 20 to 26 weeks with a level growth phase in between the periods of linear growth. Within the anterior arch there is only a slight increase in interdental spacing; in both jaws the posterior arch spaces show decreases during this period. Thus, while the jaws are increasing in absolute size, the interdental tissues do not keep'pace with the increments in posterior tooth size. c) Fields Let us define a tooth field as the tooth germ together with the space mesial and distal to it within the dental arch. Interdental spaces are shared by neighboring tooth fields. Figure 6-6,A and B show how much of a space-toath-space field is occupied by a given deciduous tooth germ. The greatest level of occupancy of a tooth field by a tooth germ is about 80% for the first deciduous mQ!¥ and lateral incisor, There is an adaptation here. By approximately 16 weeks of gestation the lateral incisor tooth germ occupies 100% or more of its available tooth field in the aligned arch, but there is often a concomitant rotation and lingual displacement which appears to keep di2 in conformance with the 80% of tooth germ occupancy in the tooth field. This lingual displacement of the lateral incisor occurs in about four to ten prenates and demonstrates the early prenatal beginnings of similar lateral incisor displacement in term prenates reported by van der Linden et al. RR In summary, soon after the tooth passes through its cap stage of development, developmental variations are discernible with suf-
Development of the Dentition and Occlusion
105
TOOTH FIELDS
A 140%
MAXILLA
120%
100%
80% 60% 40% 20%
50
100 150 200 CROWN-RUMP LENGTH (mm)
250
TOOTH FIELDS
B 140%
MANDIBLE
120%
FIG 6-7.
100%
Neonatal maxillary gum pads. Note the segmentations of the gum pads and how they correspond to the developing primary teeth. (Courtesy of Or. James McNamara.)
80% 60% 40'%
20'%
50
100 150 200 CROWN-RUMP LENGTH (mm)
250
FIG 6-6. A and B, using the concept of a tooth field, it is shown in these figures that the percentage of occupancy of a tooth field by a tooth germ will vary from tooth to tooth, with the maximum percentage at approximately 80% for both the upper (A) and lower (B) dental arch quadrants.
The size of the gum pads at birth might be determined by anyone of the following factors, according to Leighton55: (I) the state of maturity of the infant at birth; (2) the size at birth as expressed by birth weight; (3) the size of the developing primary teeth; and (4) purely genetic factors. The maxillary arch is horseshoe-shaped and the gum pads tend to extend buccally and labially beyond those in the mandible; furthermore, the mandibular arch is posterior to the maxillary arch when the gum pads contact. 55. 83
2. Neonatal Jaw Relationships ficient regularity to be considered as stable patterns or polymorphisms involving structural or spatial relationships over time. Sexual dimorphisms also are apparent. As tooth formation is a developmental continuum from the 3-week embryo to the 5-year-old child, it is not surprising to see parallels between prenatal odontogenesis and the patterns of dental formation and arrangement seen by the practicing clinician'.
B. THE MOUTH OF THE NEONA TE 1. The Gum Pads At birth, the alveolar processes are covered by gum pads, which soon are segmented to indicate the sites of the developing teeth (Fig 6_7).13.89 the gums are firm, as in an adult edentulous mouth. The basic form of the arches is determined in intrauterine life (see Fig 6-3).
" Although the upper and lower gum pads touch throughout much of the arch circumference, in no way is a precise "bite" or jaw relationship yet seen. Indeed,at birth there is such a variability in the relationships of the upper and lower gum pads that the neonatal relationship cannot be used as a diagnostic criterion for reliable predictions of subsequent occlusion in the primary dentitiqn.55 Some have held that an anterior open bite of the gum pads i~ normal and even a prerequisite' for a subsequent normal incisor relationship. Simpson and Cheung83 found that only 2% of all neonates have an anterior open bite gum pad relationship. They also reported oral habits had a definite influence on the infantile gum pads, resulting in a significant increase in the incidence of anterior open bite relationships by the age of 4 months. The mouth of the neonate is a richly endowed sensory guidance system providing input for many vital neuromuscular functions, for example, suckling, respiration, swallowing, yawning, and coughing, which are discussed iri Chapter 5.
106
Growth and Development
6-2.
3. Precociously Erupted Primary Teeth
TABLE
Occasionally, a child will be born with teeth already present in the mouth. Natal (present at birth), neonatal (erupted during the first month), and pre-erupted (erupting during th~ second or third months) teeth are almost always mandibular incisors which frequently display enamel hypoplasia. There are familial tendencies for such teeth. Such teeth should not be removed, if they are near normal, even though they may cause the mother some discomfort during nursing, unless they are certainly supernumeraries.
Sequence of Emergence
C. THE PRIMARY TEETH AND OCCLUSION 1. Development of the Primary Teeth a) Calcification The sequence of initial calcification of the primary teeth is central incisors (14 weeks), I first molars (151/2 weeks), lateral incisors (16 weeks), canines (17 weeks), and second molars (18 weeks) (Table 6_1).59 Since the primary teeth develop at different ~ necessarily maintained0 in subsequent rates, this sequence is not ~ TEETH Q developmental stages.'9 The crowns of the teeth 20 continue 15 to grow to in width until there is coalescence of the calcifying cusps, at which time most of the crown diameter of the tooth has been determined. ~ There are few genetic studies of calcification of primary teeth, but there is evidence that genetic control is exercised in some manner over crown morphology, rate and sequence of growth, pattern of calcification, and mineral content. Prenatal dental develoment is characterized by at least as much sexual dimorphism, developmental variability, bilateral asymmetry, and sequence variability as has been reported in the postnatal development of the deciduous and permanent dentitions. 27
AB
D
#$+t+1H++l A
of Primary Teeth
B
C
E
H++~Ot-H2:4t-H2:8+1 D
C
E
MONTHS between monozygous pairs. She estimates the effect of heredity on eruption of primary teeth at 78% and the effect of environment at 22%. For both blacks and whites, boys precede girls in total number of teeth erupted until about 15 months, then girls surpass boys and remain ahead throughout completion of the primary dentition (Fig 6-9).44 Tooth emergence is most highly associated with height, then weight and head circumference, though in the very early stage of emergence birth weight correlates better than height. Black children complete emergence ahead of white children and are more advanced for most measures of growth during the period of the eruption of primary teeth when socioeconomic status is similar.43 35 25
~
( Months)
AGE IN MONTHS ~
~ ~ ~~ ~ ~ 30 ~
~
MEAN
VALUE
<>
b) Eruption Eruption, that is, movement of the tooth toward occlusion, begins in a variable fashion but not until root formation has begun. The usual sequence of appearance in the mouth is shown in Table 6-2. The precise time of arrival of each tooth in the l1Jouth is not too important unless it deviates greatly from the averages (Fig 68).54.60.61.66 There are no clinically significant sexual differences in primary tooth emergence. Hatton,'l in a study of primary tooth eruption and emergence in twins, has shown no left-to-right differences or differences TABLE
FIG
6-8.
Variability of ages of emergence of primary teeth. (Adapted from Lysell. L, Magnusson B, Thilander B: Time and order of eruption of the primary teeth. A longitudinal study. Odontol Rev 1962; 13:217234, and Leighton BC: Eruption of deciduous teeth. Dental Practitioner 1968; 200:836-842.)
6-1.
Average Age for Critical Events in Primary Tooth Formation ,. CROW/I$.COMPLETED (POSTNATAL
(maxilla)
PRIMARY
TOOTH
ROOT COMPLETED
AGE. MO)
(YR)
.,
OF CALCIFICATION MAXILLA ONSET MANDIBLE 91'/2 (INTRAUTERINE AGE, 19 WK) 3 16 9 611 1014 17 2'/2 2'/2 5'/2 18 (mandible), 15'/2 MANDIBLE
MAXILLA 232'/2 3'/, 1'/2
32'/, 3'/,1'/2 1'/2
Modified from Lunt RC, Law DB: A review of the chronology Assoc 1974; 89:599-606.
of calcification
of deciduous
teeth. J Am Dent
TOOTH
Lateral Canine Lateral incisor incisor Mandibular First molar Second molar First molar Maxillary MEAN From Moyers RE. van der Linden FPGM. RioloML.et al: Standards TABLE 6-3. ---
J:
Iw
WHITE BOYS WHITE GIRLS ,,/
Female Ad vancement
W
I"
"
of
N SD SD MEAN 209 (MM) 9.73 (MM) 8.74 4.10 6.63 4.64 6.61 7.71 5.29 0.35 8.84 6.76 0.47 OA6 OA8 0.33 0.35 OA9 OA7 196 144 194 195 175 OA3 (MM) 6.74 (MM) 9.90 0.52 214 5.82 4.06 5.26 5.84 0.43 0.49 0.65 7.82 0.31 0.53 0.34 0.37 193 144 213 182 189 4.68 6A8 6A1 OA3 DAD 169 171 166 NFEMALE 212 107 Development of the Dentition and Occlusion Occlusal velopment. Universityof Ann Michigan. Arbor.MALE 1978. Mich.Center Reproduced for Human by permission. Growth and DeCentralDevelopment incisor Diameters of North American Children) Human Crown Sizes of Primary Teeth White (in This Case Mesiodistal Crown
/'
,,"
ICfl
o::J::J o U W o o I..L..
0::
W CD
~ ::J Z
20 I8
-
16
---
I 4 12
10
BLACK BOYS _. BLACK GIRLS,,/.
Female Advancement" -......
Male
Advancement
/.
'/
,,"
I '2
...J
~
oI-
+2.0 "'mU) ~~ o ~::tJm
~/ ~ )sI v._/
4 2
-2.0 Z~x
o
27 30
~
FIG 6-9. Differences in times of emergence of primary teeth for North American blacks and whites. (Adapted from Infante PF: Sex differences in the chronology of deciduous tooth emergence in white and black children. J Dent Res 1974; 53:418-421, and Infante PF: An epidemiological study of deciduous tooth emergence and growth in white and black children of southeastern Michigan. Ecol Food Nutr 1975; 4:117-124.)
c) Teeth and Systemic Disturbances Disagreement as to whether teething is responsible for systemic disturbances is very prevalent among dentists, physicians, and parents. Parents often report various symptoms and signs, including vomiting, fevers, and diarrhea, in association with teething. Although about one-third of all children record no symptoms during teething, 60% of infants exhibit disturbances such as rhinorrhea, irritability, and diarrhea which occur for a short time before tooth eruption and resolve after tooth emergence."' More serious symptoms such as upper respiratory infection, febrile'convulsions, wheezing bronchitis, and infantile eczema, which are often attributed to teething, have been shown to be unrelated to tooth emergence. '2 "Teething" as a diagnostic label should be avoided by physician and parent for all but the most trivial symptoms. Parents may be apathetic about children's complaints during times that teeth are erupting and, as a result, severe upper respiratory diseases and fever caused by other extra-oral complications may be overlooked.
sors. It is clear that common control mechanisms operating from prenatal time through the period of permanent crown formation are responsible for primary-permanent crown size correspondences. However, the values are so low that "prediction" of permanent diameters is manifestly impossible given only the size of the primary crowns.
e) Anomalies Anomalies of crown development are seen less frequently in the primary than in the permanent dentition and it is rarer for primary teeth to be congenitally missing, although thorough studies of this problem are not as plentiful as for the permanent dentition. Fewer than I% of all children have congenitally missing primary teeth, the most frequently missing being the maxillary lateral incisors, the maxillary central incisor, and the first primary molar, in that order. f) Primary Tooth Resorption It is common to suppose that the eruption of the permanent tooth is the sole factor causing primary tooth resorption; this is rIot the case, since the primary tooth may resorb even in the absence of the permanent successor.75 The basic pattern of primary tooth resorption is hastened by infIamri1ation and occlusal trauma; it is delayed by splinting (as when a space-maintainer is attached to the crown) and the absence of a permanent successor. 74
d) Size and Shape of Primary Teeth Good data on the size of primary teeth are available (Table Primary teeth in boys are generally larger than those in girls, but the sexual dimorphism is not as marked as in the permanent dentition. Primary tooth size and its mineral mass are largely inherited. There are important differences in tooth sizes between North American blacks and whites. However, racial and ethnic differences in the size and shape of primary are not as thoroughly documented as are those of the permanent teeth. Several attempts have been made to "predict" the size of the permanent teeth diameters from the size of the primary predeces6_3).70
• "g) Ankylosis of Primary Teeth Primary teeth, particularly molars, may become ankylosed (fused) to the alveolar process and their eruption prevented. Although permanent teeth can become ankylosed too, primary teeth are more likely to be involved and lower teeth twice as often as upper.) There is little evidence that ankylosis is a random phenomenon; nor is it due to trauma or recessive pressure, although this often is said to be the cause.) The etiologic picture is not yet clear, but ankylosis occurs during the normal physiologic resorption of teeth. Resorption is an intermittent process, and it is during
108
Growth and Development
the rest periods of resorption of dentin when the periodontal ligament has already been resorbed, that the osseous bridging and fusion'between bone and dentin occur, The majority of ankylosed primary teeth are observed in the late primary and the mixed dentitions, The condition often is bilateral and -a posterior open bite appears as the occlusal level of the ankylosed· teeth fails to keep up with the vertical development of adjacent teeth. Ankylosed teeth often are referred to as "submerged teeth" -an unfortunate misnomer, since they do not submerge. Treatment of this condition is described in Chapter 15.
2. Development of the Primary Occlusion . a) Neuromuscular Considerations The neuromuscular regulation of jaw relationship is important to the development of primary occlusion. Interdentation occurs sequentially, beginning in the front as the incisors erupt. As other new teeth appear, the muscles learn to effect the necessary functional occlusal movements. There is less variability in occlusal relationships in the primary than in the permanent dentition, since the primary occlusion is being established during periods of ready developmental adaptation. The teeth are guided into their occlusal position by the functional matrix of muscles during very active growth of the facial skeleton. Undoubtedly, the low cusp height and ease with which the occlusal surfaces wear also contribute to the adaptability of the primary occlusion. Definitive studies of interrelationships between skeletal morphology and primary occlusal relations are, unfortunately, lacking. Leighton,55 in one of the few quantitative studies available, has shown that where persistent sucking habits occur, there is a significantly larger mean overjet as early as 8 months and the difference increases with age. Some feel that this is the result of endogenous patterns of oromuscular behavior arising independent of skeletal morphology. It is also held that the muscle behavior is adaptive to the skeletal morphology. Leighton' s data do not exclude the possibility that the abnormal sucking habits could arise from environmental conditions (methods of feeding, use of pacifiers, and so forth) and that the persistent sucking habits either largely cause the skeletal differences or contribute to them. This latter hypothesis is the one best supported by experimental data on animals. It must be mentioned again that even Leighton's splendid study did not apply cephalometric analysis until the subjects were 3 to 4 years of age. When teeth are erupted and muscles are functioning, the arch formed by the crowns of the teeth is altered by muscular activities, although the original arch form is probably not determined by the muscles. As the primary teeth are formed, the alveolar processes develop vertically and the anterior intermaxillary space is lost in most children.
b) Primary Dental Arches Most primary arches are ovoid and display less variability in conformation than do the permanent arches (see Fig 6-44). Usually, there is generalized interdental spacing in the anterior region which, contrary to popular opinion, does not increase significantly after the primary dentition is completed.2 In fact, it has been found that the total interdental spacing between the primary teeth decreases continually with age. I Although the spacing is most likely to be generalized, there is no pattern of spacing common to all
FIG
6-10.
Arch dimensions. A, arch length. 8', bicanine diameter. diameter. C-C, arch perimeter or arch circumference.
£32,
bimolar
primary dentitions. Somewhat wider spaces, usually found mesial to all the maxillary cuspids and distal to the mandibular cuspids, are termed' 'primate spaces," since they are particularly prominent in the dentitions of certain lower primates. At birth, the primary arches are almost wide enough to hold the primary incisors. In the early stages of development, the tongue seems important in the shaping of the dental arches, for the primary dentition is molded around it, but its role diminishes with age, the establishment of occlusal reflexes, and the more mature activities of the lips after the eruption of the incisors and the cessation of nursing.53 The anterior part of the dental arches increases slightly from birth to 12 months and changes very little thereafter, though the increases are a bit greater in the maxilla than in the mandible (Fig 6-10, 6-26, and 6-27). Posterior diameters increase more markedly than those in the front of the arches (see Fig 6-28). For the first 6 months it accelerates and even exceeds, in some dimensions, the maxillary. 80 Dimensional increases in the arches seem to be associated with eruption of the primary teeth. Palatal vault width increases from birth to about 12 months and remains relatively constant throughout the first 2 years.
c) Occlusal Relations At birth, when the gum pads are in contact, the mandibular arch is posterior to the maxillary, though this difference reduces progressively up to 21 months. Attempts to register a specific "occlusal relationship" or "centric" at this time have been fruitless. With the eruption of the primary first molars the first threedimensional occlusal relationship is established. The primary posterior teeth occlude, so that the mandibular cusp articulates just ahead of its corresponding maxillary cusp (see Fig 6-44). The mesiolingual cusp of the maxillary molars occludes in the central fossae of tbe mandibular molars, and the incisors ar~:Vertical, with mini~~1 overbite and overjet. The mandibular second primary molar usually is" somewhat wider mesiodistally than the maxillary, giving rise, typically, to a flush terminal plane at the end of the primary dentition (Fig 6-11 )-a point of considerable clinical significance. Interproximal cavities, sucking habits, or the skeletal pattern may produce a "step" rather than a flush terminal plane. When the terminal plane is straight until the arrival of the first permanent molars, the latter are usually guided into an initial end-to-end relationship (Fig 6-12) considered "normal" for whites
Development
of the Dentition and Occlusion
109
FIG 6-11. A, the two primary second molars in occlusion. Note that although th-ere is a Class I molar relationship of the mesial surfaces (left), there is a flush terminal plane on the distal. e, primary and permanent tooth size relationships in the lateral segment of the dental arch. The average leeway space in the mandibular arch is greater than in the maxillary arch. This large difference in leeway space between the two arches is a factor that permits the late mesial shift of the man-
dibular first permanent molar in some instances_ Note that the figures shown are mean values. When development of a tooth size-arch space problem is expected during the mixed dentition, it is important to compute actual tooth size-space relationships for that particular mouth. Mean values are of interest but they will not provide the diagnosis for an individual case.
3 YEARS OLD
5 YE.ARS OLD
:, YEARS OLD
7 YEARS OLD
7
YEARS
OLD
I:' YEARS OLD
FIG 6-12. Two patterns of dentitional
exchange.
A, normal patterns of devel-
opment during the transitional dentition. e, more favorable patterns sometimes seen in people living on a diet coarser than that usual to North Americans. We may consider the pattern of transition in A to
e
be normal but that in to be more nearly ideal. The changes seen in column A correspond to the theories of Baume,2 while those in column represent the ideas of Friel.'8
e
110
Growth and Development
in North America. Among people whose diet includes coarse, rough food, for example, Eskimos, North American Indians, and Greek .mountaineers, the occlusal surfaces of the primary teeth wear to a great extent. This removal of cuspal interferences permits the mandible, which is growing more at this time-than the maxilla, to assume a forward position more easily (Johns EE, Moyers RE, unpublished data). Under these circumstances, the result for Greek mountain children at age 5 or 6 often is more edge-to-edge incisal relationship and a distinct mesial step terminally. When such conditions occur, the permanent incisors erupt with less overbite and the first permanent molars erupt at once into a firm neutrocclusion. In contrast, children without natural occlusal wear presumably adopt a temporary functional retraction of the mandible during clo~ure, since the relatively greater anteroposterior growth of the mandible produces natural occlusal interferences, usually in the cuspid region.68 The overjet diminishes markedly during the first 6 months of life, especially in those children who are to have normal occlusions later. 55 These anteroposterior changes are associated with skeletal growth; however, it has been shown in several studies that sucking habits impede the arrival of a balanced incisal relationship.83 The cuspid relationship steadily changes too until at age 3 years nearly one-half of children have a complete Class I cuspid relationship. The anteroposterior relations of the first primary molars on the average change slightly and steadily in a fashion similar to that of the cuspids until about 6 years in girls and 8 years in boys~ None of the anteroposterior occlusal changes in incisors, cuspids, or primary molars are related to dental age or dental developmental events. Second primary molars behave similarly, but more dramatic change in occlusion may accompany their loss. The vertical overbite decreases steadily during the primary dentition, a reflection of the skeletal maturation. There is now abundant research proof that the functional environment can alter greatly the growing 6aniofacial skeleton and its growth and hence the occlusal relationships (see Chapter 4). Particularly, it has been shown that altering the occlusal pattern evokes new neuromuscular responses which, in turn, change the skeletal morphology and finally can produce even severe malocclusions.64 It is likely that much of the occlusal vanability once considered of "genetic" or "unknown" origin has its beginnings
in altered occlusal and neuromuscular function at an early age. A discussion of the various patterns of occlusal change during the mixed dentition appears later in this chapter (see Section G). In general, a normal primary dentition allows a practitioner to be more encouraging about developing a normal mixed and adult dentition. The following normal signs of a primary dentition should be noted: a) b) c) d) e) f) g)
Spaced anteriors, Primate spaces, Shallow overbite and overjet, Straight terminal plain, Class I molar and cuspid relationship, Almost vertical inclination of anterior teeth, Ovoid arch form.
d) Disorders of the Primary Occlusion The prevalence of all mal occlusions in the primary occlusion is not as thoroughly reported as it should be. The data we do have indicate that malocclusion varies greatly with the population studied and the method of notation. Ethnic and cultural features are important not only for the obvious skeletal differences but because some cultures show much less thumb-sucking and other oral habits than others, thus having an effect on the percentage of children displaying posterior crossbites, open bites, and Class II mal occlusions .47 Some of the specific malocclusion traits in the primary qentition are shown in Table 6-4. Note the significant racial differences shown in North American children studied by the same investigator:' Boys tend to have more C1~ss 11 and Class III molar relations in the primary dentition than girls, and the prevalence of Class 11 malocclusions decreases during the primary dentition period. Bruxism in the primary dentition is a special problem which might be termed a "functional malocclusion." It is found in a bit less than 10% of all children during the primary dentition. It is almost always unconscious being manifested by occasional or habitual grinding or clenching of the teeth, and it is not necessarily pathogenic. Investigators have concluded that a genetic factor is involved, and psychosomatic symptoms have been significantly correlated with bruxism in children. 52 Allergy has also been claimed to be a factor. 63
TABLE 6-4. Prevalence
of Certain Malocclusion
Traits in 3-Year-Old
Children PREVALENCE
TYPE
POPULATION
INVESTIGATORS
Lingual crossbite I
English Finnish N Amer N Amer N Amer N Amer N Amer
Foster and Hamilton" Jarvinen and Lehtinen47
,. Class II molar relationship
Class 11cuspid relationship "Excessive" overjet Open bite Class III molar relationship
white black white black Indians
English Finnish (6 mm) English English N Amer N Amer N Amer
(2 mm) white black Indians
-- (%)
. Infante45 "lilltante45 Infante45 Infante45 Infante45 Foster and Hamilton"
,. ••
Jarvinen and -Lehtinen4? Foster and Hamilton'? Foster and Hamilton'? Infante45 Infante45 Infante45
4.0 7.7 7.1 2.1
23.5 4.3 2.7 45.0
16.2 72.0 24.0
1.0 7.1
8.0
Development
i~if I&~~ iiif II~I
of the Dentition and Occlusion
111
10. Apical end of root completed
:!.""
•• ~
9. Root almost completed,
ti~~m
!~~I
mQ~g
~00~
~~@~
O. Absence
open apex
8. Two thirds of root completed
7. One third of root completed
FIG
~. 0000 QOQC) QQQQ @~G~ ~eea ~~(@a
6.of Crown completed 1. Crown Presence ofofofcrypt 5. almost completed crypt Initialthirds calcification 3. One third crown 4.2. Two crown completed completed
Our understanding of the early signs and symptoms of potentially severe malocclusion as viewed in the pri'TIary dentition is really not very good at this time. Several retrospective studies reveal that we are not able to predict the features of malocclusion in the permanent occlusion very well from study of the primary dentition. It may be that we are looking at the wrong things in very young children, it may be that the signs are more subtle than we have known, and it certainly is true that we have much to learn. Some points have been made clear, however-sucking habits have been repeatedly shown to be involved in the origin of some malocclusions,55. 87 the skeletal pattern dominates severe malocclusion even in the young, and terminal plane relationship of the second primary molars can be very misleading as a diagnostic feature. 68
D. DEVELOPMENT OF THE PERMANENT TEETH 1. Calcification Although the calcification of the teeth has been studied in many ways, serial radiographic methods are the most practical,
6-13.
Stages of tooth development based on the work of Nolla.72 The radiograph is compared with the drawings, and each tooth is given a developmental score according to the drawing that it most nearly approximates. If the development of the tooth should lie between two stages, half values or plus scores may be used.
since the clinician evaluates patients' dental development from similar data. Nolla72 arbitrarily divided the development of each tooth into ten stages (Fig 6-13). The mean stages of calcification reached by each tooth for ages 3 to 17 years are shown in Table 6-5,A and B. It should be noted that this is an ordinal scale; }herefore, it cannot be assumed that the quantitative amounts of tooth material laid down during one stage are the same as during another. Important stages to remember are stage 2 (initial calcification) and stage 6 (the time teeth begin eruptive movements). A verage root length development at the time of emergence from the alveolar process is shown for several posterior teeth in Figure
6-l4
and Table 6-5,C ~nd D. -Girls are more advanced in' calcification of permanent teeth than are boys at each stage and more so in the later stages. Sex differences for tooth calcification are less than for bone development. Since girls are well ahead of boys by 10 years of age, the differences cannot be the result of the timing of the secretion of sex hormone. 32 The variability in calcification of the' permanent teeth is much greater than usually is assumed, probably because the most popular "standards" of tooth development distributed to the dental profession were derived from very small samples. In truth, the variability of tooth development is similar to that for eruption,
••... ..
... ..
8 7 98 8 916 15 11 5 13 12 14 18 17 8 7 10 107 8+ 10 97 7+ 998 10 10 98 989 8+ 8+ 7 6+ 7 9 76 8 78 76+ 810 76 46 56 10 99 8+ 8+ + 9 8 666 5 4 6 7 4 5 3 Growth and Development Calcification of Permanent Teeth
:; ~-••112 :a 8= ::; .I:l
8 9 7
7+ 9 AGE
A, Boys (Nolla TABLE 6-5. Stages)
,. sexual maturity, and other similar growth indicators. 33. 56 Definitive serial studies of racial differences in calcification have not been published, but such differences must indeed exist because of the well-documented racial differences in time of emergence. Similarly, the impact of socioeconomic status on calcification can be deduced from detailed reports of significant differences in timing of emergence due to economic status. 34
2. Eruption a) Interrelationships Between Calcification and Eruption Eruption is the developmental process that moves a tooth from its crypt position through the alveolar process into the oral cavity and to occlusion with its antagonist. During eruption of succedaneous teeth, many activities occur simultaneously: the primary tooth resorbs, the root of the permanent tooth lengthens, the al-
veolar process increases in height, and the permanent tooth moves through the bone (Fig 6-15). Although all these processes are interrelated, they are more independent than once thought. Teeth do not begin to move occlusally until crown formation is complete, but the rate of their eruption does not correlate well with root el2ngation (Fig 6-l6)~ 'Procedures, for predicting emergence of a permanent tooth in the mouth is described in Chapter 11. Permanent teeth do not begin eruptive movements until after the crown is completed (see Fig 6-16). They pass through the crest of the alveolar process at varying stages of root development (see Fig 6-14). It takes from 2 to 5 years for the posterior teeth to reach the alveolar crest following completion of their crowns and from 12 to 20 months to reach occlusion after reaching the alveolar margin. The roots usually are completed a few months after occlusion is attained. The moment of emergence into the oral cavity often is spoken of as the "time of eruption." Intra-oral
Dev,elopment of the Dentition and Occlusion TABLE 6-5.
Continued
C, Mean Root Lengths (mm) for Mandibular
3.7 2.7 10.9 5.3 3.0 5.3 4.2 1.2 1.4 .6 .8 19.317.7 8.0 19.017.4 4.6 6.0 15.9 13.0 11.2 12.5 14.6 17.0 11.8 14.6 7.1 7.8 17.4 14.5 17.8 15.7 13.4 3.7 12.4 15.2 16.1 17.0 16.2 4.5 2.2 2.1 3.2 12.3 12.0 7.1 13.1 12.1 14.9 2.8 4.3 7.9 2.0 6.4 4.6 9.7 3.7 2.5 1.1 1.7 .6 .9 10.6 18.817.1 18.616.4 13.0 17.614.4 14.2 15.0 13.9 13.4 5.2 14.0 17.6 9.7 17.1 10.4 15.1 16.8 16.5 3.4 15.6 16.6 15.5 15.8 4.8 15.3 14.4 2.0 2.6 5.3 10.1 12.6 11.7 13.2 15.2 1.6 15.0 8.9 5.4 10.2 14.6 5.6 3.1 1.9 7.3 8.8 6.2
SECOND SECOND BICUSPID CANINE MOLAR BICUSPID MOLAR FIRST MOLAR n.a. n.a.
FIRST FIRST
SECOND FIRST FIRST BICUSPID CANINE MOLAR BICUSPID MOLAR MOLAR 16.4 12.5 16.3 15.3 10.3 18.517.2 4.1 6.4 19.218.2 11.7 13.5 14.7 15.4 10.6 11.4 12.8 14.5 15.0 3.6 4.1 4.7 8.6 4.2 5.6 6.8 14.2 17.6 15.1 16.5 11.7 12.8 11.4 16.2 16.6 5.9 6.3 15.5 11.1 4.1 9.2 3.0 4.3 4.5 14.2 15.6 15.7 7.0 11.0 14.3 15.9 6.3 7.6 8.8 15.5 9.2 5.0 5.7 6.8 9.0 17.4 15.3 16.8 17.0 14.0 16.815.9 13.5 13.3 12.3 5.3 3.7 8.1 18.917.8 12.411.6 14.513.9 '16.7 15.9 13.9 3.5 3.4 5.3 7.3 8.3 16.1 16.9 10.0 13.7 14.6 4.6 9.8 3.1 2.5 5.2 7.8 7.3 2.8 3.6 5.6 13.4 15.4 15.2 5.4 9.6 9.5 8.1 9.3 18.917.9
70%
FIRST FIRST
50%
Teeth by Chronologic
MALE
D, Mean Root Lengths (mm) for Maxillary
35-40 %
113
Age FEMALE
Teeth by Chronologic
Age
MALE
FEMALE
50%
tD
25-30%
E FIG 6-15. FIRST MOLAR
CUSPID
FIRST BICUSPID
SECOND BICUSPID
SECOND MOLAR
FIG 6-t4. Crude approximations of mandibular root lengths at the moment of emergence through .the alveolar crest.
Developmental processes during eruption of succedaneous teeth. A, elongation of the permanent root. B, resorption of the primary predecessor. C, movement of the permanent tooth occlusally. D, growth of the alveolar process. E, the inferior border of the mandible, which shows much less growth activity than the other four processes.
114
Growth and Development
eruption achieves in a few months the first half of the crown's exposure, but its emergence occurs at a progressively slower rate thereafter. Figure 6-16 depicts in graphic form the relationships between calcification and eruption for selected teeth. Note careA
fully the common pattern of eruptive movements beginning as root formation starts. Various theories of eruption have been proposed, studied, and debated for some time. This is no place to continue such interesting arguments without new data, but some of the research on eruption has clinical significance. Eruptive movements do not correlate well with the amount of root lengthening, and rat's teeth have been shown to erupt when the roots have been destroyed experimentally. Further, it has even been suggested that the teeth erupt, allowing the roots to grow, and, therefore, root elongation might better be thought of as a result of eruption rather than one of its causes. Melcher and Beertsen65 present a useful, current review of our knowledge of eruption. Figure 6-17 depicts the mean values for time of emergence of the permanent teeth for North American white children and estimates of the range of variability.
"~
b) Factors Regulating and Affecting Eruption It is unfortunate 10 12 AGE (Years)
B mm
FEMALE
MANDIBULAR
14
1 16
18
FIRST BICUSPID
36
42~
24 • ~-J..- ..•.t>.\~ea;~!..£~':s~_/~,:"_-~.?'" 30 L~O~-:'-~CI~US!2.0!...1 [ ,•.......... • /-::::-=-..:-=-~ ~PI~an~e~__ -~.::,::,:::::c-::. ='='W'
-------
/
.
18f-L
~~:':.. ,,1\\> ..... /./ / •...-;: .•• \ (}o"';/ 12r _ ... ~'\ ce(~.':':~--·/
--
6
- ...-
f <_._.End of R0:t OL--'----'_-'----'_~~_~~_~~_~~_~~__,_ 4 14 16 6 8 10 12
18
AGE (Years)
c
4
6
8
10 12 AGE (Years)
14
16
18
FIG 6-16. A-C, tooth development and eruptive movements in females. Plots for males are similar but generally later at each stage.
-..
and remarkable
how few details we know
about some of the factors affecting eruption. Both the sequence and timing of eruption seem to be largely gene determined. Further, there are sequences and timings of eruption that are typical for certain racial groups; for example, Europeans and Americans of European origin tend to erupt their teeth later than American blacks and American Indians. 20 Most studies of eruption in humans are based on radiographic data or intra-oral visualization of the effects of the basic biologic mechanisms. We know much about when eruptive events are seen clinically. What is not known is how genes mediate the fundamental processes of calcification and eruption. Thorough study of the impact of economic status on tooth emergence has shown that the teeth of both North American blacks and whites at the poverty level (income-to-needs ratio = I) tend to be delayed in emergence when compared with children of median per capita income.34 There are important racial differences in timing of permanent tooth emergence, differences apart from socioeconomically caused variations. North American black boys and girls showed systematically earlier emergence of all teeth when compared with lowincome North American white children of European ancestry. 43.44 The greatest differences were for incisors and molars; the least, for cuspids and premolars. When economic status is similar the me;m difference between races is approximately 0.3 standard deviations. 34 The nutritional influences on calcification and eruption are relatively much less significant than the genetic, for it is only at the extremes of nutritive variation that the effects on tooth eruption have .peen shown.25 This,should not be surprising, for it is well known'that both calcification and eruption are less responsive to endocrine disturbances than is skeletal development.'7.40 Mechanical disturbances can alter the genetic plan of eruption, as can localized pathosis. Periapical lesions, pulpitis, and pulpotomy of a primary molar will hasten the eruption of the successor premolar" (Fig 6-18). If the primary tooth is extracted after the permanent successor has begun active eruptive movements, the permanent tooth will erupt earlier. If the primary tooth is extracted prior to the onset of permanent eruptive movements (prior to root formation), the permanent tooth is very likely to be delayed in its
Development
of the Dentition and Occlusion
115
A Boys
Gi rls
Moxi
110
FIG 6-17.
~\;:, o 0 Year,
Years
Emergence of permanent teeth. A, mean times and ± 1 standard deviation (late and early). e, average number of emerged teeth by age and sex. (Adapted from Moyers RE, van der Linden FPGM, Rialo ML, et al: Standards of Human Occlusal Development. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. Used by permission.)
Mond i ble
Boys
Gi rls
B
•. N N 21.58 22.39 10.32 11.26 10.68 3.99 6.56 1.18 2.53 0.67 1.71 1.57 72 .54 84 81 84 89 72 72 578.49 (SD) (SD) 9.90 70 25.10 25.18 92 10.11 13.53 13.64 12.23 12.47 12.63 14.87 17.24 18.39 13.24 11.66 12.31 12.88 6.10 6.97 9.09 9.84 4.35 5.56 8.15 4.49 5.62 5.69 6.54 70 .87 92 98 87 70 98 87 55 38 49 98 70 49 27.35 13.69 13.65 42 42 34 42 34 27.89 14.02 13.76 46 46 25 46 25 96 84 11.70 6.45 2.46 2.23 4.03 96 81 89 57 98 13.36 6.40 8.00 96 89 6.87 87 96 89 27.16 26.76 55 55 38 27.48 13.79 13.71 27.40 13.87 >~. (4.81) 5.49,
~
MEAN MEAN LOWER MEAN UPPER TOTAL LOWER (3.51) (1.66) (4.82) (2.58) (1.39) (2.80) (1.80) (2.71) (1.92) (2.38) (2.74) (2.65) (2.47) (2.65) (1.72) (0.85) (2.79) (1.49) (1.23) (0.97) (1.08) (1.13) (0.92) (1.86) (2.42) (0.87) (3.33) (1.92) (2.27) (0.70) (3.71) (1.64) (1.46) (2.16) (0.95) (1.51 (1.97) (1.90) (1.30) (2.09) (0.56) (1.37) (0.72) (0.69) (.68) ) (1.35) (0.45) (0.50) (0.66) (0.76)
FEMALE
(1.30) (1.29),
MALE
116
Growth and Development
FIG 6-18. Alteration in eruption due to a pathologic lesion at the apical area of a primary molar. Compare the eruption of the left and right mandibular
first bicuspids. Radiographs B, 7 years; C, 8 years.
were taken at yearly intervals. A, 6 years;
'.
Development eruption, since the alveolar process may reform atop the successor tooth, making eruption more difficult and slower. The possible effects of extraction of the primary tooth on the eruption of its successor cannot be correlated well with the chronologic age of the subject (although this is frequently done in research papers) ~ but can be related to the stage of development of the permanent tooth. It also has been shown that crowding of the permanent teeth affects, to a small degree, their rate of calcification and eruption.5 Intrusion or exarticulation of the primary incisors may occur accidentally during early childhood, resulting in disturbances in mineralization of the permanent successors in some instances and even occasionally intrusion of the permanent incisor. On rare occasions the injury is so severe that the permanent tooth cannot erupt normally. Early treatment, during the stages of root formation, improves the chances for normal root development of the permanent incisor. Primary anterior teeth which have suffered ~ trauma must be reviewed periodically by the clinician to identify any conditions which may be harmful to the normal eruption of the permanent successor.
3
of the Dentition and Occlusion
117
BOYS
! ~~t? 6
7
8
L
UPPER
'!
i
2
LOWER
13 YEARS
r
GIRLS
~t?
6
. 5..1 7
i
4
[ 8
2
UPPER
!of
.
9
10
11
12
13 YEARS
LOWER
c) Timing and Variability of Eruption The constant referral to tables showing mean times of eruption often obscures, in my opinion, the wide variability seen in time of intra-oral emergence. Study of Figure 6-17 will reveal that in fully 10% of all children, the "6-year-molar" will emerge either earlier than 5.0 years or later than 8.0 years and the so-called" 12year molars" will appear earlier than 9.6 years and later than 15.2 years. Eruption timing tends to be earlier in American Negro and American Indian populations and in Asiatics than in Americans of European orgin. Moreover, timing of emergence tends to be systematically late within lineages. Finally, timing is correlated within a dentition; that is, those children who erupt any tooth early or late tend to acquire other teeth similarly early or late. d) Sex Differences Except for third molars, girls erupt their permanent teeth an average of approximately 5 months earlier than boys (Figs 6-17 and 6-19). The true sex difference in timing of intra-oral emergence is much less than the sex difference in the timing of appearance of most postnatal ossification centers, and the variability of normal eruption timing is small when compared with the normal variability in skeletal development. e) Sequence of Eruption The apparent sequence of calcification development is not a sure clue to the sequence of emergence into the mouth, since the factors regulating and affecting the rate of eruption vary among the teeth. There is wide variability in the sequence of arrival of teeth in the mouth; some of the variations are important clinically. In the maxilla, the sequences 6-1-2-4-3-5-7 and 6-1-2-4-53-7 account for almost half of the cases, whereas in the mandible, the sequences (6-1)-2-3-4-5-7 and (6-1)-2-4-3-5-7 include more than 40% of all children. 57 Some problems are introduced in comparing various studies and in attempting to predict gingival emergence from the radiograph. Cross-sectional studies in which sequence is discussed are a special problem since the authors have not studied sequence at all but have attempted to derive an assumed
FIG 6-19. Normal order of eruption of the permanent
teeth.
sequence. The rate at which the incisors erupt is much faster than that of the molars at the time of immediate emergence into the mouth. If one is seeing a child at 6-month intervals, for example, it may look as if the incisor has come in first, whereas, in truth, the molar has preceded it but is moving so slowly that the incisor passes it by. Investigators who have studied eruption sequence at short intervals tend to report the mandibular molars as erupting first, 57 whereas those studying eruption at longer intervals tend to note the central incisor as erupting first. 48 There seems to be no clinical significance attached to either the 6-1 or 1-6 sequence. On the other hand, the appearance of the second molar ahead of the cuspids or premolars has a strong tendency to shorten the arch perimeter and may create space difficulties. Fortunately, the most common sequence in each arch (viz., maxillary 6-1-2-4-5-3(and mandibular 6-1-2-3-4-5-7) is favorable for maintaining the length of the arch during the transitional dentition57 (Fig 620). fJ Eruption and Bodily Growth . Tooth calcificatioIJj;orrelates positively in a rough way with h~ight, weight, body fat, and ossification of wrist bones, but such correlations rarely are significant therefore, their clinical usefulness is limited. 50 Many proper and even important research papers on such correlations have appeared, which I do not intend to demean, but the practical clinical applications of such data thus far are very limited indeed except in the most obvious generalizations. The use of "bone age" derived from carpal radiographs to plan orthodontic treatment to coincide with active periods of bone growth, as for example the pubescent growth spurt, is quite another matter and is on sounder theoretical ground.
118
Growth and Development >
dibIe fails to grow sufficiently for resorption of the anterior border of the ramus to permit their eruption. Transposition of teeth, a very rare form of ectopy, typically involves exchanged positions between cuspids and first premolars or cuspids and lateral incisors.
FIG 6-20. Favorable eruption sequence, the most common of several favorable sequences.57 g) Ectopic Development Ectopic teeth are teeth developing away from their normal position. The most common teeth found in ectopy are the maxillary first permanent molar and the maxillary cuspid followed by the mandibular cuspid, maxillary second premolar, other premolars, and maxillary lateral incisors. Girls show significantly more tooth germs in ectopy than do boys. Approximately 3% of North American children may be expected to show ectopically erupting maxillary first permanent molars.20 Ectopic eruption of maxillary first molars is associated with (1) large primary and permanent teeth, (2) a diminished maxillary length, (3) posterior positioning of the maxilla, and (4) an atypical angle of eruption of the first molar. 79 Treatment of ectopic eruption is discussed in Chapter 15. About one-half of all tooth germs in ectopy, other than first molars, are maxillary cuspids, and two-thirds of all upper ectopic cuspids are found in girls. The treatment for this difficult problem is best begun early in dental development in order to utilize the natural forces of eruption. Usually, surgical uncovering and possible repositioning are required before orthodontic tooth movements are begun. Chapter 15 contains a discussion of the treatment of ectopically erupting cuspids. A differentiation should be made between ectopy and impaction. In the latter condition, teeth cannot erupt because of impingement. Third molars and maxillary cuspids may be seen as impacted, even though they began development in normal positions, and hence are not ectopic. In other instances; they may be both ectopic and impacted. Mandibular third molars, the most frequently impacted teeth, may begin development in a normal position relative to the ramus but become impacted when the man-
h) Factors Determining the Tooth's Position During Eruption During eruption, the tooth passes through four distinct stages of development (Fig 6-21). The factors that determine the tooth's position vary with the stage. At the onset, the position of the tooth germ is thought to be dependent on heritable traits. During intraalveolar eruption, the tooth's position is affected also by the presence or absence of adjacent teeth, rate of resorption of the primary teeth, early loss of primary teeth, localized pathologic conditions (see Fig 6-18), and any factors that alter the growth or conformation of the alveolar process. There is a strong tendency of the teeth to drift mesially even before they appear in the oral cavity. This phenomenon is called the mesial drifting tendency. Once the oral cavity has been entered (intra-oral or preocclusion stage of eruption), the tooth can be moved by the lip, cheek, and tongue muscles, or by extraneous objects brought into the mouth (e.g., thumbs, fingers, pencils), and drift into spaces created by caries or extractions. When the teeth occlude with those of the opposite dental arch (occlusal stage of eruption), a most complicated system of forces determines the position of the tooth. For the first time, the muscles of mastication exert an influence through the interdigitation of the cusps. The upward forces of eruption and alveolar growth are countered by the opposition of the apically directed force of occlusion. The periodontal ligament disseminates the strong forces of chewing to the alveolar bone. The axial inclination of the permanent teeth is such that some of the forces of chewing produce a mesial resultant through the contact points of the teeth, the "anterior component of force" (Fig 6-22). The tendency forthe teeth to move forward as a result of mastication and swallowing varies greatly according to the angulations of the teeth with each other and is especially affected by the steepness of the occlusal plane. Orthodontists pay particular attention to the cant of the occlusal plane since the anterior component of force is an important determinative factor in ease of distal movements of teeth, stabilization of treated malocclusions, and crowding of teeth after dental development and craniofacial growth have diminished. The anterior component of force often is'confused with the mesial drifting tendency. The former is the result of muscle forces acting through the intercuspation of the occlusal surfaces, whereas the mesial drifting tendency is an in-
FIG 6-21. Stages of eruption. 1, pre-eruptive; 2, intra-alveolar; 3, intra-oral; 4, occlusal.
Development
of the Dentition and Occlusion
119
because alveolar growth compensates nicely throughout most of life. As the crown diminishes in height, the alveolar height increases a like amount.
E. THE PERMANENT
DENTITION
During evolution, several significant changes took place in the teeth and jaws. When Reptilia evolved into Mammalia, the dentition went from polyphyodont (many sets of teeth) to diphyodont (only two sets of teeth) and it went from homodont (all teeth alike) to heterodont (different types of teeth, i.e., incisors, canines, premolars, and molars).50 There also arose the necessity for teeth and bone to develop somewhat synchronously in order that the function of occlusion could be facilitated. The facial osseous struc-
FIG 6-22.
tures also have changed markedly but not quite so radically. Finally, the number of cranial and facial bones has been reduced by loss or fusion and the dental formula has progressed from 5-1-4-7 3-1-3-4
The anterior component of force.
-4--1--4--7 in the mammal-like reptiles to -3-_-1_-3_-4-asa generalized 2-1-2-3 mammalian pattern to 2-1-2-3 as the generalized pattern for
herent disposition of most teeth to drift mesially even before they are in occlusion. The anterior component of force is countered by the approximal contacts of the teeth and by the musculature of the lips and cheeks (Fig 6-23). The forces of occlusion may deflect a tooth in another direction if the intercuspation is incorrect. Van Seek,"7 in a most definitive study, altered the occlusal relationship of monkeys' teeth and studied the effects on the anterior component of force and mesial drifting. He concluded that occlusion plays a more important role than the transseptal tissues in mesial migration. The angle between the upper and lower teeth was a factor in the rate and direction of migration. The role of erupting third molars in mesial drift of anterior teeth appeared to be small, but the sample size did not make possible firm conclusions about this point. Although occlusal wear decreases the height of the crowns of the teeth, it does not increase the interocclusal distance (freeway space),
primates. 50The first number is the number of incisors, the second cuspids, the third premolars, and the fourth molars in each quadrant.
1. Size of Teeth In humans there is strong evidence to support the idea that tooth size is largely determined genetically, although there is experimental proof that extreme environmental variations such as malnutrition can alter tooth size in certain animals.76-78 Marked
racial differences exist in the size of the teeth, with the Lapps probably having the smallest teeth and Australian aborigines the largest.23 The sex-size difference averages 4% and is greatest for the maxillary canine and least for incisors (Table 6-6). There is strong evidence of X-linkage in relation to tooth size, since sistersister correlations are higher than brother-brother and brother-sister and female tooth size commonalities are greater than males.'o The range of size encountered varies with the tooth and is much larger than most dental anatomy books indicate. Since tooth size is so variable and facial skeletal structures not only vary greatly but also are more subject to varying environmental influences, one frequently encounters in dental practice marked disharmony between the size of the teeth and the bones in which they are placed. Tooth size and bone size seem to be under~ separate control mechanisms, an unfortunate biologic problem for clinical orthodontic practice. " Much recent researeh relates to the various theories about "ge'Iretic fields" which produce cpmmunalities of size, shape, and position during development. There are overlapping gradients which produce patterns of similarity of a tooth with its antimere on the opposite side of the same arch, its functional antimere in the opposite arch, and other teeth in its own quadrant. The details of this important research are beyond the range of this book, but the clinical implications, as we now know them, can be summarized-indeed, they must be, because they are so important.
FIG 6-23. The position of the incisors relative to the lip and tongue posture.
Left-right size corre!ations are extrelpely h~gh for individual teeth (average r = .9) and even higher if all teeth In a quadrant are
N so SO MEAN 215 (MM) (MM) 11.53 10.29 10.18 10.57 10.35 10.74 11.76 6.50 10.58 191 196 145 148 138 160 161 143 134 100 192 140 112 127 0.32 0.34 5.46 0.67 8.72 0.64 7.08 0.38 7.74 7.37 0.49 0.39 5.38 0.44 0.46 0.57 0.42 0.55 7.61 6.67 6.58 9.98 0.47 7.07 0.63 0.70 5.54 9.12 0.58 7.26 5.53 7.76 7.22 6.04 92 0.74 0.58 0.73 0.56 0.64 0.63 0.72 125 172 122 0.36 7.49 0.71 6.76 7.99 6.88 201 212 152 157 121 7.41 10.94 11.28 11.04 9.50 10.71 158 0.56 0.53 0.43 6.94 5.99 6.86 0.51 0.50 0.37 0.40 6.96 6.89 5.92 8.19 7.66 7.25 6.13 7.85 99 0.60 0.52 0.62 0.86 216 208 214 153 142 104 158 159 1'48 150 147 132 115 80N FEMALE 8.79 189 0.59 8.67 6.78 6.60 8.91 9.50 0.73 80 120 146 148 136 170 156 102 0.46 Growth and Development Standards of 5.Used Human Occlusal nden FPGM, Riolo ML, etpermission. al: Used by Development, crown Universityof dimension Michigan, Monograph of the1976. permanent Annby Arbor, dentition permission.Part Michigan, of American Center B from Negroes. RichardsonER, for Human Am J Growth Orthod MalhotraSK: 1975; and Development, 68:157-164. Mediodistal Central incisor MALE Mesiodistal Diameters of Permanent Dentition* A, North American TABLE Whites 6-6.
,.
summated. 2) In no place in the body is symmetry. so well and rigorously defined': Upper-lower size correlations also are high (average r = .7)Yln a general way, the more mesial teeth within each group in each quadrant show the \east variability in development and size2) (Fig 6-24). The most distal tooth within each group displays the greatest variability in size, is the most apt to be congenitally missing, and is most frequently abnormal in shape and aberrant in its calcification timing. The careful diagnostician,
after noting one tooth's abnormality of size or development, looks immediately for others in the most likely positions, namely, third molar, second premolar, and lateral incisor.
2. Number of Teeth a) Missing Teeth Complete
absence of teeth is termed anodontia
(no teeth),
Development
121
of the Dentition and Occlusion
lose teeth and have smaller jaws, but these two trends do not seem to be correlated.
b) Supernumerary Teeth
FIG 6-24. Genetic fields influencing dental development. The most distal tooth in each field, marked X, is the most variable in development, size, and shape and the one most apt to display agenesis.
and incomplete formation of the dentition is properly called oligodontia (some teeth). The latter condition is sometimes incorrectly termed' 'partial anodontia." Congental absence of teeth in modem man may be an expression of anisomerism (i.e., a reduction of the number of teeth by loss or fusion). In the United States of American between 2% and 7% of the population have congenital absence of some tooth other than the third molar (depending upon which research you read and accept). Not including third molars, which are reported absent as much as 25% of the time in North American whites, 35teeth most frequently absent are mandibular second premolars, maxillary lateral incisors, and maxillary second premolars, in that order. Any tooth may be congenitally absent, though these four account for the greatest percentage of all missing teeth. Most studies claim that women are more likely to have congenitally missing teeth than men. The frequency of oligodontia is usually bilaterally equal except when it involves the maxillary lateral incisors where the left tooth is more often missing than the right, which may be related to the fact that unilateral cleft palate is seen more frequently on the left side. Although congenital absence of teeth is known to result from heritable factors, no single direct genetic mechanism has been identified and the mode of genetic transfer is argued. Congenital absence of teeth is also frequently associated with gross dyplasia syndromes of far-reaching medical and developmental significance. The dentist, when congenitally missing teeth are noted, should extend the examination to look for developmental problems elsewhere. Although it is possible that oligodontia seen alone is a microform of systemic ectodermal dysplasia, in the majority of cases it is more apt to be determined by a dominant autosomal gene pattern with incomplete penetrance of the trait and variable expressivity.39 The genetics of congenitally missing teeth is quite complex and familial tendencies are well known and are of clinical importance. Not so appreciated are the relationships among agenesis, delayed development, and size diminution (see Section E-l and Fig 6-24). Lee Graber has written a very useful review of our current knowledge of congenitally absent teeth in humans and its inheritance patterns.39 Gam and his group35 have studied third molars thoroughly and found that agenesis of third molars is related to agenesis of other teeth, delayed calcification of other posterior teeth, different developmental sequences, and smaller teeth elsewhere in the mouth. In man, there is an evolutionary tendency to
Supernumerary teeth are encountered less frequently than are congenitally missing teeth. They occur more often in the maxilla, particularly in the premaxillary region, than in the mandible, and are seen about twice as often in men than in women. They may be classified according to type: a) Teeth with conical crowns are usually found at the maxillary midline, either singly or in clusters. Often they erupt ectopically and may even be inverted and erupt toward the nasal floor. Teeth of this shape occur because they develop from only one lobe at the time of odontogenesis. The most common example is the so-called "peg" lateral incisor, which has only the middle devel omental lobe. b) Teeth of normal form and size that are supplemental to those of the regular dentition. c) Teeth showing variation in size and cuspal form. These may be larger or smaller than normal or the occlusal surface may be deeply pitted. They are recognized by their anatomy, however, and are usually found near their "proper" place in the dental arch. The microform maxillary lateral incisor is seen fairly often and must be clearly differentiated from the "peg" lateral incisor. When deciding whether to use supernumerary teeth of this category or the normal tooth in the plan of occlusion, do not base the decision solely on the shape and position of the crown: supernumerary teeth frequently have abnormalities of root shape and development as well.
F. DIMENSIONAL CHANGES IN THE DENTAL ARCHES Three sets of measurements often are confused: (1) the combined widths of the teeth; (2) the dimensions of the dental arch in which the teeth are arrayed; and (3) the dimensions of the mandible or maxilla proper, that is, the so-called basal bone (Fig 6-25). It may· seem paradoxic that during growth these values change in different fashions (viz., the sizes of the teeth stay the same but Dental Arch Alveolar
Arch ..
f
Basal Arch
Fl~ 6-25. The'Telationship of the three arches. The basal arch is largely determined ,by the configuration of lhe~mandibTeitselCThe alveolar arch [oins the tooth to the basal arch and thus is 'always a compromise in size and shape between the basal arch and the dental arch. The dental arch reflects the relationship between the combined sizes of the crowns of the teeth, tongue, lip, and buccal wall function, angulation of the teeth, anterior component of force, etc .. When the combined mesiodistal diameters of the teeth are harmonious with the size of the basal arch and the relationship of the maxillary to the mandibular basal arch, the dental arch is synonymous with the combined sizes of the teeth.
122
Growth and Development
A
B
28 27 26
~ ~
25 24
w ~
Permanent
Primary
23
-.J
~
22
::E 21
20 19
246
FIG 6-26. MaAdibular bicanine width changes. A, the movement of the primary cuspids distally into the primate spaces with the eruption of the permanent mandibular incisors. Note that if one is measuring the diameter between the primary cuspids, a wider diameter is recorded as they are pushed distally on the divergent arch. 8, bicanine width versus chronologic age. C, bicanine width increments versus dental age. 0 = moment of arrival of first permanent incisor. This chart shows clearly that primary cuspid movements distally are timed by the eruption of permanent incisors. (Adapted from Moyers RE, van der Linden PGM, Riolo ML, et al: Standards of Human Occlusal Development, Monograph 5, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1976.)
C1.4 1.2
8
18
Primary
I I
1.0
I I I
~ 0.8 w ~ 0.6
I
~ 0.4 -.J
:::!
+
0.2
::E 0.0
Permanent
cr'
I
J:J
:+~
-0.2 -0.4
I
-2
o
2
4
6
YEARS
the circumference of the dental arch, wherein the teeth are placed, diminishes), while the length of the mandibular and maxillary bones increases. The size and shape of the arches are first determined by the cartilaginous skeleton of the fetal maxilla and mandible."' A close relationship then develops between the tooth germs and growing jaw bones, but dental arch size does not correlate well with the sizes of the teeth contained within it. In this section the growth changes in the dental arches are discussed'. Tooth sizes were dealt with earlier in this chapter. Growth of the bones of the craniofacial complex is treated in Chapter 4. The usual arch dimensions measured are (I) widths at the canines, primary molars (premolars), and first permanent molars; (2) length (or depth); and (3) circumference (see Fig 6-10). They are discussed separately because they change somewhat independently of one another and because there are misconceptions which are more easily dealt with by discussing one dimension at a time.
1. Width It is important when studying width changes in the dental arches to keep in mind three important facts: a) Width dimensional increase involves alveolar process growth almost totally since there is little skeletal width increase at this time (none in the mandible) and it contributes little to dental arch change. b) There are important clinically significant differences in the magnitude and manner of width changes in the maxilla and man-
dible. Dental arch width increases correlate highly with vertical alveolar process growth, whose direction is different in the upper than in the lower arch. 70 Maxillary alveolar processes diverge while the mandibular alveolar processes are more parallel. As a direct result, maxillary width increases are much greater and, a most important clinical point, they can be more easily altered in treatment. c) Dental arch width increases are closely related to the events of dental development, less to the endocrinally mediated events of overall skeletal growth such as the adolescent spurt in stature (Figs 6-26 and 6_27)70 The intercanine diameter increases only slightly in the mandi~le, and some of this increase is the result of the distal tipping of the primary cuspids into the primate space, since the mandibular incisors are not normally moved labially through time (see Fig 626). Note that in the mandible the only significant increase in intercanine width occurs during the eruption of the incisors when the'primary cuspids are m-;Jved distally into the primate spaces. It does not widen significantly thereafter (see Fig 6-26). Because the maxillary alveolar processes diverge, forming the palatal walls, width increases tend to be timed with periods of vertical alveolar growth, that is, during active eruption of the teeth. The maxillary permanent cuspids are placed further distally in the arch than the primary and erupt pointing mesially and labially. Hence their arrival is an important factor in widening and changing the shape of the maxillary dental arch. There are also important sex differences in the maxillary bicanine width increases which are not so evident in the mandible (see Figs 6-26 and 6-27).
Development
,
33 32 31
5.5mm Marked Sexual Dimorphism
30 (/) ffi
29 28
t;j 27
~ 26 ::!
25
::;:
24 23 22 21
20
2
4
6
8
10
12
14
16
18
YEARS
FIG 6-27. Width changes in maxillary bicanine diameter compared with mandibular bicanine diameter. (Adapted from Moyers RE, van der Linden PGM, Riolo ML, et al: Standards of Human Occlusal Development, Monograph 5, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1976.)
Maxillary premolar width ening of the arch coincidental On the other hand, mandibular region occur because the crowns buccally than the centers of the
increases reflect the general widwith vertical growth (Fig 6-28). width increases in the premolar of the premolars are placed further crowns of the wider primary mo-
48
of the Dentition and Occlusion
123
lars. Note that all measures in Figure 6-28 are made to centroids not buccal cusps. When the latter are used mandibular widths in the premolar region do not seem to increase so much. Maxillary first premolar width increases significantly more than does the mandibular, especially in males (see Fig 6-28). Although the alveolar process growth is almost vertical in the mandible, the crowns of the first molars erupt tipped somewhat lingually and do not upright fully until the time of the eruption of the second molars. As the first molars upright, they cause an increase in the bimolar width, but this is not, of course, an increase in the diameter of the mandible itself. Furthermore, both first molars move forward at the time of the late mesial shift to preempt any remaining leeway space and thus assume a narrower diameter along the convergent dental arch. It is important to note the reasons for the rather marked differences in width increases between the two dental arches. The only postnatal mechanism for widening the basal bony width of the mandible is that of deposition on the lateral borders of the corpus mandibularis. Such deposition occurs, but only in small amounts, and offers little help for the clinician wishing to widen the mandibular dental arch. The maxilla, in sharp contrast, widens with vertical growth simply because the alveolar processes diverge; therefore, more width increase is seen and more can be procured during treatment (see Fig 6-32). Furthermore, the midpalatal suture can be reopened with "rapid palatal expansion" (see Chapter 15) to acquire surprisingly large amounts of actual widening {)f the maxilla. There is little correlation between dental arch widths and any skeletal or facial width measurements; therefore, knowledge of the latter is of no real use in planning orthodontic treatment.
2. Length or Depth
47
A
46 45 44
43 42 41
(/) 40 ffi 39 ~ w 2
4
6
8
~ 37 ...J ::! 36 ::;: 35
B
10
12
14
16
+-+-+-+--+
34 33 32 30 29
28 27
4
6
8
10
12
14
18
+
31
16
n {]
Dental arch length (or more properly, arch depth) is measured at the midline from a point midway between the central incisors to a tangent touching the distal surfaces of the second primary molars or second premolars (see Fig 6-10). Although often measured and reported, it does not have the clinical importance of the circumference, and any changes in arch length are but coarse reflections of changes in perimeter. Sometimes one-half the circumference is referred to as "arch length."
18
YEARS
FIG 6-28. Width changes in (A) molar and (B) bicuspid regions. (Adapted from Moyers RE, van der Linden PGM, Riolo ML, et al: Standards of Human Occlusal Development, Monograph 5, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1976.)
3. ,Circumference or Perimeter The most important of the dental arch dimensions is arch circumference or perimeter, which usually is measured from the distal surface of the second primary molar (or mesial surface of the first permanent molar) around the arch over the contact points and incisal edges in a smoothed curve to the distal surface of the sec~nt\. primary molar (or first pen,nanent molar) of the opposite side (see Fig 6-10). A wide range of variability is seen in circumferential increments and the mandibular and maxillary perimeters behave a bit differently; therefore, they will be discussed separately. The reduction in mandibular arch circumference during the transitional and early adolescent dentition is the result of (1) the late mesial shift of the first permanent molars as the "leeway space" is preempted, (2) the mesial drifting tendency of the posterior teeth throughout all of life, (3) slight amounts of interprox-
124
Growth and Development 20 1.5 -2 0.5 00 1.0 w " -0.5 B ii-10 -4 -1.5 3.0 '" 2.5
A
I-...Ja: 88 86 84
::J
82
80 78 76 74
'"
a:
w I74 w "
73
~
72
"
o
2
4
10
6
12
20
71
15
70
69 68 67 66 65 64
(/)
a: w
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~ 0.0 :J -0.5 ...J
ii
-10 -1.5
+
-2.0
63
-2.5 4
6
8
10
12
14
16
18
YEARS
FIG 6-29. Perimeter changes. A, perimeter versus chronologic age. The range and sex differences (0 = males, + = females) ± 1 standard deviation are noted. e, perimeter change/year based on dental age. (Adapted from Moyers RE, van der Linden PGM, Riolo ML, et al:
imal wear of the teeth, (4) the lingual positioning of the incisors as a result of the differential mandibulomaxillary growth, and (5) the original tipped positions of the incisors and molars. The last point is a reflection of the skeletal pattern, steepness of the occlusal plane, and vertical alveolar growth, which in some instances-where incisors are tipped lingually and molars are tipped mesially-shortens the available arch perimeter markedly. 42 Note the great variability in perimeter dimensions at various ages (Fig 6-29) and notice the important sexual differences. The arch perimeter in females is particularly vulnerable to severe losses during the ages displayed. This point is made more important when one realizes that the study was done in Ann Arbor, Michigan, which has had a fluoridated water supply throughout the time of the study. In a most important report, Northway73 analyzed children from Montreal of the Growth Center, Universite de Montreal who had had little dental care and whose water supply was unfluoridated. He found that moderate caries, severe caries, and early loss of primary molars caused dramatic increases in the amount of perimeter loss (Fig 6-30). Hunter and Smith42 noted that children with crowded arches in the early mixed dentition showed less arch perimeter loss by the time of the completed permanent dentition and more continued crowding. The role of the mandibular third molar in crowding of the incisors is a much argued and studied topic which has occupied much of our attention in recent years. Briefly, some feel so strongly that the third molars are responsible for incisal crowding that they recommend prophylactic removal during their early development before they can disrupt the arch alignment or ruin orthodontic treatment results. Good research is very difficult to complete on this problem, but there is no overwhelming evidence yet to support the view that third molars are a primary" cause" of incisal crowd-
-4
-2
0
4
6
8
10
12
YEARS
Standards of Human Occlusal Development, Monograph 5, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1976.)
ing. In fact, most of the evidence denies this hypothesis. Attempts have been made to predict which third molars will become impacted and which not; which will "push" the other teeth forward and which will not. The best clinical guides on this problem are still largely subjective despite some very ingenious efforts. Some clarification may come when a sufficiently large serial sample permits analysis according to the several facial types with their varying growth patterns. It is possible that third molars exacerbate a tendency already present in some children, but that is an unproven hypothesis at this time. There is evidence to show that differential mandibulomaxillary growth and/or occlusal interferences with resultant "slide" into occlusion cause incisal crowding, but these two important factors are often forgotten. In summary, the mandibular arch perimeter shows great variability in its extensive diminution during natural development. The variation is caused by differences in skeletal pattern, sex (women's arches shorten more), and caries experience. The importance of monitoring this dimens·ion and preserving it during the critical periods of development cannot be emphasized too much for it is a dimension whose losses are difficult to recover. '; ..Maxillary arch per1meter, in contrast, typically increases slightry although it has about an equal chance to either increase or decrease (see Fig 6-29). The very marked difference in angulation of the maxillary permanent incisors, as compared with the primary (Fig 6- 31), and the greater increases in width probably account for the tendency to preserve the circumference in the upper jaw even though the permanent molars are drifting mesially.
4. Dimensional Changes During Orthodontic Therapy In Figure 6-32 the normal growth changes in both dental arches are summarized and compared with changes that can be
Development '" w E
""-u'"A
16 15 19
17 12 -, 1318
14-
E
of the Dentition and Occlusion
125
NON-MUT SEVERE
<>-----D "'
•••..•.
CAR I ES
0- LO S S E· LOS S D+E LOSS
,6.
0--0
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7
1---,-----
8
9
10
DE NTAL
u :J I--' I-
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Perimeter Maxilla Mandible
E
12
13
14
AGE
-I -5 -'-3 --42
B
r
11
(\~) "/I~
AT YR S
7
YRS 0'---0
Growth 8
y
[, ----
00000 0 0
LOSS
6
.6.- ..•••
+?+Growth ++ Growth Growth + Primary No Skeletal Growth Skeleta I Growth Permanent Tx Plus ???Tx TxTransitional
.6,
Width Width~"s/o0..,
RS 0-----0
9
'(RS
"'--4
10
Y RS
a....-----e
I I
Y RS
---.
FIG 6-31. Comparison of the angulation of the permanent and primary incisors.
.l".
I
6
/
9
7
,
I
/
o --
?
8 CHRONOLOGICAL
FIG
10 11 12 13
AGE
Some + Mild increase occurs or con be obtained Decreases greatly ++ Significant increase occurs or con be obtained Some change possible in particular instances
FIG 6-32. Summary of changes in arch dimensions resulting from grow1h, and estimates of possible expectations during treatment (Tx).
6-30.
Perimeter changes resulting from caries and loss of teeth. A, lower first and second primary molar space. B, effect of age at loss of primary molars. (From Northway WM: Antero-posterior arch dimension changes in French-Canadian children: A study of the effects of dental caries and premature extractions, thesis. School of Dentistry, University of Montreal, Quebec, Canada, 1977. Used by permission.) ,.
brought about by orthodontic therapy. It is important to note very carefully that it is far easier to increase dental arch width and length in the maxilla than it is in the mandible. In fact, it is relatively simple to increase the maxillary dental arch width and length, difficult to increase and retain the mandibular dental arch width, and difficult to move mandibular molars distally significantly to increase the perimeter. There are means to increase the perimeter in certain cases, including lip bumpers, utility arch wires,
'and functional appliances which alter the posture of the tongue or activities of the lips. It is most important to realize the strict limitations of such procedures for they ar,e successful only where specific conditions obtain which can be altered by the use of an appropriate appliance. Few mandibular arch perimeters can be lengthened permanentlY and there are no magic appliances for doing so. Success is secured when alteration of muscle function and/or the positions of teeth within the alveolar process is safely possible. The effects of orthodontic treatment on dental arch dimensions are not to be confused with the effects of orthodontic treatment on craniofacial skeletal dimensions. For a discussion of this subject read Chapter 4.
5. Over bite and Overjet Overbite (vertical overlap of the incisors) and overjet (hori-
~
126
Growth and Development
-- -= == IOVERBITE
to the primary teeth' are termed accessional teeth. From a clinical point of view, there are two very important aspects to the mixed dentition period: (I) the utilization of the arch perimeter and (2) the adaptive changes in occlusion that occur during the transition from one dentition to another. The alveolar process is one of the most actively adaptable areas of bone growth during the period of transition between the dentitions. Therefore, it is an ideal time for most major orthodontic interventions.
1. Uses of the Dental Arch Perimeter
FIG 6-33. Overbite and overjet.
zontal overlap, Fig 6-33) undergo significant changes during the primary and transitional dentitions (see Figs 6-44 and 6-52).70 During the primary dentition, the overbite normally decreases a slight amount, and the overjet often is reduced to zero. From the early mixed dentition to the completion of the permanent occlusion the average overbite increases slightly and then decreases, but there is great variability in its behavior (Fig 6_34).70 Overbite is correlated with a number of vertical facial dimensions (e.g., ramus height), whereas overjet usually is a reflection of the anteroposterior skeletal relationship. 16 Overjet is also sensitive to abnormal lip and tongue function. During growth of severe Class 11 and Class III malocclusions the overbite and overjet must adapt to the abnormal skeletal relationships and thus they behave differently from the mean changes just described.
G. THE 'MIXED DENTITION PERIOD That period during which both primary and permanent teeth are in the mouth together is known as the mixed dentition. Those permanent teeth that follow into a place in the arch Qnce held by a primary tooth are called successional teeth (e.g., incisors, cuspids, and bicuspids). Those permanent teeth that erupt posteriorly
w
-1 ::< a: Ul
:; -I-~ 2 5-3 w >-
04261 3
Permanent
Primary
1
6II4 II16 to 1I8 2 14 18
+, + I
YEARS
,.
~
I
FIG
6-34.
Overbite changes with age (reported as mean ± 1 SO). (Adapted from Moyers RE, van der Linden PGM, Riolo ML, et al; Standards of Human Occlusal Development, Monograph 5, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1976.)
Misconceptions regarding the normal changes in and uses of the dental arch perimeter probably cause more clinical failures in mixed dentition therapy than anything else. In the discussion that follows, concentration will be on the mandible, since it is by far more critical clinically than the maxilla. There are three uses of the arch perimeter: a) Alignment of the permanent incisors: they arrive typically crowded (Fig 6-35). b) Space for the cuspids and premolars. c) Adjustment of the molar occlusion: the first permanent molars, which typically erupt end-to-end, must change to a Class I relationship if normal occlusion is to be obtained. As the larger permanent incisors erupt, they find space in the arch only because (I) the arch width increases slightly, (2) there was some interdental spacing in the primary dentition, (3) the permanent incisors tip labially a bit (see Fig 6-38,A), and (4) the primary cuspids are moved distally. Still, there is a typical slight crowding which usually is not relieved until the primary cuspids are lost. When the incisors then align, they do so at some expense to the posterior space available for cuspid and premolar eruption and molar adjustment. The cuspid and premolars erupt into the normally excessive posterior leeway space. If molar adjustment is to be achieved by dental means, there must be some posterior space left after the arrival of the cuspid and premolars so that a late mesial shift of the first permanent molar may take place. Usually such a late mesial shift occurs to some extent but there are other mechanisms of occlusal adjustment and great variability can be expected. It is naive and somewhat hazardous clinically to assume the individual patient will show the exact normal changes: it is even worse to hope that the ideal can be expected except in the rarest of circumstances. , There have been divergent opinions concerning where, how, and when arch perimeter shortening takes place. These differences of opinion are not just interesting theoretical points; the planning of space management is altered significantly according to which of several concepts is correct. It has been suggested that the eruption.,of the first permanent:molar causes an "early mesial shift" which"'Closes the primate space and, other interdental spaces from the rear2 In the alternative theory the primary space is closed by the eruption of the incisors without loss of perimeter. The leeway space is the difference in size between the primary teeth and their permanent successors. Anteriorly, this is a mean negative value v (the primary teeth are bigger), even if one includes the interdental spacing around the primary incisors (see Fig 6-35). Posteriorly, £he m!an I~eway space is positive, since the_com!?ined_ widths of c + d + e exceed the combined widths of 3 + 4 + 5 (Figs 611, 6-36, and 6-37). However, the total leeway is the important
N 25 11.33 58 23.64 23.69 60 24.14 21.61 11.36 20.38 28 24 22.12 20.82 11.15 21.48 11.32 11.34 32 43 40 23.00 23.50 22.96 22.49 11.14 11.13 11.30 55 59 49 50 24.12 23.77 24.07 24.18 22.98 23.49 23.76 11.17 10.76 11.11 23.38 11.49 8.92 9.98 8.85 9.79 75 76 71 43 78 70 42 74 62 66 73 67 72 22.09 8.87 8.31 23.99 23.86 8.73 8.84 23 20 20 252 (mm) 22.83 24.26 23.84 10.87 8.69 8.79 48
127 Development
MEAN ANT POST (SO) (SO) (0.69) (1.16) (1.46) (0.62) (0.60) (1.26) (1.74) (1.28) (1.64) (0.54) (0.55) (1.40) (1.39) (1.52) (1.34) (0.56) (0.59) (1.02) (0.88) (1.15) (0.91) (1.25) (1.12) (0.96) (0.61) (0.53) (0.79) (0.94) (1.20) (0.98) (1.00) (1.05) (0.52) (0.33)
FEMALE
of the Dentition and Occlusion
ANT
DENTAL AGE (YRS)
-4 -3 -2
-1 o
2
3 4
5 6
7 8
FIG 6-35. Arch space available in the mandible by dental age (0 = arrival of first incisor) and sex. Note the increases in the available anterior
space and the decreases
clinical consideration. The method of utilization of the ·leeway space is the key factor in the transitional dentition. It has now been shown that the early mesial shift does not occur. '4> 15. 68 However, most children show a distinct "late mesial shift" with the loss of
seem to be important sexual differences in available posterior leeway space related to the occlusal status (see Figs 6-36 and 637). Some of the details and variabilities of the transitional den-
the mandibular second primary molar (Figs
lOWER
6-36
to
6-38).
There
in posterior space with time.
tition are lost or missed by the tendency of authors and researchers
ANTERIOR (1 + 2 - A + B) AN[)'POSTERIOR (3 + 4 + 5 - C + D lEEWAY SPACE BY ORIGINAL OCCLUSAL STATUS AND SEX
NN25 23 N (SO) (SD) 2.68 -2.35 -2.65 3.02 -3.16 2.60 2.58 15 12 16 14 18 ~'2.16 -3.15 -2.94 2.99 2.69 24 19 (SD)· 19 •.•
POST ANT MEAN MEAN >~. (0.47) (0.58) (1.00) (0.73) (0.70) (1.01) (0.69) (1.07) (1.24)
MALE
/
~
+ E)
FEMALE
FIG 6-36. Mean anterior and posterior leeway space arrayed according to original occlusion and sex. Note important relationships between space
available and original second primary molar occlusion. 6-37.)
(See also Fig
128
Growth and Development
LOWER ANTERIOR (1+2 - A+B) AND POSTERIOR (3+4+5 - C+D+E) LEEWAY SPACE BY ORIGINAL OCCLUSAL STATUS AND SEX Q. CD
'E'
III ~ >~0
g CD
-1 4 0 -2
-3 -4 3 2
Legend lZ2I CL I _ EtoE ~CIII
male
female
Anterior
male
female
Posterior
FIG 6-37. Relationships among leeway space, occlusal status, and sex. Note that posterior leeway space seems to be related to occlusal status
more in males than in females.
to depend upon chronologic age rather than a developmental age based on events of dentitional growth. The graphs in this chapter utilize both chronologic and biologic ages. Figures 6-29, 6-'35, and 6-38 are good examples of the use of biologic age based on the dentition rather than the moment of birth.
right side, but several possibilities are not found in actuality. Cephalometric studies (Moyers and Wainright68) show clearly a much more complicated variation of patterns of occlusal change during the transitional dentition than was previously thought. Their work shows the dominance of the skeletal pattern of growth over dentitional mechanisms of adjustment (Figs 6-40 through 6-43). A distal step in the primary dentition reflects a likely skeletal imbalance and likely will result in a Class II occlusion in the permanent dentition (see Figs 6-39,B and 6-41). A Class II skeletal pattern may worsen the occlusal relations with time (Fig 6-42). The two most common paths and hence the "normal" routes are from a flush terminal plane to Class I and from a mesial step to Class I occlusions (Figs 6-39 and 6-40).68 Of particular clinical interest are the factors that induce a flush terminal plane to change by ways other than the expected end-to-end and later Class I molar inter~tispation. If, for exa~ple, a child has a flush terminal plane in the primary dentition, a mild CI~ss II facial skeleton, and insufficient arch perimeter space to permit a late mesial shift of the first permanent molars, the occlusion likely will become Class II by the end of the mixed dentition period (see Fig 6-39,D)or an end-to-end molar relationship may obtain by the time of the eruption of the premolars (see Fig 6-39,E) depending on the severity of the Class II skeletal growth pattern. It is particularly advantageous to obtain a Class I molar relationship prior to the loss of the second primary molars, since all of the arch perimeter can be
In the maxilla, similar accommodative adjustments occur during the mixed dentition, although the matter is less critical since the upper incisors alter their inclination more and the maxillary perimeter does not display such a tendency to shorten as does the mandibular (see Figs 6-29 and 6-31). Furthermore, it is easier to alter maxillary arch dimensions during treatment (see Fig 632).
2. Occlusal Changes in the Mixed Dentition As noted earlier, the usual flush 'terminal plane of the primary dentition typically provides an end-to-end relationship of the first permanent molars. The first permanent molar normally then achieves a Class I relationship by (1) a late mesial shift after the loss of the second primary molar (see Fig 6-38, E and F); (2) greater forward growth of the mandible than the maxilla; or, most likely, (3) a combination of (1) and (2) (Fig 6-39,A). Theoretically, one might presume that there are 12 paths through the mixed dentition, since each of the three occlusal classifications on the left side of Figure 6-39
might become one of the four adult classes on the
Development
A
129
of the Dentition and Occlusion
B ..........••105
70
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4
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345
DEVELOPMENTAL
6
7
8
AGE (YEARS)
FIG 6-30. A-F, developmental
changes in tooth positions and angulations,
tr.lALE+1STD
t:.~
-2
-1
7
0123456 DEVELOPMENTAL
AGE (YEARS)
8
130
Growth and Development DISTAL
n
CLASS
STEP
I
_. AGE
30
+
56--!PROTRUSIVE LATE MESIAL
SMFT
82
108
END-TO-END
134
£
\
160
\
\
\
\ \
186
\
\
\ \ \
212
-5.25
FIG CLASS
FIG
used for alignment adjustment
(Fig
m
large leeway spaces, dentitional timely
orthodontic
intervention,
2.25
3.75
5.25
6-40.
ograph 7, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1977. Used by permission.)
of teeth and none need be allotted In minor
-.75 6.75
6-43) 0 = end-to-end, and positive values are towards Class I, negative towards Class 11.The scale is in millimeters. (From Moyers RE, Wainright R: Skeletal contributions to occlusal development, in McNamara JA Jr (ed): The Biology of Occlusal Development, Mon-
occlusal adjustment.
6-39,F).
-2.25
Computer plot of a "protrusive" pattern of occlusal change with a late mesial shift. In this and subsequent diagrams (Figs 6-41 through
6-39.
Patterns of transitional
-3.75
skeletal
adjustments
to molar
disharmonies
with
can be overcome
but no child
with
has enough mandi-
bular leeway space to achieve naturally a Class I molar relationship within a severe Class n facial skeleton.
of the skeletal growth We do know
and translating
that predicting
skeletal
lately become more proficient, future occlusal relations.
some into occlusal change,
at which
does not provide
The clinician's
is to study the patient carefully
change. we have
a sure insight into
only recourse at this time
through time until one of the paths
of occlusal
change has revealed itself and then to take appropriate
Three other interesting and frustrating patterns must be described, the homeostatic occlusions which remain as Class n, end-
therapeutic
action,
to-end,
and be comforted
or Class I from
permanent dentition why some occlusions toalveolar
the primary
(Figs 6-41
through
to 6-43,A-C).
the mixed
It is not yet known
change and some remain constant.
region apparently
acts as a buffer
TABLE
to the
The den-
zone absorbing
some
viewing
if necessary.
an end-to-end
terminal
molar
It is not enough
relationship
that it is normal,
planes do not grow
normally
6-7.
STARTING OCCLUSION
Distal step
=
52
Flush terminal plane
Mesial step
=
67
Dentition
FINISHING OCCLUSION
=
85
Class 11 End-to-end Class I Class III Class 11 End-to-end Class I Class II1 Class 1I End-to-end Class I Class I Class III
= 0=
PATTERN OF CHANGE
21
6
:'25
Homeostatic Protrusive Protrusive
I1 ,.
o
7 22
56
Retrusive Homeostatic Protrusive
end-to-end
Retrusive Retrusive Homeostatic Protrusive Protrusive
I
o
= 9 = 3 = 30 = 23 2
to relax when terminal
plane)
for a high percentage of flush
way to understand and treat malocclusions variabilities.
Patterns of Occlusal Change in the Transitional
(flush
(Table
6-7).
without
There is no
studying growth
Development
I
AGE Months
30
A
I
AGE Months
56-4HOMEOSTATIC (CLASS
30
82
56-1HOMEOSTATIC (CLASS
It + TREATMENT) I:)
'08
82
'34
t08
'60
.34
'86
t60
t86
2'2 -5.25
FIG
131
of the Dentition and Occlusion
-3.75
-2.25
-.75 6
75
2.25
3.75
5.25
,-
212
6-41.
-5.25
Homeostatic Class I1 pattern plus orthodontic treatment begun at about 11 years of age. (From Moyers RE, Wainright R: Skeletal contributions to occlusal development, in McNamara JA Jr (ed): The Biology of Occlusal Development, Monograph 7, Craniofacial Growth
-3.75
-2.25
-.75 6 .75
3.75
5.25
I
B AGE Months
Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1977. Used by permission.)
2.25
30
56 To a large extent, the occlusal relationships are at the merc) of the skeletal growth. Several distinct patterns of skeletal growth and occlusal adjustment
have now been identified,
yet clever enough in predicting It will
be learned
used routinely
which path a child is apt to follow.
later that the amount
dental adjustments
can be predicted
when planning
now able to predict within growth (see Chapter
quite accurately,
mixed dentition
practical
30
a procedure
treatment.
.34
We are
limits some aspects of skeletal
occlusal
AGE Months
to8
of space in an arch for
12), but such skeletal predictions
value, as yet, in predicting
HOMEOSTATIC 82 -HENO- TO- ENO)
but we are not'
I
160
are of little
changes.
'86
212
I
I
-5.25
-3.75
I
I
I I I -.75 0.75
-2.25
I
I
2.25
3.75
I
5.25
56
FIG
6-43.
Homeostatic patterns of occlusal development (see also Fig 6-41). A, Class I; B, end-to-end. (From Moyers RE, Wainright R: Skeletal con'tributions to occlusal development, in McNamara JA Jr (ed): The Biology of Occlusal Development, Monograph 7, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Devel-
82 t08
'34
opment, University
of Michigan,
1'977. Use9 by permission.)
.60
3~F!rst
t86
2t2
TI---r-
-5.;'5
FIG
-3.75
,. Molar Eruption
In Sections -2.25
-.75 6 .75
2.25
3.75
5.25
6-42.
"Retrusive" pattern of occlusal development. (From Moyers RE, Wainright R: Skeletal contributions to occlusal development, in McNamara JA Jr (ed): The Biology of Occlusal Development, Monograph 7, Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, University of Michigan, 1977. Used by permission.)
44
through
G-3
6-52
(serial radiographic dissections). convey
to
G-6,
(a normal views),
They depict
66-53 and 6-54 6-55 through 6-59 (skull
the reader should refer to Figures cast series), Figures
and Figures
well ideal or typical
the wide variability
growth
but cannot
seen in practice.
a) Mandible The majority
of children
to the central incisors,
erupt the first permanent molar prior
although
some children
reverse this order
132
Growth and Development
FIG 6-44. Primary occlusion at 5 years. Note the generalized interdental spacing, primate spaces (distal to lateral incisors in the maxilla and distal to cuspids in the mandible), moderate overbite and overjet, and flush terminal plane. (Courtesy of Or. R. R. Mclntyre.)
FIG 6-45. Occlusion at6 years. Note diminished overbite and overjet and beginning of a mesial step at the distal surfaces of the primary molars.
FIG 6-46. Occlusion at 7 years. All first molars and central and lateral incisors have erupted. A distinct mesial step has permitted Class I interdigitation of the permanent molars, and the erupting incisors have closed the primate spaces in both arches.
Development
of the Dentition and Occlusion
FIG 6-47. Occlusion at 8 years. Ordinarily, the mandibular lateral incisors erupt into the line of arch, completing closure of the primate spaces. Note interdental spacing in the maxillary incisor region. The permanent molars have a firm Class I occlusion by this age if a mesial step has been available at the time of their eruption.
FIG 6-48.' Occlusion at 9 years. Mandibular permanent cuspids have erupted in this case. Although this is desirable, often the mandibular cuspid and first bicuspid arrive almost simultaneously.
FIG 6-49. Occlusion
at 10 years.
First bicuspids
are erupted
permanent cuspids are appearing. In most mouths, second bicuspids erupt before the cuspids.
and maxillary the maxillary
133
134
Growth and Development
FIG 6-50. Occlusion at 11 years. Interdental spacing in the maxillary incisor region has been closed by eruption of the cuspids, and one second bicuspid has appeared in each arch. Eruption of second molars in the mandible at this time is not the most favorable sequence; it is better if they are delayed until all bicuspids have erupted.
FIG 6-51. Occlusion at 12 years. All permanent teeth except the third molars are in position. Note absence of any interdental spacing and the slight tendency to procumbency of the dentition. The procumbency typical of the recently completed dentition seems to diminish soon unless there is gross discrepancy between the size of the teeth and the alveolar perimeter.
FIG 6-52. Occlusion at 13 years. There are few changes except the tendency to less dental procumbency than seen previously.
Development (see Fig 6-19). There seems to be no clinical significance in either sequence. The first permanent molar is guided into its occlusal position during eruption by the distal surface of the second primary molar (see Figs 6-12 and 6-39). The occlusal relationship that the mandibular first permanent molar initia11y obtains with its maxillary antagonist is thus determined by the terminal plane relationship of the second primary molars (see Figs 6-11 and 612). Changes in occlusal relationship that occur during the period of the first molar eruption are not caused by that eruption, but are due to coincidental skeletal growth. b) Maxilla During formation, the crowns of the maxillary molars face d.orsally rather than occlusally. As the maxilla moves forward, space is created posteriorly, permitting appositional enlargement of the maxillary tuberosity. During this rather rapid tuberosity growth, the first permanent molar rotates, and by the time the crown pierces the gingiva, it is facing more occlusally (see Fig 6-58). Occasionally, the maxillary first permanent molar is found in ectopic eruption.
4. Incisor Eruption a) Mandible The mandibular first permanent molars are followed almost immediately by eruption of the mandibular central incisors. Although the incisors usually follow the first permanent molars iri piercing the gingiva, they reach their full clinical crown height sooner. The permanent mandibular incisors develop lingually to the resorbing roots of the primary incisors, forcing the latter labially to be exfoliated (see Fig 6-57). The lingual eruptive position is no cause for alarm if the primary incisors are resorbing normally. As soon as the primary central incisors have been exfoliated, further eruption and lingual activity moves the permanent incisors labially to their normal balanced position between the tongue and the lip and facial musculature (see Fig 6-23). The size of the primary teeth, the amount of interdental spacing, and the size of the anterior perimeter of the dental arch are factors that determine whether the permanent incisors will erupt crowded. Normally there is some crowding after the lateral incisors are erupted. The lateral incisors, as they emerge, not only push the primary lateral incisors labially but also move the primary cuspids distally and laterally, closing the primate spaces (see Fig 6-26). When the permanent incisors are disproportionately large for the arch in which they are found, the eruption of the lateral incisor may cause the exfoliation of the primary cuspid or an unusual resorption of the primary cuspid root. In other instances, such disharmony of tooth size and' arch perimeter will maintain the lateral incisors in their original lingual position. As soon as the lateral incisors emerge into the mouth, a Mixed Dentition Analysis may be made to estimate the amount of arch space available for the permanent teeth and the occlusal adjustments that accompany the transitional dentition period (see Chapter 11). When the mandibular primary cuspids are prematurely lost, the anterior arc is less stable and the incisors may be tipped lingually by hyperactivity of the mentalis muscle, a condition frequently found with Class n, Division 1 malocclusion or thumb-sucking. Lingual tipping of the incisors permits the developing permanent cuspid
of the Dentition and Occlusion
135
to slide labially, where it may erupt later in labioversion. This is a sensitive time and a sensitive region. The first symptoms of some malocclusions frequently are diagnosed at the time of eruption of mandibular incisors. Space supervision therapy (q.v., Chapter 15) begins at this time and must be synchronized well with dental development. Good timing is one of the fundamentals of good orthodontic therapy. b) Maxilla The maxillary anterior dental segment is supported by the mandibular, which has formed earlier, providing the functional stops against which the maxillary incisors erupt. Usually, the maxillary central incisors erupt just after the mandibular central incisors or concurrently with the mandibular lateral incisors (see Fig 646). The maxillary permanent incisors erupt with a more labial inclination than their predecessors, in accordance with their greater labiolingual thickness and wider diameter. Little variation is seen in eruption of the maxillary central incisor unless one is deflected by abnormal exfoliation of the primary tooth, a supernumerary tooth, or by trauma. The maxillary central incisors erupt with a slight distal inclination and some midline space between them, which space is diminished with eruption of the lateral incisors and closed as the cuspids wedge their way into the arch. The maxillary lateral incisors, on the other hand, often experience more difficulty in assuming their normal positions, for, as they are erupting, the developing crowns of the maxillary cuspids lie just labially and distally to their roots (see Fig 6-57). The cuspid in this position often can cause the crown of the lateral incisor to erupt more labially than the central incisor. After the erupting cuspid has changed its course (it often seems to have been deflected by the root of the lateral incisor), the lateral incisor then rights itself and comes into position beside the central incisor. Minor rotations may been seen in the positions of both the central and lateral incisor but they usually are corrected as the cuspids erupt (see Figs 6-48 and 6-49). Ordinarily, it is not good practice to attempt alignment of central and lateral incisor while the cuspid crown is atop the root of the lateral incisor, since orthodontic pressure against the lateral incisor's crown may press the root against the erupting cuspid crown and cause root resorption.
5:"CUSpid and Bicuspid Eruption Favorable development of occlusion in this region is largely dependent on four factors: (1) a favorable sequence of eruption; (2) a satisfactory tooth size-avaiIable spac~ ratio; (3) the attainment of a normal molar relationship with minimal diminution of the space available for the bicuspids; and (4) a favorable bucco-lingual f~lf~ionship of the alveolar processes. a) Mandible The most favorable eruption sequence in the mandible is cuspid, first bicuspid, second bicuspid, and second molar. Fortunately, this also is one of the most frequent sequences. It is useful if the cuspid erupts first, since it tends to maintain the arch perimeter and to prevent lingual tipping of incisors. When the incisors are tipped lingually, they may overerupt, since by lingual tipping they lose their centric stops with the maxillary incisors. In malocclusions, mandibular incisors erupt past the severe Class
n
136
Growth and Development
FIG 6-53. Eruption of first permanent molars when there is a mesial step on distal surfaces of the deciduous teeth. A, age 5. Note distinct mesial step established before eruption of first permanent molars. The mandibular primate space is open. 8, age 6. The erupting first permanent
molars are guided by the distal.surfaces of the second primary molars. The mandibular primate space persists. C, age 7. Erupting first permanent molars are firmly interdigitated into Class I occlusion without closing the mandibular primate space .
.
..
Development
of the Dentition and Occlusion
137
FIG 6-54. Serial radiographs of the same child at different ages. A, oentition at 5 years showing a flush terminal plane. Compar~ with Fig 6-53, noting the sequence of eruption and positions of the permanent teeth. e, dentition at 8 years. Note end-to-end molar relationship and positions and sequence of erupting teeth. C, dentition at 10 years. In this case, the mandibular first bicuspid is arriving just before the
cuspid. This is not serious if there is space for the cuspid. The maxillary first bicuspid is just ready to appear in this mouth. D, dentition at 12 years of age. The permanent teeth have settled into excellent occlusion. Note the mesial step on the distal surface of the first molars, proving that the mandibular first molars have moved mesially more after loss of the primary second molar.
FIG 6-55. A, a skull dissection of a neonate. Note the overlap of the parietal and frontal bones. Note, too, the calcifying primary teeth. e, front
view.
138
Growth and Development
FIG 6-56. A, a skull specimen at approximately 8 months of age. The mandibular left second primary molar has been lost from its crypt. Note how advanced is the calcification of the first permanent molars. By this time, one sees rapid alveolar process growth and considerable re-
sorption already on the anterior border of the ramus In anticipation of the eruption of the first permanent molar. B, front view. Note the relationship of the calcifying and erupting primary teeth.
FIG 6-57. A, the dentition and its relationship to developing bony structures at approximately 4 years of age. Now the crypt for the second permanent molar is clearly visible and the first permanent molars are moving rapidly toward the plane of occlusion with sufficient space in
the line of arch for them. Space has been provided by the resorption at the anterior border of the ramus. B, a front view of the same specimen. Note the intimate relationship of the calcifying permanent incisors to the roots of the primary incisors.
plane of occlusion until they find functional stops against the maxillary palatal mucosa. In Class 11 malocclusion, such overeruption often occurs without lingual tipping. A complication of this enhancement of the occlusal curve is the movement of the
ratio is poor, the cuspid may be stopped in its eruption by the first primary molar or the primary molar may be hastened in its exfaliiltion .• ~. Only rarely does the first biouspid experience difficulty in erupting. Bicuspid rotations sometimes occur with uneven resorption of the roots of the primary molars (Fig 6-60). If such rotations are seen to be developing, it is good practice to construct a spacemaintainer, extract the primary molar (no earlier than completion of the crown), and hold space for the erupting tooth. Since the second bicuspid is the last of the mandibular succedaneous teeth to erupt, there will not be room for it if there has been a shortening of the dental arch perimeter by mesial movement of the first molar, nor will there be room for the second bicuspid
mandibular cuspid during eruption into labioversion, a malposition far more likely to occur if the first bicuspid precedes it in eruption. It is quite normal for the cuspid to lag behind the first bicuspid during early development, but it moves more rapidly during the latter stages of eruption and usually passes the first bicuspid before breaking through the alveolar crest. Eruption of the cuspid may be hastened by extraction of the primary cuspid while the root of the permanent cuspid root has just started to form (see Space Supervision in Chapter 15). Where the tooth size-space available
Development
of the Dentition and Occlusion
139
FIG 6-58. A, the dentition at approximately 6 years. At this time, a very complicated situation exists. Note the presence of all the permanent teeth
either lingually to their primary predecessors or directly beneath them as in the molar region. B, a front view of the same specimen.
FIG 6-59. A, the dentition at approximately 9 years of age. Now one can see the maxillary cuspid erupting at an angle against the root of the lateral incisor. B, a front view of the same specimen. Note the hazardous
relationship
of the cuspids to the roots of the lateral incisors in this
projection. Great care and caution must be taken in moving lateral incisors at this stage of development.
FIG 6-60. A, uneven resorption
of the second primary molar, resulting in dis-
placement of the second premolar-or did the displacement of the second premolar cause the uneven resorption of the primary molar's
roots? B, the spontaneous position after extraction
correction
of the second premolar mal-
of the primary predecessor.
140
Growth and Development
if the tooth size-space available ratio is poor. When the secondary primary molar is lost prematurely, the erupting second molar often helps the first molar move mesially before the second bicuspid can erupt. The eruption of the mandibular second molar out of sequence may be a troublesome problem in space management if it is not detected early enough to maintain the arch perimeter. Before the primary molars are lost, a Mixed Dentition Analysis must be done to determine whether mesial movement of the first permanent molar need be controlled. When the leeway space is insufficient, the first molar must not be allowed to move mesially until the second bicuspid has had a chance at its proper position in the arch. Mandibular second bicuspids display extreme variation in their calcification and development schedule. Therefore, it is difficult to predict the exact time of their emergence in the mouth, and they often are congenitally missing. The determination of congenital absence of mandibular second bicuspids must be done carefully because of their wide developmental variability. b) Maxilla The sequence of eruption is typically different in the maxilla, being either first bicuspid, second bicuspid, and cuspid or first bicuspid, cuspid, and second bicuspid. Although the maxillary anterior segment is not prone to collapse lingually, since normally it is supported by the mandibular arch, it is very easily displaced labially by thumb-sucking, tongue-thrusting, or a hyperactive mentalis muscle. Such displacement of the maxillary anterior segment affects the eruptive pattern of the cuspids and bicuspids. The maxillary first bicuspid usually erupts uneventfully, following the mandibular cuspid and/or the mandibular first bicuspid. Since the maxillary first bicuspid is very nearly the same size as its predecessor, usually neither the primary cuspid nor the primary second molar is displaced by its arrival. The greater mesiodistal widtb of the second primary molar permits easy eruption of the second bicuspid into its place in the arch. However, this leeway in the second bicuspid region may be necessary to provide space' anteriorly for the accommodation of the wider permanent cuspid even though the anterior arc is increasing at this time. A tight situation exists in the maxillary arch, which is emphasized by the tendency to mesial drifting and the hazardous and circuitous eruptive course of the cuspid. There should be an excess of space in the arch when the second bicuspid arrives, the cuspid must follow immediately, and the first permanent molar must not be allowed to rotate and tip mesially or the cuspid is likely to be blocked out of the arch in labioversion. The eruption of the second permanent molar ahead of a cuspid or bicuspid is thus as critical in the maxilla as in the mandible. The maxillary cuspid follows a .more difficult and tortuous path of eruption than any other tooth. When the child is 3 it is high in the maxilla, with its crown directed mesially and somewhat lingually. It moves toward the occlusal plane, gradually uprighting itself until it seems to strike the distal aspect of the lateral incisor root, apparently becoming deflected to a more vertical position. It often erupts into the oral cavity with a marked mesial inclination, appearing high in the alveolar process, a cause for concern on the part of some parents. The eruption of the cuspid closes the interdental spacing between the incisors, providing space for the final uprighting of the cuspid. When in its correct occlusal position, it
has a slight mesiai'inclination. Should the arch length become shortened due to interproximal caries or an unfavorable sequence of eruption, the cuspid will have insufficient space for its final positioning. It is then left in labioversion with a decided mesial inclination. This maxillary malocclusion is analog<:lUsto the blocking out of a mandibular second bicuspid lingually. If arch length is short in both arches, the upper cuspid and lower second bicuspid arrive malposed because they are typically the last teeth ahead of the first molars to erupt in their respective arches.
6. Second Molar Eruption Normally, the mandibular second molar arrives in the oral cavity after all the teeth anterior to it. When it precedes a second bicuspid, it may tip the first molar mesially, the sequelae to which have been discussed previously. The mandibular second molar typically erupts into the mouth before the maxillary second molar. The maxillary second molar also should follow all of the teeth anterior to it into the arch. There is a greater tendency to loss of arch length in the maxilla when the primary teeth are lost prematurely. The eruption of the maxillary second molar ahead of the mandibular second molar is said to be symptomatic of a deIt also is seen with premature veloping Class II malocclusion.57 loss of maxillary primary molars and sometimes may be seen in skeletal Class II malocclusion because there may be more space than normal in the maxilla for maxillary second molar development or less space in the shortened mandible for mandibular second molar development.
H. DENTITIONAL AND OCCLUSAL DEVELOPMENT IN THE YOUNG ADULT l. Third Molar Development Third molars show more variability in calcification and eruption than do any other teeth. The third molar is unique among human teeth, since it apparently displays no sexual differences in formation nor is its formation related as closely to somatic growth and sexual maturation as are the other teeth. On the other hand, the third molar shows high constancy with its own pattern of development; that is, early calcifying third molars erupt early and complete their roots early. There is evidence of ethnic differences, since the Finns acquire their third molars later than Middle American whites.35 Greeks have a mean eruption time of 24 years and some South Indians erupt third molars as early as 13 years. North AIl,I~rican blacks erupt tpi:Fd molars earlier than do whites. 'Third molar agenesis occurs 16% of the time in middle western American whites.35 When one or more third molars are missing there is a strong tendency for agenesis of other teeth, delayed formation of other posterior teeth, differences in developmental sequences, reduction in the size of other teeth and even delayed timing and eruptive movement of the third molar in the siblings of affected children." Since the third molar may not begin its calcification until as late as 14 years, the diagnosis of agenesis cannot always be made with certainty in the mixed dentition. However, it should be noted that there is symmetry of develop-
Development ment, which aids in the diagnosis when one molar seems to be missing. When a third molar usually is missing the clinician should not be surprised to see a greater incidence of hypoplastic maxillary laterill incisors, less frequent eruption of second molars before second premolars, and smaller than normal te.eth. The question of the role of the third molar in the crowding of mandibular incisors during the late teenage period has been much debated. A number of simultaneous phenomena confuse the issue: the arch perimeter shortens, the incisor crowding increases, the third molars develop, and the mandible grows forward more than the maxilla. Events that occur together do not, of course, necessarily depend on one another. Incisor crowding has been found to correlate better with mandibular increments than with the eruption of third molars.4 More crowding is seen in men than in women. This observance is probably true because their mandibular increments are greater at this time. 4 The first molars have been found to be farther forward and the incisors more procumbent in individuals with third molars than in those with third molar agenesis. 19 Therefore, third molars could not play a primary role in the position of any teeth mesial, since the differences in first molar position and incisal procumbency appear before significant development of the third molar. The evidence favors absolving the third molar of the increased crowding (see Section F-3 earlier in the chapter). Impaction of third molars is a frequent and serious problem in modern man. Mandibular third molar impactions, which are usually the more serious, are seen more frequently with skeletal' Class Il particularly when the body of the mandible is short and acutely angled. Although a number of measures can be used to discriminate groups with impacted third molars from those without, accurate prediction of third molar impaction at age 10 or 11 years is not yet possible in a statistically significant way. Many clinicians do such predictions and the methods are ingenious and interesting, but none of the procedures yet suggested have withstood critical testing, nor are they precise enough for sure predictions in individual cases.
2. Dimensional
Changes
The dental arch perimeter decreases a surprising amount during the late adolescent and young adult periods (see Fig,6-29). During these same periods, maxillary and mandibular arch widths increase, but these increases are completed in both arches by 12 years of age in girls (see Figs 6-27 and 6-28). There are only a few studies of arch dimensional changes after age 15 years, but they seem to show a continued shortening of the perimeter.
3. Occlusal Changes Both overbite and overjet decrease throughout the second decade of life, probably due to the relatively greater forward growth of the mandible. The changes in sagittal relationships of the dentitions can be related to the growth of the jaws better than to dental events; for example, the developmental course of the third molars. Such posterior occlusal changes are due to the mesial drifting
of the Dentition and Occlusion
141
tendency, slight' interproximal wear and, most importantly, the continuing growth of the mandible (see Figs 6-36 and 6-37).
4. Resorption
of Permanent
Teeth
By the end of the second decade, most persons display idiopathic resorption of one or more teeth. Nearly 90% of all teeth show some evidence of resorption by the time a person is 19 years of age. Although most of the instances are mild and confined to apical blunting, nearly 10% show between 2 mm and 4 mm of root resorption. There is a significant increase in the frequency of the more severe types of resorption with age and an increase in both the number of resorbed teeth and the severity of the resorption when orthodontic treatment has occurred (see Chapter 13). Teeth that are likely to resorb more rapidly during orthodontic therapy can be predicted quite well by a careful examination of the radiographs prior to therapy. Obviously, there is a general potential for resorption of permanent teeth varying with the person and the tooth-a potential that may be triggered by orthodontic tooth movements. However, serious root resorption is only rarely seen during orthodontic therapy. When it does occur it is most apt to be seen in patients with a potential for resorption whose teeth have been "jiggled" (i.e., moved back and forth by the appliance or the appliance and occlusal forces).
5. Arrangement
of the Teeth in the Jaws
Most reports of occlusion are concerned with the arrangement of the crowns of the teeth; however, Dempster et al.16 have reported an exhaustive study of the relationship of the roots to the craniofacial skeleton. The bicuspid roots are the most nearly perpendicular to the plane of occlusion. The lower incisor cuspid and molar roots are directed obliquely backward. The roots of the maxillary teeth, anterior to the second bicuspid, are directed posteriorly and inward, whereas the roots of the maxillary molars are more vertical than the opposing lower molars. A number of attempts have been made to describe the dental arc mathematically in an effort to seek a basic or ideal pattern. The line of occlusal contact between the upper and the lower teeth also has been studied many times and is referred to as the occlusal curve, the occlusal plane (although it is not a plane), the curve of Spee, the compensating curve, etc. Attempts have been made, in both the natural and artificial dentitions, to relate the occlusal curve to movements of the jaw. Finally, worker; in prosthodontics have extended these ideas into a concept of a three-dimensional spherical c~rvature involving bot,h:otheright and left posterior teeth and both mahdibular condyles, suggesting that a sphere of 8 inches or 20 cm in diameter was the "correct" dimension for all occlusal arc designs. Such ideas are based on the conjecture that the roots of the teeth converge to a center. The roots do not converge toward a common center and the occlusal surfaces of the posterior teeth cannot be fully congruent with the surface of any size sphere. As might be expected, there is great variability in the positions of the teeth within the skull. It is obvious that any attempts to reduce all human occlusal patterns to one "ideal" or basic pattern are naive at best and ridiculous at worst. 69
142
Growth and Development
FIG 6-61. A, ideal intercuspation,
buccal view. 8, ideal intercuspation,
lingual
I. CLINICAL IMPLICATIONS 1. Normal Versus Ideal Occlusion The word "normal" implies variations around an average or mean value, whereas "ideal" connotes a hypothetical concept or goal. There is a particular clinical difference between a "normal occlusion" and an "ideal occlusion." Unfortunately, the' word normal has been used for years in orthodontics as a synonym for ideal, causing both semantic and treatment difficulties. It is perfectly proper to label as normal a mouth in which all of the teeth are present and occluding in a healthy, stable, and pleasing manner but with variations in position within measurable normal limits. Perhaps no one has ever seen a perfect or ideal occlusion, but that does not diminish the practical use of the concept, for every dentist treating occlusions must have an ideal pattern in mind even if "it is never achieved. Nature herself rarely shows an ideal occlusion. Her best effort usually is within a range of normality. It is perfectly reasonable, when planning orthodontic treatment, to have in mind the image of ideal intercuspation (Fig 6-61). It also is perfectly proper and practical to accept at the end of treatment an arrangement of the teeth within the jaws in positions that are neither ideal nor normal but may be stable ina particular person's face. One of the most difficult tasks in orthodontic treatment planning is that of determining just where to place the individual teeth within an abnormal facial skeleton to achieve the best possible occlusion for that particular face. It is impossible, naive, and wrong to attempt to achieve ideal or normal tooth positions in a patently abnormal set of circumstances, such as a severe skeletal dysplasia.
.
'. aptation ent Healthy adult
.
~ TABLE 6-8.
view.
2. Models of Occlusion Occlusion is certainly the common theme of all branches of dentistry, but the concepts of occlusion that are held by practitioners of the different dental fields tend to be contradictory. The working clinical occlusal hypotheses of one field are often not applicable, understood, or used in another branch of dentistry. Anyone of a number of mental images or models of occlusion may be in a dentist's mind. Some regard human occlusion as a very precise machine, the fit of whose parts must be done with great care. As in any machine, all parts are needed for it to ·run well. Such a model does not explain where the energy that runs the machine originates and avoids the important aspect of control of the machine. Another occlusal model suggested is that of teaching a pet a new' trick. Such a concept introduces the idea of neuromuscular learning. All tricks cannot be learned by all and some learn better than others. It is the dentist's duty to decide which "tricks" patients should learn for their own benefit. A patient must be taught how to adapt to a new set of dentures, for example, and once the "trick" of handling the dentures is learned the problem is over. The difficulty with this concept is that there are innumerable occlusal "tricks" that cannot be mastered by any patient. No person with a Class II skeletal pattern and occlusion can "learn" to hold his or her jaw forward in a more favorable Class I occlusal relationship because the conscious cortical control of this new mandibular position is constantly overcome by the primitive reflexes that tend to maintain the mandible posteriorly. T'iilley, an English orthodontist, has likened the treatment of occlusion to playing a never-ending game of chess with the devil.
MUSCULATURE DENTITION BONE extrusion, Traumatic occlusal Reconstructive Growth reflexes; protective Wear, Supportive anterior dentistry Resorption pathology Repair occlusal component Learning, Loss of sensory Eruption Prosthetic imprinting input and dentistry tooth reflexes occlusal responses STAGE
,.
Development The dentist sits down after the game has started and is not always able to guess what moves have been made previously. The rules that govern the game have not all been chosen by the clinician, that is, the rules of bone biology, nerve physiology, muscle learning, psychology, and other factors. The rules change as the game progresses or conditions alter. The analogy breaks down when one asks, "What is winning?" There is no victor; it is enough to keep the game going. Life, after all, is more than the mere maintenance of structures; events must be kept going, functions must be perpetuated. The best occlusion, and hence the best model of occlusion too, is that which adapts best through time.
of the Dentition and Occlusion
143
conditioning possibilities. Therefore, the prosthetic occlusion usually is established within the b9undS of the most primitively controlled neuromuscular restrictions, that is, the mandibulomaxillary relationship determined by the_unconscious swallow. Clinical goals are not necessarily either normal or ideal. Rather, they are pragmatic and are determined by the conditions of the individual patient. The determining factors are the adaptive mechanisms the clinician can yet best utilize. The goal of occlusal treatment is not just to maintain structures. It is not to meet some hypothetical norm or idea. Rather, it is to keep events going. That occlusion is best which most easily provides continuing functional homeostasis.
3. Occlusal Adaptive Mechanisms What, then, is good occlusion? What concept or model of occlusion should the dentist have? That of normal? Ideal? Perhaps that occlusion is best which best adapts to its changing functions. Such a concept implies that adaptive mechanisms are present and necessary and that there are feedback mechanisms from the oc-
REFERENCES
I.
clusal system that help provide occlusal homeostasis. Any occlusal treatment that lacks functional homeostasis is destined to clinical failure.
2.
A look at Table 6-8 reveals the adaptive mechanisms of the dentition, bone, and musculature through various stages of occlusal development and maintenance. During development, such factors as eruption, tooth movements, dental wear, and loss of primary teeth provide the period of greatest dental adaptability. The alveolar process during growth is highly adaptable, as is the craniofacial skeleton. Childhood also is a period of developmental neuromuscular learning. Clinical treatment at this time takes advantage of these responsive adaptive mechanisms .. In the healthy adult, however, most of the dental adaptive mechanisms have been lost except for wear, extrusion of the teeth, the anterior component of force, and drifting. The only bony adaptations left are those of repair and remodeling since growth is largely over. Orthodontic treatment during this period can thus still utilize the diminished rate of remodeling but cannot be helped by growth of the basal skeleton, which has practically ceased. Protective reflexes are constant adaptations but some such reflexes (see Chapter 5) can be destructive. The supportive occlusal reflexes, for example, the unconscious swallow, can be stabilizing to the occlusion of the adult although much less adaptive. If the adult dentition begins to deteriorate, there are few natural means left for dental adaptation and these mostly must be provided by reconstructive dentistry. Pathologic bone loss provides adaptation of a kind but it must not be allowed to proceed, and the dentist, during therapy, attempts to restore conditions providing bone repair. Occlusal equilibration procedures may obliterate potentially destructive reflexes. After disease and tooth loss have occurred, when growth is really not possible in usable amounts and when many of the healthy, reparative processes have gone, occlusal treatment becomes a very difficult problem if functional homeostasis is to be achieved.
3.
Finally, in the edentulous adult there are no natural dental adaptive mechanisms left and the prosthesis made by the dentist adapts and changes entirely differently than the natural dentition did. Resorption of bone is the most common bony adaptive function now seen, for the neuromusculature shows very diminished
4. 5.
6.
7.
Arnold EE: A Study of the Significance of the Interdental Spacing in the Primary Dentition, thesis. Horace H Rockham School of Graduate Studies, University of Michigan, Ann Arbor, 1954. Baume U: Physiologic tooth migration and its significance for the development of occlusion. n. The biogenesis of accessional dentition. J Dent Res 1950; 29:331-337. Biederman W: Etiology and treatment of tooth ankylosis. Am J Orthod 1962; 48:670-684. Bjork A, 1ensen E, Palling M: Mandibular growth and third molar impaction. Acta Odontol Scimd 1956; 14:231-272. Bradley RE: The relationship between eruption, calcification, and crowding of certain mandibular teeth. Angle Orthod 1961; 31:230-236. Burdi AR: The development and eruption of the human dentitions, for Forrester D1, Wagner ML, Fleming 1 (eds); Pediatric Dental Medicine. Philadelphia, Lea & Febiger, 1981, pp 55-70. Burdi AR, Lillie 1H: A catenary analysis of the maxillary dental arch during human embryogenesis. Anat Rec 1966;
154:13-20. 8. Burdi AR, Silvey RG: Sexual differences in closure of the human palatal shelves. Cleft Palate J 1969; 6: 1-7. 9. Burdi AR, Garn SM, Miller RL: Mesiodistal gradient of mandibular precedence in the developing dentition. J Dent Res 1970; 49:644. 10. Burdi AR, Garn SM, Miller RL: Developmental advancement of the male dentition in the first trimester. J Dent Res
1970; 49:889.
I k Burdi AR, Garn SM, Miller RL, et al: Sequence polymorphism in prenatal dental development. J Dent Res 1970;
49: 1554. 12. Carpenter 1V: The relationship between teething and systematic disturbances. J Dent Child 1978; 45:381-394. 13. Clinch L: Variations in the mutual relationships of the up" Sbc per and gum 1932; pads pp in the newborn child. Trans Br Studylower Orthod 91-107. 14. Clinch LM: An analysis of serial models between three and eight years of age. Dent Rec 1951; 71:61-72. 15. Davey KW: Effect of premature loss of deciduous-primary molars on the antero-posterior position of maxillary first permanent molars and other maxillary teeth. J Can Dent Assoc 1966; 32; 406-416; also J Dent Child 1967; 34:383-
394. 16. Fleming HB: An investigation of the vertical overbite during the eruption of the permanent dentition. Angle Orthod
1961; 31:53-62.
144
Growth and Development
17. Foster TD, Hamilton MC: Occlusion in the primary dentition. Br Dent J 1969; ]26:76-79. ]8. Friel S: The development of ideal occlusion of the gum pads and the teeth. Am J Orthod 1954; 40:196-227. 19. Fuder El: Third Molars and Crowding: A Longitudinal Study in the Second and Third Decade, thesis. Horace H. Rackham School of Graduate Studies, University of Michigan, Ann Arbor, 1969. 20. Gam SM: The genetics of normal human growth. De Genetica Medica-Paris H. Rome, Edizioni Dell Instituto Gregorio Mendel, 1962. 21. Garn SM: Genetics of dental development, in McNamara JA Jr (ed): The Biology of Occlusal Development, Monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977; pp 61-88. 22. Gam SM, Burdi AR: Prenatal ordering and postnatal sequence in dental development. J Dent Res 1971; 50:14071414. 23. Gam SM, Lewis AB: Tooth-size, body-size and "giant" fossil man. Am Anthropol 1958; 60:874-880. 24. Garn SM, Lewis AB: Phylogenetic and intraspecific variations in tooth sequence polymorphism, in Brothwell DR (ed): Dental Anthropology, Vol V. London, Pergamon Press, 1963, pp 53-73. 25. Garn SM, Rohmann C: Interaction of nutrition and genetics in the timing of growth and development. Pediatr Clin North Am, 1966; 13:353-379. 26. Garn SM, Burdi AR, Babler WJ, et al: Crown size-arch space relationships during human prenatal dental development. J Dent Res 1979; 58:554-559. 27. Garn SM, Burdi AR, Miller RL, Nagy J: Prenatal origins of postnatal dental variability (abstract). Am J Phys Anthropol1970; 33:130. 28. Garn SM, Burdi AR, Nagy J: Distance gradient in prenatal dental development. J Dent Res 1971; 50:785. 29. Garn SM, Lewis AB, Kerewsky RS: Size interrelationships of the mesial and distal teeth. J Dent Res 1965; 44:350354. 30. Garn SM, Lewis AB, Kerewsky RS: X-linked inheritance of tooth size. J Dent Res 1965; 44:439-441. 31. Garn SM, Lewis AB, Kerewsky RS: Shape similarities throughout the dentition. J Dent Res 1967; 46: 1481. 32. Garn SM, Lewis AB, Koski K, et al: The sex difference in tooth calcification. J Dent Res 1958; 37:561-567. 33. Garn SM, Lewis AB, Polacheck DL: Variability of tooth formation. J Dent Res 1959; 38:135-]48. 34. Garn SM, Nagy JM, Sandusky ST, et al: Economic impact on tooth emergence. Am J Phys Anthropoll973; 39:233237. 35. Garn SM, Lewis AB, Vicinus JH: Third molar polymorphism and its significance to dental genetics. J Dent Res 1963; 42:1344-1363. 36. Garn SM, Rohmann CG, Blumenthal T, et al: Ossification communalities of the hand and other body parts: Their implication to skeletal assessment. Am J Phys Anthropol 1967; 27:75-82. 37. Gowgiel JM: Experiments in tooth eruption, abstract. J Dent Res 1961; 40:736. 38. Grabb WC, Rosenstein S, Bzock K: Cleft Lip and Palate. Boston, Little, Brown & Co, 1971. 39. Graber LW: Congenital absence of teeth: A review with emphasis on inheritance patterns. J Am Dent Assoc 1978; 96:266-275.
40. Gregg JM: Immobilization of the erupting molar in the Syrian hamster. J Dent Res 1965; 44:1219-1226. 41. Hatton ME: A measure of the effects of heredity and environment on eruption of the deciduous teeth. J Dent Res 1955; 34:397-401. 42. Hunter WS, Smith BRW: Development of mandibular spacing-crowding from nine to sixteen years of age. J Can Dent Assoc 1972; 38: 178-185. 43. Infante PF: Sex differences in the chronology of deciduous tooth emergence in white and black children. J Dent Res 1974; 53:418-421. 44. Infante PF: An epidemiological study of deciduous tooth emergence and growth in white and black children of southeastern Michigan. Ecol Food Nutr 1975; 4:117-124. 45. Infante PF: Malocclusion in the deciduous dentition in white, black and Apache Indian children. Angle Orthod ]975; 45:213-218. 46. Israel H, Benitez RF, Garn SM: Eruption sequence polymorph isms of maxillary and mandibular opponents in the dentition of Ecuadorian mestizos. Arch Biol 1968; 13:239241. 47. Jarvinen S, Lehtinen L: Malocclusion in three-year-old Finnish children. Proc Finn Dent Soc 1977; 73:]62-166. 48. Knott VB, Meredith HV: Statistics on eruption of the permanent dentition from serial data for North American white children. Angle Orthod 1966; 36:68-79. 49. Kraus BS, Jordan RE: The Human Dentition Before Birth. Philadelphia, Lea & Febiger, 1965. 50. Krogman WM: The role of genetic factors in the human face, jaws and teeth: A review. Eugen Rev 1967; 59:165192. 51. Lauterstien AM, Pruzansky S, Barber TK: Effect of deciduous mandibular molar pulpotomy on the eruption of succedaneous premolar. J Dent Res 1962; 41:1367-1372. 52. Lehvila P: Bruxism and psychosomatic symptoms in children. Proc Finn Dent Soc ]975; 71:216-219. 53. Leighton BC: Early development of the deciduous dentition (orofacial muscular development). Trans Br Soc Study Orthodont 1960; 10: 100-111 . 54. Leighton BC: Eruption of deciduous teeth. Dental Practitioner 1968; 200:836-842. 55. Leighton BC: Early recognition of normal occlusion, in McNamara JA Jr (ed): The Biology of Occlusal Development, Monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977, pp 147-167. , 56. Lewis AB, Garn SM: The relationship between tooth formation and other maturational factors. Angle Orthod 1960; 30:70-77. 57. Lo RT, Moyers RE: Studies in the etiology and prevention of malocclusion. L The sequence of eruption of the permanent dentition. Am J Orthod 1953; 39:460-467. Lundstrom A: The aetiology of crowding of the teeth (based on studies of twins and on morphological investigations) and its bearing on orthodontic treatment (expansion or extraction). Trans Eur Orthod Soc ]951; pp 176-191. 59. Lunt RC, Law DB: A review of the chronology of calcification of deciduous teeth. J Am Dent Assoc 1974; 89:599606. 60. Lunt RC, Law DB: A review of the chronology of eruption of deciduous teeth. J Am Dent Assoc 1974; 89:872-879. 61. Lysell L, Magnusson B, Thilander B: Time and order of eruption of the primary teeth. A longitudinal study. Odontol Rev 1962; 13:217-234.
Development 62. MacConaill MA, Scher EA: The ideal form of the human dental arcade with some prosthetic applications. Dent Res 1949; 69:285-302. 63.' Marks MB: Bruxism in allergic children. Am J Orthod 1980; 77:48-59. _ 64, McNamara JA Jr: Functional determinants of craniofacial size and shape. EurJ Orthod 1980; 2:131-159. 65. Melcher AH, Beertsen W: The physiology of tooth eruption, in McNamara JA Jr (ed): The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977, pp 1-23. 66. Meredith HV: Order and age of eruption for the deciduous dentition. J Dent Res 1946; 25:43-66. 67. Moorrees CFA: Dentition of the Growing Child. Cambridge, Mass, Harvard University Press, 1959. 68. Moyers RE, Wainright R: Skeletal contributions to occlusal development, in McNamara JA Jr (ed): The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series.Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977, pp 89-1 I. 69. Moyers RE, Bookstein FL, Guire KE: The concept of pattern in craniofacial growth. Am J Orthod 1979; 76:136148.
I
70. Moyers ards of iofacial Human 1976.
RE, van der Linden PGM, Riolo ML, et al: StandHuman Occlusal Development, Monograph 5, CranGrowth Series. Ann Arbor, Mich, Center for Growth and Development, University of Michigan,
71. Naftolin F: Understanding the bases of sex differences. Science 1981; 211:1263-1264. 72. Nolla CM: The development of the permanent teeth. J Dent Child 1960; 27:254-266. 73. Northway WM: Antero-posterior Arch Dimension Changes in French-Canadian Children: A Study of the Effects of Dental Caries and Premature Extractions, thesis. School of Dentistry, University of Montreal, Quebec, Canada, 1977. 74. Obersztyn A: Experimental investigation of factors causing resorption of deciduous teeth. J Dent Res 1963; 42:660674. 75. Bhaskar SN (ed): Orban's Oral Histology and Embryology, 8th ed. St Louis, CV Mosby, 1976. 76. Paynter KJ, Grainger RM: Relation of nutrition to the morphology and size of rat molar teeth. J Can Dent Assoc 1956; 22:519-53 I . 77. Paynter KJ Grainger RM: Influence of nutrition and genetics on morphology and caries susceptibility. JAMA 1961; 177:306-309.
of the Dentition and Occlusion
145
phogenesis: Biological and Clinical Relevances, thesis, Horace H Rockham School of Graduate Studies, University of Michigan, Ann Arbor, 1979. Swann IL: Teething complications, a persisting misconception. Postgrad Med J 1979; 55:24-25. Thompson GW, Popovich F: A longitudinal evaluation of the Burlington Growth Centre Data. J Dent Res 1977; 56(special issue):C71-78. van Beek H: Functional Occlusion and Mesial Drift, an Experimental Study of Tooth Migration in Monkeys, dissertation. University of Amsterdam, Amsterdam, The Netherlands, 1978; pp 84-88. van der Linden FPGM, McNamara JA Jr, Burdi AR: Tooth size and position before birth. J Dent Res 1972; 51:71-74. West CM: The development of the gums and their relationship to the deciduous teeth in the human fetus. Contrib Embryol 1925; 16:25.
85. 86.
87.
88. 89.
SUGGESTED
READINGS*
I.
Carlson DA, Ribbens KA (eds): Craniofacial Growth During Adolescence, Monograph 20. Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, The University of Michigan, 1987. 2. Garn SM: The genetics of dental development, in McNamara JA Jr (ed): The Biology of Occlusal Development, Monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, The University of Michigan, 1977; pp 61-88. ' 3. Graber LW: Congenital absence of teeth: A review with emphasis on inheritance patterns: J Am Dent Assoc 1978; 96:266-275. (R) 4. Hagg U: Pubertal growth and orthodontic treatment, in Carlson DA, Ribbens KA (eds): Craniofacial Growth During Adolescence, Monograph 20. Craniofacial Growth Series. Ann Arbor, Michigan, Center for Human Growth and Development, The University of Michigan, 1987, pp 87116. 5. Kraus BS, Jordan RE: The Human Dentition Before Birth. Philadelphia, Lea & Febiger, 1965. (M) 6. Lunt RC, Law DB: A review of the chronology of calcification of deciduous teeth. J Am Dent Assoc 1974; 89:599606. (R) 7. Lunt RC, Law DB: A review of the chronology of eruption of deciduous teeth. J Am Dent Assoc 1974; 89:872-879. (R)
80. Richardson AS, Castaldi CR': Dental development during the first two years of life. J Can Dent Assoc 1967; 33:418429. 81. Richardson ER, Malhotra SK: Mesiodistal crown dimension of the permanent dentition of American Negroes. Am J Orthod 1975; 68:157-164. 82. Scott JH: The shape of the dental arches. J Dent Res 1957; 36:996-1003.
,,8. McNamara JA Jr (ed): The Biology of Occlusional Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, The University of Michigan, 1977. 9. Melcher AH, Beertsen W: The physiology of tooth eruption, in McNamara JA Jr (ed): The Biology of Occlusal De',' '. velopment, monograph 7. Craniofacial Growth Series. Ann "'Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977; pp 1-23. (R) 10. Moyers RE, van der Linden FPGM, Riolo ML, McNamara JA Jr: Standards of Human Occlusal Development, Monograph 5, Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. (M) 11. Moyers RE, Wainright R: Skeletal contributions to occlusal
83. Simpson WJ, Cheung DK: Gum pad relationships of infants at birth. J Can Dent Assoc 1973; 39:182-188. 84. Superstine J: Patterns of Early Human Dental Arch Mor-
(M)
78. Paynter KJ, Grainger RM: Relationship of morphology and size of teeth to caries. Int Dent J 1962; 12: 147-160. 79. Pulver F: The etiology and prevalence of ectopic eruption of the maxillary first permanent molar. J Dent Child 1968; 35:138-146.
*(R) = useful reviews of our current knowledge = monographs.
of the subject;
146
Growth and Development
development, in McNamara lA lr (ed): The Biology of Oc-· clusal Development, monograph 7. Craniofacial Growth Serie's. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977; pp 89-111. 12. Nanda SK: The Developmental Basis of Oca-lusion and Malocclusion. Chicago, Quintessence, 1982. (M) 13. Smith BH, Garn SM: Polymorphisms in eruption sequence of permanent teeth in American children. Am J Phy Anthro (in press.)
14. van der Linden FPGM (ed): Transition of the Human Dentition, Monograph 13. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1982. (M) 15. van der Linden FPGM: Development of the Dentition. Chicago, Quintessence Publishing Co, 1983. 16. van der Linden FPGM: Facial Growth and Facial Orthopedics. Chicago, Quintessence Publishing Co, 1986.
-.
0".·,
CHAPTER
7 Etiology of Malocclusion Robert E. Moyers, D.D.S., Ph.D.
The origin of all science is in the desire to know causes; and the origin of all false science and imposture is in the desire to accept false causes rather than none; or, which is the same thing, in the unwillingness to acknowledge our own ignorance.-" Burke and the Edinburgh Phrenologists." The Atlas, February 15, 1829
KEY POINTS 1. Rather than having specific "causes," as do some diseases, malocclusions are usually clinically significant variations from the normal range of growth and morphology. Etiologic factors contribute to the variance more often than they simply "cause" it. 2. The primary etiologic sites of malocclusion are (a) the craniofacial skeleton, (b) the dentitions, (c) the orofacial neuromusculature, and (d) other "soft tissues" of the masticatory system, though rarely is one site alone involved. 3. The different mechanisms of adaptation of the primary etiologic tissue sites provide much of the complexity and variability of malocclusions. 4. The "causes" of malocclusion are usually grouped because they are usually nonspecific and our knowledge is often imprecise. 5. Heredity is held to be an important factor in the etiology of malocclusion, but surprisingly little is known that is of precise c.linical applicability. 6. Deleterious orofacial muscle habits known to be etiologic to some mal occlusions include digital sucking, tongue-thrusting, lip-sucking, and abnormal tongue posturing. 7. That nasopharyngeal disease and disturbed respiratory function may produce mouth-breathing and altered craniofacial morphology is now widely held. Impaired
nasal respiratory function undoubtedly is etiologic to some malocclusions: current research will likely show details. 8. Dental caries is a significant cause of some malocclusions resulting from premature loss of primary teeth, and drifting and early eruption of permanent teeth.
OUTLINE A> B.
The orthodontic equation Primary etiologic sites I. 2. 3.
Neuromuscular Bone Teeth
system
4.
Soft parts (excluding
muscle)
C. * "'Time D. Causes and clinical entities I. 2. 3.
Heredity Developmental Trauma
4.
a) Prenatal trauma and birth injuries b) Postnatal trauma Physical agents a) Premature extraction of primary teeth b) Nature of food
defects of unknown origin
147
Growth and D.evelopment
148
5.
Habits
6.
a) Thumb-sucking and finger-sucking b) Tongue-thrusting c) Lip-sucking and lip-biting d) Posture e) Nail-biting d) Other habits Disease
"norms," even tho'ugh the range of population values is useful in diagnosis. Nor does an experienced clinician base treatment solely on the patient's whims, for the patient is unaware of such matters as growth and development and stability of occlusion after orthodontic treatment. There is great variability in the range of functioning craniofacial relationships and significant variability in our response or reaction to those variances: all of which makes it difficult to discuss etiology and maintain a reasonable perspective.
a) b) c)
A. THE ORTHODONTIC
7.
Systemic diseases Endocrine disorders Local diseases I) Nasopharyngeal diseases and disturbed respiratory function 2) Gingival and periodontal diseases 3) Tumors 4) Caries (a) Premature loss of primary teeth (b) Disturbances in sequence of eruption of permanent teeth (c) Loss of permanent teeth Malnutrition
It is traditional to discuss the etiology of mal occlusion by beginning with a clinical classification and working back to the causes of each problem, but our knowledge is scanty about the "causes" of many malocclusions. Further, malocclusions which appear similar and are classified alike may have quite different origins. This .discussion of etiology will center on the tissue which seems to be primarily involved. The idea of discussing etiology in terms of the primary tissue site was first suggestea by Dockrell,6 was used in earlier editions of this book, and later was adopted by such prominent orthodontic scholars as Mayne,14 Harvold,8 and Moore.'6 While it is logical to discuss the primary tissue sites wherein malocclusion may seem to have its origins, the reader is cautioned that the matter is not as simple as it may appear because of adaptability and variability. Particularly during the exuberant growth of childhood, the entire orofacial region is highly adaptive to any intrusive etiologic factors. Adaptive development may camouflage or exacerbate from a visual clinical viewpoint. The body in its wisdom and effort to maintain functional homeostasis pays little attention to the Angle classification, the ideal Sella-Nasion-" A" point cephalometric angle, or the dentist's narrowly defined concepts of what is "normal." The ability of each tissue system to adapt varies greatly, and all adaptability diminishes with aging. Therefore, the same etiologic factor may have a different effect at different ages and in different persons. A further problem in discussing the etiology of malocclusion is rooted in the great variability of skeletal and dental relationships which can function well and appear esthetic. The clinician attempts to define malocclusion within narrow quantifiable limits of single features rigidly labeled as "normal" (e.g., the molar relationship or the ANB angle), assuming all other values to be "abnormal," and therefore malocclusions requiring treatment. Patients are more pragmatic, seeking treatment only when they are aware of malfunction or unesthetic appearance: but what is malfunction or ugliness to one patient does not bother another. Only the naive or simple dentist bases treatment goals on population means or
EQUATION
The equation shown in Figure 7 - I is a brief expression of the development of any and all dentofacial deformities. Certain original causes act for a time at a site and produce a result. It is an expression of Koch's postulates, but it is an oversimplification to assume that Koch's logic applies to developmental problems (e.g., malocclusions) as it does to diseases, for there are few specific causes of precise malocclusions. Tuberculosis may always be caused by Mycobacterium tuberculosis, but open bite is not always caused by thumb-sucking. Since we cannot isolate and identify all of the original causes for ease in study, Dockrell6 has grouped them as follows: (I) heredity; (2) developmental causes of unknown origin; (3) trauma; (4) physical agents; (5) habits; (6) disease; and (7) malnutrition. It will be seen that there is a certain overlapping of these groups. The duration of operation of these causes and the age at which they are seen are both functions of time, and thus are grouped together. The primary sites principally involved are: (1) the bones of the facial skeleton; (2) the teeth; (3) the neuromuscular system; and (4) the soft parts, excepting muscle. It will be noted that each of the regions involved is made up of a different tissue. Bone, muscle, and teeth grow at different rates and in different manners. They adapt to environmental impact in different ways. Regardless of the original cause of a growth variation, it must be remembered that the place where that cause S!lOWS its effect is important. The difference in tissue response during development is a determining factor in differentiating among many clinical problems that are similar in appearance. Rarely is one site alon~ involved; usually others become affected, and we term one the site primarily involved and consider the others as being secondarily concerned. The 'result is malocclusion, malfunction, or osseous dysplasiil'-more probably a combination of all three. The orthodontic equation more fully developed is shown in Figure 7 - 2. The outline for this chapter is based on this elaboration of Dockrell's equation.6 Most malocclusions are simply c1inic~lIy significant variations from the normal range of growth or morphology. In contrast to .disease or pathologic ](}sions, malocclusion may result from a co~6i.nation of minor variations from the normal; each is too mild to be classed as abnormal but thei; combination summates to produce a clinical problem. While all parts of the face and masticatory
CAUSES
ACT AT)
TIMES ~
TISSUES
PRODUCING)
RESULTS
FIG 7-1. The orthodontic equation. (From Dockrell R: Classifying aetiology of malocclusion. Dent Rec 1952; 72:25. Used by permission.)
5. 6.
Etiology of Malocclusion CAUSES
ACT
AT. TIMES
SOME PREDISPOS· ING
PRENATAL
SOME
POSTNATAL
EXCITING
~TISSUES
OR
149
PRoDueI'NG.RESUlTS
SOME
PRIMARILY
SOME
SECONDARILY
MAY
BE THE
FOLLOWING OR A COMBINATION OF THESE
1. HEREDITY HABITS DISEASE
7.
FIG
AGE LEVelS TENT DYSPLASIA OR INTERMIT. DIFFERENT CLES SION TISSUETION 1. NEUROMUSCULAR 3. OSSEOUS MAY 1. CONTINUOUS 1. 2. ACT MALFUNC. MALOCCLU. 2. 2. TEETH LAGE 3. BONE ANDATCART!- OTHER THAN 4. SOFT TISSUES-
MUS-
MALNUTRITION
7-2.
The orthodontic equatiol'l elaborated. (From Dockrell R: Classifying aetiology of malocclusion. Dent Rec 1952; 72:25. Used by permission.)
system may subsequently adapt, often only one tissue system is involved in the beginning. The words we use in orthodontics reflect our understandings of the different primary etiologic sites; malocclusion (teeth), malfunction (the neuromusculature), and osseous dysplasia or dysgnathia (the craniofacial skeleton). In order to illustrate the idea of a single tissue system involvement at the start, three examples of crossbite are shown in Figures 7 - 3 through 7 - 5. These three problems, although bearing the same name, have disp.atate origins, one arising in skeletal asymmetry, one a functional shifting of the mandible by the muscles, and one a simple tipping of teeth. All are crossbites, yet they are entirely different in their beginnings, their treatment, and their prognosIs.
B. PRIMARY ETIOLOGIC
SITES
The neuromuscular system plays its primary role in the etiology of dentofacial deformity by the effects of reflex contractions on the bony skeleton and the dentition. Both bones and teeth are affected by the many functional activities of the orofacial region. The region is a source of enormous and varied sensory input, making possible an infinite variety of reflex activities, all of which help determine the skeletal form and occlusal stability.
1. Neuromuscular System
FIG
"
7-3.
Skeletal crossbite. Note that although the occlusal relationship seems correct on the patient's left side, there is a crossbite involving onehalf of the dental arch on the right side. The patient also has obvious mandibular prognathism, even at this early age. The patient's face shows that the crossbite is primarily the result of an osseous dysplasia rather than dental or muscular factors.
Some neuromuscular contraction patterns are adaptive to skeletal. imbalances or dentin malpositions; others are the primary etiOlbgic factor. Imbalancing contraction patterns are a significant part of nearly all malocclusions. Treatment of malocclusion must involve conditioning reflexes to bring about a more favorable functional environment for the growing craniofacial skeleton and the developing dentition and occlusion, or relapse may result.
2. Bone Since the bones of the face (particularly the maxilla and mandible) serve as bases for the dental arches, aberrat~ons in their
150
Growth and Development
FIG 7-4. A muscular or functional crossbite. It can be seen in A that the midlines do not coincide and that half of the mandibular denture is outside the maxillary denture. This patient's dentition was equilibrated very carefully and B shows the result when the patient returned to the clinic 1 week later. Note that the removal of the occlusal interferences in the primary teeth enabled the muscles to return the mandible to its proper position and to a proper occlusion. (See Chapter 10, Analysis of the Orofacial Musculature.) Treatment of this patient consisted of removing the sensory input to an imbalancing eccentric occlusal reflex (See Chapter 5). No teeth were removed, though a maxillary incisor exfoliated, nor was there time for significant bone growth to occur.
morphology tioning.
or growth
may alter occlusal
Many of the most common
result of craniofacial dures (see Chapter
skeletal
relationships
serious malocclusions
imbalances.
Cephalometric
12) aid in the identification
and func-
3. Teeth
are the proce-
and localization
of
The teeth may be a primary deformity
osseous disharmony.
or position
Orthodontic treatment of skeletal disharmony must either (I) alter the growing craniofacial skeleton or (2) camouflage it by
is the possibility and, indirectly
moving
bones.
teeth to mask its disharmony.
site in the etiology
in many ways. Gross variations
of teeth can all produce malocclusion. that malpositions through
Often forgotten
of teeth can induce malfunction
the malfunction,
One of the most frequent
of dentofacial
in size, shape, number,
alter the growth
problems
of the
is teeth that are too
FIG 7-5. A dental type crossbite. Note here that the mandibular and maxillary bases are harmonious with each other, that the midlines coincide, and that the cross bite is localized
in the right incisor region. This
crossbite is due to tipping of individual teeth. The adequate result of
tipping them back to their proper position is shown at the right. The treatment was done by a simple appliance, applying forces mostly to the teeth out of position. Correction of such cases usually occurs in a few months.
Etiology of Malocclusion
151
large for the arches in which they are found (or arches too small for the teeth they hold). Teeth may be moved in orthodontic treatment to correct the malocclusion, camouflage a skeletal dysplasia, or aid in the removal of neuromuscular dysfunction.
4. Soft Parts (Excluding Muscle) "
The role of the soft tissues, other than neuromuscular, in the etiology of malocclusion is not as clearly discernible, nor is it as important as that of the three sites discussed previously. Malocclusion, however, can result from periodontal disease and loss of the attachment apparatus and from a variety of soft-tissue lesions including the temporomandibular joint structures.
C. TIME The time factor in the development of malocclusion has two components: the period during which the cause operates and the age at which it is seen. It should be noted that the length of time that a certain cause may be operative is not always continual; in fact, it may cease and recur in an intermittent fashion. From an etiologic point of view, the most useful division of the age component is into those causes active prenatally and those whose effects are noted only after birth. A cause may be either continual. or intermittent and it may show its effect either prenatally or postnatally.
D. CAUSES AND CLINICAL
ENTITIES
With the foregoing brief description of the orthodontic equation, we are now in a position to discuss, as we are able, the various groups of causes and their specific clinical manifestations. In some instances, something is known about the effects of a specific cause but, for the most part, we are forced to generalize.
FIG 7-6. Genetics and occlusion: the occlusions of four siblings. Occlusion is similar enough to look like serial record casts of the same individual.
2. Developmental Defects of Unknown Origin Developmental defects of unknown origin is a term applied to gross defects of a rare type probably originating in failure of differentiation at a critical period in embryonic development. Examples sometimes cited include congenital absence of some muscles, micrognathia, facial clefts, and some instances of oligodontia and anodontia. Some gross craniofacial syndromes fit this category while others have known genetic factors.
3. Trauma 1. Heredity Heredity has long been indicted as a cause of malocclusion. Aberrations of genetic origin may make their appearance prenatally or they may not be seen until many years after birth (e.g., patterns of tooth eruption). The role of heredity in craniofacial growth and the etiology of dentofacial deformities has been the subject of many studies, yet surprisingly, few specifics are really known. For a discussion of the genetic aspects of the growth of the craniofacial skeleton read Chapter 4. The genetics of tooth and occlusal development are described in Chapter 6. Very little is yet understood concerning the part genes play in the maturation of the orofacial musculature. Interesting familial resemblances are seen frequently (Fig 7-6), yet the mode of transmission or even the site of gene action is not understood, except for a few clean-cut problems, for example, absence of teeth or the appearance of some gross craniofacial syndromes. Scant though our quantified knowledge, all agree heredity plays an important role in the etiology of dentofacial anomalies.
Both prenatal trauma to the fetus and postnatal injuries may result in dentofacial deformity. a) Prenatal Trauma and Birth Injuries Hypoplasia of the mandible ·can be caused by intrauterine pressure or trauma during delivery. • "Vogelgesicht," inhibited growth of the mandible due to ankylosis of the teJ!lporomandibular joint, may be a devel• "Qpmental defect or may result from trauma. • Asymmetry. A knee or a leg may press against the face in such a manner as to promote asymmetry of facial growth or retardation of mandibular development. •
• •
b) Postnatal Trauma Fractures of jaws and teeth. Habits may produce "microtrauma" tended period.
operative over an ex-
152
Growth and Development
FIG 7-7. Occlusal wear of primary teeth. Typical of occlusal wear seen among many people who exist on a primitive, coarse diet. The two pictured
•
Trauma to the temporomandibular joint has been reported to impair growth and function leading to asymmetry and temporomandibular dysfunction.
4. Physical Agents a) Premature Extraction of Primary Teeth Since premature extraction of primary teeth usually is due to caries, it is discussed under Disease later in this section.
b) Nature of Food People existing on a primitive, fibrous diet stimulate their muscles to work more and thus increase the load of function on the teeth. This type of diet usually produces less caries (less substrate for cariogenic organisms), greater mean arch width, and 'increased wear of occlusal surfaces of the teeth (Fig 7-7). The importance of occlusal wear in the transitional dentition is discussed in Chapter 6. The evidence seems to indicate that our highly refined, soft, pappy modem diets play a role in the etiology of some malocclusions. Lack of adequate function results in contraction of the dental arches, insufficient occlusal wear, and absence of the kind of occlusal adjustment normally seen in the maturing dentition. For a discussion of the role of function in the growth of the craniofacial skeleton see Chapter 4.
S. Habits All habits are learned patterns of muscle contraction of a very complex nature. Certain habits serve as stimuli to normal growth of the jaws; for example, normal lip action and mastication. Abnormal habits which may interfere with the regular pattern of facial growth must be differentiated from the desired normal habits that are a part of normal oropharynge"al function and thus play an important rQle in craniofacial growth and occlusal physiology. Concern here is with those likely to be involved in the etiology of malocclusion. The maturation of the orofacial musculature, in its normative role, is discussed in Chapter 5. Deleterious habitual patterns of muscle behavior often are associated with perverted or impeded osseous growth, tooth malpositions, disturbed breathing habits, difficulties in speech, upset balance in the facial musculature, and psychological problems. Therefore, one cannot correct malocclusion without involvement in such reflex activities.
are Greek children from the mountain province of Euritania.
a) Thumb-Sucking and Finger-Sucking Digital sucking is practiced by many children for a variety of reasons; however, if it is not directly involved in the production or maintenance of malocclusion, it probably should not be of primary clinical concern to the dentist. As we shall see, most digital sucking habits begin very early in life and frequently are outgrown by 3 or 4 years of age. Unfortunately, dentists see few children before this time. Often the family physician or pediatrician attending so young a child is unaware of the possible dental complications resulting from these habits. It should be remembered that many children practice digital sucking habits without any evident dentofacial deformity, but it also is true that the digital sucking pressure habit may be a direct cause of a severe malocclusion. The mechanotherapy for the treatment of the resulting mal occlusion may be easy but the psycho logic implications of the therapy are less clearly understood and have often been overstated. The time of appearance of digital sucking habits has significance. Those that appear during the very first weeks of life are typically related to feeding problems. The neonate surely is not yet involved in sibling rivalries, and insecurities are more apt to be related to such primitive demands as hunger. However, some children do not begin to suck a thumb or finger until it is used as a teething device during the difficult eruption of a primary molar. Still .later, some children use digital sucking for the release of emotional tensions with which they are unable to cope, taking solace in regressing to an infantile behavior pattern. All digital sucking habits should be studied for their psychologic implications, for they may be related to hunger, satisfying of the sucking instinct, insecurity, or even a desire to attract attention. Developmental psychologists have produced a number of theories to explain "non-nutritive digital sucking" (as they term it). Most early ideas concerning digital sucking were firmly based on cl~ssic Freudian theory. f~eud suggested that orality in the infant is related to pregenital organization and that sexual activity is not yet separated from the taking of nourishment. Thus, the object of one activity, thumb-sucking, is also that of another, nursing. A logical development of this theory relates to attempts to stop the thumb-sucking habit, for the Freudian belief holds that an abrupt interference with such a basic mechanism will likely lead to the substitution of such antisocial tendencies as stuttering or masturbation. Digital sucking also has been related to inadequate sucking activity. It was found in a series of studies that there was less thumb-sucking in both animals and humans when fed ad lib than
Etiology of Malocclusion
153
FIG 7-8. Malocclusion from finger-sucking.
there was when feedings were widely separated. Further, it was learned that, in general, nonthumb-sucking children took a longer time for feeding than was taken by thumb-suckers. In opposition to the theory of inadequate sucking activity is the oral drive theory of Sears and Wise,20 whose work suggests that the strength of the oral drive is in part a function of how long a child continues to feed by sucking. Thus, it is not the frustration of weaning that produces thumb-sucking but, rather, the oral drive, which has been strengthened by the prolongation of nursing. The theory of Sears and Wise is in keeping with a Freudian hypothesis that sucking increases the erotogenesis of the mouth. Benjamin, I in an inter- . esting series of experiments with monkeys, found that there was far less thumb-sucking among those whose nutritive sucking experience had been greatly reduced. This theory holds that thumbsucking is an expression of a need to suck that arises because of the association of sucking with the primary reinforcing aspects of feeding. Another very interesting theory has been proposed by Benjamin, who suggests that thumb-sucking arises very simply from the rooting -and placing reflexes common to all mammalian infants. I These primitive reflexes are maximal during the first 3 months of life. Her hypothesis was tested by covering infant's hands with mittens the very first few weeks of life so that the thumb was not accidentally involved in the placing reflex. All thumb-sucking theories are not Freudian in origin, for it has been suggested that thumb-sucking is one of the earliest examples of neuromuscular learning in the infant and that it follows all the general laws of the learning process. A multidisciplinary research team at the University of Alberta reported that children who sucked their thumbs failed to demonstrate any consistent psycho logic differences from a control sample. This team's welldocumented results strongly support the theory that digital sucking habits in humans are a simple learned response!' 10They found no support for the psychoanalytic interpretation of thumb-sucking as a symptom of psycho logic disturbance. Further proof for their ideas was presented by studying the psychologic effects of orthodontic intervention; typical orthodontic therapy for arresting the habit failed to produce any significant increase in alternative or substitutive undesirable psychologic behavior. The various theories concerning "non-nutritive digital sucking" are not completely incompatible with one another. Rather, they suggest that the thumb-sucking habit should be viewed by the clinician as a behavioral pattern of multivariate nature. It is
quite possible that thumb-sucking may begin for one reason and be sustained at subsequent ages by other factors. Most of the findings reported thus far seem to support best the learning theory, particularly if the learning of digital sucking is associated with unrestricted and prolonged nutritive sucking. For the dentist, the most important question is, simply, does digital sucking cause malocclusion? Many children who practice digital sucking habits have no evidence of malocclusion; however, Popovitch and Thompson'8 have reported a high association of abnormal sucking habits with the mal occlusion sample at the Burlington Orthodontic Research Centre in Ontario; Canada. Cook4 measured the forces of thumb-sucking, finding three distinctly different patterns of force application during sucking, all utilizing forces sufficiently strong to displace teeth or deform growing bone. Melsen et al. 15found that both digital sucking and pacifier sucking increased the tendency toward abnormal swallowing. Sucking habits were related to an increase in severe malocclusion symptoms apart from the type of swallow presented. It has been found that, although digital sucking appeared to be more detrimental than pacifier sucking, providing children with pacifiers does not solve
"
FIG 7-9. Adaptation of oral and facial musculature to thumb-sucking. malposition of tongue, mandible, and circumoral muscles.
Note
154
Growth and Development
the problem of malocclusion22 Sucking habits were strongly correlated with distocclusion and open bite and with crossbite and maxil!ary overjet. It should be remembered that the type of malocclusion that may develop in the thumb-sucker is dependent on a number of variables-the position of the digit, associated orofacial muscle contractions, the position of the mandible during sucking, the facial skeletal morphology, duration of sucking, and so forth. An anterior open bite is the most frequent malocclusion (Fig 7-8). Protraction of the maxillary anterior teeth will be seen, particularly if the pollex is held upward against the palate (Fig 7-9). Mandibular postl!ral retraction may develop if the weight of the hand or arm continually forces the mandible to assume a retruded position in order to practice the habit. Concomitantly, the mandibular incisors may be tipped lingually. When the maxillary incisors have been tipped labially and an open bite has developed, it becomes necessary for the tongue to thrust forward during swallowing in order to effect an anterior seal, thus a simple tongue-thrust is necessarily associated with a digital sucking habit. The simple tongue-thrust does not "cause" the open bite; rather, it is an adaptive abnormal tongue position during the swallowing. During thumb-sucking, buccal wall contractions produce, i'n some sucking patterns, a negative pressure within the mouth, with resultant narrowing of the maxillary arch (Fig 7- 10). With this upset in the force system in and around the maxillary complex, it often is impossible for the nasal floor to drop vertically to its expected position during growth. Therefore, thumb-suckers may be found to have a narrower nasal floor and a high palatal vault. The maxillary lip becomes hypotonic and the mandibular lip becomes hyperactive, since it must be elevated by contractions of the orbicularis muscle to a position between the malposed incisors during swallowing. These abnormal muscle contractions during suckin,g and swallowing stabilize the deformation. Some malocclusions arising from sucking habits may be self-corrective on ~essation of the habit;
FIG 7-10. Direction of application of force to the dentition during thumb-sucking. Maxillary incisors are pushed labially, mandibular incisors are pushed lingually, while buccal muscles exert pressure lingually against te~th in the lateral segments of the dental arch. for example, if the skeletal pattern is normal, the habit is stopped early, the deformity has been mild, there is a teeth-together swal- ; low, and the associated neuromuscular habits are of a mild nature. Unfortunately, many thumb-suckers produce malocclusions that require orthodontic therapy. The treatment by the dentist of digital sucking habits is discussed in Chapter 15.
b) Tongue-Thrusting Tongue-thrust swallows that may be etiologic to malocclusion are of two types: (I) the simple tongue-thrust swallow, which is a tongue-thrust associated with a normal or teeth-together swallow; and (2) the complex tongue-thrust swallow. The child normally swallows -:vith the teeth in occlusion, the lips lightly closed, and
FIG 7-11. The tongue during normal and one type of abnormal swallowing. A, normal swallowing. Teeth are in contact, lips are closed, and the dorsum of the tongue is elevated to touch the roof of the mouth. 8, abnormal swallowing resulting from hypertrophied tonsils and adenoids. As the tongue is retracted it touches the swollen tonsils and may restrict the oral airway; the' mandible drops, and the tongue "thrusts" forward away from the pharynx. With the mandible lowered,
the lips must be closed forcibly to keep the tongue in the oral cavity and to effect a seal so the swallow can be completed. This is an example of a complex tongue-thrust since the teeth are held apart during the swallow. There is a necessary strong elevating contraction of the mentalis muscle in all tooth-apart swallows to help with both the lip seal and mandibular stabilization.
Etiology of Malocclusion
155
'I FIG 7-12. Malocclusion associated with a simple tongue-thrust swallow.
the tongue held against the palate behind the anterior teeth (Fig 7 -11). The simple tongue-thrust swallow usually is associated with a history of digital sucking, even though the sucking habit may no longer be practiced, since it is necessary for the tongue to thrust forward into the open bite to maintain an anterior seal with the lips during the swallow. Figure 7-12 is an example of the simple tongue-thrust swallow and its attendant malocclusion. Complex tongue-thrusts, on the other hand, are far more likely to be associated with chronic nasorespiratory distress, mouth-breathing, tonsillitis, or pharyngitis (Fig 7-13). When the tonsils are in-. flamed, the root of the tongue may encroach on the enlarged facial pillars (see Fig 7-11). To avoid this encroachment, the mandible reflexly drops, separating the teeth and providing more room for the tongue to be thrust forward during swallowing to a more comfortable position. Pain and lessening of space in the throat precipitate a new forward tongue posture and swallowing reflex, while the teeth and growing alveolar processes accommodate themselves to the attendant upset in neuromuscular forces. During chronic mouth-breathing, a large freeway space is seen, since dropping the mandible and protruding the tongue provide a more adequate airway. Because maintenance of the airway is a more primitive and demanding reflex than the mature swallow, the latter is conditioned to the necessity for mouth-breathing. The jaws are thus
held apart during the swallow in unler mat the tongue can remain in a protracted position. The differential diagnosis of different swallows and tongue-thrusts is given in Chapter 10. The prognosis for treatment of these two tongue-thrust types is very different (see Chapter 15). Melsen et aI., 15 in one of the most definitive studies yet reported, state that both tongue-thrust swallow imd teeth-apart swallow favor the development of disto-occlusion, extreme maxillary overjet and open bite. There is an increase in tongue-thrust swallowing (simple tongue-thrust) seen with both pacifier sucking and digital sucking. Other tongue habits that often are confused with tongue-thrust swallow include tongue-sucking, the retained infantile. tongue posture and the retained infantile swallow (see Chapter 15). But perhaps the most frequent confusion arises with the skeletal open bite wherein the mandibular plane is steep and the anterior face height much greater than the posterior face height (Fig 7-14). Under these circumstances the tongue has great difficulty sealing the anterior portal during the swallow. An increase in the mandibular alveolar process height helps but cannot obviate the abnormal tongue behavior. It seems to be unfortunate that some consider this natural neuromuscular adaptation a "tongue-thrust."
FIG 7-14. FIG 7-13. Open bite associated with a complex tongue-thrust.
Skeletal open bite. For the result of orthodontic treatment, without orthognathic surgery, see Fig 10-20.
156
Growth and Development
FIG 7-15. Malocclusion associated with lip-sucking. Note labioversion of maxillary anterior teeth and anterior open bite.
c) Lip-Sucking and Lip-Biting Lip-sucking may appear by itself or it may be seen with thumb-sucking. In almost all -instances, it is th~ mandibular lip that is involved in sucking, although biting habits of the maxillary lip are observed as well. When the mandibular lip is repeatedly held beneath the maxillary anterior teeth, the result is labioversion of these teeth, often -an open bite, and sometimes linguoversion of the mandibular incisors (Fig 7-15).
angulation showed the most comprehensive correlation with craniofacial morphology and that craniocervical angulation was related to steepness of the mandibular plane. 6. Disease
a) Systemic Diseases Febrile diseases are known to upset the dentitional developmental timetable during infancy and early childhood. For the m'ost
d) Posture Persons with faulty body posture frequently demonstrate undesirable mandibular postural positioning as well21 Both may be expressions of poor general health. On the other hand, those who hold themselves straight and erect with the head well placed over the spinal column will almost reflexly hold their chins forward in a preferred position. Body posture is the summated expression of muscle reflexes and, therefore, is usually capable of change and correction. Abnormal tongue posturing is a frequent cause of open bite and should not be confused with the various forms of tongue-thrust (Fig 7-16). Some tongue posture problems can cause extensive open bites, and many are intractable to treatment.
e) Nail-Biting Nail-biting is mentioned frequently as a cause of tooth malpositions. High-strung, nervous children most often display this habit, and not infrequently their social and psycho logic maladjustment is of greater clinical importance than the habit, which is nothing but a symptom of their basic problem. It seems generally to be harder on the nails than it is on the teeth. f) Other Habits The constant holding of a very young baby supine on a hard, flat surface can mold and shape the head by flattening the occiput or producing facial asymmetry. The significance of pillowing and sleeping on the arm, though, is thought to be greatly exaggerated. The habitual sucking of pencils, pacifiers, or other hard objects can be just as deleterious to facial growth as thumb-sucking and finger-sucking. 15-IS Head posture and craniofacial morphology have been extensively studied. Solow and Tallgren21 found that the craniocervical
FIG 7-16. Open bites associated with tongue posture. A, mild and more common form. The condition shown persisted after full-bracketed edgewise treatment and two retreatments. B, a more severe case.
Eti%gy
of Ma/occlusion
157
FIG 7-17. Malocclusion and mouth-breathing. A, face of a mouth-breather. B, hypertrophied tonsils, which may result in an alteration in tongue posture, mandibular posture, the action· of the tongue during the
swallOW,and the mode of breathing. C, hypertrophied adenoid mass. Such enlarged adenoids usually make necessary increased breathing through the mouth. (B and C courtesy of Dr. Robert Aldrich.)
part, though, systemic disease is more likely to have an effect on the quality rather than the quantity of dentitional development. Malocclusion may be a secondary result of some neuropathies and neuromuscular disorders and it may be one of the sequelae of treatment of such problems as scoliosis by prolonged wearing of appliances for immobilizing the spine. The dentist must seek pediatric consultation when the child with a malocclusion has any systemic problem that might influence the course of orthodontic therapy. No mal occlusion is known to be pathognomonic of any usual childhood disease.
enlarged adenoids in certain types of faces and dentitions lead to mouth-breathing. Much research now focuses on this complicated problem which is of interest to speech scientists, otolaryngologists, allergists, and pediatricians as well as orthodontists .. Although there is extensive literature on the possible association between mode of respiration and facial form and occlusion, the evidence is simply neither complete nor explanations clear how growth and development are modified in humans by variations in air flow. There seem to be at least two fundamental problems in the research thus far, whether in animal experimentation or hU})l.anclinical studies: (I) the lack of a precise definition of what is meant by "mouth-breathing;" and (2) the failure to use adequate cephalometric methods to test rigorously the hypotheses of interest. The following summary of the current state of our knowledge should be read with these two methodologic limitations in mind. The basic assumption is that enlarged adenoids obstruct the airway, causing mouth-breathing, which necessitates changes in tongue, lip, and mandibular posture. These upsets in "soft-tissue balance" lead to alterations in craniofacial form and to malocclusion, in-
b) Endocrine Disorders Endocrine dysfunction prenatally may be manifest in hypoplasia of the teeth. Postnatally, endocrine disturbances may retard or hasten, but ordinarily they do not distort, the direction of facial growth. They may affect the rate of ossification of the bones, the time of suture closure, the time of eruption of the teeth, and the rate of re sorption of the primary teeth. The periodontal membrane and gingivae are extremely sensitive to some endocrine dysfunctions and the teeth thus are affected indirectly. No malocclusion is known to be pathognomonic of any specific endocrine disturbance. It is my opinion that any professional discussion of the effects of endocrinopathies on the child's growth should be presented by a pediatrician.
c) Local Diseases , , 1) Nasopharyngeal Diseases and Disturbed Respiratory Function.The allegations that nasopharyngeal disease and/or disturbed respiratory function affect craniofacial growth and produce malocclusion have been argued for over 100 years. LinderAronson 12 presented and Bushey3 discussed three hypotheses which bring the matter into focus: (I) adenoid enlargement leads to mouthbreathing, resulting in a particular type of facial form and dentition; (2) enlarged adenoids, though they may lead to mouth-breathing, do not influence facial form and the type of dentition; and (3)
,\Juding increased anterior face height, narrow and high palate, retroclined incisors, increased lower face height, open bite, and a tendency to crossbite (Fig 7-17). These changes are thought to be brought about by compression, disuse atrophy, and altered air pressure. In .a series. of classic studies, Harvold8 restricted the airway iir Jllcin~eys, producing:" a variety of responses in electromyographic, cephalometric, and occlusal findings, but always leading to serious malocclusion. After resumption of normal breathing, though the lips and tongue usually returned to normal, th~!lljllocclusion remained (Fig 7-18). Linder-Aronson's studiesl2 are the most detailed research on humans. His reports on the relationship between reduced respiratory function and facial type and dentition are of interest, but his reports on the effects of a change from mouth-breathing to nose-breathing are compelling. He studied children who had undergone adenoidectomies to
158
Growth and Development
.~~. -.... '\
.,
FIG 7-18. Young adult animal with (A) normal occlusion and (B) normal tongue position. C, the tongue moved forward in response to nasal obstruction. D, three years later an effective oral airway was well established. Six months after nasal respiration was resumed the lips (E) and the tongue (F) were again pqsitioned normally. G, the acquired dental malocclusion, however, was retained. (From Harvold EP: Neuro-
muscular and morphological adaptations in experimentally oral respiration, in McNamaca JA Jr (ed): Nasa-Respiratory
induced Function
and·'c~~niofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. Used by permission.)
Etiology of Malocclusion
159
clear nasal passages, finding that 5 years after the change from mouth-breathing to nose-breathing there was a normalization of the upper incisor inclination, an improvement in the lower incisor inclination during the first year, a return to normal bimolar arch width, a normal depth of the nasal pharynx, .lmd an improvement in the mandibular plane and lower face height. Furthermore, the head posture, which was altered prior to surgery, returned to normal later. Warren23 and colleagues have studied extensively the aerodynamics of the upper airway. They conclude that the present studies do not support the assumption that nasal airway inadequacy produces dental facial deformities. They document well, however, that abnormalities of oral and nasal structures can seriously compromise speech performance. Hershey et aI., colleagues of Warren, reported a marked reduction in nasal airway resistance after rapid maxillary expansion. Bluestone2 pointed out that upper-airway obstruction can be caused by tonsils and/or adenoids and can result in serious cardiorespiratory complications. However, he felt that the effects of respiratory obstruction on craniofacial and occlusal development remain to be shown.
FIG
7-20.
Fibroma at maxillary midline causing diastema.
11
In my opinion, the hypothesis that impaired nasal respiratory function affects dentitional and craniofacial development is at least somewhat correct since the anecdotal observations are so voluminous and the research findings support in an erratic and inconclusive way the supposition. However, the details of the relationship between impaired nasal respiratory function and craniofacial growth await results of research under way. 2) Gingival and Periodontal Diseases.Infections and other disorders of the periodontal membrane and gingivae have a direct and highly localized effect on the teeth. They may cause loss of teeth, changes in the closure patterns of the mandible to avoid trauma to sensitive areas, ankylosis of the teeth, and other conditions that influence the position of the teeth (Fig 7-19). 3) Tumors.Tumors in the dental area may cause malocclusion (Fig 7-20). Severe malfunction will result when they are found in the articulatory region. 4) Caries.The greatest single cause of localized malocclusion undoubtedly is dental caries. Caries may be responsible for early loss of primary teeth, drifting of permanent teeth, pre-
FIG
7-19.
Hypertrophy of the gingivae and incisal malalignment.
mature eruption of permanent teeth, and so forth. Although caries is not the sole cause of these conditions, it is responsible for most of them.
(a) Premature Loss of Primary Teeth.- In this instance, the word "premature" refers to the child's own dental development, not to population standards. Specifically, it refers to the stage of development of the permanent tooth that will succeed the lost primary tooth. When a primary tooth is lost before the permanent successor has started to erupt (crown formation completed and root formation begun), bone may re-form atop the permanent tooth, delaying its eruption. When its eruption is delayed, more time is available for other teeth to drift into space that would have been occupied by the delayed tooth (see Chapter 6). Of importance in this connection is not only the total loss of the primary teeth (Fig 7-21) but partial loss of crown substance to caries as well. Interproximal caries plays a most important role in shortening of arch length. Any decrease in the mesiodistal width of a primary molar may result in the forward drifting of the first permanent molar. Since the last edition of this book two excellent studies of the effects of caries and premature loss of primary teeth have been completed and reported, by Ronnermanl9 in Sweden and Northwayl7 in Canada. Northway17 found that the space occupied by the primary molars closed as a consequence of caries or loss of the primary teeth. The rate of loss of space was related to extractionage in the maxilla but not in the mandible. Loss of the first primary molar in the maxilla blocks out the permanent cuspids (Fig 7-22)
FIG
7-21.
Drifting of primary teeth due to early loss of a primary incisor.
160
Growth and Development AGE
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0-
6
0
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I 9 CHRONOLOGICAL
FIG 7-22. Blocked-out maxillary permanent bicuspids.
cuspids and mandibular second
~ E
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17 18 12 13
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FIG 7-24.
Canadian Children: A Study of the Effects of Dental Caries and Premature Extraction, thesis. Quebec, Canada, University of Mon-
treal, 1977. Used by permission.) need for more orthodontic treatment in those cases in which primary molars had been lost early and that it was necessary to extract more permanent teeth in the treatment of such cases. The loss of primary INCISORS ordinarily is not a matter of concern; however, should a primary incisor be lost before the crowns of the permanent incisors are in a position to prevent drifting of the more distally placed primary teeth, malocclusion of the primary dentition may result (see Fig 7-21). If a primary incisor is lost before age 4, radiographs should be taken of the developing permanent incisor and the space observed regularly. Primary CUSPIDS, when lost, may be a matter of great concern. In the maxilla, the permanent cuspid erupts so late that if the primary cuspid is removed before the central and lateral incisors have been moved together, it may permit permanent spacing of the anterior teeth. Strange as it seems, incisor spacing and labioversion of the cuspid may occur in the same case (Fig 7-25). Pri{llary cuspid loss in the mandible is more frequent and more serious. The untimely loss of these teeth may result in lingual tipping of the four mandibular incisors if there is abnormal activity of the mentalis muscle. It has been widely recommended that the primary cuspid be extracted to facilitate the alignment of the per-
CARIES
6· ..... ·6- E· LOS S D+E LOSS
6
11
I
Changes in anterior and posterior limits of 0 E space, upper. (From Northway WM: Antero-posterior Arch Dimension Changes in French-
while loss of the maxillary second primary molar tends to impact the second premolar. Lower primary molar extractions prematurely tend to cause mal eruption of the second premolar. Most space loss is due to mesial movement of the molars, but distal migration of the cuspids occurs (Figs 7-23 and 7-24). Molar and canine occlusal relationships are significantly affected by premature loss of primary molars in either arch. Ronnerman'9 found that the early loss of the primary second molar resulted in the earlier eruption of the second permanent molar. He also noted that there was a
'"
10
I
I
8
9 DENTAL
10
11
12
13
14
AGE
FIG 7-23. Changes in anterior and posterior limits of 0 E space, lower. (From Northway WM: Antero-posterior Arch Dimension Changes in FrenchCanadian Children: A Study of the Effects of Dental Caries and Premature Extraction, thesis. Quebec, Canada, University of Mon-
treal, 1977. Reproduced by permission.)
manent incisors in the man~ible (see Chapter 15). Removal of the primarY cuspid to achieve' incisal alignment sometimes must be accompanied by an appliance to prevent lingual tipping of the incisors (see Chapter IS). Many a blocked-out mandibular cuspid owes its position to the ill-planned removal of the primary cuspid, just as many an anterior malalignment is due to the prolonged retention of the same tooth. The lost of FIRST PRIMARY MOLARS is not thought by some to be of clinical import. This is because the problem does not manifest itself for some time after the tooth's removal. Study of Figures 7-22 and 7-26 reveals that the loss of the primary first molar will cause the permanent canine to move mesially and the
Etiology of Malocclusion
FIG 7-25. Labioversion
of maxillary cuspids with spacing between incisors.
first permanent molar to do the same. In the maxilla the effects are not so profound. The first bicuspid is not misplaced during its eruption, since it is a bit narrower mesiodistally than is the first primary molar. If the first mandibular primary molar is lost very early, the second primary molar may shift forward at the time the first permanent molar is erupting (see Fig 7-26). The early loss of the SECOND PRIMARY MOLAR will allow the first permanent molar to drift forward at once (see Figs
161
7-23 and 7-24):The second primary molar is wider mesiodistally than its successor, but the difference in their widths is utilized in the anterior part of the arch to provide space for the permanent cuspids. Therefore, when the second primary molar is lost early not only does the first permanent molar move directly forward but the canine drifts distally. The incisors often follow altering the midline, and the canine consequently erupts with no space to occupy (see Fig 7-22). In the mandible, where the second bicuspid is the last of the canine and bicuspids to arrive, it is the tooth blocked out of position (see Fig 7-22). Too much emphasis cannot be placed on the importance of the second primary molar during the mixed dentition stage. Loss of crown substance to caries in this tooth may be more serious than the loss of an entire other tooth. It plays an important role in the establishment of occlusal relationships and in the maintenance of arch perimeter (Chapter 6). When TWO OR MORE PRIMARY MOLARS are lost early in the development of the dentition there is, in addition to the accumulated effects of drifting already noted, the opportunity for other changes to take place. With the loss of posterior dental support, the mandible may be held in a position to provide some sort of adaptive occlusal function and a resulting accommodative posterior crossbite (see Fig 7-26). These positional crossbites"have
FIG 7-26. A, crossbite
caused by unilateral loss of a mandibular first primary molar. Loss of the tooth allowed drifting of other teeth, causing tooth interferences, and the muscles shifted the mandible to achieve an
adequate occlusal
relationship.
B, effects of premature
loss of first
primary molar at an early age. C, effects of loss of primary second molar prior to the eruption of the first permanent molar. Note the mesial position of the right first molar and earlier eruption of the right second molar. (B and C courtesy of Or. Sheldon Rosenstein.)
162
Growth and Development
TABLE 7-1. Variations in Sequence of Eruptions' MAXILLA SEQUENCE
1.6124537 2. 6124357 3.6124573 4.6123457 5.6124375 6. remaining 13 sequences
MANDIBLE
gASES
%
115 38 28 14 13
48.72 16.01 11.87 5.93 5.51
28
11.87
SEQUENCE
1.6123457 2. 6123475 3.6124357 4.6123745 5.6124537 6. remaining 12 sequences
• Adapted from Lo R, Moyers RE: Sequence of eruption of permanent dentition. Am
far-reaching effects on the temporomandibular joints, the musculature, the growth of the facial bones, and the final positions of the permanent teeth. Davey,' in a study of the loss of maxillary primary molars, concluded that the factors related to migration of the first permanent molar after loss of the second or first and second primary molars were (I) the amount of leeway space-more drift occurred in arches with less leeway space, (2) cusp height-high permanent molar cusps inhibit drifting, and (3) age when the primary teeth are lost-the greatest loss occurred when the primary molars were lost prior to the eruption of the first permanent molars. (b) Disturbances in Sequence of Eruption of Permanent Teeth.Lo and Moyers13 have shown that the normal sequence of eruption of the permanent teeth will provide the highest percentage of normal occlusions (Table 7-1). Abnormal orders of arrival may permit shifting of the teeth, with resultant space loss. The premature loss of any primary tooth may allow the earlier arrival of its permanent successor or it may delay it, according to the stage of dental development. Periapical pathology of the primary teeth particularly hastens eruption of the successor due to loss of bone and increased vascularity of the region. In severe cases, the permanent crown may erupt into position before there is sufficient root development to stabilize the tooth's position. Tumors and supernumerary teeth may deflect or impede the course of eruption and thus upset the order of arrival. Prolonged retention of primary teeth, either because of failure of the roots to resorb or because of ankylosis of the root with the alveolar process, is a common factor that disturbs the sequence of eruption. One of the most important sequences to observe is that of early arrival of the second permanent molar. When this tooth develops ahead of any anterior teeth, it may have a dramatic effect in shortening arch perimeter (see Chapter 15). (c) Loss of Permanent Teeth.-The loss of a permanent tooth results in a major upset in the physiologic functioning of the dentition, since the break in mesiodistal contacts permits shifting of the teeth. Because of their susceptibility to caries, the first permanent molars are of particular interest (see Chapter 15).
7. Malnutrition Malnutrition is more likely to affect the quality of tissues being formed and the rates of calcification than it is the size of parts (although the latter has been demonstrated in animals). In-
CASES
108 44 20
14 14 36
J Orthod
%
45.77 18.64 8.47 5.93 5.93 15.26 1953; 39:460.
sofar as local effects are concerned, the roles of fluoride intake and refined carbohydrates in caries production are well known. Although there is no malocclusion that is pathognomonic of any typical and common nutritional deficiency, good nutrition plays an important role in growth and in the maintenance of good bodily health and oral hygiene.
SUMMARY Very few malocclusions are the result of a single specific cause. For example, there is no virus that produces Class n, Division I malocclusion or an organism that specifically causes crossbite; even thumb-sucking does not always cause the same malocclusion. Rather, mal occlusion is a clinically significant variation from normal growth resulting from the interaction of many factors during development. However, there is a tendency for some malocclusions to originate within a single tissue system and to affect other tissue systems secondarily as they, in turn, adapt. Most severe types are osseous in origin, on which are superimposed dental and muscular features. Malocclusions originate because of imbalances among the developing systems that form the craniofacial complex, imbalances with which the growing face cannot cope.
REFERENCES I. Benjamin L: Non-nutritive sucking and dental malocclusion in the deciduous and permanent teeth of Rhesus monkey. " Child Dev 1962; 3:29. 2. Bluestone CD: The role of tonsils and adenoids in the obstruction of respiration, in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor Mich, Center for Human Growth and Development, University of Michigan, • 1979. ~~. 3."Bushey RS: Adenoid obstruction of the nasopharynx, in McNamara JA Jr (ed): Naso~Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 4. Cook J: Intraoral Pressures Involved in' Thumb and Finger Sucking, master's thesis, Horace H Rockham School of Graduate Studies, University of Michigan, Ann Arbor, 1958.
5. Davey KW: Effect of premature loss of primary molars on the anteroposterior position of maxillary first permanent
Etiology of Malocclusion
'I
molars and other teeth. J Dent Child 1967; 34:383. 6. Dockrell R: Classifying etiology of malocclusion. Dent Rec 1952; 72:25. 7. 'Freud S: Three Contributions to the Theory of Sex, 3rd ed. New York, Nervous and Mental Disease Publishing Co, 1919 .• 8. Harvold EP: Neuromuscular and morphological adaptations in experimentally induced oral respiration, in McNamara lA lr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 9. Haryett R, et al: Chronic thumb-sucking: The psychologic effects and the relative effectiveness of various methods of treatment. Am J Orthod 1957; 53:569. 10. Haryett RD, Hansen FC, Davidson PO: Chronic thumbsucking: Second report on treatment and its psychologic effects. Am J Orthod 1970; 57:164-178. 11. Hershey HG, Steward BL, Warren DW: Changes in nasal airway resistance associated with rapid maxillary expansion. Am J Orthod 1976; 69:274-284. 12. Linder-Aronson S: Adenoids-their effect on mode of breathing and nasal air flow and their relationship to characteristics of the facial skeleton and the dentition. Acta Otolaryngol 1970; 265(suppl):3-132. 13. Lo R, Moyers RE: Sequence of eruption of permanent dentition. Am J Orthod 1953; 39:460. 14. Mayne W: Serial extraction, in Graber TM (ed): Current Orthodontic Concepts and Techniques. Philadelphia, WB Saunders Co, 1969. 15. Melson B, Stensgaard K, Pedersen l: Sucking habits and their influence on swallowing pattern and prevalence of malocclusion. Eur J Orthod 1979; 1(4):271-280. 16. Moore A: Critique of orthodontic dogma. Angle Orthod 1969; 39:69. 17. Northway WM: Antero-posterior Arch Dimension Changes in French-Canadian Children: A Study of the Effects of Dental Caries and Premature Extractions, thesis. School of Dentistry, University of Montreal, Quebec, Canada,. 1977. 18. Popovitch F, Thompson GW: Evaluation of preventive and interceptive orthodontic treatment between three and eighteen years of age, in Cook l: Transactions of the Third International Orthodontic Congress. St Louis, CV Mosby Co, 1975.
,.
163
19. Ronnerman A: Early extraction of deciduous molars: Effect on dental development and need for orthodontic treatment. Swed Dent J 1974; 67:327-337. 20. Sears R, Wise G: Relation of cup-feeding in infancy to thumb-sucking and the oral drive. Am J Orthopsychiatry 1950; 20:123. 21. Solow B, Tallgren A: Head posture and craniofacial morphology. Am J Phys Anthropol1976; 44:417-436. 22. Svedmyr B: Dummy sucking: Study of its prevalence, duration and malocclusion consequences. Swed Dent J 1979; 3:25-210. 23. Warren DW: Aerodynamic studies of upper airway: Implications for growth, breathing and speech, in McNamara lA lr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979.
SUGGESTED
READINGS
I. Dockrell R: Classifying etiology of malocclusion. Dent Rec 1952; 72:25. 2. Haryett R, et al: Chronic thumb-sucking: The psycho logic effects and the relative effectiveness of various methods of treatment. Am J Orthod 1957; 53:569. 3. Haryett RD, Hansen FC, Davidson PO: Chronic thumb-sucking: Second report on treatment and its psychologic effects. Am J Orthod 1970; 57:164-178 .. 4. Melson B, Stensgaard K, Pedersen l: Sucking habits and their influence on swallowing pattern and prevalence on malocclusion. Eur J Orthod 1979; 1(4):271-280. 5. McNamara lA lr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 6. Popovitch F, Thompson GW: Evaluation of preventive and interceptive orthodontic treatment between three and eighteen years of age, in Cook l: Transactions of the Third International Orthodontic Congress. St Louis, CV Mosby Co, 1975.
SECTION 11
Diagnosis Robert E. Moyers, D.D.S., Ph.D.
DIAGNOSIS To treat any malocclusion well one must first recognize it iD all its forms and stages of development: such recognition constitutes the diagnosis. Orthodontic diagnosis is systematic, tentative, accurate guessing directed to two ends: classification (naming the clinical problem, if possible) and planning consequent actions made necessary by its recognition. Some diagnoses are easy, many are difficult, and a few are impossible-yet all are important, for diagnosis is the trump factor in providing orthodontic care. Orthodontic diagnosis is completed in several stages: the examination, when one gathers cursory data from observations of and listening to the patient; a tentative assignment or classification; testing the validity of initial perceptions with more definitive data (e.g., cephalograms); and placing the diagnosis in the total perspective of the patient's age, needs, self image, and other factors as the prelude to treatment planning. Orthodontic diagnostic mistakes can be made in several ways: a) By misunderstanding the role of diagnosis in orthodontics.-Diagnosis is a Greek word (MArNOEIE) meaning to discern among, to know differences between; therefore, diagnosis is the determination of the presence or absence of the abnormal or undesired. Diagnosis is thinking about a problem, classification is naming it, treatment is acting on it. b) By attaching too little significance to il.-In dentistry diagnosis is frequently simple, requiring little thought or reflection-as in diagnosing a carious lesion or the absence of teeth. In these instances, a single clinical observation places immediate emphasis on the techniques required. Few such observations, during an orthodontic examination, lead to immediate thoughts of treatment techniques. Rather, initial signs prompt the search for related indicators: one question brings more. Soon, unless the whole procedure is systematic, confusion reigns.
c) By resorting to intuition.-Diagnosis by intuition or hunch is the swiftest way to orthodontic disaster. Habitual guessing about mal occlusions or random selection of treatment methods are equally defeating. A certain conceit causes us to prefer our own ideas or theories to the truth because they are our private property whereas the truth belongs to everyone. Further, the truth about a difficult problem often makes us uncomfortable whereas hunches seem certain. But to be certain is sometimes ridiculous and to depend on personal hunches is to disavow the rich accumulation of clinical wisdom in our literature, to deny the research of many great minds, and to repudiate science itself while substituting arrogant whim for all this loss. d) By undue reliance on simplistic formula.-A friend once said to me, in response to a query about a colleague, "He's the kind of person who removes four second molars and then begins the diagnosis." All of us may wish all malocclusions to yield to simple formulary-a single cephalometric measure, one appliance, or routine removal of the same teeth in all patients-but it is much more complicated. In orthodontics only blind fools or inexperienced and gullible clinicians think a simple formula competent to deal with variability, and a thorough diagnosis protects even them. Remember diagnosis derives from the Greek word for knowledge (rNOEIE): we must know before we treat.
'.
, ~. e) By insufficient·individualization.-Classification
is the naming of typical malocclusions. When one substitutes classification for differential diagnosis one depends on the rule, whereas every patient is a particular example. How is it possible to substitute such a coarse system of sifting as The Angle Classification or the ANB angle for thoughtful, judicious diagnostics? The appreciation of subtle, minor differences is the essential factor in all successful orthodontic diagnoses. But their systematic cataloging is not enough, for they must be related to each other, to their impact on the patient, and compared to similar situations seen in the past. We seek simple rules or labels to avoid thinking; but a
165
166
Diagnosis
classifier is not always a good clinician, whereas a thorough diag~ nostician is bound to be. Classification can be an end in itself, but
diagnosis is the prelude to practice.
CHAPTER
8 The Cursory Orthodontic Examination Robert E. Moyers, D.D.S., Ph.D.
More mistakes are made from want of a proper examination than for any other reason.-DR. RUSSELL JOHN HOWARD, quoted by F.G. ST. CLAIR STRANGE,in The Hip, Chapter 5.
The first step toward cure is to know what the disease is. (Ad sanitatem gradus est novisse morbum.)-Latin Proverb
KEY POINTS 1. The purpose of the cursory examination is to reach a tentative diagnosis and classification quickly from facts gathered in a single brief appointment. 2. The cursory examination provides clues to possible treatment plans.
OUTLINE A.
Before the examination
B.
The cursory examination
I. 2.
3. The cursory examination defines the need for more definitive diagnostic data. 4. The cursory examination includes, in order: a) b) c) d) e)
f) g) h)
Consideration of general health, appearance, and attitude, Examination of the external facial features, Analysis of the facial f9rm, Description of intraoral features, Classification of the occlusion, Evaluation of available space in the dental arch, Study of the functional occlusal relationships and temporomandibular joints, Completion of part of the permanent record, including case history, dental casts, and radiographs.
3. 4.
Consideration of general health, appearance, attitude Examination of external facial features
and
a) Position and posture of lips b) Col or and texture of lips c) Method of breathing d) Soft -tissue profile e) Swallow Analysis of facial form Description of intraoral features a) Gingivae b) Faucial pillars and throat c) Tongue d) Number of teeth e) Size of teeth f) Sequence and position of erupting teeth g) Malposed individual teeth h) Occlusal relationships of the teeth
167
168
Diagnosis 5.
Classification
of the occlusion
6. 7.
Evaluation of the available space Study of the functional occlusal relationships and the temporomandibular joints 8. Completion of the permanent record a) The case history b) Record casts c) Radiographic record Often one sees the terms "examination," "diagnosis," "classification," and "treatment planning" used interchangeably. Since each term has its own precise meaning, these should not be substituted for one another. Such misusage is semantic proof of confused thinking! , The cursory examination is a procedure for gathering initial data-the compilation of sufficient facts to permit a tentative diagnosis (Fig 8-1). Diagnosis is the study and interpretation of data concerning a clinical problem in order to determine the presence or absense of abnormality. In orthodontics, the diagnosis establishes or denies the existence and character of dentofacial deformity. Once the presence of an abnormality has been determined, similar abnormalities often are grouped together for convenience in discussion; this process is the classification. After the data have been gathered, studied, and interpreted and the problem named, the treatment must be planned. Treatment planning is strategy; the treatment itself is the tactics. A necessary sequential dependence will be seen: we examine, we diagnose, we classify, we plan, we treat. Logic points to this sequence; practice management demands it. ORTHODONTIC
PATIENT
Present drugs or medication: Birth Defects: Has the patient reached puberty
INFORMATION
Welcome to our office.
Please circle
the appropriate
response where indicated.
2. 3. 4. 5 6. 7.
Thank
you.
:~:~e~~~;e~:me
Age_
Birt~~::ep~
Sex_
Street City Zip Code Patient's Occupation or School Level Business Phone Employer or School Person Responsible for Account Home Phone Relationship Occupation Employer Is patient covered by insurance for orthodontic treatment? Yes No If YES, by which company? Name of person to be contacted if patient cannot be reached: Name Relationship Address Phone Family Dentist Family Physician Referred by Family
Medical
Living? ~ Living? Nwnber of Brothers Mother
Father
Spouse _
~ _ _ _ _ _ _
Yes No Yes No Nwnber of Sisters _ Self Other
Dental
Problem Problems
Heart Disease Hearing Disorder Head or Face Injury Herpes
Food Other Yes Sometimes Yes Yes Yes Yes
Usually
_ _ No Seldom No No No No
treatment from an allergist or an ear, nose and No Treated by Whom Tonsils removed Adenoids removed
_
History
Orthodontic
Hepatitis Rheumatic Fever Other (describe beloH)
No
Does the patient have pain or clicking in jaw joints? Yes No Have any teeth been injured by accidents or blows to the mouth? Yes No Has the patient received or been requested to receive speech correction? Yes No The following habits are of interest. List information as it pertains to this patient: • Yes No when? thumb sucking until age Grinding of teeth Yes No Finger sucking until ageTongue thrusting Yes No Lip-biting or sucking Y~o Other habits
Has ,the ever had: Diabetes Epilepsy Endocrine Emotional
Yes
medical Yes
Has the patient had any unusual Specify: Date of last dental check up
History
Has the patie!)t Asthma Anemia Blood Disease Bone Disorders
hair)?
to: Seasonal grasses Drugs Snore when sleeping? Breath through mouth? Have frequent colds? Have frequent "stuffy nose"? Have frequent sore throat or tonsilitis? Have chewing or swallowing difficulty?
Has the patient received throat specialist? If YES: When Nasal Surgery
History
Father's Name Mother's Name Siblings None Patient's Marital Status Patient Living with: Spouse's Name
_ (menstruation,
Does the patient: 1. Have allergies
The following information is requested to enable me to give you the best consideration of your orthodontic problem during your initial examination in our office. In order for me to diagnose thoroughly any condition, I must have accurate background and health information on which to base my decisions. This information, which is important for my records and your health, is
confidential.
FIG 8-1. Flow chart of the orthodontic examination.
dental
experiences? of;
Were the patient's
teeth
cleaned?
Yes
1\0
History
patient
had a previous
Dat"e;...• Present orthodontic Spouse Sibling Patient's interest Wants Treatment
o~tD-pdontic
consultation Physician
consultation?
Dr.' ~ prompted by:'~ Patient Friend Other (specify):
in orthodontic treatment: Treatment If Necessary
Unwilling
Yes No or treatment?
Yes No _
Dentist
Mother
Father _
But Agrees
Uncooperative
COMMENTS: Why did patient seek this consultation? What is the primary probl~m? Has the patient than for routine
been under the care examination?
of a physician during Yes No
the past
two years,
other
_ _
What is expected from orthodontic treatment? Additional comments you wish to make:
_
Condition: Signature of individual Relationship to patient
FIG 8-2. Questionnaire to be filled out by the patient or patient's parent.
completing
this
form: Today's
Date
_ _
The Cursory Orthodontic Examination
169
A. BEFORE THE EXAMINATION Much has been written concerning the preparation for a dental examination and the psychology of "handling" children in the dental office. Elaborate parental preparation. of the child's mind for a visit to the dentist is to be discouraged lest the child become unduly apprehensive. Most children are naturally relaxed. If they are tense in the dental office, it is important to learn the source of the tension. If the child is anxious while still in the waiting room, it may help to ask the parent to remain outside during the examination. While the dentist is showing the patient to the chair, the assistant may say to the parent, "We have a rule that parents wait outside during the examination. You know how some parents are. Doctor lones will want to talk with you later." Few parents fail to respond to this approach. Not all children should be seen alone; this procedure has proved successful in instances in which the child's fears had their origins in the parent's attitude. The parent may complete a health record and questionnaire (Fig 8-2) while waiting for the discussion with the dentist if the patient is not old enough to do so. It is advantageous to have the patient complete the questionnaire as far as possible, since it enables the dentist to direct his questions, based on the answers, directly to the patient. Thus a cooperative dialogue is set up between child and dentist with the parent in the role of observer not that of explainer, advocate, or protector. A child usually will respond casually if treated casually. A good relationship will be established with most children by being busy at your work and slightly indifferent to them. Too much attention should be avoided. Often it is the dentist who is nervous, and the child quickly realizes this. The orthodontic examination is not painful and as soon as this is learned, cooperation of most young patients is ensured.
FIG 8-3. Instruments used for the cursory orthodontic examination. Left to gauge, dividers, and tongue depressor.
right: mouth mirror, explorer, tooth-measuring
occlusion change so rapidly from one observation to the next that they cannot be remembered. It is helpful to have a recent periapical radiographic survey while making the cursory examination. If such a radiographic survey is not available, securing it becomes part of the examination. The following instruments should be in place on the bracket table (Fig 8-3); mouth mirror, explorer, gauge for measuring teeth, dividers, and tongue depressor.
B. THE CURSORY EXAMINATION The purpose of the cursory examination is to provide the minimal necessary facts on which a tentative diagnosis and classification can be made. The detailed analysis on which treatment planning is based is done later (see Chapter IQ through 12). The difference between the cursory examination and the detailed analysis-treatment plan is a matter of economics. One cannot afford to do a detailed analysis of every child seen, nor do most require such attention. On the other hand, neither can one afford to undertake extended orthodontic therapy with only the facts acquired in the cursory examination. Considerable clinical skill is required to make quick, correct initial examinations of potential orthodontic patients in order to know which will require further diagnostic data before such decisions can be made. The steps to be described provide a satisfactory cursory orthodontic examination easily managed in the office of the typical family dentist. No use is made in the cursory examination of elaborate diagnostic aids (e.g., cephalograms). Such procedures are, however, described in Chapters 10 through 12. Each step should be in sequence and all observations written down. The orthodontic appraisal of a patient cannot be reduced to such simple systems of notations as those used for charting cavities and planning restorative dentistry. Furthermore, the details of a developing
1. Consideration Attitude
of General Health, Appearance,
and
The first step in any orthodontic examination is to form a general idea of the patient's health status, physical appearance, and attitude toward orthodontics. Actually, the examination should begin the moment the patient is first seen. Often it is possible to 'team much concerning his/her general appearance, stature, posture, attitude, and the parent-child relationship as the child walks into the examination room and ·:Sits. The child with an extensive medical history or an unfortunate previous dental experience may be unduly apprehensive. First questions serve not only to inform t\1e examiner but to ease the mind of the child. It may be useful fofthe dentist to ask the usual questions necessary for completion of the record card as the child tells his or her name, age, street address, school, family physician, etc. An opportunity is given to observe the child's facial features, speech mannerisms, attitude toward you, and other clues. General questions concerning the child's health and past illnesses may be asked and related to the questionnaire completed by a parent, although, of course, a complete physical examination is the responsibility of the physician. Of particular interest to the dentist are data about allergies and chronic nasorespiratory disorders. Do not hesitate to ask the child
130
170 TABLE
Diagnosis
8-1.
Growth Charts. Stature and Weights Are Given by Age Percentiles weights'
(2 to 18 years) A, boys' stature; B, boys' weights. C, girls' stature; 0, girls'
A
B
] -~ ........ ......... W ......... ........ :::::~: !55.1 :::::;::::::::::::::::::
f-
-W :c:
~~
fI4/"lf"'
......... ......... ...... 1:::::]::::::!:::::::t::::::!:::::::I::::::t::::::[:::::[::::::!::::::::!::::::::r::::j;!' .~::.:.:~ ;·;·:s :.;.:, :;:·;·t ::;::N i~ :::::v r yI v
:;:;:;:; er I~1'd AG 47.:> A: X (/) 1 98.2 v··:·····51.2 Y"1;~:;:;:;;1: => E (yearsl ;: 66.1
f-
~
5
D
;:,:::,:
44.1 0 22.0
..... ;i;):
AGE .;{ .,,::::::::::;:;::::::: i;;;f 10 }} ... ti;i;; };;;;}}
....
49.2
53.1 57.1
8
10
AGE
'Courtesy National Center for Health Statistics, 25(3, suppl): June 22, 1976.
12
14
~
(years)
16
'W I"
;t
I.
eo18 It····' " 12 r
-
1
:::::1:::1::::::1:::::::1:::::::1::::::::1::::::::1::::':'I:
:':]::::1
::::1:;>'1
,~
88.2
044'.1 70 66.1 22.0
18
(years)
Health Resources
Administration,
any question that seems necessary or pertinent. The child's answers frequently are more enlightening than' those of the parents. For appraising the child's physical development, the stature and weight charts (Table 8-1) are useful. (The relationship between facial and bodily growth is discussed in Chapter 4.) Begin the examination by forming a general impression of the child's health and appearance.
2. Examination of External Facial Features The patient should be seated in the chair so that the spine is erect and the head is placed well over the vertebral column. The
US Department
of Health, Education
and Welfare.
Monthly
Vital Statistics
Report
Frankfurt Plane should be roughly parallel to the floor. This position in the chair, althougll not usual for intra-oral dental examinations, is more useful for examining the external facial features, jaw functions, and occlusal relationships (Fig 8-4). a) Position and Posture of Lips Lip posture is best studied during normal head and mandibular posture (see Fig 8-4). Normally, the lips meet each other in an un strained relationship at the level of the occlusal plane (Fig 85). Palpate the lips to ascertain whether they are of equal tonus and muscular development. Study the role of each lip during the unconscious swallow. A detailed analysis of lip function is given
The Cursory Orthodontic Examination
171
FIG 8-4. A, improper
position
of the head for orthodontic
examination.
8,
proper position of the head. The Frankfurt plane should be parallel
in Chapter 10; however, in the cursory examination, the posture of the lips, their relative size, and their role in swallowing should be noted. b) Calor and Texture of Lips When one lip is of a color or texture different from the other, there is a reason. If, for example, the lower lip rests beneath the upper incisors during a swallow, it usually is redder, heavier, and more likely to be moist and smooth (see Fig 10-3). The less active upper lip more frequently is chapped and lighter in color.
FIG 8-5. Normal lip posture.
to the floor. Note the difference views.
in the patient's
profile in these two
c) Method of Breathing It is easiest to study the method of breathing while the patient is unaware that he is being observed. The mouth-breather's lips are separated at rest to allow inspiration, whereas the nasal-breather's lips are held lightly together. After a general impression of the breathing method is formed, ask the patient to take a deep breath and then blow it out. Most children, given such a command, will inspire through the mouth, although an occasional nasal-breather will inspire through the nose with the lips tightly closed. Then ask the patient to close his or her lips and take a deep breath through the nose. A child who is a normal nasal-breather has good reflex control of the alar muscles, which control the size and shape of the external nares. Therefore, the nasal-breather dilates the external nares reflexly during inspiration. On the other hand, although all mouth-breathers (except rare ones with nasal stenosis or congestion) can breathe through their noses, they usually do not change the size or shape of the external nares during inspiration (see Fig 10-13). Occasionally, mouth-breathers actually contract the nares while inspiring. Even the nasal-breather who has temporary nasal congestion will demonstrate alar contraction reflexly when asked to take a breath while keeping the lips closed. Unilateral nasal function may be diagnosed by placing a small mirror on the upper lip, which will cloud with condensed moisture from the nasal breathing, or by use of a cotton "butterfly" (see Fig 10-14). d) Soft-Tissue Profile "'Observation of the superficjal facial features at rest and in action complements greatly our knowledge of the occlusal relationships and the positions of the teeth. Extreme malpositions of teeth rarely are seen without accompanying muscle imbalances. The important questions are "Do the muscles of the lips and face contribute to any tooth malpositions, or are they accommodating to the malpositions?" and "How might they adapt to any corrective movements of the incisors?" Detailed analysis of the facial musculature is discussed in Chapter 10, but the role of the facial muscles must be noted in the cursory examination.
172
Diagnosis
FIG 8-6. Use of a tongue depressor swallow.
on the lower lip to check the type of FIG 8-7. Palpation of the temporal muscle for checking the swallow.
e) Swallow It is important in the cursory examination to learn how the patient swallows. Observe the patient swallowing unconsciously, noting whether the lips contract. Then gently place a mouth mirror or tongue depressor on the lower lip and ask the patient to swallow (Fig 8-6). Normal (teeth-together) swallows are completed, whereas teeth-apart swallows are inhibited, since mandibular lips and mentalis contractions are necessary in teeth-apart swallows. Palpate the temporal muscle during command swallows of saliva or a small amount of water (Fig 8-7). Teeth-together swallowers must contract this muscle to elevate the mandible and hold the teeth in occlusion; teeth-apart swallowers do not have to contract the elevator muscles. Further methods of analyzing swallowing are given in Chapter 10.
3. Analysis of Facial Form Even though detailed analysis of the craniofacial skeleton can only be done by use of the cephalogram, an appraisal of the facial form is an absolute necessity for even the shortest examination. (Detailed cephalometric analyses of the facial skeleton are given in Chapter 12.) The Facial Form Analysis method* outlined in this chapter has proved practical and worthwhile. It is subjective, therefore not * The Facial Form Analysis was developed by E.A. Cheney and J.F. Mortell to teach students at The University of Michigan to evaluate craniofacial morphology in an efficient systematic way. It is not a substitute for a cephalometric analysis, only a careful procedure for examining the patient's facial features.
FIG 8-8. The planes of the Facial Form Analysis. A, lateral view; B. frontal view.
The Cursory Orthodontic Examination
173
NASION PLANE
FRANKFURT PLA~ MIDFACIAL POINT MAXILLARY ALVEOLAR MANDIBULAR CHIN
FIG 8-9. Landmarks of the Facial Form Analysis. The midfacial point is analogous to the cephalometric A point and may be estimated by using ihe ala of the nose. The maxillary alveolar point is analogous to superior prosthion and is found at the interseptal gingival tip between
ALVEOLAR
POINT POINT
POINT
the maxillary central incisors. The mandibular alveolar point, analogous to the cephalometric inferior prosthion, is found at the interseptal gingival tip between the mandibular central incisors. The chin point is the most protrusive point of the skin overlying the chin.
quantitative, and is suggested for use only when radiographic cephalometry is not available. The Facial Form Analysis provides, however, a quick, systematic evaluation of the relationship of the various parts of the facial skeleton. The Facial Form Analysis relates the facial parts to two planes, the Frankfurt and the Nasion, in the lateral view. The Frankfurt
togenic occlusion, poor oral hygiene, delayed eruption of permanent teeth, hyperactivity of the mentalis muscle (see Fig 106), mouth-breathing, or other conditions. The appearance and health of the gingival tissues is an index of periodontal health.
Plane (Fig 8-8), on the living, joins the tragus (representing the external auditory meatus) and the orbitale (the lowest point in the bony orbit). The Nasion Plane (Izard's plane) is erected perpendicularly to the Frankfurt Plane and passes through the Nasion point (Fig 8-9). The deepest point in the bony profile of the frontonasal curvature is taken on the living as Nasion. These two
Oral health is closely related to pharyngeal conditions. Inflamed, hypertrophied, or infected tonsils may give rise to alterations in the tongue posture, mandibular posture, swallowing, or breathing reflexes (see Chapters 7 and 10).
planes in combination have limitations for cephalometric use (see Chapter 12, Requisites of a Cephalometric Analysis) since there are clinically significant sex and age differences in the relationship of skeletal landmarks to the Nasion Plane. They are useful, however, in the Facial Form Analysis as a crude, clinical evaluation of one face without metric reference to population norms. The face is related to the Midsagittal Plane alone in the frontal view (see Fig 8-8). In Figure 8-10 the landmarks used for recording findings of the Facial Form Analysis are illustrated. The locations of the landmarks on the patient, as shown for a typical case (Figs 8-10 and 8-11), are marked directly on the form, and the softtissue profile may be drawn. To make it easier to visualize the exact placement of the landmarks as they appear in the patient, vertical dotted lines are used to represent the distance between perpendiculars erected to Frankfurt at orbitale and nasion, and that same distance anterior to the Nasion Plane. The questions asked
Study of tongue activity is difficult because the tongue ordinarily is not clearly visible. Since most tongue functions are synchronized well with the circumoral muscles and the muscles of mastication, abnormal function in one will result in associative or accommodative abnormal function in the others. Abnormal
are pertinent and useful to an understanding of the clinical significance of the relationships noted. The Facial Form Analysis does not provide answers; it simply makes it easier for the clinician to identify any gross malrelationship of parts and to pose the most critical questions that must be asked before treatment is begun.
4. Description of Intraoral Features a) Gingivae Localized gingival lesions may be symptomatic
of trauma-
b) Faucial Pillars and Throat
c) Tongue
function of the tongue often is first suggested when one notes abnormal function of the lips. When the lips are parted by a mouth mirror or the cheeks are withdrawn by retractors so that the mouth may be viewed better, normal tongue activity is inhibited and tannot be observed. The diagnostic trick is to examine the tongue in its normal functions without displacement of the lips and cheeks. Much has been written concerning the tongue as a gauge of oral health. From an orthodontic point of view, considerations other than its color and texture are perhaps more important, for example, its relative size, its posttfral position, and its role and positions in s~veral reflex functions. An assessment of lingual motor skills must also be a part of any orthodontic diagnostic examination (see Chapter 10). I) Study the posture of the tongue while the mandible is in its postural position. Sometimes this can be done if the lips rest apart, or tongue. posture can be noted in the lateral cephalogram of mandibular posture. If neither ?f the procedures is fruitful, gently part the lips after cautioning the patient not to move. 2) Observe the tongue during various swallowing procedures: the unconscious. swallow, the command swallow of saliva, the
174
Diagnosis
¥)!.
Patient'
5
Name,
Date FACIAL FORM ANALYSIS
L
Lateral View
Po
Frankfurt
INasion I II IIIOrI I...L. I ~ :fX
Midfacial
Maxillary alveolar Mandibular alveolar
Chin point Draw in the profile from Nasion to chin point. 1.
What molar relationship
2. a. What is the overjet?
is indicated by facial Bkele~
9,0 b. What is the overbite?
VJJ::.
(... I fl101f.
3. What 1Sthe significance of the lOC1sorrel~'ti~ 4.
What IS molar relationshIp?
&J'£
relationship? 5. 6.
Is mandible shifted in A-P on closure? Angle between Frankfurt horizontal flat,
7.
What is the cuspid ~ JI:
and occlusal
No plane;
normal, ~
Obtusity of gonial angle,
weater
Yes
less than normal,
normal.
than norma!.)
8.
hlclination of maxillary central incisors relative to nasion plane; anteriorlv inclined, normal, vertical, posteriorly inclined.
9.
m.clination of mandibular central incisors relative to nasion plane;anteriorly inclined, normal, vertical, posteriorly inclined ..
Summary:
~.~~7TT~
~~~.
FIG 8-10. An example of a completed Facial Form Analysis, lateral view.
command swallow of water, and the unconscious swallow during chewing. Do not separate the lips to see what the tongue is doing; rather, observe the contractions of the orbicularis oris and men.talis muscles and deduce from their activity the tongue's positions during swallowing. Complete details Of the analysis of the swallow are given in Chapter 10. 3) Observe the role of the tongue during mastication. 4) Observe the role of the tongue during speech. Some have overstated the relationship between speech and malocclusion. Many patients with gross malocclusions have excellent speech because they have great motor skills ~nd can adapt the lips and tongue well to mal positions of the teeth and malrelationships of the jaw. Very few mal occlusions are the result of abnormal tongue function present only during speech. However, observation of abnormal use of
the tongue during speech may beqof use in. analyzing other malfunctions of the tongue (see Chapter 10).
, d) Number of Teeth~' 't'ounting the number of teeth 9ften is forgotten. The examiner must account for 52 teeth-20 deciduous and the 32 permanent teeth, which are developing at the time of the usual orthodontic examination. For this reason, a complete standard periapical or panoramic survey is necessary.
e) Size of Teeth Like all other biologic forms, teeth come in different sizes. From an orthodontic point of view, their most important measurement is their mesiodistal width. The tooth-measuring gauge
The Cursory Orthodontic Examination n.
Frontal
175
view
Are the following landmarks If not, indicate location.
symmetric?
I I
Orbitale Malar
---O-1-Q-I
(Or)
\.
bones
I
I I
_____ 4tn
Occlusal Plane: -_ Midlines. (Draw in maxillary and mandibular central incisors) Gonial Angles -- - - - - - ---
Chin point - Occlusal Postural Path of
I ----'r---I
- Draw in
Maxillary arch form; (taperinwtrapezoid, Mandibular arch form; tapering, ,trapezoid,
Summary: iJwvmO/U
_
QJO
4~"~~"'~~-~ ~~2-~,V~~w<-d
ovoid, liD" - type. (Ovoid) IID" - type ..
~~.
8-11.
An example of a completed
Facial Form Analysis,
frontal view,
(see Fig 8-3), or a Boley gauge that has been reduced in size, provides a simple and accurate method of measuring teeth: In Table 8-2 the mean mesiodistal widths of various permanent teeth are shown for purposes of comparison. There are important and significant racial differences in tooth dimensions. Table 8-2 data reveal the distribution of sizes for the two most common racial groups in North America. The problem of tooth size and malocclusion is always a relative one, since teeth accommodated nicely in one mouth are crowded in another. f) Sequence and Position of Erupting Teeth During development there are changes in the apparent sequence of eruption and relative positions of the teeth. There are also clinically important variations in sequence and eruptive positions (see Chapters 6 and 11). Radiogr~hs provide a static "snapshot" at a single moment, but our minds must visualize dental development as a constantly shifting and changing series of events, a "movie" of the forming occlusion. One must note, during the cursory examination, any deviations of sequence and position which must be observed later or are symptomatic of developing malocclusion.
g) Malposed Individual Teeth Malpositions of teeth must be evaluated according to their developmental status, not by their ultimate position in the line of the arch. For example, maxillary cuspids usually erupt high in the
alveolar process, point mesially and labially, and temporarily look a bit unsightly to patient and parent. Such a position is normal only if there is adequate space in the arch for the tooth and if the examiner can visualize this position as part of normal eruption. Later, the same position is a malposition.
h) Occlusal Relationships of the Teeth With the mandible in the retruded contact position or the ideal .occlusal position (see Chapter 10 and 11), the examiner should '(;onsider the occlusal relationships of the teeth in detail, beginning at one side in the molar region and advancing around the arch to the opposite side. (I) Note the precise il)tercuspation of each of the posterior teeth and whether the intercuspation is symmetric. (2) Determine precisely the anteroposterior relationship of the molars and cuspids, and deterrtline any reasons for dissimilarity between their intercuspation. (3) Study the effects of tipped and rotated permanent teeth. (4) Measure the incisor relationships, both vertical and horizontal (Fig 8-13). (5) Note any lack of occlusal stops, as in an open bite, and find an explanation for their absence. There are two definitions of open bite in current orthodontic usage. The first defines open bite as the absence of vertical incisal overlap (Fig 8-14); the second defines open bite as the absence of an occlusal stop (Fig 8-14). It is most important to use the latter definition. Some cases, for example, Class n, Division 1, may show incisal overlap and what seems to be an unimportant lack
Development,
.
• >
176
MALE
N MEAN N so so so RANGE 11.539.4-14.0 10.18 11.76 9.50 11.04 10.74 10.57 11.23 10.35 10.94 10.71 10.58 191 150 158 192 189 172 136 127 102 125 148 147 160 161 156 143 100 122 6.78 5.92 6.60 6.13 0.70 0.73 0.37 6.67 0.71 9.50 0.40 6.96 0.63 6.89 0.47 7.22 0.46 7.07 0.67 9.98 6.86 9.12 7.26 0.59 0.57 8.67 0.64 8.19 7.25 8.72 7.08 7.37 0.34 5.46 7.85 5.38 5.99 7.41 7.61 7.99 0.36 7.49 6.76 5.53 6.88 6.04 7.74 5.54 80 92 0.74 0.60 0.58 0.56 6.5-9.0 6.0-8.2 6.1-9.3 4.6-6.5 6.4-8.7 7.0-8.8 7.5-10.8 5.5-8.7 7.1-9.3 6.0-8.5 7.3-10.0 6.2-8.4 6.0-8.0 5.0-7.1 6.3-9.0 9.1-13.0 9.4-12.2 9.1-12.0 8.7-12.1 9.3-12.5 0.67 0.49 0.38 0.64 0.63 0.52 0.73 0.53 0.58 0.56 0.43 0.39 0.51 0.42 0.57 0.55 0.46 0.50 0.62 0.44 0.86 0.72 6.50 8.79 196 159 134 6.58 7.76 6.64 0.32 0.42 7.66 8.91 99 153 146 142 104 156 145 148 138 140 112 4.5-6.6 5.0-7.5 6.2-8.6 10.0-13.7 5.8-8.3 9.7-12.5 10.29 159 6.2-9.4 Diagnosis
201 212 216 208 152 157 214 215 121N 170 159 132 115
FEMALE
MANDIBLE
1976. 5, Central Craniofacial Table BJ.from Growth Richardson Series. Ann Arbor, Malhotra SK: Mesiodistal Center for crown Humandimension Growth and of the Development, Negroes. Amincisor Orthod 1975; 68:157-164 . Michigan, '.permanent -ER,MAXILLA Mesiodistal Crown Diameters, Permanent Dentition' Monograph
A, North American Whites TABLE 8-2.
University dentition ofof American Michigan,
The Cursory Orthodontic Examination
7354216
6124537
7543216
6123457
???
???
7354216
6124573
3574216
6124735
???
177
???
FIG 8-12. Symbolization
of the sequence
of eruption. A, normal sequence;
B, abnormal sequence.
FIG 8 •..... :13. Method of measuring overjet. The Boley gauge is placed against the labial surface of the lower incisor, the sliding portion of the gauge is moved back to touch the labial surface of the upper incisor, and the distance is then read off directly.
178
Diagnosis
FIG 8-14. Definition of open bite. Left, the no.rmal incisor relationship showing contact between upper and lower incisors. Middle, an open bite without overlap of the incisors. Right, an open bite with overlap of the incisors. Often, only the middle figure is described as an open bite.
of intermaxillary incisal contact. However, as treatment proceeds, and after the incisors are retracted and the occlusal plane leveled, the open bite becomes more obvious (Fig 8-15). In such instances, incisal retraction encroaches on the tongue's functional space, dramatizing with treatment a condition that was present but undiagnosed at the start.
5. Classification of Occlusion It is not enough to classify the occlusion on the basis of the first permanent molar relationship alone. The skeletal profile must be classified, the cuspid relationship noted, the incisor relationship studied, the position of the dentures to their bases observed, etc. Study carefully Chapter 9 on Classification of mal occlusion for the classification procedure is one of the most misused and misunderstood procedures in orthodontics.
The condition at the right also is an open bite, as there are no functional or occlusal stops present. The absence of occlusal contact with antagonistic teeth (functional stops) is proof of an open bite.
6. Evaluation of the Available Space One of the most important steps in the cursory orthodontic examination is the evaluation of the space available to achieve desired tooth positions and occlusal corrections. Before all of the permanent teeth are present in the mouth, this procedure is called the Mixed Dentition Analysis, details of which will be found in Chapter 11. When the permanent dentition is completed as far as the second molars, space analysis often is more critical and difficult, and the diagnostic setup (see Chapter 11) may be utilized. Perhaps evaluation of the available space is the most difficult task during the cursory examination, since a quantitative estimate of the amount of space available and needed is necessary. Most parts of the cursory examination are qualitative and subjective judgments; space analysis, even at the start, is based on precise measurements. One may be tempted to make quick, crude estimates by visual observations alone, or by ratings as "very crowded," "moderately crowded," "spaced," etc. Unless one's retinas are calibrated in millimeters, casual inspection is insufficient even for the cursory examination. The Mixed Dentition Analysis described in Chapter 1I is intended for use on dental casts. If casts are available, the Mixed Dentition Analysis should be completed on th'em during the cursory examination. Often, however, a cursory examination is done before record casts are obtained. It is better, under such circumstances, to doa Mixed Dentition Analysis directly in the mouth (Fig 8~ 16) than to make casual guesses that may bias incorrectly all other initial thoughts concerning the case. Th,e Mixed Dentition Apalysis obtained directly in the mouth is helpfHl at this time but must b~ verified later when casts are available.
7. Study of the Functional Relationships and the Temporomandibular Joints FIG
8-15.
Mild open bites, often undiagnosed at the start of treatment, are dramatized during treatment if the incisors are retracted into the functional space of the tongue.
There is a possible or potential functional element in every malocclusion. The patient's usual occlusal position may be due to occlusal interferences in the undeviated path of closure, that is, interferences .may prompt a reflex shifting of the mandible during
The Cursory Orthodontic
Examination
179
FIG 8-16. The Mixed Dentition Analysis directly in the mouth. A, measuring the lower incisor width. B, ascertaining the amount of space needed to
align two of the lower incisors. (See Chapter 11 for details of the Mixed Dentition Analysis.)
closure to an occlusal position dictated by the cusps and forcing an imbalance on the musculature (see Chapter 5); such malocclusions have been termed "functional malocclusions" (although they more properly should be labeled malfunctional occlusions). Such "slides into centric" (aren't they really slides out of centric?) may be seen at any age, but the functional slides into occlusion in the primary and mixed dentitions are of a grosser nature than those ordinarily seen in the completed, permanent dentition. They are also more important because of their potential for affecting future growth and imbalance in the craniofacial skeleton as well as distorting the form of the alveolar arches. Detailed procedures for analyzing occlusal interferences and registering'jaw relationships are given in Chapter 11. Since a brief functional analysis of the occlusion must be a part of the cursory examination, the following procedures are suggested: a) With the patient sitting upright in such a way that the head
is unsupported by the headrest, or supported in such a way that the Frankfurt Plane is parallel to the floor, have the patient open and close the jaws slowly. Pay particular attention to the chin and mandibular inc.isors during the last stages of closing. Changes in the overjet relationship as the teeth come into occlusion are typically noted. The use o( dots marked on the midlines of the face, or'i-straight edge held to the midlines, is useful in diagnosing lateral shifts of the jaws (Fig 8-17). The Facial Form Analysis makes use of such a functional evaluation (see Fig 8-10). b) Correlate the two denture midlines, asking the patient to move the mandible forward gently while you guide it so that the midlines still coincide (Fig 8-18). As the patient moves the jaw gently forward and backward with the midlines coincident, a quick and clear view of cuspal interferences and lack of coordination between the shapes of the two arch forms sometimes can be noted. Often they are found in the primary cuspid region during the mixed
180
Diagnosis
FIG 8-17. Extra-oral testing for a functional slide into occlusion. Dots are placed at selected points on the midline and the patient is asked to open and close the jaw gently. A, the jaw is wide open. Note that the dots are now aligned. B, the mandible is in a postural position. Note that
dentition. Have the patient tap the incisors together, noting whether or not incisal guidance and tapping provides complete posterior disclusion. c) Gently guide the mandible into its retruded contact position and note any cuspal interferences between the retruded contact position and the usual occlusal position. cl) Place the jaw in the retruded contact position and guide the patient slightly into lateral occlusion on either side to observe occlusal impedance to lateral function (Fig 8-19). e) Observe carefully jaw movements during the unconscious swallow (q. v.) to ascertain whether it is completed with the teeth together or the teeth apart. /) Ascertain any abnormal movements of the jaw during speech and mastication. g) Even during this quick, functional analysis of the occlusion, one may mark any interfering cusps with articulation paper, noting in the written record the teeth involved.
The temporomandibular
joints should be studied for evidence
FIG 8-18. Checking for occlusal interferences
the dots are still aligned. C, the teeth are in occlusion. In this instance, as the teeth came together, the mandible was guided by cuspal interferences into a functional crossbite and was forced to swing to the left on closure. Note the malalignment
of the dots in C.
of dysfunction, pain, or other abnormal signs and symptoms. Details are provided in Chapters 10 and 11. Most books and articles on temporomandibular dysfunction and analysis are written from a geriatric not a developmental viewpoint. Definitive studies of the early stages of temporomandibular dysfunction are lacking, but it is obvious the problem has an earlier start than is usually assumed and that many adult diagnostic criteria are inappropriate for the child. I) Place your fingers lightly over both joints and feel the condylar-meniscus relationships during opening and closing. 2) Note the amount of maximal opening. 3) Palpate individually the temporal (particularly its attachment), medial pterygoid, lateral pterygoid, masseter, and inframandibular muscles. Ask the patient to note left-right differences and score each muscle on the crude tenderness scale explained in Chapter 10. 4) Palpate the joints intra-orally, noting intercapsular pain and any loss of intimacy between meniscus and condyle.
FIG 8-19. during protrusion.
Checking for occlusal interferences
in lateral excursive occlusion.
CLINICAL
A
_____________
EXAMINATION
AGE_
SEX_
OAT£__
EXAMINEDBy
••n.·
YES-Amo
_
LAIIIAL
mm
FRENUM,
NORMAL
TONSILS. GENER ..••lEVAlU
ADENOIOS'
..••T10N
HEIGHT
WEIGHT
PATIENT ATTITUDE:
SHORT
INFLAMED
NOT VISIBLE
BROAD
MODERATE
REMOVED
_
ENTHUSIASTIC
EXTRA·ORAL FACIALSTRUCTURU,
SYMMETRICAL
ASYMMETRICAL-SPECIFY:
-~--------------
_
GOOD
_______________
PROGNATH~
_
FUNCTIONAL
ANALYSIS
MENTOLABIAL CLICKING
ON LEFT
CREPITUS
ON LEFT
CLICKING
ON RIGHT
CREPITUS
ON RIGHT
SULCUS:
""
INTEROCCLUSAL
CLEARANCE,
mm
AT REST: MANDIBULAR
PATH OF CLOSURE
INTRA·ORAl
DEVIATION OCCLUSAL mm
OVERJET: Cl •••
MOl.'
Cl'"'' C ••••
MUSCLE
RIGHT
DEVIATION
DISTAL
DEVIATION
MESIAL
INTERFERENCES FUNCTION
IMPINGING
'
EMOoE""
~
mm
DVERBIT£:
IREST TO OCCLUSION),
C••••• P.d
MO.'"'
C•••••• >I••
,,,
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CAOSSllITE V"'ER
POMMETER
MIDLINE
hol ••• l"
0
eo""cI
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MIDLINE
hof ••• I:
DmmIOlr.e"ghl
Drnm'otlltl~'
G
6
PREMATURE
6
lOSS DT
0 Cor"Cl
SUPRAHYOID PERIORAL
mm 10 ' •••• rigM
SIMPLE TONGUE
ACTIVITY,
sPEECH'
THRUST
NORMAL
THRUST
(TEETH
(TEETH
TOGETHER
APARTI
I
RETAINED
INFANTILE
SWALLOW
lE
BALANCED
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DEFECTIVE_SPECIFY
OTHERCONSIDiERATIONS
O· C""~_ Ablell""
TONGUE
MUSCLE ACTIVITY,
BREATHING,
S·S"",""Umuil,}'
1"9_.Mtd1uIH
.
••IO•.••.• lC.I
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n-AIJ'p't;'Q'fo,,,,
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o
_
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OT
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_
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_ 3.
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[)lCESS EXCESS
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ExceSSIVE
DEFICIENT PALATE
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••••".
2. Oioog •••••licR_dolppI. ). Con•••II.'ionIPpI· Cl
_
0 0
0
P•••• onObo. ••• ion
•. R_IIIP9\. ~. U•••••cldld: WiIlClllbld
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FIG 8-20. A, cursory examination
form;
e,
case history form.
The Cursory Orthodontic Examination
181
182
Diagnosis
8. Completion of the Permanent Record Three permanent records are derived from the cursory examination: the case history, record casts, and radiographs. Memory cannot be trusted to recall minute details at a later date. Furthermore, subsequent problems missed in the initiar examination but observed later may be clarified by referral to the original record. Many problems in dental practice are reasonably static and can be expected to remain unchanged until corrected. The early signs and symptoms of malocclusion often are subtle, fleeting, and ever changing; therefore, it is essential that a continuous record be kept of changes in the developing dentition. a) The Case History ,The case history (Fig 8-20) should include all of the information gathered in the cursory examination as well as the usual data concerning the patient's age, parents' names, address, family physician, school, siblings, and so forth. The case history may include, as well, any questions that arise and must be answered later. Factors to be studied in detail before treatment can be begun should be mentioned. The orthodontic case history must be written out and thus resembles more a medical case history than it does the usual codified representation of teeth and cavities used in restorative dentistry. Time spent in compiling a complete orthodontic case history is time productively invested, for this record is of continuing assistance during subsequent observations of development of the dentition during treatment. No dentist treating mal occlusion can afford to have an inadequate or improper case history. b) Record Casts It is difficult to recall minute occlusal details of every patient. It is even more difficult for the parents who see their child constantly to realize the important changes that take place with growth and orthodontic treatment. For these and obvious legal reasons, a carefully prepared set of record casts is a part of the cursory examination. Procedures for taking impressions and preparing record casts are given in Chapter 18; for their detailed analysis, see Chapter 11. c) Radiographic
Record Ifthe necessary radiographs are not available, their acquisition and study becomes the last step in the cursory examination. A
discussion of the several radiographic projections of use in analysis of the occlusion will be found in Chapter 11. A discussion of cephalometric analysis is contained in Chapter 12.
SUMMARY The cursory examination is a brief gathering of sufficient data to permit a tentative diagnosis and classification. It consists of (I) gathering a health history, (2) examination of external facial form, intra-oral features, the static occlusion, and occlusal and jaw-joint functional relationships, and (3) completing part of the permanent record for the patient.
SUGGESTED
READINGS
I. Feinstein AR: The clinician as scientist, in Vig PS, Ribbens KA (eds): Science and Clinical Judgment in .orthodontics, monograph 19. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, The University of Michigan, 1986. 2. Horowitz SL, Hixon EH: The Nature of .orthodontic Diagnosis. St Louis, CV Mosby Co, 1966. 3. Jacquez JA: The diagnostic process: problems and perspectives, in Jacquez JA (ed): The Diagnosis Process. Ann Arbor, Mich, University of Michigan Press, 1964. 4. Johnson AL: Basic principles of orthodontics. Dental Codmos 1923; 65:379-, 503-,596-,719-, 845-,957-. 5. Proffit WR, Ackerman JL: Diagnosis and Treatment Planning, in Graber TM, Swain BF: .orthodontics, Current Principles and Techniques. St Louis, CV Mosby Co, 1985. 6. Proffit WR, Ackerman JL: Rating the characteristics of malocclusion: A systematic approach for planning treatment. Am J .orthod 1973; 64:258. 7. Sackett D: The Science of the Art of Clinical Management, in Vig PS, Ribbens KA (eds): Science and Clinical Judgment in .orthodontics, Monograph 19. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, The University of Michigan, 1986. 8. Vig PS, Ribbens KA (eds): Science and Clinical Judgment in .orthodontics, Monograph 19. Craniofacial Growth Series. .,Ann Arbor, Mich, Center for Human Growth and Development, The University of Michigan, 1986.
CHAPTER
9 Classification and Terminology of Malocclusion Robert E. Moyers, D.D.S., Ph.D.
The beginning
of wisdom
is to call things by their right names.-Chinese
KEY POINTS
•
1. Classification is a grouping of clinical cases of similar appearance for ease in comparison, handling, and discussion.
•
2. Systems of classification • • •
• • • • •
• • • •
and terminology:
a) Angle Based on the anteroposterior relations of the jaws. Class I (neutroclusion): normal anteroposterior jaw relationship. Class 11 (distoclusion): the maxilla and/or its dentition are prognathic and/or the mandible and its dentition are retrognathic. Class III (mesioclusion): the mandible is prognathic and/or the maxilla is retrognathic. Most commonly used system. b) Simon Based on'three planes of head (orbital, midsagittal, and Frankfurt). Little used in its entirety, but useful terminology persists. c) Naming mal positions of teeth "Version" is added to the pirection of misplacement (e.g., linguoversion) . cl) Naming misplacement of groups of teeth I) Vertical Deep overbite-excessive vertical overlap. Open bite-localized lack of occlusal contact. 2) Transverse Crossbite-abnormal buccolingual relationships. 3) Etiologic classification (according to primary tissue site) Osseous: abnormal size, shape, position, or proportion of bones.
Proverb
Muscular: abnormal function of craniofacial musculature contributing to malocclusion. Dental: abnormal malpositions, number, size, shape, or texture of teeth. e) Syndromes
• • • • • •
of malocclusion Class I: the features associated with a Class I malocclusion.
Class II: several malocclusion syndromes provide typical sub-set types of Class II. Class Ill: a few malocclusion syndromes make up Class Ill. Other syndromes are outside the Angle classification. 1) Limitations No system is truly inclusive. All are static in concept, most are narrow in focus, and most are traditionally misapplied.
OUTLINE }\~
B.' C. D.
What is a c1assii'ication system? Purposes of classifying> When to classify Systems of classification and terminology I.
Angle system a) Class I (neutroclusion) b) Class 11 (distoclusion) I) Division I 2) Division 2 3) Subdivisions c) Class III (mesioclusion)
183
184
Diagnosis 2.
3.
4.
5.
E. F. G. H.
Simon system a) Anteroposterior relationships (Orbital Plane) b) Mediolateral relationships (Midsagittal Plane) c) Vertical relationships (Frankfurt Plane) Naming malpositions of individual-teeth and groups of teeth a) Individual teeth b) Vertical variations of groups of teeth c) Transverse variations of groups of teeth Etiologic classification; its effect on diagnosis a) Osseous (problems in abnormal growth of bones of the face) b) Muscular (problems in malfunction of den tofacial musculature) c) Dental (problems involving primarily the teeth and their supporting structures) d) Comment Ackerman-Proffit system
The Class I syndrome The Class 11syndrome The Class III syndrome Limitations of classification systems
It has been said that the introduction of the Angle system of classification of malocclusions was the principal step in turning disorganized clinical concepts into the disciplined science. of orthodontics. This may be true. But it also is true that no phase of orthodontics is less understood or more misused. Many new and simplified systems for classifying malocclusions have been introduced, and each new system soon has many modifications. The reason for this constant search for an unfailing method of categorizing cases is due not only to inadequacies in systems already presented but to their misuse as well. Someone once said that 5% of us think, 15% of us think we think, and the other 80% are looking for rules so that we won't have to think. Those who strive to devise a perfect formula that will enable them to put each case into a carefully numbered pigeonhole where all will be precisely alike and treated in exactly the same fashion obviously are in the 80% group. Unfortunately, malocclusions are not so easily sorted and typed. There is a need for clinicians in the 5% group who think, because orthodontics cannot be practiced primarily by any set of rules, however cleverly devised.
A. WHAT IS A CLASSIFICATION SYSTEM? To classify malocclusion, one must have a concept of normal occlusion. Since normal occlusion is the composite of many factors, some of which, if measured separately, might be outside the expected normal range, the simple chissification of normal or abnormal occlusion is difficult. A pe~~on with abnormally I~rge teeth may have a normal occlusion, provided other features are sufficiently large to compensate for the large teeth. Occlusion may be best conceptualized for classification purposes as a frequency distribution with a range of features typically found in Class I, Class 11, and Class Ill. No single feature measured is a valid clue to any class because of the overlap of the class distributions for single measurements. Certain signs and symptoms tend to cluster in typical malocclusions, producing syndromes or classes whose identification and labeling are useful.
Each time that a patient is examined, he or she is classified subconsciously by the examiner in many different ways. We say, for example, that this patient is an 8-year-old boy who has not yet acquired his maxillary permanent central incisors. In one sentence we have classified our patient by three different standards-sex, age, and time of eruption of permanent teeth. But this classification tells us nothing concerning the plan of treatment and the prognosis. In Chapter 7 on Etiology, care was taken to differentiate several factors involved: (I) the cause, (2) the time it was acting, (3) the site where its effect was felt, and (4) the resulting orthodontic problem. Classification systems, to be usable, must confine themselves to the last-the resulting malocclusion, as determined for a specific developmental age. A classification system is a grouping of clinical cases of similar appearance for ease in handling and discussion; it is not a system of diagnosis, method for determining prognosis, or a way of defining treatment.
B. PURPOSES OF CLASSIFYING One well may ask, then, "Why does one classify?" There are several practical reasons for so doing. Historically, certain types always have been grouped together; thus, the literature contains many articles confined, for example, to "The Treatment of Angle Class 11, Division 1 Malocclusions." It is necessary, if we are to appreciate such an article, to have a clear concept of just how an Angle Class 11, Division I case appears. All Class n, Division 1 malocclusions are not exactly alike, their etiology is not necessarily identical, their prognoses are not similar, nor do they all demand precisely the same treatment; still, it is traditional to group them together. A second reason for classifying is ease of reference. It is much easier to call a case a Class III malocclusion than to go into all of the detail necessary to describe the craniofacial morphology of mandibular prognathism. The listener will have a rough idea of the problem simply from the label "Class Ill" even though he or she does not know the etiology, the prognosis, or the best treatment procedure. Experience with previous cases bearing the same label facilitates understanding of problems that may be encountered in treatment; thus, classification aids comparison. There also is a reflexive or self-communicative reason for classification. When we name a malocclusion a severe Class 1I,'we are (I) identifying problems of which we must be wary, (2) recalling past difficulties with similar cases, and (3) alerting ourselves to possible strategies and· appliances that may be needed in treatment. Classification is done for traditional reasons, for ease of refere'J,lc.e, for purposes o.f~·comparison, and for ease in selfcommunication.
C. WHEN TO CLASSIFY One of the most common mistakes is that of trying to label each case immediately. Do not be to hasty to categorize. The classification is not the diagnosis. It is far better first to describe that which is wrong in a complete and precise manner. If, at the end of the examination, the case falls into a certain usable group,
Classification
and Terminology
of Malocclusion
185
A CLASS
IT
CLASS
I
CLASS
:m:
~-_.
~
\
j) \) \'"
FIG
9-1.
A, angle classification. Facial profile and molar relationship; note how the two change together. It would be difficult, for example, to have a Class III molar relationship in a Class 11profile. S, the relationship of the soft-tissue profile to the occlusion. A, a balanced profile
with a Class I malocclusion. S, a retrognathic profile and the Class 11malocclusion. Note how the lips reflect the overjet of the incisors. C, a Class III malocclusion. Here, the lip posture clearly indicates the presence of a Class III malocclusion.
186
Diagnosis
it should then be named. If it does not fit easily into any of the classic groupings, do not worry. Do not, in any circumstance, strain to put a case in a given classification; the fit seldom is perfect. There was good reason in Chapter 8 for leaving the process of classification until the fifth step of the cursory examination. Immediate classification may prejudice later thinking. Study the malocclusion carefully; describe it in detail; then, if possible, classify it.
D. SYSTEMS OF CLASSIFICATION TERMINOLOGY
AND
Of all the many methods of classifying mal occlusions presented to the profession, only two persist and are widely used today. One of these, the Angle system,2 is used intact, but the other, the Simon system,. is used in its entirety by very few clinicians. However, certain fundamental concepts contained in
FIG 9-2. A Class I malocclusion.
(See also Figures 9-1 and 9-9.)
the Simon system have had a great influence, it will be described briefly.
and for that reason
1. Angle System The Angle system is based on the anteroposterior relationships of the jaws with each other (Fig 9-1). Angle originally presented his classification on the theory that the maxillary first permanent molar invariably was in correct position. Subsequent cephalometric research has not substantiated this hypothesis. Emphasis on the relationship of the first permanent molars caused clinicians to ignore the facial skeleton itself and to think solely in terms of the position of the teeth. Therefore, malfunction of muscles and problems of growth of bones often were overlooked. Even today, there is a tendency in the inexperienced to center too much attention on this one tooth relationship. The first molar relationship changes during the various stages of development of the dentition (see Chapter 6). A better correlation between Angle's concepts and
/ 186
Diagnosis
it should then be named. If it does not fit easily into any of the classic groupings, do not worry. Do not, in any circumstance, strain to put a case in a given classification; the fit seldom is perfect. There was good reason in Chapter 8 for leaving the process of classification until the fifth step of the corsory examination. Immediate classification may prejudice later thinking. Study the malocclusion carefully; describe it in detail; then, if possible, classify it.
D. SYSTEMS OF CLASSIFICATION TERMINOLOGY
AND
Of all the many methods of classifying mal occlusions presented to the profession, only two persist and are widely used today. One of these, the Angle system,2 is used intact, but the other, the Simon system: is used in its entirety by very few clinicians. However, certain fundamental concepts contained in
FIG 9-2. A Class I malocclusion.
(See also Figures 9-1 and 9-9.)
the Simon system have had a great influence, it will be described briefly.
and for that reason
1. Angle System The Angle system is based on the anteroposterior relationships of the jaws with each other (Fig 9-1). Angle originally presented his classification on the theory that the maxillary first permanent molar invariably was in correct position. Subsequent cephalometric research has not substantiated this hypothesis. Emphasis on the relationship of the first permanent molars caused clinicians to ignore the facial skeleton itself and to think solely in terms of the position of the teeth. Therefore, malfunction of muscles and problems of growth of bones often were overlooked. Even today, there is a tendency in the inexperienced to center too much attention on this one tooth relationship. The first molar relationship changes during the various stages of development of the dentition (see Chapter 6). A better correlation between Angle's concepts and
Classification
and Terminology
of Malocclusion
187
A
ES 8-8
FIG 9-3. A, typical Class 11,Division 1 malocclusion
as shown in dental casts.
treatment is obtained if one uses the Angle groups to classify skeletal relationships. A Class II molar relationship may result in several different ways, each requiring a different strategy in treatment, but a Class II skeletal pattern is not misunderstood, since it dominates the occlusion and its treatment. Clinicians now use the Angle system differently than)t was originally presented, for the basis of the classification has shifted from the molars to skeletal relationships. The Angle system does not itself take into account discrepancies in a vertical or lateral plane. Although the anteroposterior relationship of the teeth may be the most important single consideration, this classification system sometimes causes the uninitiated to overlook such problems as overbite and narrowness of the arches. Despite these and other criticisms, the Angle method of classifying cases is the most traditional, most practical, and hence the most popular in use at present.
S, cephalometric
tracing of a Class I malocclusion.
a) Class I (Neutroclusion) Those malocclusions in which there is a normal anteroposterior relationship between the maxilla and the mandible fall in this class. The triangular- ridge of the mesiobuccal cusp of the maxillary first permanent molar articulates in the buccal groove of't2e mandibular first petmanent molar. The bony base supporting the mandibular dentition is direct1y beneath that of the maxillary, and neither is too far anterior or posterior in relation to the cranium (Fig 9-2). The malocclusion therefore is confined to malpositions of the teeth themselves which may be misaligned, malplaced on their boney bases, (dentoalveolar protrusion), etc. b) Class II (Distoclusion) Those malocclusions in which there is a "distal" relationship of mandible to maxilla make up Class II. The nomenclature of the Angle classification emphasizes the "distal" positioning of the
188
Diagnosis posteriorly to the mesiobuccal cusp of the maxillary first permanent molar (Fig 9-3). Although the word distal is commonly used in this manner to describe Class n, it is of course wrong! Distal refers solely to teeth surfaces or directions and the Class n malocclusion involves primarily the bony skeleton. If one wishes to describe . the relationship of the mandible to the cranial base, for example, words such as posterior or dorsal are more correct. Divisions are as follows:
FIG 9-4. A typical Class 11,Division 2 malocclusion. Class 11,Division 2 malocclusions ordinarily do not show the basic skeletal retrognathism seen in Class 11,Division 1. The maxillary central incisors seem to be tipped lingually and the lateral incisors are in labioversion. This incisal relationship is the most typical diagnostic sign for Class 11, Division 2, although the lingual tipping of the central incisors is more apparent than real. The skeletal mal relationship is rarely as severe anteroposteriorly in Division 2 as in Division 1. (See Fig 9-11 for other records of this same patient.)
mandible to the maxilla in Class n malocclusion, but of course many Class n cases are seen in which the maxilla is prognathic-quite a different craniofacial morphology but producing a similar molar relationship and hence the same classification. The mesial groove of the mandibular first permanent molar articulates
FIG 9-5. A, a Class III malocclusion. The mesiobuccal cusp of the maxillary first permanent molar occludes posteriorly to the buccal groove of the mandibular first permanent molar and the mandibular incisors occlude outside the maxillary incisors. Such an occlusal configuration may be the result of marked skeletal mandibular prognathism or midface deficiency. B, a cephalometric tracing of a Class III malocclusion due to mandibular prognathism (this is not the same patient as 9-5A). (See Fig 16-13 for more details of this patient.)
I) DIVISIONI.-Distoclusion in which the maxillary incisors are typically in extreme labioversion (Fig 9-3). 2) DIVISION2.-Distoclusion in which the maxillary central incisors are near normal anteroposteriorly or slightly in linguoversion, whereas the maxillary lateral incisors have tipped labially and mesially (Fig 9-4). 3) SUBDIVISIONS.-When the distoclusion occurs on one side of the dental arch only, the unilaterality is referred to as a subdivision of its division.
c) Class III (Mesioclusion) Those malocclusions in which there is a "mesial, i.e., a ventral," relationship of mandible to maxilla make up Class Ill. The mesial groove of the mandibular first permanent molar articulates anteriorly to the mesiobuccal cusp of the maxillary first permanent molar (Figs 9-1 and 9-5).
2. Simon System The dental arches in the Simon system are related to three anthropologic planes based on craniallandmarks4 (Fig 9-6). The planes are the Frankfurt, the orbital, and the midsagittal. They are used in cephalometric analyses frequently, but the only part of this system in routine current usage is some of the terminology.
FIG 9-6. The Simon system of classification of malocclusion. Tooth mal positions are related to three planes of space in the head.
Classification a) Anteroposterior Relationships (Orbital Plane) When the dental arch, or part of it, is more anteriorly placed than, normal with respect to the orbital plane, it is said to be in protraction. When the arch, or part of it, is more posteriorly placed than normal with respect to the orbital plane, it is said to be retraction. b) Mediolateral Relationships (Midsagittal Plane) When the dental arch, or part of it, is nearer to the midsagittal plane than the normal position, it is said to be in contraction. When the arch, or part of it, is farther away from the midsagittal plane than the normal position, it is said to be in distraction. c) Vertical Relationships (Frankfurt Plane) When the dental arch, or part of it, is nearer to the Frankfurt plane than the normal position, it is said to be in attraction. When the dental arch, or part of it, is farther away from the Frankfurt plane than the normal position, it is said to be in abstraction. Only three of these terms are in frequent use-protraction, retraction, and contraction. For example, an Angle Class II case may be due to maxillary protraction, mandibular retraction, or both. Similarly, a narrowed dental arch is said to be contracted. The principal contribution of the Simon system is its emphasis on the orientation of the dental arches to the facial skeleton. In addition to this, it separates carefully, by means of its terminology, problems in mal positions of teeth from those of osseous dysplasia; for example, maxillary dental protraction is differentiated from total maxillary protraction. In the former, only the teeth are anteriorly placed, whereas, in the latter, the entire maxilla and its teeth are protracted. This system probably is capable of more precision than the Angle system, and it is three-dimensional. However, in truth, it is cumbersome, confusing at times (e.g., attraction is intrusion of the maxillary teeth and extrusion of mandibular teeth), and little used in practice. Simon's concepts, however, have had a great impact on orthodontic thinking and even have altered the fashion in which the Angle system is used.
3. Naming Malpositions of Individual Teeth and Groups of Teeth a) Individual Teeth Lischer's nomenclature' to describe malpositions of individual teeth is in general use. It simply involves adding the suffix "-version" to a word to indicate the direction from' the normal position: I) Mesioversion-mesial
to the normal position.
and Terminology
of Malocclusion
189
2) Distoversion-distal to the normal position. 3) Linguoversion-lingual to the normal position. 4) Labioversion or buccoversion-toward the lip or cheek. S) Infraversion-away from the line of occlusion. 6) Supraversion-extended past the line of occlusion (i.e., below in the maxilla and above in the mandible.) 7) Axiversion-tipped; the wrong axial inclination. 8) Torsiversion-rotated on its long axis. 9) Transversion-wrong order in the arch; transposition. The terms are combined when a tooth assumes a malposition involving more than one direction from the normal. Thus, for example, sometimes it is said that a tooth is in mesiolabioversion. b) Vertical Variations of Groups of Teeth Deep overbite is a term applied when there is excessive vertical overlap of the incisors. Just what is excessive overlap is difficult to define, but when the soft tissue of the palate is impinged, or the health of the supporting structures is endangered, certainly that bite is excessively deep. Wide variations in depth of the bite may be seen, however, with no danger to the occlusion or health of the supporting structures. Open bite is a term applied when there is localized absence of occlusion while the remaining teeth are in occlusion (see Fig 8-14). Open bite is seen most frequently in the anterior part of the mouth, although posterior open bites are encountered also. c) Transverse Variations of Groups of Teeth Crossbite is a term used to indicate an abnormal buccolingual (Iabiolingual) relationship of the teeth (Fig 9-7). The most common cross bite is that seen when buccal cusps of some of the maxillary posterior teeth occlude lingually to the buccal cusps of the lower teeth. When one or more maxillary teeth are in crossbite toward the midline, it is termed lingual crossbite. When the lingual cusps of upper posterior teeth occlude completely buccally of the buccal cusps of the lower teeth, it is termed buccal crossbite.
4. Etiologic Classification; Its Effect on Diagnosis Although it is handy to be able to group cases easily, it is more important and practical to learn their origin. There is, for example, a wide diversity of malocclusions that must bear the label <'Class II," yet they may have differing geneses and varying prognoses and may require diverse appliances. It will be easier to clarify this situation by a retUQ1 for a moment to the etiologic concepts outlined in Chapter 7. We have seen that there are several
FIG 9-7. Crossbite. A, the normal buccolingual relationship of molars. B, buccal crossbite. C, lingual crossbite. D, complete lingual crossbite.
190
Diagnosis
primary tissue sites in which orthodontic problems may originate. Indeed, one may classify cases according to the tissue primarily involved, for the soundest method of precisely determining differences in similar clinical problems is to study each on the basis of the probable site of origin.
a) Osseous This category includes problems in abnormal growth, size, shape, or proportion of any of the bones of the craniofacial complex. When any bone of the face develops in a perverted, delayed, advanced, or otherwise asynchronous manner, the aberration may be reflected in an orthodontic problem. Class III cases, for example, may be due to mandibular hypertrophy and Class 11 to mandibular inadequacy. The clinical condition may be ascribed to a genetic cause or severe malfunctions. Each region has a potential for growth that may be altered by environment. The pattern of bony development may express itself somewhat independently of the dental area. The terms "basal bone" and "apical base" have been coined to describe the areas involved in osseous dysplasias. The remaining bone, the alveolar process, reacts largely to the needs of the dentition it supports. The alveolar process can easily be shaped and altered by tooth movements; the basal bone is less responsive to the forces of orthodontic appliances. Abnormal or perverted muscle contractions readily alter the conformation of the alveolar process, but it takes a greater muscular abnormality acting longer to affect the basal bone areas. Cephalometric analysis provides the best means of studying variations of the craniofacial skeleton. It should be remembered that other parts always are affected secondarily. Malpositions of teeth in such cases are mostly the result of abnormal growth of bone, an expression or symptom of the principal fault. Orthodontic treatment may be planned to correct the fundamental osseous dysplasia or to accommodate the 'dentition to it. Some orthodontic appliances influence the dentoalveolar area; others have a profound "orthopedic" effect on basal bone as well. Osseous dysplasia or skeletal disharmony, unfortunately, is a component of many of the malocclusions seen most frequently. Only the most naive clinician avoids analysis of the skeletal aspects of craniofacial deformity. Correction or camouflage of skeletal disharmonies of the face is one of the primary tasks of dentists who would treat any but the most simple malocclusions. The adjective "skeletal" is applied to a high percentage of Class 11 problems, indicating significant osseous involvement. Most Class III malocclusions are skeletal in origin and even such apparently localized matters as deep bite or crossbite may have a skeletal basis. b) Muscular This group includes all probleI£s in malfunction of the dentofacial musculature. Any persistent alteration in the normal synchrony of the mandibular movements or muscle contra.ctions may result in distorted growth of the facial bones or abnormal positions of teeth. ~ simple lip-sucking habit may give rise to a Class 11 dentition and profile. Sometimes several habit patterns combine to make a complicated syndrome; for' example, thumb-sucking. The sucking habit itself is a complicated neuromuscular reflex involving many muscles of the face, the temporomandibular articulation, throat, tongue, and arm. Continued sucking may narrow
the maxillary dental arch. This contraction of the maxillary arch gives rise to another complicated neuromuscular habit pattern, mandibular retraction. The narrowing of the maxillary arch results 'in tooth interference, and the mandible is then shifted p~steriorly by the muscles to a position of better occlusal function. (Hotz calls this "compulsive distoclusion, "). A Class 11 molar relationship results, but each molar may be well related to its supporting bone and neither the mandible nor the maxilla may be abnormal in size or conformation, In other words, the size of the bones and the positioning of the molars can be near normal and still a Class 11 relationship eventually obtains because the mandible is held by the muscles in a retruded position. In time, the upset of forces acting within the entire system produces the syndrome we call Class 11 (see Chapters 4, 6, and 7). Since such neuromuscular patterns of behavior are habits, they were once learned and hence are capable of being altered. Treatment is directed toward understanding the complete habit reflex, then removing precipitating influences or substituting other habits that are less detrimental. The prognosis usually is excellent if care is taken to learn well the entire syndrome and if treatment is begun early. Neuromuscular' or ' 'functional" malocclusions always eventually bring about dental, dentoalveolar, or skeletal manifestations that are not as easily reversible as the original reflex. There is near unanimity (a rare thing in orthodontics) that neuromuscular features of malocclusion should be treated as early as possible. The role of the muscles in etiology will be found in Chapter 7, their part in dentitional and occlusal development in Chapter 6, and in skeletal growth in Chapter 4. Maturation of the neuromusculature is described in Chapter 5, analysis in Chapter 10, and treatment of the functional aspects of malocclusion in Chapter 15. This category includes: • Functional "slides into occlusion" due to occlusal int~rferences . • Detrimental sucking habits (e,g., th@1b, finger, lip, etc). • Abnormal patterns of mandibular closure. • Incompetent normal reflexes (e.g., lip posture). • Abnormal muscular contractions (e.g., tongue-thrusting during swallowing, mouth breathing, etc).
c) Dental " Dental problems involve primarily the teeth and their supporting structures. The malposition of a tooth on a bone is a totally different consideration from the growth of that bone or the muscular contractions that move bones. It is fortunate, indeed, that many clinical cases primarily involve the teeth, for they often are the ..~asiest to intercept and'retain. Care must be exercised, though, to det~nnine whether the dental abnprmality is the primary problem or whether it is secondary to aberrations in osseous growth or malfunction of muscles. Treatment is aimed at moving the teeth to their normal positions, replacing lost teeth, or fitting the dentition's abnormalities to the facial skeleton and its musculature. This category includes: • Malpositions of teeth. • Abnormal numbers of teeth. • Abnormal size of teeth. • Abnormal conformation or texture of teeth.
Classification
-IDEAL - CROWDING - SPACING
FIG 9-8.
and Terminology
of Malocclusion
191
symmetry of the teeth in the dental arches are analyzed, the patient's profile is viewed, the dental arches are studied with regard to the lateral dimensions, and the buccolingual relationships to the posterior teeth are noted. The patient and the dental arches are viewed in the saggital plane using the Angle system-noting whether the deviation is skeletal, dentoalveolar, or a combination-and the patient and dentition are viewed with regard to the vertical dimension. Obviously Group 9, which combines elements of all of the interlocking sets, represents the most complex malocclusions. The system has some advantages particularly for the student or beginner in orthodontics for it teaches a perspective about the complexities of malocclusion. All three planes of space and the influence of the dentition on the profile are considered. The differentiation between skeletal and dental problems is made at the appropriate level, and arch length problems with or without an influence on the profile are recognized. Furthermore, this classifying scheme leads one convincingly to the diagnosis and to differential treatment planning since homologous malocclusions probably would require similar treatment plans, whereas analogous malocclusions may require different treatment strategies. This system has not been widely adopted for clinical use, but I include it here since I think it has great merit for the student wishing to gain an integrated perspective of classification in practice.
Diagram of the Ackerman-Proffit classification system. (From Ackerman JL, Proffit WR: Characteristics of malocclusion: A modern approach to classification and diagnoses. Am J Orthod 1969; 56:443454. Used by permission.)
d) Comment One rarely encounters a malocclusion that is solely a dental, a muscular, or an osseous problem. So intimate are the interactions of growth that a change in one tissue easily affects another. Although all three tissues (bone, muscle, and teeth) usually are in~ volved in all dentofacial deformities, one is dominant~one is most likely the primary etiologic tissue site. It is this one that largely determines the final treatment plan and prognosis, and on it we should focus our attention. The simple classification has purposes other than providing a convenient tag for designating clinical problems. When thoughtfully applied, it also may help in understanding basic differences among cases that at first glance look similar.
S. Ackerman-Proffit System Because the much-used, traditional Angle classification disregards certain essential factors of malocclusion, Ackerman and Proffit' proposed a scheme which embodies the Angle classification and five characteristics of ~alocclusion within a Venn diagram (Fig 9-8). Since the degree of alignment and symmetry of the teeth within the arches is common to all dentitions, it is represented as the universe (group I). Their profile is represented as a major set (group 2) within the universe. Lateral, anteroposterior, and vertical are depicted as deviations from the normal with their interrelationships as interlocking subsets (groups 3 through 9) within the profile set. In this system any malocclusion can thus be described by five or fewer characteristics. When one is classifying using this method, the alignment and
E. CLASS I SYNDROME Class I (neutroclusion) malocclusions are characterized by a normal molar and skeletal relationship. The skeletal profile is straight, and therefore the problem usually is dental in origin. Such problems as large teeth, open bite, and deep bite, are typical of Class I malocclusion. The lips and tongue are more likely to function normally than in Class II or Class Ill. A typical Class I malocclusion is shown in Figure 9-9. Treatment of Class I malocclusions is described in Chapters 15, 16, and 17.
F. CLASS 11 SYNDROME Class II (distoclusion, postnormal occlusion) is the most frequently encountered severe malocclusion. It is characterized by a mandibular dentition "distal" to the maxillary, the malrelationship of which may be due to a basic osseous dysplasia or to forward movement of the maxillary dental arch and alveolar processes or a combination of skeletal and dental factors. The overjet is excessive in Class I1, Division I, and the bite is likely to be deep. T):1~ retrognathic
profile:- and excessive overjet demand that the facial muscles and tongue adapt Jhemselves by abnormal contraction patterns. Typically, there is a hyperactive mentalis muscle, which contracts strongly to elevate the orbicularis oris and effect the lip seal. Figure 9-10 illustrates a typical Class I1, Division I malocclusion. Class I1, Division 2 is characterized by distoclusion, abnormal depth of bite, labioversion of the maxillary lateral incisors, and more normal lip function. The Class I1, Division 2 facial skeleton usually is not as dramatically retrognathic as that of Class I1, Division I. Figure 9-11 shows a typical Class 11, Division 2 case.
192
Diagnosis
FIG 9-9. A Class I malocclusion. A-C, before treatment. D-F, after treatment.,
.
-
.,..",
Classification
and Terminology
of MaloccLusion
FIG 9-10. Casts of a Class 11,Division 1 malocclusion.
,-
A, before treatment.
S, after treatment.
(See other such cases in Chapters
15 and 16.)
193
194
Diagnosis
(fl/'
FIG 9-11. A typical Class 11, Division 2 malocclusion treated in the permanent dentition. A, the casts before treatment. B, the casts after treatment. C, cephalometric tracings before treatment (dotted lines) and after treatment (solid lines). Note that the response is primarily dental and
that the distal movement of the maxillary first molar also opened the bite. Further, note that the maxillary central incisors were not moved labially during treatment. D, intra-oral photograph after the retention period was over.
Class I1, although described here as a single syndrome, is really a large grouping with many subtypes. Help in differentiation of the features of Class II will be found in Chapters 12, 15, and 16. It is unfortunate that so many important and disparate malocclusion types have been found to lie within the Angle Class 11 category. The best cephalometric analyses permit their discrimination. Only the most naive clinicians now would presume to treat all Class 11problems in the same way.
G. CLASS III SYNDROME
(511
Class III (Mesioclusion, prenorrnal occlusion) is characterized by mandibular prognathism and/or maxillary deficiency, a Class III molar relationship, and the mandibular incisors labially placed to the maxillary incisors. Most frequently it is a deep-seated skeletal dysplasia, although functional Class Ills are seen. In the adult, orthodontic treatment is aimed at camouflage of the skeletal pattern
AK
(525)
-12-0 --13-1
(50 (47.7)
FIG
M.R
7-0
9-12.
A, cephalogram of a Class IIImalocclusion. B, superimposed
cephalometric tracings of an adult Class III before and after treatment.
Solid lines, before treatment; dotted lines, after treatment. See Chapter 12 for an explanation of the cephalometric findings noted.
Classification to improve esthetics and function, but in the young child, growth may be directed to obtain a correction. Occasionally, surgery must be resorted to in order to treat well the severe Class Ill. Figure 9-12 illustrates a typical Class III syndrome treated in a child. Figure 9-12B shows a well treated adult'case. See Chapters 15, 16, and 17 for a discussion of the possibilities of treatment of Class III malocclusion.
H. LIMITATIONS SYSTEMS
OF CLASSIFICATION
Though the classification systems which have been described in'this chapter are in everyday use and practice it is prudent to remember some of their limitations. Most originated at a time in the development of orthodontics when our knowledge was less complete and our concepts were more simplistic, yet they survive. The field of orthodontics is alive today, with frequent improvements in clinical treatment, important new contributions to our knowledge of craniofacial growth, and significant changing demands on the profession's ability to deliver treatment to those who need it. However useful, classification schemes must not impede our flexibility to adapt new knowledge. a) None are truly inclusive. Most classification schemes omit entire regions which are now known to be an indigenous and integral part of the malocclusion, for example, the temporomandibular articulation. Most omit dimensions. For example, the Angle classification provides essentially an anteroposterior view of the face with little or no emphasis on either the vertical or lateral contributions to malocclusion. Most omit entire syndromes or malocclusion types. We now know, for example, that the simple term, Class II, in-
and Terminology
of Malocclusion
195
cludes a wide variety of quite disparate malocclusion types which probably never should have been included under a single general classification. b) All are static in concept.-Classification is done at one moment in time, and allowance is not made for future changes which might occur with growth or the removal of etiologic factors. Malocclusions adapt and change through time, yet most classification schemes do not encourage us to think in terms of such changes. c) Most are narrow in focus and perspective.-It is very difficult to fit new findings or ideas into a classification scheme or framework. Furthermore, the very simplicity of the classification, which admittedly contributes to its utility, causes us to place too much emphasis on one aspect of the total malocclusion syndrome, (e.g., the molar relationship in the Angle classification scheme). d) There is a tradition of misuse and misapplication.This problem is not just a semantic one; rather, misunderstanding about the role of classification leads to real and practical problems in diagnosis and treatment planning.
REFERENCES I. Ackerman JL, Proffit WR: Characteristics of malocclusion: A modem approach to classification and diagnosis, Am J Orthod 1969; 56:443-454. 2. Angle EH: Malocclusion of the Teeth, 7th ed. Philadelphia, SS White Dental Mfg Co, 1907. 3. Lischer BE: Principles and Methods of Orthodontics. Philadelphia, Lea & Febiger, 1912. 4. Simon P: Grundzuge einer systematischen Diagnostik der Gebiss-Anomalien. Berlin, Meusser, 1922.
CHAPTER
10 Analysis of the Orofacial and Jaw Musculature Robert E. Moyers, D.D.S.,Ph.D.
By examining the tongue of the patient, physicians find out the diseases of the body, and philosophers the diseases of the mind.-ST. JUSTIN
KEY POINTS 1. Concepts of occlusion must include not only the relationships of teeth and morphology of the craniofacial skeleton but also neuromuscular activities of the jaw and face region. 2. Sensory or motor inabilities may be involved in the etiology of malocclusion and may affect orthodontic treatment and prognosis. 3. Abnormal lip morphology or function may be identified with specific malocclusions. 4. Morphologically inadequate lips are rarer than functionally inadequate or functionally abnormal lips. Functional lip problems are more apt to respond to treatment. 5. Abnormal tongue posture is a more frequent problem than abnormal tongue size. 6. Muscle tenderness and malfunction are more clinically significant to dentists than is variation in morphology of the jaw, head, or neck muscles. 7. Both general and head posture may reveal dysfunctions of orthodontic importance. 8. Interferences with normal respiration affect head and mandibular posture and may affect craniofacial growth.
9. Though there are problems in our understanding of swallowing malfunction, the role of normal swallowing in the maintenance of occlusal stability is clear. 10. The normal infantile swallow is characterized by contractions of the facial muscles and tongue and the positioning of the tongue between the gum pads. 11. Beginning with the eruption of the teeth a transitional period occurs in which elements of infantile and mature swallowing are both observed. 12. The normal mature swallow is characterized by contractions of the mandibular elevators, occlusal contact, and little facial muscle activity. 13. The simple tongue~thrust swallow combines a teethtogether swallow with excessive facial contractions " • necessary to aid.the tongue in sealing off a well"'circumscribed open bite. ,It is usually associated with earlier digital sucking. 14. The complex tongue-thrust is a tongue-thrust with a teeth-apart swallow. It is often associated with chronic nasorespiratory difficulties and displays an ill-defined open bite. 15. The infantile swallow on rare occasions persists past childhood and constitutes then a serious clinical problem.
196
Analysis of the Orofacial and Jaw Musculature
4.
2) Semantics 3) Differing goals of treatment b) Methods of examination c) Differential diagnosis I) Normal infantile swallow 2) Normal mature swallow 3) Simple tongue-thrust swallow 4) Complex tongue-thrust swallow 5) Retained infantile swallowing behavior Mastication
5. 6.
Speech Jaw relationships
16. Since the prognosis varies greatly for treatment of open bites resulting from abnormal tongue posture, a simple tongue-thrust, a complex tongue-thrust, and a retained infantile swallow, their differential diagnosis is important. 17. Malocclusion does not ordinarily impair masticatory efficiency. 18. Malocclusion does not necessarily produce poor speech. 19. Because some speech difficulties, mostly of articulation, may be associated with some malocclusions, a simple speech screening test is useful to the dentist. 20. Temporomandibular dysfunction is related to functional occlusal developmental disorders, particularly interferences; therefore, careful analysis of the' temporomandibular joints is an imperative part of the complete orthodontic diagnosis.
OUTLINE A.
Evaluation of sensory and motor abilities I. 2.
B.
Muscle Groups I.
2.
3.
4.
C.
Sensory evaluation of the mouth Evaluation of orofacial motor skills Muscles of the face and lips a) Morphologic examination b) Functional examination c) Differential diagnosis of lips I) Morphologically inadequate lips 2) Functionally inadequate lips 3) Functionally abnormal lips Tongue a) Morphologic examination b) Functional examination c) Differential diagnosis of abnormal tongue posture Muscle of mastication a) Morphologic examination b) Functional examination c) Pain and tenderness Muscles of neck and head support a) Morphology b) Function c) Pain and tenderness
Examination of specific neuromuscular functions I.
Posture
2.
Respiration a) Methods of examination b) Differential diagnosis I) Nasal-breathers 2) Mouth-breathers Swallowing a) Role in etiology of malocclusion I) Misinformation
3.
D.
197
Analysis of the temporomandibular I. 2.
joints
Jaw movements, path of closure, and joint sounds Occlusal interferences
3. 4. 5.
Palpation of muscles and ligaments Palpation of joint capsule Registration of jaw relationships in the presence of pain or limited jaw movement The concept of normal occlusion includes the relationships of the teeth to one another, to the supporting bony structures, and to the surrounding musculature, and the functional movements of the mandible and temporomandibular joints. Occlusion should not be judged solely by the static relationships of the teeth in casts or the cephalogram, for what is apparently normal in the cephalogram or casts can be malrelated during function. Analysis of neuromuscular function is as critical to orthodontic diagnosis as is the study of teeth or bones. The purpose of this chapter is to describe a series of examination procedures for clinical analysis of the orofacial jaw musculature and its functions.
A. EVALUATION OF SENSORY AND MOTOR ABILITIES Analysis of the orofacial and jaw musculature is complicated by the many sensory and motor interrelationships among the teeth, tongue, lips, oral mucosa, jaw muscles, and pharynx. The clinical signs and symptoms arising from this elaborate multisensory system consequently are difficult to segregate and identify. The face is a region of great and varied sensory input, and dentists who are skiJled in locating sites of pain and in testing the vitality of the pulp are often less able to evaluate systematically other important sources of sensory input. Examination procedures outlined herein are not as sophisticated in sensory evaluation as in motor analysis. Since there is an intimate relationship between sensory input and motor activity, deficiencies in psychosensory evaluation hamper the 'd~gnosis of functional capability. We shall describe simple but useful methods for orofacial sensory evaluation and motor skills testing. The reader should realize that they are intended solely for cursory clinical examination, not for research.
1. Sensory Evaluation of the Mouth Several tests of lingual tactile discrimination have been devised and are used for research purposes by oral and speech physiologists.3 One of these can be simplified for use in dental practice. Several familiar geometric forms of identical size are presented to
.- •..
FIG 10-1.
Age* affects diadachakinetic perfarmance.2 Children whase .oral mavements are belaw the narmal range far their age usually are defective speakers, .often shaw patterns .of swallawing abnormality, and give evidence .of dysdiadachakinesia. The child wha has defective speech and/ar swallawing abnarmalities withaut dysdiadachakinesia has a better prognasis far speech therapy and .oral myatherapy.
Plastic geametric figures ta test .oral tactile perception. Twa sets .of figures are used. One set is placed in the patient's view, then the clinician selects a figure from the secand set and places it in the
B. MUSCLE GROUPS
198
Diagnosis
3. "kuh, kuh, kuh 4. "puh-tah-kuh,"
" "puh-tah-kuh,"
"puh-tah-kuh
..... "
patient's mauth in a manner unseen by the patient. Maving the figure araund in the mauth with tangue and lips, the patient then paints ta the matching figure befare him/her. Patients wha have great difficulty with such tactile, discriminatary functians may nat be gaad candidates far certain speech therapies .or tangue training.
1. Muscles of the face and lips a) Morphologic Examination
the patient ta .observe (Fig 10-1). An unknawn farm from a duplicate set is slipped unseen inta the patient's mauth and he .or she is asked ta identify it with the tangue. The test may be made mare difficult by using small, medium, and large squares, circles, triangles, and .other farms. Patients whase lingual tactile discriminatary abilities are limited have trouble discerning even simple differences in shape and size. There is evidence that individuals with such sensory limitatians have difficulty learning new .oral neuramuscular skills-such as thase invalved in speech-using an intraaral arthadantic appliance .or arofacial myatherapy. In anather simple test, tactile and simple matar skills are cambined by asking the patient ta use the tip .of the tangue ta caunt the number .of teeth in each arch. The dentist shauld nate nat .only the carrectness .of campleting the task:
.of
the caunt but alsa the ease and speed
2. Evaluation of Orofacial Motor Skills Variatians in the use .of the tangue, lips, and jaw muscles are just as naticeable as differences in muscle skills at the ballet class .or an the Little League baseball diamand. Na .one has yet develaped a simple, orderly test .of lingual, lip, and jaw muscle matar abilities, althaugh such a test is much needed. What is desired is a test .of the patential far better perfarmance .of such campi ex psychaneuromuscular activities as speech, swallawing, and masticatian. The dentist .often natices haw easily same patients adapt ta a new intraaral appliance and haw difficult it is far .others, sa the new appliance itself is a sart .of test .of .oral mator adapatability. But .one wauld like ta knaw the ~otor skills .of the patient befare inserting a new appliance, since such knawledge might affect the design .or chaice .of appliance. If narmal hearing and appartunity ta learn are assumed, speech itself is such a test and sa is swallawing. Blaamer] has suggested diadachakinetic perfarmance as a test .of .oral mator skills and patential. The child repeats each .of the failawing sau[1ds, first slawly ta achieve perfect farmatian and then with gradually increased speed until he .or she is repeating them as rapidly as possible: I. "puh, puh, puh " 2. "tah, tah, tah "
The marphalagic relatianships .of the lips are determined, ta an extent, by the skeletal prafile (Fig 10-2). When the mandible is in its pastural pasitian, the lips narmally tauch lightly, effecting an .oral seal (Fig IO-3,A and B). In mauth-breathers and a few nasal-breathers, the lips will be parted at rest (Fig IO-3,E). Same campetent lips will have adapted ta the malacclusian; thus, althaugh a seal is present, it is nat a lip-lip seal but a lip-taath-lip arrangement (Fig 1O-3,C and D). Differences in calar, texture, and size .of lips .often are related ta lip malfunctian. Hyperactive lips may be larger (Fig IO-3,E) and mare red and maist then hypaactive .or narmal lips.
b) Functional Examination I. Observe the lip and facial muscle cantractians during the variaus swallaws (see B-2-b, item 2, and C-3-c, item 2). 2. Observe lip functian during masticatian. Bite-size dry breakfast faad may be used ta study masticatian. During narmal masticatian, the lips are held lightly tagether. Strong cantractians .of the mentalis and circumoral muscles will be seen in teeth-apart swallawers. These same muscles alsa cantract strongly in severe Class 11malacclusians where there is large .overjet and averbite. 3. Study lip functian during speech (see belaw). Mast abnarmal lip functian during speech .of children with malacclusians i.~an adaptatian .or accammadatian ta taath pasitians, not an etialagic factar in the malpasitianing .of the teeth. 4. Palpate the jaw elevatars (e.g., the masseters). Palpatian is a rather crude way by which to identify,hypa- and hyperactive muscles, althaugh masseters sametimes enlarge remarkably with chronic hyperactivity (see Fig 10-10). It is, hawever, a gaad way t
*Rate narms far chronalagic ages have been develaped" Hawever, speed .of mavement is .only 'ane factar. Accuracy, patteming .of lingual mavement, and independence .of linguamandibular actian are thaught ta be .of equal significance in distinguishing narmal from abnarmal actian. Far .our use such narms are nat needed. We require .only a simple screening mechanism ta identify gross matar inadequacies, far they have an impact an arthadantic therapy and prognasis.
Analysis of the Orofacial and Jaw Musculature
FIG
199
10-2.
Relationship of the soft tissue profile to occlusion. A, Class I malocclusion; B, Class 11malocclusion; C, Class III malocclusion.
c) Differential
Diagnosis
of Lips
1) Morphologically inadequate Iips.- On rare occasions the upper lip is morphologically short (Fig 10-4). The significance of the morphologically short upper lip to malocclusion, speech disorders, and retention of orthodontically treated cases often is overstated. Lips originally diagnosed as morphologically inadequate may be found satisfactory later qecause the tooth movements allow normal lip function to return. ,Modem orthodontic techniques involving bodily retraction of maxillary incisors and midface orthopedics provide the opportunity for many an alleged short upper lip to fall into position and function normally. Surgical intervention for supposedly short upper lips is to be discouraged except in rare cases and then undertaken only after orthodontic therapy is completed. In my experience, it has not often been necessary, except for cleft lip. 2) Functionally inadequate Iips.- Sometimes lips are adequate in size but fail to function properly; for example, the max-
illary lip in extreme Class Il, Division I malocclusion. A hyperactive lower lip seals against the lingual surfaces of the maxillary incisors while the maxillary lip scarcely functions at all (see Fig 10-3 ,C). After retraction and proper positioning of the incisors, spontaneous normal lip function usually occurs (Fig 10-5). If it does not, a regimen of lip exercises may be prescribedj (see Chapter 18).
'. ,,3) Functionally abh'&rmallips.- One of the most frequent abnormal lip functions is associated with tongue-thrust swallowing (see Section C3). The mentalis muscle and the inferior orbicularis oris muscle are enlarged, causing the gingivae to be rubefacient and hypertrophied. Gingivitis in the mandibular incisor region in the absence of maxillary gingivitis may be indicative of hyperactive mentalis function (Fig 1O-6,A), whereas gingivitis in both anterior regions may be associated with mouth-breathing (Fig 1O-6,B). Methods for correction of abnormal n,.;ntalis muscle and lip function will De found in Chapter 18. Posen22 has invented a device, the "Pommeter," for
200
Diagnosis
FIG 10-3. A, relaxed, normal lips. S, the same subject swallowing. Note that the lip posture position does not change markedly during a normal swallow. Only the contraction of the muscles in the neck betrays that
a swallow is occurring. C and 0, adaptation of the lips to a severe skeletal Class 11malocclusion. E; lips part(3d at rest in a mouthbreather.
Analysis of the Orofacial and Jaw Musculature
201
FIG 10-4. A and e, an anatomically and the malocclusion
short upper lip prior to orthodontic treatment
associated
with it. C and D, the same patient
several years after orthodontic therapy. Note the position of the lip posture, even though orthodontics is completed.
202
Diagnosis
FIG 10-5. Change in lips with treatment. A-1, before treatment; A-2, after treatment. Notice that as the mild Class III dental correction occurred an anteroposterior
adaptation
took place in the lip posture.
dramatic example of a change in functionally inadequate treatment. B-1, before treatment; B-2, after treatment
B, more
FIG 10-6. A, gingivitis
associated
with hypertrophy
and hyperactivity
of the mentalis muscle. B, gingivitis
associated
with mouth-breathing.
lips with
Analysis of the Orofacial and Jaw Musculature quantitative perioral muscle assessment. He advocates using the measured maximum tonicity of the lips for both diagnosis and assessment of muscle response to treatment.
2. Tongue a) Morphologic Examination The tongue should be examined for size and shape, though both are subjective observations. "Large" applied to a specific tongue has only relevant meaning for a tongue which is "large" in one mouth is not in another. The best clinical sign of a tongue too large for its dental arch is the presence of scalloping on the lateral borders. Only on rare occasions is the tongue too small. Asymmetry of the tongue is more apt to be a functional than a morphologic matter. Ask the patient to protrude the tongue and note the symmetry of its position. Then ask the patient to relax the tongue, allowing it to drape over the lower lip. Functional asymmetries of the tongue change from one position to the other. Morphologic asymmetries will persist in the draped position. Any asymmetry of the tongue has important clinical implications to dental arch symmetry, dental midlines, maintenance of treated incisal relationships, open bites, etc. Neither asymmetry is easily "corrected" and treatment planning may thus often involve some sort of compromise.
203
from observed lip and facial muscle malfunction. When the lips are parted by the mouth mirror or the cheeks are withdrawn by retractors, normal tongue activity may be inhibited and what is observed is accommodation to the stretching of the lips and cheeks. The paradoxic problem of the tongue examination is to study the tongue's normal functions without displacing it or the lips. I. Observe the posture of the tongue while the mandible is in its postural position. This may be done in a cephalogram taken at the mandibular postural position or it may be done by gently and casually examining the tongue-lip relationship while the patient is seated in an upright position. During mandibular posture, the dorsum touches the palate lightly, and the tongue tip normally is at rest in the lingual fossae or at the crevices of the mandibular incisors (Fig 1O-7,A and B). 2. Observe the tongue during the various swallows-the unconscious swallow, the command swallow of saliva, the command swallow of water, and the unconscious swallow during mastication (see Section C3, later in this Chapter). The tongue tip during the normal mature swallow touches the curvature of the palate just behind the maxillary incisors. 3. Observe the role of the tongue during mastication-a difficult procedure except for obvious abnormalities associated with neurologic problems. This observation may be combined with those of swallowing during chewing (see Section C4). 4. Observe the role of the tongue in speech (see Section CS).
b) Functional Examination The tongue and lips are often integrated and synchronized in their activity; thus, one may sometimes infer tongue malfunction
FIG 10-7. Variations in tongue posture. A and B, variations in normal tongue posture. C, retracted tongue posture. D, the retained infantile tongue posture.
c) Differential Diagnosis of Abnormal Tongue Posture Tongue posture is related to skeletal morphology; for ex-
204
Diagnosis B
FIG 10-8. A, tongue posture in Class III malocclusion. The tongue is postured lower than normal. Note that the dorsum is below the incisal tip and
occlusal level. e, typical tongue posture associated with a Class 11 malocclusion that has a steep mandibular plane relationship.
ample, in severe Class III skeletons, the tongue tends to lie below the plane of occlusion (Fig 10-8,A), and in Class 11facial skeletons with a short mandible and steep mandibular plane, the tongue may be positioned forward (Fig 1O-8,B). Two significant variations from the normal tongue posture can be seen: (I) the retracted or "cocked" tongue, in which the tongue tip is withdrawn from all the anterior teeth (see Fig 1O-7,C), and (2) the protracted tongue posture, in which the resting tongue is between the incisors (see Fig 1O-7,D). The retracted tongue posture is seen in less than 10% of all children, but it is often associated with a posterior open bite since the tongue may spread laterally. The retracted tongue posture is more frequent in edentulous adults or those who have
bilateral loss of several posterior teeth. Undoubtedly the tongue has lost some of its positional sense with the removal of teeth and periodontal ligaments and it retracts itself in order to establish tactile contact laterally with the alveolar mucosa for a better seal during the swallow. The retracted tongue is unsettling to mandibular artificial dentures. The protracted tongue posture may be a serious problem, since it usually results in an open bite. There are two forms of the protracted tongue posture (Table 10-1): (I) the endogenous; and (2) the acquired adaptive. The endogenous protracted tongue posture may be a retention of the infantile postural pattern. 19 Some persons, for reasons not yet clear, do not change their tongue
TABLE 10-1. Causative and Adaptive ADAPTIVE
AN OPEN
f::> a: r (/) ~ ~
LL"::> Ul
Features of Open Bite
FEATURES , ~ TO <
w a:(/) ~fa: <::> +?a: °w+ z f-
~ 0
BITE
+
.
LL(/)a: OWW a:oa: -0> f-z-, Wa:Q §;« zXo
~u!z ;.+
0
< w(/)W a:(/)a: ±
>w
0~5
?
-+?f-
::> z
0
w w> -u -ZW:::;:' "(iio
f-
-
Forward tongue posture :J-' ZLL Nw < -' "f0< -< -z r< <>w(/) + + :J "-0 W-' "w!!l >-' Simple Retained ftongue infantile thrust swallow' ?-'< (/) ?? t;:::;: <::> ID(/) +? a: or Complex < tongue 0 thrust Skeletal COMMON open CLINICAL bite NAME Simple complex ffi:::;: tongue
0~ 0~ ~u
+ swallow) -.thrust (depends
on the
00+
Thumb-sucking tonsils Hypertrophied
+ +
+ + • Also seen with various neural deficits and certain severe craniofacial developmental - not ordinarily associated; + typically associated; ? can be associated.
syndromes;
Analysis of the Orofacial and Jaw Musculature
205
since it usually' is a transitory adaptation to enlarged tonsils, pharyngitis, or tonsillitis. The latter two may be verified by swabbing the throat with a viscous topical anesthetic and allowing the patient to swallow a tiny bit of the material. When the acutely inflamed throat is thus anesthetized, the adaptive protracted posture of the tongue may spontaneously correct to a more normal position. As long as the precipitating pain mechanism is present, the tongue will posture itself forward, and repositioning of the incisors will not be stable. Therefore, it is best to refer such patients to a physician for correlative therapy. Dramatic changes in tongue and mandibular posture often follow a tonsillectomy and/or adenoidectomy.'4 Such changes in posture may then result in significant alterations in the growth of the face." Occasionally, the nasopharyngeal condition no longer exists but the tongue reflexly remains in a forward position. To summarize, there are two clinically significant problems in abnormal tongue posture: (I) endogenous protracted tongue posture for which the prognosis is poor and around which, unfortunately, the occlusion must be built, and (2) the acquired protracted tongue posture, which usually can be corrected.
3. Muscles of Mastication a) Morphologic Examination FIG 10-9. Open bites associated with abnormal tongue posture. A, Class 11, Division 1 malocclusion 2 years out of orthodontic retention. Note the return of a very mild open bite. This patient was treated twice more and each time the bite returned to this incisal relationship. Note the absence of functional occlusal stops in the entire incisor and cuspid region. e, a severe open bite resulting from abnormal tongue posture. In this instance there was no tongue-thrust on swallowing; rather, the tongue remained in this position most of the time.
posture during the arrival of the primary incisors, and the tongue tip persists between the incisors. 17. ]9 For the great majority of patients with endogenous protracted tongue posture, the open bite is mild and not a serious clinical problem, but, on rare occasions, quite serious open bites are present (Fig 10-9). Protracted tongue postures are frequently adaptations to excessive anterior facial height, a condition which predisposes to open bite, the tongue posture necessarily adapting to enforce an anterior seal during the swallow. Proffit23.24 has drawn attention to the fact that tongue posture is far more apt to cause an open bite than tongue-thrusting simply because the tongue is always there exerting a mild continuous force. So the old question is raised again-which came first, the endogenous protracted tongue poSture creating an anterior open bite and excessive vertical anterior face height, or the skeletal pattern which predisposes to the tongue protraction? There is support for both positions. (See Chapter 4, The Growth of the Craniofacial Skeleton, and Chapter 7, The Etiology of Malocclusion). There is no known certain treatment for all problems of endogenous tongue posture.24 Surgical correction of severe skeletal dysplasia is often successful, yet the literature also reports relapse alleged to be the result of failure of the tongue to adapt to the altered skeletal morphology. 24 The acquired protracted tongue posture is a more simple matter,
There is no satisfactory quantitative way to study the morphology of muscles of mastication and it probably is not a,s important as their function. However, the relationship between "squarish" faces (see Chapter 12, Analysis of the Craniofacial Skeleton, Section G-7-b-2, Vertical Type 2) and powerful masseter function and size has long been known (Fig 10-10). Palpation of each jaw muscle at rest and in function is often useful to reveal asymmetries of muscle size and placement.
b) Functional Examination Functional analysis of the jaw musculature is best carried out with each particular synchronized function in mind (see Section C, Examination of Specific Neuromuscular Functions). Individual muscles may be lightly touched during specific functions as part of the functional analysis (see Fig 10-11).
FIG 10-10. Masseteric hypertrophy and facial form. A, note the relationship of facial breadth to facial height. e, cephalogram of the same subject.
206
Diagnosis
FIG 10-12.
FIG 10-11. Palpation of the temporal muscle to ascertain its activity during the swallow.
c) Pain and Tenderness Localized myalgia is an important diagnostic sign and symptom of temporomandibular joint dysfunction. Identification of pain of capsular origin is also important (see Section D, Analysis of Temporomandibular Joints).
4. Muscles of Neck and Head Support
Calcified stylomandibular ligament. This condition, also known as Eagle syndrome, induces limitation of head movements and pain; which sometimes are confused with temporomandibular joint symptoms. ment, which on rare occasions becomes calcified (Fig 10-12). Calcification of this ligament produces atypical head posture, restraint of head movements, and acute pain on rotation of the head. The symptoms obfuscate diagnosis of more common problems (e.g., temporomandibular disorders). It may be diagnosed by the case history, by palpation, and by analysis of the radiograph (see Fig 10-12). The condition is even rarer in children and adolescents. When encountered, irrespective of the age of the patient, consultation with an oral surgeon is advised prior to beginning orthodontic therapy.
a) Morphology Only on rare occasions does one encounter atypical morphologies of the neck and head support muscles, and then they are obvious and associated with far more serious neuromuscular disorders than those primarily related to malocclusion.
b) Function The role of these muscles in head posture is often revealed even in a casual glance at patients as they walk into the examination room and seat themselves. Observations of head posture are often more diagnostic than the patient's ability to produce extreme positions of head rotation, elevation, etc.26. 27
c) Pain and Tenderness Myalgia of the neck muscles m'ay be associated with temporomandibular dysfunction, sponct'ylitis, or other functional disorders of the region. Pain and tenderness of the neck muscles are less often encountered in children and adolescents than in adults, but when seen are of diagnostic significance. Inquire about pain in the region and palpate thoroughly all of the neck muscles, particularly those originating at the occiput and the sternocleidomastoid. It may be necessary to refer the patient to an attending physician before beginning orthodontic treatment. In milder instances such pain may diminish and cease with orthodontic therapy. Special mention must be made of the stylomandibular liga-
C. EXAMINATION OF SPECIFIC NEUROMUSCULAR
FUNCTIONS
1. Posture Generally bodily posture, and head posture in particular, are often of diagnostic significance. The general posture should first be studied unobtrusively, observing the patient sitting in the waiting room and walking to the dental chair to be seated. A particularly g;)od time to make postural observations is during weighing and the measuring of stature. Note asymmetries of shoulder position, spinal curvature, and the natural placement of the head atop the vertebral column. Posture is a reflection of the body's efficiency to maintain joints in relationships which require the least energy for. (pe furrctions imposed' on them28 Head posture is altered in moutli-breathers (see Section 2, which follows) as body posture adapts to congenital dysplasias, after accidents, or to trauma. Body posture also conveys subtle messages about self image, particularly during the gangling growing-up stages of adolescence. have shown a relationship between Solow and Tallgren26.27 facial proportions and head posture on a population basis in adults, and similar findings have been demonstrated in children. 28 A headup and chin-up posture is more associated with disproportionate anterior facial height, while posturing the head back and the chin down is more associated with shorter anterior face height.
Analysis of the Orofacial and Jaw Musculature
207
FIG 10-13. Effect of mouth-breathing on control of the alar musculature. A and B, mouth-breather inhaling and exhaling through the nose. Although the patient can breathe through his nose, the diameters of the ex-
2. Respiration It has long been claimed in orthodontic circles that mouthbreathing or interference with nasal respiration could have important effects on craniofacial growth and the positions ofthe teeth. Recent research in several laboratories has shown that, in experimental animals, this is definitely true. ]0-12. ]6 Research on human subjects has shown favorable alterations in posture and changes in craniofacial dimensions after adenoidectomies and restoration of normal nasal function5. 13-]5 Details of the significance of this research can be found in Chapters 4, 6, and 7. Since the mechanisms by which altered respiration affects facial growth has been clarified by this research-most likely due to alteration in the posture of the head, tongue, and mandible-it is important to combine the examination of posture with a study of the patient's patterns of respiration. Sometimes the literature. speaks as if all of mankind were divided into nasal-breathers and mouth-breathers. Very few persons breath .solely in one manner:29 Normal "nasal-breathers" quickly change to mouth breathing during strenuous exercise or exertive running. Herein, the term "nasal-breather" is used to mean a person who breathes mostly through the nose except during exertion. Mouth-breathers are those who breath orally even in relaxed and restful situations.
a) Methods of Examination I. Study the patient's breathing unobserved. -Nasal-breathers usually show the lips touching lightly during relaxed breathing,
ternal nares do not change. C and D, nasal-breather inhaling and exhaling. Note that the size and shape of the external nares change during inhalation.
whereas mouth-breathers must keep the lips parted (Fig 1O-l3,A and B). 2. Ask the patient to take a deep breath.-Most respond to such a request by inspiring through the mouth, although an occasional nasal-breather will inspire through the nose with the lips lightly closed. 3. Ask the patient to close the lips and take a deep breath through the nose.-Nasal breathers normally demonstrate good reflex control of the alar muscles, which control the size and shape of the external nares; therefore, they dilate the external nares on inspiration (Fig 1O-l3,C and D). Mouth-breathers, even though th"y are capable of breathing through the nose, do not change the size or shape of the external nares (Fig 1O-13,A and B) and occasionally actually contract the nasal orifices while inspiring. Even nasal-breathers with temporary nasal 'Congestion will demonstrate reflex alar contraction and dilation of the nares during voluntary inspiration. Unil';lteral nasal function may be diagnosed by Phl~ing a small, two-surfaced steel mirror on the patient's upper lip (Fig IQ-14,A). The mirror will'cloud with condensed moisture during breathing. A cotton butterfly (Fig 1O-14,B and C) may be used also. b) Differential
Diagnosis
1) Nasal-breathers.on command inspiration.
Lips touch lightly at rest, nares dilate
2) Mouth-breathers.Lips are parted at rest. Nares maintain size or contract on command inspiration with lips held together.
208
Diagnosis
FIG 10-14. A, use of a two-surfaced steel mirror to check the method of breathing. When the mirror is held in this position, if the child is a nasalbreather, the upper surface will cloud; if a mouth-breather, the lower
surface will cloud. 8 and C, use of a cotton butterfly to diagnose nasal-breathing: 8, bilateral use of nostrils; C, breathing through only one nostril.
3. Swallowing
opmental studies of the normal changes in the swallow are very few. In fact the normal change from the infantile to transitional to . mature swallowing behavior seems not to be recognized by some. Knowledge of normal development and the normal range of variability is essential as a basis for treatment of any part of the facial or occlusal systems. Racial differences in the normal ---incisor relationship have been noted. The skeletal predisposition to open bite is well recognized by clinicians, but studies of the incidence of various swallowing behaviors in correlated studies with skeletal variability are rare. t Clinicians diagnosing possible abnormal swallowing are in a ,very difficult position.at this stage of our knowledge, for they milst orient themselv~; among the well-intentioned, often-misleading, enthusiastic claims of'some; the abundant naive misinterpretation of "facts"; and the insecure, hesitant conclusions of the conscientious research scientist. But diagnoses and treatments must continue while better data are developed and our knowledge is advancing. IR
c) Role in Etiology of Malocclusion Misunderstanding about the role of swallowing in the etiology of malocclusion has lead to disagreements and affects our ability to diagnose clearly and treat properly. This misunderstanding comes from three major sources: (I) the abundance of misinformation in the literature, (2) semantic problems, and (3) differing goals of treatment. Certain aspects of these matters are also discussed in Chapters 5, Maturation of the Orofacial Musculature; Chapter 7, Etiology of Malocclusion; and Chapters 14, 15, and 18 in the third section of this book, TREATMENT. Misinformation.There are many varying origins of our concepts and "facts" about swaliowing6 The variance is due to the several fields interested in the problem: dentistry, oral physiology, speech, otolaryngology, and others. Research on the tongue' and the swallow is technically an extremely difficult matter. Clinicians began by relating variations in orofacial muscle behavior to different types of swallows. Speculation about the etiology of abnormal swallowing has been rampant, and articles abound in which certain etiologies are assumed but not tested. Serial devel-
Semantics.Even a casual reading of the literature reveals many articles written without defining the terms of reference. Improper or slovenly use of words is both a reflection of inaccurate
Analysis of the Orofacial and Jaw Musculature
209
thinking and a predisposition to illogical diagnosis and treatment. Some of the misuse of terms in this field is worthy of specific discussinn.
the dentist only if abnormal swallowing is directly related to the etiology of the malocclusion and these treatment goals.
The word normal means the common and most representative observation. Normal is not a rigid rule for all, -but a range of expected behavior. The normal height of adult men in the United States is said to be approximately 168 centimeters. Everyone does not have to be 168 centimeters, for there is a normal range around that mean or norm. At some distance from it, however, one must decide what is short and what is tall. Just as the normal height varies with age so the normal swallow varies with maturation, and the range of atypical swallowing behavior changes too. What is normal in a neonate is abnormal in an adolescent.
b) Methods of Examination" It is imperative that the patient be seated upright in the dental chair with the vertebral column vertical and the Frankfurt Plane parallel to the floor. Try to observe, unnoticed, several unconscious swallows. Then place a small amount of tepid water beneath the patient's tongue tip and ask the patient to swallow, noting mandibular movements. In the normal mature swallow, the mandible rises as the teeth are brought together during the swallow, and the lips touch lightly, showing scarcely any contractions. The facial muscles ordinarily do not show marked contractions in the normal mature swallow (Figs 10-3 and 10-15). Next, place the hand over the temporal muscle, pressing lightly with the fingertips against the patient's head (see Fig 10-11). With the hand in this position, give the patient more water and ask for a repeat swallow. During the normal swallow, the temporal muscle can be felt to contract as the mandible is elevated and the teeth are held together: during teeth-apart swallows, no contraction of the temporal muscle will be noticed. Place a tongue depressor or mouth mirror on the lower lip or hold the lower lip lightly with thumb and forefingers and ask the patient to swallow (Fig 10-16). Patients with a normal swallow can complete a command swallow of saliva while the lip is so held. Those with a teeth-apart swallow will have the swallow inhibited by depression of the lip, since strong mentalis and lip contractions are needed for mandibular stabilization in the teeth-
f-. variety of adjectives have been used to describe atypical or abnormal swallows, for example, "reverse swallow" (surely that is regurgitation), "perverse swallow" (carrying unwarranted implications of depravity), "tongue-thrust swallow," etc. It must be clear that an atypical swallowing behavior is of clinical interest to the dentist only when it is related to malocclusion, mastication, or feeding. The speech therapist has different clinical responsibilities and may logically adopt different working definitions and goals of therapy. A child with a "tongue-thrust swallow" and a perfect occlusion but a speech problem undoubtedly might be described as abnormal, but that abnormality is of more interest to the speech therapist than to the orthodontist.
Differing Goals of Treatment.Given the problems of scarcity of dependable information and the semantic variations, it is difficult for dentists to define goals of treatment. Many questions come to mind. Which diagnostic signs are important for dentists to note? How can one separate etiologic factors from diagnostic signs and symptoms? Which reflexes can be conditioned? And by which of the many therapies proposed? What should be the goals of orthodontic treatment of a patient with abnormal swallowing behavior? Many of these matters are discussed in detail elsewhere in this book, particularly in the section on TREATMENT, (Chapters 15, 16, and 17) and Chapter 18. But the goals of orthodontic treatment must be clearly in mind during the diagnostic evaluation of the swallow. They are the attainment of occlusal stability and securing the best possible occlusal function and facial esthetics. Correction of an abnormal swallow is a proper treatment goal for TABLE
apart swallow. The unconscious swallow my be examined more specifically as follows: place more water in the patient's mouth, and, with the hand on the temporal muscle, ask the patient to swallow one more "last time." After the swallow is completed, turn away from the patient as if the examination were over, but retain the hand against the head. Most patients will, in a few moments, produce an unconscious clearing swallow. Unconscious swallowing behavior is not always the same as on command, particularly in those patients who have had some form of tongue-thrust therapy or whose attention has been called to an abnormal swallow. It is common practice for the clinician to part the lips to determine whether or not the tongue is really thrusting forward. Sometimes parting the lips elicits a type of swallow which is not
10-2.
Differential Diagnosis of Swallowing Types SWALLOWING
Yes No Yes No Teeth-together Enlarged tonsilsswallow and Low gag reflex threshold SIGNS
MATURE AND ' SYMPTOMS ;'~IMPLE
No Yes
INFANTILE
TONGUE-THRUSTING
COMPLEX ,. No Yes Yes Yes No
INFANTILESWALLOWING RETAINED
Yes No
210
Diagnosis
R. L. R. L.
R. Mentalis
R. L.
L.
FIG 10-15. Electromyographic comparison of teeth-together and teeth-apart swallows. The record at the bottom (R. G.) is that of a typical mature swallow. Note the strong contractions of the temporal muscles, which indicate that the mandible has been elevated into occlusion during
FIG 10-16.
/-
Use of a tongue depressor to check the role of the lower lip during the swallow.
the swallow. The record at the top (E. B.) is of a child of the same age. Note, however, that this child has a teeth-apart swallow, since there is little or no activity of mandibular elevators and a far greater relative activity of the facial muscles.
Analysis of the Orofacial and Jaw Musculature
211
otherwise there. If all of the signs or symptoms of one of the swallowing atypicalities is present, I do not hesitate to part the lips gently to seek confirmatory visualization of the thrust itself, but the use of visual observation alone will produce a higher rate of tongue-thrusts than is the true case. Think llot in terms of one sign or symptom but of the constellation of signs. and symptoms which constitute the typical etiology and clinical designation (Tables 10-1 and 10-2). c) Differential
Diagnosis
I) Normal Infantile Swallow.During the normal infantile swallow, the tongue lies between the gum pads and the mandible is stabilized by obvious contractions of the facial muscles. The buccinator muscle is particularly strong in the infantile swallow as it is during infantile nursing. The normal infantile swallow is seen in the neon ate and gradually disappears with the eruption of the buccal· teeth in the primary dentition.'8 It, therefore, is less often seen in the dental examination of children. The cessation of the infantile swallow and the appearance of the mature swallow are not a simple on-and-off phenomenon. Rather, elements of both intermix during the primary dentition and sometimes even into the early mixed dentition. This normal appearance of features of both the infantile and mature swallow is termed the "transitional swallow." Diminishing of buccinator activity is part of the transitional period, but the most characteristic feature of the start of cessation of the infantile swallow is the appearance of contractions of the mandibular elevators during the swallow as they stabilize the teeth in occlusion. 18 2) Normal Mature Swallow.The normal mature swallow is characterized by very little lip and cheek activity, and the contraction of the mandibular elevators bringing the teeth into occlusion. 19 The amount of lip activity during the normal mature swallow depends on the ability of the tongue to effect a complete valve seal against the teeth and alveolar processes. During the mixed dentition, when some teeth are llJissing and there is normal interdental spacing, the lips may contract a bit to secure the seal. All of these features are not seen all of the time in all kinds of swallows in young children during the transitional period.9 For this reason it is important to study several swallows-the command swallow of saliva, the command swallow of water, the unconscious swallow of saliva, and swallowing during mastication. The most important and discriminative of these is the unconscious swallow. The one most apt to mislead is the command swallow of water, and the one most apt to be occasionally observed with "tonguethrust" is the swallow during mastication. 3) Simple Tongue-thrust Swallow.The simple tonguethrust swallow typically displays contractions of the lips, mentalis muscle, and mandibular elevators (see Fig 10- 15); and the teeth are in occlusion as the tongue protrudes into an open bite. There is a normal teeth-together swallow, but a "tongue-thrust" is present to seal the open bite. The so called "tongue-thrust" is simply an adaptive mechanism to maintain an open bite created by something else, usually thumb-sucking. The open bite in a simple tonguethrust is well circumscribed; that is, if one studies the teeth or the casts in occlusion, the open bite has a definite beginning "andending
FIG 10-17. Examples of open bites associated
with a simple tongue-thrust.
Note
in'each instance that there is a highly circumscribed open bite and good occlusal fit posteriorly even if the molar relationship is not correct. A, B, and Care examples before treatment; D is the same subject shown in C but after correction of the molar relationship and retraction of the incisors. Although correction of the malocclusion is not yet complete,
the opeO. bite has been corrected
withq~t tongue therapy.
spontaneously
,.
(Fig 10- 17). When a patient is observed with a simple tonguethrust, check carefully for an history of chronic digital pacifier sucking, for that is the most frequent primary etiologic factor. A simple tongue-thrust swallow may also be found with hypertrophied tonsils which are not enlarged and/or inflamed sufficiently to prompt a tooth-apart swallow. Problems in respiration are usually not associated with a simple tongue-thrust. When one fits together
212
Diagnosis
FIG 10-18. OpE!.nbite associated with complex tongue-thrust.
the dental casts of a patient with a simple tongue thrust, they have a precise and secure intercuspation, even though a malocclusion may be present, because the occlusal position is continually reinforced by the teeth-together swallow. Some who write about "tongue-thrusting" group simple and complex tongue thrusting together and seem not to recognize their differences in etiology and orthodontic prognosis. It is true that the incidence of simple tongue thrusts diminishes with increasing age, its treatment is simpler and its prognosis more certain; but none of these are reasons for postponing treatment of the associated malocclusion and swallowing misbehavior (see Chapters 15 and 18). 4) Complex Tongue-thrust Swallow.The complex tonguethrust swallow is defined as a tongue-thrust with a teeth-apart swallow. Patients with a complex tongue-thrust combine contractions of the lip, facial, and mentalis muscles, lack of contraction of the mandibular elevators (see Fig 10- 15), a tonguethrust between the teeth, and a teeth-apart swallow. The open bite associated with a complex tongue-thrust usually is more diffuse and difficult to define than that seen with a simple tongue thrust (Fig 10-18). Indeed, on occasion, complex tongue-thrusters have no open bite at all! Examination of the dental casts typically reveals a poor occlusal fit and instability of intercuspation, because the intercuspal position is not repeatedly reinforced during the swallow. This point may not be of interest to speech therapists, but it surely is important to dentists, since persistent teeth-apart swallows do not stabilize the occlusion. Swallows of water or food may produce teeth-apart swallows, so it is important to test the patient's unconscious swallow carefully when a complex tongue-thrust is suspected. Patients with a complex tongue-thrust usually demonstrate ,occlusal interferences in the retruded contact position. They also are far more likely to be- mouth-breathers and to have a history of chronic nasorespiratory disease or allergies. The incidence of complex tongue-thrusting does not diminish as much with age as does the simple tongue-thrust. Treatment of the complex tongue-thrust is described in Chapter 18. 5) Retained Infantile Swallowing Behavior.Retained infantile swallowing behavior is defined as predominant persistence of the infantile swallowing reflex after the arrival of permanent teeth. Fortunately, very few people have a true retained infantile
FIG 10-19. An open bite due to a retained infantile swallow. Usually, the teeth occlude on the last molar in each quadrant. This patient was treated by a very competent orthodontist who had banded all of the patient's teeth with an edgewise mechanism. These photographs were taken 1 month after removal of the retainers.
swallow. Those who do demonstrate very strong contractions of the lips and facial musculature, even a massive grimace. The tongue thrusts strongly between the teeth in front and on both sides: Particularly noticeable are contractions of the buccinator muscle. Such patients may have inexpressive faces, since the seventh cranial nerve muscles are not being used for the delicate purposes of facial expression but rather for the massive effort of stabilizing the mandible during the swallow. Patients with a retained infantile swallow have serious difficulties in mastication, for ordinarily they occlude on only one molar in each quadrapt (Fig 10-19). The gag threshold is typically low. These patients may restrict themselves to a soft diet and state frankly that they do not enjoy eating. Food oftt;n is placed on the dotsum of the tongue and "mastication" occurs between the tongue tip and PJllate because of the inadequacy of occlusal contacts. The prognosis for conditioning of such a primitive reflex is very poor. The retained infantile swallow may be associated with skeletal craniofacial development syndromes and/or neural deficits. True retained infantile swallowing behavior is, fortunately, rare. Excessive anterior face height often produces severe frontal open bites and extremes of adaptive swallowing behavior as the neuromusculature attempts to cope with the skeletal imbalance (Fig 10-20)24 Such strained adaptive swallowing behavior must be
Analysis of the Orofacial and Jaw Musculature
TABLE 10-3. Place and Manner of Articulatory y.~
A
(ch)
Valving*
VALVE PV-c PV-o(FRICATIVES) CONSTRICTED PV-c t(GLIDES) dPV-c (NASALS) (AFFRICATES) (STOPS) S m I NARROWED ARTICULATORY tf dz ~(~) f(sh) M(hw) '!'!.
~ (n2) !l
~ j(y)
Ult
CLOSED VALVE fh
MANNER
e(th) {l(th)p~
OF ARTICULATORY
VALVING
k 9
ARTICULATORY
Notes: 1. Palatopharyngeal valve closed and open are indicated by PV-c and PV-o, respectively. 2. The presence of voicing is indicated by underlining. 3. The English spelling equivalents of phonetic symbols are indicated in parentheses. 'Adapted from Bloomer HH: Speech defects associated with dental abnormalities and related abnormalities, in Travis LE: Handbook of Speech Pathology and Audiology. New York, Appleton-Century-Crofts, 1971, pp 715-765. tNote that although the phonetic symbol Ul as in "yell" and the English sound Ul (as in "judge") are orthographically the same, they are acoustically different. -
TABLE 10-4. Mini-test of Speech Articulation By place of articulation
We ~ought my father/ two
1. Bilabials-hw 2. Labiodentals-f
1
'!'!.i!:! p ~
1
1 2
3
4
V
.Qew sun lamps.
4
3. Linguodentals-th!b 4. Linguoalveolars-t
Q .Ql s ~
5. Linguopalatals-:\"
sh zh tsh dzh!
6. Linguovelars-k
2 ng
7. Glottopharyngeal-h
4
4
You should choose a red
5
5
5
5
coat ha~ger.
676 By manner of articulation A. Stops-p
~ tQk2
B. Fricatives-f C. Affricates-tsh
D. Glides-hw E. Nasals--;i!:!.Q
V
th s z sh zh h dzh
'!'!.I Y r ng
~obby pulled Qown two go carts.
The tqing is very full. Send his shoe measure to Charlie Jones.
Why '!'!.on't you let her !un?
213
214
Diagnosis
FIG 10-20. Open bite associated with skeletal dysplasia. A, lateral cephalograms before and after orthodontic treatment. B, facial views before and
after treatment. C, intra-oral views before and 2 years out of retention. Case treated without surgery. (Continued.) --->
,. . i.. .•
Analysis of the Orafacial and Jaw Musculature
215
FIG 10-20 (cont.). carefully discriminated swallow.
from the complex and retained infantile'
Table IQ-I summarizes the important differentiating characteristics and symptoms of several problems, whereas Table 10-2 compares tongue-thrusting and swallowing functions. 4. Mastication Patients with common malocclusions do not have impaired masticatory efficiency to the extent that might be assumed; therefore, tests of mastication are not part of the routine orthodontic examinations-though, as noted earlier, the swallow during mastication may be of interest.
5. Speech* Dentists are not speech pathologists, but they should be familiar with a few simple techniques of speech analysis in order that children with obvious speech disorders may be referred to a speech pathologist for diagnosis or therapy. The fol\owing paragraphs in this section provide an orientation to spe'ech production as it pertains to orthodontics. The relationship between speech and malocclusion often is overstated, since many patients with gross malocclusions have intelligible speech. Because of the remarkably adaptive characteristics of the lips and tongue, satisfactory speech can be produced in mouths with severe malocclusions. If abnormal tongue activity is noted during speech, there is *Professor H. Harlan Bloomer, fonner Professor of Speech Pathology and Director of the Speech Clinic, The University of Michigan, helped in the writing of this section. He devised the ingenious speech tests described herein.
a basic question that must be answered: "Is the abnormal tongue activity adaptive or etiologic to the malocclusion, is it attributable to an etiology unrelated to either?" Usually it will be found to be adaptive, but it may reflect an etiology that is common to both the speech defect and the neuromuscular aspects of the malocclusion. Maturational delays in development of oral motor coordinations or neural pathologies affecting oral coordinations, though not adaptive to the malocclusion, may contribute to it. On the other hand, environment, or factors of learning or deafness (peripheral or central) may produce abnormal speech in a normally formed mouth. The existence of a disorder of speech articulation can be detected by having the patient repeat a few key sentences designed to assist in the identification of defective consonants. The basic units of American speech which contribute to meaning are the 25 consonants, 14 vowels, and prosodic elements such as melody, stress, and rhythm. Consonants and vowels are formed by a complex series of oral pharyngeal and laryngeal movements which create the musculoskeletal. valves that continually modulate the sounds of speech. A critical phase of articulatory movements in consonant production can be described as an "articulatory position" or "place" and the corresponding consonants can be classifie.d in this context according to their "place of articulation." ~'However, "place of articulation" is significant only insofar as it contributes to the' 'manner of articulation. " "Manner" refers to the acoustic features which characterize speech sounds. In Table 10-3 a more complete classification of consonant phonemes is presented according to: (I) the presence or absence of voicing; (2) the anatomic structures by which the valves are created (place); (3) the degree of (palatopharyngeal) valve closure required to produce the phoneme; and (4) the manner of articulation (glides, fricatives, affricates, stops, nasals). Reference to such a table (and to Table 10-4) can help us to understand how abnormalities of
216
Diagnosis
structure and maladaptive movements of the articulators may in~ terfere with the production of satisfactory consonant phonemes. Although this table is relatively simple, some tables and charts provide elaborate and detailed information concerning the phonetic parameters of speech. A simple test the dentist may use to evaluate the relationship between speech and malocclusion asks that the patient count from 1 to 10 or 1 to 20. The dentist (1) watches closely how the tongue and lips adapt to the structures with which they are supposed to articulate and (2) listens to how the consonants sound. Consonants One' tests wand
n
Vowels
w- and -n
Two tests t-
00
Three tests th and r
th- and -r
ee
Four tests f and r
f- and -r
o
Five tests f and v
f- and -v
Six tests sand k
s- and -ks (x)
Seven tests s
s-, -v-, and -n -t
Eight tests! Nine tests n
Eleven
!, ~, and !! !, and
a
-n and -n
Ten tests t and n
Twelve !, ~, Etc.
e
~
-t and -n
e
-1-, -v-, and -n
e
t/w-, -1-, and -v
e
This simple procedure provides a test often consonants, seven of which (th, r,f, v, s, I, k) are frequent offenders. It also includes eight of the 14 vowels and diphthongs common in American speech, listed with appropriate diacritical markings. The fricative consonants require very precise positioning of the speech organs and, consequently, are those sounds which are frequently defective. They may be affected in quality by maladaptive placement of the tongue or lips or by malocclusion. Of these, the sibilants, a subgroup of the fricatives, are the ones most likely to be distorted. The proficiency of a patient to make such consonants can be tested in various ways. The mini-test of speech articulation presented in Table 10-4 was devised as a simple procedure to test speech articulation by place of articulation and by manner of articulation. In this test, the subject is requested to read or to repeat after the examiner a brief series of short sentences while the examiner observes and ndtes whether the consonant failures or successes fall into the numbered or lettered categories around which the sentences are structured. Inasmuch as more than one instance of the articulatory category may be provided, it is suggested that the examiner listen especially for the consonants underlined as belonging to the selected category under test. The first test sentences identify consonants by place of articulation, that is, the position assumed by the oral articulators at a critical point in the enunciation of the consonant. Many of the 25 consonant phonemes that occur in American English occur in articulatory pairs; for example, p and b, sand z, in which the
lips and tongue function in nearly identical ways to produce the sound. The audible distinction between them is created by the presence or absence of voicing. In the listing of the phonemes in the mini-test, the voiced member of each pair is underlined. In the test sentences, the articulatory position being tested is indicated by a numeric subscript that identifies the "place of articulation" group to which the consonant belongs. There are, of course, other instances of consonant occurrence, and the informed listener can easily pick them out and listen for them as the speaker repeats the sentence (for instance, the t in "bought," the z in "choose," the d in "should"). The second group of sentences identifies the consonants by manner of articulation classified as (a) stops, (b) fricatives, (c) affricates, (d) glides, and (e) nasals. Instances of voiced consonants are underlined, and each example of the consonant that illustrates the category is identified by a subscript asterisk. Whenever feasible, words have been selected in which the initial consonant is illustrative of the sound to be tested. Inasmuch as American orthography is only partially phonetic, it is desirable to indicate the consonants by phonetic symbols, such as those employed in the International Phonetic Alphabet. For readers who are not phonetically trained, the consonants have been paired with the equivalent English spellings to illustrate the pronounciation; for example, tsh for the ch in Charlie, zh for the middle consonant in measure, and so forth. As in the first sentences, some consonants occur in several places, but only one instance· of each has been identified by the asterisk. Some patients, by concentrating, will produce perfect speech, whereas, when speaking unobserved, they may make repeated errors. Oral sensory deficits or lack of orofacial motor skills may be common to both swallowing and speech disorders; however, the presence of abnormal tongue function during swallowing is not necessarily an indication that there will be abnormal tongue function during speech. In observing a patient's speech the dentist should be especially alert for articulatory error in cases of severe crossbite, severe maxillary over-jet, anterior openbite, and visible interdental lingual protrusion during speech. These are the malocclusions in which the sibilants's' and 'z' are most likely to be distorted. The patient's position in the dental chair provides a particularly good angle from which to observe lingual artigulatory positions and movements.
6. Jaw Relationships Study of jaw relationships is an analysis of muscle function, but the technical and clinical procedures for such study are given in Chapter II since such registrations are used primarily for analysis,o.f occlusion. Section 5, which follows, is an analysis of the temporomandibular joints, includil)g specific techniques for jaw registration when joint dysfunction is present or suspected.
D. ANALYSIS OF TEMPOROMANDIBULAR JOINT DYSFUNCTION There is increasing evidence that temporomandibular joint disorders may have origins early in development.4. 7. 20. 21 Epidemiologic studies show that a high percentage of children display
Analysis of the Orofacial and Jaw Musculature many of the signs and symptoms associated with temporomandibular disturbances in adulthood4.7 It can no longer be assumed that,temporomandibular dysfunction is solely a degenerative and geriatic disorder. Furthermore, there is good evidence that these early temporomandibular signs and symptoms"are often associated with particular morphologic malocclusions, for example, Class II (including end-to-end) malocclusions, crossbite, deep bite, and perhaps open bite!' 7. 20. 21 Temporomandibular symptoms are enhanced when there is an occlusal interference.' This section deals with the functional analysis of temporomandibular joint disorders in children and adolescents. Such analysis must, of course, be supplemented by a thorough occlusal analysis (Chapter 11) and a cephalometric analysis (Chapter 12).
1. Jaw Movements, Path of Closure, and Joint Sounds When the head is in its natural postural position, the mandible reflexly closes on a smooth arc with little deviation anteroposteriorly or mediolaterally (see Chapter 8). There are many reasons for uneven or erratic jaw movements on closure-including past trauma to the joint, occlusal interferences, an exfoliating primary tooth, pain, etc. Observe the patient closing the jaw in a relaxed manner without prompting or guidance on your part, noting the amount, direction, and timing of any deviations from a smooth closure path. Then, holding the fingers lightly over both jaw joints, repeat the process to identify "clicks" or crepitus. A stethoscope is particularly useful for identifying temporomandibular joint sounds: One or both condyles may slide over the edge of the meniscus late on jaw opening, slipping back into place after the initiation of closure. In other instances, the condyle 'may be felt to move onto the posterior edge of the meniscus very late in closure. All abnormal closure movements and joint sounds must be correlated with occlusal interferences and muscle and joint pain. The extent of maximal jaw opening should be measured. Many authorities consider less than 40 mm to represent restricted jaw opening. Brandt4 considers this an artificially high threshold for determining restricted jaw movements, suggesting that 35 mm is more appropriate for children and adolescents.
2. Occlusal Interferences It is essential to check for interferences in the retruded contact position and the intercuspal position, and during protrusive and lateral occlusal contacts (see Chapters 8 and 11). Interferences may be marked with articulation paper or registered in very thin wax. Children with temporomandibular dysfunction may show disharmonious occlusal interferences in either the retruded contact position (centric relation) or the intercuspal position (centric occlusion, uswll occlusal position)., WilliamsonJO has noted the importance of posterior disclusion during incisal guidance. The patient may be taught to move the jaw forward to edge-to-edge incisal relationships. Interferences can be noted during this maneuver or during tapping in the incisal position. Lateral working bite disclusion may not be seen until the permanent cuspid is fully erupted, and working side interferences of an irregular nature are frequently observed in malocclusion. Balancing (nonworking side) interferences are particularly troublesome at all ages, irrespective of how nice the morphologic occlusal relationship may seem in the intercuspal position.
217
3. Palpation of Muscles and Ligaments Each muscle involved in mandibular
movements should be
routinely palpated at rest and in isometric contractions (tell the patient to clench the teeth) in an attempt to educe reflex responses to pain. Often, unbeknownst to the patient, muscles or parts of the muscles are painful upon palpation. The masseter, lateral pterygoid, and temporal is are those which most frequently demonstrate myalgia in patients with temporomandibular dysfunctions associated with malocclusion. Inform the patient that you are going to press several of the muscles of the face and jaws and you want him or her to respond if the pressure hurts. Then, with your finger, press on the muscle at the base of the patient's thumb to show how pressure alone feels. I use a four-point scale, asking the patient the score each time I press a muscle site or tendinous attachment. The values are: o pressure only, no pain; I = pain on pressure only; pain is in2 = chronic pain, pain prior to palpation-the creased with pressure; patient flinches and/or grabs the den, 3 = chronic pain-the tist's hand. Even though the patient acknowledges pain, it is necessary to palpate carefully all muscles and their tendons in order to localize and corroborate. Wearing rubber gloves, systematically and evenly press the bellies and then the attachments (as able) of the masseter, medial pterygoid, temporalis, and lateral pterygoid muscles, in that order, noting the patient's scoring for each muscle. It is especially important to separate temporal tendinous pain and lateral pterygoid pain from joint capsular pain. Some patience and practice are required to be certain of the anatomic site being pressed. For the temporal is tendon it is easier if one begins by sliding the finger along the anterior border of the ramus. As the coronoid process is approached, ask the patient to open and close the jaw gently, which movement reveals the exact site of the tendinous attachment. When palpating the lateral pterygoid muscle and tendon, make certain your finger is not pressing the joint itself. Palpation of the temporomandibular joint and capsular ligament is also necessary (see Section 4, Palpation of Joint Capsule, which follows).
'4. Palpation of Joint Capsule Palpations of the joint capsllles may reveal intracapsular pain, the timing of "clicks," and the nature of orepitus. Begin by touching lightly both joints during unguided opening and closure. Repeat the procedure while the.)aw is moved into protrusive and lateral eXj;~rsive positions. Next gently maneuver the jaw into the retruded contact position with one hand 'lightly on the chin and the other touching lightly each of the capsules (externally) in sequence. Then palpate each of the joint capsules intraorally, noting the pain scores. If specific occlusal interferences have been registered earlier, it is often particularly revealing to have the patient tap lightly on the noted interference while pressing the capsular ligament. "Clicks" disclose a loss of intimacy of condyle and meniscus relationships, and crepitus (rare in children) may point to early arthritic symptoms. The significance of "clicking," though debated, is far better understood in adults than in children. It is
/ 218
Diagnosis
SUMMARY
FIG'10-21. Diagnostic splint. The flat bite plane allows the mandibular muscles to position the mandible without afferent input from contacting cusps.
known that joint sounds in children are not closely associated with pain, limited joint movements, and occlusal interferences.4 5. Registration of Jaw Relationships or Limited Movement
in the Presence of Pain
When any muscle or joint is painful, all of the muscles capable of moving that joint display "splinting," the simultaneous contraction of all the muscles to reduce movement and further damage to the joint. Splinting is sometimes called' 'guarding" in the dental literature, and lay persons often speak of "stiff" joints after a sprain. All these terms refer to a naturallJrotective reflex on the part of the body which makes registration of jaw relationships quite difficult. Splinting must be differentiated from anxiety or too active attempts by the patient to cooperate during jaw registration. If splinting is suspected, place a cotton roll between the molars on each side and ask the patient to hold them lightly in place for a few minutes. Then gently remove the cotton rolls, and obtain the registration before the patient brings the teeth together. This simple procedure temporarily "deprograms" the memory of the occlusal interference which has been shunting the jaw away from the reflexly determined position. When a serious and persistent interference is present and temporomandibular dysfunction has been positively identified, it is necessary to place a maxillary diagnostic splint to relieve all occlusion for a period. For such diagnostic (not treatment) purposes, I do not use splints with occlusal coverage, preferring the design shown in Fig 10-21. The splint shown is simple to construct and easy for the patient to use. Further, it can be equilibrated quickly in the mouth. Note that its construction requires no assumption on your part of a "correct" jaw relationship. Wearing it simply discludes the teeth, allowing the muscles to relax since the affe;ent avoidance signal from the interfering tooth is lost. Muscle tension and pain often diminish within 2 weeks, at which time the occlusal analysis can be completed more accurately. Its use facilitates occlusal equilibration and it is especially useful in those serious cases where the casts must be mounted on an articulator for more precise analysis. See Chapters 8, 11, and 18 for other discussions of functional analysis, jaw registrations, and occlusal equilibration techniques.
Evaluation of the sensory and motor abilities of the orofacial muscles; study of the specific muscle groups of the jaws, mouth, and face; examination of critical specific neuromuscular functions; and analysis of the temporomandibular joints are necessary parts of the complete orthodontic diagnosis. Sensory and motor evaluation, though difficult to quantify, may reveal patients with neurologic disorders or neuromuscular inabilities affecting the success of orthodontic treatment. Muscle groups of the head, face, and mouth should be examined morphologically; but more important, they should be studied in function. Specific procedures are used for the facial and lip muscles, tongue, muscles of mastication, and the muscles providing head and neck support. Neuromuscular functions of concern to orthodontics include posture (general and specific), respiration, swallowing, mastication, speech, and jaw relationships. Brief observations of posture, respiration, mastication, and speech may be sufficient to determine their possible roles and the need for referral. Specific and more detailed procedures are needed for swallowing and jaw relationships, since they not only are very closely related to malocclusions but correction of abnormal swallowing and jaw relationships are part of the actual treatment of malocclusion and thus the dentist's responsibility. Temporomandibular dysfunction is closely related to occlusal dysfunction and to aberrant craniofacial morphology and growth. Therefore, analysis of the temporomandibular joints is an important part of orthodontic diagnosis.
REFERENCES 1. Bloomer H: Speech defects in relation to orthodontics. Am J Orthod 1963; 49:920. 2. Bloomer H: Speech defects associated with dental malocclusions, In Travis, LE: Handbook of Speech Pathology. New York, Appleton-Century-Crofts, 1971. 3. Bosma JF: Second Symposium on Oral Sensation and Perception. Springfield, Ill, Charles C Thomas, 1970, part V, Evaluation of oral sensation and perception in children and adults, pp 300-440. 4, Brandt, D: Temporomandibular disorders and their association with morphologic malocclusion, in Carlson DS, McNamara JA Jr, Ribbens KA (e.ds): Developmental Aspects of Temporomandibular Joint Disorders? monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Cenler for Human Growth and Development, University of Michigan,
',1985.
,~.
5. gushey RS: Adenoid obstruct~on of the nasopharynx, in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 6. Cole RM, Cole JE: Myofunctional therapy in tongue thrust swallow and related problems, in Clark JW (ed): Clinical Dentistry, vol 2. Hagerstown, Md, Harper & Row, 1978, vol 2, chpt 12, pp 1-20. 7. Egermark-Eriksson I, Carlsson GE, Ingervall B: Prevalence pf mandibular dysfunction and orofacial parafunction in 7,
Analysis of the Orofacial and Jaw Musculature 11, and 15-year-old Swedish school children. Eur J Orthod 1981; 3: 161-172. 8. 'Egermark-Eriksson I, Ingervall B, Carlsson GE: The dependence of mandibular dysfunction in children on functional and morphologic malocclusion. Am J Orthod 1983; 83:187-194. 9. Hanson ML, Barnard LW, Case JL: Tongue-thrust in preschool children. Am J Orthod 1969; 56:60-69. 10. Harvold EP: Neuromuscular and morphological adaptations in experimentally induced oral respiration, in McNamara JA Jr (ed): Naso-Respiratory Function nad Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 1,1. Harvold EP, Chierici G, Vargervik K: Experiments on the development of dental occlusions. Am J Orthod 1972; 61:38-44. 12. Harvold EP, Vargervik K, Chierici G: Primate experiments on oral sensation and dental malocclusion. Am J Orthod 1973; 63:494-508. 13. Linder-Aronson S: Adenoids-their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the dentition. Acta OtolaryngoI265(supp!.) 1970. 14. Linder-Aronson S: Effects of adenoidectomy on the dentition and facial skeleton over a period of five years. Transactions of the Third International Orthodontic Congress, London, 1973, p 85. 15. Linder-Aronson S: Naso-respiratory function and craniofacial growth, in McNamara JA (Jr (ed): Naso-Respiratory Function and Craniofacial Growth" monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 16. Miller AJ, Vargervik K: Neuromuscular changes during long-term adaptation of the Rhesus monkey to oral respiration. in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 17. Moyers RE: The role of musculature in orthodontic diagnosis and treatment planning, in Kraus BS, Reidel RA (eds): Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1962. 18. Moyers RE: The infantile swallow. Trans Eur Orthodont Soc 1964;40:180. 19. Moyers RE: Postnatal development of the orofacial musculature, in Patterns of Orofacial Growth and Development, report 6. Washington, DC, American Speech and Hearing Association, 1971. 20. Moyers RE: The development of occlusion and temporomandibular joint disorders, in Carlson DS, McNamara JA Jr, Ribbeps KA (eds): Developmental Aspects of Temporomandibular Joint Disorders, monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. 21. Nesbitt B, Moyers RE, Ten Have T: Adult TMJ symptomatology and its association with childhood occlusal relations: A preliminary report, in Carlson DS, McNamara JA Jr, Ribbens KA (eds): Developmental Aspects of Temporomandibular Joint Disorders, monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. 22. Posen AL: Application of quantitative perioral assessment to orthodontic case analysis and treatment planning. Angle Orthod 1976; 46:69-76.
219
23. Proffit WR: Equilibrium theory revisted. Angle Orthod 1978; 48: 175-186. 24. Proffit WR: The facial musculature in its relation to the dental occlusion, in Carlson DS, McNamara JA Jr (eds): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 26. Solow B, Tallgren A: Head posture and craniofacial morphology. Am J Phys Anthropol1976; 44:417-436. 27. Solow B, Tallgren A: Dentoalveolar morphology in relation to craniocervical posture. Angle Orthod 1977; 47:157-163. 28. Vig PS: Respiratory mode and morphological types: Some thoughts and preliminary conclusions, in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 29. Warren DW: Aerodynamic studies of upper airway: Implication for growth, breathing and speech, in McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth. monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1979. 30. Williamson EH: Temporomandibular dysfunction in pretreatment adolescent patients. Am J Orthod 1977; 72:429433.
SUGGESTED READINGS Bosma, JF (ed): Symposium on Oral Sensation and Perception. Springfield, Ill, Charles C Thomas, 1967. Bosma JF: Second Symposium on Oral Sensation and Perception. Springfield, Ill, Charles C Thomas, 1970. Bosma JF (ed): Third Symposium on Oral Sensation and Perception. Springfield, Ill, Charles C Thomas, 1972. Bosma JF (ed): Fourth Symposium on Oral Sensation and Perception, pub!. NIH 73-546. U .S. Department of Health, Education and Welfare, Bethesda, Md, National Institutes of Health, 1973. Bryant P, Gale E, Rugh J: Oral Motor Behavior: Impact on Oral Conditions and Dental Treatment, pub!. NIH 79-1845. US. Department of Health, Education and Welfare, Public -..;Health Service, National Institutes of Health, 1979. Carlson DS, McNamara JA Jr: Muscle Adaptation in the Craniofacial Region. monograph 8. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1978. Carlson DS, McNamara JA Jr and Ribbens KA (eds): Develop" mental Aspects of Te.mporomandibular Joints Disorders, 'monograph 16. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. Cleall JF: Deglutition: A study of form and function, Am J Orthod 1965; 51:566. Cole RM, Cole JE: Myofunctional therapy in tongue thrust swallow and related problems. in Clark JW (ed): Clinical Dentistry, Hagerstown, Md, Harper & Row, 1978, vol 2, ch 12, pp 1-10. Mason R: Tongue thrust, in Bryant P, Gale E, Rugh J: Oral Motor Behavior: Impact on Oral Conditions and Dental Treatment, pub!. NIH 79-1845. U.S. Department of Health,
220
Diagnosis
Education and Welfare, Public Health Service, National Institutes of Health, 1979. McNamara JA Jr (ed): Naso-Respiratory Function and Craniofacial Growth, monograph 9. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth-and Development, University of Michigan, 1979. Moyers RE: 'The role of musculature in orthodontic diagnosis and treatment planning, in Kraus BS, Reidell RA (eds): Vistas in Orthodontics. Philadelphia, Lea & Febiger, 1962 .
Stelmach GE: Conceptualizing oral motor behavior: An examination of the cognitive and control aspects, in Bryant P, Gale E, Rugh J: Oral Motor Behavior: Impact on Oral Conditions and Dental Treatment, pub!. NIH 79-1845. US Department of Health, Education and Welfare, Public Health Service, National Institutes of Health, 1979. Subtelny JD: Malocclusions, orthodontic corrections and orofacial muscle adaptation. Angle Orthod 1970; 40: 170.
.'
CHAPTER
11
Analysis of the Dentition and Occlusion Robert E. Moyers, D.D.S., Ph.D.
If we could first know where we are and whither we are tending, we could better judge what to do and how to do it.-ABRAHAM LINCOLN
KEY POINTS 1. In addition to direct visual observations of the patient's dental casts, radiographs, cephalograms, and photographs are used in analyzing dental and occlusal development. 2. Calcification is studied by reference to appropriate standards to understand the individual's pattern of tooth formation. 3. Eruption may be predicted by the use of tables of development or by use of crown-root ratio tables.
9. Arch dimensional changes as a result of expected growth must be differentiated from changes which the clinician can (or cannot) make as a part of treatment. 10. It is possible to anticipate some of the several patterns of occlusal change during the transitional dentition. 11. Registration of jaw relationship is necessary during analysis of occlusal development status, but the methods and assumptions differ somewhat from those used in reconstructive dentistry for adults.
4. Congenital absence of teeth may be discerned at the earliest practical time by use of data on the onset of calcification. 5. Tooth size is primarily important when related to the space available and the clinician's ability to increase that space. 6. The Bolton analysis is used.to relate ratios for maxillary versus mandibular tooth sizes, to predict overbite and overjet. 7. The Howes' and Sanin-Savara analyses reveal teeth discordant in size with others and help one understand the clinical consequences of such disharmonies. Pont's Index is of little use for the same purpose, though the diagnostic setup is helpful. 8. A Mixed Dentition Analysis is used to predict the sizes of unerupted permanent teeth and evaluate the probabilities for their inclusion within the arch.
OUTLINE A. .,
Diagnostic data I. 2.
Intra-oral e~amination Dental casts
3.
Radiographs a) Intra-oral periapical survey b) Bite-wing radiographs c) Lateral jaw projections d) Occlusal plane projections e) Panoramic radiographs f) Oblique cephalograms g) Lateral cephalograms Photographs
4.
221
222 B.
Diagnosis
Analysis of tooth development I.
Calcification
2.
Eruption a) Predicting emergence I) Method 1: Use of tables of development 2) Method 2: Wainright's rule b) Sequence of eruption Number of teeth Position of teeth Anomalies
3. 4. 5.
C.
Size of teeth I.
Individual teeth
2.
Size relationships of groups of teeth a) Bolton tooth ratio analysis b) Sanin-Savara tooth size analysis Relationships of tooth size to size of supporting structures
3.
4.
D.
Arch dimensions I. 2.
E. F.
Changes in arch dimensions Asymmetries of arch dimension and tooth position
Prediction of future occlusal relationships Registration of jaw relationships I. 2. 3.
G. H.
a) Howes' analysis b) Pont's Index c) Diagnostic setup Relationships of tooth size and available space during the mixed dentition (Mixed Dentition Analysis) a) Procedure in the mandibular arch b) Procedure in the maxillary arch c) Modifications d) Problems
Retruded contact position Ideal occlusal position Steps in procedure
The temporomandibular joints Relationships of the teeth to their skeletal support
A. DIAGNOSTIC DATA 1. Intra-Oral Examination Most intra-oral features are noted (see Chapter 8). Some pertinent items tition and occlusion can be seen only oral hygiene, gingival health, tongue dental restorations, etc.
in the cursory examination in the analysis of the denintra-orally, for example, size, shape and posture,
2. Dental Casts The record dental casts are one of the most important sources of information for the dentist doing orthodontic treatment, and the time required for their precise construction is time well spent. Technical details of impression taking, cast pouring, and trimming are given in Chapter 18. A good set of dental casts should show the alignment of the teeth and the alveolar processes as far as the impression material can displace the soft tissues (Fig 11-1). From the occlusal view, one can analyze the arch form, arch asymmetry , alignment of the teeth, palate shape, tooth size, tooth shape, ro-
tations of teeth, and other information. While one is holding the casts together in the usual occlusal position, the occlusal relationships can be observed, as well as midline coincidence, attachment of the frena, the occlusal curve, and axial inclinations of teeth. The lingual occlusion can be studied only with dental casts (see Fig 11-1).
3. Radiographs a) Intra-Oral Periapical Survey The periapical survey is useful for any orthodontic diagnosis, for from it may be learned the eruption sequence, congenital absence of teeth, impactions, dental abnormalities, supernumerary teeth, developmental progress of teeth, etc. (Fig 11-2). The intraoral periapical surveyor a panoramic radiograph is an essential part of the permanent record of any case to be treated orthodontically since it defines the exact status of each tooth before therapy. b) Bite-wing Radiographs Bite-wing radiographs, although essential for the detection of interproximal caries, are of little use in the orthodontic analysis. c) Lateral Jaw Projections Lateral jaw projections are useful during the mixed dentition, since they show the relationship of the teeth to one another and to their supporting bone and are an aid in assessing the developmental status and relative eruptive positions of individual teeth (Fig 11-3); however, they are inferior to both the oblique and panoramic radiographs for such purposes. d) Occlusal Plane Projections Occlusal plane projections are used to locate supernumerary teeth at the midline and to ascertain accurately the position of unerupted maxillary cuspids (Fig 11-4). e) Panoramic Radiographs In panoramic radiographs, one can (I) visualize the relationships ·of both dentitions, both jaws, and both temporomandibular joints; (2) study the relative developmental status of the teeth and progressive resorption of primary teeth; and (3) ascertain pathologic lesions. As ordinarily taken, the panoramic radiograph shows differential enlargement and therefore cannot be used for "cephalometric measurements" (Fig 11-::5).
j)
Oblique Cephalograms The oblique cephalometric view, a cephalometric projection of 0f!e side of the face,' is of particular use in analysis of the developing dentition, since it combines most of the advantages of the lateral jaw view, the intra-oral periapical survey, and the panoramic radiograph, plus provides a standardized cephalometric registration that makes possible measurements of bone size, eruptive movements, etc. (Fig 11-6,A). Cephalometric procedures are discussed in Chapter 12. g) Lateral Cephalograms The lateral cephalogram is the orientation most frequently used in evaluating the relationships of the dentition to the osseous
Analysis of the Dentition and Occlusion
FIG 11-1. A good set of diagnostic dental casts. A, right side. B, front. C, left side. D, lingual view. E, maxillary occlusal view. F, mandibular occlusal view.
FIG 11-2. A complete set of periapical
radiographs.
223
224
Diagnosis
FIG 11-3. A typical example of a well-taken
lateral radiograph
of the jaw.
FIG 11-4. An occlusal plane radiograph.
FIG 11-5. Example of one type of panoramic radiograph. In this form, the film must be cut and spliced. The panoramic projection, as can be seen,
provides excellent views in one film of most items to be considered in analyzing a case in the mixed dentition.
Analysis of the Dentition and Occlusion
FIG 11-6. Cephalograms.
A, oblique view; B, typical lateral cephalogram.
FIG 11-7. A and B are good examples of correct extra-oral photographs. (Courtesy of Or. Michael Riolo.) C and D are good examples of intra-oral photographs.
225
226
Diagnosis
skeleton (Fig 11-6,B). Analyses of the lateral cephalogram are used to study morphology and growth, to diagnose malocclusion and craniofacial dysplasia, to plan orthodontic treatment, and to assess treatment progress and quality of result. Many orthodontists consider it the single most important piece of -diagnostic data. Indeed, it is easily argued that the more inexperienced the dentist doing the orthodontics the more use that can be made of analysis of the lateral cephalogram. The postero-anterior cephalogram is less frequently useful in analysis of the dentition. No one treating but the most simple of malocclusions can afford to work without meticulous cephalometric analysis of each and every case. Cephalometric procedures are discussed in detail in Chapter 12. 4. P.hotographs Standardized intra-oral and extra-oral photographs are supplemental to other diagnostic data. Parents and patients usually can interpret conditions and changes during treatment better in photographs than in casts or radiographs (Fig 11-7). Photographs also serve to record changes in appliances used during treatment. Furthermore, some developmental anomalies actually may be visualized better in the intra-oral photograph than elsewhere; for example, mottled enamel, discoloration of enamel due to antibiotic therapy, hypoplastic enamel, and amelogenesis imperfecta.
B. ANALYSIS OF TOOTH DEVELOPMENT 1. Calcification* Calcification standards derived from populations of children (see Fig 6-13) may be used in the following ways: (I) to compare the individual patient to an appropriate population in order to determine whether the dental development is normal, advanced, or retarded; (2) to ascertain whether there are individual teeth developing aberrant to the general pattern; and (3) to predict the time of completion of root development, diminution of pulp size, or intra-oral eruption. Ordinal stages of development, for example those of Nolla9 described in Chapter 6, must not be assumed to describe the same amount of development for each stage. Nor is any stage necessarily exactly the same in one tooth as in another. Such ordinal stages have limited use in research where quantification is necessary but are of help in understanding the dentitional development of an individual child. Before planning any orthodontic treatment in the mixed dentition, it is essential to know the developmental status of each tooth and the probable time each will achieve future developmental stages. The use of group averages simply is not sophisticated enough for a practical clinical analysis. Research is done by the hundreds but treatments are done 9ne by one. The purpose of dentitional evaluation is to evaluate the developmental status of each tooth in one child; therefore, more is learned by comparing the child to itself than to a table of values or norms of a group to which the child does not belong.
*See also Chapter 6.
FIRST MOLAR
CUSPID
FIRST BICUSPID
SECOND BICUSPID
SECOND MOLAR
FIG 11-8. Approximate root development gence, mandibular teeth.
at the time of alveolar crest emer-
2. Eruption a) Predicting
Emergence There is great clinical utility in being able to predict the time of alveolar or gingival emergence. A few useful rules of thumb have been developed for use in practice. All are based on a knowledge of the physiology of eruption (see Chapter 6). £ruptive movements begin when crown formation is completed (see Fig 6-16), the alveolar crest is pierced when a typical stage of root development is reached (Fig 11-8), and occlusion is achieved when root length is almost completed but the apex is still unformed. Yariations from population means are more apt to be due to localized conditions than is sometimes realized; for example, caries or pulpitis in the primary predecessor or gingival and/or periodontal inflammation all hasten resorption of the primary and eruption of the permanent tooth independently of the root length achieved. 1) Method 1: Use of Tables of Development.By referring to Table 6-5, one can, in a crude way, predict the eruption of an individual tooth in the following fashion. First, compare the stage of calcification of the tooth to the mean stage of development for the appropriate chronologic age. For example, if one wishes to predict the time of alveolar emergence of a mandibular cuspid in a 6-year-old girl, one learns by referring to Table 6-5 that, on the average, the root formation has just begun. If the average 6year-old girl has just begun eruption of the mandibular cuspid, it can be predicted that this tooth, in the average girl, will pierce the alveolar crest at age 8, when it achieves approximately 70% of its root length (just past Nolla's developmental stage 8). By comparing the individual patient's deviations from the normal pattern, crude estimates of the time of piercing the alveolar crest and reaching occlusal contact can be made. Note that thes~ estimates are based on alveolar crest, not gingival emergence.
i)' Method 2: Wainright's Rule.Use of Wainright'sl4 Rule, based on data from the patient alone, is quicker, more precise, and more practical. Suppose we wish to predict the alveolar emergence of a first mandibular premolar whose root length equals the crown height (crown-root ratio = I: 1.00); we then locate the appropriate row in the left column of Table II-I,A (change in root: crown ratio per year). We note from the table that only 5% of all first premolars are erupted with this amount of root, 28% have emerged when the ratio is 1:1.25,56% when it is 1:1.50, and so forth. By multiplying the factor 0.30 (found at the bottom
TABLE 11-1.
Analysis of the Dentition and Occlusion
227
Crown Root Ratios and Eruption' A, Mandibiular' ERUPT. ERUPT.N ERUPT.N ERUPI. PREMOLAR SECOND PREMOLAR MOLAR FIRST NMOLAR CANINE 43. 45. 100. 100. 100. 246. 47. 86. 63. 98. 93. 64. 100. 29. 33. 112. 33. 108. . %114. 128. 176. 135. 72. 213. 221. 146. 29. 152. 96. 79. 102. 66. 47. 109. 43. 51. 77. 45. 56. 28. 85. 99. 91. 97. 25. 92. 89. 70. 96. 100. 27. 61. 83. 107. 18. 87. 10. 34. 85. 10. 35. 87. 86. 8. 5 3 38 12. 96. 98. 99. O. 61. 69. 1. 11. O. .1. 3N . 1. 132. 116. 119. 52. 80. 93. 87. 77. 63. 0.26 0.30 0.25 0.37
0.32
FIRST
AS OBSERVED
• Note the root portion of these ratios increases at an annual rate presented in the bottom row. To predict the percent erupted N years from that observed, simply add N times the value in the bottom row to the denominator of the ratio and look up values at the new ratio.
S, Maxillaryt %163. ERUPT. ERUPT.N 10. O. 1. 194. 139. 177. 83. 172. 40. 10. 52. 101. 230. 147. 71. 96. 67. 171. 67. 68. 92. 38. 186. 145. 54. 58. O. 2. O O. O. . 137. 176. 121. 124. 106. 141. 196. 30. 6. 77. 60. 17. 26. 41. 25. 74. 59. 61. 11. 86. 93. 39. 5. 4. 254. 256. 129. 104. 102. 91. 97. 98. 99. 138. 87. 78. 97. 94. 60. 96. 49. 94. 96. 100. 91. 100. 107. 49. 3 30. 99. 9. 100.14. 100. 100.8. 100. 5 6.
SECOND FIRST MOLAR NMOLAR SECOND PREMOLAR PREMOLAR CANINE 74. 147. 185. 153. 155. 156. 121. 92. 28. 4. 6.
FIRST
AS OBSERVED
tTable parts A and B show the percentage of teeth which have been found to be erupted through the alveolar crest for each radiographically crown/root ratio. For example, in the normative growth data set only one mandibular canine out of 77 has penetrated the alveolar process crown/root ratio was 1 to 1.25, yet 100% of 52 cases had erupted when the crown/root ratio was 1 to 3.00.
C, Wainright's
observed when the
Guide:j:
c ...
-------
...
--
) CROWN
..
---------
1:0.5 1: 1.0
33.3 50.0
1: 1,5
60.0
1:2,0
66.7
1,2.5
71.4
113.0
75.0
Crown: Root Ratio
Percent Total Length That is Root
(%Root) :j:A transparency is made of this figure and the transparency is superimposed over the radiographic image of each tooth, so that the axis of the tooth is parallel to the vertical lines and the radiographic crown height exactly fills the stippled area. One can then quickly estimate the crown/root ratio or percent of total tooth length that is prE)sently root length. Use this determined value to learn the percent of a population observed that shows eruption with equivalent root development. Note that the crown/root ratio and the percent root values change in a predictable manner with age. The coefficients at the bottom row of Table 11-1 parts A and B can be used to predict expected root development for each future year.
228
Diagnosis
of the column) by three and adding it to the denominator, the ratio is changed to I: I. 90, the age when approximately 90% of all mandibular first premolars are erupted. In other words, there is a 90% probability of it's being emerged in 3 years, 100% probability of emergence in less than 4 years, 86% in 2 'I; (I. 00 + 30 x 2 '/2 = 1.75), etc.
b) Sequence of Eruption One should always ascertain the implications to therapy of the sequence of eruption exhibited by the patient (see Chapter 6), for certain sequences tend to shorten the arch perimeter, whereas others are useful in retaining arch perimeter. It should not be assumed that any observed sequence of development will persist and.be the exact sequence of emergence in the mouth.
3. Number of Teeth Strange'as it may seem, failure to count the teeth is a common mistake. Counting must include not only the teeth seen but those developing-or not developing-within the jaws. Particular mention should be made of the determination of the congenital absence of teeth. Reference to tables of dental development (see Table 65) provides help in determining the congenital absence of teeth. Table 11-2 provides a very rough guide in simpler form. Variation in development is so great, and is greatest in those teeth most apt to be congenitally missing, that the table must be used with care. In using it in practice remember that girls generally develop teeth earlier than boys, blacks earlier than whites, and that there are strong familial patterns of early and late development. If a child does not show a particular tooth by the date shown in the table the chances are roughly 95 out of 100 that the tooth is congenitally missing. Careful serial study of the trabecular pattern of bone in radiographs of the region is eventually confirmatory, of course, but the idea is to be ready for any necessary clinical intervention at the earliest possible time.
4. Position of Teeth Position of teeth is far better quantified in the cephalogram
TABLE
than in the mouth or on casts but such cephalometric analysis must use cephalometric standards appropriate for sex, age, and even race, a procedure not always done in practice. The position of teeth must be evaluated in the light of the normal position for that tooth at the appropriate stage of development. For example, maxillary lateral incisors flare slightly while crowns of the erupting cuspids are changing their direction of movement toward the occlusion. As soon as the cuspid has uprighted itself and moved off the root of the lateral incisor, the crown of the lateral incisor moves back into alignment in the dental arch (see Figs 6-50 and 6-59). Thus, this slight labial position of the maxillary lateral incisors, called by Broadbent "the ugly duckling stage," is not a malposition in the mixed dentition, but is a malposition in the completed permanent dentition. Simply noting malpositions of teeth is of little use; their significance to anticipated or expected tooth movements must be determined as well (see Chapter 12).
5. Anomalies An immediate decision concerning the effects of any anomalies of development, size, shape, or position of teeth on the anticipated therapy should be made. It is usually a mistake to postpone decisions concerning anomalies.
C. SIZE OF TEETH 1. Individual Teeth When considering the size of teeth, several measurements and concepts seem confusing. Indeed, the word "arch" is used to designate any or all of the dimensions shown in Figure 11-9 (we even say "arch" when we mean archwire). Some definitions may help clarify the important concepts involved. The basal arch is the arch formed by the corpus mandibularis or maxillaris. Its dimensions probably are unaltered by the loss of all permanent teeth and resorption of the alveolar process. It is the arcal measurement of the apical base. The alveolar arch is the arcal measurement of the alveolar process.
The dimensions
11-2.
of the alveolar arch may not coincide
Dental Arch
Estimating Probable Congenital Absence of Teeth TOOTH
Central incisor Lateral incisor Cuspid 1st premolar 2nd premolar 1st molar 2nd molar 3rd molar
MAXILLA
6 18 12 3
months months' months years 4'/2 years' 2'2 years 5 years 8 years'
MANDIBLE
6 6 12 3
months months months years 4'/2 years' 2'/2 years 5 years 8 years'
The figures are conservative estimates based on radiographic observations without respect to sex. The values represent roughly2 standard deviationsfromthe mean time of initiallyobservable calcificationin the radiograph.Those teeth marked with an asterisk are notoriouslyvariable in their development (see Chapter 6, part 6.E.2., number of teeth,fora discussionofgeneticfieldsintoothdevelopment).
Alveolar
Arch
Basal Arch
FIG.1;1-9. The relationship of the three arche&. The basal arch is largely determined by the configuration of the mandible itself. The alveolar arch joins the tooth to the basal arch and thus always is a compromise in size and shape between the basal arch and the dental arch. The dental arch reflects the relationship between the combined sizes of the crowns of the teeth, tongue, lip, and buccal wall function, angulation of the teeth, anterior component of force, etc. When the combined mesiodistal diameters of the teeth are harmonious with the size of the basal arch and the relationship of the maxillary to the mandibular basal arch, the dental arch is synonymous with the combined sizes of the teeth.
Analysis of the Dentition and Occlusion with those of the basal arch if, for example, the teeth are tipped labially off the basal arch. The dental arch usually is measured through the contact points of the teeth and represents a series of points where the muscle forces acting against the crowns of the teeth are balanced. When the crowns are tipped markedly off the basal bone, the dental arch and alveolar arch are not synonymous. The combined mesiodistal widths of the teeth constitute still another measurement. One aims, by orthodontic treatment, for all of the teeth to be so aligned that the combined widths of the teeth will be identical with the dental arch measurement and the dental arch will be well positioned over the basal bone. Then gross differences in the dental arc;h, alveolar arch, and basal arch perimeters will not obscure cosmetics or complicate occlusal function and stability. The distribution of crown sizes for the primary dentition is given in Table 6-3; that for the permanent teeth, in Table 6-6. For orthodontic diagnostic purposes, size of teeth is entirely a relative matter. Large teeth do not always result in a malocclusion, since the available space may be sufficiently large to include them nicely. Simple size of teeth tells little. Comparison of tooth size and available space (see Section C-4, later in this chapter), determination of the effects of the size of the teeth on overbite and overjet (see Section C-2), and the identification of disharmonies of tooth size within the arch are, however, of great clinical import. The localization of intra-arch and interarch disharmonies and their implications to treatment planning are aided by use of the Bolton tooth ratio analysis I. 2 and the Sanin-Savara'2 analysis of mesiodistal crown size (see next section).
2. Size Relationships of Groups of Teeth The precise alignment of teeth and attainment of perfect posterior intercuspation can be frustrating when crown size discrepancies are present. For example, it is not unusual to achieve a perfect Class I molar relationship during orthodontic treatment and yet not be able to achieve a similar cuspid intercuspation because of tooth-size discrepancies in the lateral segments. While left-right symmetry of size is usually assured, the anteroposterior tooth sizes are often not so harmonious. Not only can a single tooth's size discrepancy be troublesome, but the accumulation of minor differences along the arch can produce difficulties in achieving precise occlusion. The examination of the dentition during treatment planning must include the identification of the effects of tooth size, both local and general, upon the ultimate overbite, overjet, and posterior occlusion. Fortunately two practical methods are available to help, the Bolton tooth ratio analysis I. 2 and the Sanin-Savara analysisl2 of mesiodistal crown size. a) Bolton Tooth Ratio Analysis Boltonl. 2studied the interarch effects of discrepancies in tooth size to devise a procedure for determining the ratio of total mandibular versus maxillary tooth size and anterior mandibular versus maxillary tooth size. Study of these ratios helps in estimating the overbite and overjet relationships that will likely obtain after treatment is finished, the effects of contemplated extractions on posterior occlusion and incisor relationships, and the identification of occlusal misfit produced by interarch tooth size incompatibilities.
229
Figure 11-10 is the suggested data form for use in recording and computing both the overall and anterior tooth ratios. The procedure is as follows: the sum of the widths of the mandibular 12 teeth is divided by the sum of the maxillary 12 teeth and multiplied by 100. A mean ratio of 91.3, according to Bolton, will result in ideal overbite-overjet relationships, as well as posterior occlusion. If the overall ratio exceeds 91.3, the discrepancy is due to excessive mandibular tooth material. In the . chart, one locates the figure corresponding to the patient's maxillary tooth size. Opposite is the ideal mandibular measurement. The difference between the actual and the desired mandibular measurement is the amount of excessive mandibular tooth material when the ratio is greater than 91.3. If the ratio is less than 91.3, the difference between the actual maxillary size and the desired maxillary size is the amount of excess maxillary tooth material. A similar ratio (anterior ratio) is computed for the six anterior teeth (incisors and cuspids). An anterior ratio (77 .2) will provide ideal overbite and overjet relationships if the angulation of the incisors is correct and if the labiolingual thickness of the incisal edges is not excessive. If the anterior ratio exceeds 77 .2, there is excessive mandibular tooth material; if it is less than 77 .2, there is excess maxillary tooth material. Bolton Analysis predictions do not take into account the sexual dimorphism in maxillary cuspid widths. Since maxillary cuspids are disproportionately larger in men than in women, an ideal overbite and overjet, as defined by Bolton, is less apt to be achieved in men. When one is contemplating the extraction of four premolars, it is useful, before selecting the teeth for extraction, to ascertain the effects of various extraction combinations on these ratios. b) Sanin-Savara Tooth Size Analysis Scholars at the University of Oregon (Sanin and Savara,'2 and colleagues) devised a simple and ingenious procedure to identify individual and group tooth size disharmonies. It makes use of precise mesiodistal measurements of the crown size of each tooth, appropriate tables of tooth size distributions in the population, and a chart for plotting the patient's measurements. The teeth should be measured with a tooth-measuring gauge or a finely pointed Boley gauge. Table 11-3, A-D displays tooth-size data for North American whites and blacks (see Chapter 6) in percentiles and the charts shown in Fig 11-11 show the way the method reveals the effects of tooth size discrepancies.
3. Relationships of Tooth Size to Size of Supporting Structures a) Howes' Analysis " Howes3.4 devised a-formula for determining whether the apicalbases could accommodate the' patient's teeth. The procedure is as follows. Tooth material (TM) equals the sum of the mesiodistal widths of the teeth from the first permanent molar forward. Premolar diameter (PMD) is the arch width measured at the top of the buccal cusps of the first premolars. Premolar diameter to PMD tooth material ratio (--) is obtained by dividing the premolar
TM
diameter by the sum of the widths of the 12 teeth. Premolar basal arch width (PMBA W) is obtained by measuring, with the bowed end of the Boley gauge, the diameter of the apical base on the
230
20 40 30 90 80 70 MAX M 10 EDIAN 6109.0 068.0 MIN N 17.7 10.0 10.6 52.9 52.1 51.2 9.6 9.3 10.4 10.9 11.2 11.1 55.2 54.1 10.5 10.3 50.7 11.4 56.3 48.5 59.6 11.8 12.2 8.0 53.2 10.1 9.9 10.7 8.9 53.6 11.0 61.0 58.0 18.3 18.0 17.6 17.2 34.4 34.3 33.6 32.3 19.2 18.9 35.7 37.4 19.8 30.8 16.6 20.7 18.4 34.6 18.6 35.2 59.0 10.1 6.86.9 5.4 5.45.5 9.39.4 7.1 6.8 6.6 6.0 7.0 6.9 5.7 7.5 5.3 9.9 33.2 32.9 31.2 35.1 34.1 11.3 11.0 8.7 5.1 29.9 7 9 38.0107.0 11.0 6.6 12.1 7.1 5.2 6.4 6.0 7.0 7.3 5.5 33.4 .8 .2 .1 4.8 7.1 7.3 10.7 5.6 33.7 9.6 107.0 64.0 83.0 67.0 6.76.9 21.8 22.8 5.35.4 31.5 8.4 8.2 9.1 9.0 5.8 7.7 9.8 58.0 56.2 55.8 10.7 8.6 54.5 54.4 53.1 51.1 22.4 22.1 23.6 24.5 5.2 5.0 5.6 30.5 29.4 33.3 23.9 10.0 27.8 47.3 19.4 11.6 59.1 34.7 8.9 4.7 6.8 5.0 6.6 4.6 8.6 7.5 6.5 8.7 55.1 23.2 31.6 6.7 6.6 55.7 8.8 7.6 10.3 9.1 23.3 5.5 32.3 8.78.8 56.7 6.7 6.5 6.3 6.1 7.3 7.2 9.2 9.7 8.5 8.3 8.1 59.9 58.5 56.0 55.0 53.7 61.0 10.4 52.4 8 65.0 6.9 57.3 .5 4.6 7.8 7.0 9.0 57.8 102.0 106.0 5.6 3.7 7.1 6.9 7.2 55.0 7.9 7.8 7.6 7.4 6.4 6.2 23.3 23.2 22.7 21.9 25.1 24.4 25.4 20.5 27.8 6.9 5.5 5.7 6.7 23.6 .9 .4 8.1 6.8 24.0 80.0 69.0 10.110.3 .10.8 9.5 11.1 7.7 10.4 36.2 9.4 8.8 53.5 50.4 49.6 48.7 31.3 18.6 17.3 19.0 17.0 42.3 15.7 21.1 56.0 10.9 7.9 9.5 51.4 17.9 52.2 18.1 9.7 108.0 39.4 86.0 5.9 6 .6 62.0 87.0 32.6 8.4 8.6 26.3 65.0 63.0 53.0 97.00 37.0 38.0 95.0 89.0 98.0 74.0 79.0 97.0 .10.010.1 >:34.5 52.8 33.3, 37.4 42.0 47.0 . 33.634.0 35.3 9,0 2p.6 Diagnosis
Tooth Sizes Arrayed as Oeciles' A, North American White Men TABLE 11-3.
PERCENTILES
FOR TOOTH
SIZE
,
11
MIN TOOTH 20 40 30 70 MAX 90 M 10 EDIAN 6 088.0 80 N 6.7 10.8 10.1 1004 22.5 5.2 6.0 5.9 7.8 7.7 6.9 6.7 11.5 11.3 11.1 7.17.3 6.8 6.5 9.9 9.7 10.2 23.6 23.3 22.8 24.5 8.5 9.2 9.8 804 25.9 5.65.7 7.77.8 904 10.5 5.5 504 5.8 604 704 10.8 10.6 1804 20.1 19.5 19.3 7.9 12.5 5.1 6.2 8.2 25.6 25.1 27.0 8.3 10.7 6.1 12.0 11.6 8.8 8.6 9.5 10.9 9 21.2 1 12.8146.0 8 13.5 7 27.3 27.8 12.5 9.2 604 1904 6.1 7.5 10.3 7.7 5.6 7.0 11.1 704 18.6 7.1 24.0 11.6 .0 2.0303.0 .2 04 .7 .5 .1 4.3 8.8 9.9 6.5 4.7 11.8 5.8 7.6 19.0 7.5 704 1004 5.3 24.3 9.5 11.3 7.2 7.8 10.2 10.3 10.9 8.9 8.7 7.37.5 12.0 10.6 9.1 .9 .3 5.9 10.7 9.2 18.7 18.5 17.9 7.3 7.1 7.0 8.1 18.1 17.8 17.0 23.1 15.2 8.2 6.0 6.1 5.7 9.6 19.5 8.3 8.0 7.2 7.6 7.5 24.3 7.07.0 6.6 7.9 7.1 25.2 9.0 9.6 12.2 9.3 5.5 498.0 344.0 432.0 529.0 351.0 260.0 114.0 74.0 2504 9.0 8 904 158.0 20.2 19.8 18.9 20.6 16.2 6.5 19.1 6.2 323.0 125.0 171.0 106.0 84.0 98.0 23.9 23.2 24.6 21.3 24.8 104.0 82.0 492.0 302.0 162.0 109.0 124.0
231
Analysis of the Dentition and Occlusion
Communicative Disorders (See Garn SM, Osborne McCabe KO: The effect prenatal factors on crown dimensions. Am JAnn Phys Anthrop 1979; Tables 5:665-677.) Ann Arbor, Arbor, Michigan. The and data CStress. and were 0 courtesy extracted of from Professor the Collaborative S.M.RH, Garn, Center Perinatal forFOR Human Project Growth ofof the and National Development, Institute University of Neurological of Michigan, and PERCENTILES TOOTH SIZE
University of Michigan,
"
,.
232
Diagnosis
A 103 105 12 104 106 107 108 109 84.0 80.3 81.3 82.1 83.1 79.4 77.6 85.8 78.5 86.7 87.6 88.6 89.5 90.4 100 101 12 95.0 94.0 95.9 96.8 97.8 98.6 91.3 99.5 92.2 94 95 96 97 98 99 HO 84.9 102 93.1 100.4 Over-all Ratio 12_mm. -Over-all S. D. (0") 1.91 12 43.5 43.0 45.0 40.5 6 42.5 41.5 42.0 41.0 44.5 44.0 Sum maxillary 6_mm. ratio .Range 87.5 - 94.8 If anterior ratio 6_mm. exceeds 77.2: 40.0 Sum mandibular Mandibu lar Maxi Ilary Mandibular Maxillary Mandibular 12_mm. = x 100 = • '!o Mean 91.3 = 0.26 Sum maxillary
638.2 42.1 41.7 41.3 40.9 42.5 39.0 37.4 35.5 38.6 37.8 37.1 34.4 34.0 33.6 33.2 31.3 48.0 49.5 49.0 48.5 46.0 SO.O 54.0 53.0 55.0 54.5· 53.5 51.0 SO. 5 6 6 40.5 40.1 39.8 36.7 35.1 36.3 35.9 30.9 32.0 32.4 31.7 47.0 45.5 47.5 46.5 52.0 51.5 52.5 34.7 39.4 32.8
AnteriorMandibular Ratio Maxillary = -x 100 = Anterior Range 74.5 80.4 Analysis
ratio Patient
Mean S. D. (,,) 77.21.65 = 0.22
'!o
Patient Analysis If the over-all
ratio exceeds 91.3 the discrepancy
is in excessive
mandibular arch length. In above chart locate the patient's maxillary 12 measurement and opposite it is the correct mandibular measurement. The difference between the actual and correct mandibular measurement is the amount of excessive mandibular
arch
Actual mandibular
length.
If anterior Actual mandibular If over-all
12
Correct
mandibular
12
Excess mandibular
Actual maxillary
Correct
maxi Ilary 12
Excess maxillary
B
Correct
mandibular
Excess mandibular
6
6
12
ratio is less than 91.3:
Actual maxi Ilary 12
6
ratio is less than 77.2: Correct
6
Excess maxillary
maxi Ilary 6
6
12
Bolton Tooth Ratio Analysis (Means are in percent units; standard deviations are in parentheses)
Female University 73.5 91.012.8) 73.4 90.6 77.2 91.3(3.5) (3.6) (2.0) (1.7) (1.9) of Michigan
teethSchool Sample
Male Total
Bolton Sample
Anterior
FIG 11-10. (University
Bolton Analysis.'·2 A, the Bolton Analysis of tooth size discrepancies. The sizes of the individual teeth are measured and recorded on the
values.
form.
and
The anterior
B, the figures of ideal
cases.
ratio and the overall
in the Bolton The
ratios
Analysis shown
ratio are computed are based
here
are from
separately.
on selected a normative
samples
sample
of Michigan
Growth
The differences
noted
a contrived
important
ideal.
in setting
The
treatment
Study)
for comparison
are those
sexual goalS
between
differences for overbite
with the Bolton
a normal
noted and
standard
are sometimes overjet.
Analysis of the Dentition and Occlusion A
. "
0 ~ ~
Inc. 1
.. ,
InC.2 c.•. 2 ;)m.t
-
~
Small
Min 10 20
AveroQe I
,
,
;:lm.2
~
C. Pm.2 Inc.2 M.2 M. I
233
8
<0
Small
r-"--,
I
~
I
,
30 40 50 60 70 80 90 Molt
~
1-
~
Large
.
Average I
Large
r-"--,
Min IQ 20 30 40 50 60 70 80 90 Mall.
~ ~ ~
InC.t
~ •• "~
Pm.1
FIG 11-11. Sanin-Savara analysis. A, blank form. 8, an illustrative case. Note the relative. smallness of the maxillary lateral incisor and the man-
dibular second premolar (see Chapter 6, section E.2.).
dental casts at the apices of the first premolars. The ratio of the . PMBAW premolar basal arch width to tooth material (----) is obtained
maxillary incisors. Pont suggested that the ratio of combined incisor to transverse arch width (as measured from the center of the occlusal surface of the teeth) was ideally 0.8 in the bicuspid area and 0.64 in the first molar area. He also suggested that the maxillary arch be expanded 1 to 2 mm more during treatment than his ideal to allow for relapse. In recent years there has been an unfortunate revival of the use of the Pont's Index in a most sloppy and indiscriminate manner; some practitioners depend on it almost entirely for determining the "proper" arch width. Used alone in such an unsophisticated way, it is useless; at best, it is only a very crude guide.
TM
by dividing the premolar basal arch width by the sum of the width of the 12 teeth. Basal arch length (BAL) is measured at the midline (Fig 11-12) from the estimated anterior limits of the apical base to a perpendicular that is tangent to the distal surfaces of the two first molars. The ratio of basal arch length to tooth material BAL (--) TM ' is obtained by dividing the arch length by the sum of the widths of the 12 teeth. Figure 11-12,B shows the mean values and the range of values found for both arches from a study of normal occlusion. Howes3.4 believed that the premolar basal arch width (he called it the canine fossa diameter) should equal approximately 44% of the mesiodistal widths of the 12 teeth in the maxilla if it is to be sufficiently large to accommodate all the teeth. When the ratio between basal arch width and tooth material is less than 37%, Howes considered this to be a basal arch deficiency necessitating extraction of premolars. If the premolar basal width is greater than the premolar coronal arch width, expansion of the premolars may be undertaken safely. Since this method was introduced, rapid palatal expansion has come into more common use (see Chapter 15), and clinicians have much more opportunity to alter the apical base itself than once was thought. Nevertheless, Howes' analysis is useful in planning treatment of problems with suspected apical base deficiencies and deciding whether to (I) extract teeth, (2) widen the dental arch, or (3) expand rapidly the galate. Mandibular apical base restrictions are more critical than maxillary. In the author's opinion, the Howes' analysis is more logical and superior to the Pont's IndexlO (see below) because the Howes' analysis is applicable to eacQ.arch and has been represented as an aid to thoughtful diagnosis and planning while the Pont's Index is often used as a rigid rule and an illogical excuse for not extracting. b) Pont's Index In 1909, Pont 10 devised a method of predetermining an "ideal" arch width based on the mesiodistal widths of the crowns of the
Researchers at The University of Washington applied the Pont's Index to patients who had undergone complete orthodontic treatment and were out of retention for at least 10 years7 No permanent teeth had been extracted in any of the patients. They found very poor correlations between the combined maxillary incisor widths and the ultimate arch width in the bicuspid and molar areas, and concluded that measuring the mesiodistal widths of incisors to predetermine maxillary bimolar and interbicuspid widths is of no value. Mandibular arch form and mandibular intercanine diameter have been repeatedly found to be more reasonable treatment guides for both mandibular and maxillary ultimate arch widths than the Pont's Index. The Pont's Index is naive in concept and, in my opinion, of little use in rational treatment planning. c) Diagnostic
Setup
It is useful in difficult space management problems to ascertain,;. before orthodontic'tleatment is begun, precisely the amount and direction each tooth must be moved. Useful as the Mixed Dentition Analysis is (see Section C-4), it is at best a mathematical representation of the problem during the mixed dentition. A popular practical technique for visualizing space problems in three dimensions in the permanent dentition is that of cutting off the teeth from a set of casts and resetting them in more desirable positions (Fig 11-13). This procedure is called a diagnostic or prognastic setup. The record casts are not used for this technique, since they must be saved for comparison with the diagnostic setup and with progressive record casts.
234
Diagnosis
Relationship of Tooth Material to Supporting Bone
B 98
85 Material (TM) _
8~_(.84r:l\ 78.5
Tooth
Diameter (PMD) Premolar
PT': .%
.... ~7..~..\.~31:9
43.'.,.39.5
::::;::."" ~3.5.. ..... 4~./ 4r ..405.. p;::o~ 51.514r455 ..... 3.6;5..I.3~1
?~..5
.. 39'5l'"Jg5
P';":W.% Le~~~~I(~~t)
.. ":'~'%
r
.
3.7.5
51.5.4r4'5 :3<7:5..
~11:4\.~~
.
3~We55 ..
FIG 11-12. A, Howes' analysis measurements.
8, see text for details of use.
Steps in the technique are as follows: a) Obtain an accurate wax bite (see Section F). Trim the posterior portion of the bases of the casts with the wax bite interposed so the bases are flush (see Fig ll-13,A). b) Drill a hole through the alveolar portion of the cast well below the gingival margin of the teeth. e) Insert a fine saw blade through the hole and cut up to the
crest of the gingival margin between two of the teeth. Cut along the line of the arch, well beneath the gingival margin of the teeth, and come up again at the point of the gingival crest below the contact point on the opposite side of the tooth. Repeat this for all the teeth to be cut off the cast. Do not cut through the contact points. Cutting up to the gingival crest will permit gentle breaking of the plaster without damage.
Analysis of the Dentition and Occlusion
FIG
235
11-13.
The diagnostic setup. A, before, and 8, after the teeth have been cut off and set in a corrected
d) Align the teeth and wax them into the desired positions (see Fig ll-13,B). It is best not to cut off all of the teeth so that the bite relationship can be kept. One may combine the cephalometric analysis and prediction of incisal positioning and angulation with the prognastic setup as a means of visualizing incisorprofile relations and as an aid in the selection of teeth for extraction. A more accurate method involves taking a wax bite in the retruded contact position, mounting the casts on an adjustable articulator, and finishing the diagnostic setup within the limits of the jaw relationships thus imposed (see Section F). When extractions are contemplated as part of the orthodontic treatment, the diagnostic setup will demonstrate vividly the amount of space created by the extractions and the tooth movements necessary to close the space. It will also aid in choosing which teeth to extract.
4. Relationships of Tooth Size and Available Space During the Mixed Dentition (Mixed Dentition Analysis) The purpose of a Mixed Dentition Analysis is to evaluate the amount of space available in the arch for succeeding permanent teeth and necessary occlusal adjustments. To complete an analysis of the mixed dentition, three factors must be noted: (1) the sizes of all the permanent teeth anterior to the first permanent molar; (2) the arch perimeter; and (3) expected changes in the arch perimeter which may occur with growth and development (see Chapter 6). The Mixed Dentition Analysis helps one estimate the amount of spacing or crowding which would exist for the patient if all the primary teeth were replaced by theIr successors the very day the analysis is done, not 2 or 3 years later. It does not predict the amount of natural decrease in perimeter which may occur during the transitional period without the loss of teeth. Many methods of Mixed Dentition Analysis have been suggested; however, all fall into two strategic categories: (1) those in which the sizes of the unerupted cuspids and premolars are estimated from measurements of the radiographic image, and (2) those in which the sizes of the cuspids and premolars are derived from knowledge of the sizes of permanent teeth already erupted in the
position.
mouth. The method presented here is of the latter type and is advocated for the following reasons: (1) it has minimal systematic error and the range of such errors is. known; (2) it can be done with equal reliability by the beginner and the expert, as it does not presume sophisticated clinical judgment; (3) it is not timeconsuming; (4) it requires no special equipment or radiographic projections; (5) although best done on dental casts, it can be done with reasonable accuracy in the mouth; and (6) it may be used for both dental arches. The genetic fields within which permanent tooth size is controlled extend to involve a number of teeth (see Chapter 6); therefore, people with large teeth in one part of the mouth tend to have large teeth elsewhere. A number of researchers have studied the correlative relationships between groups of teeth in the permanent dentition, no one more exhaustively than Garn (see Chapter 6). Very high correlations exist between left-right groups of teeth in the same arch and there is a decreasing correlation gradient, generally from front to back within an arch. Important as these findings are to our understanding of the genetics of tooth development (see Chapter 6) few are of practical use in treatment planning or prediction; exceptions to this statement are the left-right relationships and the correlation between the sizes of the mandibular incisors and the combined sizes of the cusp}ds and bicuspids in either arch, which is high enough to predict the amount of space required for the unerupted teeth during space manageme,nt procedures. Mixed Dentition Analyses have been misused in several ways. First, they have been applied mechanically without proper regard for)~e biologic dynamics~of a critical stage in dentitional developme·nt (see Chapter 6). Second"naive assumptions have been made (e.g., a universal 1.7-mm late mesial shift). Third, many have presumed them to have an accuracy that is not present in any of the methods yet developed. None of the Mixed Dentition Analyses are as precise as one might like, and all must be used with judgment and knowledge of development. See Suggested Readings for articles on errors in these methods and comparisons of different Mixed Dentition Analyses. The mandibular incisors have been chosen for measuring, since they are erupted into the mouth early in the mixed dentition,
e
236
Diagnosis
FIG 11-14. A tooth-measuring
gauge.
are easily measured accurately, and are directly in the midst of most space management problems. The maxillary incisors are not used in any of the predictive procedures, since they show too mu<;h variability in size, and their correlations with other groups of teeth are,of lower predictive value. Therefore, the lower incisors are measured to predict the size of upper as well as lower posterior teeth. a) Procedure in the Mandibular Arch I. Measure with the tooth-measuring gauge (Fig 11-14) or a pointed Boley gauge, the greatest mesiodistal width of each of the four mandibular incisors. Record these values on the Mixed Dentition Analysis form (Fig 11-15). 2. Determine the amount of space needed for alignment of the incisors. Set the Boley gauge to a value equal to the sum of the widths of the left central incisor and left lateral incisor. Place one point of the gauge at the midline of the alveolar crest between
TOTAL SPACE AVAILABLE
cuspid and biscuspids.
Mandible:
Maxilla:
Right
fj ~
b
Left
c
Arch Segments Lengths
Arch Segments Lengths
mm mm mm
e:
Long method.-Experienced clinicians may choose to use the 50% prediction since it is a more precise estimate. Those who are inexperienced or without the use of cephalometrics and a precision appliance method would do well to proceed more conservatively (i.e., use the 75% level of prediction). Prediction of the combined widths of cuspid, first bicuspid, and second bicuspid is done by use of probability charts (Table 11-4). Locate in the left column of the mandibular chart the value that most nearly corresponds to the sum of the widths of the four mandibular incisors. To the right is a row of figures indicating the range of values for all the cuspid and bicuspids sizes that will be found for incisors of the indicated size. For example, note that for mall incisors of 22.0 mm combined width the summated mandib-
Left
Vd
e~h
Right
a:
t: h: g: Total:
mm mm mm
b:
c: d:
mm
Total:
_
TOTAL SPACE REQUIRED
- mm. mm.1 ,
the central incisors and let the other point lie along the line of the dental arch on the left side (Fig 11-16). Mark on the tooth or the cast the precise point where the distal surface of the lateral incisor will be when it has been aligned. Repeat this process for the right side of the arch. If the cephalometric evaluation shows the mandibular incisor to be too far labially (see Chapter 12), the Boley gauge tip is placed at the midline, but moved lingually a sufficient amount to simulate the expected uprighting of the incisors as dictated by the cephalometric evaluation. 3. Compute the amount of space available after incisor alignment. To do this, measure the distance from the point marked in the line of the arch (step 2, above) to the mesial surface of the first permanent molar (see Fig 11-16). This distance is the space available for the cuspid and two bicuspids and for any necessary molar adjustment after the incisors have been aligned. Record the data for both sides on the Mixed Dentition Analysis form (see Fig 11-15). 4. Predict the size of the combined widths of the mandibular
mm.1 mm. MANDIBLE + MAXILLA mm.1
ular cuspid and bicuspid widths range from 22.6 mm at the 95% level of confidence to 18.7 mm at the 5% level. This means that
Class I occlusion of molars (estimated) (measured) and (predicted) bicuspids
of all the people in the universe"whose lower incisors measure 22.0 film, 95% will have cuspid and bicuspid widths totaling 22.6 mm or less. No one figure can represent the precise cuspid-bicuspid
right Estimated possibilities of increasing space available
left
maxilla:
mm
mm
mandible
mm.
mml
FIG 11-15. Mixed Dentition Analysis form.
surp for all people, since. th.ere is a range of-posterior tooth widths seen"even when the incisors are ipentical. The value at the 75% level is chosen as the estimate, since it has been found to be the most practical from a clinical standpoint. In this instance, it is 21 .4 mm, which means that three times out of four the cuspid and bicuspids will total 21.4 mm or less. Note also that only five times in a hundred will these teeth be more than I mm greater than the estimate chosen (21 .4 mm). Theoretically, one should use the 50% level of probability, since any errors would then distribute equally both ways; clinically, however, we need more protection on the down side (crowding) than we do on the up side (spacing).
20.0 24.0 23.5 23.0 22.5 22.0 21.0 20.5 25.5 25.0 24.5 21.5 19.5-20.2 17.8 18.8 18.6 19.2 20.1 21.3 22.2 22.0 21.1 21.7 21.4 22.1 21.8 22.5 21.6 23.0 23.1 22.8 22.6 22.4 23.7 23.5 22.7 23.2 24.2 24.1 20.3 20.8 18.5 19.5 19.3 20.1 20.5 20.3 21.2 21.0 18.9 18.7 19.4 21.5 19.9 20.7 23.3 23.9 22.9 18.2 21.4 20.1 18.7 19.6 18.9 230.1 20.2 20.4 20.67 21.1 20.9 22.1 16.7 18.3 19.7 18.5 17.5 18.1 18.4 2.9 17.4 17.9 128.9 19.1 20.0 19.1 19.7 20.2 20.9 21.9 22.3 20.4 23.6 23.4 20.0 20.4 20.6 21.6 21.2 19.7 17.5 20.0 19.8 19.6 19.3 18.2 18.0 17.7 20.2 19.1 19.0 20.8 19.5 17.2 17.0 18.8 19.2 19.3 18.2 20.6 19.0 18.8 237 17.8 Analysis of the Dentition and Occlusion 19.4:.19.6 2.~.3 obtain wish for 75% distribute thethe horizontal to predictive the prediction choose. normally values row values Ordinarily of forof toward both expected the thus the appropriate Icrowding protects use mandibular width the 75% the of and male the clinician and of spacing, or cuspids probability female maxillary oncrowding and the table. rather cuspid premolars safe Reading isthan side. and a much corresponding the bicuspid Note downward mean more thatwidths. of the serious in50% the mandibular to the appropriate since clinical level although incisors of problem probability vertical the are and values column used you the MALES 95 Probability Tables for Predicting the Sizes of Unerupted Cuspids and Bicuspids' anent mandibular incisors and find that value in A, Mandibular Bicuspids and Cuspids
238
Diagnosis
Space
Method for Localization of Needs In the Mixed Dentition
FIG 11-16. Mixed Dentition Analysis measurements. A, method for localizing space needs. e, marking the distance in the line of arch that is needed for the alignment of central and lateral incisors. This distance shows how much of the arch perimeter will be taken up during alignment of the mandibular incisors. It is repeated for both sides. C, measuring the space left in the arch after incisor alignment. After it has been ascertained how much space is needed for the incisors, it·is necessary to measure the space left for cuspids and premolars and molar adjustment.
Short method.-A shorter, but less precise method has been developed which is of merit,13 but does not allow for sexual dimorphisms with equal accuracy. a) Add the widths of the mandibular incisors and divide by two. b) To the value obtained add 10.5 mm to predict the combined widths of the mandibular cuspid and bicuspids and 11.0 mm to predict the combined widths of the maxillary cuspid and bicuspids. Whether using the long or short method, record the estimated values for the combined cuspid and bicuspid widths in the Mixed Dentition Analysis form for both sides and each arch (see Fig IllS). 5. Compute the amount of space left in the arch for molar adjustment by subtracting the estimated cuspid and bicuspid size from the measured space availablt; i~ the arch after alignment of the incisors. Record these values for each side.
From all the values now recorded, a complete assessment of . the space situation in the mandible is possible.
the width of the lower incisors are used to predict upper cuspid and bicuspid widths. Figure 11-17 illustrates an application of the Mixed Dentition Analysis to a specific problem. note that the localization of any space shortages helps greatly in selection of the space-management appliance. Discussion of the treatment of space problems is found in Chapter 15. It is good practice to study the radiographs when the Mixed Dentition Analysis is done in order to note absence of permanent teeth, unusual malpositions of development, or abnormalities of crown form. For example, mandibular second bicuspids sometimes have two lingual cusps. When they are s~ formed, the crown is larger than might be expected from the probability chart; therefore, a higher predictive value is used. One may, of course, measure the ,size of the crowns of the unerupted cuspid and premolars in periapical radiographs for supplemental information or corroboration of the Mixed Dentition Analysis estimate.
c) Modifications b) Procedure in the Maxillary Arch The procedure is similar to that for the lower arch, with two exceptions: (J) a different probability chart is used for predicting the upper cuspid and bicuspid sum (see Table 11-4) and (2) allowance must be made for overjet correction when measuring the space to be occupied by the aligned incisors. Remember that
A technique for Mixed Dentition Analysis that compensates nicely for radiographic enlargement of tooth images in periapical films is available6 It is based on the assumption that the degree of magnification for a primary tooth will be the same as that for its underlying permanent successor on the same film. (I,) Measure the width of the primary tooth on the x-ray film (Y') and the width
Analysis of the Dentition and Occlusion
239
B TOTAL SPACE AVAILABLE Mandible:
Right
Left Arch Segments Lengths
.,
L ,.3 ':'i' 0
h9'
J.:: I·
f,
'l1 '1
·£;.7·
FIG 11-17.
Arch Segments Lengths
mm mm mm mm
Iq,S IjJ: [
(,.7 ~J., er
'f
Total.
Illustrative case to show the application
mm mm
n.T_
mm mm
TOTA{ SPACE REQUIRED
;'1. 'I ~:'I.LL
~1l.S ~/.
~
S'
;'/.$
~:J'7 MANDIBLE
MAXILLA
:.JLL:L-
-I( ./
:11.5 mm.
width of cuspids and bicuspids (predicted) needed to achieve Class I occlusion of molars (estimated)
Estimated possibilities of increasing space available
"/.5'
mm.
~~._ ~
~mm.
:/,1.{
mm.
and MANDIBLE. In this instance distal movement of the maxillary molars could provide sufficient space to correct the molar relationship and the overjet and overbite (67.4 mm vs 71.5). In the mandible, however, a more serious problem obtains (55.7 mm vs 64.5-64.5 = 21.7 + 21.4 + 21.4) and there is little chance to gain the estimated needed 6.8 mm by increasing the perimeter, even when the molar correction is obtained by maxillary tooth movements alone. "
+
,. :J. S I mm.
right maxilla: ) J. S mandible ----0..Q
~mm.
left
mm.:L..l:~ mm 0.0
mm mm
of the Mixed Dentition Anal-
ysis. A, the patient's casts. S, completed mixed dentition analysis measurements, predictions for probability tables, and estimations from study of casts (molar and overjet correction) are entered into the form. T!1e total arch perimeter needed is entered above MAXILLA
240
Diagnosis
of its underlying permanent successor (X') on the x-ray film. (2) Measure the primary tooth (Y) directly in the mouth or on the dental cast. The width of the unerupted permanent tooth (X) can then be calculated by simple mathematical proportion: X:X' X'Y Y'Y' or w= ~·Y'· For example, if the image of the second primary molar on the x-ray film (Y') is 1O.S mm, the image of the underlying second premolar (X') is 7.4 mm, and the width of the second primary molar as measured on the cast (Y) is 10.0 mm, then X = 7.4 x 10
--IO-.-S- or
X
=
7.0 mm. This procedure is particularly
u~eful
when planning treatment for space supervision problems (see Chapter IS) in which every fraction of a millimeter must be accounted for. Inaccuracy in radiographic tooth size measurements is not the dentist's fault. It occurs because the developing teeth are not always placed exactly at right angles to the central ray; therefore, the radiographic image of the tooth, when slightly rotated or tipped, is significantly larger than the actual size of the tooth. The tables used herein are based on size variations and relationships in teeth of North American whites and mayor may not be valid for other ethnic groups. d) Problems A problem arises when considering the space left for molar adjustment. If this value in the chart is negative, that is, the pre-. dicted sizes of 3, 4, and S are greater than the space left after the alignment of the incisors, then crowding will occur in the arch even without any forward molar adjustment. When the first permanent molars are in an end-to-end relationship (i.e., a flush terminal plane of the second primary molars), approximately 3.S mm of space (one-half a cusp width) is required to convert to a Class I molar relationship. This needed 3.S mm might be acquired, without orthodontic intervention, in any of three ways: (1) 3.S mm more late mesial shift of the mandibular first permanent molar than the maxillary; (2) at least 3.S mm more forward growth of the mandible than the maxilla; or (3) some combination of dental 'J ~SIO I') Ol.?;, 'J/I/ adjustment and differential skeletal growth. Since we cannot yet Perimeter p'erimeter Maxilla Mandible predict accurately the amount of differential skeletal growth that will occur, treatment planning must be based on dental adjustment factors. If differential skeletal growth occurs during this period, alterations in the molar relationship will result and the Mixed Dentition Analysis predictions must be altered accordingly. When there is a Class I molar relationship in the mixed dentition (mesial step of the second primary molars), no part of the arch perimeter need be preempted for molar adjustment and all the space can be made available for incisors, cuspids, and bicuspids. It has become the fashion in-many Mixed Dentition Analysis procedures to assume that every child will require precisely 1.7 mm of late mesial shift. Such fallacious reasoning is unfortunate, since it leads to errors in treatment planning. One cannot assume average mesial shift or leeway space values any more than one can assume average tooth sizes. As was stated earlier, though some children will require no mesial shift of the first permanent molars (Class I molar relationship), the greatest number of children will require approximately 3.S mm late mesial shift or differential skeletal growth (end-to-end molar relationship). It is best to quantify the amount of mesial shift necessary to bring the molars into a >
Class I relationship (see Fig II-IS). The treatment plan is then devised to accomplish the precise amount of correction needed in each arch. Perhaps the most severe limitation of Mixed Dentition Analyses is their inability to reflect the position of the incisors with respect to the skeletal profile. There are a number of crude rules of thumb for determining how much arch perimeter reduction occurs for each degree or millimeter the incisor edge is changed in the cephalometric visualization of treatment. For example, one degree of tipping or I mm of lingual displacement of the mandibular incisal edge is said to be equal to I mm of arch shortening on each side. Useful as such estimates are the simple truth remains: We must use some clinical judgment to fit the Mixed Dentition Analysis into the facial skeleton both at the profile and over the apical bases. A problem is imposed when the occlusal curve is assumed to be a flat plane. Mixed Dentition Analyses assume, by projection to a flat plane, no vertical occlusal curve. Often in the mixed dentition there is indeed a flat occlusal plane, but many times the Curve of Spee is exagerrated or complicated. Enhanced and elaborated occlusal curves are, unfortunately, seen frequently with some of the most severe malocclusions. The arch perimeter is usually longer than it is measured when the Curve of Spee is exaggerated or shows complicated vertical curves. As a result the clinician may assume there is sufficient space for all the teeth until the arch is made level during treatment. Then it becomes obvious that the Mixed Dentition Analysis is a two-dimensional visualization of a complex three-dimensional problem.
D. ARCH DIMENSIONS
,
1. Changes in Arch Dimensions A discussion of the expected changes in arch dimensions during growth and development and methods of measuring arch
--
0??++ -TxTxTransitional ?+ No 0Growth ++ 0-0+Primary 0Skeletal Growth Growth Permanent Tx ,.Growth +0 ?0
•
(El
Width Width
o --
?
10
Plus Skeleta I Growth
Growth
Some + Mild increase occurs or con be obtained Decreases greatly ++ Significant increase occurs or con be obtained Some change possible in particular instances
FIG 11-18. Expected arch dimensional
changes.
Analysis of the Dentition and Occlusion
241
FIG 11-19. Method of using dividers to measure from the median raphe to estimate asymmetries of the dental arches.
dimensions is found in Chapter 6. Clinically, the problem of arch dimensions is how to analyze what space is needed and which dimensions can be increased therapeutically to acquire the needed space. Figure 11-18 summarizes in a simplistic way dimensional changes in the primary and mixed dentitions that occur during growth and those that might be induced with treatment. What nature does and what we are able to do clinically often are different; for example, the mandibular arch perimeter, one of the most critical of all dimensions, usually decreases markedly at the time of exfoliation of the primary teeth and is not easily increased significantly by simple therapy in the mixed dentition. Since maxillary dimensions can be altered much more easily by treatment, it is natural for Mixed Dentition Analyses to emphasize mandibular measurements. Experienced clinicians are able, in some instances, to produce changes in the mandibular arch perimeter which one could never predict from the Mixed Dentition Analysis alone. They can do so because they can discern those cases in which the possibility for incisal or molar repositioning is present and they have the skill and the use of an appliance which makes possible the improvement (see Chapter 15). Figure 11-18 is a conservative guide for use in passive space-management treatment.
E. PREDICTION OF FUTURE OCCLUSAL RELA TIONSHIPS It has been known for some time that predictions of future skeletal relationships are not good predictors of the eventual occlusal relationships. Studies have also shown that the traditional ways of noting the occlusion in the primary and early mixed dentition provide few good clues for the permanent dentition. In Chapter 6 it was noted that while an end-to-end molar relationship (flush terminal plane) was "normal" at the start of the mixed dentition, it offers no proof that either ideal or "normal" development will obtain as the permanent dentition is completed. Moyers and Wainright8 have demonstrated at least five different patterns of occlusal development during the mixed dentition (see Chapter 6). Of these five, three are of particular importance when predicting future occlusal relationships in the early mixed dentition since these
2. Asymmetries of Arch Dimension and Tooth Position Figure 11-19 shows a simple method by which to estimate asymmetries of tooth position in the arch. Figure 11-20 illustrates the use of a symmetrograph to determine asymmetry within the max.illary arch. The symmetrograph, a transparent plastic device with an inscribed grid, may be purchased or made. Place the maxillary cast on its base and carefully mark the median raphe with a series of tiny dots. The medilin raphe is a proper representation of the skeletal midline. Orient the symmetrograph so that its midline is directly superimposed over the median raphe and parallel to the occlusal surface. Total and partial arch asymmetry are quickly visualized and localized, as are drifting, tipping, and rotations of individual teeth. This simple step is most useful in planning individual tooth movements and determining appliance design. A similar analysis of the mandibular dentition is likely to be less precise, since mandibular landmarks are not as reliable as the median raphe.
FIG 11-20. Use of a symmetrograph to determine asymmetry in the dental arch.
"
,
242
Diagnosis I
C
B
D I; (
C
'" "
",
~',,,
"
"9&
"
'"
,8& ~ &
;
,~~ I
A
~~
~ Wj~~) ,&) ~~1&f'"~~~ ~'''' '" ~
(11121
f" 8~']&~ '~8~,,, ,"',
,',
'"
"'B
FIG 11-21, Variations in occlusal relationship
with each molar relationship in the
mixed dentition. A, mesial step. e, flush terminal step. D, Class III (super mesial step).
"
plane. C, distal
three start the same (end-to-end) but finish quite differently. Because normality is seen at one age is no proof it will continue. Many children display an end-to-end relationship in the early mixed dentition and later develop a Class I molar relationship of the permanent dentition. This favorable change is most apt to occur in children who show the following characteristics:" a) Skeletal Morphology The cranial base is shorter than normal. The mandibular plane angle is less than normal. The occlusal plane is flatter than normal. The maxillary length is slightly shorter than normal. b) Skeletal Growth Changes The occlusal plane flatness is maintained. The mandibular plane maintains its flatness. Mandibular length increases are greater than normal. c) Dental Features Maxillary mesial drift is much less than normal. Maxillary first molars are more distally placed than normal. The dental arches are wider than normal. The mandibular first molar is more mesially placed prior to the loss of the primary molars. Some children begin with a normal end-to-end molar relationship and steadily worsen into Class II; we call these "retrusives." They show the following characteristics: ,. a) Skeletal Morphology Occlusal and mandibular planes are steeper than normal. The midface and anterior cranial base are longer than normal, The posterior maxillary height is greater. b) Skeletal Growth Changes Maxillary length increases are greater than normal. Anterior face height increases are greater than normal.
Children who maintain their end-to-end molar relationship through time have been difficult to characterize and identify early except by eliminating the possibility of classifying them as "retrusives" or the more favorable "protrusives." It is most important to note that the amounts of leeway space available in no way discriminates which group a child is apt to join during development. Figures 11-21 and 11-22 are designed to help the clinician estimate what sort of occlusion may result when various combinations of occlusal, arch space, muscular, and skeletal features are seen. Note that this is an aid for use only in the early mixed dentition and is not a substitute for serial observations of change. Deleterious changes should be heeded, particularly when they indicate a "retrusive" Class II occlusal type or a hitherto unsuspected Class III malocclusion. To use Figure 11-22 begin by noting the present occlusal features and assign a tentative occlusal pattern. The columns headed "Leeway Space Difference" and "Lips" itemize aggravating factors which may alter the occlusal change pattern. The columns headed "Skeleton" are those cephalometric measures which are known to influence the occlusal change pattern the most. Pay particular attention to those noted (--) for they in combination dominate. There is no magic formula, no substitute for careful, clinical notation and judgment. It is, however, reassuring to know that careful study and analysis provide a practical clinical payoff. I cannot emphasize too much the need for early study of the cephalogram. "
F.'REGISTRATION OF JAW RELATIONSHIPS The primary purpose of registering jaw relationships for orthodontic analysis is to determine any clinically significant differences in these three jaw positions: the intercuspal position, the ideal occlusal position, and the retruded contact position. It is important to ask at the start which jaw position is to be registered and for what purpose. The ideal occlusal position and the retruded contact position are used for different purposes and should not be
243
Analysis of the Dentition and Occlusion Cl.
.~ -0
'§ .~
::!;
1*
oLL(5
~I::l g~S
------------- ---
-I I-I??- ?-?-----ill -- -i--Ill-I?-I~~ I ??I ill.,., ., K-0.,
+
-x+ -IMax.~ -Plane -?+I7EE. x+ x7IT? x7IT? xn? + +7? 77tsors Leeway ?7Mandibular Space ?x ?+ >1* 7+ + +Occlusal 7IT nIT Flat n* + Flat 7? ??77x+ 17 IT? 0c' n* Heiaht Excessive IT 17 nII Difference Post. ill I? IMand. E.E. IT 1* nm* Steep ill? Mand> nIIT* I Face Steep CIT n* IT3mm m* m* IT
Lips
Favorable
Factor;
o No Likely
Effect;
? x
-
+
EE IJSPids
A-B
CraniofacialPlaneSkeleton
reI.
Questionable
Factor;
- Unfavorable
Factor; - - More Unfavorable
Factor;
Unlikely Observation
FIG 11-22. Summary chart to aid in the prediction of expected occlusal changes. Locate the present molar relationship in the extreme left column then find the patient's
cuspid and incisal relationship
Now reading across in the appropriate
(see Fig 11-21).
sible effects of various other factors; leeway space, lips, skeletal relationship, etc., on the anticipated changes in the original occlusal relationship.
selected row ponder the pos-
confused (see Chapter 5). Neither the ideal occlusal position nor the retruded contact position is necessarily synonymous with the patient's intercuspal position. Many dentists who are particular about registration of jaw relationships on casts are rather casual about the cephalometric occlusal orientation. One should know which jaw relationship was obtained when the cephalogram was exposed. This is especially important for mal occlusions in which there is a strong functional element, patients with a temporomandibular disturbance, and young children whose temporomandibular joints are not fully matured. For such cases it is advised to have a wax bite in place in the mouth when the x-ray exposure is made and to note on the film which jaw registration was used.
1. Retruded Contact Position Every dentist has a favorite technique for recording retruded contact position (centric relation, terminal axis, etc.). It is used in restorative and prosthetic dentistry when it is necessary to mount casts reliably on an articulator. It is used in restorative dentistry, periodontics, and orthodontics as a starting position for occlusal equilibration (see Chapter 18). It is not so precisely useful in children with malocclusion, since mobility or the immaturity of their temporomandibular joint structures often permits a more posterior retruded contact position than will be noted when the patient is older or the malocclusion corrected. Changes in the retruded
contact position (centric reJationship) can and do occur frequently during and after orthodontic therapy-a point often confusing to dentists working primarily with adult patients. Since most patients prefer the wax bite method are reflexly prehensile when biting, illustrated in Figure 11-23 to the usual method for it minimizes sensory input from the incisors. Since no wax touches the incisors, the· tendency of most people to bite protrusively is diminished. The use of a solid sheet of wax is definitely contraindicated, since the tongue is displaced, and accurate recording of the retruded contact position becomes much more difficult.
I
2. Ideal Occlusal Position The ideal occlusal pOSItIOn is a pOSItIOn of muscle balance-on the undeviated path of reflex jaw closure and the position of the jaws during the ,unconscious swallow. Unfortunately, it is rather awkward to say to the pat(ent, "Won't you please swallow unconsciously in order that may record your jaw relationship?" The ideal occlusal position cannot be recorded as reliably as the retruded occlusal position; hence, it does not have practical use for precise restorative and prosthetic construction techniques. The ideal occlusal position is not dependent on teeth as is the intercuspal (usual occlusal) position, nor is it a bony relationship as is the retruded contact position; rather, it is ajaw relationship determined malby a primitive reflex (Chapter 5). When there is a Class occlusion or a functional crossbite, the retruded contact position
I
II
244
Diagnosis
FIG 11-23. Procedure for registering the ideal occlusal relationship in the primary or mixed dentition. A, the original eccentric relationship. e, bite registration wax is rolle.d to form a scroll and adapted to the maxillary cast in the midpalatal region. C, the fit in the maxillary arch. Note the vertical size of the occlusal wax pads. Ordinarily, the wax bite willstay in position by itself, but sometimes it is necessary to reinforce
it with hard base plate wax. Do not use the base plate wax over the occlusal pads. D, softening the occlusal pads. The patient is seated upright with the Frankfurt Plane parallel to the floor. The bite registration wax is introduced into the mouth and the patient is told to close the jaws gently until he or she just feels the wax. (Continued.)
may be of less clinical usefulness than the ideal occlusal position. The ideal occlusal position is used for equilibration procedures in the primary and mixed dentitions (see Chapter 18). It also is used for diagnosis of all functional malocclusions.
into the impression made in the wax by the lower teeth (Fig 1123,D). The wax bite is reinserted and the procedure repeated, usually two or three times, until the jaw has been closed far enough to record the relationship but not so far as to perforate the wax (Fig 11-23,E). The wax insulates the teeth from those of the opposite arch, enabling one to record a late stage in the balanced path of closure (Fig 11-23 ,G). The final wax bite record thus obtained should be kept with the casts as a part of the patien(s permanent records (Fig 11-23 ,F). It also may serve to show the direction and extent of functional malocclusions and those interfering teeth that need grinpi.ng during equilibration procedures in the primary and mixed dentition (see Chapter 18).
3. Steps in Procedure A length of beeswax or special jaw registration wax, 1 cm wide and approximately 13 to 15 cm in length, is rolled from each end a~d adapted across the palate and occlusal surfaces of the posterior teeth on the maxillary cast (Fig 11-23,8). The rolled portion of the wax becomes an occlusal pad into which the mandibular teeth will bite; therefore, the' rolled portion should be flattened and made parallel to the occlusal plane. The wax is removed and the portion directed toward the lower teeth on either side is softened. With the patient sitting upright in the chair and the Frankfurt Plane parallel to the floor, the wax is reinserted into the mouth and the patient instructed to dose the jaws gently until the teeth just feel the wax. The dentist must not guide, direct, or touch the patient's jaws or give directions concerning biting or retruding. The patient is simply told to close the teeth gently until wax is first felt. The wax is then removed and a hot spatula is plunged
G. THE TEMPOROMANDIBULAR
JOINTS
The analysis of temporomandibular function and relationships is essential to orthodontic treatment planning. The arbitrary division of a book into chapters written around discrete topics is a necessary but artificial interference to the thoughtful integration of all aspects of the diagnosis. The patient reader will find a cursory
Analysis of the Dentition and Occlusion
245
FIG 11-23 (cont.). E, the bite wax placed on the maxillary cast after first jaw closure. Usually it is necessary to soften the wax about two or three times and to reintroduce it into the mouth in order to obtain the final registration. Do not let the patient bite through the wax. F, the final wax bite registration. G, the wax bite record in place on the casts. Com-
pare with A. Note that the midlines now coincide. This registration is much more critical anteroposteriorly and mediolaterally than it is vertically. Therefore, it does not matter that the teeth are not in occlusion. Indeed, they must not be or the old, eccentric occlusionship will be recorded instead of the ideal occlusal relationship.
procedure for analysis of temporomandibular function and dysfunction in Chapter 8, The Orthodontic Examination, and more detailed procedures in Chapter 10, Analysis of the Orofacial Musculature. The impatient reader may also argue that analysis of the temporomandibular joint belongs in the chapter on occlusion, but I placed it arbitrarily in Chapter IQ for reasons of logic and avoidance of redundancy.
SUMMARY The dentition and occlusion are analyzed directly by studying the patient and indirectly by studying data such as casts, radiographs, and photographs. Calcification, eruption, congenital absence, tooth size disharmonies, the relationships between teeth and osseous bases, occlusal changes, and other features are quantified and integrated during analysis to plan orthodontic treatment.
REFERENCES H. RE LA TIONSHIPS OF THE TEETH TO THEIR SKELETAL SUPPORT The appraisal of the buccolingual relationships of the teeth to alveolar processes and skeletal support usually is best determined from the dental casts, though the posteroanterior cephalogram is very useful (Chapter 12). The relationship of the dentition to the skeletal profile is done in the cephalometric analysis (see Chapter 12). It is important when using casts for analysis (e.g., the Mixed Dentition Analysis or the diagnostic setup) to keep in mind the relationships of the teeth to their supporting bases and the skeletal profile. Sophisticated diagnosticians try to relate tooth positions on diagnostic casts to their positions in the cephalogram after treatment and growth, a very difficult task indeed given the present state of the art of growth prediction.
I. Bolton W A: Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod 1958; 28:113. 2. Bolton W A: The clinical application of a tooth-size analy. sis. Am J Orthod 1962; 48:504. 3.' R~:.ves AE: A polygon portrayal of coronal and basal arch dimensions in the horizontal plane. Am J Orthod 1954; 40:811. 4. Howes AE: Expansion as a treatment procedure-Where does it stand today? Am J Orthod 1960; 46:515. 5. Huckaba GW: Arch size analysis and tooth size prediction. Dent Clin North Am July 1964, p 431. 6. Hunter WS: Application of analysis of crowding and spacing of the teeth. Dent Clin North Am 1978; 22:563. 7. Joondeph OR, Riedel RA, Moore AW: Pont's Index: Clinical evaluation. Angle Orthod 1970; 40:112.
246
Diagnosis
SUGGESTED 'READINGS 8.
9. 10. 11.
12. 13.
14.
s development, in McNamara lA (ed): The Biology of OciM\yers RE, Wainrightmonograph RL: Skeletal contributions Growth to occlulusal Development, 7. Craniofacial Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977. Nolla CM: The development of the permanent teeth. J Dent Child 1960; 27:254. Pont A: Der Zahn Index in der Orthodontie. Z Zahn Orthod 1909; 3:306. Richardson E, Malhotra SK: Mesiodistal crown dimensions of the permanent dentition of American Negroes. Am J Orthod 1975; 68:157. Sanin C, Savara BS: Analysis of permanent mesiodistal crown size. Am J Orthod 1971; 59:488. Tanaka MM, lohnston LE: The prediction of the size of the unerupted canines and premolars in a contemporary orthodontic population. J Am Dent Assoc 1974; 88:798. Wainright RL: Prediction of alveolar penetrance by mandibular buccal teeth (submitted for publication).
McNamara lA lr (ed): The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977. van der Linden FPGM (ed): Transition of the Human Dentition, monograph 13. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1982. Moyers RE, van der Linden FPGM, Riolo ML, et al: Standards of Human Occlusal Development, monograph 5. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1976. Nanda SK: The Developmental Basis of Occlusion and Malocclusion. Chicago, Quintessence, 1982.
CHAPTER
12 Analysis of the Craniofacial Skeleton: Cephalometries Robert E. Moyers, D.D.S., Ph.D. Fred L. Bookstein, Ph.D. W. Stuart Hunter, D.D.S., Ph.D.
You who wish to represent by words the form of man and all aspects of the ways his parts are put together, drop that idea. For the more minutely you describe, the more you will confuse the mind of the reader and the more you will prevent him from knowtedge of that which you describe. So it is necessary to draw and describe.-LEoNARDO DA VINCI, Notebooks (translation by R.E.M.)
KEY POINTS 1. Cephalometries is a radiographic technique for abstracting the human head into a geometric scheme. 2. Cephalometries is used to describe morphology and growth, to diagnose anomalies, to predict future relationships, to plan treatment, and to evaluate treatment results. 3. Cephalometric comparisons are made to standards, to ideals, or to the subjects themselves. 4. Conventional and standardized methods are used in exposing and tracing cephalograms.
10. Cephalometric limitations and problems include conventions or assumptions, fallacies, and blatant misuses of the method. 11. Future cephalometric improvements can be expected to include technical advancements, new concepts, and innovative applications.
OUTLINE A.
I.
S. The basic elements used in geometric analysis of cephalograms are curves, landmark points, and lines. 6. A cephalometric analysis is. a collection of numbers to compress information from the cephalogram for clinical use. 7. Measurements are made of size and growth, pattern, morphology, deformation, and displacement. 8. Both the measures which comprise an analysis and the cephalometric analysis itself have important characteristics which determine their clinical worth. 9. Different analyses are necessary for different purposes.
Purposes of cephalometries
. 2. 3. 4. 5.
B. C.
Description a) Comparison b) Comparison c) Comparison Diagnosis' ~. Prediction
with standards with ideals with self
Planning treatment Evaluation of treatment results
History Obtaining the cephalogram I. 2.
Cephalometric equipment Conventions in taking cephalograms a) The lateral projection b) The posteroanterior projection c) Oblique projections 247
248 D.
E.
Diagnosis Anatomic structures in the cephalogram Techniques of tracing cephalograms
F.
Geomet?i\ 1. BasilO\elements methods a) Curves 11) Edges of surfaces 2) Curves in space 3) Transversals of surfaces b) Points and landmarks, classified I) True anatomic points 2) Implants 3) Extremal points 4) Intersection of edges of regression as "points" 5) Intersection of constructed lines c) Points and landmarks, described 1) In the lateral projection (a) Unilateral landmarks (b) Bilateral landmarks 2) In the PA projection (a) Landmarks on midline structures (b) Landmarks on bilateral structures d) Lines ("planes") 2. Numerical methods a) b) c)
G.
5.
7.
8.
Why How What I) 2) 3) 4) 5) What
d) Understanding cephalometric I. Definition 2. 3. 4.
6.
use numbers? . do we measure? do we measure? Size and growth Pattern Morphology Deformation Displacement do we do with measures? and using the cephalogramanalyses
Requisites of individual measures in an analysis Requisites of a cephalometric analysis Evaluating morphology (variations in form) a) Basic morphologic analysis I) Purposes 2) Basis 3) Method b) Vertical analysis I) Purpose 2) Basis 3) Method, pattern analysis 4) Method, growth analysis 5) Method,'functional analysis c) Profile analysis I) Purpose 2) Basis 3) Method d) Analysis of symmetry I) Purpose 2) Basis 3) Method An analysis for prediction of morphology
9. 10.
a) Purpose b) Basis c) Method d) Remarks Analysis of growth a) Purpose b) Basis c) Method A method for discriminating Class 11 types a) Purpose b) Basis I) Horizontal types 2) Vertical types 3) Combining horizontal and vertical types a) Method I) Identifying horizontal types 2) Identifying vertical types A method of discriminating Class III types a) Purpose b) Basis c) Method I) Variations in form 2) Profile analysis 3) Vertical analysis 4) Analysis of incisal adaptation 5) Class Ill, summarized Visualizing treatment objectives A method for evaluating the effects of orthodontic treatment a) b) c) .
H.
Purpose Basis Methods I) General effects 2) Regional effects (a) Maxilla (b) Mandible 11. A general assessment of deformation in triangles a) Purpose b) Basis c) Method Some problems and limitations of cephalometries =I. Assumptions a) Symmetry b) Occlusal position c) Orientation on the transmeatal axis d) Adequacy of one or two planar projections 2. Fallacies
a) The f~llacy of false precision b) The fallacy of ignoring the patient c) The fallacy of superpositioning d) The fallacy of using chronologic age e) The fallacy of the "ideal" 3. Misuses of cephalometric analyses I. The future of cephalometrics Appendix: A Brief Cephalometric Atlas A. Overall facial dimensions I. 2.
Vertical distances (facial height) AP distances (facial depth)
Analysis of the Craniofacial 3. B.
c.
Bilateral distances (facial breadth or width)
Regional anatomic dimensions I.
Mandible
3.
Anterior cranial bas
(cranial floor)
Craniofacial 2. Maxilla constants ~
Clinicians are faced with the problem of developing systems of knowledge that are more powerful than common sense, more practical than intuition. Because skeletal dysplasia is associated with a high percentage of severe malocclusions, craniofacial morphology must be analyzed carefully before treatment begins. The analysis is carried out routinely in orthodontics by means of a standardized radiographic procedure called cephalometries. This chapter introduces the reader to the methods, applications, and limitations of radiographic cephalometries in clinical practice. Cephalometries is a technique for abstracting the complexities of the live human head into a geometric scheme. Current practice utilizes a two-dimensional radiographic image on film, the cephalogram. From the cephalogram is derived a cephalometric analysis in which anatomic structures are reduced to landmark points supposed to indicate shapes and relative locations of curves. The input to cephalometries is biology; the output, geometry. The purpose of cephalometries is to interpret this geometric expression of cranial anatomy. Conventionally, it proceeds in two stages. First, the geometric abstraction is "measured" using distances and angles; then, these measures are compared with population standards, ideals, or their own earlier values. From the comparisons emerge "analyses," "predictions" or "forecasts," "facial types," and assessments of "growth" and "the effects of treatment. " In this chapter we explain these current cephalometric conventions, including our reasons for placing so much of the preceding sentence in quotation marks, and introduce certain simpler and more direct methods of arriving at the same goals.
A. PURPOSES OF CEPHALOMETRICS Cephalometries is a tool for dealing with variations in craniofacial morphology. Its purpose is always comparison. In practice these comparisons are made for one of five reasons: (I) to describe morphology or growth; (2) to diagnose anomalies; (3) to predict future relationships; (4) to plan treatment; or (5) to evaluate the results of treatment.
Skeleton: Cephalometries
249
an individual patient is compared; in this sense, they present "normal" form* b) Comparison With Ideals Certain clinicians have also contrived subjective ideals of facial forms for use in clinical comparisons. The difference between standards and ideals is important. Standards are objective measures statistically derived from populations. Ideals are arbitrary, subjective concepts of facial esthetics represented with numbers. They cannot be used interchangeably. Note that the patient is not a member of the population from which the norm or ideal was derived. c) Comparison With Self The patient may also be described by cephalometric comparisons with his or her earlier cephalogram. Comparisons with self involve no notion of "norm" in the sense of an ideal. The findings may be compared· with norms, for "amount" tion" of growth.
or "direc-
2. Diagnosis In orthodontics, diagnosis is the determination of significant deviations from the normal. The diagnostic purpose of cephalometries is to analyze the nature of the problem and to classify it precisely. For instance, cephalometric diagnosis leads to assignment to facial types and classes. Since some aspects of facial morphology are relatively stable under treatment, cephalometric diagnosis contains a strong component of prediction.
3. Prediction Description, diagnosis, and prediction are conceptually and practically quite different. To make a cephalometric prediction is to observe certain quantities, assume they will behave in determinate ways, and extrapolate the consequences. The clinician would like to be able to predict future form in the absence of treatment, then estimate the effects of particular treatments on that prediction. We are not yet able to predict well several important aspects of craniofacial growth, for example, changes in principal directions of growth, the precise onset of periods of accelerated growth, or the cessation of such periods. Therefore, the most practical prediction currently involves the exploitation of "craniofacial constants" to supply predictions of shape approximately independent of net amount of growth remaining.
1. Description Cephalometric description aids ·in the specification, localization, and understanding of abnormalities. (Cephalometries is a description, not a prescription.) The cephalometric description of a patient comprises three kinds of comparisons: (a) comparison with a standard; (b) comparison with an ideal; or (c) comparison with self. a) Comparison With Standards Research populations provide extensive statistics for details of craniofacial morphology and growth. Measures of central tendency-mean, median, mode-are often used as norms with which
4..Planning Treatment, ~. "If the clinician can describe"diagnose, and predict craniofacial morphology, a clearer plan of orthodontic treatment can be derived. All treatment occurs after the initial cephalogram in a face which is constantly changing (and being changed). Clinicians use the cephalogram to define expected changes resulting from growth and treatment and to plan appropriate biomechanics. Planning orthodontic treatment is applied prediction. *These populations usually include cases which would be characterized clinically as malocclusions.
250
Diagnosis
5. Evaluation of Treatment Results Successive cephalograms are used to discern the progress of treatment and to plan any changes in treatment which may seem necessary. Evaluation of treatment results is re.current description and diagnosis.
B. HISTORY By the sixteenth century the artists Diirer and da Vinci had sketched series of human faces with straight lines joining homologous anatomic structures; variations in the lines highlighted structural differences among the faces (Fig 12-1). Much later, anthropologists invented an instrument, the craniostat, for orienting dry skulls, which improved the art of comparisons. But several professions, ours among them, needed a method for studying serial changes; the successive forms of the living head. This required a modification of the craniostat for use with the live patient, that is, a standardized radiographic procedure.
The first paper on on what we today would call "cephalometrics" was probably that by Pacini in 1922." Credit for standardizing and popularizing the procedure goes to Broadbent,IO whose classic paper of 1931 was received with great interest throughout orthodontics. Hofrath IXpublished in German during the same period. Also at that time Simon's31 system of gnathostatics, a method for orienting orthodontic casts, was in use. These ideas from anthropometrics and gnathostatics naturally evolved and fused into a new technology: radiographic cephalometries. Other workers experimented with cephalostats during this period; from Higley'sl7 instrument, for instance, has evolved the design of most modern cephalometers (Fig 12-2).
C. OBTAINING THE CEPHALOGRAM 1. Cephalometric
Equipment
A cephalometric apparatus consists of a cephalostat or head holder, an x-ray source, and a cassette holder (see Fig 12-2).
B
A
.
c
FIG 12-1. Anatomic drawings from Diirer, On Measurement
(circa 1570).
Analysis of the Craniofacial
Skeleton: Cephalometries
251
the left* side of the subject toward the film. The central beam of the x-rays coincides with the transmeatal axis, that is, with the ear rods of the cephalostat. Under most circumstances, the distance from the midsagittal plane to the film is held constant, usually at 7.0 inches (18 cm). (In the Broadbent-Bolton cephalometer, this distance is varied according to the subject.) Constancy of distance from midsagittal plane to film makes compensation for enlargement easier. The patient's head is placed with the Frankfurt Plane parallel to the floor and the subject's teeth together in their usual occlusal position (Fig 12-3). The lateral cephalogram also may be taken with the mandible in its postural position, which may be achieved by exposing the film after the patient has swallowed or has repeated several times the words "Michigan" or "me." If the ear rods are too large or too firmly placed in the external auditory meati or if there is inflammation within the ear, a false mandibular position may obtain.
FIG 12-2. Patient in a cephalometer.
Note use of the lead apron.
Cephalostats are of two types. The Broadbent-Bolton 10 method utilizes two x-ray sources and two film holders so that the subject need not be moved between the lateral and posteroanterior (PA) exposures. Although this method makes more precise threedimensional studies possible, it requires two x-ray heads and more space and it precludes oblique projections. The Higley'7 method, used in most modern cephalostats, uses one x-ray source and film holder with a cephalostat capable of being rotated. The patient is repositioned in the course of the various projections. This method is more versatile, but care must be taken so that the horizontal relationship of the head does not alter during repositioning. The x-ray source must produce sufficiently high voltage (usually above 90 kYp) to penetrate the hard tissues well and to provide good delineation of both hard and soft structures. A small focal spot (frequently obtained by a rotating anode) results in sharper radiographic images. The x-ray film is held within a cassette that usually also contains intensifying screens to reduce the exposure from that otherwise required. In conjunction with the cassette film holder, a fixed or moving grid may be used to produce sharper images. A grid resembles a venetian blind in the open position. It absorbs the secondary (scattered) radiation produced by deflections from the bones and permits only those tays coming directly from the source to proceed to the film. Scattered radiation tends to obscure images, making bony shadows appear fuzzy and landmarks more difficult to locate.
2. Conventions in Taking CephaIograms a) The Lateral Projection The midsagittal plane of the subject's head is conventionally placed 60 inches (152.4 cm) from the target of the x-ray tube with
b) The Posteroanterior Projection The head is rotated by 90 degrees so that the central ray perpendicularly bisects the transmeatal axis (Fig 12-4). In the PA cephalogram it is crucial that Frankfurt Plane be accurately horizontal, beca.use when the head is tilted, all vertical displacements measured are altered. Maintaining the identical horizontal orientation from lateral to posteroanterior projections is critical when comparative measures are made from one to the other. e) Oblique Projections The right and left oblique cephalograms are taken at 45 and 135 degrees to the lateral projection, the central ray entering behind one ramus to obviate superimposition of the halves of the mandible (Fig 12-5). As in the posteroanterior projection, the Frankfurt Plane must stay horizontal; any tipping will alter most measurements. The oblique cephalogram is particularly useful for patients in the mixed dentition.
D. ANATOMIC STRUCTURES CEPHALOGRAM
IN THE
Figure 12-6 is a lateral cephalogram of a skull of a 9-yearold child on which markers have been placed along the sagittal plane of the cranial base and at the suture sites. In addition, the accessible surfaces of the zygomatic bones were covered with thin lead foil. Figure 12-7 is a tracing of the skull shown in Figure 12-6. The major bony structures in the tracings are as follows: a) Sphenoid bone. Figure 12-8 shows in heavy outline those structu'res of the sphenoid bone seen most readily in the lateral and PA cephalograms. ~. 'b) Zygomatie bones. Figure I~-9 depicts the structures of the zygomatic bones ordinarily visualized in the lateral and posteroanterior cephalograms. e) Maxillae. Figure 12-10 shows the maxillary structures as visualized in the lateral and PA cephalograms. d) Mandible. Figure 12-11 illustrates mandibular structures seen 'in the lateral and posteroanterior cephalograms.
*European convention
is the subject's
right side to the film.
FIG 12-3. Typical lateral cephalogram.
FIG 12-4. Posteroanterior Figure 12-3.
cephalogram
of the patient shown in
,.
252
Diagnosis
FIG 12-5. Oblique cephalograms 12-3 and 12-4.
of the patient shown
in Figures
FIG 12-6. Cephalogram of a child's skull with lead markersirl"place (see text). (From Enlow OH: The Human Face.,New York, Hoeber Medical Division, Harper & Row, 1968. Reproduced by permission.)
Analysis of the Craniofacial
Skeleton: Cephalometries
253
254
Diagnosis
FIG 12-7. Tracing the cephalogram shown in Figure 12-6. A = sphenooccipital synchondrosis; B = sphenoethmoidal synchondrosis; C = cribriform plate; C = foramen cecum. The structures traced with dotted lines sometimes are not seen in the radiographs.
FIG 12-8. The sphenoid bone. Left, lateral projection: A = lesser wings; B = greater wings; C = pterygoid processes. Right, posteroanterior projection: A = lesser wings; B = greater wings; C = pterygoid pro-
cesses; 0 = dorsum sella; E = floor of the hypophyseal fossa; F = spheno-occipital synchondrosis. The greater wing at G is the floor of the middle cranial fossa and coincides with the orbital outline.
'"
FIG 12-9. The zygomatic bones. Left, lateral projection:A = zygomatic frontal suture; B = zygomatic temporal suture. Right, posteroanterior pro-
jection; C condyles.
inferior surface
of the occipital
bone;
0
occipital
Analysis of the Craniofacial
255
Skeleton: Cephalometries
RIG 12-10. The maxillary bones. Left, lateral projection: A = frontomaxillary sutures; B = pterygomaxillary fissure. Right, posteroanterior pro-
jection: A = frontomaxillary sutures; B veolar process.
palatal surface; C
al-
O/~\O ."
FIG 12-11. The mandible. Left, lateral projection. Right, posteroanterior projection showing the coronoid process, marked A.
E. TECHNIQUES OF TRACING CEPHALOGRAMS Most cephalometric analyses are made from tracings rather than directly from the cephalogram. (Otherwise, the superposition of successive images is impossible.) For tracing, the cephalogram is taped to a tracing box or x-ray illuminator that has an even, well-diffused light source. Frosted acetate film 0.003 inch thick is taped to the top margin of the film, allowing the tracer to lift the tracing from time to time to inspect the cephalogram. Tracing is easier when done in a darkened room with all of the light box covered by black paper except that portion occupied by the cephalogram. To maintain fineness of line one should use a pencil with a lead 0.3 to 0.5 mm in diameter. The initial (pre-treatment) cephalogram is conventionally traced in black; subsequent films may be traced in a series of colors. Tracing should be systematic. One should begin with a general inspection of the cephalogram, then locate and identify standard landmarks, trace anatomic structures in a logical sequence, and, finally, construct derived landmarks and lines. One cannot obtain accurate cephalometric tracings without a thorough knowledge of the underlying anatomy. Although not every anatomic structure is traced, one must recognize them all in order to locate the important elements. Reference to preceding or succeeding films during trac-
ing improves accuracy. Ahhough bilateral landmarks may be averaged, it is better to draw both right and left shadows.
F.· GEOMETRIC METHODS 1. Basic Elements A tracing has some actual biological information, namely, locations of curves and landmarks. It also contains some nonbiological
information-artifacts-such
as noncurves
(edges of
regression, * such as the symphysis or cragial base) and nonpoints (like Articularet). a) Curves . The curved images in the ct;:phalogram are of three different biologic types: (I) edges of regression; (2) curves in space; and (3) transversals of surfaces.
'Edge of regression, the points on a surface that also lie on the silhouette of the surface as seen from a particular vantage point, e.g., a skyline or the earth's horizon. tSpecific chapter.
landmarks
are described
in Section F-l-c
later in this .
I 256
FIG
Diagnosis
12-12.
Alveolar crest and col. Right, image of an upper molar as seen in a periapical view. Left, the true nature of the "crest" of the alveolar process is seen when viewed at 90 degrees to the central ray. The col is the dip between the buccal and lingual alveolar crests.
1) Edges of RegressionSurfaces.- The edges of surfaces are sometimes properly shown. The anterior border of the coronoid process, for instance, really is a fairly sharp edge (see Fig 12-3). But .sometimes that which we perceive as an edge of a surface is neither an edge nor a horizon. For example, the line we call the "alveolar crest" line represents a col, a saddle-shaped depression in the crest of a mountain ridge (Fig 12-12). 2) Curves in Space.-
In a cephalogram curves are seen but are foreshortened and simplified by flattening: for instance, the image of the mandibular canal in Figure 12-3. The resulting image in not realistic.
3) Transversals of Surfaces.-
Transversals
of surfaces are nei-
ther edges nor true anatomic loci but places where a bone of irregular shape is viewed most parallel to the central ray. Some surfaces are nearly parallel to the central ray and hence appear as a line, a problem inherent in reducing three dimensions to two. Examine, for example, the radiographic shadow of the bony orbit in Figure 12-4 and compare it with a real bony orbit on a dry skull. b) Points and Landmarks, Classified A landmark is a point serving as a guide for measurement. An ideal landmark is located reliably on the skull and behaves consistently during growth. It should not be assumed that all landmarks are equally reliable and valid. The reliability (reproducibility, dependability) of a landmark is affected by the quality of the cephalogram, the experience of the tracer, and confusion with other anatomic shadows. The validity (correctness or use as proof) of the landmark is determined largely by th~ way the landmark is used. Cephalometric points and landmarks are of the following kinds: (I) true anatomic points; (2) implants; (3) extremal points; (4) intersections of edges of regression; and (5) intersections of constructed lines.
1) True AnatomicPoints.- An'atomic "points" are really small regions which might be located on the solid skull even better than in the cephalogram. Each point has its own scale and its own uncertainty in one or two dimensions (Fig 12-13). Examples include the anterior nasal spine (ANS), infradentale (Id), cusp tips The sella (S) or incisal edges (Is), or nasion (Na) (Fig l2-l3,A). is a special case: the single point summarizes an extended curve by its center (Fig 12-13,B). 2) Implants.-
Implants are artificially inserted radiopaque
markers, usually made of an inert metal. They are not landmarks in the usual sense of having a name which identifies their location. They are "private points"; their position from subject to subject is not homologous, making cross-sectional studies of implants very difficult. They may be located more precisely than traditional points and provide precise superpositioning, but they cannot be used to measure accurately any aspect of the single form.
3) Extremal Points.- Extremal points are points characterized by their properties relative to the entire outline: a) Points which are extrema of curvature, for example, incision superius (Is). b) Points whose coordinates are largest or smallest of all points on a specific outline, for example, "A point", "B point," gnathion (Gn), or condylion (Co). These points have less precision of location than true anatomic points. For example, gnathion ("the most anterior inferior point on the chin") moves as the mandible opens and changes its position during development. c) Points defined in pairs, for example, the two Gonions (Go) used to m.easure mandibular width in the PA projection. 4) Intersection of Edges of Regression as "Points.""Points" defined as the intersection of images are really lines looked at down their length. For instance, articulare (Ar) and pterygomaxillary fissure (PTM) are not points at all and are in no way part of the solid skull. Such "points" exist only in projections and are dependent on subject positioning. 5) Intersection of Constructed Lines.- Intersections of constructed lines are used as "points," example, "gonion" sometimes is defined as the intersection of the ramal and mandibular lines. c) Points and Landmarks,
Described
1) In the Lateral Projection (Refer to Figs 12-13,A and B).- Precise definitions of the points and measures used in current cephalometrics lead to improved use in practice. All definitions are from Riolo et al.'o (a) Unilateral Landmarks.Nasion (Na): The frontonasal suture at its most superior point on the curve at the bridge of the nose. Anterior nasal spine (ANS): The most anterior point on the maxilla at the level of the palate. The ANS is of limited use for analyses in the posteroanterior projection, as the actual spine often cannot be seen and its location varies considerably according to radipgraphic exposure, but~1t is useful for vertical measurements. Subspinale (' 'A" point): The lTJostposterior point on the curve between ANS and PR (SPr; see following item). "A" point usually is found approximately 2 mm anterior to the apices of the maxillary central incisor roots. "A" is not an anatomic point, of course. Its vertical coordinate is unreliable and therefore this point is largely used for posteroanterior measures. "A" point is routinely obscured and/or rapidly moving during the eruption of the upper central InCisors. Superior prosthion
(SPr or PR) (also termed supradentaLe):
Analysis of the Craniofacial
c
0
Skeleton: Cephalometries
257
>
..J tt a:: z
FIG 12-13. Cephalometric landmarks and lines (for definitions, see text). A and B, some landmarks in the lateral cephalogram. C, landmarks in the
posteroanterior
cephalogram
(see Fig
12-53). 0,
m~tTic lines used in the lateral cep'halogram.
some cepha!o-
258
Diagnosis
The most anterior inferior point on the maxillary alveolar process, usually found near the cemento-enamel junction of the maxillary central. incisors. Incision superius (Is): The incisal tip of the most anterior maxillary central incisor. • Incision inferius (li): The incisal tip of the most labial mandibular central incisor. .• Infradentale (Id) (also termed inferior prosthion): The most anterior superior point on the mandibular alveolar process, usually found near the cemento-enamel junction of the mandibular central InCISorS. Supramentale ("B" point): The most posterior point of the bony curvature of the mandible below Infradentale and above Pog..onion. "B" point usually is found near the apical third of the roots of the mandibular incisors and may be obscured during eruption of these teeth. When the profile of the chin is not concave, "B" point cannot be determined. Pogonion (Pog): The most anterior point on the contour of the chin. Pogonion usually is located by a tangent perpendicular to the mandibular line or a tangent dropped to the chin from nasion. The astute reader will notice that these three definitions do not quite agree. Gnathion (Gn): The most anterior inferior point on the lateral shadow of the chin. Gnathion may be approximated by the midpoint between pogonion and menton on the contour of the chin. Menton (Me): The lowest point on the symphyseal outline of the chin. Basion (Ba): The most inferior posterior point in the sagittal plane on the anterior rim of the foramen magnum-the tip of the posterior cranial base. Posterior nasal spine (PNS): The most posterior point 0'1 the bony hard palate in the sagittal plane; usually the meeting point of inferior and superior surfaces of the hard palate. Vertical measures using PNS are more reliable than horizontal ones. Sella (S): The center of the hypophyseal fossa (sella turcica). It is selected by eye, since that procedure has been shown to be as reliable as a constructed center. (b) Bilateral Landmarks.The following are bilateral landmarks. Both left and right points are located and used, though some clinicians use the midpoint between the two, an unfortunate convention of less precision. Orbitale (Or): The lowest point of the bony orbit. In the PA cephalogram, each may be identified; in the lateral cephalogram, the outlines of the orbital rims overlap. Usually, the lowest point on the averaged outline is used for the construction of Frankfurt Plane. Gonion (Go): The most posterior inferior point at the angle of the mandible. It may be determined by inspection (see Fig 1213,A). Bisecting the angle formed by the junction of the ramal and mandibular lines, and extending this bisector through the mandibular border, is a method of constructing gonion, but the result is different (see Fig 12-13,B) . Condylion (Co): The most posterior superior point on the condyle of the mandible. Articulare (Ar): The intersection of three radiographic shadows: the inferior surface of the cranial base and the posterior surfaces of the necks of the condyles of the mandible. Articulare
is systematically used for condylion when the latter is not reliably discernible. Note that displacement of the condyle moves articulare. Pterygomaxillary fissure (PTM): A bilateral teardrop-shaped area of radiol ucency, the anterior shadow of which is the posterior surfaces of the tuberosities of the maxilla. The landmark is taken where the two edges, front and back, appear to merge inferiorly. Porion (Po): The "top" of the external auditory meatus. Sometimes, because porion is quite unreliable, the "top" of the shadow of the ear rods is called "machine porion," but it is a quite different point. Porion is taken as the point of contact of the tangent to the meatus from orbitale used in constructing the Frankfurt Plane. Sphenoethmoidal point (SE): The intersection of the shadows of the great wing of the sphenoid and the cranial floor as seen in the lateral cephalogram. Frontomaxillary nasal suture (FMN): The most superior point of the suture where the maxilla articulates with the frontal and nasal bones. FMN is on the anterior cranial base, unlike nasion; therefore, FMN may be preferred when measuring or defining the cranial base.
2) In the PA Projection (Refer to Fig 12-13,C).(a) Midline Structures.-Crista galli: A vertically elongated diamond shape whose location helps establish the Midsagittal Line (A, in Fig 12-13,C). The floor of the hypophyseal fossa (B). The septal structures of the nose (C). (b)Bilnteral Structures.-Frontozygomatic sutures: These are seen as dark lines on a gray background (D). Zygomatic processes: The lateral surfaces can usually be seen (E).
Mastoid processes (F). Gonial areas of the mandible (G). Foramina rotunda (singular. foramen rotundum): In the medial inferior portion of the orbital outlines (H). d) Lines ("Planes") (Refer to Fig 12-13,D) Because cephalometric geometry appertains to the cephalogram we will use the term lines, in order to emphasize their abstract character, though "planes" is in common usage. In reality many of the so-called cephalometric planes are not flat. For instance, the occlusal "plane," drawn in the cephalogram as a straight line, represents a very complicated three-dimensional relationship of • cusp contacts. Most analyses invoke one or more cephalometric lines, usually of the following typ'e,s: ;'1) Lines joining true anatomic points. For instances, the palatal line joins the anterior nasal ;pine (ANS) and posterior nasal spine (PNS). 2) Anatomic tangent lines. • Lines through an anatomic point and tangent to an outline elsewhere. For example, the facial line is defined as joining nasion to pogonion; but pogonion is (usually) just the point of tangency of this line at the chin. • Lines formed by double tangents, that is, lines tangent to a structure, or structures, at two points. For example, the ra-
Analysis of the Craniofacial mal line usually touches the mandible both at th~ posterior border of the ramus and along the condyle; the mandibular line touches both near menton and near gonion, and the Frankfurt "Plane" touches orbitale and porion. Conventionally, cephalometric lines are used to form the rays of angles and to provide orientations for measuring distances. Of. the many cephalometric lines in use, those utilized in'the analyses described later are shown in Fig 12-130 and characterized as follows.
Skeleton: Cephalometries
259
S.O.
3+T 2
3 S.O.
2
+
+
Posterior maxillary line (PM vertical): A line drawn inferiorly from SE along the posterior shadow of the maxillary tuberosity, passing through PTM. Anterior maxillary line (facial line): A line drawn parallel to PN! vertical through nasion (F).
. Upper Maxillary Line (UM): The line through SE and FMN. Palatal line: A line joining PNS and ANS. Functional occlusal line (FOL): A line averaging the points of posterior occlusal contact from the first permanent molars to the primary molars or bicuspids. It makes no reference to incisor and cuspid landmarks. Mandibular line: Several mandibular lines are in use. The usual mandibular line, which cannot always be drawn, is simply a double tangent to the lower border of the mandible. Another mandibular line is doubly tangent to the height of the contour of the lower border of the mandible at the mandibular notch and to the symphyseal curve (near menton). Yet another version is the line joining gonion and menton (E). Although all mandibular lines may provide essentially the same information, the practitioner should choose one and use it. Midsagittal line: A line representing the midline of the head in the PA projection. It is constructed as the bisector of crista galli and the upper nasal septal structures (see Fig 12-13,C). Frankfurt "Plane" (or Frankfurt "horizontal"): The common tangent to the upper external auditory meatus (at porion) and the inferior border of the orbit (at orbitale). Frankfurt "Plane" is traditional and is easy to locate on the actual patient. It is unfortunate that the cephalometric landmarks on which it depends are so unreliable. Sella-nasion:
A line joining sella and nasion.
2) Numeric Methods
During childhood and adolescence many important changes occur simultaneously in the head and face. Careful cephalometric procedures offer an opportunity to segregate and analyze clinically significant developmental events. The measures must be chosen to exclude, as much as possible, whatever confounds or is of little interest. There are four basic questions: (a) Why use numbers? (b) How do we measure? (c) What do we measure? (d) What do we do with the measurements? a) Why Use Numbers? Nothing in the head, including the mandible itself, looks like the tracing of the mandible. The tracing is a simplification of selected portions of the cephalogram, but the tracing is not a quantification. Basically, numbers are used to make fine distinctions. It is not enough to say, "This child has a big mandible." We must be able objectively to relate one person's mandible to
-,+
FIG 12-14. Two cephalometric variables that are normal separately but abnormal when taken together. Note that the variable X is within 1 SO on both the ordinate and abscissa but is outside the ellipse of normality when the two measures are taken together. others of the same age, sex, and ethnic group and even to other parts of the child's own face. A "big" mandible in one 9-yearold North American white boy is "small" in another. We work with quantities, not words. Values are distributed statistically to establish a "normal" range, to identify outlying values, and to detect abnormality objectively. I) The normal range is far more useful clinically than the norm (mean) alone. In analyzing a mandible, for instance, the patient's measures must be compared with the appropriate population range to learn both just how "big" the mandible is and whether other measures are appropriately "big". Some measures show more variance than others, an important clinical point that is concealed if one uses the mean alone. All of the cephalometric procedures presented later in this chapter readily permit comparison of the patient's measures to the normal range as well as to the normal mean. 2) The detection of outlying values likewise serves important clinical functions. Determining the facial measures that contribute most importantly to a skeletal dysplasia to identify an abnormal facial type focuses the mind on sites of primary clinical attention. Extremeness of any variable is a substantive finding with which treatment planning must cope. 3) Abnormality must be detected objectively or it cannot be dealt with practically. Let us consider, for instance, values for a particular patient on two variables, X ana Y (Fig 12-14). Our patient is normal on each variable taken separately, but the combination is abnormal. Cli9.ically, we call this "imbalance," which thee;xperienced clinician intuitively senses from studying the face and cephalogram. When variables' don't go well with one another, they reflect important clinical problems, and a third variable must be devised to measure the imbalance directly. In the analysis of Class 11malocclusions, for instance, if the position of the maxilla is partly characterized by the angle SNA and that of the mandible by SNB, their "difference" is the angle ANB. The angle SNA may be slightly larger than normal and SNB slightly less than normal, yet their difference may be clinically rather large (Fig 12-13, see also Fig 12-15).
260
Diagnosis
A
FIG 12-15. The angle ANB is shown in several different faces of varying morphology. The angle is precisely the same in each, showing its limited discriminatory capabilities. b) How Do We Measure? Reduction of the living head to usable numbers requires a series of simplifications each of which necessarily loses information. 1) Tissue ~ absorption. As the x rays traverse the head with its many tissues, all information is reduced to a single number, the x-ray absorptivity. Variations between tissues having the same absorptivity are ignored. 2) Three dimensions ~ two dimensions. All absorptivities are summed along the paths ofthe x-ray beams, producing densities in a two-dimensional cephalogram: a quantitative picture of areas of varying darkness. Variations along the beam are ignored. 3) Cephalogram ~ tracing. All information about darkness is discarded and replaced by a tracing of edges. 4) Forms ~ landmarks. Much of this information is then cast aside when forms are reduced to landmarks. Information about curving form is discarded as the data are reduced to a configuration of points alone. c) What Do We Measure? A configuration of landmarks and outlines as our ultimate representation of the living head and face can be used to understand natural and clinically planned alterations in form, growth, displacement, remodeling, etc. We do this by measuring in three different ways: • Pairs of points define lengths of line segmentsdistances-the primary use of which is to measure growth (Fig 12-16). • Triples of points define angles and triangles for measuring , pattern (constants), form change, and deformation. (See Figs 12-17 and 12-19.) Some measures involving triples of landmarks may mislead. For instance, an angle which changes (e.g., angle ANB) is difficult to use in analysis unless we can discern whether it is A, N, or B (or some combination) which is changing. ,.
•
e AA'.
•
A
•B'
•BB
•
B'
FIG
12-17.
Triples of points. A, used to form the angle S-N-ANS and to register changes in that angle during growth or treatment. B, used to define a triangle for the measurement of deformation. •
Quadruples of points may be used to study displacements, that is, translations and rotations. The four points must comprise two pairs, each pair at fixed distance (Fig 1218).
1) Size and Growth (Distance Between Points and Change in Distance Between Points).The rearrangements associated with development are many and varied, and include cellular activities, translations of cells and tissues, and increases in size. Of these, increase in size measures-linear distances between
points-is the only one which can fairly be discerned as growth from the cephalogram. There are great variations in the amount of growth in different directions, at different ages, in different parts, etc. Some growth appears as accelerations ("spurts") which are endocrinally mediated such as the increase in mandibular length at pubescence (Fig 12-19). More even increments may reflect remodeling in specific regions as they adapt gradually to primary growth or to translation elsewhere. Irregular, localized growth occurs in response to a change in the immediate environment, as in the area of muscle attachment (when muscle function is altered) or in the alveolar process (during ~ruption of a tooth). Change in distance between two landmarks on the same/structure mayor may not be a measure of growth; change in distance between points on different structures is prob~bly not a measure of growth at all but a complex mixture of developmental activities. Measurement of growth is not as simple as it seems. Deducing
A' A o
B • oD,
C'O) FIG 12-16. Pairs of points defining lengths of line segments. When A' is superposed over A, it is assumed that "growth" is the distance between B andB'.
C2·~.D2
FIG 12-18. Displacement. When registration is made onA-B, C and to displace.
0
are seen
Analysis of the Craniofacial
Skeleton: Cephalometries
261
B mm I11
Mo-N
97
126
CO-GN
114
102
'Regions
of Greatest Constancy
c
98
PTM-A
46 60.0
90.4
120.8 AGE
151.2
181.6
212.0
IN MONTHS
Three growth measures in the same individual
(2026)
75
N_S_GN65~
60 60.0
90.4
120.8
151.2
181.6
212.0
AGE IN MONTHS Three constants in the same Individual (2026)
FIG 12-19. Growth measures and "constants."
A, anatomic regions of greatest
constancy. B, three growth measures in the same individual (subject 2026). (Anatomic abbreviations are shown in Fig 12-13 and defined in the text.) C, three "constants" in the same individual (2026). Note that there are minor fluctuations around 0 change. 0, ratios of dis-
tances. These measures from the Counterpart Analysis (discussed later in this chapter) are used not only to measure effective growth but also to compare relative growth in different parts of the face as both the maxilla and mandible grow. Certain ratios thus show prop~~ionate
growth of theypper
and lower jaws (Table 12-1).
262
Diagnosis
FIG 12-20. Two mandibular registrations of the same growth change. In the upper figure, the registration is on the symphysis and the inferior border. In the lower, the registration is on the condylar region. In the upper figure the mandible appears to grow upward and backward. In the lower it appears to grow downward and forward. Yet each is depicting exactly the same growth. mandibular growth from cranial-base registrations far removed is intrinsically confusing though often attempted. Such distant registrations summate translations, growth, and shape changes for all intervening structures, making it difficult for one to know how much of the total "growth change" is mandibular (Figs 12-20 and 12-21). Aspects of growth may be measured by size comparisons in areas of the face which do not show confounding effects such as displacements between structures. For instance, "total mandibular length," variously measured, is of great interest when studying the effects of Class II treatment. Keep in mind that the vertical displacement of menton from the cranial base is of interest separately, as are ramal height, corpus length, and the angle between them, for they help reveal how total mandibular growth changes may have taken place. Lower face height (lip commissures to chin) is directly perceived by the layman and is thus worth measuring if only for its convenience in discussions with the patient and his or her family. But other aspects of facial form, just as directly perceived, cannot be measured as "sizes" in this way: they are determined as proportions, by points in threes or fours. 2) Pattern (Persistence of Form Through Time).Even during periods of the most active growth, certain aspects of facial form remain relatively unchanged (see Fig 12_19)25.27 We know this intuitively-the facial pattern peJ;I11itsrecognition of a person unseen for many years. We have difficulty in locating important differences among faces from measurement of separation of landmarks only because distances grow over time more or less. Pattern measures, which show relative stability through time, permit certain discriminations not possible with growth measures. The three main kinds of measures which may be unchanging over time are: a) angles (see Figs12-17,A and 12-19), b) proportional divisions (see Fig 12-19), and c) ratios of distances (see Fig 12-19 and Table 12-1)
3) Morphology' (Difference in Form).Form is bounded biologically; cephalometric configurations are collections of landmarks to represent biologic form: But form is easier to name or describe than it is to measure. One may name and measure simple geometric shapes-circles, squares, rectangles-with ease, but there are no circles or squares in the head. It is important to keep clearly in mind the difference between form (shape) and changes in form. Confusion arises in cephalometries by attempting to measure form and form change (deformation) in the same units-degrees or millimeters (see topic 4, Deformation, which follows). In craniofacial diagnosis it is necessary to compare the morphology of a single case with some population standard. This comparison is made to understand how a patient differs from the norm, not to measure the complicated forms which comprise the craniofacial complex. In Section G we suggest referring selected "constants" to their ranges as appropriate for sex, ethnic group, etc., in the diagnosis of the form variations. Study of the relation of the patient to a population in this way will help localize those parts of the face most deviant from appropriate population norms, making differences in form more obvious. Several of the analyses presented later in this chapter make use of pattern measures (constants) to diagnose form differences between the patient and an appropriate population distribution. A more sophisticated tensor method has been devised which makes use of form differences of triangles (see Fig 12-45)2-9 4) Deformation.-
Much of the skeletal change we observe,
FIG 12-21. Superpositioning in the cranial base to assess crudely the overall effects of growth and treatment on the craniofacial pattern.'
263
MALE N FEMALE N so so 12 60 67 1.01 53 50 0.04 .04 0.99 1.04 1.06 1.02 1.05 1.08 1.09 1.10 1.07 36 1.03 1.04 23 60 28 45 47 0.06 52 61 10 12 0.07 0.09 0.08 .07 0.07 0.10 0.08 NA NA NA 0.97 0.99 0.06 42 71 1 62 29 0.05 .02 0.04 1.03 30 67 73 15 48 .10 0.06 0.95 1.00 58 64 0.05 TABLE MEAN 12-1. 67 ular Skeletal Unit (yr) Ratio (B-2 + B-3)/(B-5 + B-6) . MALE Counterpart Analysis Ratios (see Fig 12-28) Maxillary to Mandibular AGE A. Skeletal, Horizontal Dental Unit Ratio (B-1 )/(B-4)
cephalometric analysis, displacement, movement of parts irrespective of size or shape change, must be separated from all other changes. In Fig 12-2], registered on the cranial base, the mandible may appear to have grown, and have been tipped and carried downward and forward, but we cannot read growth, in the mandible or elsewhere, from this diagram. Registration on the symphysis, or on the mandibular canals, may provide a better appreciation of mandibular size change (see Fig 12-20). d) What Do We Do With Measures? The obvious answer to the question of what we do with these data is that we use them to achieve the five purposes discussed in Section A of this chapter. The use of cephalometric measures is the subject of Section G.
G. UNDERSTANDING AND USING THE CEPHALOGRAM-CEPHALOMETRIC ANALYSES 1. Definition A cephalometric analysis is a collection of numbers intended to compress much of the information from the cephalogram into a usable form for diagnosis, treatment planning, and/or assessment of treatment effects. An analysis provides information about sizes and shapes of craniofacial components and their relative positions and orientations.
NA = no data available.
during both growth and treatment, is deformation of form, but the study of such deformations is difficult with most current cephalometric analyses. It is easier to describe deformation of a mandible than to describe its form: shape change is easier to describe than shape itself (see Fig 12-46). Deformation is measured as a pair of size changes in two perpendicular directions. For instance, for all Class II malocclusions grouped, the average change in the triangle S-M-N over normal growth is an extension of 1.14% per year horizontally (along SoN) and 2.14% per year vertically (menton moving straight downward, as in Fig 12-23).5 Changes of all distances, angles,_ and proportions relating S, N, and M can be derived from this single summary. 5) Displacement.(translation, "rotation"; rigid motion relating two pairs of points at fixed separation) (see Fig 12-18).-In
]n practice, the unit of analysis really is the single patient over time, for all cephalometric analyses are intrinsically longitudinal. A cephalometric analysis helps the clinician perceive better four important aspects of craniofacial morphology: a) what the face is now (current morphology), b) what is was (past growth), c) what it will be (expected growth), or d) what the clinician wishes it to be (idealized or corrected morphology). Cephalometric analysis should begin with identification of a problem to be solved, not with selection of an "analysis." Different problems require different solutions, and no one cephalometric analysis is appropriate for all clinical needs. What follows in this section is a list of analyses, like a menu, from which may be selected that most appropriate for a particular clinical need.
2. Requisites
of Individual
Measures
in an Analysis
All cephalometric analyses are collections of measures, norms, and/or ideals which in combination provide information needed for treatment planning, and assessment. The total analysis is depindent on the worth of the individual measures which comprise it and on the adequacy of their combination. a) One should know whether the value to which the measure is compared is a sample mean or an esthetic objective. "]deals" are not "norms." b) One should know how the value, whether mean or ideal, changes with age, how it varies by sex or ethnic group, and how it co-varies with other measures in the analysis. Is the measure a -shaped configuration due to typical measure of growth with periods of acceleration; is it a growth measure showing steady,
"s"
264
Diagnosis
even increments; or is it a "constant" which is relatively invariant? Measures of growth behave differently from measures of pattern, and many traditional cephalometric measures are not good depictors of either pattern or growth. c) Measures which are esthetic objectives shollld be explained as to their origin and clinical application. Ideals are contrived configurations; a value which is "ideal" for one face may be inappropriate for another. Clinicians who prepare and advocate cephalometric ideals are trying to give us images of faces they like, facial shapes to be achieved during treatment. Potential users should ask how the values were determined, how they relate to normal means, and how they vary according to sex, ethnic groups, facial type, and age . .d) When measures are derived from research populations one should know the nature of that population and the variability of the measure. Many measures commonly used show marked changes in value during growth and significant differences between the sexes and among various ethnic groups. As no patient is a member of the sample from which a mean was obtained, the mean is useful only if the sample which it summarizes is appropriate to the clinical comparison. All norms should be described statistically and identified as to the population they sample: the method of sampling must be specified. Furthermore, the norm is properly construed as a range, not a single value (see Fig 12-22). In clinical use, the extent of the range and its changes with facial type and age often are of more practical interest than the simple mean itself. e) For any particular measure one should know the circumstances under which it is systematically misleading. (For instance, anteroposterior [AP] measures of HA" point are consistently misleading during the eruption of maxillary permanent incisors, because "A" point is obscured by the incisors' crowns). fJ For any value of a measure, ideal or not, one must understand the full range of configurations which have that measure (see Fig 12-22). g) Each measure should have a clearly understood subject matter: size, shape, relative position, or relative orientation. Some current measures are mixed in nature, embodying both size and position. A large angle SNA may be due to a long maxilla, a maxilla more ventrally positioned than normal, a short anterior cranial base, or any combination of these factors. As the measure is not specific, the clinician cannot use it for effective discrimination. 11
3. Requisites of a Cephalometric Analysis Our literature offers many so-called "cephalometric analyses." These have several purposes and are of widely varying utility. Here are some criteria to aid in evaluating them. a) An analysis should comprise "a set of measures each of which meets the requirements of individual measures listed earlier (see Section G2). b) The purpose(s) for which the analysis is (or are) intended must be clearly stated-diagnosis, prediction, assessment of treatment effects, etc. c) Each measure in the analysis should have a specific function, and there should be minimal redundancy. A parsimonious set of proper measures is more practical than a large set of poorly selected measures whose purposes are obscure. d) Given the quantities of the analysis for an individual, one
A
Mean 80° S.D. 4° +1 I S.D I .•.\ I I I I I I I I I I I I I I_ -1 76 S.D. 78 74 80 82 84 . I 72
Mean 80° 72
I
74 I
76 I
I
78 I
I
FIG
I
86
88
86
88
S.D. 1° 80
I
I
82 I
84
I
I
I
I
I
I
+ 2 S.D.
- 2 S.D. -3
I
I
-'5$'5.0
S.D.\'"
-1+ 3 S.D.
12-22.
Identical means with different variances.
Note that measures A and
e have
a mean of 80 degrees, but mean A has a SD of 4 degrees and mean B has a SD of 1 degree. Suppose that a patient has the measure A and e, each showing 80 degrees. For measure A, 83 degrees is within the range of normal; for measure e, this is such an extreme measure that it would be seen only about twice per hundred in a normal distribution. Therefore, the same numeric value has clinical significance
for
e, but
not for A.
should be able to reconstruct the major features of the craniofacial form. If this is impossible with a particular analysis, then significant parts of the facial form are unrepresented in it. e) Ideally, faces having the same analytic values would grow in the same way and respond to a particular treatment in a similar fashion. Unfortunately, cephalometric analyses have not yet become that specific in their classifications .. f) Simple combinations of the variables in an analysis ought to segregate similar cases with similar prognoses. g) Treatment which purposefully alters one measure should have predictable effects on other measures. h) Specific measures of the analysis applied to a patient should correspond to particular aspects of of the treatment intervention planned. For example, an XYZ angle of 7 degrees should prescribe one aspect of a consistent, specific therapeutic procedure. But if an angle of 7 degrees means one treatment in one face, and another, totally unrelated treatment in another face, then this measure by itself probably is useless to the clinician. To state that a particular angle "therefore must be reduced 3 degrees" is not a treatment prescription, as it does not tell how to reduce the angle in that particular face. When a patient's measures are close to the mean, the analysis is of lesser importance. Modern orthodontic biomechanics is quite sophisticated, so that the \;linician can camouflage mild skeletal dysplasia by clever treatment involving only tooth repositioning and remodeling of the alveolar process. The most critical test of any cephalometric analysis is the detail it reveals and the clinical insight it provides for patients having several measures far from their expected values. For such patients, routine treatment is inadequate. Should only the mean value be known and no idea of variance given, the clinician cannot know how far from the norm the patient's measures are (see Fig 12-22). One might even regard the means as reasonable treatment goals, but would not do so if important measures were known to be far from their normal values.
Analysis of the Craniofacial 4. Evaluating
Morphology
This is a textbook;
(Variations therefore,
Skeleton: Cephalometries
265
in Form)
we must recommend
(sI TIER
some
cephalometric procedures for clinical use. There is no published advice about designing a best cephalometric analysis (but see Bookstein, 1983, for a not particularly constructive critique of some bad ones). What follows, in this section, is th,e senior author's (REM) personal preference, found suitable in his practice, but not claimed to be optimal. The analyses presented in this section arose from ransacking a large collection of conventional cephalometric variables, including many with other eponymous proponents (e.g., Down's analysis, Tweed's analysis, McNamara's analysis, etc.). We selected those variables that had the smallest mean square for time trend and highest autocorrelation in our data base of Michigan school children aged 5 to 18. Other lists of variables no doubt could be constructed that serve this same purpose as adequately or better; these are Moyers'. The variables utilized display relatively weak time trends and thus will be called "constants" in what follows: "constants" in the sense that the average time trend is small. We do not mean to imply that they do not, in fact, vary, nor that they show no trends in individuals, only that the mean trend of each variable is nearly flat. If we are persuasive in sections A through F, then this Section G should soon be superseded by other analyses more in keeping with the design criteria we set forth earlier.
""7 2"d TIER
ANALYSI~l SYMMETj
3rd TIER
""7 41h TIER TYPING
I
INTEGRATION TREATMENT PLANNING
a
FIG 12-24. Elaborated cephalometric flow chart (see text). lection of serial growth data on North American white children, largely of North European ancestry. The measures may be constant for other ethnic groups-that has not yet been tested-but they would in any case undoubtedly have different means. 3) Method.-
a) Basic Morphologic Analysis
a) Trace the patient's
1) Purposes.This analysis has two purposes: a) Diagnosis. To identify any skeletal basis for the malocclusion by comparison of the patient's skeletal morphology with appropriate standards. b) Screening. To identify the need for more specific cephalometric analysis (Figs 12-23 and 12-24). 2) Basis.-
A small set of selected "constants"
-measures
which are relatively unchanging through time-are used for the comparison. ]8.20 They were developed for this specific purpose from the University of Michigan Growth Study, an extensive col-
lateral cephalogram and measure each of the angles included in the analysis (Fig 12-25,A). An alternative set of measures is provided (Fig 12-25,B) if any landmarks in the preferred set cannot be used. b) Compare the patient's values for each angle with the appropriate Z-score chart* (Fig 12-25 ,C). e) Try to discern the implications of any measure more than I standard deviation (SO) from the mean. In particular, try to understand the effects of combinations of atypical measures. By the end of Chapter 18 you may be able to tell whether they aggravate, compensate, obscure the principal symptoms, which deviant measures can be changed by orthodontic treatment, and which cannot be changed, but can be masked by treatment. cl) Any measure or combination of measures deviating significantly from the mean signals the need for another more specific analysis.
b) Vertical Analysis 1) Purpose.The purpose of vertical analysis is to localize and quantify any vertical skeletal contributions to the malocclusion.
j
"
2) Basis.-
A selected set of, "constants'
, (except those using
1 x-x
*The Z score for a variable X is the new variable ---
. It has a
Sd (X)
FIG 12-23. Basic flow chart for cephalometric analyses. The Basic Morphologic Analysis is used first to discern which other analyses may be necessary for a specific patient.
mean 0 and a standard deviation ] (see Chapter I) and so purports to allow deviations from "normal" on diverse variables to be compared on a common (dimensional) scale. Any variable that is a score of 1.96 is thus "equally abnormal" (in this sense) regardless of the original variable irrespective of the units of the original measure. Therefore, measures, even if in different units (e.g., degrees and millimeters), can be compared.
266
Diagnosis
B
c
FEMALES -15.0.X ISD. 2
MALES
-3
Crania/ Bos~ Ba-SE-FMN
-2
-tS.D X
15.0. 2
3 I .u. 155,
1
Ba-S-Na
II~ 1
Crania/Base-Maxilla S-N-A
I 751
I
SE-FMNA
-3
-2
': .• ",
J. ....
I•... ,I., ,I... ,I. ..•. ~.
1'25 130 135 140.0 'I' , ,11 . , , ,I. , , , I 120 125 130.2 I
I, ..145h,
~
~ 90
85
3
95
135
I~ 155, .• J I . , . ,. , 140 1'45 i
~
W1 110
105
I
Crania/Bas8-Mandiblt1(H) Ba-SEeMe
55
60
Ba-SE-Pag
60 I
65
80
Crania/ Base-Mandible(Vj Ba-SE/Mand.
Line
55
1
60
PM Vert /Mand. Une Maxilla-Mandible Mend. Line/A - B Fl.flCl.Occl.Ln./A-B (not
0
cooslont)
Skelelal Profile FMN-A'B
1145
,
FIG 12-25. Basic Morphologic Analysis. A, preferred measures. B, alternate me~sures. C, Z-score chart for use in practice. The patient's exact measures taken from the cephalogram are recorded on the appropriate scales according to sex. Note that the mean values are arrayed
the functional occlusal line) and measures of relative stability from the same data as the Basic Motphologic Analysis (Michigan Growth Study). ,. 3) Method,
Pattern
Analysis.-
a) Trace the lateral cephalogram
and construct the PM vertical, upper maxillary, palatal, functional occlusal, facial, and mandibular lines (see Figs 12-13,D and 12-26). b) Measure the anterior-superior angles where the PM vertical line intersects the other lines. c) Refer to Figure 12-26,B to identify those measures which deviate from the standards. Note that the angle to the Functional
in the center of the scale and range out
±3
SO on either side. In
this fashion, one can quickly discern those basic skeletal measures of clinical significance.
Occlusal Line is not a constant, but it is clinically important to note, bow the occlusal and~'alveolar regions have adapted to the unfolding skeletal pattern of growth. Note too that the more stable lines are in constant relationships, but the rate or duration of growth along those directions varies, hence the need to do a vertical growth analysis when the pattern is shown to be abnormal and during pubescence (see Tables 12-3,A to 12-3,J in the Appendix. 4) Method, Growth Analysis.Rigid proportionate relationships of face height are often presumed or presented as treatment ideals. Natural age changes and important sex differences (especially during and after pubescence) in facial proportions are
Analysis of the Craniofacial
Skeleton: Cephalometries
267
A
FIG 12-27. The effects of mandibular position on the profile. The dotted line shows the mandibular postural position; the solid line, the occlusal position. Note the improvement in the skeletal profile when the mandible is "at rest."
12-3 which presents mean values and standard deviations of all usual facial height measures (see Fig 12-48) for both sexes from age 4 to 18 years as well as several similar statistics for the most frequently used facial proportions. Such comparisons help define desired treatment changes.
B90
- --
.. 3' -\5.0. -2 2X .. 15.0.
MALES
VERTICAL
ANALYSIS
PM Vert/FMN-SE
-3
'~85
Maxilla PM Vert/Pal.
line
MAlES
90
95
5) Method, Functional Analysis.Vertical analysis should include the skeletal relationships when the teeth are occluded and apart in the mandibular postural position (Fig 12-27), particularly if a large interocclusal distance was noted during the cursory examination. Differences in these two mandibular positions affect diagnosis and treatment planning, particularly in young children with Class II malocclusion, Class. III malocclusion, and/or excessive vertical overlap (see Chapter 15).
I
FEMALES
85
90
100
105 1110
c) Profile Analysis
Occlusion PM Vert
10eel. Line
(not a constant
MAlES
in Class D)
~5
FEMALES .j..... 175
I
100 1051 110
I
Mandibl. PM Vert/Mond.
115
Line
MAlES
FEMALES
FIG 12-26. 'Vertical Analysis. A, lines and measures of Vertical Analysis I(pattern analysis.). B, Vertical Analysis I (pattern) Z-score chart. ignored in such narrowly defined "ideals." Study of the graphs of height changes presented in the Appendix to this chapter is a useful supplement to sensible ~~e of any vertical cephalometric analysis. Growth in face height is much more varied and complicated than may be realized. For example, Figures 12-49 and 1250 and Table 12-3 show distinct sexual dimorphisms in growth of some facial height measures (particularly in adolescence), changes in facial proportions with time, and significant differential timing of decelerations in facial height increments. If the vertical pattern analysis reveals abnormality in any angle of at least one standard deviation, use the vertical growth analysis to aid in localizing any disproportions. Compare each of the patient's measures to Table
1) Purpose.The purpose of the Profile Analysis is to evaluate the craniofacial skeletal and dentoalveolar profiles and to localize the regions contributing to any "imbalance," that is, obvious retrognathism or prognathism of either jaw. Several studies, notably those of Graber's and Lucker,22 found that a straight profile is considered more pleasing at all ages. 2) Basis.The analysis presented here is derived from the Counterpart Analysis devised by Enlow et al. (Fig 12-28).13 They found the ratio of maxillary to mandibular skeletal and dental unit distances to be relatively invariant, with a mean value quite close to 1.0 for both sexes (Table 12-1).
":. 3)Method.-" " a) At lines parallel to the functional occlusal line measure the distance to PM vertical from "A" point, superior prosthion, inferior prosthion, and "B" point (see Fig 12-28). b) Compare maxillary unit distance, skeletal, with mandibular unit distance, skeletal. In Fig 12-28 this becomes (B2 + B3)/(B4 + B6). e) Compare the maxillary and mandibular unit distances, dentoalveolar; in Fig 12-30, this is (Bl + B3) = (B4 + B6). cl) Study the soft-tissue profile and occlusal relations at the
268
Diagnosis
5. An Analysis for Prediction of Morphology
FIG 12-28. The Profile Analysis (modified Counterpart Analysis). The complete array of counterpart measures are shown in Fig 12-19,0. (From Enlow OH, Moyers RE, Hunter WS, et al: A procedure for the analysis of intrinsic facial form and growth. Am J Orthod 1969; 56:6-23. Reproduced by permission.) postural and occlusal positions to identify mandibular translations on closure and opportunities for clinical utilization of the interocclusal distance (see Fig 12-27). This is especially important in some Class 11treatments. (See Chapters 15 and 16 and also Section G-9 later in this chapter.) e) Try to estimate the effects on the unit distance ratios and the profile of altering any of these distances or angles (see Section G-5). A further simplified version is sometimes used for analysis of the profile of "nongrowing" adult patients (see Fig 12-40). See Chapter 17 for its application in orthodontic treatment of older patients with malocclusions complicated by periodontal disease and/or loss of teeth.
Some introductory comments are necessary on the prediction of craniofacial growth, a popular topic these past few years.'9 Properly defined (see Section F-2-c), craniofacial skeletal growth measures are very difficult to predict precisely enough for practical use. Clinically we would like to be able to predict accurately for one specific individual (I) the amount of remaining growth of critical anatomic parts, (2) the timing of important growth events, such as the onset and cessation of the pubescent growth" spurt," (3) "growth vectors" and their changes in any conventional registration, and (4) the specific effects of orthodontic treatment on craniofacial growth. But at this time these characteristics of growth are not predictable-some are not even defined or definable, e.g., growth vectors and changes in growth vectors during treatment. Most current "growth predictions" or "forecasts" based on one cephalogram are too crude to be clinically useful." Practical prediction of craniofacial skeletal growth is not yet available. In the meantime, prediction of skeletal morphology is u~eful and simple. a) Purpose The method described here has as its purpose the estimation of the future relationships of the most stable and least adaptive parts of the face. It does not predict how the alveolar and other adaptive areas will behave, when growth in a particular direction will change its rate or stop, nor does it predict the effects of treatment on growth or morphology. It simply displays how the most important stable regions will likely relate to one another in the future. That display makes possible a better visualization of treatment objectives (see Section G-9, Visualizing Treatment Objectives,
later in this chap~er).
d) Analysis of Symmetry B
A
1. Purpose.-
Analysis of symmetry is done to identify any mediolateral skeletal asymmetry which might be related to the malocclusion. Asymmetry may be either dysplastic (i.e., part of the fundamental morphology) or compensatory or adaptive to accidents, trauma, or alterations in the functional environment.
2. Basis.- Left-right symmetry is generally presumed. Since we do not yet know the amount considered clinically significant for particular malocclusions (e.g. crossbite), the basis for this analysis is somewhat different than most, and these comparisons are within the patient, not to standards. It must be remembered that this procedure detects only two-thirds of the asymmetries for it ignores those in the AP direction.
\\J
" I I \
:
DK
I".
12-6
'J L
--.-
3
3. Method.a) Trace the PA cephalogram, locating all structures shown in Fig 12-13,C, and construct the midsagittal line. b) Measure distances at right angles to the midsagittal line for the skeletal landmarks shown in Fig 12-13,C, noting left-right differences vertically and mediolaterally (see Table 5). c) Measure the distances to dental landmarks of particular interest, for example, the dental midlines, the positions of individual teeth, etc. (Fig 12-29).
FIG 12-29. Analysis of symmetry. A, registering on the shadows of crista galli and its immediate region, an arbitrary midsaggital plane is drawn. The structures on the left side of the head are traced as shown, then the cephalogram is turned over and the structures on the right side are traced, thus permitting the superpositional observation of localized asymmetry. e, measurement of asymmetry both horizontally and vertically in the posteroanterior cephalogram.
Analysis of the Craniofacial A
Skeleton: Cephalometries
269
c
E
F
Ba
FIG
12-30.
Prediction of future morphology. A, summary sketch of procedure. S, method for estimating the position of the mandible after growth. C, method for estimating cranial base change anteroposteriorally. D,
b) Basis This analysis approximates average growth changes as extensions at the average rates along directions which do not, on average, rotate with respect to cranial base. Other ways of carrying out this same purpose are more precise but more complex5. 7
composite to show effects of cranial base prediction on maxillary prediction. E, method for estimating maxillary position after growth. F, composite prediction of growth.
d) Holding the angle SE-FMN-A constant, register on the just estimated predicted position of FMN and extend the line FMN-A the distance indicated in Table 12-6 for the correct age and sex and the time period to be predicted. Then trace the outline of the palate and central incisor (Fig 12-30,0 and E). e) Figure 12-30,F displays the complet~ traced prediction.
c) Method
'.
a) Complete the Basic Morphologic Analysis of the lateral cephalogram (see Section G-4-a.). ,. b) Holding the angle Ba-SE-Me "constant," extend the line from SE to Me by the distance indicated in Table 12-6 (see Appendix) as the average amount for the patient's age and sex for the time period to be predicted, and trace the outline of the mandible and the mandibular first molar (Fig 12-30,8). c) Extend the line SE-FMN the distance indicated in Table
a) Purpose The purpose of growth analysis is to assess the patient's growth by comparison with appropriate standards.
12-6 the average amount for the correct age and sex for the time period to be predicted, and trace the nasal bone and forehead region (Fig 12-30,C).
The tendency for children to maintain the same relationship to normative values during growth is called canalization or channelization. This relative stability is better for constants, of course,
6. Analysis of Growth
b) Basis
270
Diagnosis
but it is far less certain for growth measures; hence, the need for regularly monitoring them. The standards of The Univers}ty of Michigan Growth Study2) are the source of the tables of selected growth measures presented in the Appendix to this chapter. These standards were derived from an extensive collection of serial growth data on North American white children largely of North European ancestry. The values cannot be assumed to be pertinent for children of other ethnic origins and circumstances. Reference to Riolo et al. 23 is recommended for readers seeking information about normative age means and variances of measures not listed in the Appendix to this chapter. c) Method a) Measure the distance as defined. b) Compare the patient's value with those in the appropriate table in the "mini-atlas" at the end of this chapter (Tables 123,A to 12-3,1, Tables l2-4,A to l2-4,F, Tables 12-5,A to 125,G, and Figures 12-55 to 12-62). A good generalization to keep in mind is that ± I SD includes about 67% of the total population, ± 2 SD includes approximately 95%, and ± 3 SD more than 99% of all normal cases.
7. A Method for Discriminating
Class 11 Types
The analysis described here is a simple noncomputerized method of discriminating several of the quite different morphologies which comprise the large designation "Class 1I malocclu-. sion. " 19 Its place in the overall scheme of cephalometric analysis is shown in Figures 12-23, 12-24, and 12-31. a) Purpose a) To localize and quantify any possible skeletal contributions to Class II malocclusion.
BASIC MORPHOLOGIC ANALYSIS
CLASS IT ANALYSIS
VERTICAL CLASS IT ANALYSIS
FIG 12-31. Flow chart for discrimination of Class 11malocclusion.
b) To identify dental displacements II malocclusion.
associated with the Class
c) To assign the patient to one of the Class II types.
b) Basis "Class II" is a loose, subjective designation including an assortment of problems ranging from simple to the most difficult. 19 It is useful for the clinician to group together cases whose features are sufficiently similar to permit a common treatment. Such groupings, to be useful, must be natural and determined by the measurable morphologic features of the patients to be treated. Subjective groupings are less reliable than those which result from statistical clustering of cephalometric measures. 26 Six horizontal types of Class n malocclusions have been identified as well as five vertical types. 1) Horizontal Types.There is a continuum from cases with normal skeletal characteristics but Class II dental features (type A) through those with mild skeletal features (type F) to four distinctly different skeletal types (types B, C, D, and E). The diagrams in Figure 12-32 provide ways of mentally depicting the six horizontal groups. Four (Types B, C, D, and E) might be termed syndromal types of Class n, for they have distinctively combined skeletal and dental features. Type F, the largest group of all, has less well defined, less characteristic features of skeletal Class n, yet is clearly not Class I. In type F each individual has some Class n characteristics, although not sufficiently severe to be termed either type B, C, D, or E. Each type F case looks like. a milder version of type B, C, D, or E and may be so designated (FB). Type A has scarcely any Class n skeletal features. See Table 12-2 for data on the distribution of one pool of clinical samples. Other forms of Class n undoubtedly exist but are not seen in North American whites often enough to be characterized as a "type." Type A is characterized by a normal skeletal profile and normal AP position of the jaws. The mandibular dentition is placed normally on its base but the maxillary dentition is protracted, resulting in a Class n molar relationship and greater incisal overjet and overbite than normal (see Figs 12-32 and 12-36,A). Type A is sometimes referred to as a "dental Class n." Type F is a large, heterogeneous group with mild skeletal Class II tendencies. It is useful to think of each type F as a milder, nonsyndromal form of types B, C, D, or E (see Fig 12-32, Fig l2-36,B, and Table 12-2). Type B displays midface prominence associated with a mandible of normal length. Measures of maxillary prognathism are greater than normal, but the mandible is in a normal relationship anteroposteriorly (see Figs 12-32 and 12-36,C and G). profile, though the maxilla Type C cases display a Class arid~\Tlandible are furthe~ back beneath the anterior cranial base than normal. Type C cases have smaller facial dimensions than other Class n types on average. The lower incisors are tipped labially, and the upper incisors are either upright or tipped off the base labially according to the vertical category (see Figs 12-32 and 12-36,D). Significantly more women than men are seen in type C. Type D displays a skeletal profile which is retrognathic because there is a smaller than normal mandible. The midface is
n
normal or slightly diminished.
The mandibular incisors are either
271
8
A ~
Lj
NORMAL
A (Maxi Ilary Dental Pratractian)
D (Mandibular Retrognathism ond Maxi lIary Retrognathism
o
+Maontal
B (Mid- Face Prognathisml
Protraction)
E (Maxillary Prognathism and Dental Protraction and Mandibular
q Ljl
Dental Procu,:"bency)
C (Maxillary Retrognathism + Dental Protraction
F (Combination of Slightly Abnormal Variables) and
Mandibular Retrognathism + Dental Procumbency)
FIG 12-32. Horizontal Class 11types. A, schematic comparisons of the horizontal types. In this arbitrary depiction, normal is perfect anteroposterior alignment (see top drawing). B, one may fancy the Class 11syndromal
types as the fingers of a hand where the bones are distinctly separated from one another, yet in the palm (type F) their distinctness is obscured.
upright or lingually inclined, whereas the maxillary incisors are typically labially positioned (see Figs 12-32 and 12-36,E). Type E shows a "Class 11" profile even though there is a prominent midface and a normal or even prominent mandible. Bimaxillary protrusion Class 11 malocclusions are more apt to be horizontal type E. Both dentitions have a tendency to be forward on their bases, and the incisors are often in strong labioversion (see Figs 12-32 and 12-36,F).
horizontal. Under these ~onditions the incisors adapt to more vertical positions than normal and a skeletally imposed deep. bite results (see Figs 12-33,B and 12-36,A, C, and D). Type 3: The characteristic feature of vertical type 3 is a palatal line tipped upward anteriorly associated with a decreased anterior upper face height and resultant predisposition to an open bite. When the mandibular line in vertical type 3 is steeper than normal, a severe skeletal anterior open bite is inevitable. The features of type 3 are shown in Figures 12-33,C and 12-36,B. . Type 4: In vertical type 4, the mandibular, functional occlusal, and palatal lines are all tipped downward though the mandibular line is near normal, leaving the lip line unusually high on the maxillary alveolar process. The gonial angle is relatively obtuse. Because of the length of the midface in horizontal type B, with which all vertical type 4 malocclusions are associated (see Table 12-4 in the Appendix), the upper incisor~ are usually tipped labially, and the lower incisors are tipped lingually. (Upper incisors are usually normal or labial in all other type B Class 11malocclusiQn.s.) (See Figs 12-33,D and 12-36,G). Fortunately, type 4 is rare ...
2) Vertical Types.- The five vertical types are not as clearly differentiable as the four syndromal horizontal types. Certain vertical types are characteristically identified with certain horizontal groups (see Table 12-2). It is not necessary for a case of a horizontal type (especially types A or F) to be associated with any of the described vertical Class 11 types, for the subject could have normal vertical measures. The vertical types are depicted in Figure 12-33. Type 1: The dominant feature of vertical type I is an anterior face height disproportionately greater than that of the posterior face (Fig 12-33,A). The mandibular and functional occlusal lines are steeper than normal, and the palate may be tipped somewhat downward while the anterior cranial base tends to be upward. Type I is often called a "steep mandibular plane" case or a "high angle" case and probably corresponds to the surgeon's so-called "long face" syndrome (see Figs 12-33,A and 12-36,E). Type 2: Vertical type 2 is essentially a "square face". The mandibular line, functional occlusal line, and palatal line are more horizontal than normal and often seem nearly parallel. The gonial angle is smaller than normal, and the anterior cranial base appears
Type 5: In type 5, the mandibular and functional occlusal lines are placed normally, but the palatal line is tipped downward, and the gonial angle is smaller than normal. The result is a skeletal deep bite similar to but different than that seen in vertical type 2 (Figs 12-33,E and 12-36,F). In type 5 the lower incisors are found in extreme labioversion whereas the upper incisors are nearly vertical. 3) Combining Horizontal and Vertical
Types.-
In Table
272
TYPE % 100.0 11.4 45 Incomplete 25.4 5.3 3.6 1.9 27.3 1.7 60.0 18.9 33.4 21 data 37.4 Diagnosis
NO. NO. 132 233 80 37 13 25 190 418 177 52 25 12
Normal D. Vertical Types
697
Distribution Horizontalof Class 11Types TABLE A. 12-2.
-
12 NO. %%
697
27.3 F E 190 100.0 12.0 3.6 11.4 7.4 38.6 1.7 3.6 26.5 27.3 7.4 Maxillary Prognathism and C,D 69 21.4 1.7 190 52 269 9.9 A 185 84 80 5225 12 25 149 B, B. Horizontal: Mandibular Dental Class 11 DESCRIPTION TYPERetrognathism
0IT OP TL Unclassified
H
TYPE
NO.
----- -
A 12
~L
Total
12-2,E the joint distribution of horizontal and vertical types in a sample of 697 Class II malocclusions are displayed. Note that since type A is not truly a skeletal Class II malocclusion, a normal vertical is usually displayed. However, milder versions of the two most common Class II vertical types, types I and 2, are found in association with type A. There is a similarity between horizontal and vertical distributions of types Band E (high percentages of them are vertical types 2 or 5), but they differ in their dental features. Only type B manifests the anomalous, difficult vertical type 4. There are similarities in the distribution of vertical types in horizontal types C and D. c) Method 1) Identifying Horizontal Types.The procedure for identifying horizontal types utilizes an arborization which segregates these types. On the left side of Figure 12-34 are arrayed five questions to aid in the differential typing of Class II malocclusions. These questions are answered after comparing the patient's values of specific measures to normative standards (Fig 12-35). The measures used in this procedure are mostly constants found useful in differentiating the horizontal and vertical types described earlier. For example the first question, "Is the subject a skeletal Class
E. Matrix of Horizontal and Vertical Types -15 10 40 39 18 84 I1 46 45 68 16 45 54 54 18 24 11 32 233 0 132 697 15 14 8013 185 69 52 165 190 410 4'4 E 23 547825 1 03BAF24 Normal VERTICAL R Data (H aV)C ZY NE TYPE Incomplete
~
I1?" is answered by particular measures of A-B relationship whose means and range are displayed above the first dotted line in Fig 12-.35. Skeletal Class il cases show values above the mean. In this instance the arbitrary cutoff value is 0.5 SD above the mean. If the patient falls above of this value, he or she is assumed to be in skeletal Class 11, and type A has been eliminated as a possibility, as have some of the milder forms of type F (Fig 12-34). When analyzing a patient exhibiting skeletal Class 1I, it is useful to determine which anatomic regiClns are the principal contributors to the dysplasia. The second question, "Is the midface prognathic?" and the third question, "Is the mandible retrognathic?" help us. Values above the cutoff (0.5 SD) for mid face prognathism i~dicate maxillary cont;fbutions to the Class 11; those below the cutoff value (0.5 SD) for mandibular retrognathism indicate mandibular involvement. Types Band E show midface prognathism; types C and D have mandibular inadequacy. Type F is a combination of mild maxillary and mandibular skeletal f~atures by these conventions and definitions. The remaining two questions pertain to dental features of Class 11 whose measures are less constant than the skeletal measures but are characteristicalJ~ typical of the clinical types; therefore the cutoff value is largef, namely, 0.75 SD. Assigning choices to each of the five questions leads one through the arborization to the bottom of the chart, where a hor-
Analysis of the Craniofacial izontal type is named. Those position,s of the arborization which' have no letters indicate rare or ambiguous outcomes of this classification procedure. A heavy vertical line within the arborization indicates a point on a path only rarely followed. 2) Identifying Vertical Types.In Figure 12-33 the five vertical types are depicted. The measures used for their discrimination are angles cut upon the posterior maxillary vertical line. Figure 12-26,B is a Z-score chart for comparing the patient's values with those of the population at large. Remember that many patients with horizontal Class Il malocclusions, especially of types A and F, have vertical features within normal ranges. Vertical type I shows typically large values for angles of PM vertical with
Skeleton: Cephalometries
A
c
the lIlandibular, occlusal, and palatal lines. Vertical type 2 manifests small values for the same angles. Vertical type 3 usually shows a relatively small palatal line angle alone. Vertical type 4, found only in association with horizontal type B, shows high angles for palatal, occlusal, and mandibular lines and a relatively obtuse gonial angle. Vertical type 5 shows a relative large angle of PM vertical with the palatal line, nearly normal angles with the occlusal and mandibular lines, and a small (nearly orthogonal) gonial angle. Figures 12-32, 12-33, and 12-36 may be studied to understand better the various types. The assumption of this procedure is that the identification of the clinical type leads to more logical treatment planning (Chapter 14) and treatment for Class Il types (Chapters 15 and 16). 8. A Method of Discriminating
273
E
Class III Types
Although a variety of mal occlusions are grouped together under the general category called "Class Ill," few quantitative discriminative studies of types within Class III have been done.12 The literature speaks generally about mandibular prognathism (Class III resulting from mandibular hyperplasia), midface deficiency (Class III resulting from relative AP shortening of the maxillary region), and "pseudo" or "functional" Ciass III (Class III molar relationship resulting in part from a functional forward shift of the mandible on closure to occlusion). Anterior crossbites whose incisal relations simulate some Class III dental features are not truly Class III malocclusions. Analysis of possible Class III morphology must include (I) the general facial morphology, (2) identification of disharmonious regions, (3) the vertical position of the mandible in posture and occlusion, and (4) the position and angulation of the incisors. Proper cephalometric analysis as early as possible is essential since the skeletal aspects of Class III are often overlooked in young children (Fig 12-37). Figure 12-38 is a simplified version for use with adults. a) Purpose The purpose of the analysis is to localize the primary morphologic sites contributing to the Class III malocclusions.
FIG 12-33. A, vertical type 1. e, vertical type 2. C, vertical type 3. D, vertical type 4. E, vertical type 5. CLASS
Mid-face
Prognathic?
Mandible RelrOf}lIo!llic Mandibular
HORIZONTAL
+,-
Skeletol Class II?
.? leeHl
+I-
Procumbtlnl
5014294026542757661197191947"100558\21133222761128 E (El 8+ 8 C+ C D+ D F F
F
F
FE FE Fa Fe Fe Fe Fo Fo A A A A
N~697 Unclassified:: 12 Incomplele
b) Basis The basis for discriminating Class III types is a self-compariso'n of the patient's maxillary skeletal and dento-alveolar unit distances to the patient's own mandibular skeletal and dento-
n PLOT,
Dolo ~ 25
FIG 12-34. Arborization (decision tree) for diagnosis of Class 11 horizontal types. (From Moyers RE, Guire KE, Riolo M: Differential diagnosis of Class 11 malocclusion. Am J Orthod 1980; 78:47'7-494. Reproduced by permission.)
III .. 1 Ll..u tl~ Horizontal ,80 -3 I110 I~5 -2 50 2 -ISO 274 -ISD 341.8 -2 3I.J X X ISO -3 2 lS0 ISO Diagnosis , 90 lS0 "60 29 17570 70 -SE-FMN-A -______ _____ 65 1 95 ________ --------1 .185 I. -------1 60 155 301 125 70 B?7j 80 ,~~, , '1'~5" Bo-Se-B
rl
I/Md PI SNB pe by the IIA-Po
I I90 1 MALE 85 FEMALE ) I 85 I' "siJl ' I '7b 72d5' Ba-Se-B I/MdPI Class 11Z-score chart and arborization. A, the blank Z score form. lIFOP Pal SNA I/F.OP PI./A-B ~o 85 11 FOP
1.1
I .!...L 1
______
1
A
f
,
.•
,,~
arborization process. 350, Z score form for the Vertical Analysis. Note the steep mandibular line. _. ,
OJ
Analysis of the Craniofacial
c
CLASS
PLOT,
IT
HORIZONTAL
A
n,?
Skeletol Closs
Skeleton: Cephalometries
Mid-foce Proqnotllic? MondJ/)le Retroqnotllic ,? Mondib/llor teetll Proc/lmbent Moxillory teeM Proc/lmbent
+,-
5014294026542757661197191947'1100558121133222761128 E (El B+ B C+ C D+ D F F
N=697 Unclassified Incomplete
=
Data
=
-3
-2
MALES
MALES
FEMALES
Occlusion
PM Vert /Oee!. Line (not a constant in Class
ANALYSIS
-IS.o.
Maxilla
PM Vert/Pal. Line
VERTICAL
FC
FC
Fe Fe A A A A
25
Base
PM Vert/FMN-SE
FE FE Fe Fe
12
o Cranial
F F
MALES
III
FEMALES
Mandible
PM Vert/Mand. Line FEMALES
"
X
IS.O.
2
3
275
276
Diagnosis
A
o
8
C
E
F
G
FIG 12-36. Cephalometric A-2 (horizontal
tracings of typical Class 11 types. A, type A and vertical type 2). e, Class
Class 11 type type F-3. C,
I1
Class 11type 8-2. D, Class I1 type C-2. 11type E-5. G, Class 11type 8-4.
E,
Class
11 type
0-1.
F,
Class
Analysis of the Craniofacial Skeleton: Cephalometries
ASSUMED OCCLUSAL
Mid - Face De ficJency
Mid-Face Deficiency Plus Mandibular ProQnathism
Only
Growth +~rowth
Growth 81
+
CLASS ill SYMPTOMS
Mondi buler Prognathism On Iy
1- No Growth
r C
277
D
Gro~1
r
No Growth
E
FIG 12-37. Class III cephalometric
analysis flow chart.
alveolar unit distances by means of the Counterpart Analysis (Fig 12-28). Further comparisons are made of the individual distance of each horizontal Counterpart Analysis measure to appropriate norms for age and sex (see Table 12-4).
c) Method 1) Variations in Form.First use the Basic Morphologic Analysis as a screening mechanism to identify any evident Class III skeletal features (see Fig 12-25). If the Z-score chart shows all values within I SO of the means, the malocclusion likely is dominated by dental or functional features (see Fig 12-25,C). 2) Profile Analysis
(See Also Section G-4-c).-
In Figure
12-28 a useful simplification of the Counterpart or Enlow Analysis7 is shown. This method is one of the best for understanding the basis for a skeletal Class III malocclusion since it emphasizes the
relative relationships of parts in one face (see Table 12-1). The norms of reference are of these relations, not of explicit sizes. A skeletal Class III malocclusion is presumed when the Skeletal Unit Distance Ratio is 0.9 or less (at least 2 SOs from the mean of 1.0). When the midface measures (B-1, B-2, and B-3 in Fig 1228) are in harmony, that is, are nearly equal to the measures contributing to mandibular prognathism (B-4, B-5, and B-6 in Fig 12-28), real size is of less consequence. When they are not, the analysis helps localize the probable primary site of the problem (Fig 12-39). Though the Profile Analysis identifies a Class III and helps localize it, it is still necessary to compare the patient's dimensions with appropriate tables displaying means and ranges for sex and age (see Table 12-4, which shows real distances as means for sex and age). Dentoalveolar Class III problems are discriminated in a similar way by use of the dentoalveolar unit distance ratio. 3) Vertical Analysis.The Vertical Analysis (see Fig 1226), applied to cephalograms of both the postural and occlusal positions (see Fig 12-27), helps identify any functional contribution, often an important complicating factor in Class III malocclusion. Reference to Table 12-3 is helpful in discriminating and localizing, even at an early age, vertical contributions to and complications of Class Ill. 4) Analysis of Incisal Adaptation.An important feature in Class III malocclus}<:ms is the way the incisors cope with the dy:sgnathia. Determining factors. are the jaw(s) primarily involved and the cant of the occlusal and mandibular lines. It is an unfor-
FIG 12-38. Simplified profile analysis pected during treatment.
used for adults when little growth is ex-
tunate convention to relate incisal angulation to distant structures in the cranial base (e.g., Frankfurt Plane or S-N line). Sometimes it is more revealing to note how the incisors and occlusal line have adapted (Fig 12-40). The mean incisal angles (see Figs 12-35 and 12-40) may not be realistic goals to be achieved in treatment of skeletal Class III malocclusion, but the means provide a way of testing how the incisors have adapted. The comparisons may
278
(51)
Diagnosis
/ (477) (51)
. (52.5) (58)
~
57
(54.5) (51)
056/(536)
5.5. 11-2
FIG 12-39. Examples of the Class III analysis. A, midface deficiency. B, mandibular prognathism. C, combination of midface deficiency and man-
G.M. 11-8
dibular prognathism. Numbers in parentheses are the mean lengths (mm) for age and sex of patient (Modified Counterpart Analysis).
give clues about how to place the incisors when the severity of skeletal relationships makes it impossible to impose normal or ideal incisal angulations (see Section G-9). 5) Class
Ill,
Summarized.-
9
The methods outlined are useNORMAL
ful for identifying and understanding a particular Class III case (see Figs 12-38 and 12-39). They will also help in discriminating severe skeletal Class III from the simpler problems with only dental and functional symptoms. Some basic principles for orthodontic treatment of Class III patients are given in Chapters 15 and 16. A brief discussion of the combined orthodontic-surgical correction of severe Class III mal occlusion is found in Chapter 17.
TYPICAL CLASS
9. Visualizing Treatment
II
Objectives
Depiction of expected future relationships was first developed by Ricketts22 and has come to be termed Visual Treatment Objectives. Any diagnostic cephalometric analysis is outdated at once for it reveals only the relationships at the start of treatment. Treatment planning therefore must cope with expected changes due to growth, displacement, and pattern persistence as well as the effects of treatment itself-a very complicated problem indeed! In addition the clinician would like to have in mind some image of how the face is intended to look after treatment is over. Such images are expressed as cephalometric value~' in sets which we may classify as (1) ideals, (2) norms, or (3) "archetypes." Ideals are assumed esthetic values; norms are statistically derived population means; while "archetypes" 21 are ideal values for all individuals of the same type. All are used to visualize treatment objectives, and each has problems associated with it in practice. The use of the method of morphology prediction described
TYPICAL CLASS ill
FIG·1?-40. Incisal adaptation to the profile. Due'to variations in the steepness of the mandibular line and the occlusal line, it may be unrealistic to use normal incisal angulations as a goal in treatment. Note in particular that, as the mandible becomes more prognathic (Class Ill), not only does the inter-incisal angle increase, but the proportions of the inter-incisal angle contributed by the upper incisor and lower incisor change greatly.
Analysis of the Craniofacial Skeleton: Cephalometries in Section G-5 above is useful as a Visual Treatment Objective (see Fig 12-30).
10. A Method for Evaluating Treatment
in this context. However, only a gross, not particular, interpretation can be expected (see Fig 12-41). 2) Regional
the Effects of Orthodontic
It is difficult to separate growth changes from treatment effects, important events taking place simultaneously, but there are simple procedures to help one visualize and comprehend better the effects of treatment during growth. The method is not sensitive to some treatment effects on growth, for example, deformation (see Bookstein5) nor does it clearly separate tooth movements from orthopedic effects (see Baumrind et al.'). It is, however, a useful introduction to the study of treatment effects. Innovative and revealing new techniques have been developed recently of interest to those intent on pursuing this topic. Bookstein's5 method of deformation of triangles (described briefly in Section G-II) has been successfully used to report the mean effects of different appliances, and Baumrind et aI.' have reported a method using more conventional techniques to separate orthodontic from orthopedic effects of therapy.
a) Purpose 1) To improve one's understanding treatment.
of what happens during
2) To separate growth changes from dentoalveolar alterations resulting from orthodontic therapy. 3) To localize and specify the effects of treatment. For example, has the wearing of a headgear in a Class II case (I) restrained expected maxillary growth forward?, (2) held the maxillary dentition from being carried forward by maxillary growth?, (3) moved the maxillary dentition dorsally?, (4) extruded the maxillary molars?, and similar questions.
279
Effects.-
(a) Maxilla.- Changes within the maxilla may be assessed by superpositioning on the superior and internal aspects of the palatal bone (Fig 12-42). One should avoid the palatal curvature directly behind the incisors since it is altered during the retraction and repositioning of maxillary anterior teeth. Translation of the entire maxilla occurs during growth alone and may also be an important goal of treatment in some Class 11 and Class III cases. Such changes can be observed by the cranial base registrations noted above (Fig 12-41). This method does not quantify nor does it separate the displacements of growth from those produced by treatment, which can only be conjectured. changes within the mandible (b) Mandible.-Disceming may be visualized by registration on the mandibular canals and the lingual aspect of the symphysis (Fig 12-43). Use of the medial axis technique (Fig 12-44), currently only a research method, has promise in this application as well. Neither quantitatively separates growth from treatment effects, and both depend on knowledge of normal growth and adaptation, eruption of the teeth, natural drifting of the teeth, etc.; but they are superior to studying mandibular change with distant registrations. Tensor methods (see Section G11) are efficient in revealing mean mandibular shape changes resulting from treatment (see Fig 12-46).
\ \ \ \ \
I I I
b) Basis 1) Prediction of morphology using pattern measures (see Section G-5). 2) Techniques for localizing areas for better visualization and measurement.
I
'~\ t\
\
'-..,
\\
\
/" /" (
c) Methods
\
\
/
\
1) General effects.Growth takes place unevenly but generally while orthodontic treatment is planned to be localized selectively. The cranial base displays small amounts of wellunderstood normal change, and orthodontic treatment forces are thought to have but minor effects on the area. Cranial base landmarks are therefore not useful registrations even for visualizing the general effects of craniofaciargrowth and attendant treatment. The frontomaxillarynasal suture (FMN), sphenoethmoid registration (SE), and basion (Ba) (see Fig 12-13), are favored landmarks. Registration at SE minimizes the effects of the minor changes in cranial base length and angle which occur (Fig 12-41). FMN is chosen rather than nasion since the latter is not of the cranial base and displays more varied behavior which obfuscates interpretation
AK
-12-0 --13-1
"'j //
/\
., FIG 12-41. Evaluating the general effects of treatment. Here registration is on the sphenoethmoidal registration point and orientation is on the sphenoethmoidal-PTM line (posterior maxillary line.) The case shown is a Class III malocclusion with midface deficiency treated by face mask and full banded therapy.
280
B
FIG 12-42. Evaluating maxillary treatment changes. Registration is on the palatal curvature (same case as in Fig 12-41).
11. A General
Assessment
of Deformation
f;;,J ~
c
in Triangles
a) Purpose
The tensor method of Bookstein2.
4.7.8
constructs the distance
measures and shape variables that are most sensitive to particular comparisons of clinical interest. By dealing directly with digitized landmark locations, it avoids the need for any a priori choice of variables, "constants" or otherwise, and is nevertheless a complete cephalometric analysis.
b) Basis Tensor biometrics is the expression of a rigorous new approach to the statistics of landmark points. It has close ties with the techniques of "finite" element analysis familiar in engineering, but is not equivalent (see Bookstein8•9). c) Method An explanation of the tensor computations requires more space than is available in an introductory text such as this. Rules for hand computation are found in Bookstein,' for automatic computation in Bookstein,s or Bookstein!
G
. FIG 12-44. Medial axis method. The axis is defined bya line joining a series of points, each of which is equidistant to the external outline. In practice, registration is always over one of the trifurcations. The examples shown reveal essentially the same information as is gained from metallic implants experimentally placed in the mandible of monkeys. Note the growth adaptation in the condyle and regions of muscle attachment. Shown are superposed oblique tracings of serial data from seven Class mandibles. 11
d) Examples Here we precis some research findings from the literature that
have exploited this method to organize reports of systematic shape changes throughout the head. The method defines "form" as the geometric configuration of a set of landmarks, and "change" as the simultaneous change in all possible size and shape measures of form. The underlying mathematical model is of deformation, not rotation or translation.
FIG 12-43.
1) Normal Growth.The most precise characterization of the" growth axis" from age 6 to 14 years is in terms of the relation of Menton to the Sella-Nasion line (Fig 12-45). In the lateral view, the most autocorrelated (i.e., predictable) measure of splanchnocraniaUorm for males from 8 to 14 years is very 'fl()arly the angle between Sella-Nasion and Mandibular lines. The least predictable aspect of form i's associated with size change "along" the growth axis.
Evaluating mandibular treatment changes. Registration is on the dorsal shadow of the symphyseal region on the shadow of the mandibular canal. (Same case as in Figs 12-41 and 12-42.)
2) Treatment Changes.The principal skeletal effect of intraoral treatment of Class 11 by Activator or Function Regulator
Analysis of the Craniofacial CONTROL
"v'"' 2~
~
CERVICAL
Skeleton: Cephalometries ACTIV'R
281
FRANKEL
V
:h
v ..'"v mO'" MEN
~IG 12-45. The use of tensors to show form difference. This set of figures shows the mean biorthogonal analyses, by sex, for sella-nasion-menton, a typical cephalometric triangle. The subjects for this analysis were all normal children followed between the ages of 11 ± 1 and 15 ± 1 years from the University of Michigan Elementary and Secondary School Study. The dilatations are annualized and printed in units of percent per year. The panel at upper left displays the mean annual change for the 42 males of this sample, that at the upper right the mean annual change for the 29 females. The lower right diagram represents the relative tensor analysis comparing the sex-specific changes. Either subgroup mean clearly corroborates the growth axis noted by previous investigators. With respect to the cranial base, menton appears to be displaced by growth along a line roughly perpendicular to basion-nasion. In this analysis the baseline becomes the connection of nasion to a point 10% of the way from sella to menton, as drawn. It is this triangle, not basion-nasion-menton or any triangle on PtM, which locates the growth axis with greatest precision. Form differences in two groups at the start of orthodontic may be compared in a similar way. 11 is the relative displacement of Menton downward away from the anterior cranial base (Fig 12-46). These treatments have no net effect on the Maxilla, whereas extraoral treatment (cervical) alters maxillary form in a manner best measured by the angle ANSS-N. This method reveals the deformations of form (I) accompanying growth (see Fig 12-17) and (2) occurring in a patient under treatment. Figure 12-46 shows how the method has been applied to study the effects of treatment with different appliances. Computer programs and data bases of normative growth and successfully treated cases expedite and extend greatly the application of the method. (See Suggested Readings at end of this chapter for further details.)
H. SOME PROBLEMS AND LIMITATIONS OF CEPHALOMETRICS Although the cephalometric analysis is the single most useful tool in orthodontic diagnosis and treatment planning, a practical clinician will nevertheless thoroughly study the limitations of the method so as to minimize its systematic errors. II To ignore its
MEN
FIG 12-46. The use of tensors to show treatment effects. problems is to deny oneself the full use and advantages system of cephalometries. 17
of the
1. Assumptions In any method some things must be taken for granted as a basis for action.
a) Symmetry Analysis, particularly in the lateral projection, is based on presumed skeletal symmetry. All faces have minor asymmetries which are clinically unimportant, but more serious imbalances may be obscured by the method or neglected by the dentist. Routine study of the PA projection is a good antidote (see Section G-4-d, Analysis of Symmetry).
b) Occlusal Position Cephalograms must be taken in some occlusal pOSItion: it makes a difference which one (see Chapters 5 and 11). It is conventional to position the mandible in the usual occlusal position when taking the cephalograms since this is where the patient' 'bites." In malocclusions with an important functional element this convention may be misleading. One should study carefully the patient's mandibular functional movements prior to recording the cephalogram. Suspicions noted visually may be confirmed quantitatively in the cephalogram by two procedures: (1) Use wax bites of both the usual occlusal position (centric occlusion) and the retruded contact position (centric relation) to record two lateral cephalograms. In extreme cases the patient may wear a diagnostic spli'2t.for several days before the cephalogram is ebtained (see Chapters II and 18). (2) Use the postural position as well as an occlusal position for both the lateral and PA projections (see Fig 12-27).
c) Orientation on the Transmeatal Axis It is convenient to use ear rods to orient the patient's head. The central ray is supposed to pass along the transmeatal axis. But of course the external auditory meati are just as apt to be asym-
282
Diagnosis
metric as any other cephalic structures. Special cephalostatic procedures have been designed without ear rods so the central ray is 90 degrees to the midsagittal plane, but they are not in common use. d) Adequacy
of One or Two Planar Projections
Almost all routine cephalometric analysis is done using only the lateral projection. Much can be learned from PA, oblique, and basalar views. The future may bring a practical true three-dimensional cephalometric method (see Grayson et al. 16).
2. Fallacies Any method may involve specific miscalculations, omissions, blunders, oversights, errors, or inaccuracies which are not the fault of the method itself. We speak here not about such mistakes but about fallacies: misrepresentations intrinsic to the method. a) The Fallacy of False Precision If one makes a series of separate cephalograms of the same head, traces each cephalogram, locates "A" point, nasion, and "B" point, and measures the ANB angles, it will be discovered that the standard error of that measure is greater than 1.5 degrees. 11. 20 Therefore, any decision, such as a choice of treatment procedure, based on the value of ANB angle, alone or in combination with other measures, must have a gray area of approximately ± 1.5 degrees where the treatment prescription is ambiguous .. This problem is compounded when a clinician compares a case he or she has traced to standards developed, and therefore filmed and traced, by another. b) The Fallacy of Ignoring the Patient Means are population averages which have nothing to do with the specific characteristics of particular patients. A patient's measure need not be increased by, for example, 4 mm just because it differs by 4 mm from the mean. There are many beautiful faces in good occlusion which have measures far from the norm. It is not necessary to treat malocelusion with relation to a fixed cephalometric goal. Rather, cephalometrics should provide a range of satisfactory treatment goals which, combined with other information from dental casts, case history, and observation of the patient, make possible an individualized treatment plan. c) The Fallacy of Superpositioning Superpositioning, registering of two or more tracings of an individual on particular structures, occasionally helps one to visualize growth or treatment changes (see Fig 12-20 and Figs 1241 through 12-44). Localized rem6deling can be shown by superpositions nearby. As one moves away from the registration site the changes observed are a combination of summated growth in several regions, effects of treatment, enhancement of errors in positioning, etc. For example, in Figure 12-41, where registration is in the cranial base region, the chin seems to have "grown" downward and forward, but one may as well say that the condyle
has been growing upward and the chin has been translated away from the articular fossae. Little growth occurs at the chin itself. The many changes between chin and sella are summated and directed downward and forward not by growth but by the artifact of superpositioning. If one superposed on the symphysis (see Fig 1220), it would be misleading to speak of upward and backward growth of the cranial base! Some of the problems of superpositioning techniques are overcome by the analyses of deformations (see Sections F-2-c and G-II). d) The Fallacy of Using Chronologic Age Although it is conventional to use chronologic age (birth age) for comparisons and reference, developmental age is a better criterion: it reduces the variance of sizes, angles, and proportions within age classes. Some orthodontists take routine radiographs of the wrists of patients to assign their "carpal age," an index of bone maturation (see Chapter 11, and note several examples of the use of developmental age throughout this book). e) The Fallacy of the "Ideal" Practical problems arise when "ideals" for skeletal relationships are oversimplified into numbers inflexibly and arbitrarily imposed on every patient. The use of contrived "ideals" as standards sometimes produces a set of ipso facto findings by setting up artificial criteria for abnormality and then uncovering the incidence and prevalence of these variations. By definition, abnormal must always refer to the normal, which can only be determined from an appropriate population. One cannot discover "abnormality" by comparison with subjective ideals based on personal perceptions of facial esthetics, nor can one label such ideals as normal. It is one thing to say "I like faces which look like this"; it is quite another, and most illogical thing to say "any face which doesn't look like faces I like is abnormal."
3. Misuses of Cephalometric Analyses Even when we protect ourselves from misleading assumptions or fallacious misconceptions we may err simply by misuse of any analysis. The following rather loose listing contains some of the more common misuses of cephalometrics. It is not intended to be inclusive, but it does reveal how this splendid and practical method is abused and misapplied. As we have noted, cephalometrics itself has limitations. The problems in this list of misuses are not those of cephalometrics, but of the user. a) An analysis is misused if to'o rigid aq application of mean values is made. The total range and variance are more practical than the mean itself (see Fig 12-22). Because means are population aveI;ages, they usually are. very poor treatment goals. Occasionally means'of tooth positions are usefu,l, but only when the array of skeletal values is close to the means for sex and age. When skeletal values deviate from the mean, dentitions must adapt. The clever clinician does not apply the same mean value to all faces but determines those adaptational compromises to be made in treatment which are most apt to be pleasing and stable. b) An analysis is misused when it is applied inappropriately.
Analysis of the Craniofacial
Skeleton: Cephalometries
283
Values derived from 12-year-old North American white boys who sought orthodontic treatment in a dental school, for example, are obviously of little use in assessing the specific clinical needs of a 6-year-old black girl in practice: there are too many differences resulting from age, sex, race, etc. The sample.<;from which many of our most popular cephalometric analyses were derived have not been adequately described in the literature, making it very difficult for the clinician to know whether or not the analysis is appropriately useful. c) An analysis is misused when it is applied in a way for which it was not intended. Analyses contrived to visualize treatment goals (e.g., those of Tweed26 or Steiner,25 both designed to depict goals of treatment) are used improperly when used for growth studies. , d) Standards derived from cross-sectional samples, in most instances, cannot properly be used in lieu of longitudinal data to assess expected growth. For establishing growth standards, a small serial sample is much better than a cross-sectional sample having the same number of radiographs. (This is true whether or not the investigator has "smoothed" the annual means.) e) The substitution of a subjectively derived "ideal" for a statistically developed population norm misinforms and misleads. "Ideals" represent artificial constructs of faces one clinician likes; norms present real values of a particular group. They cannot be used interchangeably.
anterior face height
FIG 12-47. Measures of facial height. Anterior and posterior facial height.
I. THE FUTURE OF CEPHALOMETRICS There is no theory of cephalometrics; if there were, it would suggest what to do next. The techniques of cephalometrics are on call, awaiting conceptual advances in growth and treatment effects. Progress is dependent on new concepts, but new technology makes possible the asking and testing of new questions impossible to conceive just a few years ago.
APPENDIX: A BRIEF CEPHALOMETRIC ATLAS Included here are graphic and statistical descriptions of the cephalometric measures mentioned in the text plus a few others in common use. The data have all been derived from The University of Michigan Growth Study and are reproduced with permission. All definitions are from Riolo et al.,23 to which the reader is referred for further information about the many cephalometric measures not included in this short atlas. The Appendix is arranged in the following sections for ready clinical use: a) overall facial dimensions b) regional anatomic dimensions
c) craniofacial constants
'. FIG 12-48. Measures of facial height, continued. measures.
Maxillary and mandibular height
284
Diagnosis
A. OVERALL FACIAL DIMENSIONS
C. Anterior Upper Facial Height MEAN SO SO MEAN 47.17 48.89 3.41 47.89 3.33 48.42 47.07 3.28 48.58 2.87 NA NA 45.34 44.23 43.28 40.91 39.74 3.62 3.13 44.76 45.84 3.46 41.86 2.53 2.33 41.00 3 2 2.41 1.96 .06 .03 .59 MALE FEMALE 51.48 3.31 2.80 53.38 2.69 49.72 50.09 50.54 3.18 3.58 4.26 2.92 4.17 3.65 3.44 3.66 38.59 37.50 43.26 3.25 .40 53.29 50.22 3.32 51.19 3.99 53.79 50.34 55.11
1. Vertical Distances (facial height) 7 11 13 15 12 58 6 16 17 14 18 10 9 4
AGE
Facial proportions change with age, and there are significant sexual differences, particularly from the onset of pubescence. Rules of thumb about facial height ratios supposed to be I!0rmal may therefore be quite misleading and seen inappropriate because of differential regional growth. Because of so many misconceptions about the achievement of facial height; ignorance about sexual differences and the wide variances observed; and the frequent, rather naive use of narrow "ideals" for both sexes and all ages, these graphs and tables are worthy of study (see also Chapter 4 and Section G of Chapter 12). • • •
Measurements used: Figures 12-47 and 12-48. Graphic data: Figures 12-49 and 12-50. Tabular data: Table 12-3. TABLE 12-3. Facial Height Measures D. Anterior Lower Facial Height MEAN MEAN SO SO MALE FEMALE 62.575.94 62.877.12 60.396.58 60.016.42 59.62 57.27 63.05 61.66 58.94 56.67 71.33 6.90 73.70 66.96 5.43 5.85 4.16 4.69 74.98 63.98 6.46 6.12 6.08 5.64 5.35 63.24 61.24 10.13 10.00 8.49 7.75 7.05 7.26 6.16 NA 61.616.23 60.06 62.81 59.52 62.40 59.90 58.73 55.48 75.79 69.63 65.78 5.80 65.29 5.37 8.66 11.93 9.31 8.13 NA
A. Anterior Facial Height (SE-Mer MEAN SO SO MEAN NA NA 107.91 107.10 104.89 101.30 105.36 108.32 110.24 112.76 103.70 101.98 124.62 127.08 129.57 130.09 111.15 114.66 117.18 121.11 6.17 98.65 99.75 92.98 97.67 112.91 6.07 5.51 111.58 99.13 114.43 112.94 6.47 7.61 6.58 7.30 6.37 6.85 6.51 6.40 6.75 7.76 10.25 6.90 7.19 11.37 10.44 11.25 12.76 7.01 7.68 7.23 8.59 9.04 7.79 6.64 6.98MALE 106.69 113.18 7.04 17 15 16 14 13 12 18 11 10 8 7 6 5 FEMALE 49 AGE
• NA = no data available
B. Posterior Facial Height MEAN MEAN SO SO NA NA 76.59 105.99 104.75 103.90 77.79 79.17 82.23 86.38 5.72 92.48 5.93 5.99 94.22 5.24 92.10 4.62 91.87 4.90 88.45 4.80 3.10 3.59 4.28 5.01 4.35 4.49 4.58 74.16 76.39 77.77 84.59 79.89 81.81 83.65 95.39 90.48 4.86 4.76 4.74" 4.52 5.22 5.17 4.56 6.58 5.58 8.89 7.85 7.70 7.40MALE 101.12 84.65 92.79 86.54 97.29 91.91 88.26 3.50 6.94 . 16 10 11 9 67 12 13 18 15 14 17 4;8
FEMALE
5 AGE
"
E. Posterior Upper Facial Height >. 3.15 46.95 MEAN MEAN so so NA NA 41.58 39.47 2.71 47.99 3.20 2.36 2.45 41.53 42.51 2.89 43.79 2.96 2.70 44.86 44.62 2 2.85 3 3.17 1 2.91 .53 .11 .99 MALE FEMALE 49.64 3.17 48.16 3.27 3.31 3.32 3.77 54.02 54.72 54.77 55.47 2.50 50.53 50.66 50.67 3.49 3.97 4.20 4.55 40.62 45.74 46.94 49.03 48.44 3.54 2.93 51.32 51.88 2.99 49.97 51.04 3.58 3.95 45.70 - 42.50
Analysis of the Craniofacial F. Posterior Lower Facial Height
I. Posterior Maxillary
MEAN so MEAN so 4.97 41.57 40.01 NA 4.82 37.61 36.21 44.08 47.10 45.42 3.40 43.18 4.27 3.92 41.21 3.89 5.63 5.30 4.50 50.52 49.98 49.18 41.81 5.59 42.82 NA 6.53 5.56 5.52 39.42 38.91 41.45 40.27 3.58 37.66 3.48 3.35 3.18 3.32 36.95 36.10 38.39 3.59 3.37 3.35 36.67 3.39 2.69 35.26· 3.31 3.42 35.97 2 .52 MALE FEMALE 2.62 34,10 42.28 37.95 3.73 3.25 34.86 6 18 14 15 16 17 13 12 11 10 85 7 49
Skeleton: Cephalometries
Height
MEAN MEAN so so 11.32 21.27 3.12 2.37 3.53 20.50 13.17 8.51 NA 4.25 5.27 5.02 14.15 13.76 10.02 NA 23.76 3.01 22.56 2.50 2.39 2.51 2.73 18.74 19.89 3.35 17.92 15.81 15.46 3.07 2.94 20.62 6.67 9.06 15.71 14.70 14.18 10.86 18.95 19.84 18.88 17.25 4.03 4.59 5.51 3.17 2.96 2.80 2.67 2 3 43.71 3.47 3.26 3.91 .27 .14 .64 .35 MALE FEMALE 5.38 2.82
AGE
G. Anterior Maxillary Height
J. Posterior Mandibular
MEAN so MEAN so 23.17 2.63 2.95 23.27 24.41 2.52 23.79 23.25 26.32 NA 24.82 24.94 24.72 25.89 25.03 25.52 3.63 3.01 23.85 23.69 2.83 2.79 25.16 2 3 2.92 3.14 .35 .97 .05 MALE FEMALE .69 NA 29.67 25.18 26.91 26.61 26.21 30.43 30.54 2.54 24.86 2.34 25.00 2.59 2.69 2.81 3.06 24.03 26.04 26.23 3.41 3.44 3.59 3.90 3.18 4.33 3.63 3.60 28.85 26.05 3.57
10 11 12 14 15 16 17 8 76 5 13 18 49
H. Anterior Mandibular
Height
MEAN MEAN so so 31.83 24.81 27.42 2.42 3.08 6.25 32.78 3.25 25.24 2.54 7 3.35 .56 MALE FEMALE NA 4.56 NA 26.29 28.13 25.27 25.15 27.99 25.64 24.36 25.40 25.52 25.93 26.61 2.46 3.80 5.52 6.40 35.11 3.43 3.34 3.85 4.13 23.78 27.11 2.51 22.67 22.76 23.77 22.96 22.25 22.69 23.24 32 5.88 7.66 2.85 3.84 3.89 4.16 .69 .42 .64 26.76 21.18 4.64 22.32
AGE
Height
MEAN so so MEAN 4.88 37.95 35.46 4.50 3.70 32.26 5.20 6.52 36.37 NA 42.71 40.35 38.05 4.56 5.61 5.88 37.04 37.84 36.79 34.12 35.33 NA 38.80 39.07 44.03 39.73 44.55 45.24 3.78 35.67 4.38 35.77 3.82 35.87 4.12 3.20 37.19 2.97 30.31 34.92 5.11 36.16 35.04 34.00 8.28 3.91 5.24 4.72 4.53 5.35 7.48 5 6.61 .06 MALE FEMALE 42.48 4.85 5.33 4.20 6.96 37.87 12 18 16 17 15 13 14 10 8 7 6 5 49 AGE
K. Ratio of Total Anterior to Total Posterior Facial Height >.
. ~ 11
MEAN so so MEAN .06 1.25 1.22 .07 .04 1.20 1.21 1.22 1.23 1.23 1.24 1.25 .05 1.25 • 1.25 1.27 1.28 1.30 .02 1.26 1.27 1.26 .06 .07 .08 .06
FEMALE •MALE
285
286
Diagnosis L. Ratio of Lower Anterior to Total Anterior Facial Height MEAN SO SO .01 .02 .03 .60 .59 .58 .61 .58 .57 .56 .60 .59 ..03 03 .04 .55 .57 .04 ..MEAN 60 .58 .03 MALE FEMALE
10 11 12 13 14 15 16 6 7 9 18 17 8 45
AGE
M. Ratio of Posterior Facial Height
Mandibular
MEAN SO SO MALE FEMALE MEAN .03 .04 .24 .23 .25 .26 .03 .02 .29 .30 .32 .31 .27 .26 .28 .29 .31 .30 .28 .27 .,02 .02 04 05 03 .25
16 17 10 12 13 7 5 18 14 15 11 8 6 49
AGE
Height to Total Posterior
Analysis of the Craniofacial Skeleton: Cephalometries A
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FIG 12-49. Graphs of growth in facial height. A, anterior face height. B, posterior face height. C, anterior upper face height. 0, posterior upper face
height. E, anterior lower face height. F, posterior lower face height.
(Continued in Fig 12-50.)
25
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FIG 12-50. Graphs of growth in facial height (continued from Fig 12-49.) A, anterior maxillary height. B, posterior maxillary height. e, anterior
mandibular
height. D, posterior mandibular
2. AP Distances (Facial Depth) As Enlow et al. I. 3 have noted, anatomic lengths are often of less clinical import than effective lengths (i.e., the amount contributed to the profile). Most of the measures contained in this section quantify the amount by which a given bone or region affects the profile, incisal, or molar relationship. Actual anatomic lengths of some bones are given in Section B, Regional Anatomic Dimensions.
•
• •
Measurements used: Figure 12-51 Graphic data: Figure 12-52 Tabular data: Table 12-4.
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Analysis.
height.
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+ +().~ + , ++-. t.~ Vl ().~ o~+ Legend 4.5~
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290
Diagnosis
TABLE 12-4. Measures of Facial Depth ("Length") A. Maxillary Dentoalveolar MALE
• NA
=
MEAN MEAN N N SD SD 56. 62. 52.40 60.89 54.08 52.30 52.47 53.56 54.06 56.25 57.57 57.88 59.65 60. 67. 64. 15. 51.34 53.54 54.13 55.57 57.39 57.97 60.67 61.83 63.42 64.74 NA 27. 53. 48. 52. 47. 45. 28. 12. NA 3.55 3.53 3.06 2.60 5.00 3.16 3.28 3.22 3.38 3.48 3.34 3.74 3.17 2.90 3.12 3.63 3.51 3.53 4.20 3.95 3.67 27. 71. 67. 11. 62.43 59.24 61.15 73. 58. 36. 30. 23. 66.49 53.50 53.49 59.62 60.42 49. 63. 61. 15. 10. 2.75 5.03 2.66 3.00 3.26 3.27 3.61
Effective "Length"
-
(B-1)
FEMALE
no data available.
B. Maxillary Skeletal Effective "Length" SD MEAN MEAN N N SD 27. 62. 67. 51.52 57.25 56.16 52.56 51.13 51.37 52.81 54.02 54.95 56.80 23. 73. 60. 36. 30. 50.01 61.21 51.98 51.78 52.15 60.15 52.83 54.48 55.97 56.67 56.77 57.87 27. 49. 53. 63. 61. 48. 47. 45. 28. NA 10. 12. 3.13 2.70 2.66 3.63 4.19 2.74 3.04 3.01 2.61 3.00 2.75 2.98 2.94 2.43 3.20 2.78 3.06 2.71 3.03 3.12 56. 71. 11. 51.30 54.01 55.62 50.93 67. 58. 64. 15. 53.82 59.02 52.25 NA 52. 15. 3.72 2.39 2.77 2.90 3.04 2.87 2.82 3.19
C. Mandibular
.71.
MALE
Dentoalveolar
MEAN MEAN N N SD 62. 27. 45.91 45.77 48.45 49. 27. 3.12 4.22 3.43 •23. ~·4.48 48.77 63.87 59.71 60.43 55.67 55.24 50.95 30. 58. 60. 15. "63. 61.11 59.05 56.54 53.36 52.05 NA 28. 45. 47. 52. 61. NA 10. 4.06 7.13 6.42 5.68 4.55 4.69 4.13 6.45 6.10 5.04 4.63 4.03 3.96 4.45 56. 11. 48.37 49.18 49.01 48.55 15. 3.63 2.93 3.61 3.11 58.45 57.40 53.75 36. 64. 67. 73. 64.19 60.28 57.12 57.18 53.60 50.14 50.6 48. 53. 12. 8.82 6.32 5.46 6.22 6.21 5.09 4.37 'r67. .53 .SD
(B-2)
FEMALE
Effective "Length"
MALE
FEMALE
(B-4)
Analysis of the Craniofacial D. Mandibular
Skeletal Effective Length (B-5)
NA NA
MEAN MEAN N N SD SD 62. 27. 47.75 5.00 3.35 43.52 56.16 52.28 49.66 54.85 49. 7.97 6.22 4.71 64.03 59.92 57.66 71. 49.30 46,96 48.17 47.57 46.15 63. 27. 5.19 4.87 4.82 3.94 67. 56. 57.00 53.97 53.90 47.33 64. 58. 67. 60. 73. 43.55 54.71 54.42 51.04 51.20 50.10 46.73 45. 47. 52. 48. 61. 53. 15. 7.28 6.68 5.68 5.69 4.91 4.32 3.29 5.84 6.39 5.26 5.28 4.18 3.76 59.38 30. 36. 23. 15. 61.37 57.16 57.97 28. 12. 10. 11.00 8.32 8.31 7.19 7.59 7.36 7.56 11.
MALE
FEMALE
E. Posterior Cranial Base Effective Length (B-3) MEAN MEAN N N SD SD 15. 2.50 NA 33.85 49. 2.48 34.29 63. 2.24 2.73 35.72 2.47 2.78 37.48 61. 2.92 36.69 38.08 2.59 37.44 39.10 45. 3.20 37.35 38.76 37.56 39.75 40.29 11. 32.30 33.43 2.36 NA 27. 56. 33.77 33.94 34.62 27. 2.39 2.61 71. 62. 35.26 36.13 35.51 2.35 2.74 67. 36.89 53. 35.71 73. 2.79 36.55 67. 60. 38.26 48. 52. 2.83 2.76 2.93 37.61 65. 59. 40.06 47. 2.73 3.20 23. 30. 37. 15. 38.91 39.76 28. 10. 12. 2.72 3.11 3.35 2.38 2.81 2.99 2.29
MALE
FEMALE
F. Ramus Depth (B-6) MEAN MEAN N N SD SD 27. 37.71 37.39 35.67 36.66 49. 27. 2.80 3.32 NA NA 35.10 37.22 36.50 63. 2.71 2.70 36.19 35.95 38.21 3.54 2.96 36.35 38.47 36.83 37.64 37.50 58. 30. 40.86 40.70 39.10 41.40 40.84 45. 3.20 3.72 3.71 3.86 56. 11. 35.14 37.19 15. 3.03 3.98 4.20 71. 62. 35.76 2.94 3.13 67. 73. 37.87 53. 61. 2.59 3.20 36.80" 60. 39.37 48. 37.76 23. 64. 36. 15. 40.36 41.82 52. 47. 28. 10. 12. 3.66 3.14 3.61 4.04 4.69 3.42 3.16 3.60 3.07•. 2.99 67.
MALE
FEMALE
Skeleton: Cephalometries
291
292
Diagnosis G. Anterior Cranial Base (SE-FMN) MEAN MEAN INCREM. I28. NCREM. OF N .86 MEAS. MEAS. N NA NA NA 56.46.221.69 45.243.50 49. 27. 2.31 3.19 2.75 2.72 1.19 .08 11.44.44 60. 52.672.19 41.73 61. 15. 2.25 3.34 -1.55 3.36 2.82 ' 67.50.48 71.49.531.16 50.251.14 47.73 53. 63. 3.35 3.15 2.80 3.09 .94 1.37 1.29 54.52 53.75 52. .84 .62 59. 15. 47. 3.57 10. 4.38 2.98 1.99 3.77 .86 60.421.11 56.32-.07 12. 2.16 4.42 37. 57.601.52 56.40 55.54 3.14 2.66 45. 4.37 4.38 .56 NA 27.44.53 46.44 73. 53.671.00 51.631.37 53.121.49 48. 2.79 62.48.372.14 49.10 3.33 3.00 67. 2.95 3.88 56.081.56 54.97 1.22 23. 61.81 60.94 55.51-.81 .52 30. 65. 59.311.71
MALE
FEMALE S.D.
H. Anterior Cranial Base (S-Na) N MEAN MEANS.D. 62 71.18 70.16 56 27 49 3.63 2.63 2.83 2.09 2.72 3.21 2.80 74.59 74.15 77.16 76.51 60 48 61 3.07 2.99 3.44 3.08 72.77 67 72.50 11 70.98 723 5.34 53 15 2.65 3.01 3.32 2.94 1.64 76.56 75.41 75.97 80.79 79.74 78.13 37 65 45 3.17 3.42 3.20 4.17 4.22 75.24 83.52 1S6.D. .77 4.15 76.08 82.29 81.98 79.02 47 10 12 4.23 3.90 4.31 3.85 70.25 1.78 27 2.45 73 67.56 71 4.95 63 3.00 67 28 52 3.28 15 76.47 75.74 30 59 3.33
MALE
FEMALE
3. Bilateral Distances (Facial Breadth or Width) The data in this section
are from measures
in the P A
cephalogram. • Measurements used: Figure 12-53. • Graphic data: Figure 12-54. • Tabular data: Table 12-5.
FIG 12-53. Measures of width (breadth). 1, bigonial diameter. 2, molar intersection diameter. 3, upper molar-alveolar crest diameter. 4, medial point on condyles, diameter. 5, lateral point on condyles, diameter. 6, bicondylion diameter. ~
Analysis of the Craniofacial A
Skeleton: Cephalometries
293
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Graphs of width measures. Diameters are shown for the following. A, zygomatic-coronoid intersection. S, bicondylion. C, medial point on condyles. D, lateral point on condyles. E, molar fosae intersection. F, upper molar-alveolar crest. G, bigonial. Legend +l.lALE+\STD
o.~
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TABLE 12-5. Facial Width Measures A. Bilateral Zygomatic
Coronoid MALE
MEAN N MEAN SO SO N 72.51 67.80 84.83 85.33 45. 35. 28. 17. 86.88 78.37 72.08 84.08 86.89 80.45 76.55 83.82 86.58 85.64 49. 47. 48. 24. 12. 82.15 76.19 70.77 92.35 95.17 79.64 84.33 85.00 86.25 88.39 90.86 89.49 35. 41. 27. 33. 21. 30. 34. 17. 24. 19. 11. 4.03 5.29 5.13 5.76 5.61 4.92 6.42 6.43 4.26 4.67 4.86 7.65 4.15 8. 6. 4.90 3.94 5.86 3.95 7.27 5.41 4.38 5.29 4.99 5.53 5.35 5.96 6.08 NA NA NA A N4.10 A 57. 78.49 42. 39. 18. 7NA 78.60 92.95 .•N 5.23 6.09 73.54
• NA
Intersect Distance" FEMALE
not available.
B. Bilateral Lateral Point on Condyle Distance MEAN MEAN N SO SO N 117.23 43. 35. 115.24 116.90 100.78 94.16 115.72 114.28 112.45 114.48 109.44 111.45 107.10 105.70 104.57 120.91 52. 50. 97.60 120.09 29. 120.80 26. 35 115.95 113.56 111.67 109.64 107.22 106.19 9. 22. 25. 30. 35. 46. 38. 43. 10. 14. 37. 31. 18. 5.54 11. 5.11 2.97 7. 3.98 4.74 4.65 4.66 5.11 4.77 4.92 4.73 5.29 4.36 6. .N 3.50 3.85 6.03 6.19 5.14 4.65 4.03 4.18 3.85 5.78 5.09 NA NA NA NA A4.39 .61. 56. 20. 51. 118.53 117.29 46. 112.80 57. 103.19 99.54 16. 9NA 9.21 5.22 4.64 5.27
C. Bilateral Condylion
; 104.64 MEAN N MEAN N SO SO 82.89 86.99 4.66 6. 3.94 4.28 43. 35. 87.67 89.69 92.97 31. 11. 4.35 18. 5.01 5.38 4.51 3.90 3.81 3.96 NA NA NA NA NA N A ~. 94.0& 37. 4.71 5.95 100.40 57. 100.45 52. 101.00 50. 95.70 97.03 98.89 46. 38. 30. 99.27 4.70 4.96 4.60 5.02 4.68 101.54 101.34 46. 103.44 104.55 35. 25. 4.71 4.19 5.53 5.58 102.40 105.20 22. 4.91 103.40 103.86 107.43 107.70 107.08 16. 14. 10. 7. 5.67 3.99 3.76 5.32 5.16 5.76 9. 9 8.40 20. 8 91.82 8.25 56. 51. 35. 4.23 26. 29. 4.81
43.
294
61.5.6Q 3.93·,
MALE
FEMALE
Distance MALE
FEMALE
Analysis of the Craniofacial D. Bilateral Medial Point on Condyle Distance
-
N MEAN N MEAN SD4.96 SD 20. 75.17 75.35 11. 3.43 43. 56. 76:21 88.56 90.08 80.81 87.36 87.43 79.40 81.14 84.48 82.64 85.70 86.72 46. 57. 50. 26. 29. 15. 91.28 82.52 83.84 86.18 86.25 86.36 88.29 92.70 91.72 80.99 89.71 89.73 NA 38. 46. 37. 43. 30. 35. 25. 22. 18. 14. NA 10. 3.89 4.77 4.69 4.49 4.74 4.26 5.40 5.22 5.78 4.71 4.16 5.03 5.35 4.46 4.42 35. 3.62 61. 52. 35. 51. 31. 4.72 4.78 4.09 4.08 4.26 5.87 4.95 5.17 5.50 79.50
MALE
FEMALE
E. Bilateral Upper Molar Aveolar Crest Distance MEAN N MEAN SD N 50.77 46.63 45.49.65 49.63 56.94 55.87 29. 47. 54. 47.79 55.28 49.131.57 57.72 54.83 55.76 56.15 57.17 57.65 45. 35. NA 5. 53.54 NA 59.00 56.28 57.02 57.49 58.97 58.82 NA 21. 29. 36. 35. 23. NA 4. 1. NA 1. 3.93 2.67 2.23 2.61 2.56 2.19 13. 2 4. 8. 5. NA N .13 .52 .67 2.05 4.31 3.11 2.54 2.85 3.16 2.94 .SD NA A 58.91 12. 3. 16. 2.21 2.90
MALE
FEMALE
F. Bilateral Molar Fossae Intersect Distance MEAN N MEAN N SD SD~. ;. 30. 48. 12. 45.06 45.88 45.98 47.11 47.87 47.55 36. 21. 28. 42.56 45.84 46.79 47.10 47.68 47.93 47.95 48.17 NA 31. 21. 41. 40. 27. 20. NA 3.49 2.52 2.81 3.04 2.85 1.88 4.53 2.39 2.51 2.49 2.54 2.33 1.95 48.38 48.17 48.92 10. 49.14 7. 2.08 8. 3.70 2.81 52. 35. 11. 48.14 2.90 2.02' 3.1'3 47.49, 9.
MALE
FEMALE
Skeleton: Cephalometries
295
296
Diagnosis G. Bigonial Distance (mm) MALE
MEAN N MEAN N SO SO 78.54 19 81.87 11 3 .43 81.23 84.33 43 87.99 32 3.50 4.05 102.88 86.32 88.50 92.17 95.39 95.68 445 61 92.13 95.50 98.39 100.13 57 49 23 30 22 43 38 35 3.56 4.80 4.77 4.92 4.44 5.64 4.28 4.76 5.39 .13 91.81 97.91 105.64 16 14 6 7 9.34 .79 76.21 78.40 2 6 3.79 32 84.28 18 2.85 3.38 90.61 95.89 93.14 56 89.96 94.60 97.01 51 35 36 48 4.75 4.50 4.23 4.35 4.26 4.75 103.93 105.82 95.31 29 27 6.05 .84 5 6 .94 .35 9 3.42 _4.51
B. REGIONAL ANATOMIC DIMENSIONS
FEMALE
c. CRANIOFACIAL
CONSTANTS
1. Mandible • •
Measurements used: see Figure 12-13A and B. Graphic and tabular data: Figures 12-55 through 12-59.
2. Maxilla Measurements used, graphic data, and tabular data are shown in Figures 12-60 and 12-61. See also Section A-2 of this Appendix, AP Distances.
In Section G-5 a method for estimating future morphologic relationships was presented which utilized certain craniofacial "constants." The angular relationships in this method persist, but the landmarks advance along the rays of the angle as growth takes place (see Fig 12-32). In practice, one adds the average increment for appropriate age and sex to the patient's starting landmark along the constant direction. • • •
3. Anterior Cranial Base (Cranial Floor)
Measurements used: see Figure 12-30. Plotted data: see Figure 12-63. Tabular data: see Tables 12-6.
Measurements used and graphic data are shown in Figure 1262. Tabular data are found in Table 12-4,G and H.
140
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FIG 12-55.
FIG 12-56.
Overall mandibular
Mandibular
.
LE+1STD
o
AGE (YEARS)
length (condylion-pogonion)
•••••
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Analysis of the Craniofacial
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15
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Analysis of the Craniofacial
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"
registration point-frontal-maxillo-nasal
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300
Diagnosis
TABLE 12-6. A. Ethmoid Registration Menton
Point-Menton
N N MEAN IINCREM.' NCREM. MEAS. MEAS. 62. 27. 11. 104.082.59 101.482.38 99.80 05.903.56 94.58 99.10 3.77 27. 4.54 44.60 1OF 4.65 4.74 3.57 5.21 .89 4.97 .51 .31 NA 67. 71. 73. 60. 67. 58. 36. 30. 15. 116.752.48 119.793.04 123.343.55 130.65 121.61 108.982.12 111.372.38 116.042.13 120.97 120.274.23 123.662.68 113.912.53 11.632.29 5.15 48. 53. 61. 52. 47. 28. 12. 6.80 4.77 5.74 5.32 5.29 5.49 4.79 6.00 7.42 7.74 7.46 8.08 4.85 .70 56. 97.83 02.332.52 49. 15. 4.61 3.80 NA NA NA 64. 23. 1MEAN 137.532.39 114.262.62 125.79 134.04 135.141.09 122.65 106.862.77 09.343.43 63. 45. 10. -2.04 8.40 5.49 5.57 7.50 2.45 3.38 5.53 1.03
(SE-Me)
MALE
FEMALE S.D.
MALE
FEMALE S.D.
MALE
FEMALE S.D.
S.D.
B. FMN-A
PT MEAN N MEAN IINCREM. NCREM. OF N.50 MEAS. MEAS. 62.37.82 56.37.87 30. 37. 65. 59. 39.72 39.64 2.93 3.94 3.64 3.27 28. 45. 53. 12. 4.13 3.96 3.01 2.98 3.73 3.33 -.56 -.05 -.3.77 1.32 1.27 .08 .18 .98 .19 5.07 NA NA NA 27.36.59 67.39.49 11.35.93 73. 41.84 37.59 40.02 3.05 2.53 52. 27. 10. 3.04 3.35 3.37 4.72 3.49 1.16 1.28 1.01 1.37 1.78 .24 .66 43.90 42.58 43.02 42.04 39.12-.59 36.31 39.45 35.87 3.41 47. 49. 2.82 -.43 .43 15 44.91 . NA .14 71.38.98 23. 60. 67. 44.76 40.83 39.78 38.79-.33 37.12-.47 34.63 38.74 38.49 36.06 4.02 3.19 3.53 63. 48. 61. 3.27 3.66 3.48 2.10 2.69 1.05 1.43 .86 .29 . 15.
C. SE-FMN N MEAN INCREM. OF N.86 MEAS. ,. 37. 59.311.71 55.54 54.97 2.66 3.14 47. 3.77 1.22 53.75 2.95 52. 3.88 61.81 53.671.00 55.51-.81 56.32-.07 48. 10. 4.38 12. 3.57 3.19 4.42 3.36 .86 27.44.53 11.44.44 41.73 45.243.50 51.63 NA 27. NA 2.31 15. 2.25 3.34 -1.55 NA NA 1.37 56.46.221.69 62.48.372.14 71.49.531.16 49.101.37 63. 3.35 3.15 3.33 2.72 3.00 1.14 59. 56.081.56 57.601.52 56.40 28. 45. 2.98 4.37 4.38 .56 67. 54.25 .84 .62 30. 23. 60. 15. 60.421.11 60.94 53.121.49 2.16 1.99 .52 73. 52.672.19 61. 2.75 2.79 .08 .94 67.50.48 "MEANINCREM. 50.25 "53. 49. 53. 2.80 3.09 46.4465 ..47.73 1.19 )2.82 .29
Analysis of the Craniofacial
REFERENCES 1. Baumrind S, Korn EL, Isaacson RJ, et al: Quantitative analysis of the orthodontic and orthopedic effects of maxillary traction. Am J Orthod 1983; 84:384-~98. 2. Bookstein FL: The Measurement of Biologic Shape and Shape Change. Berlin, Springer, 1978. 3. Bookstein FL: Looking at mandibular growth: Some new geometrical methods, in Carlson DS (ed): Craniofacial Biology, monograph 10. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1981, pp 83-103. 4. Bookstein FL: Foundations of morphometrics. Ann Rev Ecol Syst 1982; 13:451-470. 5. Bookstein FL: Measuring treatment effects on craniofacial , growth, in McNamara JA Jr, Ribbens KA, Howe RP (eds): Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983, pp 65-80. 6. Bookstein FL: The geometry of craniofaciai growth invariants. Am J Orthod 1983; 84:384-398. 7. Bookstein FL: Tensor biometrics for changes in cranial shape. Ann Hum Biol 1984; 413-437. 8. Bookstein FL, Chernoff B, Elder R, et al: Morphometries in Evolutionary Biology. The Geometry of Size and Shape Change, With Examples From Fishes. Philadelphia, Academy of Natural Sciences of Philadelphia, 1985. 9. Bookstein FL: Size and shape spaces for landmark data in two dimensions. Statistical Science 1986; 1:181-242. 10. Broadbent BH: A new x-ray technique and its application to orthodontia. Angle Orthod 1931; 1:45. 11. Delaire J: Quelques pieges dans les interpretations des tt~leradiographies cephalometriques. Rev Stomatal chir maxillogac 1984; 85:176-185. 12. Ellis EE, McNamara JA Jr: Components of adult Class III malocclusion. J Oral Max Surg 1984; 42:295-305. 13. Enlow DH, Moyers RE, Hunter WS, et al: A procedure for the analysis of intrinsic facial form and growth. Am J Orthod 1969; 56:6-23. 14. Graber LW: Psychological considerations of orthodontic treatment, in Lucker GW, Ribbens KA, McNamara JA Jr (eds): Psychological Aspects of Facial Form, monograph 11. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development. 1980. 15. Graber LW: Psycho-Social Implications of Dentofacial Appearance, Doctoral dissertation, Horace H. Rackham School of Graduate Studies, University of Michigan, Ann Arbor, Michigan, 1980. 16. Grayson G, Cutting C, Bookstein FL, et al: Am J Orthod (in press). 17. Higley LB: A new and scientific method of producing temporomandibular articulation radiograms. Int J Orthod Oral Surg 1936; 22:983. ' 18. Hofrath H; Die Bedeutung der Rontgenfem- und Abstandsaufnahme fUr die Diagnostik der Kieferanomalien. Fortschr Orthod 1931; 1:232. 19. Houston W: Relationships between skeletal maturity estimated from hand-wrist radiographs and the timing of the adolescent growth spurt. Eur J Orthod 1980; 2:81-93. 20. Houston WJB: The analysis of errors in orthodontic measurements. Am J Orthod 1983; 83:382-390.
Skeleton: Cephalometries
301
21. Jenkins H: Orthodontics, Its Geodesics, Genetics, and Genesis: Of the Science of Biologic Shape and Function. Toronto, Sarie Jenkins, 1983. 22. Lucker GW, Ribbens KA, McNamara JA Jr: Psychological Aspects of Facial Form, monograph 11, Craniofacial Growth Series. Ann Arbor Mich, Center for Human Growth and Development, University of Michigan, 1980. 23. McNamara JA Jr, Bookstein FL, Shaughnessy TG: Skeletal and dental changes following functional regulator on Class II patients. Am J Orthod 1985; 88:91-110. 24. Moyers RE, Bookstein FL: The inappropriateness of conventional cephalometries. Am J Orthod 1979; 75:599-617. 25. Moyers RE, Bookstein FL, Guire KE: The concept of pattern in craniofacial growth. Am J Orthod 1979; 76:136148. 26. Moyers RE, Guire KE, Riolo M: Differential diagnosis of Class II malocclusion. Am J Orthod 1980; 78:477-494. 27. Moyers RE, Wainright R, Primack V: Craniofacial "constants," their use in cephalometries (submitted for publication) . 28. Pacini AJ: Roentgen ray anthropometry of the skull. J Radiol 1922; 42:230,322,418. 29. Ricketts RM: Planning treatment on the basis of the facial pattern and an estimate of its growth. Angle Orthod 1957; 27:14-37. 30. Riolo ML, Moyers RE, McNamara JA Jr, et al: An Atlas of Craniofacial Growth: Cephalometric Standards from The University School Growth Study, The University of Michigan, monograph 2. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, The University of Michigan, 1974. 31. Simon PW: Grundzuge einer systemische Diagnostic der Gegiss-Anomalien. Berlin, Meusser, 1922. 32. Steiner CC: Cephalometries in clinical practice. Angle Orthod 1959; 29:8-29. 33. Tweed CW: Clinical Orthodontics, St Louis, CV Mosby, 1966. 34. Webber RL, Blum H: Angular invariants in developing human mandibles. Science 1979; 206:689-691.
SUGGESTED READINGS Baumrind S, Franz R: The reliability of head film measurements. 1. Landmark identification. Am J Orthod 1971; 60:111-127; 2. Conventional angular and linear measurements 1971; 60:505-517. Broadbent BH: The face of the normal child. Angle Orthod 1937; 7:183. Horowitz SL, Hixon EH: Nature of Orthodontic Diagnosis. St Louis, CV Mosby, 1966. Houston WJB: The analysis of errors in orthodontic measurement. Am J Orthod 1983; 83:382-390. Moyers RE, Bookstein FL: The inappropriateness of conventional cephalometries. Am J Orthod 1979; 75:599-617. Riolo ML, Moyers RE, McNamara JA Jr, et al. An Atlas of Craniofacial Growth. Cephalometric Standards from the University of Michigan School Growth Study, monograph 2, Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan. 1974.
SECTION III
Treatment Robert
E. Moyers, D.D.S., Ph.D.
TREATMENT Concepts of treatment in most of dentistry have their roots in our medical heritage, but malocclusion is not a disease or an injury and therefore is not "cured," as are tuberculosis, syphilis, or septicemia, or healed, as is a fracture. Koch's postulates do not apply to malocclusions for there is no specific organism which always produces a particular occlusal problem each time it invades a facial or jaw site. Malocclusions are but unfavorable variations of normal craniofacial morphology and/or function. Research on their origins is, therefore, not based in microbiology and pathology, but in growth and development. Because there is no theoretical possibility of producing a vaccine or providing immunity against malocclusion, the opportunities for its prevention are much less than for a disease, and such preventive procedures as are available are imprecisely implemented in practice. How do we "treat" or "correct" a mal occlusion when we undertake. orthodontic therapy? We alter the relationship of parts of the face, jaws, or occlusion to provide a more "normal" function or more "ideal" facial appearance. Therefore, "treatment" is dependent on perceptions of "normal" and "ideal" faces, and such perceptions define the clinician's goal. During a visit to China, a friend asked a medical colleague there, "How do you treat tuberculosis?" "We don't treat tuberculosis" was the reply, "We treat the patient." What are we "treating" when we undertake orthodontic therapy? An abnormal variation in bony or dental structures which hampers favorable function? A facial morphology which harms appearance? A face which fails to meet someone's expectations or perceptions of facial attractiveness? We may say we are "treating" mandibular deficiency or a deep bite, and we may actually change their measurements; but orthodontics, if it is successful, places such structural changes in the broad perspective of the person involved: we don't just treat malocclusion, we treat the patient.
What then constitutes "good" orthodontic treatment? That is a very difficult question indeed, for it is much harder to quantify idealized facial beauty than it is to specify the characteristics of successful surgery, and "normal" comprises a wide morphologic range. I Surgeons, through precisely controlled clinical studies, have agreed on the characteristics of successful operations on the knees, namely, minimal time in bed after surgery, minimal time before the patient can walk unaided, absence of limping, absence of pain, etc. Physicians often have sure and measurable signs indicating the abatement of an infectious disease (e.g., diminished fever), but there is only convention, general agreement, or personal opinion describing a few traits of "well-treated" malocclusions, and none are as reliable as is a thermometer recording of body temperature. Further, there is a considerable range of acceptable values for some occlusal traits after treatment. For example, some clinicians consider minimal incisal overlap ideal, while others establish sufficient overbite to produce disci us ion of all posterior teeth during protrusive jaw movements. The definitions of "good" orthodontics vary with the clinician, the original problem, and the appliance used. The absence of definitive clinical research makes universal definitions of "good" or "correct" treatment impossible, I but that fact offers no excuse for inadequate or "poor" therapy because there is agreemef1,t on some features of well-treated mal occlusion . The following chapters, describing the concepts, goals, and some methods of dealing with malocclusions, are arranged according to the developmental age of the patient, since maturation is the primary determining factor of both the strategies and tactics in orthodontic treatment (Figs I and 2). A continual emphasis is made to help the reader keep the strategies of treatment separate from the tactics available, since the two are often blatantly confused in the literature. Strategy is planning; tactics are treatment. 303
304
Treatment
--
---
-
-Muscles 0+Palatal 0 + of Translation of Growth 0 Growth Size Movement Parts Teeth Gutdance 0+ orof Expansion Training Shape Eruption of Boney Encouragemen~
Change
Strategies "Rapid"
in
of
Treatment
(Chap. Parts 15) Boney 17) 16)
Immediate
KEY:
:;-optimal 0, can be -,
poor
FIG
1.
or only period
done but may not be time or can't be done
Relationships
of developmental
best tlme at this time
ages to strategies of treatment.
I Grawth
1
Active skeletal grawth
D!n1ition
Mixed
Primary
no growth
I
Permanent
(lass 01 teeth)
-I I
Oral Health
HH}~_
Healthy f.. 1.
(Peridantal disorders)
I Treatment
k
tac1ics
interception
I
growth guidance
I ..•
I
correction
"
Habit
Appliances
control
f
.HH •• :~
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control
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I~ .-
I "
camouflage and casmetlC therapy
and law orthOpediC appliances
I
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.
----r-
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~
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')O>. PrecISion tooth placement.H ••••appliances +-I
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...•...
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Age
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-.l
f4 o
5 Childhood
10
20
15
Adolescence
r ·i I
FIG 2. Timing of different aspects of growth and treatments.
25 Adulthood
.....~..
Treatment -
-2Size 1-Parts 2,3 of Growth 2 1Muscles 2 34Training 1Movement Palatal 4Growth 3Boney 1 Teeth Guidance orof1- 324of Eruption Expansion ofTranslation 2,3 Shape Encouragement SURGERY maxilla -extra-oral to to dentition Crozal. Bionator,etc. Frankel, (Schwartz, ) (Activator, Appl Appl Appl Begg,etc, Appl Lingual (Edgewise, to chin separate iances i ances s I)
Change
Strategies "Rapid"
In
of
305
Boney Parts Treatment
Irrrnediate
KEY:
~primary 2, 3, 4,
roles
secondary roles adjunctive roles usually contraindicated not appl tcable
FIG 3. Relationships of strategies of treatment and tactics of treatment. Strategy is defining goals; tactics are the method, appliance, and other factors employed to gain success (Fig 3), Precision in timing and techniques is emphasized, but these alone do not provide "good" orthodontics, for professional ethics and sensitivity to each patient's personal needs are also necessary if one is to treat the patient, not just the malocclusion.
REFERENCE
I,
"
Moyers RE: Good Orthodontics in Singer J, Ribbens KA (eds), On The Nature of Orthodontics, Los Angeles, The University of Southern California, School of Dentistry, and Ann Arbor, Center for Human Growth and Development, University of Michigan, 1985; also in Graber LW: Orthodontics: State of the Art, Essence of the Science, St Louis, CV Mosby, 1986, pp 3-11,
CHAPTER
13 Force Systems and Tissue Responses to Forces in Orthodontics and Facial Orthopedics Per Rygh, Dr. Odont. Robert E. Moyers, D.D.S.,
Ph.D.
Every body continues in its state .of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.-SIR ISAAC NEWTON, Philosophae Naturalis Principia Mathematica, Laws of Motion I
OUTLINE A.
I)
Forces within the masticatory system I.
Inherent natural forces a)
2.
B.
2)
3)
Tongue-thrusting Digital sucking Occlusal dysfunction
4)
d) Traumatic occl~sion e) Bruxism Therapeutically introduced forces
Force systems in orthodontic and functional jaw orthopedic appliances I.
2. 3.
306
from the action of the muscles of
b) Originating within the teeth c) Originating from the circumoral musculature d) Equilibrium theory Abnormal forces a) b) c)
3.
Originating mastication
Classification of therapeutically employed forces a) Natural b) Biomechanical Strategies for controlling forces in clinical practice Concepts of anchorage a) Classification of anchorage
4.
According to the manner of force application (a) Simple anchorage (b) Stationary anchorage (c) Reciprocal anchorage According to the jaws involved (a) Intramaxillary (b) Intermaxillary According to the site of anchorage (a) Intra-oral (b) Extra-oral (c) Muscular According to the number of anchorage . Onits
(a) Single or primary anchorage (b) Compound anchorage (c) Reinforced anchorage b) Control of anchorage Principles of biomechanics in fixed orthodontic appliances a) Some definitions b) Orthodontic forces and tooth movements I) Types of tooth movement 2) Equivalent force systems
Force Systems and Tissue Responses to Forces in Orthodontics 3)
c)
C.
Selection forces
and control
of orthodontic
Some clinical implications and applications I) Translation 2) "Light" wires 3) Intrusion 4) Extra-oral traction
Periodontal and other tissue responses to orthodontic forces I.
2.
Physiologic tooth movement a) Resorptive bone wall b) Depository bone wall Experimental and orthodontic tooth movement a) Dentoalveolar tissue reactions I) Pressure side 2) Tension side b) Hyalinization I) Definition Tissue degeneration 3) Elimination of damaged tissue 4) Reconstruction of supporting tissues Factors influencing orthodontic tooth movement a) Character of bone b) Physiologic activity c) Force application I) Tipping 2) Translation d) Applied force and time I) Continuous 2) Interrupted-continuous force 3) Intermittent Root resorption 2)
3.
4.
D.
Controlled alteration of craniofacial growth I.
2.
E.
Other effects of orthodontic treatment I. 2. 3. 4. 5.
F.
The nasomaxillary sutural system a) Posterior forces against the maxilla b) Anterior forces against the maxilla c) Transverse forces in the maxilla The mandible and temporomandibular joint a) Functional protrusion b) Functional restriction and redirection c) Intermaxillary fixation Long-term effect on the periodontium and gingivae Root resorption Tooth malpositions Effects of adjunctive surgical procedures Temporomandibular function after orthodontic treatment
Retention, relapse, and occlusal stabilization
Malocclusions are treated, irrespective of the appliance employed, by a purposeful alteration of the forces within the craniofacial region. Anyone proposing orthodontic treatment, therefore, must understand the natural forces inherent within the masticatory system, comprehend and master the therapeutic application of forces, appreciate the biologic response of tissues to clinically applied forces, and be fully aware of the long-term sequelae of orthodontic treatment.
and Facial Orthopedics
307
Orthodontists' and other research workers have probed these matters for nearly a century: the results constitute some of the brightest and most useful pages in orthodontic history, resulting in a rich and very extensive literature (see Suggested Readings). This chapter is but an introduction to this important subject, it is not an exhaustive or definitive presentation.
A. FORCES WITHIN THE MASTICATORY SYSTEM 1. Inherent Natural Forces a) OrigiTUltingT:rom the Actio~ of the Muscles of Mastication - The normal activities of mastication, swallowing, breathing, etc., all produce continuous and varied changes in the forces affecting the teeth and. bones. Most of the energy for such forces originates from contractions of the muscles of the fifth cranial nerve, the so-called muscle of mastication. One of the most important of these muscle activities is that of posture, since the continuous pressure of muscle tensions against the teeth and bones likely have more effect than transitory contractions'3 The result of all the forces transmitted through the intercuspation of the teeth during occlusal function is termed the anterior component offorce (see Chapter 6). Another important and often forgotten combining resultant force is that of swallowing, for the repeated effects of the tooth-together swallow, when the teeth are in correct intercuspation, is an important element of occlusal stability .64.66
b) Originating Within the Teeth Eruption and the mesial drifting tendency (which must be carefully differentiated from the anterior component of force) are inherent natural forces originating within the teeth and the periodontiUlJl (see Chapter 6). Although these forces are not thoroughly understood theoretically, clinical advantage is taken of them, particularly in mixed dentition treatment.
c) Originating From the Circumoral Musculature The tongue and the lip and cheek muscles impose varying forces against the crowns and the alveolar process during posture, swallowing, speech, mastication, and respiration.47. 81.82Posture, because it is continuous, is considered the most important.82
d) Equilibrium Theory The equilibrium theory of tooth position simply holds that although a variety of forces act on the teeth from many directions, in varying amounts and duration, tooth positions remain relatively stable. 117 If the inherent natural forces are in equilibrium, when are they in equilibrium? During a moment of function as a single swa!l0w? Over a reasonaple period of time, for example, a day? Throughout a lifetime? The equilibIjum theory is a useful concept clinically, but it is difficult to prove or disprove because of (I) the simple logistics, experimental design, and sample size of necessary studies; (2) the instrumentation necessary to measure all forces at any time-let alone a lifetime-for a satisfactory sample; (3) the difficulties of identifying singular abnormal forces in each individual; and (4) many factors beyond practical control in such a study. Proffit,83 examining the equilibrium theory and the research thus far bearing on it, concludes the two most important factors
308
Treatment
TABLE 13-1. Equilibrium Components' COMPONENT
INTENSITY
DURATION
Forces of Occlusion Lip and/or tongue pressures Swallow Speech Rest Forces of Eruption
Very High
Very Short
High Low Low Very low
Short Short Long Long
• Adapted from Proffit WRB2
in the equilibrium of teeth are (I) the resting pressures of the lip, cheek, and tongue, and (2) the forces produced by metabolic activity in the periodontium, since these forces are of low intensity for,a long duration (Table 13-1). Little is known, however, about many of the factors in the equilibrium theory over a lifetime, or their variance in faces of different morphology. The latter is particularly significant clinically. X2
The existence of the field of orthodontics is testimony that the equilibrium can be upset and reestablished under new circumstances. 2. Abnormal Forces Abnormal forces originating within the masticatory system, while natural, may be unsettling to the occlusion, tooth positions, or temporomandibular joint equilibrium. a) Tongue-Thrusting
Tongue-thrusting
is thought
to create
open bites, but though of high tensity, are short in duration and are less apt to alter tooth positions than low-intensity forces applied over long duration (e.g., tongue posture). Abnormal tongue posture accompanies the complex Proffit82-83 holds that tongue swallow pressures,
tongue-thrust and -is associated with some vertical skeletal dysplasias (the so-called skeletal open bite). Protracted tongue posture is sometimes a residuum of infantile neuromuscular behavior ~see Chapters 5, 7, and 10). b) Digital Sucking Thumb- and finger-sucking can change tooth positions if these forces are of appropriate magnitude and duration. Cook 13 identified several different patterns of abnormal forces associated with thumbsucking, which may account for the variation in appearance and prevalence of the open bites associated with digital sucking (Fig
13-1). c) Occlusal Dysfunction
Occlusal interferences
and the resultant slide into the inter-
cuspal position, a slide directed by the cusps of the teeth, has been shown to produce crowding of the mandibular incisors. 11.22 Orthodontically treated cases which were equilibrated displayed less mandibular incisal crowding during and after retention than those which were not. 65-66 d) Traumatic Occlusion The forces of traumatic occlusion (jiggling occlusal forces) are absorbed by the periodontium, including the supercrestal connective tissue, by a combination of compressional and tensional inflammation or loss of the atta hment mechanism when there is counter TraumaticNor~Iusion does not produce aggravate gingival a healthyforces. periodontium. do s traumatic occlusion inflammation or cause loss of the attachment when gingivitis is present. However, traumatic occlusion may aggravate active periodontitis, accelerating the loss of the connective tissue attachment, which may result in less regaining of the attachment after orthodontic and/or periodontal treatment is over. 112
ALPHA
e) Bruxism
Bruxism mayor may not alter the tooth position depending on whether or not it is associated with a slide into the intercuspal position.
+ o
3. Therapeutically BETA
+ o
GAMMA'
Introduced
Forces
Dentists purposely introduce new forces to alter tooth positions, permit changes in the mandibular position, or to affect craniofacial morphology or growth. Orofacial forces may be altered by (I) neuromuscular conditioning, (2) functional appliances which modify and redirect the patient's own neuro)TIuscular activities, or (3) fixed orthodontic appliances which have stored within them intentional forces controlled by the clinician.
B. FORCE SYSTEMS IN 'ORTHODONTIC AND FUNCTIONAL JAW ORTHOPEDIC APPLIANCES TIME
FIG 13-1. Three different patterns of forces active against the palate during thumb-sucking. (From Cook JE: Intraoral Pressures Involved in Thumb and Finger Sucking, thesis. University of Michigan, Ann Arbor, 1958. Used by permission.)
1. Classification
of Therapeutically
Employed Forces
a) Natural
Energy generated by contractions of jaw and facial muscles may be transferred through functional appliances to direct the
f
Force Systems and Tissue Responses to Forces in Orthodontics eruption of teeth, impede eruption, or move an erupted tooth. Functional appliances are also used to condition, strengthen, or redistribute mus'cle forces against the jaws and dentition. Thus, an Activator or Bionator might be used to prevent the eruption of the mandibular incisors and guide the eruption of the cuspids and premolars, while simultaneously repositioning the mandible more ventrally (see Chapter 18). Synchronously, the lips'are trained by the appliance to seal more efficiently during the swallow, while the tongue learns to assume a correct position during the swallow.
TABLE
309
and Facial Orthopedics
13-2.
Outline of Kinds of Anchorage
INTRAMAXILLARY
--{SINGLEREINFORCED STATIONARY RECIPROCAL {SIMPLE
COMPOUND
INTRA-ORAL
b) Biomechanical Biomechanical forces are artificial clinically induced forces whose energy is derived primarily from contrived mechanical devices (e.g., archwires, coil springs, auxiliary springs, vertical loops in archwires, elastics, screws, etc.) (see Section C-3-d, Applied Force and Time).
INTERMAXILLARY
{SIMPLE EXTRA-ORAL
2. Strategies for Controlling Forces in Clinical Practice Orthodontists have devised many ingenious appliance systems to deploy natural and biomechanical forces, but all use one or more of the following strategies: (I) elimination of unwanted forces, as a habit control appliance; (2) redistribution of natural forces, an approach inherent in all functional appliances; (3) stimulation or strengthening of natural forces (e. g., lip bumpers, vestibular shields, and the labial pads of Frankel appliances); or (4) introduction of artificial forces (e.g., those in precision bracketed appliances, lingual archwires, or screws inserted in "functional appliances"). In 1,2, and 3 control of the appliance remains with the patients' own neuromuscular system. Artificial appliance forces are adjusted for amount and duration of force by the dentist.
OCCIPITAL CRANIAL FACIAL {CERVICAL
RECIPROCAL
2) According to the Jaws Involved.(a) Intra-Maxillary.-Anchorage
(b) Intermaxillary.-
AncC
•
Anchorage obtained outside the oral cavity.
Cervical.-Utilizing
the neck for anchorage (e.g., neck
straps).
• •
•
Occipital.-Utilizing
the occipital region for anchorage (e.g., head gears). Cranial.-Involving the cranium as a source of anchorage (e.g., high pull head gears). Facial.-Involving aspects of the face as a source of anchorage (e.g., face masks).
(c) Muscular.-Anchorage Anchorage 13-2).
is classified
distributed to both jaws.
(a) Intra-oral.-Anchorage established within the mouth, that is, utilizing the teeth, mucosa or other intra-oral structures. (b) Extra-oral.-
a) Classification of Anchorage
established in the same jaw.
3) According to the Site of Anchorage.-
3. Concepts of Anchorage Anchorage is the word used in orthodontics to mean resistance to displacement. Every orthodontic appliance consists of two elements: an active element and a resistance element. The active parts of the orthodontic appliance are concerned with tooth movements: the resistance elements provide the resistance (anchorage) that makes tooth movements possible. According to Newton's Third Law there is an equal and opposite reaction to every action. Therefore, in orthodontics, all anchorage is relative and all resistance is comparative.
STATIONARY
derived from action of muscles
(e.g., vestibular shields).
and named in several ways (Table
4) According to the Number of Anchorage Units.-
1) According to the Manner of Force Application.. (a) Single or Prim'ary Anchorage.-Anchorage (a) Simple Anchorage.-Resistance
to tipping, that is, the
involving
only one tooth.
tooth is free to tip during movement.
(b) Compound Anchorage.-Anchorage (b) Stationary
Anchorage
Resistance to bodily movement, translate only.
(an absurd designation).that is, the tooth is permitted to
(c) Reciprocal Anchorage.- Two or more teeth moving in opposite directions and pitted against each other by the appliance. Usually, the resistance to each other is equal and opposite.
involving two or
more teeth.
(c) Reenforced Anchorage.- The addition of nondental anchorage sites (e.g., mucosa, muscle, head, etc.). b) Control of Anchorage In practice, care is taken to maintain control of anchorage so
310
Treatment F
F,-D
I
i
c
c
t
t
(0)
(b)
FIG 13-4. Strain. C = areas of compression;
T = tension.
a) Some Defini~
FIG 13-2. The effect of force on a rigid free body. that the conditions for movements of teeth are optimal in the active elements of the appliance and satisfactory for withstanding movement in the resistance elements. Routine precautions include (I) securing anchorage as far as possible outside the teeth themselves, for example, in the mucosa, muscles, cranium, etc.; (2) selecting larger numbers of teeth in the resistance parts of the appliance; and (~) varying the amount, direction, and manner of force application between active and resistance elements. Adherence to the principles of anchorage control is an essential factor in successful orthodontics. 4. Principles of Biomechanics Appliances
in Fixed Orthodontic
An orthodontic appliance is a system storing and delivering forces against the teeth, muscles, or bone and creating a reaction within the periodontal ligament and alveolar bone that causes movements of the teeth or alters bone morphology or growth. If planned tooth movements are to be appreciated, the theoretical mechanics of the orthodontic force system must be understood.
Mechanics is the science which deals with the action of forces on the form and motion of bodies. In this instance, the bodies are the teeth, the periodontal ligaments, and the bones. The forces are those delivered by orthodontic appliances or by muscle contractions against the teeth, directly or through the intercuspation. Force is energy or strength brought to bear causing motion or change in a body-a push or a pull acting in a straight line (Fig 13-2). A force has magnitude, point of application, and direction (sense and line of action). 10 Therefore, forces are represented and treated mathematically as vectorslO8 (Fig 13-3). Strain is a change in form or size of a body as it responds to an applied force (Fig 13_4).24 A coil spring undergoes strain as it is stretched; a wire strains as it is bent. Stress is the internal molecular resistance to the deforming action of external forces.24 Stress is equivalent, in rigid bodies, to the strength of the body. Translation occurs when a force is applied to a body through the center of resistance.9 Pure bodily movement (translation) appears in the line of action of the applied force (Fig 13-5). The greater the force, the greater the translation. Center of resistance is the term used in orthodontic biomechanics in place of the center of mass or center of gravity since teeth are not free bodies which can be balanced perfectly on a point for they are constrained by their periodontal attachments to the roots (see Fig 13_5).108 In single-rooted teeth, the center of resistance is on the long axis of the tooth one-third to one-half the way from the alveolar crest to the apex. In multirooted teeth it is just apically to the furcation. Rotation occurs when a forcejs applied away from the center of resistance (Fig 13_6).9 The potential fot rotation is termed a moment and is' measured as the product of the force and the
I!I 1
Line of Action Sense~
-z'...
••
-
I
F-
Point of
~J---s-Appli'cation
•
0
I
>
'III
1
-
FIG 13-5.
~Magnitude~
Translation is a movement in which crown and root are moved in the same direction.
FIG 13-3. Forces may be treated as vectors and represented
I
as arrows.
Force Systems and Tissue Responses to Forces in Orthodontics
/\
" \
..
F--
\
" \ --\
" ""
\\
\
\
\
I, I\
\
\
I , I
\
I
I
,
/
,
,,~'-"'\t/ \
\./ "
\" I
FIG 13-6. Moment (gm) = F (force) X distance between point of application and center of resistance.
I
,""
I
f
,
I f
t.---,
("
I
'l ,I
I
\ .....
I I
/
,
~::,:~
,,)
311
B ,'"
I \
,,"
\
...l
A
and Facial Orthopedics
,//
~
FIG 13-"9. TheJo?c'e in A, passing through the center of resistance, will result in translation of the tooth. The force in 8, at the bracket, will also translate the tooth but, in addition, will cause a rotation because of the moment created at the center of resistance. (From Smith RJ, Burstone CJ: Mechanics of tooth movements. Am J Orthod 1984; 85:294-307. Used by permission.) CENTER OF ROTATION
FIG 13-7. Equivalent moments with varying forces and distances. perpendicular distance from the line of action to the center of resistance (see Fig 13-6).'0 An equivalent moment can be produced by varying the force and the distance (Fig 13_7).108 A force applied away from the center of resistance will cause the same translation as through the center, but the body will also turn on an axis (see Fig 13-6). A couple is an arrangement of two forces of equal magnitude and opposite parallel but noncollinear lines of action (Fig 13- 8).9 A couple produces pure rotation, since translational tendencies are canceled. The center of rotation is the point (or points) around which a body seems to have rotated. The difference between center of resistance and center of rotation is important in orthodontics. The center of resistance of a tooth is fixed and not changed by orthodontic forces, but the manner of force application can be chosen to determine the instantaneous center of rotation (Figs 13-9 and 13_10).'08 Further, during most tooth movements a series of different centers of rotation appear.
b) Orthodontic Forces and Tooth Movements In practice, teeth are never moved by one simple force; rather, the movement is determined by several forces, natural and contrived, acting differently. It is probably impossible to depict mathematically all the complicated force systems operating against the teeth; however, it is useful to analyze the'purposeful forces within
'--', \
.\
\
,,\
,\
\
\
.~-~\ \
1/
,
\I
REFERENCE BASE
I
,
\'- /b
FIG 13-10. The areas a and b represent the cusp tip before and after movement. A line has been drawn connecting these points. At the midpoint of this line a perpendicular has been constructed. The point at which this perpendicular intersects any other perpendicular constructed in a similar manner (in this figure, the apex has been selected as the other point) is the center of rotation. (From Smith RJ, Burstone CJ: Mechanics of tooth movements. Am J Orthod 1984; 85:294-307. Used by permission.) appliances (Fig 13_11).108 It must be remembered that each time the teeth are brought together, another complicated temporary force system intrudes. The parallelogram method (n:membered by all of us from our first physics course) is used to determine the result or forces within orthodontic appliances (see Fig 13_11).108 Sometimes it is useful to segregate a single force ••into its components in order to determine sePar.ate horizontal and' vertical effects (Fig 13-12).
'.
' FIG 13-8. A couple.
F2
50gm
1) Types of Tooth Movements.Theoretically, all tooth movements fall into one of three categories: (1) translation, (2) rotation, or (3) a combination of translation and rotation. Translation simply means that the crown and the root are going in the same direction at the same time (see Fig 13-5). Tipping is the orthodontic term for rotation when the crown is going in one direction and the root another (see Fig 13-6). "Rotation," in orthodontic jargon, is restricted to circular motions around the long axis of a tooth, as when a buccal cusp is going distally and a
312
Treatment
150g
C:g
)
1200g-mm
FIG 13-11
FIG 13-14.
Parallelogram representing forces on the tooth. (From Smith, RJ, Burstone CJ: Mechanics of tooth movements. Am J Orthod 1984; 85:294-307. Used by permission.)
Equivalent systems.
r-------O I
I I I I I
I I
----
c
What is the amount of force to be used? What is the distance the force must act? What is the duration of time the force should act?
•
How will the force be dissipated during movements of the tooth?
• •
What is the direction of force application desired? What is the distribution of stress created within the periodontal ligament by the orthodontic force?
:b I
____________ J
FIG 13-12. Parallelogram of forces, horizontal and vertical. lingual cusp mesially (Fig 13-13). Application. )
• • •
(See also Section C-3-c, Force
2) Equivalent Force Systems.-Most orthodontic forces are applied by means of a bracket attached to the crown, but it is the forces at the center of resistance that determines how a tooth moves. The bracket, being some distance from the center of resistance, produces a large moment causing forces at the bracket to produce mostly rotational effects (see Fig 13-9,B). One must analyze the force system at the bracket to determine the equivalent force system at the center of resistance. Smith and Burstone108 note that two force systems are equivalent if (I) the sums of forces in the X direction are identical, (2) the sums of forces in the Y direction are identical, and (3) the sums of moments around any point are identical (Fig 13-14).
When an orthodontic wire is shaped to make a simple spring and the forces in that spring are measured at different deflections, it will be found that the deflection is proportional to the load (Hooke's Law).9. 69 Orthodontic springs that have a low load deflection rate deliver more constant forces, since there is less change in force with each unit change in activation.69 This principle underlies the theory of the "light-wire" appliances. The ideal orthodontic force application has a large range (the distance through which the wire can be activated without permanent deformation) and a low load deflection rate. However, we need to know several other factors as well, namely, the characteristics of the alloy used, the cross-sectional size of the wire, and the length of the wire. In clinical practice, it is desirable to apply known forces over a predetermined distance for a specified length of time. In order to achieve these goals, it is necessary to understand how the diameter of the wire and the length of the spring effect the characteristics of the spring. Increasing the length without altering the diameter of the wire has a dramatic effect on the load, since the force that is created is reduced to one-eighth when the length is doubled (Fig 13-15)69 Considerable variation in the force, duration of force expenditure, direction of force application, and
3) Selection and Control of Orthodontic Forces.- When designing an orthodontic appliance, a number of questions must be answered:
--A
..
--
-
............•.
•...•
B
,,,,
""
FIG 13-15. FIG 13-13. Rotation around the long axis of the tooth.
Effect of increasing the length of a spring on load (Mulligan's "diving board" effect). (From Mulligan T: Common Sense Mechanics. Phoenix, Ariz, C. S. M., 1982. Used by permission.)
Force Systems and Tissue Responses to Forces in Orthodontics
and Facial Orthopedics
313
Cl 0 0
~/
o
0 Cl
FIG 13-17. Bypassing teeth to gain advantageous
forces for intrusion.
a particular response can only be done by understanding the biomechanical principles involved. The center of resistance of upper . molars is not in the crown, where the face bow is attached to a tube, but in the root area (Fig 13-18),'08 If the line of action passes through the center of resistance, translation will occur (Fig 1319) 5. 6. 38 If it passes occlusally, the center of rotation will be altered and distal crown tipping plus extrusion will result (see Fig 13_19)5.6.38 If the line of action passes apically to the center of resistance, distal root tipping and intrusion will occur (see Fig 1319).5. 6. 38 The line of action is varied in practice by choosing the site of anchorage (occipital, cervical, "hi-pull," etc.) and changing the length of the outer bow of the extra-oral traction assembly (see Fig 13-19).
FIG 13-16. Loops and helices in arch wires: some examples. distribution of forces within the periodontal ligament is achieved by skillful use of loops and helices in the archwires (Fig 13-16). The theoretically optimal orthodontic force for any given tooth movement is that which initiates the maximal tissue response without pain or root resorption and maintains the health of the periodontal ligament throughout the movement of the tooth85.96 (see Section C). The rate of tooth movement is determined by a number of other variables, for example, the effects of occlusion and intercuspation of the teeth, the root surface area of the tooth to be moved, whether the direction of tooth movement is aided by natural tooth drift or not, etc.
c) Some Clinical Implications and Applications
C. PERIODONTAL AND OTHER TISSUE RESPONSES TO ORTHODONTIC FORCES
1. Physiologic Tooth Movement Growth of the craniofacial structures is accompanied by alterations in the position of the teeth as a result of tooth migration. Such changes are seen particularly in the vertical, but also in the sagittal and transversal planes. The dentoalveolar system occupies and fills out the increasing space formed between the basal parts of the maxilla and mandible as a result of growth. Two mechanisms seem to be involved: (I) continuous tooth migration, the rate and amount of which is il-
1) Translation.-If one wishes to move a tooth bodily, the forc~ system at the bracket must be equivalent to a force with no couple of the center of resistance. ]08
2) "Light" Wires.- The short distances between brackets can produce very heavy forces even with small wires alone do not necessarily produce "light" by increasing interbracket distance, incorporating or bypassing teeth, lighter forces are possible 13-17)69
"Light" forces. However, loops in the wire, (Figs 13-16 and wires.69
3) Intrusion.-Intrusion is best produced by light, continuous forces which can be created by vertical loops between brackets or by utilizing the cantilever principle (a pure force acting at the end of attachment, and an equal and opposite force at the other, accompanied by a moment) and bypassing teeth (see Figs 13- 15 and 13-17).69
4) Extra-Oral Traction. - Various head gears and neck straps are used for different effects, but selecting the best appliance for
--. "-8
.•... .•...
\
- no tipping
=. g])..-A-
--
"'\
f
C - clockwise tipping counter-clockwise tipping /
..- /'
/
/ -,"... ,
-
•
=
=
Center of Resistance Tension (line of action of force)
FIG 13-18. Extra-oral application of force to upper molars. (After Bowden DEJ: Theoretical considerations of headgear therapy: A literature review. Part 1, Mechanical principles. Br J Orthod 1978; 5:145-152; Part 2, Clinical response and usage. BrJ Orthod 1978; 5:173-181. Used by permission.)
314
Treatment
A
_
~
---...........
B
FIG 13-19. Effects of varying types of head gears on force application to upper molars. (After Jacobson A: A key to the understanding of extraoral forces. Am J Orthod 1979; 75:361-386. Used by permission.)
lustrated by deciduous teeth which become ankylosed and where the bony union between tooth and bone prevents any tooth movement; and (2) tooth eruption with root lengthening.60 Specific processes within the periodontal ligament in interplay with the alveolar bone are responsible for tooth eruption, and the periodontium can be looked upon as a growth zone. During active craniofacial growth the positional changes of the teeth are considerable, and the potential for tissue reconstruction is, therefore, very high.
a) Resorptive Bone Wall Alveolar bone resorption occurs on the side toward which the tooth is moving during the physiologic tooth movements while, at the same time, reconstruction of the ligamentous support between tooth and bone is taking place. On the microscopic level, this situation is characterized by the presence of osteoclasts residing in scattered resorptive lacunae on the alveolar bone wall, indicating active resorption (Fig 1320). After a while resorption ceases, and the Howship's lacunae will be occupied by other cells depositing new layers of bone in which new periodontal fibrils become embedded (Fig 13-21). This mechanism of reestablishment of the fiber attachment, which was . demonstrated by means of the electron microscope,91.93 is valid for both the alveolar bone wall arid root cementum whenever the fiber attachment has been disrupted (see Fig 13-21). Simultaneously, active bone resorption starts in new locations. Thus, the alveplar wall retracts bt'the occurrence of alternating areas of resofption and repair. 43Exactly how fiber remodeling and relinking occur during resorption is still not fully understood. The fibroblasts have been attributed with the ability of both producing and breaking down collagen fibers, and it is likely that such cells play an important role. 113
b) Depository Bone Wall FIG 13-20. Osteoclast engaged in active resorption of alveolar bone
(x
6,000).
On the side opposite the direction in which the tooth is moving, the tissue reaction is comprised mainly of the apposition of bone, together with the rearrangemenl of the periodontal fibers.
) Force Systems and Tissue Responses to Forces in Orthodontics
and Facial Orthopedics
315
tissue in the body. ]07 It is also noteworthy that collagen synthesis seems to be higher in the periodontal ligament than in gingival tissue. 109 Petrovic and coworkers have reported that alveolar bone turnover is higher during summer than during winter. Furthermore, the formation rate of alveolar bone in the mandible is associated with the ..mandibular growth pattern']] The dentoalveolar structures have an inherent ability to react to various stimuli. When teeth are exposed to muscular or other forces of some duration, the periodontal supporting tissues react by reconstructive adaptations to allow the tooth to establish a more convenient position. Such functional adjustment is seen both in the deciduous and permanent dentitions. This adaptive response is an important baseline factor for the understanding and practice of orthodontic treatment.
2. Experimental
and Orthodo_ntic Tooth Movement
Alterations in the dentoalveolar system account for many of the changes seen during orthodontic therapy. Tooth movement goals are often combined with growth adaptation when one aims not only to move teeth within the alveolar processes but also, for example, 'to transmit therapeutic forces to the craniofacial suture system, limiting or enhancing maxillary growth. Recent research has given us a better histologic picture of the changes that occur in the circummaxillary suture system, temporomandibular joints, and the basal parts of the mandible during treatment. In recent years we have become more aware of the interplay between force applications and response. Histologic studies--obtained from both animal and human material--of the basic
FIG 13-21. Deposition of new layers of alveolar bone (nB) in which new fibrils (F) are embedded. Small arrows indicate demarcation line between new and old bone (oB). Large arrow indicates direction of tooth movement. N = osteoblast. (x 20,000). (From Rygh P: Ultrastructural changes of the periodontal fibers and their attachment in rat molar periodontium incident to orthodontic tooth movement. Scand J Dent Res 1973; 81 :467-480. Used by permission.) Not only are existing fibers in the periodontal ligament entrapped passively by the advancing front to form Sharpey's fibers, but new fibers are also secreted simultaneously by fibroblasts migrating from the bone. New Sharpey's fibers are therefore formed, together with incorporation of new fibrils into existing fibers.26 The periodontalligament maintains its original width in spite of the tooth's positional changes. The human periodontal ligament is about 0.2 to 0.25 mm wide. This width is a reflection of the cellular activity in the periodontal space. Teeth which' are under larger functional demands have wider periodontal spaces than teeth under little or no functional demand. The width of the periodontal ligament of impacted teeth is approximately one-third of that found with erupted teeth,14 whereas teeth under active orthodontic movement have a wider than normal ligament. The components of living tissue are constantly being removed and replaced. This natural physiologic process, referred to as "turnover," is especiillly high in the periodontium. This is illustrated by the synthesis of collagen, which has been reported as being higher in periodontal tissue than in any other connective
mechanisms of cellular changes andfiber reconstruction have provided valuable information for use in the clinical situation. Orthodontic forces that produce tooth movement without damaging the tooth or related structures are within a relatively small range. Orthodontic forces are usually much heavier than the natural forces responsible for physiologic migration, if we disregard mere orthodontic guidance of tooth eruption.
.a) Dentoalveolar Tissue Reactions A distinct pressure and tension zone is developed on either side of the tooth after the application of force. On the two other aspects of the roots, more complex situations arise with a combination of pressure and tension reactions, dominated by stretching of periodontal fibers (Fig 13-22). Adaptation of the bone is riot restristed to resorption and apposition around the tooth in the periodontal space. Bone mod-
FIG 13-22. Orthodontic tooth movement in direction of the arrow with reactions in the periodontal ligament and in marrow spaces.
316
Treatment
ification is seen in the marrow spaces and under the periosteum on the external surfaces of the alveolar processes. These changes occur in order to maintain the structure and thickness of the alveolar bone. A tooth is not simply moved through bone; one could say that the supporting structures move with a tooth rhat is moved into a new position as a response to a change in its environment (see Figs 13-22, 13-32, and 13-33) .. 1) Pressure Side.-Direct resorption of the alveolar bone wall is seen on the pressure side of moving teeth. Progenitor cells have differentiated into specialized cells--osteoclasts-which are responsible for resorption of the alveolar bone wall. In young individuals the resorption process may begin as soon as 12 hours after force application and can be expected after 40 hours.85 . The microscopic picture of the reconstructional changes, especially on the pressure side, is much more dramatic than that seen under normal physiologic tooth migration. Figure 13-23 illustrates that the periodontal width on the pressure side has been greatly increased in order to allow space for a very high cellular activity and for proliferation of vascular structures. A chain of osteoclasts is seen along the alveolar wall, and if one were able to visualize the situation in three dimensions, the osteoclasts would seem to be attached to the alveolar bone wall like bees in a beehive. During rapid orthodontic tooth movement the fibrous supporting apparatus on the pressure side is reconstructed by almost complete
FIG 13-24. Interradicular bone ridge' (B) between pressure side (P), with osteoclasts (0) (behind which extensive breakdown an'(j formation of fibrous structures have occurred in highly vascularized periodontal membrane, and tension side (T), with stretched fibrils (F). Note extensive breakdown and formation of fibrous structures that have occurred in the richly vascularized periodontal membrane on the pressure side. (Rat molar tissue; 10 g continous force for 28 days.) Insert indicates site of tissue sample. breakdown of the old fibers and fiber bundles and by ensuing formation of new fibrous elements (Fig 13-24). The vascular system provides many of the undifferentiated cells that are partly responsible for reconstructional changes. The osteoclasts seem to be derived from cells transported by way of the blood vessels while osteoblasts and fibroblasts are derived from An abundant blood supply is seen where rapid relocal cells.] sorption and reconstruction take place (see Figs 13-23 and 1311
24).96
The transmission of mechanical stimuli into specific cellular activity-such as increased mitotic activity and differentiation of specialized cells in the periodontal ligament of a tooth that has been exposed to an external force-is not fully understood. Melcher"9 has postulated that cells of the periodontal tissues secrete substances capable of stimulating differentiation of specialized cells. There is reason to believe that prostaglandins play a role. These polyunsaturated fatty acids are synthesized in the target tissue and induce such inflammatory reactions as increased vascular permeability and chemotaxis. Increased prostaglandin levels are found on the pressure side of the periodontal ligament of teeth moved orthodontically. Such prostaglandins, when taken from orthodontic pressur~ zones, induce bone re sorption even when transferred to in vitro ,. . media.96
,
FIG 13-23. Tissue on pressure side shows increased periodontal membrane width; proliferation of vascular elements, as indicated by oxytalan and elastic-like fibrils (small arrows) related to blood vessels; and bone resorption by osteoclasts (0). Large arrow indicates direction of tooth movement. T = tooth; B = alveolar bone; bv = blood vessel. (Rat molar tissue; 10 g continuous force for 14 days; aldehyde fuchsin Halm; stain.)
The changes that occur in alv~olar bone during tooth movement have also been interpreted in relation to a piezoelectric effect through strain-generated potentials, arising as a result of mechanically induced deformation of collagen or hydroxyapatite crystals. ]27 Electronegative potentials are generated on the concave surface, while electropositive potentials are noted on the convex surface (Fig 13-25). The electrical energy thus produced is believed to affect the adjacent cells. It has been demonstrated that when electrodes are placed into bone, osteogenesis wi.ll occur around the negative electrode while resorption of bone may occur
'.
Force Systems and Tissue Responses to Forces in Orthodontics
+
and Facial Orthopedics
317
+
+ FIG 13-25. Piezoelectric effect arises as a result of mechanically induced deformation of hydroxyapatite or collagen structures. around the positive electrode.2s In addition, alterations of oxygen tension and in the availability of circulating hormones, calcium ions, and cyclic AMP'S have been shown to influence cell differentiation. While present histologic techniques provide extensive information on the response of cells, fibers, and hard tissue, we know little about the behavior of the ground substance, blood and tissue fluids. It has been generally accepted that these elements provide.
FIG 13-27. Tension side; Arrows indicate direction of movement of tooth (T). A, chain of osteoblasts (OB) adjacent to the surface of alveolar bone (B) produces new bone. B, interface between new bone (nB) and periodontal membrane with osteoblast (OB), electron microscopic view (x 7,000). the teeth with a cushion-like mechanism protecting them against functional loads. Obviously, new insight into the reactions of tissue fluids to orthodontic loads is needed. 2) Tension.~Cellular increase occurs after 30 to 40 hours following application of an orthodontic force.94 Wbile the remodeling of fibrous elements on the pressure side is dramatic and characterized by extensive breakdown and rebuilding, the stretched periodontal fibers seem to be reconstructed by changes of the original fibrils (Fig 13-26). It has been suggested that macrophages contribute to collagen breakdown even by other mechanisms than phagocytosis: modulation of fibroblast growth and function. Macrophages have been found in great numbers in areas of tension96 There is evidence indicating that an inflammation-like breakdown and rebuilding process of fibrou.s elements characterize areas of orthodontic tension. 96 As stretching occurs, new unmineralized material is laid down around the parts of the fig~rs that are in close relation to the alveolar bont; wall. After some'hme the whole of the alveolar wall on the tension side will be covered by'a layer of osteoid, produced by osteoblasts (Fig 13-27 ,A). Mineralization of the osteoid then occurs in the deepest layers26 (Fig l3~27,B).
FIG 13-26. Tension side. Stretched fibrous apparatus (F) is reconstructed by changes of original fibrils, except near blood vessels (BV). Arrow indicates direction of movement of tooth (T) from alveolar bone ridge (B). (Rat molar tissue; 10 g continuous force for 28 days.) Insert indicates site of tissue sample.
b) Hyalinization The most frequent complication preventing rapid tooth movement occurs when the applied force presses the tooth so hard against the alveolar bone wall that the periodontal membrane responds with local degeneration and sterile necrosis instead of proliferation and differentiation of cells that would have been able to
,/
318
Treatment lage of the contents, which mainly consist of compressed erythrocytes. If the local force in these areas is not removed, there will then follow breakdown of the blood vessels as well as their contents.
I
Not only is cell differentiation prevented from taking place because of increased pressure in the area, but phagocytosis is also hindered. The breakdown of the blood vessels and their contents
FIG 13-28. Right, hyalinization (H) of the periodontal membrance with indirect and undermining resorption of bone (B). 0 = osteoclasts. Note wide periodontal membrance adjacent to hyalinized area. Left, site of tissue sampling. (Courtesy of K. Reitan.) perform the necessary reconstructional adaptations. Since this phenomenon is currently almost unavoidable in clinical orthodontics and since the situation may lead to permanent damage on the involved tooth and its periodontium, the process will be described in some detail.
is therefore accomplished by alternative mechanisms to those seen under normal conditions. Rygh and Selvig98 found that, in rats, hemoglobin undergoes an intermediate stage of crystallization when being broken down (Fig 13-29). While small, constant forces stimulate cellular proliferation, a strong force, although of short duration, will cause tissue damage, characterized by swelling of the intracellular reticuloendothelial system, followed by disintegration of the mambraneous walls and, in later phases, by breakdown of the cellular muscle left isolated within the hyalinized tissue. Studies on human premolars have'shown that most of the cells in a hyalinized zone are reduced to isolated nuclei after 2 day's exposure to continuous force between 70 g and 120 g. Degenerative influences on the fibrous system cannot be recognized until they have been occurring for several days. Since a hyalinized zone seldom lasts longer than 2 to 3 weeks, only a minimal breakdown of the collagen fibrils occurs. When fibril breakdown is seen, the fibrils split longitudinally.
3) Elimination of Damaged Tissues.hyalinized zone occurs by two mechanisms:
Elimination of the (I) resorption of the
1) DeJinition.- Evidence for the hyalinization of tissue (the term generally used to describe the locally compressed and degenerated periodontal membrane) has been derived from light microscopy, where the tissue appears glass-like when hematoxylineosin staining has been used. The process of hyalinization is dependent on the local morphology of the compressed area, the magnitude of the applied force on the tooth, and the duration of this force, although it may be seen temporarily during physiologic tooth migration in the interdigitations of the maxillary suture system during growth.49 In humans, it takes approximately I to 2 days for a hyalinized zone to develop. The tooth is not capable of further movement until this local tissue damage has been removed and the adjacent alveolar bone wall resorbed. The bone resorption that follows the hyalinization is of an indirect or undermining nature because there are no living cells present within the compressed periodontal membrane to do the job (Fig 13-28). The periodontal ligament tissue changes associated with a hyalinization process follow a complex sequential pattern. One is able to recognize three separate phases: (I) tissue degeneration, (2) elimination of the damaged tissue, and (3) reconstruction of the supporting tissue. 2) Tissue Degeneration.- Degeneration of vascular and cellular elements are the first signs of a beginning hyalinization. After a human premolar has been subjected to a continuous orthodontic force of 70 gm for 2 days, one is able to recognize in the electron microscope degenerative changes in the endothelial cells lining the blood vessels. There is breakdown of the walls, followed by spil-
t·
(
FIG 13-29. Crystallization of hemoglobin in hyalinized zone. Two sets of parallel dense bands, a and b, intersect a 50° angle (x 180,000). (From Rygh P, Selvig KA: Erythrocytic crystallization in rat molar periodontium incident to tooth movement. Scand J Dent Res 1973; 81 :62-73. Used by permission.)
Force Systems and Tissue Responses
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319
FIG 13-30. Phagocytosis in area of repair. Remnants of cell nucleus (N) and cell cytoplasm (CC) are engulfed in vacuoles of phagocytes (x 8,000).
(From Rygh P, Selvig KA: Erythrocytic crystallization in rat molar periodontium incident to tooth movement. Scand J Dent Res 1973; 81 :62-73. Used by permission.)
alveolar bone by osteoclasts differentiating in the peripheral intact periodontal membrane and in adjacent marrow spaces, and (2) invasion of cells and blood vessels from the periphery of the
•
compressed zone by which the necrotic tissue is r~moved. The cellular invasion takes 'place quite slowly until the adjacent portion of the alveolar wall has been removed. The invading cells possess the ability to penetrate the hyalinizect zone by pushing cellular extensions into the area. Collagen breakdown occurs around these extensions as a result of enzymatic attack. Portions of hyalinized collagen and other debris are included into the scavenger cell and broken down by phagocytosis (Fig 1330). These mechanisms could be clarified by electron microscopy studies!' It is believed that all tissue that has been damaged by the compression is removed, including the collagen fibers making up the periodontal ligament in these areas. This observation should be borne in mind when considering the development of more extensive damage, such as root resorption.
,
Alveolar Bone.-Some earlier studies revealed that application of extremely high forces to a tooth is capable of producing cell death in alveolar bone that is closely associated with a hyalinized area.72 Electron microscopic findings indicate that with the moderate forces now used clinically, cell necrosis does not occur in the alveolar bone, and that· degeneration and necrosis occurring during hyalinization are restricted to small, localized areas in the periodontal membrane. 92
3. Factors Influencing Orthodontic Tooth Movement Local tissue reactions are influenced by the anatomic characteristics of the supporting bone into which the tooth is to be moved, the physiologic activity of the tissues which surround the tooth, and the force application.
a) Character of Bone 4) Reconstruction of Supporting Tissues.-
Reconstruction of the fibrous apparatus gradually occurs following the elimination of the hyalinized remains. New collagen fibrils are produced and attached to cementum and the alveolar wall by the general mechanism described in Section IIl,C, I ,b. Hyalinized zones seen during treatment with modem orthodontic appliances and moderate force application are usually small (I mm to 11/2 mm in diameter) and do usually not last beyond 3 weeks . • The Periodontal Ligament Following Hyalinization.-When compared with the periodontal ligament before tooth movement started, the posthyalinized area is wider, richer in cells, and has an increased blood circulation. If the original orthodontic force is not reactivated, the periodontal ligament will soon adopt the preexperimental appearance and width. However, if the force is reactivated, the alveolar bone wall toward which the tooth is moving will probably undergo direct resorption.
Remodeling processes in bone depend on the activity of cells which act upon its surfaces. It is therefore essential that the alveolar bone is penetrated by many canals that transmit blood vessels and that its deeper aspects contain cancellous bone with marrow spaces. The marrow space offers a large surface area for cellular activity, which is indispensable for tooth movement. 86 On the other hand, if the bone involved in ,tooth movement is of a compact character (cortical bone), the surface area where cellular reactions can take place is vastly reduced. Then tooth movement is more difficult and much slower, and the chance of creating overcompression and hyalinization is much greater. When one is planning orthodontic treatment, the tooth should remain in spongey bone during movement. Practically, the tooth should be kept in the ·center of the alveolar process, as much as possible, rather than being allowed to move against the compact cortical bone, which occupies a more superficial position in the alveolar process. It should be kept in
320
Treatment
mind that tooth movement in a labiolingual direction may easily impinge on the surface layers of cortical bone, for example, through lingual movement of the root (torque) of upper anterior incisors in patients with a horizontal overjet. The anatomic differences between maxilla and-mandible should not be overlooked. Different rates of bone remodeling may also be due to the considerable individual variation in the bone character. Extraction spaces contain tissue undergoing reconstruction, which is rich in cells and vascular supply. Such an area is ideally suitable for tooth movement, and due advantage should be taken of this by commencing treatment as soon as possible following an extraction. Thereby one also avoids atrophy and narrowing of the alveolar process, resulting in bone loss and cortical bone formation at the extraction site.
b) Physiologic Activity Restructuring of the supra-alveolar fiber system after experimental tooth movement is slower than is the case in the periodontal ligament. Thus, the strong relapse tendency seen after orthodontic rotation of teeth is thought to be the result of the lower turnover of gingival collagen. 106 Turnover varies from one patient to the next and is dependent on a number of variables such as hormonal balance, patient age, and health of the patient62 The histologic picture of the periodontal ligament of a growing person is very different from that of an adult, arid the readiness for tissue proliferation and cell differentiation into specialized cells seems to correspond to these differences (Fig 13-31). One therefore has to consider these variations during treatment planning, especially if the patient is receiving medication (e.g., cortisone, epileptic medication), as the threshold for tissue changes or cellular reactions will be influenced.
FIG 13-32. Tipping movement with displacement of tooth iri' the periodontal membrane marginally and, in opposite direction, apically. There is cellular response on alveolar bone surfaces. Alveloar process moves with the tooth.
c) Force Application 1) Tipping.-If a force is applied against the crown of a tooth, and if this force has a "one-point-contact," then a tipping effect is produced. Tipping, the most simple form of tooth moVement, tends to concentrate compression on a small periodontal area. Its greatest effects are usually seen at the marginal root area. With a small but continuous force a relatively large displacement of the tooth will occur following tissue changes in the marginal area. These changes allow the center of rotation to move gradually toward the middle third of the root. Corresponding tissue changes are seen apically during tooth tipping with tension and pressure zones in close proximity to each other but on opposite sides of the root apex (Fig 13-32). Local pressure zones and areas of hyalinization are a common occurrence in the marginal regions of the periodontal membrane during tipping movements. Owing to the development of a fulcrum, the portion of the root apical to this fulcrum will, of course, move in the opposite direction to that of the crown. The compressive forces generated at the root apex can cause extensive hyalinization and therefore increase the risk for apical root resorption. In a clinical situation, tipping movements are often used when moving teeth in a labiolingual direction. The labial and lingual bone plates consist of dense cortiCal bone (see Fig 13-32) and compensatory apposition of bone at these sites following initial tipping movements is comparatively slow. Caution is therefore essen~i~l when planning such tooth movements.
FIG 13-31. A, periodontal ligament (control) from buccal apsect of premolar in 12-year-old patient. B, periodontal ligament (control) from buccal aspect of premolar in 40-year-old patient. (Courtesy of K Reitan.)
2) Translation.-Bodily movement of a tooth is usually produced from a two-point contact of the applied force. It involves moving the tooth parallel to its long axis; therefore, the force is distributed over relatively large areas of the alveolar bone wall (Fig 13-33). When small forces are used, the hyalinized zones that occur will generally be of shorter duration than those seen during tipping movements. The reason for this is that the local forces in these hyalinized zones are smaller, thus allowing direct resorption of the alveolar bone wall to occur. The tooth movement
Force Systems and Tissue R€!sponses to Forces in Orthodontics
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321
zones are established, the periodontal ligament has the time to become reconstructed. There is an increase in cell proliferation which is suitable for further tissue changes following reactivation of the force.
FIG 13-33. Parallel (bodily) movement. Force is distributed over large areas of the alveolar bone walls. following such applied forces is quite favorable since there is steady bone resorption as well as steady bone apposition along the stretched periodontal fibers on the tension side. d) Applied Force and Time 1) Continuous.-Continuous force (Fig 13-34) leads to gradual compression of the periodontal membrane on the pressure side . of the tooth. If the force is within the limitations where tissue reactions occur, reconstructional changes of the fibrous element as well as direct resorption of the alveolar bone wall take place. If the force is unnecessarily reactivated, the vascular supply is easily compromised and the result is a "damage-repair" effect. Elimination of a hyalinized zone occurs between 2 and 4 weeks, and if reactivation of the force is made before this time, tissue damage can easily occur. 2) Interrupted-Continuous. - An interrupted-continuous force (see Fig 13-34) means that the continuous force that is applied to a tooth is effective over only a small amount of tooth movement, after which it stops and needs to be reactivated. Even if hyalinized W 0::
4. Root Resorption Although tooth structures generally show considerable resistance against resorption, it is more a question of degree rather than immunity. Whereas the roots of the permanent teeth are very resistant, the roots of the deciduous teeth are readily resorbed as part of the developmental physiologic process of tooth loss. The root surface is protected by a barrier. Since unmineralized hard tissue (osteoid, cementoid, predentin) is re~9rbed only with great difficulty, it is now assumed that the cementoid and the cells producing cementum constitute a protective covering. However, the greater resistance to resorption of the teeth as compared to that of the alveolar bone (which is the premise for all orthodontic treatment) is explained by the fact that the teeth are permanent
INTERMITTENT
U o?? l.L l.L
I
3) lntermittent.-An intermittent force (see Fig 13-34) is one that affects a tooth periodically or over a time when many interruptions of the force occur. This type of force occurs when removable appliances are used. On the pressure side, the circulation will not be as easily disturbed or hindered unless the force applied is too high. Thus, hyalinizations that involve only a portion of the periodontal ligament occur more often than with fixed appliances. The intermittent force is thought to act as an incitement for cell proliferation. Increase in the cell numbers and direct bone resorption along the alveolar bone wall are characteristic of this type of tooth movement. The periodontal space increases because the tooth tends to return to its original position following the removal of the force. In spite of the favorable condition on the side where resorption is seen, tooth movement often will be slower than that seen during application of continuous force, as the time over which the appliance is used is a very important factor. Formation of new tissue and apposition of bone are seen to occur more rapidly under active or constant stretching. Therefore, if the tooth is often allowed to return to its original apposition, one can expect a limited amount of apposition to occur.
....... ::: ;:.;:»: ..
....
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~:,:,:, rn _'~:: >? m> ........................ J.. INTERRuF'.H;6-~ON.tI['Jl!Ql! 0""'"
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o ::> I-
z(9
L TIME FIG 13-34. Schematic representation
of various manners of orthodontic force applications.
/ 322
Treatment
depositories of mineral salt, with continuous apposition, while the bony system is a mineral reservoir for the whole organism, with physiologic resorption and apposition going on all the time. The initiation of resorption depends on barrier alterations. Thus, osteoclasts always appear on a raw bone smface unprotected by a barrier. Development of root resorption seems to be an interrelationship between (1) temporary damage of the tooth surface barrier and (2) general resistance against resorption and remodeling of the alveolar bone. Some particular features are common for various situations leading to root resorption: (I) increase of pressure (tooth eruption, tumors); (2) tissue damage in the periodontal membrane (mechanical, chemical);34.35 (3) increased blood supply (hyperemia connected with certain types of inflammation, hypertrophy, epulis); (4) infection; and (5) individual predisposition (systemic diseases, endocrine disturbances,' allergy, medication). Root resorption occurring during orthodontic treatment seems to be related to local damage of the periodontal ligament-in particular with hyalinization. During hyalinization the tissue damage in the periodontal ligament alters the biochemical environment. There is reason to believe that the initial breakthrough of cementum is connected with the removal of the hyalinized parts of the peri-
odontal ligament. Biologically active substances are released by destruction of tissue within the hyalinized zone. These may affect the development of various cells around the hyalinized zone. Macrophages in various stages of maturation accumulate around the hyalinized zone and remove the necrotic tissue (Fig 13-35) while they release prostaglandins, which in turn stimulate bone resorption. The barrier effect of the cementoid tissue behind the hyalinized zone seems to be reduced or gone, and macrophages fuse and become resorbing cells (clasts) (see Fig 13-35). A small breakthrough is adequate to start the process. When a re sorption lacuma has been formed, the ensuing events will depend on whether application of force is continued. If it is, resorption will continue. The resorption lacuna seems a favorable, protected environment for the resorbing cells during the application of a force of a magnitude used in clinical orthodontic treatment. Once a resorption lacuna is established, the cementum on the edges of the lacuna is resorbed from the rear, even when the cementum has a normal periodontal surface.95 If the application of force is absent or below a certain level, repair will commence in the resorption lacunae with the deposition of cementum. Root resorption ceases if the orthodontic treatment is interrupted or stopped. The repair taking place will cause new deposits of precementum on the root surface, thus establishing a new barrier. Rest periods without force application should be included in treatment of patients with a tendency for root resorption. The individual's predisposition for root resorption is attributed to systemic disorders altering bone metabolism. For example, patients with increased osteoid tissue resorb alveolar bone with great difficulty, and root resorptions may occur as a result of the application of orthodontic force.
D. CONTROLLED ALTERATION CRANIOFACIAL GROWTH
FIG 13-35. Root resorption by odontoclasts (0) in cementum (e) and dentin (D). Hyalinized necrotic tissue (H) is removed by macrophages (M). Giant cells (G) are seen, probably formed through fusion of macrophages. Hyalinized tissue is detached from root surface, as seen by artifact (A), indicating that osteoid barrier connecting cementum and periodontal fibers is altered. Arrow indicates direction of tooth movement. (Hem-eosin stain.)
OF
The question of whether craniofacial morphology and growth could be purposefully altered has been long debated (see Chapter 4). The reasons for the time needed to resolve this argument are of interest. Many in North America thought it was impossible and were preoccupied with developing precision bracketed appliances to move teeth and reshape the alveolar processes. Claims were made in the European literature concerning the stimulation of mandibular growth with functional jaw orthodontic appliances, but there was no satisfactory scientific evidence. It seems ironic that the question of whether bone growth and morphology could be altered should have been argued so heatedly by orthodontists who have done much of the best research and routinely apply the biologii: concepts in practice. In fact, if bone wer~;'not so plastic and adaptable, orthodontics would not exist. The biologic concepts of this important subject are discussed in Chapter 4, and the cephalometric analysis of treatment effects and their segregation from growth is discussed in Chapter 12.
1. The NasomaxilIary Sutural System Experimental and clinical studies prove that it is possible to influence sutural adaptation and maxillary growth. A prerequisite is a patent suture before natural fusion (synostosis) has occurred. Purposeful nasomaxillary displacement is possible because the su-
Force Systems and Tissue Responses to Forces in Orthodontics tures uniting membranous bones depend largely on local conditions for tbeir growth and physiologic adaptation. The position, orientation, direction, and even number of facial sutures seem to be closely related to various forces. Their proliferlltion is dictated by the tensions received from the bones which they unite and the soft tissue by which they are surrounded: increased tension leads to increased sutural width and length. Much of our most basic and practical knowledge of altered nasomaxillary growth has come from animal experimentation, yet it may seem difficult to understand what experimental changes mean clinically, as the laboratory model is so different from dental practice. In experimental animals a normal craniofacial form is made abnormal, while in humans the clinician wants tp change an abnormal skeletal relationship into a more normal one. Further, animals are often under better control than patients. During compression by heavy extra-oral forces the sutures become 2 to 3 times wider than normal and show signs of great cellular activity. The serpentine configuration with interdigitations disappears, and the fibers lose their orientation. The bone surfaces reveal Howship's lacunae with active osteoclasts. This stage of direct re sorption is frequently preceded by local hyalinization (Fig 13-36). Hyalinization is even observed in control animals during normal growth. During tension of a suture, osteoblasts and Sharpey's fibers are incorporated into the bone surfaces by deposition of new bone layers. The sutures react to pressure and tension much in the same way as seen on the alveolar bone surface of the periodontal ligament during tooth movements (Fig 13-37). Reorganization with normalization of width and formation of new interdigitations occur when the force recedes. Yen125 et aI. found that the rate of collagen synthesis in stressed sutures was reached in 3 days, and higher values were maintained up to day 14. The rate of noncollagenous protein synthesis peaked
FIG 13-36. Hyalinization in the intermaxillary suture of the palate of a Rhesus monkey after experimental compression. (From Linge L: Tissue Changes in Facial Sutures Incident to Mechanical Influences. An Experimental Study in Macaca mulatta, thesis. University of Oslo,
1973. Reproduced courtesy of the author.)
and Facial Orthopedics
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FIG 13-37. Heavy, rapid expansion of the intermaxillary sutdre of the palate of a Rhesus monkey. (From Linge L: Tissue Changes in Facial Sutures Incident to Mechanical Influences. An Experimental Study in Macaca mulatta, thesis. University of Oslo, 1973. Reproduced courtesy of
the author.) at 5 days and was significantly different only on day 5. They suggest, therefore, a more significant role for collagenous protein synthesis in the control of remodelin&.
a) Posterior Forces Against the Maxilla Head gears and cervical traction devices can restrain alveolar process development and inhibit maxillary corpus growth. The gross" orthopedic effects" of heavy, continuous, extra-oral forces to the maxilla have been well documented in extensive animal studies. It has been shown by radiographic techniques that in small monkeys, during the late deciduous dentition stage, the midfacial complex can be moved posteriorly into a Class III relationship within 3 months, using heavy, continuous force (400 g per side) applied for 24 hours per day, producing a posterior displacement of up to the width of two teeth.7. 9. 41. 49. 55. 56.115 Posterior movement of the maxilla by external cervical forces in humans has been demonstrated. 19. ; 1& The response of the maxilla and maxillary dentition is complicated, depending on several factors including the direction of force application, mode of attachment of the extra-oral device, amount and duration of force, and the patient's craniofacial morphology. Class 11intermaxillary elastics are commonly used to move maxillary teeth distally, but their effect on nasomaxillary skeletal growth and morphology is not well known. The effect of. intermaxillary Class 11traction on mandi'tJuJill'growth has been studied. 57. 5&. 77 It has also been demonstrated, in humans, that both tooth movements and maxillary skeletal alterations can concomitantly effect the position of the mandible, as the mandibular elevators must accommodate the mandible to the maxilla during function. Theoretically, at least, extra-oral traction to the maxilla should also have an indirect effect on mandibular growth and morphology, although this point is not fully documented.78
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Treatment
b) Anterior Forces Against the Maxilla Face masks can move maxillary teeth forward.17 They can also promote maxillary growth and sutural adaptation, resulting in a more ventral positioning of the corpus maxillarus. Heavy experimental forces of 300 to 400 g produce exten"sive anterior displacement of the maxillary complex on monkey~ after three months.41 Sutural opening associated with fewer interdigitations occurs in the circummaxillary sutures. A simultaneous rotation of the maxilla in an upward direction is often seen associated with varying reactions in different sutures. 16Histologic studies confirm that the displacement seen cephalometric ally is mediated by resorption and remodeling of the sutural articulations of the maxilla. 75 Anterior movement of the maxillary complex has been demonstrated in patients by external forces through facial masks 76 Heavy forces applied as early as from 5 to 8 years of age seem to render the best results" (P. Rygh, unpublished data). It has been claimed that the use of face masks inhibits mandibular growth in the same way as the use of chin chaps, but no documentation has yet been presented. c) Transverse Forces in the Maxilla Widening of the maxilla by devices which separate the median palatal and associated sutures is a proven clinical procedure49, 61.75 The sutural response is largely tensional, and the maxillary translations, after sutural separation, are rapid and dramaticl24 (see also Chapter 15). Although palatal expansion therapy has been used for many years to correct transverse inadequacies, only recently have we benefited from studies of the changes in the teeth and supporting structures in response to such lateral expansion. 124Strong reciprocal lateral forces are necessary to separate the median palatal suture, and some damage should be expected, particularly in the buccal periodontium of the maxillary molars and bicuspids. Greenbaum and Zachrisson32 compared three groups of patients. The first underwent rapid maxillary expansion with a fixed split-acrylic appliance, the second underwent slow maxillary expansion with a Quad-Helix appliance, while the third or control group underwent routine edgewise appliance treatment but with no palatal expansion. The expansion groups showed an average mean increase in distance between the first molars of about 4.5 mm. The periodontial condition was good in all groups and attachment levels were similar, although there was individual variation in response. Marked periodontal breakdown occurred in a few individuals undergoing rapid maxillary expansion because expansion occurs before molar rotation when this appliance is used. These findings show that the periodontal condition can remain within acceptable levels with either rapid or slow expansion but that rotated molars are at some risk with the rapid maxillary expansion. The skeletal changes associated with extensive maxillary skeletal expansion are surprisingly stal5le, and the periodontium can be maintained in a healthy state with good oral hygiene. 123-125 However, resorption of the buccal aspects of the roots of which the palatal widening device has been placed has been demonstrated histologically.2 Such resorption may not be seen in periapical radiographs until it is quite extensive.
2. The Mandible and Temporomandibular
Joint
Most of the arguments about the clinician's
ability to alter
craniofacial growth have centered on the mandible and whether or not its growth could be "stimulated," restricted, or altered. As the number and quality of research studies improved and cephalometric methods were refined, it became possible to gain per~ spective on this important topic (see also Chapter 4). a) Functional
Protrusion
Extensive experimentation on mandibular functional protrusion has been carried out, notably by Petrovic and coworkers77. 78 and by McNamara, Carlson, and colleagues. 55.57.58Using devices similar to functional orthodontic appliances on rats (Petrovic) and monkeys (McNamara and Carlson), demonstrable histologic and radiographic changes have been produced (Fig 13-38). Cephalometric findings in humans are less clear because it is hard to discriminate dentoalveolar changes from condylar change and the growth changes which would have happened were appliances not worn. Pancherz, using Activators73 and Herbst appliances,74 reports significant changes in mandibular corpus a~d overall length. Others, for example, Janson40 and Bookstein," show that most of the differences between treated and untreated cases are the result of alterations localized in the dentoalveolar area. Bookstein4 noted the importance of shape changes often not discerned with conventional cephalometrics but revealed by tensor analysis. There is no doubt that functional appliances bring about more significant alterations in facial growth and morphology than was once thought. b) Functional Restriction and Redirection Experimental studies have shown conclusively that orthopedic forces similar to those used with human chin cup treatment produce significant alterations in mandibular form and growth. 77Graber30. 31 concluded, after studying the effects of chin cup force on children during the late primary and early mixed dentition period, that there was a definite alteration of mandibular growth direction and mandibular morphology. Ramus height growth was retarded, and the direction of mandibular growth was significantly altered. 31 c) Intermaxillary Fixation Intermaxillary fixation in monkeys rapidly altered the histologic character os the condylar cartilage, resulting in profound changes in the joint and mandibular growth. 12
E. OTHER EFFECTS OF ORTHODONTIC TREATMENT Occasionally anecdotal comments are made about alleged del~terious effects of .,O'l'thodontic treatment on the periodontihm, roots, and temporomandi,bular joints, but for some time there were no satisfactory clinical research studies. Research reports on all these matters now provide better perspective. 1,28,33.79.84.99,102.103.105.123The results are reassuring if meticulous oral hygiene is maintained at all times during orthodontic treatment and if adherence to established occlusal principles is maintained during treatment and retention. 79.99The data show that periodontal health can be maintained during orthodontic treatment and that periodontal and temporomandibular dysfunctioo are not correlated with previous orthodontic treatment. 100.101
Force Systems and Tissue Responses to Forces in Orthodontics
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FIG 13-38. Temporomandibular joint region of a typical growing monkey. A, magnification, x 12. 8, higher-power (x 40) magnification of the growing cartilage. C, temporomandibular joint region of an animal who has been in protrusive function for 6 weeks. Note the increase in the thickness of the condylar cartilage, particularly along the posterior aspect as compared with A and 8 (magnification at x 12). (Courtesy of JA McNamara, Jr.)
1. Long-Term Effects on the Periodontium and Gingivae Sadowsky99. 101 studied the long-term periodontal effects of orthodontic treatment on adults who had completed full fixed appliance therapy during adolescence. Their condition as adults was compared with that of control subjects of similar race, sex, age, socioeconomic level, and dental awareness who had similar malocclusions. The data showed that orthodontic treatment during adolescence did not contribute in any way to the long-term status of gingival or periodontal health. No significant amount of either damage or benefit to the periodontal structures could be attributed directly to the fact that the subjects had undergone orthodontic therapy. Nor did the lack of orthodontic therapy during adolescence appear to influence subsequent development or nondevelopment conducted a similar of periodontal disease in adults. Polson79• study noting bacterial plaque, visual gingival inflammation, bleeding after probing, location of the gingival margin, periodontal pocket depth, and loss of attachJT1ents. All of his subjects had orthodontic treatments at least 10 years prior to the study and none was over 36 years of age at the time of the research. He determined, "When the overall clinical results were considered, it was concluded that orthodontic treatment performed during adolescence had no discernible effect upon later periodontal health. "RO RO
2. Root Resorption Shortening of the roots as a result of external resorption has long been known to be a side effect of orthodontic treatment. 3
Since root resorption also occurs in patients who have not undergone orthodontic treatment, it too has been studied, and root resorption seems to vary with age between the sexes and among the teeth.'4. 35. 53. 54.70 Some investigators have concluded that patients showing signs of root resorption prior to orthodontic treatment also 29. 70 experience more resorption than average during treatment. In one of the most exhaustive clinical studies on this subject, Linge and Linge5o.51 reported the results of 719 consecutively treated orthodontic patients who had been treated with either edgewise therapy exclusively (74%), removable appliances exclusively (11 %), or a combination of both (14%). Mean root shortening for the four maxillary incisors was 0.73 mm and 0.67 mm for girls and boys, respectively. The average most severe single root resorption per patient was 1.34 mm for both sexes. After a statistical search for clinical risk factors with regard to apical root resorption, they found that patients starting treatment later than 11 years of age experie~ced significantly mors:-root resorption than patients starting earlief.Highly significant risk factsm were previous trauma to the teeth, the correction of impacted maxillary cuspids, and the use of rectangular wires and Class 11 elastics. They found that fixed appliances cause significantly more apical root resorption than removable appliances. They also noted that sex, overbite, overjet, and duration of time the bands were in place were not closely related to the amount of apical root resorption.50 Postretention observations indicated that apical root resorption usually ceases with the termination of orthodontic treatment. 1R.
Careful taking of the case history prior to beginning ortho-
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Treatment
don tic treatment and periodic radiographic monitoring during treat~ ment are essential requisites in minimizing root resorption.
3. Tooth Malpositions Gingival recession and cemental exposure may occur when teeth are left in extreme positions within the alveolar process.27. 110.126Such malpositions result in a thin alveolar bone plate that is more susceptible to resorption.I26 The gingival recession that occurs is always accompanied by bone dehiscence. When such malpositioned teeth with gingival recession are moved orthodontically back into a more favorable position, repair can occur. 114.116 Although the bone dehiscence which appears because of uncontrolled expansion of the teeth through the cortical plate may be repaired in healthy younger patients,23. 42 it is obvious that such mal positions should not be present at the end of orthodontic treatment.
clinical studies to support or deny this opinion either. What is well documented, however, in many clinical research studies is the significant role that occlusal disharmonies can play in the etiology of TMJ disorders, occlusal disharmonies caused by many factors including drifting of teeth, poorly contoured restorations, ill fitting prothesis, etc. Poorly completed orthodontic treatments are just as apt to cause trouble, but it is the resulting poor occlusion with which the neuromuscular cannot cope that is the significant etiologic factor, just as it is in the other branches of dentistry. It must be kept in mind that there are significantly more temporomandibular disturbances in children with mal occlusions than in the random population.67 If, at the end of orthodontic treatment, there is little difference between treated and untreated cases, then the orthodontic treatment has made a significant contribution to the reduction of temporomandibular disorders, because the treated patients had more disturbances at the start.
F. RETENTION,
RELAPSE, AND OCCLUSAL ST ABILIZA TION
4. Effect of Adjunctive Surgical Procedures Several minor surgical procedures often accompany orthodontic treatment or are used to stabilize orthodontic results. 44.48.90 Edwards21 recommends fibrotomy to help prevent rotational relapse, but it should be avoided on the labial or buccal portions of very thin gingivae. The removal of gingival papillae in extraction closure sites enhances the restitution of normal connective tissue. 21 However, excising gingival clefts whenever the tissues are thin, deficient, or receding is not recommended. 124Gingival deficits and periodontal defects are sometimes seen around previously impacted cuspids after their surgical uncovering and repositioning. 120.124
5. Temporomandibular Treatment
Function After Orthodontic
Assertions have been made that orthodontic ally treated patients have more problems of the temporomandibular joint than others. Obversely, it has been claimed that orthodontic ally treated patients have less temporomandibular difficulties. 67.100Obviously, one of these hypotheses is wrong. Fortunately, several retrospective studies have tested these divergent hypotheses, and all studies are in substantial agreement. 39.45.100Sadowsky and BeGole,Ioo for example, examined subjects between the ages of 25 and 55 years who had been treated orthodontic ally with full-banded appliances from 10 to 35 years earlier and compared them with a group of adults with similar but untreated malocclusions. The orthodontically treated group had fewer temporomandibular signs and symptoms than the untreated group, but the differences· were not statistically significant. The amount of shift from the retruded contact to the intercuspal position was significantly greater in the controls than in the orthodontically treated group. There was no difference in joint sounds or parafunctional habits, although the contro; group had significantly more pain and tenderness. Allegations have been made that the extraction of bicuspids accompanying orthodontic therapy predisposes to later temperomandibular dysfunctions, but such claims have not been supported by sound clinical studies. Further, it has been put forth that second molar extractions are less apt to lead to the appearance of TMJ signs and symptoms than are bicuspid extractions. There are no controlled
Retention, in orthodontics, is maintaining newly moved teeth in position long enough to aid in stabilizing their correction. Relapse is the term applied to the loss of any correction achieved by orthodontic treatment. Occlusal stabilization must involve homeostasis; that is, the masticatory system should be self-stabilizing after orthodontic therapy. There have been many ideas about and concepts of retention. Orthodontic stability has been said to be dependent on the angulation of the mandibular incisors, the relationship of the teeth to their apical bases, the posterior occlusal relationships, etc. A longterm study of retention and relapse found diverse causes of relapse, 11.22.37.64.67but two were most important: (I) an occlusion not harmonious with the mandibular position during the unconscious swallow, and (2) disharmonious growth after orthodontic therapy. Many studies have described the relapse of individual tooth positions, whereas these two factors relate to relapse more generally. It is very important, when assessing "relapse," to segregate those changes resulting because of orthodontic intervention from those which would have appeared if treatment had not occurred.8. 36.46.52 Riedel88 has discussed a number of popular explanations of retention and relapse and the available clinical research evidence about them. •
•
Theorem i.-Teeth that have been moved tend to return to their former positions. While this is not true for all tooth " l!I0vements, it is true'.for rotations.2o. 21.106The concept applies more to incisors than to posterior teeth, whose intercuspation aids retention.
•
Theorem 2.-Elimination of the cause of malocclusion will prevent recurrence. Many "causes" of mal occlusion are not known, although this theorem is true for such obvious single etiologic factors as tongue-thrusting, thumb-sucking, abnormal lip positions, etc.
•
Theorem 3.-Malocclusion should be overcorrected as a safety factor. This rationale is popular in practice, but there are few data to support it.
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•
Theorem 4.-Proper occlusion is a potent factor in holding teeth in their corrected positions. The occlusion usually reJerred to is the intercuspal position. The occlusal relationship obtaining during primitive reflex functions (e. g., the unconscious swallow) is important in ocelusal stabilization.64 Correct intercuspation is an essential factor in occlusal stabilization.67
•
•
Theorem 5.-Bone and adjacent tissues must be allowed time to reorganize around newly positioned teeth. This is the rationale for the use of retainers after active tooth
Treatment goals are usually stated in cephalometric terms for individual tooth positions with insufficient attention- to accommodating for skeletal variations. Nor are treatment goals often phrased in terms of occlusal dynamics. Most mal occlusions are stable before therapy. If they are not at the end of treatment, it may be the fault of the dentist. All treated malocclusions must eventually be returned from control by appliances to control by the patient's own musculature. Proper goals of treatment, careful mechanotherapy, precise occlusal equilibration, and well-chosen retention procedures play a role in achieving occlusal homeostasis. Few clinical research workers have concentrated on the dif-
movements. There is good histologic evidence that it takes some time for the tissues to return to normal after tooth movements. 85.86.96However, this theorem presumes that newly moved teeth are no longer the victims of unsettling forces. If there is occlusal disharmony during the unconscious swallow, it makes very little difference what kind of retainer is worn or for how 10ng.64. 66 The moment the retainers are removed, relapse will begin until the occlusion returns to harmony with the muscles. Indeed, when retainers are removed, if an occlusal interference persists, a "slide into occlusion" will cause the incisors to relapse to crowdingY Stability will return but at the expense of the incisal correction. •
•
•
•
Theorem 6.-lf the lower incisors are placed upright over basal bone they are more likely to remain in good alignment. This theorem has some value but has been overextended, since it often avoids the implications of varying facial types and the mesial migration of the teeth throughout life. Further, the incisal angle deemed "correct" at 12 years of age may not be so for the same person at age 18, as the mandible usually grows disproportionately more than the midface. Finally, the most appropriate incisal angulation varies with skeletal features, for example, the steepness of the mandibular plane (see Chapter 12). Theorem 7.--Corrections carried out during periods of growth are less likely to relapse. This theorem seems valid and logical, but there is little solid evidence to support it. Treatment during growth presumably allows the tissues involved to adjust better. 73 Theorem 8.-The farther the teeth have been moved, the less is the likelihood of relapse. This theorem is strange in logic and there is no evidence to support it. Theorem 9.-Arch form, particularly the mandibular arch, cannot be altered permanently by appliance therapy. The strongest support for this idea comes from the analysis of cases treated by multi banded therapy after most growth is over. 89.104Treatment during the mixed dentition with bite plates, extra-oral traction, or functional jaw orthopedic appliances73 has shown some natural widening of the mandibular arch diameters. The best evidence, though, shows that purposeful alteration of the bicanine diameter in the mandibular arch is hazardous to stability irrespective of the appliance. 89.104Arch form changes occurring in response to alterations in the muscular environment may be more stable. To Riedel's theorems might be added the following:
Theorem JO~-Many treated malocclusions require permanent retaining devices. This is less true for cases treated to meticulous occlusal goals and with respect for the dynamThe less the denics of growth and occlusal functionM.66 tist knows about occlusal physiology the more will be the temptation to retain permanently.
ficulties of relapse and retention (Riedel and c-oworkers are a notable exception,88. 89.104)which is a pity. Though proper studies are difficult to design and tedious to execute, the rewards are great. We have much to learn in this important field, and until the research is completed it is well to be reminded that many confidently held assumptions about "good" treatment procedures have not been confirmed by clinical investigations.
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107. Skougaard MR, Levi BM, Simpson J: Collagen metabolism in skin and periodontal membrane of the marmoset. J Periodont Res 1969; 4:28. 108. Smith RJ, Burstone CJ: Mechanics of tooth movements. Am J Orthod 1984; 85:294-307. 109. Sodek J: A new approach to assessing collagen turnover by using a micro-assay. Biochem J 1976; 160:243. 110. Steiner GG, Pearson JK, Ainamo J: Changes of the marginal and periodontium as a result of labial tooth movement in monkeys. J Periodont 1981; 52:314-320. Ill. Stutzmann J, Petrovic A, Shaye R: Analyse der Resorptionsbildungsgeschwindigkeit des menschlichen AIveolarknochens in organotypischer Kultur, entnommen vor und wahrend der Durchfuhrung einter Zahnbewegung. F ortschr Keiferorthop 1980; 41 :236 . 112. Svandberg GK: Effect of trauma from occlusion on the periodontium, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984, pp 101-126. 113. Ten Cate AR, Deporter DA: The role of the fibroblast in collagen turnover in the functioning periodontal ligament of the mouse arch. Arch Oral Bioi 1974; 19:339. 114. Ten Hoeve A, Mullie RM: The effect of anteroposterior incisor repositioning on the palatal cortex, as studied with laminography. J Clin Orthod 1976; 10:804-822. 115. Tuenge RH, Elder JR: Posttreatment changes following extraoral high-pull traction to the maxilla of Macaca mulatta. Am J Orthod 1974; 66:618. 116. Wainwright WM: Faciolingual tooth movement. Its influence on the root and cortical plate. Am J Orthod 1973; 64:278-302. 117. Weinstein S, et al. On an equilibrium theory of tooth position. Angle Ortho 1963; 33:1-26. 118. Wieslander L, Buck DL: Physiologic recovery after headgear treatment. Am J Orthod 1974; 66:294. 119. Wisth PJ: Periodontal status of neigh boring teeth after orthodontic closure of mandibular extraction sites. Scand J Dent Res 1975; 83:307-313. 120. Wisth PJ, Norderval K, Boe OE: Periodontal status of orthodontically treated impacted maxillary canines. Angle ·Orthod 1976; 46:69-76. 121. Woodside DG, Altuna G, Harvold E, et al: Primate experiments in malocclusion and bone induction. Am J Orthodont 1983; 83:460-468. 122. Zachrisson BU: Gingival condition associated with orthodontic treatment. 11. Histologic findings. Angle Orthod 1972; 41:352-357. 123. Zachrisson BU: Periodontal changes during orthodontic treatment, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periqdontium, monograph 15. Craniofacial " :.9rowth Series. Arii-l'Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984, pp 43-66. 124. Zachrisson BU, Alnaes L: Periodontal condition in orthodontically treated and untreated individuals. I. Loss of attachment, gingival pocket depth and clinical crown height. Angle Orthod 1973; 43:402-411. 125. Zachrisson BD, Alnaes L: Periodontal condition in orthodontically treated and untreated individuals. H. Alveolar bone loss: Radiographic findings. Angle Orthod 1974; 44:48-55.
Force Systems and Tissue Responses to Forces in Orthodontics 126. Zachrisson S, Zachrisson BU: Gingival condition associated with orthodontic treatment. Angle Orthod 1972; 42:26-34. 127. Zengo AN, Pawluk Rl, Basset CAL: Stress-induced bioelectric potentials in the dentoalveolar-complex. Am J Orthod 1973; 64: 17.
SUGGESTED READINGS McNamara lA lr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984. McNamara lA lr, Ribbens KA, Howe RP (eds), Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. Barber AF, Sims MR: Rapid maxillary expansion and external root resorption in man: A scanning electron microscope study. Am J Orthod 1981; 79:630-652. Burstone Cl: Biomechanics of the orthodontic appliance, in Graber TM, Swain B (eds) , Current Orthodontic Concepts and Techniques, 2nd ed. Philadelphia, WB Saunders, 1975. Hocevar RA: Understanding, planning, and managing tooth movement: Orthodontic force system theory. Am J Orthod 1981; 80:457-477. Linge BO, Linge L: Apical root resorption in the upper front teeth during orthodontic treatment: a longitudinal radiographic study of incisor root lengths, in McNamara lA lr, Ribbens KA (eds), Malocclusion and the periodontium, monograph 15. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984, pp 165-184. Melcher AH, Beersten W: The physiology of tooth eruption, in
and Facial Orthopedics
331
McNamara lA lr (ed) The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977, pp 1-240. Mulligan T: Common Sense Mechanics, Phoenix, Ariz, C.S.M, 1982. Proffit WR: Equilibrium theory revisited: factors influencing position of the teeth. Angle Orthod 1978; 48:175-186, Reitan K: Biomechanical principles and reactions, in Graber TM, Swain BF (eds), Current Orthodontic Concepts and Techniques, Philadelphia, WB Saunders, 1975. Rygh P: Periodontal responses to orthodontic forces, in McNamara lA lr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984, pp 17-42, Riedel RA: Post-pubertal occlusal changes, in McNamara lA lr (ed), The Biology of Occlusal Development, monograph 7. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977, pp 113-144. Sadowsky C, BeGole EA: Long-term status of temporomandibular joint function and functional occlusion after orthodontic treatment. Am J Orthod 1980; 78:201-212. Sadowsky C, Sakols El: Long-term assessment of orthodontic relapse. Am J Orthod 1982; 82:456-463. Smith Rl, Burstone Cl: Mechanics of tooth movements. Am J Orthod 1984; 85:294-307. Weinstein S, et aI. On an equilibrium theory of tooth position, Angle Orthod 1963; 33:1-26. Zachrisson BU, Alnaes L: Periodontal condition in orthodontically treated and untreated individuals. 1. Loss of attachment, gingival pocket depth and clinical crown height. Angle Orthod 1973; 43:402-411. Zachrisson B U, Alnaes L: Periodontal condition in orthodontically treated and untreated individuals. n. Alveolar bone loss: Radiographic findings. Angle Orthod 1974; 44:48-55.
"
CHAPTER
14 Planning Orthodontic Treatment Robert E. Moyers, D.D.S., Ph.D.
"
Always take hold of things by the smooth handle.-THoMAs JEFFERSON
Nothing in progression can rest on its original plan. We might as well think of rocking a grown man in the cradle of an infant.-EDMuND BURKE
2.
OUTLINE A.
Selection of orthodontic cases in general practice I. 2. 3.
4. 5. 6.
7.
B.
C.
D. E.
Treatment planning in the primary dentition I. 2.
Reasons for treatment Conditions that should be treated
3. 4.
Conditions that may be treated Contraindications to treatment in the primary dentition
Treatment planning in the'transitional I. 2.
Reasons for treatment Conditions that should be treated
3.
Conditions that may be treated
dentition
Treatment planning in the permanent dentition Limiting factors in orthodontic therapy I.
332
Is there a problem? What is the problem? How is the problem typified? a) Timing of treatment b) Skeletal pattern c) Available space What treatments are available for this problem? Which available treatment is most appropriate? How is successful treatment defined? a) Ideal treatment b) Compromise treatment c) Symptomatic (palliative) treatment How will the treatment be stabilized?
Factors related a) Limiting b) Limiting c) Limiting
to the individual patient skeletal factors dental factors neuromuscular factors
3.
F.
Factors related to the individual dentist a) Aptitude b) Training c) Experience d) Attitude e) Adherence to poor methods Factors related to the nature of orthodontics a) The nature of developmental oral biology b) Patient cooperation and treatment success c) Paucity of adequate compromising alternative treatments
Some common mistakes
Not all patients with "malocclusion" want or need orthodontic treatment. Not all patients needing orthodontic treatment should be treated by the typical family dentist. This chapter is written assuming that the reader has the interest and desire to treat as many orthodontic patients as possible without co~promising the quality of the result. Many dentists have a great desire to extend their orthodontic service to more patients, but most dental schools do no~ have the time in the,ctlITiculum to teach orthodontics past the introductory level. Short courses a,nd occasional lectures are plentiful but provide no clinical experience. The dentist skilled in many aspects of dentistry and wishing to further his or her orthodontic abilities is thus stymied by the very nature of orthodontic treatment--one cannot learn orthodontics in "short" courses because malocclusions cannot be treated in a short time. Ethical dentists seeking supervised clinical teaching, but unable to leave their practices for an extended period, are unwilling to try new and unfamiliar treatments on patients without supervision. Enthusiasm is no substitute for experience and ability, nor does sincerity
Planning Orthodontic Treatment
How Typified?
Treatments Available?
333
How To Stabilize?
Which Mastered?
(Refer)
(Dismiss) Classification 9
Treatment 15, 16, 17
Treatment 15, 16, 17
Treatment 15,16, 17
FIG 14-1. Flow of questions arising at the start of malocclusion treatment. Pertinent chapters in this text are noted below. guarantee correctness. One must protect oneself and one's patients f~om well-intentioned but ill-planned therapy. Meticulous planning before orthodontic treatment actually is begun prevents much misunderstanding and trouble. Careful orthodontic planning is essential for every dentist, but especially so for the less experienced or illtrained. The purposes of this chapter are (I) to provide a procedure for testing whether one can provide a satisfactory treatment for a particular problem and (2) to outline a plan for organizing orthodontic treatments.
A. SELECTION OF ORTHODONTIC IN GENERAL PRACTICE
CASES
The selection of any malocclusion for treatment derives from the answers to seven questions which follow one another in logical sequence (Fig 14-1): (I) Is there a problem? (2) What is the problem? (3) How is the problem typified? (4) What treatments are available for this problem? (5) Which of the available treatments is most appropriate for me to use? (6) How is successful treatment defined? and (7) How will the treatment be stabilized?
1. Is There a Problem? The question of whether a problem exists is in our minds
during the cursory examination (see Chapter 8). Having determined that a problem exists, one does not place immediately a favorite appliance but rather asks the next question.
2. What Is the Problem? The purpose of the diagnosis is to defin'e and describe in a definitive manner the nature of the problem (see Chapters 10-12). Orthodontic problems are not described in terms of the appliance to be used (e.g., a "head gear case") but rather in terms of abnormal skeletal morphology, abnormal dentitional and occlusal features, and atypical neuromuscular function. The more precise and quantitative the diagnosis, the easier it is to answer the next question.
3. How Is the Problem Typified? Before starting any treatment, it is useful to typify the case by its characteristics and possible treatment strategies. The Angle Classification and many other classification systems are inadequate for this purpose. The procedure suggested herein consists of asking three questions sequentially, the answers to which segregate most malocclusions into 18 categories according to their primary characteristics (Fig 14-2). Such a simple approach does not complete the diagnosis for it does not include every important variable (e.g., the mediolateral and vertical aspects of the malocclusion), it simply
FIG 14-2. An arborization (decision tree) to segregate various treatment protocols. Arborization is based on three decisions: A, timing of treatment; B, craniofacial skeletal pattern (three choices are available.
namely, skeletal Classes I,ll, and Ill); and C, the availability of space in the arch (abundant, sufficient, or deficient).
334
Treatment
aids in the screening and grouping of similar cases for ease in planning treatment. All mal occlusions grouped by this method have the same fundamental nature with respect to developmental age, anteroposterior relationships, and available space in the arch periI]1eter, and they differ only in other aspects of.the malocclusion. The procedure is designed to keep the dentist's mind on possible basic treatment strategies to avoid being diverted by trivial and superficial features. Treatment planning should not necessarily be directed to the ugliest aspects of the mal occlusion nor to features most worrisome to the parent or child. Successful therapy is founded on a thorough understanding of the fundamentals of the malocclusion, not the patient's worries. Superficialities respond easily if basics are understood and controlled. Figure 14-2 is an arborization (decision tree) developed from the possible answers to three questions: (a) What is the timing of treatment? (b) What is the facial skeletal pattern? (c) Is space available within the dental arch alone to correct the malocclusion? As each question is asked, the most appropriate available answer is chosen, and the diagram is followed to the next question. Finally, one arrives at one of the 18 protocols at the bottom of the chart. All cases which end in the same category will have similar basic features with respect to developmental age, skeletal pattern, and available space, but may differ in other features. Advanced clinicians probably do something like this intuitively, but those who are inexperienced need guidance to keep a focus on the most critical features in determining treatment strategies. a) Timing of Treatment The question of timing (line A in Fig 14-2) is asked first because the strategies and tactics for early; as opposed to late, treatment are so different. Must the treatment for this patient take into account facial and dental development, or is most growth already accomplished? If growth is mostly completed, therapy will consist largely of tooth movements neither greatly aided nor hampered by growth. Early treatment is treatment which must cope with active growth or might utilize its dynamics. A method is required to assess the stage of occlusal development and estimate the time left before establishment of the permanent occlusion (i .e., determine if there will be sufficient time to complete any interceptive and guidance procedures). After the permanent occlusion is established (second molars in occlusion), little skeletal growth remains, especially in girls, and the opportunities for occlusal guidance are diminished. Furthermore, the mechanotherapy changes at this time as well as interceptive and guidance appliances (holding arches, functional appliances, simple extra-oral traction devices, etc.) give way to the multi bracketed precision appliances necessary for proper positioning of the permanent teeth. A crude and arbitrary rule of thumb, based on the calcification stage of the mandibular cuspid and first premolar, may be used to separate early from late treatment. When these teeth have not yet reached calcification stage 7'/2 (roughly one-half the root formed), the patient may be considered eligible for early treatment planning (see Chapter 6, Development of the Dentition and the Occlusion, and Chapter 11, Analysis of the Dentition and Occlusion). Chapter 15 deals with early treatment.
Late treatment, in this context, is defined as treatment begun too late to be greatly aided, complicated, or confounded by growth. Of course some facial growth and dentitional development remain in patients after the cuspids and premolars have reached stage 7'/2, but there may be insufficient time to achieve the basic goals of treatment without changing the strategy and appliances used earlier (see Chapter 16 on adolescent treatment). Nor should one forget that growth and bone remodeling persist throughout life, a fact which makes orthodontics possible in adults (Chapter 17). Often we are prone to equate growth solely with the exuberant changes of childhood and pubescence, whereas it is more proper to consider all skeletal changes throughout life. With aging, the bone turnover rate decreases but persists, so treatment is still possible, but at a much slower rate. One can take quick advantage of growth only when growth is most active and time is available to utilize it. Skilled orthodontists with an experienced sense of timing often can start "early" treatment at a later developmental date. Diphasic treatment, that is, treating the skeletal problem early when growth is more active and treating dental mal alignment after the permanent teeth have erupted, purposefully separates two basic treatment goals. The concepts of "early" and "late" treatment are useful working hypotheses only and offer no guarantee that unexpected late growth will neither disrupt nor disturb.
b) Skeletal Pattern In Chapter 8, The Orthodontic Examination, a simple noncephalometric method was presented for initially assessing the facial skeleton (the Facial Form Analysis). On the basis of this analysis or, better, a cephalometric analysis, the Basic Morphologic Analysis (Chapter 12), the patient is arbitrarily assigned to one of three skeletal categories: Class I, essentially a well-balanced facial profile; Class II, a retrognathic profile; or Class Ill, a prognathic profile. This step is illustrated in line B of Figure 14-2.
c) Available Space It is necessary to decide, before, beginning treatment, whether there is sufficient space to provide for alignment of all teeth, any necessary occlusal adjustments, and the placement of the teeth over their bases (see line C in Fig 14-2). In Chapter 11, Analysis of the Dentition and Occlusion, methods for mixed dentition analyses and "diagnostic setups" were given. The Mixed Dentition Analysis alone cannot show how the teeth fit in the facial skeletal profile. Only a combined cephalometric and mixed dentition analyses can be so revealing. Having performed both, the dentist can now categorize the patient as having "abundant," "sufficient," or "deficient" space. Abundant means there is more than enough space to align all of the teeth properly within the craniofacial skeleton as well as enougl}. to permit any required developmental occlus!ll adjustments. Sufficient means that there is only enough arch perimeter to align the teeth buf none is left to aid in achieving a Class I occlusion (Le., there is insufficient space for a late mesial shift). Deficient means there is insufficient arch perimeter to ac-' commodate all of the teeth. This categorization is based primarily on the lower arch, since it is more critical in matters of space. Basic treatment of all cases within the same protocol category will be similar, though individual cases in the group will vary in some aspects (e.g., vertical relations). For instance, all malocclusions sorted to protocol 13 wiII show most permanent teeth as
Planning Orthodontic Treatment erupted, a Class 11facial skeleton, and inadequate arch space within which to align the teeth, though there may be dissimilarity in superficial or localized aspects of the malocclusions. Figure 143 should be studied carefully, for it illustrates the application of the method to actual cases. One is now in a position to select a treatment for the malocclusion just typified.
4. What Treatments Are Available for This Problem? It is impossible even for the most experienced orthodontic clinician to know all of the available methods of treatment for each particular malocclusion. We are all limited to those treatments we have been taught, or have learned on our own. This raises the qQestion: Of known available treatments, how does one decide which, if any, is most appropriate for a given patient?
routinely in practice. In the real and practical sense, this simply is not true, for if it were, the knowledge could be taught more easily, unexpected difficulties in treatment would not be encountered, and relapse would be infrequent. Furthermore, there would have evolved a more universal agreement about treatment methods and goals. The many, diverse opinions so strongly held by clinicians of integrity are testimony to our ignorance of how appliances really work. Difference of opinion always causes more trouble than difference of facts. If the facts were well known there would be more general agreement about treatment. Let us pursue this point by developing a simple equation of orthodontic success: M (malocclusion) + T (treatment) = 5 (success). That is, a known mal occlusion plus a specific treatment should make it possible for us to quantify success. As we develop this idea a bit we might be able to say (where A in the equation is one patient):
5. Which Available Treatment Is Most Appropriate? A principal limitation in treatment is the developmental age of the patient. Certain strategies are appropriate at certain ages and less useful or even contraindicated at others (Fig 14-4). All appliances have limitations, but those that have stood the test of time must have certain virtues for particular, though not necessarily universal, applications. Treatment can drag on and on because the dentist fails to recognize the inadequacies of the appliance chosen or doesn't know another. Many a malocclusion is finished with an inadequate result because the dentist does not' know the best appliance or treatment procedure for the case or refuses to use other than a favorite method. So varied are the mal occlusions and so complex the details of their corrections that all clever clinicians are constantly adding to their repertory of treatment methods. Only the naive and stubborn marry themselves to but one appliance or method. Those who do so, if their standards are to remain high, must limit the patients treated, either consciously or unconsciously, to those malocclusions which respond well to that particular favorite appliance or procedure. Incompetence* in orthodontics is of two kinds - poor performance and poor thinking. Poor performance may be an innate inability to complete a task without making a mess of it. Poor performance also may derive from attempting treatment with an unfamiliar method or appliance but with no real training in its use. One does not achieve a competent performance in orthodontics solely by listening to a persuasive lecturer or by looking at pictures of treated cases completed by someone else. The second kind of incompetence in orthodontics, poor thinking, originates when a person chooses inflexible adherence to rules, formulae, or "philosophies" of treatment over differential analytical treatment planning. Blind faith in or rigid adherence to one approach to all problems causes one to fail to discern obvious and meaningful developmental signs or significant responses to therapy, and thus one is unable to react practically to them when they appear. It is generally believed that we know how orthodontic appliances work and that successful orthodontists use such knowledge
*The ideas on incompetence in this paragraph were much influenced by an article by an eminent American historian, Barbara W. Tuchman: A nation in decline? New York Times Magazine, Sept 20, 1987, P 20.
335
M(A)
+
T(J)
= 0.75(5)
M(A)
+
T(2)
= 0.50(5)
M(A)
+
T(3) = 0.25(5)
M(A)
+
T(4J
=
?
(5).
In other words, the same kind of mal occlusion treated four different ways yields different success ratios varying from unknown or questionable success to success 75% of the time. Until we have better clinical research on a wide variety of malocclusions using several different methods, all of us have difficulty knowing which is truly the best method for a case. It is certain, however, that a treatment unknown to us or little known could hardly be used. In the list above, suppose that only T(3) or T(4) was known, then there would be much less chance for success than if treatments T(J) or T(2) had been mastered. Those who develop treatment methods are rarely able to be objective about the limitations of their own methods. At present, it is difficult, quite difficult, to determine which treatment is the best for each malocclusion. We must fall back on our own experience or listen to those we trust, but sincerity of view is no guarantee of truth. When considering treatments one knows for a particular problem, one must ask, (I) How did I learn about this treatment? and (2) What are my experiences and skills with it? Few of us are willing to learn a complicated and difficult method of treatment by' applying it to our own patients without supervision. So, for a given malocclusion, though many treatments may be available, we may know but one or two, but we must assure ourselves that at least one of those known and mastered is appropriate or we should not b~gin treatment.
_.
6. How Is Successful Treatment Defined? There are three kinds of orthodontic treatment goals: (I) ideal; (2) compromise; and (3) symptomatic treatment. In Chapters 15 through 17 it will be noted that the goals of successful treatment vary widely according to developmental age, severity of the dysplasia, history of oral disease, loss of teeth, and other factors. Treatment planning involves choosing the most appropriate goal for each case, but that goal-ideal, compromise, or sympto-
336
Treatment
Address
alignment 3+4+5 molar Space
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of 2 and I adjustment left ofler
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.'
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size
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5
Remarks:
I
11
Bl TIMING (Al
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I I~(8) ~------EARLY ill] ITIT
11
~
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-'L
of
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1
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Overbile"
'1.8~
against
the chart below
I I-LATE--------11
I
-!----
SKELETAL PATTERN
I
.
SPACE (C)
FIG 14-3. Examples of the arborization applied to actual cases. Look at the photographs, make each of the three decisions in sequence, and
check your choices grouping ...•
each
photographic
Il:: 1
I I I I I
I -I ~ @
1(3
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338
Treatment Summary Patient's
Name
WI'lliflM.
Child
---p __
guidance phase I of diphasic treatment interception
of Treatment
B.
_ Youth ___ _~ __ ___ ___
Plan age
pre-adolescence mid-adolescence post-adolescence phase 11of diphasic treatment
'I_I Adult ___ ___
___
Specified 1.
Necessary
NollE"
2.
Compromises
3.
sex~
dateS~o/cfI "
healthy, little growth expected combined with periodontics and restorative combined with surgery
"
4.
FIG 14-4. Summarization of the treatment plan. Under the appropriate age group, each treatment should be designated properly. Any necessary compromise with an ideal result should be specified (e. g., extraction
of all four first bicuspids). The goals must be stated simply in order of importance, but the strategies should be stated in the sequence in which they will be employed during treatment.
matic--{)ught to be determined by the features of the malocclusion, not the inclinations or abilities of fhe dentist.
with. teeth apparently ni<.:eiyaligned, is a most impractical result. The"main reason for abandoning the ideal goal is simply that the nature of a particular mal occlusion does not permit an ideal result: for example, extraction of teeth is necessary. The goals listed here and in Chapters 15 through 17 include concepts of oral health, function, and cosmetics, whereas the family may be concerned largely with esthetics. One must be very careful not to impose too rigidly one's own concepts and standards of esthetics. Often a trait has been accepted without question or even cherished as a family characteristic until the dentist calls attention to it.
a) Ideal Treatment First, always define the ideal goal for the case under study and do not abandon it without clearly being forced to do so. But what is "ideal" from an esthetic point of view may not be ideal from the standpoint of periodontal health, occlusal function, or practicality. The ideal goal often is rejected because such a goal seems "impractical." In orthodontics, practicality often is determined largely by stability of result. An unstable occlusion, even
Planning Orthodontic When the nature of the case does not permit ideal treatment, the only compromise treatment that can be accepted, of course, is that which most clearly approximates the ideal. If the clinician does not know how to obtain an ideal result, two alternatives are available: the patient may be referred to a specialist, or a compromise treatment plan must be developed. The latter alternative cannot be followed ethically unless the first alternative has been suggested, its superiority explained to and rejected by the patient, and the nature of the compromise and its difficulties have been understood and accepted. When patients cannot afford the cost of ideal treatment, it is well, before suggesting a compromise treatment, to remember that no patient can afford an unstable result and that most mal occlusions are stable until clinical intervention be&ins. An alternative procedure under these circumstances may be 'not to treat at all in the hope that at a later time the ideal treatment can be achieved.
b) Compromise Treatment When contemplating compromise treatment, it is well to ask several questions: "What is being compromised?" "Why is compromise treatment considered" and "Who pays how big a price for the compromise? Some malocclusions simply cannot be treated ideally, and any therapy is a compromise with perfection. On the other hand, to compromise the goal because of one's own inability to treat to the best result may be to ask the patient to pay too high a price and raises serious questions of professional ethics. Unfortunately, there are three common problems in orthodontics that do not lend themselves to compromise. A Class II malocclusion cannot be treated partially toward a Class I relationship or it will be unstable and revert to the original condition, for occlusal dysfunction tends to destroy partly corrected Class II occlusions. The second matter difficult to compromise is that of gross discrepancies in tooth size-available space ratios. If there is a discrepancy of 3 mm in a quadrant, there is no 3-mm tooth that can be extracted to alleviate that exact amount of crowding. The dentist must extract a tooth in each quadrant which is about 7 mm in width. Although the space is thus easily provided for alignment of 3 mm of crowding, 4 mm of space closure remains to complete the treatment. The tooth movements necessary to effect 4 mm of space closure and a harmonious functional occlusion are much more difficult than the tooth movements that provided the 3 mm of alignment. A third uncompromising situation is the inability of the jaw musculature to adapt to certain occlusal interferences. For example, some are tempted to extract a single mandibular incisor to relieve crowding. The incisors are then easily aligned, but they may now have no antagonistic occlusal stops in the upper arch and erupt toward the palate, and the posterior intercuspation usually has been altered so that is cannot be corrected by tooth movements or even equilibrated into stability. Unfortunately, there are not as many compromise methods of treatment in orthodontics as we would like and as many as are available for other dental services. One of the most difficult tasks in orthodontics is that of planning sensible and practical compromise treatment. An even more difficult problem is the retreatment of cases worsened by unfortunate mistakes in compromise therapy. Sometimes, unwanted compromise treatment is forced on the dentist by the failure of the patient and family to carry out their responsibilities. Some cases are very difficult to terminate under
Treatment
339
such circumstances as minimal patient cooperation after extraction of teeth. Whatever the compromise, a basic rule to remember is to compromise
stability last of all.
c) Symptomatic (Palliative) Treatment Treatment of the symptoms of malocclusion rather than the malocclusion itself is rarely advised except as a temporizing expedient to be followed by treatment of the basic problem. An example of acceptable symptomatic therapy is the retraction of maxillary incisors in extreme labioversion during the early mixed dentition to minimize their accidental fracture. But even the palliative retraction of procumbent maxillary incisors often may be done just as easily by simultaneously treating the Class II occlusal and skeletal relationship which accompanies it. Figure 14-4 is a form I use in my practice to outline and summarize the treatment plan. Note that the goals are specified in order of importance but the steps of treatment are noted in sequence. Precise definition of goals makes easier the decision concerning disposition of the case. One wants to treat only those patients one can treat well to a stable result, refer those patients needing treatment that one cannot provide, and keep under careful surveillance'those patients for whom the best treatment must come later. There is no excuse for continued observation of a case because of ignorance or indecision. Observation alone effects few improvements: proper intervention is more successful. Referrals can be made for diagnostic consultation as well as for treatment. The patient should not have to suffer longer for more expensive treatment at a later time because of the diagnostic inabilities of the first dentist he or she consults, nor should a colleague's task be made more difficult by another's earlier indecision.
7. How Will the Treatment Be Stabilized? Retention is planned when estimating the probable treatment result, when setting the goals of treatment. Before a dentist prepares a cavity for an inlay, there is a clear mental image of the cavity outline, the depth of the preparation, the slope of the cavity walls, and other details. Without such a mental image as a goal, one could scarcely begin. In like fashion, before a malocclusion can be corrected, the clinician must have a precise concept of how the treated result will appear. Every dentist knows perfect intercuspation of the teeth. That is not what is meant; rather, one must be aware at the very start of treatment of the detailed deviations from perfect intercuspation that can be expected in a case because of the very nature of the problem; for exabple, if the maxillary incisors are disproportionately wide for the mandibular incisors, the best mechanotherapYPllnnot effect a perfect posterior occlusion cO~cUmitant with an ideal overbite and overjet relationship. Under such circumstances, one treats to ; perfect posterior occlusion and admits that the nature of the case will require a bit more overjet than would have appeared had the tooth widths been more harmonious. It is advisable to write into the treatment plan any expected difficulties of retention or any tendencies to relapse. Such a notation serves to remind one, as treatment ends, of details that were fresh in mind during the thorough study done at the start of treatment. Retention principles are discussed in Chapter 13. Specific details are given in Chapters 15 through 18.
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Treatment
B. TREATMENT PLANNING IN THE PRIMARY DENTITION
1. Reasons for Treatment* Treatment in the primary dentition is undertaken for the following reasons: a) To remove obstacles to normal growth of the face and dentition. b) To maintain or restore normal function.
2. Conditions That Should Be Treated in the Primary Dentition Are: a) Anterior and posterior crossbites. , b) Cases in which primary teeth have been lost and loss of
arch space may result. c) Unduly retained primary incisors which interfere with the normal eruption of the permanent incisors. d) Malpositioned teeth which interfere with normal occlusal function or induce faulty patterns of mandibular closure. e) All habits or malfunctions which may distort growth.
3. Conditions That May Be Treated a) Distoclusions that are at least partly positional. Occlusal equilibration or tooth movements may restore normal function. The rest of the problem may be treated at this time or later. b) Certain distocclusions of a skeletal nature are best treated at this age, but the patient must be socially mature, and the cases must be carefully chosen. c) Open bites due to tongue-thrusting or digital sucking habits.
b) The malocclusion cannot be treated more efficiently in the permanent dentition. Emphasis should be placed on guidance of growth, interception of a developing malocclusion, and elimination of the first symptoms of what might become more serious malocclusions in the permanent dentition.
2. Conditions That Should Be Treated Conditions that should be treated in the mixed dentition (see Chapter 15) are: a) Loss of primary teeth endangering the available space in the arch. b) Closure of space due to the premature loss of primary teeth; the lost space in the arch must be regained. c) Malpositions of teeth that interfere with the normal development of occlusal function, cause faulty patterns of eruption or mandibular closure, or endanger the health of the teeth. d) Supernumerary teeth that may cause malocclusion. e) Crossbites of permanent teeth. f) Malocclusions resulting from deleterious habits. g) Oligodontia, if closure of space is preferable to prosthesis. h) Localized spacing between the maxillary central incisors for which orthodontic therapy is indicated. i) Neutroclusion with extreme labioversion of the maxillary anterior teeth (maxillary dental protraction). j) Class II (distoclusion) cases of a functional type. k) Class II (distoclusion) cases of a dental type. I) Class II (distoclusion) cases of a skeletal type, particularly if diphasic treatment is indicated. m) Space supervision problems.
3. Conditions That May Be Treated 4. Contraindications to Treatment in the Primary Dentition Treatment in the primary dentition is contraindicated when: a) there is no assurance that the results will be sustained, b) a better result can be achieved with less effort at another time, and/or c) the social immaturity of the child makes treatment impractical.
Conditions that may be treated in the mixed dentition (see Chapter 15) are: a) Class II malocclusions of a skeletal type, particularly if diphasia treatment is indicated. b) Class III malocclusions, where early treatment is feasible. c) All malocclusions accompanied by extremely large teeth. If serial extractions are to be undertaken, treatment must be instituted in the mixed dentition. d) Gross inadequacies
C. TREATMENT PLANNING IN THE TRANSITIONAL DENTITION The mixed dentition period is the time of greatest opportunity for occlusal guidance and interception of malocclusion. At this time, the dentist has the greatest challenges and finest opportunities for efficient orthodontic therapy. ,.
1. Reasons for Treatment Any case may be treated in the mixed dentition (see Chapter 15) provided that: a) The treatment does not impede normal growth of the dentition. *See also Chapter
15.
D. TREATMENT PERMANENT
or disharmonies
of the apical bases.
PLANNING IN THE DENTITION t
All mal occlusions possible to correct may be treated in the permanent dentition of the young adult (see Chapter 16), although, as·,noted earlier, that is- not necessarily the best time for some problems. Orthodontic therapy can be carried out for older healthy adults, but the strategies and tactics change radically when periodontal disease and/or loss of teeth has occurred (Chapter 17).
E. LIMITING FACTORS IN ORTHODONTIC THERAPY 1. Factors Related to the Individual Patient So much variability is seen among orthodontic
patients that
Planning Orthodontic Treatment sophisticated diagnostic techniques have been developed for identifying the individual characteristics of each patient to be treated.
a) Limiting Skeletal Factors The most limiting skeletal factors are those of gross osseous dysplasia, wherein one or more parts of the craniofacial skeleton are disharmonious with other parts. The clinical problem is disharmony within an individual face rather than deviations in absolute size from population norms (see Chapters 4 and 12).
341
training in orthodontics than in other clinical subjects. Therefore, the general dentist desiring broader abilities in orthodontics begins with a handicap of which he or she may not be aware. Furthermore, though many orthodontic short courses are available for the general practitioner, few, if any, can include the actual treatment of malocclusions. Furthermore, in many short courses, there are evidences of commercialism and parochialism in teaching. The dentist who would treat mal occlusions must analyze carefully the advantages and disadvantages of past training and the methods available for improvement.
b) Limiting Dental Factors Primary limiting dental factors include disharmony between the total tooth size and available space in the arch perimeter, variations in the number of teeth, intra-arch tooth size disharmonies, and interarch tooth size disharmonies. The beSt-planned orthodontic treatments can go awry because the number and size of teeth for the patient are not in harmoney with themselves or other features (see Chapters 6 and I I).
c) Limiting Neuromuscular Factors The most important and frequent limiting neuromuscular factors are abnormal reflex activities, including lip functions, tonguethrusting, swallowing, and functional mandibular movements adaptive to occlusal disharmonies. Less frequently seen, but more severe, neuromuscular factors include the retention of endogenous orofacial infantile neuromuscular behavior and neuromuscular behavior associated with gross developmental syndromes or neuropathologic conditions (see Chapters 5 and 10).
2. Factors Related to the Individual Dentist Just as patients and malocclusions vary, so there is wide variation in the aptitude, training, experience, personality, and attitude of dentists, variations which have a marked effect on the quality of treatment results.
a) Aptitude Aptitude, or native ability, is clearly differentiable from training or experience. The influence of technical aptitudes on dentistry is well known; less appreciated in orthodontics are intellectual or conceptual aptitudes. Those who would treat malocclusions must adopt a long-term view, for treatment awaits biologic responses and growth. Such a philosophic point of view comes easily to some but not to all. Successful orthodontics requires a biologic point of view on the part of the dentist-an aptitude clearly differentiated from, but not in conflict with, technical and mechanical skills. Finally, specific diagnostic capacities are advantageous to the dentist in orthodontics. For most malocclusions, there are several satisfactory treatment plans that might be followed. The dentist who always demands a clear view of "right" and "wrong," the identification of an only' 'best" way to treat every case, and similar certainties will encounter difficulties in orthodontics. Such narrow views are useful in achieving technical skill; they are handicapping when developing broad diagnostic and treatment planning capacities in orthodontics.
b) Training Most dentists in North America have had less undergraduate
c) Experience The finest graduate training problem in the world is not an adequate substitute for personal clinical experience, since the cases treated are completed by adherence to primary diagnostic decisions and treatment plans of the clinical intructor, not those of the graduate resident. Cases treated in graduate residency programs are carefully selected for their teaching value: in orthodontic specialty practice one treats everything and does so alone. In general practice one has the luxury of referral.
d) Attitude Any of us may have unconscious personal biases or handicapping attitudes toward ourselves and our clinical work. If we have unjustified self-esteem or overrate the training we have had, we may be handicapped in our clinical efforts. Perhaps the most important single attitude for the clinical orthodontist is that of objective criticism of one's own clinical efforts.
e) Adherence to Poor Methods One is ethically obligated to use the best method available, but as new discoveries and innovations are made, the best methods of one time period become the poorer methods in another. Good orthodontists are constantly on the lookout for improvements in treatment methods. Adherence to unfounded or poorly based methods is inexcusable, as the dissemination of orthodontic knowledge to the profession through journals and textbooks is now so thorough and widespread. There is, unfortunately, evidence of "cultism" still remaining in orthodontics, but such parochial attitudes are found far less frequently in the experienced and well-trained practitioner.
3. Factors Related to the Nature of Orthodontics Orthodontics is a difficult clinical practice with many limiting factors that are common to the field itself and that apply to all who treat malocclusions. "The rules of the game" of orthodontics are somewhat at variance,.with successful principles applicable in otllerJields of clinical de~tistry. Often the dentist is unaware that the factors by which one achieves success in restorative and prosthetic dentistry are not necessarily the same factors that guarantee success in orthodontics.
a) The Nature of Developmental Oral Biology The nature of developmental biology is such that although there is considerable variation in morphology, the unfolding of the growth pattern, and the response to orthodontic therapy, the clinician is still limited by the unpredictable nature of growth itself.
342
Treatment
While growth takes place at specific sites, in a specific fashion, in specific directions, it occurs within a rather specific individualized time pattern. As yet, we are limited in our predictive abilities and our control of growth processes, including our inability to condition all neuromuscular reflexes, flroduce growth of bones at will, stabilize all occlusions exactly where we might wish them to stabilize, etc. b) Patient Cooperation and Treatment Success The finest orthodontic treatment plan and the most meticulously made orthodontic appliance will achieve little if parents and patient are not enthusiastically supportive of the dentist's efforts. In orthodontics, as much as in any other clinical field, the patient determines the success of treatment. Dentists who treat malocclusions must exhibit skill in psychology, patience, and an understanding of interpersonal dynamics if they are to be successful. Compromise treatment to an inadequate result is sometimes the only recourse when the dentist cannot sustain the patient's interest. c) Paucity of Adequate Compromising Alternative Treatments The allure of compromise treatment may arise through inexperience, willingness to be satisfied with poor results, inadequate technical skills, or lack of sufficient training. Only in a few specific instances is compromise treatment best for a patient and those are defined by the circumstances of the case itself, not the dentist's abilities. For a discussion of the problems of compromise in orthodontic therapy, see Section A-6-b.
this as a most difficult group of malocclusions. The more inexperienced clinicians often fail to respect the dominance of skeletal morphology on occlusal relationships. To attempt Class II treatment without cephalometric analyses is to run great risks logistically, ethically, even legally. Some Class II malocclusions are relatively easy to treat, while others are difficult for the most clever and experienced orthodontist. Not to be able to differentiate these at the start of treatment is a serious handicap. Open bites may be caused by many different factors. As soon as a thorough differential diagnosis and an understanding of the etiology of open bite is appreciated, it is quickly seen that some open bi~es are easy to treat and others are nearly impossible without surgical intervention. After teaching undergraduate dental students for a number of years and counseling many general practitioners concerning orthodontic problems, I have bec?me convinced that the key to orthodontic success in general practice lies in (I) a thorough knowledge of growth and development, on which is based (2) a practical diagnostic ability. That is to say, success is not based primarily on the choice of a favorite appliance. The dentist who fails to recognize the primary role of growth and development and the overriding importance of the differential diagnosis will have continual trouble in planning many orthodontic treatments irrespective of the technical skills mastered, the appliances used, or the short courses attended.
SUGGESTED READINGS F. SOME COMMON MISTAKES It is my opinion, based on many years of consultations with general dentists about troublesome cases, that the most common mistakes are rooted in failure to appreciate initially the serious complications which may accompany treatment of three rather common malocclusions: namely, space problems, Class II malocclusions, and severe open bite. Difficulties in treatment of space problems may arise because an inadequate diagnosis has been made and the case thus was classified erroneously (e.g., a gross discrepancy case was treated as a space supervision case). In other instances, the clinician treating the patient has had mistaken ideas concerning the growth of the dental arches and limitations in making more space available. It is most difficult for the inexperienced clinician to comprehend just how severe a shortage of 2 to 3 mm in each mandibular quadrant sometimes really is. Other difficulties arise in the handling of discrepancy cases by extraction of teeth when the clinician does not have the skills and techniques for closing the spaces remaining after alignment is achieved while achieving a satisfactory functional occlusion. It is understandable that the general dentist might have problems with the Class II syndrome, since all orthodontists recognize
Feinstein AR: Clinical Epidemiology: The Architecture of Clinical Research, Philadelphia, WB Saunders, 1985. Horowitz SL, Hixon EH: The Nature of Orthodontic Diagnosis, St Louis, CV Mosby, 1966. Proffit SR, Ackerman JL: Diagnosis and treatment planning in orthodontics", in Graber TM, Swain BF (eds), Orthodontics, Current Principles and Techniques, St Louis, CV Mosby, 1985. Sackett DL,Haynes RB, Tugwell PX, et al: How to read clinical journals. I. Why to read them and how to start reading them critically. Can Med Assoc J 1981; 124:555-558. Part II, To learn about a diagnostic test, Can Med Assoc J 1981; 124:703-710. Part Ill, To learn the clinical course and prognosis of disease, Can Med Assoc J 1981; 124:869-872. Part IV, To determine etiology or causation. Can Med Assoc J 1981; 124:985-990. Part V, To distinguish useful from useless or even harmful therapy. Can Med Assoc J 1981; 124: 11561162. Sackett DL, Haynes RB, Tugwell P: Clinical Epidemiology: A Basic Science for Clinical Medicine. Boston, Little, Brown & CpIJ1pany, 1985. " ';. VigPS, Ribbens KA eds. Scienqe and Clinical Judgment in Orthodontics, monograph 19. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1986.
CHAPTER
15 Early Treatment Robert E. Moyers, D.D.S., Ph.D. Michael L. Riolo, D.D.S., M.S.
What you should put first in all the practice of our art is how to make the patient well; and if he can be made well in many ways, one should choose the least troublesome.-HIPPOCRATES, On Joints
OUTLINE A.
Understanding early treatment I. 2. 3.
B.
C.
Rationale for early treatment Benefits of early treatment Difficulties in early treatment
Defining goals in early treatment I. 2. 3.
Dentition and occlusion Musculature Craniofacial skeleton
4.
Treatment planning
2.
Assessment of the results of early treatment I. 2.
D.
c)
Defining a satisfactory response What to do when early treatment is unsatisfactory
Clinical problems and procedures I.
Number of teeth a)
b)
Congenitally missing teeth I) Causes 2) Diagnosis 3) Treatment (a) Maxillary lateral incisors (b) Mandibular second bicuspids (c) Multiple absence of teeth Loss of permanent teeth (trauma, caries, and other causes) I) Treatment of loss of individual teeth (a) Maxillary central incisors (b) Maxillary lateral incisors (c) Cuspids (d) First bicuspids (e) Second bicuspids (f) First permanent molars (g) Mandibular incisors 2) Multiple loss of permanent teeth
3.
..
Supernumerary teeth I) Diagnosis 2) Treatment (a) In the primary dentition (b) Teeth with conical crowns (c) Supplemental teeth of normal size and shape (d) Supernumerary teeth showing variations in size and shape 3) Discussion Variations in size and shape of teeth a) Diagnosis b) Large teeth c) Small teeth d) Anomalies of tooth shape I) Maxillary lateral incisors 2) Mandibular second bicuspids 3) Miscellaneous anomalies of shape Spacing of teeth a) Localized SPlicing I) Etiology (a) Absent teeth (b) Undue retention of primary teeth (c) Sucking habits 2) Spacing between maxillary central inCisors (a) (b)
Examination and differential diagnosis Supernumerary teeth at the midline
(c)
Congenitally incisors
missing
lateral
(d)
Enlarged frenum
or malpos'ed
labium
343
344
Treatment
4.
(e) Imperfect fusion at th~ midline (f) Spacing as a part of normal growth b) Generalized spacing I) Small teeth 2) Large tongue 3) Sucking habits 4) Abnormal tongue posture Problems singular to the transitional dentition a) Space management I) General considerations 2) Maintenance of arch perimeter (a) Caries of primary teeth (b) Loss of individual primary teeth (c) Multiple loss of primary teeth 3) Regaining space in the arch perimeter (a) Mesial drift of permanent molars (b) Distal movement of first permanent molars 4)
b)
Space supervision (a) Mesial step (Class I) protocol (b) Flush terminal plane (end-to-end) protocol (c) Distal step (Class 11) protocol 5) Gross discrepancy problems (a) Diagnosis (b) General rules (c) Treatment protocol (d) Precautions Difficulties in eruption I) Alterations in sequence of eruption (a) Premature eruption of individual teeth (b) 2)
5.
Delayed teeth
eruption
of individual
Ectopic eruption of teeth (a) Maxillary first permanent molars (b) Maxillary cuspids (c) Mandibular incisors (d) Other teeth 3) Transposition of teeth (a) Etiology (b) Diagnosis (c) Treatment 4) Impaction of teeth (a) Diagnosis (b) Mandibular third molars (c) Maxillary cuspids (d) Mandibular and maxillary second bicuspids (e) Second molars (f) Other teeth 5) Ankylosed primary teeth 6) Ankylosed permanent teeth Lateral malrelationships of the dental arches a) Differential diagnosis I) Dental malrelationships 2) Muscular or functional mal relationships 3) Osseous or skeletal dysplasia (skeletal crossbite)
b)
6.
Treatment I) Dental crossbite (individual teeth) (a) Case analysis (b) Appliances 2) Dentoalveolar contraction and/or crossbite (a) Case analysis (b) Appliances 3) Gross disharmony between osseous bases (a) Case analysis (b) Appliances Class 11 (distocclusion, postnormal occlusion) a) Differential diagnosis I) Skeletal morphology 2) Dental and occlusal mal positions 3) Arch form 4) Neuromuscular ("functional") features b) General strategies for Class 11treatment I) Differential restraint and control of skeletal growth 2) Differential promotion of skeletal growth 3) Guidance of eruption and alveolar development 4) Movement of teeth and alveolar processes 5) Translation of parts during growth 6) Training of muscles 7) Surgical translation of parts c) Tactics for Class 11therapy I) Functional appliances 2) Orthopedic devices (a) Extra-oral traction to the dentition (b) Extra-oral traction to the chin (c) Palatal widening 3) Bracketed appliances 4) Muscle training 5) Surgery d) Rationale for early Class 11treatment I) Skeletal morphology 2) Dental and occlusal aspects 3) Neuromuscular features e) Planning differential early treatment of Class 11 mal occlusion I) Treatment of horizontal type A (a) Basic strategy (b) Suggested tactics (c) Common problems or complications 2) Treatment of horizontal type F (a) Basic strategy (b) Suggested tactics (c) Common problems or complications (d) Variations (e) Retention 3) Treatment of horizontal type B (a) Basic strategies (b) Suggested tactics (c) Common problems or
Early Treatment
4)
complications (d) Variations (e) Retention Treatment of horizontal type D (a) Basic strategieS (b) (c)
•
7.
Suggested tactics . Commom problems or complications (d) Variations (e) Retention 5) Treatment of horizontal type C (a) Basic strategies (b) Suggested tactics (c) Common p\"oblems or complications (d) Variations (e) Retention 6) Treatment of horizontal type E (a) Basic strategies (b) Suggested tactics (c) Common problems or complications (d) Variations (e) Retention Class III (mesiocclusion, prenormal occlusion) and pseudo Class III a) Differential diagnosis I) Patient examination (a) Profile (b) Molar relationship 2) Cephalometric analysis (a) Basic morphologic analysis (b) Profile analysis, skeletal (c ) Vertical analysis 3) Pseudo Class III 4) Skeletal Class III
11 .
(a) (b) (c)
8.
9.
10.
Midface deficiency Mandibular prognathism Midface deficiency and mandibular prognathism b) General strategies for early treatment c) Rationale for early treatment d) Tactics for early treatment 1) Pseudo Class III 2) Midface deficiency 3) Mandibular prognathtsm 4) Midface deficiency and mandibular prognathism Labioversion of maxillary incisors (excessive overjet) with Class I molar relationship a) Diagnosis b) Treatment Anterior crossbites, simple a) Diagnosis b) Treatment I) Single tooth 2) Several teeth Bimaxillary protrusions a) Bimaxillary prognathism
12.
345
b) Open a) b) c)
Bimaxillary dental protrusion bite Definition Diagnosis Treatment I) Anterior open bite, simple 2) Posterior open bite, simple 3) Complex or skeletal open bite Deep bite (excessive overbite or vertical overlap) a) Definition b) Diagnosis c) Treatment
13. 14.
Craniofacial malformations; Cleft palate Temporomandibular dysfunction a) Definition b) Diagnosis c) Treatment Such terms as early treatment, interceptive treatment, tooth guidance, preventive orthodontics, growth guidance, etc., may be more obfuscating than useful. They are surely not synonyms. In this chapter the term early treatment means, simply, orthodontic therapy undertaken during the most active stages of dentitional and craniofacial skeletal growth. This definition implies two consequences: (I) it is advantageous to treat some malocclusions during active growth and (2) methods are av~ilable for such treatment. Some early treatments are simple and easy, others are among the most difficult in orthodontics. Too much emphasis has been placed on one-phase "simple" early treatment in the hope that more comprehensive treatment could be obviated. This problem has been exacerbated by the conflict between the concepts of functional jaw orthopedic therapy, done early when growth is greater, and precision bracketed appliances, which are most efficient in the permanent dentition. There has resulted an unclear perception of the goals of early treatment, confusion about the relationships between early and later therapy, and misunderstanding about the roles of orthodontists, pedodontists, and family dentists in early treatment. All dentists need perspective on the full range of orthodontics. Family dentists must have explicit details of treatment procedures which they might provide. The implications of difficult and more comprehensive problems are outlined and explained here diagnostically, but details of their treatment are beyond the mission of this book.
A. UNDERSTANDING
EARLY TREATMENT
1. Rationale for Early Treatment ,. a) Some malocclusions can be prevented or intercepted.The words "prevent" and "intercept" may lead to misunderstanding. Neither term can be used properly in the generic sense to embrace all early orthodontic treatments. It is as misleading to promote enthusiastic advocacy of early treatment of all malocclusions because some might be intercepted as it is to denounce interceptive treatment because early development of all malocclusions cannot be halted. The theory and rationale underlying the concepts associated with each term vary and are not generally interchangeable, so one should not, as has been done, argue against the practice of one strategy using the theory of another. I All are
346
Treatment
good terms when properly applied, the clinical (and semantiC) problem is when and to what extent each is appropriate. Only a few studies give accurate reports on those malocclusions which can be prevented or intercepted21. 49 Popovitch and Thompson:9 at the Burlington Orthodontic Research Centre in Canada, judge that while few malocclusions can truly be prevented,. roughly 25% can be intercepted. One-fourth is a significant amount, and many can be intercepted with theory; appliances, and knowledge now readily available to the family dentist. b) It is the dentist's responsibility to obviate. when possible. lengthy or complicated treatment.-In the past, some who did not know how to improve severe skeletal dysplasia in young children chose to wait and camouflage it later by positioning of teeth. Now, diphasic treatment is sometimes considered more logical and sensible. During phase one, craniofacial skeletal growth is controlled and the morphology improved so that later tooth positioning (phase two) is relatively easier. c) Treatment is easier in some cases.-Early orthopedic control of skeletal mOrPhology is easier in some cases than later correction of the craniofacial skeleton, and often easier than positioning teeth to camouflage skeletal dysplasia. d) More alternative methods are available for treating patients at a young age.-When growth has largely ceased, treatment options are limited to moving teeth or orthognathic surgery. When the patient is young, one may be able to remove etiologic factors, enlist natural growth forces, provide differential growth responses, and obtain a balanced profile prior to eruption of most permanent teeth. Appliances used are varied, sophisticated, and practical. Some of the orthopedic appliances used look simple, and therein lies a trap for the inexperienced, for guidance of the developing dentition and growing craniofacial skeleton is a very complicated matter: the construction may be simple, the applied biology is generally more sophisticated and difficult than after pubescence. The traditional precision bracketed appliances used in treatment during the newly completed adult dentition involve very sophisticated biomechanical theories (see Chapters 13 and 16), and our knowledge of these appliances is well advanced. Ironically, the theory and treatment effects of "functional" or "orthopedic" appliances are less understood. Similarly, we know more about the biology of tooth movements, which is utilized with precision bracketed appliances, than we do about the biologic alteration of facial growth, which is the basis of early functional orthopedics. e) The clinician can utilize growth better in the young. and there is more growth available.--Growth can only be controlled while growth is happening. The earlier one starts treatment, the more total growth one can effect.
2. Benefits of Early Treatment
,_
Many reasons have been advanced for considering early treatment. The following are some of the more compelling: a) The possibility of achieving a better result.-With modem precision bracketed appliances beautiful results are obtained routinely if the skeletal dysplasia is not too severe. However, it is difficult to camouflage gross craniofacial morphology by tooth movements alone. b) Some forms of treatment can only be done at an early age. c) Early treatment of serious deleterious habits is easier than treatment after years of ingrained habit reinforcement.
d) There are psychological some children.
advantages to early treatment in
e) Younger patients are often more cooperative and attentive. f) Compromise of quality of treatment is less apt to be necessary. There are two reasons why early treatment may obviate compromise of quality: (1) it may remove etiologic factors and restore normal growth and (2) it may reduce the severity of the skeletal pattern, making possible easier and more precise tooth positioning in the adolescent.
3. Difficulties in Early Treatment a) Misperceptions exist about the goals of early treatment.- This is an important difficulty in defining clearly the goals. Early treatment has sometimes been equated with a naive attempt to "prevent" or intercept all malocclusions. More logical goals are the removal of primary etiologic factors and"the correction of skeletal dysplasias prior to the eruption of teeth, neither of which necessarily results in precise positioning of teeth. Misperceptions about goals of early treatment arise when the focus is on the particular appliance itself rather than the purposes of treatment. It is not a question of functional or orthopedic appliances versus bracketed appliances but of the goals of early versus later treatment. Because mistakes are made in either treatment period or with one appliance system, one cannot argue that the use of the other is, ipso facto, justified or better. In recent years, some enthusiastic proponents of functional jaw orthopedics have urged the use of those appliances by describing alleged deficiencies and misuses of precision bracketed appliances, implying such problems do not occur with their favorite systems. But there are problems with any appliance, which may be related to misperceptions about the goals of treatment, not the appliance itself. b) Improper early treatment can be harmful.-Just as growth can be directed advantageously, it can also be misdirected. It does no good to drive faster if you're on the wrong road. Nor does it help to start early if you do not know where you are going or have no map. c) Diphasic treatment may lengthen the chronologic treatment time.-Time of treatment is properly measured by the number of hours spent by the dentist and patient together: treatment time is not measured on the calendar. Frequently, diphasic treatment achieves better results with less' 'clinic time" but longer' 'calendar time." When the chronologic time is lengthened, patient cooperation may wane. Ill-conceived or improph early treatment not only may do damage or prolong therapy, it may exhaust 'the spirit of .cooperation, making Later treatment more difficult. , ;d) The subleties of early ma~occlusion introduce chance in the diagnosis and treatment plannlng.-When growth has diminished, the features of a malocclusion are clearly seen and the diagnosis is more certain. Early diagnosis and treatment planning are more tentative, and periodic cephalometric reassessment is a necessity. Too much emphasis has been placed on particular appliances, and insufficient attention has been paid to the difficulties of diagnosis and treatment planning for early treatment. There is a far greater need for better treatment planning than there is for new functional-appliance" gadgetry. " The best car is useless without a map and a driver who knows where to go. Those who do
Early Treatment no more planning for early treatment than to choose a single {avorite appliance for most treatments do so because they are ignorant of the subtle variabilities and difficulties of orthodontic practice in the young patient.
B. DEFINING GOALS IN EARLY TREATMENT The general principles of diagnosis and treatment planning are presented in Section 2, Diagnosis (Chapters 10-14), though a few specific comments are pertinent here.
1.,Dentition and Occlusion The several tooth size analyses (Mixed Dentition, Howes', Bolton, and Sanin-Savara analyses) are useful (see Chapter 11), but it is difficult to understand fully their varying implications in faces of widely different shapes. It is also important to realize the possible effects of time and growth on the results of the analyses. While time and growth do not alter tooth size, they change tooth positions and bony and soft tissue relationships which are not part of the dental analyses. The dentition and occlusion must be analyzed repeatedly during development.
2. Musculature Current clinical analysis of muscular function (see Chapter 10) is neither quantitative nor precisely discriminating, making it difficult to appreciate the clinical implications of the enormous variability of facial muscle behavior. The facial muscles and the tongue have been recently rediscovered by some dentists, but the rediscovery sometimes has been accompanied by a plethora of biologic and clinical nonsense. Some of the most enthusiastic promoters of methods of orofacial neuromuscular analysis and training are neither physiologists nor dentists and lack the knowledge and perspective which comes from being directly responsible for guiding and correcting occlusal disorders. Dentists, appreciative of our own ignorance and need for further knowledge in these matters, should not assume that other disciplines are more advanced. Scholarly speech scientists, otolaryngologists, and physiotherapists are just as frustrated and cautious as we are and are just as involved in sound research, which always provides the ultimate answers.
3. Craniofacial Skeleton Some cephalometric procedures fail us when we most need them (i.e., during active growth), Qut this is no excuse for avoiding cephalometric study of all cases (see Chapter 12). No dentist interested in orthodontic treatment can long afford to be without cephalometric data, for they most reveal and facilitate understanding of morphology, growth, and the effects of treatment. The question is often asked, "In which case should one take a cephalogram?" It is proper to procure radiographs routinely to diagnose caries and to ascertain the presence and normal development of all teeth. Is it any less important to be assured of normal skeletal growth? It is said that when Christopher Columbus sailed for America he didn't know where he was going, when he got there he didn't
347
know where he was, and when he returned to Europe he didn't know where he had been. Columbus lived prior to the invention of modem navigational instruments and can be excused. To begin treatment for a child with a skeletally involved malocclusion without a cephalogram is to start a trip of unknown duration toward an indeterminate goal without a map. Cephalograms are the maps of the head, though we are still learning how to read them better with improving cephalometric growth analyses.
4. Treatment Planning The essence of early treatment planning is timing, involving the integration of several kinds of developmental data applied specifically to one particular patient (see Chapter 14). Anyone can recognize a full-blown malocclusion; optimal treatment planning is therefore dependent on the earliest possible diagnosis. Orthodontic treatment deferred until adolescence lessens the difficulty of treatment planning, for the permanent dentition is completed and most skeletal growth has ceased, but the delay reduces options, may complicate treatment, and may compromise results.
c. ASSESSMENT OF THE RESULTS OF EARL Y TREATMENT One must take care not to transfer concepts of success which are valid and useful in adolescence to the younger child. Constant rediagnosis is the theme of clinical assessment during growth for that "simple anterior crossbite" may later prove to have been an early expression of a mild skeletal Class Ill. One asks not just did I succeed or fail, but what has improved?, which features persist?, which may worsen with time despite my treatment? etc. The purpose of assessment during diphasic and all early treatment is to define the improvements obtained and to prescribe what is left to do. Despite much enthusiasm and "oversell" of some early treatment appliances, particularly various forms of functional jaw orthopedic devices, we know very little about how they work and why response is so varied. Assessment of early treatment results wilt' continue to be hard until we know about how each type of appliance works in each specific facial type, at each age, and for each sex.
1. Defining a Satisfactory Response Early treatment may be deemed satisfactory conditions obtain:
if the following
a) Primary etiologi~ factors have been removed or are cOhtrolled .. ,' b) Tooth positions and space needs are satisfactory and can be kept there until the end of the mixed dentition. c) Skeletal deviations originally present have been improved at the rate and extent originally planned and can be controlled until the dentition is completed and skeletal growth has diminished. When evaluating the skeletal response to early treatment, it is important to identify significant deviations still present (I) due to those portions of the craniofacial skeleton not affected by the therapy and (2) which have not responded to treatment as well as envisaged. In Chapter 12 some methods for assessing the response to orthodontic treatment are described.
348
Treatment
2. What to Do When Early Treatment Is Unsatisfactory There is no guarantee that any orthodontic therapy will proceed as planned. Separation of the effects of treatment and changes resulting from growth is a difficult and sophisticated analytic problem not yet completely solved. When early treatment seems to have gone poorly, three plans of action are available: (I) determine and try a more appropriate treatment; (2) defer further treatment until a later time, assuming one knows clearly what to do at that later time; and (3) refer the patient to a colleague for further treatment. Specific rules are impossible because of the wide variety of cases, treatments, and patient responses, but one dictum is certain, namely, complete diagnostic records prove their worth when treatment progress must be assessed . . Early treatment is most apt to fail when there is no clear reason for starting and no well-defined goals and strategies. One may be tempted, when confronting a malocclusion, to think of trying something, and often an appliance or treatment remembered from a recent conversation, article, or presentation at a dental meeting comes to mind. "Why not try that?" we say to ourselves. So it is done without discriminating thought or plan-we just want to see what will happen. Such cases usually involve months of stumbling around and wondering why this attractive gadget didn't "work." It didn't work because we didn't do our work correctly. And an important ethical principle is involved: no one has the right to begin treatment without a reasonable understanding of the treatment process and reasonable expectations of success. When disappointing results are finally recognized and a clear treatment plan is still not obvious, referral to a more experienced colleague is an ethical obligation.
D. CLINICAL PROBLEMS AND PROCEDURES 1. Number of Teeth
a) Congenitally Missing Teeth By missing teeth is meant those teeth whose germ did not develop sufficiently to allow the differentiation of the dental tissues. Somewhat fewer than 4~ of the population have one or more teeth congenitally missing. Missing teeth constitute a clinical problem seen more frequently than supernumerary teeth. The teeth most frequently found congenitally missing are mandibular second bicuspids, maxillary lateral incisors, and maxillary second bicuspids, in that order (see Chapter 6). Complete absence of all teeth, called anodontia, is seen only rarely. Oligodontia, often-and incorrectly--called "partial anodontia," is the term used when some of the teeth are missing. 1) Causes.There are five principal known causes of congenital absence of teeth: a) Heredity.-There is a familial distribution of congenital absence of teeth in many instances, and heredity is an etiologic factor of importance (see Chapter 6). b) Ectodermal Dysplasia.-Congenitally missing are noted frequently in conjunction with other clinical manifestations of disturbances in the development of ectodermal tissue; for example, anhidrosis and absence of the hair follicles.
FIG 15-1. Tooth sac before calcification.
Note that the mandibular
second bi-
cuspid tooth sac can be seen clearly even though very little calcification has started.
c) Localized lnj7.ammations or Infections. d) Systemic Conditions.-Rickets, syphilis, and severe intrauterine disturbances are claimed by some to lead to the destruction of developing tooth germs. e) Expression of Evolutionary Changes in the Dentition.-Some authorities believe that, in the future, man will have neither third molars nor maxillary lateral incisors, just as we seem already to have lost fourth molars. 2) Diagnosis.The diagnosis of congenitally missing teeth is based wholly on the findings in the radiograph. The differential problem is one of distinguishing absence of teeth from greatly delayed calcification, remembering the great individual variations in their patterns of development. A magnifying lens is very useful for studying the details of the alveolar bone in the radiographs when congenital absence of teeth is suspected. Well-taken radiographs will show the tooth sac before calcification begins (Fig 15-1). If, instead of a circumscribed homogeneous area in the bone (indicative of a tooth germ before calcification begins) there is trabeculation, one can assume the absence of the germ (Fig 152). There can be no calcification without the germ. Mandibular second bicuspids show great variation in differentiation and calcification. Often it will seem that the germ is dorinant (Fig 15-3). So~etimes one can detect minute signs of activity indicative of delayed or slow calcification rather than failure of the tissue to differentiate. Ordinarily it is possible when the patient is 4'/2 to 5 years of age to discern in well-taken intra-oral radiographs the presence or absence of all teeth but third molars. For this reason, it is urged that a complete dental radiographic surveyor panoramic film be obtained of each patient at this age. Such a survey is one of the most important single steps in orthodontic diagnosis and early treatment. Few things are more embarrassing than to discover the
Early Treatment
349
all of the other teeth to ascertain any genetic field effects on general tooth size. Finally, there are suggestions that congenital absence of teeth is associated with certain variations in craniofacial morphology, so a cephalometric analysis is required. 3) Treatment.-( a) Maxillary Laterallncisors.Two courses of treatment are available: (I) moving the cuspids mesially for use in place of lateral incisors and (2) opening space for a prosthesis.42. 56. 57 The choice is dependent on: • Age of the patient. • Conformation of cuspids. • Position of cuspids. • Suitability of central incisors and cuspids as abutments. • Desires of the patient. • Depth of bite. (l) Moving the cuspids to serve as lateral incisors. are:
Advantages42.67
• • •
It is unnecessary to prepare abutment teeth. There is less chance for maxillary third molars to become impacted. It is permanent (not necessary to replace at a later date). Disadvantages
• • • •
FIG 15-2. Congenital absence of mandibular second bicuspids. A, note fine trabeculae of bone of the alveolar process beneath the second primary molar. B, a similar situation in three of four quadrants. Even though the bicuspid is present in one quadrant, it is delayed in development, malformed, and unerupted. congenital absence of a tooth in a child who has been under one's care for several years. If for no other reason than this problem of congenitally missing teeth, one should have on file for each young patient a complete radiographic survey at an early age. One should not forget the relationship between congenital absence of teeth and generalized tooth size diminution (see Chapter 6). When one tooth is not developing, it is important to measure
are:
Advanced orthodontic skills and complete precision bracketed appliance are required. Case selection is more particular than for the prosthetic procedure. More time is required. It is more difficult if the cuspids are completely erupted. Follow this procedure
•
if:
•
The cuspids are unerupted or only partially erupted and appear of normal size and favorable shape. The central incisors are of normal mesiodistal diameter.
• •
The maxillary molars already have drifted mesially. There are no contraindications to orthodontic therapy. Steps in .treatment:
•
Remove the maxillary primary cuspids, if still present, to
FIG 15-3. Delayed development
of second bicuspids. Contrast their root development
with that of the first bicuspid and cuspid.
350
Treatment
FIG 15-4. Directing the eruption of maxillary cuspids when the lateral incisors are congenitally
•
•
•
hasten the eruption of the maxillary permanent cuspids before the bicuspids. Removal of bone atop the cuspids sometimes hastens and directs their eruption. All erupted maxillary teeth are banded or bracketed and a labial archwire is placed. The central incisors are brought together on the midline and the cuspids guided during eruption against them. The archwire should have no stops so the permanent molars and bicuspids may drift mesially and be brought into a full Class II relationship. Grind the labial surfaces of the cuspids and flatten their incisal edges in simulation of lateral incisors. Since the cuspid is thicker labiolingually than-a lateral incisor, it is also necessary to reduce the lingual surface significantly to allow the cuspid to be placed more lingually in the line of arch than is usual. It is best to do the reshaping in several stages to avoid pulpitis. All of the grinding is followed by thorough polishing and the application of fluoride. Finally, check the new occlusion for occlusal interferences; there will always be some, particularly the lingual cusps of bicuspids in lateral excursive movements. If satisfactory esthetics have not been obtained by grinding and reshaping of the cuspids alone-and this sometimes is seen when the incisal edges are acutely angled-acid etch the tooth and add composite.
Prognosis: If care is taken in choosing the case, this procedure can produce satisfactory results (Fig 15-4). It is most likely to be indicated when early treatment is possible. If there is any doubt concerning the success of this plan of treatment, do not begin it. Much depends upon skillful use of the precision bracketed appliance, since exact placement of roots is necessary for esthetics and stability. (2) Alternative procedure: Opening prosthesis Advantages are:
missing. (Courtesy
of Dr. William Northway.)
• •
Ordinarily, less movement of teeth is required. Only a short time is required.
•
Can be used on all patients. Disadvantages
•
• •
are:
It may be necessary to prepare abutment teeth. The bridge may have to be redone at a later date. Esthetic problems may be difficult, for example, matching shades, hiding gold margins, pontics, etc.
Steps in treatment: Preliminary treatment is likely to involve moving the central incisors together and/or moving the lateral segments of the maxillary arch distally. A retainer with a pontic may be worn until the appropriate time for a bridge or a bridge using acid-etched abutments may be placed as a temporary expedient. (b) Mandibular Second Biscuspids.-Again, there are two accepted procedures: (I) holding space for a bridge; and (2) moving the first permanent molars forward the width of one cusp. The choice depends largely on the age of the patient and whether the mandibular second primary molar has been retained. A third choice often suggested, that of ~~eping the second primary molar perma·ne.ntly in place, is to- be discouraged. To retain the primary molar is to guarantee a malocclusion and eventually a prosthesis. Although the crown can be reduced in size, the roots flare so widely the first molar cannot move mesially as far as is desirable. To retain the second primary molar unduly results in lack of alveolar bone development on the mesial aspect of the mesial root of the first permanent molar. When a bridge is contemplated, the correct first permanent molar relationship should be established by the time of arrival of the first bicuspid and before eruption of the second molar.
Early Treatment Early diagnosis is the key to t~ problem because it greatly lessens the amount of work involved and ensures a more satisfactory result. The following are considerations in choice 2, namely, moving mandibular first permanent molars mesially. Advantages are: • • •
It is unnecessary to prepare abutment teeth. There is less chance for impacted mandibular third molars. The effect is permanent (need not be redone at a later date). Disadvantages
•
•
are:
It requires skilled and carefully timed use of a precision bracket mechanism to obtain proper occlusion and root parallelism. There may be a need for a short subsequent treatment to position the second molar, especially if the initial treatment is delayed.
Follow this procedure if: This procedure is indicated in primary and early mixed dentition cases and in young adults who are having other orthodontic therapy. It is particularly appropriate when there is anterior crowding and the first bicuspids must be moved distally (see Chapter] 6). Sfeps in treatment-if diagnosed in primary dentition: Remove the mandibular primary second molars and allow the mandibular first permanent molars to move mesially beneath the gum. This movement will take place quickly, but these teeth usually erupt before they are complete]y forward. ]n almost every instance it is necessary to place an appliance and band the molar to upright it.
~
Steps in treatment-if diagnoseiin mix2d dentition: After the first permanent molar has erupted, it is more difficult to move it mesially without tipping. To do so properly requires bodily movement over a considerable distance and the use of multi banded
.1
techniques. An interesting method developed by Professor van der Linden involves sequential slicing and sectioning of the second primary molar, thus permitting more gradual mesial mov~ment of the permanent molar (Fig ]5-5). It also guarantees full vertical development of the alveolar process avoiding the typical denudement of the mesial root of the first permanent molar. Prognosis: The prognosis is favorable in all instances, but the task is easier when begun earlier. In all cases, occlusal equilibration will be necessary, since the final result is a Class III molar relationship, but this should be of )ittle concern. Discussion: In the past, I have been much too optimistic concerning the average dentist's ability to move the first molar forward properly. In the first edition of this book, mesial movement of the first molar was recommended with enthusiasm, since I had done it satisfactorily many times. Unfortunately, there are many complications here for the unskilled. When this seems the desired approach, study the problem carefully and approach it with caution. It is impossible to change your mind and reverse the movements. (c) Multiple Absence of Teeth.-So
many variations appear
351
in the more severe types of oligodontia that it is difficult to formulate a general rule. Treatment may require a blending of orthodontic and prosthetic skills. The problem often is complicated by small conically shaped teeth. Severe oligodontia is best handled by a specialist, at least for the orthodontic aspects of the problem. This problem is discussed in more detail in Chapter 17. b) Loss of Permanent Teeth (Trauma, Caries, and Other Causes) The loss of fully developed, erupted permanent teeth is a major orthodontic problem. In the anterior region, trauma is the principal cause, whereas caries is largely responsible for early loss of the first permanent molars. Important to an understanding of the effects of loss of permanent teeth is a knowledge of physiologic tooth drifting after extraction. The tendency to drifting is more marked in the maxilla, and the process begins more rapidly than in the mandible. It is difficult to predict reliably, however, the extent and direction of drifting in any given patient. The direction and extent of drifting are affected greatly by the facial form, particularly the steepness of the occlusal plane. The time of the loss also affects drifting. Occlusal interferences may appear and exacerbate the drifting.
(1) Treatment of Loss of Individual Teeth.-:-( a) Maxillary Central Incisors.-Loss of central incisors is a common problem, particularly in boys, whose baseball bats and hockey sticks are notable etiologic agents. The opposite central incisor tends to drift across the midline, and the lateral incisor and cuspid on the affected side move mesially. Spacing may occur between the lateral incisor and cuspid or distal to the cuspid. The lateral segments of the arches do not move mesially until considerable time has elapsed. An acrylic plate with a pontic of a snug fit may be placed at once and worn until an age when a permanent restoration can be inserted. Alternatively, a pontic may be placed supported by a wire framework held in place by acid-etch composite on the lingual of adjacent teeth (Fig 15-6). If drifting already has begun, treatment with an appliance is necessary to regain the lost space. (b) Maxillary Lateral Incisors.-Loss of the lateral incisor causes mesial drifting of the cuspid and distal tipping of the central incisor. The treatment is similar to that for the central incisor. It is possible to move the cuspid forward and use it for a lateral incisor, a procedure described in the section on congenitally missing teeth earlier in this chapter. t
(c) Cuspids.- This condition, seen rarely, gives rise to distal tipping of the central and lateral incisors with possible mesial mpvement of the first bicuspid. The suggested course of action is to move the bicuspid distally an9 the incisors mesially, holding space until a bridge can be placed. (d) First Bicuspids.-The loss of a first bicuspid without control of the rest of the occlusion is a difficult situation to handle. The incisors and cuspid drift distally and the posterior teeth tip mesially. Spacing probably will appear in the anterior segment. Only rarely can the dentist tip the remaining teeth back to nearnormal positions with simple mechanics; more frequently, multibanded mechanotherapy is required.
352
Treatment
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FIG 15-5. Moving the mandibular first molars mesially when the second bicuspid is congenitally missing. A, diagrammatic representation of a procedure developed by Professor van der Linden. If started early, the natural eruptive and drifting movements bring about most of the mesial correction. Later treatment requires more orthodontic move-
men!. When the distal half of the <:;rown is sectioned
and its root
removed (4). a temporary pulp dressing is placed. B. photographs and radiographs of a patient treated by this method. (Courtesy of Dr. William Northway.) "
Early Treatment cial, and often complicated, tions include:
treatment planning.
IS. 23
353
Considera-
a) The number of molars lost;
FIG 15-6. Orthodontic treatment after loss of the maxillary central incisors. A, the result.S, pontics attached to a Hawley retainer. C and D, temporary bridge of composite resin.
(e) Second Bicuspids.- The same general considerations ply for the second as for the first bicuspids.
ap-
(j) First Permanent Molars.-Special consideration must be given to the first permanent molars because they often are lost . early in life as a result of caries. 2. 23. 54. 64 If the first molar is lost before the eruption of the second bicuspid, the latter may drift into the space left by the first molar. When first molars are lost, a dipping in the line of occlusion occurs owing to the change in the axial inclination of the remaining posterior teeth. There also may be a concomitant closure of the bite. The result of the loss of one or more first molars at any age invariably produces a difficult clinical task. Immediate steps should be taken to control and direct the drifting of the remaining teeth while an orthodontic plan is developed. The loss of one or more first permanent molars requires spe-
b) The presence and status of the third molars; c) The status of other first molars; d) The basic malocclusion, other than that associated with the loss of the first molars, particularly the depth of the bite; and e) The eruptive stage of the bicuspids and second molars. It is impossible to define precise rules of procedure for every combination of variables. The following suggestions reveal our bias for avoidance of a bridge if possible, but it should be noted that the orthodontic skills required vary considerably among the different clinical conditions listed (Fig 15-7). When one molar is lost: If the loss is early or there are other orthodontic problems the preferred treatment is to move the second molar forward, allowing it to do so by itself as far as possible prior to insertion of an orthodontic appliance (assuming third molars are present). Equilibration is always necessary and may be difficult. If the other first molar in the same arch does not have a good prognosis, consider its extraction, since it is easier to get a stable result when both first molars in one arch are missing. When two first molars are lost in the same arch: If the teeth are lost early or if there are other orthodontic problems, move the second molars forward to occupy the position of the first molars. It is necessary to band both arches and equilibrate the occlusion carefully when all movements are over. If treatment is completed very early, the upper third molars may erupt in favorable positions, although there surely is no guarantee that will do so. Lower third molars are more apt to erupt reasonably well when the first molar is lost than when the second is removed. When opposing first molars are lost: When two first molars on the same side are lost, one may move the second molars mesially, for that is the most conservative procedure, if started early. It is necessary to bracket all the teeth in both arches, control the midlines precisely, and manage carefully the difficult biomechanics, particularly if the molars were lost at different times. Careful equilibration, of course, is required at the end of treatment. When one upper and one lower molar on opposite sides are
FIG 15-7. Orthodontic movement of mandibular second molars when the first molars have been lost (db refers to patient identification). (Courtesy
of Or. William Northway.)
354
Treatment
lost: When an upper and lower molar are lost on opposite sides, treatment planning becomes more complicated than any of the situations described previously. Local conditions should be determining and general rules are of less use. The earlier the loss, the easier it is to decide on moving the second molarS' mesially. When the problem is associated with a severe malocclusion, extraction of the remaining two first molars may be considered. When three molars are lost: If perfect occlusion obtains otherwise and caries is well controlled, then bridges may be indicated. If the second molars have drifted mesially and/or other malocclusion is present, then moving the second molars mesially may be indicated. However, the mechanics of this procedure are difficult, particularly if the bite is closed. The presence or absence of third mol!trs and their condition are determining factors. One must always consider the extraction of the last permanent molar since it is easier to control all factors with symmetric mechanics. When four molars are lost: The extraction of four first molars as a prophylactic measure was once routinely recommended, but this abominable practice is rarely seen. IS However, in caries-prone children the loss of all four molars may be observed. 2. 64 When all four first molars are lost, or must be extracted, prior to the eruption of the second molars, it seems better to move the second molars mesially, but that decision may be altered if the third molars are absent. If the third molars are normal in size, position, and developmental status, and there is not a predisposition to a deep bite, then moving the second molars mesially may be preferred to using bridges.
2) Treatment:-(a) In the Primary Dentition.-Supernumeraries are encountered only rarely in the primary dentition. When seen, they usually are well-formed supplemental teeth. A good rule to follow is to leave them in place unless they are causing some form of malocclusion or malfunction, for example, a functional crossbite because of tooth interference.
(g) Mandibular Incisors.-The same principles discussed for maxillary incisors apply for lower incisors, but care must be taken immediately to prevent the extrusion and/or lingual displacement of the incisors or cuspids adjacent to the site of loss. A simple round, labial archwire to maintain the midlines, level the occlusal plane, and hold space temporarily is often all that is required. An acid-etched replacement may suffice for some time when all anterior teeth have normal centric stops and there is no crowding.
size, and position have been studied. To extract the wrong tooth may cause disharmony and shifting of the midline of the dental arch. There are uncommon instances in which the supernumerary tooth is of good formation and in better position to remain in the arch than the normal tooth.
2) Multiple Loss of Permanent Teeth.-When more than one tooth is lost, the same principles are kept in mind as were noted for the loss of individual teeth. When the teeth are lost simultaneously, as in the case of trauma, there is less immediate drifting of the remaining teeth. Figure 15-6 illustrates a case where the maxillary central incisors were lost by accident. No simple rules can be stated, but do not overlook the possibilities of improving the occlusion with orthodontic treatment before inserting a prosthesis. Multiple and sequential loss of teeth in adults is a common problem requiring orthodontic attention prior to reconstructive dentistry (see Chapter 17)." c) Supernumerary Teeth Supernumerary teeth are encountered less frequently than congenitally missing teeth. Their role in the etiology of malocclusion is presented in Chapter 7. 1) Diagnosis.-Diagnosis is based on the radiographic findings and on careful measurement of the teeth in question. Occlusal view radiographs are especially helpful in locating and diagnosing supernumerary teeth.
(b) Teeth with Conical Crowns.-These teeth only rarely can have functional use in the mouth. The decision whether to treat is based on ascertaining whether they may be direct causes of some form of malocclusion. Often they are so placed that the normal teeth must change their course of eruption. If such is the case, remove the supernumerary teeth, taking care not to harm the follicles of the other teeth. If the supernumerary teeth can do no harm, they may be left in position until a later time. They follow no set pattern of eruption, so they must be observed at regular intervals, and removed eventually. (c) Supplemental Teeth of Normal Size and··Shape.-Maxil-. lary lateral incisors are the teeth seen most frequently in this category, although supplemental maxillary central incisors are observed as well and one of us (R.E.M.) has seen eight supplemental bicuspids! Rarely is the size of the crown of the supernumerary teeth exactly that of the normal teeth. If the problem is unilateral, measure all three teeth: that is, the two normal teeth and the supernumerary tooth. The mesiodistal diameter of two of the teeth will be found to be the same. The odd-sized tooth is the accessory member. Do not remove a tooth until the root formation, crown
(d) Supernumerary Teeth Showing Variations in Size and Shape.-Such teeth should be removed as soon as it is possible to do so without damaging nearby normal teeth. 3) Discussion.-Early diagnosis and careful observation will enable one to decide on the timing. Timing is important, since the supernumerary tooth seldom is a major orthodontic problem if it is dealt with early in the development of the dentition. To neglect the condition may create a more severe clinical task. Treatment with appliances usually is required for alignment after the removal of the supernumerary tooth, but some cases t are self-corrective.
2. ~ariations in Size an~""Shape of Teeth Variation is a rule of naturel and teeth are no exception. Malalignment and jumbling of the teeth frequently are an expression of a disharmony between the size of teeth and the dimensions of the basal arch (Fig 15-8). There are limitations to the extent that the bony arches can be changed to accommodate large teeth. We are particularly restricted in altering the mandibular arch perimeter, a perimeter which steadily decreases with time. Cephalometries provides information concerning variations in the pattern of growth and dimensions of the facial skeleton; however, it is impossible to make a set of measurements of the
Early Treatment
355
FIG 15-8. Dental casts of two mouths with teeth exactly the same in size. As the ipcisors are markedly crowded in the cast at the left and aligned
in the cast at right, the difference must be the result of the size of the osseous bases.
facial bones and decide exactly how much tooth substance would provide an ideal occlusion, nor is this necessarily desirable. Knowledge concerning variation in size of teeth, however, is available and is of great assistance in diagnosis. Since there is such variation in size of teeth from one individual to another, it is advantageous to learn, in each instance, the dimensions of the structures with which one must work. The mean mesiodistal widths
problem of teeth that are too large for their arch (or is it an arch too small for the teeth?) is discussed later under Space Management (Section D-4-a). In reading the section on space management, pay particular heed to the sections on space supervision and gross discrepancy problems.
of the permanent teeth and their range in size can be found in Table 6-5. There is a rather high correlation, for biologic data, among all the widths of teeth. This fact makes it possible to measure certain of the first teeth to erupt and to predict, with some reliability, the size of the teeth not yet erupted, a procedure explained in Chapter 11. The determination of whether teeth will fit into a given arch is one of the most difficult of all orthodontic diagnostic decisions. But to try to make it without even knowing the size of the teeth is to handicap oneself unnecessarily. a) Diagnosis Diagnosis is carried out by use of the tooth-measuring gauge shown in Figure 8-3. A Boley gauge may be used instead, although its larger size makes it less handy in the mouth. Always record the measurements of the teeth as part of the written examination record. Help also will be obtained from the other occlusal diagnostic procedures described in Chapter 11. The position of the teeth within the facial skeleton is learned from the cephalogram. Leighton and Hunter36 and Hunter25 have shown that crowded mandibular arches are more likely to be found in faces with steeper mandibular and occlusal lines, a shorter posterior face height, and a shorter mandibular corpus. How positions may be altered to relieve crowding is often a matter of clinical judgment though certain cephalometric analyses are useful to estimate the best positions of the teeth to fit the skeletal profile and provide the most esthetic lip outline (Chapter 12). Occasionally there will be disharmony of crown sizes within the same moath, a finding complicating the achievement of good occlusion regardless of one's orthodontic skills.8 The Sanin-Savara analysis (see Chapter 11) is invaluable in this instance. b) Large Teeth The term "large teeth" is relative, for teeth that are large for one dental arch may not be large for another (see Fig 15-8). The
c) Small Teeth Always measure the teeth to make sure that the problem is truly one of small teeth. Small teeth usually result in generalized diastemata, whereas with the various sucking or tongue habits the space problem is more localized. Orthodontic therapy often is contraindicated in cases of generalized small teeth because the tongue and lips often return the teeth to their original positions after the spaces have been closed. Many times this patient is best left alone unless the esthetics are unusually poor, when a series of jacket crowns sometimes may be used or the teeth may be built up with acid-etch composites. In other instances, the arch may be consolidated and bridgework placed. d) Anomalies of Crown Shape Developmental anomalies showing alteration in coronal conformation are seen in all of the permanent teeth. The teeth affected most frequently are the (I) third molars, (2) maxillary lateral incisors, and (3) mandibular second bicuspids. Only the last two present practical clinical problems.
1) Maxillary Lateral Incisors.- The term "peg lateral" is applied when only the middle lobecalcifies. Treatment is determined by two factors: (I) the age at which the condition is discovered; and (2) the size and position of the malformed crown and its root. ·H. the crown and root 6f the lateral incisor are such that the placement of a jacket crown is ill~advised, the tooth must be extracted. If the condition has been noted before eruption of the cuspids, proceed as in the case of congenitally missing lateral incisors. When the condition is noted after eruption of cuspids, a bridge to replace the lateral incisor may be considered instead of orthodontics. If the "peg lateral" incisor has a strong root and sufficient crown for the preparation of a satisfactory jacket crown, this type of prosthesis is favored. Alternatively the "peg lateral" incisor
356
Treatment
FIG 15-9. Orthodontic and restorative treatment of a "peg lateral" incisor. A, at the start. e, before orthodontic treatment. C, after placement
of composite resin.
may be built up with composite after orthodontic therapy (Fig 159). At the first observation of a "peg lateral" incisor, care must be taken to preserve sufficient space in the arch to insert a restoration of proper mesiodistal width. An acrylic plate often is of use in opening space or for centering the tooth in the space between the central incisor and the cuspid. Banding several anterior teeth and the first molars will permit the use of a labial archwire to open spaces with coil springs or elastic chains. It also makes possible accurate placement of each tooth and provides better root angulation.
separate problem requiring singular treatment. Among the anomalies that may create orthodontic problems are: claw form incisors, giant and pygmy forms, dilacerations, odontomas, taurodontia, germination (twinning), fused teeth, Hutchinson's incisors, dens indente, hypoplastic teeth, and cone-shaped teeth (Fig 15-11). Certain developmental defects in the texture of d~.ntal tissues, for example, amelogenesis imperfecta, result in altered coronary conformation because of excessive wearing down of the teeth.
2) Mandibular Second Bicuspids.This tooth frequently is seen with two lingual cusps. The tooth is thus wider mesiodistally; otherwise, the extra cusp is of little concern. When such a tooth is seen in the radiograph before its eruption, take steps to ensure that a bit more space is available in the arch (by using higher probability values in the Mixed Dentition Analysis). Bizarre ovoid or "egg-shaped" crowns (Fig 15-10) also are observed, and are extremely difficult to place in a satisfactory intercuspation. 3) Miscellaneous Anomalies of Shape.-Many other anomalies of coronal shape may be observed. Each anomaly presents a
3. Spacing of Teeth
a) Localized Spacing 1) Etiology.-Localized spacing may be due as a result of many causes other than variations of normal spacing. Treatment is highly individualized, but a knowledge of the general principles of etiology and diagnosis is helpful. Problems in localized spacing and in excessive spacing at one or a few contact points usually are attributable to (1) missing teeth, (2) undue retention of primary teeth, or (3) a deleterious sucking habit. One specific problem, that of spacing between the maxillary central incisors, is seen so frequently as to merit detailed discussion later in this section.
(a) Absent Teeth.Congenitally Missing Teeth.-These
•
may cause localized spacing, but the problem may not be seen in just one spot because adjacent teeth often drift into the space. (See Section D-I-a, Congenitally Missing Teeth, for a discussion of this problem.)
•
Unerupted Teeth.-Sometimes a tooth is impacted or remains unerupted. The spacing problem js then localized, and the plan of treatment is determined by the chances of bringing the tooth into its normal relationship. (See Section .p-4--b-4), Impaction~bf Teeth.) p'femature Loss of Permanent,Teeth.-This matter is discussed in section D-I-b., Loss of Permanent Teeth.
•
(b) Undue Retention of Primary Teeth.-Belated loss of primary teeth may force the erupting permanent teeth into unnatural positions. Later, when the primary tooth is exfoliated, a space results. This sequence of events is seen most frequently in the FIG 15-10. Abnormally shaped mandibular second bicuspids.
Early Treatment
357
FIG 15-11. Treatment of anomalously
formed maxillary central incisors. (Courtesy
maxillary cuspid region. Obviously, the easiest and most practical treatment is removal of the primary tooth before it has deflected the permanent tooth.
of Dr. William Northway.)
•
• (c) Sucking Habits.-The patient's sucking habits may cause a localized spacing of the teeth. One should read Chapters 7, 10, and 12 to understand this problem and plan its treatmenL 2) Spacing Between Maxillary Central Incisors.-One of the mal occlusions of most concern to patients is diastema between the maxillary central incisors. Excessive spacing in such a prominent place in the dentition is unsightly, although it does little to reduce masticatory efficiency. Treatment is solely for cosmetic and psychologic effects. The data in Table 15-1 suggest that too much emphasis has been placed on the labium frenum and too little on structures and development at the midline. It also is of interest that in this series of patients nearly one-fourth were developing normally. (a) Examination and Differential Diagnosis.-Because there are several possible causes of the condition, requiring different forms of therapy, a careful examination is the only means of arriving at a correct diagnosis. The following are the steps in examination:
•
• •
Decide definitely whether the spacing is localized between the central incisors or whether generalized diastemata are presenL Measure the teeth and compare their sizes with the averages given in Table 6-6. Lift the upper lip and, while it is displaced, look for blanching of the soft tissue lingual to and between the central incisors. The absence of blanching is not diagnostic; the presence of blanching points to a malposed labium frenum. Determine, if possible, whether the space is increasing. Secure periapical radiographs of the region, including both lateral incisors. Clarity in the alveolar regions is more important than interproximal details of the exposed crowns. It is essential that the central ray be directed perpendicular to the alveolar septum between the central incisors. If all the details of the suture are not clearly shown, take additional radiographs at several atypical angulations on either side until a diagnosis can be made. Study carefully Figures 15-12 to 15-15.
(b) Supernumerary Teeth at the Midline.- The diagnosis of this condition is based solely on radiographic studies unless the supernumerary tooth has erupted. A supernumerary tooth is the
TABLE 15-1. Percentage Problems
>.
of Cases Showing Variou~ Types of Midline Spa.ci·ng
Supernumerary teeth at the midline (3) Congenitally missing lateral incisors (9) Unusually small teeth (2) Enlarged or malposed labium frenum (20) Spacing a part of normal growth (19) Imperfect fusion at midline of premaxilla (27) Combination of imperfect fusion and congenitally missing lateral incisors (2) Total (82)
3.7% 11.0%
2.4% 24.4% 23.2% 32.9% 2.4% 100.0%
358
Treatment -
•
•
FIG 15-12. Midline spacing in the maxilla resulting from congenital lateral incisors.
absence of
only condition likely to cause an increase in the space between the maxillary central incisors. This is discussed in Section D-Ic, Supernumerary Teeth. Treatment involves removal of such extra teeth as soon as diagnosed without end~ngering the adjacent teeth. Early removal may permit the eruptive force of the incisors to close the space at the midline. (c) Congenitally Missing Lateral Incisors . - Treatment of this condition is discussed in Section D-I-a, Congenitally Missing Teeth. Figure 15-12 illustrates a typical midline diastema resulting from congenital absence of lateral incisors.
(d) Enlarged or Malposed Labium Frenum.Diagnosis.-The enlarged or malposed labium frenum occasionally may be diagnosed by observation alone or by lifting the lip. However, it is impossible to detect all enlarged or malposed frena in this manner. The final diagnosis must be based on the radiograph. The normal osseous septum between the maxillary central incisors is V-shaped and bisected by the intermaxillary suture, which sometimes is not visible in the radiograph. When the labial frenum inserts on the palatal side of the septum, the fibers of the frenum run across the bone, rounding it over so that the septum is shaped like a spade (see Fig 15-13). On occasion, a shallow trough is seen. Even when the fibers insert so deeply as not to cause blanching when the lip is displaced, the condition may be diagnosed in the radiograph . Treatment.-Treatment consists of bringing the incisors together before excising the frenum. The incisors may be bracketed, a short wire ligated into place, ~nd the teeth pulled together by ligatures or light elastics. Under no circumstance should free elastics be used around the necks of unbanded teeth for this movement. It is much too easy for the patient to let one of the elastics slip up the neck of a tooth, destroying the supporting structures and endangering the tooth itself. After the central incisors have come into juxtaposition, excise the frenum and maintain, the orthodontic appliance in position while healing is taking place. The scar tissue formed will help in retention. Obversely, if excision is undertaken before orthodontic movement, the teeth must be moved through the newly formed scar tissue. Although some prefer to remove the frenum by cautery, any of the several techniques involving excision by scalpel are to be preferred because there is better control and less scar tissue is formed. Sometimes the orthodontic force itself will cause pressure atrophy of the frenum fibers, making excision of the frenum unnecessary.
(e) Imperfect Fusion at the Midline.-The midline is a common site of development faults, such as epithelial rests and inclusion cysts. The condition illustrated in Figure 15-14 may be related to imperfect fusion at the midline, for histologic study of the tissue included within such osseous bifurcations has shown connective and epithelial tissue. A wide variety of forms will be observed, all of which must be differentiated from the normal suture. A distinctly W -shaped osseous septum may be associated with this condition, as well as a circumscribed irregular ovoid area. The separation of the osseous septum may be shalloWOD continue well
-FIG
15-13.
Spade-shaped interosseous tip between the maxillary central incisors, usually associated with an enlarged maxillary labial frenum.
into t~e alveolar process": ~" For treatment, one should pro-ceed exactly as for a malposed or enlarged labium frenum except that the included tissue, rather than the frenum, must be excised. The excision must be carried out thoroughly or regeneration will occur, forcing the teeth apart again. One satisfactory method, after the incisors have been brought together, is to lift a V -shaped mucosal flap directly over the septum between the central incisors. The flap should flare well laterally so that later it will lie easily in place. After the alveolar bone is exposed, a surgical fissure or tapered fissure bur may be inserted gently into the cleft in the bone. With the motor turning at a slow
Early Treatment
359
."
FIG 15-14. A-C, variations in imperfect fusion are seen at the midline in the maxilla. The suture is seen clearly above the bifurcation in the interosseous tip. Invaginated epithelial and periosteal tissue will be found at the split tip. 0 and E, imperfect midline in the dental septum. Note the split of the septum or the W-shaped osseous tip between the central incisors in D. E is a view after treatment. The orthodontic
appliance brought the teeth together. The invaginated tissue was removed surgically and the appliance used served as a retainer during healing. Mere clipping of the labial frenum will not correct this problem. F-H, views of a septum from three different radiographic angulations.
360
Treatment
.' FIG
15-15.
Spacing between maxillary central incisors closing normally, with eruption of the lateral incisors. speed, the bur will remove the included tissue and will freshen the edges of the bone as well. After excision, suture the flap into place. The orthodontic appliance, which has brought the teeth together, must be replaced during healing (see Fig 15-14). Occasionally, fibers of the frenum will insert into the suture. The same procedure may be used for their excision.
(j) Spacing as Part of Normal Growth. - The central incisors erupt with a space between them (see Fig 6-46). This space is diminished when the lateral incisors erupt and finally is closed by the wedging of the erupting cuspids. In the absence of abnormal midline structures or gross variations in tooth size, it can be assumed that the midline space will close naturally (Fig 15-15). b) Generalized Spacing Any of several etiologic factors may be involved in generalized spacing of the teeth. It is important to ascertain the presence of true generalized spacing. More frequently, a localized spacing problem is encountered. 1) Small Teeth.-If the teeth are unusually small for the size of the alveolar arch that includes them, generalized spacing may result. If the teeth, when measured, are very small and there are no other apparent causative factors, the smallness of the teeth alone may be at fault. Such a condition is' rare and the best treatment may be by means of jacket crowns, buildup with acid-etch composite, or consolidation of the arch and the placement of bridges. Whether such a heroic measure as a series of jacket crowns is to be undertaken is an individual matter, dependent on the wishes of the patient and the cosmetic problem. Some problems of spacing due to small teeth may best be left alone. 2) Large Tongue (Macroglossia).-Another rather rare cause of generalized spacing is an unduly large tongue. Diagnosis is
made by careful examination of the tongue when extended as well as in situ. The lateral edges of the tongue, when it is too large for the alveolar arch, usually display scalloping where the tongue rests against the lingual surfaces of the mandibular teeth. Treatment is . contraindicated unless gross mal occlusion is present, in which case a wedge of tissue is excised from the tongue. This rather heroic approach is not advocated unless a debilitating malocclusion is present. 3) Sucking Habits.-Sucking habits may cause rather generalized spacing of the teeth, although they are more likely to cause a localized spacing of the maxillary anterior teeth. See Chapter 7 for a discussion of digital sucking and Chapter 18 for suggested therapy in thumb-sucking and tongue-thrusting. 4) Abnormal Tongue Posture.-Abnormal tongue posture may also cause generalized spacing (see Chapter 10). The prognosis is dependent on the reason for the atypical postural position. Endogenous protracted postures are most intractable, while those associated with nasorespiratory dysfunction (e. g., mouth breathing) often are correctable when normal respiratory function returns. Tongue-thrust may also create generalized spacing (see Chapters 10 and 18).
4. t~oblems
Singular
t?"Jhe Transitional
Dentition
·a) Space Management 1) General Considerations.-Space management is a general term that includes four subdivisions: space maintenance, space regaining, space supervision, and gross discrepancies. At! problems in space management fall into one of the four categories. The differential diagnosis among them is determined primarily by the Mixed Dentition Analysis (see Chapter 11), but other predispositions to crowding must not be overlooked. 19.46 Crowded man-
Yes
SUPERVISION REGAINING DISCREPANCY MAINTENANCE ?No Yes Yes No Yes No Yes No 361 - Yes 6. prognosis 2. Good Loss of space Dentition in arch Analysis SIGNS AND SYMPTOMS Symptoms and Space Management Categories
dibular arches have been shown to be associated with steep mandibular and occlusal lines, short posterior face height, short mandibular corpus, lingual inclination of incisors, and mesially inclined molars. Further, the lower incisors and symphysis are less protrusive in crowded ca&es. In Table 15-2 the distribution of symptoms associated with space management problems of the four subtypes are compared. The effects of molar relationship on arch perimeter changes during the mixed dentition are discussed under space supervision, since the problem is more critical in that category. However, its significance should not be forgotten when treating other space problems. The reader is reminded of the several patterns of occlusal change described in' Chapter 6, for their identification is important to the diagnosis and treatment plan. The presence of a "homeostatic Class II," "homeostatic end-to-end," or "retrusive" pattern of transitional occlusion alters seriously the strategy and the prognosis. Note that this section is written assuming a "Protrusive" pattern from an initial flush terminal plane or a "homeostatic Class I" pattern from an original mesial step since they constitute the majority of cases and the treatment is similar. It is also assumed that allowance for correction of incisal mal positions has been made when compiling the Mixed Dentition Analysis (see Chapter 11). Before undertaking any space management therapy, one should understand thoroughly the contents of Chapter 6, Development of the Dentition and the Occlusion, and the Mixed Dentition Analysis found in Chapter 11, Analysis of the Dentition and Occlusion .
Early Treatment
molars. A carious lesion on the distal surface of the second primary molar, in particular, allows the first permanent molar to tip mesially, The first step in maintaining arch perimeters is to preserve intact the size of the primary molar crowns. A most important preventive orthodontic appliance is a proper restoration in a primary molar. In Chapter 7, the role of caries in the etiology of mal occlusion is discussed. Research affirms the etiologic role of caries in many space management malocclusions.
(b) Loss of Individual Primary Teeth.-Much attention has been given to the necessity for placing space-maintainers when a primary tooth has been lost. 28.29.40,14,16 TQO often, however, the effect of the tooth loss on the total arch length is not noticed. A space-maintainer to hold space after the loss of a single tooth is placed only if the following conditions obtain: (I) the permanent successor is present and developing normally; (2) the arch length has not shortened; (3) the space from which the tooth has been lost has not diminished; (4) the molar or cuspid interdigitation has been unaffected by the loss; and (5) there is a favorable Mixed Dentition Analysis prediction. There is no reason to insert a spacemaintainer if the permanent successor is absent, not should one maintain 4 mm of space for a tooth known to be 7 mm in width. The type of space-maintainer to be used depends on the site of the loss and the operator's
•
Primary incisors.-Primary
2) Maintenance of Arch Perimeter .-Space
maintenance is undertaken only when the following conditions obtain: (I) loss of one or more primary teeth; (2) no loss of arch perimeter, and (3) favorable Mixed Dentition Analysis prediction. The problem of maintenance of arch perimeter is not peculiar to the mixed dentition, for the arch perimeter is likely to shorten quickly at any time following the loss of either a primary or a permanent tooth, and it continues to diminish gradually throughout life." However, certain difficulties in the mixed dentition are so singular as to require separate techniques and separate discussion. 46 Here, the explanation will be confined to problems of perimeter maintenance which may appear in a normally developing dentition as a result of caries or unwanted loss of teeth. It is necessary to separate space maintenance cases carefully from (I) space regaining and (2) space supervision,
(a) Caries of Primary Teeth.- The most frequent cause of arch perimeter loss in the mixed dentition is caries of the primary
preference.
"
incisors may be lost prematurely as a result of trauma, usually as the infant is learning to stand and walk. Multiple loss of incisors from caries is, of course, also seen. Sometimes spacemaintainers are not necessary. in treatment; however, this is not a rigid rule. Before the permanent teeth have developed sufficiently to maintain the dimensions of the arch, the loss of a primary incisor 9.an result in rapid closure of space i~ee Fig 7-19). In every case of premature loss of primary incisors, make a record cast and occlusal plane radiographs for diagnosis and serial study. In children in whom space loss is likely to occur, an acid-etch composite pontic not only serves as a space-maintainer but aids esthetics as well. It is attached to a mesh or braided wire held in place on the lingual of the incisors adjacent to the space.63 Leave this in place until the eruption of the permanent incisor. Space-maintainers for primary incisors are less apt to be needed if the primary tooth has been lost after the child is 4 years of age.
362
Treatment
.'
FIG 15-16. Effect of the loss of primary molars. A, the loss of second primary molars. In both arches, the first permanent molar has a strong tendency to drift mesially and rotate on its long axis. In the mandibular arch, it may tip lingually also. e and C, effects of the loss of first
primary molars. Fm this amount of space to be lost, the first primary molars must be lost very early (before eruption of the first permanent molar).
•
FIG 15-17.
the root of the primary cuspid. Resorption of the primary cuspid's root is likely, particularly if the cuspids cannot move labially and distally. Unilateral loss of a mandibular primary cuspid poses a special problem since the dental midline can quickly be misplaced. The resultant unilateral mesial drifting of teeth complicates and stabilizes the asymmetry. The immediate extraction of the other primary cuspid should be considered, and close monitoring of subsequent sequelae is advised. Following the loss of primary cuspids, the mandibular arch perimeter may be shortened from the front, since the lips may tip the . permanent incisors lingually, causing them to lose their occlusal stops and increasing the overjet and the overbite. As a result, the erupting mandibular permanent cuspids may move anteriorly across the roots of the lateral incisors, finally emerging in labioversion. If other posterior teeth also move anteriorly, it is more difficult to correct the cuspid's malposition. Such cuspid malposition is best averted by prevention of lingual tipping of the incisors with an appliance as a well-adapted lingual archwire. Do not tip the mandi~ular incisors labially with any appliance ahhis time unless you 'are very carefully uprighting them from a position of linguoversion. In the maxillary arch, the problem is similar, but the variation in the sequence of eruption and the permanent cuspid's position enhances its chances to move labially. The upper arch is more apt to shorten posteriorly, but there also is a better chance for distal orthodontic movement of the first
A, band and loop space maintainer of correct design. e, a lingual archwire used as a perimeter space maintainer. C, band and loop maintainer preventing labial movement of the primary cuspid. The horizontal section should be straight, not concave.
permanent molar to provide room in the arch for better placement of cuspids and premolars. • First primary molars.-In most cases, the loss of the first primary molar is not as serious as the loss of the second
Primary cuspids.-Although
the primary cuspids may be removed prematurely because of caries, the eruption of large permanent incisors is a more frequent cause of their unwanted loss. Not infrequently, a large lateral incisor will erupt lingually to the central incisors in the mandible, in its normal eruptive position, but because of its large size there is no room for it in the arch. The combination of eruptive force and tongue pressure 'forces the lateral incisor against
Early Treatment primary molar.50 The severity of the problem is dependent on the sequence of eruption of the succeeding teeth, the molar intercuspation and, most important of all, the dental age of the patient. Arch perimeter loss is most likely to occur when the first primary molar is lost vhy early (Fig 1516). It also may occur when the cusps of the~permanent molars are shallow or there is an end-to-end molar relationship combined with an unfavorable eruption sequence. 16 Many types of space-maintainers have been designed to hold space in this region, but do not insert an appliance that locks the position of the primary cuspid position (Fig 15-17), which must have the chance to move labially and a bit distally. After loss of a first primary molar, one may insert a removable plate or a lingual archwire if other space problems are expected in that arch. If the perimeter is not threatened, a single unit space-maintainer, for example, a preformed stainless steel crown on the second primary molar with a loop engaging the cuspid, may be placed. An alternative is to attach a similar loop to the buccal and/or lingual surfaces of the second primary molar with compos-
363
teeth and natural eruptive placement of the permanent teeth. The mixed dentition is a dynamic, rapidly changing entity ill-suited to the application of the static prosthetic approach so successful in aged adults. Appliances used with the mixed dentition must neither inhibit nor divert the growth changes taking place. The design of any appliance depends on the individual situation. Several suggestions will be found in Chapter 18. 3) Regaining Space in the Arch Perimeter.-Space regaining, as used in this section, means that all of the following conditions obtain: (J) one or more primary teeth have been lost; (2) some space in the arch has been lost to mesial drift of the first
ite.72
•
Second primary molars.-The
most rapid losses in the perimeter of the arch usually are due to a mesial tipping and rotation of the first permanent molar after removal of the second primary molar (Fig 15-18).16 When this tooth is lost, always maintain space until the arrival of the second bicuspid. Before inserting any appliance to maintain the second primary molar space, determine that no space has been lost. Never place a space maintainer when space regaining is indicated. If the first permanent molar has erupted fully, the space maintainer may consist of a preformed stainless steel crown form or a band on the first
primary molar carrying a wire loop to engage the first permanent molar or a similar loop held in place by composite.3 The first permanent molar may be banded and the strut placed mesially to engage the distal surface of the first primary molar. Overlays or crown forms for the first permanent molar are contraindicated because they prevent the tooth from erupting to its full clinical crown height. If the first permanent molar has not yet erupted, the free-end acrylic block type of maintainer may be used (see Fig 1835). The old-fashioned distally extended "shoe" which en~ gaged the erupting first permanent molar sub-mucosally is ,contraindicated because it is unhygienic and inflexible. (c) Multiple Loss of Primary Teeth.-Usually, when several primary teeth are lost, the arch perimeter is shortened-and regaining, not maintenance, is indicated. Sometimes it will be necessary to extract more than one primary tooth at the same appointment. If such is necessary, it is best to insert the appliance the very day the teeth are removed. A lingual archwire or multiple acrylic space-maintainer will serve well. It is not necessary to cast elaborate frameworks and meticulously carve occlusal patterns for "primary partial dentures." A block of acrylic to provide a smooth occluding surface, maintain the vertical height, and prevent extrusion of the opposite teeth will suffice. Many of these appliances will not even require clasps. Indeed, the occlusal carvings or acrylic tooth pontics may interfere with the normal exfoliation of primary
FIG
15-18.
A, effects of early loss of primary molars. Note that the maxillary first molars have rotated, tipped, and translated mesially. B, the lower arch in the same mouth. In the mandibular arch, the first permanent molars, in addition to translating and rotating as they tip mesially, also have tipped lingually. The lingual tipping of the mandibular molars during mesial drifting often is due to the effects of occlusion.
364
Treatment
permanent molar; and (3) the Mixed Dentition Analysis shows that if one could recapture what was once there, there would be adequate room for all the teeth and the normal mixed dentition adjustments. Regaining what was once there is entirely different from creating that which has never been present. Loss of arch perimeter usually is the result of caries or premature loss of primary teeth (see Chapter 7).61 Such cases must be differentiated carefully from those in which the tooth sizeosseous base relationship is so poor that there is insufficient space for the permanent teeth. The discussion at this point is centered on patients who once had sufficient length of the arch perimeter but, because of environmental reasons, had it shortened by mesial movement of the first permanent molars or by lingual tipping of the incisors. Correction should be where the loss has occurred. Note the molar relationship, cuspid interdigitation, and overjet, since they provide the key to the site of the shortening. After locating where the arch has shortened, determine, by means of the Analysis described in Chapter 11, the exact amount of space that must be regained and the most logical tooth movements to recover that space. Usually, distal movement of first permanent molars is required. But before moving first permanent molars distally it is necessary to understand the nature of the mesial movements that caused the shortening of the arch perimeter. (a) Mesial Drift of Permanent Molars.-Mesial drift of the first permanent molars involves three separate kinds of tooth movements, namely, mesial crown tipping, rotation, and translation. There are distinct differences in the mode of mesial movement between the upper and lower first molars, differences caused by variations in the crown shape, number of roots, and occlusal relationships. Furthermore, the time of loss of the crown of the primary second molar is a determining factor in the type of movement seen. Maxillary first permanent molars quickly tip mesially with the loss of crown substance of the maxillary second primary molars (see Figs 15-16 and 15-18). Mesial tipping causes the distobuccal cusp to become more· prominent occlusally. Because of the large lingual root of the maxillary first permanent molar, rotation of the crown also is seen with mesial tipping, the distobuccal cusp becoming more prominent buccally as well. When the second primary molar is lost prior to the eruption of the first permanent molar, translation of the first permanent molar during its eruption may be seen. Mandibular first permanent molars display mesial tipping, crown rotation, and translation as well but they are more likely to show lingual tipping during mesial movement. The lingual tipping is caused by the absence of a lingual root and the fact that occlusal function occurs buccally to the center of mass of the lower molar, a condition aggravated as the first molar drifts mesially. Figure 15-18 illustrates clearly the differences in mesial drifting of maxillary and mandibular first permanent molars. (b) Distal Movement of First Permanent Molars.- The basic tooth movement necessary in space regaining is distal movement of first permanent molars, which must recapitulate in reverse the movements that occurred as the teeth drifted mesially. Therefore, the selection of the space-regaining appliance is dependent on whether tipping, rotation, translation, or combinations of these movements are required. Some common mistakes in choosing
space-regaining appliances should be noted. (1) Often, too complicated an appliance is chosen when a simple appliance would let the tooth fall back more easily into its former position. (2) A firm purchase on the tooth often is not necessary except for translation. Actually, tipping and rotation back into position usually occur more readily with the use of finger springs rather than a banded appliance. (3) There is failure to achieve all of the necessary movements. It should be noted that surprising amounts of arch perimeter space often are created just by distal tipping and rotation of the first molar. Therefore, tipping and rotation should be achieved prior to attempting translation. Although this sequence may necessitate the use of two space-regaining appliances, it often will save months of treatment time and frequently permits the use of simpler appliances. A wide variety of space-regaining appliances are available (see Fig 15-19). No more complicated appliance should be used than is required to achieve the necessary space. Do not overextend the space-regaining appliance. Simple finger springs cannot move molars bodily nor can they easily lengthen an ar~h perimeter past its original dimensions and retain a permanent result. Space-regaining appliances are intended to be used solely for recovering space that once was there. Space regaining is not space creating. The timing of space regaining is important, since the position and stage of development of the second permanent molar often is a limiting factor. When the simpler space-regaining appliances cannot complete the task, one may resort to extra-oral traction, but before using extra-oral traction, the patient's case should be reassessed completely to make certain that the original diagnosis still obtains. When the loss of perimeter length is so extensive as to be beyond the scope of the simpler appliances, or when there is insufficient time to recover the space before the eruption of the bicuspids and second permanent molars, a far more difficult clinical situation is present, and comprehensive multi banded appliance therapy usually is indicated. The construction and adjustment of several popular spaceregaining appliances are described in Chapter 18. It should be noted that similar appliances also are useful when constructing bridges to replace lost first permanent molars, as they may be used for the uprighting and distal movement of second molars prior to their preparations as abutments (see Chapter '17). Figure 15-19 illustrates typical cases where space regaining was needed. 4) Space Supervision.-Space
supervision
is the term ap-
plied when it is doubtful, according to the ~ixed Dentition Analysis, whether there will be room for all the teeth. The prognosis for space supervision is always questionable, whereas prognosis is ,!lways good for regaining space and for space maintenance. Space-supervision cases are those}hat will have a better chance of getting through the mixed dentition with clinical guidance than they will without.44 Each case involves a calculated risk; therefore, space supervision is not to be undertaken without patient cooperation and parental understanding. Successfully treated, such cases are among the most comforting victories in interceptive orthodontics; but when fought through and lost, they provide some most disheartening moments, since, if extractions of permanent teeth ultimately are necessary, large amounts of space closure will be required. Misdiagnosed space supervision cases that require ex-
Early Treatment
.'
PASSIVE
BEND
BEND
BEND
NO.I
N02
N03
FIG 15-19. Examples of space-regainers. A, recurved helical spring regainer (courtesy of Dr. Fred DuPrai). Note the use of the Adams clasp on the opposite side. e, knee spring for use in tipping molars distally. C, split-saddle acrylic space-regainer, useful when greater distances must be regained than in e. Note another type of regainer on the opposite side of the arch, a coil spring lying beneath acrylic and acting against the first molar. D, method of adjusting the spring on the split-saddle regainer. E, method of increasing the adjustment in a split-saddle regainer. As the molar moves distally, the appliance becomes more fragile. It is then possible to tie the distal portion forward with a piece of dental floss or stainless steel ligature to permit the addition of acrylic posteriorly. In this way the appliance is reactivated without adjustment of the spring. (Continued.)
~-. .',
365
366
Treatment
..
FIG 15-19 (cont.). F and G, slingshot regainer. Note the use of a light elastic joined to buccal lingual hooks (courtesy of Or. Fred DuPrai). H and I, the sliding yoke space-regainer. H, buccal view. A steel edgewise wire 0.022 inch x 0.028 inch is used. A ball of solder is placed mesial to the cuspid bend of the wire. A coil spring is then threaded onto the wire, the sliding yoke is added, and the wire is bent well distal to the molar to be moved. I, the sliding yoke is an edgewise buccal tube the inside diameter of which is exactly that of the wire. To the buccal tube is soldered at a right angle a small piece of stiff wire to engage the mesial of the molar. Note that the acrylic must be trimmed in a straight line on the lingual. This appliance is best anchored on the opposite side by an Adams clasp. It is more efficient in the maxillary than in the mandibular arch. J, the expansion screw regainer. These units are bought prefabricated and inserted into the acrylic appliance (courtesy of Dr. Fred DuPrai). K, an example of a removable acrylic regainer followed by a lingual archwire as a maintainer (courtesy of Dr. William Northway). (Continued).
Early Treatment
367
tractions of permanent teeth are more difficult to treat than gross discrepancy cases because (I) more space closure is needed and (2) the patient's cooperation often lags after the planned interceptive procedure has failed. Do not oversell space supervision to the parents. Select space supervision cases with great care and maintain careful records, since help from a colleague may be required later. Success is greatly dependent on the clinician's knowledge of the details of mixed dentition development. 17.5062 (See Chapter 6.) Because of the critical effect of the skeletal pattern on molar relationship and the utilization of available space (Fig 15-20), three space sur;;rvision protocols are needed. However, several basic principles obtain in all three: (I) space supervision is not begun until the mandibular cuspid and first premolar show approximately one-quarter to one-third of the root formed; (2) primary teeth are extracted serially to provide an eruption sequence of cuspid, first premolar, and second premolar in the mandible and of first pr5:molar, cuspid, and second premolar in the maxilla; (3) an effort is made to keep the mandibular teeth erupting well ahead of the maxillary; (4) one takes care that a late mesial shift of the mandibular first permanent molar does not occur. (a) Mesial Step (Class /) Protocol.- This protocol (Table 153) is used when there is a normal skeletal profile and the first permanent molar has alread)' achieved a Class I molar relationship at the time of instituting space supervision (Fig 15-21 ,A). Figures 15-21 ,A-H depict diagrammatically the various steps in the mesial step protocol, and Figure 15-22 illustrates cases treated in this manner.
FIG 15-19 (cont.). L, the use of a maxillary plate (Cetlin) as a regainer. Note the palatal anchorage and eyelets in the archwire for placement of extra-oral anchorage (courtesy of Dr. William Northway). M, use of a screw for space regaining. N, a combination of appliances to achieve space regaining (courtesy of Dr. William Northway).
CLASS
SPACE
SHORTAGE
I
-1.Omm
NEEDED FOR MOLAR ADJUSTMENT
-O.Omm
TOTAL
- 10 mm
SHORTAGE
FIG 15-20. Effect of the molar relationship on the available space. Three hypothetical situations are shown in which it is predicted that there will be a shortage of 1 mm on each side in the mandible. Where there is a Class Imolar relationship, the only problem is the 1-mm shortage. However, where there is an end-to-end molar relationship, one must account for the width of half a cusp (approximately 3.5 mm) in addition. Where there is a Class II molar relationship, one must allow
The first step, the removal of the mandibular primary cuspids, is begun when the mandibular permanent cuspid has clearly begun root formation (Fig 15-21,C). The purpose of the first step is to provide space in the arch for the alignment of the mandibular incisors and to' induce the mandibular cuspid to erupt before the first bicuspid. One of the most- important single steps in space supervision is the correct placement of the mandibular permanent cuspid after alignment of the incisors. Several months after the primary cuspids have been removed, it will be found by palpation that the permanent cuspid can no longer erupt normally without
END
TO
-
CLASS
END
-
1.0
IT
1.0
-7.0 -
8.0mm
4 5mm
for the 1-mm shortage plus the width of an entire cusp (approximately 7 mm). Naturally, under such circumstances, both the end-to-end and the Class molar relationships are treated by Class mechanics (Le., moving the maxillary dentition distally while preserving the mandibular dentition intact). Further, such patients are poor candidates for intermaxillary elastics, since the elastic traction tends to shorten the mandibular arch length while moving the maxillary molars distally. 11
11
368
Treatment
TABLE 15-3. Space Supervision
Protocol for Mesial Step or Class I Cases
STEPS
PURPOSES
1. Removal of C
extraction of and D, slicing of E of E
TIMING
1.
3 is
2
When:3 can no longer erupt normally
1. 3. Prevent mesial of 6 2~ (a) Align Allow:3incisors to erruptdr\ft distally
stage 6 + or 7
Erupt 5 eruption before 47 of 4 . (b) (b) Erupt:3 Hasten
3. When 4's eruption is halted by E
moving into labioversion. It is now time for the second step (Fig 15- 21 ,E)--the removal of the primary first molar and the slicing of the mesial surface of the second primary molar. The purpose ()f the second step is to allow the cuspid to erupt distally into the line of arch and to hasten the eruption of the first bicuspid. After the cuspids have arrived in the arch there usually is insufficient space for the eruption of the first premolar, since it becomes halted at the mesial surface of the second primary molar. A holding archwire is now inserted and the mandibular second primary molars are extracted. A lingual archwire may be used (Fig 15-21 ,H) but a utility archwire is often more satisfactory since it provides precise incisor control and positioning (Fig 15-23). A lip bumper is also a handy device for maintaining the lower arch perimeter and has (I) it helps correct excessive two additional advantages:4•7.ll mentalis muscle activity and (2) it can increase the arch perimeter in some instances. The purposes of this third step are to prevent the mesial drift of the first permanent molar and to cause the second premolar to erupt before the second permanent molar. All of the steps in space supervision are shown in sequence in Table 15-3. (b) Flush Terminal Plane (End-ta-End) Protocol.-The protocol for space supervision with a flush terminal plane (endto-end) relationship (Table 15-4) is quite similar to that for a mesial step-with one important exception. Since the molars are not in a Class I relationship and a late mesial shift cannot be allowed to occur, it is necessary to achieve a Class I molar relationship by guidance of the eruption of the maxillary first permanent molar or its movement distally. Figure 15-24 diagrams how the distal tipping of a maxillary molar during the transitional dentition helps achieve a Class I molar relationship without a late mesial shift in the mandible. A Sved plate with helical springs may be used. The Sved plate frees the occlusion, which aids in the distal tipping of the maxillary first permanent molar, helps flatten the mandibular occlusal plane, and removes any occlusal interferences. The Cetlin
n of 4 E andibular 5 eruption before 5, 7lingual slice emove
TABLE 15-4.
..
Space Supervision STEPS
Protocol for Flush Terminal Plane
1. Max.-appliance. erupt normally
appliance, a modification of the Sved plate, is also quite satisfactory. Study Figure 15-25 carefully, for the details of each step of treatment are depicted in the diagrams. Note that this protocol in its simplest form is proper only with a straight (Class I) profile and a flat occlusal plane. The presence of a flush terminal plane or end-toend first permanent molars can be quite deceptive if one thinks of these occlusal features only as defining "normal." As the craniofacial skeleton becomes more retrognathic, the occlusal plane steepens, or one suspects a "retrusive" transitional occlusal pattern, this protocol must be modified. When all the skeletal features are Class 11, even though the occlusion is end-to-end, the distal step (Class 11) protocol is used. Study the several cases shown in Figure 15- 26; they are of varying severity utilizing treatments appropriate to the difficulties seen. Figure 15-26 illustrates cases treated by this protocol. (c) Distal Step (Class 1/) Protocol.-In the preceding space supervision protocols it has been assumed that the problem is seen in a balanced or nearly balanced facial skeleton. A space supervision problem combined with a distal step is a much more serious matter, and the space problem is quite secondary to the skeletal contributions to the Class 11(distal step). Many other problems are encountered in addition to that of the space shortage. The basic skeletal dysplasia must be treated and the teeth positioned in the best possible way to accommodate after the skeletal correction is over. Furthermore, there usually are vertical occlusal problems to be corrected, and abnormal tongue and lip contractions are frequently seen. Of particular importance is the necessity to retract the incisors to fit the skeletal profile, a move which shortens the arch perimeter from the front. Leveling the occlusal curve, which is often necessary, also shortens the arch perimeter. Distal step space supervision is the first part of a diphasic treatment begun at the same time as the flush terminal plane and mesial step protocols. However, 9istal step space supervision therapy
Of
End-to-End
PURPOSES
of 6:3 1. (a) 1. Tip isincisors 6stage distally 6erupt 3. (a) 3. When Prevent 4'sto mesial eruption +4noordrift 7 is halted (b) Align by 2. When:3 can longer 2. (a) Allow:3 distally (c)E Erupt:3 before
Cases
" ":" TIMING
.'
,.
FIG 15-21. Space supervision protocol for Class I or mesial step cases. A, the mesial step. B, typical crowding in the mandibular arch. Note that the primate space is closed. C, the first step-removal of mandibular primary cuspids. D, the effects of the first step. E, the second stepremoval of the first primary molar and slicing of the mesial surface of the second primary molar. F, the effects of the second step, re-
moving the first primary molar and slicing the second primary molar. Note, too, that the mesial surface of the second primary molar may be shaped by a small finishing stone to facilitate the eruption of the first bicuspid. G, the third step-placement of a lingual archwire and removal of the· second primary molars. H, the results of the third step.
369
370
Treatment
A MIXED DENTITION ANALYSIS
A90!iL!:L Su _M__ Dole
_~
Address
.n. ~.2.(,
Space lert after aliC)nment of 2 ..ond I Low., Pred ieled size of
~O.~
_
, I Ri
I
Poren'
_
~:.
lift L.ft
hi
:).3. (. .S-
RIQhI
~~.~
- I.
3"4"5
L{
Space 'eft for molar adjustment
Spoce left after olionmenl of 2 and I Predicted
size of
3" 4 .• 5
Spoce left for molor adjustmenl RemOlks:
Overjet"
Molar relationship"
.3. J. ~. ~J..AAAr
~
r
Ov••.bil.·
'I./ ~
.
~~.r-r
FIG 15-22. Space supervision with a Class I molar relationship. A, the Mixed Dentition Analysis for the patient. B, at the start of treatment. C, at the time of extraction of the mandibular primary cuspids. D, a re-
the spontaneous improvement in the incisor region, although the contact is not correct between the right lateraHncisor and the cuspid. This photograph was taken 2 years after the beginning of treatment.
movable acrylic arch-holding appliance was inserted immediately after extraction of the primary cuspid because the patient had a hyperactive mentalis muscle which might have collapsed the incisors lingually. Ordinarily, it is better practice to place a lingual archwire in such cases. E, 9 months later, at the time of extraction of the first
4 years after the G, 1 year later than F. H, 1_ year later than G-or start pf space supervision-'procedures. Compare H with A_ It is doubtful thai such a result would have oc€urred spontaneously by chance alone. Only the intervention and careful supervision of the loss of the primary teeth and the eruption of the permanent teeth could have guided such a result.
primary molars. F, after the loss of the second primary molars. Note
Early Treatment
371
FIG 15-23. Space supervision utilizing lip bumpers and a maxillary utility wire. (Courtesy of Dr. William Northway.)
..
B
FIG 15-24. Molar correction during space supervision in flush terminal plane cases. A, the maxillary molar is restrained during the downward and forward growth of the maxilla. Thus, it comes to occupy a relatively different occlusal relationship with the mandibular first permanent molar. B, the maxillary first molar is tipped distally a slight amount, thus changing the axial inclination of the tooth during subsequent vertical development. The tooth is not moved distally in a translatory fashion; rather, its angle of.yertical development is changed so that it cl3mes to occupy a relatively different occlusal relationship with the mandibular first molar after some time has passed.
..
FIG 15-25. (Legend appears on facing page.)
,.
372
Early Treatment is secondary to the treatment of the facial skeleton and must be accompanied or followed by a period of precision bracketed appliance therapy to finish the alignment of the permanent teeth. Figure 15-27 illustrates the treatment of a distal step supervision case. Read carefully Section D-6-e on early treatment of Class 11 maJocclusions before undertaking any distal step space supervision. Class 11 mal occlusion accompanied by space problems is one of the most difficult categories in early treatment. 5) Gross Discrepancy Problems.-Gross discrepancy problems are those in which there is a great and significant difference between the sizes of all the permanent teeth and the space available for them within the alveolar arch perimeter. Gross discrepancy problems ordinarily cannot be diagnosed until the early mixed dentition, as no clinically useful correlation has been shown to exist between the size of the primary teeth and those of the permanent dentition. Gross discrepancy cases are treated at several ages, often too dependent on the time the problem is first observed. The protocol and rationale described here relate to the early treatment of gross discrepancy cases (i.e., during the mixed dentition). Treatment in adolescence is discussed in Chapter 16; in adulthood, in Chapter 17. Gross discrepancy problems have been erroneously termed "serial extractions" in the American literature. Concepts of serial extraction were developed first by Kjellgren in Sweden and Hotz in Switzerland who used the term to embrace all planned sequential extractions of any teeth in order to take advantage of eruption and natural drifting. Thus, serial extraction truly includes space supervision, as well as gross discrepancy therapy. The original use of the term serial extraction is thus preferred to the more restrictive North American usage. Table 15-2 data establish clearly how different gross discrepancy problems are from those of space maintenance and space regaining. The difference between space supervision cases and gross discrepancy problems is largely one of strategy. In space supervision, the goal is to squeeze all permanent teeth into what obviously is minimal space. In the gross discrepancy problem, it is accepted at the start that insufficient space is available and therefore extraction of permanent teeth is ultimately necessary. Those skilled in space management can obviate the need for some
FIG
15-25.
Protocol for flush terminal plane supervision. A, the developing flush terminal plane. 8, the typical incisal configuration at the start of treatment. C, the first step-removal of the mandibular primary cuspids and tipping of the maxillary first molar distally. D, the results in the mandibular arch of the first step. E, the second step-removal of the first primary molar and slicing of the mesial surface of the second primary molar. Note that by this time there is some improvement in the first permanent molar relationship. F, the results in the mandibular denture of removal of the first primary molar and slicing and contouring of the second primary molar. G, the third stepplacing the lingual archwire and removal of the second primary mandibular molars. By this time, the first permanent molars often have a Class I molar relationship. H, the results of the third step while awaiting the eruption of the second bicuspid.
373
gross discrepancy cases, but many problems defy the best mixed dentition treatment irrespective of the appliance used. (a) Diagnosis.-A most meticulous Mixed Dentition Analysis is necessary (see Chapter 11); however, it must be remembered that the skeletal pattern has a significant effect on the alignment of teeth within the dental arch. The discussion herein assumes a balanced facial skeleton. A Mixed Dentition Analysis provides insufficient evidence on which to base a Class 11 mal occlusion treatment plan. One must also study the facial skeleton to determine how the orthodontic treatment will correct or camouflage the skeletal dysplasia and to quantify what effects the comprehensive orthodontic therapy will have on the available space.68 Tooth movements undertaken to overcome a Class 11 skeletal dysplasia ordinarily shorten the arch perimeter signifiCantly. (b) General Rules.-No one undertakes the extraction of permanent teeth casually. 53.41 Nor should dentists extract permanent teeth as a part of orthodontic therapy unless they have the technical skills to correct all the sequelae of those extractions. Extraction itself provides space, only some of which may be absorbed by spontaneous alignment of crowded teeth. The remaining space closure is critical to success. Therefore, most cases in which permanent teeth are extracted require comprehensive precision appliance therapy to close the remaining spaces, to parallel the roots, to establish the occlusal plane, and to correct the intercuspation. A few general rules for less experienced clinicians provide insurance against involvement in unwanted complications. The following were suggested by Eisner. The more a case deviates from them the more comprehensive is the mechanotherapy required to complete the case. When a case satisfies the requirements of all the rules, it may be treated by the protocol that follows with a reasonable chance for success and a minimum chance of trouble.
•
Rule J: There must be a Class I molar relationship bilaterally. Rule 2: The facial skeleton must be balanced anteroposteriorly, vertically, and mediolaterally. R.ule 3: The discrepancy must be at least 5 mm in all four quadrants. Rule 4: The dental midlines must coincide.
•
Rule 5: There must be neither an open bite nor a deep bite.
• • •
Only a few discrepancy cases will meet all the requirements of these rules, and the more a case··deviates from them the more difficult it will be to treat.
,.(c) Treatment Protocol.;;- These procedures involve the planned sequ~fitial removal of primary and p,ermanent teeth to alleviate the major dental aspects of the malocclusion seen in some gross discrepancy problems. Treatment may be started when the mandibular first bicuspid has at least a portion of its root forming (Fig 1528,A). The first active step in treatment is the removal of the mandibular first primary molar, which is executed when approximately one-third of the root of the mandibular first bicuspid has formed (Fig 15-28,B). As soon as the mandibular first bicuspids are seen erupting into the extraction site, the maxillary first primary molar may be removed (Fig 15-28,C). Delaying the extraction of
A
'a
Pulienl
MIXED DENTITION l"I'I
ANALYSIS
\{,'
Dote
Address
_
_
Porent
FIG 15-26. Space supervision with an end-to-end molar relationship. A, the Mixed Dentition Analysis. Note that there is scarcely enough room to align the incisors and no available space is predicted for molar adjustment. B, the casts at the start of treatment. Note that the patient's right side showed a Class 11molar relationship whereas on the left the molars tend toward Class I. Because the midlines do not coincide, it usually is found in such cases of disparate molar relationship in the mixed dentition that such patients have an end-to-end molar 3+4+5 alignment of 2 and Iwax bite record is taken. C, the Sved relationship molar when a functional adjustment Space left
ofter
plate was used to tip the maxillary molars distally during typical serial extractions of the primary teeth in the mandible. (Continued).
Riaht Space left after alignment of 2 and I Pred icted
3+4+5
Space molar
size of
left for adjustment
-
1.0 ,S
Molar
relationship'
,q.NI..A -
3. S" """""
Overjet.
~aN~~~~M.
-~:.S' ,HS '"'1'"
'-:. Q S' J.J.
Space Predictedleft size for of
Remarks:
374
Lower
~C'I'
It ¥.d..:.lQ~
~
"ti -.t-vJ..
~
.R~
L/ . .:( ~
Overbile·
~.
~
r
.
W~
_
.'
FIG 15-26 (cont.). 0, later, after the third step in treatment. Note that all mandibular teeth have erupted well ahead of the maxillary, as was planned. Now both molar relationships tend toward Class I. Further, there is just barely enough room to align all the mandibular teeth, so none of the molar correction has Been achieved by a late mesial shift. E, after complete eruption of all the cuspids, bicuspids, and molars.
375
376
Treatment
.'
FIG 15-27. Space supervision
,_.~. in Class 11. A, the developing
distal step. B, the casts treatment.
(Continued).
Early Treatment
FIG 15-27 (cont.). e, after 1 year of treatment. An Activator appliance was used to hold the mandible arch perimeter, optimize mandibular growth. has been achieved and the open bit is not yet corrected mandibular cuspids had all
aid in correcting
the open bite, and
Note that a Class I molar relationship space situation is better, although the completely. D, views obtained after the erupted and the open bite had closed
377
successfully. To ensure that the Activator did not jeopardize the integrity of the mandibular arch perimeter, treatment was changed to extra-oral traction, which served to restrain the Class II growth of the midface and hold the maxillary arch perimeter during eruption of the cuspids. Note that the maxillary second primary molar has been sliced to allow the first bicuspid to drop into occlusion. (Continued).
378
Treatment
FtB 61
FIG 15-27 (cont.). E, casts of the patients after eruption of the second permanent molars and after the retention period was over. F, 20 years after activ.~ treatment. Note maintenance of the postetior occlusion but relapse of the incisal correction ...
Early Treatment
379
FIG 15-28. One protocol for serial extraction
of primary and permanent teeth in
cases of gross discrepancy. A, at the start of treatment. Note the Class I molar relationship and the beginning of root development of the cuspid and the first bicuspid. 8, the first step-removal of the lower first primary molar. C, the second step-removal of the upper first primary molar. 0, the results of steps 1 and 2. Note that the first bicuspid erupts quickly, ahead of the cuspid. As it does so, its root develops and the alveolar process is completely formed in the region. This alveolar development provides bone into which the cuspids may naturally move distally. E, the third step-removal of the mandibular first bicuspid. This tooth is removed after it has erupted into the mouth, delaying the extraction until intra-oral eruption permits the formation of normal alveolar height in the region. F, the fourth stepremoval of the maxillary first bicuspid. G, the results of steps 3 and 4. The permanent cuspids now move distally into the extraction site readily, since there is sufficient bone for them. As they erupt and drift distally, they often upright themselves, although it is always necessary to bracket them in order to close the spaces and make the roots perpendicular. H, schematic presentation of the results of the serial extraction procedures. One hopes the teeth will look like this at the time of bracket placement.
380
Treatment
FIG 15-29. Oblique cephalograms showing the excellent vertical position of the cuspids that can be achieved by careful timing of serial extraction
procedures.
the maxillary first primary molar guarantees the earlier arrival of the mandibular first bicuspid, allowing the mandibular arch to progress ahead of the upper (Fig 15-28,D). When the mandibular first bicuspid has erupted to its approximate clinical crown height, it may be extracted. It is not advisable to extract the bicuspid earlier, since the eruption of the bicuspid forms alveolar bone in the area into which the cuspid eventually will move. To enucleate the first bicuspid is to delay the natural distal drifting of the cuspid, since the alveolar process will resorb and new alveolar bone will not appear until the cuspid is in position to erupt. 73 Paradoxically,
waiting for the eruption of the first bicuspid before it is extracted actually hastens the treatment (Fig 15-28,E). In similar fashion, when the maxillary first bicuspid has erupted to full height, it may be extracted (Fig 15-28,F). The results of the preceding steps are shown in Figure 15-28,G. Usually, the alignment of the incisors improves spontaneously and the cuspid eruption is delayed slightly but, as the cuspid erupts, its root often is in a surprisingly good vertical position (Fig 15-29). Indeed, one of the primary reasons for treatment of gross discrepancy problems in the mixed dentition is to ease difficulties in cuspid positioning, a significant problem
FIG 15-30. (Legend appears on facing page.)
'"'
Early Treatment
381
MIXED DENTITION ANALYSIS Oot~
Address
~" allonment 3+4+5 molar Space
"3. PIf Iq.
-~.
of 2 and I odjustment left ofter
Pred icted Space left
size for
Co
of
Parent
_
_
r\:HJTII
'I
Jq, -)3, '7. I3
Lower
Rlaht
:rt:~~~~:t OfQf~e~ndI
Pred icted
size
of
3+4"1"5 molar
Molar
adjustment
3, q
Overjet'
relationship
11·
1.1.
J.3.
~ - 4·7
-s-.~
Space left for Remark"
Left
z
~
r ,.
Overbite
=
4.8,.,.........
FIG 15-30. A, records of a patient treated by serial extraction. B, serial radiographs of the patient shown in A (JS refers to patient data; courtesy
of Dr. William Northway). c-I, gross discrepancy treated in the mixed d~n!ition. C, the Mixed Dentition Analysis. (Continued.)
in later treatment. The amount of space closure that will be required after the incisors and cuspids are in position is, of course, determined by the extent of the original discrepancy. Only rarely does one encounter a case in which the discrepancy in each quadrant is exactly the same as the width of the tooth extracted in that quadrant. Some natural spontaneous space closure can be obtained by slicing the proximal surfaces of the second primary molars, but only small amounts of spontaneous closure ordinarily occur without tipping of the teeth, loss of parallelism of the roots, and loss of vertical dimension. Hence, there is a need
for precise control of the teeth during the finishing stages of treatment of a gross discrepancy problem. Figure 15-30 illustrates cases treated by the protocol just described. A.variety of protocols for planned extractions of primary and permanent teeth in early treatment of gross discrepancies have been reported in the literature. 68 That presented here is one of the most common and frequently used. Other sequences involve serial removal of combinations of first and second premolars, .all second premolars,26 or a lower premolar and upper second permanent molar, according to the demands of the case. The removal of all
,
382
Treatment
,.
FIG 15-30 (cont,). D and E, intra-oral views at the start of treatment.
F and G, intra-
oral photographs after removal of the bands. H, facial profile at the start of treatment. I, profile at the end of treatment.
four second permanent molars in discrepancy cases has recently been enthusiastically revived and advocated but is not recommended as a routine treatment for gross discrepancy problems. Second molar extraction is an old strategy with specific utility.35.37.52The procedure has special problems which are discussed in Chapter 16, since the removal of second permanent molars, when indicated, is part of adolescent gross discrepancy treatment. It must be noted that there is a quite different response of maxillary third molars to second molar extractions than there is for mandibular third molars.24. 34.65.75 Mandibular third molars rarely attain satisfactory positions after second molar extractions without an additional period of necessary bracketed appliance therapy several years after the extractions (Fig 15-31).
(d) Precautions.-It must be borne in mind that discrepancy cases are the most frequent ones in orthodontics in which extraction of permanent teeth plays a routine therapeutic role. When the diagnosis suggests removal of teeth, extraction alone does not solve all the problems of treatment at once. It provides space in the arch, but extraction cases usually require extensive movements of teeth and precision appliancing to complete a perfect result. Unfortu-
FIG 15-31. Typical effect of extraction
of second molars. A, before orthodontic
treatment; patient was 13 years, 2 months of age. B, after treatment; patient was 17 years, 5 months of age. C, patient at 18 years, 11 months of age. These studies show an unusually good response, yet note the inperfect position of the mandibular third molars. Ordinarily, another period of orthodontic treatment is required. (Courtesy of Dr. George Eastman.)
Early Treatment
FIG
383
15-32.
Premature eruption of the second bicuspids resulting from early loss of the second primary molars during root development of the bicuspids. Had these molars been lost before the start of root development,
eruption of the second bicuspids than hastened.
might have been delayed, rather
nately, one can remove only a whole tooth in each quadrant and far too often the clinician removes approximately 7 mm of space to permit alignment, which absorbs only a fraction of the space created. Some consider it good clinical judgment never to extract unless an appreciable percentage of the width of the bicuspid is needed for alignment in each quadrant. Many cases tempt one to extract asymmetrically yet attempt to absorb the space provided on both sides of the arch. It is a sound policy to avoid extraction---or to extract bilaterally except in the presence of malocclusions that are distinctly unilateral. Dentists who have mastered the manipulation of a precision multibracketed appliance have distinct advantages when treating extraction cases, for they can, by their technical skills, more satisfactorily close the spaces and consolidate the arch without cre- . ating traumatic occlusion and possible periodontal problems. Dentists who have only removable appliances in their armamentarium must necessarily adopt more conservative attitudes toward the extraction of the permanent teeth.
There is entirely too much loose wntmg on the subject of extractions. Such cases should not be undertaken unless the dentist is prepared to give each case the study and careful attention it demands. 14 There are not as many places for compromise in orthodontic therapy as we might desire. Unfortunately, the gross discrepancy problem is one of those uncompromising situations, for there is simply no easy way to deal with the problem of large teeth. One either leaves them in place or treats the problem comprehensively. Any other course of action is likely to leave the mouth in worse shape than it was at the start. The gross discrepancy problem is a common one in practice, and there is no one safe practical approach that universally guarantees easy success in treatment.39 Early diagnosis makes it possible to treat the case at an optimal time. It is good policy never to begin the treatment of a gross discrepancy case unless you are prepared to follow it through to a final result.
b) Difficulties in Eruption 1) Alterations in Sequence of Eruption.-Certain variations in the order of eruption of the teeth have been shown to be symptomatic of certain malocclusions (see Chapters 6 and 7).55 It also is true that the normal sequence of eruption provides the best chance for maintaining the arch perimeter intact. Class II cases often show upper molars erupting ahead of the corresponding lower molars. A serious problem occurs in difficult space management situations when the second permanent molar erupts ahead of any cuspids or bicuspids. If noted early, a holding arch will prevent premature shortening of the arch perimeter. If noted only after a loss of arch perimeter, use of extra-oral traction or a lip bumper may be necessary to recover the loss.
FIG
15-33.
Idiopathic failure of teeth to erupt.
(a) Premature Eruption of Individual Teeth.-Permanent teeth may erupt unusually early if the primary predecessor has lost a considerable amount of bone from around its roots. Periapical lesions may result in eafly loss of the primary tooth, extensive bon~'resorption, and increased circulation in the region. All of these conditions hasten the arrival of the permanent tooth (Fig 1532). When a tooth arrives so early as to have insufficient root length to maintain itself in position, instruct the patient to avoid, temporarily, eating tough, chewy foods and take steps to stabilize the tooth. A bracketed appliance, if used, should be made with great care lest the tooth be inadvertently extracted. An easier method employs composite which is placed in all embrasures after acidetching the enamel of !,he problem tooth and adjacent teeth. Such
384
Treatment
FIG 15-34. A and B, radiographs of a patient treated orthodontically to elevate a mandibular second premolar whose normal eruption was impeded by the retention of an ankylosed second primary molar. The first bicuspid and the ankylosed second primary were extracted, and orthodontic forces moved the second bicuspid up to the plane of occlusion. Note, however, that the prolonged retention of the primary
molar permitted
caries on the mesial
root on the first permanent
molar and the orthodontist's heroic efforts to move the bicuspid occlusally did not cause normal bony attachment to the denuded mesial surface of the first molar. (Courtesy of Dr. Gloria Kerry, periodontist who treated the sequelae of this procedure). "
FIG 15-35. A case of ectopically erupting maxillary first permanent molars. This case is a bit atypical, since ectopic eruption of maxillary first permanent molars often is an indication of a shortage of space in the arch. A, note the undermining of the distal surface of the second primary molars, the tipped position of the maxillary first permanent
molars, and the Class 11relationship
of the permanent
molars. B,
left, occlusal view of the maxillary case; right, side view to show the tipping of the maxillary first molar and an anterior crossbite. (Continued).
Early Treatment splinting cannot be left in position very long. Check the growth of the root and alveolar bone by taking serial radiographs, and remove the plastic when increased root growth assures stability. (b) Delayed Eruption of Individual Teeth~-Individual
teeth
may be delayed in eruption because of retarded tooth development, idiopathic failure to erupt (Fig 15-33), obstructions occlusally (Fig 15-34), or premature loss of the primary predecessor. When a primary tooth is removed prior to the initiation of root formation of the permanent successor, and hence the start of its eruption, bone may reform atop the permanent .tooth before eruptive movements can begin; thus, eruption actually is delayed by the premature loss of the primary tooth. The critical factor is the amount of. root formation of the permanent tooth at the time of loss of its predecessor. 17.22 The mandibular second bicuspid is the tooth most likely to develop in a manner disharmonious with adjacent teeth, and thus its eruptive development must be watched more carefully (see Chapter 11). Unduly retained primary second molars or their root fragments may be obstructive impediments to eruption. Idiopathic failure to erupt is also seen and may be difficult to diagnose. It is usually tediously difficult to treat (see Fig 1533). All such cases in delayed eruption must, of course, be differentiated from ankylosed permanent teeth.
2) Ectopic Eruption of Teeth.- The word "ectopia" its adjective "ectopic"
and are terms sometimes misused in dentistry.
385
Ectopia means out of the normal position, or misplaced. It means this and nothing more. Wrong therapy sometimes is advocated simply because the incorrect use of a word leads to incorrect ideas concerning treatment. Any tooth may be in ectopia during eruption, although some are more frequently so than others. Only those teeth in which ectopic eruptions most often are a clinical problem will be dealt with here. (a) Maxillary First Permanent Molar.- The following, combination, usually account for the abnormality. 6. 12.51 • •
The teeth in ectopia are significantly larger than normal. The maxillary first permanent molar is erupting at an abnormal angle, indicating that the tooth germ probably was abnormally placed.
•
The maxillary length (depth) is shorter, and tuberosity growth may lag significantly. The morphology of the distal surface of the maxillary second primary molar and of the mesial surface of the maxil-. lary first permanent molar are ideally suited for locking of the latter tooth during its eruption.
•
In
In the typical case, the erupting maxillary first permanent molar is tipped mesially to engage closely the distal surface of the primary second molar and becomes caught at the cervix of the primary tooth. Destruction of the primary tooth crown may proceed unless the permanent tooth becomes freed (Fig 15-35,A). Ectopia
FIG 15-35 (cont.). C, results of carving the second primary molars off the work casts
areas have been sliced to permit activation.
to reproduce the mesial anatomy of the first permanent molars. D, left, the completed space-regain er, which has been made on the prepared cast shown in C, right, the same appliance after the saddle
The appliance can now be worn as a space-maintainer simply by filling the cracks with self-curing acrylic resin. Note the spontaneous correction of the incisor crossbite.
E, the treatment result.
386
Treatment
of the maxillary first permanent molar frequently is bilateral. When it is unilateral, excessive tooth width is not as important an etiologic factor <\sthe misplacement of the developing tooth germ. Treatment consists of the following: •
Separating wire procedure:
a) The first consideration is preservation of the length of the arch. The fate of the second primary molar crown is not as important as the fate of the space that the primary crown occupies. As the permanent tooth erupts ectopically, it can quickly shorten the amount of space into which the cuspid and bicuspids must erupt. . b) Do not slice the distal surface of the second primary molar. Such slicing will allow the first permanent molar to erupt, but the tooth will tip even farther out of position. Malocclusion will always result, for the slicing will guarantee insufficient room for the cuspid and bicuspids. c) Insert brass separating wire between the second primary and the first permanent molar as the first step in treatment. Tighten the wire every few days, forcing the permanent tooth distally. Later, you may have to use a doubled separating wire. When the permanent molar is freed, it will erupt to normal position. Remember that a second primary molar that has been damaged, as it usually is in this situation, is more likely to be lost early. Therefore, there is still a chance for the arch length to shorten when the primary molars are lost. If the separating wire procedure fails to dislodge the permanent molar or if you are unable to insert a separating wire, follow these steps. Figure 15-35,A-E shows the steps in treatment of a typical case by this method.
•
Alternative procedure:
a) On the maxillary work cast remove the second primary molar, carving the plaster to simulate the mesial surface of the first permanent molar (Fig 15-35,C). b) Construct an acrylic appliance of the split-saddle type, allowing the plastic to fit into the carved portion of the cast so that it may meet snugly the mesial surface of the first permanent molar as that tooth is freed (Fig 15-35,0) .. c) Extract both maxillary second primary molars and insert the appliance after having split it with a separating disk. The appliance must be placed at once following the extractions, as one would insert an immediate denture.
(c) Mandibular Incisors.-Only rarely are the mandibular incisors in ectopic eruption, although the lateral incisor frequently is thought to be. When an incisor in the lower arch is or seems to be in ectopia, the condition is most likely caused by the prolonged retention of a primary predecessor or excessively large permanent teeth. Mandibular lateral incisors normally erupt lingually to their final position. However, they soon are moved into the line of arch by the tongue unless there is insufficient room for them. (d) Other Teeth.-Although any tooth may erupt ectopically due to local causes, the most serious ectopias are those in which the tooth germ itself forms ectopically. When planning treatment, always keep in mind three objectives: (I) placement of the tooth in its normal position; (2) retention of a favorable sequence of eruption; and (3) maintenance of arch perimeter. 3) Transpositions of Teeth.- Transposition of teeth, a rare. but clinically difficult developmental anomaly, almost invariably involves the permanent cuspid.40 Transpositions may occur in either jaw and may be unilateral or bilateral. In the maxilla, three times as many transpositions are reported with the first bicuspid as with the lateral incisor. Almost all mandibular transpositions are with the lateral incisor. 4R
(a) Etiology.-The causes of all transpositions have not yet been fully explained, although retained primary cuspids are the best documented single etiologic factor. 58 This is a significant practical point since the timing of primary cuspid removal is critical to several aspects of mixed dentition treatment, for example space management (see Section 0-4-a). The eruptive path of the maxillary permanent cuspid is more variable than that of any other tooth and it is more frequently impacted. The relationships between impaction and transposition are not to be overlooked (see Section 0-4-b-4, Impaction of Teeth). The roots of retained primary cuspids may deflect permanent cuspids to impactions or transpositions. It is also possible that there may be an actual transposition of the anlage of the teeth. There is no evidence of sexual or racial differences in transposition of cuspids. 5R
d) At subsequent appointments, adjust the springs until the desired amount of regaining is obtained (Fig 15-35,E). e) When the regaining is cOlIlpleted, fill the crack in the appliance with quick-curing acrylic resin. The plate now may be worn as a space-maintainer adjusting it to permit eruption of the cuspid and bicuspids. Details of construction and adjustment of this appliance are given in Chapter 18.
(b) Diagnosis.-Oiagnosis consists of two steps (I) identification and (2) classification into complete or incomplete transposition. Incomplete transpositions display crown misplacement only; complete transpositions involve the whple tooth. Incomplete transpositions left unattended may develop into complete, or nearly complete, transpositions. Radiographs taken at several angulations and, 'Careful palpation oLttre roots are essential to diagnosis and treatment planning. Do not delay, a diagnosis and concomitant treatment plan for these cases. If uncertain about either the diagnosis or how to proceed, refer at once to an orthodontist, for development worsens some incomplete transpositional problems.
(b) Maxillary Cuspids.-Maxillary cuspids may develop ectopically, in which case they may become impacted. 70 (See Section 0-4-b-4, Impaction of Teeth). Cuspids also are forced into ectopic eruption when there is insufficient space in the arch (see Section 0-4-a, Space Management).
(c) Treatment.-Early recognition in the eruptive path of the permanent retained primary tooth, opening space covering of the transposed permanent placement into position."
makes possible a change cuspid by removal of the in the arch, surgical untooth, and its orthodontic
Early Treatment
387
purpose, routine early radiographs are invaluable. Impacted teeth mayor may not be in ectopia (Fig 15-37): maxillary cuspids, for example, frequently are; mandibular second bicuspids seldom are. It is important to observe in each case whether the impacted tooth is also misplaced. (b) Mandibular Third Molars.-The clinical implications of third molar development and incisal crowding are discussed more thoroughly in Chapter 16, since adolescence is the age at which their prophylactic removal has been advocated. 32. 38.45 Two im-
FIG 15-36. Transposed maxillary cuspid and first bicuspid. When the cuspid is completely transposed, either from the start or neglect of the case, treatment to correct arch positions is far more difficult. 60 Leaving the teeth transposed is then sometimes a prudent alternative. However, all teeth must still be positioned well, and occlusal equilibration and shaping of crowns for esthetics is required. Individual conditions determine whether to treat to the normal or transposed positions (Fig 15-36).31 4) Impaction of Teeth.-Impactions are teeth so closely lodged in the alveolar bone they are unable to erupt. Unfortunate common misusage applies the term to any tooth that does not erupt. Although there are hereditary patterns leading to impacted teeth, the etiologic factors of most concern are malposed tooth germs, prolonged retention of primary teeth, localized pathologic lesions, and shortening of the length of the arch. Any tooth can be impacted, but the teeth involved most frequently are the mandibular third molar, maxillary cuspid, maxillary third molar, mandibular and maxillary second bicuspids, and maxillary central incisor, in that order. The cause varies greatly with the tooth. Thus, mandibular third molar impactions are said to be due largely to evolutionary changes whereas those of the mandibular second bicuspids usually are the result of space closure. (a) Diagnosis.-Impaction is diagnosed most frequently and easily when a tooth is long delayed in erupting, yet every effort should be made to make a diagnosis at an earlier date. For this
portant questions are as yet incompletely answered: (I) does the eruption of lower third molars cause incisal crowding? and (2) how does one predict the eruptive positioning of lower third molars? Although eruption of this tooth often is indicted as a primary cause of anterior crowding, one should remember that, even if its eruption is a factor, it cannot exert any effect until the patient is about 15 to 16 years of age. Most problems in crowding appear before this time. See Chapters 6 and 7 for discussions of current views on the role of mandibular third molars in"incisor alignment. Several methods for predicting the final position of a lower third molar from study of an earlier relationship have been advanced. Such an analysis, if accurate, would be very useful. Unfortunately, no method so far has been proven sufficiently valid, when tested on serial growth data, to recommend it for routine clinical use. Figure 15-38 illustrates the problems. The present methods, some of which are most ingenious, do not account sufficiently for several critical factors, for example, mandibular morphology. (c) Maxillary Cuspids.- This tooth may be simply impacted, as sometimes happens when the primary cuspid fails to resorb, or it may be impacted ectopically. When the case is a simple impaction, follow these steps: a) Measure the space available for the tooth. If insufficient, space must be gained as the first step in treatment. The size of the impacted tooth may be learned by measuring the cuspid on the opposite side of the arch or estimated by using the average width when the other teeth are average in size. b) Uncover the impacted tooth. Remove the primary tooth, if present, and carefully expose the crown of the permanent cuspid. The tendency is to uncover the cuspid crown insufficiently. 5. 10.71 To the portion of the crown exposed to the oral cavity a bracket
FIG 15-37. A, a maxillary cuspid impacted but not ectopic. B, maxillary cuspid both impacted and ectopic.
388
Treatment
FIG 15-38. Variability in the developmental position of third molars. A, favorable development. 8, unfavorable development.
or eyelet may be bonded and used to connect the tooth by elastic chain or steel ligatures to a labial archwire.9.59 Later, the bracket usually must be repositioned. Occasionally, the oral surgeon can selectively remove bone and gently reposition the impacted tooth, stabilizing it with surgical cement. 33 Several months of treatment time may be saved when this surgical repositioning is possible.20 Figure 15-39 illustrates cuspid impaction treatment. In recent years the advantages of autogenous transplantation of impacted maxillary cuspids has been appreciated and the surgical techniques have been perfected principally through the work of lames Moss43 and other clinicians in the United Kingdom. A brief discussion of this will be found in Chapter 16 since, though the transplantation can be undertaken at any age, it is more applicable at adolescence when full-bracketed orthodontic therapy is undertaken.
pacted or severely malposed; their repositioning at the earliest opportunity is usually advantageous. Study carefully the position of the crowns of the lower second molar in all cases as soon as possible and monitor its developmental changes carefully during treatment. When it is badly malposed, it may worsen when anterior teeth are extracted. It may be caught under the crown of the first molar and become more firmly locked in place if that tooth is uprighted or moved distally in mixed dentition space management. Usually second molar impactions may be freed rather easily if treatment is begun early (i.e. while active root development is under way). Special wire separating springs are sometimes used, but we usually prefer to insert a wire into a buccal tube on the first molar imbedding the distal extension in a mass of composite placed on any convenient surface. After the crown is somewhat uprighted and erupted, a compressed coil spring may be placed between the first and second molars (Fig ]';;-40). (Figure 16-5 shows the treatment methods and results of the case shown in Figure]
(d) Mandibular and Maxillary Second Bicuspids.-The impaction of these teeth is largely a matter of loss of arch perimeter. They will erupt spontaneously only if the molars are moved distally before the root length of the bicuspids is too advanced. After their roots are formed, they will no longer erupt spontaneously and traction must be applied. Figure 15-34 shows the problems that may arise when a primary molar is retained too long and an impacted lower bicuspid is brought to the occlusion after vertical alveolar development is mostly completed. (e) Second Molars.-Mandibular
second molars may be im-
"
5-40.)
-.
--#,".
if) Other Teeth.-When other teeth are impacted, the following principles should be held in mind when planning treatment: remove interferences to eruption before root formation is completed, hold sufficient space in the arch, and bring appliance forces to bear in a gentle manner. 5) Ankylosed Primary Teeth.-Occasionally, a primary molar fails to maintain itself at the level of occlusion (Fig 1541). This condition has been erroneously called "submergence."
Early Treatment
FIG 15-39. Orthodontic treatment of impacted maxillary cuspids.
FIG 15-40. Impaction of second molars. (See also Fig 16-5.) A, radiographs in the early mixed dentition. B, the same patient at age 14 years, 2 months.
389
390
Treatment
,
FIG 15-41. Ankylosed mandibular primary molars. A, typical examples. B, serial intra-oral radiographs. Note the progressive loss of occlusal height in the mandibular second molar region. All the other teeth grow vertically, but the ankylosed second primary molar cannot. C, serial casts of a patient with eight ankylosed primary molars. In the top
illustration
there is no evidence
of ankylosis.
No appliance therapy
was used, only the carefully timed removal of the primary molars to coincide with the rapidly developing eruptive period of their successor teeth.
Early Treatment Great variations are seen, and although many are of no practical significance, it is not unusual to see a primary molar buried beneath the cervix of adjacent teeth and partially covered by soft tissue. Investigators believe that most "submerged" teeth are anky losed to the alveolar process. Treatment is planned a's if all such primary molars were ankylosed. When a primary molar becomes ankylosed, there is a localized arrest of eruption and alveolar growth, adjacent teeth then proceed to greater occlusal heights. At times, first permanent molars tip mesially over the crowns of ankylosed second primary molars. In treatment, four possibilities must be avoided: (l) loss of the length of the arch; (2) extrusion of teeth in the opposite arch; (3) interference with the eruption of succeeding permanent teeth; apd (4) inhibition and permanent reduction of vertical alveolar bone development. Judicious use of space-maintainers and regainers is advisable. Never permit the presence of an ankylosed tooth to jeopardize the length of the arch. Should opposing teeth begin to extrude, the ankylosed tooth may be built up with composite resin to restore its occlusal height until it is time for it to be extracted. Some ankylosed primary molars cause no harm except possible eventual interference with the eruption of their successors-which may be avoided by timely extraction of the ankylosed teeth. Ankylosed primary molars may be left in place until the proper time for the eruption of the teeth beneath them. Extraction of each ankylosed primary molar is timed to coincide with the early stages of acceleration in eruption (see Chapter 6) as is done in space supervision (see Section D-4-a-4). Indeed; with careful supervision, ankylosed primary molars may serve as excellent maintainers of the length of the arch. Figure 15-41, B shows an interesting series of casts of a case with all primary molars ankylosed. Each ankylosed primary molar was extracted on a schedule permitting a normal sequence of eruption of the permanent successors.
391
FIG 15-43. A-F, example of dental crossbite treatment combined with space supervision. (Courtesy of Dr. William Northway.)
6) Ankylosed Permanent Teeth.-First molars are the permanent teeth most apt to become ankylosed. When an ankylosed permanent molar is retained into adulthood, the effects can be devastating, since local vertical alveolar growth has been inhibited. Two courses of action are available: (I) loosening and repositioning the tooth with forceps; and (2) extraction. Routine success with the loosening method should not be expected even when the tooth is retained by a complete orthodontic appliance. Still, one should first try loosening the tooth for the alternative, extraction, creates a major treatment problem. Figure 15-42 illustrates some of the problems of ankylosed permanent molars.
5. Lateral
Malrelationships
of Dental Arches
Failure of the two dental arches to occlude normally in lateral relationship, known as lateral or posterior crossbite, may be due to localized problems of tooth position or alveolar growth, or to gross disharmony between maxilla and mandible. It may involve one or more teeth in the lateral segments, and it may be unilateral or bilateral (Fig 15-43). Regardless of the cause or the severity of,the malocclusion, some neuromuscular adjustment of the mandible must occur to provide satisfactory function. Crossbites may originate in the dentition and alveolar process, the craniofacial skeleton, the temporomandibular musculature, or combinations of any of these (see Chapter 7). The importance of lateral mal reIationships in the etiology of some temporomandibular disorders must not be overloaded. FIG
15-42.
Ankylosis of permanent molars. Views of monozygotic twins, one with (A) and one without (B) an anklyosed permanent molar.
a) Differential Diagnosis The principal concern of the examiner is to localize precisely where the primary aberration lies. Is it confined to the maxilla?
192
Treatment
.1andible? Both? Does it involve only the alveolar process or is t a gross discrepancy in the "fit" of one jaw to the other? Is it lnilateral malpositioning of teeth or bilateral contraction of the ntire dental arch? Occlusal dysfunction and temporomandibular ymptoms often accompany early crossbite, so thorough examilation of the joints and their function is indicated (see Chapters 7 nd 10).
1) Dental Malrelationships.-Dental crossbite involves only he localized tipping of a tooth or teeth (see Fig 15-43) initially ausing little effect on the size or shape of the basal bone. Muscular ldjustments must be made to provide an adequate accommodative lcelusion. The midlines coincide when the jaws are apart and liverge as the te<;th come into occlusion. Some of the teeth in Tossbite will not be centered buccolingually in the alveolar pro:ess; therefore, the most important single diagnostic point is to ocalize asymmetry of the dentoalveolar arch.
2) Muscular or Functional Malrelationships.-"Muscular Tossbites" display functional adjustment to tooth interferences. [hey are similar to the dental cross bites except that muscular idjustment is more significant than mal positioning of teeth (Fig 5-44)27 A functional analysis of the occlusal relationship pro'ides both the differential diagnosis and identification of interfering eeth (see Chapter 11). There is no clear-cut differentiation between he dental and muscular types of crossbite except, perhaps, the reatment. In one (dental), teeth must be moved; in the other muscular), the occlusal adjustments can be gained by equilibraion, which permits reflex changes in mandibular positioning (see :hapter 18). The pure muscular type is seen most often in young :hildren. Both dental and muscular types require occlusal and nuscular adjustments to complete their correction. Although many nuscular crossbites are corrected solely with occlusal equilibraion, it is insufficient for some. For these, a lingual archwire
=IG 15-44. \ functional or muscular type of cross bite of the primary dentition. ~, intra-oral view. e, the casts before (above) and after (below)
designed for expansion (e.g., the Quad Helix archwire) is indicated (see Chapter 18). Figure 15-45 illustrates a case of functional crossbite treated by a combination of dentoalveolar expansion and equilibration. 3) Osseous or Skeletal Dysplasia (Skeletal Crossbite).Aberrations in bony growth and/or morphology may give rise to crossbites in two ways: (1) asymmetric growth of the maxilla or mandible; and (2) lack of agreement in the basic widths of the maxilla and mandible (Figs 15-46 and 15-47). Asymmetric growth of the maxilla or mandible may be the result of inherited growth patterns, trauma which impedes the normal growth on the affected side, or a long-standing functional mandibular displacement. Crossbites due to asymmetric bony growth are most difficult to treat, particularly when the condition has advanced untended for many years. The teeth are moved to provide the best possible occlusion in the circumstances, the maxilla is made wider by a palatal separating appliance, or, in extreme cas~s, orthognathic surgery is necessary at a later date. Lack of harmony between the maxillary and mandibular widths usually is due to a bilaterally contracted maxilla. In such cases, the muscles shift the mandible to one side to acquire sufficient occlusal contact for mastication (see Fig 15-46). For this reason, cross bites associated with skeletal dysplasia can be expected to have associated signs and symptoms of temporomandibular dysfunction. A more severe condition is that in which the mandibular denture occludes completely within the maxillary arch (see Fig 15-47). When this mediolateral problem is combined with a skeletal Class 11 malocclusion, it produced one of the most severe of all malocclusions (Fig 15-48). In mandibular hypertrophy and prognathism, the mandible is excessively 'wide for 'the maxilla as well as unduly long; therefore, a mediolateral occlusal problem exists in addition to the Class III malocclusion.
occlusal equilibration.
F
~
Early Treatment
393
FIG 15-45. A crossbite of the primary dentition treated by equilibration
and the use of a Porter ("w"- shaped) lingual appliance.
FIG 15-46. Maxillary dental arch contraction producing a functional crossbite. A, the cast placed so that the midlines are together, thus demonstrating
that the contraction
is bilateral.
seems to portray a unilateral
a, the
usual occlusal position, which
crossbite.
394
Treatment
FIG 15-47 . Osseous disharmony between the mandible and the maxilla, producing a typical bilateral skeletal-type crossbite. Often, in such cases, the mandibular teeth occlude completely inside the maxillary teeth.
FIG 15-48. (Legend appears on facing page.)
..
Early Treatment
395
.'
FIG 15-48. Case of severe mediolateral osseous dysplasia in conjunction with mandibular insufficiency. This boy was first seen for neuromuscular analysis when he was 2 years old. tie could eat nothing but "pappy" baby food and had not learned to chew. The }esults of the first phase of therapy, with an Activator, are shown in A-C (left, before; right, after). Note that although.there is now bilateral occlusal function, a severe Class I1 relationship remains. At this time, he could chew E, cephalogram of adequately. D, the original lateral tephalogram. patient at 9 years of age after first stage of orthodontic therapy with Activator. F, cephalogram of patient at 19 years, 0 months of age when all skeletal measurements were well within normal range for his age and sex.
396
Treatment
FIG 15-49. Method of using dividers to measure from the medium raphe to estimate asymmetries of the dental arch.
Study carefully the closure pattern of the mandible, noting at which stage of closure lateral deviations occur. When the lateral shifting occurs late in closure, it usually is the result of a tooth interference (see Chapter 10). If the deviation of the midlines of the lower and upper face increases throughout opening, the primary fault is likely to be skeletal asymmetry. In cases of bilaterally symmetric dental arches in each jaw with one arch grossly wider than the other, the patient may demonstrate several different closure paths and several ~cclusal relationships. Place the mandible so that the midlines of the upper and lower face coincide. Many patients who show a crossbite on one side only will thus exhibit bilateral dental arch contrac'tions (see Fig 15-46). One also may use a set of dividers on the dental cast for more precise localization of the asymmetrically placed teeth (Fig 15-49). A symmetrograph is also useful for analysis of crossbite (see Chapter 11). A posteroanterior cephalogra~ is a necessity in all but the most obvious and simple of the muscular and dental types of posterior crossbite. A cephalometric method for localizing skeletal and dental asymmetries is described in Chapter 12.
b) Treatment There is sound clinical research to support the earliest possible treatment of all posterior crossbites. (See Suggested Readings.) 1) Dental Crossbite (Individual Teeth).-(a) Case Analysis.-Rarely is one tooth alone tipped. In most cases, its antagonist in the opposite arch is out of position also. Thus, the maxillary first molar may be tipped lingually and the mandibular first molar is tipped slightly buccally, so both teeth must be moved. Always measure the amount of space into which the tooth is to be moved. Many individually malposed teeth are wider than the space for them in the arch. If such is the case, that space must be increased before the crossbite can be corrected. (b) Appliances.-Simpl~ through-the-biteela~tics (Fig 1550) are sometimes effective formolars in crossbite when both teeth are out of position and there is adequate space' for them: If the problem is largely a matter of tipping a single tooth rather than reciprocal tipping of two teeth, an acrylic plate with auxiliary spring· will serve well. Lingual archwires with recurved auxiliary springs also are satisfactory in some cases. 13 On occasion, a labial archwire is the most efficient. 2) Dentoalveolar
Contraction
and/or
Crossbite.-Cross-
bites in this category usually involve several posterior teeth (see Fig 15-46). ·(a) Case Analysis.-It
FIG 15-50. Diagram of through-the-bite elastics.
is important to learn how much of the
cond.it!on is due to actual dehtoalveolar contraction and how much to muse'ular adaptive positioning of the mandible (see Chapter 10). The more it is a matter of the mandible adopting a new position of closure for more efficient functioning, the better the prognosis. 30 If the midline.s ar:.~together when the pl!tient occludes in his or her accustomed position, there usually is very little muscular adaptation, and the case is purely one of narrowing of the maxillary alveolar arch (see Chapter 8). If the mJdlines are not together when the patient occludes in his or her accustomed position, some functional adaptation probably has taken place.
Early Treatment
397
FIG 15-51. A-F, use of the Quad Helix appliance for the correction of a cross bite in the early mixed dentition. "
(b) Appliances.-After locating any tooth interferences when the midlines coincide, remove by grinding those interferences involving primary teeth (see Chapter 18). In such cases, the primary cuspids are likely to be the offenders. Do not hesitate to grind contacting inclined planes on these teeth so that, as they meet, the mandible will tend to return to its normal position (see Fig 1544,B). When only the primary dentition is present, sometimes one' can correct minor problems by occlusal adjustment alone. •
•
•
1
Bilateral contraction of the maxillary arch.-For this condition, the Quad Helix lingual arch wire or Rapid Palatal Expander are excellent (see Chapter 18). Although these appliances may widen the osseous base, they may also move teeth and remodel the alveolar processes. Figure 1551 illustrates a case of this type. Unilateral contraction of the maxillary arch.- True unilateral contraction seldom is seen, which is fortunate, for it is more difficult to treat than when reciprocal action may be used. Gross unilateral maxillary development problems may be very difficult. The Quad Helix lingual wire may be adjusted for unilateral arch expansion. Mandibular dentoalveolar contraction.-Unilateral contraction in the mandible is rare. Bilateral narrowing caused by lingual tipping of teeth is well handled by a Quad Helix lingual archwire (see Chapter 18).
3) Gross Disharmony Between Osseous Bases.-(a) Case Analysis.- These cases are of two {ypes: those in which the maxilla is relatively narrow and those with excessive maxillary width and/or mandibular narrowness. In either the basic problem may be complicated by a skeletal Class II or Class III morphology. Sometimes the cast analysis alone makes obvious where the primary problem lies, but a posteroanterior cephalogram is still a necessity. If a Class 11 is present, it is important to complete the Class 11 cephalometric analysis to localize the anteroposterior dysplasia. Often the treatment of the mediolaterat osseous disharmony' is but the first step in a complicated treatment of skeletal Class 11. Whatever
the condition, early analysis and treatment is advantageous, since this condition is more difficult to handle when growth is largely complete. A functional wax bite aids in both the cast and cephalometric analysis (see Chapters 10-12). Careful cephalometric evaluation of the intermaxillary space in the mandibular postural position is revealing, for the correction utilizes vertical development of the alveolar processes. (b) Appliances. - When the problem is mediolateral maxillary insufficiency, the appliance of choice is the palate splitting device (see Chapter 18 for design). The Quad Helix appliance may be used in milder cases but it is more difficult to avoid excessive tooth tipping with it in severe cases. Figure 15-52 illustrates a case of maxillary narrownes~ in which the patient was treated at an early age with a palate splitting device. Figure 15-48 illustrates a case of marked mandibular insufficiency treated with ~ conventional activator because a Class 11 correction also was required. The improved anteroposterior relationship aided the mediolateral problem, and the vertical development of the alveolar processes was guided and controlled by the appliance. A Bionator or Activator with a built-in expansion screw (see Chapter 18) is favored by some. The primary goal, however, is usually not expansion of the mandibular basal bone, which is impossible, but the utilization of vertical alveolar development to widen the mandibular dentoalveolar arch diameter and to curtail width increases in the maxilla.
FIG 15-52. Rapid palatal expansion
treatment
in the early mixed dentition.
398
Treatment
6. Class 11 (Distocclusion,
Postnormal
Occlusion)
The term "Class n"* is an unfortunate generalization which groups together mal occlusions of widely varying morphologies often having but one common trait, their abnormal molar relationship. Angle can be easily forgiven, for as-his classification system was devised prior to the invention of cepljalometry and detailed knowledge of growth of the craniofacial skeleton. The Angle classification was a significant advance in orthodontics, but its continual simplistic misuse is unfortunate, particularly after the introduction of cephalometrics and the appreciation and delineation of a wide variety of types within "Class n." Class n is a common severe malocclusion. When combined with serious space management problems, it becomes a most difficijlt malocclusion to treat well. In Class n, secondary features of the malocclusion-that is, aspects other than the molar relationship and anteroposterior skeletal dysplasia-are important to the treatment plan. Vertical skeletal dysplasia, muscle dysfunctions, and space for alignment of teeth are frequent complicating factors in Class n. A vast literature on the diagnosis and treatment of Class II malocclusion presents many strategies of treatment, numerous appliances, and quite differing opinions about this malocclusion. The following pages constitute only a brief outline and are not intended in any way to suggest that all Class n mal occlusions should be treated routinely in general practice. However, as Class II is the most common severe malocclusion, every dentist must have a correct understanding and perspective of it whether the patients are treated or referred.
a) Maxillomandibular relationship anteroposteriorly. The profile is typically retrognathic or convex due to mandibular retrognathism, midface protrusion, or both; b) The cranial base. Increased length in the anterior cranial base contributes to midface protrusion, whereas increased obtusity of the cranial base angle or lengthening of the posterior cranial base will tend to position the temporomandibular articulation more retrusively; c) Vertical dysplasia. Anterior face height or critical portions of anterior face height often may be disharmonious with analogous posterior face heights. These disproportions may appear as abnormal positions of the palatal, occlusal, and mandibular lines. 2) Dental and Occlusal Malpositions.The dental aspects of Class n largely are adaptations to the skeletal and muscular pattern, although they may exist alone sufficiently exaggerated to produce Class n dental relationships in a balanced facial skeleton. The dental features must be studied in the cephal~gram (see Chapter 12), and the dental casts (see Chapter 11), as well as in the patient. Occlusal line malrelationships and vertical dentoalveolar abnormalities often are adaptations to the total skeletal dysplasia. •
a) Differential Diagnosis 1) Skeletal Morphology.-Because of the immense variability within Class n, it is illogical to treat all cases alike. Differential diagnosis is the basis for differential treatment. Therefore, diagnosis includes identification of the discriminating Class n features of the individual case to be treated. A cephalometric analysis is a necessity when diagnosing and planning treatment of Class II malocclusions, and it should provide localization and identification of the anatomic regions at fault to suggest individualized treatment prescriptions. The cephalometric methods described in Chapter 12 help locate the site(s) which contribute to the total malocclusion and aid in the classification of each case into a horizontal and vertical type. Typically, the variant skeletal characteristics are found in one or more of the following:
* The term "Class 11" will be used here in only the most general sense (see Chapter 10, Classification and Terminology of Malocclusion). Unfortunately, there is as yet no standard method of identifying and classifying the types of Class 11malocclusion except for Angle's Divisions I and 2, which are inadequate. The types described in Chapter 12 and later in Sections a, Differential Diagnosis, and e, Planning Differential Early Treatment of Class 11Malocclusions, are based on epidemiologic studies of a large sample of malocclusions designated by the orthodontists who treated them as "Class II." (See Moyers, Riolo, and Guire, Suggested Readings.) Procedures for discrimination of the several horizontal and vertical types in this class are described in Chapter 12. Differential treatment procedures based on typal differences of older patients are given in Chapters 16 and 17.
Incisors.-The upper and/or lower incisors may be tipped labially off their boney bases (see Fig 15-58). Labioversion of incisors is particularly evident when the posterior face height is less than the anterior face height, producing a steep occlusal line. When the anterior and posterior vertical heights are balanced and the midface is normal, the maxillary incisors are more likely to be normally inclined. Excessive overjet is a feature of some Class n types as is excessive depth of bite. The gross deviations in incisor relationships often result in the loss of functional incisal stops, permitting the incisors to erupt past the functional occlusal line.
•
Molars.-Mesial displacement of maxillary molars is a common finding in Class II (see Fig IS-56). Upper molars tip, rotate, and translate during mesial drifting, which contribute to an increase in the depth of bite. The more the maxillary posterior teeth have drifted mesially, the easier it may be to correct the overbite relationship by "derotating," distal tipping, and distal placement of the molars. Study the lateral cephalogram and maxillary cast carefully in order to identify the details of mesial positioning of maxillary posterior teeth. Cuspids.-The angulation and position of cuspids is a rediagnosis. Correlate the angulavealing feature of Class tion of the maxillary cuspid with possible mesial drifting of the molars and the angulation of the cuspids in both arches " .with the space analysis. " • 'Occlusalline.-The Functiot}al Occlusal Lin~ is an important reflection of the vertical skeletal features of the Class n type. Anteriorly, the failure of the incisors to form occlusal stops at the level of the Functional Occlusal Line often betrays the role of the tongue and lip in aggravating the incisal features of the malocclusion (see Fig IS-58).
•
n
3) Arch Form.-In
Class
n, the maxillary
arch is more likely
Early Treatment
399
to be narrow and elongated and thus disharmonious with the mandibular arch form (see Fig 15-56). Since coordination of the arches is an early and important part of Class II treatment, identification of arch form disharmonies is essential. 4) Neuromuscular ("Functional") Features.The neuromuscular features seen at diagnosis often seem to be largely adaptive to the skeleton and tooth positions typical of Class II malocclusion (Fig 15-56). But one must not discount too quickly the possible role of the neuromusculature itself in producing and maintaining the malocclusion (recall Chapter 7). The establishment of normal muscular function at the earliest possible time is a primary goal of all early treatment. Lip positions imposed by the fa~ial skeleton may cause increased labioversion of the maxillary incisors and/or lingual tipping of the mandibular incisors. In other instances, both upper and lower incisors are tipped off their bases. Since the lips and tongue must effect an anterior seal during swallowing and in the production of certain speech sounds, their efforts to do so in the presence of a skeletal dysplasia often result in some aggravation of the incisal relationships. A functional mandibular retraction is a common feature of Class II malocclusion in the primary and mixed dentitions. Though seen less often in the completed permanent dentition, it'is a common finding in adolescent and adult patients with temporomandibular difficulties. Therefore, all patients with Class 11 malocclusions must be examined especially carefully for temporomandibular symptoms and dysfunction. Other common neuro- . muscular factors which may accompany the Class 11 state are mouth-breathing and abnormal tongue activities. Carefully study Chapter 5, Maturation of the Orofacial Musculature, and Chapter 10, Analysis of the Orofacial Musculature, to understand and identify the neuromuscular features of Class 11.
FIG 15-54. Schematic drawing of response to functional jaw orthopedic treatment. (Courtesy of Professor van der Linden.)
b) General Strategies for Class
Il Treatment
Strategy is planning: in this instance, planning how to cope with a Class 11 malocclusion. If one's perceptions of Class II are incorrect or incomplete, it affects how one plans treatment. Also, if one has limited tactical resources and/or mastery of but one or two appliances useful in Class II treatment, then one is handicapped in planning therapy and able to treat only those malocclusions or those aspects of a mal occlusion in which a particular appliance does well. Since there are many complicated aspects to Class 11 malocclusion, a variety of clinical strategies have been developed. through the years. Some of the strategies listed are more appropriate for some Class 11 types than others. The time at which Class 11 treatment is begun is critical, and the strategies which can be employed depend on the age of the patient.
,/
1) DifferentiaI~estraint and Control of Skeletal Growth.The use of extra-oral traction to inhibit maxillary development is a frequent method of treatment of some types of Class 11 malocclusions (Fig 15-53).
,
• 2) Differential Promotion of Skeletal Growth.-Some within Class 11are characterized by mandibular insufficiency. nicians employ functional appliances to improve or promote dibular growth, affecting the size and shape of the mandible
types Climan(Fig
IS-54).
FIG 15-53. Schematic drawing depicting response to treatment of Class 11malocclusion by extra-oral traction. (Courtesy of Professor van der Linden.)
3) Guidance of Eruption and Alveolar Development.Malpositions of pennanent teeth may be the result of skeletal dysplasia, or the teeth may have been guided into malpositionsby the abnormal functioning of lips and tongue. During eruptive de-
/
400
Treatment
velopment the alveolar process must adapt to the skeletal dysplasia which characterizes Class H, often resulting in greater alveolar height anteriorly than posteriorly, narrowed maxillary alveolar arches, and other effects. The clinician may prevent excessive alveolar maldevelopment by guiding the erupt~on of the teeth and purposely controlling alveolar growth, and the permanent teeth often can be guided to better positions during eruption than they would have achieved untended. 4) Movement of Teeth and Alveolar Processes.-Lay persons often equate orthodontics with tooth movements. Dentists know that one does not move teeth through the bone, but that the roots of the teeth provide handles by which one can control and direct alveolar morphology (see Chapter 13). One of the most common strategies of orthodontic treatment is that of moving teeth to reshape the alveolar processes and provide better occlusion. Such tooth movements and alveolar changes are also used to camouflage serious skeletal dysplasias, particularly when skeletal growth is largely completed . 5) Translation of Parts During Growth.-lt is possible during growth to change physically the relationship of skeletal parts. A common procedure illustrates this point. Because a narrow maxilla is frequently found in Class H malocclusions, it is possible to use palate-widening devices which physically separate the midpalatal suture, moving the halves of the maxilla apart. The space created at the midline of the maxilla fills in with bone, and maxillary and mandibular growth then proceeds more normally than it otherwise would have done (see Fig 15-52 and Chapter 18). 6) Training of Muscles.-Abnorrnal muscle function is a frequent and important aspect of the Class H malocclusion and is often a prominent etiologic factor in its development. One of the primary purposes of functional appliances is to alter the reflex activities of the facial and jaw muscles. Myotherapy is often employed, adjunctively, in Class H treatment. 7) Surgical Translation of Parts.-On occasion the skeletal dysplasia is so severe that orthodontic treatmen! alone cannot correct the problem, and orthognathic surgery is then employed in conjunction with orthodontic treatment. Such surgical procedures are usually carried out in adulthood after growth is mostly completed (see Chapter 17). Because control of unfavorable growth is a prominent feature of Class Il strategy, it is obvious that the methods employed for early treatment are different than those used during adolescence, when skeletal growth is waning, and adulthood, when growth is most over. c) Tactics for Class II Therapy Strategy is planning; tactics involve management and execution. In orthodontic treatment, tactics means the use of orthodontic appliances, although this term also includes removal of etiologic factors and myotherapy. 1) Functional Appliances (Functional Jaw Orthopedic Appliances).-Functional appliances an~ employed to alter the neuromuscular environment of the developing dentition aJjd masticatory
muscles. They are also used to disarticulate teeth, to promote mandibular growth, guide the ,eruption of the permanent teeth, control alveolar development, etc. 2) Orthopedic Devices.-In orthodontic usage the word "orthopedic" conveys the idea of physically promoting changes in shape or position of the craniofacial skeleton. (a) Extra-oral Traction to the Dentition.-Extra-oral forces may be applied to control the position of the maxillary dentition, to restrain maxillary corpus growth forward, or to move the maxillary teeth distally. Similar extra-oral traction appliances are sometimes employed to move mandibular teeth as well. (b) Extra-oral Traction to the Chin.-Extra-oral forces are applied vertically by means of a chin cup to diminish anterior face height, a frequent feature of Class H malocclusion (vertical type I).
.'
(c) Palatal Widening.-Palatal-widening appliances are used to translate physically the maxillary halves in order to improve their positions and thus affect subsequent growth. 3) Bracketed Appliances.-Banded and bracketed orthodontic appliances are commonly used to improve the positions of teeth and to reshape the alveolar processes. 4) Muscle Training.-Myotherapy is a common adjunctive treatment tactic in Class 11 therapy. It should not be forgotten that functional appliances are efficient providers of myotherapy.
5) Surgery.-Orthognathic surgery offers immediate translation of parts of the severely dysgnathic craniofacial skeleton. Orthognathic surgical procedures have become highly developed and are an important part of orthodontic treatment for severe skeletal Class 11 problems, but their use is primarily limited to adulthood (Chapter 17). d) Rationale for Early Class II Treatment 1) Skeletal Morphology.The primary goal of early Class skeletal treatment is to achieve a m\'1re favorable skeletal morphology prior to the complete eruption of the permanent dentition. Therapy aims at restraint of midface growth, ,promotion of mandibular growth, widening of the maxilla, control of dentoalveolar: adaptation, or planned combinations of these strategies. The approach should be based_.more on the particular details of the patient's own skeletal morPhology than the appliance. As a rule, the more severe the skeletal dysplaSia, the more advantageous is early treatment. The vertical skeletal aspects of Class H, difficult to compensate for with tooth movements alone in adolescence, are improved in earlier years by controlling the basal skeletal growth and by differential management of the alveolar processes and occlusal plane. 11
Since there are distinct sexual differences
in the onset of the
pubescent growth spurt and in the cessation of craniofacial growth (see Chapter 4), the rationale for skeletal Class H therapy varies
401
Early Treatment with the sex: that is, girls generally ought to be treated earlier, in which case results are achieved sooner. Obversely, the tendency for craniofacial growth in men to continue past the second decade of life is a complicating factor irrespective of the time treatment was begun. Logic and the clinical research evidence now available support the use of early skeletal Class II treatment, since achieving a balanced skeletal profile prior to the eruption of most permanent teeth minimizes tooth movements, is less taxing to anchorage, diminishes actual treatment time, and reduces some kinds of relapse tendencies. 2) Dental and Occlusal Aspects.The first of the dental aims of early Class II treatment is to obtain normal molar and incisal relationships and establish normal occlusal function prior to the eruption of the cuspids, premolars, and second permanent molars (see Fig 15-56). If these aims are achieved in concert with skeletal correction, the arrival of the remaining teeth usually results in good occlusal function and an occlusal plane better related to the profile. Early reduction of excessive labioversion of incisors not only creates functional incisal stops, helping to control the occlusal plane, but also reduces the chances of their accidental fracture and improves esthetics and lip function. In Class II there often is disharmony between the upper and lower arch forms. Accordingly, a second dental aim is widening the maxillary arch form, thereby aiding incisal retraction, improving occlusal function, and easing anteroposterior skeletal correction and improving occlusal relations. Distinct sexual differences in the eruption of teeth and in the amount of space available for alignment of teeth (see Chapter 6) necessitate more critical early planning of treatment for girls. Exact protocols for early treatment of the dental features of Class II malocclusion vary greatly but include the following points differentially according to skeletal typal features: (\) distal rotation, tipping, and movement of the maxillary molars to correct the Class 11 molar relationship, a procedure that may open the bite and lengthen the maxillary arch perimeter; (2) restraint of the maxillary dentition while the midface grows forward, thus changing the relative position of the maxillary dentition to its base; (3) retraction and intrusion of maxillary incisors reducing the dentoalveolar protrusion, producing normal incisor function, and improving lip and tongue movements; and (4) control of the mandibular arch perimeter and fitting of the mandibular incisors to the skeletal profile, Functional Occlusal Plane, and maxillary incisors. Note that protocols 1-3 involve quite different treatment tactics than the midface orthopedics necessary for some skeletal Class 11types, though these may be undertaken simultaneously. 3) Neuromuscular Features.-Early treatment of the neuromuscular aspects of Class 11 malo~clusion is undertaken to establish a normal neuromuscular environment that will aid function and growth and neither aggravate nor distort the unfolding skeletal pattern (see Fig 15-57). Such therapy often consists of control of deleterious habits and treatment of the skeletal and dental features in order that normal neuromuscular function can obtain. Sometimes, in the primary dentition, the neuromuscular pattern is the dominant Class II theme, for example, nasorespiratory or airway problems, faulty posture, or deleterious sucking habits. The aims for treating the neuromuscular
features ?f Class \I in the mixed
dentition are similar; however, the permanent molars and incisors must be corrected, as a Class II muscle pattern already controls them (see Fig 15-57). In Class 11 malocclusions without severe skeletal features, correction of the dental symptoms alone may restore near-normal function of the muscles. In other cases, primarily those with a severe skeletal pattern, it is much harder to achieve adaptation and conditioning of the muscles, and myotherapy must be part of the mechanotherapy and continued throughout the retention period. This point underlies the rationale for the use of functional jaw orthopedic appliances in some cases, for these appliances aid in skeletal, dental, and neuromuscular correction simultaneously. The establishment of normal muscular function at the earliest possible age is one of the most important steps in treatment of Class II malocclusions.
.'
Il
e) Plllnning Differential Early Treatment of Class Most Class 11 mal occlusions are first seen by one's family dentist, who may prefer not to get involved in extensive or complicated Class 11treatment. This brief outline of Class II treatment is provided to give a general background and an understanding of the principles involved. It will aid in (I) the recognition and grouping of cases according to their significant differences, (2) referral as soon as the problem is recognized, (3) explanations to the parents and patients, and (4) cooperation with a colleague who might be treating the case. It is also intended to be of benefit in the selection of cases for treatment and in the recognition of the more difficult problems which may be referred. In the United States of America there has been an enthusiastic interest in Class II treatment by general dentists in recent years, a healthy development. Unfortunately, this new enthusiasm has been prompted largely by the promotion of appliances often without sufficient accompanying teaching of diagnosis and craniofacial growth. Inadequate training in craniofacial growth and orthodontic diagnosis in dental school leaves many at a disadvantage when evaluating the claims and promises of zealots. Orthodontists will appreciate the sketchiness of the discussion which follows. It makes no pretense of depth or detail and is intended only as a brief, but correct, orientation on standard clinical practice for the correction of Class 11malocclusion. It is intended primarily as an orderly introduction to the various concepts and strategies employed in treatment of Class 11. We define clinical Class \I types* for several reasons: a) To group cases with similar needs for ease in planning . . b) To locate the site(~).of skeletal imbalance.
'0 To estimate the effects of growth on the present imbalanced form. (Growth alone does not correct Class II; it often exacerbates the problem.) cl) To determine the best treatment for the special needs of a particular case. Many treatments may get by, but which is best?
*The cephalometric methods by which Class II types are identified are presented in Chapter 12 and should be studied closely for the understanding of this section.
402
Treatment
I TOTAL SPACE AVAILABLE Maxilla:
.'
Mandible: Right
~ e~h
Vd
~
Right Segments Lengths
e:
Arch
Segments
Lengths,. a' ------------11 .••
mm mm mm
h: g:f' Total:
c
b
Left Arch
Left
~.
T:tat.
~~~
;.
mm
::
TOTAL SPACE REQUIRED
('J.9
FIG 15-55. and space supervision.
MANDIBLE
MAXILLA
A-I, treatment of a Class 11type A malocclusion by extra-oral traction Incisor
(Courtesy of Dr. William Northway.)
widths
(measured) width of cuspids and bicuspids (predicted)
____
mm.
~mm.
~
mm.
~mm.
needed to achieve Class I occlusion of molars (estimated)
Estimated possibilities of increasing space available
+
so+ s:
0
~mm.
mm.
right maxilla: s: mandible:~_mm
0
left mm~O_mm ~.
S9.S-III.Q;
0
mm
G.!. S'(~)
"
1) Treatment of Horizontal Type A.-In Horizontal Type A malocclusion there is maxillary dental protraction with a normal skeletal profile (Fig 15-55) . (a) Basic Strategy.-The basic strategy in treatment is to retract the maxillary dentition to a normal molar and incisal relationship without altering the favorable skeletal relationship, displacing the mandibular dental arch, or disturbing the vertical dimensions.
•
•
(b) Suggested Tactics.Rotate, tip, and translate the upper first permanent molars without extrusion, using extra-oral traction to a face bow fitted to first molar bands. The angulation of the outer bow and direction of the pull are determined by the steepness of the occlusal line. Retract (tip .and translate) the upper incisors, intruding as necessary. Place brackets on permanent incisors only .
.I •
/
Early Treatment •
Fit the angulation and position of the maxillary incisors to the skeletal profile.
• •
Establish compatible upper and lower arch forms. Retain with conventional Hawley retainers.
(c) Common Problems or Complieations.-Only mild Vertical Type I or Type 2 features are ordinarily seen with horizontal type A. More severe vertical features complicate the picture and require different treatment. Mandibular space management problems (se~ Section 4-a) are treated on their own schedule. 2) Treatment of Horizontal Type F.-The characteristics ofthis type are mild skeletal Class II features accompanying Class II dental relationships (Fig 15-56).
(a) Basic Strategy.-Determine from the cephalometric analysis which of the four syndromal types (B, C, D, or E) the case most nearly resembles. Every horizontal type F is a mild version of either type B, C, D, or E. The vertical types are similar but milder too. Treat according to the tactics of the type. (b) Suggested Taeties.- There are no tactics special for Type F; in fact, success may come with the use of any standard method for correction of Class II malocclusions. The best results are obtained when the tactics are those of the related syndromal type (see below).
(c) Common Problems or Complieations.-Superposed space management problems are the most common difficulties. A gross space discrepancy greatly complicates matters requiring diphasic treatment (i.e., bands and brackets at a later age though the skeleton is corrected early). (d) Variations.-The variations seen are those of the syndromal types B, C, D, and E, but in milder form. (e) Retention.-Retention
is determined as "itis for the related
syndromal type. 3) Treatment of Horizontal Type B.-Type B characteristics are maxillary prognathism and midface protrusion, accompanied by a normal mandible (Fig 15-57).
a) Basic strategies.-The • •
403
in conjunction witb extraoral traction. If the maxillary incisors are flared and tipped labially, they should be retracted first. Often the mandibular arch is normal and the occlusal plane is flat. Under these circumstances little treatment may be necessary in the lower arch.
(c) Common Problems or Complieations.•
If the maxillary arch is narrowed, a preliminary phase of treatment involving maxillary expansion is necessary prior to the start of extra-oral traction·.
•
If there is an enhanced Curve of Spee, the upper arch must be leveled and the maxillary incisors placed in ideal positions (i .e., retracted and angulated properly prior to instituting extraoral traction). It is also necessary to band the lower molars and place brackets on the lower incisors, leveling and intruding the lower arch. These two steps control the overbite and overjet. • Like all other Class II malocclusions, those in Horizontal type B may be complicated by difficult space management problems. Space supervision in the lower arch may be car-" ried out concomitantly with the Class II correction in the maxilla. A gross discrepancy problem necessitates diphasic treatment; that is, serial extractions may be undertaken while extra-oral traction is correcting the mid face prognathism. Later, all the teeth must be bracketed and space closure and detailed tooth positioning completed. Type B constitutes a fairly common form of Class II and requires specific treatment emphasizing midface orthopedics. Harm can be done, especially in severe malocclusions, with improper or misapplied treatment. In adolescence the need for differential treatment is even more critical as there is less growth remaining to be controlled (see Chapter 16).
(d) Variations.-Horizontal Type B malocclusion is most frequently associated with Vertical Type 2, a skeletal deep bite with flat and nearly parallel occlusal and mandibular lines. The use of a maxillary extra-oral traction device with a flat bite plane (like that of the Cetlin or Sved appliance) is advantageous. Some employ <;ervical extra-oral traction assuming that the downward pull of the neck strap will open the bite. Vertical Types 4 and 5 are serious complications of horizontal type B which should be identified at the very start since they are quite complicated and difficult. Indeed, it is the author's opinion that the relatively rare Class II Type B-4 malocclusion may be the most difficult of all Class II problems.
basic strategies in treatment are:
To reduce dento-alveolar protrusion, if present. To produce orthopedic midface changes altering the maxilla's position relative to the mandible and the anterior cranial base.
b) Suggested Taeties.-Extra-oral traction to produce maxillary skeletal change is indicated for Type B patients, but mere distal movement of maxillary teeth is insufficient. Functional jaw orthopedic appliances are contraindicated. If the incisors are well placed, the Cetlin or Sved appliance may be used advantageously
(e) Retention.-In early treatment of Horizontal Type B, "~etention" means contr.Qlling the midface growth at least until theeompletion of the pe~manent dentition. Therefore, after the molar relationship has become Class I and the incisor relationship is normal, extra-oral traction may be continued and the case monitored until the arrival of the second molars. Severe Class II Type B cases, particularly in men and boys, may show persistent horizontal midface growth to the end of the second decade of life. Use of a traditional Hawley retainer under such circumstances may be quite insufficient. It is sometimes necessary to continue nocturnal extra-oral traction until the cephalometric analysis gives assurance that midface growth is over.
404
Treatment
FIG 15-56. A-D, treatment of a Class 11type F malocclusion,
(Continued.)
"
Early Treatment
02 Horizontal Measure
-3
MALE -ISO. X
-2
Md.Pl/A-B
3
ISO. 2 80
-3
-2
FEMALE ISO. 2 -ISO. X
3
85
Pol PI./A-B SE-FMN-A SNA
70
90
I
SE-N-A
I
70
---
90
1
I
Ba-Se-B
65
~a-Se-Gn
t60
801-
I
SNB
-------1
85 I
.JL 70 1
"
lIF.O.P.
l/Md PI
ES 03
CLASS
II PLOT,
HORIZONTAL
Skeletal Class O?
Nandiblll IMlrognolhic Mandibular ProcumlHtnl
.~ 1116'"
MO.lillory",'h P'OCumb,nl
+1-
+,-
5 0 ,
1 0 0 5 5 8 1211 332227 F[F[FeFeFcFCFoFo
N'697 Unclassified'
6 " 28 AAA
A
12
Incomplete Data· 25
"
FIG
15-56 (cont.).
405
406
Treatment
N'G9? Unclassified' 12 _. Incomplele Dolo' 25"<'
FIG 15-57. A-L, treatment of a Class 11type B malocclusion. William Northway.)
(Courtesy of Or.
CA 10-1
Early Treatment 4) Treatment of Horizontal Type D.~Horizontal type 0 malocclusion is characterized by mandibular insufficiency with maxillary dental protraction (Fig 15-58). basic strategies in treatment are intended to promote optimal mandibular growth, to reduce maxillary dentoalveolar protrusion and align the maxillary teeth, and to improve lip and facial muscle function.
(a) Basic Strategies.-The
(b) Suggested Tactics. - Type 0, the most frequent of the four syndromal types, lends itself well to early treatment with functional appliance therapy (Activator, Bionator, Frankel applians;e, etc.) since abnormal neuromuscular function is a characteristic feature. The mandibular lip and mentalis muscle are hyperactive-functioning beneath the maxillary incisors during the swallow and thus maintaining the mandibular incisors in an upright position. A properly constructed appliance restores normal lip and tongue function quickly while positioning the mandible ventrally to promote its growth, and, at the same time, improve maxillary dental features. Differential control of alveolar development levels the occlusal plane. Arch coordination is essential. (c) Common Problems or Complications.-When the maxillary arch is narrowed, it should be widened prior to the placement of the functional jaw orthopedic appliance. When the narrowness is not severe, a modified functional appliance with its own max- . illary widening device is sometimes sufficient. In more severe cases a Quad Helix or palate-splitting device is used in conjunction with bands and brackets to achieve coordination of upper and lower arch forms prior to the beginning of functional appliance therapy. In Vertical Type I cases in which the mandibular line and occlusal lines are steeper than normal, great care must be taken to prevent eruption of the maxillary molars, since this aggravates the vertical aspects of the case and interferes with the anteroposterior correction. Maintaining acrylic occlusal stops for the upper teeth and selectively grinding away the plastic to permit controlled eruption of the lower posterior teeth results io an improved and flatter occlusal plane. 'd) Variations.-For Vertical Type 2· cases the construction bite may be taken with more vertical opening than for types I and 3 in order to correct the skeletal deep bite by differential growth of ramus and alveolar process. In Vertical Type 3 the mandibular growth is treated as for Vertical Type I, but it is necessary to free the appliance to permit the extrusion and retraction of the maxillary incisors, for there is a strong tendency to open bite. The characterizing feature of Vertical Type 3 is inadequate anterior upper face height, so the open bite becomes worse as the lower face grows downward and forward. Functional appliances are usually insufficient to handle the problem alone. When Vertical Type 3 is unrecognized early or improperly handled, it will assuredly reveal itself later. Space management problems are treated concomitantly according to the development of the dentition. As in all gross discrepancy cases, if extractions are undertaken, bracketed appliances are necessary later for space closure, paralleling of roots, and final detailed esthetic placement of the incisors and cuspids.
407
(e) Retention.-Retention of Type 0 malocclusions, when treated early, consists primarily of guaranteeing that the improved mandibular growth persists; therefore, the functional appliance itself makes an ideal retainer. It is necessary to monitor craniofacial growth regularly at least until the completion of the permanent dentition (exclusive of third molars) and often even longer in boys.
4) Treatment of Horizontal Type C.-Horizontal Type C malocclusion is characterized by mandibular insufficiency, generalized small facial dimensions, and bimaxillary dental protrusion (i.e., both the maxilla and mandible are small and the teeth in both arches are off their bases). Horizontal Type C is more frequent among girls than boys.
a) Basic Strategies.- Type C Class 11 malocclusions are deceptively difficult to treat. Extra-oral traction seems contraindicated because of the retrognathic maxilla. Functional jaw orthopedic appliances are difficult to use because they may challenge the integrity of the mandi~ular dentition, which is tipped off its base. A high percentage of Type C Class 11 mal occlusions display inadequate space for all the permanent teeth. Because of the extreme labioversion of the incisors in both arches, analysis of space requirements must be done with great care, accounting for fitting of the incisors to the skeletal profile, a step which reduces each arch perimeter. Perhaps the most important strategy in early treatment 'of Type C is that of prompting optimal mandibular growth. When the skeletal profile has been improved, one must then reanalyze the space requirements. Unfortunately, one is not always able to synchronize skeletal correction and serial extraction of teeth in Type C as well as is possible in other malocclusions. Type C is a most difficult form of Class 11, and treatment at any age is not to be undertaken lightly, for there is so much that is abnormal, and so many features to control and change. (b) Suggested Tactics.-In the early mixed dentition a functional jaw appliance may be used to improve the skeletal profile and vertical dimension. If extractions are a foregone conclusion, they may be undertaken serially according to the schedule of dentitional development. In borderline extraction cases, the space requirements must be reanalyzed as the skeletal profile and vertical dimensions improve. Do not expect Type C cases to show remarkable improvement in space requirements with skeletal treatment. Do expect a high percentage to require extractions, and all will require bracketed appliance therapy ~ubsequent to the functional jaw therapy. " Class 11 Type C 11Jl\locclusions require a panoply of sophisticited orthodontic diagnostic and technical skills for their treatment. Early maltreatment may' intensify the problem, making correction even more difficult. These are difficult cases to conclude satisfactorily,
even for the most experienced clinician.
(c) Common Problems or Complications.- The most common complication in treatment of Type C Class 11 malocclusion is that of difficult space 'management, even after extractions. Type C cases are difficult to treat early and even more arduous to treat during adol~scence (see Chapter 16).
408
Treatment
. Horizontol Measure
MALE -3
-2
-IS.o. X
FEMALE
lSD
2
3
-3
I I1
MdPI/A-B Pal PL/A-B ______
eo
j:l
I I
1
85
-2
-ISH X
lS.o. 2
3
I
60
90
85 I
95
1
I
SE-FMN-A
I
85
SNA SE-N-A
I I
Ba-Se-B Ba-Se-Gn SNB
----I
---
80 I
--L
85 I
l
I 60
70 !
lIFOP l/Md PI.
65
FIG 15-58. A-C, treatment of a Class 11type 0 malocclusion. (Continued.)
20
Early Treatment
CLASS
Skeletal
n: PLOT,
HORIZONTAL
A
Class II.'" 1 1 1
Mid-face Prognathic?
1 1 1 1
Mandible Retragnathic .?
1
1
I
Mandibular teeth Procumbent Maxillary teeth Procumbent
1 1 1 1
+1-\ +,-
+,-
1
I 1
5 0 1 429402654275766119719194711 E (El B+ B C+ C 0+
N=697 Unclassified Incomplete
=
1 00 F F
5 5 81211
3322276
1128
FE FE Fe Fe FC FC Fo Fo A A A
A
LH 9-10
12
Data
0 F F
=
25
FIG 15-58 (cont.).
409
410
Treatment
(d) Variations.-Vertical Type 2 appears three times as frequently as Type I in Horizontal Type C malocclusion. This is in contrast to Types D and F, in which Vertical Types and I and 2 appear with about equal frequency (see Table 12-3). (e) Retention.-The complicated details and variations of Class II Type C retention are many. Functional appliances are sometimes combined with precision bracketed therapy and the appliances are subsequently continued as retainers. 6) Treatment of Horizontal Type E.-This type is characterized by maxillary prognathism and bimaxillary dentoalveolar protrusion.
(a) Basic Strategies.-Horizontal Type E malocclusion is most closely related to Horizontal Type B and may be thought of as bimaxillary dentoalveolar protrusion within a Type B skeletal pattern. North American blacks, when they display Class 11 malocclusions, are more apt to show this type than any other. The needs of the skeletal profile should dominant the choice of strategies in early treatment. Extra-oral traction to control midface growth and retract the maxillary dentition is the basic strategy; however, the space needs of the mandible and the labioversion of mandibular incisors greatly complicate matters. Accordingly, one is more apt to resort to extraction in both arches in TypeE than in Type B. (b) Suggested Tactics.-When Horizontal Type E is treated, extra-oral force is applied to the maxillary dentition and the maxilla as in type B and an attempt is made to position the mandibular incisors correctly over basal bone. When there is insufficient room for all the teeth, the skeletal correction may be combined with serial extraction and the case treated as if it were a Type B gross discrepancy problem. (c) Common Problems or Complications.-The two most common problems in Horizontal Type E are skeletal deep bite and bimaxillary dentoalveolar protrusion. Early treatment provides a better chance to combat the skeletal vertical dysplasia, but extensive work after all the permanent teeth are erupted may still be necessary to position the teeth properly. One should expect, when beginning early treatment of Type E, to have a necessary period of bracket therapy later, for early treatment, while greatly improving the skeletal aspects, certainly is not total treatment. The lip and facial musculature often present complications in treatment planning.
III
(Mesioclusion, 7. Class Pseudo Class
III
e) Retention.-Retention problems include monitoring the skeletal Class 11 growth pattern, maintaining the final tooth positions, and preventing the reappearance of the vertical dysplasia. Retention is particularly difficult if maxillary growth persists, as it sometimes does in boys, who constitute the majority of patients within this type.
Occlusion)
and
Three rather distinct types of malocclusion may all appear to be mesioclusions (Fig 15-59). True Angle Class Ill, or mesioclusion, is a skeletal dysplasia involving mandibular hypertrophy, marked shortening of the midface, or a combination of these two. The pseudo-, or apparent, Class III is a positional malrelationship; a reflex functional mandibular protraction. A third condition, simple linguoversion of one or more maxillary anterior teeth, is an abnormal axial inclination of maxillary incisors with no real Class III features. It will be noted that the first condition is a problem of skeletal morphology and osseous growth, the second an acquired muscular reflex, and the third a problem in dental positioning. In all three conditions, the maxillary anterior teeth are back of the mandibular, but only the first two show the mandibular molars ahead of their normal position. Linguoversion of maxillary anterior teeth is a Class I (neutroclusion) malocFlusion discussed later in this chapter (see Section 9, Anterior Crossbites, ~imple). The first two are discussed together here for clarification of the differential diagnosis .. ~
a) Differential Diagnosis 1) Patient Examination.The differentiation of true and pseudomesioclusion requires a precise examination of the patient for the following items.
(a) Profile.-Study the profile carefully for evidence of the effects of the skeletal dysplasia on the soft tissues and facial musculature. The lip relationship during occlusion and mandibular posture is particularly revealing, for the profile improves as the mandible drops from occlusal contact relationship to the postural position only for the pseudo-Class III patient. Skeletal Class III cases are more likely to have an even anteroposterior pattern of closure. Translation of the mandible forward in pseudomesioclusion can be confirmed by gently placing the fingertips over the temporomandibular
joint during .opening and closure.
(b) Molar Relationship.-Note the relative positions of the first molars both in occlusion and in the postural position. •
True mesioclusion.-A
distinct Class III relationship per-
sists in both positions.
•
Pseudomesioclusion.-There
is apt to'be a shift from a Class I to a Class III relationship as the mandible closes
, (see Fig l5-61) .•
(d) Variations.-Vertical Type 5, sometimes seen, is much more difficult to handle than Type 2.
Pre-normal
~.
Manipulate the mandible posteriorly to ascertain if it is possible to assume a more normal relationship with the maxilla. One also should use articulation paper to locate points of occlusal contact and interference. Read carefully the section on crossbites, for pure pseudomesioclusions are in reality anterior cross bites sometimes involving maxillary narrowness plus an occlusally prompted forward positioning of the mandible. Mild cases of skeletal Class III may have a functional element, particularly in young children; therefore, the cephalometric analysis is critical.
Early Treatment
411
A
FIG 15-59. Three kinds of Class Ill. A, midface deficiency, 8, mandibular prognathism, C, midface deficiency and mandibular prognathism. The values shown are maxillary skeletal and dentoalveolar length and mandibular skeletal and dentoalveolar length (see Chapter 12, Counterpart and Profile Analyses). Numbers in parentheses are appropriate age and sex norms. Comparisons to these norms helps localize the primary site of the disproportion. Note the difference in the three types when compared to the norms.
5.5. 11-2'
"
G.M, 11-8
412
Treatment
2) Cephalometric Analysis.The purposes of the cepha-' lometric analysis (see Chapter 12) are (I) to separate pseudo from true Class III malocclusions, (2) to identify the specific morphologic features of any skeletal dysplasia, since discriminate characteristics determine the specific strategies and tactics of treatment, and (3) to ascertain the relative importance of skeletal and functional features when they are combined. The cephalometric analysis, more than any other single diagnostic procedure, aids in determining the timing of treatment and indicates the choice of appliances. Obtain lateral cephalograms in the usual occlusal (intercuspal) and postural positions, as well as the posteroanterior view. The cephalometric analyses referred to in this section are described in Chapter 12. (a) Basic Morphologic Analysis. -This screening analysis (see Chapter 12) helps one to localize the sites of skeletal dysplasia. If the maxillo-mandibular relationship is near normal, and all other measures are within one standard deviation of the mean, a severe skeletal Class III is not present. Further analysis is required if any single measure is over one stanclard deviation in the Class III direction or if the combination of cranial base-maxilla and cranial base-mandible
measures together show anteroposterior
c1usal Line. Face height measures are more apt to be normal with midface deficiency than with mandibular prognathism, although anterior upper face height and anterior maxillary height sometimes are often mildly deficient. (b) Mandibular Prognathism.-Patients with mandibular prognathism show a Class III maxillo-mandibular relationship, an excessive cranial base-mandible dimension both horizontally and vertically, and may show a diminished cranial base angle. The Profile Analysis reveals unit distance ratios significantly less than 1.0, because both the mandibular skeletal unit distance and mandibular dentoalveolar unit distance are excessive. In severe cases, the maxillary dentoalveolar unit distance may also be excessive as the maxillary teeth tip labially to obtain function with the mandibular incisors which have been carried forward by the excessive mandibular length. The Vertical Analysis is critical in mandibular prognathism. Anterior face height is usually excessive when compared with posterior face height, and lower face height is quite abnormal anteriorly. Mandibular prognathism is sometimes seen without excessive anterior face height (i.e., the mandibular border is not steeply positioned).
dysplasia.
(b) Profile Analysis, Skeletal.-The Profile Analysis (see Chapter 12) enables one to localize skeletal and dentoalveolar contributions to the Class III profile. Tables of growth mejlsures are provided at the end of Chapter 12 to support the profile analysis. They also aid in assessing the effects of growth and treatment on the correction. (c) Vertical Analysis.-The Vertical Analysis is often critical in skeletal Class III since it reveals dentoalveolar adaptations to the basic skeletal pattern. By use of the tables of vertical growth measures at the end of Chapter 12, help is provided in assessing the response to therapy. 3) Pseudo Class I1I.- The pseudo Class III shows normal values for the Basic Morphologic Analysis, when one has discounted the functional mandibular translation, which may be done by taking the lateral cephalogram with the mandible withheld to the retruded contact position by a wax bite in situ. Mildly deficient values for the maxillary dentoalveolar unit distance may be seen in the profile analysis, and the maxillary incisors may be more upright than normal. The vertical analysis will be uormaL 4) Skeletal Class I1I.- There are three basic categories of skeletal class III malocclusion: midface deficiency, mandibular prognathism, and a combination of the'two (Fig 15-59).
,
(a) Midface Deficiency.-In the Basic Morphologic Analysis, patients with Class III midface deficiency display a Class III maxillo-mandibular relationship, a diminished cranial base-maxilla value, and normal cranial base-mandibular values. The profile analysis usually shows shortened maxillary skeletal unit and maxillary dentoalveolar unit distances. The mandibular skeletal, unit distance is near normal, but the mandibular dentoalveolar unit distance may be slightly above normal. The Vertical Analysis usually shows a normal Mandibular Line and' a near normal Oc-
(c) Midface Deficiency and Mandibular Prognathism.-Some patients show a combination of mild midface deficiency and mild mandibular prognathism, for which treatment differs from that required by either the pure midface deficiency or mandibular prog, nathism. The prognosis usually is not as poor as for the serious mandibular prognathism. b) General Strategies for Early Treatment Treatment strategies for the three types of Class III malocclusion are quite clear and different. For pseudo-Class Ill, one's aim is to obtain normal dental and occlusal relationships by prompting a normal neuromuscular environment for a normally developing craniofacial skeleton. Cases of skeletal Class HI with midface deficiency require midface orthopedic traction to promote maxillary growth forward to match a more normally placed mandible. Patients with mandibular prognathism must have the excessive mandibular growth restrained and/or redirected. Cases combining the features of midface deficiency and mandibular prognathism require combined strategies. c) Rationale for Early Treatment \.\!. ~\\\\~ ~\~~.\ \\Q\l\\ ~\\.Q\l\\\\~\\\.~\ \\ \~ lhe te~ea.tch e\l\.d\O\\~\O possible to alter the growth of thecraniofacjal skeleton in early Class III conditions (see Fig 15-62). These treatment procedures require thorough knowledge of craniofacial growth and considerable.skill in manipulatini'a variety of functional and orthopedic appliances. Current treatments are more successful and satisfying than those done previously, and the number of patients requiring orthognathic surgery in adulthood has been greatly diminished.
d) Tactics for Early Treatment 1) Pseudo-Class I1I.-In the early dentition, the patient sometimes can be treated by equilibration alone (see Chapter 18) or by the placing of an acrylic inclined plane on the mandibular
/' 412
Treatment
2) Cephalometric Analysis.The purposes of the cephalometric analysis (see Chapter 12) are (I) to separate pseudo from true Class III malocclusions. (2) to identify the specific morphologic features of any skeletal dysplasia, since discriminate characteristics determine the specific strategies and tactics of treatment, and (3) to ascertain the relative importance of skeletal and functional features when they are combined. The cephalometric analysis, more than any other single diagnostic procedure, aids in determining the timing of treatment and indicates the choice of appliances. Obtain lateral cephalograms in the usual occlusal (intercuspal) and postural positions, as well as the posteroanterior view. The cephalometric analyses referred to in this section are described in Chapter 12. (a) Basic Morphologic Analysis. -This screening analysis (see Chapter 12) helps one to localize the sites of skeletal dysplasia. If the maxillo-mandibular relationship is near normal, and all other measures are within one standard deviation of the mean, a severe skeletal Class III is not present. Further analysis is required if any single measure is over one stanoard deviation in the Class III direction or if the combination of cranial base-maxilla and cranial base-mandible
measures together show anteroposterior
clusal Line. Face height measures are more apt to be normal with midface deficiency than with mandibular prognathism, although anterior upper face height and anterior maxillary height sometimes are often mildly deficient. (b) Mandibular Prognathism.-Patients with mandibular prognathism show a Class III maxillo-mandibular relationship, an excessive cranial base-mandible dimension both horizontally and vertically, and may show a diminished cranial base angle. The Profile Analysis reveals unit distance ratios significantly less than 1.0, because both the mandibular skeletal unit distance and mandibular dentoalveolar unit distance are excessive. In severe cases, the maxillary dentoalveolar unit distance may also be excessive as the maxillary teeth tip labially to obtain function with the mandibular incisors which have been carried forward by the excessive mandibular length. The Vertical Analysis is critical in mandibular prognathism. Anterior face height is usually excessive when compared with posterior face height, and lower face height is quite abnormal anteriorly. Mandibular prognathism is sometimes seen without excessive anterior face height (i.e., the mandibular border is not steeply positioned).
dysplasia.
(b) Profile Analysis, Skeletal.- The Profile Analysis (see Chapter 12) enables one to localize skeletal and dentoalveolar contributions to the Class III profile. Tables of growth me)lsures are provided at the end of Chapter 12 to support the profile analysis. They also aid in assessing the effects of growth and treatment on the correction. (c) Vertical Analysis.- The Vertical Analysis is often critical in skeletal Class III since it reveals dentoalveolar adaptations to the basic skeletal pattern. By use of the tables of vertical growth measures at the end of Chapter 12, help is provided in assessing the response to therapy. 3) Pseudo Class III.- The pseudo Class III shows normal values for the Basic Morphologic Analysis, when one has discounted the functional mandibular translation, which may be done by taking the lateral cephalogram with the mandible withheld to the retruded contact position by a wax bite in situ. Mildly deficient values for the maxillary dentoalveolar unit distance may be seen in the profile analysis, and the maxillary incisors may be more upright than normal. The vertical analysis will be normal. 4) Skeletal Class III.- There are three basic categories of skeletal class III malocclusion: midface deficiency, mandibular prognathism, and a combination of the two (Fig 15-59). (a) Midface Deficiency.-In the Basic Morphologic Analysis, patients with Class III midface deficiency display a Class III maxillo-mandibular relationship, a diminished cranial base-maxilla value, and normal cranial base-mandibular values. The profile analysis usually shows shortened maxillary skeletal unit and maxillary dentoalveolar unit distances. The. mandibular skeletal. unit distance is near normal, but the mandibular dentoalveolar unii distance may be slightly above normal. The Vertical Analysis usually shows a normal Mandibular Line and a near normal Oc-
(c) Midface Deficiency and Mandibular Prognathism.-Some patients show a combination of mild midface deficiency and mild mandibular prognathism, for which treatment differs from that required by either the pure midface deficiency or mandibular prognathism. The prognosis usually is not as poor as for the serious mandibular prognathism. b) General Strategies for Early Treatment Treatment strategies for the three types of Class III malocclusion are quite clear and different. For pseudo-Class Ill, one's aim is to obtain normal dental and occlusal relationships by prompting a normal neuromuscular environment for a normally developing craniofacial skeleton. Cases of skeletal Class III with midface deficiency require midface orthopedic traction to promote maxillary growth forward to match a more normally placed mandible. Patients with mandibular prognathism must have the excessive mandibular growth restrained and/or redirected. Cases combining the features of midface deficiency and mandibular prognathism require combined strategies. c) Rationale for Early Treatment The research evidence is quit~ clear now, showing that it is possible to alter the growth of the craniofacial skeleton in early Class III conditions (see Fig 15-62). These treatment procedures require thorough knowledge of craniofacial growth and considerable. skill in manipulatinfa variety of functional and orthopedic appliarices. Current treatments are more successful and satisfying than those done previously, and the number of patients requiring orthognathic surgery in adulthood has been greatly diminished.
d) Tactics for Early Treatment 1) Pseudo-Class I1I.-In the early dentition, the patient sometimes can be treated by equilibration alone (see Chapter 18) or by the placing of an acrylic inclined plane on the mandibular
Earry Treatment
incisors (see Fig 15-66). The inclined plane acts as an extension of the lower incisal edges contacting the lingual surfaces of the maxillary anterior teeth. On closing, the mandible is forced to be retruded, and the maxillary anterior teeth, if they are tipped lingually, will be moved labially. The bevel of the appliance should be ground very carefully so that all teeth contact is even and the load well distributed to avoid trauma. The appliance may be cemented into position with a stiff mix of zinc oxide and eugenol and removed by slicin& the acrylic with an abrasive disk. Do not worry about the large posterior open bite when the appliance is first inserted; it soon closes when the incisors are corrected. Periodic observations may show that occlusal grinding is necessary to keep the load evenly distributed and to avoid the introduction of unwanted new closure patterns. Prescribe a semisolid diet for
413
the short period of treatment (usually only about I week). If marked improvement is not seen quickly, the case should be reassessed, for the original diagnosis probably was erroneous. This appliance is sometimes presented to the profession with too much enthusiasms. It has but limited use, but in a selected few cases it is advantageous. In the mixed dentition, make doubly sure of the diagnosis before proceeding. A maxillary labial archwire may be used alone or in conjunction with the mandibular inclined plane. Again, failure to achieve quick improvement likely means a misdiagnoSis. Remember that the continual thrusting forward of the mandible and the locking of the teeth in pseudomesioclusion can only result in eventual perversion of the growth pattern of the facial skeleton and the eventual appearance of mild Class III skeletal features. Thus, the
c
E
'ts 15
FIG 15-60. Neuromuscular type of Class III malocclusion. A, at age 8, treatment was by occlusal equilibration alone. B, the harmonious result obtained in a few days. C, the patient's postural position at the start of treatment. 0, the patient's usual occlusal position, showing the functional mandibular protraction. E, the improved occlusal position ob-
tained
after occlusal
equilibration.
F, 9 years
after the occlusal
eql:Jilibration. No other orthodontic therapy was undertaken. Obviously, this patient has a mild skeletal Class III problem, but the occlusal equilibration at the right time prevented the problem from becoming more complicated.
414
Treatment
older the patient the more difficult and lengthy the treatment. Steps in treatment Fjrst locate and remove all tooth interferences. This may involve grinding of primary teeth or moving interfering permanent teeth. Do not grind permanent teeth in the mixed dentition period for this purpose, since the areas removed may be needed later for occlusal stability after the positions of the teeth have been altered by growth. Arch coordination' should be achieved as soon as possible, lest the buccolingual malrelationships may inhibit and constrict maxillary growth. Treatment is more difficult in the mixed dentition than in the primary, the prognosis is less favorable, and the results are not so dramatic. Nonetheless, if the case is one of pure pseudo-mesioclusion, the results usually are satisfactory. Figure 15-60 illustrates a case of this kind treated successfully when the patient was 8 years of age. 2) Midface Deficiency.-When mild midface deficiency is diagnosed in the primary or very early mixed dentition, I prefer to use the Frankel Function Regulator-Ill (FR-Ill; see Fig 18-44). In the mixed dentition the FR-Ill appliance may also be used
for mild midface deficiency cases, however, for the more serious problems the De Laire face mask is preferred (see Chapter 18). Striking results may be obtained with this device-which translates the maxilla forward, improving the skeletal profile, and seems to have a mild restraining influence on mandibular growth (Fig 1561). 3) Mandibular Prognathism.-Patients with mandibular prognathism require appliance therapy that is quite different from that used for midface deficiency. While some advocate FR-Ill therapy for these problems, Graber has reported that chin cup treatment utilizing heavy extraoral tractions rotates the mandible posteriorly, decreases the gonial angle, restricts vertical condylar growth, and causes the corpus of the maxilla to rotate slightly clockwise. The result is an improvement in the A-B relationship of the skeletal profile, maintenance of the Mandibular Plane Angle, and change in the articular angle and in the orientation of the ramus to the cranial base (Fig 15-62). Woodside reports success with the Activator-showing similar effects horizontally but transferring some of the expected mandibular horizontal growth in a more vertical direction. With either chin cup or activator therapy the dentoalveolar development is altered both vertically and horizon-
FIG 15-61. A-K, treatment of Class
I1
midface deficiency in the mixed dentition. (Courtesy of Dr. William Northway.)
Early Treatment
c
B
A A
•.•
.
415
-0
10
__
UnloadedCondyles
___
loaded
Condy1es
09
o
08 07
06 \\~
"o--
6.~'" ~"" "'0·,,····0
_--.
Untreated
Class III
o ..···.{)·
Untreated
Class 111 Nine Years
Six Years
*-. 0---0
05
~~ o!_:----~
0'
-"'1ft> , 09,
" "
03 02
--"'~-~ Untreated
Class
Treated
Class III
0'
111 . SIX Years
Nme Years
,
TIME IN ,""fEKS
SKELETAL
CLASS
SKELETAL
ID
UNTREATED (CHANGES BETWEEN SIX AND NINE YEARS)
CLASS ill
CHIN-CAP TREATMENT (CHANGES BETWEEN SIX AND
NINE YEARS)
SNB ANGLE INCREASES
1
ANB ANGLE
2.
ANB ANGLE INCREASES
MANDIBULAR PLANE ANGLE DECREASES
3
MANDIBULAR CONSTANT
4
ARTICULAR ANGLE DECREASES
4.
ARTICULAR ANGLE INCREASES
5
RAMUS HEIGHT INCREASES SUBSTANTIALLY
5
RAMUS HEIGHT INCREASE SUBNORMAL
DECREASES
SNB ANGLE DECREASES
FIG 15-62. A-C, responSe of mandibular prognathism to extra-oral chin cup therapy. (From Graber LW: Chin cup therapy for mandibular prognathism. Am J Orthod 1977; 72:23-41. Reproduced by permission.)
PLANE ANGLE
tally in order that alveolar process adaptations may help mask the skeletal dysplasia (Fig 15-63).
4) Midface Deficiency and Mandibular Prognathism.Skeletal Class III patients showing both midface deficiency and mandibular prognathism often are less difficult to treat than patients with mandibular prognathism alone, since some improvement may be obtained in the midface by face mask therapy, and some in the mandible by either chin cup or functional appliance therapy. Devices which combine chin cup traction and midface protraction are appropriate for these cases.
prove the vertical morphology and aid in leveling the line of occlusion (see section D). a) Diagnosis
This condition must be carefully differentiated from a skeletal Class 11, Division I malocclusion in which the lower teeth may have drifted forward, causing anterior crowding yet maintaining a Class I molar relationship.
b) Treatment 8. Labioversion of Maxillary Ineisors (Excessive Overjet) With Class I Molar Relationship This condition seems similar to a Class n Horizontal Type A malocclusion, since the anterior teeth of the maxilla are in labioversion; the maxillary posterior teeth, however, remain in Class I. There is a good facial skeletal morphology or a Class n molar relationship would have resulted. The cause may have been a thumb- or finger-sucking habit so the condition may be accompanied by an open bite and maxillary narrowness. It also is found with a deep overbite owing to overeruption of the mandibular incisors. Though the overbite may not be as severe as is sometimes seen in Class n, Division I, this is not a condition to be taken lightly. The following discussion focuses on cases without a marked Curve of Spee. Cases with a marked Curve of Spee and an impinging overbite are much more severe and must be treated by a multibanded appliance to level the occlusal plane, intrude, torque, and retract the incisors. Such tooth movements shorten the arch perimeter, further complicating the case. Banded therapy may be preceded or accompanied by use of a functional appliance to im-
If there is an active tongue-thrust, abnormal tongue posture, or finger-sucking habit, the first step in treatment is correction of the habit. A Hawley retainer is most unsatisfactory for treatment of this malocclusion, though it is often used. A primary problem is the damage done to the palatal gingivae by the appliance and the lower incisors when the plastic is cut away to permit maxillary incisal f retraction. Another appliance sometimes recommended is the oral shield, though its range of utility is quite limited (Fig 15-64). Use of the oral. shield helps correcC'abnormal lip and sucking habits while utilizing lip force to move the maxillary anterior teeth lingually. It provides no vertical control of the incisors. The oral shield is not indicated for treatment of any kind of distoclusion. A functional appliance, such as a Bionator, Activator, or Function Regulator-I, are efficient for these cases during the transitional dentition since they control abnormal lip and tongue activities while retracting the maxillary incisors and helping level the occlusal curve as the permanent posterior teeth erupt. Molar bands and bracketed incisors in each arch can effect an efficient correction of these problems in the late mixed dentition.
416
Treatment
"
E BEFORE -AFTER _n_
FIG 15-63, Treatment of Class III malocclusion.
A and 8, before treatment.
C
and D, after treatment. This patient was treated with a Monobloc (Activator) appliance. (Courtesy of Or. Ross O. Fisk, Department of Orthodontics, Faculty of Dentistry, University of Toronto). E, cephf
alometric tracings of a Class III patient befor,e and after treatment. Notice the dental adjustments made possible by the downward displacement of the mandibular growth. (Note: the case in E is not the saFP~ as shown in A-D. "'~.
Early Treatment
417
.'
FIG 15-64. Treatment of labioversion in a Class I malocclusion by means of an oral shield. A, at the start of treatment. B, after 3 months. C, after 6 months. Note recession of the gingival tissue around the neck of the mandibular
cuspid as the incisor relationship
improved.
The shield
should have been remade so that traumatic occlusion was not introduced. The shield itself provided the trauma that produced the periodontal lesion. D, a modification of the maxillary acrylic palate appliance, which also may be used for such problems.
"
418
FIG
Treatment
15-65.
Crossbite of a maxillary incisor before qeft) and after right) treatment. In this instance, there was insufficient space for the lateral incisor
and all teeth in the right lateral segment had to be moved posteriorly until the crossbite could be corrected. (Courtesy of Dr. Aaron Posen.)
The archwires level and idealize the arch forms, while the maxillary incisors are intruded and retracted.
tural position·and in occlusion. If a Class 11or Class III relationship is seen at either position, the problem is not a simple anterior crossbite, for the latter is solely a matter of lingually tipped maxillary anterior teeth without serious disruption of- the molar relationship. If there is any doubt, a cephalometric analysis is needed .. Simple anterior crossbites may involve one or more teeth.47
9. Anterior
Crossbites,
Simple
Simple anterior crossbites are dental malocclusions resulting from abnormal axial inclinations of maxillary anterior teeth. They must be clearly differentiated from mesioclusions, which they may seem to resemble4. 13.62.69 The simple anterior crossbite has many other names (e.g., "in-locked" incisors and "scissors bite"). The use of the word "simple" implies that some anterior crossbites are more complicated, and indeed they are, particularly those which accompany a Class III malocclusion or are part of a skeletal deep bite (see Section D-7 and elsewhere in this chapter). It is stretching the outline of this chapter a bit to discuss anterior cross bite of several teeth in two places (Sections D-7 and 0-9), but there are good reasons for doing so. Primarily we want to direct the reader to the importance of the differential diagnosis and the correct treatment regardless of the original classification or designation of the condition. All anterior crossbites are not "simple" !
a) Dwgnosis The molar relationship
should be noted carefully in the pos-
b) Treatment 1) Single Tooth.-A single anterior tooth in crossbite may be brought into alignment easily, provided there is space in the arch for it. If there is-not, space must be created before tipping the offending tooth labially (Fig 15-65). When there is sufficient space, the tooth may be brought directly into line. An auxiliary spring attached to a lingual archwire or maxillary acrylic plate may be used, or the locked tooth may be brought to a light labial archwire by means of ligatures. An acrylic inclined plane, shown in Figure 15-66, also is effective. It must be adjusted carefully and not \eft in place unduly long. Figure 15-67 illustrates an anterior crossbite treated with an inclined plane. 2) Several Teeth.Treatment of several teeth in crossbite requires the observance of the same fundamentals needed for a single tooth. Lingual archwires with auxiliary springs are effective, labial archwires and banded anterior teeth are also excellent, and the inclined' plane appliance is sometimes recommended, though we think it inefficient for this purpose. Figure 15-68 illustrates successful treatment of such cases.
10. Bimaxillary
Protrusions
a) Bimaxillary Progn.lfthism
FIG
15-66.
Acrylic inclined plane extension of incisal edges of the mandibular incisors, sometimes used for treatment of lingual crossbites of anterior maxillary teeth.
" Bimaxillary prognatnism must be differentiated from bimaxillary dental protrusion. Bimaxillary prognathism is a skeletal problem in which both maxilla and mandible have a relationship more forward than normal with respect to the cranium and cranial base (Fig 15-69). In true bimaxillary prognathism, both the maxilla and the mandible are forward with respect to the anterior cranial base while the axial inclinations of the teeth are nearer normal than in bimaxillary dental protrusion. There are distinct ethnic variations in the normal po-
Early Treatment
419
."
FIG 15-67. Above, an anterior crossbite treated with mandibular inclined plane: left, before therapy; right, after therapy (courtesy of Or. John Mortell).
Below, a skeletal Class III malocclusion was attempted.
Note the difference
on which a similar treatment
in the response to treatment.
FIG 15-68. A, dental-type crossbite of several teeth before (left) and after (right) treatment (courtesy of Or. Aaron Posen). B, this anterior crossbite looked like a skeletal Class III malocclusion, but the ready response
to treatment disproves that diagnosis. ment; right is after treatment.
A and B, left is before treat-
420
Treatment
FIG 15-69. Bimaxillary prognathism. The values are for the skeletal and dental length measures of Enlow's Counterpart Analysis (see Chapter 12). Norms for the appropriate age and sex, in this instance a female of 10 years, 2 months, are in parentheses. Note that there is bimaxillary prognathism as well as bimaxillary dentoalveolar protrusion.
sition and size of both the maxilla and mandible. The North American black, (or example, has a normal maxillo-mandibular skeletal relationship which, by North American white'standards, might be termed "bimaxillary prognathism" (see Chapter 12). The cephalometric analyses must first reveal bimaxillary prognathism (Basic Morphologic Analysis plus above normalvalues in the Profile Analysis for both maxillary and mandibular skeletal unit distances). Forward positions of the dentoalveolar region only are shown by the maxillary and mandibular dental unit distances and abnormal angulations of the incisors to the functional occlusal line (Figs 15-69 and 15-70). Because bimaxillary prognathism is a problem in the basic morphology and growth pattern of the bony skeleton, interception is not a very satisfactory strategy. A common mistake is made when the basic skeletal morphology is not recognized and attempts are made to impose too "flat" a dental profile in a facial skeleton
FIG 15-70. Bimaxillary dental protrusion. The Counterpart Analysis (See Chapter 12) reveals both maxillary and mandibular lengths near the norms for a boy of 7 years, 2 months, but the dental alveolar lengths are about two standard deviations above the mean.
FIG 15-71. Anterior open bite.
with both the maxilla and mandible abnormally forward. Lip and soft tissue adaptation then is often not as pleasing -as anticipated. b) Bimaxillary Dental Protrusion Bimaxillary dental protrusion is procumbency of both dentitions on the bOIJYbas.es (see Fig 15-70) and'must be discriminated from bimaxillary prognathism. There may be familial tendencies, as in bimaxillary prognathism, but bimaxillary dental protrusiqn can also arise from mesial drifting of the teeth in both arches. The .condition also is seen when larger than normal teeth are found in conjunction with normal or smaller than normal osseous bases. In our opinion, bimaxillary dental protrusion is not treated very satisfactorily at an early age (see Chapter 16).
11. Open Bite a) Definition Open bite is the failure of a tooth or teeth to meet antagonists in the opposite arch (Fig 15-71). During the normal course of eruption, it is expected that the teeth and their supportive alveolar bone will develop until occlusal antagonists are met. Any interference with the normal course of eruption and alveolar development may result in an open bite. The causes of open bite generally may be grouped under three headings (see Chapter 7): (I) disturbances in the eruption of the teeth and .alveolar growth, for example, ankylosed primary molars; (2) mechanical interference with eruption and alveolar, growth, for example, a finger-sucking habit; and (3) vertical skeletal dysplasia. The last, though less frequently seen, is a quite different and much mote difficult problem. Unfortunately, there are two current definitions of open bite (Fig 15-72). Throughout thi~ book, the term "open bite" means the latk of functional antagonistic teeth. This definition is not only functionally correct, it is more pragmatic. b) Diagnosis The definition of open bite is, in a sense, the diagnosis, but to plan treatment one needs to learn the etiology and to localize precisely the extent of the inadequate vertical development. We may divide open bites into (I) simple open bites, those confined to the teeth and alveolar process; and (2) complex, those based on primary vertical skeletal dysplasia-the so-called "skeletal open
Early Treatment
FIG
421
15-72.
The definition of open bite. Left, normal incisal relationship. Center,
bite with vertical overlap of the incisors. This latter type of open bite
an open bite without vertical overlap of the incisors. Right, an open~n bites" -which are more varied and much more difficult to treat.
not diagnosed. eted appliances may be used to move the incisors to correct overbite and overjet relationships, and functional appliances (e.g., Activator, Bionator, or Frankel appliance), are especially indicated in the early mixed dentition.
When the vertical cephalometric analyses (see Chapter 12) reveal no abnormal measures and the sole problem is the failure of some teeth to meet the line of occlusion, the condition is termed simple open bite. When the vertical cephalometric analysis reveals disharmonies in the skeleral components of anterior face height (e.g., very short upper face height, or total anterior face height disproportionately small for the total posterior face height), dentoalveolar vertical development sometimes cannot cope with the skeletal morphology well enough to guarantee anterior functional occlusal stops: the result is termed complex or skeletal open bite (see Fig 15-73). In simple open bite alveolar adaptation cannot or does not take place; in complex open bite alveolar adaptation does take place but it cannot be sustained. The use of Vertical Analysis 11 and the tables of vertical growth measures presented in Chapter 12 provides localization of the problem in the craniofacial skeleton and makes possible monitoring of treatment during growth.
c) Treatment 1) Anterior Open Bite, Simple.-When studying anterior open bites before treatmfnt, take care to'note the relationship of the osseous bases to the dentition. Preoccupation with the dentoalveolar aspects of the open bite may lead 6fie-tQ...overlook a more basic skeletal problem. Always suspect a habit of some sort when~an open bite is first seen, since the majority of simple anterior open bites are caused by digital sucking habits or abnormal tongue posture, If, 9uring eruption, the teeth repeatedly encounter a fingei~ thumb, of tongue, eruption is impeded and an open bite results. In'young children treatment consists, first, of controlling the habit which alone may be sufficient to permit the teeth to erupt to normal position. Habit control is discussed in Chapter 18. Retention, after treatment, of any malocclusion due to a sucking habit is almost impossible unless the habit is overcome completely and normal lip and tongue function are restored. Often the best way to break the habit is to correct the open bite itself. This is certainly true for a simple tongue-thrust that is maintaining an open bite created by an earlier sucking habit. Brack-
2) Posterior Open Bite, Simple.-Open bites in the posterior region are rare in young children and usually result from a lack of vertical alveolar development, either ankylosed primary molars or "idiopathic failure to erupt." Lateral "tongue-thrusts" are largely tongue postures adaptive to an open bite resulting from another cause. A common example illustrates the point. Ankylosed primary molars result in a localized cessation of alveolar development, creating a posterior open bite. The tongue must spread laterally to seal the open bite space during reflex swallowing, When the primary teeth are removed, the tongue's continued lateral swallowing movements may impede the eruption of the bicuspids. In early treatment the appliance of choice is either the Activator or Bionator whose lingual flanges and palatal covering prevent the tongue from entering the posterior open bite. Plastic stops against the incisors permit more vertical posterior alveolar growth as the ankylosed teeth are removed on a schedule determined by the development of their permanent successors. The condition is much more difficult to treat later when the tongue reflex has become more fixed, the open bite has increased, less potential vertical growth remains, and the eruptive forces of the teeth are diminished. 3) Complex or Skeletal Open Bite.-Complex or skeletal open bite (Fig 15-73) is a symptom of a variety of serious skeletal qysplasias including suSh varied morphologies as Class 11, vertical type I (steep mandibular plane, or excessive anterior total face height), mandibular prognathism, and several of the craniofacial syndromes (e.g., Downs' syndrome). The most frequently encountered skeletal open bite is that seen in Vertical Type 3 (upward tipped Palatal Line and inadequate development of anterior upper face height; see Chapter 12). Skeletal contributions to open bite are often overlooked in young children, which is unfortunate, since the later they are discovered the more difficult the treatment. One reason early or incipient skeletal open bite is unnoticed is the insensitivity of many cephalometric analyses to any but the most
422
Treatment
,.
FIG
15-73.
Gross skeletal dysplasia resulting in an open bite. Surgery was undertaken early in the patient's life to correct a bifid nose, causing
further impedance to normal growth of the nasomaxillary complex. A, note the upward slope of the palate. (Continued.)
gross vertical dysplasias. If a skeletal open bite is suspected, the vertical analyses described in Chapter 12 provide methods of diagnosis, localization, prediction of future severity, and assessment of the response to treatment. Some skeletal open bites in young children involve abnormal maxillary development, in association with nasorespiratory dysfunction (see Chapter 7). It is impossible to. provide detailed rules for early treatment of the many kinds of skeletal open bite, but a few guide lines and principles are helpful. a) The earliest possible diagnosis is essential because the condition is not self-correcting and. usually worsens with time. b) Removal of all possible etiologic factors a~ soon as diagnosed is important. Consultation with the pediatrician or otolaryngologist may be important. When referring the patient to the physician, send along the cephalogram and a summary of your cephalometric findings. Explain to your colleague the implications of the condition to future craniofacial growth. When you document the case well, understanding and cooperation is usually assured; however, do not expect all pediatricians and otolaryngologists to be experts in craniofacial growth. c) Since these cases may be very difficult and require pro-
long<;:dand varied appliance therapy, they challenge the experience and skills of the best orthodontists. Early mistakes in treatment can compound the problem.
12. Deep Bite (Excessive Overbite or Vertical Overlap) a) Definition A wide range of incisal overlap is seen 'with normal posterior occlusal relations. Depth of bite (see Fig 15-74) becomes a defined clinical problem when occJpsal or temporomandibular function is, or ·inay become, impaired and when facial esthetics is harmed. The depth of bite must be related to the health of the soft and supporting structures, temporomandibular function, and the effects of future skeletal growth on these factors. Incisors in labioversion may seem to have normal overbite, but their correction by simple tipping may produce a deeper bite. Therefore, deep bite as a clinical problem is not defined in terms of miIIimeters seen today but in the light of future changes on esthetics and function. Closed bite (excessive overbite resulting from loss of posterior teeth), only rarely seen in young children, must not be confused with deep bite. Brief comments on treatment of closed bite in
I..
Early Treatment
423
.'
FIG 15-73 (cont.). B-O, the crossbite. E, the disharmony arches. (Continued.)
in the dimensions of the dental
children, however, appear later in this section (part c, Treatment.)
b) Diagnosis The factors contributing to excessive overbite vary with the type of occlusion. Their determination is the most important step in diagnosis. Excessive overbite is not to be viewed as an isolated entity: it must be seen as a part of the total malocclusion. In good occlusions, the amount of overbite is determined largely by dental factors, that is, crown length and tooth position. In Class I malocclusion the depth of bite is controlled by dental factors, for example, length of the crowns of the incisors, elevation of the
maxillary first molars, and the angle between the long axes of the cen~ral incisors as well as' by skeletal features. However, in Class H, the skeletal morphology dominates dental features. Diminished anterior lower face height and shortened ramus height, in particular, dominate the dental factors mentioned above. Consequently, depth of bite is usually more difficult to correct and retain in Class H than in Class I malocclusion. Cast analysis alone or observations based solely on the usual occlusal position are insufficient: a proper cephalometric analysis and determination of the interocclusal freeway space are necessary. The amount of freeway space is a critical factor in prognosis
424
Treatment
..
G
St. S. 11-5
VERTICAL
-3
Cranial 80S.
-2
-IS.D.
ANALYSIS
IS.D.
X
MALES
PM VertlFMN-SE
Maxilla PM Vert/Pol.
Line
MAlES
FEMALES
Occlusion PM Vert/Occ!. Line MAlES (not a constont In Cia •• Dl FEMALES
~ PM Vert/Mond.
Line
MAlES
H
FIG 15-73 (cont.). F, the cephalometric tracing of a patient with an open bite. G, the Z scores for the vertical analysis reveqling three measures more than one standard deviation above the mean and indicating a skeletal basis for the open bite. H, superposed before and after tracings showing the treatment produced dentoalveolar adaptations to effect a closure of the open bite.
"
2
3
Early Treatment
-
, ---, -.. -I--.-.-~-3.I16-1 10-1
0
I,-IS.D. -_.90 ..95 85 MAlES MAlES ,X- .. ANALYSIS 290 -2 -IS.o. IS.O. IS.D. 85 I Vert/Oee!. (not 0 constant In Cia •• DJ Vert 10eel. Line L1n. PM..L......: Vert/Mand. Lln. Vert/Pal Vert Pal L1n. FEMAlES
Occlusion ~ .O«lusieJn
90
I
FEMAlES
T.p. T.p.
I
\
--
VERTICAL VERTICAL 90 I
~@ B115
,@
425
I
FIG 15-74. Simple deep bite. A, cephalometric ment. B, the vertical
analysis.
tracing prior to orthodontic
C, the cephalometric
tracing
treatafter
treatment.
0, the verticaL.aflalysis
that'!."'ree measures
Z scores after therapy showing
were affected f!"vorably by therapy.
426
Treatment
(see Chapters 10 and 11). When there is a larger than normal distance between the postural and the intercuspal (usual occlusal) position, greater opportunities exist for correction by guiding vertical alveolar development. Study the freeway space carefully. Measure the interocclusal distance in the cepnalogram and the direction of mandibular movement from posture to o~clusion. You may have the patient wear a flat maxillary bite plan for a few days to reduce the occlusal sensory input, then the interocclusal distance can be measured more accurately. A detailed vertical cephalometric analysis is required (see Chapter 12), but many cephalometric analyses do not discriminate vertical details well. Proper treatment planning depends on specific localization of skeletal contributions to the deep bite.
c) Treatment When an excessive overbite is seen in the primary.dentition, it is likely to have a skeletal basis. Activator type appliance may be used to direct differential alveolar growth, reduce the interocclusal distance, and improve skeletal morphology. If the overbite seems excessive in the mixed dentition when there is a Class I molar relationship and normal sk~letal morphology, it usually is due to one or more of the following related factors: a) Overdevelopment
vertically of the incisal regions, elevation of the maxillary first molars (i.e., the anatomic crown of the molar has not erupted to its full clinical crown height). c) Failure to recognize a normal stage of development. The overbite is greater just after eruption of the permanent incisors and decreases with eruption of the posterior teeth. b) Inadequate
None of these factors requires heroic orthodontic treatment. Eruption of the first molars can be aided by the use of a flat maxillary bite plane or a monobloc and the incisors depressed with utility archives. Such appliances may help, too, if the curve of Spee is excessive. Tb.,efunctional jaw orthopedic appliances, (e.g., Activator) are ideally suited to direct vertical skeletal development and to control adaptive alveolar growth in Class I deep bite as well as Class II. With a Class II molar relationship, treatment of overbite must be directed to the total Class II problem. Understanding of the different vertical types within Class II helps one in planning therapy (see Section D-7 in this chapter and see Chapter 12). The choice of appliances is largely determined by the type of Class II malocclusion, but the functional appliances are especially advantageous for early treatment of Vertical Type 2. The more severe the skeletal aspects of the deep bite, the more there is to be gained by early treatment.
13. Craniofacial Malformations Although gross craniofacial deformities appear rarely, each instance poses enormous problems in clinical management for the surgeon and orthodontist. Babies with severe congenital malformations require immediate surgical, medical, and dental attention of a very specialized nature. Troubled parents turn instinctively to
the family pediatrician and dentist for advice. Ordinarily, gross craniofacial abnormalities are not the responsibility of the family dentist, but the dentist has the obligation to steer the parent to a craniofacial anomalies center (sometimes called a cleft palate team or center), for the team approach is essential for these children. Fortunately, such centers are well developed and widespread throughout the world. They are made up of clinicians from many fields sharing research and treatment responsibilities and individualizing the therapy for each child. Surgeons, speech therapists, pedodontists, orthodontists, psychologists, and prosthodontists are all involved in planning the joint treatment. However, the speech therapist and orthodontist will spend the most time in corrective work and guiding the development of more difficult cases. The most common of the serious congenital deformities is that of cleft lip and/or palate (Fig 15-75), which occurs in approximately one in 700 North American white children. In recent years important progress has been made in cleft lip and palate treatment. The schedule of lip and palate surgery, varies according to the nature and extent of the clefting, and there are frank differences of opinion among the best surgeons about the exact timing and surgical techniques for both lip and palate procedures. Generally, the lip is closed very early and the palate some months later. Some now advise that some neonates have the maxillary segments and premaxilla positioned by appliances and tension bandages prior to lip surgery. The responsibility for these decisions resides with the attending surgeon of the cleft palate team. Subsequent orthodontic treatment attempts to normalize the growth of the deformed maxilla and the effects of surgery on craniofacial growth. Even the best surgery results in significant effects on subsequent growth of the entire facial skeleton and occlusion. It is the duty of every family dentist to be thoroughly acquainted with a craniofacial anomaly or cleft palate team long before the need for their services arises. In this way, when advice is sought, the answer is prompt and authoritative.
14. Temporomandibular
Dysfunction.
a) Definition The current literature on temporomandibular
dysfunction ap-
pears largely in journals dedicated to adult dental rehabilitation, where the problem is primarily viewed as one of degenerative geriatric disease and dysfunction. There is increasing evidence that some of the signs and symptoms associated with temporomandibular dysfunction in adults are first seen in young children (see Suggested Readings) and that certain occl~sal disorders in childhood predispose to later temporomandibular dysfunction. Accordingly, it is proper to consider temporomandibular dysfunction as an.i~portant aspect of the development of malocclusion.
b) Diagnosis Class n, deep bite, open bite, and asymmetry are the skeletal morphologic variations most associated with temporomandibular joint dysfunction in children. Functionally unstable mal occlusions in childhood most associated with temporomandibular signs and symptoms include functional crossbites and functional Class II and Class III molar relationships. Of special concern are end-to-end molar relationships which do not completely change to a Class I occlusion during the late mixed dentition and pubescent periods.
Early Treatment
427
"
FIG 15-75. A, a unilateral cleft palate prior to orthodontic treatment. B, the Friel . lingual archwire in place. C, the result of maxillary expansion with the Friel lingual archwire. 0, after positioning of the teeth with a
standard orthodontic appliance, prosthesis.
Because end-to-end occlusion of the first permanent molars has been described as normal (see Chapter 6 for a discussion of why end-to-end is not necessarily normal), its potential for trouble is often overlooked. An end-to-end molar relationship combined with a mild Class 11 skeletal morphology and slight deep bite make a collection of symptoms which should be carefully watched for early signs of temporomandibular dysfunction and/or pain (see Chapter 11). The most critical diagnostic features are those of functional occlusal disorders, erratic mandibular movement on
associated with temporomandibular pain, sounds, tendonitis, or myalgia of the jaw muscles should be considered for treatment.
opening and closure, atypical joint sounds, limited jaw opening, and pain of the jaw musculature (see Chapter 10 and 11) .. Trauma to the facial region has been shown to be a significant etiologic factor in temporomandibular dysfunction in children ..
c) Treatment Clinical studies of the value of early treatment of temporomandibular dysfunction are just appearing in the literature. While it is obvious that most problems of the temporomandibular joint have their origins much earlier tha'n the time of their typical treatment, the most appropriate age for the treatment of each problem has not yet been determined. It is generally agreed, however, that functional malocclusions in early childhood merit special attention, particularly when associated with skeletal dysplasia. Correction of functional malocclusions by occlusal equilibration, functional appliance therapy, or tooth movements (according to the circumstances) in such instances is surely indicated. The "treatment" of every end-to-end molar relationship in the mixed dentition is not indicated. However, any occlusion not in solid intercuspation and
the patient is now ready for a
REFERENCES
I.
Ackerman JL, Proffit WR: Preventive and interceptive orthodontics: A strong theory proves weak in practice. Angle Orthod 1980; 50:75-86. 2: Adamson K: The controversy concerning the first permanent molar. Aust Dent J 1962; 7:191-201. 3. Artun J, Marstrander PB: Clinical efficiency of two different types of direct bonded space maintainers. J Dent Child 1983; 50:197-204. 4. Bergersen EO: A cephalometric study of the clinical use of the mandibular labial bumper. Am J Orthod 1972; 61 :578t 602. 5. Bishara SE, et al: Management of impacted canines. Am J Orthod 1976; 69(4):371-387. '6~ Bjerklin K, Kuror-f Ectopic eruption of the maxillary first permanent molar: Etiologic>factors. Am J Orthod 1983; 84: 147-155. 7. Bjerregaard J, Bundgaard AM, Melsen B: The effect of the mandibular lip bumper and maxillary bite plate on tooth movement, occlusion and space conditions in the lower dental arch. Eur J Orthod 1980; 2:257-265. 8. Bolton W A: The clinical application of a tooth-size analysis. Am J Orthod 1962; 48:504-529. 9. Boyd RL: Clinical assessment of injuries in orthodontic movement of impacted teeth. Part I. Methods of attachment. Am J Orthod 1982; 82:478-486.
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Treatment
10. Boyd RL: Clinical assessment of injuries in orthodontic movement of impacted teeth. Part H. Surgical recommendations. Am J Orthod 1984; 86:407-418. 11. Bundgaard M, Bjerregaard 1, Melsen B, et al: An electromyographical study of the effect of a mandibular lipbumper. EurJ Orthod 1983; 5:149-156. 12. Canut lA, Raga C: Morphological analysis of cases with ectopic eruption of the maxillary first permanent molar. Eur J Orthod 1983; 5:249-253. 13. Clifford FO: Crossbite correction in the deciduous dentition: Principles and procedures. Am J Orthod 1971; 59:343-349. 14. Cry er SS: Third molar eruption and the effect of extraction of adjacent teeth. Dent Pract 1967; 17:405-416. 15. Daugaard-lensen I: Extraction of first molars in discrepancy cases. Am J Orthod 1973; 64:115-136. 16. Davey KW: The effect of premature loss of primary molars on the anteroposterior position of the maxillary first permanent molars and other maxillary teeth. J Dent Child 1967; 34:383-394. 17. Fanning EA: Effect of extraction of deciduous molars on the formation and eruption of their successors. Angle Orthod 1962; 32:44-53. 18. Farman IG, Eloff 1, Nortje C, et al: Clinical absence of the first and second permanent molars. Br J Orthod 1978; 5:93-97. 19. Fischer TJ, Psaltis GL: Serial guidance in the developing dentition. Compendium Continuing Ed 1981; 2: 163-171. 20. Fournier A, Turcotte 1, Bernard C: Orthodontic considerations in the treatment of maxillary impacted canines. Am J Orthod 1982; 81:236-239. 21. Freeman ID: Preventive and interceptive orthodontics: A critical review and the results of a cliriical study. J Prev Dent 1977; 4:7-23. 22. Garfinkle RL, Artese A, Kaplan RG, et al: Effect of extraction in the late mixed dentition on the eruption of the first premolar in Macaca nemestrina. Angle Orthod 1980; 50:23-27. 23. Holm U: Problems of compensative extraction in cases with loss of first permanent molars. Trans Eur Orthod Soc 1970; pp 409-427. 24. Huggins DG, Mc Bride LJ: The eruption of lower third molars following the loss of second molars: A longitudinal cephalometric study. Br J Orthod 1978; 5: 13-20. 25. Hunter S: Application of analysis of crowding and spacing of the teeth. Dent Clin North Am 1978; pp 563-578. 26. 100ndeph DR: Second premolar serial" extraction. Am J Orthod 1976; 69:169-184. 27. Kisling E: Occlusal interferences in the primary dentition. J Dent Child 1981; 48:181-191. 28. Kisling E, Hoffding 1: Premature loss of primary teeth: Parts I-Ill. J Dent Child 1978-1979; 45:109-113; 45:279287; 46:34-38. 29. Kisling E, Hoffding 1: Premature loss of primary teeth: Part V. Treatment planning with d~e respect to the significance of drifting patterns. J Dent Child 1979; 46:300-306. 30. Kutlin G, Howes RR: Posterior crossbites in the deciduous and mixed dentitions. Am J Orthod 1969; 55:491-504. 31. Laptook T, Silling G: Canine transposition approaches to treatment. J Am Dent Assoc 1983; 107:746-748. 32. Laskin DM: Indications and contraindications for removal of impacted third molars. Dent Clin North Am 1969; 13:919. 33. Laskin S, Graber TM: Logical repositioning of the teeth. J Am Dent Assoc 1970; 80:1320-1326.
34. Lawlor 1: The effects on the lower third molar of the extraction of the lower second molar. Br J Orthod 1978; 5:99-103. 35. Lehman R: A consideration of the advantages of second molar extractions in orthodontics. Eur J Orthod 1979; I: 119-124. 36. Leighton BC, Hunter WS: Relationship between lower arch space/crowding and facial height and depth. Am J Orthod 1982; 82:418-425. 37. Liddle DW: Second molar extraction in orthodontic treatment. Am J Orthod 1977; 72:599-616. 38. Lindquist B, Thilander B: Extraction of third molars in cases of anticipated crowding in the lower jaw. Am J Orthod 1982; 81:130-139. 39. Little RM, Wallen TR, Riedel RA: Stability and relapse of mandibular anterior alignment-first premolar extraction cases treated by traditional edgewise orthodontics. Am J Orthod 1981; 80:349-365. 40. Mader C, Konzelman lL: Transposition of teeth. J Am Dent Assoc 1979; 98(4):412-413. , 41. Mayne WR: Serial extraction, in Graber TM, Swain BS (eds): Current Orthodontic Concepts and Techniques. Philadelphia, WB Saunders, 1975, pp 179-274. 42. McNeil RW, 100ndeph DR: Congenitally absent maxillary lateral incisors: Treatment planning considerations. Angle Orthod 1973; 43:24-29. 43. Moss JP: The indications for the transplantation of maxillary canines in the light of 100 cases. Br J Oral Surg 1975; 12:268-274. 44. Musselman Rl, Chadha JM: Timed extractions. Dent Clin North Am 1978; pp 711-724. 45. NIH CONSENSUS Development Conference for Removal of Third Molars. J Oral Surg 1980; 3:235-236. 46. Norton LA, Wickwire NA, Gellin ME: Space management in the mixed dentition. J Dent Child 1975; 41:32-38. 47. Payne RC, Mueller BH, Thomas HF: Anterior cross bite in the primary dentition. J Pedodontics 1981; 5:281-294. 48. Platzer KM: Mandibular incisor-canine transposition. JAm Dent Assoc 1968; 76(4):778-784. 49. Popovich F, Thompson GW: Evaluation of preventive and interceptive orthodontic treatment between three and eighteen years of age, in Cook lR (ed): Transactions of the Third International Orthodontic Congress. St Louis, CV Mosby, 1975. 50. Posen AL: The effect of premature loss of deciduous molars on premolar eruption. Angle Orthod 1965; 35:249-252. 51. Pulver F: The etiology and prevalence of ectopic eruption of the maxillary first permanent molar. J Dent Child 1968; 35:138-146. 52. Richardson ME: The relative effects ot; the extraction of various teeth on the development of mandibular third molars. Trans Eur Orthod Soc 1975; 79-85. 53, ~igenberg Q: Seria!.extraction-Stop, look and be certain. I1:mJ Orthod 1964; 50:327-336. 54. Salzmann lA: Effect on occl~sion of uncontrolled extraction of first permanent molars: Prevention and treatment. J Am Dent Assoc 1943; 30:1681-1690. 55. Savara BS, Steen lC: Timing and sequence of eruption of permanent teeth in a longitudinal sample of children from Oregon. J Am Dent Assoc 1978; 97:209. 56. Schroder U, Granath L: A new interceptive treatment of cases with missing maxillary lateral incisors. Swed Dent J 1981; 5:155-158. 57. Schwanninger B, Shaye R: Management of cases with up-
Early Treatment per incisors missing. Am J Orthod 1977; 71:396-405. 58. Shapira Y: Transposition of canines. J Am Dent Assoc 1980; 100(5):710-712. 59.' Shapira Y, Kuftinec M: Treatment of impacted cuspids. The hazard lasso. Angle Orthod 1981; 51 (3):203-207. 60. Shapira Y, Kuftinec MM: Orthodontic management of mandibular canine-incisor transposition. AmJ Orthod 1983; 83:271-276. 61. Simon JF, Farrage JR, Misner LR: Regaining space in the mixed dentition. Dent Clin North Am 1978; pp 669-684. 62. Sleichter CG: The influence of premature loss of deciduous molars on premolar eruption. Angle Orthod 1963; 33:279283. 63. Swaine TJ, Wright GZ: Direct bonding applied to space maintenance. J Dent Child 1976; 42:21-25. 64. Thilander B, Skagius S: Orthodontic sequelae of extraction of permanent first molars. A longitudinal study. Trans Eur Orthod Soc 1970; pp 429-442. 65. Trisovic D, Markovic M, Starcevic M: Observations of the development of third mandibular molars. Trans Eur Orthod Soc 1977; pp 147-157. 66. Tsamtsouris A, White GE: Space maintainers for the integrity of the arch perimeter. Part I. The transpalatal arch appliance. J Pedodontics 1977; 1(2):91-98. 67. Tuversson DL: Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod 1970; 58: 109-127. 68. Tweed CH: Treatment planning and therapy in the mixed dentition. Am J Orthod 1963; 49:881-906. 69. Valentine F, Howitt JW: Implications of early anterior crossbite correction. J Dent Child 1970; 37:420-427. 70. Vanarsdall RL, Corn H: Soft-tissue management of labially positioned unerupted teeth. Am J Orthod 1977; 72(1 ):5364.
71. Von der Heydt K: The surgical uncovering and orthodontic positioning of unerupted maxillary canines. Am J Orthod 1975; 68(3):256-276. 72. Way DC: Direct bonding and its application to minor tooth movement. Dent Clin North Am 1978; pp 757-770. 73. Weber AD: A longitudinal analysis of premolar enucleation. Am J Orthod 1969; 56:394-402. 74. West E: Treatment objectives in the deciduous dentition. Am J Orthod 1969; 55:617-632. 75. Wilson HE: Long-term observation of the extraction of second molars. Trans Eur Orthod Soc 1974; pp 215-221. 76. Wright GZ, Kennedy DB: Space control in the primary and mixed dentitions. Dent Clin North Am 1978; 22:579-601.
SUGGESTED READINGS Sections A-C A. Understanding Early Treatment B. Defining Goals in Early Treatment C. Clinical Problems and Procedures Ackerman JL, Proffit WR: Preventive and interceptive orthodontics: A strong theory proves weak in practice. Angle Orthod 1980; 50:75-86. Popovich F, Thompson GW: Evaluation of pre:ventive and interceptive orthodontic treatment between three and eighteen years of age, in Cook JT (ed): Transactions of the Third International Orthodontic Congress, St Louis, CV Mosby, 1975.
429
D-I-a: Congemlally Missing Teeth Graber LW: Congenital absence of teeth: Review with emphasis on inheritance patterns. J Am Dent Assoc 1978; 96:266275. McNeil RW, Joondeph DR: Congenitally absent maxillary lateral incisors: Treatment planning considerations. Angle Orthod 1973; 43:24-29. Schroder U, Granath L: A new interceptive treatment of cases with missing maxillary lateral incisors. Swed Dent J 1981; 5:155-158. Schwanninger B, Shaye R: Management of cases with upper incisors missing. Am J Orthod 1977; 71:396-405. Tuversson DL: Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod 1970; 58: 109-127. D-l-b: Loss of Permanent Teeth (Trauma, Caries, and Other Causes) Adamson K: The controversy concerning the first permanent molar. Aust Dent J 1962; 7:191-201. Holm U: Problems of compensative extraction in cases with loss of first permanent molars. Trans Eur Orthod Soc 1970; pp 409-427. Salzmann JA: Effect on occlusion of uncontrolled extraction of first permanent molars: Prevention and treatment. J Am Dent Assoc 1943; 30:1681-1690. Thilander B, Skagius S: Orthodontic sequelae of extraction of permanent first molars: A longitudinal study. Trans Eur Orthod Soc 1970; pp 429-442. D-3: Spacing of Teeth Edwards JG: The diastema, the frenum, the frenectomy: Clinical study. Am J Orthod 1977; 71:489-508. Popovich F, Thompson GW, Main PA: Persisting maxillary diastema: Differential diagnosis and treatment. J Can Dent Assoc 1977; 43:330-333. D-4-a: Space Management Artun J, Marstrander PB: Clinical efficiency of two different types of direct boned space maintainers. J Dent Child 1983; 50:197-204. Fischer TJ, Psaltis GL: Serial guidance in the developing dentition. Compendium Continuing Ed 1981; 2:163-171. Hunter S: Application of analysis of crowding and spacing of the teeth. Dent Clin North Am 1978; pp 563-578. Kisling E, Hoffding J: Premature loss of primary teeth. Part V. Treatment planning with due respect to the significance of drifting patterns. J Dent Child 1979; 46:300-306. Norton LA, Wickwire NA, Gellin ME: Space management in the mixed dentition. J Dent Child 1975; 42:32-38. Singer J: Effect of the passive lingual archwire on the lower denture. Angle Orthod 1974; 44:146-155. Wright GZ, Kennedy DB: Space control in the primary and ~- mixed dentitions. Dent Clifl; North Am 1978; 22:579-601. D-4-a-3: Regaining Space Bergersen EO: A cephalometric study of the clinical use of the mandibular labial bumper. Am J Orthod 1972; 61:578-602. Bjerregaard J, Bundgaard AM, Melson B: The effect of the mandibular lip bumper and maxillary bite plate on tooth movement, occlusion and space conditions in the lower dental arch. Eur J Orthod 1980; 2:257-265. Bundgaard M, Bjerregaard J, Melsen B, et al: An electromyo-
430
Treatment graphical study of the effect of a mandibular lip bumper. Eur J Orthod 1983; 5:149-156.
D-4-ac4: Space Supervision Fanning EA: Effect of extraction of deciduous molars on the formation and eruption of their successors~ Angle Orthod 1962; 32:44-53. Norton A, Wickwire NA, Gellin ME: Space management in mixed dentition. J Dent Child 1975; 42:112-118. Savara BS, Steen JC: Timing and sequence of eruption of permanent teeth in a longitudinal sample of children from Oregon. J Am Dent Assoc 1978; 97:209-214. D-4-a-5: Gross Discrepancy Problems Joondeph OR: Second premolar serial extraction. Am J Orthod 1976; 69: 169-184. Weber AD: A longitudinal analysis of premolar enucleation. Am J Orthod 1969; 56:394-402. D-4-b-2: Ectopic Eruption of Teeth Bjerklin K, Kurol J: Ectopic eruption of the maxillary first permanent molar: Biologic factors. Am J Orthod 1983; 84:147-155. Canut JA, Raga C: Morphological analysis of cases with ectopic eruption of the maxillary first permanent molar. Eur J Orthod 1983; 5:249-253. Pulver F: The etiology and prevalence of ectopic eruption of the maxillary first permanent molar. J Dent Child 1968; 35: 138-146. D-4-b-3: Transposition of Teeth Laptook T, Silling G: Canine transposition-approaches to treatment. J Am Dent Assoc 1983; 107:746-748. Mader C, Knozelman JL: Transposition of teeth. J Am Dent Assoc 1979; 98(4):412-413. Shapira Y: Transposition of canines. J Am Dent Assoc 1980; 100(5):710-712. Shapira Y, Kuftinec MM: Orthodontic management of mandibular canine-incisor transposition. Am J Orthod 1983; 83:271-276. D-4-b-4: Impaction of Teeth Boyd RL: Clinical assessment of injuries in orthodontic movement of impacted teeth. Part I. Methods of attachment. AI!! J Orthod 1982; 82:478-486. Boyd RL: Clinical assessment of injuries in orthodontic movement of impacted teeth. n. Surgical recommendations. Am J Orthod 1984; 86:407-418. Fournier A, Turcotte J, Bernard C: Orthodontic considerations in the treatment of maxillary impacted canines. Am J Orthod 1982; 81:236-239. Shapira Y, Kuftinec M: Treatment of impacted cuspids. The hazard lasso. Angle Orthod 1981.; 51(3):203-207. Vanarsdall RL, Corn H: Soft-tissue management of labially positioned unerupted teeth. Am J Orthod 1977; 72(1):53-64. Von der Heydt K: The surgical uncovering and orthodontic positioning of unerupted maxillary canines. Am J Orthod 1975; 68(3):256-276. Williams BH: Diagnosis and prevention of maxillary cuspid impaction. Angle Orthod 1981; 51:30-40. Section D-5: Lateral Malrelationships of the Dental Arches Frank SW, Engel GA: Effects of maxillary Quad-Helix appli-
ance expansion on cephalometric measurements in growing patients. Am J Orthod 1982; 81:378-389. Hultgren BW, Isaacson RJ, Erdman AG, et al: Growth contributions to Class n corrections based on models of mandibular morphology. Am J Orthod 1980; 78:310-320. Kisling E: Occlusal interferences in the primary dentition. J Dent Child 1981; 48:181-191. Kutlin G, Harves RR: Posterior crossbites in the deciduous and mixed dentitions. Am J Orthod 1969; 55:491-504. Leighton BC: The early development of cross-bites. Dent Pract 1966; 17: 145-152. Section 6: Class II (Distocclusion, Postnormal Occlusion) Moyers RE, Riolo KE, Guire RL, et al: Differential diagnosis of Class n malocclusions. Part I. Facial types associated with Class II malocclusions. Am J Orthod 1980; 78:477494. Section 7: Class III (Mesiocclusion, Pseudo Class III
Prenormal
Occlusion) and
Graber LW: Chin cup therapy for mandibular prognathism. Am J Orthod 1977; 72:23-41. Jacobson A, Evans WG, Preston CB, et al: Mandibular prognathism. Am J Orthod 1974; ,66:140-171. Section 9: Anterior Crossbites, Simple Clifford F: Crossbite corrections in the deciduous dentition: Principles and procedures. Am J Orthod 1971; 59:343. Payne RC, Mueller BH, Thomas HF: Anterior crossbites in the primary dentition. J Pedodontics 1981; 5:281-294. Section i3-a: Cleft Palate Bishara SE, Krause CJ, Olin WH, et al: Facial and dental relationships of individuals with unoperated clefts of the lip and/or palate. Cleft Palate J 1976; 13:238-252. Cronin DG, Hunter WS: Craniofacial morphology in twins discordant for cleft lip and/or palate. Cleft Palate J 1980; 17: 116-126. Dahl E; Craniofacial morphology in congenital clefts of the lip and palate. Act Odontol Scand 28:(suppl 57), 1970. Fraser FC: The genetics of cleft lip and cleft palate. Am J Hum Genet 1970; 22:336-352. Hunter WS: Review: The Michigan Cleft Twin Study. J Craniofacial Genet Develop Bioi 1981; 1:235-242. Pashayan HM: What else to look for in a child born with a cleft of the lip and/or palate. Cleft Palate J 1983; 20:54-82. Robertson NRE: Oral Orthopaedics and Orthodontics for Cleft Lip and Palate: A Structured Approach. London, Pitman Medical Books, 1983. Robertson NRE: Facial form of patients with cleft lip and palate: The long-term influence of presurgical oral orthopaedics. Br Dent J 1983;J55:59-61. Ross~RB, .Johnston MC'Cleft Lip and Palate. Baltimore, Willlams & Wilkins, 1972. Section 13-b: Other Craniofacial Malformations Gorlin RJ, Pindborg 11, Cohen MM Jr: Syndromes of the Head and Neck, 2nd Ed. New York, McGraw-Hill, 1976 .. Pas hay an HM: What else to look for in a child born with a cleft of the lip and/or palate. Cleft Palate J 1983; 20:54-82. Smith DW: Recognizable Patterns of Human Malformations, 3rd Ed. Philadelphia, WB Saunders, 1982.
Early Treatment Section 14: Temporomandibular Dysfunction Moyers RE, Nesbitt BA, Ten Have T: Adult temporomandibular joints disorder symptomatology and its association with childhood occlusal relations: A preliminary report, in Developmental Aspects of Temporomandibular Joint Disorders. monograph 16. Craniofacial Growth Series, Center for Human Growth and Development, The llniversity of Michigan, Ann Arbor, Michigan, 1985.
431
Moyers RE, Nesbitt BA, Ten Have T: Childhood indicators of adult temporomandibular dysfunction. In press. Nesbitt BA, Moyers RE, Ten Have T: Adult temporomandibular joint disorder symptomatology and its association with childhood occlusal relations: A preliminary report. Speck lE, Zarb GA: Temporomandibular pain-dysfunction: Suggested classification and treatment. J Can Dent Assoc
1976; 42:305-310 .
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-.
-. -,
CHAPTER
16 Adolescent Treatment Robert E. Moyers, D.D.S., Ph.D .
.' "Adolescence
is the beginning of the end." -ST
ANLEY
M.
GARN
OUTLINE D. A.
Understanding Adolescent Treatment 1. General characteristics of adolescent malocclusion 2. 3.
B.
432
a)
Advantages of adolescent treatment Some difficulties in adolescent treatment
Defining Goals in Adolescent Treatment I. Skeletal 2. Dental
3.
C.
6. Temporomandibular Clinical Problems I. Number of teeth
a) Axial inclinations b) Incisal relations c) Midlines d) Arch form e) Spacing f) Curve of Spee-Occlusal Occlusal and functional
2. Line
4. Soft-tissue profile and esthetics 5. Compromises Assessment of Results of Adolescent Treatment 1. Occlusion
2.
a) Occlusal plan b) Molar relationships c) Cuspid occlusion d) Incisor position e) Functional occlusal relations f) Root positions g) Alignment Soft tissues
3.
a) b) c) d) Facial
4. 5.
Alveolar process and periodontium Root resorption
Lips Tongue Swallow Gingivae esthetics
3.
4.
"
joints
Congenitally missing teeth I) Maxillary lateral incisors a) Goals b) Methods c) Problems 2) Mandibular second premolars 3) Multiple absence of teeth a) Loss of permanent teeth (trauma, caries, and other causes) b) Supernumerary teeth Variations in size and shape of teeth a) "Large teeth" b) Small teeth c) Anomalies of tooth shape Spacing of teeth a) Localized spacing b) Generalized spacing Problems singular to the young adult dentition a) Crowding I) Simple crowding (a) Definition .~. (b) Diagnosis (c) ,Treatment 2) Complex crowding (a) Definition (b) Diagnosis (c) Treatment b) Delayed eruption 1) Impactions (a) Maxillary cuspids (b) Second molars (c) Third molars
Adolescent
5.
2) Ankylosed permanent teeth c) Juvenile periodontitis Lateral malrelationships a) Background and definition of the problem b) Diagnosis I) Skeletal 2) Dentoalveolar 3) Neuromuscular c) Treatment I) Goals 2) Methods (a) Skeletal (b) Dentoalveolar correction (c) Neuromuscular 3) Specific problems (a) Bilateral maxillary corpus deficiency (b) Unilateral maxillary corpus asymmetry (c) Bilateral maxillary dentoalveolar contraction (d) (e) (f)
6.
7.
8.
Unilateral maxillary dentoalveolar contraction Unilateral or bilateral mandibular dentoalveolar contraction Gross disharmony skeletal bases
between
Class 11 (Distocclusion, postnormal occlusion) a) Background I) Differential diagnosis 2) Strategies of treatment 3) Tactics b) Rationale for adolescent Class 11 therapy c) Differential treatment I) Horizontal type A (a) Basic strategy (b) Tactics (c) Problems and complications 2) Horizontal type F (a) Basic strategy (b) Tactics (c) Problems and complications 3) Horizontal type B (a) Basic strategy (b) Tactics (c) Problems and complications (d) Retention 4) HorizontaI" type D (a) Basic strategies (b) Suggested tactics (c) Problems and complications (d) Retention 5) Horizontal type C (a) Basic strategies (b) Suggested tactics (c) Problems and complications (d) Retention 6) Horizontal type E
the
9.
10.
11.
12.
Treatment
433
(a) Basic strategies (b) Suggested tactics (c) Problems and complications (d) Retention Class III (mesiocclusion, prenormal occlusion) a) Rationale for adolescent Class III therapy b) Diagnosis c) General strategies d) Tactics e) Differential treatment (1) Midface deficiency (2) Mandibular prognathism (3) Midface deficiency and mandibular prognathis.m f) Problems and complications g) Retention Localized incisal malrelationships a) Labioversion of maxillary incisors (1 ) Diagnosis (2) Treatment b) Simple anterior crossbite (1) Diagnosis (2) Treatment c) Simple deep bite (1) Diagnosis (2) Treatment d) Simple open bite (1 ) Diagnosis (2) Treatment e) Simple crowding (see D-4-a-l) Bimaxillary protrusions a) Bimaxillary prognathism b) Bimaxillary dental protrusion Deep bite a) Simple deep bite (see 8-c) b) Complex (skeletal) deep bite Open bite a) Simple open bite (see 8-d) b) Complex (skeletal) open bite Temporomandibular dysfunction a) Background b) Treatment
This chapter was written on the assumption that the reader is familiar with the outline and con'tents of Chapter 15. To obviate redundancies, each clinical problem is discussed primarily only in either Chapter 15 or 16 according to the age of patients at which it",i~ most apt to be eneoimtered in practice. Treatment methods are described in both chapters when they differ because of developmental age. There are really very few proper clinical research reports on the effects of adolescent orthodontic treatment as scientifically sound as modem clinical studies on, for example, the effects of certain drugs. Therefore, one cannot write with the scientific certitude possible when describing skeletal growth or occlusal development: Accordingly, Chapters 15 and 16, and most other clinical writing at this time, reveal more personal clinical experiences and perceptions tban is sometimes realized. Wherever pos-
434
Treatment
sible, sound clinical studies are noted and practices discounted by good researc-h are mentioned. Well-designed clinical research studies on treatment effects of various appliances on differing occlusions are beginning to appear (cf Baumrind et aI.2-4• ]4 and Bookstein et al. 5) and will undoubtedly change ideas presented here. Sound clinical research must take precedence over mere opinion, however sincerely believed. Some mal occlusions are best treated in adolescence and a few are singular to this stage of development. No malocclusion can be treated until it is first recognized by someone: patient, parent, or dentist. More malocclusions are probably treated in adolescence than any other period, not because it is always the best time for therapy, but rather because this is the time at which patient and parent often become aware of the problem. Furthermore, the treatment of many malocclusions has been traditionally postponed until the permanent teeth can be bracketed. Within an outline similar to Chapter 15, the background of each clinical problem will be provided first, followed by critical aspects of the diagnosis. Finally treatment goals, methods, and possible difficulties will be discussed. There are far too many satisfactory procedures and appliances for all to be included in an introductory text, and many are well presented elsewhere. Specific technical details of treatment are not given when they are beyond the scope of this book. This chapter deals primarily with the logic, rationale, and principles of treatment, not with technical details. Its purpose is to give a broad yet sound perspective on treatment of malocclusion in adolescence-a perspective to provide the basis for treatment, irrespective of the appliance or whether the patient will be treated by general dentist, pedodontist, or orthodontist.
A. UNDERSTANDING TREATMENT 1. General Characteristics
ADOLESCENT of Adolescent MaloccIusion
a) Dentition and occlusal relationships are established. b) Skeletal growth may be mostly over and decelerating. c) Muscle function is matured. d) Functional malocclusions are less frequent since they have largely been accommodated by dentoalveolar, skeletal, and/or mandibular joint adaptations. e) Temporomandibular dysfunction is more frequent since dental, skeletal,and joint adaptability have diminished. f) Psychological aspects are more significant than at younger ages.
2. Advantages of Adolescent Treatment a) Control of all permanent teeth, except third molars, is now
possible. b) It is beneficial to treat when bone turnover rates are still high though adult dimensions are nearly achieved. Repair and remodeling occur readily in response to orthodontic forces though the basic craniofacial morphology is largely established. c) Motivation for treatment is high, especially when facial esthetics are affected.
d) Treatment-goals can be more surely defined, since one does not have to counter, as much as earlier, the unpredictable dynamics of growth. e) Since treatment is less dictated by developmental events, treatment options are lessened.
3. Some Difficulties
in Adolescent
Treatment
a) The best opportunities for control and manipulation of severe skeletal dysplasia are past. b) Sports and social activities, so important to adolescents, often compete with plans for orthodontic treatment. c) The time necessary for treatment may be longer for certain malocclusions. d) Tooth positioning is often more difficult when the occlusion is fully established and root formation is complete than was tooth guidance during eruption.
.'
B. DEFINING GOALS IN ADOLESCENT TREATMENT Since precise tooth poslttoning is the principal strategy in adolescent treatment, cephalometric analysis for treatment planning is essential and many analyses have been designed solely to determine the placement of teeth within particular skeletal morphologic patterns. We may group treatment goals for discussion, quantification, and planning as follows: (I) skeletal; (2) dental; (3) occlusal and functional; (4) soft-tissue and facial esthetics; and (5) compromises.
1. Skeletal Improvement in the craniofacial skeleton by orthodontic treatment is still possible in adolescence, although the greatest opportunities for so doing may be over by this age. A primary aim of some clinicians is to predict the time of the adolescent growth spurt to utilize it in the planned orthodontic correction. A number of maturity indicators, particularly the hand-wrist radiograph, have been used in such predictions. Despite their popularity, the evidence is strong that predictions of peak facial growth velocity (or more often Peak Height Velocity) based solely on carpal radiographs are uncertain and of very limited practical value. However most authorities see merit in studying several indexes of maturity, especially for those instances where developmental events are obviously abnormal. See Suggested Readings for modem references on. this topic. When the 1J1~xillo-mandibular relationships are to be alt~red, it is important to ascertain whether the maxilla, the mandible, or both are to be changed 'and to quantify the amount of change sought in each jaw (see Chapters 12 and 14). Although mandibular impedence or enhancement is more difficult after pubescence, midface changes are possible with intensive orthopedic forces. Vertical change is most apt to occur within the dentoalveolar process or by rotation of the mandible following dentoalveolar changes. Planned horizontal and vertical skeletal changes should be quantified and monitored regularly by cephalometric analysis.
Adolescent Treatment 2. Dental a) Axmllnclinations The roots of posterior teeth should be approximately parallel to one another, especially those roots adjacent to extraction sites. Artistic positioning of the crowns of anterior teeth usually results in a slight divergence of the roots. The root angulation of the anterior teeth is lingual and an interincisal angle 'of 130 degrees may serve as a rough guide. However, the percentage of the 130 degrees contributed by upper incisors and lower incisors varies greatly with the maxillo-mandibular relationship and the steepness of the mandibular and occlusal lines (see Chapters 12 and 14).
435
tastes vary, yet there are some commonly accepted standards. The incisor positions should not strain the lip musculature and the incisal overlap should be harmonious with the lip line. Little display of the gingivae during smiling is desirable. The lips should be without strain at rest and in function. Obversely, the incisors should not be retracted excessively lest the lip drape at rest given an aged or edentulous appearance to the soft-tissue profile. Excessive retraction of the incisors also robs the lips of proper participation in facial expressions.
5. Compromises
b) Incisal Relations Ideally the overbite should be approximately one-third of the lower incisal crown. The overjet-which is determined by the axial inclination of incisors, the skeletal relationship, the relation of the widths of upper to lower teeth (Bolton Index, see Chapter 11) , and the labiolingual thickness of the crowns-should provide incisal centric stops in the intercuspal (usual occlusal) position.
c) Midliness The dental midlines should coincide with each other and with the mid-sagittal plane of the craniofacial
skeleton.
When defining goals for adolescent treatment, one begins with the ideals, listed above, accepting compromises only when the conditions of the case force one to do so. In adult treatment, one often is forced to begin with compromise (see Chapter 17). In adolescent treatment every necessary compromi~e in the treatment plan should be quantified in terms of the skeletal profile and tooth positions, and all of the "trade-offs" and consequences of compromise should be noted and understood at the start. Often a hastily, casually, or unwittingly accepted compromise at the beginning has serious consequences later. Adolescent treatment should aim for idealism.
d) Arch Form The arch forms should be symmetric and coordinated with each other and should, as much as possible, be concordant with the forms of their skeletal bases. The mandibular intercanine diameter should rarely increase during adolescent treatment, since such an increase has been shown repeatedly to be unstable irrespective of the appliance use 17.24.26
e) Spacing Ideally, all teeth in both arches should have firm interproximal contacts and there should be neither crowding nor rotations of the teeth. However, the Bolton Index (see Chapter 11) may reveal that such perfect results are impossible and that some spacing or crowding is inevitable.
1) Curve of Spee-Occlusal
Line
Generally the occlusal line should be level and its final relationship to the mandibular line determined prior to treatment, according to the steepness of the mandibular line and the A-B relationship (see Chapter 12). The desired angulation of the incisors to the occlusal line is usefully decided prior to treatment.
3. Occlusal and Functional The desired occlusal pattern .(group function or cuspid rise) should be determined at the start and brackets placed accordingly. The treated occlusion should display no deflective interferences during mandibular occlusal movements or in the retruded contact position (centric relation). There should be no balancing interferences and the posterior teeth should disclude during protrusive movements.
4. Soft-Tissue Profile and Esthetics It is harder to quantify esthetic goals of treatment and personal
C. ASSESSMENT OF RESULTS OF ADOLESCENT TREATMENT All of the goals previously described may be used as criteria for assessing the results of adolescent treatment (Fig 16-1). Every general practitioner must be able to evaluate the clinical results of orthodontic colleagues in order that patients may be sent for the best treatment available. But there is another good reason why general practitioners must have a precise, clear picture of the possibilities of good orthodontics: that is to set high standards for the cases they choose to treat themselves. One must demand of oneself the same high-grade results one insists on from the orthodontist. Evaluation of orthodontic treatments must be done precisely and with caution for there are many variables which determine the quality of a treated result. Unless one knows exactly the conditions under which a case was treated, it is wise and professionally prudent to be cautious in conclusion and discreet in comment; nonetheless there are guiding principles to use in evaluating any tn;a~ed case. "~. • When adolescent treatment is progressing in an unsatisfactory manner or an unsatisfactory result is observed at the "end" of treatment there are no easy alternatives. Poor treatment does not stabilize or improve with time. Retreatment to the standards to be described is really the only satisfactory solution. For this reason adolescent treatment must be accompanied not only by meticulously designed original goals but also by persistent monitoring throughout treatment. Should an unsatisfactory result necessitate a consultation or referral to a colleague for advice andJ.or retreatment, complete original diagnostic records are invaluable.
436
Treatment
A1bPI SE-FMN-A Ba-Se-B 'lIFOP I/Md Measure Pol SNA SNB SE-N-A Ba-Se-Gn I/MdPI./A-B PI I/A-Po l/FOP Horizontol
----------
MdPL/A-B
-3 FEMALE
-2
-ISO. X
ISO. 2
3
o
JW /2-5
JW 12-5
CLASS
A1c
n
PLOT,
HORIZONTAL
Skeletol Closs II? Mld-foce Prognothic? Mondible Retrognothic .;) Mondibulor teeth Procumbent
+,-
Moxillory teeth Procumbent
50'4294026542757661197191947'1100558121133222761128 E (El B+ B C+ C 0+ 0 F F
F
F
FE FE Fe Fe 'C 'C Fo Fo A A A
N=697 Unclassified Incomplete
=
JW
12
Data
A
=
25
FIG 16-1. Records of well-treated
adolescent
cases. A, case of well-treated
Case 11type B-2 malocclusion. A-1·, before treatment: a, cephalometric tracing with profile analysis measurements and norms for 12-
year-old girls; b, Class!hanalysis borization. (Continued.)
Z-score
chart; c, horizontal
ar-
Adolescent
A29 J.W. • Before (12-5) A After (15-7)
VERTICAL -3
Cranial 8as~ PM Vert/FMN-SE
-2
- tS.D.
ANALYSIS X
3
2
t S.D.
MALES
90
85
90 I
85
Maxilla MALES
PM Verl/Polline
95
90
I
A95
FEMALES
Occlusion PM Verl/Oce!.
line
MALES
(not 0 constant in Closs DJ
~5
FEMALES
1051110
175
I
Mandib/~ PM Vert/Mond.
Line
MALES
I
i 95
125
I
115
I
120
I
130
I
125
I
FIG 16-1 (cont.). A-2, after treatment. This patient was treated with hi-pull extra-oral tractiol"), and a full edgewise appliance.
(Continued.)
Treatment
437
438
Treatment
FEMALES
-3
~ Bo-SE-fMN
SE-FPolNA
CranlaIBou-Moll(/1b116(HJ Bo-SE-Me . Bo-SE -Pog . CrolllOlBou-MOI7(/iblftfV) Bo-SE/Moncl. Line
-IS.O. l<'
IS.o. 2
~~ 14!.b I~~ 11~~~~-Ll I 120 ,~t ,..,! ...• ~..
Ba-S-No Cronio/8Qstl-Noxi/lQ $-N-A
-2
l
'"
3
I~.
I~
j,~",
;l~$
I I
.0
,
las
~.
190;
u' .. 11
I I
••
I
60
!
eo
PM VertlMond.Une Moxillo-Mandlbltl Mood. Une/A-a
F~.OcclLn./A-B
~
(nOlo""",.1OtrI1
fMN-A-B
I ,
''i45
150 ,
1" I CK 12-0
FIG 16-1 (cont.). B, case of well-treated Class III rT)alocclusion. B-1, pretreatment records: b, the cephalometric tracing with modified counterpart analysis data indicate maxillary deficiency and a severe Class III A/B relationship; c, the basic morphologic analysis Z-score chart, B-2,
-. postlJeatment records. Note the improvement in the skeletal relationsh'ip anteroposteriorly and the compensation in the dentoalveolar area, This patient was treated with face mask traction and a complete edgewise appliance,
Adolescent 1. Occlusion The following is a checklist of occlusal features useful in evaluating the results of orthodontic treatment. The classic article by Andrews provides excellent reading on this topic. I
a) Occlusal Plan Irrespective of the merits of various theories of occlusion, the intended plan of occlusion should be readily obvious on any treated case. If a cuspid rise occlusion was chosen, then the entire occlusion should be consonant with that theory. If group function was the plan, then the occlusion should be judged by the principles of that approach.
b) Molar Relationships Much orthodontic treatment focuses only on first molar occlusion, but the occlusal relations of all molars and bicuspids should be studied carefully and the lingual molar occlusion is particularly revealing.
c) Cuspid Occlusion While the cuspid occlusion is as important as the molars, it is not always possible to have equally good molar and cuspid relationships if there are tooth size disharmonies. More compromises in cuspid occlusion and overbite and overjet are necessary in men and boys because of the sexual dimorphism in maxillary cuspid size. d) Incisor Position Incisors must be placed well over the basal bone in each arch and well related to one another. Careful root positioning determines incisal stability and esthetics. While lay persons may judge an orthodontic case by incisal alignment alone, the dentist must ask how the incisors have been fitted to the skeletal profile and how they participate in all occlusal functions.
e) Functional Occlusal Relations The occlusion must be studied in the retruded contact position (centric relation) and in the intercuspal position (centric occlusion). Gnathologically oriented orthodontists often attempt to achieve a point centric in the retruded contact position; others will devise an occlusal plan which permits a "long centric." Under either scheme, they must obtain a complete AP occlusal correction at the end of treatment and the cusp-fossa relationships must be meticulously correct. There should be no occlusal interferences in the retruded contact position nor any between the retruded contact and intercuspal positions. It is especially important that there be no balancing interferences (more apt to appear at the conclusion of extraction treatment). In protrusive occlusion the incisors should contact symmetrically and there must be complete posterior disclusion (see Chapter 15, Section D 14, Temporomandibular Dysfunction) . fJ
Root Positions
In extraction cases, it is important that the roots be parallel and directly beneath. the crowns to avoid loss of interproximal contact. In treated crossbite cases, root positions must agree with crown correction.
Treatment
439
g) Alignment It is naive to consider alignment of the crowns the most critical feature of a treated orthodontic case. Crown size disharmonies may still be present at the end of treatment when there is a Bolton discrepancy. Disharmonies of tooth size and the adaptation of occlusal function to continuing growth may deny perfect alignment in some cases.
2. Soft Tissues Facial and tongue musculature play an important role in stabilizing orthodontically treated ~ases, and the facial soft tissues determine, to a great extent, esthetic results. The time of treatment and the time of the evaluation are important since there are significant soft-tissue growth changes during childhood and adolescence28 One must also decide whether or not any adaptive functions which accompanied the mal occlusion are still present after treatment.
a) Lips The lips should be studied at rest as well as in action. With the patient at rest, relate the lip line to the maxillary incisors. Note the action of the lips in speech and breathing as well as facial expression. In all functions they should be relaxed, well adapted to the skeletal profile and the incisors, at no time strained, and revealing minimal gingivae except during a full smile.
b) Tongue At rest the tongue should lie mostly within the mandible with the dorsum visible and the tip below the mandibular incisal edges. If the tongue tip lies atop the lower incisors at rest, one may expect a residual open bite when the teeth are in occlusion.
c) Swallow The unconscious swallow is probably the single most important occlusal stabilizing feature (Chapter 10 gives details for evaluation of the swallow). Test whether or not the teeth are in occlusion during the unconscious swallow, observe the position of the tongue during the swallow, and note any abnormal tongue activities.
d) Gingivae Gingival health after orthodontic treatment reflects not only oral hygiene but also the positions of the teeth achieved at the end of orthodontic therapy. 29 Especially vulnerable is the gingival height of mandibular incisors" and the gingival relationship to maxillary molar and bicuspid roots after palatal expansion. 10 ., 3. Facial Esthetics Because each face is unique, it is impossible to produce identical results for all patients; rather, orthodontic treatment should enhance the patient's individual esthetic features. Especial care must be taken in evaluating the child patient for there is a tendency to apply adult standards of facial esthetics. Serial studies of the variability and change in soft-tissue and integumental growth are rare28 The nose shows continued growth into adulthood, which alters facial esthetics. Faces which seemed to be rather full in the
440
Treatment
dentoalveolar region in adolescence may look much better after adult nasal growth is completed. The two most common problems in facial esthetics involve extraction. In some cases choosing not to extract strains the limits of the alveolar process to achieve alignment, yet time, growth, occlusal function, etc., may improve the eventual facial esthetics. In other instances, unfortunately, the same factors produce crowding and mal alignment. Extractions which produce adult faces in young adolescents are to be deplored, for those same faces a few years later may look almost edentulous. No formulas are infallible when planning treatment and it is always easier to second-guess treatments after the fact. Criticism comes easier than craftsmanship. Facial esthetics is a matter of personal judgment, so one's owl} opinions about esthetics should be imposed with caution on colleagues who saw the patient at another time.
clusal and interproximal wear, alveolar remodeling, and normal craniofacial growth. If the occlusion was not equilibrated well at the end of active treatment, adaptive homeostasis is less easy and some relapse may be seen irrespective of how long retainers are worn. Furthermore new restorations may upset the orthodontist's occlusal result. All of these events may seem minor, but in the patient susceptible to temporomandibular disturbance-and that includes many of the more severe skeletal malocclusions-minor occlusal disturbances can be disruptive. The diminution of temporomandibular joint symptoms and the maintenance of temporomandibular health and function are primary goals of all orthodontic treatment, and therefore, assessment of temporomandibular joint function is an integral part of the evaluation of any orthodontic case.
D. CLINICAL PROBLEMS*
4, Alveolar Process and Periodontium The height of the interseptal tip, the contours, and the general health of the alveolar bone and thickness of the periodontal ligament space may be studied in the periapical radiographs.
,.
1. Number of Teeth a) Congenitally
Missing
Teeth
5. Root Resorption There is no question that root resorption occurs in some orthodontic patients more frequently than in others and is often associated with the necessity to translate and intrude incisors over a considerable distance. 15. 16 Minor root blunting may be considered a sort of "scar" of treatment. On the other hand, excessive root resorption, particularly where roots were short originally, is an occasional tragedy of orthodontic treatment. Unless the dentist judging treatment after the fact has the original radiographs and can prove (not an easy thing to do) that the orthodontic treatment was the sole cause of the root resorption, critical comments should be carefully phrased and professionally presented to the patient. Idiopathic root resorption is a fact of life. I have seen cases with normal roots at the end of orthodontic treatment that several years !lIter showed root resorption. I have also seen cases in which the orthodontist apprised the patient of the presence of active root resorption at the start of treatment and they were willing to take the calculated risk of a bit more resorption. See Chapter 13 for a discussion of root resorption.
6. Temporomandibular
Joints
Orthodontic treatment has been blamed for some difficulties in the etiology of temporomandibular
joint disorders, but there is
good evidence that temporomandibular abnormalities are an integral part of many skeletal dyplasijis32 and that orthodontic treatment diminishes rather than exacerbates temporomandibular symptoms.30
If treatment was completed before eruption of second molars, their emergence may produce occlusal interferences which exacerbate temporomandibular symptoms in susceptible patients. In a similar way, the eruption of the mandibular third molar may elevate the distal marginal ridges of the mandibular second molar, creating occlusal interferences. The well-treated orthodontic case achieves an occlusal homeostasis and thereby adapts to such features as tooth drift, oc-
• • •
Definition of the problem and background: Diagnosis: See Chapter 15. Treatment: See Chapter 15.
See Chapter 15.
1. Maxillary Lateral Incisors.(a) Goals.-If a bridge or bridges are to be placed, the goals of treatment must include attentive detail to the positioning of the central incisors and cuspids which may be abutment teeth. When the cuspid and all other maxillary posterior teeth are to be moved mesially, obviating the need for a bridge, then the principal new goal is the meticulous placement of the cuspid root to parallel the central incisor. The first bicuspid and all posterior teeth are moved forward into a Class 11 relationship. (b) Methods.-A precision bracketed appliance is necessary, usually in both arches. As the cuspid is moved mesially and turns the corner of the arch, its crown is gradually reshaped to simulate a lateral incisor (Fig 16-2). The labial surface must be flattened, the incisal edge squared, and the lingual surface reduced considerably to achieve an esthetic overbite and overjet. The opposite lateral incisor which is present is usually smaller than normal size • (see Chapters 6, 7, and 15) and therefore should be placed to accept additive composite build-up for esthetics and stability. CarefuL.and somewhat difficl\!t· mechanics are required to position all of th~ maxillary teeth correctly, b~t the results in most cases are well worth the effort." (c) Problems.-Moving the first bicuspid forward into the cuspid region usually creates balancing interferences; therefore, its lingual cusp must be reduced gradually during its mesial move* All of the cases shown in this chapter were treated by the author unless another clinician is credited. In a book of this size and scope, examples of every problem discussed cannot be shown; therefore, only some representative cases appear.
Adolescent
Treatment
441
FIG 16-2. Moving the maxillary cuspid mesially to serve as a lateral incisor. A, panoramic radiographs after previous orthodontic treatment by a colleague. Note the excellent result obtained. There was a maxillary retainer with a lateral incisor pontic in place. The adjacent central
incisor had a serious crown fracture replacement. The patient's mother is a dental hygienist, and the patient is a dental student. Despite the splendid orthodontic result obtained, they asked me to treat the case again to obviate the need for a bridge. Band C, results after treatment.
ment. If a cuspid rise occlusion is desired, the bracket height on the first bicllspid must be placed atypically to guarantee its extrusion. (When using cuspids to replace lateral incisors I have generally found group function occlusion to be more satisfactory). Particular attention must be paid to the positioning of the molars and they must be equilibrated by occlusal grinding to secure the occlusal result.
pids by mesial movement of all posterior teeth is not a difficult technical problem for anyone skilled in precision bracketed appliance therapy. While the problem is best treated earlier (see Chapter 15), it can still be treated well in adolescence with bracketed appliances. Its treatment with removable appliances is not recommended since ultimate parallelism of the roots is essential
2) Mandibular Second Premolars.The goals of treatment are to obviate the need for a bridge, secure a more correct intercuspation, and guarantee the height and health of the alveolar bone on the mesial aspect of the mesial root of the first molar. If a primary second molar is retained unduly, this usually results in an undesirable relationship of the alveolar septum between the second primary molar's root and the first permanent molar (see Fig 1722). Treatment of congenitally missing mandibular second bicus-
f?r a stable result. .,~' ~..The method illustrated in ~ig 15-5 was developed by Professor van der Linden and has advantages over simply extracting the primary molar and moving the permanent molar forward. 3) Multiple Absence of Teeth.-See
Chapter 17.
a) Loss of Permanent Teeth (Trauma, Caries, and Other Causes) • •
Definition of the problem and background: see Chapter 15. Treatment: see Chapter 15. While the general principles
442
Treatment outlined in Chapter IS for treatment of lost permanent teeth at an early age apply in adolescence as well, there are two significant differences. First, one can not take such ready advantage of the natural forces of eruption and mesial drifting. Second, precision bracketed appliances-can now be used more easily.
When one or more first molars are lost, the same difficult problems are encountered as at an earlier age except that the shape and size of crowns of the third molars are seen more clearly and one can take better advantage of their eruption. b) Supernumerary Teeth See Chapter IS. It is a rare event when supernumerary teeth are encountered in the completed adult dentition. The major problem at this late date is not the supernumerary tooth itself, but the basic malocclusion, on which the treatment planning should be focused.
2. Variations in Size and Shape of Teeth • • •
Definition of the problem and background: Diagnosis: see Chapters IS, 8, and 11. Treatment:
see Chapter IS.
a) "Large Teeth" This problem is really that of simple crowding (see Section 4, Problems Singular to the Young Adult Dentition). b) Small Teeth See Chapter 15. Esthetics are more critical at this age than during childhood and "permanent" treatment combining orthodontics and restorative dentistry can be quite sucessful. The introduction of composites, laminates, and porcelain veneered crowns offers esthetic and functional success previously not possible. c) Anomalies of Tooth Shape See Chapter 15. A more permanent treatment of crown anomalies is possible when started in adolescence. Moreover, problems handled earlier often may be treated again, advantageously, to an esthetic result not possible earlier. Anomalies in root length and morphology are more obvious in adolescence and often play an important role in treatment planning (e.g., deciding whether to remove first or second bicuspids in extraction cases).
3. Spacing of Teeth a) Localized Spacing See Chapter 15. Diagnosis of localized spacing is easier when the permanent dentition is complete and treatment to a more esthetic finished result is possible. b) Generalized Spacing See Chapter 15. After growth is largely over one may adopt a different approach to the problem of generalized spacing. Usually the solution requires combining prosthetic or surgical skills with orthodontics, so cooperative treatment planning is essential. Occasionally prosthetics alone is sufficient. More typically, consol-
idation of the teeth within the arch is done by orthodontics prior to placing bridges with pontics representing accessory bicuspids or molars in the spaces created orthodontically. I prefer to avoid surgery except in the most gross instances of macroglossia. Modem restorative procedures make possible results of the highest quality 'with infrequent resort to surgery.
4. Problems Singular to the Young Adult Dentition a. Crowding Dealing with crowding in the young adult dentition is different than managing space in the mixed dentition. Crowding is a result to be treated after the fact. Space management is controlling development.
1) Simple crowding.(a) Definition.-Simple crowding is defined as disharmony. between the size of the teeth and the space available for them. It is crowding uncomplicated by skeletal, muscular, or occlusal functional features. Simple crowding is most frequently associated with a Class I molar relationship, although it may be found with Class II horizontal type A (maxillary dental protraction and the normal facial skeleton). (b) Diagnosis.-First, complete a diagnosis setup without advancing the lower incisors or expanding the bicanine, or bimolar alveolar arch diameters (see Chapter 11) unless the lower posterior teeth are obviously tipped lingually. The diagnostic setup under these constraints answers the question of whether or not alignment, simple uprighting, and rotation alone will solve the problem. The diagnostic setup, a cephalometric analysis, and judgment of facial esthetics and the lip musculature are critical in defining a simple crowding case and planning its treatment. There are no infallible cephalometric rules providing easy determination of quantifiable amounts of arch perimeter increase for measurable changes of incisor position or angulation. Nor are there specific and reliable rules for combining lip, teeth, and bony measurements from the cephalogram to provide simple answers about extractions: all have built-in subjective factors of judgment. One may advance and reposition the incisors in the cephalometric tracing to visualize two-dimensionally and statically how such repositioning encroaches on the lip muscles. In the end, however, one is forced to make a clinical judgment, which at best integrates three semiquantified factors, namely the a~ount of new space which would be made by incisor repositioning, the amount of space whi~h might be created t;>y. changing arch form and dimensions, and tne amount of such dental ch,anges the lips might tolerate. Schemes for including the third molar region in a "total arch analysis" have been presented and are useful provided one understands (1) the importance of experience in making judgments about esthetics, and (2) the large Standard Error in methods thus far suggested for predicting third molar eruption. Several well-designed studies of posttreatment changes indicate that widening the mandibular cuspid diameter, irrespective of the appliance used, is not well maintained. 17,24,26 Those who claim otherwise for their favorite appliance have the obligation to
Adolescent present patient results, as others have done, many years after active therapy.
(c) Treatment.•
Non-extraction.-
Treatment planning is Simply choosing
the appliance to achieve the results displayed in the diagnostic setup. Precision bracketed appliances are particularly advantageous in these cases, while lip bumpers are useful adjuncts since they increase the arch length and condition the lip musculature (see Fig 15-23). Small amounts of space often may be created in either arch by their use during alignment and positioning. Larger amounts than possible with lip bumpers can be garnered with extra-oral traction but such increases are difficult to maintain in the •
lower jaw. Extraction.Treatment planning is primarily concerned with the choice of teeth to be extracted and the tooth
movements necessary for positioning and closure of any residual spaces after alignment. First bicuspids: In cases of anterior crowding, first bicuspids are closest to the problem; thus, their extraction simplifies alignment, is the least apt to upset the molar occlusion, and is the best alternative for maintaining vertical dimensions. The disadvantages of first bicuspid extractions have been greatly exaggerated by some in recent years. When the facial esthetics are good at the start, despite severe incisal crowding, removal of first bicuspids can harm appearance only if the appliance mechanics are mishandled .. It is essential to maintain parallelism of the cuspid and second bicuspid roots after space closure. Second bicuspids: Second bicuspids are sometimes chosen for extraction when there is a lesser space discrepancy making space closure and vertical control easier after anterior alignment. They may be the choice when one wishes to maintain the soft-tissue profile and esthetics. It may be disadvantageous to take out second bicuspids where the crowding is extensive and solely in the incisor region since anchorage control is more difficult. Second bicuspids show more variability in development and morphology and thus are sometimes chosen for extractions irrespective of the site or amount of crowding. Second molars: In recent years there has been a revival of the advocacy of second molar extractions (see Chapter 15). They are rarely the teeth of choice in simple crowding, except in horizontal type A or horizontal type B (see D6, Class 1I) where the removal of maxillary second molars may aid dorsal movement of the maxillary dentition when the third molars are normal in size and shape. Often the removal of second molars provides too much space in the wrong place for simple crowding. Further, the mandibular third molar's development and eruption may be complicated and an additional later period of orthodontic treatment made necessary by second molar extractions (see Section 4-a-2, Complex Crowding, and Suggested Readings). Other alternatives: Differences in crown size, location of carious or restored teeth, and occlusal factors revealed in the diagnostic setup sometimes suggest the extraction of first bicuspids in one arch and seconds in the other. The extraction of a first bicuspid in one quadrant and the second on the opposite side of the same arch is rarely indicated due to differences in crown size. It may be necessary, however, due to asymmetry, caries, or to avoid
Treatment
443
extraction of a sound tooth. The therapeutic extraction of first permanent molars in simple crowding is almost always contraindicated. If one or more first molars have already been lost (see Chapter 15) the extraction of other first molars may be considered, but the treatment planning is complicated, as noted in Chapter 15, and the necessary tooth movements are extensive and difficult. 2)
Complex Crowding.-
(a) Definition.-Complex crowding is crowding caused and complicated by skeletal imbalance, abnormal lip and tongue functioning, and/or occlusal disfunction as well as disharmony between the sizes of the teeth and the available space. (b)Diagnosis.- The diagnosis of complex crowding itself is secondary to the diagnosis of any skeletal dysplasia. Tooth repositioning necessary to camouflage skeletal dysplasia usually aggravates complex crowding; therefore, first estimate the effects of treatment of the skeletal dysplasia on the crowding. Expected growth may affect additionally the crowding. The use of a Visual Treatment Objective is very helpful for the diagnosis and treatment planning of complex crowding (see Chapter 12 and appropriate sections later in this chapter). (c) Treatment.- The choice of which teeth to extract for the correction of complex crowding is critical. Review carefully the considerations discussed above for extractions in Simple Crowding. Often one bicuspid in each quadrant will be found to be the most logical solution, but the choice is seldom simple. Complex crowding cannot be understood by study of the casts alone for it is more than a tooth size-available space problem, and can be made worse by ill-conceived "treatment." Failure to appreciate the importance of skeletal morphology in the etiology and treatment is a common mistake. Some typical severe mal occlusions suggest particular extraction procedures; for example, in Class II horizontal type B, when the crowding is all in the lower arch, it may be advantageous to extract upper second molars and two lower bicuspids. Under no circumstances should second molars be extracted unless the third molars are normal in size and development. Lower second molars may be considered for extraction only when they are severely malplaced and inadequate alveolar development denies their complete eruption. Never be casual about the extraction of lower second molars. Though at first it may seem the most logical choice to relieve the crowding, even apparently well-positioned third molars may not erupt into satisfactory positions after second molar extractions (see Figs 15-31 and 16-3). Therefore, a subsequent period of active treatment is necessary. Far too often th~ .removal of lower second molars has been a cheap, quick fix which leaves the unwitting patiel)t with another problem and another treatment years later 27 (see Suggested Readings). In my opinion, there is far too much overenthusiastic advocacy of the extraction of second molars in the absence of well-documented study of consecutively treated cases. Upper third molars are surprisingly cooperative after second molar extractions, often erupting nicely into position, but lower third molars respond quite differently and their behavior after second molar extractions is, at present, only crudely predictable (Fig 16-3). Whatever the extraction choice, it must be followed by
444
Treatment
FIG 16-3. Two examples of second molar extractions in orthodontic treatment. A, an excellent result. Note that in one quadrant a first molar was extracted. Observe too that neither of the lower third molars, even in this splendid result, is positioned correctly and that the patient might benefit from a bit of further treatment even at this late date. B, a less satisfactory result. Note in the lower arch the differing positions of the erupting second molars. After complete and successful orthodontic treatment the third molars in the lower arch were not able to position themselves adequately. Note too, the difference in the size of the two upper third molars as they erupt. This difference is not as noticeable in the earlier radiograph. (Courtesy of Dr. George A. Eastman.)
Adolescent Treatment precisely controlled tooth movements to close the spaces, parallel the roots, fit the incisors to the profile, and define a secure occlusion. Whoever makes the decision about extractions is ethically reponsible for their sequelae. b) Delayed eruption
1) Impactions (a) Maxillary cuspids.-Background: When impacted maxillary cuspids are first discovered in adolescence, root formation is apt to be already completed. Thus the chance for utilization of the natural eruptive forces is likely past. The teeth are truly impacted, but they mayor may not be in ectopia. Diagnosis: Diagnostic factors of interest include the position of ,both crown and apex, the space available to accommodate the cuspid in the arch, and the position and health of adjacent teeth-especially the roots of the lateral incisor, the intactness of the labial cortical plate of bone, the willingness of the patient to undergo prolonged orthodontic treatment, and the relationship of the condition to other orthodontic treatment needed. All require a meticulous radiographic perspective. The size of an impacted cuspid may be determined by measuring the antimere. If both cuspids are impacted, measure the crown width of the maxillary first and second premolars and estimate the size of the cuspid crown by referring to appropriate tooth size charts (Chapter It). Do not forget that sexual dimorphism in crown size is more obvious in
A
the maxillary cuspid than any other tooth. Measurement of crown size of impacted cuspids in the radiograph is flawed by distortion due to the angulation and the curvature of the film. Study carefully, in the radiograph, the health and morphology of the cuspid's root as well as its position. Treatment: Two treatment procedures are possible in adolescence: (I) surgical exposure followed by orthodontic movement and (2) autogenous transplantation. Surgical exposure and orthodontic movement: Surgical exposure and orthodontic movement of the tooth into position are favored in most instances because, though more prolonged, the treatment is less hazardous. If the primary cuspid is still in position and the unerupted ·permanent cuspid is ideally located, surgical exposure may be made after the initial stages of orthodontic bracket engagement and leveling elsewhere in the arch. At the time of surgical exposure a cuspid bracket is positioned on the crown of the tooth. Following subsequent healing, traction may be applied by an elastomeric chain and later direct tying to the archwire. In the past, stainless steel lariats were passed around the neck of the tooth or threaded pins were inserted into holes drilled into the crown to apply traction. The development of direct bonding techniques obviates the need for such drastic procedures and a healthier gingival attachment results.31 If a bracket may not be advantageously positioned, a lingual button or cleat may be bonded in place and tied tightly with a
••
.•
/
FIG 16-4. Treatment of bilateral palatally impacted maxillary cuspids.
445
446
Treatment
twisted stainless steel ligature, which is passed through the surgically incised mucosa and secured to the archwire, or placed passively around adjacent brackets. When healing is complete, this ligature may be tied directly to the archwire, whose tension aids the tooth's eruption. When the crown becomes more fully exposed, the attachment may be replaced with a bracket. OI1hodontic positioning of impacted cuspids is tedious since the forces must be gentle and continuous and the distance is great. Because of the surgical uncovering, the ultimate gingival contour may not be perfect. When the crown is in position, paralleling of the root is necessary to satisfy occlusal needs, develop the cuspid eminence, and guarantee stability of the result. Figure 16-4 illustrates a treated maxillary cuspid impaction. More extreme malpositions necessitate other tactics. When the apex is reasonably placed but the crown is not, the surgeon may carefully remove bone around the crown and gently reposition it without altering the apex. The crown is then held in place with surgical cement during healing and prior to instituting traction. Autogenous transplantation: Autogenous transplantation may be indicated in older patients or those unwilling to tolerate prolonged orthodontic treatment. It is also useful in cases of transposition, extreme malposition of the impacted tooth, and dilaceration. It is usually a one-stage surgical procedure-the root is not filled. 18The impacted tooth is carefully removed and placed beneath the mucosal flap while an artificial alveolus is cut in the bone. Then the cuspid is carefully placed and splinted during healing. Professor James P. Moss of Great Britain, more than anyone else, has studied and perfected the details of the procedure and has reported large numbers of consecutively treated cases followed years after treatment with surprisingly good results.]8 Although transplantation is sometimes done as a single form of treatment without orthodontics, better results are obtained when combined with orthodontics. It may be advantageous to have a period of preliminary orthodontic therapy before the surgery. The surgeon mayor may not choose to use the orthodontic appliance as the splint. After surgery it is important that the transplanted cuspid have a period of secure passive splinting prior to any continuing tooth movements, but the transplanted tooth must not be in traumatic occlusion. Orthodontic treatment after transplantation should be minimal and not be started until the alveolar process has reformed around the transplanted tooth, and the tooth's vitality is assured. Autogenous transplantation is quicker and allows suc-
cessful treatment of some cases which could not be handled by simple surgical exposure and orthodontic movements alone. It requires skillful surgery and an appreciation by the surgeon of the orthodontic problem, just as the orthodontist must be aware of the surgical difficulties
(b) Second Molars.-Second molars may be impeded in their eruption when they become locked under the distal bulge of the first permanent molars. The locking may be relieved by the use of "disimpaction springs" which separate the second molar from the cervix of the first and free it to continue its eruption. In more severe cases of semi-impaction, or after second molar root length is completed, a compression loop spring may be fashioned and fitted into a buccal tube on the first molar and formed to contact a bracket or button attached by composite resin to the exposed crown of the second molar (Fig 16-5). (See also the earlier comments about second molar extractions in complex crowding, and the discussion of third molars which follows) .. '
(c) Third molars.- The extraction of obviously impacted third molars has been advocated early in adolescence when their removal is easier and is less apt to damage adjacent teeth. In severe instances this logic is sound, but it must be remembered that there is. as yet, no thoroughly dependable method for predicting which third molars will erupt successfully, which will impact totally, and which partially. Some of our best clinicians have worked on this problem, producing ingenious predictive formulae, but none has yet been found reliably unerring in a practical percentage of all instances. Nor can one yet estimate well the effects of orthodontics on third molar position or development. 23 There seems to be too much exuberant advocacy of early removal of third molars, an advocacy unsupported by sound clinical research. There is little logic in their prophylactic removal for their alleged role in mandibular incisal crowding is unsubstantiated9. 23; however, their utility in combined orthodontic-restorative rehabilitation later is well known (Chapter 17). Retained third molars are often very useful in cases where orthodontics is combined with adult full-mouth rehabilitation. (2) Ankylosed Permanent Teeth.-First molars, maxillary cuspids, and maxillary incisors are the permanent teeth most apt to be ankylosed. The etiology is generally unclear, though a history
A
FIG 16-5. Treatment of "locked" (semi-impacted) mandibular second permanent molars. This is the same case as shown in Fig 15-40. A, a method for preliminary uprighting. A lingual button is bonded to the occlusal surface of the second molar, and an elastomeric chain is
attached to the button and joined to a wire inserted in a tube on the first molar. e, later, conventional orthodontic appliances complete the eruption. In this instance a compressed coil spring is used. C, the result with the patient some years out of retention.
Adolescent Treatment
447
."
FIG 16-6. Ankylosis of a mandibular first permanent molar. A, in the initial stages of ankylosis, age 9 years. B, after successive attempts to
of trauma is associated with incisor ankylosis. The goal of treatment in adolescence is to establish, if possible, proper occlusion: three methods are used: surgical, orthodontic, and restorative. The tooth should first be surgically exposed, carefully luxated, and splinted into an improved position. Subsequent orthodontic movements to an ideal position should then. be attempted, though ankylosis usually reappears. I have had less success with orthodontic movement after luxation than some reporting in the literature. If ankylosis recurs and the tooth is to be retained consider building it up to occlusion with composite until growth is apparently over and a permanent restoration can be placed. There is a danger in retaining ankylosed teeth, namely localized cessation of alveolar growth which may bare the roots of adjacent teeth and predisposes to periodontal difficulties (see Figs 16-6 and 17-22). One must look past the occlusion and the present condition. Extracting an ankylosed permanent tooth may indeed be the conservative answer and leaving it a troublesome radical "solution." If an ankylosed molar must be extracted, do not overlook the possibility of orthodontic closure of the edentulous space (see Chapter 17 and Fig 17-17).
loosen and replace the tooth occlusally, age 11 years. (Courtesy of Dr. Michael Riolo.)
Extensive bony pathosis can result in tooth loss in severe cases. Juvenile periodontitis requires the immediate attention of a periodontist, and orthodontics should not be started until the periodontist approves. Furthermore, careful monitoring by the periodontist should continue throughout orthodontic treatment (see Suggested Readings).
5) Lateral
Malrelationships
a) Background and Definition of the Problem As noted in Chapter 15, it is important to attempt to reconstruct the developmental history of all l~teral malrelationships. Functional crossbites, so frequent earlier, are only rarely seen in adolescents since the musculature has imposed itself during growth ev,el)tually producing asyfnmetric adaptive changes in the skeleton, alveolar arch, and/or tooth positions. Inherent skeletal asymmetry is far more difficult to counter at this age than the less obvious and milder dental and alveolar adaptations seen in an earlier simple functional crossbite.
b) Diagnosis c) Juvenile Periodontitis Juvenile periodontitis is a rapidly progressive, apparently bacterial disease appearing about the time of pubescence and characterized by bony lesions in the incisor and first molar regions.
1) Skeletal.-Posteroanterior cephalograms in the postural and occlusal positions are necessary for one to identify and differentiate both mediolateral and vertical skeletal asymmetry (see Chapter 12). Mandibular landmarks which change between the
448
Treatment
two vertical positions are evidence of residual neuromuscular occlusal dysfunction. The temporomandibular joint region should be searched for evidence of condylar or fossa asymmetry of either shape or position. Posteroanterior, lateral, and oblique cephalograms and panoramic or special radiographic .projections of the temporomandibular joint may be necessary. Asymmetries within the joint or condylar neck region are proof of long-standing adaptations to asymmetric dysfunction. (2) Dentoalveolar.-Asymmetry of tooth positions and alveolar development, both buccolingually and vertically, may be diagnosed from the PA cephalogram (see Chapter 12). Cast analysis of asymmetry (see Chapter 11) provides better visualization buccolingually, but vertical asymmetries are often obscured on the cast owing to the usual method of trimming the bases. Therefore, the Posteroanterior cephalometric analysis is critical to the diagnosis (see Chapter 12). It is important to determine the site and extent of dentoalveolar adaptation. When the asymmetry is confined to the alveolar process and teeth in the maxilla, the prognosis is the most favorable. Correction of mandibular alveolar asymmetry is usually limited to uprighting the teeth, idealizing the archform, and leveling the plane of occlusion. Frank skeletal asymmetry outside the alveolar region is much more difficult to foil, camouflage, or nullify at this age by orthodontics alone. (3) Neuromuscular.-Simple functional crossbites are rare at this age, but a neuromuscular component may persist and play an important role in temporomandibular dysfunction and associated symptoms. Therefore, be prepared to do a thorough analysis of the neuromusculature and temporomandibular joint in all adolescents with lateral malrelationships (see Chapter 10 and Section D12 later in this chapter).
c) Treatment (1) Goals.The primary goal of all treatment is to provide coordinated arch forms and balanced occlusal and temporomandibular joint function. Esthetic tooth positioning is secondary, but is usually easy to obtain when functional relationships have been normalized. If there is skeletal asymmetry it must be accomodated . functionall y, though one may attempt to provide camouflage esthetics by tooth positioning. I
(2) Methods.-
(a) Skeletal.-Skeletal •
•
•
methods include the following:
Maxillary corpus symmetry is restored by rapid palatal expansion, or by gradual palatal ex.pansion with a Quad-Helix appliance. Some vertical mandibular skeletal morphologic shape and size change may be still possible (not corpus width) by the use of functional jaw orthopedic appliances, although the best time for their use is past. If orthognathic surgery is necessary it usually is done later, although preliminary orthodontic treatment might be completed at this time.
(b) Dentoalveolar Correction.-The
most common therapy
may be to camouflage or counter skeletal asymmetry, alveolar asymmetries. Methods include: •
•
•
•
or to correct
Correction of maxillary alveolar process asymmetry by expansion with a Quad-Helix appliance and vertical development with an Activator or Bionator. The rapid palatal expansion method so efficient for maxillary corpus underdevelopment is less efficient when the asymmetry is confined to the alveolar process. In fact, its bilateral action and rigidity temporarily impede vertical asymmetric development and correction. Idealizing maxillary tooth positions and archform. This is done with bracketed appliances after a period of maxillary alveolar process correction. Idealizing mandibular dental and alveolar archform. This is done with bracketed appliances and may be begun after periods of maxillary expansion and/or functional jaw orthopedic appliance therapy directed at the mandible. Control of the occlusal plane height-a most important feature of treatment.
(c) Neuromusculizr.- The dentoalveolar correction outlined in (b) should diminish occlusal dysfunction and establish normal temporomandibular function, a primary neuromuscular goal. Functional jaw orthopedic methods enable one to position the mandible more favorably mediolaterally and vertically and to guide alveolar development buccally (in the maxilla) and vertically. Changes in mandibular form, muscle attachments, and improved symmetry of mandibular closure movements should also result. (3) Specific Problems.-Each clinical problem discussed is assumed to be the primary malocclusion. When they are combined with an AP skeletal problem, or a vertical dysplasia, the difficulties of treatment planning and execution are greatly enhanced: one must take care in assigning the primary name for the malocclusion. It is impossible to describe all of the combinations and permutations which may be seen, yet the clinician treating the problem must integrate the various diagnostic features into an individualized treatment plan, a far more difficult task at this age than earlier.
(a) Bilizteral Maxi/lizry Corpus Deficiency.-Bilateral
me-
diolateral maxillary skeletal deficiency is often associated with AP deficiency as well resulting in a skeletal Class III mal occlusion (see D-7. Class Ill, later in this chapter). Rapid palatal expansion is usually necessarry to secure correct buccolingual dental and alveolar relationships. A period of bracketed appliance therapy of both upper and lower teeth is usually necessary (see Fig 16-7). If the rapid palatal expansion does not secure sufficient widening, latir:orthognathic
surgery should ~e considered.
(b) Unilizteral Maxi/lizry Corpus Asymmetry.-Asymmetric maxillary corpus asymmetry is far less frequent than bilateral deficiency and must be verified before beginning treatment. Although the Quad- Helix appliance can be adjusted for unilateral expansion, I prefer to treat unilateral maxillary corpus asymmetry in the same way as bilateral corpus deficiency. The result will be an overexpans ion of the dentoalveolar process on the more favorable side, but that is not a problem, for occlusal function and the bracketed
Adolescent
Treatment
449
c
FIG 16-7. Rapid palatal expansion treatment for bilateral maxillary corpus deficiency. A, periapical radiograph at the start of treatment. Note the two supernumerary teeth. B, intra:oral photograph at the start of treatment. Note the bilateral cross bite and the malposed cuspids. C, a rapid palatal expansion appliance in place in the arch. D, radiograph obtained a short time after palatal widening had been achieved. E, photograph taken at the same time. F, the rapid palatal expansion
device is left in place, but inactive, as the median palatine suture fills wilh. bone and the maxillary central incisors drift toward the midline. G, radiographs of the midline at tt)e end of treatment and after the removal of the supernumerary teeth. H and I, studies obtained after the removal of the complete banded appliance and after the retention period. (Courtesy of Dr. Robert Aldrich.)
450
Treatment
appliances soon achieve alveolar arch coordination.
(c) Bilateral Maxillary Dentoalveolar Contraction.- The Quad-Helix appliance is the choice for an initial period of treatment, followed by upper and lower bracketed appliances to complete arch coordination and individual tooth positioning. (d) Unilateral Maxillary Dentoalveolar Contraction.- The Quad-Helix appliance may be adjusted for unilateral expansion of the teeth and alveolar process, although some bilateral expansion invariably occurs. Bracketed appliances may be inserted as soon as the maxillary expansion is under way; thus, alignment, arch coordination, and securing occusal relationships are all synchronized. Vertical occlusal asymmetries may be difficult at the end of treatment. (e) Unilateral or Bilateral Mandibular Dentoalveolar Contraction.- The Quad-Helix appliance is useful for uprighting mandibular teeth only when there is mandibular dentoalveolar contraction. As soon as this phase has begun, bracketed appliances may be placed in the mandible to aid in alignment and individual tooth positioning. Placement of maxillary bracketed appliances is also necessary for arch coordination, which may be difficult, especially initially. (f)
Gross Disharmony Between the Skeletal Bases.-It
IT
(Distocclusion,
Postnormal
2) Strategies of Treatment.-Of the general strategies for Class II treatment discussed in Chapter 15, those related to guidance of eruption and alveolar development, differential promotion of skeletal growth, translation of parts during growth, and differential restraint and control of skeletal growth are of greatly diminished use by adolescence. The primary strategy remaining in adolescents is movement of teeth and alveolar processes, plus controlling or promoting such residual growth as may remain. Posttreatment muscle conditioning. is still available as a retention strategy but the use of muscle forces to promote mandibular growth is largely past. Surgical considerations may assume more strategic importance in severe cases. The primary strategy is no longer manipulation of development but camouflage of skeletal dysplasia by tooth positioning. This principal new strategy means important changes in tactics.
is
indeed unfortunate when gross mediolateral disharmony between the maxilla and mandible is not diagnosed until adolescence, for this serious skeletal dysplasia can be treated far more advantageously at younger ages (see Chapter 15). Irrespective of whether there is bilateral or unilateral crossbite, the problem is usually primary skeletal dysplasia in the maxilla or the mandible with secondary dentoalveolar adaptation in the other. When there is bilateral maxillary corpus deficiency resulting in a bilateral maxillary lingual crossbite [see (a)], the treatment is fairly direct. It is usually successful, though difficult at this age, if there is not an associated skeletal Class III malocclusion. When the problem is primarily that of maxillary skeletal hyperplasia and the mandibular teeth all are in total bilateral lingual crossbite-the socalled "Brodie syndrome"-the problem is much more severe and exceedingly difficult to correct at this late age. Gross mandibular corpus expansion mediolaterally is impossible since there is no patent midline suture. Heroic and very skillful use of fixed precision bracketed appliances to contract the maxillary dentoalveolar processes and expand the mandibular (in conjunction with use of a mandibular Quad-Helix appliance) is required to avoid surgery. The cant of the occlusal and mandibular planes and the amount of vertical freeway space are critical diagnostic features. 6. Class
1) Differential Diagnosis.The differential diagnosis for the different types of Class 11 malocclusion is discussed in chapters 12 and 15; general strategies and tactics for Class II therapy are discussed in Chapter 1521 The differences in both strategies and tactics of Class 11treatment at different ages are important, though differential treatment planning ba~ed on development often is not presented in the literature.
Occlusion)
a) Background Class 11is the most frequently occurring severe malocclusion. Furthermore, treatment of severe types is made more difficult with time and the cessation of development. Elaborate details of mechanotherapy cannot be presented; however, the principles of treatment, critical diagnostic differentiations, and certain complications and problems are appropriate here. A clear understanding of the principal goals and strategies of treatment is necessary as a basis for further study and development of skills in Class 11.
3) Tactics.-Bracketed appliances, the chief tactic, assume a far more important role at this age, though palatal-widening devices and extra-oral midface traction are useful. Functional appliances may still be used to advantage in a few late skeletal developers (usually boys).
b) Rationale for Adolescent Class
II Therapy
Although some forms of Class 11malocclusion may be more advantageously treated at a younger age, the opportunity for early treatment sometimes never occurs because the patient is not seen until adolescence. Treatment in adolescence may be the second phase of diphasic treatment, the skeletal aspects having been treated earlier and the tooth positioning and occlusal niceties postponed until the arrival of most permanent teeth. Pragmatic reasons for treating at this age include postponing treatment to allow social maturity. This is done to provide an intense shorter period of treatment, or to make certain that the family and patient have fully accepted the responsibilities and consequences of orthodontic therapy. Finally, some cases are just .as easy (even easier) to treat in adolescence as earlier (e.g., horizontal types A and F).
c) Differential Treatment " .8}gnificant differenc;~ in severity of the several types of Class 11are often not appreciated by the inexperienced2! In this chapter it is presumed that the reader has a thorough command of the diagnostic discrimination of Class 11 types (see Chapter 12) and an understanding of the basic treatment strategies for each type (see Chapter 15). The diminished growth potential and the arrival of the permanent teeth significantly change the tactics of Class 11 treatment from those used.earlier (see Chapter 15). 1) Horizontal Type A.-Maxillary a normal skeletal profile is characteristic
dental protraction of this type.
with
Adolescent Treatment
451
MM
--12-1
---16-2
G
MM
--12-1
MM
---16-2
--12-1
---16-2
G
"
'-
'-/---
G
FIG 16-8. Class 11,type F malocclusion.
A, records before treatment.
S, after treatment.
This type resembles
a mild type B.
(a) Basic Strategy.-One attempts to retract the maxillary dentition to normal occlusal relationships without altering the craniofacial skeleton, displacing the mandible, or disturbing the vertical dimension.
parallel occlusal and mandibular lines) may be seen with horizontal type A. Severe vertical types are not found with horizontal type A.
(b) Tactics.-All maxillary teeth are bracketed and/or banded, and extra-oral traction is used to move the maxillary dentition dorsally en masse to a Class I occlusion. The direction of the extraoral traction force is determined by the steepness of the occlusal line. Unless the lower dental arch is perfect in shape, position, and individual tooth alignments (rarely the case), it is advantageous to bracket all mandibular teeth to position them ideally during the maxillary retraction.
2) Horizontal Type F.-Mild skeletal Class II features with Class II dental relationships is characteristic of this type.
., /a) Basic Strategy;-.2..Since every horizontal type F malocclusion is a milder form of one of the four syndromal types (B, C, D, or E) the strategies are the same as for the more severe syndromal forms, but the execution is easier (Fig 16-8). (b) Tactics.- There are no specific tactics for treating type
(c) Problems and Complications.• •
I
Simple crowding (see section D-4) Mild vertical type I (steeper than normal occlusal and mandibular lines) or vertical type 2 (skeletal deep bite with
F, since the II treatment always that ticular type
symptoms are so mild that almost any standard Class may achieve success. However, the best tactic is most appropriate for the syndromal type which a parF most resembles.
452
Treatment
•
o
• JW
--12-5
•
-- -15-7
FIG 16-9. Superposed tracings of a horizontal type B malocclusion. same case shown in Fig 16-1,A.
This is the
(c) Problems and Complications.• •
Simple crowding (see section 04) Complex corwding (see section 04). Treatment requires not only alignment but also positioning of the teeth to fit the vertical dysplasia and the skeletal profile.
3) Horizontal Type B.-Maxillary prognathism (midface protrusion) associated with a normal mandible is characteristc of this type.
(a) Basic Strategy.-One attempts to reduce the midface prognathism and associated dentoalveolar protrusion, if present, without alterating the favorable mandibular relationship. (b) Tactics.-Intense, heavy orthopedic forces to the completely bracketed maxillary dentition are necessary. The direction of the force is determined by the steepness of the occlusal and mandibular lines, but vertical type I is a rarity with horizontal type B. Although the mandible may be normal, it is necessary to bracket all the mandibular teeth to achieve ideal positions and arch coordination. Functional jaw orthopedic appliances are contraindicated in horizontal type B. Figure 16-9 illustrates a treated Class 11, horizontal type B. (See also Fig l6-I,A.)
(c) Problems and Complications.•
Simple crowding.
•
Complex crowding necessitating extractions draws attention to the selection of teeth to be extracted. Combinations to be considered are a bicuspid in each quadrant, or maxillary second molars and mandibular bicuspids. The choice of which bicuspid in the lower arch to extract is dependent on restorations present and the site of the principal crowding. When there is no crowding in the maxilla, the extraction of maxillary second molars may be considered, for this greatly aids the dorsal movement of the maxillary dentition (see section 0-4-a. Crowding). Absence of crowding in the mandible may permit the consideration of extraction of
maxillary first bicuspids, where there is maxillary crowding, or second molars, when there is none. Inadequate response may lead one to consider the extraction of maxillary second molars, but that is not a useful solution if the inadequate response is the result of lack of patient cooperation. In older adolescents whose growth has definitely diminished, the extraction of maxillary bicuspids may work out well, particularly if the case has marked maxillary dental protraction such as in type A. In cases of narrow maxillary arch, a preliminary period of expansion to achieve buccolingual arch coordination is necessary in some instances. Vertical dysplasia is a characteristic feature of horizontal type B. Standard therapy will accommodate most vertical type 2 problems, but types 4 and 5 are serious complications requiring sophisticated control of vertical forces. Vertical type 4, only found with horizontal type B, is one of the most difficult of all Class II malocclusions to treat (see Chapter 12).
(d) Retention.-A
flat bite plane on the maxillary retainer is
often advantageous. insufficiency combined 4) Horizontal Type D.-Mandibular with maxillary dental protraction is characteristic of this type.
(a) Basic Strategies.- The basic strategies are the same as those used in childhood (i.e., to promote mandibular growth, to reduce the maxillary dentoalveolar protrusion, and to improve lip and facial muscle function); but the chances for achieving easy skeletal improvement are much less at this age. (b) Suggested Tactics.- The choice of tactics is primarily dependent upon two factors: the developmental age of the patient, (i.e., the potential for further mandibular growth) and the severity of the mandibular skeletal deficiency. Boys who have not completed their pubescent growth spurt have the greatest chances for success. The most difficult to treat without compromise are girls who have a severe mandibular deficiency and have completed pubescence. Assessment of the growth potential is critical in the determination of tactics. One may begin with an intensive period of functional jaw orthopedics, perhaps combined with banded therapy for arch coordination, alignment, and retraction of maxillary anterior teeth. The Bionator, open-face Activator, and Frankel appliance can all be used in conjunction with bracketed appliances (the Frankel with more difficulty). For vel).' severe cases I prefer to use the Herbst appliance alone after achieving arch coordination. Six months of aggressive treatment and a rediagrtosis to assess treatment response is sufficient to provide data for designing continuing treatment tactics. Possibilities, depending on severity and response of initial facial treatment, include extra-oral traction to retract the upper dental arch, Class 11 intermaxillary elastics, continuing the initial treatment, or extraction of teeth to provide space for necessary occlusal correction. Hi-pull extra-oral traction is more apt to be useful in vertical type I cases, and continuing functional jaw orthopedic treatment may be more useful with skeletal deep bite
Adolescent Treatment
453
(vertical type 2) problems.
for the patient to wear a functional appliance adjunctively throughout much of the treatment.
(c) Problems and Complications.-It must be remembered that the primary skeletal problem in horizontal ~pe D is the mandible, not the maxilla; therefore, extra-oral orthopedic traction is not the recommended primary treatment method. It may be used secondarily and adjunctively, particulary in the severe vertical type I cases, where control of the vertical dimension is essential. To fail to appreciate the advantages of controlling lip and tongue function may lead to problems. The initial period of functional jaw orthopedics helps promote and test the potential for mandibular growth, and also provides immediately improved lip and tongue function so critical to success. , Complex crowding may be a complication. If there is a doubt, do not extract until after the initial period of functional jaw orthopedic therapy. In more severe cases, even with minimal crowding, extractions may be necessary to provide space for occlusal correction.
The most serious problem with type 2 cases is failure to appreciate their complications and difficulties. Often these are deceptive in appearance, and casual diagnosis and sloppy treatment planning traps one rather quickly. Do not start the treatment of these patients without a meticulous diagnosis and treatment plan; even then they are difficult cases. One should not expect results of type C treatment to be as esthetic and stable as those achieved for other forms of Class n. (See Fig 16-10.)
(d) Retention.- These problems are often advantageously retained with the removable functional appliance used in the initial phase of treatment. 5) Horizontal Type C.-Mandibular illary dental protrusion, and generalized are characteristic of this type.
insufficiency, bimaxsmall facial dimensions
(a) Basic Strategies.-Horizontal type C malocclusions are difficult to treat at any age and a good argument can be made for deferring their treatment until adolescence. They are more frequent in girls who possess, at this age, diminished probabilities for utilizing skeletal growth. Complex crowding is routinely present and may be so severe that the extraction of four premolars still leaves problems in alignment and occlusal correction. In adolescence, treatment of horizontal type C is a strategy of compromises selected to overcome and camouflage the individual features of a particular malocclusion. (b) Suggested Tactics.-An initial period of functional jaw orthopedic therapy may be tried even when the chances for success are not high simply because the least improvement of the mandible is such a useful contribution to the profile. The functional jaw orthopedic therapy should be under way before extractions are made, if they are needed. Extra-oral traction is contraindicated except for vertical control of maxillary molars or the obvious retraction of the maxillary dentition on its base. Horizontal midface orthopedic forces would only aggravate an already complex problem. (c) Problems and Complications.-Severe vertical type I requires intensive hi-pull extra-oral orthopedic forces to restrain posterior vertical maxillary development. The severe deep bite which accompanies some vertical type 2 cases may be aggravated if the extractions are ill timed or rigorous control of arch coordination and tooth positions is not maintained at all times. Often it is advantageous, in the severe deep bite case,
(d) Retention.-Retention is difficult, not because of continuing growth, but because the tooth positions which provide the best facial esthetics and lip function sometimes are difficult to achieve and stabilize in treated type C. Prolonged monitoring during the retention period is suggested. (6) Horizontal Type E.-Maxillary prognathism plus bimaxillary dentoalveolar protrusion are characteristic of this type. Horizontal type E looks like a severe bimaxillary dentoalveolar protrusion superposed on a Horizontal type B. Though far less prone to Class n than whites, North American blacks with Class n usually display type E.
(a) Basic Strategies.-Treatment strategies are largely determined by the needs of the skeletal profile and the facial soft tissues. Orthopedic reduction of midface protrusion and retraction of dentoalveolar prominence are routines of treatment. (b) Suggested Tactics.- The tactics are quite similar to those used to treat horizontal type B, but there is a more frequent need for extractions in both arches. Another way to define the tactics is to think of these as severe horizontal type B cases with complex crowding in both arches. Of course, there may not be actual crowding, but one extracts for the same reasons, namely, to improve the profile and the esthetic positions of the teeth. Extra-oral traction to both arches is usually necessary and is continued throughout active treatment. The maxillary protrusion must be reduced to the extent that profile esthetics and occlusal correction can then be accommodated within the extraction spaces. (c) Problems and Complications.-Extremely severe cases may require the extraction of maxillary second molars in addition to the removal of four bicuspids."" When a severe deep bite is primarily a skeletal feature, as in vertical type 5, its control is difficult when absorbing the extraction . sites.
'.
(d) Retention.-Well-treated horizontal type E cases ordinarily do not present retention problems except for the vertical correction in severe cases. In such instances a bite plane on the maxillary retainer is suggested. 7. Class III (Mesiocclusion,
Prenormal Occlusion)
By adolescence two types of malocclusion which may be designated Class III in childhood are rarely seen: the pseudo- (or functional) Class nI malocclusion and and the anterior crossbite.
FIG 16-10. Class 11,type C-2 malocclusion. A, before treatment. B, after treatment. This case was complicated by disproportionately large maxillary central incisors. An initial period of Activator therapy was followed by full edgewise treatment. No extractions were made. Note the labial angulation of lower incisors before and after treatment. (Continued.)
.'
Cl C.D. 9-0
CLASS
n
PLOT,
HORIZONTAL
A
+.-
Slreletal Class II." MId-face Prognathic? Mandible Retragnathic?
Maxillary teeth + Procumbent M;;:;~~o:e:~eth~
+ - + - + - +:.. + - + - + - : +,~
~
~.,
~
~
~
~
I j.~. I 1
50142940265427576611971919471; E (El 8+ B C+@O+
N=697 Unclassified Incomplete
454
=
12
Data
=
25
0 F F
1005581211 F F
FE FE Fe Fe
33222761128 FC
Fc Fe Fe A A A
A
Adolescent Treatment
455
C4 C.D.
---9-0
C.D.
C.D.
--t4-6
---9-0 --14-6
---9-0
--t4-6
Cs C.D .
• • -2
'6~
('.
I
1,1".,
70 7-"? .
I
Before (10-3) After (14-6)
HOfllonlal eo Measure 1 8 ,
-3! I""
MdPL/A-B
60
PaL PI-/A-B
c.:w 90
_______
8~ 9~
I.
90 ~ -3 -15.0 -2 X MALE 3xISO 23 -IS.o IS.o ;90 i6'~" I' 1
60 8~
2 7))i~ ~
FEMALE
,
1
,
SE-FMN-A SNA
90 ,'
70 .1,1",,-1I 7~
8~ ,
Bo-Se-Gn
e~
,
60
80
--'--'-I
SNB
70 I/Md
9~
'70 I 7~ :• I -CLASSO I ., I ,60 ,6~
I
PI.
110
lIA-Po
I
~o
3~, ..u,
20
FIG 16-10·(cont.). C, the Class 11arborization
before "and after treatment. and superposed
cephalometric
tracings
and shape response
Note in
to treatment.
O. the
extensive mandibular size
456
Treatment
The latter is never a Class m, even when it looks like it. The malfunction of the pseudo-Class m, with its malfunction, will have imposed itself on the facial skeleton and will likely have produced a very mild skeletal Class m malocclusion by this age. Cephalometric differentiation within Cla~ m is not as well developed as that for Class Il but is equally important, for treatment strategies and tactics depend solely on the site or sites of the skeletal dysplasia (see Chapter 12). It will be useful when planning treatment for a Class III malocclusion in adolescence to refresh one's memory about the treatment of Class m in childhood (see Chapter 15), since knowledge of the developmental features of the different Class m types sharpens ones treatment-planning strategies for adolescent Class m.
a) Rationale for Adolescent Class
III Therapy
The primary reason for treating Class m mal occlusion in adolescence is simply that, if postponed, the probabilities of needing orthognathic surgery combined with orthodontic therapy are greatly increased. As noted in Chapter 15, some Class III malocclusions can be treated quite successfully in early childhood. Unfortunately, some apparently brought under control in childhood revert dramatically during the exuberance of male adolescent growth. There is a limit to how many times a mandibular prognathism can be "treated" orthodontically before one resigns oneself to the necessity of surgery. Obversely, those clinicians who dismiss the opportunities for Class m orthodontic treatment in adolescence will have unnecessarily burdened a number of patients with later surgical correction. One can rationalize the treatment of'Class m in girls during adolescence easier than that of boys, because treatment in girls is less apt to be thwarted by pubescent growth spurting and they are nearer adult dimensions than boys at each chronologic age.
b) Diagnosis Diagnosis at this age has two aspects (I) definition and localization of morphologic abnormality, and (2) estimation of any remaining growth potential. In Chapter 12 cephalometric methods useful in Class III diagnosis were described and attention was drawn to the problems of predicting growth. Despite much wellintentioned, enthusiastic writing on the subject, there is no reliable method of predicting precisely the onset, acceleration rate, duration, or cessation of the pubescent growth spurt. Predictive mathematical models for the sigmoid curve of the pubescent growth spurt simply do not exist in a form applicable to orthodontic practice. Yet one must still make estimates, however crude, of the possible duration of continuing mandibular growth. The carpal radiograph and a study of the patient's parents and siblings are useful if care is exercised.] ]-13 Most important is study of the individual patient-and it is a great help when one has two or more serial cephalograms prior to starting orthodontic treatment.
c) General Strategies The strategies of Class III treatment in adolescence include the following: (1) ventral displacement of the midface6.25 (2) inhibition of mandibular growth7.8 (3) redirection of mandibular growth34 and (4) dental and alveolar process repositioning. The choice of strategies, of course, is dependent on the facial morphology and estimates of the duration of continuing mandibular
growth. Only rarely will one be able to utilize functional repositioning of the mandible during adolescent treatment. Although one searches diligently for functional aspects of the malocclusion, they are rarely a significant factor.
d) Tactics Cases of midface deficiency are best treated with face mask orthopedics combined with fully bracketed arches in both jaws. Mandibular prognathism alone may be treated with chin cup therapy to inhibit mandibular growth. Woodside's34 method of combining chin cup and mandibular block therapy to achieve mandibular alignment is also useful when the mandibular line is not unduly steep. Class m elastics and extractions sometimes permit mild mandibular prognathisms to be camouflaged by tooth movements and alveolar process repositioning. Some cases combine midface deficiency with mandibular prognathism, and both face mask and chin cup therapy may be used succesively.
e) Differential Treatment 1) Midface Deficiency.-DeLaire6 has suggested the use of the face mask for the treatment of midface deficiency. Intensive orthopedic traction is applied to the fully banded maxillary dental arch in an attempt to produce ventral midface displacement. 25 The direction of the force is determined by the steepness of the occlusal and mandibular planes. During orthopedic traction, arch coordination and individual tooth positioning are obtained. The prognosis is good provided the diagnosis has been"'sound. Figure 16-11 illustrates a case of Class m midface deficiency. 2) Mandibular Prognathism.-Mandibular prognathism is a more severe problem in adolescence than midface deficiency, particularly when the mandible is already hyperplastic prior to the adolescent growth spurt. The vertical aspects of the morphology are critical-for when the freeway space is large and the mandibular plane is not steep, there may be opportunities for camouflage of the mandibular prognathism by redirecting mandibular growth, dental alveolar repositioning, and even face mask therapy. Lip length and function are important considerations in redirecting mandibular growth vertically to mask mandibular prognathism. The needs of the case define the tactics, and careful monitoring of growth during treatment is essential. Figure 16-12 shows a treated Class m mandibular prognathism. (See also Fig 17-5.) Lee Graber7. 8 has shown the responsf to chin cup treatment in younger children (see Chapter 15), and this tactic sometimes can still be used in milder cases of mandibular prognathism during a4~lescence. Combining:-Function Regulator-m or Activator therapy with fully bracketed applian~es in both arches is useful only in mild cases of mandibular prognathism at this age because of the length of treatment time. One must be prepared to accept defeat in some cases of mandibular prognathism, particularly in boys, whose dramatic growth during treatment may be a problem (Fig 16-13). In such instances, secure cephalometric and cast records, remove the appliances, place retainers to maintain the arch and tooth positioning improvements, and monitor the case cephalometrically until such time as orthognathic surgery is indicated.
Adolescent Treatment A
FIG 16-11. Class Ill, midface deficiency. A, cephalometric analysis (modified Counterpart Analysis). Figures in parenthesis are the norms for 17year-old males. B, this boy decided against orthodontic treatment.
"
457
458
Treatment
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FIG 16-12. Orthodontic prognathism.
treatment of a skeletal Class III malocclusion,
mandibular
A, records at time of transfer to my office. (Continued.)
•
459
FIG 16-12 (cont.). B, after 2 years of occlusal guidance chin cup and face mask therapy. C, after 2 more years of intensive chin cup and face mask treatment. Note the increasing mandibular prognathism. (See Figure 17-5 for the continuing treatment of this case.)
(56) (61)
(60) (59)
460
Treatment
(53) (55.5)
(52) (50)
(54.5)
FIG 16-13. Mandibular prognathism. A, pretreatment records at time of transfer to my office; patient was age 9 years 0 months. S, at the start of orthodontic treatment with edgewise appliances plus extra-oral chin cup traction; patient was age 11 years 2 months. (Continued.)
(58)
(536) (51)
Adolescent Treatment
o
E
F
461
s.s.
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16-2 .....
18-0--
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(61.21 (6651
(60) (57.6)
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71
73
(61.4)
(64.21 SS 18-0
FIG 16-13 (cont.). C, progress records at 12 years 9 months. D, cephalometric
record
at 16 years 2 months, active orthodontic therapy having been abandoned 1 year earlier. E, cephalogram at 18 years 0 months. F, composite cephalometric comparisons from age 9 to 18 years. Note the
marked
effects of the adolescent
spurt on both the amount
and
direction of mandibular growth. Observe too how the maxilla lags behind the mean values in later years while the mandible exceeds the mean more each time.
"
.
•...
462
Treatment
FIG 16-14. Mandibular prognathism plus midface deficiency. A, pretreatment records, patient was age 11 years 8 months. (Continued.)
(3) Midface Deficiency and Mandibular Prognathism.Those cases revealing skeletal contributions in both maxilla and mandible are often advap.tageously treated in adolescence even though the total AP skeletal discrepancy is quite severe. They may not respond as well, however, if the· tactics are focused on one region only. Combining face mask therapy for the midface deficiency plus the necessary mandibular tactics often provides surprisingly satisfactory results (Fig 16-14). f) Problems and Complications The problems and complications are usually of two kinds: (1) continuing growth, and (2) unreasonable or naive enthusiasm during treatment planning. Skeletal Class III problems in adolescence
are at best difficult. Thorough differential diagnosis and treatment planning are essential if success is to be achieved, they are even more necessary if one must resort to a second period of orthodontic treatment combined with orthognathic surgery. The records of the ca~e at the start and the te~ponse to orthodontic treatment are very us~ftil during the planning of any ~ubsequent orthodontic-surgical treatment (see Chapter 17). g) Retention Retention of midface deficiency problems may utilize a Function Regulator-Ill or a conventional maxillary Hawley appliance with labial pads as those in the Function Regulator-Ill. Retention for mandibular prognathism cases may utilize conventional Hawley
Adolescent Treatment
463
FIG 16-14 (cont.). B, posttreatment records, patient was age 17 years 10 months, 18
months out of retention. Treatment consisted of fully banded edgewise appliances plus face mask orthopedic traction.
retainers. In either event the retention period is more prolonged than for other typical malocclusions.
absence of centric incisal stops, and a simple deep bite (see Section 8-C, Simple Deep Bite). The angulation of the incisors to their bases, to the occlusal plane, and to each other must be noted and the normality of the skeletal profile guaranteed.
8. Localized Incisal Malrelationships The problems discussed in this section are unrelated to the skeletal morphology and result from localized dentoalveolar or neuromuscular variations. Most were present at an earlier age and are treated more advantageously prior to adolescence (see Chapter 15).
a) Labioversion of Maxillary Incisors (1) Diagnosis.-Labioversion of the maxillary incisors in the absence of a skeletal Class 11malocclusion may result from digital sucking, atypical lip or tongue behavior, or an abnormal Bolton Index. In extreme cases there is an enhanced Curve of Spee,
(2) Treatment.The most efficient treatment results from using fully bracketed appliances in both arches to position the anterior teeth while mainfaining the normal posterior occlusion. Arch 'coordination and leveling are critical for stability of results and assuring adequate space for precise incisor positioning. If the diagnosis is correct, there should be no complications. If residual abnormal lip function persists, labial pads similar to those of the Frankel appliance may be added to the Hawley retainer.
b) Simple Anterior Crossbite (1) Diagnosis.-It
is unfortunate when simple anterior cross-
464
Treatment
B
FIG 16-15. Deep bite (excessive vertical incisal overlap). A, simple deep bite. All vertical analysis measures are normal. Note the enhanced mandibular occlusal curve and the excessive vertical height of the mandibular incisor but the normal position of the maxillary incisor (see also Fig 15-74 for more details of this case). B, complex deep bite.
The functional occlusal line posterior maxillary vertical angle is 1 SD less than the mean, and the mandibular line angle is more than 3 SDs below the mean. Note the slight improvement when the mandible is in its postural position.
bites persist into adolescence for they are more advantageously treated earlier. First, make certain that the patient's skeletal profile is normal and that the molar relationship is a firm Class 1. If both are normal and the lower arch is sound, then simple displacement of maxillary teeth or a severe tooth size disharmony is a likely cause.
space") is an important factor in treatment planning. When the freeway space is minimal or even absent the problem is more severe.
(2) Treatment.-Bracket all the maxillary teeth idealizing the arch form and leveling the occlusion as the incisors are positioned labially. Pay particular attention to root parallelism and the interincisal angle. Band the lower arch in order to level the occlusal line and establish secure anterior centric stops. If the maxillary teeth are disproportionately small (e.g., when the simple anterior cross bite is associated with peg lateral incisors) then positioning of the teeth to permit esthetic buildup of the smaller crowns with composite is critical to retention. In other instances, use of a simple Hawley retainer suffices.
c) Simple Deep Bite (1) Diagnosis.-A simple deep bite is localized to the teeth and alveolar processes in the anterior region (see Vertical Cephalometric Analyses in Chapter 12). The upper and/or lower incisors have extruded past the occlusal line in the cephalometric tracing (Fig 16-15). The result may be labial version of the upper incisors and impingement of the lowers into the palatal mucosa. The denial of a skeletal contribution to the condition is critical to the diagnosis. These patients frequently show temporomandibular dysfunction and a limited range of functional occlusal movements (see Chapters 10 and 11). The extent of the intermaxillary distance (" freeway
(2) Treatment.-In the presence of a normal or greater than normal freeway space, treatment consists of banding or bracketing all teeth in both arches, establishing coordinated arch forms, and intensive arch-leveling mechanics. Rigorous intrusion of the incisor teeth is necessary as an assurance of success and stability of result. I prefer to retain theses cases with a Bionator or Activator which opens the bite slightly in the posterior region. As the posterior teeth develop vertically and settle into occlusion, some occlusal equilibration is necessary. When there is minimal intermaxillary occlusal space in the postural position, and yet no obvious skeLetal deep bite morphology, an initial cautious period of functional jaw orthopedic therapy is useful. The construction bite must be taken by opening the n;truded contact positiQI't minimally. Begin by inserting an Activator or Bionator which covers tl)e posterior occlusal surfaces, but do no grinding of the plastic. If the muscles can accommodate to this within a few weeks then grind the posterior plastic away according to which posterior teeth must be brought to the occlusal line. Leave the anterior teeth solidly imbedded in the plastic. It may be necessary to take another construction bite later to open the bite a bit more or to construct an entirely new appliance. When the response is favorable, banding and bracketing in both arches provides finishing details, as when the freeway space is normal. The initial treatment phase is required in order to provide muscle
Adolescent adaptation more certainly. Retain with the same functional appli-' ance used in the first phase of treatment.
d) Simple Open Bite (1) Diagnosis.-When the basal skeleton is-normal and the open bite is confined to the teeth and alveolar processes the condition is called a simple open bite. Complex open bite (see Section D-IO-b later in this Chapter) results from skeletal dysplasia so severe the alveolar processes cannot cope sufficiently to maintain occlusal stops (Fig 16-16). The vertical cephalometric analyses are essential to the differential diagnosis (see Chapter 12). Anterior simple open bite usually results from digital sucking or abnormal tongue behavior (see Chapters 7 and IQ). It is more comIIlon in children than adolescents, for by adolescence many simple tongue thrusts are lost. By adolescence, too, some vertical effects on the facial skeleton may have occurred and what was an earlier simple anterior open bite becomes more complex (see Section D-IQ-b). Posterior simple open bite (discussed here for understanding rather than integrity of the chapter's outline) is rarer than simple anterior open bite and frequently is the result of a lateral spreading of the tongue at rest. The abnormal tongue posture usually begins when it is necessary to secure a posterior seal during the swallow because ankylosed primary molars are present or their early loss creates a vertical open space. The persistence of the spreading tongue posture impedes eruption and full vertical development of succedaneous permanent teeth. This condition is sometimes confused with "idiopathic failure to erupt." Maxillary apical base insufficiency also may necessitate an abnormal posterior spreading of the tongue. (2) Treatment.The treatment of simple open bite in adolescence consists of identifying and controlling localized etiologic factors first, then bracketing teeth and coordinating arch forms. In a few cases, these steps alone may be sufficient. More typically, vertical elastic traction is necessary to acquire full centric stops on all teeth. Check the occlusion carefully with articulation paper to determine that each tooth has been seated fully into occlusion. Allow the patient to wear the banded appliances for the initial period of retention, but do not remove them until normal swallowing and lip function obtain at all times. Persistent hyperactive mentalis muscle activity may be treated with a modified vestibular shield (see Chapter 18). An activator with full posterior occlusal coverage but no posterior grinding, with selected anterior teeth relieved from plastic contact, may be worn at night to help in the control of persisting tongue or digital sucking problems. For posterior simple open bite, a Hawley retainer with extended lingual flanges vertically is useful to control the tongue during retention.
e) Simple Crowding For a discussion of simple crowding,
9. Bimaxillary
see Section D-4-a.
Protrusions
Our nomenclature does not always clearly differentiate between skeletal and dental protrusions. Bimaxillary prognathism is a skeletal dysplasia characterized by ventral positioning of both the maxilla and mandible with respect to the profile and anterior
Treatment
465
cranial base (Fig 16-17). Bimaxillary dental protrusion is procumbency of both dentitions and their alveolar processes on their bony bases (see Fig 16-17). In this section, an assumption of a Class I occlusion and the absence of skeletal Class II or Class III features is made.
a) Bimaxillary Prognathism Ethnic variations in the normal positions of the maxilla and mandible may obfuscate the diagnosis. Most cephalometric analyses are based on Europeans or North European whites, whose standflTds are quite inappropriate for analyzing North American blacks, Japanese, North American Indians, Mexicans, and many other groups. For these reasons, the diagnosis for bimaxillary _prognathism may be more subjective than that for other skeletal dY8plasias. The diagnosis must also account for the lips and facial muscles. Treatment may be in response to concerns over facial esthetics. Bimaxillary prognathism may exist alone, in conjunction with Class II (horizontal type E), or combined with maxillary dental protrusion. The Basic Morphologic Analysis and the Profile Analysis are usefully discriminating (Chapter 12). Treatment planning involves three steps, all concerned with esthetic judgments. First, diagnostic setups utilizing the extraction of different teeth helps to estimate improvements in anterior dental esthetics. Second, cephalometric tracing of the presumed new incisal positions after extractions permits estimates of the reduction of the A and B points on the skeletal profile. Third, using the softtissue tracing of the lateral cephalogram plus photographs, estimates of the effects of extraction on static soft-tissue drape (i.e., in lips, facial muscles, etc.) are revealing. Improved facial expression may be the most important consequence of treatment, but it is almost impossible to imagine prior to therapy. Treatment consists of symm6tric extraction (usually first bicuspids) in each quadrant and the retraction of anterior teeth to camouflage the skeletal dysplasia. In moderate cases, orthodontic treatment alone may be successful. In severe cases, the esthetic improvement from orthodontics sometimes is inadequate though the occlusion is fine. More severe cases may be treated by combined orthodontics and orthognathic surgery (Fig 16-18). The orthodontist and surgeon will judge the success of the case by the improved occlusion, dental esthetics, and skeletal balance. The patient invariably judges success by the soft-tissue change and improved facial expressions.
b) Bimaxillary Dental Protrusion Bimaxillary dental protrusion may be seen alone or combined with bimaxillary prognathism. It is also found in Class Il, horizontal type C (see Fig 16-10). The diagnosis is made by the Profile Analysis and by measurin~.the angle of the upper and lower incisors~o the functional occlusal line. Examine the swallow and do a careful functional occlusal an;lysis, for bimaxillary dental protrusion may be associated with a complex tongue-thrust (toothapart swallow) or abnormal tongue posture. The first step in treatment planning is to do diagnostic trial setups to test the advantages of different patterns of extraction. Trace the presumed new incisal positions on the lateral cephalogram to estimate improved profile esthetics. When the occlusal line and/or the mandibular line is steep, the upper and lower incisor angulations must be adjusted accordingly (see Chapter 12).
466
Treatment
A2 VERTICAL
-3
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~
OcclClsion
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82
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I
-IS.o.
ANALYSIS X
tS.o.
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1I
MAlES Line
I
I
T...
VERTICAL
-2
-3 Cranial 80S. PM Vert/FMN-SE
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I
(nol a constant Lin. in Cion C) PM" Vert/Mond PM Vert /Ocel Line Occlusion
~
3
2
110 I 90 95 I I I MAlE ,:.~5., ,Itl~. t~I~.I,I~ 1L:L:J30 100 105 110. t 115 120 125
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- tS.o.
ANALYSIS
MAlES
I 1
1
I
I
I
I~
FIG 16-16. A, simple open bite, cephalometric tracing: A •• simple open bite, vertical analysis of the same case. B" complex or skeletal open bite,
cephalometric tracing. B2, complex open bite, vertical analysis. Note the contribution of the tipped Palatal Line .
,
.
Adolescent Treatment
467
FIG 16-17. Bimaxillary prognathism. Note in this instance there is also bimaxillary dental alveolar protrusion. This patient is a beautiful young lady of Incan ancestry. In 8, the dotted lines represent "ideal" positions as
determined by a popular cephalometric American, white, subjective values.
analysis based on North
These procedures are treatment of cause and not camouflage; therefore, the results are generally more satisfactory than the treatment of bimaxillary prognathism The retention is usually routine and uneventful when lip and tongue function are normal.
10. Deep Bite a) Simple Deep Bite For a discussion of simple deep bite, see section D-8-c.
b) Complex (Skeletal) Deep Bite
FIG 16-18. Bimaxillary dental alveolar protrusion, before and after treatment.
Complex deep bite is a deep bite associated with basic skeletal features with which the alveolar processes cannot cope. The occlusal, mandibular, and palatal lines appearqJarallel and the gonial angle is less than normal; in fact, it may near orthogonality. Total anterior face height approximately equals posterior total face height (see fig 16-15). Complei deep bite is frequently associated with ClassII (vertical types 2, 4, and-'5) and occasionally with Class III (see Section D-7). Both Vertical Analyses are required for a definitive diagnosis. Early childhood is the best time to treat complex deep bite, for functional jaw orthopedic appliances can then guide the eruption of the permanent dentition and help control vertical skeletal growth. Mild cases in adolescence are treated with full-banded or bracketed appliances. In moderate cases a flat maxillary bite plane or functional jaw orthopedic appliance is used in conjunction with full-banded therapy. Adolescent treatment of moderately severe
468
Treatment
cases is usually more successful in boys than girls since boys normally have more remaining growth to utilize in treatment. Severe cases of complex deep bite may require orthognathic surgery later. Even in the most severe problems, I prefer to attempt treatment in adolescence and force the decision toward surgery by the inadequate response to conservative therapy. On occasion I have been pleasantly surprised by the response to ske"letal deep bite treatment in adolescence. Patients and parents are delighted to avoid surgery if possible. However, complex deep bite can be one of the most difficult malocclusions to treat orthodontically: it certainly is so when combined with severe AP skeletal dysplasia. 11. Open Bite Basic concepts of open bite are discussed in Chapter 15. Open bite may be associated with Class 11or Class III malocclusion (see Sections D-6 and D-7), but in this section it is assumed that there is no anteroposterior skeletal dysplasia. a) Simple Open Bite For a discussion of simple open bite, see Section D-8-d. b) Complex (Skeletal) Open Bite Complex or skeletal open bite is the result of a vertical dysplasia so severe that compensatory alveolar growth cannot cope (see Fig 16-16). The abnormal lip and tongue functioning observed with a complex open bite is usually adaptive in coping with the skeletal dysplasia, though the condition is held by many to be associated with "mouthbreathing" and chronic nasorespiratory dysfunction (see Chapters 7 and 10). Both Vertical Analyses are a necessary part of the cephalometric diagnosis. In complex open bite these analyses often show the palatal plane tipped upward, the mandibular plane steeper than normal, and anterior face height excessive relative to posterior face height. The skeletal dysplasia may be confined to anterior lower face height. The gonial angle may be obtuse and the ramus angled posteriorly. The mandibular. alveolar process height may be excessive anteriorly, and the occlusal and mandibular lines divergent. The maxillary arch is often narrow and there may be excessive height to the alveolar process, producing unfortunate gingival display. Complex open bite is frequently associated with Class 11(vertical type 1) and skeletal Class III malocclusions, particularly mandibular prognathism. In this section it is assumed that the skeleton is normal anteroposteriorly. In addition to the skeletal dysplasia, two neuromuscular features characterize the more severe cases, that is, those cases in which orthognathic surgery must be considered: (1) a strained high maxillary lip line exposing much gingivae and, (2) little or no freeway space. Upper posterior face height measures are critical in this instance. When the posterio'r upper face height is excessive the palatal plane is tipped upward, but not because of the more frequent short anterior upper face height. Tooth positioning alone cannot cope with the resultant maxillary vertical hyperplasia. Complex open bite typically is difficult to treat orthodontically. In moderate cases, one attempts to achieve some esthetic cover-up of the skeletal dysplasia by alveolar process compensation. Extractions may be necessary, even when simple crowding is absent, to provide space for tooth positioning and alveolar remodeling. If initial orthodontic treatment does not succeed in more
severe cases, surgery at a later age may be indicated. Growth tends to aggravate, not obscure, all cases of complex open bite.
12. Temporomandibular
Joint Dysfunction
a) Background Temporomandibular dysfunction and associated signs and symptoms are more frequently seen in adolescence than in childhood. Reread Chapter 15, Section D-14, for a discussion of the developmental aspects of temporomandibular dysfunction in childhood. The origins are important to an understanding of the clinical problem in adolescence. A history of facial trauma or temporomandibular joint trauma is often found. Temporomandibular joint dysfunction may be seen with a variety of malocclusions in adolescence, although it is most frequently associated with Class 11, deep bite, open bite, and skeletal asymmetry. Of particular importance are those cases with occlusal dysfunction-such as an abnormal distance between the retruded contact and intercuspal positions and markedly deviant or erratic paths of mandibular closure. A meticulous examination of the joints and associated musculature is essential for every adolescent malocclusion (see Chapters 10 and 11). Many adolescents are unaware of myalgia or pain in tendons and the joint region because the condition has appeared so gradually that they have accommodated through time. Precise palpation may elicit points of tenderness of diagnostic significance (see Chapter 10).
b) Treatment Treatment 'consists of correcting the mal occlusion to the finest and most precise functional occlusal results, giving particular attention to the joints. Detailed attention to tooth positioning, occlusal equilibration, and precise occlusal coordination are essential. Intermaxillary elastic traction during treatment is contraindicated in patients with TMJ symptoms. Retention should not be started until perfect occlusal coordination is seen, but occlusal equilibration may be begun while the bracketed appliances are still in place (see Chapter 18). References have been made in the literature implicating adolescent orthodontic treatment as a causative factor in adult temporomandibular dysfunction, but sound long-term clinical studies clearly show orthodontic treatment is not a significant etiologic factor on a population basis.30 Any poor occlusal treatment at any age can contribute to temporomandibular ;ain or joint derangement. Temporomandibular dysfunction is often construed as primarily a problem in geriatric dentistry, for most treatment is now do.n~ on older patients .•Recent research indicates there may be impOrtant occlusal developmental ~tiologic factors which have been overlooked. 20.22.32Definitive studies have established two important points: (I) tempor~mandibular dysfunction is an integral part of thl'f development of some malocclusions,32 and thus is present before orthodontic treatment begins, and (2) orthodontically treated patients have no more temporomandibular dysfunction than is seen in the random population.30 Therefore, orthodontic treatment significantly reduces the prevalence of temporomandibular joint disorders in adolescents, for the condition is more prevalent in mal occlusions before their treatment.
Adolescent Treatment
REFERENCES I. Andrews LF: The six keys to normal occlusion. Am J Orthod 1972; 63:296. 2. Baumrind S, Franz R: The reliability of head film measurements. 1. Landmark identification. Am J-Orthod 1971; 60: 111-127; 2. Conventional angular and linear measurements. 1971; 60:505-517. 3. Baumrind S, Korn EL, Isaacson RJ, et al: Superimpositional assessment of treatment associated changes in the temporomandibular joint and the mandibular symphysis. Am J Orthod 1983; 84:443-465. 4. Baumrind S, Korn EL, Isaacson RJ, et al: Quantative analysis of the orthodontic and orthopedic effects of maxillary traction. Am J Orthod 1983; 84:443-465. ? Bookstein FL, McNamara JA Jr, Shaughnessy TG: Skeletal and dental adaptations following functional regulator therapy on Class 11 patients. Am J Orthod 1985; 88:91-110. 6. DeLaire J: L'articulation fronto-maxillaire, bases theoriques et principles genereaux d'application de forces extra-orales postero-anterieures sur masque orthopedique. Rev Stomat (Paris) 1976; 77:921-930. 7. Graber LW: Chin cup therapy for mandibular prognathism. Am J Orthod 1977; 72:23-41. 8. Graber LW: The alterability of mandibular growth, in McNamara JA Jr (ed), Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. 9. Graber TM, Kaineg TF: The mandibular third molar: Its predicative status and role in lower incisor crowding. Proc Finn Den Soc 198i; 77:37-44. 10. Greenbaum KR, Zachrisson BU: The effect of palatal expansion therapy on the periodontal supporting tissues. Am J Orthod 1982; 81:12-21. 11. Hagg U, Taranger J: Maturation indicators and the pubescent growth spurt. Am J Orthod 1982; 82:299-309. 12. Houston W: Relationships between skeletal maturity estimated from hand-wrist radiographs and the timing of the adolescent growth spurt. Eur J Orthod 1980; 2:81-93. 13. Houston WJB, Miller JC, Tanner JM: Prediction of timing of adolescent growth spurt from ossification events in handwrist films. BrJ Orthod 1979; 6:145-152. 14. Johnston LE Jr: A comparative analysis of Class 11 treatments, in Vig PS, Ribbens KA (eds), Science and Clinical Judgment, monograph 19, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1986. 15. Langford SR: Root resorption extremes resulting from clinical RME. Am J Orthod 1982; 81:371-7. 16. Linge BO, Linge L: Apical root resorption in the upper front teeth during orthodontic treatment: a longitudinal-radiographic study of incisor root lengths, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984. 17. Little RM, Wallen TR, Riedel RA: Stability and relapse of mandibular anterior alignment-first premolar extraction cases treated by traditional edgewise orthodontics. Am J Orthod 1981; 80:349-365. 18. Moss JP: The indications for the transplantation of maxillary canines in the light of 100 cases, Br J Oral Surg 1975; 12:268-274.
469
19. Moyers RE': Studies of orthodontic relapse. Paper presented to the 60th Congress of the European Orthodontic Society, Florence, Italy, 1984. 20. Moyers RE, Ten Have T: Childhood indicators of adult temporomandibular disorders. Presented at the European Orthodontic Society, Helsinki, 1985. 21. Moyers RE, Riolo ML, Guire KE, et al: Differential diagnosis of Class 11 malocclusions, Part I. Facial types associated with Class 11 malocclusions. Am J Orthod 1980; 78:477-494. 22. Nesbitt BA, Moyers RE, Ten Have T: Adult temporomandibular joint disorder symptomatology and its association with childhood occlusal relations: A preliminary report, in Carlson DS, McNamara JA Jr, Ribbens KA (eds), Development Aspects of Temporomandibular Joint Disorders, monograph 16, Craniofacial Growth Series. Ann Arbor Mich, Center for Human Growth and Development, University of Michigan, 1985. 23. NIH Consensus Development Conference for Removal of Third Molars. J Oral Surg 1980; 3:235-236. 24. Pancherz H: Long-term effects of activator (Andersen appliance) treatment. Odontol Revg 1976; 27(suppl 35):11-42. 25. Petit H: Adaptation following accelerated facial mask therapy, in McNamara JA Jr, Ribbens KA, Howe RP (eds), Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. 26. Riedel RA: Post-pubertal occlusal changes, in McNamara JA Jr (ed), The Biology of Occlusal Development, monograph 7, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1977. 27. Rindler A: Effects on lower third molars after extraction of second molars. Angle Or.thod 1977; 47:55-58. 28. Riolo ML, Ten Have T: The effect of different kinds of appliance therapy on the soft tissue profile, in Vig PS, Ribbens KA (eds), Science and Clinical Judgment in Orthodontics, monograph 19. Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1986. 29. Sadowsky C: Long-term effects of orthodontic treatment on the periodontium during adolescence, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984. 30. Sadowsky C, BeGole EA: Long-term status of temporomandibular joint function and functional occlusion after orthodontic treatment. Am J Orthod 1980; 78:201-212. 31. Shapira Y, Kuftinec M: Treatment of impacted cuspids. The hazard lasso. Angle Orthod 1981; 51 :203-207. 3:Z.. Thilander B: TempOtomandibular joint problems in chil-dren, in Carlson DS, McNamara JA Jr, Ribbens KA (eds), Developmental Aspects of Temporomandibular Joint Disorders, monograph 16, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1985. 33. Tuversson DL: Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am J Orthod 1970; 58:109-127. 34. Woodside DG, Reed RT, Doucet JD, et al: Some effects of activator treatment on the growth rate of the mandible and position of the midface, London, Transactions of the Third
470
Treatment International
480.
Orthodontic Congress,
London,
1975, pp 459-
35. Zachrisson BU: Periodontal changes during orthodontic treatment, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograpb 15, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984.
SUGGESTED READINGS A. Understanding Adolescent Treatment Bjork A: Prediction of mandibular growth rotation. Am ] Orthod 1969; 55:585-599. Bowden BD: Epiphyseal changes in the hand/wrist area as indicators of adolescent. Aust Orthod ] 1976; 4:87-104. Carlson DS, Ribbens KA (eds), Craniofacial Growth During Adolescence, monograph 19, Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1987. Grave KC, Brown T: Carpal radiographs in orthodontic treatment. Am] Orthod 1979; 75:27-45. Hagg U, Taranger J: Maturation indicators and the pubescent growth spurt. Am ] Orthod 1982; 82:299-309. Hagg U, Taranger J: Dental development assessed by tooth counts and its correlation to somatic development during puberty. Eur] Orthod 1984; 6:55-64. Houston WJB, Miller JC, Tanner JM: Prediction of the timing of the adolescent growth spurt from ossification events in hand-wrist films. Br] Orthod 1979; 6:145-152. Houston WJB: Relationships between skeletal maturity estimated from hand-wrist radiographs and the timing of the adolescent growth spurt. Eur] Orthod 1980; 2:81-93. Lewis AB, Roche A, Wagner B: Growth of the mandible during pubescence. Angle Orthod 1982; 52:325-342. Pileski RC, Woodside DG, lames GA: Relationship of the ulnar sesamoid bone and maximum mandibular growth velocity. Angle Orthod 1973; 43:162-170. Singer J: Physiologic timing of orthodontic treatment. Angle Or-, thod 1980; 50:322-333.
D-4-a: Crowding Dale lG: Guidance of occlusion: serial extraction. in Graber TM, Swain BF (eds), Orthodontics, Current Principles and Techniques, St Louis, CV Mosby, 1985. Huggins DG, McBride LJ: Eruption of lower third molars following loss of lower second molars: longitudinal cephalometric study. Br] Orthod 1978; 5:13-20. Richardson ME: The etiology and prediction of mandibular third molar impactions. Angle Orthod 1977; 44:165-172. Rindler A: Effects on lower third molars after extraction of second molars. Angle Orthod 1977; 47:55-58. Schulhof FR: Third molars and orthodontic diagnosis. ] Clin Orthod 1976; 10:272-281. D-4-b( 1): lmpactions, Cuspids Boyd RL: Clinical assessment of injuries in orthodontic movement of impacted teeth. Am] Orthod 1982; 82:478-486. Boyd RL: Clinical assessment of injuries in orthodontic movement of impacted teeth. n. Surgical recommendations. Am ] Orthod 1984; 86:407-418. Fournier A, Turcotte J, Bernard C: Orthodontic considerations in the treatment of maxillary impacted canines. Am] Orthod 1982; 81:236-239. Moss JP: The indications for the transplantation of maxillary canines in the light of 100 cases. Br] Oral Surg 1975;
12:268-274.
Shapira Y, Kuftinec M: Treatment of impacted cuspids. The hazard lasso. Angle Orthod 1981; 51(3):203-207. Vanarsdall RL, Corn H: Soft-tissue management of labially positioned unerupted teeth. Am] Orthod 1977; 72(1):53-64. Von der Heydt K: The surgical uncovering and orthodontic positioning of unerupted maxillary canines. Am] Orthod
1975; 68(3):256-276. Williams BH: Diagnosis and prevention of maxillary cuspid impaction. Angle Orthod 1981; 51:30-40. 4-b-( 1): lmpactions, Molars Bishara SE, et al. Third molars, a review. Am]
B. Defining Goals in Adolescent Treatment C. Assessment of Results of Adolescent Treatment Andrews LF: The six keys to normal occlusion. Am]
Thilander B, Skagius S: Orthodontic sequelae of extraction of permanent first molars: a longitudinal study. Trans Eur Orthqd Soc 1970; pp 429-442.
Orthod 1983;
83:131-137. Orthod
1975; 63:296.
Cryer BS: Orthodontic considerations in predicting and preventing third molar impactions: A review. ] Soc Med 1981;
74:909-910.
D-l-a: Number of Teeth Graber LW: Congenital absence of teeth: Review with emphasis on inheritance patterns. ] Am Dent Assoc 1978; 96:266-
275. McNeil RW, Joondeph DR: Congenitally absent maxillary lateral incisors: treatment planning considerations. Angle Orthod 1973; 43:24-29 .... Schwanninger B, Shaye R: Management of cases with upper incisors missing. Am] Orthod 1977; 71:396-405. Tuversson DL: Orthodontic treatment using canines in place of missing maxillary lateral incisors. Am] Orthod 1970;
58:109-127. D-l-b: Loss of Permanent Teeth (Trauma, Caries, and Other Causes) Holm U: Problems of compensative extraction in cases with loss of first permanent molars. Trans Eur Orthod Soc 1970; pp
409-427.
Kaplan RG: Some factors related to mandibular third molar impaction. Angle Orthod 1975; 45: 153-158. Richardson ME: The etiology and prediction of mandibular third molar impaction. Angle Orthod 1977;47:165-172. Richardson ME: The development of third molar impaction and •. its prevention.
Intl,{. Oral Surg 1981; 10:122-130.
4-b'(2): Ankylosed Permanent Teeth Biederman W: The problem of the ankylosed tooth. Dent Clin North Am 1968; pp 409-424. Konstat MM, White G: Ankylosed teeth: A review of the literature. ] Mass Dent Soc 1975; 24:74-78. Skolnick IM: Ankylosis of maxillary permanent first molar. ] Am Dent Assn 1980; 100:558-560. D-4-c: Juvenile Periodontitis McLain JB, Proffit WR, Davenport RH: Adjunctive orthodontic therapy in the treatment of juvenile periodontics: report of
Adolescent Treatment a case and review of the literature. Am J Orthod 1983;
83:290-298. D-6: Class
11
Malocclusion
It is impossible to contrive a list of a few good articles on treatment of Class Il malocclusion in adolescence, as there are so many. This article listed here describes the differential diagnosis of Class II types, an important aspect of Class n therapy often omitted in the many articles which emphasize biomechanics. Moyers RE, Riolo ML, Guire KE, et al: Differential diagnosis of Class II malocclusions. Part 1. Facial types associated with Class II malocclusions. Am J Orthod 1980; 78:477-
494.
DJ:
Class III Malocclusions
Graber LW: Chin cup therapy for mandibular prognathism. Am J Orthod 1977; 72:23-41. Jacobson A, Evans WG, Preston CB, et al: Mandibular prognathism. Am J Orthod 1974; 66:140-171.
471
D-lO: Open Bite' D-l/: Deep Bite The clinical problem of the skeletal aspects of open and deep bite is primarily a matter of cephalometric analysis. Unfortunately many current cephalometric analyses do not discriminate well the particular elements contributing to vertical dysplasia (see Chapter 12). The following article seems more helpful than most. Kim VH: Overbite depth indicator with particular reference to anterior open bite. Am J Orthod 1974; 65:586-611. D-l2:
Temporomandibular Dysfunction Most of the literature on temporomandibular dysfunction relates to its geriatric sequelae and their treatment. There is increasing evidence that temporomandibular joint dysfunctions have important developmental etiologies (see Chapter 15). Their treatment in adolescence is only now being formalized, and results may be expected to be well documented in the future. At the time of this edition of the Handbook there are a plethora of anecdotal case reports but scarcely any extensive clinical ..studies of quality.
-.,
-.....
CHAPTER
17 Adult 'Treatment Robert E. Moyers, D.D.S., Ph.D. Katherine W. L. Dryland Vig, B.D.S., M.S. Raymond J. Fonseca, B.A., D.M.D .
.' OUTLINE Introduction A.
B.
Orthodontic treatment for adults with good oral health (R.E.M.) 1. Diagnosis a) Cephalometric analysis b) Occlusal and temporomandibular evaluation c) Soft-tissue profile and esthetics d) Attitude and motivation 2. Planning treatment 3. Illustrative cases Orthodontic treatment of malocclusions complicated by periodontal disease and loss of teeth (R.E.M.) 1. Background 2. Strategies for treatment a) One clinician b) Generalist plus one specialist c) Two or more specialists 3. General rules 4.
5.
6.
472
Essential diagnostic procedures a) Radiographs 1) Cephalograms 2) Periapical survey b) Casts I) Record 2) Diagnostic setup c) Periodontal charting d) Occlusal analysIs Sequence of treatment a) Hygienic phase of periodontal therapy b) Preliminary single tooth restorations (including endodontics) c) Orthodontic treatment d) Surgical phase of periodontal therapy e) Orthodontic retention f) Restorative procedures Choice of orthodontic appliances
a) b)
7.
8.
Occlusion Space 1) Tooth movements 2) Extraction 3) Enlarging teeth 4) Reduction of tooth size c) Anchorage Simple problems in anterior alignment a) Midline diastema b) Diminished size of lateral incisors c) Missing teeth Uprighting molars a) The problem I) Upper molars 2) Lower molars b) Goals in treatment 1) Rationale 2) Uprighting versus uprighting and mesial translation c)
d)
e)
f)
Appliance design I) Removable acrylic appliances 2) Bracketed appliances Diagnosis I), ¥adiographs 2) The patient 3) Casts Planning treatment 1) Complete a diagnostic setup 2) Define individual tooth movements 3) Design the appliances 4) Imagine possible problems Treatment protocols 1) Uprighting mesially inclined lower second molars
'\
Adult Treatment 2)
9. 10. 11.
Uprighting mesially inclined second and third molars 3) Contraindications, modifications and complications (a) Contraindications (b) Modifications (c) Complications 4) Moving mesially inclined molars forward (a) Principles of treatment (b) Illustrative cases Problems due to inadequate space Oligodontia Vertical problems in the anterior region a) Etiology b) Diagnosis c) Treatment I) Simple deep bite 2) Deep bite with labioversion of maxillary incisors 3)
"Simple" open bite (a) Diagnosis (b) Treatment (c) Retention 4) Complicated vertical problems C. Orthodontic treatment combined with orthognathic surgery (K.W.L.V. and R.J.F.) I. Historical aspects 2. Selection of patients 3. Case Management 4. Case Referrals 5. Classification of skeletal dysplasias 6. Timing and sequence of treatments 7. Case reports Adult orthodontic treatments are characterized by three features: (I) waning craniofacial growth; (2) decision making by the patients themselves: and (3) malocclusion often complicated by periodontal' disease and loss of teeth. There are important differences between adult and adolescent orthodontics, differences which create problems yet offer certain advantages to the dentist. In adulthood craniofacial growth rarely complicates or aids treatment, and the cephalometric diagnosis is a simpler morphologic analysis in which prediction is less important (see Chapter 12). The bone turnover rate is slower, so tooth movements do not occur as rapidly. Patient cooperation is a different kind of problem, for there are no parents to enlist for help. An adult's patience and span of enthusiasm diminishes more rapidly, but motivation for treatment is usually high. Orthodontic treatment for adults more frequeI].tly involves intercollegial relationships in an intensely cooperative fashion-the periodontist, the restorative dentist, and the surgeon may join in the treatment. Finally, temporomandibular disorders are a frequent complication of adult orthodontics. There is an increasing literature on adult orthodontics, but it is not yet well codified; however, the problems of adult orthodontics segregate logically into three categories: a) Orthodontic treatment for adults with good oral health, b) Orthodontic treatment of malocclusions complicated by periodontal disease and loss of teeth, and
473
c) Treatment of severe skeletal dysplasias requiring both orthognathic surgery and orthodontics. Such important areas cannot be treated with full detail here; however, the principles pertaining to each of the three categories will be outlined, some treatment details will be presented, and illustrative cases will be shown.
A. ORTHODONTIC TREATMENT FOR ADULTS WITH GOOD ORAL HEALTH (REM) 1. Diagnosis a) Cephalometric analysis Because craniofacial growth is largely completed in adults, prediction is less necessary; therefore, tooth movements are planned to fit the current craniofacial morphology with emphasis on the occlusion and profile esthetics. The Basic Morphologic, Vertical, Profile Analyses (Chapter 12) are suggested for use on adult patients. Severe skeletal Class 11 and Class III malocclusions are more apt to require orthognathic surgery, and some patients who might have been treated solely by orthodontics in adolescence may, in adulthood, be treated better by combining orthodontics and surgery.
b) Occlusal and Temporomandibular Evaluation Temporomandibular signs and symptoms, often obscured by the adaptive aspects of adolescent growth, assume more significance in the adult; therefore, analysis of the temporomandibular joint and its functions must be an integral part of the examination (see Chapter 11). The centric concept is of greater validity in the adult, making precise registration of jaw positions and articulator mounted casts more frequently a necessary feature of the evaluation.
c) Soft-Tissue Profile and Esthetics Attempts to quantify such lips have been generally rather functioning facial musculature patient (see Chapter 10). Facial factor for the adult patient.
adaptive and mobile structures as crude, yet an orderly study of the and lips is essential for the adult esthetics is a primary motivating
d) Attitude and Motivation If you ask children why they are having orthodontic treatment, they often say their parents brought them or that everyone has their "teeth straightened. Adults-may be If ss forthright and relate what they think the dentist expects to hear, avoiding or repressing the real reasons they seek orthodontic therapy. Discussions allow tqe. true motivating fa<;tors to emerge, which often are esthetics and -the fear of eventual loss o( teeth. It is imperative that both the patient and the dentist recognize and appreciate the patient's reasons for seeking orthodontic treatment.
2. Planning Treatment The most important difference between planning treatment for adults and adolescents is that of growth diminution. In adults, the lessened turnover rate of bone diminishes the percentage of cases in which ideal results can be obtained without surgery; therefo~e, compromised plans result more often. Reduced rates of cra-
474
Treatment
niofacial growth do not mean cessation of dentoalveolar
and oc~
clusal adaptations, Behrents ] in the most definitive study to date of adult craniofacial development, found measurable skeletal and occlusal changes as late as the fifth decade of life. Pathologic adaptations of alveolar bone and/or the temporomandibular joints are more frequently associated with adult malocclusions. 3. Illustrative
Cases
Most mal occlusions correctable
in adolescence
can also be
treated in a healthy adult (Figs 17-1 through 17-5). The treatment goals will be similar and result can be of equal quality, though the time to complete the treatment is longer and strategies and tactics may vary for the adult. Healthy, intact adult dentitions are no piace for hasty or shoddy orthodontics, for most of the ingredients for quality results are present. Compromised goals are more logical when the dentition itself has already been compromised by loss of teeth and periodontal disease, the topic of the next section.
B. ORTHODONTIC TREATMENT OF MALOCCLUSIONS COMPLICATED BY PERIODONT AL DISEASE AND LOSS OF TEETH (REM)
Rules
Three general rules apply irrespective of the strategy: including retention, before starting any therapy. b) Share all diagnostic data and treatment plans. c) Consult regularly with one another about progress and problems during treatment. THE RESULT WILL BE NO BETTER THAN THE POOREST INDIVIDUAL TREATMENT PROVIDED. a) Plan all treatment,
This simple, true, and important statement emphasizes how carefully one must choose colleagues for collaborative therapy. Some excellent dentists are neither experienced in, nor inclined toward, this kind of joint treatment.
4. Essential
Diagnostic
Procedures
The following diagnostic data and procedures may be required when treating a single case; it is not necessary fdr each clinician to gather them all, but collectively they must be available. It is efficient to duplicate and distribute all radiographs and written records, though dental casts probably should be taken by each clinician, since each clinician uses them in different ways.
a) Radiographs
1. Backgroud This section provides logical rules to help the family dentist serve some of these patients and presents the rationale for referring others for treatment by specialists.
2. Strategies
3. General
1) Cephalograms.-Usually the orthodontist takes the cephalograms for they are essential to his or her analysis and treatment planning, but the summarized cephalometric findings may be shared. Duplicate cephalograms can be provided for study by the others if needed.
for treatment
a) One Clinician Ideally, the three kinds of treatment these patients require should be provided by a single clinician, but few of us are equally capable in orthodontics, periodontics, and reconstructive dentistry. Sometimes the more skilled we are in one area the less we may appreciate the knowledge and proficiency required in another. Furthermore, on graduation from most dental schools the dentist has more advanced skills and experience in restorative dentistry than in periodontics and has rarely had but the briefest introduction to clinical orthodontics. Simple cases can be treated best by a generalist alone, but they are not plentiful. Training and experience, not ambition or pretension, should determine whether the family dentist requires collaboration with the periodontist, restorative specialist, and/or the orthodontist.
b) Generalist Plus One Specialist The most common situation is that in which the family dentist is prepared to do the reconstructive dentistry and periodontics but needs help with the orthodontics. A few simple rules for shared responsibilities in diagnosis, treatment planning, and treatment are described later. Their observation protects colleagues and guarantees better therapy for the patient.
c) Two or More Specialists More difficult cases which combine extensive treatment by specialists require planned interaction and continuing consultation to guarantee success.
2) Periapical Survey.-AIl clinicians must have periapical surveys available before, during, and after treatment. The panoramic radiograph is useful but does not provide sufficient alveolar detail.
b. Casts (1) Record.-Record
casts at the start of treatment are nec-
essary for each clinician. In some instances, they may need to be mounted on an articulator. After orthodontic therapy is over, the restorative dentist will require another set of diagnostic casts. 2) Diagnostic setup (see Chapter ll).-Rearranging the teeth on an extra set of casts provides the opportunity for all clinicians to visualize the probableoccusal relationships after orthodontic treatment (see Figs 17-10 and 11-19). It also makes possible comparisons of different orthodontic solutions. When the tentative treatment plans al1,9diagnostic setups are assembled, the case' can be studied together.
c) Periodontal Charting The periodontist's charting of pocket depth, attachment level, mobility, and other data are of special interest to the orthodontist as well. Many tooth movements which seem possible when studying casts alone are put in more difficult perspective by the findings of the periodontist.
d) Occlusal Analysis Perceptions
of occlusion
are different among the different
Adult Treatment
475
FIG 17-1. A-E, closure of midline diastema in a 64-year-old woman. Note that the permanent retention was placed before the orthodontic appliance
was removed. An acid-etch quite sufficient.
("Maryland
FIG 17-2. A-E, missing maxillary lateral incisor. Note the diminished size of the other lateral incisor and the second premolars (see Genetic Fields
of Tooth Development,
Chapter 6).
bridge")
retainer is usually
.'
FIG 17-3. Treatment
of a Class I malocclusion
treatment.
8, after treatment.
appliance
was used.
F.S. ---Before --After
FIG 17-4. Treatment of an adult skeletal Class 11malocclusion a skeletal deep bite.
476
complicated
by
in an adult woman. A, before
A fully bracketed,
maxillary, edgewise
Adult Treatment
4n
B
o
BASIS· ~RPHOl.OGIC
ANALYSIS
C.K . • •
BEFORE AFTER
-2
MALES -15.0 X IS.O.2
-3
Crankll Base Bo-SE-FMN
-2
FEMALES -IS.O.X IS.O.2
3
j~..~5 .i4!o- . ..:l-. '1' I.. 'I~' ·1···,I ... ,I. ... I .••. h .. ~' ... ,.,
. r,is ..
Bo-S-No
II
Crania/Base-Maxilla S-N-A
I
I'
I
125 130.2
••
I
135
I140 1145 I
10
SE-FMNA
••
1
CraniaIBa$(l-Mand1~fHJ Bo-SE-Me Bo-SE-Pog Cranial Bau-MandiblefVJ Bo-SE/Mand.
Line
PM Vert lMond. Une Mazilla-Mandible Mand. Line/A - B Funct. 0ccI. Ln.1 A- B (not 0 constant)
Skeltlfal Profile FMN-A'B
ISO 1
155 I
FIG 17-5. Mandibular
prognathism.
This patient was treated
in adolescence
(see Fig 16-12 for details on controlling the adolescent growth spurt in the mandible). A, intra-oral views at age 16 years when growth
apparently
had diminished
greatly and mandibular
first premolars
were extracted. B, counterpart analysis. C, counterpart analysis after treatment. D, basic morphologic analysis before and after treatment.
478
Treatment
fields in dentistry, and the possibilities and methods of correction vary greatly. Therefore, each dentist forms ideas independently yet shares them with colleagues to take advantage of one another's experience and strategies. These records may seem superfluous; they are not. They constitute the minimal information required before treatment planning can begin.
5. Sequence of Treatment The sequence of treatment described here is best for most cases, though one alternative is discussed later: e.g., periodontal surgery prior to orthodontics.
a) Hygienic Phase of Periodontal Therapy The hygienic phase of periodontal therapy must be completed before any orthodontic treatment is begun. No orthodontics can begin until the mouth is clean and the patient is maintaining good oral hygiene. The other dentists may gather data and plan treatment while the hygienic phase is completed, but no teeth should be extracted without consultation. Often a tooth which is condemned periodontally may be useful during the orthodontic treatment to help stabilize the orthodontic appliance, and orthodontic treatment sometimes salvages teeth assigned for extraction. Orthodontics should not be perceived as alignment of crowns and improved occlusal relations alone, for root movements are also essential, producing far more extensive alveolar bone remodeling than is sometimes realized. Indeed, surprising amounts of favorable bone remodeling during orthodontics often changes the initial treatment plan.
b) Preliminary Endodontics)
Single Tooth Restorations
(Including
Some teeth may be so brokendown or pulpally involved that some restorative dentistry is necessary before orthodontics can begin. Only temporary restorations should be placed at this time" since the occlusal relationships will be altered by the orthodontic treatment.
c) Orthodontic Treatment Maintenance of good oral hygiene in-patients who have a history of periodontal disease may be a special problem during orthodontic treatment. The frequency of periodontal reevaluation and hygienic therapy varies greatly depending on the severity of the ravages of the periodontal disease and the patient's persistence (it's much harder to keep the mouth clean when appliances are in place) .
d) Surgical Phase of Periodontal Therapy Ordinarily any surgical treatment follows the orthodontic phase, but there may be occasions when it is necessary to do some surgery prior to the orthodontics. Orthodontic treatment remodels the alveolar process, often diminishing the need for periodontal surgery. The timing of surgery is decided by the periodontist in consultation with the orthodontist, but if the hygienic phase is successful, the surgery usually can wait advantageously. These are good cases for a conservative approach to periodontal therapy.
e) Orthodontic Retention After active orthodontic tooth movements, the retention, planned before treatment began, is necessary. Sometimes it is possible to use the passive orthodontic appliance itself as the retainer; on other occasions conventional orthodontic retainers are needed. There are also cases in which temporary bridges can be placed while the passive orthodontic appliance is still in place; then, when the orthodontic appliance is removed, the bridges become the retainers. f) Restorative Procedures
6. Choice of Orthodontic Appliances The choice of orthodontic appliance for a specific case is based on three fundamental factors: occlusion, space, and anchorage. Understanding the importance of each of these enables the dentist to design the most efficient appliance for a specific problem. The periodontic and reconstructive lit'erature contains many articles in which "simple" removable, appliances are advocated as if they were always the most efficient for these cases; but as a general rule, they are not. The cases shown later in this chapter were chosen as typical of each category and demonstrate the use of a variety of appliances. Bracketed appliances are usually favored for two practical reasons: (I) control of anchorage; and (2) versatility.
a) Occlusion Occlusal relationships must be studied carefully: statically on casts (intercuspal position) and functionally in the patient. The relationships of the cusps and inclined planes during the unconscious swallow, in the retruded contact position (centric relation), and in mastication are all-important, since occlusal function itself either aids or counteracts desired tooth movements although the teeth are apart most of the time. When occlusal function counteracts desired tooth movements or temporary traumatic occlusal relationships are established by orthodontics, it is necessary to insert a discluding appliance-a temporary bite plane which does not cover the occlusal surfaces of the posterior teeth-permitting orthodontic tooth movements to continue (Fig 17-6). These bite planes must be worn faithfully, for each time they are taken out of the mouth, the teeth-in their transitory positions-will be at the mercy of occlusal function. Bracketed appliances have a distinct advantage since the archwires serve as splints for the teeth at all times, yet are easily adjusted. "Jiggling" of teeth during function, due to occlusal interferences creat~d by the orthodontic treatment, can be very damaging and should be obviated. . Resist the temptation.,tli!-equilibrate the teeth as they are moved. Do 'not remove each new interfer~nce which appears, since the very cusp tip, which is interfering transitorily, may be needed later as a centric stop at retention time. Restorations, which were carved to fit the original malocclusion, may be recontoured during orthodontic treatment, but even this must be done with caution until the final occlusal relationship is near. The role of equilibration in retention of these cases is discussed later.
b) Space A careful analysis of the space available is essential before
Adult Treatment
479
at the end of orthodontic treatment, and the amount of space needed relative to the amount made available by extractions. It is easy to remove a tooth; it is often difficult to close the remaining excess space left after alignment. 3) Enlarging Teeth.-Often a diagnostic setup or the Bolton analysis (see Chapter 11) reveals disharmonies of tooth size within an arch or between the combined sizes of the upper and lower teeth. Sometimes an esthetic stabilizing solution is to enlarge one or more teeth (Fig 17-7).
FIG 17-6. Schematic drawing of a maxillary, flat bite plane used to diselude teeth during certain adult orthodontic treatments. (See also Fig 17-20.) starting any orthodontic treatment: it is particularly important for adults who have periodontal disease and missing teeth. Possibilities for improved use of available space are : (I) moving teeth to increase the arch perimeter; (2) extraction; (3) enlarging the crown size with restorations; or (4) judicious reduction in the crown size. There are limitations with each of these possibilities. 1) Tooth Movements.There are restrictions to the amount and direction of tooth movements, for example, arches cannot be expanded ad libitum, loss of bone prohibits movement in certain' directions, and the bone'turnover rate in aged patients is so slow some movements are quite impractical. Therefore, the movements desired for a specific patient must be tested against the specific conditions of that patient's alveolar process, arch size, skeletal profile, health, age, etc.
4) Reduction of Tooth Size.- When small amounts of space are needed to bring teeth into better alignment, reduction of the size of teeth is sometimes possible. A diagnostic setup and radiographs are used to disclose the amount of enamel available on each tooth (or the possibilities for reshaping restorations), and the site where the space is most needed (see Fig 17-20).
c) Anchorage In orthodontics, anchorage is resistance to tooth movement (see Chapter 13). Adults with loss of teeth and periodontal disease have reduced sources of anchorage. The ravages of periodontal disease constitute a primary problem in appliance design. Some of the strategies employed to augment anchorage are ligating teeth together on the archwire, reinforcing anchorage with bite plates, discluding with bite planes, and using extra-oral traction.
7. Simple Problems
in Anterior
Alignment
The cases discussed here are those in which the posterior occlusion is stable and needs little or no correction.
a) Midline Diastema 2) Extraction.-Extraction must be considered in some cases, but the decision to extract should be forced by the evidence of the data (e.g., a diagnostic setup). Of interest is the effect of extractions on the ultimate occlusal relationships, restorations required
The causes and treatment of excessive space at the midline (see Chapter 15) should be reread before starting treatment of an adult midline diastema because the principles outlined there apply here. As a general rule, the teeth are brought together prior to any
FIG 17-7. A:-E, orthodontic treatment of a "peg" lateral incisor and a microform
lateral incisor on the opposite side. There was also a complicating
developmental
defect in the midline alveolar septum.
480
Treatment
surgical correction of the midline fault, though supernumerary teeth, of course, are removed before the start of orthodontic treatment. A common situation is that of lateral incisors, which are diminished in size. It does no good to bring the central incisors together if tight contact cannot be obtained in the lateral region. A diagnostic setup will show the ultimate alignment and which teeth may be built-up with composite or jacket crowns to improve esthetics and aid retention. Retention of the central incisors in a new position may consist of (I) a thin casting, bonded to the lingual surfaces (as for a "Maryland" bridge); (2) a mesh wire embedded in composite on the lingual surfaces; or (3) nothing but tight interproximal contacts, depending on the needs of the individual case (see Fig 17-1).
b) Diminished Size of Lateral Incisors Maxillary lateral incisors may be diminished in size, varying from a well-shaped microform to a "peg" (see Chapter 6). It is essential to examine carefully the periapical radiographs to make certain that no septal fault is present (see Chapter 15) and to identify any reductions in root size. Precise measurements must be made of all anterior teeth (see Chapter II for techniques in analyzing the effects of asynchronous tooth size on occlusion). The size of the left lateral incisor must be compared with that of the right and both to other teeth in the arch. A diagnostic setup provides precise information about the best positions of each tooth needed by the end of treatment. Inlay wax may be added to the small teeth on the casts, carving new crowns to appreciate the effects of the orthodontic treatment and the ultimate restoration prior to beginning treatment. An illustrative case is shown in Fig 17-7.
c) Missing Teeth
second molar tips mesially while rotating around the palatal root. It may also translate bodily (Fig 17-8). Lower Molars.-In
the lower arch the reaction of the second
molar is similar, but lingual tipping accompanies mesial tipping. Because the forces of occlusion are buccal to the centroid of the lower molar, the more the tooth tips mesially, the more the occlusion tends to drive the tooth lingually. There is less rotation in the lower molar since there are only two roots, but translation is common, particularly if the first molar was lost early in life .(see ~I~).
/
b) Goals in Tr(!atment A normal angulation of the molar is desired since it provides (I) improved alveolar support, (2) better oral hygiene, and (3) a more advantageously designed bridge. 1) Rationale.The advantages of an upright tooth parallel to the anterior abutment of a possible bridge are" obvious. Lang8 has shown that molar uprighting also reduces the Gingival and Periodontal Indexes, the pocket depth, and attachment loss. These improvements begin in the hygienic phase of periodontal therapy and further improvement is seen after the orthodontic treatment is completed. Convincing evidence for the advantageous remodeling of the alveolar bony support for uprighted molars is shown in Fig
17-9. 2) Uprighting Versus Uprighting and Mesial Translation.-It is relatively easy to upright the second molar and even the third molar when the first molar has been lost (see Figs 17II to 17-16). After they are uprighted the occlusal relationships may not be correct and a decision must be made about how much translation is needed and in which direction. Three alternative final
Maxillary anterior teeth are frequently lost in accidents, and maxillary lateral incisors are among the teeth most often absent congenitally. The same principles outlined earlier pertain to this treatment also. It is advisable to use a precision bracketed appliance, since parallel placement of the roots of the teeth is necessary for the best possible bridge. When one lateral incisor is missing, the size of the other must be measured carefully for it is usually diminished in size. Generalized size reduction can also be expected (see Chapters 6 and 7). After space has been created a maxillary acrylic palate with a pontic may serve as a retainer during the construction of the bridge. It is also possible to attach a pontic directly to the archwire during the latter part of treatment (see Fig 17-7, 17-22, and 17-23).
positions are available, resulting in (I) a final edentulous space equal to the width of the lost first permanent molar, (2) an eden'tulous space equal to the width of one cusp after uprighting and some mesial translation, and (3) complete closure of the second molar forward into contact with the second bicuspid. The choice is dictated by the conditions present, the age of the patient, and the skills of the dentist. What is ideal for one patient may be impossible for another. Treatment procedures for each of these conditions are described later in this section.
8. Uprighting
The choice of appliance is dictated by the required tooth movements. The appliance must be able to replicate, in reverse, the tipping, rotating, translating, and extrusion that occurred to
Molars
a) The Problem
prod,u.ce the malposition .•
The tooth most frequently losf to caries and/or periodontal disease is the first permanent molar. As a result, the second and third molars may drift mesially, leaving the region more susceptible to periodontal disorders and complicating the replacement of the first molar. Other complications which may result include occlusal interferences and attendant temporomandibular joint dysfunction, loss of vertical dimension, extrusion of antagonistic teeth, etc. Upper Molars.-
c) Appliance Design
When first molars are lost, the maxillary
CO
1) Removable Acrylic Appliances.-Although the periodontic and restorative literature often advocates the use of removable appliances with auxillary springs for molar uprighting, they are indicated only in the most ideal of circumstances. These appliances are very usefull for simple space regaining in the early mixed dentition (their use is described in Chapter 15). They may be used in adult patients only when there is no major occlusal discrepancy, no extrusion, good periodontal health, and v.ery little
Adult Treatment
481
alveolar bone loss, and the third molar is either absent or presents no complications. Such conditions rarely obtain. problems can be handled 2) Bracketed Appliances.-Most best by bracketed appliances. The descriptions herein utilize 0.022inch edgewise brackets with no built-in torque or angulation.
d) Diagnosis Several questions must be in mind. How does this local problem affect the total occlusion? What effects will molar uprighting have on occlusal relationships? On vertical occlusion?
1) Radiographs.- The periapical radiographs must be studied to assess the health and extent of the alveolar process, the root lengths, and any root resorption. The positions :>f the roots of the second molar, third molar, and second bicuspid must be noted. Are they parallel? Have the teeth tipped or translated? These observations in the radiographs define the tooth movements (see Fig 17-9). One must realize that the periapical radiograph does not record the organic matrix of bone, only the radiopaque inorganic fractions. In Figure 17-9 the uprighting movements provided an environment into which the deposition of the inorganic salts could recur. Far too frequently we think, or say, "no bone is present," when viewing a radiograph like that in Figure 17-9, which is wrong for it is obvious that the critical and useful organic matrix was present. 2) The Patient.-Study the patient's profile and evaluate the lips and soft tissue. Study the vertical dimensions of the patient, both in occlusion and at rest.
FIG 17-8. Typically mesial drifting movements of first permanent molars.
FIG 17-9. A and B, uprighting of mandibular second molar. Note the amount of bone which replaced the "pocket" on the mesial surface. The
:
3) Casts.-From the dental casts, one can study the occlusal relations noting the positions of the second and molars and the bicuspids, extrusion of antagonistic teeth, the bite and overjet, malpositions of other individual teeth, etc. the shape and height of the alveolar ridge of the edentulous can .be seen best on casts.
basic third overAlso, space
amount of mesial transilatory movements which have taken place after uprighting can be seen in the trabecular pattern of the bone just distal to the distal root.
482
FIG
Treatment
17-10.
A diagnostic setup prior to molar uprighting.
c 1 ••
I
e) Planning Treatment 1) Complete a Diagnostic Setup.-A dignostic set-up provides an idealized depiction of the possibilities of orthodontic treatment (Fig 17-10). 2) Define Individual Tooth Movements.-Are these tooth movements possible? In what sequence should they occur? 3) Design the Appliances.Which and brackets? Will an acrylic bite plane occlusal interferences? Is this a locally there other aspects of mal occlusion that same or a slightly modified appliance?
teeth should have tubes be necessary to remove defined problem or are can be treated with the
FIG
17-12.
A-C, other methods . (After van Arsdale.)
A
of uprighting
and distal movement
of molars.
4) Imagine Possible Problems.-What can go wrong? How can problems be obviated? Design, in your mind, backup procedures should any of these problems actually occur. f)
Treatment Protocols
1) Uprighting Mesially Inclined Lower Second Molars (Refer to Figs 17-11 to 17-16).a) A sectional appliance involving double molar tubes on second molars and brackets on the premolars and cuspid only is required in the quadrant in which the tlrst molar is missing, if there are no extruded opposite teeth or other occlusal problems. A bopded lingual archwi'rt? may be inserted from cuspid to cuspid in the' lower arch to maintain the arch width and aid anchorage. It may not be needed if the mandibular arch is perfectly aligned, there is a normal overbite and overjet with tight, vertical centric stops in the incisor region, and no "slide" into occlusion (Fig
B
c
17-11).
~ FIG A-C,
17-11. the use of a segmental
uprighting spring.
b) In more complicated cases all teeth should be bracketed or banded. Level the arch first with a twisted wire (0.015 inch or 0.017 inch) from the cuspid through the third molar. This may be followed by a rectangular braided wire (0.017 inch x 0.025 inch). Arch leveling usually takes two to four appintments spaced 3 to
Adult Treatment
A
B
483
(Fig 17-13 ,A). Place simultaneous uprighting springs for both the second and third molars (Fig 17-13,B). c) When both the second and third molars are upright, insert a 0.018-inch round, straight wire to engage all of the brackets and tubes. If there are interdental spaces at this time, they may be closed by use of elastic chains or a compressed coil spring at the edentulous site (Fig 17-13,C). d) Insert a 0.018 inch x 0.025 inch rectangular finishing wire (Fig l7-13,D) and proceed with the tooth preparations. Insert a temporary bridge and place the final bridge later. 3) Contraindications, tions.-
Modifications,
and Complica-
c
(a) Contraindications.-Conditions in which molar uprighting may be undertaken, but which are beyond the scope of this book, include: (1) most cases found in severe skeletal dysplasias, (2) open bite, (3) absence of several anterior teeth, (4) extensive alveolar bone loss of anterior teeth, and (5) severe dysfunction of the temporomandibular joint.
FIG 17-13. A-D, simultaneous distal movement of second and third molars. Careful control of anchorage by this and other means obviates the need for extraction of the third molar. (After van Arsdale.)
(b) Modifications.-Mild extrusion of antagonistic teeth may be handled by the insertion a maxillary bite plane, judicious grinding of the lower molar as it is uprighted (if that tooth is to be used as an abutment), and, in most cases, by placing an appliance in the upper arch to level the occlusion. Maxillary cases are treated in a fashion similar to the lower. It can be expected that more rotation will take place as the maxillary molar moves distally, and provision for that rotation must be made in adjustments of the uprighting springs. Maxillary molars also tend to drift mesially a bit more rapidly suggesting a solution to the problem by mesial movement obviating the need for a bridge (see Section 7-f-(4), but this solution is much more difficult in the upper arch due to the palatal root. Typical cases are shown in Figs 17-14 through 17-16.
4 weeks apart and will achieve a sutprising amount of the tooth movements needed. c) Insert a round 0.018-inch archwire in the bracket slot and in the main tube of the second molar. Add a sectional uprighting spring inserted in the lower tube on the second molar (Fig 17IIA). d) After the molar is upright, place a rectangular wire (0.018 inch x 0.025 inch) to secure final positioning of the crowns and alignment of the roots (Fig 17-11,C). A Hawley retainer may be worn while the teeth are prepared fora bridge. A temporary bridge may be placed prior to the insertion of the ultimate bridge. Other methods of uprighting molars are shown in Fig 17-12. 2) Uprighting Mesially Inclined Second and Third Molars (Refer to Fig 17-13).a) Place double buccal tubes on both second molars and a single buccal tube on the third molar of the side to be treated. Place brackets on all other teeth in the lower arch. b) Level the arch with twist wires, braided rectangular wires, and round wires (0.015, 0.016, and 0.018 inch wires in sequence)
(c) Complications.-Unwanted opening of the occlusion may appear with uprighting of lower molars, particularly if only partial arch wires have been used as suggested earlier. Undesirable bite opening is a clear sign of improper mechanics or adjustment of the appliance. Frankly, this is an undesirable complication arising from failure to adjust the appliance for intrusion while tipping. It is not enough to grind away the cusp of the offending tooth on the premise that it will be included in the bridge, unless the appliance mechanics continue tO,depress the tooth. This problem is a principal reason for not using removable appliances for simple molar uprighting, for they have no vertical control of th~ .uprighting tooth .• ~. • Occasionally a patient will tire of the whole procedure before uprighting is completed. When this happens only two alternatives present themselves: (I) persuade the patient to continue: or (2) have the bridge constructed under unfavorable circumstances. 4) Moving Mesially Inclined Molars Forward.-Moving second and/or third molars mesially to obviate the need for a bridge is a fine orthodontic service for adult patients and can be done in highly selected cases, but it requires considerably more skillful control of the appliance then simple uprighting. This procedure is
484
Treatment
FIG 17-14. Treatment of absent mandibular first molars: uprighting for a bridge on one side, uprighting and mesial movement on the other. A, pre-
,. treatment casts. B, various stages of treatment including the finished result ready for placement of a bridg~.
Adult Treatment
485
plane is worn at all times. Only after the arch is leveled and the molar uprighted is forward traction applied with a gentle, continuous force and depressing action. Since these cases have a tendency to reopen interproximal contact quickly, retention is begun by tightly tied steel ligatures holding the molar forward while the complete archwire is still in place. A well-fitted Hawley retainer will suffice after this step and after occlusal equilibration is completed (see Fig 17-17).
(b) Illustrative Cases.-The cases shown in Figures 17-16 and 17-17 offer proof that this can be a sensible conservative procedure when carried out properly. They also show certain dangers and complications (Fig 17-18). If tempted to treat a case of this type, reread this section carefully and study thoroughly the cases shown before beginning. 9. Problems Due to Inadequate Space
FIG
17-15.
Molar uprighting and transilatory movement. A, the basic uprighting spring. B, a closing vertical loop, bringing the molar mesially.
easier in adolescents, particularly when the third molar is erupting, and is much simpler in patients who have had no periodontal disease. The alveolar area of the edentulous region should be studied carefully in the radiographs, in the mouth, and on the dental casts. Mapping of pocket depths and alveolar crest heights on the teeth to be moved, and detailed study of the alveolar bone are necessary. One hopes for a healthy high and broad alveolar process with a distinct "collar" of bone on the mesial of the molar(s) to be moved. Teeth do not just move through bone, they carry bone with them. A poor alveolar housing at the start of treatment is not improved by mesial movement of the tooth. This orthodontic procedure should be carried out only by dentists thoroughly experienced in orthodontic mechanics.
(a) Principles of Treatment.-It is absolutely necessary to level both arches with complete appliances as the first step of treatment. Except where there is a very shallow bite, a flat bite
In this section are considered minor space problems treatable without extraction of teeth. The diagnostic setup often reveals that the consolidation of interdental spacing, coordination of arches, and uprighting and rotating of crowns will provide surprising amounts of space, which may be distributed throughout the arch (see Figs 17-19 and 17-20). Two other opportunities for the creation of space are available; the distal movement of posterior teeth and careful reduction of the mesiodistal diameter of crowns. For these cases the precision bracketed arch wire appliance is much more useful and conservative than removable appliances, since the arch wire allows precise control of each tooth and a maximal utilization of any space found or created. The cases chosen for illustration (Figs 17-20 and 17-21) have one thing in common; optimal utilization of the total arch perimeter by idealizing the angulation and rotations of individual teeth. Their placement in an ideally shaped arch is the first requirement. Reducing the diameter of the crowns is not undertaken until near ideal positions have been obtained. If such' 'stripping" of the crowns is to be done, it should be meticulously planned and utilize recontouring of fillings as much as possible. It is better to take the time to reduce every tooth a bit than to attempt to acquire space in one or two sites alone. Fig 17-19 illustrates a case where tiny reductions of each tooth in the arch permitted the unlocking of a lateral incisor. Extra-oral traction was worn throughout. Beginning on the posterior teeth, one tooth on each side per appointment was reduced a fraction of a millimeter and elastomeric chains drew each tooth posteriorly and kept it in tight contact. At the next appointment the procedure was carried out on the next tooth mesially. In this way, th~. teeth were stripped and moved distally like ~beads on a string until the midline correction occurred and the space had all accumulated wHere it was needed. A maxillary acrylic bite plane is necessary, and must be ground concomitantly to permit the tooth movements (see Fig 17-20).
10. Oligodontia FIG
17-16.
Molar uprighting in an orthognathic surgery case. A, early uprighting biomechanics. B, radiograph of the result after uprighting, orthognathic surgery, and mesial movement of the molar.
Oligodontia, often erroneously called "partial anodontia," presents some of the most demanding problems in adult orthodontics and collaborative restorative dentistry. There are few simple rules for general aplication because the;:cases vary so much.
486
Treatment
FIG 17-17. Mesial movement of molars to obviate the need for a bridge. A, before treatment.
S, after treatment.
-.
"
-~ ..,
Adult Treatment
487
FIG 17-18. Uprighting molars and unsuccessful after uprighting was completed.
attempt at mesial movement. A,
S, denuding of the lingual root when
mesial movements were attempted. C. result after removal of appliances. D, similar problem on the opposite side of the arch.
FIG 17-19. Diagnostic setup prior to treatment of a lingually locked lateral crossbite (see also Fig 17-20).
'.
"
-.'
488
Treatment
A2
FIG 17-20. Treatment of a single-tooth crossbite in a periodontic patient on Dilantin therapy. Before the start of orthodontic treatment, this patient had a radical gingivectomy to remove the fibrotic gingivae which resulted from the drug therapy. A, records at the start of orthodontic treatment. A-l, postsurgical and hygienic phase of periodontic treatment. A-2, the periodontal chart. A-3, the appliance in place. It had been ascertained that judicious, minimal stripping of restorations and all the contact points in the posterior part of the arch would provide sufficient space to bring the lateral incisor into the line of occlusion.
B, progress during treatment. B-1, the patient wore a headgear. At each appointment one contact point was slightly reduced. An elastomeric chain was then placed to move the most posterior tooth distally. At the next appointment the second tooth mesially was stripped and the elastomeric chain was extended one more tooth. In this photograph the chain has been moved to the cuspid region. B-2,the discluding bite plane in situ (see Fig 17-6). B-3, after the lateral incisor had been brought through the crossbite. B-4, during retention.
Adult Treatment
489
FIG 17-21. A-C, stripping teeth to provide space for a blocked out mandibular second premolar. Extensive restorations may be recontoured Perhaps nowhere in orthodontics is it more important to have all of the treatment planned before any is begun. In these cases, the' orthodontist's goals are defined precisely by the needs of the reconstructive dentist. When there are many congenitally missing teeth, the morphology of crowns and roots of remaining teeth often is atypical in size and shape (Chapter 6). The cases shown (Figs 17- 22 and 17-23) illustrate some of the potentials for orthodontic treatment. The congenital absence of single teeth is discussed in Chapter 15, since it ought to be treated as early as possible.
11. Vertical Problems
in the Anterior
Region
Open bite and deep bite may present difficulties to the restorative dentist, and it is natural to think of orthodontic improvements as a possible first step in treatment. A reading of the periodontic and restorative dental literature on this problem is a frustrating and enlightening experience for an orthodontist, for some of the "treatments" advocated show a lack of appreciation of the variety of open and deep bites, their complications, and the orthodontic possibilities for their correction. Before orthodontic therapy is begun it is essential that all clinicians involved understand the etiology and the nature of the vertical occlusal problem.
a) Etiology The etiologies of deep bite and open bite are many and complicated, as these are among the most deceptive of malocclusions. It is necessary to understand the basis for the open bite or the deep bite and whether or not it is still possible to effect a satisfactory orthodontic treatment (see Chapters 7, 12, 15 and 16). Difficulties are enhanced if periodontal disease and tooth drifting have exacerbated the basic malocclusion and if there has been extensive alveolar bone loss.
advantageously.
b) Diagnosis The primary diagnostic problem in both deep bite and open bite is to ascertain the site of the dysplasia. It may be localized within the dentoalveolar area or it may be inherent in the craniofacial skeleton itself. Study the patient, noting the lip line, tongue posture, and the resting vertical dimension. Definitive answers on the role of the craniofacial morphology itself can only be found in the cephalometric analysis (Chapter 12). Even in the healthy, growing child, vertical dysplasias are generally considered to be difficult to treat and retain. Since differential control of growth itself is the only real treatment, other than surgery, for severe vertical dysplasias, it follows that tooth movements and alveolar remodeling alone can only suffice for those mal occlusions in which the skeletal contribution is minor.
c) Treatment 1) Simple Deep Bite.-When it can be shown that abnormal depth of bite is localized in the dentoalveolar region of one or both arches and there is a normal intetocclusal pi stance in the mandibular postural position, treatment by arch leveling mechanics alone may be possible. If there is, in addition, an excessive overjet, c~o:",ding in either anterior region or excessive alveolar bone loss, thelreatment becomes more comglicated. Leveling tends to elevate the posterior teeth and depress the anterior teeth while improving incisal centric stops and reducing the depth of bite (Fig 17-24).
2) Simple Deep Bite With Labioversion of Maxillary Incisors.-If neither occlusal plane is flat and the maxillary incisors are labially tipped and spaced, a diagnostic setup before beginning treatment will reveal the extent to which mandibular arch leveling
490
Treatment
FIG 17-22. Severe case of oligodontia. A, casts prior to treatment. Note the retained and built-up ankylosed primary molars still in situ. B, during orthodontic treatment. Note the failure of alveolar development because of the unnecessarily retained primary molars. C, after active orthodontic therapy. There is a serious problem in left-right tooth size
disharmonies (e.g., the central and lateral incisors). D, a temporary bridge in place. E, the final results. Note the accessory cusp on the only maxillary molar. This cusp could not be removed without endodontic therapy, and it was decided that the abnormally shaped tooth would be left in place.
Adult Treatment
FIG 17-23. Severe oligodontia. A, prior to orthodontic treatment. Notice the depth of bite, the many retained primary teeth, and the two prostheses, especially the mandibular and its dependence on retained primary cuspids. B, radiographs of the teeth before and during treatment. Note in B-1 and B-2 the active resorption on the roots of maxillary teeth. B-5 and B-6, progress radiographs used to monitor the resorption during treatment. (Continued.)
",
'.-
-. ".
491
492
Treatment
.'
FIG 17-23 (cont.). C, mandibular reconstructive dentistry was completed prior to the maxillary orthodontics. C-1, the initial twist leveling wire with which most of the orthodontic treatments were carried out. C-2 and C-3,
later stages of the very brief treatment. place.
0, the final restorations
in
FIG 17-24. A and B, the effects of arch leveling mechanics alone on the amount of incisal overbite. This is the same case shown in Figure
and retraction of upper incisors alone will correct the problem. Before undertaking such treatment, a Bolton analysis should be made (see Chapter 11) since it will show clearly how much residual overbite and overjet will remain due to differences between the total upper tooth mass and the lower. When the lower arch is uncrowded and flat, and the depth of bite is isolated to the maxillary anterior dentoalveolar region, the problem is more complicated because extensive intrusion of the upper incisors must be carried out during their retraction. Maintenance of anchorage in these cases, particularly when there has been periodontal disease, is often difficult. Fig 15-25 compares two skeletal deep bite cases, one with labioversion of the upper incisors and one without.
17-18.
3) "Simple" Open Bite.- There really is no such thing as a "simple" open bite. The term here means an open bite due to loyaJ factors, not a resulr:'Of gross vertical skeletal dysplasia.
(a)Diagnosis.-An important question before planning treatment is, what causes the open bite to be maintained? Often in adults it is an abnormal tongue posture ,or a localized open bite caused by some habit such as pipe smoking but maintained by the tongue to seal the open bite during the swallow. A diagnosis cannot be completed unless three questions can be answered: (1) Is the open bite due to vertical skeletal imbalance? (2) if not, what is the etiologic factor which created the open bite? and (3) how are centric incisal stops maintained? If there are no enamel-to-enamel
Adult Treatment
493
A
I
3-2 -2 322I ~..-
PM Vtlrl/FMN-SE VerI/Pal (nOI 0 c~lonlln Cta"10IFEMALES Dl MHif1R 75 ANALYSIS R I I PM 85 1-'S.O. MALES 115110 Cranil1l Btll.MALES VERTICAL ANALYSIS 115 110 130 95 PM VerI/Mane!. Line 90 170 VERTICAL 130 125 105 115 MALE~, X -15.0. X90 I125 lS.D. 15.0. I IFEMALES 120 120 105 85 I 105II110 75 PM Vert IOcel. Line FEMALE~I~ 1 85: 90~
IA2
I
-3
C.B.47-1
@
I ~
Line 90 I
MALES
FIG
I
I 82
I
~.·~\~·"~1~
17-25.
A, deep bite in an adult periodontic
patient. Note the severity of the
Fig 17-27.)
mandibular line angle. B, another complex deep bite case. (See also
centric stops in the incisal region, one may suspect that the tongue at rest provides "centric stops". In this regard, it is important to analyze the unconscious swallow-for any "simple" open bite, by definition, has a normal tooth-together swallow. It will be useful to reread the sections in Chapter 7 on etiology, in Chapter 10 on the analysis of the musculature, and in Chapter 15 on the treatment of these problems in young children, in Chapter 16 on adolescent treatment, and in Chapter 18 for comments on myotherapy.
(b) Treatment.-First, remove all etiologic factors, if possible. Next, plan tooth movements in the arch (or arches) in which the anterior teeth are away from the functional occlusal line. For instance, if the mandibular occlusal plane is perfectly flat from molars to incisors and all teeth lie along it but the maxillary anterior
teeth are elevated above the maxillary occlusal plane, it may be necessary to place an appliance only in the upper arch. When the teeth have been brought down to a normal relationship and incisal stops are established throughout the entire arch, check again to be reassured of the absenc.~of any etiologic factors. Fig 17-26 shows the- treatment response to a mod~rately severe skeletal open bite.
c) Retention.-Retention in these cases is difficult and varied depending particularly on the amount of alveolar bone loss and cessation of etiologic factors. A "permanent" fixed splint, usually from upper cuspid to upper cuspid is often necessary. 4) Complicated Vertical Problems.-A wide variety of very difficult vertical dysplasias are seen in the adult population. See
494
Treatment
B 1. L. 19-1
VERTICAL
-3
Cranial 80S.
-2
-lS.o.
ANALYSIS X
\S.o.
MALES
PM Vert/FMN-SE
3
2 85
90 90
1
85
Maxilla PM Vert/Pal
Line
MALES
FEMALES
90
85
Occlusion PM Verl/Oeel. (not
0
constant
Line
MALES
in Closs
il)
~5
FEMALES
100
105 1110
115 1
100
1051 110
Mandibl. PM Vert/Mond.
Line
MALES
FIG 17-26. A and B, orthodontic treatment of a moderately severe skeletal open bite in an adult patient. (For more details of this case see Fig 10-
20.) Note the extent of the maxillary treatment.
Figures 17-25, 17-26, 17-27, and 10-20. Some malocclusions that are treatable with difficulty during growth become impossible by orthodontics alone after growth is largely over. Those discussed earlier, it will be noted, were limited to the anterior dentoalveolar region. The most complicated problems are invariably the result of vertical skeletal imbalance, that is, complex or skeletal Opell bite (see Chapters 12, IS, and 16). They are made even more diffi~ult when teeth are lost and periodontal disease has diminished the alveolar process. The orthodontic aspects of treatment usually consist of alignment of the teeth in preparation for orthognathic surgery or orthodontic tooth movements prior to restoring the vertical dimension with full-mouth rehabilitative reconstructions.
C. ORTHODONTIC
dentoalveolar
remodeling
by
TREATMENT COMBINED WITH ORTHOGNATHIC SURGERY (KWLV, and RJF) Combining orthognathic surgery with orthodontic treatment was a logical development. As appliances became available to move teeth in any desired direction, severe skeletal discrepancies became a major problem'iil preventing ideal arch relationships from being attained with correction of tooth position alone. Extra-oral traction appliances, in the United States, were introduced by Kingsley7 and Case' at the turn of the century. This method of treatment provided distal vectorial forces to the maxilla sufficient to modify developing Class II malocclusions (see Chap-
FIG 17-27. Severe case of incisal overlap in a patient with loss of teeth and periodontal disease. The patient was treated by orthodontics to open the bite, underwent restorative dentistry, and received a gingivoplasty
in the mandibular incisal region. A, photo before treatment. treatment. (This is the same patient as in Fig 17-25, B.)
B, after
Adult Treatment ters 13 and 15). The applications of extra-oral force to unfavorable mandibular patterns of growth were also attempted using the chin cap. The modification and redirection of certain unfavorable mandibular Class n growth patterns in some children may be resolved by functional jaw orthopedic appliances (see Chapter 15). In the nongrowing individual, orthodontic manipulation or camouflage of severe skeletal dysplasias* is difficult and often impossible. Orthognathic surgery provides a method of correcting the skeletal dysplasia and follows a presurgical phase of orthodontic treatment to correct the dentoalveolar component of the mal occlusion .
1. Historical Aspects of Orthognathic Surgery Of the current surgical techniques for repositioning the facial bones, many were pioneered in Europe to treat trauma and gunshot wounds during World Wars I and n. The technical advances during the Second World War, provided the basis of many of the elective surgical procedures in use today. Rene Le Fort9 noted that the midface consistently sustained fractures at sites of weakness which provided the logical site for osteotomy cuts in the Le Fort I, n, and ill procedures. These form the basis of the Le Fort classification. To eliminate facial scars, an important aspect of elective surgery, intra-oral surgical approaches were developed. A major contribution was made by Obwegeser and TraunerlO when they described a method of sagittally splitting the mandibular -ramus. Although the foundations for present-day procedures were. laid in Europe, the development and refinement of orthognathic surgery occurred in the United States. Techniques and research in vascularization and perfusion of pedicled flaps provided the surgeon with a viable means of manipulating the mid facial skeleton.2. 3
2. Selection of Patients Perhaps one of the most important aspects of this combined treatment approach is to decide which patients will benefit from this complex treatment. 2.4. 6 Most patients who would benefit from combined orthodontics and surgery exhibit extremes of normal skeletal variation, often family characteristics (e.g. the mandibular prognathism of the Hapsburgs). Not surprisingly, many individuals with severe dental malocclusions do not have facial esthetic concerns. As surgery is elective in these patients, it is particularly important that the patient is well informed before a decision is made to start treatment. This type of surgery requires hospitalization, and a general anesthetic, and it is therefore important when recommending this type of procedure to inform the patient of the "risks" and benefits involved.
3. Case Managememt Before a combined surgical-orthodontic approach was developed, the best result that orthodontic treatment alone could *The term "skeletal discrepancy" is used in the literature of surgery, but "dysplasia" is more frequently used in orthodontics and is used in this chapter for consistency with the rest of the book. However, the difference in meaning is important. A discrepancy is a wide variance between two things which should be alike or harmonious, while dysplasia is bad or unfortunate development. Irrespective of the term, the cases may be extremes of normal variation or anomalous morphology.
495
provide for severe malocclusions associated with craniofacial skeletal dysplasias was camouflaging the skeletal pattern by dentoalveolar compensations. This orthodontic treatment created problems for the surgeon, for when the maxillo-mandibular discrepancy was resolved by surgery, the dentoalveolar components were not ideally related. Cooperation between surgeon and orthodontist during initial diagnosis and treatment planning provides a coordinated approach. The orthodontist and surgeon determine, before any treatment is begun, the optimal relationship of the skeletal and dentoalveolar components. * The orthodontist first moves the teeth into an optimal relationship to their underlying dental bases, so that when the skeletal dysplasia is surgically corrected, the teeth fit together in coordinated arch relationship with favorable changes in facial appearance. The orthodontic appliance used to prepare the dental arches before surgery is kept in place to provide intermaxillary fixation during healing after surgery or as adjunctive fixation if rigid osseous fixation has been used.
4. Case Referral Before referring a patient for orthognathic surgery, the dentist should provide the patient with general information about available surgical procedures to correct the problem and address the patient's concerns. The general dentist will need judgment and diagnostic ability to recognize the relative contributory factors of a severe mal occlusion , namely, skeletal and dental (see Chapter 12). If a child has a severe skeletal dysplasia, then referral to an orthodontist may be the first choice, since modific.ation or redirection of the unfavorable growth pattern using a functional appliance or extraoral traction head gear may be indicated. However, an adult with a severe skeletal dysplasia does not respond well to growthmodifying appliances. Correction of skeletal malrelationships in adults may be achieved by surgical manipulation rather than growth modification. It is important to elicit the patient's concerns, which may be focused on the appearance of the teeth or their function. Often an individual with a skeletal open bite will complain that "my front teeth do not come together when I bite." However, further questioning may also reveal facial esthetic concerns described as "I am unable to keep my lips together" or "my chin is too far back. " Screening patients prior to referral to the appropriate specialists is an important aspect in provision and delivery of care, especially when the treatment is of an elective nature. The family dentist's judgment and advice are important and helpful to the prospective orthodontic-surgery patient. Care should be taken to give a clear, objective explanation of the bdnefits to be gained and also the risks. There is little evidence to support the contention that correction of any malocclusion will result in increased longivity of the more ide;lly related dentition. Patients should not, therefore, embark on a complex orthodontic and surgical correction for the wrong reasons.
5. Classification of Skeletal Dysplasias In classifying the relationship of the maxillary complex to the *Many texts are available that provide detailed information in the diagnosis and treatment planning of the surgical/orthodontic management of these patients (see Suggested Readings).
496
Treatment
Normal
.'
FIG
Mandibular Excess
Maxi Ilary Deficiency
Dento-Alveolar Compensation
Combination of Maxillary Deficiency and Mandibular Excess
17-28.
Diagrammatic
representation
of craniofacial
dysplasias
(see text).
mandible (Fig 17-28) it is convenient to subdivide the midface into the skeletal maxilla or dental base and the maxillary dentition. Likewise in the mandible, the dentition needs to be eveluated in relation to the mandibular skeletal or dental base (Fig 17-28). The overall relationship of the maxilla to the mandible can now be divided into skeletal and dentoalveolar components and various combinations. In defining the problem it is useful to generate a problem-oriented approach and then to establish priorities of importance.4• The jaw relationship and its contribution to the malocclusion, together with the patient's facial and dental concerns, are important factors in treatment planning and patient selection. It is also necessary to relate the facial complex to the cranium (see Fig 1728). This simplistic analysis of the relations of dental and skeletal components to the cranium has become conventional in the cephalometric literarure. No attempt will be made here to describe the numerous methods of cephalometric analysis available. Suffice it to say, that in spite of its two-dimensional limitations and other limiting factors, it still provides the basis for clinical diagnosis and treatment planning (see Chapter 12). Having clinically evaluated the skeletal and dental components in three dimensions, it is important for the general dental practitioner to be in a position to determine the ideal age at which the patient should be referred to the orthodontist/surgeon.
6, Timing and Sequence of Treatmets " Often skeletal discrepancies may be modified in the growing child by means of an orthopedic appliance. These appliances appear to have the most predictable response in the mixed dentition but rarely can correct severe skeletal dysplasias. When the general dentist recognizes a severe skeletal dysplasia, referral to the appropriate specialist should be made. Modification of a severe skeletal discrepancy in adults is not possible by redirection of growth, but surgical correction may be indicated. Orthodontic treatment places the teeth in the correct relationship to the jaws before surg~ry. The orthodontic appliance will rem~in in place during surgery arld;.lllay provide fixati"on during healing. After surgical fixation is released, another shorter period (4 to 6 months) of orthodontics is indicated to detail the occlusion before retainers are fitted. The goals of this section have been to provide an overview for a combined treatment procedure which is a fundamental part of the orthodontist's and the oral and maxillofacial surgeon's training and clinical practice. The optimum facial and dental result, necessitates close collaboration between the general dentist, surgeon, and orthodontist. To illustrate the principles of patient selection and treatment planning, some representative case reports are described. For more detailed information, see Suggested Readings at the end of the chapter.
Adult Treatment 7. Case Reports*
a) Case Report 1 P.E., a l2-year-old girl, was initially seen at the University of Iowa for treatment with a chief complaint of disliking her excessive "gummy" smile (Fig 17-29). Presurgical evaluation was performed, and a problem list and treatment plan w~re formulated. 1) Problem
List.-
interalar width combined to achieve an esthetic balance of nose, lip, tooth, and chin. The addition of a 5 mm advancement of the chin achieved better facial balance.
b) Case Report 2 J .S., an l8-year-old man was referred to the Dentofacial Team at the University of North Carolina for correction of his prognathic lower jaw (Fig 17-30).
(a) Esthetics
• •
1) Problem
Frontal: lip incompetence; excessive exposure of teeth and gingivae at rest and in function. Eight millimeters of incisor exposure with lips in repose. Narrow alar width. Profile: Slightly obtuse nasolabial angle relative mandibular retrusion, convex profile, deficient chin.
(b) Cephalometric Analysis.-
• • • •
Moderately steep angle of mandibular plane. Ten millimeters of lip incompetence. Retrogenia. Increase in vertical maxillary height.
(c) Occlusal Analysis.-Moderate crowding of maxillary and mandibular incisors Class 11 malocclusion. 2) Treatment
Plan.-
(a) Presurgical Orthodontic Treatment Plan Is to Align and Decompensate Dental Arches. (b) Surgical Treatment-Maxillary
•
•
Fort I osteotomy (one-piece) Anterior impaction of 6 mm. Posterior impaction of 5 mm. Advancement of 2 mm. Allow autorotation of mandible to achieve optimal incisal relationship Advancement genioplasty of 5 mm.
(c) Postsurgical Orthodontic Treatment to Detail the Occlusion.3) Follow-Up (Subjective).-Postoperative healing was uncomplicated and associated with minimal morbidity. Intermaxillary fixation was maintained for 6 weeks. Within 6 weeks after the surgery the maxillary and mandibular osteotomies were clinically stable. Postsurgical orthodontic treatment was completed uneventfully within another 3 months ... By total maxillary osteotomy, genioplasty, and orthodontic treatment the objectives were achieved. Superior movement of the maxilla surgically improved facial esthetics by decreasing anterior facial height, differentially decreasing the amount of gingivae and tooth exposure, and achieving lip competence. The more acute nasolabial angle, improved lip posture and a small increase in the
List.-
(a) Esthetics.-Frontal
and profile: Good facial balance ex-
cept for a prognathic mandible.
(b) Cephalometric Radiographic Analysis.-Mandibular
ex-
cess in profile view.
(c) Occlusal Analysis.-Aligned maxillary and mandibular arches. Anterior open bite with tendency to bilateral posterior crossbite. 2) Treatment Plan.-Orthodontics to align and decompensate teeth. At surgery, bilateral vertical ramus osteotomies of the mandibular rami were performed by an intraoral approach. The mandible was set back 6 mm and immobilized for 6 weeks. Following release of fixation, function was reestablished of interarch elastics.
by the use
3) Follow-up.-Restoration of normal facial proportion was achieved. Follow-up assessment of the occlusion after surgery and orthodontics indicated a stable result.
Osteotomy.-
Le a) b) c) d)
497
c) Case Report 3 T.F., a 17-year-old girl, had been under orthodontic treatment since age 14 for her skeletal and dental malocclusion. (Fig 1731). She was presented at the Dentofacial Program at the University of North Carolina and a problem list and treament plan was formulated. .1) Problem
List.-
a) Esthetics.Frontal: Increased lower third of the face, narrow alar
• •
bases, and deficiency in paranasal areas.
Profile: Concave profile, full everted lower lip, prominent chin, flattening in paranasal and infraorbital regions.
(b) Cephalometric Analysis.-Posterior vertical maxillary excess with Class III skeletal pattern: maxillary deficiency and ma~dibular excess. Mod~te
chin prominence.
(c) Occlusal Analysis.-Minimal crowding of labially inclined maxillary and retroclined mandibular incisors. Class III canine and molar relationship and 6-mm negative overjet. 2) Treatment
Plan.-
(a) Presurgical Orthodontic Treatment.-Correct • clinations.
"'
incisal in-
Align and level maxillary and mandibular arches.
498
Treatment
.'
D, presurgical phase of orthodontic treatment archwires with soldered lugs for intermaxillary menJ and leveling of dental arches with closure Anterior open bite has developed vyith increased
FIG 17-29. Case report 1. A, patient aged 12 years. A-1, note increased vertical lower facial height with lip strain. A-2, convex profile with long face. 8, dental occlusion before treatment. C, patient aged 15 years. C-1, orthodontic treatment involved extraction of first premolars. Note increased vertical facial dimension with growth. C-2, at full smile, note excess gingival display. C-3, profile view. Note lip incompetence.
complete. Surgical fixation. Note alignof extraction space. vertical face height
during growth. (Facing page) E, patient at 17 years of age. E-1, note facial esthetic change following orthognathic surgery. E-2 and E-3, profile views indicate good facial balance and proportion with lip competence. F, comparison of patient smiling before and after surgery. G, excellent dental occlusion with closure of anterior open bite. (Periodontal condition was under treatment). H, cephalometric superimposition showing vertical superior impaction of the maxilla with autorotation of the mandible and genioplasty. I, comparison of facial profile before and after surgery. Note reduction in vertical lower facial height with lip competence and good chin projection.
Adult Treatment
499
500
Treatment
."
FIG 17-30. Case report 2. A, patient at 17 years of age following orthodontic treatment; patient had unfavorable growth resulting in mandibular prognathism with asymmetry of chin'.' A-2, dental occlusion with lower retainer in place. Note that midlines are not coincident. Mandibular
midline reflects skeletal asymmetry. B-1, after presurgical phase of orthodontic treatment. Note mandibular asymmetry. B-2, profile view shovying mandibular progfiathism. C, 'dental occlusion before surgerj. Note midlines are not coincidElnt, but mandibular dental midline is on the skeletal (chin) midline. (Continued.)
Adult Treatment
501
G -4/2/76 --6/23/77
J~S'
o
-
FIG 17-30 (cont.).
occlusion
0-1, facial symmetry following mandibular surgery. 0-2, profile view
open bite. G, cephalometric superimposition of presurgery and postsurgery lateral skull radiographs. Note correction of skeletal mandibular excess and asymmetry following mandibular surgical setback procedure.
indicates balanced facial proportions. E, at full smile, note correction of skeletal and dental midlines to coincide with the midsagittal facial midline. F, following
surgery and orthodontics,
an excellent dental
was achieved,
..-., with correction
of asymmetry
and anterior
502
Treatment
.'
FIG 17-31, Case report 3. A, 15-year-old girl. A-1, note vertically increased facial height and lip incompetence. A-2, profile view confirms increased vertical facial proportion with mandibular prognathism. A-3, at full smile no excess of gingival display is noted. B, dental occlusion indicates open bite and enamel hypoplasia. C, cephalometric tracing ~ .. shows Class III malocclusion and skeletal mandibular prognathism. 0-1, facial change following surgical maxillary impaction and mandibular setback. 0-2, at full smile, note incisor display has not been reduced by maxillary intrusion, which was planned to superiorly move the posterior maxilla by tipping. E, profile view confirms balanced facial proportions. (Continued.)
Adult Treatment
503
F
FIG 17-31 (cont.). F, cephalometric tracing of postsurgical result. Note change in position of lower lip with mandibular setback and vertical autorotation. G, dental occlusion following orthodontics and surgery. Note correc(b) Surgery.•
•
One-piece Le Fort I osteotomy to reposition maxilla 3 mm superiorly in molar area to allow for autorotation of mandi- . ble and favorable vertical proportions. Mandibular set-back of 6 mm by bilateral sagittal split osteotomies to produce a Class I canine and molar relationship.
(c) Postsurgical Orthodontic Treatment.-Occlusal detailing and finishing with settling in of the occlusion aided by interarch elastics. (3) Follow-up.-After
the teeth were orthodontically aligned and leveled, the maxilla was superiorly repositioned and the mandible was set back surgically. The full lower lip was still present postoperatively, but the patient decided against chieloplasty ..
d) Case Report4 M.Z. is a 34-year-old woman who attended the dentofacial program at the University of Michigan with concerns about her protruding upper front teeth and the gingival display when she smiled. She also had concerns regarding her retruded chin and obtuse throat-neck angle.
1. Problem List.(a) Esthetics.-Frontal: slight facial asymmetry with an increased lower facial height and at full smile she shows increased gingival display (Fig 17-32,At). Profile confirms the increase of lower facial height with lip strain to produce an anterior oral seal. This accentuates the severe mandibular deficiency and the obtuse throat neck form (Fig 17-32,Az)' (b) Cephalometric Analysis.-Increased
mandibular
plane
tion of anterior open bite by maxillary and mandibular procedures and excellent interdigitation of posterior occlusion.
angle with proclined maxillary and mandibular incisors in a position of increased overjet and incomplete overbite. The mild asymmetry is shown by the duplicated lower borders of the mandible .
(c) Occlusal Analysis.-Mandibular first molars were missing with mesial drifting and tipping of the second molars. Unerupted third molars were removed. The canine relationship was Class II on the right and Class I on the left because of the shift of the dental midline to the right together with the mandibular asymmetry.
2. Treatment Plan.(a) Presurgical orthodontic treatment involved uprighting the mandibular molars, which tends to increase the vertical facial height. This is, therefore, an important presurgical orthodontic tooth movement. If this was accomplished in the postsurgical phase of orthodontic treatment it would build in a relapse tendency. In the maxillary arch, extraction of the maxillary first premolars was indicated. This provided space for alignment and some retraction of the maxillary incisors while providing space for the osteotomy cuts for a segmental (three-piece) maxilla.
(b) Surgical Treatment.-Segmental
maxillary osteotomy to
superiorly reposition the.!llaxilla, aU,torotation of the mandible to clo~e the anterior open bite together with a sagittal split osteotomy to advance the mandible and a genioplasty to augment the chin. (c) Postsurgical orthodontic treatment to settle in the occlusion, with light archwires and rubber bands/elastics using a Class II vector of force. Following removal of the fixed appliances and fitting of retainers, bridges were indicated to replace the missing mandibular first molars. Note: Intermaxillary fixation was not used in this patient as rigid osseous fixation for both the maxillary and the mandibular osteotomies provided adequate stabilization following simultaneous two jaw surgical correction.
504
Treatment
M.Z. 3-15-85
Initial
\
er-+- ~ ~ ~
FIG
17-32.
A, and A2• initial full face and profile views of the patient. Note increased vertical facial height with excessive gingival display on smiling. Profile shows the lip strain and obtuse throat neck angle. A3. cephalometric lateral skull radiograph showing anterior open bite, proclined maxillary and mandibular incisors and mesially tipped mandibular second molars. A•• tracing of·the initial cephalogram. (Facing
page.)
B" anterior view of occlusion.
Note anterior open bite and
the mandibular midline deviated to the right. B2 and B3• right and left buccal views. Note the tipped mandibular second molars. C, and C2• full face and profile following presurgical orthodontic treatment. With uprighting of the mandibular first molars the open bite and vertical fac.ial height has been increased with lip strain on the profile view to achiev.e a lip contact. (Continued.)
Adult Treatment
505
506
Treatment
Adult Treatment
FIG 17-32 (cont.). (Facing page) 0" segmental aligning of the maxillary arch with soldered lugs on the surgical archwires. O2 and 03, left and right posterior views to show uprighting of the mandibular molars with space for prosthetic replacement following surgery for the missing mandibular first molars. 0" occlusal view of maxillary arch showing alignment with some retraction of some maxillary incisors and adequate space for the osteotomy cuts. E" patient 2 years postsurgery. Orthodontic treatment was completed 4 months after surgery. Note the
507
acceptable smile with no gingival display. The alar base which had a nasal cinch has not increased significantly (E2). Profile view shows well balanced vertical proportions with an excellent chin neck contour and a labiomental fold following an augmentation genioplasty. (Above) F" occlusal view to show coincident dental midlines with closure of the anterior open bite which has remained stable after retainers were discontinued. F2, posterior view of buccal occlusion to show bridge to replace the mandibular first molar. F3, maxillary occlusal view showing closure of space at the osteotomy sites. (Continued.)
",
508
Treatment
FIG 17-32 (cont.). G" orthodontic debanding. The terminal molars are upright and ready for bridge placement. G2, following bridges to replace the missing first molars. H, panoramic radiograph after presurgical phase of orthodontic treatment to upright the mandibular terminal molars. Note alignment of the dentition and space for the osteotomy cuts in the maxillary arch. I, cephalometric radiograph immediately postsurgery showing rigid osseous fixation in the maxilla together with screws for fixation after the sagittal split mandibular osteotomy. (Continued.)
-
-. .
Adult Treatment
J
509
M.l.
Pre-Surg __ - - -12-4-85 Post-Surg1-10-86
\
I
v4 ~~
L
M.Z. ot
YfiMlr
FIG 17-32 (cont.). J, tracing to show superimposition
Post-Surgery
of the pre- and postsurgicallateral
skull radiographs. K, panoramic film following postsurgical result prior to bridge placement. Note the three screws bilaterally to stabilize the mandibular osteotomy and the transosseQus wires at the mandioular 'symphysis for the genioplasty. In the maXillary arch, note the plates and screws for stabilizing the three-piece maxillary osteotomy. L, tracing 2 years postsurgery indicating stability of both the dental and skeletal components.
3. Follow-up Post operative healing was uneventful and as she did not have intermaxillary fixation she was able to function immediately. Patients prefer this method of stabilization, although the diet has to
be carefully supervised and kept to a liquid/soft diet during the early phase of healing. However, the ability to talk and swallow (and even to laugh) during the period when there is maximum
510
Treatment
swelling provides a more comfortable situation. Orthodontic treatment was commenced within the first month after surgery at which time the surgical arch wires were removed and light archwires were placed. Traditionally, the orthodontist does not,start postsurgical treatment for 6 weeks after surgery because of intermaxillary fixation. The segmental osteotomy in the maxilla allowed differential repositioning of the anterior and posterior segments to close the open bite which also allowed closure of the extraction space.
Acnowledgment We are indebted to the orthodontic departments at the Universities of North Carolina and Iowa for their participation in the treatment of these case reports (K. W .L. V ., R. J .F.).
REFERENCES 1.
2.
3.
4.
4a. 5. 6.
6a. 7. 8.
9. 10.
Behrents G: Growth in the Aging Craniofacial Skeleton, monograph 17. Ann Arbor, Mich, Craniofacial Growth Series. Center for Human Growth and Development, University of Michigan, 1985. Bell WH, Levy BM: Revascularization and bone healing after posterior maxillary osteotomy. J Oral Surg 1971; 29:313-322. Bell WH, Fonseca RJ, Kennedy JW, et al: Bone healing and revascularization after total maxillary osteotomy, J Oral Surg 1975 33:353-362. Bell WH, Proffit WR, White RP: Surgical Correction of Dentofacial Deformities, vols 1 and 2. Philadelphia, WB Saunders, 1980. Proffitt WR: Contemporary Orthodontics. Philadelphia, WB Saunders Co, 1986. Case CB: Occipital and cervical anchorage, Trans Am Soc Orthod 1912; 136-147 .• Epker BN, Wolford LM: Middle-third facial osteotomies: Their use in the correction of acquired and developmental dentofacial and craniofacial deformities, J Oral Surg 1975; 33:491-514. Epker BN, Fish LC: Dentofacial Deformities, Volumes I and 2. St Louis, CV Mosby Co, 1986. Kingsley NW: Oral Deformities. New York, Appleton and Coy, 1880. Lang NP: Das proprosthetische Augrichten von gekippten untem Molaren in hinblickal1f den parodontalen Zustand. Schweiz Mschr Zahnheilk 1977; 87:560-569. Le Fort R: Etude experimentale sur les fractures de la machoire superieure, Rev Chirurgical190l; 23:08. Obwegeser H, Trauner R: Surgical correction of mandibular prognathism and retrognathia with consideration of genioplasty. Oral Surg Oral Med Oral Patho11957; 10:677. ,.
SUGGESTED READINGS Section B: Orthodontic treatment of malocclusions complicated by periodontal disease and loss of teeth Alstad S, ZachrissonBU: Longitudinal study of periodontal conditions associated with orthodontic treatment in adolescents. Am J Orthod 1979; 76:277-286. Atherton JD, Kerr NW: Effect of orthodontic tooth movement
upon the gingivae. Br Dent J 1968; 124:555-560. Barrer G: The adult orthodontic patient, Am J Orthod 1977; 72:617-640. Brown IS: The effect of orthodontic therapy on certain types of periodontal defects, J Periodontol1973; 44:742-756. Dorfman HS: Mucogingival changes resulting from mandibular incisor tooth movement. Am J Orthod 1978; 74:258-277. Geiger: AM: Gingival response to orthodontic treatment, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1984. Horn BM, Turley PK: The effects of space closure of the mandibular first molar in adults, Am J Orthod 1984; 85:457469. Karring T, Nyman S, Thilander, B: Bone regeneration in alveolar bone dehiscences related to orthodontic tooth movements, Eur J Orthod 1983; 5:105-114. Norton A: Periodontal considerations in orthodontic treatment. Dent Clin North Am 1981; 25:117-129. Poison M: Long-term effect of orthodontic treatment on the periodontium, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, Monograph 15, Craniofacial Growth Series, Center for Human Growth and Development, Ann Arbor Mich, 1984. Rygh P: Periodontal responses to orthodontic forces, in McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15, Craniofacial Growth Series, Center for Human Growth and Development, Ann Arbor, Mich 1984. Sadowsky C: Long-term effect of orthodontic treatment on the periodontium during adolescence, in: McNamara JA Jr, Ribbens KA (eds), Malocclusion and the Periodontium, monograph 15, Craniofacial Growth Series, Ann Arbor Mich; Center for Human Growth and Development, 1984. Sadowsky C, BeGole EA: Long-term effects of orthodontic treatment on periodontal health. Am J Orthod 1981; 80:156-172. Stepovich ML: A clinical study on closing edentulous spaces in the mandible. Angle Orthodont 1979; 49:227-233. Thilander B: Indications for orthodontic treatment in adults, in Thilander B, Ronning (eds), Introduction to Orthodontics. Stockholm, Tandlakarforlaget, 1985. Tuncay, OC et al: Molar uprighting with T-Loop springs. JAm Dent Assoc 1980; 100:863-866. Wagenburg BD, Eskow RN, Langer B: Orthodontic procedures that improve the periodontal prognosis, J Am Dent Assoc 1980; 100:370-373. Zachrisson BU: Cause and prevention of injuries to teeth and supporting structures during orthodontic treatment, Am J Orthod 1976, 69:285-300. Zachrisson BU: Periodontal changes during orthodontic treat" . ment, in McNamara JA Jr, Ribbens KA (eds), Malocclu·sion and the Periodontium"monograph 15, Craniofacial Growth Series, Center for Human Growth and Development Ann Arbor Mich, 1984.
0
Section C: Orthodontic Treatment Combined with Orthognathic Surgery Bell WH, Proffit WR, White RP: Surgical Correction of Dentofacial Deformities, vol 1 and 2. Philadelphia, WB Saunders, 1980. Epker BN, Fish L: Dentofacial Deformities: Integrated Orthodontic Surgical Correction. St Louis, CV Mosby, 1983.
CHAPTER
1-8
Orthodontic Techniques Robert E. Moyers, D.D.S.,
Ph.D.
OUTLINE D. A.
Basic construction
technics
1. 2.
B.
The bending of wire Joining metals a) Soldering b) Spot welding 3. Record casts Basic clinical technics 1. 2. 3.
Orthodontic impressions Separation of teeth Molar band formation a) b)
4.
5. C.
Fitting preformed bands Attachments for molar bands 1) Buccal tubes 2) Lingual sheaths c) Cementation of bands Brackets for incisors, cuspids, and premolars a) Preformed bands with attached brackets b) Bonding attachments Elastics
Fixed appliances 1. Lingual arch wire a) Description 1) Removable 2) Fixed b) Modifications 1) Loop lingual 2) Porter lingual archwire 3) Quad-Helix lingual archwire c) Attachments 1) AuxilIary springs 2) Lingual locks 2. Fixed space maintainers 3. Palate-separating devices 4. Edgewise mechanisms 5. Light-wire appliances 6. Other fixed appliances
E.
a) Twin-wire appliance b) Universal appliance Attached removable appliances 1. Active appliances a) Extra-oral traction devices I) Head gears 2) Face masks 3) Chin cups b) Lip bumpers ("plumpers") c) "Active plates" 1) Schwartz appliance 2) Space-regaining appliances 3) Anterior spring aligners (Barrer appliance) d) Crozat appliance e) Vacuum formed appliances ("invisibles") 2. Passive appliances a) Bite planes b) Occlusal splints c) Multiple space maintainers d) Retainers Loose removable appliances (functional appliances, functional jaw orthopedic appliances, etc.) 1. Background a) Definition b) Purposes c) History d) Modes of action 1) Muscles 2) Dentition' and alveolar processes 3) Craniofacial skeleton (a) Claimed skeletal responses (b) Role of timing in treatment intervention 2.
3.
Vestibular appliances (oral shields, oral screens) a) Description b) Construction Functional jaw orthopedic appliances a) Definition 511
512
F.'
Treatment b) Uses and indications c) Types d) Activators and derivatives e) Frankel Function Regulator f) Myodynamic or elastic appIlances g) Others 4. Repositioning splints 5. Tooth positoners a) Description b) Construction c) Limitations 6. Herbst appliance 7. Hybrids and perversions Myotherapeutic exercises 1. Purposes 2. Limitations 3. 4.
G.
Principles Specific procedures a) Orbicularis oris and circumoral muscles b) Mandibular posture Correction of deleterious oral habits 1. Basic considerations 2.
H.
Digital sucking (finger-sucking, thumb-sucking) a) Phase I: Normal and subclinically significant sucking b) Phase II: Clinically significant sucking c) Phase Ill: Intractable sucking d) Choice of appliance 3. Tongue-thrusting a) Causes b) Diagnosis c) Treatment 1) Simple tongue~thrust 2) Complex tongue-thrust 3) Retained infantile swallow 4. Abnormal tongue posture 5. Lip-sucking and lip-biting 6. Fingernail-biting Occlusal equilibration (occlusal adjustment) 1. Equilibration in the primary dentition 2. Equilibration in the mixed dentition 3. Equilibration in the permanent dentition a) Rationale b) Procedure
A. BASIC LABORATORY TECHNIQUES
FIG 18-1. Bending of wire for orthodontic appliances. A, correct way. Wire is near the hinges of the pliers, and the pliers are used as a portable vise. All force of application is done with the finger. e, improper way of bending wire. c) Grasp the wire in the pliers so that it may be bent downward by the fingers of the free hand against the rounded beak of the pliers to avoid nicking the wire (see Fig 18-1). Never bend a round wire over a sharp beak. d) Check the first bend made, before marking the location of the next bend, and repeat the process. e) Take care to make all bends at right angles to the long axis of the wire, unless a different angle is specifically required: it is much easier to control the arch wire by ke~ping all bends in the same plane. . .1) Never make a ne::v~bend until the last bend made is perfect.
,
1. The Bending of Wire All bends in orthodontic wires usually ar~ placed by the fingers; one should regard the pliers as a portable vise for holding the wire while making the bend (Fig 18-1). The procedure is as follows: a) If possible, establish a fixed relationshin of the wire before making any bends. b) Place the wire in position and mark it with a wax pencil (a mascara eyebrow pencil works well) where the bend is to be made.
2. Joining Metals a) Soldering Soldering should f;>edone without appreciable alteration of the qualities of the metals being joined. Orthodontic soldering is carried out with a small, specially designed orthodontic burner or torch or with various electric devices. A good flame for orthodontic soldering has a small, well-defined point. It is easiest to solder when the metal is held just at the apex of the middle flame cone. The operator should be seated in a relaxed manner with the elbows
Orthodontic
Techniques
513
FIG 18-3. Typical modern Corporation.)
orthodontic
spot welders.
(Courtesy
Unitek
a flow of electric current through the portions of the pieces in juxtaposition. The parts to be joined are held together by electrodes (Fig 18-3). As the current passes through the electrodes and the metal pieces between them, resistance is built up within the ~etals to be welded. The heat generated is sufficient to cause a union of the parts touching each other. A true weld is formed, and no solder or flux is used.
FIG 18-2. Various methods of bracing fingers and hands while soldering wires and attachments. close to the body. Some brace the heels of the hands together, whereas others prefer to use the fingertips (Fig 18-2). The fingers, hands, and arms remain braced as the body, bending at the hips, leans toward the flame. Orthodontic solder is available in several forms (e.g., disks and bars) but the fine wire is most suited for orthodontic use . A fluoride flux is necessary when one is soldering stainless steel. A true solder joint does not result when stainless steel and solder are joined; rather, there is an intimate mechanical union. With modern stainless steel alloys, however, surprising results may be obtained. Slightly more solder and a slightly cooler flame is needed than for soldering the gold alloys. All auxiliary springs should be wrapped around the arch wire twice to protect the solder joint and the annealed portion of the spring wire (see Fig 18-19). b) Spot Welding Spot welding is the joining of two metal pieces by heat from
3. Record Casts Casts (often erroneously called "models") are one of the most important sources of information about each orthodontic case, since they provide a permanent three-dimensional record of the malocclusion. A base is a necessity for it aids in proper articulation of the teeth and protects them against breakage. Bases are made in two ways: by oriented base-formers (Fig 18-4), or by a model trimmer. . Modern model trimmers have devices attached to them that m;ure trimming swift and easy. 1'he casts may be polished with talc or soaked in a soap solution and rubbed after drying (Fig
18-5).
B. BASIC CLINICAL TECHNIQUES 1. Orthodontic
Impressions
A'suitable tray is chosen to provide proper clearance from the teeth and soft tissues. When the teeth are in extreme malpositon or the arch is abnormally shaped, soft wax may be added to the
514
Treatment
FIG 18-4. Rubber base formers .
..
FIG 18-5. A good set of orthodontic
study casts.
Orthodontic Techniques
515
h) Always hold the tray in place until the impression material is fully set.
2. Separation of Teeth To separate teeth before bands can be fitted, a length of 0.020inch brass ligature wire may be rotated through the embrasure beneath the contact point but above the soft tissue (Fig 18-7). Twist the two loose ends and tuck them into the embrasure. When a series of separating wires is to be placed, put the wires through the embrasures and allow them all to lie loosely before twisting the first one. After the separating wires have been in place no longer than a few days, cut and remove them by rotating the wire out of the embrasure just as it was inserted. Other methods of separation are shown in Fig 18-8. 3. Molar Band Formation
FIG 18-6. Good upper (A) and lower (B) impressions.
impression tray; for example, to carry the impression material well up into the vestibule in Class n, Division I cases. Fig 18-6 shows a well-taken set of impressions. Note how the impression material was carried to the limits of the vestibule. The following points may aid in taking correct impressions of malocclusions. a) Always use the exact size of tray required. b) Add wax where needed to ensure a complete impression of the supporting bony structures. c) Mix the impression material in the proportions suggested by the manufacturer. Do not beat air into the impression material, as if mixing cake batter. Rather, smooth the material against the side of the bowl with the flat side of the spatula. Time the mixing. d) Have the patient rinse his or her mouth well before the impression is taken. e) Seat the patient upright, with the eye-ear plane parallel ~o the floor. /) When taking the upper impression, tip the tray up in the back to drive the excess material forward so that it is extruded into the labial vestibule and not down the throat. For the upper impression, stand behind the patient and hold the tray level with the occlusal plane. g) When taking the lower impressions, rotate the tray into the mouth, keeping the tray parallel with the occlusal plane. Have the patient extrude his or her tongue to push any excess impression material forward and maintain the tray in position by placing each index finger over the occlusal part of the tray and each thumb under the mandible.
A number of different methods are available for forming and fitting molar bands, but only fitting preformed bands will be described here. Regardless of the method chosen, the finished band should be adapted closely to the contour of the tooth, be free of occlusion, and extend 0.5 to I mm below the free margin of the gum (Fig 18-9). On the mesial and distal surfaces, the occlusal edge of the band should lie just at the marginal ridge and should be festooned so that it will not cut the transseptal periodontal fibers. There is an important difference in the crown-root angulation between upper and lower molars which affects band formation. The path of insertion of the upper molar band is in line with the long axis of the tooth, whereas in the lower band, the path of
A
FIG 18-7. Method of separating teeth. A, soft brass separating wire is wrapped around a fountain pen, then cut. B, individual loops of cut wire are rotated into position around the contact point.
516
Treatment
A
DentCJt Floss
Step I
Step 2
Step 3
Step 4
B
c
"
FIG 18-8. Other methods
of separating
teeth. A, elastic thread
method.
B, Maxian elastic separator.
C, elastic separating
loops.
1.Seat the band by al-ternate
2. Ginog;ival
:'111
edge must
\ I
~" .. ,:, ..:.:~:.::.\h ..,."., ..:]\
1\
at the line angles
lie
",. ... ~.
3.
FIG 18-10.
FIG 18-9. Upper and lower molar bands correctly contoured ence with intercuspation .
pressure
to avoid interfer-
Fitting of maxillary molar bands. Note use of band driver.
.
FIG 18-11. Examples of preformed orthodontic bands. (Courtesy of Rocky Mountain Metal Products Company.)
,
Orthodontic Techniques
517
FIG 18-12. Attachments for molar bands. A, single buccal tube and lingual button. B, a double buccal tube for the molar. C, the lingual tube, which
receives the Ellis-type lingual archwire. (Courtesy of Rocky Mountain Metal Products Company.)
insertion is in line only with the crown. The technique is to force the band on to the crown so that it adapts to the contours of the tooth (Fig 18-10).
Isolate and dry the teeth to be cemented, mix the cement for a prolonged setting time, and coat thoroughly the inside of the band. Wax or masking tape covering the occlusal surface helps control the escape of the cement during the transfer from slab to mouth and while driving the fitted band to place. After the cement has fully set, clear the excess from the occlusal surface and the gingival crevice.
a) Fitting Preformed Bands Preformed bands are popular because one can easily achieve a good fit routinely and their cost is low. They are made of stainless steel and come in a sufficiently large number of sizes to fit nearly all teeth with only occasional contouring (Fig 18-11). It is, however, necessary to maintain a large inventory of bands at all times.
4. Brackets
for Incisors,
Cuspids,
and Bicuspids
a) Preformed Bands With Attached Brackets b) Attachments for Molar Bands 1) Buccal Tubes.-Buccal tubes hold labial archwires and/or. the inner bow of head gear appliances in position on first molars. Each of the multi banded appliance systems has one or more special buccal tubes. When second molars are erupted, they may receive the buccal tube, and brackets are placed on the first molar bands. 2) Lingual Sheaths.-Lingual sheaths of many variations receive and attach lingual archwires (Fig 18-12).
c) Cementation of Bands Molar bands do not fit as well as inlays; therefore, the cementation is different. Generally, a heavier mix is required with a longer setting time to permit final seating and adaptation. Zinc phosphate cement is popular, but I prefer a heavy mix of silicophosphate cement (e.g., Kryptex) which is very strong and has the additonal advantage of freeing FI- ions on dissolution.
FIG 18-13. A and B, bonded appliances in situ. (B courtesy of Unitek Corporation.)
:
Bands for the anterior teeth and the bicuspids are also available with a variety of attachments. Each of the several bracketed orthodontic appliances has its own particular bracket design. Preformed bands are available in a large assortment of sizes. They are selected in much the same manner as described for the molars and adapted to the tooth by driving into position and burnishing. Preformed bands usually are supplied with brackets and lingual seating lugs attached. Anterior bands must be fitted accurately, placed at the correct height on the tooth and cemented well. Since the bands and brackets provide a means of joining teeth together, one misplaced band or bracket affects the position of several teeth. A set of dividers may be used to obtain correct placement of the bands, but special gauges for doing this more easily are available. Anterior bands are cemented much as molar bands, but a thinner mix is used.
b) Bonding Attachments Bonding
of brackets
directly
to the crownr. has largely
518
Treatment
FIG 18-14,
.'
Uses of elastomeric chain. (Courtesy of Unitek Corporation.) superseded the use of anterior bands and even of some molar bands. The brackets are bonded to etched enamel with composite materials similar to those used to restore anterior teeth. Brackets may be bonded directly, one at a time, or indirectly by placing the brackets for an entire arch simultaneously. Direct bonded appliances are more esthetic than anterior bands, can be placed more accurately, and provide better oral hygiene (Fig 18-13).
able from each manufacturer showing the actual forces for a given size of elastic stretched over various distances.
5, Elasties
a) Description The lingual archwire is a round wire (0.032 to 0.040 inch in diameter) that is closely adapted to the lingual surfaces of the teeth and attached to bands, usually on the first permanent molars (Fig 18-15). It is a most useful appliance, particulary during the mixed dentition period, since the archwire maintains the arch perimeter. Auxiliary springs may be added to move teeth (see Fig 18-19).
Elastics are available as robber bands, elastic thread, and formed shapes for specific proposes (Fig 18-14). They are used to move teeth, to ligate archwires to brackets, for intermaxillary traction, and for separation. Elastics are always attached to brackets and archwires-NEVER around the naked tooth. Data are avail-
C. FIXED APPLIANCES 1. Lingual Arehwire
FIG,1~8-15,'
"'
The lingual archwire. A and B, details of archwire adaptation to the gingival margin of the working cast. C, position of the horizontal lingual tube. The archwire is doubled on itself and is held in place within the tube by friction.
Orthodontic Techniques
519
1) Removable.~ The removable lingual arch wire has precision fitting shafts that fit into corresponding sheaths on the molar bands (see Fig 18-12 and 18-15). It is used as an active appliance or as a device to maintain the arch perimeter. 2) Fixed.- The fixed lingual archwire is soldered to molar bands and is used for the maintenance of arch length or retention. When it is used to maintain the arch perimeter, it sometimes is called a holding arch.
b) Modifications 1) Loop Lingual.~Placing a vertical loop in the archwire just mesial to the point of attachment to the molar band permits adjustment of the length of the wire and easier positioning and rotating of the molars (Fig 18-16). 2) Porter Lingual Archwire.-A useful modification of the lingual archwire is the Porter appliance which is used to correct crossbites and mild maxillary contraction (Fig 18':: 17) . It utilizes reciprocal anchorage to tip the teeth buccally. 3) Quad-Helix Lingual Archwire.~ The Quad-Helix, a useful improvement of the Porter archwire, makes possible continuous slow expansion of the buccal segments and/or separation of the midpalatal suture (Fig 18-18).
c) Attachments 1) Auxiliary Springs.~ The attachment of auxiliary springs is made in an embrasure (Fig 18-19).
FIG 18-16. The loop lingual archwire. A, use in a space supervision case. Note the relationship of the archwire to the gingival margin. B, in place on a cast.
2) Lingual Locks.-Some locks hold by friction while others use a lockwire of dead, soft steel whose malleability permits repeated bendings without breaking.
2. Fixed Space Maintainers Fixed space maintainers usually are made of preformed steel crown forms or bands with bars or wire projections to maintain
FIG 18-17. A, the' Porter lingual archwire. In this instance, the appliance was made for correction of a functional crossbite in the primary dentition, one of its most frequent uses. B, an example of a modified maxillary
removable Porter lingual archwire. McNamara, Jr.)
(Courtesy
of Dr. James
A.
520
Treatment
FIG 18-18. The Quad Helix appliance. This removable version utilized horizontal lingual tubes.
FIG 18-20. A. the band and loop space maintainer.
FIG 18-19. Correct positioning
B. a band and loop space
maintainer and a space maintainer using a primary crown form. The band and loop space maintainer may also incorporate an occlusal rest. (Courtesy of Rocky Mountain Metal Products Company.) of auxiliary springs.
FIG 18-21. A, rapid palatal-expansion using acid-etch bonding
appliances (see also Fig 16-7). B,. a type of acrylic that has been cured to a wire
framework. B2• a similar appliance incorporating ment of a face mask (see Fig 18-27).
hooks for attach-
Orthodontic space after premature loss of primary teeth (Fig 18-20). They may also be constructed of wires held in place by composite. The advant;ige of fixed space maintainers is their permanence; a disadvantage is their lack of adaptability to growth changes. Sometimes two "simple" space maintainers may be more difficult and costly to make and less satisfactory than one lingualarchwire. Do not disregard the entire arch perimeter and the developing occlusion simply because one tooth is missing. A variety of ingenious space maintainers have been suggested, and several types are available in prefabricated form (see Fig 18-20).
3. Palate-Separating Devices •Rapid separation of the midpalatal suture in cases of maxillary insufficiency is obtained by means of screw devices fixed to the teeth (Fig 18-21 ,A). The suture is opened rather quickly (in about 2 to 3 weeks) and the space created at the midline then fills with bone, permitting the central incisors to return to juxtaposition (Fig 18-21). (See also Fig 16-7.)
4. Edgewise Mechanism The edgewise mechanism was the last and most advanced of the several appliances invented by Dr. Edward H. Angle. It is a multibanded precision appliance consisting of a rectangular labial arch wire fitted and ligated into horizontal slots in brackets and terminating in rectangular tubes on the second molar bands (Fig 18-22). The archwire originally was 0.022 x 0.028 inch, with the narrow (0.022 inch) dimension lying against the facial surfaces of the teeth: hence its name. Control in all directions is posible,
FIG 18-22. The basic edgewise
bracket, showing a method of ligation and the
and all individual directions.
Techniques
teeth may be moved simultaneously
521 in three
The edgewise bracket is versatile since it will accept any shape of wire up to 0.022 inch in diameter (edgewise brackets with 0.018 inch slots have become popular in recent years). A series of progressively larger light twist and round wires are used initially to align, rotate, and tip the teeth and to level the occlusal plane, permitting the greatest movements with light forces yet allowing more easy insertion of the the rectangular wire. Loops can be incorporated into the archwire to affect individual tooth and sectional arch movements. The modem edgewise mechanism is quite different from Angle's original appliance but its ingenious design enabled the adoption of many ideas from other multibanded systems . The idea that each tooth has a proper position and angulation within an ideally shaped arch in order to achieve an ideal coordinated occlusal relationship with teeth of the opposing arch is an important concept if used in treatment with edgewise appliances. The edgewise appliance is not particularly well suited for use during the mixed dentition and is difficult to use in the primary dentition. It finds its greatest application in the treatment of comprehensive malocclusions of the adolescent permanent dentition. Though difficult to master, the edgewise mechanism is the most popular because of its versatility. Several systems (often erroneously called "philosophies") of treatment, (e.g., Tweed, Straightwire, Bioprogressive) are based on use of the edgewise mechanism. Though the brackets are similar, the steps of treatment, means of obtaining anchorage, methods of delivering torque, etc., differ. Descriptions of its construction and manipulation can be found in the publications in Suggested Readings at the end of this chapter.
use of adjunctive springs. (Courtesy of Rocky Mountain Metal Products Company.)
522
Treatment 5. Light-Wire Appliances The so-called "light-wire" appliances were designed by P.R Begg, an Australian orthodontist. Since some types of tooth movements evoke more tissue resistance than others, and some movements occur faster than others (see Chapter 13), Begg reasoned that by selectively choosing the movements required and relating the reciprocal reactions properly, several tooth movements might be carried out simultaneously, if each movement were carried out within its ideal force range and as many movements as possible were mutually reciprocal and beneficial. Such ideas prompted many innovations in bracket and archwire design (Fig 18-23). Lightwire appliances now differ from the original design, but employ Begg's concepts of tooth movement and anchorage control. Standard light-wire therapy does not utilize extra-oral traction, frequently involves extraction of teeth and, uses fewer auxiliaries than edgewise therapy .
6. Other Fixed Appliances
."
a) Twin-Wire Applillnce The twin-wire appliance consists of a pair of steel wires 0.010 or 0.011 inch in diameter placed in stainless steel end tubes which fit into buccal tubes on the first molar bands. The twin wires in
FIG 18-23. Examples of light-wire brackets and the use of locking pins and rootaligning springs. (Courtesy of Rocky Mountain Metal Products Company.)
the anterior section fit into a lock type of bracket (Fig 18-24). The twin-wire appliance is much less popular today than it once was, since it is simply not efficient for many important tooth movements, (e.g., translation and paralleling of roots). It has, therefore, been largely superseded by the edgewise and light-wire appliances.
FIG 18-24. The twin arch bracket and sliding cap, and a typical twin arch bandup. Note the end tubes, which fit into buccal tubes on the molars. From the end tubes, the two small twin wires extrude to attach to
the anteriors, which are banded. (Courtesy of Rocky Mountain Metal Products Company.)
Orthodontic
Techniques
523
A
FIG 18-25. A, universal bracket. The two wires are held in place by lock pins (courtesy of Unitek Corporation). 8, photographs of a case treated
with the universal appliance. Sequence indicates progression of treatment (courtesy of Dr. Jorge Fastlicht).
524
Treatment
.'
FIG 18-26. Extra-oral traction appliances. A-C, the Jenkins director, a combination modified Activator and face bow. Note that the appliance is made in three segments, which allows for easy adjustment of the
b) Universal Appliance The universal appliance, the design of Dr. Spencer Atkinson, is a multibanded precision appliance consisting of one flat and one round wire used in combination (Fig 18-25). The appliance is versatile, and has loyal adherents, though it has never attained great popularity.
D. ATTACHED REMOVABLE APPLIANCES Removable appliances-those designed to be taken from the mouth by the patient-are divided into two classes: attached and loose. Attached removable appliances maintain a fixed relationship to the dentition by means of clasps. Loose removable appliances fit imprecisely and are designed to alter neuromus~ular function during specific oral activities. Both attached and fixed removable appliances will be considered under two general headings: (I) active appliances and (2) passive appliances. The appliances de-
buccal segments to various sizes of arches. A, an upper view. B, an under view. C, cephalograms of patient before and after treatment with this appliance (courtesy of Or. O. Harvey Jenkins). (Continued.)
scribed are but popular and useful examples of each category; it is impossible to mention all of the many variations on each theme.
1. Active Appliances
a) Extra-Oral Traction Devices , Extra-oral traction devices utilize anchorage outside the oral cavity lor efficient application of force in directions not otherwise possible. Extra-oral traction may be used to move teeth, to reinforce the anchorage of intraoral appliances, to produce orthopedic responses in the midface and mandible or to restrain or alter craniofacial bony growth. 1) Head Gears.-The mode of attachment and direction of head gear force application varies with the task assigned. Fig 1826 illustrates a variety of "head gears" most of which are used to produce dorsal forces in the maxillary region. '
Orthodontic
....;c
Techniques
525
\."~5~~--~ _
FIG 18-26 (cont.). D, simple neck strap, sometimes called cervical traction. An elastic strap attaches to a face bow. The inner, smaller bow fits into buccal tubes on molar bands; the outer bow attaches to the neck strap. E, straight-pull head gear, which attaches to a face bow. F, hi-pull head gear (occipital traction) attached to a face bow. The high pull obviates
2) Face Masks.-Face masks, an old method which has undergone a dramatic revival in recent years, are used largely to produce ventral effects in the maxillary region (Fig 18-27). 3) Chin Cups.-Chin cups are devices to utilize extra-oral traction to restrain or alter mandibular growth (Fig 18-28). b) Lip Bumpers ("Plumpers") The lip bumper is a heavy labial arch wire which is inserted into buccal molar tubes. The wire has a flange of plastic added anteriorly to engage the lip and is stopped anteriorly to the molar tubes with a vertical loop or compressed coil spring (see Figs 1829 and 15-23). Lip bumpers may be used to maintain the arch perimeter, position the molars distally, or permit changes in incisal position. c) "Active Plo1es" Active plates is the term applied to attached, removable appli-
extrusion of upper molars. G, hi-pull head gear with "J" hooks which attach through the corner of the mouth to an archwire Iigated in brackets on bands cemented to the teeth. H, combination hi-pull head gear and neck strap.
ances which derive their anchorage from the palatal or alveolar mucosa and the teeth which they contact. Although active plates are used in many ingenious ways, they do not constitute a complete appliance system. Important points in construction are the means of retention and the fit of the plastic to the teeth (Fig 18-30). 1) Schwartz Applia~ce.-The original Schwartz appliance and iJs many derivatives' use arrowhead, or similar, clasps to fix the plate tightlfm position while' auxiliary springs are added to '" tip teeth (see Fig 18-30r (Upper and lower Schwartz plates joined by a pair of safety-pin springs-"Schwartz Double Plate"-are a kind of functional appliance.) 2) Space-.Regaining Appliances.-One of the most popular and practical uses of active plates is to regain space in the arch perimeter after premature loss of primary molars (see Fig 18-30). These same mechanical principles sometimes may be used in adults to upright second permanent molars which have tipped mesially
526
Treatment
A-I
A-2
FIG 18-27. Patient in a face mask.
FIG 18-30.
FIG 18-28.
Active plates. A, some methods of retaining attached removable acrylic appliances. A-1, eyelets, also modified into arrowhead shapes; A-2, the Adams clasp. (Continued.)
The chin cup used for extra-oral traction. after the loss of first permanent molars (see Chapter 17).
adjustment, and (5) it requires a small inventory of supplies and instruments.
3) Anterior Spring Aligners (Barrer Appliance).The anterior spring aligner (Harrer appliance) is a device used to align anterior teeth slightly by means of tension stored in the spring clips used to retain it in place. The appliance is constructed on a work cast on which the incisors have been aligned ideally (see Fig 18- 30). It is usually necessary to reduce slightly the mesiodistal diameters of the teeth.
Its disadvantages are: (1) it demands a high degree of skill to fabricate: (2) it looks deceptively simple, whereas it is exceedingly difficult to master; (3) it takes much longer to affect results; (4) closures of space after extraction of teeth is most difficult; (5) maintenance of anchorage without loss requires great skill; (6) few dental schools teach the use of the appliance. In recent years, family dentists and pedodontistis in North America have shown a great interest in the Crozat appliance:-which is surprising, as many skilled and experienced orthodontists have tried it and found it wanting. It is an old and respected appliance of limited use and with numerous disadvantages that often are unnoticed. Many extravagant and ill-founded claims have been made in recent years for this appliance, for example, that it obviates the extraction of teeth, that one need not take a cephalogram, and that it is a functional orthopedic or gnathologic appliance. Such rash statements are misleading to those attempting to learn and evaluate the appliance and are unfair to the skilled orthodontists Who have taught its use and utilized it w~11~inpractice for man"y ·years. I occasionally use the appliance, but only in highly selected cases; usually in adults for whom maintenance of oral esthetics during treatment is essential (e.g., I once used it to treat a malocclusion in a television announcer).
d) Crozal Appliance The Crozat appliance consists of body wires, lingual arms, and a high labial archwire (in the maxillary appliance) held in place by specially designed molar clasps (Fig 18-31). The Crozat appliance is best fabricated from precious alloy wire components soldered together. . Its advantages are: (1) it is sightly, (2) it is easy to maintain oral hygiene, (3) it uses light forces, (4) it requires little time for
e) Vacuum-Formed Appliances ("Invisibles")
FIG 18-29. Lip bumpers (see also Fig 15-13).
Thin sheets of thermoplastic material are fabricated over working casts on which one or a few teeth have been slightly repositioned (Fig 18-32). The appliance can bring about only slight tooth movements as a part of retention or as the sole treatment.
Orthodontic Techniques
527
c
PASSIVE
BEND
BEND
NO. I
NO.2
FIG
BEND NO.3·
4
18-30 (cont.).
B, examples of active plates. Note the need for good retention. C, space-regaining appliances. C-1, recurved helical spring regainer (courtesy of Dr. Fred DuPrai). Note the use of the Adams clasp on the opposite side. C-2, knee spring for use in tipping molars distally. C-3;, !!plit-saddle acrylic space-regainer, useful when greater distances must be regained than in C-2. Note another type of regainer spring on the opposite side of the arch, a helical spring lying beneath acrylic yet acting against the first molar. C-4, method of adjusting the spring on the split-saddle regainer. C-5, method of increasing the adjustment in a split-saddle regainer. As the molar moves distally, the appliance becomes more fragile. It is then possible to tie the distal portion forward with a piece of dental floss or stainless steel ligature and add acrylic posteriorly. In this manner, the appliance is reactivated without adjustment of the spring. (Continued.)
528
Treatment
.'
FIG 18-30 (cont.). C-6 and C-7, "slingshot"regainer. Note the use joined to buccal lingual hooks (courtesy of Or. Fred C-9, the sliding yoke space-regainer. CoS, buccal 0.028-inch steel edgewise wire is used. A ball of mesial to the cuspid bend of the wire. A coil spring onto the wire, the sliding yoke is added, and the
" of a light elastic OuPrai). C-S and view; a 0.022- x solder is placed is then threaded wire is bent well
distal to the molar to be moved. C-9, the sliding yoke is an edgewise buccal tube, the inside diameter of which is exactly that of the wire. To the buccal tube is soldered, at a right angle, a small piece of stiff
wir~ 10 engage the mesial'of the molar. Note that the acrylic must be trimmed in a straight line on the lingual. This appliance is best anchored on the opposite side by an Adams clasp. It is more efficient in the maxillary than in the mandibular arch. C-10, the expansion screw regainer. These units are bought prefabricated and are inserted into the acrylic appliance. (Courtesy of Or. Fred OuPrai.) D, spring incisal alignment appliances (Barrer appliances). Incisors are cut off the working casts and aligned into position. The appliance is constructed on the perfected cast.
Orthodontic Techniques
529
FIG 18-31. The Crozat appliance. A, the basic upper appliance; B, the basic lower appliance (both courtesy of Dr. Robert Smythe). C, the Crozat appliance used in a patient with cleft palate (courtesy of Dr. S. D.
Gore, Jr.). D, a lower appliance with auxiliaries Lakes Orthodontic Laboratories).
2. Passive Appliances
They are also used during mixed-dentition treatment of deep bite ma]occlusions or as a prelude to bite registration for patients with acute temporomandibular dysfunction or myalgia (Fig ]8-33).
Passive appliances are used (1) to maintain the status quo within the dentition (e.g., space maintainers and retaining appliances), (2) to disclude the dentitions during orthodontic treatment, (3) to disclude the teeth prior to registration of bite relationships, and (4) as adjuncts to the treatment of temporomandibular dysfunction.
(courtesy of Great
b) Occlusal Splints Occlusal splints are a sort of bite plane which cover the occlusal surfaces to provide a new occlusal relationship (Fig ]8-
a) Bite Planes Bite planes are used to disclude the teeth in order to achieve tooth movements more easily during bracketed appliancqherapy. cl"
LJ
FIG
1'8-32.
The vacuum formed retainer, sometimes called the "invisible" appliance. Before forming this appliance, one may cut a few teeth from the cast to make minor alignments.
FIG 18-33. A bite plane for use during active orthodontic
Fig 17-20).
treatment
(see also
530
Treatment
FIG 18-34. An occlusal bite splint.
o'
the first and second
FIG 18-35. A, acrylic multiple space-maintainer. B, acrylic space-maintainer with built-in regainer. The first permanent molar has not yet erupted, and
primary
molars are lost. Sometimes
the first
molar tends to drift mesially before eruption. In this appliance, the saddle is constructed high enough to touch the occlusion. Often this is enough to keep the permanent molar distally. However, if it has tipped mesially, the saddle may be split and the appliance used as a space-regainer to tip the molar distally.·
FIG 18-36. A, Hawley retainers. Note the different methods of retention and the use of a flat bite plane. B, Ricketts retainers.
Orthodontic 34). They are used for mandibular repositioning (see 4, Repositioning Splints) arid discluding the dentitions romandibular therapy. Their use during multi bracketed therapy is confounding and usually contraindicated, restrict tooth movements.
Section Ein tempoappliance since they
c) Multiple Space Maintainers Acrylic appliances, which cover the lingual mucosa and lingual surfaces of the teeth with plastic extending into the areas where primary teeth have been lost, make useful multiple space maintainers (Fig 18-35). The plastic not only holds the space in the line of arch but also may be built up to engage opposing teeth, to maintain the plane of occlusion, and prevent extrusion of teeth in,the opposite arch.
d) Retainers The Hawley retainer and its many modifications are passive, removable plastic appliances used to retain the new positions of teeth after active orthodontic therapy is completed (Fig 18-36), but the term "Hawley appliance" is often misapplied to a wide variety of removable active appliances. The maxillary retainer may incorporate a flat bite plane, and a variety of labial arches and clasps may be utilized depending on the type of tooth movements which have just been carried out.
E. LOOSE REMOVABLE APPLIANCES (FUNCTIONAL APPLIANCES, FUNCTIONAL JAW ORTHOPEDIC APPLIANCES, ETC.) 1. Background
It may be difficult for the reader to gain a fair perspective about the proper place of functional appliance therapy in dental practice and teaching. Differences arise because of the variance in terminology associated with functional therapy, imprecise understanding of the purposes of functional therapy, a lengthy and convoluted history of the methods employed, and disputes about how (or even if) such appliances really work. Therefore, before descriptions of specific loose removable appliances are given, it is necessary to (1) define them, (2) list their clinical purposes, (3) recall their history and (4) examine the evidence for their modes of action.
a) Definition Loose removable appliances are those designed to alter the neuromuscular environment of the orofacial region to improve occlusal development and/or craniofacial skeletal growth (see Figs 18-37 through 18-48). Most loose removable appliances, though not all: ,. a) utilize muscle forces to effect dental and bony changes, b) disarticulate the teeth, c) encourag~ a new mandibular position, require a tight lip seal during swallowing, and e) selectively alter the eruptive paths of teeth. cl)
b) Purposes .Functional jaw orthopedic appliances are designed to alter the function of the facial and jaw muscles in order to (I) provide a
Techniques
531
more favorable environment for the developing dentition, (2) optimize the growth of the craniofacial skeleton, (3) change the directions of craniofacial skeletal growth, (4) inhibit skeletal growth selectively, and/or (5) guide erupting teeth into more favorable positions. All functional appliances are not capable of achieving all of these purposes: certain appliances sometimes improperly labeled as functional or orthopedic appliances (e.g. the Crozat appliance) certainly cannot.
c) History One of the oldest concepts in orthodontics (dentofacial orthopedics) is the importance of muscle function in the etiology and treatment of malocclusion. It was noted in American orthodontic textbooks before the start of the 20th century and in the writings of Robin25 (France, 1902) and Andresen3 (Norway, 1910). Therapeutically, the concepts evolved into two strategies: (1) myofunctional exercises, first advocated by Rogers26 in the United States about 1918; and (2) the use of appliances to alter mandibular position and muscle function (Kingsl~y, 19 1880; Robin25 1902; and Andresen,3 1910). Time and clinical experience have proved myofunctional exercises to be generally inefficient, and the ideas of Kingsleyl9 and Robin25 have had little lasting impact on dentistry. However, by 19364 Andresen' s work began to receive serious attention, though the rationale expounded for "functional jaw orthopedics" had a very shaky theroretical basis. Simply put, Andresen's "Activator" was an intraoral appliance which looked like Robin's Monobloc (which Robin proposed for curing "glossoptosis") and acted like Kingsley'sdevices for "jumping the bite," but Andresen's Activator lies passively in the mouth until "activated" by contractions of jaw and facial muscles. During the swallow the Activator causes the jaw to be held forward and the lips to seal, while preventing mouth breathing. European dentists took up Andresen's ideas and, before any theoretical basis could be proven or controlled clinical studies appear, variations on Andresen's original theme were suggested while a number of perversions of his concept were presented and competed for attention. A European colleague once remarked to me that during this period (just before and after World War 11) there was no self-respecting German professor of orthodontics who had not designed a removable orthodontic appliance which was held to be superior to all others and, of course, carried his name. (A few years later, North American orthodontists played the same game with cephalometric analyses). Meanwhile, across the Atlantic, American orthodontists had forgotten their colleagues KingSley and Rogers and were busy perfecting Angle's bracketed appliances, which were affixed to the teeth. Americans were generally unsatisfied with the published pl;1C!tographsof treatment results shown in European journals of thafperiod and avoided trying. or teaching functional jaw orthopedic therapy. In 1951 Harvold, a pupil of Andresen, joined our staff at the University of Toronto and began to teach us the concepts of functional jaw orthopedics. Later, largely because of his teaching at Toronto, Michigan, and California, American orthodontists began to take some notice. Still it was not until the 1970s that more than a few graduate departments included serious functional jaw orthopedic teaching in their programs. About the same time, sound experimental studies of the effects of altered neuromuscular function on skeletal growth appeared in the liter-
532
Treatment
ature on both sides of the Atlantic. Then an interesting transformation in North American orthodontic thinking suddenly took place. Some orthodontists who had for years derided teaching such as ours at Toronto and Michigan, embraced the concepts of functional appliance therapy and, like new religious converts, began to propound their favorite appliances through articles,_ short courses, and table clinics. Appliances and ideas that had been used in Europe for up to 40 years were presented as "new" to American dentists, and numerous additional appliances and variations appeared in repetition of the European experience a generation earlier. Now, thanks to the years of clinical experience, good experimental data, and sound clinical evidence, we are in a better position to evaluate their use. Today we have a clearer clinical perspective, but there is no reason for the extravagant claims and rash excesses which sometimes are associated with the commericalized teaching and promotion of functional jaw orthopedic therapy in the United States of America. Such activities are a sad commentary on our profession and are demeaning to one of the oldest and most useful clinical methods we have. Perhaps this phase will soon be over and these methods can be evaluated in a more objective, professional perspective.
d) Modes of Action Functional appliances alter purposefully the neuromuscular environment of the orofacial region by either (1) applying forces in new amounts, directions, and times or (2) eliminating or diminishing forces against the teeth and bones. Functional jaw orthopedic appliances have been used on thousands of patients for many years and hundreds of articles have been written describing their utility, but there are differences in opinion about their modes of action. That they often succeed to the satisfaction of many discerning clinicians is not disputed: that we understand precisely (I) how they work, (2) why they do better in some cases than others, and (3) how they achieve differential effects on muscle action, tooth development, and bony changes are still not fully understood. Experimentation on animals has provided important information (see Chapter 4), but the conditions of the laboratory experiment are different than those in clinical practice, and the craniofacial morphologies of experimental animals are dissimilar to that of humans. Well-designed clinical stud-
A
ies are few indeed, and prospectively planned clinical research on functional jaw orthopedic treatment effects scarcely exists. Most clinical papers are generally flawed by (I) too much emphasis on anecdotal clinical case reports, (2) absence of objective reporting, (3) small sample sizes, (4) biases in the selection of cases, (5) inefficient and ineffective cephalometric methods, (6) lack of proper controls, and similar flaws. Despite these criticisms, logic, clinical experience, and research results provide some general agreements. What follows is an attempt to provide perspective and facts about functional jaw orthopedic effects: perspective amidst a plethora of well-intentioned but poorly planned clinical studies; facts, not hunches, hopes, or professorial pontifications. This is a formulation of the most sensible, reasonable clinical conjectures possible at this time. The reader should be neither dismayed nor disenchanted: good clinical research is difficult, but the number of sound studies is steadily increasing and we shall soon know more with certainty. 1) Muscles.-Andresen's3.4 original concept of an "activated" muscle transmitting a functional stimulus to bone is unsupported. Rather, functional appliances are held to be devices which alter the amount, direction, and/or the duration of forces while transmitting them against the teeth and bones. This concept draws attention to the importance of the construction bite for functional appliances. There are two schools of thought: that the construction bite should be taken (I) within or (2) purposely beyond the vertical interocclusal distance (Fig 18-37). Most clinicians now advocate varying the construction bite according to the individual patient, but exceeding the interocclusal distance is more common than not, and discussion centers on how far beyond the interocclusal distance to make the construction bite. Sander2? 28 noted that when the construction bite is taken in an extremely forward position, the mandible, during sleep, often discludes from the appliance, thus negating the desired effects. Graf15 observed that for each millimeter of forward mandibular displacement 100 g of force were created. It has also been shown that contractions of the lateral pterygoid muscle are inhibited while the jaw occludes against a functional appliance in a forward biting position.5 The appliance in place thus creates two new sorts of forces: stretch, if the construction bite is taken past the interocclusal dis-
B
.
-
.......
/ FIG 18-37. A, usual method of constructing the Andresen appliance. Wax bite is constructed in this instance within the limits of the freeway space.
e, Harvold's method. The mandible is held down and forward well past the freeway space .
Orthodontic
Techniques
533
FIG 18-38. Adaptation of the facial muscles to altered mandibular position. A and B, the original position; C, after insertion of a wax bite used for
construction
tance, and the forces resulting from muscle activities prompted by the foreign body within the mouth. The temporomandibular joints, like most other joints in the body, provide a sensory guidance system for jaw functions and positions. Masticatory and adaptive positions of the jaw must alter continuously during growth and dentitional development. Such natural adaptive changes are at least partially controlled from the temporomandibular joint receptors coordinated within the brain itself. Ahlgrenl•2 showed that children with malocclusions displayed much more complicated chewing patterns than those with normal occlusion and that treatment of the malocclusion (with an Activator) resulted in a normalizing of the chewing cycles. Sander,27.28 who studied neuromuscular responses to functional appliance therapy, observed phases of disorientation of masticatory patterns following the insertion of the appliance and preceding a phase of adaptation as chewing activities normalized. He showed that functional treatment should not be stopped until the patient has adapted to an harmonic three- or four-phase pattern of chewing. These favorable neuromuscular adaptations are not seen in patients wearing Class II elastics because the actions of the elastics interfere with the capacity of the sensory guidance mechanisms to adopt new harmonic chewing patterns. McNamara20. 21. 23reached similar conclusions on the basis of experiments in altered mandibular positioning of Rhesus monkeys (Macaca mulatta), noting that the activities of muscles alter and adapt predictably and rather rapidly to mandibular repositioning whereas structural changes are more gradual (Fig 18-38). "In contrast to the functional protrusion experiment, no uniform neuromuscular response could be determined," he noted regarding the results of experiments using extrinsic Class II traction forces to protrude the mandible. It is obvious on the basis of both experimental and clinical research that feedback from the subjects' own joint and muscle receptors are an important factor in functional appliance therapy. Both Sander's and McNamara's reports emphasize that stability is not achieved until occclusion, function, and masticatory reflexes are harmo-
nized. Fully adapted muscle activities are as esential to orthodontic stability as any other goal of treatment. A functional appliance within the mouth causes contractions of the mandibular elevators during swallowing; the same neuromuscular response seen in children with tooth-together (normal) swallows. Further, the presence of the appliance alters tongue and lip posture and activities. If the appliance is loose, the tongue must position it during the swallow, which repeated often alters tongue posture favorably. FrankeP' drew attention to the importance of the lip seal when determining the construction bite, reasoning that the lips must seal around the appliance to hold it" in" place and enable the swallow to be completed. Thus, the tight lip seal and tongue contractions against the appliance contribute to the alteration of forces created by the presence of the appliance. More importantly, the appliance retrains the muscles promoting a normal tooth-together swallow, a tight lip seal during the swallow, and improved tongue posture at all times. To summarize, functional appliances not only create new favorabIe forces within the mouth which act ag"ainst the teeth and bones but also are muscle-training devices. Rogers'26 concept of myotherapeutic exercises,has really only found practical application in functional jaw orthopedic appliances. ;-
of a functional
jaw orthopedic
appliance.
2) Dentition and Alveolar Processes.- There is general agreement that one of tile major contributions to successful treat'inept with functional appliances lies in their ability to control differentially the vertical height' of the teeth. Stopping some teeth and permitting others to develop vertically aids in leveling the occlusal plane and the correction of deep or open bites. Both Harvold'6 and Woodside31 have noted the advantages of altering the cant and position of the occclusal plane in Class II treatment with functional jaw orthopedic appliances in the mixed dentition. Frankel13 observed that under functional therapy there were significant increases in the distances between the mandibular border and the forming apices of the teeth when treatment occurred during
534
Treatment been found that the functional appliances can, when the maxillary teeth are left covered, restrict vertical maxillary alveolar development. In the absence of extra-oral traction to a functional appliance, little actually distal movement of the molars takes place to correct Class 11malocclusion; rather, the teeth are guided during eruption to a relatively more distal and buccal position. Attention has been carefully drawn to the role of the severity of the skeletal dysplasia on the clinician's ability to achieve success only through dentoalveolar adaptation-a most important fact. Finally, it should not be forgotten that vertical alveolar development in the maxilla, because of the divergence of the alveolar processes, results in an increase in both the width of the maxillary arch and its perimeter, useful responses forsome crossbite and space problems.
FIG 18-39. Diagram illustrates the fitof Activator-type appliances inside the mouth. A, ground to allow eruption of both upper and lower molars. Typically, in Class malocclusion, upper molar eruption is "indexed" and not ground in order to maximize adaptation of mandibular eruptive movements. e, method of grinding the inside of Activators. These appliances fit loosely in the mouth. As the tongue lifts the appliance during swallowing, the patient bites into the appliance, at which time the muscle forces are transmitted through the plastic, coming in contact with the mesial surface of each upper tooth, as shown. The wire spring itself is not active against the molar until biting takes place; thus, force is applied by the muscles, through the spring, but not until a swallow or bite. C, method for trimming the acrylic around the incisors. Note that the acrylic is removed lingually to the maxillary incisors after they have been tipped somewhat by the labial archwire. Their incisal edges may be engaged in acrylic in order to prevent their extrusion. In the mandibular arch the acrylic never touches the lingual surfaces of the crowns of the incisors. Acrylic is placed over the incisal edge and onto the labial surface of the lower incisor in order to minimize labial movements. Both upper and lower incisal edges may be stopped with acrylic, particularly when the eruption of posterior teeth is required. They may be left unstopped and the posterior teeth in both arches indexed in the treatment of open bite. 11
eruption and dental development. The result is important positional changes in the apical base and alveolar process en toto with respect to the corpus mandibularis. Functional appliances are used to guide the teeth during eruption which, as noted above, helps in alterations of the occlusal plane, but also may determine new occlusal positions of the teeth (Fig 18-39). Harvoldl6 maintains that such is the principle mode of correcting Class 11malocclusions with Activators. Several studies have shown that the mandibular dentition tends to move forward under functional jaw orthopedic therapy for Class 11malocclusion, even when precautions are taken to prevent such changes. Janson18 observed that with Bionators, much of the Class 11 correction is gained in alveolar remodeling when the craniofacial skeleton shows anteroposterior harinony. She also observed that the dentoalveolar changes noted by Harvold16 and Woodside31 as the principal elements in Class 11 correction occurred more favorably during the prepubescent period than during the pubescent spurt itself; that is, the timing of a favorable response is more related to eruptive development than increases in skeletal growth rate. It has generally
3) Craniofacial Skeleton.The greatest arguments about the modes of action of functional appliances center on the question, "Do functional appliances alter the craniofacial skeleton?" Before plunging into this interesting debate, it should be mentioned that most cephalometric analyses applied to this probl~m have not been up to the task (see Chapter 12). The skeletal changes looked for might be (1) increases in size, (2) restraint of expected size increases, (3) alterations in the relative size or position of skeletal parts, (4) changes in the shape of bony parts, etc. The experimental evidence is overwhelming that, in controlled laboratory animals, alterations in the neuromuscular environment bring about all four kinds of changes noted above. The classic studies of McNamara, Carlson, and Petrovic (see Chapter 4) show conclusively that significant changes in the development of the condylar and other regions can be produced in experimental animals. Few modem bone biologists dispute these points. However, it is proper tOlnote the implications of these experimental findings to clinical practice with functional appliances.
a) Claimed Skeletal Responses.- The descriptions in the clinical literature regarding the skeletal responses to functional jaw orthopedic appliances can be grouped roughly under the following explanations: a) "Stimulation" or enhancement of mandibular growth. b) No changes in the amount of mandibular growth, but creation of more favorable directions of growth. c) No demonstrable skeletal effects, but important alterations in eruptive positions of teeth and adaptations of the teeth and) adaptations of the alveolar processes. d) Restraint of midface growth. e) Deformation (i.e., shape change) of skeletal structures. Experimental evidence of skeletal changes with ;ilterl"d function may be summarized as foilows: '. a) Important change~ 1n .amount, timing, and/or direction of condjIar growth. , b) Adaptive alterations within the basilar portion of the temporomandibular articulation. c) Changes in the muscle-bone interface (i.e., the attachment sites of muscles to bone). cl) Shape changes in bones and/or regions of bones. e) Immobilized repositioning of the mandible (denied masticatory function). This shows an immediate and profound effect on the morphology of the condylar cartilage and a dramatic diminution in growth changes of the region.
Orthodontic The experimental conditions of the laboratory, of course, cannot be replicated in practice, but there is no logic or theory to conclude, as some do, that craniofacial growth is so rigidly patterned that it cannot be altered by vaiiations in its functional environment. Such inferences from the available experimental data are strange conclusions for orthodontists to make, since those deductions would imply that altered function resulting from appliance forces applied directly to teeth produce adaptive responses in alveolar bone but that no other altered function or force application to bone (e.g., via the patient's own muscles) would have any effects. The biology of bony adaptation and growth does not change according to the favored appliance or clinical biases of the orthodontist treating the case. In attempting to make clinical sense out of apparently conflicting research findings, it is well to remember that bone growth and remodeling are under a variety of naturally controlled mechanisms and respond to many kinds of environmental changes. Function, and hence some form of stimulation, is a necessary factor 'in all bone growth and even repair remodeling. The critical question remains: Can purposeful alteration in environmental stimuli result in natural bony responses which can be used advantageously in orthodontic therapy? I draw the following conclusions at this time: a) The experimental evidence is overwhelming that alterations in the functional environment of bone brings changes in the morphology and growth of bony tissues. b) The supportive clinical evidence is less compelling but conflicts in no way with laboratory findings. c) Difficulties in design of clinical studies and simplistic measuring methods have often led to ill-founded and even misleading conclusions (see Chapter 12). d) All orthodontic treatment produces bony changes which are more extensively distributed in the head and face than can be appreciated with the usual methods of cephalometric analysis. e) There are some similarities in the treatment effects of quite different appliances.
b) Role of Timing in Treatment Intervention.-If
one would alter craniofacial growth, a logical question arises, "Are there not some times in which such alterations can be more easily achieved?" Obviously, basal bony changes occur at a much less rapid rate in ,adulthood, and most rapidly in early childhood and during the pubescent growth spurt, while alveolar bony changes are most changing during the eruption of teeth. One school of thought emphasizes the advantage of treatment during the pubescent growth spurt and hence the importance of being able to predict, for the individual, the time of the adolescent spurt. Both theoretical and practical difficulties arise in making such predictions, since much of the spurt is over before it can be predicted by the methods developed thus far. Further, some individuals, particularly girls, display no significant spurts. Finally, much of this reasoning is based on data from spurts in stature, yet some facial regions do not show spurting and some that do are not well synchronized with spurts in stature. In some instances the amount of growth increase during the spurt is trivial. If emphasis is taken from trying to predict the time of Peak Height Velocity in stature increments to the rate of bone turnover and the amount of expected growth remaining in the child's face, a more logical argument for early
Techniques
535
treatment is made. Demisch9.1O concluded, after studying the response to Activator ther¥. that favorable bony treatment effects occurred quite independently of the spurts in craniofacial skeletal growth.
2. Vestibular Appliances (Oral Shields, Oral Screens) a) Description The oral shield is a device fitting in the vestibule which shuts off the ingress of air through the mouth and directs contraction of the lips against any anterior teeth in labioversion (Fig 18-40). It is used to retrain the lips, to correct simple labioversion of the maxillary anterior teeth and as a habit-correcting appliance-for it helps retrain and strengthen lip action (Fig 18-41). It probably should I}ot be inserted if the child has nasorespiratory distress or a nasal obstruction. The oral shield is of no use for correction of a Class 11 malocclusion.
b) Construction The vestibular shield is constructed on work casts to the vertical vestibular limits of both arches after all undercuts, embrasures, voids, etc., have been filled (see Fig 18.,...40). A sheet of thermoplastic material, such as Plexiglas, or the usual powderliquid acrylic resin may be used. Breathing holes may be bored if necessary.
3. Functional Jaw Orthopedic Appliances a) Definition Functional jaw orthopedic appliances are loose, removable, intra-oral devices which reposition the mandible in order to alter the muscle forces against the teeth and craniofacial skeleton. They are of many varieties and types according to the rationale of the user and the nature of the malocclusion to be treated.
b) Uses and Indications Functional jaw orthopedic appliances are used where dysfunction has played a role in the etiology of the mal occlusion an<,IJorwhere enhanced or altered normal functional activities may provide optimal conditions for the growth and development of the craniofacial skeleton and the occlusion. They are used to correct anteroposterior malocclusions, particularly Class 11, both open and deep bites, as well as crossbites or lack of arch coordination. Because they are dynamic appliances, depending on altered neuromuscular activities to effect bony growth and occlusal development, their use is much more frequent in the mixed dentition. Very few clinicians advQ5=atetreatment of adult mal occlusions with flll1ctional jaw orthopedic appliances.
c) Types Functional jaw orthopedic appliances have been classified many times and in many ways. Graber'sI4 classification, while not all inclusive, is very useful. He labels as myotonic those appliances which depend primarily on mandibular displacement anteroposteriorly or vertically. Myodynamic appliances (sometimes termed elastic appliances) not only translate the mandible anteroposteriorly and vertically, but also attempt to utilize and translate muscular
536
Treatment
."
,.... \
FIG 18-40. The oral shield. A, cast ready for construction of the oral shield. A vestibular impression is taken and filled with plaster to the outline of the labial surfaces of the teeth. Plexiglas or acrylic is then fitted to the cast. B, cast with completed oral shield in place. C-E, use of the oral shield in treating Class I, type 2 malocclusion. C, at the start of treatment. D, after 3 months. E, after 6 months. Note the recession
of gingival tissue around the neck of the mandibular cuspid. As the incisor relationship improves, one must grind away the inside of the oral shield so that the shield itself does not cause traumatic occlusion of one of the teeth. Here such clearance was not provided and, of necessity, the gingival margin had to recede.
Orthodontic
Techniques
FIG 18-41. The modified oral shield used for training of the mentalis muscle. A, an oral shield is made in the usual fashion, and base plate wax is added to the lower labial surface in a quantity sufficient to inhibit contraction of the mentalis muscle on swallowing. Wax is added and contoured until inhibition of mentalis contraction is seen in the patient. Then, the wax is converted to acrylic. B, electromyograms of a patient before and immediately after insertion of the oral shield. Note the diminution of activity in the mentalis muscle. Usually the patient must wear the appliance for several months before the muscle becomes quiescent. Then the labial plumper is gradually ground down before being abandoned. When used to train the mentalis muscle, the oral shield is not inserted until the incisor correction has been obtained. C-1, face of a girl at the beginning of treatment for open bite. C-2, same patient at the end of treatment. Note the persistence of the hyperactive mentalis muscle. This is the kind of case on which the modified oral shield works very well.
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538
Treatment
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FIG 18-42. Activators.
A-1, an Activator
appliance
before trimming.
Note that
teeth to erupt vertically.
The spring serves simply as an adjustable
the molar spring is free, as it was covered during the curing of the acrylic. It is a common mistake to allow the laboratory to grind the Activator before delivery to the dentist, as the technician cannot possibly know the correct individual grindings required for a particular patient. Further, one typically wants to leave the maxillary teeth "indexed" in Class 11 treatment at the start, permitting more mandibular
guide plane down which the maxillary molars may erupt. 8, -classic Activator being used in treatment. 8-1, intra-oral view at the beginning of treatment; 8-2, facial profile at that time. 8-3, the appliance in place ,in the mouth 1 y~ar l~ter; 8-4, the occlusion 1 year later. Note the reduction of the overjet, the improvement in the open bite, and the correction of the molar relationship as the cuspids and pre-
eruptive adaptations. A-2, this Activator has been worn for some time. Note that the acrylic has now been ground to permit the max-
molars erupt. 8-5, the profile 1 year after start of treatment. 8-6, patient profile at the end of treatment. 8-7, cephalogram at the end of treatment. (Continued.)
illary teeth to be guided distally as they erupt and the mandibular
Orthodontic Techniques
539
11
\',
\\ I',
I' 1\
\\\,'
....•....
.•...•.• ........•.
-'
."'.
,,'. '.
FIG 18-42 (cont.). B-8 and B-9, the casts after retention. B-10 to B-12, cephalometric tracings: solid line signifies patient features at the start of treatment; dotted lines, at the end of active treatment; dashed lines, at the end movements and activities to move teeth and reshape alveolar arches.
d) Activators and Derivatives The Activator, the original functional jaw orthopedic appliance, has been frequently modified from its original design, and many derivatives have appeared (see Fig 18-42). The Activator itself consists of a loose plastic device fitted on the lingual side of both upper and lower dentitions and constructed to a bite which has altered the mandible's functioning position (see Fig 18-42). A labial bow contains the maxillary incisors, while the lower incisors are capped with acrylic. There are many variations on the Activator (Fig 18-43). The Bionator, developed by Balters,.· 7 is one of the more popular derivatives of the Activator (Fig 18-44). The Bionator design reduces the amount of acrylic, has a palatal wire, and has a wire with buccinator wings to reduce cheek pressures. The Bionator's reduced bulk makes it possible to be worn both day and night.
e) Frankel Function Regulator Frankel, 12 seeking the advantages of mandibular displacement as developed for the Activator, plus a means of reducing the compressive forces of the buccal musculature, devised an appliance which fits between the teeth and the cheeks and lips rather than between the tongue and teeth (Fig 18-45). The vestibular position of the appliance alters the effects of abnormal lip and buccal wall contractions on the dentition and enhances the role of tongue activities.
of the retention period. 8-10, cranial base orientation. B-11, orientation on the palatal plane. 8-12, oriented on the mandibular plane and registered at the lingual symphysis.
/) Myodynamic or Elastic Appliances The Bimler appliance,8 the best known of the myodynamic appliances, is essentially a flexible bimaxillary wire appliance with two palatal pads acting against the maxillary alveolar processes and auxiliary springs to achieve tooth movements. Bimler's ideas influenced the development of other elastic appliances (e.g., the Kinetor of Stockfisch).
g) Others The literature is filled with many variations on the functional jaw orthopedic theme. Most, however, fit conceptually under one of the three categories above, or are active plates (see Section Dc.) or hybrids (see Section G).
4. Repositioning Splints Repositioning splints are used in certain phases of temporomandibular therapy (I)'tO reposition the mandible forward in order to;eestablish normal meniscus-condyle relations or (2) to allow the condyles to seat superiorly on the dorsal slopes of the articular eminence. Repositioning splints look similar to regular splints (see Section D-2-b. and Fig 18-34) but are provided for different reasons, namely, to alter purposefully the positions of the mandibular condyles.
5. Tooth Positioners
540
Treatment
,"
FIG 18-43. A, the open-front Activator, occlusal view, with the appliance on the lower arch. Note that there are no acrylic stops for the incisors. This appliance may be worn during the day, and it is possible to speak easily with it in place. B, an activator with a coffin spring. The appliance may be split in two for mild expansion forces or the coffin
a) Description The tooth positioner is a flexible appliance made of soft rubber or plastic which surrounds the crowns of all teeth in both jaws (Fig 18-46) and has been fabricated on casts whose tooth positions have been idealized. It is used as a retainer and to complete the niceties of tooth positions after removal of fixed appliances.
b) Construction To construct a tooth positioner, two very accurate impressions are taken of each dental arch and poured in stone or plaster. One set of casts is used as a reference; the other set is mounted on an adjustable articulator by means of a .wax recording of the patient's retruded occlusal position and a transfer facebow. This
spring may be left in unactivated, to teach a more superior tongue posture. C, the expansion Activator. Because only the maxillary arch is expanded, the acrylic must be freed from the lingual of the lower teeth. (Courtesy of Great Lakes Orthodontic Laboratories.)
registration is important since it permits the patient to bite into tne tooth positioner without displacing the condyles. The teeth to be aligned are cut off the cast and reset to improved positions.
c) Limitations It is easy to overextend this appliance. It is no substitute for proper manipulation of the arch wires and should not be used to attempt gross tooth movements, to attempt significant occlusal change, to direct the growth of the jaws, or to reposition the mandible. Nor is it a substitute for proper occlusal equilibration. If the positioner is not constructed exactly to the patient's retruded occlusal position (and thus within accommodating limits of the
FIG 18-44. A-C, the Bionator appliance.
Baltes designed the Bionator as a streamlined version of the Activator, incorporating wire buccal loops to minimize the contractive forces of the buccal wall musculature,
much as Frankel did in the Function Regulator. The Bionator has no jack screw expansion mechanism. (Courtesy of Great Lakes Orthodontic Laboratories.)
Orthodontic Techniques
541
.'
FIG 18-45. The Frankel Function Regulator (FR). A, the FR-II appliance from the lateral view. Note the labial lip pads in the lower arch. B, the appliance in place on the maxillary cast. C, a screw mechanism
permitting gradual advancement of the mandibular lip pads. D, the FR-III appliance. Note that the labial lip pads are now in the maxilla. (Courtesy of Great Lakes Orthodontic Laboratories.)
ideal occlusal position) and at a tolerable vertical dimension, the result may be undue straining of the temporomandibular joints. An improperly made positioner can do harm. Since the patient cannot speak or eat with the appliance in place, it can only be worn for a limited time each day. Short periods of vigorous "chewing" into the appliance seem more beneficial than long periods of passive wear, as when sleeping.
frequently used in correction of severe Class IT malocclusion due to retrognathia. Unlike the functional jaw orthopedic appliances, it cannot ordinarily be removed by the patient; therefore the protruded jaw function is continually assumed. It is likely that the classic animal experiments of McNamara, Carlson, Petrovic and others (see Chapter 4) are more nearly replicated clinically with the Herbst appliance than with any other functional jaw orthopedic appliance. Details of construction, indications for its use, and reports of its treatment effects will be found in the Suggested Readings at the end of this chapter.
6. Herbst Appliance The Herbst appliance,17 an old idea recently revived by Pancherz,24 consists of maxillary and mandibular metal frameworks cemented or bonded to the teeth and joined by two hinged sleeveplunger joints which permit jaw closure only in a determined occlusal relationship (Fig 18-47). The Herbst appliance is most
FIG 18-46. A, teeth setup for construction of positioner. B, the positioner.
7.
Hybrids and Perversions
A wide variety of ingenious modifications of functional jaw orthopedic appliances have been presented through the years (Fig
542
Treatment
A2
.'
FIG
18-47.
Hybrids and perversions of functional appliances. Some modifications in use defeat or pervert the basic concepts and principles of functional jaw orthopedics. For example, an Activator held in position with Adams' clasps or attached to a head gear and face bow (A2) can no longer function in the manner originally envisioned. While some hybrid appliances may have particular uses, I think they should
18-48) since Andresen's concepts were first ennunciated. Others have wedded functional jaw orthopedics with other clinical strategies, for example, moving individual teeth or using extra-oral traction in combination with an "Activator." As a general statement, it seems true that many of the hybrid appliances result in denying certain aspects of functional jaw orthopedic theory and practice and therefore 'are often contraindicated. For example, head gear forces attached to' an "Activator" immediately deny the ap- ' pliance the opportunity to act as an Activator. This particular hybrid seems indicated only for Class II Type F mal occlusions (mild skeletal problems involving both maxilla and mandible; see Chapters 12 and 15), whereas pure extra-oral traction is more appropriate for type B (maxillary prognathism), and typical functional jaw orthopedic appliances are indicated for type D (mandibular retrognathism). Those who have completed a definitive differential Class II cephalometric analysis of the patient are in a better position to select the most efficient appliance for a particular case. It is not unfair to say that some so-called "functional" appliances are a perversion of the concept and hence of limited use except in mild skeletal dysplasias (i.e, where almost any appliance will secure some improvements).
not carry the original
name when the original
function
has been
altered (e.g., in this instance, the appliance is no longer an Activator). Another popular modification, sometimes called a Bionator, is shown (B2). This removable appliance is not a Bionator, since its basic forces and principles are not those of Baltes' design, nor are they in keeping with the principles he enunciated
F. MYOTHERAPEUTIC
EXERCISES
One person, more than any other, alerted American orthodontists to the relationship of muscles to malocclusion. As early as 1906, A.P. Rogers26 suggested that muscle exercises be used as an adjunct to mechanical correction of malocclusion. He described the role of muscle imbalance in the etiology of malocclusion and pictured the muscle environment of the teeth as "living orthodontic appliances."
1. Purposes The principal purpose .?f myotherapy is the creation of normal orora~ial muscular function to aid growth and the development of normal occlusion. It is not to increase the size or strength of muscles, often the primary purpose of exercises for large muscles elsewhere in the body. Coordinated normal function is the principal reason for orofacial myotherapeutic exercises.
2. Limitations The theory of myotherapeutic
exercise is sound: its routine
Orthodontic Techniques
543
FIG 18-48. The Herbst appliance. A, lateral view with the appliance in place on the work cast. Note the arbitrarily advanced position of the mandible and the hinged tube and cylinder mechanisms attached to the two appliances. B, as the jaw is opened and closed, it can only function in the forward position. Note the piston and cylinder and their hinge attachment to the two halves of the appliance. C, front view. D, use in daily practice is difficult, and even impractical in most instances. Clinicians have found that myofunctional appliances are generally more useful than exercises alone (see Section E, Loose Removable Appliances, and Section F-4, later in this section).
3. Principles a) Study the possible role of muscle dysfunction in the etiology and maintenance of the malocclusion. b) Remove, if possible, such etiologic factors as deleterious habits (see Section G), tonsils, and/or adenoids (see Chapter 7). c) Establish early, with minimal mechanotherapy, the proper arch form and cuspal relationship. d) Remove by occlusal equilibration any interferences in the primary dentition (see Section H). e) Begin appropriate myofunctional appliance therapy (see Section C and E). f) Be certain of occlusal functional harmony during reflex activities before ceasing applianc,e therapy.
4. Specific Procedures a) Orbicularis Oris and Circumoral Muscles If the lips cannot seal because of procumbency of the incisors, it is best not to begin exercises until the incisors are retracted sufficiently for the lips to exert some effect against the teeth; then, the new tooth positions may prompt normal lip and swallow activities (see Fig 18-51). An oral shield (vestibular screen), modified as shown in Fig 18-41 may be useful. Simple small adhesive
occlusal view of the disengaged maxillary appliance. This version utilizes acrylic cured to a metal framework. The acrylic may be bonded to both upper and lower teeth, or one arch or both may be left free. Ifthe acrylic is not bonded, great care must be exercised to maintain good oral hygiene. E, the mandibular appliance disengaged. (Courtes~ of Great Lakes Orthodontic LabQratories:: stickers placed on the lips may serve as reminders to the patient during muscle relearning. Do not forget the role of musical instruments in lip dysfunction. Playing any brass instrument will soon produce improved lip tonicity. It is equally important to avoid, if possible, the singlereed instruments (e.g., the clarinet) for patients with hypofunction of the maxillary lip, labioversion of the upper incisors, and/or a Class II malocclusion.
b) Mandibular Posture Solow and Tallgren29. 30 have shown aSSOCIatIOnsbetween head posture and body posture arid between head posture and craniofacial morphology. When a child has faulty body posture it is difficult to hold the mandible in its most advantageous position. When the spine is straight and the head is well placed over it with the person's eyes looking ahead, the mandible is in a favorab1e position of posture. Simply asking the patient to walk upright with shoulders squared and eyes ahead sometimes produces immediate ~ffe.cts in appearance-and self-image. Functional jaw orthopedic appliance therapy may have favorable effects on mandibular posture (see Section E3). The relationship between "mouth breathing" and mandibular posture are discussed in Chapter 7.
G. CORRECTION OF DELETERIOUS ORAL HABITS Before attempting to control any suspected deleterious oral habit, it is important to bear in mind the role of the musculature
//
544
Treatment
in normal development of occlusion (Chapters 5 and 6) and the role of habits in the etiology of mal occlusion (Chapter 7). Usually there is no strong reason for plunging into a rigorous regimen of habit control; therefore, time can be taken to study the problem thoroughly. It seems wise to concern ourselves with the control of oral habits that actually are deleterious to the occlusion; other undesirable oral habits may be the responsibility oCother professionals. We dentists should confine our efforts to the clinical problem we must treat: occlusion. It is unfortunate that so much misinformation concerning this important subject appears in lay and professional journals, and it is noteworthy that much of the loose writing comes from those who do not have to treat the occlusal problem. One should define at the start that which is to be treated. Sometimes it is an open bite, sometimes a psychological problem, sometimes a neuromuscular reflex. Always ask such questions as "What precisely is the habit to be controlled?" "Should any of the therapy be directed toward the parents?" The most common oral habits disruptive to occlusion are thumb-sucking, finger-sucking, tongue-thrusting, nail-biting, lip-biting, and lip-sucking. Functional mal occlusions also cause lip or tongue habits deleterious to occlusal development (see Chapters 7 and 15).
1. Basic Considerations Regardless of which oral habit is being corrected, two basic considerations apply: a) The rationale. Since the problem is one of controlling a
biologic process, the rationale of therapy must be physiologic, not mechanical. The attempt always should be to alter the afferent arm of the neuromuscular response, which should be perceived in terms of muscle releaming. It follows that devices such as restraints, mitts, and elbow braces, which supply little but mechanical restraint, are to be shunned. The rationale of therapy is that of conditioning responses, not punishment or physical control (see Chapter 7). b) The primacy of the malocclusion. It must be determined whether the mal occlusion is of primary or secondary concern. We are dentists, and our minds and eyes are tuned to dental problems and dental solutions, but orthodontic appliances do not treat emotional disturbances or reduce family tensions.
2. Digital Sucking (Finger-Sucking, Thumb-Sucking) The term "thumb-sucking" has been used to cover a wide variety of oral sucking habits. In this discussion we shall limit our remarks to the strictest interpretation of the term (i. e., repeated forceful sucking of the thumb with associated strong buccal and lip contractions, the type of sucking most likely to be related to mal occlusion (fig 18-49). The facial morphology present makes an important difference. A straight profile with a firm Class I occlusion seems to withstand the effects of thumb-sucking better than a typical Class 11 facial skeleton. Do not disregard the face in which the habit appears, for a mild habit in some faces is more detrimental than a severe one in others. Just as the factors that
FIG 18-49. Correction of thumb-sucking with an appliance. A, malocclusion before treatment. 8, appliance in place on cast. Appliance is made of O.036-inch stainless steelwire soldered to four stainless steel primary crown forms. The spurs are very, very short, sharp, and strategically placed. C, appliance in place and the teeth in occlusion. D, corrected
malocclusion; time required for treatment was 4 months. The appliance did not correct the malocclusion; it treated the patient's habit. The return of normal lip and tongue function acted to close the open bite and align the incisors.
Orthodontic make up the habit vary, so do the faces in which it acts. It is the combination of the habit plus a growing face that gives the clinical problem. The clinical aspects of the problem may be divided into three distinct phases of development.
Techniques
545
A
a) Phase I: Normal and Subclinically Significant Sucking This phase extends from a child's birth to about 3 years of age depending on the child's social development. Most infants display a certain amount of thumb- and finger-sucking during this period, particularly at the time of weaning. Ordinarily, the sucking is naturally resolved toward the end of Phase I. However, should the infant show any tendencies to the "thumb-specific" type of vigorous sucking, a definite prophylactic approach may be taken because of possible occlusal harm. The use of a proper pacifier (Le., a fIat oval shape (Fig 1850) toward the end of Phase I is usually less harmful, at least from a dental point of view, than repeated vigorous thumb-sucking. Some children chew on a finger during teething, but this activity ceases when the teeth erupt.
B
FIG 18-50. A, the Nuk Sauger nipple. B, the Nuk Sauge~exerciser.
b) Phase ll: Clinically Significant Sucking The second phase extends roughly from age 3 to age 6 or 7 years. Continual purposeful digital sucking during this time deserves more serious attention from the dentist for two reasons: (I) it is an indication of possible clinically significant anxiety, and (2) it is the best time to solve dental problems related to digital sucking. A firm and definite program of correction is indicated at" this time.
c) Phase Ill: Intractable Sucking Any thumb-sucking persisting after the child's fourth year presents the qentist with a problem, for its persistence may be proof of problems other than simply malocclusion. A thumb-sucking habit seen during Phase III may require psychotherapy. Frequent consultation between dentist and psychologist or physician is indicated in order that an integrated approach may be made. Any thumb-sucking habit persisting until Phase III may be a symptom of a problem more significant than the associated malocclusion. The steps in treatment are gradual and sequential. a) Control of undesirable oral habits is usually begun in Phase IT. It is wise to begin with a discussion of the problem with the child alone. No threats or shaming should be used; instead, a calm, friendly attempt should be made to learn about the child's attitudes toward the habit. Many children will say that they suck their thumbs only when they are asleep, and also declare sincerely that they want to be rid of the habit. One can use these statements to advantage by saying, "It's mighty difficult to control what you do while sleeping, isn't it?" "Wou'ld you like a little help to remind that thumb to stay out of your mouth when you are not awake to do so?" If the child can be brought along gently to give an honest and cooperative reply, one can suggest that such a reminder is available if the child cannot handle the problem al()Ee. The child may be shown casts or photographs of mouths of children who have had detrimental sucking habits. S}1ow the treated result, too, to establish what can be done with the dentist's help. In other words, use this first discussion to learn about the child and to teach the methods available for correction of the habit. Be gentle,
for this may be the child's first friendly discussion concerning the matter. Leave the child with the idea that there is much the two of you can do together and that later you will dicuss the situation again. Excellent results have been obtained by use of a card that the child is given for scoring each morning to indicate whether the thumb was sucked during the night. It should not be a printed form, but rather a card with the child's name written on especially for this purpose. Two columns are drawn and labeled simply YES and NO or + and -. Make an appointment for the child to return in 2 weeks or less and to bring the card. Instruct the child that the thumb may be sucked, but a score must be kept for you so that you can learn about the severity of the habit. Do not encourage the disturbed, insecure child to lie to please you. Rather, affirm that one adult is interested in the problem and can discuss the sucking without scolding or shaming. A surprising number of children will bring the habit under control themselves under this program. It may be varied a bit by prescribing finger-size plastic bandages that can be purchased in any drug store (e.g., "BandAids") to be placed on the thumb each night by the child (NOT the parent) to remind the thumb to stay out of the mouth. And even when it is necessary to resort to an appliance (see later in this discussion), the child is ready psychologically for it and the appliance serves merely to remind the thumb when the child is asleep and cannot do so. b) As the child enters the period of trying to control the habit alone, a talk should be had with one or both parents. Emphasize that no one should discuss the problem with the child nor should it rn;"a subject forfamily discussion, since the dentist and the child will take care of it between them. Above all else, no disparaging remarks are to be made by anyone concerning the habit. Specifically ask the parents to watch the other children and grandparents within the family circle. The child thus loses the attention-getting aspects of the habit and is encouraged to work in a mature way with the dentist. A few children will cease the habit completely at this stage. Most will not, but will benefit greatly by the removal of family tensions centered on his or her thumbsucking and will thus be prepared to work with the dentist.
----
, 546
Treatment
c) If the child is in Phase IT, the next step is the insertion of a habit-correcting appliance. If the child is in Phase III, the next step is consultation with the family physician, a competent clinical psychologist, or a psychiatrist. Many school systems have such personnel who are conversant with this proble~. After such consultative advice is sought, the therapy becomes a joint effort. Usually, appliances are not inserted until the child's overall problems are defined and the thumb-sucking is seen in proper perspective.
b) Diagnosis Careful differentiation must be made among a simple tonguethrust, a complex tongue-thrust, retention of an infantile swallowing pattern, and faulty tongue posture (see Chapters 7 and 10). The prognosis usually is excellent for correction of a simple tonguethrust, good for a complex tongue-thrust, and very poor for retained infantile swallowing patterns. Chapter 10 provides detailed procedures for examining orofacial muscular activities and determining a differential diagnosis.
d) Choice of Appliance The ideal appliance to aid in the correction of a thumb-sucking habit would (I) offer no restraint whatever to normal muscular activity, (2) not depend on one's remembering to use it, (3) have no shame attached to its use, and (4) not involve parents. Perhaps the best appliance is a lingual arch wire with short spurs soldered at strategic locations to remind the thumb to keep out (see Fig 1849). This appliance is not a mechanical interference with the thumb and so should not take the form of an ungainly lingual screen or so-called "rake." It should be well adapted, out of the way of normal oral functioning, and contain sufficient sharp, short spurs to provide mild afferent signals of discomfort each time the thumb is inserted. Note carefully the rationale for this appliance. A clear signal of discomfort or mild pain reminds the neuromuscular system, even when the child is asleep, that the thumb best not be inserted. At that point, the child knows the need for help to remind the thumb to keep out when unable to do so, for example, when asleep. It is wrong to place any appliance as the first step in treatment, since the adjustment is likely to be too difficult. The permissive and more gradual approach outlined here is kinder, more practical, easier, takes less time, requires fewer appliances, and provides better conditioning of responses than the traditional mechanistic approach. It allows the child to conquer the problem. The oral shield can be u'sed to aid in the correction of thumbsucking (see Section C), but it requires an unusual amount of patient cooperation and is not used continually. Some of the huge and grotesque appliances suggested are mechanical deterrents only and thus provide nothing but frustation for the child. Thumbsuckers usually have that in abundance anyway. Advise the parents of the rationale and ask their help the first night or two. It is advisable for them to take time to qUiet the child just before bedtime and give an extra amount of attention and affection for a few days. Children in Phase III often will remove the appliance several times. It should always be recemented and the incident reported to the other clinician working on the problem. Always credit the child with successful therapy for this helps their self-image and gains them favorable faiTIiiy support. Children who overcome thumbsucking themselves in this fashion are grateful and appreciative patients thereafter and greatly matUl;e psychosocially during the treatment.
3. Tongue-Thrusting
a) Causes There are several causes of tongue-thrusting; it may be seen as a residuum of thumb-sucking or as a habit by itself. Frequently, it is learned early in life when there was tonsillitis or pharyngitis. Any chronic pain in the throat may prompt the tongue to be positioned forward, particularly during swallowing (see Chapter 7).
c) Treatment 1) Simple Tongue- Thrust.The simple tongue-thrust is defined as a tongue-thrust with a teeth-together swallow. The malocclusi~n usually associated with it is a well-circumscribed open bite in the anterior region (Fig 18-51). Read Chapter 10 for detailed descriptions of the procedures for examining the tongue and swallowing. If there is excessive labioversion of the maxillary incisors, treatment of the tongue-thrust should not begin until the incisors have been retracted. Many simple tongue-thrusts correct spontaneously during orthodontic therapy (see Fig 18-51). Steps in treatment are as follows: a) Acquaint the patient with the abnormal swallow by placing the index finger on the tip of the tongue and then on the junction of the hard and soft palate and saying to the patient, "Most people swallow with this part of the tongue on this part of the palate. Now put your tongue tip up here, close your teeth, close your lips and swallow while holding the tongue in this position." The use of tactile signals helps the patient understand where the tongue should go (Fig 18-52). The patient should be instructed to practice correct swallowing at least 40 times a day and to record the fact on a card. Practice may be with small amounts of water or bitesize dry breakfast food. Small orthodontic elastics can be held by the tongue tip against the palate during practice swallows. If the swallow is correct, the elastic will be retained; if incorrect, the elastic will be swallowed. Space the practice over two or three sessions each day. b) When the new swallowing pattern has been leamed on the conscious level, it is necessary to reinforce it subconsciously. At the second appointment, the patient should be able to swallow correctly at will. However, abnormal unconscious swallows will be seen. Flat, sugarless fruit drops now can be used to reinforce the unconscious swallow. Preferred drops are biconcave and of some citric acid flavor, such as lemon to promote the flow of saliva. The patient is instructed to place one of the fruit drops on the tip of the tongue and to hold the fruit drop against the palate in the correct position until. the candy has dissolved completely (Fig '1&::-53).The candy must not ~ sucked outside the therapeutic program. Have the patient time how long the candy is held in place, using a watch with a second hand (Fig 18-53), recording the time in minutes and seconds, and immediately replacing the fruit drop in its correct place to start retiming. At first the child will be able to hold the fruit drop in place for only a few seconds,but gradually the periods will lengthen. While reenforcing the correct swallowing unconsciously, the timing procedure~ provides a bit of distraction and self-competition. This is the best procedure I have discovered for transferring control of the reflex from the conscious to unconscious levels. One practice session per day involving the
Orthodontic
Techniques
547
B
~.-. FIG 18-51. A, an open bite resulting from a simple tongue-thrust. Note how circumscribed the open bite appears. Band C, corrected simple tongue-thrust. B, the casts of a patient with simple tongue-thrust in mild Class 11malocclusion at the beginning of extra-oral traction and
space supervision therapy. C, after the molar relationship had been improved, the incisors retracted, the open bite spontaneously corrected.
FIG 18-52. The use of tactile signals to the tongue (A and B) and visual signals (C and D) for teaching correct tongue position during swallowing.
Photographs C and D show a set of casts cut in two and a soft red plastic sponge that may be used to simulate tongue positions.
548
Treatment
A-I
-
,...,
A-2
!
FIG 18-53.
A, use of sugarless fruit drops to aid in tongue correction. B, the distractive technique for correcting the unconscious swallow.
dissolution of one fruit drop is usually satisfactory. The timing procedure should not be omitted, since its distractive effects are most important. These steps will correct a large percentage of simple tongue-thrusts. However, one additional step is sometimes necessary. c) A well-adapted soldered lingual archwire having short (2mm), sharp, strategically placed spurs can now be inserted (see Fig 18-49). Protectively, the tongue is withdrawn from Jlle abnormal position and placed properly during swallowing. Do not place such an appliance as the first step in therapy. It is much too traumatic to the patient, and many patients will simply rip it out of the mouth. However, if steps a and b have been carried out properly, the patient can then accept the appliance. Simple tonguethrusts are usually correctable by these three sequential procedures. When one is not, the condition may have been misdiagnosed and is not truly a simple tongue-thrust.
To summarize, the treatment moves through three phases: conscious learning of the new reflex, transferral of control of the new swallow pattern to the subconscious level, and reinforcement of the new reflex. 2) Complex Tongue-Thrust.-A complex tongue-thrust"is defined as a tongue-thrust with a teeth-apart swallow. The malocclusion seen with a complex tongue-thrust has two distinguishing features: (I) a poor occlusal fit is present which usually prompts a slide into occlusion, and (2) there is a generalized anterior open 'bite (Fig 18-54). One almost can diagnose a complex tonguethrust from the casts alone. When the casts are taken in the hands and fitted together, there is uncertainty about what is precisely the patient's usual occlusal position: there is no firm secure intercuspation. The prognosis for correction of a complex tongue-thrust is not as good as for a simple tongue-thrust, since there are two neuromuscular problems: the abnormal occlusal reflex and the abnormal swallow. Check carefully by palpation the mandibular elevators during the swallow (Chapter 10). In the complex tonguethrust they do not contract, and the mandible is stabilized by tongue and infra-mandibular muscle contractions. It is possible to have a complex tongue-thrust but no open bite if the tongue is positioned evenly atop all teeth during the swallow. The patient's attention, must be brought to the problem and the difficult prognosis explained carefully at the start of therapy. The patient should know, at the start of treatment, cessfW. therapy lies with Contrary to popular clusion first. When the
FIG 18-54. An open bite resulting from complex tongue-thrust. In this instance, the mandible dropped before the tongue-thrusts; the neat, circumscribed area of the open bite seen in the simple tongue-thrust (Fig 18-51,A) is not observed.
t~~t much of the responsibility for sucHimself or herself. practice, it is advisable to treat the ocorthodontic treatment is in its retentive
stages, careful occlusal equilibration is completed. The muscle training then begun is similar to that for a simple tongue-thrust, with minor modifications. (I) When teaching the patient to swallow properly, great emphasis must be placed on keeping the teeth together, and step I of the treatment usually is prolonged. (2) It is always necessary to use step 3, for considerable time must be taken to reinforce the newly learned reflexes. A maxillary lingual
Orthodontic- Techniques
549
FIG 18-55. Cast of patient with treated complex tongue-thrust. A and 8, intraoral views at the beginning of treatment. C and D, the soft tissue of the face before treatment. E-G, occlusal views at the end of treat-
Note the persistence of the mamelons on the lower incisors, indicating that even yet there are not full occlusal 'stops in the incisor region. I and J, facial soft tissue views at the end of treatment. Note
ment. This patient was treated orthodontically twice previously before this correction was obtained. H, occlusal views at the end of retention.
some improvement
arch wire with short, sharp spurs may be used as a retainer. Even after the patient has mastered the new swallow and theabnormal actions of the lip and mentalis muscles are seen no longer, it is prudent to leave the lingual arch wire in place: complex tonguethrusts are tenaciously retained activities. Our present state of knowledge does not allow a correction of all cases of complex tongue-thrust. Until we are wiser concerning these matters, it is important to do meticulous tooth positioning, and careful equili-
-,
in the.posture
of the lips at rest.
bration followed by persistent myotherapy. Despite the clinician's best efforts, partial relapse may be seen in some cases (Fig 1855). 3) Retained Infantile Swallow.-Retained infantile swallow is defined as the undue persistence of the infantile swallow well past the normal time for its departure. Very few people have a retained infantile swallow; those who do ordinarily occlude on just
550
Treatment
FIG 18-56. Severe open bite. A, open bite resulting from retained infantile swallow. Usually the teeth occlude on one molar in each quadrant. This patient was treated by a very competent orthodontist and underwent full edgewise therapy; the photograph was taken 1 month after removal of the retainers. B, open bite due to a skeletal morphologic pattern-the "long face syndrome." Treatment was solely orthodontic.
one molar in each quadrant (Fig 18-56). They also demonstrate strong contractions of the facial muscles during swallowing, The tongue protrudes markedly, and it is held between all of the teeth during the initial stages of the swallow. Persons with retained infantile swallows do not have expresive faces, since the muscles of the seventh cranial nerve are being used for the massive effort of stabilizing the mandible and not fOr the delicate facile movements of facial expresion. They also have serious difficulties in mastication and may have a low gag threshold. The retained infantile swallow must be differentiated from the open bite associated with disproportionately long· anterior face height-the so-called "long face" syndrome. In the latter, primarily a severe skeletal dysplasia, the tongue adapts to the disharmonious morphology in a more passive way simply to effect an anterior seal during the swallow and the swallow is usually completed with the teeth together (Fig 18-56,B). Undue anterior facial height is a skeletal dysplasia which may require both orthodontics and orthognathic surgery: the retained infantile swallow is a problem in abnormal neuromuscular development. Little is known concerning the exact etiology of this severe problem, b~~ should these patients lose their teeth, satisfactory denture prosthesis is difficult. The prognosis for correction of the retained infantile swallow is poor. Fortunately, the true retained infantile swallow is rare.
4. Abnormal Tongue Posture The continuous effects of abnormal tongue posture may produce more open bites than the more obvious tongue thrusts. There are two forms of the protracted tongue posture: (1) the end~genous
and (2) the acquired. During the arrival of the teeth, the tongue normally changes its posture and comes to rest inside the encircling dentition. Some children have an inherently abnormal tongue posture and the tip of the tongue persists in lying between the incisors. Fortunately, the great majority of the endogenous protracted posture problems are not unesthetlc and there is stability of the incisor relationship even though a mild open bite is seen (Fig 18-57,A). On rare occasions, serious open bites have been present from the first stages of eruption (Fig 18-57,B). The acquired protracted tongue posture is a more simple matter, 'since it usually results from chronic pharyngitis, tonsillitis, or other nasorespiratory disturbance. It may be prudent to refer the patient to an otolaryngologist before starting the orthodontic therapy for as long as the precipitating cause is present, the tongue will posture itself forward and any positioning of the incisors may be unstable. Sometimes the nasopharyngeal condition no longer exists but the tongue remains ina forwarq position. The posture in those circumstances usually can be induced to change by the simple expedient of attaching sharp spurs to a bonded anterior sectional lingual wire or"airectly to the'teeth. - An adaptive tongue posture is sometimes seen when the maxilla is narrower than the mandible. Since the tongue must aid in the encircling seal to complete the swallow, it may adapt a posture atop the lower teeth. When rapid palatal expansion is completed and posterior intercuspation is correct, a normal posture usually returns. Posterior open bites are more often postural problems than "lateral tongue-thrusts". To summarize, there are two clinically significant problems in abnormal tongue posture: (1) the endogenous protracted tongue
Orthodontic
Techniques
551
H. OCCLUSAL EQUILIBRATION (OCCLUSAL ADJUSTMENT) Occlusal equilibration (occlusal adjustment) is the systematic reshaping of the occlusal anatomy of teeth to minimize the role of occlusal disharmonies (interferences) in reflexly determined mandibular occlusal positions. Occlusal equilibration is done for quite different reasons during active facial growth and occlusal development than in adulthood. Balanced function is a desired factor in normal occlusal development, since functional crossbite or functional Class Il or III malocclusions may, in time, create important skeletal complications and temporomandibular dysfunction (see Chapter 15).
1. Equilibration
FIG 18-57. Open bite resulting from abnormal tongue posture. A, a Class 11, Division 1 malocclusion with the patient 2 years out of retention. Note the return of a very mild open bite. This patient was treated twice more, with the occlusion returning each time to this relationship. B, a severe open bite caused by abnormality of tongue posture. There was no marked tongue-thrust on swallowing; rather, the tongue remained in this position most of the time.
posture, for which the prognosis is pOor and around which the occlusion must be built; and (2) the acquired protracted tongue posture, which usually is correctable after the precipitating causes have been corrected.
5. Lip-Sucking
and Lip-Biting
These habits are seen most frequently with an excessive overjet and/or overbite. In Class IT, Division 1 cases, the lip habits frequently are severe and their treatment should not be started until the incisors have been positioned correctly. SQIIle lip habits are then self-correcting, but the hyperactive mentalis muscle remains. The modified oral shield shown iJl Fig 18-41 is useful.
6. Fingernail-Biting Nail-biting ordinarily is not seen until after a child is 3 or 4 years of age. Psychologists think it a reflection of anxiety or personality maladjustment. The habit reaches its peak incidence during the teens. Children who bite their nails may have malocclusion, but no specific malocclusion is pathognomonic of nailbiting.
in the Primary Dentition
Equilibrative procedures serve different purposes in the primary and mixed dentitions than in the permanent: the techniques for treatment differ, too. Before attempting any equilibration, reread pertinent sections of Chapters 10 and 11. Cases treated by this procedure are illustrated in Chapter 15. The following articl~s and instruments are needed for equilibration in the primary de'ntition: a) Articulation paper. b) Diamond points. / c) Diamond disk. d) Record casts. It is useful to try the equilibrative procedure on casts before attempting it in the mouth. Casts oriented in the ideal occlusal position (see Chapter 11) may be marked with articulation paper and the plaster scraped away to simulate tooth grinding. Written records kept of the surfaces ground and the order of the grinding will be of value when one is actually doing the grinding in the mouth. Remember where the interferences are most likely to appear (Fig 18-58). The Procedure is as follows: a) Teach the child to tap the teeth together, with the midlines coinciding. Since this is the occlusal position they are reflexly avoiding, learning it requires some guidance from the dentist. Place your thumbs beneath the mandible on either side, grasping it firmly while touching the gingivae in the cuspid region with the index fingers (Fig 18-59). Gently move the mandible to the desired position while giving verbal suggestions and tactile signals with the fingers on the gingivae. The initial occlusal interferences to be ground now will be seen clearly (Fig 18-60). c) Mark the midline interferences with articulating paper (Fig
1.8-61).,
~.
, ;.d) Grind out the midline ipterferooces, which are usually found first in the cuspids and later in the molars (Fig 18-62). e) Teach the child to protrude his or her jaw with the midlines together and the teeth touching. This may be done by placing your index finger against the gingivae at the mandibular midline and asking the child to follow with his or her jaw as you gently withdraw your finger (Fig 18-63). The reason for this check of protrusive interferences is shown in Figure 18-64. f) Mark the protrusive interferences with articulation paper. g) Grind away the protrusive interferences.
552
Treatment
FIG 18-58. A·1, the usual site of cuspid interference in the primary dentition.
to the transverse ridge. B-2, the usual areas of interference and
A-2, the area usually removed on the lingual of the maxillary cuspid. " . grinding on the marrdibular second primary molar. B-3, the typical A-3, the area usually ground on the mandibular primary cuspid.• relationship of the primary s!lcond molars when there is occlusal A-4, the corrected primary cuspid relationship. B-1, the usual areas interference. B-4, the usual areas of interference on the mandibular
ground on the maxillary second primary molar. Note the relationship
first primary molar.
Orthodo,!tic Techniques
FIG 18-59. Teaching the patient to tap his or her teeth together and the midlines coincident. h) Apply topical fluoride to all surfaces that were ground. Typical effects on the functional aspects of a Class II or Class III malocclusion are shown in Figure 18-65.
2. Equilibration in the Mixed Dentition Proceed in the mixed dentition as in the primary, grinding only primary teeth. Any permanent teeth that are interfering should" not be ground but be moved with appliances. Since their position is likely to change many times before final adult occlusion is established, the areas ground might be needed later as occlusal stops.
3. Equilibration in the Permanent Dentition The reasons for equilibration of the occlusion as presented in most textbooks of occlusion. periodontics, or restorative dentistry rarely embrace the orthodontic perspective, since the problems of stabilizing a deteriorating adult dentition ravaged by disease and loss of teeth are in the minds of the writer. Equilibration of an orthodontic correction of a malocclusion in a healthy adolescent or young adult is undertaken with a quite different rationale, namely, to maximize favorable occlusal and alveolar adaptations to the expected developmental and functional changes which occur naturally with time. Occlusal equilibration is one of the most important techniques to assure stabilization of an orthodontically corrected occlusion (see Chapter 13).
553
a) Rationale' Reasons for occlusal equilibration of the orthodonticaIly treated occlusion include: a) To stabilize the corrected occlusion. b) To alter favorably abnormal swallowing and other reflexes (Fig 18-66). c) To provide a favorable functional environment for further developmental changes. d) To supply artificial wear to those occlusal surfaces, which, in the malocclusion state, were not worn or were worn abnormally. e) To minimize occlusal slides prompted by occlusal interferences, a principal cause of mandibular incisal crowding during retention (Fig 18-67). What follows is the barest outline, for I have presumed the reader is familiar with the rudiments of procedures used routinely in periodontics and restorative dentistry: if one is not, see Suggested Readings at the end of this chapter. Equilibration is no substitute for meticulous positioning of teeth. It can, however, minimize the muscle's response to those occlusal interferences, which cannot be removed with mechanotherapy. In difficult cases, or if one is inexperienced in this procedure, begin by mounting casts with a face bow bite registration on an adjustable articulator. Then follow these steps, scraping away the occlusal interferences of the plaster teeth with a small knife, until the desired result appears. Note in writing the sequence of occlusal grinding on each tooth surface for reference later when actually doing the equilibration on the patient. b) Procedure a) If a cusp is making premature contact in the retruded contact position, the opposing groove or incline should be ground if the cusp interferes in only one or two functional key positions (Fig
18-68). b) The prematurely contacting cusps in the retruded contact position should be ground if there is interference in all of the three key positions (Fig 18-69). c) A forward slide into occlusion should be corrected by grinding on the interfering mesioclusal inclines of the upper teeth or the distoclusal inclines of the lower teeth. Occlusal stops should be maintained for .premolars and molars without loss of vertical dimension (Fig 18-70). d) A lateral slide into occlusion should be corrected by widening of the central fossa at the level of the occlusal stop (Fig 1871). e) If the lateral slide on the contacting teeth is away from the midline, grind as shown in Fig 18-72.
\
\
) FIG 18-60. A, typical interferences that appear when midlines are coincident, B, an atypical unilateral interference with the mlOllnes togemer.
554
Treatment
FIG 18-61. Marking the interferences with articulation paper when the midlines are together. A, the correct position of the articulation paper, illustrated on casts. 8, typical positions of midline interferences. Note that the markings persist on the lingual slopes of the buccal cusps in the upper arch. In a normal occlusion, these markings would be in the central fossae.
FIG 18-62. Method of grinding the midline interferences. A, primary cuspid, lateral view. Note the areas of grinding and the change in relationship achieved by that grinding. 8, primary molar. The method is similar to that for the cuspid.
FIG 18-63. Teaching the patient to protrude his or her jaw with the midlines coincident. The index finger is pushed against the gingivae in the region of the lower central incisor, 'and the patient is instructed to advance the mandible, following the finger.
o·
.......•..•
Orthodontic Techniques
18-65.
FIG
AP correction of functional mary molars.
FIG
malocclusion.
A, primary cuspids. 8, pri-
18-64.
The reasons for checking and grinding the protrusive intenerences. These casts were taken after the midline interferences had been ground. By advancing the lower cast a very small amount (note that the incisors are not yet end to end), a typical interference is seen between the maxillary cuspid and the mesial marginal ridge of the mandibular first primary molar. Another interference seen frequently is between the lingual cusp of the maxillary first primary molar and the mesial marginal ridge of the mandibular second primary molar.
I
'
I, I I I•••••
, "
I
I -0#.' I
. Before '. ~quJ/ibrot/~n I ................................................ I
I
f
I
.
.•...•...•.•.•.•.•.•...•.. ..•....•.•.• •.••.•.•.•.............. .•...•..•..•.•.•.•...•.•......•••.•.• .....••••..•••..•.........•••............••................•.. ......•..........•....•..••....•••....•....•............•..
After EqUJ/ibrofion
Unconscious (Saliva)
I
""
I
I
I'"'''' """
I
II
I
Unconscious (Bolus) Command (Saliva)
Unconsciaus
(Saliva)
Unconscious (Bolus) Command '(Saliva)
Cammand (H~)
"""",) t,,,th oport _ te6th together FIG
0
18-66.
The effect of occlusal equilibration
on the swallow relex.
5
10 Number
555
15 of Subjects
20 (Total
28)
25
556
Treatment
A P-A
o
.25 .50 .75 1.0 L25 1.5
1.75
2.0 2.25 2.5
2.75
1.42
slid@ at @nd of tr@atm@nt
Lat@ral slid@ at @nd of tr@atm@nt
V@rtical slid@ at @nd of tr@atm@nt
P-A
.45
slid@ 1 y@ar aft@r r@t@ntion
Incisal
crowding
1 y@ar aft@r r@t@ntion
usual Comparison
of r@lapsf symptoms
using
Eiiil r@t@ntion plans.
and n@w _
B
.'
3.5
30 2.5
20 FIG 18-67. A and e, the effects of occlusal equilibration on "slides" into occlusion
10
and mandibular incisal crowding.
---
5 6mos
---
Iyr
Mean "Slide": Mean "Slide": Mean Incisal
Old Retention
New Retention Program Crowding:
Mean Incisa I Crowding:
FIG 18-68. A, working. e, usual occlusal position. C, balancing.
Program
Old Retention
Program
New Retention Program
Orthodontic Techniques
557
FIG 18-69. A, working. B, usual occlusal position. C, balancing.
J) As a final step, remove any minor interferences that may remain between the retruded contact position and the ideal occlusal position.
REFERENCES
FIG 18-70. A, usual occlusal position. B, retruded contact position. fJ Adjust the working side on the guiding inclines, including the incisal edges and the buccal cusps of the upper teeth and the lingual cusps of the lower teeth (Fig 18-73). g) Adjust for protrusive contact on the incisal edges of the upper teeth, except in unusual cases. , h) Do whole grinding on only one of two interfering cusps or inclines if they both serve as occlusal stops. i) If a cusp or incline that interferes in balance is out of occlusion in the usual position, grind on that cusp or incline.
1. Ahlgren J: Mechanisms of mastication. Acta Odontal Scand 1966; 24 (suppl): 44. 2. Ahlgren J: The neurophysiologic principles of the Andresen method of functional jaw orthopedics. A critical analysis and new hypothesis. Swed Dent J 1970; 63:1-9. 3. Andresen V: Beitrag zur Retention, Z Zahnaevztl Orthop 1910; 3:121. 4. Andresen V: Ueber das sogenannte "norwegische System der Funktions-Kiefer-Orthopadie," Dtsch Zahnaerztl Wochenschr 1936; 39:235,283. 5. Auf der Mauv HJ: Electromyographie recordings of the lateral pterygoid muscle in activator treatment of Class 11, division 1 malocclusion cases. Eur J Orthop 1980; 2;161171. 6. Balters W: Krafteinwirkung oder formgestaltende Reiszsetzung? Zahnarztl Welt 1952; 7:437-441. 7. Balters W: Reflexmechanismus und Funktiona-blauf. Fortschr Kieferorthop 1955; 16:325-327. 8. Bimler HP: Die elastischen Gebissformer. Zahnarztl Welt 1950; 11:315-319.
FIG 18-71. A, usual occlusal position. B, retruded contact position. C, same after grinding.
I 558
Treatment
FIG 18-72. A, usual occlusal position. S, retruded contact position. C, same after grinding .
.'
FIG 18-73. Working side interference.
9. Demisch A: Langzeitbeobachtungen uber die Stabilitat der Okklusion nafh Distalbisstherapie mit dem Berner Aktivator. Schweiz Mschr Zahnheilk 1980; 90:867-880. 10. Demisch A: Herren' s dentofacial orthopedics. In Graber TM, Neuman BF (eds), Removable Orthodontic Appliances, 2nd ed. WB Saunders Co, Philadelphia, 1984. 11. Frankel R: The theoretical concept underlying treatment with function correctors. Trans Eur Orthod Soc 1966; 233250. 12. Frankel R: Biomechanical aspects of the form/function relationship in craniofacial morphogenesis: A clinician's approach in McNamara JA Jr, Ribbens KA, Howe RP (eds), Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. 13. Frankel R, Frankel C: A functional approach to treatment of skeletal open bite. Am J Orthod 1983; 84:54. 14. Graber LW: Chin cup therapy for mandibular prognathism. Am J Orthod 1977; 72(1):23-41. 15. Graf EJ: Funktionelle Krafte bei bimaxillaren Regulationsapparaturen, doctoral thesis. Univ of Bern, 1962. 16. Harvold E: The Activator in Interceptive Orthodontics. St Louis, CV Mosby Co, 1974. 17. Herbst E: Dreissigjahrige Erfahrungen mit dem RetentionsScharnier. Zahnartliche Rundschau 1934; 43:1515-1524, 1563-1568, 1611-1616. 18. Janson I: Skeletal and dentoalveolar changes in patients
treated with a bionator during prepubertal and pubertal growth in McNamara JA Jr, Ribbens KA, Howe RP (eds) Clinical Alterations of the Growing Face, monograph 14. Craniofacial Growth Series, Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983. 19 .. Kingsley NW: Oral Deformities. New York, D Appleton & Co, 1880. 20. McNamara JA: Neuromuscular and skeletal adaptations to altered function in the orofacial region. Am J Orthod 1973; 64:579. 21. McNamara JA: Functional determinants of craniofacial size and shape. Eur J Orthod 1980; 2:131. 22. McNamara J A, Carlson D:Quantitatjve analysis of TMJ adaptations to protrusive function. Am J Orthod 1979; 76:593-611. 23. McNamara JA, Hivton RJ, Hoffman DL: Histologic analy'; sis of temporomandibular joint adaptation to protrusive function in young adult rhesus monkeys. Am J Orthord 1982; 82:288. 24. Pancherz H: Long-term effects of activator (Andresen appliance) treatment. Odontol Rev (suppl) 1976;27:35. 25. Robin R: Observation sur un nouvel appareil de redressement, 1902; Rev Stomatol 9:423. 26. Rogers AP: Exercises for the development of the muscles of the face, with a view to increase their functional activity. Dent Cosmos 1918; 60:857-876. 27. Sander FG: Zur Frage der Biomechanik des Aktivators-Ent-
Orthodontic Techniques
28.
29. 30. 31.
wicklung und Erprobung neuer Untersuchungsmethoden, Wiesbaden, Estdeutscher, 1980. Sander FG: The effects of functional appliances and Class ITelastics on masticatory patterns, in McNamara JA Jr, Ribbens KA, Howe RP (eds), Clinical Aherations of the Growing Face, monograph 14. Craniofacial Growth Series, Ann Arbor, Mich, Human Growth and Development, University of Michigan, 1983. Solow B, Tallgren A: Head posture and craniofacial morphology. Am] Phys Anthropol1976; 44:417-436. Solow B, Tallgren A: Dentoalveolar morphology in relation to craniocervical posture, Angle Orthod 1977; 47:157-164. Woodside DG: The Harvold-Woodside activator, in Graber TM, Neuman B (oos), Removable Orthodontics, 2nd ed. Philadelphia, WB Saunders Co, 1984.
SUGGESTED READINGS C-4: Edqewise Mechanisms 1. Lindquist IT: The Edgewise Appliance, in Graber TM, Swain BF (eds), Orthodontics: Current Principles and Techniques, St Louis, C V Mosby, 1985, pp 565-639. 2. Ricketts RM, Bench RW, Gugino CF, et al: Bioprogressive Therapy, Denver, Rocky Mountain Orthodontics, 1979. 3. Roth R: Treatment mechanics for the straightwire appliance, in Graber TM Swain BF (eds), Orthodontics: Current Principles and Techniques, St Louis, CV Mosby Co, 1985, pp 665-716. 4. Thurow RC: Edgewise Orthodontics, 4th ed. St Louis, CV Mosby Co, 1982. 5. Tweed CH: Clinical Orthodontics, 2 vols. St Louis, CV Mosby Co, 1966. C-5: Light-Wire Appliances 1. Begg PR, Kesling PC: Begg Orthodontic Theory and Technique, 3rd ed. Philadelphia, WB Saunders Co, 1977. 2. Thompson WJ: Modem Begg: A combination of Begg and straightwire appliances and techniques in Graber TM, Swain BF (eds), Orthondontics: Current Principles and Techniques, St. Louis, CV Mosby, 1985, pp 717-789. C-6: Other Fixed Appliances 1. Fastlicht, J: The Universal Orthodontic Technique. Philadelphia, WB Saunders Co, 1972. D-I-a: Extra-oral Traction Devices Head Gears 1. Bowden DEl: Theoretical considerations of headgear therapy: A literature review. Part 1. Mechanical principles, Br ] Orthod 1978; 5:145-152; Part 2. Clinical response and usage. Br] Orthod 1978; 5:173-181. 2. Hershey HG, Haughton CW; Burstone CJ: Unilateral facebows: A theoretical and laboratory analysis, Am ] Orthod 1981; 79:229-249. 3. Jacobson A: A key to the understanding of extraoral forces. Am] Orthod 1979; 75:361-386. 4. Worms FW, Isaacson RJ, Speidel TM: A concept and classification of centers of rotation and extraoral force systems. Angle Orthod 1973; 43:384-401. Face Masks 1. Petit H: Adaptation following accelerated facial-mask therapy in McNamara JA Jr, Ribbens KA, Howe RP (eds),
559
Clinical Alteration of the Growing Face, monograph 14. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1983, pp 253-289. Chin Cups 1. Graber LW: The alterability of mandibular growth, in McNamara JA Jr (eds), Determinants of Mandibular Form and Growth, monograph 4. Craniofacial Growth Series. Ann Arbor, Mich, Center for Human Growth and Development, University of Michigan, 1975. 2. Thilander B: Chin-cup treatment for Angle Class III malocclusions. Trans Eur Orthod Soc 1965; 41:311-327. D-I-b: Lip Bumpers 1. Bjerregaard J, Bundgaard AM, Melsen B: The effect of the mandibular lip bumper and maxillary bite plate on tooth movement, occlusion, and space conditions in the lower dental arch. Eur] Orthod 1983; 84:147-155. D-I-c: Active Plates 1. The active plate in Graber TM, Neuman B (eds), Removable Orthodontic Appliances, 2nd ed., Philadelphia, WB Saunders Co, 1984, pp 12-53. E-2: Vestibular Appliances 1. The use of muscle forces by simple orthodontic appliances, in Graber TM, Neuman B (eds), Removable Orthodontic Appliances, 2nd ed., Philadelphia, WB Saunders Co, 1984. E-3: Functional Jaw Orthopedic Appliances Books 1. Graber TM, Neumann B: Removable Orthodontic Appliances, 2nd ed., Philadelphia, WB Saunders, 1984. 2. Graber TM, Rakoski T, Petrovic AG: Dentofacial Orthopedics with Functional Appliances, St Louis, CV Mosby Co, 1985. 3. Harvold EP: The Activator in Interceptive Orthodontics, St Louis, CV Mosby Co, 1974. Articles or Chapters Activators 1. Graber TM: The Activator: Use and modifications, in Graber TM, Neumann B (eds), Removable Orthodontic Appliances, 2nd ed., Philadelphia, WB Saunders Co, 1984; pp 198-243. 2. Reey RW, Eastwood A: Passive activator: Case selection, treatment response and corrective mechanics. Am] Orthod 1978; 73:378-409. 3. Woodside 00: The Harvold-Woodside activator, in Graber . TM, Neumann B (e;ds),Removable Orthodontic Appliances, , ~.2nd ed., Philadelphia, WB Saunders Co, 1984; pp 244310. Bionators 1. The Bionator, in Graber TM, Neumann B (eds), Removable Orthodontic Appliances, 2nd ed., Philadelphia, WE Saunders Co, 1984; pp 357-375. Frankel Function Regulator 1. The Frankel Function Regulator, in Graber TM, Neumann B (eds), Removable Orthodontic Appliances, 2nd ed., Philadelphia, WB Saunders Co, 1984; pp 520-573.
560
Treatment
2. McNamara JA Jr, Huge S: The Frankel appliance. Am J Orthod 1981; 80:478-495.
G. Correction of Deleterious
Bimler Appliance
I. Bimler HP: The Bimler Appliance in Graber TM, Neumann B (eds), Removable Orthodontic Appliances, 2pd ed., Philadelphia, WB Saunders Co, 1984, pp 410-519. Herbst Appliance
1. Pancherz H: The mechanism of Class
Herbst appliance treatment: A cephalometric investigation. Am J Orthod 198282:104-113.
IT
correction in
Oral Habits
I. Hanson ML: Oral myofunctional therapy. Am J Orthod 1978; 73:59-67. H. Occlusal Equilibration
(Occlusal Adjustment)
I. Ramjford SP, Ash MM Jr: Occlusal adjustment of natural teeth, chapter 13, in Occlusion, 3rd ed. Philadelphia, WB Saunders Co, 1983.
. "
-.
-.•....
Index A Ackerman-Proffit system,
well-treated cases, records of, 436-438 classification
191
Acrylic inclined plane extension in lingual crossbite, 418 regainer, split-saddle, 527 space maintainer, multiple, 530 Activators, 539 casts and, 539
Adult, 472-510 cephalometry, 473 treatment, 472-510 with good oral health (see Treatment, of adults with good oral health) treatment plan for, 473-475 Affective states: and postural
open-front, 540 before trimming, af:er wear, 538
of, 142
malrelationships during, lateral, 447-450 periodontitis during, 447 treatment during (see Adolescent treatment) Adolescent treatment, 432-471 advantages of, 434 difficulties with, 434
Airway: upper, reflexes, 76 Alar musculature: and mouth-
bone (see Bone, alveolar) crest, 256 development guidance in Class 11 malocclusion, 399-400 process, 63 in appliances, removable loose, 533-534 in Class 11 malocclusion, 400
435
Anchorage cervical,
classification,
functional, 435 incisal relations, 435 midlines, 435 occlusal, 435 skeletal, 434
cranial, 309 extra-oral, 309 facial, 309
profile, 435
singular to the young adult, 442-447 understanding,
434
309
compound, 309 concepts of, 309-310 control of, 309
intermaxillary, intra-maxillary, intra-oral, 309
309 309
in malocclusion with periodontal disease and tooth
spacing, 435 problems clinical, 440-468
result assessment,
440
309
compromises, 435 definition of, 434-435 dental,435 esthetics, 435
sofHissue
207
result assessment,
goals arch form, 435 axial inclinations,
equivalence, 16 overbite and, 126
Aligners: spring, anterior, 526 Alimentray tract: reflexes, 76 Alveolar
538
Adaptation: mechanisms Adolescence
Age
breathing,
435-440
loss in adult, 479 muscular, 309 occipital, 309 primary, 309 reciprocal,
309
309
simple, 309 single, 309 stationary, 309 Angle system: of malocclusion classification, 186-188 Angulations: developmental changes in, 129 Ankylosis molar first permanent mandibular, 447
position, 86
cephalography of, 538-539 for Class 11, type D-2 malocclusion, 453 classic, 538 derivatives of, 539 fit inside mouth, 534
reinforced,
permanent, 391 primary, 390 permanent teeth, 391 during adolescence, 447
446-
of primary teeth, 107-108, 388-391 Anomalies craniofacial,
426
principles of biomechanics in, 310-313 functional (see Appliance, removable, loose below) in gross disharmony between osseous bases, 397 Herbst, 541, 543 hybrids,
of primary teeth, 107 of shape during adolescence, during adolescence, tions, 442 crown, 355-356
442 varia-
356
Appliance acrylic, removable, for uprighting molar in adult, 480-481 '•. Activator (see Activator) • active, 524-428 Barrer, 526 Bionator, 540 bonded, in situ, 517
541-542
jaw (see also Appliances,
removable, loose below) definition, 535 forces in, 308-313 indications,
535
types, 535-539 uses, 535 light-wire, 522 in maloccusion Class
craniofacial growth and, 53 of crown shape, 355-356 face, origin of, 22-26 of incisor, maxillary central, 357
miscellaneous, of teeth, 228
elastic, 539 fixed,518-524
11,
400
with periodontal disease and tooth loss in adult, 478-479 myodynamic, 539 palatal expansion, 520 passive, 529-531 perversions, 541-542 Quad Helix, 397 removable, attached, 524-531 removable, loose, 531-542 action modes, 532 alveolar processes 534
in, 533-
background, 531-535 craniofacial skeleton in, 534 definition, 531 dentition in, 533-534 history, 531-532 muscles in, 532-533 purposes, 531 role of timing in intervention, 535
bracketed, in molar uprighting, 481 for crossbite, dental, 396 Crozat, 526, 529 in dentoalveolar contraction, 397
space-regaining, 525-526 for sucking correction, 546 of thumb, 544
design in molar uprighting treatment plan, 482
traction, extra-oral, twin-wire, 522
Schwartz,
525
524-525
561
"
562
Index
Appliance (cont.) universal, 524 vacuum-formed, 526 vestibular, 535 construction, 535 description, Arborization
contraction
in orthognathic surgery with orthodGntic treatment, 497
535
applied to actual cases, examples, 336-337 of Class II malocclusion
dur-
ing adolescence, 454 to segregate various treatment protocols, 333 Arch asymmetries, dividers to estimate, 396
contraction, maxillary, producing functional crossbite, 393 dental 123-124
depth, 123 dimensional changes in, 121-126 dimensional changes in young adult, 141 length, 123 perimeter,
123-124
perimeter changes, 124 perimeter changes due to caries and tooth loss, 125
perimeter, uses of, 126128 primary, development, 108 primary, dimensions of arch, 108 quadrants, prenatal, width, 122-123 dimensions,
361-
regaining space in, 363364 prenatal shape, 104 relationship of the three arches, 121, 228 space available in mandible by dental age, 127 Archwire
description, fixed, 519
240-241
loop, 519 modifications, 519 Porter, 519 Quad-Helix, 519, 520 removable, 519 loops in, 313 Arteries: carotid, in fetus, 29 Articulare, 258 Articulation: speech, mini-test of,213 Articulatory valving: place and manner of, 213 Attachments for archwire, lingual, 519 bonding, 517-518 Attitude of adult toward orthodontic
changes in, 240-241 changes, expected, 240 changes in, growth and treatment causing, 125 form during adolescence, 435 in mal occlusion Class II, 398-399 leveling mechanics in incisal overbite, 492 malrelationships gross disharmony between osseous bases, 397 lateral, 391-397 lateral, differential diagnosis, 391-396 in mixed denti-
tion analysis, 236-238 maxillary
473
evaluation in cursory orthodontic examination, 169170 Auricular development: proper, 24 Axiversion, 189
im-
for, 517
correctly contoured, formation, 515-517 maxillary,
issues concerning, theoretical and clinical, 56-57
Birth order: and growth, Bite
54-55
Behavioral Bicanine
development,
mandibular, 122
516
fitting of, 516
preformed with attached brackets, 517 examples of, 516 fitting, 517 separation of teeth before, 515 method,515-516
10
during adolescence, 467-468 cephalometry
width changes,
simple, during adolescence, diagnosis, 464 simple, during adolescence, treatment, 464-466
351
387
simple, with labioversion of maxillary incisors, 489-492
congenitally missing, moving mandibular first molars in, 352 delayed development,
simple, vertical problems in anterior region and, 489 skeletal, 467-468 skeletal, with Class II malocclusion in adult, 476 treatment, 426
349
eruption of, premature, 383 impaction, 388 loss of, treatment, 353 mandibular, abnormally shaped, 356 mandibular, blocked-out, 160 mandibular, congenitally missing, 349 mandibular, congenitally missing, treatment, 350351 mandibular, congenitally missing, treatment, prognosis, 351
prognathism during adolescence, 466, 467 418-420,
466-
dental,420 Biologic activities: classes of alterations in, 7 Biology
open (see Open bite) overbite (see Overbite) planes, 529 flat, maxillary, 479
for adult,
wax on maxillary cast, 245 -wing radiography, 222 Bolton Analysis, 232-233 Bolton Tooth Ratio Analysis, 229 Bonding attachments, Bone alveolar deposition 315
size variations,
dental protrusion, 466-467 dentoalveolar protrusion, 467
protrusions, 467
of, 425
diagnosis, 423-426 in periodontic patient, 493 simple, during adolescence, 464
eruption (see Eruption, bicuspid) first transposition, second
464,
complex, 467-468 definition, 422-423
width changes in,
loss of, treatment,
12
crossbite (see Crossbite) deep, 422-426
timing of growth, 56 Basion, 258
unerupted, probability tables for size prediction, 237 \yi~th changes in, 123 -, ~. Bimaxillary
of, 517
attachments
growth, 55-56
Bionator appliance, 540 Birth injuries: and malocclusion, 151
functions,
mandibular, 356
Bands
9
Biomechanics: principles in fixed orthodontic appliances, 310-313
mechanisms,
mandibular, shape variations, 356
B
cementation molar
compensatory 56-57
developmental, molecular, 9
Bicuspid brackets for, 517-518
518-519
treatment,
space maintainer, 520 Bandup: arch, twin, 522 Barrer appliance, 526 Basicranium, 54-56
maxillary, 123
"light," 313 lingual,518-519 attachments for, 519
103
asymmetries and tooth position, 241
mandibular,
perimeter maintenance, 363
helices in, 313
bandup, twin, 522 bracket, twin, 522
circumference,
of, 397
in mixed dentition analysis, 238
517-518
of new layers,
after hyalinization, 319 character and orthodontic tooth movement, 320 ,
deposition,
319-
44
developing bony structures at 4 years, 138 formation endochrondral, 39 intramembranous, 39-42 growth displacement, 47, 48 drift, 47-48 endochondral, 40 fields, 44-46
563
Index in mandible,
60
study, comparative anatomy, 43 study, implants for, 43 study methods, 42-44 study with natural markers, 43-44 study, radioisotopes 43
in, 42-
study, vital staining in, 42 in malocclusion, 149-150 marker, tetracycline monkey),42 movement, 9
as (in
remodeling, 45-47 resorption, 44 ridge, interradicular,
ligament,
Cap: sliding, 522 Caries
AP distances,
arch perimeter maintenance and primary teeth, 361 causing arch perimeter changes, 125 malocclusion and, 159
I maloc-
Breath: deep, in examination respiration, 207 Breathers
in space, 256 in deep bite, 425 deformation, 260, 262-263
mouth (see Mouth-, breathing) Breathing method, evaluation, 171 mirror, steel, to check, 208 diagnosis,
in triangles, general assessment of, 280-281 for description, 249 comparison with ideals, 249
48\
in tongue-thrusting after treatment, 549 Cementation: of bands, 517
lateral, 222-226 of malocclusion
of ignoring the patient, 282 of superpositioning, 282 of using chronologic age, 282
Class 1II, 194 with periodontal disease - and tooth loss, 475
flow chart for, 265 form
222
Cephalometer: patient in, 251 Cephalometry, 247-305 of adults, 473 analysis counterpart 263
change, 260 difference in form, 262 persistence of form through time, 262
analysis ratios, -,
breathing) Bruxism, 81 forces of, 308
counterpart analysis ratios, dental horizontal and
Buccal tubes, 517 Buccoversion, 189
counterpart analysis ratios, skeletal horizontal and
vertical,
263
vertical, 263 counterpart, simplified, definition, 263
288
flow chart for, basic, 265 identical means with different variances,
264
with self, 249 with standards,
facial height in (see Face, height) fallacy of false precision, 282 of the "ideal," 282
Cephalography of Activators, 538-539 of cranial base, 63
oblique,
comparison comparison 249
for diagnosis, 249 displacement, 260, 263 equipment for, 250-251
Central tendency: measures of, 13
of
281
curves in, 255-256
stody, good set of, 514
Branchial arches: period of organization of, 19-20 Branchial fistula, 24
c
symmetry,
configurations in, 262 constants, 260 craniofacial constants in, 296-301
maxillary, bite wax placed on, 245
Brain: anterior, lack of development, 23
Calcification
atal axis, 281-282
diagnostic setup, 475 record, 475
in molar uprighting, record, 182, 513
288-292
AP distances, graphs of, 289 assumptions, 281-282 adequacy of one or two planar projections, 282 occlusal position, 281 orientation of the transme-
loss, 475 of,
attached, preformed bands with, 517 for bicuspids, 517-518 for cuspids, 517-518 edgewise, basic, 521 for incisors, 517-518 light-wire, 522 universal, 523
Bumpers: lip, 525, 526 Bypassing, 313
gional, 296 anatomic structures in, 251254
of malocclusion, with periodontal disease and tooth
arch, twin, 522
mouth (see Mouth-,
of stylomandibular 206
diagnostic, 222 good set of, 223
depository, 314-315 resorptive, 314
nasal, differential 207
of permanent teeth, 111-112 of primary teeth, 106 standard~ for teeth, 226
Activators and, 539 of Class n, Division clusion, 193
of,
zygomatic, cephalometry 251, 254 Brackets
requisites of, 264 requisites of individual measures in, 263-264 anatomic dimensions in, re-
Carotid artery: in fetus, 29 Cartilage: condylar, role of, 61 Casts
316
sphenoid, cephalometry 251, 254 wall
misuses of, 282-283
interrelationships with eruption, 112-114
mechanisms of, 44-48 movement, 47-48 rudiments of, 39-48
tensors to show fonI,l. difference, 281 -.variations in, 265-268 future of, 283 geometric methods, 255-263 basic elements, 255-258 of growth, 260-262 analysis of morphology, 269-270 constants, 261 measures, 261 measures along constant rays, 299
two mandibular
registra-
tions of same growth change, 262 history, 250 landmarks bilateral, 258 classification, 256 description of, 256-258 illustration, 257 reliability of, 256 validity of, 256 limitations of, 281-283 lines, 258-259 of malocclusion Class
n, 270-273
Class n, combining horizontal and vertical, 271272 Class n, distribution 272
of,
Class n, flow chart for discrimination of, 270 Class n, horizontal 270-271
type,
Class n, horizontal types, diagnosis, arborization for, 273 Class n, horizontal types, diagnosis, decision tree for, 273 Class n, horizontal types, identification of, 272273 Class Class Class Class Class Class Class Class 271 Class
n, tracings, 276 n, type A, 270 n, type B, 270 n, type C, 270 n, type D, 270-271 n, type E, 271 n, type F, 270 n, types I through n, vertical
5,
type, 271
Class n, vertical types, identification of, 273 Class n, Z-score chart, 274 Class 1II, 273-278, 412 Class 1II, analysis, examples of, 278 Class 1II, analysis of incisal adaptation, 277-278 Class 1II, analysis, profile, 277 Class Ill, analysis, 277
vertical,
Class Ill, archetypes, 278 Class Ill, flow chart for, 277 Class Ill, method, 277-278 Class Ill, variations in form, 277 Class Ill, visualizing treatment objectives, 279
278-
564
lrulex
Cephalometry (cont.) of mandible, 251, 255
description
mandibular position in, effects on profile, 267 of maxilla, 251, 255 measurement how do we measure? 260 what do we do with measures? 263 what do we measure? 260 of morphology, 262 analysis, basic, 265 analysis, basic, illustration of,266
of, 256-258
distance between points, 260 external,
256
implants,~256 intersection of constructed lines, 256 . intersection of edges of regression, 256 at intersection 256
of images,
pairs of points defining lengths of line segments, 260
analysis, basis of, 265
sphenoethmoidal,
analysis for diagnosis, 265 analysis, growth, 266-267, 269-270
triples of points, 260 true anatomic, 256
analysis, method,
265
analysis for prediction of morphology, 268-269 analysis, profile, 267-268 analysis, profile, illustration, 268 analysis, purposes of, 265 analysis for screening, 265 analysis of symmetry, 268 analysis, vertical, 265-267 analysis, vertical, functional,267 analysis, vertical, illustration,267 evaluation of, 265-268 of malocclusion (see malocclusion above) numeric methods, 259-260 why use numbers? 259260 obtaining cephalogram, 251
250-
of open bite, 424 simple, during adolescence, 465 for orthodontic treatment evaluation,
279
general effects, 279 mandible, 279 mandible, changes, 280 maxilla, 279 maxilla, changes, 280 regional effects, 279 after orthognathic 503
surgery,
in orthognathic surgery with orthodontic treatment, 497 pattern, 260 discussion of, 262 plane, 258-259 point(s) change in distance between points, 260 classification, 256
258
for prediction, 249 problems in, 281-283 projection lateral, 251 lateral, typical, 252 oblique, 251, 253 posteroanterior, 251, 252, 258-259 posteroanterior, bilateral structures, 258 posteroanterior, midline structures, 258 purposes of, 249-250 radiographic, 43 regression surfaces, edges of, 256 size, 260-262 of skull of child, 253 in, 262
taking cephalogram, tions in, 251
conven-
tracing, 254 techniques, 255 transversals of surfaces, 256 for treatment planning, 249 for treatment result evaluation, 250 understanding the cephalogram, 263-281 using the cephalogram, 263281 of zygomatic bone, 251, 254 Cervical anchorage,
Chondrocranium: of,31
526
development
Class (see under Malocclusion) Classification: definition, 168 Cleft lip, complete, 24 lip and nose, 23 mandibular, 26 palate, unilateral, 427 Condylar cartilage: role of, 61 Condylion, 258 Congenitally missing .teeth (see Teeth, congenitally missing) Contraction, 189 dentoalveolar, 396-397 appliances for, 397 case analysis, 396 mandibular, 397 mandibular, unilateral or bilateral, during adolescence, 450 maxillary, bilateral, during adolescence, 450 maxillary, unilateral, during adolescence, 450 of maxillary arch, 397 Couple, 311 Cranial anchorage, base
309
anterior, 292, 296, 298
of sphenoid bone, 251, 254 superpositioning
cup, 459, 525 for extra-oral traction,
309
cephalograms of, serial, 63 in Class I1 malocclusion, 398 growth sites in, 55 floor, 296 periosteal surfaces in, 55 vault, 54
asymmetry after orthodontic treatment, 500-501
controlling factors in, natural,51-53 craniofacial anomalies in,
53 ethnic differences
timing of growth, 54 Craniofacial anomalies,
genetic "theory" of, 50 genetics ill, 51 hypotheses, 48-51 hypotheses, Moss, 50 hypotheses, Petrovic's, 50 hypotheses, Scott's, 50 hypotheses, servosystem,
50 hypotheses, Sicher's, 50 hypotheses, sutural dominance, 50 malfunctions in, 53 mandible and, 324 neurotrophism in, 52-53 overall pattern of, 67 principles, diagrammatic representation, 46 racial differences in, 67 temporomandibular and, 324 skeleton
growth "adult,"
rep-
67-68
changing concepts acting as paradigms, 49 concepts in, changing, 51
joint
analysis of, 247-305 development, interaction with orofacial muscles,
94 goals for,
37-72 regional, 53-67 role in ortho38-39
in re:novable appliance, loose, 534 Cranium
426
dysplasia, diagrammatic resentation, 496
in, 67
general body growth and, 52
growth of, growth of, growth of, dontics,
constants in cephalometry, 296-301
skull, cephalometry of, 253 3-year-old, malocclusion traits in, 110 Chin
controlling factors in, disruptive factors, 53 controlling factors in, "function," 52
.growth,54 issues concerning, theoretical and clinical, 54
plete obliteration, Cervical traction, 525 518
factors in, 51-
53
early treatment, 347
craniofacial growth and, 53 'ch,anges in fetus, third to~' •. ninth months, 34
Chain: elastomeric, Children
controlling
current, 50-51 functional, 49 genetic, 48-49 alteration of,
compensatory mechanisms and growth, 54 functions, 54
Cervical cyst, 24 tervical sinus: failure of com24
concepts, concepts, concepts, controlled 322-324
48-
(See also Cranial) at birth, 35 'Crista galli, 258 Crossbite, 423 anterior, simple, 418, 419 acrylic inclined plane extension in, 418 during adolescence, 464
463-
during adolescence, nosis, 463-464 during adolescence, ment, 464
diagtreat-
I
J.
565
Index diagnosis, 418 treatment, 418 buccal, 189 definition, 189 dental appliances for, 396 case analysis, 396 treatment, 396
maxillary ectopic eruption, 386 ectopic with impaction,
dental type, 150,419 dentoalveolar contraction Contraction, dentoalveolar) functional, 150, 392 arch contraction
(see
418
lar first primary, muscular, 150, 392
387
background,
445
of primary dentition, equilibration and Porter lingual appliance for, 393 single-tooth, in periodontics in adult, 488
surgical exposure, 445-446 transplantation, autogenous, 446 treatment,
skeletal (see Dysplasia, skeletal)
442-447
443
diagnosis, treatment,
443 443-445
diagnosis, treatment, Crown
442
thyroglossal,
eruption (see Eruption, cuspid) excellent vertical position after serial extraction, 380 impaction (see Impaction, . cuspid)
cross-sectional, disadvantages derived, 10 direct, 10 ,.
growth (see Growth, data) longitudinal, 10 advantages of, 10-11 disadvantages of, II overlapping, II semi longitudinal , 11 DE space: changes in, 160 Decision tree (see Arborization) Deep bite (see Bite, deep) Dental arch (see Arch) casts (see Casts)
prenatal beginnings, "
94
of
100-104
spatial patterns, IO~~ 105 • primary cuspid interference in, 552 equilibration in, 551-553 radiography of (see under Radiography) relationship to developing bony structures at 4 years, 138 in removable appliance, loose, 533-534 at 6 years, 139
99-146
in young adult, 140-141 teeth,
of lip, upper, 21 mandible, 32
ters, 176 mesiodistal diameters of, 120
of, II
muscles,
defects of unknown origin in malbcculsion, 151 definition, 9
face, maximal, period of, 22 of facial muscles, 32-34
at 9 years, 139 permanent, 119-121 equilibration in (see Equilibration, in permanent dentition) mesiodistal crown diame-
II
31
concepts of, basic, 6-17 of craniofacial skeleton, interaction with orofacial
analysis, modifications, 238-240
period of, 126-140 problems singular to, 360391
advantages of, II
Development, 1-164 behavioral, 10 of chondrocranium,
ectopic, in permanent 118
J31
Data
pressure side, 316 tension and, 317
analysis, illustrative case to show application of, 239
occlusal changes in, 128-
D
conical, as supernumerary tooth, 354 diameter, mesiodistal, permanent dentition, 176
protrusion, bimaxillary, 467 tissue reactions, 315-317
of dentition,
space needs in, 238 occlusal change patterns in, 130
26
tionships during adolescence, 448
analysis of, 179, 235-240 analysis, form for, 236
equilibration in, 553 method for localization
Cyst cervical, 24
(see Contraction,
delay of second bicuspids, 349
analysis, problems with, 240
removal in equilibration, 552 unerupted, probability tables for size prediction, 237
442-443 443
shape anomalies, 355-356 Crozat appliance, 526, 529 Crystallization: of hemoglobin in hyalinized zone, 318 Cup (see Chin cup) Curve of Spee: during adolescence, 435 Cuspid brackets for, 517-518
445
primary, loss of, arch perimeter maintenance in, 362
simple, during adolescence, 442
with orofacial
muscles, 94 mixed
permanent, maxillary, blocked-out, 160
complex, during adolescence, 443-445 definition,
interaction
moving to serve as lateral in- . cisor, 349 occlusion, result assessment, 439
treatment with space supervision, 391
complex
growth on, 59-60 of temporomandibular joint growth on, 66 exchange, two patterns of, 109
transposition, 387 maxillary, impaction during adolescence, 445-446 diagnosis, 445 orthodontic movement, 445-446
Crowding during adolescence,
of nasomaxillary
(see mixed above)
dentoalveolar) diagnosis of lateral malrela-
of mandibular growth on, 66
moving mesially to serve as lateral incisor, 441
161
contraction
analysis, 221-246 development of, 99-146 in young adult, 140-141 diagnostic data for, 222-226 early treatment of, goals for, 347 effects
impaction, treatment, 389 labioversion, with spacing between incisors, 161
lateral, locked, diagnostic setup prior to, 487 lingual, 189 molar loss causing, mandibu-
transitional Dentoalveolar
genetic fields
influencing, 121 Dentin: forming tissues, arrangement of, 102 Dentition
eruption direction, 350 impaction, 387-388 impaction during adolescence (see below )
producing,
maxillary, 393 . of incisor, maxillary,
definition,
development,
interference in primary dentition, 552 loss of, treatment, 351 malposition in malocclusion CIlISs 11, 398
of masticatory muscles, 34 of maxillary complex, 31 nasal fin, 21 nostril floor, 21 of occlusion,
99-146
primary, 108-111 in young adult, 140-141 of oral structures, 26-31 summary, 35 palate bony, 31-32 normal,28 perioral region, 2Q-22 of permanent teeth, 111-121 prenatal dental, 100-105 principles of, 8 of salivary gland, 30-31 study methods, of teeth, 30
10-11
temporomandibular 33
joint, 32,
themes of, 8 complexity, changing, 8 shifts from competent to fixation, 8 shifts from dependent to independent, timing of, 16 of tongue,
8
26
diagram of, 26 Developmental
biology, 9
566
Index
Developmental
events, 7-8
Developmental signs: divisions of,9-1O Diagnosis definition, 168 effect of etiologic classification of malocclusion on, 189-191 Diagnostic setup: for space management, 233-235 Diastema fibroma causing, midline
Elastics, 518 Elastomeric chain, 518
alteration due to pathology primary molar, 116
Electromyography of facultative muscles, 82
bicuspid, 135-140 mandible, 135-140 maxilla, 140
of mandible~ wide open position, 94 of obligate muscles, 82 of orofacial muscles, 77-78 of swallowing, Embryo
210
face developing in, 20 sketches of, 19
159
difficulties,
Emotion: and postural position,
closure of, 474
86
.treatment in adult, 479 Differentiation: definition, 9
Divider method: for measuring from medium raphe to estimate asymmetries of dental arch, 396 Diirer: anatomic drawings from, 250 Dysostosis: mandibulofacial,
25
Dysplasia craniofacial, diagrammatic representation, 496 ectodermal, congenitally missing teeth in, 348 skeletal, 149, 392, 396 classification, 495-496 with mandibular insufficiency, 394-395 open bite and, 214 open bite due to, 422 vertical in Class 11 malocclusion, 398
Ear: in Pierre Robin syndrome, 25
Early treatment (see Treatment, early) Ectodermal dysplasia: missing teeth in, 348
Enlow's
method: to study ground bone sections, 44 Equation, orthodontic, 148-149 elaborated, 149 Equilibration, balancing,
551-557 556-557
in crossbite of primary dentition, 393 cuspid removal in, 552 functional malocclusion, correction, 555
AP
grinding in, 557-558 incisal crowding and, 556 interferences marking of, 554 midline, grinding method, , 554 midlines in, 553
procedure, 553-557 rationale, 553 in primary dentition,
551-553
tapping teeth together in, 553 teaching patient to protrude jaw with midlines coincident, 554
diagram of,
idiopathic failure of teeth to erupt, 383 incisor, 135 l~teral, 360 mandible, 135 maxilla, 135 interrelationships with calcification, 112-114 molar, first, 131-135
permanent, 136 molar, second, 140 of permanent teeth, 112-117 bodily growth and, 117118 ectopic development 118
swallow reflex and, 555
in,
factors affecting, 114-117 factors determining tooth position, 118-119
Equilibrium theory: of forces within masticatory system, 307-308 Eruption,
226-228
stages of, 118 timing, 117 variability in, 117 position of teeth, examination " . of, 175 "~. pr~eocious, of primary teeth, 106 predicting emergence, 228
226-
tables of development, 226 Wainright's rule for, 226228 premature,
383-385
of bicuspid,
of, 177 teeth, 113
in sequence of
eruptions, Esthetics
162
during adolescence, 435 in adult, 473 facial, result assessment, 439-440 in orthgnathic surgery with orthodontic treatment, 497, 503 Ethmocephaly simplex, 23 Ethmoid registration, 300 Ethnicity: cranjofacial growth and,67 Evolutionary changes: longterm, 7 Examination: intra-oral, 222 Examination, orthodontic, cursory, 167-182 appearance evaluation, 170 attitude evaluation 170
169-
in, 169-
available space evaluation, 178
mandible, 131-135 maxilla, 135
sequence of, 117 sequence, favorable, 118 sex differences in, 117
Edgewise mechanism,
through-the-bite, 396
guidance in mal occlusion Class 1I, 399-400
molar grinding in, 552 in permanent dentition, 553557
"slides" into occlusion and, 556
539
ectopic, 385-386
factors regulating, 114-117 normal order of, 117
Ectopic eruption (see Eruption, ectopic) Edgewise bracket, 521
appliance,
383-386
in mixed dentition, 553
retruded contact position, 557-558
Edgewise treatment: full, for Class 11, type 0-2 malocclusion, 453 Elastic
445-
molar, first, permanent, maxillary, 384, 385-386
Ectopic development: in permanent teeth, 118
521
variations
clusion, 157 Endodontics: in malocclusion
protrusive, reasons for checking and grinding, 555
E
symbolization of succedaneous
rangement of, 102 Endocrine disorders: and maloc-
with periodontal disease and tooth loss in adult, 478
sequence of, 228 alterations in, 383-385 disturbances of permanent teeth, 162 examination of, 175
of cuspid, maxillary, 386 of cuspid, maxillary, with impaction, 387 of incisor, mandibular, 386
Enamel forming tissues; ar-
Digital sucking (see Sucking) Distal step protocol, 368-373 Distocclusion (see Malocclusion, Class 11) Distoversion, 189
cuspid, 135-140 mandible, 135-140 maxilla, 140 delayed, 385 during adolescence, 447
in
second, 383
of primary teeth, 106 root ratios and, crown, 227
definition, before the flow chart form for,
168 exam, 169 of, 168 181
head position for, improper, 171 health evaluation, 169-170 instruments for, 169 questionnaire to be filled out by patient or patient's parent, 168 soft-tissue profile examination, 171 Exercise growth and, 12 myotherapeutic (see Myotherapeutic exercises) Exerciser: Nuk Sauger, 545 Extraction in malocclusion with periodontal disease and tooth loss, 479 molar, second in orthodontic 444
treatment,
typical effect of, 382 premature, of primary teeth, 152 serial cephalography
showing
vertical position of cuspids in, 380
I
..•.
567
Index protocol for gross discrepancy problems, 379 records of patients treated by, 381-382 Eye: slant in Treacher Coli ins syndrome,
25
F Face anchorage, 309 anomalies, origin of, 22-26 breadth, 292-296 cartilaginous skeleton in embryo, 32 craniofacial (see Craniofacial) depth, 288-292 measures of, 290-292
examination, 198
morphologic,
organization, summary of, 35 orofacial (see Orofacial) orthopedics, forces in (see Forces) , period of organization of, 1926
25
growth, prenatal, 18-36 height anterior, 284 anterior lower, 284
posterior upper, 284 ratio of lower anterior to total anterior, 286 ratio of posterior mandibu-
maxillary dentoalveolar fective, 290
ef-
maxillary skeletal effective, 290 posterior cranial base effective, 291 mask, 459, 525, 526 midface (see Midface) muscles, 74-75 adaptation to altered mandibular position, 533 development, 32-34 examination, functional, 198
in jaw appliances, in masticatory 308
of,
308-313
system, 307-
abnormal forces, 308
equilibrium 308
theory, 307-
tance, 295 zygomatic coronoid intersect distance, 294
natural forces, inherent, 307 originating from circumoral musculature, 307
Facial Form Analysis, 172 completed, 174 example of, 175 landmarks of, 173 Family pattern, 16 size and growth, 12 Faucial pillars: examination of" 173 Fetus
originating from muscles of mastication, 307 originating 307
branchial,
24
thyroglossal, 26 Fixation: intermaxillary, 324 Flush terminal plane protocol, 368, 372-373 Food: nature of, in malocclusion, 152 Foramen rotundum, 258 Force(s), 306-331 anchorage and (see Anchorage)
within teeth,
vertical, parallelogram 312
of,
Frankel function regulator, 541
539,
Frankfort Plane, 189, 259 horizontal, 85, 259 Frontozygomatic sutures, 258 Fruit drops: sugarless, for tongue correction, 548 Functional appliance (see Appliance, removable, loose)
Gagging, 82-83 Gears: head, 524-525 Genetic changes, long-term, 7 concepts in craniofacial growth, 48-49 control, ubiquitous, modulated by environment, 8 factors in growth, II fields influencing dental development, 121 theory in craniofacial growth,
50 Genetics in congenitally 348
missing teeth,
in craniofacial growth, 51 in malocclusion, 151
lometry, 255-263 basic elements, 255-258
posterior, 323 transverse, 324 of occlusal dysfunction, 308 of occlusion (see Occlusion, force) orthodontic
Gingiva diseases in malocclusion, 159 effects of orthodontic treatment on, long-term, examination of, 173
325
control of, 312-313
excessive
craniofacial growth and, 53 periodontal responses to, 313-322
extensive display, 504-508 hypertrophy, with incisal malalignment, 159 result assessment with, 439
selection of, 312-313 tissue responses to, 313322 tooth movements "
G
Genioplasty, 509 Geometric methods in cepha-
against maxilla anterior, 324
carotid arteries in, 29
craniofacial changes dur'ing,34 radiographic changes during, 34 summary, 36 Fibroma: causing diastema, 159 Finger-sucking (see Sucking) Fingernail biting, 551 malocclusion and, 156 Fistula
tive, 291
parallelogram
tance, upper, 295 molar fossae intersect dis-
tal posterior, 285 vertical distances, 284-288
effective, 290 mandibular skeletal effec-
horizontal, 312
components,
face in, upper, frontal section,21 third to ninth months, 34
length, 290-292 mandibular dentoalveolar
definition, 3 IO effect on rigid free body, 3 IO equivalent systems, 312
equilibrium 308
lar height to total posterior facial height, 286 ratio of total anterior to to-
treated as vectors, 310
of bruxism, 308
lateral point on condyle distance, 294 measures of, 292
external features, examination of, 170-172
posterior, 284 posterior lower, 285
applied, and time to orthodontic tooth movement, 321
upper, frontal section, in fetus, 21 width, 292-296 bigonial distance, 296 condylion distance, 294
measures, graphs of, 293 medial point on condyle distance, 295 molar alveolar crest dis-
measures of, 283
ners, schematic representation, 321 to upper molars, extra-oral, 313
proportions, changes in, 22 reflexes, 80 in Treacher Collins syndrome,
developing in embryo, 20 development, maximal, period of, 22 dimensions, overall, 284-288 esthelics, results assessment, 439-440
anterior upper, 284 growth, graphs of, 287, 288
anterior component of, 119 application to dentition during thumbsucking, 154 orthodontic, various man-
and, 311
strategies for controlling, in clinical practice, 309 therapeutically employed biomechanical, 309 classification, 308-309 natural, 308-309 therapeutically 308
introduced,
during thumb sucking, 308 of tongue-thrusting, 308 on tooth, parallelogram representing, 312 of traumatic occlusion, 308
display, 504
Gingivitis: with hypertrophy and hyperactivity of mentalis muscle, 202 Gold wires: to stabilize mandibular incisors in ancient Gonion, Growth,
Greek skull, 3 258 1-164
adult physique and, 12 arch dimension changes due to, 125 basicranium, 55-56 birth order and, 12 bodily, and eruption of permanent teeth, 117-118 bone (see Bone, growth)
568
Index clinical,
Growth (cont.) cephalometry
of (see Cepha-
lometry of growth) charts, by stature and weight for boys and girls, 170 climate in, 12 concepts of, basic, 6-17 of cranial vault, 54 craniofacial (see Craniofacial growth) of craniofacial skeleton (see Craniofacial skeleton, growth) data evaluation,
II
gathering methods,
10-11
types of, 10 definition, 8-9 evaluation, 16-17 questions to be asked, 1617 reasons for, 16 exercise and, 12 face, prenatal, 18-36 in facial height, graphs of, 287,288 family size and, 12 heredity in, 11 illness and, 12 mandible (see Mandible, growth) muscles, orofacial (see Orofacial, muscles, growth)
I
14
significance of, 16 variables affecting, 11-12 Gum pads: in newborn, 105
H Habits in malocclusion, oral, deleterious,
152-156 correction
of,543-551 Hawley retainers, Head
to molars
improper position for cursory orthodontic examination, 171 support muscles function, 206
normal, spacing as part of, 360
Herbst appliance, 541, 543 Heredity (see Genetic)
normality (see Normality)
Histography: 76
nasomaxillary complex (see Nasomaxillary complex, growth) nutrition in, 11 pattern,
12-13
clinical implications of, 13 contributions to, 12 definition, physical,
12
10
plotted in different ways, 14 psychological disturbance and, 12 race and, 12 seasonal effects on, 12 secular trends in, 12 skeletal, in Class II malocclusion, 399 . socioeconomic factors in, 12 standards, general, I7 study methods, 10-11 temporomandibular joint (see Temporomandibular joint, growth) translation of parts during, in Class II malocclusion, 400 variability in, 13-16
of muscle activity,
History: case, form for, 181 History: of orthodontics, 3-4 Howes' Analysis, 229-233 measurements in, 234 Hyalinization, 317-319 alveolar bone after, 319 crystallization of hemoglobin in hyalinized zone, 318 definition, 318 elimination of damaged tissues, 318-319 in intermaxillary suture (in monkey),61 of palate, 323 periodontal 319
ligament after,
reconstruction of supporting tissues, 319 right, 318 tissue degeneration,
in adult, 480
semi-impacted molar, mandibular second· permanent, 446 Implant in bone growth study, 43 in cephalometry, 256 Impressions, orthodontic, 513515
inferior, 258
Hemoglobin: crystallization of, in hyalinized zone, 318
318-319
Hyperactivity: of mentalis cle, and gingivitis, Hypertrophy: of mentalis cle, and gingivitis, Hypophyseal fossa: floor 258
mus202 mus202 of,
moving maxillary cuspid mesially to serve as incisor, 441
second, 388
upper, good, 515 Incision
Height facial (see Face, height) mandible (see Mandible, height) maxilla (see Maxilla, height) ramus, 297 Helices: in arch wires, 313
maxillary, size variations, 355-356
peg, 479 size diminished,
lower, good, 515
morphology, 206 pain of, 206 tenderness of, 206
maxillary, shape variations, 355-356
387
diagnosis, molar
second, treatment, 389 third, mandibular, 387
530
gears, 524-525 force application and,314
Impaction, 387-391 during adolescence, 445-447 bicuspid, second, 388 cuspid, maxillary, 387-388 with ectopia, 387 treatment, 389
superius, 258 Incisor brackets for, 517-518 central, maxillary anomalously formed, 357 loss of, treatment, 351, 353 spacing between incisors, 357,360 with spade-shaped interosseous tip, 358 cephalometric analysis of incisal adaptation, 277278 crowding and equilibration, 556 eruption (see Eruption, incisor) lateral congenitally absent, midline spacing in maxilla due to, 358 congenitally missing, 358 eruption, 360 maxillary, during adolescence, 440-442 maxillary, congenitally missing, treatment, 349350 " f!1axillary, congenitally- >. "missing, treatment, prognosis, 350 maxillary, goals for, 440 maxillary, loss of, treatment, 351 maxillary, methods for treatment, 440 maxillary, missing, in adult, 474 maxillary, problems with, 440-441
treatment
malalignment with gingival hypertrophy, 159 malposition in mal occlusion Class II, 398 malrelationships, localized, during adolescence, 463465 mandibular ectopic eruption, 386 loss of, treatment, 354 wires stabilizing in ancient Greek skull, 3 maxillary crossbite of, 418 (see Labiover-
labioversion
sion, of incisors, maxillary) in overbite, and arch leveling mechanics, 492 overlap excessive vertical, during adolescence, 464 with periodontal disease and tooth loss, 494 severe, 494 "peg lateral," treatment, 355, 356 position relative to lip and tongue posture, 119 result assessment,
439
primary, and arch perimeter maintenance, 361 spacing after labioversion cuspids,
of
161
Infant, swallowing in, 92-93 retained, 549-550 Infradentale,
258
Infraversion, Ingervall's
189 diagram:
of postural
position, 85 Instruments: for examination, cursory orthodontic, Intercuspation:
169
ideal, 142
Intermaxillary
anchorage,
Intermaxillary
fixation,
J09 324
Intermaxillary suture: hyalinization in (in monkey), 61 Intra-maxillary Intra-oral anchorage,
anchorage, 309
309
569
Index examination,
222
feawres, description 178 Intrusion, 313 "Invisibles," 526, 529
lengtp) Ligament(s) jaw, palpation, 217 periodontal, 320 after hyalinization,
J Jaw appliance (see Appliances, jaw) closure path, 217 ligaments, palpation, 217 movements, 217 'muscles, 75-76, 196-220 palpation, 217 Pierre Robin syndrome, 25 radiography lateral projections, 222 well taken lateral, 224 reflexes, 80-81 relationships, 216 in newborn, 105 registration of, 242-244 registration in pain or limited movement, 218 tooth arrangement in, 141 in Treacher Collins syndrome, 25 treatment,
functional,
re-
sponse to, 399 Joint (see Temporomandibular joint)
Knee spring, 527
craniofacial growth and, 53 in malocclusion, 162 Malocclusion Ackerman-Proffit classifica-
319
calcification
Light wire, 313 bracket, 522 Lingual archwire (see Archwire, \ \
lingual) Lingual locks, 519 Lingual sheaths, 517 Linguoversion, 189 Lip -biting, 551 malocclusion and, 156 bumpers, 525, 526 mandibular, for space supervision, cleft, 23
371
complete, 24 color of, 171 diagnosis, 203
en-
largement, 358 Labioversion, 189
with deep bite in adult, 489-492 diagnosis, 463 treatment, 463 treatment, 417 Labium frenum enlargement, 358 malposition, 358 Landmark (see Cephalometry, landmark) Lateral malrelationships (see Malrelationships, lateral) Learned reflexes, 84 Leeway space arrayed by original occlusion and sex, 127 occlusal status, relationships among, 128
angle system in, 186-188 ' anteroposterior relationships, 189
with balance prufile, 185 before and after treatment, 192 end-to-end protocol, 368 flush terminal plane protocol, 368 labioversion in, treatment, 417
differential,
199-
mesial step cases, space su-
functionally 203
abnormal,
199-
pervision protocol, 369 mesial step protocol, 367368
functionally
inadequate,
199
lower, during swallowing, 210
439
-sucking, 551 malocclusion and, 156 texture of, 171 treatment,
change after, 202
upper anatomically
molar relationship in labioversion, 415-418 syndrome, 192 treatment in adult, 476 Class
n,
187-188,398-410
during adolescence low)
(see be-
alveolar processes in, 400
posture, 170-171 incisor position and, 119 normal, 171 result assessment, strain, 504-508
161 415-
tion system, 191 during adolescence, general characteristics, 434
birth injuries and, 151 bone in, 149-150 caries and, 159 Class I, 186, 187
"plumpers," 525 position, 170-171
L
of cuspids, maxillary, of incisors, maxillary, 418, 463
stylomandibular, of,206
in Pierre Robin
syndrome, 25 Malformations (see Anomalies) Malnutrition
midlip tissue, lack of development,23 normal,200
K
Labial frenum: maxillary,
Macrostomia:
Length face (see Face, length) mandible (see Mandible,
of, 173-
short, 201
appliances for, 400 cephalometry of (see Cephalometry, of malocclusion, Class Il) with deep bite, in adult, 476 diagnosis, differential, 398-399 distal step protocol for, 368-373
development of, 21 Lischer's nomenclature, 189
Division I, 187 Division I, casts of, 193 Division 2, 188
Load: effect of increasing the
"functional"
length of a spring on, 312 Locked molar: mandibular second permanent, ment, 446
treat-
Locks: lingual, 519 Loops: in arch wires, 313
M
features, 399
homeostatic pattern with orthodontic treatment from age eleven, 131 malpositions in, dental and occlusal, 398 morphology 398
in, skeletal,
muscle training in, 400 neuromuscular features, 399,401
Macroglossia:
and spacing, 360
orthopedic
devices in, 400
profile, 185 retrognathic profile and, 185 space supervision 378
in, 376-
surgical translation of parts, 400 syndrome, 191-194 traction, extra-oral, response to treatment, 399 treatment, early, dental aspects, 401 treatment, early, occlusal aspects, 40 I treatment, early, planning differential, 401-402 treatment, early, rationale for, 400-401 treatment, early, skeletal morphology in, 400-401 treatment, general strategies for, 399-400 . treatment, tactics for, 400 type A (See also under Class n during adolescence, type A below) type A, horizontal, complications of treatment, 403 type A, ment, type A, oral, sion,
horizontal, treat402-403 traction for, extraand space supervi402
type B, 406 type B (See also under Class n during adolescence, type B below) type B, horizontal, complications of treatment, 403 type B, horizontal, tion in, 403-406
reten-
type B, horizontal, ment' 403-406
treat-
type B, horizontal, tions in, 403
varia-
type C (See also under Class n during adolescence, type C below) type C, horizontal, complications of treatment, 407 type C, horizontal, tion in, 410 type C, horizontal,
retentreat-
me~r, 407-410 type D, 408-409 type D (See also under Class n during adolescence, type D below) type D, horizontal, complications of treatment, 407 type D, horizontal, tion in, 407
reten-
type D, horizontal, ment, 407
treat-
570
Index
Malocclusion
(cont.)
type D, horizontal, tions, 407, 410
varia-
type C, horizontal, suggested, 455 type D, horizontal, 455
tactics,
syndrome,
452-
tongue posture in, 204 treatment, 416
basic
treatment, early, general strategies, 412
type E (See also under Class n during adolescence, type E below) type E, horizontal, complications of treatment, 410
type D, herizontal, strategies, 452 type D, horizontal, cations, 455
type E, horizontal, tion in, 410
reten-
type D, horizontal, lems, 455
prob-
type E, horizontal, ment, 410
treat-
type D, horizontal, tion, 455
reten-
type F, 404-405 type F (See also under Class n during adolescence, type F below) type F, horizontal, complications of treatment, 403 type F, horizontal, ment, 403
treat-
typical, 194 Z-score chart and arborizaClass
tion, 274 n, during adolescence, 450-455
arborization,
454
background,
450
compli-
type D, horizontal, tactics, suggested, 452-455 type D-2, 453-454 type E, horizontal, 455 type E, horizontal, strategies, 455
basic
type E, horizontal, cations, 455
compli-
type E, horizontal, lems, 455
prob-
type E, horizontal, tion, 455
reten-
type F, horizontal, type F, horizontal, strategy, 451 type F, horizontal, 451
451 basic
treatment strategies, 450 type A, horizontal, 450451
type F, horizontal, 451
tactics,
type A, horizontal, lems, 451
prob-
type A, horizontal, 451
tactics,
type B, horizontal,
452
type B, horizontal, strategy, 452 type B, horizontal, cations, 452
basic
type B, horizontal, lems, 452
prob-
type B, horizontal, tion, 452
reten-
compli-
type B, horizontal, superposed tracings of, 452 type B, horizontal, tactics, 452
vertical analysis, 412 Class III, during adolescence, 455-463 diagnosis, 457 strategies, general, 457 tactics, 457 treatment, differential, 457-463 treatment rationale, 457 classification, 183-192 angle, 185 etiologic, 189-191 purposes of, 184 system, definition,
type E, horizontal tactics, suggested, 455
records,
during adolescence low)
184
systems of, 186-191 systems, limitations of, 195 when to classify, 184-186 clinical entities in, 151-162 developmental defects of unknown origin in, 151 early, subleties of, 346-347 endocrine disorders and, 157 etiologic sites, primary, 151
Class III, 188, 410-415
cephalography
treatment, early, rationale for, 412 treatment, early, tactics for, 412-415 true, 410
diagnosis, differential, 450 rationale for therapy, 450 tactics, 450 treatment, differential, 450
type A, horizontal, basic strategy for, 451 type A, horizontal, complications, 451
194-195
(see be-
of, 194
cephalometry of (see Cephalometry, of malocclusion, Class III)
etiology, swallowing in, 208 food in, nature of, 152 functional correction, 555
AP,
gingival disease in, 159 habits, 152-156
diagnosis, differential, 410 midface deficiency, 411, 412
heredity in, 151
midface deficiency, early treatment, 414, 415
lip-sucking in, 156 malnutrition in, 162
midface deficiency treatment during adolescence, 456
mastication
molar relationship 410
midsagittal plane, 189 mouth-breathing in, 157
in, 185,
morphologic analysis, 412 . neuromuscular type, 413 profile analysis, 412 prognathism, mandibular, 411, 412
type C, horizontal, type C, horizontal, strategies, 455 type C, horizontal, cations, 455
455 basic compli-
pseudo, 410-415
type C, horizontal, lems, 455
prob-
pseudo, early treatment of, 412-414
type C, horizontal, tion, 455
reten-
prognathism, mandibular, early treatment, 414-415
skeletal, 412 skeletal, mandibular
in-
clined plane in, 419
149-
interception of, 345 lip-biting in, 156
mediolateral 189
in, 215 relationships,
nail-biting in, 156 oa~opharyngeal diseases ·~ii~ ". 157-159 neuromuscular system in, 149 neutroclusion, 187 in oral habits, deleterious, 544 orbital plane, 189 periodontal disease in, 159 with periodontal disease in ancient Greek skull, 3 with periodontal disease and tooth loss, 475-494
alignment, anterior, simple problems in, 479-480 appliances in, 478-479 background, 475 diagnostic procedures, essential, 475-478 periapical survey, 475 radiography in, 475 rules for, general, 475 space inadequacy, 485 treatment, periodontal, 478 treatment sequence, 478 treatment strategies, 475 vertical problems in anterior region, 489 vertical problems in, complicated, 493-494 physical agents and, 152 posture and, 156 prevention of., 345 respiratory function disturbance in, 157-159 Simon system, 188-189 soft parts in, 151 systemic diseases in, 156-157 teeth in, 150-151 terminology, 183-192 time factor in, 151 traits in 3-year-old 110
children,
trauma causing, 151-152 prenatal, 151 treatment, flow of questions arising at start of, 333 tumors and, 159 vertical relationships,
189
Malrelationships dental, 392 functional, 392 incisal, localized, during adolescence, 463-465 lateral, during adolescence, 447-450 diagnosis, diagnosis, 448
447-448 dentoalveolar,
diagnosis, 448
neuromuscular,
diagnosis, 448
skeletal,
447-
goals, 448 methods, 448 methods, 448
neuromuscular,
methods,
skeletal,
448
problem background, 447 problem definition, 447 treatment, 448-450 muscular, 392 Mandible anatomic dimensions
in, re-
gional,296 bone growth in, endochondral,60
study of, 15 -, -., ... .. ~ line, 571 259 craniofacial growth 450 and, 324 367 415-418 extraction 363 in orthodontic second 364 simultaneous movement of movement 390 382 muscles 485 205-206 385 450 Maxilla first line tenance and, 362-363 205 for orthodontic maintenance treatment and, 363 first, distal movement of, Molar results assessment, supervision 439 374-375 mesial drift of, 364 treatment, 444 II, 398 in 185, Class 410 III malocclusion, Mastication, Mask: distal, second face, in mesial, adult, and 459, 81 third, in 482 525, adult, 483 526 486 457 353 tion of, 307 adult, 481 matrix, backwards, forward, 64 65 in adult, 483Class 13 ankylosis, 391 I, in labioversion, cence, 446 tenderness, eruption alteration 206 due to adolescence, 448 anterior, 259 loss bilateral, of, effect 450 of, 362 64 studies, 58-59 Maturation: definition, 9389 contraction, dentoalveolar, mandible, first, pathology arch 394 perimeter in, 116 mainfect fusion ercises, at, 543 359 evaluation ism, mandibular) of, 279 in malocclusion, righting, malposition system) permanent Forces, transilatory, 485 in in 215 masticatory malocclusion and molar uping adolescence, reconstruction, rotation, anterior, height impaction inclined, impaction, ment against measures, molar) in 64 285, maxilla) 482-483 adult, during treatment, 492 283 297 484 adolespain loss of, of, 206 early, effects of, relationship anatomic primary mixed) gional, dimensions, 296 reMasseteric Mandibulofacial reflex: dysostosis, (in cat), 86 25 cephalometry eruption, 140 of, 251, 255 nants of, 89 retruded permanent, ment, sitions, contact, 353-354 loss 88 determiof, treateffect unilateral, during on available adolescence 450 space, extraction. typical effect of, impaction, palatal 388 expansion in, 449 band impaction grinding ing osseous forces crossbite, originating in disharmony equilibration, 161 from with ac552 midline, variations mesial in drift imperin Mechanics, 310 mandibular 285, permanent, 298 anosteotomy, width, genitally mandibular, length (see (see 497 59 Impaction, (in Band, missing, (see rat), absent, Forces, molar) (see 90 (see 352 Force, treatMesioversion, Models: of occlusion, 189 mandibular, 142-143 causupper, posterior, topically 259 phy of,94 259 erupting, 384development, 34 mesially lower, asymmetry, uprighting inclined, unilateral, mesially moving durexamination, functional, ·system, lar, first) force in during three types of, 64 length, permanent 59 maxillary, ecMastoid second, mandibular, in vision, masticatory processes, arch ankylosis perimeter 371 258 system) of, within system kylosis of, 447 ular second molars in, forces against adolescence, 456 prognathism protraction sive, and of, pterygoid active and pasposture in myotherapeutic exretruded contact, comparicorpus examination, (see morphologic, (see Malocclusion, (see PrognathDentition, wide open, electromyograMesioclusion Menton, 258 son with intercuspal poMixed three-piece, m second andibular, dentition bicuspid 509 is conwhen Class Ill) adolescence, rect, 10 deficiency, bilateral, rapid Maxillary eruption Metals: joining, 512-513 (see (see Prognathism, Eruption, manmocorrection end-to-end during relationship, space superspace loss of, moving of mandibdeficiency) treatment during adolescence, Midface Class deficiency Ill, treatment during bimaxillary Mesial step protocol, 367-368 with mandibular prognathism Measures: complex, development of (see central Bimaxillary) tendency, of, 31 Measurements: Mean freeway anteroposteriorly, space, of growth, 85 398 indiMaxillomandibular relationship: dibular, with midface distal during movement of, 364448-
Index
572
Index
Molar (cont.) mandibular, movement when first molar is lost, 353 mandibular, uprighting adult, 481
in
permanent mandibular, "locked," treatment of, 446 primary, in occlusion,
109
primary, uneven resorption of, 139 third development,
140-141
developmental position variability, 388 impaction during adolescence, 446 impaction, mandibular, 387 uprighting, 483 upper application of force to, 313 head gears in force application to, 314 uprighting, 480-485 in adult, 480-485
complications, 483 contraindications, 483
in orthognathic 485
480
surgery,
digastric, tendon of (in rabbit),90 early treatment of, goals for, 347 face (see Face, muscles) facultative, 82 activity
head (see Head, support muscles) jaw, 75-76, palpation,
196-220 217 to ten-
hypertrophy and hyperactivity of, with gingivitis, 202 modified oral shield to neck (see Neck, muscles) neuromuscular (see .." Neuromuscular) obligate, 82 electromyographic in, 82
move-
treatment goal, 480 treatment plan, 482 treatment protocol, 482483 with unsuccessful attempt at mesial movement, 487 width changes in, 123 Molecular biology, 9 Moment, 310-311 Moss' hypothesis: in craniofacial growth, 50 Motivation: of adult for orthodontic treatment, 473 Motor abilities: evaluation of, 197-206 Mouth
orbicularis
207
activity
oris, in myothera-
peutic exercises, 543 orofacial (see Orofacial, muscles) portal, 76 pterygoid, 75 in removable appliance, loose, 532-533 striated, tension increase in, 78 temporal, palpation to ascertain swallow activity, 206 training in Class II malocclusion,400 Myodynamic appliance, 539 Myotherapeutic exercises, 542543 limitations,
(See also Oral)
-breathing in alar musculature,
in anchorage, 309 circumoral, in myotherapeutic exercises, 543 in crossbite, 392
train, 537
483
problem, 480 radiography in, 481 rationale for, 480 spring for, 482 with transilatory ment, 485
activity, histography of, 76 alar, and mouth-breathing, 207
malrelationships, 392 of mastication (see Mastication, muscles) mentalis
appliance in, removable acrylic, 480-481 casts in, 481
modifications,
Muscle(s)
electromyographic in, 82 groups, 198-206
542
principles, 542-543 procedures, 543 purposes, 542
N
207
evaluation, sensory, 197-198 in newborn, 105-106
length, relationship sion, 79
appliance in, bracketed, 481
diagnostic setup, 482 with mesial translation,
diagnosis, differential, in malocclusion, 157
concepts of, 13-16 esthetic, 13
Nail-biting, 551 malocclusion and, 156 Nasal
evolutionary, 13 functional, 13 statistical, 13 Nose
(See also Nose)
breathing, differential sis, 207
diagno-
fin, development of, 21 pit, 24 septum, Scott's hypothesis concerning, 50 spine anterior, 256 posterior, 258 suture, frontomaxillary, Nasion
(See also Nasal)
cleft, 23 lack of development,
258
in growth,
57-60
compensatory mechanisms in, 59 effects on dentition and occlusion, 59-60 timing, 59 vertical, 59 issues concerning, clinical, 60 periosteal surfaces in, 58 Nasomaxillary sutural system, 322-324 Nasopharyngeal disease: and mal occlusion , 157 -159 Neck muscles 206
morphology,
206
pain of, 206 tenderness of, 206 strap, 525 throat angle, obtuse, 504-508 Neonate (see Newborn) Neural crest, 23 Neuromuscular diagnosis in lateral malrelationships during adolescence, 448 functions, specific, examina" ~ tion of, 206-216 "'~. system: in malocclusion, 149 Neurotrophism: in craniofacial growth, 52-53 Neutroclusion, 187 Newborn gum pads in, 105 jaw relationship, 105 mouth of, 105-106 tongue posture in, 91 Nipple: Nuk Sauger, 545 Normality
II
o
growth, 57-58 amounts and directions, 58-59
function,
21
nipple, 545 Nutrition:
-sella, 259 Nasofrontal suture, 57 Nasomaxillary complex, displacement in, 58 functions, 57
23
septal structures, 258 Nostril: floor development, Nuk Sauger exerciser, 545
Observations:
in growth data, 10
Occipital anchorage, 309 Occlusal adjustment (see Occlusal
Equilibration) equilibration
(see
Equilibration) Occlusal splints, 529-531 Occlusiol! adaptive mechanisms, 143 . alignment, result assessment, 439 analysis, 221-246 of mal occlusion with periodontal disease and tooth loss, 475-478 in orthognathic surgery with orthodontic treatment, 497, 503 appliances
in mal occlusion
with periodontal disease and tooth loss in adult, 478 centric,
87-88
change(s) expected, 243 patterns in mixed dentition, 130 "protrusive"
pattern of,
computer plot of, 130 in young adult, 141 classification, 178 contact duration of, 87 frequency of, 87 cuspid, results assessment, 439 development of, 99-146 homeostatic patterns "of, 131 in young adult, 140-141 diagnostic data for, 222-226 dysfunction, forces of, 308 early treatment of, goals for, 347
573
Index effects
status, and relationships
of mandibular growth on, 66 of nasomaxillary on, 59-60
/
growth
of temporomandibular growth on, 66
joint
at 8 years, 133 at 11 years, 134 evaluation, in adult, 473 excursive, lateral, checking for occlusal interferences in, 180 force , direction of, 87 magnitude of, 87 functional slide into, extraoral testing for, 180 guidances as active or passive,81 interferences with jaw, 217 during protrusion, for, 180 line
checking
during adolescence, functional, 398
among leeway space, 128 at 10 years, 133 at 13 years, 134 transitional adjustment, terns, of, 130
pat-
in mixed dentition, changes, 128-131 models of, 142-143 molars in second, primary, 109 at 9 years, 133 normal vs. ideal, 142 plan, results assessment,
439
structures, development 26-31
sequence patterns, Oligodontia in adult, 485-489 severe, 490-491 Open bite(s), 422
102-104
178, 189, 420-
adaptive features, 204
of, 424
complex, 421-422 during adolescence, 468 tongue-thrust in, 155,212, 548 treatment, 421-422 definition, 178,420,421
primary disorders,
simple, 421 during adolescence,
future, prediction of, 241242 ideal, procedure for registering, 244 to soft tissue profile, 199 to teeth, 175-178 results assessment, 439 "retrusive" pattern of, 131 at 7 years, 132 at 6 years, 132 stabilization, 326-327
motor skills, evaluation 198
of,
adaptation of, 89-94 adaptation to thumb-sucking, 153 analysis, 196-220 electromyography 78
of, 77-
466
during adolescence, cephalometric tracing, 465
growth of, 89-94 growth, behavioral, 90-94 growth, functional, 90-94
skeleton and dentition, 94 maturation
of, 73-98
movement,
77
treat-
study methods, 77-78
treatment in adult, 493 skeletal, 421-422 during adolescence, 468 treatment, 421-422 treatment in adult, 494 tongue posture in, 156 tongue posture abnormality causing, 551
Orthognathic surgery: historical aspects, 495 Orthognathic surgery with orthodontic treatment case report&, 497 management of cases, 495 referral of cases, 495 selection of patients for, 495 sequence of treatments, 496 timing, 496-497 Orthognathics: molar uprighting in, 485 Orthopedic devices in Class 11 malocclu-
Osteoclast: in resorption of alveolar bone, 314 Osteogenesis, 39-42 Osteotomy Le Fort I, 503 maxillary,
497
three-piece, 509 Overbite, 125-126
incisal, and arch leveling mechanics, 492
during adolescence, ment, 466 in adult, 492-493
posterior, 466 posterior, treatment, 421 retention, in adult, 493
3
study methods, anatomic, 76-77 study methods, behavioral, 78-79
in adult, 492
for dentist in practice, use of book, 5
pressure and, 77 study methods, 76-79
diag-
diagnosis,
growth in, 38-39 scope, 4 studying, problems in, 2-3 for dental student, 2-3
age and, 126 deep, 189 excessive (see Bite, deep)
during adolescence, nosis, 466
anterior, 466 anterior, treatment, 421
3-4
history of, 3-4 purpose of book, 4-5 role of craniofacial skeletal
sion,4oo facial, forces in (see Forces)
force and, 77
growth, structural, 90 . interaction with craniofacial
dysplasia and, skeletal, 214 severe, 550
radiography of (see under Radiography) relationships functional, result assessment, 439
35
tactile perception, plastic geometric figures to test, 198
muscles, 73-98
pre-normal (see Malocclusion, Class Ill)
tions, 108 relations in, 108-110
of,
Orbitale, 258 Orofacial
during adolescence, 468 causative features, 204 cephalometry
muscle, 537
summary,
cap stage, 102 initiation of, 100-102
technics (see Technics, orthodontic) treatment (see Treatment) Orthodontics definition,
correction
Odontogenesis bell stage, 102 bud stage, 102
diagnosis, 420-421 dysplasia causing, skeletal, 422
110-111
(See also Mouth) habits, deleterious, of, 543-551
intraoral (see Intraoral) screens, 535 shields, 535, 536 modified, to train mentalis
position, ideal, 243-244 postnormal (see Malocclusion, Class I1)
development, 108-111 at 5 years, 132 neuromuscular considera-
Opinion: in growth data, 10 Oral
traumatic, forces of, 308 at 12 years, 134 wear of primary teeth, 152 Odontoclasts: root resorption by, 322
with abnormal tongue posture, 205 435
tongue-thrust causing, 547 treatment, 421-422
functional,
physiology, neuromuscular, basic concepts, 79-84 reflexes (see Reflexes, -. . orofacial) -.,.". Orthodontic appliances, fixed, principles of biomechanics in, 310313 equation, 148-149 elaborated, 149 examination (see Examination, orthodontic)
Overjet, 125-126 excessive, 415-418 measurement method,
177
p Pain of head support muscles, 206 jaw relationship registration in, 218 of muscles of mastication, 206 of neck muscles,
206
Palatal line, 259 Palate
forces (see Forces, orthodontic)
bony, development, 31-32 cleft, unilateral, 427 closure, 28, 30
impressions (see Impressions, orthodontic)
development, expansion
normal, 28
574
Index
Palate (cont.) appliance, 520 rapid in bilateral maxillary corpus deficiency, 449 rapid, in early mixed dentition, 397 fusion, 30 relationship to tongue, 27 separating devices, 521 shelves formation and elevation of, 27-28 fusion of, 28 widening in Class II malocc1usion, 400 Perception: oral tactile, plastic geometric figures to test, 198 Periodontal disease with incisal overlap and tooth loss, 494 with malocclusion (see Malocclusion, with periodontal disease and tooth loss) with mal occlusion in ancient Greek skull, 3
Periodontal responses: to orthodontic forces, 313-322 Periodontics crossbite and, single-tooth, adult, 488
in
447
325
Perioral region: development 20-22
of,
56
in cranial floor, 55 in cranial vault, 54 in mandible, 63 in nasomaxillary complex, 58 Permanent record (see Record, permanent) Petrovic's hypothesis: in craniofacial growth, 50 Phagocytosis,
Porter lingual appliance, 393 Porter lingual archwire, 519 Position (see Mandible, position) Positioners (see Teeth, positioners) Posture
Q
second, mandibular
blocked, providing space for, 489
319
Photograph, 226 extra-oral, correct, 225 Physical growth (see Growth) Pierre Robin syndrome, 25 Piezoelectric effect, 317 Plan for treatment (see Treatment plan)
Quantitative measurements: in growth data, 10 Questionnaire: for patient or patient's parent,
elevation of, 384 problems during adolescence, 441 Prenatal
Prognathism bimaxillary, 418-420 during adolescence, 467 mandibular,
151
466,
411, 502
with midface deficiency, complications, 462 with midface deficiency, problems, 462 with midface deficiency, records, 462-463 with midface deficiency, retention, 462-463 after orthodontic treatment, 500 records of, 458-459 records, pretreatment, at start of treatment, progress records, 460.c.461 treatment during adolescence, 457-461 treatment in adults, 477 treatment, early, 414-415 maxillary, 272 Prosthion inferior, 258 superior, 256-258 Protraction, 189 Protrusions bimaxillary, 418-420 dental, 420 functional,
324
fissure, 258
Quad Helix appliance, 397 Quad-Helix lingual archwire, 519,520
body, examination of, 206 malocclusion and, 156 Premolar,
plot of, 130 Psychological disturbance: and growth, 12 Pterygoid length, and active and passive protraction of mandible (in rat), 90 muscle, 75 Pterygomaxillary
with midface deficiency, 462-463
charting, in malocclusion with periodontal disease and tooth loss, 475 effects of orthodontic treat-
Periosteal membranes, Periosteal surfaces
point)
discussion of, 412
deep bite and, in adult, 493
ment on, long-term, result assessment, 440
examples of, 527 "Plumpers:" ~ip, 525 Pogonion, 258 Point (see Cephalometry, Polymorphisms, 102 Pont's Index, 233 Porion, 258
facial growth, 18-36 trauma and malocclusion,
Periodontal ligament, 320 after hyalinization, 319
Periodontitis: juvenile, Periodontium
occlusal interferences during, checking for, 180 "Protrusive" pattern: of occlusal change, computer
Planning (see Treatment, planning) Plates, active, 525, 526
168
R Race craniofacial growth and, 67 growth and, 12 Radiographic cephalometry, 43 Radiography, 222-226 bite-wing, 222 of fetus, third to ninth months, 34 intra-oral periapical survey, 222 jaw projections, lateral, 222 well taken lateral, 224 of mal occlusion with periodontal disease and tooth loss, 475 of molar, for uprighting, 481 occlusal plane projections, 222,224 in orthognathic surgery with orthodontic treatment, 497 panoramic, 222 example of type of, 224 periapical, complete set of, 223 "f2r permanent record, t8i Radioisotopes: in study of bone growth, 42-43 Ramus depth, 291 height, 297 Rankings: in growth data, 10 Ratings: in growth data, 10 Reconstruction: of mandible, 492 Record casts, 513
permanent case history, 181, 182 completion of, 182 record casts, 182 radiography, record of, I ffl< Redirection: functional, 324 Reflex(es) airway, upper, 76 alimentary tract, 76 determinants of mandibular registration 84-89
positions,
facial, 80 jaw, 80-81 learned, 84 masseteric (in cat), 86 orofacial complex, 81-84 simple, 80-81 swallow, an,d equilibration, 555 . tongue, 81 unlearned, 84 Regainers, 525-528 acrylic, split-saddle, 527 coil spring, 365 examples of, 365-367 expansion screw, 366 maxillary plate used for, 367 recurved helical spring, 365 removable acrylic, 366 screw, expansion, 528 sliding yoke, 528 slingshot, 366, 528 split saddle, 365, 527 vacuum-formed, 529 Relapse, 326-327 theorems concerning, I through 10, 326-327 Reliability: of landmark in cephalometry, 256 Remodeling: of bone, 45-47 Resistance: center of, 310 Resorption of permanent teeth, 141 of primary teeth, 107 uneven in second primary molar, 139 Respiration, diagn~sis, 208
207 differential,
207-
examination methods, 207 function disturbance and malocclusion, 157-159 Restorations: in malocclusion with periodontal disease and tooth loss in adult, 478 Restriction: functional, Retainers, 531
324
(See also Regainers) Hawley, 530 Retention, 326-327 theorems concerning, I through 10, 326-327
575
Index Retraction,
189
Retrognathic profile: and Class . n malocclusion, 185 Retrognathism:
mandibular,
272
Retruded contact position, 243 "Retrusive" pattern: of occlusal development, 131 Roentgenography (see Radiography) Root crown ratios, and eruption, 227 development, length
226
mean, by chronologic 113
age,
at moment of emergence through alveolar crest, 113 position, result assessment, 439
440
center of, 311 of mandible (see Mandible, rotation of)
of supernumerary teeth, 354 variations in, 354-356 Sheaths: lingual, 517 Shields, oral, 535, 536 modified, to train mentalis muscle, 537 Sicher's hypothesis: of craniofacial growth, 50 Simon system, 188-189 Sinus: cervical, failure of complete obliteration, Size (see Teeth, size) Skeletal
Analysis, 229, 233
Schwartz appliance, Science
525
divisions of,
normal, changes wrought by new paradigms during scientific revolution, 48 Scott's hypothesis: in craniofacial growth, 50 Screen: oral, 535 Screw: regainer, expansion,
528
be-
crossbite (see Dysplasia, skeletal) responses to loose removable
208-
Semi-impacted molar: mandibular second permanent, 446 Sensory abilities: evaluation of, 197-206 Sex differences in eruption of permanent teeth, 117 emergence of permanent teeth by, 115
problems, 233-235 needs in mixed dentition, localization method for, 238 regainer (see Regainers) relationships to tooth size during mixed dentition, 235-240 supervision, 364-373 Class I molar relationship, 370 in Class
n,
376-378
flush terminal plane protocol, 372-377 with mandibular lip bumper and maxillary utility wire, 371
Spacing, 104, 356-360 during adolescence, 435, 442 between maxillary central incisors, 357~358, 360 in congenitally missing teeth, 356
373
treatment protocol, 373382 maintainers band, 520 band and loop, 362 fixed, technics, 519-521 loop, 520 multiple, 531 multiple, acrylic, 530 in malocclusion with periodontal disease and tooth loss, 485
generalized, 360 during adolescence, localized, 356-357
442
during adolescence,
442
from incisor congenital sence, 358
ab-
problems, percentage of cases showing, 357 as part of normal growth, 360 ., qf small teeth, 360 sucking and, 360 tongue and, large, 360 of unerupted teeth, 356 Speech analysis, 215-216 articulation, mini-test of, 213
Sphenoethmoidal
and, 83-
point, 258
Sphenoid bone: cephalometry of, 251, 254
310
551
spacing and, 357, 360 subclinically significant, 545 thumb- (see Thumb-sucking) Supernumerary
teeth, 121
during adolescence, 442 diagnosis, 354 at midline, 357-358 354
in primary dentition, 354 in variations in size and shape, 354 Supradentale, 256-258 Supramentale, Supraversion,
sucking and, 357 midline
13
Subspinale, 256 Sucking, 152-155,544-546 appliance to correct, 546 clinically significant, 545 intractable, 545-546
treatment, 354 conical crowns,
etiology, 356-357 in permanent tooth premature loss, 356
orofacial physiology 84
Strap: neck, 525 Stress: definition,
lip-sucking, normal,545
type A malocclusion, 402
during adolescence, 435 in adult, 473 result assessment with, 439
ond premolar, 489 gross discrepancy problems, 373
regainer, 527 for uprighting molar, 482 Standard deviation, 13
of boys, 170 of girls, 170 study of, IS Strain, 310
molar rela-
tionship, 374
profile
in arch perimeter, regaining of, 363-364 for blocked mandibular sec-
alignery anterior, 526 auxiliary, 519 correct positioning, 520 effect of increasing the length of a spring on load, 312 knee, 527
in end-to-end
protocol for Class I, 369 with traction in Class n
Sold~ring, 512-513 bracing fingers and hands during, 513 Space
repositioning, 539 Spot welders, 513 Spot welding, 513 Spring(s)
Statistical normality, Stature
Skull: specimen at 8 months, 138
12
Splint diagnostic, 218 occlusal, 529-531
with crossbite treatment, 391
molar correction during, 371
precautions, 382-383 serial extraction protocol in, 379
-nasion, 259
360-383 and symptoms,
appliance, 534-535 Skeleton, craniofacial (see Craniofacial, skeleton)
diagnosis,
Self: comparison with, in cephalometry, 249 Sella, 258 Semantics: of swallowing, 209
24
bases, gross disharmony
growth, Soft tissue
Salivary gland: development, 30-31
developmental, 9-10
shape) diagnosis, '355
Sliding cap, 522 Socioeconomic factors: in
s Sanin-Savara
management, categories, 361
tween, during adolescence, 450
resorption, 321-322 by odontoclasts, 322 orthodontic treatment and, 325-326 result assessment, Rotation, 310
in adult, 478-479
leeway space and, 127 Shape anomalies (see Anomalies,
258 189
Surgery adjunctive, 326 craniofacial growth and, 53 Sutural membranes, 56 Suture frontozygomatic, 258 nasal, frontomaxillary, Swallow activity,
258
temporal muscle pal-
pation to ascertain, 206 checking type of, 172 evaluation in orthodontic examination,
172
reflex, and equilibration, 555 result assessment, 439 retained infantile, 549-550 tongue-thrust,
155
576
Index
Swallowing, 81-82, 208-215 diagnosis of types, differential, 209 electromyography of, 210 examination methods, 209212 in infant, 92-93 infantile behavior in, retained, 212-215 lip during, lower, 210 in malocclusion etiology, 208 misinformation about, 208 requirements of, 82 semantics of, 208-209 tongue in, 154 tongue-thrust swallow, complex,212 treatment goals, 209-212 Symmetrograph: to determine asymmetry in dental arch, 241
T Technics, orthodontic, 511-560 clinical, basic, 513-518 laboratory, basic, 512-513 Teeth absence, 356 multiple, during adolescence, 441-442 anomalies, 228 arrangement in jaws, 141 congenitally missing, 348 during adolescence, 440 causes, 348 diagnosis, 348-349 expression of evolutionary changes in dentition, 348 heredity in, 348 spacing in, 356 treatment, 349-354 development of, 30 analysis, 226-228 stages based on work of Nolla, I11 enlarging in adult, 479 fields, 104-105 force on, parallelogram representing, 312 formation, early stages, 101 groups in malposition, naming, 189 transverse variations, 189 vertical variations, 189 impaction (see Impaction) large, 355 during adolescence, 442 loss arch perimeter changes resulting from, 125 with incisal overlap and periodontal disease, 494
with malocclusion (see Malocclusion, with periodontal disease and tooth loss) treatmentr 351-354 in malocclusion, 150-151 malposed individual, 175 malpositions naming, 189 orthodontic treatment and, 326 measuring gauge for, 236 missing congenitally (see Teeth, congenitally missing) treatment in adult, 480 movement in adult, 479 cusp tip before and after movement, 311 experimental, 315-319 orthodontic (see below) physiologic, 313-315 tipping, 320 types of, 311-312 movement, orthodontic, 315319 applied force and time, 321 character of bone in, 319320 factors influencing, 319321 force application, 320-324 forces and, 311 physiologic activity, 320 translation, 320-321 number, 228, 348-354 e,xaminationof, 174 problems during adolescence, 440-443 occlusal relationships of, 175-178 permanent ankylosed, during adolescence, 446-447 calcification of, 111-112 development of, 111-121 emergence, 115 emergence by age, 115 emergence by sex, 115 eruption (see Eruption, of permanent teeth) loss of, 162, 351-352 loss during adolescence, 441-442 loss of, multiple, 354 loss of, premature, spacing in, 356 missing, 120-121 resorption of, 141 size of, 119-120 supernumerary, 121 position(s), 228
arch dimension asymmetries and, 241 developmental changes in, 129 positioners, 539-541 construction, 540 limitations, 540-541 teeth setup for construction of,541 primary, 106-111 ankylosis, 107-108,388391 anomalies, 107 calcification of, 106 emergence, differences in times of, 107 emergence variability in ages, 106 eruption of, 106 eruption, precocious, 106 formation, average age for critical events in, 106 loss of, arch perimeter maintenance in, 361 loss of, multiple, arch perimeter maintenance in, 363 loss, premature, 159-162 occlusal wear of, 152 resorption, 107 sequence of emergence, 106 shape, 107 size, 107 size, crown, 107 undue retention of, 356357 relationships to skeletal support, 245 separation before bands, 515 method, 515, 516 shape (see Shape) size, 228-240 analysis of Sanin-Savara, 229 diagnosis, 355 examination of, 174-175 osseous bases in, 355 reduction in adult, 479 relationship to supporting structure size, 229-235 " .relationships to available •. space during mixed dentition, 235-240 relationships of groups of teeth, 229 sizes arrayed as deciles, 230-231 supernumerary teeth, 354 variations in, 354-356 variations during adolescence,442 small, 355
during adolescence, 442 spacing of, 360 spacing (see Spacing) stripping for space for blocked mandibular second premolar, 489 succedaneous, eruption of, 113 supernumerary (see Supernumerary teeth) systemic disturbances and, 107 threshold of receptors surrounding, 87 transpositions (see Transpositions of teeth) unerupted, spacing, 356 Temporomandibular joint capsule palpation, 217-218 craniofacial ,growth and, 324 development, 32, 33 dysfunction, 426-427 during adolescence, 468 during adolescence, background, 468 during adolescence, treatment,468 analysis, 216-218 definition, 426 diagnosis, 426-427 treatment, 427 evaluation in adult, 473 functional relationships of, study of, 178-181 functions, 66 analysis, 244-245 after orthodontic treatment, 326 growth, 66-67 effects on dentition and occ1usion, 66 issues concerning, clinical and theoretical, 66-67 mechanisms and sites, 66 guidances active, 89 passive, 89 result assessment, 440 sounds, 217 Tendon: of digastric muscle (in rabbit), 90 Tension active, 79-80 dentoalveolar tissue reactions and, 317 increase in striated muscle, 78 passive, 79-80 relationship to muscle length, 79
total, 79 Tensors: to show form difference, 281 Tetracycline: as bone marker (in monkey),42
577
Index Throat
procedures, 348-427 rationale for, 345-346
cast after, 549
examination
of, 173
neck angle, obtuse, 504-508 Thrusting (see Tongue, -thrusting) Thumb-sucking, 152-155 correction with appliance, 544 force application to dentition in, 154
appliance, extra-oral, 525
Tipping: of teeth, 320 Tongue correction with sugarless fruit drops, 548 development of, 26 diagram of, 26 examination of, 173-174 functional, 203 morphologic, 203 large, and spacing, 360 posture, abnormal, 360, 550551 203-
with open bite, 205 open bite due to, 551 posture and incisor position, 119
524-
definition,
Treacher Collins syndrome, Treatment
posture in newborn, 91 posture in open bite, 156 posture, variations in, 203 reflexes, 81
of adults with good oral health, 473-475 . attitude in, 473
tics, 341-342 paucity of adequate compromising alternative treatment, 342 with orthognathic surgery (see Orthognathic surgery with orthodontic treatment) palliative, 339 plan for adult for orthodontic treatment,
-thrusting, 154-156,546-550 causes, 546 complex, open bite in, 155, 212 complex, open bite due to, 548 diagnosis, 546 forces of, 308 212
treatment, complex thrust, 548-549 complex thrust,
appliance,
25
ment, 497 planning, 332-342 available space, 334-335 available treatments, 335 cephalometry for, 249 common mistakes in, 342 definition, 168 in in in in
changes due to, 125 compromise, 339 definition, 168 dimensional changes during, 124-125
problem, discussion of, 333-334
Unerupted teeth: spacing, Universal appliance, 524 Universal bracket, 523 "U"
principle,
improper, 346 problems, clinical, 348427
156
45
v Vacuum-formed appliance, 526 Vacuum-formed regainer, 529 Validity: of landmark in cephalometry, 256 Valving: articulatory, place and manner of, 213 Variability, 13-16 significance of, 16 Velopharyngeal incompetency, 83 Vestibular appliance (see Appliance, vestibular)
w Wainright's Rule: to predict eruption emergence, 226-228 Weights of boys, 170 of girls, 170 Welders: spot, 513 Welding: spot, 513 Wire archwire (see Archwire) bending of, 512 gold, to stabilize mandibular incisors in ancient Greek skull,3 "light," 313 brackets, 522 twin-wire
appliance,
522-524
selection of cases in gen-
diphasic, 334 early, 334, 343-431 benefits of, 346 difficulties in, 346-347 diphasic, 346 goals for, defining, 347 goals of, misperceptions of, 346
early treatment, 347 permanent dentition, 340 primary dentition, 340 primary dentition, contraindications, 340
159
522-524
u
473-475
in molar uprighting, 482 in orthognathic surgery with orthodontic treat-
diagnosis, 473 illustrative cases, 475 motivation of, 473
in swallowing, 154 tactile signals to, 547
treatment,
of individual patient, 340341 from nature of orthodon-
Transplantation: of cuspid, maxillary, in impaction, 446 Transposition of teeth, 386-387 bicuspid, first, 387 cuspid, maxillary, 387 diagnosis, 386 etiology, 386 treatment, 386-387 Transversion, 189 Traumatic occlusion: forces of, 308
adolescent (see Adolescent treatment)
relationship to palate, 27 result assessment, 439
Twin-wire
limiting factors in, 340-342 of dentist, 341
9
posture in malocclusion, Class Ill, 204
open bite due to, 547 swallow and, complex, treatment, 546-550
treatment planning, 347 understanding, 345-347 unsatisfactory, management, 348 ideal, 338-339 late, 334
in Class 11 type A malocclusion, 402 Translation, 310, 313 tooth movement and, 320321 Translocation:
of,
symptomatic, 339 Tubes: buccal, 517 Tumors: and malocclusion,
satisfactory response to, definition of, 347
chin cup for, 526 in Class 11 malocclusion, 399,400
Thyroglossal ..cyst, 26 fistula, 26
diagnosis,
results, assessment 347-348
visual sigllals to, 547 Tooth (see Teeth) Torsiversion, 189 Traction
cervical, 525 extra-oral, 313
forces during, 308 orofacial muscle adaptation to, 153
differential 205
treatment, simple thrust, 546-548
.,
eral practice, 333-339 skeletal pattern, 334 summarization of plan, 338 timing of, 334 in transitional dentition, 340 protocols, arborization to segregate various protocols, 333 stabilization successful,
of, 339 335-339
z Z-score chart: for Class 11 malocclusion,
274
Zygoma development lack: in Treacher Collins syndrome, 25 Zygomatic bone, cephalometry 254 processes,
258
of, 251,
