Mosbys Orthodontic Review 2e

To review for the ABO clinical exam, please go to the ABO website below:

www.americanboardortho.com/professionals/ clinicalexam/default.aspx.

SECOND EDITION

MOSBY’S

ORTHODONTIC REVIEW Jeryl D. English, DDS, MS

Professor, Chairman, and Program Director Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas

Sercan Akyalcin, DDS, MS, PhD

W. Bonham Magness, D.D.S. Endowed Professor Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas

Timo Peltomäki, DDS, MS, PhD

Professor, School of Medicine University of Tampere Chairman, Oral and Maxillofacial Unit Tampere University Hospital Tampere, Finland

Kate Litschel, DDS, MS Private Practice Woodbridge, Virginia

3251 Riverport Lane St. Louis, Missouri 63043 MOSBY’S ORTHODONTIC REVIEW, SECOND EDITION

ISBN: 978-0-323-18696-4

Copyright © 2015 by Mosby, an imprint of Elsevier Inc. Copyright © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.

International Standard Book Number: 978-0-323-18696-4

Vice President and Publisher: Loren Wilson Executive Content Strategist: Kathy Falk Content Development Manager: Jolynn Gower Senior Content Development Specialist: Brian Loehr Content Coordinator: Sarah Vora Publishing Services Manager: Julie Eddy Project Manager: Jan Waters Design Direction: Margaret Reid

Printed in China Last digit is the print number: 9 8 7 6 5 4 3 2 1

To my orthodontic family—faculty, colleagues, residents, and alumni—for their assistance and encouragement. To my family and especially to my wife, Kathy, whose love, encouragement, and support have helped make this book a reality. —Jeryl D. English To the three most influential women in my life; my mother, my sister, and my better half… —Sercan Akyalcin I want to thank my wife, Sari, and my children, Tuomo, Anna, and Saara, for reminding me that there are values more precious than the field of orthodontics. —Timo Peltomäki I want to show gratitude to my intelligent friend and Teacher, Reverend Wanarathana Kowlwewe for teaching me the true meaning of good work. —Kate Litschel

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Contributors Sercan Akyalcin, DDS, MS, PhD W. Bonham Magness, D.D.S. Endowed Professor Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas

David A. Covell, Jr., DDS, PhD Associate Professor and Chair Department of Orthodontics Oregon Health and Science University Portland, Oregon

David M. Alfi, DDS, MD Department of Dental Surgery Texas Children’s Hospital Houston, Texas

G. Fräns Currier, DDS, MSD, MEd Professor, Program Director, and Chair Department of Orthodontics University of Oklahoma Adjunct Professor of Pediatric Dentistry Chair, Division of Developmental Dentistry Department of Orthodontics and Pediatric Dentistry University of Oklahoma Oklahoma City, Oklahoma

Burcu Bayirli, DDS, MS, PhD Associate Professor Orthodontics University of Washington School of Dentistry Seattle, Washington Barry S. Briss, DMD Past Professor and Chairman Department of Orthodontics Tufts University School of Dental Medicine Boston, Massachusetts Peter H. Buschang, PhD Professor and Director of Orthodontic Research Department of Orthodontics Baylor College of Dentistry Dallas, Texas Thomas J. Cangialosi, DDS Professor and Chairman Department of Orthodontics Rutgers University School of Dental Medicine Newark, New Jersey Winthrop B. Carter, DDS Associate Professor, Director Advanced Specialty Education Program in Periodontics Department of Periodontology Oregon Health and Science University School of Dentistry Portland, Oregon Chun-Hsi Chung, DMD, MS Chauncey M. F. Egel Endowed Chair Associate Professor and Director of Postdoctoral Program University of Pennsylvania School of Dental Medicine Department of Orthodontics Philadelphia, Pennsylvania

Thuy-Duong Do-Quang, DDS, MS Department of Oral Surgery Zahnklinik Schloss Schellenstein Olsberg, Germany Steven A. Dugoni, DMD, MSD Private Practice San Francisco, California Jeryl D. English, DDS, MS Professor, Chairman, and Program Director Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas Jaime Gateno, DDS, MD Professor Department of Surgery, Oral and Maxillofacial Surgery Weill Medical College Cornell University New York, New York Chairman Department of Oral and Maxillofacial Surgery The Methodist Hospital Research Institute Houston, Texas Peter M. Greco, DMD Clinical Professor Department of Orthodontics University of Pennsylvania School of Dental Medicine Philadelphia, Pennsylvania André Haerian, DDS, MS, FRCD(c) PhD Adjunct Clinical Assistant Professor Department of Orthodontics and Pediatric Dentistry University of Michigan Ann Arbor, Michigan v

vi

CONTRIBUTORS

Brody J. Hildebrand, DDS, MS Assistant Clinical Professor Department of Graduate Prosthodontics Baylor College of Dentistry Dallas, Texas International Team for Implantology (ITI) Basel, Switzerland Frank Tsung-Ju Hsieh, DDS, MSD Private Practice Scappoose, Oregon Onur Kadioglu, DDS, MS Assistant Professor Department of Developmental Dentistry The University of Oklahoma Health Sciences Center Oklahoma City, Oklahoma Hitesh Kapadia, DDS, PhD Seattle Children’s Hospital Seattle, Washington Sunil Kapila, DDS, MS, PhD Robert W. Browne Endowed Professor and Chair Department of Orthodontics and Pediatric Dentistry The University of Michigan Ann Arbor, Michigan Chung How Kau, BDS, MScD, MBA, PhD, Morth, RCS (Edin), DSC, RCPS, FFD RCSI (Ortho), FAMS (Ortho) Professor and Chair Department of Orthodontics The University of Alabama at Birmingham School of Dentistry Birmingham, Alabama Richard Kulbersh, DMD, MS Chairman and Program Director Department of Orthodontics School of Dentistry University of Detroit Mercy Detroit, Michigan Kate Litschel, DDS, MS Private Practice Woodbridge, Virginia

James A. McNamara, Jr., DDS, MS, PhD Thomas M. and Doris Graber Endowed Professor of Dentistry Department of Orthodontics and Pediatric Dentistry School of Dentistry Professor Emeritus of Cell and Developmental Biology School of Medicine Research Professor Emeritus Center for Human Growth and Development The University of Michigan Ann Arbor, Michigan Laurie McNamara, DDS, MS Adjunct Clinical Lecturer Department of Orthodontics University of Michigan Ann Arbor, Michigan John Morton Director of Research and Technology Align Technology, Inc. San Jose, California Peter Ngan, DMD Professor and Chair Department of Orthodontics West Virginia University Morgantown, West Virginia Jonathan L. Nicozisis, DDS, MS Private Practice Princeton Professional Park Princeton, New Jersey Faculty and Speaker’s Bureau Member Aligntech Institute Valmy Pangrazio-Kulbersh, DDS, MS Adjunct Professor Department of Orthodontics School of Dentistry University of Detroit Mercy Detroit, Michigan

Steven D. Marshall, DDS, MS Visiting Associate Professor Department of Orthodontics University of Iowa College of Dentistry Iowa City, Iowa

Timo Peltomäki, DDS, MS, PhD Professor, School of Medicine University of Tampere Chairman, Oral and Maxillofacial Unit Tampere University Hospital Tampere, Finland

Kathleen R. McGrory, DDS, MS Clinical Director, Associate Professor Dan C. West Endowed Professor Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas

Stephen Richmond, BDS, MScD, PhD, DOrth, RCS (Edin), FDS, RCS (Eng), FDS, MILT Professor Department of Dental Health and Biological Sciences University Dental Hospital Cardiff University South Glamorgan, Wales

CONTRIBUTORS

Christopher S. Riolo, DDS, MS, PhD Affiliate Professor Department of Orthodontics University of Washington School of Dentistry Seattle, Washington Michael L. Riolo, DDS, MS Associate Professor Orthodontics University of Detroit Mercy School of Dentistry Detroit, Michigan P. Emile Rossouw, BSc, BChD, BChD (Hons-Child-Dent), MChD (Ortho), PhD, FRCD(C) Professor Department of Orthodontics University of North Carolina Chapel Hill, North Carolina Anna Maria Salas-Lopez, DDS, MS Clinical Associate Professor Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas Marc Schätzle, DDS, MS, PhD Assistant Professor, Dr. med. dent., Odont. Dr., MOrtho RSCEd Specialist in Orthodontics Department of Orthodontics and Pediatric Dentistry Center for Dental and Oral Medicine and CranioMaxillofacial Surgery University of Zürich Zürich, Switzerland Kirt E. Simmons, DDS, PhD Clinical Assistant Professor of Surgery Department of Otolaryngology University of Arkansas for Medical Sciences Director, Craniofacial Orthodontics Department of Pediatric Dental Department Arkansas Children’s Hospital Little Rock, Arkansas Karin A. Southard, DDS, MS Professor Emeritus Department of Orthodontics University of Iowa Iowa City, Iowa Thomas E. Southard, DDS, MS Professor and Chair Department of Orthodontics University of Iowa Iowa City, Iowa Larry Tadlock, DDS, MS Private Practice Keller, Texas

John F. Teichgraeber, MD, FACS Professor Division of Pediatric Plastic Surgery Department of Surgery Medical School The University of Texas Health Science Center at Houston Houston, Texas Angela Marie Tran, DDS, MS Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas Terry M. Trojan, DDS, MS Chair and Graduate Program Director Department of Orthodontics University of Tennessee School of Dentistry Memphis, Tennessee Orhan C. Tuncay, DMD, FCPP Former Chairman and Gerald D. Timmons Professor Department of Orthodontics Kornberg School of Dentistry Temple University Philadelphia, Pennsylvania Private Practice Rittenhouse Orthodontics Philadelphia, Pennsylvania James L. Vaden, DDS, MS Professor and Chairman Department of Orthodontics University of Tennessee Memphis, Tennessee Sam A. Winkelmann, DDS, MS Associate Clinical Professor Department of Orthodontics The University of Texas School of Dentistry at Houston Houston, Texas James J. Xia, MD, PhD, MS Professor Department of Surgery, Oral and Maxillofacial Surgery Weill Medical College Cornell University New York, New York Director, Surgical Planning Laboratory Department of Oral and Maxillofacial Surgery The Methodist Hospital Research Institute Houston, Texas

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Preface Orthodontics is an ever-developing and rapidly growing branch of dentistry. Therefore there is a high need for both the training students and practicing professionals to keep pace with the growth of this relatively young specialty. Moreover, orthodontics is a clinically-driven practice with the mentorship model using case studies being one of the most efficient ways to learn. Mosby’s Orthodontic Review is designed to not only have answers to questions regarding what professionals need to know about orthodontics but also to provide a comprehensive understanding of clinical knowledge and excellent patient care. It should be the understanding of the reader that there is no specific “recipe” to use in a given case that makes orthodontics formulated. Malocclusions are composed of many aspects in all dimensions of the space, and all underlying tissues contribute to the complexity of the problem. It is the provider’s ultimate responsibility to collect necessary information and to properly analyze the findings. This will eventually lead to correct diagnosis, well-established treatment goals, and systemized treatment mechanics. I, on behalf of the co-authors, would like to thank our readers for purchasing this textbook. We believe this new edition will provide an excellent review of orthodontic concepts that will help solidify your knowledge on clinical orthodontics and keep the reader up-to-date with new information and technologies.

Who is the intended audience for this book? This book is intended for three different segments of the profession: students and orthodontic residents, general dentists, and orthodontists. Senior dental students that are about to join the dental practice and community will find this textbook very useful as they prepare for the National Board Dental Exam. Orthodontic residents and recent graduates will also benefit from reviewing the text in preparation for the American Board of Orthodontics (ABO) written and clinical examinations. Second, we intend this book to be a good resource for general dentists in their clinical practices and in their discussion of cases with orthodontists. Basic cephalometric radiographs and treatment plans are included so that discussions are easily understood and communicated. Last but not least, experienced orthodontists will be provided updates in clinical issues and technological advancements in our profession.

What is unique about the format of this book? We have chosen to use a question-and-answer format for each chapter. With this format, the reader can quickly focus on a specific area of interest to answer a question, such as the indication for removal of third molars, interpretation of threedimensional images, or how long to wear a bonded lingual 3×3 retainer. Each chapter on treatment or treatment planning viii

is subjective; we wanted expert clinicians to share their thoughts and treatment experiences when correcting various malocclusions. Numerous clinical case reports are presented, incorporating learning around real patient scenarios.

How is this book organized? In organizing this book, we begin with basic foundational information first and then delve into more subjective areas of treatment planning and clinical treatment in the later chapters. Chapter 1 is a review of craniofacial growth and development with current updates based on clinical research. Chapter 2 is a review of the development of the occlusion with a focus on arch development and eruption sequence. Chapter 3 focuses on the appropriate timing for early orthodontic intervention in specific malocclusions. Chapter 4 addresses orthodontic records and case review. Chapter 5 discusses three-dimensional imaging. Chapter 6 emphasizes the diagnosis of orthodontic problems in three tissues (dental, skeletal, and soft tissue) and in three planes of space (anteroposterior, transverse, and vertical). We have included a 3D-3T diagnostic grid to aid in creating a problem list. Diagnosis is objective, but all problems must be listed to avoid something being overlooked. Misdiagnosis is costly when one overlooks or ignores a patient’s problem, such as periodontal disease. We have updated a section on specific objectives of treatment, as well as expanding on superimposition of cephalometric radiographs. In Chapters 7 and 8, basic concepts in orthodontic appliances and biomechanics are discussed. The remaining 18 chapters focus on specific areas of orthodontic treatment; these areas are subjective and depend on both the training and experience of the clinician. Areas addressed in these chapters include the Invisalign system, minor tooth movement, implants, hygiene, craniofacial deformities, and more.

What is on the accompanying website? Sample cases can be viewed on the ABO website under the Clinical Examination section by visiting www.americanboardortho. com/professionals/clinicalexam/default.aspx. These cases represent the latest updates for cases required by the ABO.

Who are the contributors and why were they asked to participate? Because we are targeting both general dentists and orthodontists for this book, we asked some of the very best clinicians and educators to write chapters. We also included younger faculty members so that their perspectives could be included. These authors understand the needs of prospective students and residents, as well as what information the practicing professional will find useful.

It has been challenging to select the chapter topics and to sequence them in a meaningful manner. Writing a book or a chapter in a book demands a great deal of time from the contributors. We appreciate their hard work, especially when faced with publisher deadlines. We are extremely pleased with the contributions to this book. We expected more than was reasonable and got more than we expected.

PREFACE The efforts of these authors are clear in their dedication to clinical excellence. Jeryl D. English Sercan Akyalcin Timo Peltomäki Kate Litschel

ix

Note from the Editor I would be remiss if I did not thank Adriana Cavender and Gloria Bailey for their help in typing and formatting the chapters. I would also like to thank the people at Elsevier, especially Brian S. Loehr and Sarah L. Vora for their advice and professionalism. This book would not have come to fruition without the contributions and support of my co-authors, Dr. Akyalcin and Dr. Peltomäki. I am dedicated to contributing to the education of dental students, orthodontic residents, general dentists, and orthodontists, and I am confident that this book will serve as an excellent teaching resource on orthodontic diagnosis and treatment. Jeryl D. English

x

Contents 1

Craniofacial Growth and Development, 1

15

Peter H. Buschang

2

Development of the Occlusion, 14

G. Fräns Currier

16

Timo Peltomäki

3

Appropriate Timing for Correction of Malocclusions, 24 Chun-Hsi Chung and Steven A. Dugoni

4

Orthodontic Records and Case Evaluation, 36 Jeryl D. English, Thuy-Duong Do-Quang, and Anna Maria Salas-Lopez

5

Three-Dimensional Imaging in Orthodontics, 53 Diagnosis of Orthodontic Problems, 60 Jeryl D. English, Larry Tadlock, Barry S. Briss, and Kate Litschel

7

17

8

Biomechanics in Orthodontics, 112

18

Treatment Planning, 120 James L. Vaden and Terry M. Trojan

10

Treatment Tactics for Problems Related to Dentofacial Discrepancies in Three Planes of Space, 137 Burcu Bayirli, Christopher S. Riolo, and Michael L. Riolo

11

19

12

The Invisalign System, 154

20

21

14

Class III Correctors, 186 Peter Ngan

Orthodontics and Craniofacial Deformities, 271 Kirt E. Simmons

22

Temporomandibular Disorders, 286 Peter M. Greco

23

Retention and Relapse in Orthodontics, 293 Sercan Akyalcin, Hitesh Kapadia, and Jeryl D. English

24

Soft Tissue Diode Laser Surgery in Orthodontics, 302 Kathleen R. McGrory, Sam A. Winkelmann, and Angela Marie Tran

25

Secrets in Computer-Aided Surgical Simulation for Complex Craniomaxillofacial Surgery, 309 James J. Xia, Jaime Gateno, John F. Teichgraeber, and David M. Alfi

Treatment of Class II Malocclusions, 164 Richard Kulbersh and Valmy Pangrazio-Kulbersh

Oral Hygiene: Possible Problems and Complications, 263 David A. Covell, Jr., Winthrop B. Carter, and Frank Tsung-Ju Hsieh

Orhan C. Tuncay, Jonathan L. Nicozisis, and John Morton

13

Vertical Dimension and Anterior Open Bite, 250 Thomas J. Cangialosi

Phase I: Early Treatment, 145 Laurie McNamara and James A. McNamara, Jr.

Skeletal Anchorage in Orthodontics, 235 Onur Kadioglu, Brody J. Hildebrand, and Marc Schätzle

André Haerian and Sunil Kapila

9

Adult Interdisciplinary Orthodontic Treatment, 220 Valmy Pangrazio-Kulbersh

Orthodontic Appliances, 98 P. Emile Rossouw

Phase II: Nonsurgical Adolescent and Adult Cases, 206 Steven D. Marshall, Karin A. Southard, and Thomas E. Southard

Chung How Kau and Stephen Richmond

6

Minor Tooth Movement, 198

26

Three-Dimensional Update on Clinical Orthodontic Issues, 329 Sercan Akyalcin

xi

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Craniofacial Growth and Development

C HA P T ER

1

Peter H. Buschang

C

linicians require a basic understanding of growth and development in order to accurately perform diagnoses. According to the World Health Organization, growth and development are among the best measures available of individuals’ health and well-being. Knowledgeable clinicians understand that general somatic growth provides important information about their patients’ overall size, maturity status, and growth patterns. Because the timing of maturity events, such as the initiation of adolescent or attainment of peak growth velocity, is coordinated throughout the body, information derived from stature or weight—noninvasive and relatively easily obtained measures—can be applied to the craniofacial complex. In other words, the timing of peak height velocity (PHV) can be used to estimate the timing of peak mandibular growth velocity. Knowledge of general somatic growth is also useful when evaluating the size of patients’ craniofacial dimensions. An individual’s height and weight percentiles provide reliable measures of overall body size, against which craniofacial measures can be compared. For example, excessively small individuals (i.e., below the fifth percentile in body size) might also be expected to exhibit excessively small craniofacial features. Finally, the reference data available for somatic growth and maturation are based on large representative samples, making them more generally applicable and more precise at the extreme percentiles than available craniofacial reference data. Postnatal craniofacial growth is a complex, but coordinated and ongoing process that clinicians must understand in order to properly plan treatments and evaluate treatment outcomes. The cranial structures are the most mature, followed by the cranial base, maxillary, and mandibular structures, which are the least mature and exhibit the greatest growth potential. Knowledge about a structure’s relative growth is important because it serves, along with heritability, as an indicator of its response potential to treatment and other environmental influences. The fact that the mandible is the least mature structure helps to explain why it is the component of the craniofacial complex most often affected in individuals with Class II or Class III skeletal discrepancies. It is essential that clinicians understand that the maxilla and mandible, the two most important skeletal determinants of malocclusion, follow similar growth patterns. Both are displaced anteriorly and, especially, inferiorly; both tend to rotate forward or anteriorly; both rotate transversely; and both respond to displacement and rotation by characteristic patterns of growth

and cortical drift. It is also useful to understand that patients should be expected to adapt skeletally to orthodontic, orthopedic, and surgical interventions, and that the adaptations mimic growth patterns exhibited by untreated patients. Perhaps most importantly, clinicians must understand the tremendous therapeutic potential that the eruption and drift of teeth provide. The maxillary molars and incisors, for example, undergo more eruption than inferior displacement of the maxilla, making them ideally suited for controlling vertical and anteroposterior (AP) growth. Clinicians also often do not appreciate that adults show many of the same growth patterns exhibited by children and adolescents, simply in less exaggerated forms. It has been well established that craniofacial growth continues through the 20s and 30s, and perhaps beyond. Skeletal growth of adults appears to be predominantly vertical in nature, with forward mandible rotation in males and backward rotation in females. The teeth continue to erupt and compensate depending on the individual’s growth patterns. Adults also exhibit important soft-tissue changes; the nose grows disproportionately and the lips flatten. Vertical relationships between the incisors and lips should also be expected to change with increasing age. Finally, malocclusion must be considered as a multifactorial developmental process. Although genes have been linked with the development of Class III and perhaps Class II division 2 malocclusions, the most prevalent forms of malocclusions are largely environmentally determined. Equilibrium theory and the notion of dentoalveolar compensations provide the conceptual basis for understanding how closely linked tooth positions are with the surrounding soft tissues. Such an understanding makes it possible to predict the types of compensations that occur. For example, compensations explain why the development of malocclusion is associated with various habits, assuming the habits are of long enough duration. In fact, anything that alters mandibular posture might be expected to elicit skeletal and dentoalveolar compensations. This explains why individuals with chronic airway obstructions develop skeletal and dental malocclusions that are phenotypically similar to malocclusions associated with weak craniofacial musculature; both populations of patients posture their mandibles similarly and undergo similar dentoalveolar and skeletal compensations. Based on the foregoing, the following questions are intended to provide a basic—although only partial—understanding of growth and development and its application to clinical practice. 1

CHAPTER 1 • Craniofacial Growth and Development

2

1. At what ages do most children enter adolescence, and when do they attain peak height velocity? The adolescence growth spurt starts when decelerating childhood growth rates change to accelerating rates. During the first part of the growth spurt, statural growth velocities increase steadily until PHV is attained. Longitudinal assessments provide the best indicators of when adolescence is initiated and PHV is attained. Studies of North American and European children1 show that girls are advanced by approximately 2 years compared with boys in the age of initiation of adolescence and age of PHV. Based on the 26 independent samples of girls and 23 samples of boys, the average ages of PHV are 11.9 and 14.0 years, respectively. Girls and boys initiate adolescence at 9.4 years and 11.2 years, respectively. Maximum adolescent growth velocity in body weight usually occurs 0.3 to 0.5 year after PHV (Fig. 1-1).

2. What is the mid-childhood growth spurt, and how does it apply to craniofacial growth? The mid-childhood growth spurt refers to the increase in growth velocity that occurs in some, but not all, children several years before adolescence. Mid-childhood growth spurts in PHV Boys 7 6

Frequency

5 4

2 1 13.4 13.5 13.6 13.7 13.8 13.9 14 14.1 14.2 14.3 14.4

A

Age PHV Girls 6

Frequency

5 4 3 2 1 0

B

3. Which skeletal indicators are most closely associated with peak height velocity? According to Grave and Brown,9 PHV in males and females occurs slightly after the appearance of the ulnar sesamoid and the hooking of the hamate, and slightly before capping of the third middle phalanx, the capping of the first proximal phalanx, and the capping of the radius. According to Fishman’s10 skeletal maturity indicators, capping of the distal phalanx of the third finger occurs less than 1 year before PHV, capping of the middle phalanx of the third finger occurs just after PHV, and capping of the middle phalanx of the fifth finger occurs less than 1 ⁄2 year after PHV. Based on the cervical vertebrae, PHV occurs between cervical vertebral maturation stage CS3 (concavities on the inferior borders of the second and third vertebrae, and both the third and fourth vertebrae are either trapezoid or rectangular horizontal in shape) and CS4 (concavities on the inferior borders of the second, third, and fourth vertebrae, and both the third and fourth vertebrae are rectangular horizontal in shape).11

4. What is the equilibrium theory of tooth position?

3

0

stature and weight have been reported to occur between 6.5 and 8.5 years of age; they tend to occur more frequently in boys than girls.2,3 Based on yearly velocities, mid-childhood growth spurts have been demonstrated for a variety of craniofacial dimensions—also between 6.5 and 8.5 years of age— occurring simultaneously or slightly earlier for girls than boys.4–7 Applying mathematical models to large longitudinal samples, Buschang and colleagues8 reported mid-childhood growth spurts in mandibular growth for subjects with Class I and Class II molar relationships at approximately 7.7 years and 8.7 years of age for girls and boys, respectively.

11.4 11.5 11.6 11.7 11.8 11.9

12

12.1 12.2

Age

FIG 1-1 Frequency distribution of 26 sample ages of PHV for boys (A) and girls (B). (From Malina RM, Bouchard C, Beunen G: Human growth: selected aspects of current research on well-nourished children, Ann Rev Anthropol 17:187-219, 1988.)

Although Brodie12 was among the first to identify the relationship between muscles and tooth position, it was Weinstein and colleagues13 who experimentally established that the teeth are maintained in a state of equilibrium between the soft-tissue forces. Based on a series of experiments, they concluded that: 1. The forces (produced naturally or by orthodontic appliances) exerted on the crowns of teeth are sufficient to cause tooth movements. 2. Each tooth may have more than one stable state of equilibrium. 3. Even small forces (3 to 7 gm), if applied over a long enough period, can cause tooth movements. Proffit,14 who revisited the equilibrium theory 15 years later, noted that the primary factors involved were the resting pressures of the lips, cheeks, and tongue, as well as the eruptive forces produced by metabolic activity within the periodontal membrane. He further noted that extrinsic pressures, such as habits and orthodontic forces, can alter dentoalveolar equilibrium, provided that they are sustained for at least 6 hours each day. Proffit14 also identified head posture and growth displacements/rotations as secondary factors determining equilibrium. As the mandible rotates, the incisors move and dental equilibrium is reestablished. Björk and Skieller,15 for example,

Craniofacial Growth and Development • CHAPTER 1

have shown an association between changes in lower incisor angulation and true mandibular rotation (e.g., the greater the true forward mandibular rotation, the greater the lower incisor proclination).

The best direct epidemiologic evidence comes from the National Health Survey,16,17 which evaluated approximately 7400 children between 6 and 11 years of age and over 22,000 youths 12 to 17 years of age. Unilateral and bilateral distoclusion occurred in approximately 16.1% and 22.7% of Caucasian children and 7.6% and 6.0% of African-American children, respectively. Comparable prevalence among Caucasian youths was 17.8% and 15.8%, and 12.0% and 6.0% among AfricanAmerican youths. Based on overjet measurements provided by the National Health and Nutrition Examination Survey (NHANES) III, Proffit and associates18 estimated that the prevalence of Class II malocclusion (overjet ≥ 5 mm) decreases from over 15.6%, for youths 12 and 17 years of age, to 13.4% for adults. They also showed that Class II malocclusion is more prevalent among African-Americans (16.5%) than Caucasians (14.2%) and Hispanics (9.1%).

6. What is the prevalence of incisor crowding among individuals living in the United States, and how does it change with age? According to the initial NHANES III data,19 incisor irregularities increase from an average of 1.6 mm for children 8 to 11 years, to 2.5 mm for youths 12 to 17 years, to 2.8 mm for adults 18 to 50 years of age. Although incidences are similar at the youngest age, African-American youths and adults show significantly less crowding than Caucasians and Hispanics. Based on the complete NHANES data set, including 9044 individuals between 15 and 50 years of age, approximately 39.5% of US adults have mandibular incisor irregularities ≥ 4 mm and 16.8% have irregularities ≥ 7.20 Adult males tend to show greater crowding than females; Hispanics show greater crowding than Caucasians, who in turn display greater crowding than African-Americans. Based on the available data for untreated subjects followed longitudinally, rates of crowding increase precipitously between 15 and 50 years of age, especially during the late teens and early 20s (Fig. 1-2).20

7. What is the prevalence of Class III dental malocclusion among adolescents and young adults living in the United States? Worldwide prevalence of Class III malocclusion has been estimated to be 6.8%, with higher prevalence in Southeast Asia (15.8%) and the Middle East (10.2%), than Europe (4.9%) and Africa (4.6%).21 Based on the National Health Surveys16,17 conducted on large samples of children and adolescents during the 1970s, which evaluated the subjects’ molar relationships, approximately 4.9% of children 6 to 11 years of age and 6% of adolescents 12 to 17 years of age have bilateral Class III malocclusion. Based on overjet measurements provided

4

3 Millimeters

5. What is the prevalence of Class II dental malocclusion among adolescents and young adults living in the United States?

3

2

1

0

8 to 11

18 to 50

12 to 17 Age Whites

Blacks

Hispanics

FIG 1-2 Average mandibular alignment scores; US persons, 1988-1991. (Adapted from Brunelle JA, Bhat M, Lipton JA: Prevalence and distribution of selected occlusal characteristics in the US population, 1988-1991, J Dental Res 75[special issue]:706-713, 1996.)

by the NHANES III, approximately 4.9% of Caucasians, 8.1% of African-Americans, and 8.3% of Mexican-Americans have Class III malocclusion. Importantly, the majority (> 75%) of cases presents with mild (overjet = 0 mm) Class III malocclusions.

8. Skeletally, are Class III dental malocclusions primarily a problem of maxillary or mandibular growth? Although the maxilla alone and the two jaws combined have both been shown to contribute to Class III skeletal discrepancies, the mandible has most often been cited as the primary determinant.22–24 In their large cross-sectional study of 848 Class III’s from 6 to 16 years of age, Reys and colleagues25 showed that the sagittal position of the maxilla at all age intervals was normal, whereas the sagittal position of the mandible was abnormal and the mandibular dimensions were larger. Sugawara and Mitani26 came to similar conclusions. Most recently, Wolfe and colleagues,27 who followed Class III’s longitudinally between 7 and 15 years, verified that the AP position of the maxilla and the changes in AP position over time were the same as in Class I dental malocclusions; the growth differences were in the mandible. Corpus length increased significantly more over time and the mandible became more divergent in Class III dental malocclusions than Class I dental malocclusions.

9. Do the third molars play a role in determining crowding? Although third molars have been related with crowding,28–31 most contemporary studies show little or no relationship. In 1979 a National Institutes of Health (NIH) conference came to the consensus that there is little or no justification for extracting third molars solely to minimize present or future crowding of the lower anterior teeth.32 Ades and co-workers33 found no differences between subjects whose third molars were impacted, erupted in function, congenitally absent, or


4

extracted at least 10 years before post-retention records were taken. Sampson and colleagues34 also showed no differences in crowding between subjects whose third molars have erupted completely or partially, remained impacted, or were missing. A randomized controlled trial that followed 77 patients for 66 months showed a 1.0 mm difference in anterior crowding between patients whose third molars had and had not been removed; the authors concluded that removal of third molars to reduce or prevent late crowding cannot be justified.35 Based on the NHANES data, individuals who had erupted third molars displayed significantly less crowding than those who did not have erupted third molars.20

10. Does horizontal or vertical mandibular growth affect crowding? Based on the notion that the lower incisors are carried into the lower lip as the mandibe “grows forward,” late mandibular growth has been suggested as a major contributor to postretention crowding.36 Although incisor compensation to backward mandibular rotation has been demonstrated,15 crowding as a result of anterior growth displacements remains to be established. However, changes in lower incisor crowding have been shown to be related to vertical growth. Both treated and untreated patients who undergo greater inferior growth displacements of the mandible, and associated greater eruption of the lower incisors, show greater crowding than those who undergo less vertical growth and less eruption.27,38 Supporting the idea that growth predisposes patients to crowding, Park and coworkers showed that adolescents undergo more postretention crowding than similarly treated adults.39 Since vertical mandibular growth continues well beyond the teen years, patients would be well advised to wear their retainers into their early and mid-20s.

11. How much should the maxillary and mandibular incisors and molars be expected to erupt during adolescence?

12. How does untreated arch perimeter change between the late primary dentition and the permanent dentition? Based on a centenary curve extending between the mesial aspects of the first molars,42 arch perimeter increases during the early mixed dentition and decreases during and after the transition to the permanent dentition. Maxillary perimeter increases 4 to 5 mm between 6 and 11 years of age and decreases 3 to 4 mm between 11 and 16 years. In contrast, mandibular arch perimeter increases approximately 2 to 3 mm initially and then decreases 4 to 7 mm, with greater decreases in females than males (Fig. 1-3).

13. How do untreated maxillary and mandibular intermolar widths change during childhood and adolescence? Bishara and colleagues43 reported that intermolar widths increase 7 to 8 mm between the deciduous dentition (5 years of age) and the early mixed (8 years of age) dentitions, and an additional 1 to 2 mm between the early mixed and early permanent (121⁄2 years of age) dentitions, with little or no sex differences. Between 6 (first molar fully erupted) and 16 years of age, Moyers and colleagues42 showed greater increases for males than females for both maxillary (4.1 versus 3.7 mm) and mandibular (2.6 versus 1.5 mm) intermolar widths. Based on a sample of 26 subjects followed longitudinally between 12 and 26 years of age, DeKock44 reported no significant change for females and only slight increases (1.4 and 0.9 mm for maxilla and mandible, respectively) in intermolar width for males (Fig. 1-4).

80

69

78

67 Millimeters

Millimeters

Based on natural structure superimpositions, the maxillary first molars and central incisors erupt approximately

5 to 6 mm and 4.5 to 5 mm, respectively, between 10 and 15 years of age.40 In contrast, the mandibular molars and incisors erupt 3 to 5.5 mm and 2.5 to 4.5 mm, respectively. Males showed greater eruption than females for both the maxillary and mandibular teeth. Also using natural structure superimpositions, Watanabe and colleagues41 demonstrated that the rates of eruption were greater in males than females, attaining peak velocities at approximately 12 and 14 years of age for females and males, respectively.

76 74

A

63 61

72 70

65

6

7

8

9

10 11 12 13 Chronologic age Male

14

Female

15

16

59

B

6

7

8

9

10

11

12

13

14

Chronologic age Male

Female

FIG 1-3 Maxillary (A) and mandibular (B) arch perimeters between 6 and 16 years of age. (Adapted from Moyers RE, van der Linden FPGM, Riolo ML, McNamara JA Jr: Standards of human occlusal development. Monograph #5, Craniofacial Growth Series, Center for Human Growth and Development, University of Michigan, Ann Arbor, Michigan, 1976.)

15

16

Craniofacial Growth and Development • CHAPTER 1 48

46

46

44 Millimeters

Millimeters

44 42 40 38

A

5

42 40 38

6

7

8

9


14

15

16

36

B

6

7

8

9

Female


14

15

16

Female

FIG 1-4 Maxillary (A) and mandibular (B) intermolar widths between 6 and 16 years of age. (Adapted from Moyers RE, van der Linden FPGM, Riolo ML, McNamara JA Jr. Standards of human occlusal development. Monograph #5, Craniofacial Growth Series, Center for Human Growth and Development, University of Michigan, Ann Arbor, Michigan, 1976.)

14. Without treatment, how do maxillary and mandibular arch depths change during childhood and adolescence? Maxillary and mandibular arch depths, midline distances between the incisors and a line drawn tangent to the distal crown of the deciduous second molars or their permanent successors, show different growth patterns over time. Maxillary arch depth increases 1.4 and 0.9 mm in males and females, respectively, during the eruption of the permanent incisors.45 Mandibular arch depth shows little change over the same period. With the loss of the deciduous molars, maxillary arch depth decreases 1.5 and 1.9 mm, whereas mandibular arch depth decreases 1.8 and 1.7 mm in males and females, respectively.45 Based on subjects with normal occlusion, Bishara and co-workers43 showed increases (1.1 to 2.8 mm) in maxillary and mandibular arch depths between the deciduous and early mixed dentitions; between the mixed and early permanent dentition, maxillary arch depths increased only slightly (0.5 to 0.7 mm) and mandibular depths decreased 2.6 to 3.3 mm (Fig. 1-5). DeKock44 reported decreases (approximately 3.0 mm) in arch depth between 12 and 26 years of age, with rates diminishing over time.

15. How do untreated maxillary and mandibular intercanine widths change over time? During the transition from the deciduous to permanent incisors, mandibular intercanine width increases approximately

3 mm.45 Maxillary intercanine width also increases during that transition, and then again (approximately 1.5-2.0 mm) with the emergence of the permanent canines; mandibular intercanine widths decrease slightly after the emergence of the permanent canine.45 Bishara and co-workers43 reported similar—albeit somewhat smaller—increases in maxillary and mandibular intercanine widths between the deciduous and early mixed dentition; maxillary intercanine width increased 2-2.5 between the early mixed and early permanent dentitions; mandibular widths changed only slightly between the late mixed and early permanent dentitions. Intercanine widths of children followed by the University School Growth Study, Michigan,42 increased approximately 3.0 mm between 6 and 9 years of age; maxillary widths increased an additional 2.5 mm with the emergence of the permanent canines (Fig. 1-6).

16. What differences exist in intermolar widths between subjects with normal and Class II malocclusion? Lux and colleagues46 reported that maxillary intermolar widths were significantly smaller in subjects with Class II division 1 malocclusion than subjects with Class II division 2, Class I malocclusion and normal occlusion. The narrow maxillary arch of division 1 subjects was apparent at 7 years of age and persisted through 15 years of age. Bishara and co-workers’43 comparisons also showed that the differences between maxillary and mandibular intermolar widths were larger in subjects with normal occlusion than in their Class II division 1 counterparts.

Millimeters

37 35 33 31 29 27

11

13

Male-Mx

15

17 Female-Mx

19 Age

21

23

Male-Md

25

27 Female-Md

FIG 1-5 Maxillary (Mx) and mandibular (Md) molar arch depths between 11 and 27 years of age. (Adapted from DeKock WH: Am J Orthod 1972;62:56-66.)

CHAPTER 1 • Craniofacial Growth and Development 35

30

33

28 Millimeters

Millimeters

6

31 29 27 25

A

26 24 22

6

7

8

9

10 11 12 Chronologic age Male

13

14

15

Female

16

20

B

6

7

8

9


14

15

16

Female

FIG 1-6 Maxillary (A) and mandibular (B) intercanine width between 6 and 16 years of age. (Adapted from Moyers RE, van der Linden FPGM, Riolo ML, McNamara JA Jr. Standards of human occlusal development. Monograph #5, Craniofacial Growth Series, Center for Human Growth and Development, University of Michigan, Ann Arbor, Michigan, 1976.)

Comparing arch shape of subjects with Class I and Class II malocclusions, Buschang and colleagues47 showed that subjects with Class II division 2 malocclusion have the shortest and widest maxillary arches, whereas subjects with Class II division 1 had relatively longer and narrower maxillary arches.

17. Which craniofacial structures might be expected to be the least mature and show the greatest relative growth between 5 and 17 years of age? Differences in the relative growth of the craniofacial structures have long been established. Hellman,48 who was among the first to quantify relative growth, showed that cranial widths are consistently more mature than cranial depths, which are in turn more mature than cranial heights. Until the 1970s, growth of the splanchnocranium and neurocranium was categorized based on Scammon’s49 typology and was thought to follow either a general (i.e., somatic) or neural pattern. Baughan and co-workers50 introduced three distinct growth patterns: a cranial pattern for the cranium and cranial base, a facial pattern for the maxilla and mandible, and a general pattern for the long bones of the body. Buschang and colleagues51 demonstrated that the craniofacial complex is actually integrated between Scammon’s neural and general growth curves. Accordingly, relative craniofacial growth and maturation cannot be neatly categorized; it follows a developmental gradient moving from the more mature measures, such as head height (B-Br; the most mature that they evaluated) through anterior cranial base (S-N), posterior cranial base (S-B), maxillary length (ANSPNS), upper facial height (N-ANS), corpus length (Go-Gn), and ramus height (Ar-Go). After 9 to 10 years of age, ramus height is actually less mature than stature; it has approximately 10% of its growth remaining in boys 151⁄2 years of age (Fig. 1-7).

18. What sex differences exist in facial heights during infancy, childhood, and adolescence? Anterior and posterior facial heights are 3% to 5% larger in males than females between birth and 5 years of age.52 Facial

heights are 1% to 10% larger in males than females during childhood and adolescence. Sex differences during childhood are small but statistically significant.53,54 Differences decrease slightly as females enter their adolescent phase of growth and then increase substantially after males enter adolescence. Male and female ratios of total anterior facial height to total posterior facial height remain similar throughout childhood and adolescence (Fig. 1-8).

19. What sex differences exist in mandibular size and position during infancy, childhood, and adolescence? During the first 5 years of life, males have significantly larger mandibles than females, with sex differences increasing from 3% to 5% during the first year to 9% to 13% by age 5.55 During childhood, males continue to exhibit significantly larger overall mandibular size (Co-Pg) than females, primarily due to increased corpus length (Co-Pg). Sex differences in ramus height (Co-Go) during childhood are smaller and increase through adolescence.53,54 Sex differences in the Y-axis (N-S-Gn), the gonial angle (Co-Go-Me), and mandibular plane angles (S-N/ Go-Me) are not statistically significant during childhood or adolescence (Fig. 1-9).

20. What craniofacial features characterize the morphology of hyperdivergent (skeletal open-bite) patients? Compared with patients with Class I normal occlusion, hyperdivergent patients display decreased posterior-to-anterior face height ratios, smaller upper-to-lower facial height ratios, small ramus heights, larger anterior heights, as well as increased mandibular, gonial, and palatal planes.56–60 Associated with increased lower face heights and steeper mandibular plane angles, patients with hyperdivergent tendencies demonstrate excessive dentoalveolar heights, especially in the maxilla.29,58,59,61,62 Children 6 to 12 years of age with high mandibular plane angles undergo significantly less true and apparent forward rotation than children with low mandibular plane angles.63


100%

7

100

b–br 90

90%

Relative size

s–n

ans–pns 80

80%

s–b n–ans

go–gn 70

70% ar–go

Stature

60%

5.5

7.5

9.5

11.5

13.5

15.5

Chronologic age

FIG 1-7 Relative (percentage of adult) size of seven craniofacial measures and stature for boys 41⁄2 to 151⁄2 years of age. (Adapted from Buschang PH, Baume RM, Nass GG: A craniofacial growth maturity gradient for males and females between 4 and 16 years of age, Am J Phys Anthrop 61:373-381, 1983.)

Difference (mm)

10 8 6 4 2 0 5

6

7

8 N-Me

9

10

11 12 Age (yrs)

N-ANS

13

14

S-Go

15

16

17

18

S-PNS

FIG 1-8 Sex differences (male minus female) in facial heights. (Modified from Bhatia SN, Leighton BC: A manual of facial growth: a computer analysis of longitudinal cephalometric growth data, New York, 1993, Oxford University Press.)

21. Which aspects of the maxilla and mandible undergo an adolescent growth spurt? Treatments are often planned based on whether or not patients are approaching, or have attained, their maximum growth. This is one of the reasons why adolescence is commonly thought

to be an optimal time to treat. As such, it is important to understand that growth spurts do not occur in the AP positions of either the maxilla25,64,65 or the mandible.65–68 In other words, the chin does not undergo an anteriorly directed growth spurt. However, the vertical aspects of both maxillary65,68,70 and mandibular25,65,68,69 growth exhibit adolescent spurts with peaks. Peak maxillary growth velocities are usually attained more

8

CHAPTER 1 • Craniofacial Growth and Development 10

Difference (mm)

8 6 4 2 0 2

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Age (yrs) Co-Pg

Go-Pg

Co-Go

FIG 1-9 Sex differences (male minus female) in mandibular size. (Modified from Bhatia SN, Leighton BC: A manual of facial growth: a computer analysis of longitudinal cephalometric growth data, New York, 1993, Oxford University Press.)

than 6 month before peak mandibular velocities.65 The maxilla tends to peak before PHV,70 whereas the mandible peaks after PHV.71,72

22. How much change is expected in the anteroposterior maxillomandibular relationships of Caucasians during adolescence? The University of Michigan’s mixed-longitudinal study of untreated subjects54 showed improvements of maxillomandibular skeletal relationships between 10 and 15 years of age; the ANB angle decreases 1 to 1.1 degrees and the A-N-Pg angle decreases 3 to 3.1 degrees. Adolescents followed by the Philadelphia Center for Research in Child Growth73 demonstrated a decrease of 1.3 and 3.6 degrees for ANB and N-A-Pg angles, respectively, in males; these two measures decreased less than a degree in females between 10 and 15 years of age. The growth study conducted by King’s College School of Medicine and Dentistry in London56 showed a 0.5- to 0.8-degree decrease of ANB and 2 to 3 degrees of decrease of N-A-Pg between 10 and 15 years of age. Untreated FrenchCanadian males and females between 10 and 15 years show 0.6- and 0.2-degree decreases of the ANB angle, respectively.74 Although the average changes are small, individual variation is large, with approximately 30% and 26% of 10-year-olds classified as prognathic and retrognathic, respectively, changing to orthognathic by 15 years of age. Similarly, approximately 30% of those who are orthognathic at 10 years of age become either prognathic or retrognathic at 15 years.74

23. Does the mandible undergo transverse rotation like the maxilla? If so, how are the two related? Björk and Skieller75 showed that posterior maxillary implant widths increased approximately 0.4 mm/year between 4 and 20 years of age. This compares well with the findings of Korn and Baumrind,76 who reported increases of 0.43 mm/year in the posterior-most region of the maxilla for children 81⁄2 to 151⁄2 years of age. Korn and Baumrind76 were also the first to

document transverse widening of the mandible based on metallic bone markers; they showed that the mandible widened 0.28 mm/year or approximately 65% as much as the maxillary. Gandini and Buschang,77 who evaluated 25 subjects 12 to 18 years of age with bone markers in both jaws, showed significant width increases between the posterior maxillary (0.27 mm/year) and mandibular (0.19 mm/year) bone markers. For every 1 mm that the maxillary width increased, mandibular width increased 0.70 mm. Iseri and Solow,78 who followed children annually from 8 to 16 years of age, also reported bilateral width increases of the mandibular body in all subjects. Annual rates decreased from 0.34 mm/year at the younger ages to 0.11 mm/year at 15, demonstrating a clear age effect.

24. Does the glenoid fossa change its position during postnatal growth? Inferior and posterior displacement of the glenoid fossa should be expected to occur along with growth at the spheno-occipital synchondrosis, elongation of the posterior cranial base, and associated displacement of the temporal bone.79 Using articulare as a surrogate measure of the glenoid fossa, Björk80 reported that the distance between the fossa and nasion increases 7.5 mm between 12 and 20 years of age. Based on superimpositions performed on naturally stable cranial base reference structures of 118 children and 155 adolescents, Buschang and Santos-Pinto81 demonstrated that the glenoid fossa was displaced 0.45 to 0.53 mm/year posteriorly and 0.25 to 0.45 mm/ year inferiorly, with greater displacements during adolescence than childhood.

25. How much and in what direction should condylion and gonion be expected to grow and remodel during childhood and adolescence? The condyle grows superiorly and slightly posteriorly, whereas gonion drifts superiorly and posteriorly in approximately equal amounts. Björk and Skieller’s15 implant studies showed that, depending on the type of true rotation that occurs, the c ondyle


is capable of growing in both anterior (forward rotators) and posterior directions (backward rotators). Also using metallic implants for superimposing, Baumrind and colleagues8/2 demonstrated that the condyle grows predominantly in a superior (2.5 mm/year) and slightly posterior (0.3 mm/year) direction between 81⁄2 and 151⁄2 years of age; gonion drifts superiorly (0.9 mm/year) and posteriorly (1.0 mm/year) at similar rates. Using naturally stable mandibular reference structures for superimpositions, Buschang and Santos-Pinto81 reported 2.3 to 2.7 mm/year superior and 0.2 to 0.3 mm/year posterior growth of the condyle for large samples of children 6 to 15 years of age. Peak adolescent condylar growth velocities approximated 3.1 mm/year (at 14.3 years) and 2.3 mm/year (at 12.2 years) for males and females, respectively.83

26. How does the bony chin remodel during childhood and adolescence? Relative to metallic bone markers inserted into the mandible, each of the 21 cases evaluated by Björk and Skieller15 demonstrate stability (i.e., lack of modeling) of the cortical region located slightly above pogonion. The remainder of the mandible’s external surface models, with both the type and amount of modeling depending on the individual’s rotational pattern. On average, there is vertical bone growth associated with the eruption of the teeth; the anterior cortical region demarcated vertically by infradentale and inferiorly by the incisor apex undergoes resorption (but this is highly variable), and the cortical bone below the pogonion and below the symphysis is depository.82 The same modeling patterns are evident when the mandible is superimposed on naturally stable reference structures.84 The lingual surface of the symphysis undergoes substantially greater amounts of bony deposition than the anterior or inferior surfaces.

27. At what age might the craniofacial sutures be expected to start closing? The age at which sutures begin to close is variable and depends largely on how closure is measured. Todd and Lyon85 were among the first to evaluate sutural closure. Based on a series of 514 male skulls, they described the closure based on gross examination of the ectocranial and endocranial

surfaces. They showed that closure begins at approximately the same time on both surfaces, but that ectocranial closure progresses more slowly. Gross examination of 538 male and 127 female skulls demonstrated that the cranial sutures can start closing as early as the late teens or as late as over 60 years of age.86 By the early 30s or 40s, most people can be expected to show signs of sagittal, coronal, and lambdoid suture closure. Behrents and Harris87 identified remnants of the premaxillary-maxillary suture in 50 skulls and showed that the facial aspect of the suture was already closed in children 3 to 5 years of age. Using stained sections from 24 subjects, Persson and Thilander88 reported that closure of the midpalatal and transverse sutures can begin as early as 15 years of age but can be delayed in some individuals into the late 20s or early 30s. Based on histological and microradiographic evaluations of growth activity, Melsen89 showed that the midpalatal sutures showed evidence of growth through 16 years of age in girls and 18 years of age in boys. Kokich’s90 histological, radiographic, and gross examinations of 61 individuals showed no evidence of bony union of the frontozygomatic suture before 70 years of age (Table 1-1). While sutures become more complex during childhood and adolescence, they show little change in adults.91 Even though they start closing in adults, only relatively small portions (3-7%) of the sutures exhibit true fusion.91,92

28. How much do lip length and thickness change during childhood and adolescence? Subtelny93 showed that upper and lower lip lengths increase similarly (approximately 4.5 mm) and progressively between 6 and 15 years of age. After full eruption of the central incisors, the vertical relationship of the maxillary incisor and upper lip is maintained through 18 years of age. Vig and Cohen,94 who measured upper and lower lip heights relative to the palatal and mandibular planes, respectively, reported increases of approximately 5 mm for the upper and 9 mm for the lower lip between 5 and 15 years of age. Subtelny93 also showed that increases in lip thickness were considerably greater in the vermilion regions than in the regions overlying skeletal structures. During the first 18 years of life, upper lip

TABLE 1-1 Estimated Ages for the Initiation of Sutural Closure REFERENCES Todd and Lyon Todd and Lyon66 Todd and Lyon66 Todd and Lyon66 Todd and Lyon66 Todd and Lyon66 Sahni et al.67 Sahni et al.67 Sahni et al.67 Behrents and Harris68 Persson and Thilander69 Melsen70 Kokich71 66

9

SUTURE

AGE OF MALES

AGE OF FEMALES

Sagittal and sphenofrontal Coronal Lambdoidal and occiptomastoid Sphenoparietal Sphenotemporal, maso-occipital Squamosal, parietomastoid Sagittal Coronal Lambdoid Premaxillary-maxillary Midpalatal and transpalatal Midpalatal and transpalatal Frontozygomatic

22 24 26 29 30-31 37 31-35 31-35 41-45 3-5 20-25 15-16 80s

N/A N/A N/A N/A N/A N/A 41-45 31-35 31-35 3-5 20-25 17-18 80s

10


thickness at Point A increased approximately 7.8 and 6.5 mm in males and females, respectively. Nanda and colleagues95 showed that upper lip length (Sn-Stoupper) increased 2.7 mm (males) and 1.1 mm (females) between 7 and 18 years of age; lower lip length (ILS-Stolower) increased 4.3 mm in males and 1.5 mm in females.

29. Does the soft-tissue facial profile change during childhood and adolescence? The changes that occur depend on whether or not the nose is included when measuring the soft-tissue profile. Subtelny93 reported that total facial convexity (N′-Pr-Pog′) decreased 5 to 6 degrees between 6 and 15 years of age; soft-tissue profile (N′-Sn-Pog′) showed little or no change over the same time period. Bishara and colleagues96 showed that the angle of total facial convexity (Gl′-Pr-Pog′) decreased approximately 7 degrees between 6 and 15 years of age. In contrast, the angle of facial convexity, which does not include the nose, maintained or increased slightly.

30. How does the nose change shape during childhood and adolescence? It was originally reported that the “hump” on the nasal dorsum develops during the adolescent growth spurt93 and that nasal shape changes were due to the elevation of the nasal bone.97 Similar types of shape changes actually take place during childhood (6 to 10 years) and adolescence (10 to 14 years).98 The upper portion of the dorsum rotates upward and forward (counterclockwise) approximately 10 degrees between 6 and 14 years of age. The lower dorsum shows both downward and backward (clockwise) and upward and forward (counterclockwise) rotation, depending on the relative vertical/horizontal growth changes of the midface.98 Changes in the nasal dorsum are more closely associated with angular changes of the lower dorsum than of the upper dorsum.

31. According to present evidence, when does growth of the craniofacial skeleton cease? Behrents99 reported both size and shape changes in adults. Based on 70 distances and 69 angular measures, he showed growth changes after 17 years of age for 91% of the distances and 70% of the angular measures evaluated. Eighty percent of the distances and 41% of the angles showed growth changes after 30 years of age; 61% and 28% of the distances and angles, respectively, showed growth changes after 35 years of age. Lewis and Roche,100 who evaluated 20 adults followed between 17 and 50 years of age, showed that cranial base lengths (S-N, Ba-N, Ba-S) and mandibular lengths (Ar-Go, Go-Gn, Ar-Gn) attained their maximum lengths between 29 and 39 years of age, after which they shortened slightly.

32. How does the mandible rotate during adulthood? Behrents99 reported that the mandible rotates in a counterclockwise manner in adult males and clockwise in adult

females, with associated compensatory alterations of the dentition. He also showed that the Y-axis (N-S-Gn) decreases slightly in males and does not change in females. Relative to the pterygomaxillary (PM) vertical, the mandible comes forward in adult males (approximately 2 mm) but not in females. The mandibular plane angle (S-N/Go-Gn) decreases in males and increases in females. Behrents also showed greater posterior vertical development of the mandible in adult males than adult females. Bishara and colleagues101 showed that adult males 25 to 46 years of age undergo greater increases of SNB and S-N-Pg than females, whereas females undergo significant increases of N-S-Gn. Forsberg and colleagues102 reported an increase (0.3 mm) of the mandibular plane angle in males and females between 25 and 45 years of age.

33. What generally happens to the nose during adulthood? The nose develops substantially during adulthood, with the tip growing forward and downward an average of 3 mm after 17 years of age.99 Individual adults can exhibit much greater amounts of nasal growth. Males display significantly more nasal growth than females. Formby and colleagues103 showed that nose height increases 0.6 mm, nose length increases 1.7 mm, and nose depth increases 2.3 mm between 18 and 42 years of age. Between 21 and 26 years of age, Sarnas and Solow104 demonstrated 0.8- to 1.0-mm increases in nose length.

34. What generally happens to the upper lip length during adulthood? Upper lip length increases 0.5 to 0.6 mm between 21 and 26 years of age.104 Over the same period, upper incisor display (Sto-OPmax) decreases slightly (0.3 mm) in males and does not change in females. Formby and colleagues103 showed that upper lip length increases 0.8 to 1.7 mm and upper incisor display (lip to incisal edge) decreases 1.0 mm between 18 and 42 years of age. Behrents99 demonstrated that upper lip length (ANSSto) increases significantly in both males (2.8 mm) and females (2.2 mm), whereas the maxillary incisor to palatal plane distance increases only 0.06 to 0.08 mm after 17 years of age, thereby supporting an even greater decrease in upper incisor display.

35. How does the soft-tissue profile change during adulthood? Sarnas and Solow104 showed that the soft-tissue profile angle (including the nose) increased (0.3 degree) in males and decreased (0.4 degree) in females between 21 and 26 years of age. Behrents99 provides the best longitudinal data demonstrating a straightening and flattening of the soft-tissue lip profile during adulthood. The lips become substantially less pronounced with increasing age.99,101,102 The perpendicular distances of the upper and lower lips relative to the soft tissue plane decreased approximately 1 mm in adults; angular changes indicate approximately 4- to 6-degree flattening of the lips.99


REFERENCES

1. Malina RM, Bouchard C, Beunen G: Human growth: selected aspects of current research on well-nourished children, Annu Rev Anthropol 17:187–219, 1988. 2. Tanner JM, Cameron N: Investigation of the mid-growth spurt in height, weight and limb circumference in single year velocity data from the London 1966-67 growth survey, Ann Hum Biol 7:565–577, 1980. 3. Gasser T, Muller HG, Kohler W, et al: An analysis of the midgrowth and adolescent spurts of height based on acceleration, Ann Hum Biol 12:129–148, 1985. 4. Nanda RS: The rates of growth of several facial components measured from serial cephalometric roentgenograms, Am J Orthod 41:658–673, 1955. 5. Bambha JK: Longitudinal cephalometric roentgenographic study of the face and cranium in relation to body height, J Am Dent Assoc 63:776–799, 1961. 6. Ekström C: Facial growth rate and its relation to somatic maturation in healthy children, Swed Dent J (Suppl 11), 1982. 7. Woodside DG, Reed RT, Doucet JD, Thompson GW: Some effects of activator treatment on the growth rate of the mandible and position of the midface. In Transactions 3rd International Orthodontic Congress, St Louis, 1975, Mosby, pp 459–480. 8. Buschang PH, Tanguay R, Demirjian A, et al: Mathematical models of longitudinal mandibular growth for children with normal and untreated Class II, division 1 malocclusion, Eur J Orthod 10:227–234, 1988. 9. Grave KC, Brown T: Skeletal ossification and the adolescent growth spurt, Am J Orthod 69:611–624, 1976. 10. Fishman LS: Radiographic evaluation of skeletal maturation, Angle Orthod 52:88–112, 1982. 11. Baccetti T, Franchi L, McNamara Jr. JA: The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics, Semin Orthod 11:119–129, 2005. 12. Brodie AG: Muscular factors in the diagnosis, treatment and retention, Angle Orthod 23:71–77, 1953. 13. Weinstein S, Haack DC, Morris LY, et al: On an equilibrium theory of tooth position, Angle Orthod 33:1–26, 1963. 14. Proffit WR: Equilibrium theory revisited: factors influencing position of the teeth, Angle Orthod 48:175–186, 1978. 15. Björk A, Skieller V: Facial development and tooth eruption: an implant study at the age of puberty, Am J Orthod 62:339–383, 1972. 16. Kelly JE, Sanchez M, Van Kirk LE: An assessment of occlusion of the teeth of children 6-11 years. DHEW publication no. (HRA) 74-1612, Washington, DC, 1973, National Center for Health Statistics. 17. Kelly JE, Harvey C: An assessment of the teeth of youths 12 to 17 years. DHEW publication no. (HRA) 77-1644, Washington, DC, 1977, National Center for Health Statistics. 18. Proffit WR, Fields Jr. HW, Moray LJ: Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES III survey, Int J Adult Orthod 13:97–106, 1998. 19. Brunelle JA, Bhat M, Lipton JA: Prevalence and distribution of selected occlusal characteristics in the US population, 1988-1991, J Dent Res 75(special issue):706–713, 1996. 20. Buschang PH, Schulman JD: Incisor crowding in untreated persons 15-50 years of age: United States, 1988-1994, Angle Orthod 73:502–508, 2003. 21. Hardy DK, Cubas YP, Orellana MF: Prevalence of angle class III malocclusion: a systematic review and meta-analysis, Open J Epidemiol(p 2):75–82, 2012. 22. Sanborn RT: Differences between the facial skeletal patterns of class II malocclusion and normal occlusion, Angle Orthod 25:208–222, 1955.

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23. Jacobson A, Evans WG, Preston CB, Sadowsky PL: Mandibular prognathism, Angle Orthod 66:140–171, 1975. 24. Mackey F, Jones JA, Thompson R, Simpson W: Craniofacial form in Class III cases, Br J Orthod 19:15–20, 1992. 25. Reyes BC, Baccetti T, McNamara Jr. JA: An estimate of craniofacial growth in class III malocclusion, Angle Orthod 76:577–584, 2006. 26. Sugawara J, Mitani H: Facial growth of skeletal Class III malocclusion and the effects, limitations and long-term dentofacial adaptations to chincap therapy, Semin Orthod 3:244–254, 1997. 27. Wolfe SM, Araujo E, Behrents RG, Buschang PH: Craniofacial growth of Class III subjects six to sixteen years of age, Angle Orthod 81:211–216, 2011. 28. Bergstrom K, Jensen R: Responsibility of the third molar for secondary crowding, Sven Tandlak Tidskr 54:111–124, 1961. 29. Janson GR, Metaxas A, Woodside DG: Variation in maxillary and mandibular molar and incisor vertical dimension in 12 year old subjects with excess, normal, and short lower anterior facial height, Am J Orthod 106:409–418, 1994. 30. Vego L: A longitudinal study of mandibular arch perimeter, Angle Orthod 32:187–192, 1962. 31. Kaplan RG: Mandibular third molars and postretention crowding, Am J Orthod 66:411–430, 1974. 32. Judd WV: Consensus development conference at the National Institutes of Health, Indian Health Service Dental Newsletter 18:63–80, 1980. 33. Ades AG, Joondeph DR, Little RM, Chapko MK: A long-term study of the relationship of third molars to changes in the mandibular dental arch, Am J Orthod Dentofacial Orthop 97:323–335, 1990. 34. Sampson WJ, Richards LC, Leighton BC: Third molar eruption patterns and mandibular dental arch crowding, Aust Orthod J 8:10–20, 1983. 35. Harradine NW, Pearson MH, Toth B: The effect of extraction of third molars on late lower incisor crowding: a randomized controlled trial, Br J Orthod 25:117–122, 1988. 36. Proffit WR, Fields Jr. HW: Contemporary orthodontics, ed 3, St Louis, 2000, Mosby. 37. Alexander JM: A comparative study of orthodontic stability in Class I extraction cases, Dallas, Texas, 1996, Thesis, Baylor University. 38. Driscoll-Gilliland J, Buschang PH, Behrents RG: An evaluation of growth and stability in untreated and treated subjects, Am J Orthod Dentofacial Orthop 120:588–597, 2001. 39. Park HJ, Boley JC, Alexander RA, Buschang PH: Age-related long-term posttreatment occlusal and arch changes, Angle Orthod 80:247–253, 2010. 40. McWhorter K: A longitudinal study of horizontal and vertical tooth movements during adolescence (age 10 to 15), Dallas, Texas, 1992, Thesis, Baylor College of Dentistry. 41. Watanabe E, Demirjian A, Buschang PH: Longitudinal posteruptive mandibular tooth movements of males and females, Eur J Orthod 21:459–468, 1999. 42. Moyers RE, van der Linden FPGM, Riolo ML, McNamara Jr. JA: Standards of human occlusal development, Ann Arbor, Michigan, 1976, Center for Human Growth and Development, University of Michigan Monograph #5, Craniofacial Growth Series. 43. Bishara SE, Bayati P, Jakobsen JR: Longitudinal comparisons of dental arch changes in normal and untreated Class II, Division 1 subjects and their clinical implications, Am J Orthod Dentofacial Orthop 110:483–489, 1996. 44. DeKock WH: Dental arch depth and width studied longitudinally from 12 years of age to adulthood, Am J Orthod 62:56–66, 1972. 45. Moorrees CFA, Reed RB: Changes in dental arch dimensions expressed on the basis of tooth eruption as a measure of biologic age, J Dent Res 44:129–141, 1965.

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46. Lux CJ, Conradt C, Burden D, Domposch G: Dental arch widths and mandibular-maxillary base widths in Class II malocclusions between early mixed and permanent dentitions, Angle Orthod 73:674–685, 2003. 47. Buschang PH, Stroud J, Alexander RG: Differences in dental arch morphology among adult females with untreated Class I and Class II malocclusion, Eur J Orthod 16:47–52, 1994. 48. Hellman M: The face in its developmental career, Dent Cosmos 77:685–699, 1935. 49. Scammon RE: The measurement of the body in childhood. The measurement of man, 1930, University of Minnesota Press. 50. Baughan B, Demirjian A, Levesque GY, La Palme-Chaput L: The pattern of facial growth before and during puberty as shown by French-Canadian girls, Ann Hum Biol 6:59–76, 1979. 51. Buschang PH, Baume RM, Nass GG: A craniofacial growth maturity gradient for males and females between four and sixteen years of age, Am J Phys Anthropol 61:373–381, 1983. 52. Laowansire U, Behrents RG, Araujo E, Oliver DR, Buschang PH: Maxillary growth and maturation during infancy and early childhood, Angle Orthod 83:563–571, 2013. 53. Bhatia SN, Leighton BC: A manual of facial growth: a computer analysis of longitudinal cephalometric growth data, New York, 1993, Oxford University Press. 54. Riolo ML, Moyers RE, McNamara JA, Hunter WS: An atlas of craniofacial growth, Monograph #2, Ann Arbor, Michigan, 1974, Center for Human Growth and Development, The University of Michigan. 55. Liu YP, Behrents RG, Buschang PH: Mandibular growth, remodeling and maturation during infancy and early childhood, Angle Orthod 80:97–105, 2010. 56. Sassouni V: A classification of skeletal types, Am J Orthod 55:109–123, 1969. 57. Bell WB, Creekmore TD, Alexander RG: Surgical correction of the long face syndrome, Am J Orthod 71:40–67, 1977. 58. Cangialosi TJ: Skeletal morphologic features of anterior openbite, Am J Orthod 85:28–36, 1984. 59. Fields H, Proffit W, Nixon W: Facial pattern differences in long-faced children and adults, Am J Orthod 85:217–223, 1984. 60. Nanda SK: Patterns of vertical growth in the face, Am J Orthod Dentofacial Orthop 93:103–106, 1988. 61. Subtenly JD, Sakuda M: Open-bite: diagnosis and treatment, J Dent Child 60:392–398, 1964. 62. Isaacson JR, Isaacson RJ, Speidel TM: Extreme variation in vertical facial growth and associated variation in skeletal and dental relations, Angle Orthod 41:219–229, 1971. 63. Karlsen AT: Association between facial height development and mandibular growth rotation in low and high MP-SN angle faces: a longitudinal study, Angle Orthod 67:103–110, 1997. 64. Jamison JE, Bishara SE, Peterson LC, DeKock WH, Kremenak CR: Longitudinal changes in the maxilla and the maxillarymandibular relationship between 8 and 17 years of age, Am J Orthod 82:217–230, 1982. 65. Buschang PH, Jacob HB, Demirjian A: Female adolescent craniofacial growth spurts: real or fiction, Eur J Orthod, 2013 (advance access). 66. Bishara SE, Jamison JE, Peterson LC, DeKock WH: Longitudinal changes in standing height and mandibular parameters between the ages of 8 and 17 years, Am J Orthod 80:115–135, 1981. 67. Chvatal BA, Behrents RG, Ceen RF, Buschang PH: Development and testing of multilevel models for longitudinal craniofacial growth prediction, Am J Orthod Dentofacial Orthop 128:e45–e56, 2005. 68. Alexander AE, McNamara Jr. JA, Franchi L, Baccetti T: Semilongitudinal cephalometric study of craniofacial growth

69. 70. 71. 72. 73. 74. 75. 76.

77. 78. 79.

80. 81. 82.

83. 84. 85. 86. 87. 88. 89. 90. 91.

in untreated class III malocclusion, Am J Orthod Dentofacial Orthop 135:700.e1–700.e14, 2009. Baccetti T, Franchi L, McNamara Jr. JA: Longitudinal growth changes in subjects with deepbite, Am J Orthod Dentofac Orthop 140:202–209, 2011. Krogman WM: Biological timing and the dento-facial complex, ASDC J Dent Child 35:175–185, 1968. Thompson GW, Popovich F, Anderson DL: Maximum growth changes in mandibular length, stature and weight, Hum Biol 48:285–293, 1976. Lewis AB, Roche AF, Wagner B: Pubertal spurts in cranial base and mandible. Comparisons within individuals, Angle Orthod 55:17–30, 1985. Saksena SS, Walker GF, Bixler D, Yu P: A clinical atlas of roentgeno-cephalometry in norma lateralis, New York, 1987, Alan R. Liss. Roberts RO: Adolescent maxillomandibular relationships: growth pattern, inter-individual variability, and predictions, Dallas, Texas, 2006, Thesis, Baylor College of Dentistry. Björk A, Skieller V: Growth of the maxilla in three dimensions as revealed radiographically by the implant method, Br J Orthod 4:53–64, 1977. Korn EL, Baumrind S: Transverse development of the human jaws between the ages of 8.5 and 15.5 years, studied longitudinally with the use of implants, J Dent Res 69: 1298–1306, 1990. Gandini LG, Buschang PH: Maxillary and mandibular width changes studied using metallic implants, Am J Orthod Dentofacial Orthop 117:75–80, 2000. Iseri H, Solow B: Change in the width of the mandibular body from 6 to 23 years of age: an implant study, Eur J Orthod 22:229–238, 2000. Baumrind S, Korn EL, Issacson RJ, et al: Superimpositional assessment of treatment-associated changes in the temporomandibular joint and the mandibular symphysis, Am J Orthod 84:443–465, 1983. Björk A: Cranial base development, Am J Orthod 41:198–225, 1955. Buschang PH, Santos-Pinto A: Condylar growth and glenoid fossa displacement during childhood and adolescence, Am J Orthod Dentofacial Orthop 113:437–442, 1998. Baumrind S, Ben-Bassat Y, Korn EL, et al: Mandibular remodeling measured on cephalograms. 1. Osseus changes relative to superimposition on metallic implants, Am J Orthod Dentofacial Orthop 102:134–142, 1992. Buschang PH, Santos-Pinto A, Demirjian A: Incremental growth charts for condylar growth between 6 and 16 years of age, Eur J Orthod 21:167–173, 1999. Buschang PH, Julien K, Sachdeva R, Demirjian A: Childhood and pubertal growth changes of the human symphysis, Angle Orthod 62:203–210, 1992. Todd TW, Lyon Jr. DW: Endocranial suture closure: its progress and age relationship, Am J Phys Anthropol 7:325–384, 1924. Sahni D, Jit I, Neelam S: Time of closure of cranial sutures in northwest Indian adults, Forensic Sci Int 148:199–205, 2005. Behrents RG, Harris EF: The premaxillary-maxillary suture and orthodontic mechanotherapy, Am J Orthod Dentofacial Orthop 99:1–6, 1991. Persson M, Thilander B: Palatal suture closure in man from 15 to 35 years of age, Am J Orthod 72:42–52, 1977. Melsen B: Palatal growth studied on human autopsy material: a histologic microradiographic study, Am J Orthod 68:42–54, 1975. Kokich VG: Age changes in the human frontozygomatic suture from 20-95 years, Am J Orthod 69:411–430, 1976. Korbmacher H, Huck L, Merkle T, Kahl-Nieke B: Clinical profile of rapid maxillary expansion–outcome of a national inquiry, J Orofac Orthop 66:455–468, 2005.


92. Knaup B, Yildizhan F, Wehrbein H: Age-related changes in the midpalatal suture. A histomorphometric study, J Orofac Orthop 65:467–474, 2004. 93. Subtelny JD: A longitudinal study of soft tissue facial structures and their profile characteristics, Am J Orthod 45:481–507, 1959. 94. Vig PS, Cohen AM: Vertical growth of the lips—a serial cephalometric study, Am J Orthod 75:405–415, 1979. 95. Nanda RS, Meng H, Kapila S, Goorhuis J: Growth changes in the soft-tissue profile, Angle Orthod 60:177–189, 1991. 96. Bishara SE, Hession TJ, Peterson LC: Longitudinal softtissue profile changes: a study of three analyses, Am J Orthod 88:209–223, 1985. 97. Posen JM: A longitudinal study of the growth of the noses, Am J Orthod 53:746–755, 1969. 98. Buschang PH, De La Cruz R, Viazis AD, Demirjian A: Longitudinal shape changes of the nasal dorsum, Am J Orthod Dentofacial Orthop 103:539–543, 1993.

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99. Behrents RG: Growth in the aging craniofacial skeleton, Ann Arbor, Michigan, 1985, Center for Human Growth and Development, University of Michigan, Monograph #17, Craniofacial Growth Series. 100. Lewis AB, Roche AF: Late growth changes in the craniofacial skeleton, Angle Orthod 58:127–135, 1988. 101. Bishara SE, Treder JE, Jakobsen JR: Facial and dental changes in adulthood, Am J Orthod Dentofacial Orthop 106:175–186, 1994. 102. Forsberg CM, Eliasson S, Westergren H: Face height and tooth eruption in adults—a 20 year follow-up investigation, Eur J Orthod 13:249–254, 1991. 103. Formby WA, Nanda RS, Currier GF: Longitudinal changes in the adult facial profile, Am J Orthod Dentofacial Orthop 105:464–476, 1994. 104. Sarnas KV, Solow B: Early adult changes in the skeletal and soft-tissue profile, Eur J Orthod 2:1–12, 1980.

CHAPTER

2

Development of the Occlusion

Timo Peltomäki

D

evelopment of the occlusion, in other words, eruption of the teeth and formation of the interrelationship be tween the teeth of the upper and lower jaws, is a ge netically and environmentally regulated process. Coordination between tooth eruption and facial growth is essential to achieve a functionally and esthetically acceptable occlusion. Most or thodontic problems arise through variations in the normal tooth eruption/occlusal developmental process. Therefore, ev ery developing malocclusion and dentofacial deformity must be evaluated against normal development. In this chapter, normal eruption timing and sequence of primary and permanent teeth are discussed. Since occlusion is regarded as a dynamic rather than a static structure, changes in the dental arch dimensions are then discussed. Finally, various common deviations in the occlusal development are addressed.

1. What are the stages of tooth development? Tooth development is a genetically regulated process character ized by interactions between the oral epithelium and the un derlying mesenchymal tissue.1 During the first stage of tooth development, called the initiation stage, a platelike thickening of the oral epithelium (dental placodes) can be seen in his tological examination. This is followed by the bud stage with epithelial ingrowth and formation of budshaped tooth germs. Next, the mesenchymal tissue condenses around the epithelial buds and progressively forms the dental papilla. Gradually the dental epithelial tissue grows to surround the dental papilla. From this stage the epithelium can be called the enamel organ. It gains a concave structure; therefore, this stage is called the cap stage. A third structure, the dental follicle, originates from the dental mesenchyme and surrounds the developing enamel organ. During this stage the shape of the crown becomes evident, but the final shaping of a tooth oc curs during the next stage, called the bell stage. During the bell stage, cytodifferentiation begins and toothspecific cell populations are formed. Some of these cells differentiate into specific dental tissueforming cells. During the secre tory stage, the differentiated cells start to deposit the specific dental matrix and minerals. Once the dental hard tissue in the crown has been formed and completely calcified, tooth development continues with the root formation and tooth eruption. Root formation takes place concomitantly with the devel opment of the supporting structures of the teeth (periodontal ligament, cement, alveolar bone). The epithelial buds of the 14

permanent teeth (except permanent molars) develop from the dental lamina of the primary teeth.

2. What are the stages of tooth eruption? Eruption of teeth can be divided into different stages.2 The first stage is called preemergent eruption when the developing tooth moves inside the alveolar bone but cannot yet be seen clinically. This movement begins once the root formation has started. Resorption of bone, and in the case of a permanent tooth, resorption of the roots of the primary teeth, is neces sary to allow preemergent eruption. In addition, an eruption force (origin still unknown) must exist to move the tooth. Emergence, the moment when a cusp or an incisal edge of a tooth first penetrates the gingiva, usually occurs when 75% of the final root length is established. Next, postemergent erup tion follows and a tooth erupts until it reaches the occlusal level (Fig. 21). Eruption speed is faster during this stage and therefore the stage term postemergent spurt is sometimes used. Eruption does not stop once the tooth has come to occlusion but continues to equal the rate of the vertical growth of the face. On average, a molar tooth erupts about 10 mm after hav ing reached the occlusal contact. It is also important to know that eruption of a tooth causes the alveolar bone to grow. In other words, each tooth makes its own alveolar bone. This has a clinical bearing: if a tooth fails to erupt, no alveolar bone devel ops; if a tooth is lost, alveolar bone is also gradually lost. Shortterm eruption of teeth seems to follow daynight (cir cadian) rhythm.3 Eruption occurs mainly during early hours of sleep, although some intrusion can happen during the day, particularly after meals. Furthermore, it has been found that tooth eruption and secretion of growth and thyroid hormones have a similar circadian pattern.3

3. What are the eruption timing and sequence of primary teeth? There is a large individual variation in the eruption schedule of both primary and permanent teeth. Delay or acceleration of 6 months from the average eruption timetable is still within the normal range. Despite variation in the eruption schedule, the eruption sequence of teeth is usually preserved. Generally the first primary teeth to erupt are the lower cen tral incisors (on average at 7 months), followed soon by the upper central incisors (on average at 10 months). Thereafter, the upper and lower lateral incisors emerge (on average at 12 months), then the upper and lower first molars (on average

Development of the Occlusion • CHAPTER 2

15

A A

B B FIG 2-1 A, The mesiolingual cusp of the lower right first permanent molar (arrow) has emerged. B, Two months later the occlusal surface can be seen. Next, postemergent eruption follows and a tooth erupts until it reaches the occlusal level.

TABLE 2-1 Average Eruption Timing and Sequence of Primary Teeth TOOTH

TIME (IN MONTHS)

Lower central incisors Upper central incisors Upper and lower lateral incisors Upper and lower first molars Upper and lower canines Upper and lower second molars

7 10 12 16 20 28

at 16 months). Primary canines erupt on average at 20 months and finally the second molars on average at 28 months. Primary dentition is thus fully formed by the age of 21⁄2 years with calci fication of the roots of the primary teeth completed 1 year later (Table 2-1).

4. What are typical features of primary dentition? Spacing in the primary dentition is a typical feature and a requirement to secure space for the larger permanent inci sors (Fig. 2-2, A). About 70% of children have spaces in the

FIG 2-2 A, Spacing in the primary dentition is a typical feature and is a requirement to secure space for the larger permanent incisors. B, If there is crowding in the primary dentition, crowding is inevitable in the permanent dentition.

front area of primary teeth. The largest spaces, called primate spaces, are located between the upper primary laterals and canines and between the lower primary canines and first molars. It is estimated that if the total amount of space per dental arch is 0 to 3 mm, there is 50% probability of crowd ing in the permanent dentition. If there are no spaces or even crowding in the primary dentition, crowding is inevitable in the permanent dentition (see Fig. 2-2, B).4 During the full primary dentition stage (3 to 6 years), not much happens in the dimensions of the dental arches; however, overjet and overbite may decrease.5

5. What is the terminal plane, and what are the different terminal plane relationships in the primary dentition? Terminal plane denotes the anteroposterior relationship (dis crepancy) between the distal surfaces of the upper and lower second primary molars. It can be a flush terminal plane, or there may be a mesial or a distal step (Fig. 2-3). Occurrence of dif ferent terminal planes differs greatly according to the method used to define terminal plane and the population studied. In the Caucasian (European descent) population, about 60% of children exhibit mesial step (in about 40% the mesial step is less than 2 mm and in 20% more than 2 mm), about 30% e xhibit

16

CHAPTER 2 • Development of the Occlusion

A

B

C

FIG 2-3 Terminal plane denotes the anteroposterior relationship between the distal surfaces of the upper and lower second primary molars. In the Caucasian population about 60% of children exhibit mesial step (A), about 30% flush terminal plane (B), and about 10% distal step (C). (From Bath-Balogh M, Fehrenbach MF: Illustrated dental embryology, histology, and anatomy, ed 2, St Louis, 2006, Saunders.)

flush terminal plane, and about 10% distal step.6 In children of African-American descent, the prevalence of distal step is lower (5%) and mesial step higher (89%).7

6. What does the terminal plane relationship of the primary second molars predict on the permanent molar relationships? The terminal plane relationship determines the anteropos terior position of the permanent first molars at the time of their eruption. Differential forward drift of the lower and up per first permanent molars (generally more forward drift of the lower molar) and differential maxillary and mandibular forward growth (generally more forward growth of the man dible) play a role in this transition. In about 80% of the indi viduals with mesial step less than 2 mm, Angle’s Class I molar relationship results. If the mesial step is more than 2 mm, a Class III molar relationship results in 20% of the subjects. The flush terminal plane results in either a Class I (56% of subjects) or Class II (44% of subjects) molar relationship, de pending on the amount of mandibular anterior growth and forward drift of the lower first primary molars in relation to the upper ones. Distal step of the primary second molars al most invariably results in a Class II molar relationship in the permanent dentition.6

7. How is Angle’s classification of occlusion defined? Angle’s original classification of occlusion is based on the an teroposterior relationship between the upper and lower first permanent molars. In Class I occlusion, the mesiobuccal cusp of the upper first molar occludes with the buccal groove of the lower first molar. Class I occlusion can further be divided into normal occlusion and malocclusion. Both subtypes have the same molar relationship, but the latter is also characterized by crowding, rotations, and other positional irregularities. Class II occlusion is when the mesiobuccal cusp of the upper first molar occludes anterior to the buccal groove of the lower first molar. Two subtypes of Class II occlusion exist. Both have a Class II molar relationship, but the difference lies in the posi tion of the upper incisors. In Class II division 1 malocclusion,

the upper incisors are labially tilted, creating significant overjet. On the contrary, in Class II division 2 malocclusion, the upper central incisors are lingually inclined and the lateral incisors are labially inclined. When measured from the first incisors, overjet is within normal limits in individuals with Class II divi sion 2 malocclusion. Class III malocclusion is opposite to Class II; the mesiobuc cal cusp of the upper first molar occludes more posterior than the buccal groove of the lower first molar.

8. What are the eruption timing and sequence of permanent teeth? The eruption sequence can be checked with the help of erup tion charts and is a useful tool for the orthodontist to assess the dental age of a patient (Table 2-2). As a general rule, a tooth should erupt once two-thirds of its root is formed. Permanent teeth erupt in two different stages. The first transitional period occurs between the ages of 6 and 8 and is followed by an approximately 2-year intermediate period. The second transitional period starts on average at the age of 10 years and lasts around 2 years. In general, teeth erupt earlier in girls than in boys. As in the primary dentition, there is a great individual variation in the eruption timing of permanent teeth. Delay or acceleration of 12 months from the average eruption timetable is still within the normal range. The first transitional period, between 6 and 8 years, can be divided further into three yearly stages. At 6 years the up per and lower first molars (also called 6-year molars) and the permanent lower central incisors erupt (Fig. 2-4). At 7 years the upper central and the lower lateral incisors emerge and erupt. The first transitional period is completed by the erup tion of the upper lateral incisors at the age of 8 years. By this time all the permanent upper and lower incisors and first molars have erupted, for a total of 12 permanent teeth. The term mixed dentition is used to describe a dentition contain ing both primary and permanent teeth. The second transitional period can also be divided into three yearly stages. The first period is characterized by the eruption of the lower canines and lower and upper first premolars within the same time frame at about 101⁄2 years of age. This is followed


17

TABLE 2-2 Average Eruption Timing and Sequence of Permanent Teeth TRANSITION PERIOD First

AGE

TEETH

FEMALE (TIME IN YEARS)

MALE (TIME IN YEARS)

6 years

Lower first molars Upper first molars Lower central incisors Upper central incisors Lower central incisors Upper lateral incisors

5.9 6.2 6.3 7.2 7.3 8.2

6.2 6.4 6.5 7.5 7.7 8.3

Lower canines Upper first premolars Lower first premolars Upper second premolars Lower second premolars Upper canines Lower second molars Upper second molars Upper and lower third molars

9.9 10.0 10.2 10.9 10.9 11.0 11.7 12.3 17-25

10.8 10.4 10.8 11.2 11.5 11.7 12.1 12.7 17-25

7 years

Second

8 years 10 years 11 years 12 years

A

incisors. The long canines require a long time to become fully mineralized and therefore start the mineralization early (at 12 months) despite late eruption. Upper lateral incisors have an opposite mineralization/eruption pattern: a fairly late start of mineralization at 18 months and much earlier eruption than canines. The mineralization of premolars and second molars begins between ages 21⁄2 and 31⁄2 years. Signs of mineralization of the third molars can be seen at approximately 10 years, with particularly large variation. As a general rule, completion of crown formation (mineralization) takes 4 years, and the root formation takes another 5 years ±1 year, depending on the size of the tooth.

10. How do the initial location and size of the permanent incisors compare with the primary teeth?

B FIG 2-4 The first transitional period starts at approximately the age of 6 years with the eruption of the upper and lower first molars (A) and the lower central incisors (B).

soon by the eruption of the upper and lower second premolars and usually somewhat later by the upper canines (at the age of 11 years). The second molars (12-year molars) complete the second transitional period at the age of 12 years. Eruption of the third molars occurs much later with large individual variation (range, 17 to 25 years).

9. When does the mineralization of the permanent teeth occur? Radiologically visible mineralization of the permanent first molars starts approximately at the time of birth and is followed 6 months later by the upper and lower central and lower lateral

In the maxilla and mandible, the permanent incisors develop on the palatal/lingual side of the roots of the primary incisors with considerable crowding. Upper lateral incisors are located even more palatally than the central ones. Total mesiodistal di mension of the upper permanent incisors is about 8 mm larger than that of the primary incisors. In other words, in the upper front area there is lack of space, approximately the size of an upper lateral incisor. In the lower arch, the difference is less (5 to 6 mm), approximately the mesiodistal dimension of a lower incisor.

11. How is the space deficit between the primary and permanent incisors solved? For the upper permanent incisors, several factors are available to regain this 8 mm or so space deficit. First, the upper incisors generally erupt to a wider dental arch circumference than the primary incisors, which is the most effective way to gain space for these teeth. Second, when the central permanent incisors erupt, they push the primary lateral incisors distally. The same “pushing effect” repeats when the permanent laterals erupt and push the primary canines distally. With this “pushing effect” the

18


existing spaces of primary dentition are also closed and used for the larger permanent incisors to accommodate. Another mechanism of space-gaining in the permanent dentition is the transverse growth of the maxilla at its midpalatal suture. Thus, despite the initial lack of space in the maxillary anterior area, space conditions are generally resolved for the permanent inci sors. Naturally, if the above factors are not available or working, crowding and/or crossbite, particularly of the upper laterals, can be seen. In the mandibular anterior area, comparable pushing takes place as in the maxillary anterior area to make space for the erupting permanent incisors. However, lower anterior teeth do not generally erupt to a wider dental arch circumference than the primary ones, and no transverse growth can take place in the anterior area of the mandible. If considerable spacing in the pri mary dentition (> 5 to 6 mm) does not exist, crowding is com monly seen once the permanent lower incisors have erupted. This is called physiological crowding.

12. Is anterior spacing common once permanent incisors have erupted? Despite the initial crowding of the permanent incisors in the maxillary bone, spacing is a common finding in the upper ante rior area once the incisors have erupted. A large space (> 2 mm) between the upper central incisors, called midline diastema, may exist due to a strong labial frenum. Upper lateral incisors may be inclined distally due to the pressure of the erupting canines on their roots. This normal spacing condition in the upper front area is called ugly duckling. Once the permanent canines erupt, upper spaces usually close and uprighting of the lateral incisors can be seen. On the other hand, spacing in the mandibular an terior area is very seldom seen. Rather, some crowding is typical for this developmental stage.

13. What are nonsuccedaneous teeth, and how is space secured for them? Nonsuccedaneous teeth are teeth that do not succeed decidu ous teeth (i.e., all permanent molars). In the upper dental arch, space is created for the molars by bone apposition at the free posterior border of the maxilla. Also, the transverse palatal suture may make a contribution. For the lower molars, bone apposition occurs on the posterior side of the mandibular ra mus, and bone resorption occurs on the anterior portion of the ramus. During normal occlusal development, upper and lower first molars usually drift forward because of excess space due to the leeway space. This anterior drift of the first molars opens up space for the second molars to erupt.

14. What is leeway space, and what is its importance? The space occupied by the primary canines and molars is greater than that required for the corresponding permanent teeth. This size difference of the primary and permanent teeth is known as the leeway space. On average, 1 to 1.5 mm of excess space exists in each upper quadrant and 2 to 2.5 mm in the lower quad rants with large individual variation. A significant contribution of the leeway space comes from the difference in the second

primary molars and their counterparts. The primary molars are on average 2 mm larger than the second premolars. During normal occlusal development, about 2 mm of the leeway space is used by the anterior drift of the molars. Lower molars usually drift more mesially than the upper ones, which often strength ens the Class I molar relationship. Physiological crowding in the lower front area may also be reduced from the leeway space, allowing the permanent canines to drift distally.

15. Is the eruption sequence of teeth important? The eruption sequence presented in Question 8 is the most op timal one for a proper occlusion to develop. However, varia tions from this normal sequence are frequently seen during the second transitional period, and these variations may have clini cal significance. Sometimes the lower second molars erupt before the second premolars. This may cause anterior drift of the first permanent molars too early and, as a consequence, space loss for the sec ond permanent premolars. Therefore, it is preferable that the second premolars erupt before the second permanent molars. Since the leeway space provides the space needed by the up per canines, they should erupt after the permanent premolars. If not, lack of space may cause the upper canines to erupt too labially.

16. What changes occur in the dental arch length during occlusal development? Dental arch length has a special meaning in orthodontics. Arch length denotes the distance from the most labial surfaces of the central incisors to the line connecting the mesial (or distal) points of the first permanent molars in the midsagittal plane. Measurements and changes in the dental arch dimensions are largely based on the studies of Moorrees.5 Changes in the arch length occur in two different phases during occlusal de velopment. During the first transitional period, upper dental arch length increases slightly (on average 0.5 mm) because of the more labial eruption of the upper permanent central inci sors. Essentially, this eruption pattern creates a larger dental arch circumference compared with the positions of the pri mary incisors. An additional increase of approximately 1 mm can be seen when the permanent lateral incisors erupt. During the second transitional period, arch length commonly de creases because the leeway space allows permanent premolars and first molars to drift forward. Therefore, the average upper dental arch length is slightly longer or the same at 3 years than at 15 years. In the lower dental arch, no clinically significant changes occur in the arch length during the first transitional period be cause lower permanent incisors erupt into the same arch cir cumference as the primary incisors. A considerable shortening of the lower dental arch length takes place during the second transitional period. As discussed earlier, larger leeway space in the lower compared with the upper dental arch allows more anterior migration of the premolars and molars, which leads to the shortening of the arch length. The average lower dental arch length is thus slightly longer at 3 years than at 15 years.


19

According to Moorrees,5 2- to 3-mm shortening of the lower dental arch length can be seen from the full primary dentition to the permanent dentition.

may increase the pressure from lips, causing crowding. More forward drift takes place in the lower dentition than in the up per, which also increases crowding.

17. What changes occur in the dental arch width during occlusal development?

19. Do wisdom teeth play a role in the lower anterior crowding?

During the eruption of the maxillary permanent incisors, in tercanine dimension (measured between primary canines) increases on average by 3 mm. Before or at the time of eruption of the permanent canines, another increase of approximately 2 mm takes place in canine-to-canine distance. The increase in the upper intercanine distance may be caused by the distalizing pressure of the erupting permanent incisors on the permanent canines and growth in width of the maxilla at the midpalatal suture. A steady increase (total 4 to 5 mm) in the distance be tween the upper first permanent molars can be seen after their emergence. In the lower dental arch, a comparable increase of the inter canine distance as in the upper arch occurs during the eruption of the permanent incisors (3 mm on average). However, unlike in the upper arch, no additional increase in the canine-canine distance takes place in the lower arch during the later stages of dental development. This early establishment of the lower intercanine distance has an important clinical bearing in that attempts to increase lower intercanine distance by orthodon tic means usually leads to relapse.8 After the emergence of the molars, the distance between the lower first molars increases steadily corresponding to the upper arch. There are two ways to measure dental arch width. The more common method is to measure the distance between the cor responding contralateral teeth at the cusp tips (e.g., intercanine or intermolar width). Another measurement can be made at the palatal/lingual gingival level of the teeth; this measurement describes the width of the bony arch.5 The increase in the in tercanine distance is greater when measured from the cusp tips of the teeth than at the gingival level, particularly in the up per dental arch. This may be because the labio-lingual crown diameter of the permanent canines is greater than that of the primary canines.

Eruption of wisdom teeth often occurs simultaneously with the appearance or increase in lower anterior crowding. It is a common belief that this is because of pressure created by the erupting wisdom teeth. However, a randomized controlled study suggests that wisdom teeth play a minor role, if any, in the late lower incisor crowding.10 Individuals with congenitally missing third molars may also have this crowding. Thus, there is no evidence to support a recommendation to extract third molars in order to prevent late incisors from crowding.11

18. What changes occur in the dentition once permanent teeth (excluding wisdom teeth) have erupted? Appearance of, or actual increase of, already existing crowding, called late or secondary crowding, in the lower anterior area is a typical finding in late dental development in the late teens and early 20s. This crowding occurs before or simultaneously with the emergence of wisdom teeth and may take place both in orthodontically untreated or treated subjects. Several factors are thought to play a role in this crowding in the lower an terior area.9 Maxillary and mandibular differential growth is considered to have an effect on the late crowding. Growth of the maxilla ceases earlier than growth of the mandible. Because of overbite, lower anterior teeth cannot move forward to the extent of the lower jaw growth but tilt lingually to a smaller circumference, which results in crowding. In addition, the mat uration of soft tissues that occurs during the teenage period

20. What are the most common reasons for interference with normal tooth eruption? As stated earlier, great individual variation occurs in the tim ing of eruption of permanent teeth. Premature tooth eruption is possible, but delayed tooth eruption is more common. This may occur only on one side or on both sides of the dental arch. Reasons for the delayed tooth eruption may be divided into rare systemic factors and more frequent local factors.12 Systemic factors usually involve a disease process with the whole dentition commonly affected. Bone metabolism for necessary resorption of the alveolar bone and/or roots of the primary tooth may be disturbed, and eruption may therefore be delayed or even hindered. If a permanent tooth fails to fully or partially move from its crypt position in the alveolar process into the oral cavity without evident cause (presumably due to malfunction of the eruption mechanism), this condition is called primary failure of tooth eruption (PFE).13 PFE is rare and usually affects posterior teeth. Due to incomplete eruption of posterior teeth, severe lateral open bite is seen. Recent studies suggest that parathyroid hormone receptor 1 gene is causative for PFE.14 Local factors that delay tooth eruption may be mechanical in nature, and once the obstruction is eliminated, further tooth eruption may take place. Local factors include supernumer ary teeth, heavy fibrous gingival tissue because of premature loss of a primary tooth, crowding, and sclerotic alveolar bone. Ankylosis of a tooth also causes delay or prevention of a tooth eruption. As a general rule, if a permanent tooth has erupted but its counterpart does not within 6 months, an eruption problem is evident and further investigation is recommended.

21. What is tooth ankylosis, and what is its clinical significance? Ankylosis of a tooth is defined as the union/fusion between a tooth and alveolar bone. This means that the periodontal ligament is obliterated in one or more locations, and there is contact between the cementum of a tooth and alveolar bone. Ankylosis is more common in the primary, particularly primary molars, than in the permanent dentition (Fig. 2-5). Prevalence of primary molar ankylosis is 5% to 10%. Ankylosis is thought to be related to the noncontinuous resorption process of the

20


FIG 2-5 Because of ankylosis of the lower right primary second molar, a vertical deficiency in the occlusal level developed since the ankylosed teeth could not erupt and the adjacent teeth continued erupting.

roots of the primary teeth. In other words, during the resorp tion phase of the root, there are periods of rest and reparation. During the reparative phase, fusion of the cementum and al veolar bone may develop. Causative factors for ankylosis are currently unknown. An ankylosed tooth cannot erupt; consequently, the tooth appears to submerge with continued alveolar growth. In real ity, an ankylosed tooth does not submerge, but when it fails to erupt, a vertical deficiency in the occlusal level develops as the adjacent teeth continue erupting. The term infraocclusion is used to describe this condition and the amount of infraocclu sion of an ankylosed tooth depends on when the ankylosis oc curred. It is known that a molar erupts on average 1 mm yearly. This means that if the vertical defect is large, one may speak about early ankylosis. On the other hand, late ankylosis denotes infraocclusion as minor (1 to 2 mm), and ankylosis had evi dently occurred near the time of exfoliation of a primary molar.

22. What is ectopic eruption? Ectopic eruption of a tooth means that the tooth erupts away from the normal position. This condition can have a multifac torial underlying etiology. Sometimes a tooth erupts ectopi cally because of an abnormal initial position of the tooth bud. Upper first molars and canines are most commonly observed to erupt ectopically, followed by lower canines, upper premo lars, lower premolars, and upper lateral incisors. In the perma nent dentition, the upper first molars erupt most commonly ectopically (prevalence approximately 4%) (Fig. 2-6). The mo lar may then erupt too far anteriorly and make contact with the distal root of the second primary molar. As a consequence, the first permanent molar may fail to erupt on both sides or only on one side. It may also happen that an ectopically erupting first permanent molar causes severe resorption (called undermining resorption) of the roots of the second primary molar, leading to early exfoliation of that primary molar. This causes a more anterior eruption of the first permanent molar, resulting in space loss and future crowding of that quadrant. Because of insufficient space, the upper and lower lateral incisors may also erupt ectopically and too distally. The clinical significance of this may be an early loss of the primary canines from under mining resorption.

FIG 2-6 Both upper first molars have erupted ectopically, too far anteriorly. This may lead to early exfoliation of the upper second primary molars by undermining resorption and space loss in these quadrants.

23. What are eruption problems of the upper permanent canines? Canines, particularly maxillary canines, have the longest way of all teeth to erupt from their initial position to the occlusion. Initially the upper canines are located high in the maxilla, in the canine fossa, close to the base of the nose. In preemergent eruption, they move downward along the distal aspect of the roots of the lateral incisors. When the child is 9 to 10 years old, these teeth should be palpable in the fornix between the permanent lateral incisor and the primary first molar. If not, ectopic eruption or impaction may be expected. Maxillary canines are the last teeth to erupt and are therefore strongly influenced by spacing conditions. The canines’ long path of eruption, coupled with their late emergence timing, causes their high prevalence of impaction (about 2%). Most of the impacted upper canines are palatally located. Interestingly, nearly 50% of patients with palatally located up per canines present with anomalous (peg shaped) or congeni tally missing upper lateral incisors. Because of this clinical link, it has been proposed that a common genetic etiology may be responsible for canine impaction and hypodontia.15 Another explanation for this observation could be that a guiding struc ture for the proper eruption of the canine is missing, and, therefore, the canine is palatally displaced. In a computed tomography (CT) study, researchers found that even in cases of normal eruption of upper canines, the continuity of the periodontal ligament of the lateral incisor may be temporarily lost with no resorption sign in the root.15 When the path of eruption abnormally diverges so that the canines make contact with the roots of the lateral incisors, re sorption of the incisor may be expected unrelated to the size of the dental follicle of the canine.16

24. What is a typical eruption problem of the second permanent molars? If space is not adequate for the upper second permanent mo lars, they often tilt buccally and distally before their emergence


and eventually erupt too buccally. On the contrary, the lower second permanent molars tend to tilt lingually because of in sufficient space. When the second molars erupt like this, they may not occlude properly and a scissor-bite or buccal crossbite may develop. In the scissor-bite, the upper second molar is po sitioned too far to the buccal and the lower second molar is too far to the lingual.

25. Which factors have an effect on tooth position? When a tooth is erupting, it is affected by two forces that dictate its vertical position: a force causing eruption brings a tooth to the oral cavity, but a force from the occlusion has an oppos ing effect. In addition, external forces from the cheeks and lips and internal forces from the tongue play a role in the bucco lingual position of a tooth. According to Proffit,17 forces from the cheeks, lips, and tongue are not in balance; however, peri odontally healthy teeth do not move. The balancing factor is probably the periodontal ligament, an active element capable of stabilizing tooth position. On the other hand, if support from alveolar bone and periodontal ligament is reduced, teeth are prone to move. Light but long-lasting forces (force from the soft tissues at rest, periodontal ligament, and gingival fibers) are more im portant than heavy but short-lasting forces (biting, swallow ing) to cause a tooth to move or to maintain its position.

26. What is the relationship between occlusal development and facial growth? Eruption of permanent teeth does not stop once a tooth has reached occlusion. Eruption of teeth causes an elongation of den toalveolar processes that continues at a rate that parallels the rate of vertical growth of the face, and vertical growth of the man dibular ramus in particular. In an optimally growing individual, growth of the anterior and posterior face height is approximately equal. This means that the amount of eruption of the anterior and posterior teeth that have already reached the occlusal contact is in balance. During the period between 8 and 18 years of age, anterior and posterior face heights increase about 20 mm.18,19 At the same time, each tooth erupts about 10 mm (1.0 mm/yr) to keep contact with its opposing tooth. In some individuals, however, growth of the anterior and posterior face is not in balance, and either ante rior or posterior growth rotation of the mandible occurs. This is followed by overeruption of posterior or anterior teeth in poste rior rotation pattern versus anterior rotation pattern, respectively.

27. When is occlusal development completed, and can possible continued occlusal development cause adverse effects when teeth are replaced by dental implants? It has been found that anterior facial height may continue to increase still between ages 25 and 45 years (and probably beyond) in healthy individuals. At the same time overjet and overbite remain the same, indicating continuous eruption of incisors to adapt face height increase.20 A dental implant, which does not have a periodontal ligament to allow move ment, can be compared to an ankylosed tooth. In individuals

21

with post-adolescence changes in the occlusion, a dental im plant remains stable while the adjacent teeth erupt, causing a vertical step in the incisal and gingival lines (Fig. 2-7).21 No reliable methods are available to predict in whom continued occlusal and facial development takes place in clinically sig nificant amounts and causes adverse effects with dental im plants. Interestingly, it has been found that dental implants in the upper front area may exhibit major vertical steps in the same amount in persons with early (151⁄2 to 21 years) or late (40 to 55 years) implant placement.22 Therefore, from the occlusal development point of view, placement of den tal implants should be postponed as long as possible. It is advisable to inform the patient of the possibility of adverse infraocclusion due to continued unpredictable occlusal development.

28. Can individuals be found with variations in the number of teeth? Variation in the number of teeth is a frequent finding in any patient population. Instead of the normal 20 primary teeth and 32 permanent teeth, individuals with excessive or reduced numbers of teeth can be seen. In the permanent dentition, one or two teeth are often congenitally missing. This condi tion is called hypodontia or agenesis of teeth. If more than six permanent teeth are missing, the condition is called oligodontia. Anodontia, which is characterized by complete failure of tooth development, is extremely rare. If supernumerary teeth are present, it is called hyperdontia.

29. How common is hypodontia, and which teeth are most often affected? Based on epidemiological studies worldwide, the prevalence of congenitally missing permanent teeth has been found to vary according to the population studied as well as to gender. Studies from Europe and Australia show the prevalence of hy podontia ranging between 5.5% and 6.3%, whereas in North America (both Caucasians and African-Americans), the preva lence is 3.9%.23 These numbers exclude the third molars, but when they are included the prevalence is considerably higher, since one or more wisdom teeth are missing in about 20% to 25% of the subjects. On the other hand, prevalence of congeni tally missing primary teeth is only 0.1% to 0.4%. The preva lence of hypodontia is significantly higher (1.37 times) in girls than in boys.23 Hypodontia commonly runs in families, an indication that genetic factors are involved. Missing teeth can be inherited as part of a syndrome or isolated in an autosomal-dominant or autosomal-recessive way. Several gene defects have been found to be associated with hypodontia. The main genes known today to be involved in hypodontia are MSX1, PAX9, and AXIN2.1 Individuals who are missing several teeth often have distur bances in other organs of ectodermal origin (e.g., a condition called ectodermal dysplasia). The most commonly missing permanent teeth are the lower second premolars (more than 40% of the missing teeth), followed by the upper laterals and upper second molars. The number of other congenitally missing teeth is c onsiderably

22


FIG 2-7 Upper right incisor was replaced with an implant at the age of 33 years. Because of continued facial growth and eruption of teeth, the implant (comparable to an ankylosed tooth) became gradually infraoccluded.

lower. As a general rule, the last tooth within its dental group is the one most likely to be congenitally missing. In other words, third molars are more likely to be missing than the first and second molars, second premolars more often than the first ones, and lateral incisors more often than the central incisors.

30. Can hypodontia be associated with other dental anomalies? Different tooth and eruption anomalies are found together more frequently in some individuals than can be explained by chance alone. Hypodontia, small teeth (peg-shaped up per lateral incisors), delay in tooth formation and eruption, infraocclusion of primary molars, palatal displacement of upper canines, transposition of teeth, and distally displaced unerupted premolars have been found to be associated.15,24–26 These interrelated anomalies are examples of dental anom aly patterns (DAP).27 Understanding of DAP calls for a closer look of a patient who only has one missing tooth, for example.

31. How common is hyperdontia? Prevalence of hyperdontia is lower than that of hypodon tia. In the primary dentition, the prevalence of hyperdon tia is about 0.5% and in the permanent dentition about 1%. Supernumerary teeth are most often (85%) located in the upper jaw, particularly in the premaxilla area. A supernumerary tooth

FIG 2-8 Supernumerary teeth are most often located in the upper jaw. A supernumerary tooth is seen in the midline of the premaxilla and is called a mesiodens.

may be typical or atypical in shape. An atypical supernumer ary tooth is often found in the midline of the premaxilla and is called a mesiodens (Fig. 2-8). Overall, mesiodens is the most prevalent supernumerary tooth, followed by extra molars and lower second premolars.28


32. Does variation in tooth size have an effect on occlusion? Variation in tooth size is a relatively common finding and may have an effect on occlusion. It is estimated that the prevalence of “tooth size discrepancy” (also called Bolton discrepancy29) is about 5%.30 Upper permanent lateral incisors show the largest variation in size. If they are significantly smaller or larger than average, ideal occlusion is difficult to establish. As a general rule, if the mesiodistal dimension of an upper lateral incisor is smaller than that of a lower incisor, normal overjet and over bite are difficult to obtain. REFERENCES 1. Thesleff I: Epithelial-mesenchymal signalling regulating tooth morphogenesis, J Cell Sci 116:1647–1648, 2003. 2. Lee CF, Proffit WR: The daily rhythm of tooth eruption, Am J Orthod Dentofacial Orthop 107:38–47, 1995. 3. Risinger RK, Proffit WR: Continuous overnight observation of human premolar eruption, Arch Oral Biol 41:779–789, 1996. 4. Leighton BC: The early signs of malocclusions, Trans Eur Orthodon Soc 353–368, 1969. 5. Moorrees CFA: The dentition of the growing child. A longitudinal study of dental development between 3 and 18 years of age, Cambridge, Massachusetts, 1959, Harvard University Press. 6. Bishara SE, Hoppens BJ, Jakobsen JR, Kohout FJ: Changes in the molar relationship between the deciduous and permanent dentitions: a longitudinal study, Am J Orthod Dentofacial Orthop 93:19–28, 1988. 7. Anderson AA: Occlusal development in children of African American descent. Types of terminal plane relationships in the primary dentition, Angle Orthod 76:817–823, 2006. 8. Bishara SE, Ortho D, Jakobsen JR, et al: Arch width changes from 6 weeks to 45 years of age, Am J Orthod Dentofacial Orthop 111:401–409, 1997. 9. Richardson ME: The etiology of late lower arch crowding alternative to mesially directed forces: a review, Am J Orthod Dentofacial Orthop 105:592–597, 1994. 10. Harradine NW, Pearson MH, Toth B: The effect of extraction of third molars on late lower incisor crowding: a randomized controlled trial, Br J Orthod 25:117–122, 1998. 11. Southard TE, Southard KA, Weeda LW: Mesial force from unerupted third molars, Am J Orthod Dentofacial Orthop 99:220–225, 1991. 12. Suri L, Gagari E, Vastardis H: Delayed tooth eruption: pathogenesis, diagnosis, and treatment. A literature review, Am J Orthod Dentofacial Orthop 126:432–445, 2004.

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13. Proffit WR, Vig KWL: Primary failure of eruption: a possible cause of posterior open-bite, Am J Orthod 80:173–190, 1981. 14. Frazier-Bowers SA, Puranik CP, Mahaney MC: The etiology of eruption disorders— further evidence of a “genetic paradigm,” Semin Orthod 16:180–185, 2010. 15. Pirinen S, Arte S, Apajalahti S: Palatal displacement of canine is genetic and related to congenital absence of teeth, J Dent Res 75:1742–1746, 1996. 16. Ericson S, Bjerklin C, Falahat B: Does the canine dental follicle cause resorption of permanent incisor roots: a computed tomographic study of erupting maxillary canines, Angle Orthod 72:95–104, 2002. 17. Proffit WR: Equilibrium theory revisited: factors influencing position of teeth, Angle Orthod 48:175–186, 1978. 18. Bishara SE: Facial and dental changes in adolescents and their clinical implications, Angle Orthod 70:471–483, 2000. 19. Thilander B, Persson M, Adolfsson U: Roentgen-cephalometric standards for a Swedish population. A longitudinal study between the ages of 5 and 31 years, Eur J Orthod 27:370–389, 2005. 20. Forsberg CM, Eliasson S, Westergren H: Face height and tooth eruption in adults—a 20-year follow-up investigation, Eur J Orthod 13:249–254, 1991. 21. Thilander B, Odman J, Lekholm U: Orthodontic aspects of the use of oral implants in adolescents: a 10-year follow-up study, Eur J Orthod 23:715–731, 2001. 22. Bernard JP, Schatz JP, Christou P, Belser U, Kiliaridis S: Longterm vertical changes of the anterior maxillary teeth adjacent to single implants in young and mature adults. A retrospective study, J Clin Periodontol 31:1024–1028, 2004. 23. Polder BJ, Van’t Hof MA, Van der Linden FPGM, KuijpersJagtman AM: A meta-analysis of the prevalence of dental agenesis of permanent teeth, Community Dent Oral Epidemiol 32:217–226, 2004. 24. Peck L, Peck S, Attia Y: Maxillary canine-first premolar transposition, associated dental anomalies and genetic basis, Angle Orthod 63:99–109, 1993. 25. Peck S, Peck L, Kataja M: Prevalence of tooth agenesis and peg-shaped maxillary lateral incisor associated with palatally displaced canine (PDC) anomaly, Am J Orthod Dentofacial Orthop 110:441–443, 1996. 26. Baccetti T: A controlled study of associated dental anomalies, Angle Orthod 68:267–274, 1998. 27. Peck S: Dental Anomaly Patterns (DAP). A new way to look at malocclusion, Angle Orthod 79:1015–1016, 2009. 28. Schmuckli R, Lipowsky C, Peltomäki T: Prevalence and morphology of supernumerary teeth in the population of a Swiss community, Schweiz Monatsschr Zahnmed 120:987–993, 2010. 29. Bolton WA: The clinical application of a tooth-size analysis, Am J Orthod 48:504–529, 1962. 30. Proffit WR, Fields HW, Sarver DM: Contemporary orthodontics, ed 4, St Louis, 2007, Mosby.

C H A PT E R

3

Appropriate Timing for Correction of Malocclusions Chun-Hsi Chung • Steven A. Dugoni

P

roffit1 states that “in determining the optimal timing for orthodontic treatment, two considerations are important: effectiveness (how well does it work?) and efficiency (what is the cost-benefit ratio?).” Both must be kept in mind when deciding when to treat various orthodontic problems. A child who has a malocclusion that interferes with facial growth, dentitional development, and/ or has a negative impact on psychosocial status should have treatment initiated in the primary or mixed dentition. Otherwise, treatment of the malocclusion can be delayed until the child is in the permanent dentition. An understanding of craniofacial growth and development and dentitional development is essential to differentiate the timing of orthodontic treatment for different problems. If treatment is started too early, it is not efficient (high costbenefit ratio) because of extended treatment time. If treatment is started too late, it may not be effective because the opportunity for modifying skeletal growth may be missed; moreover, it can be more extensive and difficult, requiring a higher incidence of extraction and/or orthognathic surgery. This chapter addresses the appropriate timing for the commonly seen orthodontic problems from primary dentition to permanent dentition.

1. What is early treatment, and at what age is early treatment indicated? Early treatment (Phase I) can be defined as “orthodontic treatment started in either primary or mixed dentition that is performed to enhance the dental and skeletal development before the eruption of the permanent dentition. Its purpose is to either correct or intercept a malocclusion and to reduce the need or the time for treatment in the permanent dentition.”2 It is typically a short duration (a few months to 1 year) of treatment, and then the child is monitored until the late mixed dentition or early permanent dentition for possible comprehensive orthodontics known as Phase II treatment. Two-phase treatment is not needed for the majority of children who present in the primary or mixed dentition stage of development. It has been reported that about one-third of children are treated with two phases of orthodontic care, whereas the other two-thirds are treated with one-phase treatment (Phase II only) in the late mixed dentition or permanent dentition.3 24

2. What is the appropriate timing for the treatment of an anterior crossbite with a functional shift (pseudo Class III)? Children who have an anterior crossbite with a functional shift should be treated early due to the negative impact on facial growth and development. The incisors are usually in edge-to-edge bite in centric relation (CR); however, in centric occlusion (CO) the child has to shift the mandible forward into incisal crossbite so that the posterior teeth can occlude. A child could be Class I in CR but a Class III in CO (pseudo Class III). A proper diagnosis and careful documentation of the CR-CO discrepancy is essential, with records that can include clinical measurements, photographs, models, and a lateral headfilm.4 The treatment can be started as early as 5 to 6 years old in the primary dentition to correct the anterior crossbite and eliminate the functional shift. This correction helps to establish normal function and allows normal growth and development of the maxilla and mandible. Fig. 3-1 shows Patient 1, a 5 yr:5 mo child in primary dentition, with anterior crossbite and functional shift. The patient was treated with a removable appliance with finger springs to push upper incisors labially. The crossbite was corrected in 3 months, and 2 years later significant forward growth of the maxilla was noted (Fig. 3-2). At age 13 before Phase II treatment, a Class I molar and canine relationship was maintained (Fig. 3-3).

3. What is the appropriate timing for treatment of a skeletal Class III malocclusion, and what kind of treatment is involved? For a skeletal Class III malocclusion, treatment with orthopedic appliances should be started in the early mixed dentition (age 6 to 8) to obtain optimal results.5 The orthopedic skeletal changes from treatment diminish when the child enters adolescence. However, studies have shown that some skeletal modification can still be accomplished using orthopedic appliances in the early permanent dentition.6 A common treatment protocol for a skeletal Class III malocclusion in children would utilize a protraction facemask with a rapid palatal expander (RPE) to advance the maxilla forward. The mandible typically moves downward and backward accompanied by a slight increase in lower facial

Appropriate Timing for Correction of Malocclusions • CHAPTER 3

A

B

D

25

C

E

F

FIG 3-1 A 5 yr:5 mo child in primary dentition presented with anterior crossbite in centric occlusion (CO), retroclined upper incisors, extruded upper and lower incisors, and a deep bite (A-C). An anterior edge-to-edge bite and posterior open bite were noted in centric relation (CR) (D). The CO-CR discrepancy (functional shift) was about 2 mm. A lateral cephalogram was taken in CO (E) and cephalometric tracing showed SNA 80°, SNB 81.5°, ANB -1.5°, SN-MP 30° (F).

height.7–11 Efforts to restrain mandibular growth (i.e., chincup) may not be effective long-term because the adolescent mandibular growth spurt is very significant and the skeletal Class III can return.12 Fig. 3-4 shows Patient 2, a 7-year-old child, with skeletal Class III (Wits: -11 mm). The patient was treated with RPE and facemask, and the results showed maxillary forward movement and significant improvement of skeletal Class III (Wits: -4 mm) (Fig. 3-5). It should be noted that occasionally Class III orthopedic treatment is required more than once for the skeletal Class III cases because of the significant mandibular forward growth tendency throughout adolescence.

4. What is the timing of treatment for a Class II malocclusion, and what kind of treatment is involved? Recent randomized clinical trials have suggested that skeletal effects of early treatment using headgear or functional appliances at age 9 (Phase I) generally are positively impacted; however, this improvement cannot be sustained over time. They found that by the end of Phase II orthodontic treatment, the differences between those who had received Phase I treatment and those who had not were indistinguishable.13–19 Thus, they suggested that moderate to severe Class II malocclusions do not benefit more from two-phase treatment than from a conventional one-phase treatment started in the late mixed dentition. However, it should be noted that the stages of tooth eruption do not correlate very well with the stages of skeletal

growth. The timing of treatment often must be adjusted because skeletal and dental developments are not synchronized. Children requiring Class II skeletal correction require treatment with growth modification, which is most successful if started at the beginning of the adolescent growth spurt and ended about the time rapid growth subsides. There is considerable individual variation, but puberty and the adolescent growth spurt occur on average nearly 2 years earlier in females than in males.19 This has an important impact on the timing of orthodontic treatment, which should be initiated earlier in females than in males to take advantage of the adolescent growth spurt. For girls the growth spurt starts at about age 101⁄2 to 11, and for boys it starts at about age 121⁄2 to 13.20 Thus, for girls the timing for skeletal Class II correction should be approximately 2 years earlier than for boys. For boys the growth spurt starts usually in the late mixed dentition or early permanent dentition stage; however, for girls it may start 2 years before the permanent dentition stage. If treatment for skeletal modification for a girl starts at age 10 when her growth spurt initiates, a first phase would be needed for about 1 year and then continue with a second phase of treatment. It should be noted that treatment of Class II malocclusion should typically be delayed until the initiation of the growth spurt, but a Phase I (7 to 9 years old) treatment is indicated if the child has a psychosocial issue due to the malocclusion. Parents should know the later Phase II treatment is very possible and that this two-stage treatment will be more costly and time consuming.

CHAPTER 3 • Appropriate Timing for Correction of Malocclusions

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FIG 3-2 Patient 1: Anterior crossbite was corrected in 3 months at age 5 yr:8 mo (A-C). Note the posterior open bite appeared (B-C). A month later at age 5 yr:9 mo, the posterior occlusion was reestablished from eruption of posterior teeth as shown on the lateral cephalogram (D). The tracing showed an SNA 80°, SNB 78.5°, ANB 1.5°, and SN-MP 36° (E). To evaluate the growth, a cephalogram was taken at age 7 yr:7 mo (F), and the cephalometric tracing showed significant forward maxillary growth. The SNA was 82°, SNB 79° (ANB: 3°), and SN-MP 33° (G). Superimposition of ceph tracings is from age 5 yr:11 mo to 7 yr:6 mo (H).

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FIG 3-3 Patient 1 at age 13 before Phase II treatment (A-C).


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FIG 3-4 Patient 2, a 7-year-old child, presented with skeletal and dental Class III malocclusion, anterior crossbite, and posterior crossbite (A-C). The lateral cephalogram was taken and the tracing showed SNA: 81°, SNB: 79°, ANB: 2°, Wits: -11 mm, MP-SN: 46° (D-E).

Fig. 3-6 shows a male age 12 yr:9 mo with a skeletal and dental Class II. Fig. 3-7 shows the posttreatment result with restraint of forward maxillary growth and the continued forward growth of the mandible. A cervical headgear was worn approximately 11 hours a day to correct the dental and skeletal Class II.

5. What is the timing of treatment for a posterior crossbite with a lateral functional shift, and what kind of treatment is involved? A posterior crossbite with a functional shift should be treated as soon as it is diagnosed to prevent the possible asymmetrical positioning and growth of the condyles.21 Treatment can be initiated as early as the primary dentition (5 to 6 years old). The primary cause for the functional shift is a narrow maxillary arch. In order to have at least one side of functional occlusion, the mandible needs to shift to one side, resulting in the midline discrepancy in CO. If left untreated, this condition may lead to asymmetrical growth of the mandible. Correction of the crossbite with the functional shift can be accomplished with maxillary expansion (Fig. 3-8).

6. What is the timing for treatment for bilateral posterior crossbite without a functional shift, and what kind of treatment is involved? For a child with bilateral posterior crossbite, treatment can be started in the early mixed dentition stage (8 to 9 years), although it can also be successfully treated in the late mixed dentition or early permanent dentition. There is no evidence

to support that treatment in the early mixed dentition results in greater stability than in late mixed dentition. If the maxillary arch is significantly narrow with reduced arch perimeter, early treatment in mixed dentition (Phase I) is indicated to expand the maxillary arch. Expansion can increase the arch perimeter that reduces dental arch crowding and reduces the incidence of canine impaction. Correction of the crossbite is accomplished by maxillary expansion (Fig. 3-9).

7. Is early treatment indicated for a skeletal open bite, and what kind of treatment is involved? A skeletal open bite often displays a high mandibular plane angle, longer lower facial height, and super-eruption of the maxillary teeth with increased dentoalveolar height.22–24 A dental open bite is typically related to thumb or digit sucking habits. The skeletal open bite demonstrates more molar and incisor eruption than a dental open bite.24 Skeletal open-bite malocclusions should be treated early to be successful and if indicated can be initiated in the mixed dentition (age 7 to 9 years). If a skeletal open-bite patient is left untreated until the permanent dentition, the opportunity for growth modification could be lost and correction of the open bite may be compromised. Control of the vertical dimension is the key to successful treatment of patients with a skeletal open bite. The treatment could involve using a bonded RPE with a high pull headgear to reduce vertical maxillary growth and encourage forward rotation of the mandible.25 Fig. 3-10 shows a girl with high mandibular plane angle and anterior open bite. She was treated with a high pull headgear with a bonded RPE and a maxillary 2×4


28

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FIG 3-5 Patient 2 was started with a bonded Haas-type rapid palatal expander (RPE) and a protraction at age 7 yr:2 mo (A-C). At age 8 yr:8 mo, the appliances were removed and a cephalogram was taken (D). The cephalometric tracing (E) showed SNA increased 3.5° to 84.5°, SNB increased 0.5 to 79.5°, ANB increased from 2° to 5°, the Wits decreased from -11 mm to -4 mm, SN-MP increased 1° to 47°. The superimposition showed maxilla moved forward significantly (F). At age 11 yr:5 mo, the correction of anterior crossbite was maintained (G-I).

appliance. The mandibular plane angle was closed by 2 degrees, and her severe Class II skeletal pattern was reduced.

8. What is the appropriate timing for treatment of a digit-sucking habit, and what kind of treatment is involved? A digit-sucking habit is common in children in the primary dentition, and the habit can have a short-term effect on facial and dental development.26 If a prolonged digit-sucking habit continues after the permanent incisors begin to erupt, a significant malocclusion would develop with flared and spaced maxillary incisors, lingually positioned mandibular incisors, an anterior open bite, and a narrow maxillary arch. The best prognosis is when the habit is stopped before the eruption of permanent incisors (age 6 to 7). For children in the mixed

entition or permanent dentition, the habit should be treated d once the problem is detected. An 80% spontaneous correction of the anterior open bite caused by the digit sucking has been reported in patients from age 7 to 12 after they discontinued the habit.27 Habit appliances can involve use of a tongue crib, an RPE (Haas-type) with crib-loops on the acrylic halves, or crib-loops on a Nance button to act as a reminder and a physical block for the digit habit (Fig. 3-11).

9. What is the appropriate timing for correction of anterior crowding? Mild crowding of 1 to 2 mm of the lower incisors is considered normal in the early mixed dentition stage of development, because the permanent incisors are normally wider than the primary incisors (incisal liability). This mild crowding is typically


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FIG 3-6 A 12 yr:9 mo boy in mixed dentition with Class II malocclusion, protruded upper incisors, 8 mm overjet (A-C). A lateral cephalogram and cephalometric measurements showed skeletal Class II (SNA: 88°, SNB: 80°, ANB: 8°), FMA: 28° (D-E).

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FIG 3-7 A cervical headgear was used with orthopedic force to restrain maxillary forward growth and allow normal mandibular growth. The Class II molar relationship was corrected to Class I (A-C). A lateral cephalogram was taken at 16 yr:3 mo, and the ANB was reduced from 8° to 2° (D-E). The superimposition demonstrated no maxillary forward growth and significant mandibular forward growth (F).

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FIG 3-8 A 7-year-old child presented with a unilateral posterior crossbite and functional shift to the right (A-C). Following rapid palatal expander (RPE) treatment, the posterior crossbite was corrected and the functional shift was eliminated (D-F).

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FIG 3-9 An 8 yr:4 mo child presented with bilateral posterior crossbite and anterior crossbite (A-C). After rapid palatal expander (RPE) and facemask treatment, all the crossbites were corrected at age 11 yr:2 mo (D-F).

relieved from the slight increase in the width of the mandible in the region of the canines, the distal movement of canines, and the labial eruption path of the mandibular permanent incisors.26 Moderate crowding of 2 to 5 mm should begin treatment by the late mixed dentition to utilize the leeway space. Studies have shown that approximately 70% of the crowding cases in the mixed dentition can be treated successfully with

maintaining the leeway space.28–30 Procedures performed in the mixed dentition to expand or to develop arches to gain space for alignment may be unnecessary and not stable long term.31 For severe crowding (> 10 mm) without skeletal problems, serial extraction should be considered. It is usually initiated in the early mixed dentition and involves a sequence of e xtraction


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FIG 3-10 An 8 yr:8 mo girl presented with high mandibular plane angle and anterior open bite (A-E). She was treated with a high pull headgear with a bonded rapid palatal expander (RPE) and a maxillary 2×4 appliance. At 9 yr:11 mo the vertical mechanics were able to close the mandibular plane angle by 2 degrees, reduce her severe Class II skeletal pattern, reduce her severe overjet, and correct her posterior crossbite (F-J).

of primary and permanent teeth. This allows the remaining permanent teeth to erupt within the alveolus and through keratinized tissue, and it simplifies later orthodontic treatment.32 Fig. 3-12 shows a 7 yr:10 mo child with Class I and severe crowding. Serial extraction of primary canines, first primary molars, and first premolars was performed. Progress photographs are shown at age 10 yr:10 mo, and at age 12 yr:7 mo the

patient was ready for comprehensive orthodontic care. Serial extraction therapy reduced the severity of the malocclusion and shortened the treatment time. Sometimes expansion in the mixed dentition is helpful for the relief of crowding; however, proper diagnosis is essential to use this approach for the cases with constricted maxillary and mandibular arches.

32


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FIG 3-11 An 8 yr:4 mo child presented with thumb-sucking habit, anterior open bite, and posterior crossbite (A-C). A tongue crib with a quadhelix was used (D-E); the posterior crossbite was corrected, and the anterior open bite was closed at age 10 yr (F-H).

10. When should you treat impacted teeth and supernumerary teeth? Teeth may be impacted due to either soft-tissue or hard tissue (bone or supernumerary tooth) obstruction or an ectopic eruption pathway, and this requires early orthodontic intervention in the mixed dentition. Spontaneous eruption is more likely to occur once the obstruction factor is removed (thick soft tissue, bone, or supernumerary tooth). Occasionally space needs to be created for the impacted tooth, and the tooth needs to be brought into the arch orthodontically. If the impaction is severe, then surgical uncovering may be needed with attachment of a chain to assist in movement of the tooth into the arch. Maxillary permanent canines are the second most frequently impacted tooth that occurs in 2% of the population. When identified in the mixed dentition, extraction of primary canines may be indicated to correct the path of ectopic eruption and possibly avoid surgical and/or orthodontic intervention. If the canine position does not improve 1 year after removal of the primary canine, then orthodontic and surgical intervention should commence in the late mixed dentition.33 The mesiodens is typically located in the maxillary anterior midline region and is the most common supernumerary tooth. Supernumerary lateral incisors may occur but at a far less rate

of occurrence compared to mesiodens. The presence of supernumerary teeth may disrupt normal occlusal development, and they should be removed soon after detection. Fig. 3-13 shows a case with a severe impaction of the maxillary right central incisor with inadequate space to position the impacted incisor. A mesiodens was removed 1 year prior.

11. Why and when should you consider space-regaining procedures in the mixed dentition? Early loss of primary teeth without maintaining the space typically results in space loss from migration of adjacent teeth. Usually space loss of 3 mm or less in one arch can be regained but if the space loss is greater than 4 mm, extraction of permanent teeth may be necessary. The early loss of second primary molars with mesial drifting of the first permanent molars should be treated once it is detected in the mixed dentition. It can be treated simply by a removable appliance with a finger spring to push the molars distally (see Fig. 3-14), headgear therapy, or a lip bumper. In a more severe case of space loss, fixed appliances with active coils would be indicated. A Nance appliance may be needed to provide anchorage while regaining space. This space loss may cause the impaction of the second premolars by mesial drifting of the first molars. Although this


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FIG 3-12 A 7 yr:10 mo child presents with Class I, severe crowding (A-F). Serial extraction of primary canines, primary first molars, and first premolars was performed. Progress photographs at age 10 yr:10 mo (G-K). At age 12 yr:7 mo (L-Q), the patient is ready for comprehensive orthodontic care.

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FIG 3-13 An 8 yr:9 mo child presented with an impacted maxillary right central incisor caused by a mesiodens that was extracted at age 7 yr:11 mo. Space was opened with fixed appliances and a coil spring to open space for the maxillary right central incisor. Surgical uncovering and attachment of a chain was necessary to move the central incisor into the dental arch.32

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D FIG 3-14 A 6-year-old child with early loss of maxillary left second primary molar and a mesially erupting maxillary right first molar that caused resorption of maxillary right second primary molar (A-B) and significant loss of maxillary arch length. At age 8, the upper first molars were successfully distalized and uprighted (C-D) to gain space for eruption of the second premolars.

type of problem can still be treated in the permanent dentition, it will be more difficult, and often extraction of permanent teeth is needed. If an ectopic first molar is detected early before the second primary molar exfoliates, an elastic or metal spring separator can be used to unlock the first permanent molar from the distal of the second primary molar, circumventing the need for additional orthodontic intervention.

12. What is the appropriate timing for orthognathic surgery? Generally it is best to perform orthognathic surgery of excessive jaw structures when growth is completed. Conversely, it is appropriate to treat jaw deficiencies before growth is complete but rarely before the adolescent growth spurt.26 For instance,


mandibular prognathism cases requiring orthognathic surgery should be treated after growth is completed. Mandibular retrognathism cases requiring orthognathic surgery can be treated before growth is complete but usually after the adolescent growth spurt. Orthognathic surgery for maxillary vertical excess should be delayed until after growth is complete; however, maxillary vertical deficiencies may be treated earlier. For maxillary transverse deficiency problems, surgery should not be considered until late adolescence. Superimposition of serial cephalograms can be used to evaluate if the patient is still growing and help determine the timing for surgery of Class III cases with a prognathic mandible. Occasionally a patient can present with a Class III malocclusion with a mandibular asymmetry due to unilateral hypertrophy of the condyle that can continue to grow into the late 20s. Surgery for these cases should be delayed until cessation of condylar growth, and this can be confirmed with a technetium bone scan. REFERENCES 1. Proffit WR: The timing of early treatment: an overview, Am J Orthod Dentofacial Orthop 129:S47–S49, 2006. 2. Bishara SE, Nemeth R: Current challenges and future dilemmas facing the orthodontic profession, Angle Orthod 72:88–90, 2002. 3. Gottlieb EL, Nelson AH, Vogels III DS: 1990 JCO study of orthodontic diagnosis and treatment procedures. 2. Breakdowns of selected variables, J Clin Orthod 25:223–230, 1991. 4. Chung C-H, Hufham DC: A corrected cephalometric tracing technique for diagnosis and treatment planning of anterior crossbite with functional shift, J Clin Orthod 35:500–504, 2001. 5. Baccetti T, McGill JS, Franchi L, McNamara Jr. LA, Tollaro I: Skeletal effects of early treatment of Class III malocclusion with maxillary expansion and face-mask therapy, Am J Orthod Dentofacial Orthop 113:333–343, 1998. 6. Kapust AJ, Sinclair PM, Turley PK: Cephalometric effects of face mask/expansion therapy in Class III children: a comparison of three age groups, Am J Orthod Dentofacial Orthop 113:204–212, 1998. 7. Takada K, Petdachai S, Sakuda M: Changes in dentofacial morphology in skeletal Class III children treated by a modified maxillary protraction headgear and a chin cup: a longitudinal cephalometric appraisal, Eur J Orthod 15:211–221, 1993. 8. Ngan P, Wei SH, Hagg U, et al: Effect of protraction headgear on Class III malocclusion, Quintessence Int 23:197–207, 1992. 9. Ngan P, Yiu C, Hu A, et al: Cephalometric and occlusal changes following maxillary expansion and protraction, Eur J Orthod 20:237–254, 1998. 10. Ngan P, Hagg U, Yiu C, et al: Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction, Semin Orthod 3:255–264, 1997. 11. Turley PK: Managing the developing Class III malocclusion with palatal expansion and facemask therapy, Am J Orthod Dentofacial Orthop 122:349–352, 2002. 12. Sugawara J, Asano T, Endo N, et al: Long-term effects of chincap therapy on skeletal profile in mandibular prognathism, Am J Orthod Dentofacial Orthop 98:127–133, 1990. 13. Tulloch JF, Phillips C, Koch G, et al: The effect of early intervention on skeletal pattern in Class II malocclusion:

14. 15. 16. 17.

18.

19.

20. 21. 22. 23.

24. 25. 26. 27. 28. 29. 30. 31.

32. 33.

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a randomized clinical trial, Am J Orthod Dentofacial Orthop 111:391–400, 1997. Tulloch JF, Proffit WR, Phillips C: Influences on the outcome of early treatment for Class II malocclusion, Am J Orthod Dentofacial Orthop 111:533–542, 1997. Tulloch JF, Phillips C, Proffit WR: Benefit of early Class II treatment: progress report of a two-phase randomized clinical trial, Am J Orthod Dentofacial Orthop 113:62–72, 1998. Wheeler TT, McGorray SP, Dolce C, et al: Effectiveness of early treatment of Class II malocclusion, Am J Orthod Dentofacial Orthop 121:9–17, 2002. Dolce C, Schader RE, McGorray SP, et al: Centrographic analysis of 1-phase versus 2-phase treatment for Class II malocclusion, Am J Orthod Dentofacial Orthop 128:195–200, 2005. King GJ, McGorray SP, Wheeler TT, et al: Comparison of peer assessment ratings (PAR) from 1-phase and 2-phase treatment protocols for Class II malocclusions, Am J Orthod Dentofacial Orthop 123:489–496, 2003. O’Brien K, Wright J, Conboy F, et al: Effectiveness of early orthodontic treatment with the Twin-block appliance: a multicenter, randomized, controlled trial. 1. Dental and skeletal effects, Am J Orthod Dentofacial Orthop 124:234–243, 2003. Marshall WA, Tanner JM: Puberty. In Falkner F, Tanner JM, eds, Human Growth, ed 2, vol 2, New York, 1986, Plenum Publishing. Pirttiniemi P, Kantomaa T, Lahtela P: Relationship between craniofacial and condyle path asymmetry in unilateral crossbite patients, Eur J Orthod 12:408–413, 1990. Chung C-H, Wong WW: Craniofacial growth in untreated skeletal Class II subjects: a longitudinal study, Am J Orthod Dentofacial Orthop 122:619–626, 2002. Chung C-H, Mongioivi VD: Craniofacial growth in untreated Class I subjects with low, average, and high mandibular plane angles, Am J Orthod Dentofacial Orthop 124:670–678, 2003. Cangialosi T: Skeletal morphologic features of anterior open bite, Am J Orthod 85:28–36, 1984. Sankey W, Buschang P, English J, et al: Early treatment of vertical skeletal dysplasia: the hyperdivergent phenotype, Am J Orthod Dentofacial Orthop 118:317–327, 2000. Proffit WR: Contemporary orthodontics, ed 5, St Louis, 2013, Mosby. Worms F, Meskin LH, Issacson RJ: Open bite, Am J Orthod 59:589–595, 1971. Gianelly AA: Crowding, timing of treatment, Angle Orthod 64:415–418, 1994. Brennan MM, Gianelly AA: The use of the lingual arch in the mixed dentition to resolve crowding, Am J Orthod Dentofacial Orthop 117:81–85, 2000. Dugoni S, Lee JS, Dugoni A: Early mixed dentition treatment: postretention evaluation of stability and relapse, Angle Orthod 65:311–319, 1995. Little RM, Riedel RA, Stein A: Mandibular arch length increase during the mixed dentition: postretention evaluation of stability and relapse, Am J Orthod Dentofacial Orthop 97:393–404, 1990. Kluemper GT, Beeman CS, Hicks EP: Early orthodontic treatment: what are the imperatives? J Am Dent Assoc 131:613–620, 2000. Bedoya M, Park J: A review of the diagnosis and management of impacted maxillary canines, J Am Dent Assoc 140:1485–1493, 2009.

C H A PT E R

4

Orthodontic Records and Case Evaluation Jeryl D. English • Thuy-Duong Do-Quang • Anna Maria Salas-Lopez

I

n a problem-oriented approach to diagnosing and treatment planning of patients with malocclusions, it is necessary to gather relevant information in a consistent manner in order to start a comprehensive database of information for each patient. First, the orthodontist must establish a case history of each patient, noting the chief concerns, including medical and dental history. Second, a thorough clinical examination of the patient should be conducted to obtain accurate measurements and objective findings, which are the basis of the orthodontic diagnosis. This clinical examination should include a facial evaluation, both in the frontal and profile views, as well as an examination of the patient’s extraoral and intraoral soft tissue. The clinical examination should also contain an assessment of the dentition and a functional analysis of the temporomandibular joint (TMJ). Finally, complete orthodontic records should be taken, which consist of digital or plaster of Paris study models, panoramic and cephalometric radiographs, bitewing and periapical radiographs of the anterior teeth in adults, and extraoral and intraoral photographs. Any additional records that the orthodontist deems necessary should be included. In general, these orthodontic records document the patient’s initial condition and supplement the diagnostic information obtained through the patient interview and examination. The orthodontist can now analyze the collected data for problems in the areas of clinical examination, study cast analysis, radiographic analysis, and photographic analysis (Box 4-1). After completion of the analysis, a list of problems in each of these areas can be developed and prioritized. In addition, a 3D-3T diagnostic grid is recommended as an aid in ensuring that all three dimensions (3D) of a malocclusion as well as all three tissues (3T) are evaluated. The three dimensions include sagittal, transverse, and vertical plane; the three tissues include skeletal, soft-tissue, and dental structures. It is critical to understand that incorrect diagnosis is usually related to lack of information. A comprehensive diagnosis provides a summary of the most important problems from each of the four areas listed above. CLINICAL EXAMINATION

1. Which key points should be clarified in the patient’s medical and dental history? It is important to note the patient’s chief concern and specify whether treatment is sought for functional reasons, esthetic 36

improvement, or both.1 Medical conditions, diseases, hospitalizations, and current medications should be recorded. Drugs that may trigger hyperplastic gingival response, such as phenytoin, calcium channel blockers, and immunosuppressives,2 as well as medications that may inhibit orthodontic tooth movement, such as bisphosphonates3 or prostaglandininhibitors,4 are important to document on the patient’s problem list.5 Allergies, especially to nickel or latex, should be noted by the orthodontist. Any facial or dental trauma, extractions, and habits should be listed and the oral hygiene regimen assessed. Possible familial patterns of malocclusion should be explored by collecting information about whether parents or siblings have undergone orthodontic treatment.6 Finally, voice change in boys and menarche in girls can be used to assess the stage of the patient’s development.7

2. Which aspects should be covered in the clinical examination? In general, the face, oral cavity, and surrounding areas (including dentition) and TMJs should be examined. This specifically includes assessment of asymmetries, lip position in closure and repose, classification of the perioral musculature, and measurement of the incisor display at rest (see the following cephalometric and photographic analysis questions). The health of all oral tissues and the patient’s periodontal status, especially in adults, should be evaluated. Periapical and bitewing radiographs are essential in evaluating all adult patients.8 It is imperative to test probing depths for adult patients and document a periodontal screening index (PSI) to document the status of the periodontium prior to any orthodontic treatment.9 The condition of the teeth with detailed recording of caries as well as dental and occlusal anomalies in the transverse, sagittal, and vertical plane should be noted along with assessment of the maxillary and mandibular apical bases, determination of facial and dental maxillary and mandibular midlines, and palpation of unerupted teeth.

3. Which aspects of jaw and occlusal function should be evaluated? There are five main areas of interest to the orthodontist: mastication, speech, breathing mode, orofacial dysfunctions, and TMJ function. Mastication, including swallowing patterns as well as the presence of speech problems, such as articulation distortion, stuttering, or dyslexia, requires evaluation. Depending on the severity, this may necessitate referral to a

Orthodontic Records and Case Evaluation • CHAPTER 4

BOX 4-1

Data Areas Used for Analyses

• Clinical examination • Case history • Chief complaint • Temporomandibular joint (TMJ) function analysis • Periodontal and caries analyses • Study cast analysis • Radiographic analysis • Panoramic x-ray • Lateral cephalometric and posterior-anterior x-rays • Periapical and bitewings • Photographic analysis

A

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Ideally, mandibular movements should be painless and, for adults, within a normal range of 50-mm maximal opening and 10-mm lateral excursions. The amount of maximal mouth opening is age related and therefore generally less than 50 mm for children. Functional shifts between centric occlusion (CO) and centric relation (CR) outside the normal range of 1.5 mm need to be recorded, because they have been correlated with increased temporomandibular disorders (TMDs).16 CO-CR discrepancy may result in a false bite commonly referred to as Sunday bite, which is the forward postural position of the mandible adopted by patients with Class II profiles in order to enhance their appearance. Shifts can also be related to occlusal interferences, requiring posturing into pseudo Class III malocclusions.17 TMD is subdivided into true pathologies of the TMJ (TMJ disorders) and myofascial pain dysfunction (MPD),18 which affects masticatory and cervical muscles.19 Any clinical diagnosis should be substantiated by radiographic evidence, as well as computed tomography (CT) and/or magnetic resonance imaging (MRI) scans as needed. However, most patients presenting with MPD usually lack clinical or radiographic evidence of pathologic TMJ changes.18

5. Which areas should be explored in the patient’s social and behavioral evaluation?

B FIG 4-1 A, Open bite malocclusion caused by a thumb-sucking habit. B, Malocclusion caused by a tongue-thrusting habit.

specialist. The patient should also be asked about the prevalent respiration mode, mouth versus nasal breathing, and possible sleep disorders or problems with restricted airways, such as snoring. These may be associated with conditions such as tonsillar or adenoid enlargement, nasal obstruction, allergies, and retruded mandible. However, the etiologic significance of respiration mode in relationship to facial growth and development of malocclusions remains controversial throughout the literature.10,11 Deleterious habits (i.e., lip biting or thumb or finger sucking [Fig. 4-1, A]), cheek biting, bruxism, nail biting, and tongue thrusting [see Fig. 4-1, B]) are imperative to document. They might be partially etiologic to open bite12 and posterior crossbite13 or, in case of tongue thrusting, compensatory factors of a presenting malocclusion.14

4. How is the temporomandibular joint function examined? The patient should be initially questioned about existing TMJ problems and the history of symptoms verified through manipulation and auscultation of the TMJ for sounds such as clicking, popping, or crepitus. Palpation of the TMJ and masticatory muscles is necessary to detect tenderness or pain. In addition, the patient’s range of motion (ROM) should be recorded by observing and measuring maximal mouth opening, right and left lateral excursions, and protrusive movement.15

The patient’s motivation to seek orthodontic treatment should be assessed, because attitude and expectations concerning treatment are closely related to motivation. In general, internally as opposed to externally motivated patients show better cooperation.20 Progress in school and reaction to past medical or dental treatment may also be indicative of the patient’s compliance level. A history of prolonged sucking habits, poor educational advancement, sleepwalking in younger children, and enuresis in older children may be related to emotional problems. In addition, patients affected by conditions such as autism and attention deficit disorder (ADD)/attention deficit hyperactivity disorder (ADHD) should be identified to determine the best mode of treatment.

6. What are the ages that need to be considered in orthodontic care? Chronologic, skeletal, dental, mental, and emotional age are differentiated in the assessment of the development of a patient. Chronologic age does not correlate well with the other ages; thus, assessment of the skeletal or physiologic age helps to determine the biologic age.21 This is most commonly done by evaluation of a hand-wrist radiograph of the non-working hand or both hands in children under 6 years of age.22 It is indicated in children above the 95th or under the 5th percentile of somatograms and prospective orthognathic surgery patients. The method determines developmental and somatic maturity with a variability of ±1 year, although in patients less than 10 years of age, poor correlation to chronologic, dental, or mental age has been observed. Understanding the timing and sequence of formation of both the primary and permanent dentition is essential for diagnosis of the dental age. It is best determined by the stages of individual tooth mineralization, since this process is not

38

CHAPTER 4 • Orthodontic Records and Case Evaluation

affected by early tooth loss. Various tests have been developed to assess the mental and emotional age of a patient that may not closely correlate with the developmental age. The latter can be roughly determined by evaluation of the secondary sexual characteristics. A child is considered an early or late developer if a difference of ±2 years is found between chronologic and dental age.

7. What methods can be applied to assess the physical growth and maturation status of an individual? Evaluation of the skeletal maturity of a patient is important to maximize efficiency and effectiveness of orthodontic treatment through proper timing. If a treatment plan demands a skeletal dentofacial orthopedic modification, the patient should be treated as close as possible to the peak velocity of growth.23 The use of headgear or functional appliances, like the Twin Block or Herbst appliance, appears more effective if applied at or slightly after the onset of the pubertal growth spurt in the late mixed dentition.24,25 Information regarding active growth cessation is crucial, especially in patients undergoing orthognathic surgery. Gender-specific growth curves classify a child under a height and weight percentile to establish norms for chronologic age. Currently, hand-wrist radiographs are the gold standard of growth assessment. The skeletal age is evaluated by analysis of a predictable ossification sequence of long bones of the wrist and carpal bones of the hand in children up to 9 years and metacarpals after 9 years of age.26,27 Specific skeletal maturational events can then be linked to identify the patient’s progression on the pubertal growth curve.28 Application of this method is indicated in orthognathic surgery patients ranging in age from 16 to 20 years and in patients with marked discrepancy between chronologic and dental age. More recently, it has been shown that the peak pubertal growth can also be estimated by evaluation of the maturation level of the cervical vertebrae pictured on a cephalographic radiograph.29,30 Shape as well as concavity of the inferior border of C2 through C6 is sequentially assessed in this method,31 thereby eliminating the need for an additional hand-wrist radiograph, because a cephalogram is routinely taken for every prospective orthodontic patient.32–34

8. How is the malposition of individual teeth classified? A malposed tooth can be inclinated, centrically or eccentrically malpositioned, totally displaced, rotated, transposed, or localized by various combinations thereof. According to Liescher’s nomenclature, the malposition of a tooth is termed mesioversion if it is displaced toward the facial midline (Fig. 4-2, A); it is classified as distoversion if it is located farther away from the midline (see Fig. 4-2, B). If an incisor or canine is misplaced outside the arch form toward the lip, this is described as labioversion (see Fig. 4-2, C); if a posterior tooth is dislocated toward the cheek, it is described as buccoversion. A tooth is known to be linguoverted if it is inclined toward the tongue (see Fig. 4-2, D).

The term infraversion is applied if a tooth is not erupted to the occlusal plane (see Fig. 4-2, E), whereas supraeruption describes an overerupted tooth. A tooth rotated on its own axis is classified as torsiversion. Transposition or transversion denotes a positional interchange of two adjacent teeth,35 which is found most commonly in the maxilla with an incidence described as high as 1 in 300 patients.36,37 The transposition of an upper canine with the first premolar is shown in Fig. 4-2, F.

9. Which tooth most often displays an anomaly? In general, third molars are most commonly affected by size and shape variations, followed by upper lateral incisors and lower second premolars. Anomalies can result from genetic factors as well as environmental influences, such as nutrition or diseases during the prenatal period of tooth development. Upper lateral incisors have been described as absent, pegshaped, hypoplastic, and dens evaginatus or invaginatus. Pegshaped laterals are found in 1% to 2% of the population and are characterized as being small, conical, and tapered toward the incisal (Fig. 4-3, A). Shovel-shaped incisors mark another morphological variant. These teeth show pronounced lingual ridges and cingula and are more common in the Asian, Eskimo, and Native American populations.38 In contrast, cusps of Carabelli on permanent molars have the greatest incidence among Caucasians (see Fig. 4-3, B).39 The term taurodontia describes a tooth whose crown and pulp chamber are elongated with little or no constriction at the cementoenamel junction (CEJ), resulting in a short root. The incomplete division of a single tooth germ is known as gemination (see Fig. 4-3, C). These teeth clinically appear as fused with a notch in the crown but generally display a single root and pulp chamber. Truly fused teeth, however, result from union of the dentin of two adjacent tooth buds. Consequently, tooth count normally reveals one less individual tooth in the affected arch. Twinning is the complete division of one tooth germ into two teeth, resulting in one more individual tooth than the normal complement. If two adjacent teeth are joined only at the cementum, they are described as being concrescent. A dens evaginatus is characterized by a talon cusp (see Fig. 4-3, D). Invagination of the enamel organ into the crown, thereby extending into the dentin and root of a tooth, is known as dens invaginatus or dens in dente. It is more common in the permanent dentition with an incidence of about 2% and usually affects the upper lateral incisor.40 The teeth can be hypoplastic (microdontia) (see Fig. 4-3, E) or hyperplastic (macrodontia) (see Fig. 4-3, F) in size, and discolorations can be of intrinsic or extrinsic origin. Mineralization abnormalities can also be observed sporadically or as part of a syndrome, such as dentinogenesis and amelogenesis imperfecta (see Fig. 4-3, G), characterized by deficient calcification as in hypermineralization or deficient matrix formation as in hyperplasia of the affected tooth component.


A

B

C

D

39

E

F FIG 4-2 A, Mesioversion of maxillary right central incisor. B, Distoversion of maxillary right lateral incisor. C, Labioversion of maxillary left central incisor. D, Linguoversion of maxillary central incisors. E, Infraversion of mandibular left second deciduous molar. F, Transposition of maxillary right cuspid and first premolar.

ORTHODONTIC MODELS

10. What are the significant areas of cast analysis? Dental casts obtained from impressions that extend far enough into the sulcus to allow accurate reproduction of the soft-tissue anatomy should accurately represent the dentition and immediate supporting structures. The objective of studying cast analysis is the three-dimensional (3D) assessment of the maxillary and mandibular dental arches and their occlusal relationships. This encompasses the metric analysis of arch width, length, symmetry, and palatal height as well as tooth size and space analysis in relation to the apical bases and examination of the interarch occlusion. The apical base arch is the area of alveolar bone on the level of the root apices of the teeth, whereas the basal arch is formed by the maxillary and mandibular corpus. Its dimensions are stable and unaffected by tooth loss or alveolar resorption. The dental arch perimeter is measured through the contact points of the teeth and ideally should

be congruent to the sizes of the alveolar and basal arches. It should be noted that the mandibular arch is often referred to as the diagnostic arch because of the cortical bone on the facial and lingual surfaces. In contrast to the intermolar width, which significantly increases in the maxillary arch between 3 and 13 years of age, the mandibular intercanine distance increases during the transition of primary to permanent dentition41 (see Chapter 2) and then decreases slightly until adulthood. As part of the cast analysis, the individual arch shape should be appreciated. It has been shown that the most common arch form is the ovoid arch, followed by tapered and squared arch shapes (Fig. 4-4).42 Arch length discrepancy, also referred to as arch circumference discrepancy, is identified as the difference between the available arch length and the required arch length. It is determined by measuring the mesiodistal tooth widths of the permanent teeth from the mesial of the permanent mandibular first molars for the mandibular arch and permanent maxillary first molars for the maxillary arch.

40


A

B

C

D

F

E

G FIG 4-3 A, Maxillary peg lateral incisors and retained left deciduous cuspid. B, Cusp of Carabelli on maxillary first molars. C, Gemination of mandibular central and lateral incisors. D, Dens in dente with talon cusp. E, Microdontia of maxillary tooth with generalized spacing. F, Macrodontia of maxillary lateral incisors. G, Amelogenesis imperfecta.

11. What is the Bolton analysis? The Bolton analysis offers a method to determine the ratio of the mesiodistal widths of the maxillary versus the mandibular permanent teeth, also known as tooth size discrepancy, and its interarch effects. When looking at interarch relationships, it is essential to treat the anterior teeth separately from the posterior units. Tooth size discrepancies in the anterior region can

be corrected only with compensations in the anterior region and not through treatment changes in the posterior teeth. Thus, the Bolton analysis consists of an anterior ratio analysis, designed to identify incompatibilities in anterior teeth, or a whole dentition ratio, which, when compared to the anterior ratio, determines the discrepancies of the posterior teeth. The anterior ratio is calculated by dividing the sum of the mesiodistal widths of the mandibular six anterior teeth by the sum


41

A

C

B

FIG 4-4 Arch forms. A, Ovoid; B, tapered; C, square.

of the mesiodistal widths of the maxillary anterior teeth and then multiplying the result times 100. The mean anterior ratio is 77.2, whereas the mean overall ratio is 91.3. The latter is calculated according to the same principle as the anterior ratio but is calculated by dividing the sum of the mesiodistal widths of the mandibular right first molar tooth to the left first molar tooth by the sum of the mesiodistal widths of the maxillary first molar to first molar teeth.43,44 Studying the Bolton ratios using standardized tables for comparison of the anterior and overall ratio relationship helps to estimate the overbite and overjet relationship that likely will be obtained through orthodontic treatment as well as to identify occlusal discrepancies produced by interarch tooth size incompatibilities. It has been found that there is a high incidence of tooth size discrepancies throughout all malocclusion groups.45 Statistically, about 5% of the population display some disproportion among individual tooth sizes, with the upper lateral incisor being most commonly affected. However, application of the Bolton analysis should be handled with care, since arch length discrepancies seem to be specific for gender and ethnicity.46

12. What represents the basis for Angle’s dental classification? The Angle classification, first published in the 1890s, is based on the anteroposterior occlusal relationship of the permanent first molar that was termed the key to occlusion. According to Angle, a Class I normal occlusion is defined by the interlocking of the mesiobuccal cusp of the upper first molar into the mesiobuccal groove of the lower first molar (Fig. 4-5, A).

A Class II malocclusion is defined by the buccal groove of the mandibular first molar being distally positioned when in occlusion with the mesiobuccal cusp of the upper first molar. If the maxillary anterior teeth are also proclined with a large overjet, the resulting malocclusion is classified as Class II division 1 (see Fig. 4-5, B). If a patient presents with retroclined maxillary incisors often in combination with a deep overbite, the malocclusion is termed Class II division 2 (see Fig. 4-5, C). A Class III malocclusion is diagnosed when the buccal groove of the mandibular first molar is mesially positioned to the mesiobuccal cusp of the upper first molar in occlusion (see Fig. 4-5, D).47 According to the National Health and Nutrition Examination Survey (NHANES) III study, 30% of the US population presents with a normal occlusion and 50% to 55% presents with a Class I malocclusion. The prevalence of Class II malocclusion is 15% to 20%, whereas less than 1% of the population is affected by a Class III malocclusion.48 It has often been criticized that the Angle classification only addresses malocclusions in the sagittal dimension without evaluation of dental alignment and amount of crowding. Only dentoalveolar relationships are described without any further skeletal or dentoskeletal evaluation, and even here, the system fails to address all possible malocclusion groups, such as subdivisions that represent the condition of a unilateral malocclusion (also see questions in Chapter 2).49

13. How are asymmetric occlusal relationships classified? Asymmetric occlusal relationships can result from asymmetry within an individual arch or from asymmetric skeletal

42


A

B

A

C

D FIG 4-5 A, Angle’s Dental Class I malocclusion. B, Angle’s Dental Class II, division 1 malocclusion. C, Angle’s Dental Class II, division 2 malocclusion. D, Angle’s Dental Class III malocclusion.

r elationships. If the center of the mandible is not aligned with the facial midline in rest position as well as occlusion, a true asymmetry is present and termed laterognathy. If a midline shift of the mandible is discernible only in occlusion within a symmetrical skeleton, a functional shift is most likely the cause of this phenomenon called laterocclusion (Fig. 4-6). If this patient’s posterior crossbite with functional shift is not treated early with a maxillary expansion appliance and equilibration, the facial asymmetry becomes permanent. The relative contributions of skeletal and dental compo nents to occlusal asymmetries must be distinguished in order to develop treatment plans that will achieve skeletal and dental symmetry.50 It should be noted that mandibular and/or condylar trauma may contribute to the development of skeletal asymmetries. Ankylosis of primary molars with resultant tipping of the adjacent teeth into the space as well as ectopic eruption of maxillary permanent first molars that often leads to premature loss of the primary second molar and subsequent loss of arch length may contribute to dental arch asymmetry. Congenitally missing or supernumerary teeth as well as space loss caused by interproximal caries or premature loss of primary or permanent teeth can result in asymmetric occlusal relationships as well as dental midline shifts.51

B FIG 4-6 Functional shift. A, Patient is relaxed in centric relation (CR). B, Patient is biting in centric occlusion (CO) with obvious mandibular functional shift.

14. Are digital models as reliable for diagnosis as plaster of Paris models? OrthoCAD or e-models for 3D study cast analysis have been shown to reproduce the dentition with an accuracy of ±0.01 mm, thus rendering a reliable tool for assessment of a patient’s occlusal relationships.52 These programs also quickly provide several tools to aid diagnosis and treatment planning, such as Bolton and space analysis, as well as occlusograms. In addition to improving acquisition, storage, and retrieval of the study models, the digital representation facilitates communication with other practitioners.53,54

15. When would a diagnostic setup be useful? A prognostic or diagnostic setup is a technique that involves cutting teeth off a working cast and resetting them into a more desirable position to visualize space concerns and ascertain amount and direction of tooth movement before treatment is initiated. This may be especially helpful in interdisciplinary cases or cases using osseointegrated implants, unusual extraction patterns as well as prediction of treatment outcomes. Digital models, however, offer a less time-consuming tool to address the previously described issues.


43

16. What are indications for mounting orthodontic casts on the articulator? Advocates of mounted orthodontic study casts stress the importance of this technique in revealing determinants of CO-CR discrepancy, such as anteroposterior changes, vertical discrepancies, occlusal plane cants, and functional shifts caused by premature tooth contacts,55 especially since a study revealed that 34% of adolescents and 66% of adults present with CO-CR discrepancies greater than 2 mm.56 However, there is no evidence to support the need to mount orthodontic models.57,58 The key assumption of articulator mounted models (i.e., that the relative position of the condyle to the occlusion will remain stable) is never met in growing patients. Considering CR registration and transferring as another potential error source,17 it can be concluded that mounted casts do not enhance the diagnostic profile of children and adolescents. Mounted models are indicated in treatment planning and splint fabrication for orthognathic surgery patients, especially those undergoing a bimaxillary procedure, as well as recording of excursive movements in interdisciplinary cases when restorative dentistry is planned or if a CO-CR shift greater than 2 mm is present.17,55

A

B

ORTHODONTIC RADIOGRAPHS

17. What are the advantages of a panoramic radiograph over a series of intraoral periapical radiographs? Some patients can be diagnosed with missing teeth (Fig. 4-7, A) or supernumerary teeth (see Fig. 4-7, B and C) at the clinical examination without radiographs. However, panoramic radiographs offer a broader view of the entire maxillary and mandibular arch including the TMJ (see Fig. 4-7, D). Thus, it is more likely to show any pathologic lesions and mandibular asymmetries as well as supernumerary or missing teeth, variations in development or eruption timing, impaction, and deviations in tooth morphology while offering limited information about gross periodontal health, sinuses, and root parallelism.59 It is also a useful tool in assessing quality and quantity of alveolar bone for implant or temporary anchorage device (TAD) placement and their proximity to vital structures, such as the mandibular canal. Although exposing the patient to much lower radiation doses than a full mouth series, a disadvantage of the rotary panoramic radiograph technique is possible distortion of the x-ray in the anterior region.

18. When are supplemental intraoral periapical films indicated? Although panoramic radiographs offer a reliable screening tool for detection of dental abnormalities,60 additional periapical xrays are needed if the panoramic radiograph suggests a pathologic condition that requires depiction in greater detail for more accurate evaluation.59 It is also indicated to assess the periodontal status in adult patients as well as for the evaluation of root morphology and length in cases of root resorption61 and appreciation of the periodontal ligament (PDL) space to rule out possible ankylosis.

C

D FIG 4-7 A, Congenitally missing maxillary lateral incisors. B and C, Supernumerary teeth: two maxillary mesiodens (B) and five mandibular incisors (C). D, Panoramic radiograph demonstrating tooth agenesis.

19. What is the primary rationale for taking a posteroanterior cephalometric film? It is indicated in patients with significant clinical facial asymmetries who display a large discrepancy of the border of the mandible in the lateral cephalogram as well as for evaluation of severe dental midline discrepancies (Fig. 4-8). The horizontal symmetry of the mandible as well as angulation of its condyles and craniofacial anomalies can also be further explored via a submentovertex cephalogram as needed.62

44


FIG 4-8 Posteroanterior cephalometric film for asymmetry.

20. What are the different applications of a lateral cephalometric radiograph? With the introduction of cephalometric analysis in 1931 by Hofrath63 in Germany and Broadbent64 in the United States, the orthodontist was given a tool to accurately evaluate the un derlying anatomic basis for malocclusion and reveal details of skeletal and dental relations. Information from assessment of the configuration of the facial skeleton, relation of the jaw bases, axial inclination of the incisors, as well as soft-tissue morphology, growth pattern, and direction can be used in diagnosis and treatment planning and prediction and recapitulation of treatment responses.65,66 Critical limitations of the cephalogram lie foremost in the 2D representation of 3D structures. Therefore, advances in craniofacial imaging techniques will overcome these restrictions.67

21. What are the important hard- and softtissue points in cephalometric analysis? LANDMARKS Landmarks describe anatomic points that are used in measuring a cephalogram for analysis (Fig. 4-9). When these measurements are compared with “normals,” they aid in diagnosis and treatment decisions to correct the underlying problems. Cephalometric landmarks are divided into two types: anatomic and derived. Anatomic landmarks are those representing actual anatomic structures of the skull. Derived landmarks are constructed points from anatomic structures. Certain structures fall in the midsagittal plane and are therefore identified as a single point. Many other structures occur on both sides of the face, resulting in two radiographic points that are not coincident because of enlargement by the x-ray beam. To obtain a single, measurable point, these points are “bisected,” thereby taking an average of the two points.68

FIG 4-9 Cephalometric radiograph showing the landmarks.

Hard-Tissue Landmarks Midsagittal Landmarks Sella (S): Center of the hypophyseal fossa (sella turcica). Nasion (N): Most anterior point of the junction of the nasal and frontal bones (frontonasal suture). Anterior nasal spine (ANS): Most anterior bony point on the maxilla at the base of the nose. Posterior nasal spine (PNS): Posterior limit of the bony palate, radiologically constructed at the intersection of the continuation of the anterior wall of the pterygomaxillary fissure and the nasal floor. “A” point or subspinale (A): Innermost arbitrary measure point on the curvature from the maxillary ANS to the crest of the maxillary alveolar process. “A” point is the most anterior point of the maxillary apical base and is usually located at the level of the maxillary central incisor root tip. “B” point or supramentale (B): Deepest arbitrary measure point on the anterior bony curvature of the mandible. It is usually located at the level of the root tip of the lower central incisor representing the most anterior point of the mandibular apical base. Pogonion (Pog): Most anterior point on the contour of the bony chin (mandibular symphysis). Menton (Me): Most inferior point on the mandibular symphysis. Gnathion (Gn): Most anterior inferior point on the curvature of the symphysis of the mandible. It is usually located halfway between the pogonion and menton. Bilateral Landmarks Orbitale (Or): Lowest point on the inferior margin of the orbit. Porion (P): Most superior point on the anatomic external auditory meatus (mechanical porion not used).


Articulare (Ar): A point midway between the two posterior borders of the left and right mandibular ramus at the intersection with the basilar portion of the occipital bone. Gonion (Go): Midpoint of the curvature at the angle of the mandible. Represents the junction of the ramus and body of the mandible at its posterior inferior aspect.68 Soft-Tissue Landmarks Glabella (Gla): Most anterior midsagittal point on the prominence of the forehead. Subnasale (Sn): Point at which the nasal columella merges with the upper lip integument in the midsagittal plane. Stomion (St): Located at the junction of the upper and lower lip. If lip incompetence in rest position is present, the most inferior point on the upper lip should be used to represent stomion.68

22. What are the important diagnostic reference planes? Reference lines connecting two landmarks are constructed before angular, linear, and proportional measurements are made. Sella-nasion (SN) is the major horizontal cranial reference plane, whereas the Frankfort horizontal (FH) forms the reference to the face and the Y-axis determines the growth pattern. Lateral cephalograms should be taken in the natural head position (NHP) that is registered when the patient looks at a mirror in front of himself or herself at eye level (Fig. 4-10). Since the NHP is not affected by intracranial landmarks and is more accurately reproducible, true vertical and horizontal reference lines can be traced.68 ANATOMIC PLANES Sella-nasion (SN): Plane formed by connecting S point to N point. It represents a relatively stable anatomic structure known as the anterior cranial base. During growth and treatment, the SN plane remains relatively constant and can be used as a reference point to measure positional change of the maxilla and mandible.

Frankfort horizontal (FH): Formed by connecting porion and orbitale. Palatal plane (PP): Formed by a line connecting ANS to PNS. PP and FH are usually nearly parallel. Mandibular plane (MP): A line drawn from menton to constructed gonion. The inferior border of the mandible may vary somewhat from the line drawn through gonion, especially in cases with steep (high) MP angles. Drawing the line through bisected gonion is the most reproducible representation of MP. Y-Axis (SGn): The line from sella to gnathion. It is used as an indicator for facial growth tendency by measuring the angle formed between SGn and FH.

23. Which linear and angular values are essential for both the general dentist and orthodontist to know and characterize the three different planes of space in orthodontic diagnosis? ESSENTIALS OF THE CEPHALOMETRIC ANALYSIS Table 4-1 provides a summary of the following findings.68 Anteroposterior Skeletal Measurements SNA angle: Draw a line from nasion to A point, and measure the angle formed between this line and the SN plane. Norm = 82° ± 3

SNB angle: Draw a line from nasion to B point and again measure the angle formed with the SN plane. The SNB angle represents the anteroposterior position of the mandible to the cranial base. Norm = 80° ± 3

TABLE 4-1 Cephalometric Analysis Summary Anteroposterior Skeletal Measurements

Mean/Standard Deviation

SNA SNB ANB

82° ± 3 80° ± 3 2° ± 2

Vertical skeletal measurements SN-MP SGn-FH (Y-axis)

Incisor measurements U1-SN U1-NA L1-MP L1-NB U1-L1

Soft tissue measurements Pog-NB E plane

FIG 4-10 A cephalometric radiograph showing the diagnostic reference planes and measurements.

45

32° ± 5 59° ± 3 103° ± 5 +3 mm ± 2 93° ± 7 +3 mm ± 2 130° ± 2 +3 mm ± 2 −2 mm ± 2

E, Esthetic; FH, Frankfort horizontal; L1, lower incisor; MP, mandibular plane; Pog, pogonion; SGn, sella-gnathion; SN, sella-nasion; U1, upper incisor.

46


SNA and SNB angles indicate the anteroposterior position of the maxilla and mandible relative to the cranial base. Values higher than the norms indicate prognathism for that particular jaw and lower values indicate retrognathism. However, these measurements can be erroneously affected by the shape or flexure of the cranial base: A more horizontal SN line gives a different value than a more divergent SN line. An SNA of 88° would indicate maxillary prognathism, whereas the maxilla may actually be in a normal spatial relationship. Because of excessive cranial base flexure, it may only appear to be prognathic. Therefore, the relative relationship of the maxilla to the mandible determined by measuring the ANB angle is a more significant measurement.

Positive values are recorded if the incisor is located anteriorly to the NA; negative values are recorded if the incisor is posterior to it.

ANB angle: Subtract the angle SNB from SNA. Measurement of ANB furnishes a relative determination of the relationship of the maxilla to the mandible.

L1-NB (lower incisor to NB line): The anteroposterior position of the lower incisor relative to the mandible can be determined by measuring the linear distance from the most labial surface of the lower incisor perpendicular to the NB line.

Norm = 2° ± 2

An ANB in the range of 0.5 to 4.5 degrees indicates a Class I skeletal pattern. Positive numbers indicate that the maxilla is ahead of the mandible. A negative angle represents a mandible that is more anteriorly positioned than the maxilla. ANB has a negative value if SNB is greater than SNA. An ANB value greater than 4.5 degrees indicates an anteroposterior skeletal problem with a Class II skeletal pattern. An ANB of 0° or less indicates a Class III skeletal pattern. Vertical Skeletal Measurements SN-MP: The mandibular plane angle is measured between SN and MP. Norm = 32° ± 5

It is a measure for vertical growth patterns. SN-MP can be erroneously affected by excess cranial base flexure. A steep MP angle may appear normal if the anterior cranial base is flexed more anteriorly. SGn-FH (Y-axis): Anteroinferior angle formed by the intersection of a line drawn from sella to gnathion and the Frankfort horizontal. Norm = 59° ± 3

The Y-axis determines the overall growth pattern of the face. A patient with a vertical growth tendency would have a high Y-axis value and exhibit a “long face” tendency. Incisor Measurements U1-SN (upper incisor to SN): Line through the long axis of the upper incisors forms an angle with the SN plane horizontal. Norm :103° ± 5

Measures the inclination of the upper incisors to the SN plane. It aids in the decision whether to extract to reduce incisor proclination and crowding or to expand to resolve crowding if the upper incisors are retroclined. U1-NA (upper incisor to NA line): Determines the anteroposterior position of the upper central incisors by the most labial surface of the upper incisor perpendicular to the NA line. Norm : =3 mm ± 2

L1-MP (lower incisor to mandibular plane): Line through the long axis of the most proclined lower central incisor forms an angle with MP. Norm : 93° ± 7

It is used as a treatment goal: The more the lower incisor is flared, the greater the angle. If L1-MP is greater than 100°, further labial movement of the lower incisors should be avoided. Abnormal vertical relationships result in erroneous values of this angle.

Norm : =3 mm ± 2

Positive values are recorded if the lower central incisor is anteriorly positioned to this line; negative values are recorded if it is posterior to it. U1-L1 (interincisal angle): Angle formed by intersection of the long axis of the most proclined upper and lower central incisors. Norm :130° ± 2

Used as a treatment goal, since normal incisor angulation is critical for anterior guidance and treatment stability. Soft-Tissue Measurements Pog-NB (pogonion to NB line): The prominence of the chin is often an important diagnostic consideration in orthodontics, especially in regard to extractions. The millimetric distance of pogonion is measured perpendicular to the line NB. Norm : =3 mm ± 2

The soft-tissue covering of the bony chin can be relatively thick or thin. A thick soft tissue could exaggerate a bony chin or produce the appearance of a normal chin in a person with a deficient bony chin button. A thin soft-tissue covering could give the appearance of normality in a case with a prominent bony chin or could exaggerate a “weak” chin, resulting in an unbalanced profile. E plane (esthetic line): The distance between the most protrusive point of the lower lip and the esthetic line (tip of nose to tip of chin). Norm : =2.0 mm ± 2

This line indicates the soft-tissue balance between lips and profile. Protrusive upper and/or lower incisors will cause a protrusive lower lip (positive values beyond the esthetic plane).

24. Which predictive analysis is a mandatory part of the diagnostic process in orthognathic surgery cases? The visual treatment objective (VTO) is a tool to predict desirable anteroposterior and vertical changes that will occur


as a result of changes in the denture bases and tooth position caused by growth, orthodontic treatment, and orthognathic surgery. It is used in the development of the treatment plan as well as to present anticipated treatment results for different treatment options of orthodontic camouflage or orthognathic surgery to a prospective patient.69 Since the growth prediction is based on average changes, this method is more reliable in adults or late adolescents with little or no remaining growth. In summary, the accuracy of the prediction is dependent on the accuracy of the treatment effect and future growth.70

25. Why do orthodontists superimpose serial cephalograms? Superimpositions are used to retrospectively study changes in jaw and tooth positions brought about through ortho dontic treatment and growth.71 To study maxillary changes, pretreatment and posttreatment cephalograms are superimposed on the lingual curvature of the palate.72 The mandibular composite is registered on the internal cortical outline of the symphysis with best fit on the mandibular canal to assess mandibular tooth movement as well as incremental growth of the lower jaw.73,74 Superimposition of the cephalometric records on sella enables the evaluation of overall growth and treatment changes.75 This technique is also used in orthognathic surgery cases to confirm growth cessation in the craniofacial region by superimposing two sequential cephalograms taken within a 6- to 12-month interval. The lack of bony changes affirms that no further growth has taken place in that time interval.

ORTHODONTIC PHOTOGRAPHS

26. What are the views captured in orthodontic photographs? For evaluation of the craniofacial and soft-tissue relationships, a facial profile view, a frontal view, and a smiling frontal photograph should be routinely taken for each prospective patient. The photos should be oriented to the FH and taken with relaxed lips and exposed ears. In addition, they should be one-quarter life size from the top of the head to the bottom of the chin. Moreover, a sequence of intraoral photographs at 1:1 ratio to life size should be recorded in CO, consisting of a frontal view with the teeth in maximal intercuspation, as well as right and left lateral views. The picture series should be completed with maxillary and mandibular occlusal views that show a clean dentition free from saliva or bubbles. These intraoral photographs are an important aspect in the documentation of existing dental conditions, such as tooth discoloration and oral hygiene status at initiation of treatment. In addition, the frontal photograph can be used to identify the patient’s facial type (Fig. 4-11, A-C) and lip competency (see Fig. 4-11, D and E), whereas the profile view can be helpful in determining the patient’s profile (see Fig. 4-11, F-I).

47

In evaluation of the buccal corridors, the smiling photograph can prove to be helpful (see Fig. 4-11, J and K). Dark buccal corridors may be indicative of a maxillary transverse deficiency, and intermolar width may need to be increased with an expansion appliance. To compare the relation of dental midlines to the facial midline, have the patient sit upright and face the orthodontist. Dental floss placed along the facial skeleton, from soft-tissue glabella through the philtrum to soft-tissue pogonion, can be used to identify deviations of the dental midlines (Fig. 4-11, L-N). Achieving upper and lower dental midlines with each other and with the facial midline is an esthetic goal for every orthodontic patient. In addition, coincident midlines serve a functional purpose to assist in establishing good buccal interdigitation.

27. Which aspects should be noted in the diagnosis of frontal photographs? The symmetry of the face should be evaluated by dividing the face into vertical thirds measured from trichion to glabella, glabella to subnasale, and subnasale to menton. This is known as the Rule of Thirds (Fig. 4-12, A). The evaluation of the lower third is especially important because it is most profoundly affected by orthodontic treatment. It can be further divided into one-third from subnasale to stomion and two-thirds from stomion to soft-tissue menton. The Rule of Fifths (see Fig. 4-12, B) describes the ideal transverse relations of the face. For this assessment, the face is divided into a centered fifth bordered by vertical lines through the inner canthi of the right and left eye. Ideally, it should be coincident with the alar base of the nose. The medial fifths represent the width of the eyes and should be coincident with the gonial angles of the mandible. The outer fifths are measured from the outer canthus to the helix of the ear on each side. With the aid of these reference lines, facial disproportions and asymmetries in the vertical and transverse planes can be appreciated.76,77

28. What are the goals of facial profile analysis? On the profile photograph, facial convexity and the anteroposterior position of the jaws should be evaluated. Furthermore, attention should be paid to lip posture and tonicity as well as incisor prominence with the nasolabial angle (NLA) as an excellent reference. The NLA is very important in the decision to extract teeth (Fig. 4-13). In the patient with an acute NLA, the extraction would be beneficial to the facial profile. However, extraction in a patient with an obtuse NLA would be detrimental to facial esthetics. The overall facial proportions and mandibular angle should be assessed. It is important to take into consideration that mentioned characteristics are influenced by race and ethnicity, as well as gender.76,78

48


A

C

B

D

F

E

G

FIG 4-11 Frontal facial photographs: dolichofacial (A), mesofacial (B), and brachyfacial (C); lips: competent (D) and incompetent (E); profile photographic analysis: convex (F), straight (G).


H

I

J

K

L

M

N FIG 4-11, cont'd Profile photographic analysis: concave (H) and bimaxillary protrusion (I); buccal corridors: normal (J) and dark (K); midlines: coincident (L), Upper Dental Midline (UDML) shift to left (M), and UDML shift to right (N).

49

50


B

A

FIG 4-12 A, The Rule of Thirds. B, The Rule of Fifths.

A

B

C

FIG 4-13 Profile analysis—nasolabial angle (NLA): normal (A), acute (B), and obtuse (C).

REFERENCES 1. Rivera SM, Hatch JP, Dolce C, et al: Patients’ own reasons and patient-perceived recommendations for orthognathic surgery, Am J Orthod Dentofacial Orthop 118(2):134–141, 2000. 2. Meraw SJ, Sheridan PJ: Medically induced gingival hyperplasia, Mayo Clin Proc 73(12):1196–1199, 1998. 3. Igarashi K, Mitani H, Adachi H, et al: Anchorage and retentive effects of a bisphosphonate (AHBuBP) on tooth movements in rats, Am J Orthod Dentofacial Orthop 106(3):279–289, 1994. 4. Arias OR, Marquez-Orozco MC: Aspirin, acetaminophen, and ibuprofen: their effects on orthodontic tooth movement, Am J Orthod Dentofacial Orthop 130(3):364–370, 2006. 5. Tyrovola JB, Spyropoulos MN: Effects of drugs and systemic factors on orthodontic treatment, Quintessence Int 32(5):365–371, 2001. 6. Mossey PA: The heritability of malocclusion: part 2. The influence of genetics in malocclusion, Br J Orthod 26(3):195–203, 1999. 7. Hägg U, Taranger J: Menarche and voice change as indicators of the pubertal growth spurt, Acta Odontol Scand 38(3):179–186, 1980.

8. Mathews DP, Kokich VG: Managing treatment for the orthodontic patient with periodontal problems, Semin Orthod 3(1):21–38, 1997. 9. Zachrisson BU: Clinical implications of recent orthodonticperiodontic research findings, Semin Orthod 2(1):4–12, 1996. 1 0. Kluemper GT, Vig PS, Vig KW: Nasorespiratory characteristics and craniofacial morphology, Eur J Orthod 17(6):491–495, 1995. 11. Vig KW: Nasal obstruction and facial growth: the strength of evidence for clinical assumptions, Am J Orthod Dentofacial Orthop 113(6):603–611, 1998. 12. Cozza P, Baccetti T, Franchi L, et al: Sucking habits and facial hyperdivergency as risk factors for anterior open bite in the mixed dentition, Am J Orthod Dentofacial Orthop 128(4):517–519, 2005. 13. Larsson E: Sucking, chewing, and feeding habits and the development of crossbite: a longitudinal study of girls from birth to 3 years of age, Angle Orthod 71(2):116–119, 2001. 14. Fraser C: Tongue thrust and its influence in orthodontics, Int J Orthod 17(1):9–18, 2006. 15. Laskin DM: The clinical diagnosis of temporomandibular disorders in the orthodontic patient, Semin Orthod 1(4):197–206, 1995.


16. Fu AS, Mehta NR, Forgione AG, et al: Maxillomandibular relationship in TMD patients before and after short-term flat plane bite plate therapy, Cranio 21(3):172–179, 2003. 17. Clark JR, Hutchinson I, Sandy JR: Functional occlusion: II. The role of articulators in orthodontics, J Orthod 28(2):173–177, 2001. 18. Laskin DM: Etiology of the pain-dysfunction syndrome, J Am Dent Assoc 79(1):147–153, 1969. 19. Griffiths RH, Laskin DM: The President’s conference on the Examination, diagnosis and management of temporomandibular disorders, 1983, Anonymous American Dental Association. 20. Mehra T, Nanda RS, Sinha PK: Orthodontists’ assessment and management of patient compliance, Angle Orthod 68(2):115– 122, 1998. 21. Hunter CJ: The correlation of facial growth with body height and skeletal maturation at adolescence, Angle Orthod 36(1):44– 54, 1966. 22. Fishman LS: Chronological versus skeletal age, an evaluation of craniofacial growth, Angle Orthod 49(3):181–189, 1979. 23. Malmgren O, Omblus J, Hägg U, et al: Treatment with an orthopedic appliance system in relation to treatment intensity and growth periods. A study of initial effects, Am J Orthod Dentofacial Orthop 91(2):143–151, 1987. 24. Pancherz H: The effects, limitations, and long-term dentofacial adaptations to treatment with the Herbst appliance, Semin Orthod 3(4):232–243, 1997. 25. Baccetti T, Franchi L, Toth LR, et al: Treatment timing for twin-block therapy, Am J Orthod Dentofacial Orthop 118(2):159– 170, 2000. 26. Fishman LS: Maturational patterns and prediction during adolescence, Angle Orthod 57(3):178–193, 1987. 27. Fishman LS: Radiographic evaluation of skeletal maturation. A clinically oriented method based on hand-wrist films, Angle Orthod 52(2):88–112, 1982. 28. Moore RN: Principles of dentofacial orthopedics, Semin Orthod 3(4):212–221, 1997. 29. Hassel B, Farman AG: Skeletal maturation evaluation using cervical vertebrae, Am J Orthod Dentofacial Orthop 107(1):58–66, 1995. 30. Baccetti T, Franchi L, McNamara JA Jr: An improved version of the cervical vertebral maturation (CVM) method for the assessment of mandibular growth, Angle Orthod 72(4):316–323, 2002. 31. Lamparski DG: Skeletal age assessment utilizing cervical vertebrae, Master’s thesis, Pittsburgh, University of Pittsburgh, 1972. 32. Franchi L, Baccetti T, McNamara JA Jr: Mandibular growth as related to cervical vertebral maturation and body height, Am J Orthod Dentofacial Orthop 118(3):335–340, 2000. 33. Flores-Mir C, Burgess CA, Champney M, et al: Correlation of skeletal maturation stages determined by cervical vertebrae and hand-wrist evaluations, Angle Orthod 76(1):1–5, 2006. 34. Kucukkeles N, Acar A, Biren S, et al: Comparisons between cervical vertebrae and hand-wrist maturation for the assessment of skeletal maturity, J Clin Pediatr Dent 24(1):47–52, 1999. 35. Lischer BE: Principles and methods of orthodontics, Philadelphia, 1912, Lea & Febiger. 36. Thilander B, Jakobsson SO: Local factors in impaction of maxillary canines, Acta Odontol Scand 26(2):145–168, 1968. 37. Shapira Y, Kuftinec MM: Maxillary tooth transpositions: characteristic features and accompanying dental anomalies, Am J Orthod Dentofacial Orthop 119(2):127–134, 2001. 38. Kharat DU, Saini TS, Mokeem S: Shovel-shaped incisors and associated invagination in some Asian and African populations, J Dent 18(4):216–220, 1990. 39. Tsai SJ, King NM: A catalogue of anomalies and traits of the permanent dentition of southern Chinese, J Clin Pediatr Dent 22(3):185–194, 1998.

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40. Hülsmann M: Dens invaginatus—its etiology, incidence and clinical characteristics (I). A review, Schweiz Monatsschr Zahnmed 105(6):765–776, 1995. 41. Ward DE, Workman J, Brown R, et al: Changes in arch width. A 20-year longitudinal study of orthodontic treatment, Angle Orthod 76(1):6–13, 2006. 42. Nojima K, McLaughlin RP, Isshiki Y, et al: A comparative study of Caucasian and Japanese mandibular clinical arch forms, Angle Orthod 71(3):195–200, 2001. 43. Bolton WA: The clinical application of a tooth-size analysis, Am J Orthod 48(7):504–529, 1962. 44. Bolton WA: Disharmony in tooth size and its relation to the analysis and treatment of malocclusion, Angle Orthod 28:113, 1952. 45. Crosby DR, Alexander CG: The occurrence of tooth size discrepancies among different malocclusion groups, Am J Orthod Dentofacial Orthop 95(6):457–461, 1989. 46. Smith SS, Buschang PH, Watanabe E: Interarch tooth size relationships of 3 populations: “does Bolton’s analysis apply?,” Am J Orthod Dentofacial Orthop 117(2):169–174, 2000. 47. Angle EH: Classification of malocclusion, Dent Cosmos 41(2):248–264, 1899. 48. Proffit WR, Fields HW Jr., Moray LJ: Prevalence of malocclusion and orthodontic treatment need in the United States: estimates from the NHANES III survey, Int J Adult Orthodon Orthognath Surg 13(2):97–106, 1998. 49. Siegel MA: A matter of Class: interpreting subdivision in a malocclusion, Am J Orthod Dentofacial Orthop 122(6):582–586, 2002. 50. Burstone CJ: Diagnosis and treatment planning of patients with asymmetries, Semin Orthod 4(3):153–164, 1998. 51. Kronmiller JE: Development of asymmetries, Semin Orthod 4(3):134–137, 1998. 52. Costalos PA, Sarraf K, Cangialosi TJ, et al: Evaluation of the accuracy of digital model analysis for the American Board of Orthodontics objective grading system for dental casts, Am J Orthod Dentofacial Orthop 128(5):624–629, 2005. 53. Marcel TJ: Three-dimensional on-screen virtual models, Am J Orthod Dentofacial Orthop 119(6):666–668, 2001. 54. Zilberman O, Huggare JAV, Parikakis KA: Evaluation of the validity of tooth size and arch width measurements using conventional and three-dimensional virtual orthodontic models, Angle Orthod 73(3):301–306, 2003. 55. Cordray FE: Centric relation treatment and articulator mountings in orthodontics, Angle Orthod 66(2):153–158, 1996. 56. Agerberg G, Sandström R: Frequency of occlusal interferences: a clinical study in teenagers and young adults, J Prosthet Dent 59(2):212–217, 1988. 57. Rinchuse DJ, Kandasamy S: Articulators in orthodontics: an evidence-based perspective, Am J Orthod Dentofacial Orthop 129(2):299–308, 2006. 58. Ellis PE, Benson PE: Does articulating study casts make a difference to treatment planning? J Orthod 30(1):45, 2003. 59. Quintero JC, Trosien A, Hatcher D, et al: Craniofacial imaging in orthodontics: historical perspective, current status, and future developments, Angle Orthod 69(6):491–506, 1999. 60. Ferguson JW, Evans RI, Cheng LH: Diagnostic accuracy and observer performance in the diagnosis of abnormalities in the anterior maxilla: a comparison of panoramic with intraoral radiography, Br Dent J 173(8):265–271, 1992. 61. Sameshima GT, Asgarifar KO: Assessment of root resorption and root shape: periapical vs panoramic films, Angle Orthod 71(3):185–189, 2001. 62. Forsberg CT, Burstone CJ, Hanley KJ: Diagnosis and treatment planning of skeletal asymmetry with the submental-vertical radiograph, Am J Orthod 85(3):224–237, 1984. 63. Hofrath H: Die Bedeutung der Röntgenfern-und Abstandsaufnahme für die Diagnostik der Kieferanomalien, J Orofacial Orthop/Fortschritte Kieferorthopädie 1(2):232–258, 1931.

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64. Broadbent BH: A new X-ray technique and its application to orthodontia, Angle Orthod 1(2):45–66, 1931. 65. Steiner CC: The use of cephalometrics as an aid to planning and assessing orthodontic treatment, Am J Orthod 46(10):721–735, 1960. 66. Ricketts RM: Perspectives in the clinical application of cephalometrics. The first fifty years, Angle Orthod 51(2):115–150, 1981. 67. Harrell WE Jr., Hatcher DC, Bolt RL: In search of anatomic truth: 3-dimensional digital modeling and the future of orthodontics, Am J Orthod Dentofacial Orthop 122(3):325–330, 2002. 68. Salas-Lopez A: Cephalometric tracing technique manual, 2006, University of Texas Dental Branch at Houston, Department of Orthodontics. 69. Bench RW: The visual treatment objective: orthodontic’s most effective treatment planning tool, Proc Found Orthod Res 4(2):165–194, 1971. 70. Toepel-Sievers C, Fischer-Brandies H: Validity of the computerassisted cephalometric growth prognosis VTO (Visual Treatment Objective) according to Ricketts, J Orofac Orthop 60(3):185–194, 1999. 71. Efstratiadis SS, Cohen G, Ghafari J: Evaluation of differential growth and orthodontic treatment outcome by regional cephalometric superpositions, Angle Orthod 69(3):225–230, 1999.

72. Björk A, Skieller V: Growth of the maxilla in three dimensions as revealed radiographically by the implant method, Br J Orthod 4(2):53–64, 1977 Apr. 73. Björk 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 5(1):1–46, 1983. 74. Cook AH, Sellke TA, BeGole EA: The variability and reliability of two maxillary and mandibular superimposition techniques. Part II, Am J Orthod Dentofacial Orthop 106(5):463–471, 1994. 75. Ghafari J, Engel FE, Laster LL: Cephalometric superimposition on the cranial base: a review and a comparison of four methods, Am J Orthod Dentofacial Orthop 91(5):403–413, 1987. 76. Peck H, Peck S: A concept of facial esthetics, Angle Orthod 40(4):284–318, 1970. 77. Morris W: An orthodontic view of dentofacial esthetics, Compendium 15(3):378, 1994. 78. Bishara SE, Jakobsen JR, Hession TJ, et al: Soft tissue profile changes from 5 to 45 years of age, Am J Orthod Dentofacial Orthop 114(6):698–706, 1998.

Three-Dimensional Imaging in Orthodontics

C HA P T ER

5

Chung How Kau • Stephen Richmond

T

he advances of three-dimensional (3D) technology have accelerated at a tremendous pace over the past two decades with newer machines and advanced software support. This now means that applications for the clinical settings can be created and used in routine diagnosis, treatment planning, and patient education. Orthodontists will find that these advances will also impact the profession, and this chapter aims to give the reader the basic foundation on which to understand this interesting and exciting topic.

1. Imaging techniques and devices—what do these mean to the orthodontist? New technologies reach the commercial and clinical environments on a daily basis and filter through every aspect of the medical and dental field. Orthodontists too are exposed to this fast pace of change, and these advancements have allowed innovative methods for facial diagnosis, treatment planning, and clinical application. With continuing innovations and the use of powerful computer software tools, the past two decades have seen a reintroduction of both hard- and soft-tissue imaging devices in rapid succession. The orthodontist needs to embrace these new methods of diagnosis and treatment planning, because the images produced add a new dimension to present-day concepts and test the foundations of our knowledge.

2. What does it mean to have a 3D image, and how is it obtained? Three-dimensional image reconstruction is a complex task using mathematical principles. The 3D image is essentially an object that appears to have an extension in depth. In photography, a 3D image is reconstructed by the principles of stereoscopic vision when two images are pieced together from two or more cameras at known distances and angles. In radiography, multislice or multi-views of an object are cleverly reconstructed using complex mathematical algorithms to produce a representation of the object.

3. What is a possible classification of these devices? Three-dimensional images may be obtained in a variety of ways. A possible classification system is listed in Table 5-1.

4. What are some clinical applications? There are a number of reported and possible clinical applications. These will be discussed under two main headings: surface imaging and hard-tissue imaging. SURFACE IMAGING Facial Growth Significant investigations have been done in the past on hardtissue growth of the cranial skeleton. However, reported studies focusing on and analyzing soft-tissue morphology and growth are comparatively few in relation to the general orthodontic literature.1 Yet the external profile is by far the most visible entity from which clinicians and laypeople make perceptions and formulate judgments. In this current day and age, with a greater emphasis being placed on the balance between the hard and soft-tissues, it is important to have reliable and readily available data on the external soft-tissue profile. At present, there is a lack of emphasis on the longitudinal development of the soft tissues. Most of the available data on the changing soft-tissue profile have been obtained from cephalometric data with an additional small number from limited 3D data. Soft-tissue studies are difficult and the tissue structures are inevitably affected by movements and distortions. However, careful patient positioning and good technical detailing have allowed these images to be reproducible to a high level of clinical acceptability. Early 3D imaging research has shown that the growth of facial structures broadly follows in line with gender and age. Growth is present in a number of facial structures and may be visualized as surface and volume changes (Fig. 5-1). Furthermore, the system is so sensitive that asymmetric growth is identified in 33% of 11- to 12-year-olds. In the majority of these cases, the asymmetrical growth levels out over 1 year of assessment. However, there are a small proportion of children who continue to grow asymmetrically (Fig. 5-2). Average Faces and Superimposition Average faces of 3D images from a cohort of same-age individuals may also be created.2,3 This procedure involves prealignment of the images by determining their principal axes (based on computing the tensor of inertia of each 3D image) followed by best fit alignment of the images and then by averaging the image coordinates normally to the facial plane. For each point representing the obtained average facial plane, the standard deviations are calculated allowing construction 53

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CHAPTER 5 • Three-Dimensional Imaging in Orthodontics

TABLE 5-1

Tabular Representation of Surface Imaging Devices

METHOD

SOURCE

INDUSTRY EXAMPLES

Direct contact

Manual probe

Photogrammetry Lasers

Conventional photography 670 to 690 nm Class I or II FDAapproved laser lights

a. Polhemus 3 Space Digitizer b. ELITE a. Stereophotogrammetry a. Fixed units • Medical Graphics and Imaging Group, UCL • Cyberware Laboratory 3030 / SP • Others a. Portable and mobile • Minolta Systems (Model versions 700, 900, 910, 9i) • Polhemus hand-held (FASTSCAN) a. Single camera b. Multiple camera • Moire patterns • OGIS Range Finder RFX-IV • CAM, three-dimensional shape system • C3D-dimensional stereophotogrammetry (Glasgow)—computer aided • 3 dMD™ Face System • Others a. Motion-Analysis™ a. CT scans b. CBCTs a. MRI b. Ultrasound

670 to 690 nm Class I or II FDAapproved laser lights Structured light

Distorted light patterns and photogrammetric light capture

Video imaging Radiation sources

Video sequencing Radiation pulses

Others

C3D, CAM, CBCT, cone beam computed tomography; CT, computed tomography; FDA, Food and Drug Administration; MRI, magnetic resonance imaging; OGIS, SP, UCL, University College London.

FIG 5-1 Facial growth as illustrated by average facial changes in males and females. Red areas indicate positive changes, whereas blue areas indicate negative changes.

FIG 5-2 Asymmetrical growth of a child’s face over a 2-year growth period. Note the asymmetrical shuffling of the mandible.

of the “standard deviation” faces that indicate variation from the average face. The results obtained may be used for the identification of facial anomalies in patients (Fig. 5-3). The face examined is superimposed onto the average face using the best fit technique, and then a divergence map can be constructed showing the regions with abnormal deviations. The deviations can be identified and quantified in terms of linear, area, and volumetric measurements.

can only be extrapolated from research using 2D data. As a result, clinicians are not able to provide an accurate picture to the patient and to give advice regarding the morbidity involved. The successful application of 3D imaging technology provides a means for further analysis in clinical trials.4 Initial research data show that the amount of swelling is greatest 1 day after surgery but improves significantly with time. Two-jaw surgery produces a greater amount of swelling but reduces at a faster rate than single-jaw surgery. Furthermore, approximately 60% of the initial swelling is reduced after 1 month for both singleand two-jaw orthognathic surgery. Fig. 5-4 depicts surgical examples.

Surgical Evaluations Patients are often anxious to know the treatment effects following orthognathic surgery, and current information available

Three-Dimensional Imaging in Orthodontics • CHAPTER 5

A

B

D

C

E FIG 5-3 A-C, 11-year-old girl with right unilateral cleft lip and palate. D, Superimposition of patient on the average 11-year-old face; color map indicating the magnitude of deviation around the cleft region (red, 10.9 mm; green, 6.5 mm; cyan, 3.3 mm retrusive compared with the average face). E, Zonal method of evaluation, twelve zones indicating area and depth of deviation from the average face.

FIG 5-4 A-D, Facial swelling changes associated with a patient presenting with a Class II division 1 malocclusion. E-L, Facial swelling changes associated with patients with Class III malocclusions. Note that the swelling process is similar in all cases in the submasseteric region and improves with time.

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HARD-TISSUE IMAGING Probably the greatest impact in 3D imaging techniques to both orthodontics and dentistry has been the introduction of cone beam technology. This relatively low-radiation technique permits all possible radiographs to be taken in under 1 minute. The orthodontist now has the diagnostic quality of periapicals, panoramic cephalograms, occlusal radiographs, and temporomandibular joint (TMJ) series at their disposal, along with views that cannot be produced by regular radiographic machines like axial views and separate cephalograms for the right and left sides. A number of clinical applications have already been reported in the literature (Fig. 5-5).5 Impacted Teeth and Oral Abnormalities The incidence of maxillary ectopic cuspids occurs in approximately 3% of the population. The distribution and location have been reported at 80% palatally and 20% buccally. The tube shift method (also known as the parallax technique) has been the traditional method of locating these cuspids and provides an arbitrary position and approximation of the level of difficulty for the management of the cuspid. This investigative technique uses two conventional radiographs and the location of the tooth identified by the movement of the objects respectively to the way in which the radiograph was taken. In addition, the extent of the pathology caused by the ectopic tooth and its surrounding structures has also been evaluated by these radiographs.6 However, clinical reports using 3D conventional computed tomography (CT) scans have shown that the incidence of root resorption to the adjacent teeth has been larger than previously thought.7 A recent report found that the use of cone beam CT (CBCT) technology could add value to the management of patients with such anomalies.8 The authors used the technology to precisely locate ectopic cuspids and to design treatment strategies that allowed minimally invasive surgery to be performed and helped to design effective orthodontic strategies.

FIG 5-5 Cone beam image with traditional 3D views for evaluation. (Courtesy of Mr. Arun Singh, Imaging Sciences, US.)

Another interesting use of the CBCT is the location of incidental oral abnormalities in patients. Some centers in the United States have begun to adopt CBCT imaging into routine dental examination procedures. Initial reports have suggested that there were higher incidences of oral abnormalities than previously suspected (e.g., oral cysts, ectopic/buried teeth, and supernumeraries) (Fig. 5-6). The value of these findings must be taken with caution, since the number of elective treatments that may be carried out may be limited. This leads to the question of whether to intervene in every abnormality located on these 3D images and the extent to which the patient needs to be informed. In the event that these abnormalities were to lead to pathologic episodes, what responsibilities would the clinician and patient hold in the decision-making process? This could lead to a host of future medicolegal problems on how clinicians and patients manage the information. Airway Analysis The CBCT technology provides a major improvement in the airway analysis, allowing for its 3D and volumetric analysis. Airway analysis has conventionally been carried out using lateral cephalograms. A recent study on 11 subjects, using lateral cephalograms and CBCT imaging, found moderate variability in the measurements of upper airway area and volume.9 Threedimensional airway analysis no doubt will be useful in understanding the reasons why clinical conditions like sleep apnea and enlarged adenoids affect the way clinicians manage these complex conditions. Assessment of Alveolar Bone Heights and Volume Implantologists have long appreciated the third dimension in their clinical work. Conventional CT scans are used routinely to assess bone dimensions, bone quality, and the alveolar heights, especially when multiple units are proposed. This has improved the clinical success of the prosthesis and has led to more accurate and aesthetic outcomes in oral rehabilitation. The introduction of CBCT technology means that both the cost and the effective radiation dose can be reduced, suggesting that its frequency of use may increase. The CBCT has already been in use in implant therapy10 and may be useful in orthodontics for the clinical assessment of bone graft quality following alveolar surgery in patients with cleft lip and palate.11 The images produced resulted in higher precision evaluation of bone sites and therefore gave the clinician a greater chance of restoring the site with implants as well as in the decision process of whether to move teeth orthodontically into the repaired alveolus (Fig. 5-7). Temporomandibular Joint Morphology Condylar resorption occurs in 5% to 10% of patients who undergo orthognathic surgery. Recent 3D studies have tried to understand how the condyle remodels and preliminary data suggest that much of the condylar rotation resulting in remodeling is a direct result of the surgical procedures alone.12 TMJ


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FIG 5-6 Assessment of impactions in the anterior maxillary region. (Courtesy of Dr. JE Zoller, University of Cologne.)

FIG 5-8 Temporomandibular joint (TMJ) morphology. (Courtesy of Dr. JE Zoller, University of Cologne.)

FIG 5-7 Assessment of buccal/lingual bone in the maxillary molar region. (Courtesy of Mr. Arun Singh, Imaging Sciences, US.)

changes following distraction osteogenesis treatment and dentofacial orthopedics still need further study. The quality of the images of the TMJ with CBCT machines is comparable to conventional CTs, but the image-taking is faster and less expensive and provides less radiation exposure. This has opened a new avenue for imaging the TMJ (Fig. 5-8).13

5. What types of analyses are available? A number of analyses have been reported in the literature. These techniques are often extensions from traditional methods of analysis using landmarks and points. Future analysis will focus on the use of surface areas and volumes for evaluation and quantification of diagnostic parameters and treatment changes.

6. Where are we with this technology? Surface imaging and hard-tissue imaging is revolutionizing the orthodontic specialty. To date, there are dozens of schools in

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the United States that possess both the surface imaging system and cone beam technology. In the next few years, there will be several papers in the literature discussing diagnostic and clinical outcomes and applications. THE VIRTUAL PATIENT Changes in imaging technologies allow orthodontic clinicians to now merge soft-tissue images, skeletal hard-tissue images, and study model information into one platform to analyze the patient. This virtual patient environment presents a unique method of creating diagnostic information and also helps the clinician to plan for future treatment plans.14 Fig. 5-9 represents a fused image of a patient’s skin texture and associated skull image. This method will open new frontiers of analysis and understanding of patients.

7. Are there limitations in the systems? Yes, there are. Take the CBCT device, for example. It is excellent in imaging hard-tissue structures and most soft-tissue components; however, it does not have the ability to precisely map out the muscle structures and their attachments. These intricate structures would have to be imaged using conventional magnetic resonance imaging (MRI) technology, which incidentally does not predispose the patient to radiation exposure. In addition, the CBCT soft-tissue images do not capture the true color texture of the skin. Therefore, in order to obtain photograph-quality resolution, manipulation of the images is still required. Successful attempts to map tissue texture maps onto conventional CTs have been reported and may be similarly applied to this new technology.15 When they become available, perhaps they can successfully replace the photographs taken during records. Another criticism made is the long capture time for a full view of a subject (scan time of 30 to 40 seconds), during which involuntary muscle movements (nostrils and breathing) lead to inaccuracies in soft-tissue capture. These limitations mean that the 3D devices like stereophotogrammetry and laser scanning are still better soft-tissue alternatives for surface texture capture.

8. What are the costs involved? These devices are expensive in the current market. A surface imaging device costs approximately $50,000, whereas the cone beam technology costs $200,000. The cost of a maintenance contract for each machine is often 10% of the retail price. Another substantial cost to consider is the need for someone to operate the machines as well as someone to interpret the results.

9. What is the best clinical setting for the different imaging devices? At present, the best clinical setting is a pooled resource center. These centers often take the form of a designated imaging laboratory or faculty institution. Hard- and soft-tissue images can be imaged and transited to the doctor’s office via weblink or CD-ROM.

10. Are there medicolegal issues with these devices? Yes and no. It is less likely that surface capture systems will pose a problem unless the surface scans are used for advertisements or teaching; patient consent is required in such circumstances. The main problem arises when CBCT radiation technology is used. The issues of radiation protection and clinical diagnosis become more evident at this point. For example, is the orthodontist responsible for the diagnosis of pathology outside of the realms of his clinical responsibility? Some clinicians “get around” the problem by informing their patients in writing that they are responsible for only the orthodontic diagnosis. These patients are encouraged to seek the advice of other specialists. At present there are no strict guidelines governing these issues, although in the future there most certainly will be regulations in these areas to protect both the clinician and the patient.

11. What does the future hold? The future for orthodontists is promising and bright. The longawaited incorporation of the third dimension to our soft-tissue and radiographic records is now a reality. There is still room for improvement, but these technologies appear to be here to stay.

FIG 5-9 A fused image of a patient’s skin texture and associated skull image.


REFERENCES 1. Riolo ML, Moyers RE, TenHave TR, et al: Facial soft tissue changes during adolescence. In Carlson DS, Ribbens KA, editors: Craniofacial growth during adolescence. Monograph 20, Ann Arbor, 1987, Center for Human Growth and Development. 2. Kau CH, Zhurov AI, Richmond S, et al: The 3-dimensional construction of the average 11-year-old child face—a clinical evaluation and application, J Oral Maxillofac Surg 64(7):1086–1092, 2006. 3. Kau CH, Zhurov A, Richmond S, et al: Facial templates: a new perspective in three dimensions, Orthod Craniofac Res 9(1):10–17, 2006. 4. Kau CH, Cronin A, Durning P, et al: A new method for the 3D measurement of postoperative swelling following orthognathic surgery, Orthod Craniofac Res 9(1):31–37, 2006. 5. Blais F: Review of 20 years of range sensor development, J Electron Imag 13(1):231–240, 2004. 6. Chaushu S, Chaushu G, Becker A: The role of digital volume tomography in the imaging of impacted teeth, World J Orthod 5(2):120–132, 2004. 7. Ericson S, Kurol PJ: Resorption of incisors after ectopic eruption of maxillary canines: a CT study, Angle Orthod 70(6):415–423, 2000. 8. Mah J, Enciso R, Jorgensen M: Management of impacted cuspids using 3-D volumetric imaging, J Calif Dent Assoc 31(11):835–841, 2003. 9. Aboudara CA, Hatcher D, Nielsen IL, et al: A three-dimensional evaluation of the upper airway in adolescents, Orthod Craniofac Res 6(Suppl 1):173–175, 2003. 10. Hatcher DC, Dial C, Mayorga C: Cone beam CT for pre-surgical assessment of implant sites, J Calif Dent Assoc 31(11):825–833, 2003. 11. Hamada Y, Kondoh T, Noguchi K, et al: Application of limited cone beam computed tomography to clinical assessment of alveolar bone grafting: a preliminary report, Cleft Palate Craniofac J 42(2):128–137, 2005. 12. Bailey LJ, Cevidanes LH, Proffit WR: Stability and predictability of orthognathic surgery, Am J Orthod Dentofacial Orthop 126(3):273–277, 2004. 13. Tsiklakis K, Syriopoulos K, Stamatakis HC: Radiographic examination of the temporomandibular joint using cone beam computed tomography, Dentomaxillofac Radiol 33(3):196–201, 2004. 14. Kau CH: Creation of the virtual patient for the study of facial morphology, Facial Plast Surg Clin North Am 19(4):615–622, 2011. http://dx.doi.org/10.1016/j.fsc.2011.07.005, viii. 15. Khambay B, Nebel JC, Bowman J, et al: 3D stereophotogrammetric image superimposition onto 3D CT scan images: the future of orthognathic surgery. A pilot study, Int J Adult Orthod Orthognath Surg 17(4):331–341, 2002.

SUGGESTED READING Aldridge K, Boyadjiev SA, Capone GT, et al: Precision and error of three-dimensional phenotypic measures acquired from 3dMD photogrammetric images, Am J Med Genet 138(3):247–253, 2005.

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Bottollier-Depois JF, Chau Q, Bouisset P, et al: Assessing exposure to cosmic radiation on board aircraft, Adv Space Res 32(1):59–66, 2003. Bottollier-Depois JF, Trompier F, Clairand I, et al: Exposure of aircraft crew to cosmic radiation: on-board intercomparison of various dosemeters, Radiat Prot Dosimetry 110(1–4):411–415, 2004. Brenner D, Elliston C, Hall E, et al: Estimated risks of radiationinduced fatal cancer from pediatric CT, Am J Roentgenol 176(2):289–296, 2001. Frederiksen NL: X rays: what is the risk? Tex Dent J 112(2):68–72, 1995. Harrison JA, Nixon MA, Fright WR, et al: Use of hand held laser scanning in the assessment of facial swelling: a preliminary study, Br J Oral Maxillofac Surg 42(1):8–17, 2004. Isaacson KG, Thom AR, editors: Guidelines for the use of radiographs in clinical orthodontics, London, 2001, British Orthodontic Society. Kau CH, Cronin AC, Durning P, et al: A new method for the 3D measurement of post-operative swelling following orthognathic surgery, Orthod Craniofac Res 9(1):31–37, 2006. Kau CH, Richmond S, Savio C, et al: Measuring adult facial morphology in three dimensions, Angle Orthod 76(5):771–7776, 2006. Kau CH, Richmond S, Zhurov AI, et al: Reliability of measuring facial morphology using a 3-dimensional laser scanning system, Am J Orthod Dentofacial Orthop 128(4):424–430, 2005. Kau CH, Zhurov AI, Bibb R, et al: The investigation of the changing facial appearance of identical twins employing a three-dimensional laser imaging system, Orthod Craniofac Res 8(2):85–90, 2005. Kau CH, Zhurov AI, Scheer R, et al: The feasibility of measuring three-dimensional facial morphology in children, Orthod Craniofac Res 7(4):198–204, 2004. Kiefer H, Lambrecht JT, Roth J: Dose exposure from analog and digital full mouth radiography and panoramic radiography, Schweiz Monatsschr Zahnmed 114(7):687–693, 2004. Mah J: 3D imaging in private practice, Am J Orthod Dentofacial Orthop 121(6):14A, 2002. Mah J, Bumann A: Technology to create the three-dimensional patient record, Semin Orthod 7(4):251–257, 2001. Mah J, Enciso R: The virtual craniofacial patient. In McNamara JA, editor: Craniofacial growth series, 2003, Center for human growth and development. Palomo JM, Hunt DW Jr., Hans MG, et al: A longitudinal 3-dimensional size and shape comparison of untreated Class I and Class II subjects, Am J Orthod Dentofacial Orthop 127(5):584–591, 2005. Palomo JM, Subramanyan K, Hans MG: Creation of three dimensional data from bi-plane head x-rays for maxillo-facial studies, Int Congress Series 1268C:1253–1253, 2004. Rogers LF: Radiation exposure in CT: why so high? Am J Roentgenol 177(2):277, 2001. Schulze D, Heiland M, Thurmann H, et al: Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography, Dentomaxillofac Radiol 33(2):83–86, 2004.

C H A PT E R

6

Diagnosis of Orthodontic Problems Jeryl D. English • Larry Tadlock • Barry S. Briss • Kate Litschel

C

arolus Linnaeus (1707-1778), Swedish botanist and taxonomist, is considered to be the founder of the binomial system of nomenclature and the originator of modern scientific classification of plants and animals. To paraphrase a quote attributed to him: “Without classification there is only chaos.”1 In systems that are described as being in disorder, there is an underlying phenomenon whereby order can be found from seemingly random data. Before Edward Hartley Angle devised his scheme of classification of malocclusion, there was no reliable or simple method to describe a malocclusion.2 Thus, in a very real sense, he gave order to what otherwise might have been a chaotic situation in the fledgling specialty of orthodontics. His scheme worked because it was simple and reliable, and we still use it this very day. Similarly, we might look at diagnosis and treatment planning as bringing order to what, at first glance, seems to be chaotic random data. We look at the data and create order from it by developing a diagnosis, treatment objectives, treatment options, a treatment plan, and finally an appropriate treatment. This diagnostic roadmap should lead to successful treatment and results. The second law of thermodynamics (law of entropy) was formulated in the middle of the nineteenth century by the earlier observations of Carnot and later by Clausius and Thomson.3 Their key insight was that the world is inherently active and the spontaneous production of order from disorder is the expected consequence of basic laws (physics). The law of entropy, as it turns out, has a similar relationship to life itself, our biology, our evolution, and our ecological system. The major revolution in the past decade is the recognition of the “law of maximum entropy production” (MEP) and with it an expanded view of thermodynamics. This new idea shows that the spontaneous production of order from disorder is the expected consequence of basic laws.3 Is there a commonality to these two concepts (chaos theory and the law of entropy) and with what we do? If so, what do they have to do with orthodontics? Although it may be a leap of faith to equate these rather esoteric and complicated concepts of science and nature to orthodontic diagnosis, it may not be as far-fetched as one might think. On a daily basis, we are all faced with patients who seek treatment for the correction of particular problems, some of which are relatively simple and some of which are rather complex. Certainly, the patients’ reasons for seeking our help are multivariant. Nevertheless, no matter the reason, we are obliged to assess their problem, answer their questions, and provide them 60

with information pertinent to their chief complaint. Thus, we perform a thorough diagnosis, create a list of problems, discuss treatment options, and then establish a treatment modality to achieve the goal. The sequencing of the previous sentence is logical and purposeful in its design. After all, it would make little sense to reverse its order and state it this way: “We achieve the goal, we treat the problem, we create treatment options, we set treatment objectives, and we diagnose.” Orthodontics is both art and science. By its very nature, there is more than one road map to a successful treatment for any particular problem, and each orthodontist may have a different approach. In the end, however, each of us must formulate that treatment based upon a sound diagnosis. Orthodontists, like physicians, develop what is frequently referred to as the differential diagnosis. What does this mean, and why is it different from the medical diagnosis? In medicine, a patient presents with certain symptoms. The physician, after interviewing the patient and making a preliminary examination, develops a hypothesis of what he thinks the problem is and develops a differential diagnosis, which is nothing more than a list of possible causes for the patient’s complaint. Not until he performs a variety of tests is he able to narrow the list down and arrive at the single most likely definitive diagnosis (e.g., appendicitis). In orthodontics, however, the differential diagnosis represents a somewhat different concept. It is, in fact, a complete description of the malocclusion; it includes those multifactorial conditions that exist at a particular moment in time that make the malocclusion unique unto itself. In other words, we do not simply describe a malocclusion as Class II. Rather, we add to that basic Angle classification a description of all the salient entities that make the malocclusion different from others of the same classification (e.g., division 1, division 2, subdivision, crowding, deep bite, and crossbite). In this chapter the questions ask about the treatment of a particular malocclusion. Suggested treatment approaches are described in the answers and are meant to associate the treatment decision to an understanding of the underlying problem based upon a proper diagnosis. Because there are many ways to correct a particular problem, these suggested treatments are for illustrative purposes only. It is important to note that treatment (mechanotherapy) and diagnosis are entities that are joined at the hip and cannot be separated. A poor treatment result will most certainly result from a poor diagnosis. As orthodontists, we acknowledge and understand that we treat in three planes of space: the sagittal, the vertical, and the

Diagnosis of Orthodontic Problems • CHAPTER 6

transverse. Although these three dimensions can be thought of as three separate entities, they are not. Why? Treating one will most certainly have a separate or collective effect upon each of the others, either in a positive or a negative way. Therefore, having a complete understanding of all of them and how they interrelate and interact is important when formulating the treatment. Let us consider, for example, the vertical dimension. The vertical dimension dictates many of the decisions made by the orthodontist when devising a treatment plan. In the case of a patient with a dolichofacial pattern, the comprehensive treatment goal often includes a plan to control the vertical dimension and to not make it worse.4–7 The vertical dimension seems to be the one dimension that gives the orthodontist much cause for concern because, when presented with a patient with this pattern, all that we do for the patient seems to affect the vertical in a negative way. By the same token, in those cases that present with the opposite form of facial pattern (i.e., brachyfacial), the opposite seems to be the case. In these instances, increasing the vertical dimension is often one of the objectives of treatment. And yet, in patients who present with a Class II division 2 malocclusion and a 100% overbite, for example, the vertical dimension resists our attempt to increase it. To make the correct diagnosis, the orthodontist must consistently develop a diagnostic database. DIAGNOSTIC DATABASE

1. What comprises the diagnostic database? The diagnostic database is composed of multiple clinical, functional, and record analyses that allow the clinician to formulate a comprehensive diagnosis and begin to work toward a treatment plan that is most beneficial to the patient.8 CASE HISTORY A thorough case history including family and patient history helps establish any pre-existing developmental problems. Medical conditions relating to orthodontic treatment and psychological aspects of treatment should be explored. CLINICAL EXAMINATION The most important diagnostic tool is the clinical examination of the patient. The general state of the patient in terms of growth and development should be assessed, along with the development and health of the dentition and surrounding structures. A frontal and profile analysis should be performed to discover any discrepancies that would fall into the problem list. The patient’s chief complaint should be noted and evaluated. FUNCTIONAL ANALYSIS In the functional analysis, head posture and freeway space are evaluated. The dentition is evaluated for any discrepancies in function, such as functional shifts or pseudo-bites. Swallowing function should be explored to discover tongue-thrust habits that may lead to relapse after orthodontic treatment is completed. The temporomandibular joints (TMJs) are palpated

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and the patient is questioned concerning joint function and noise. Any discrepancies from normal should be further evaluated through clinical and radiographic examination as needed. RADIOLOGIC EXAMINATION Panoramic radiographs are useful in orthodontic diagnosis as a survey of the total dentition, the TMJs, and surrounding structures. Periapical radiographs or vertical bitewings should be taken on all adult cases to evaluate bone heights. Occlusal views or a cone beam scan may be beneficial in cases with impacted teeth to determine their three-dimensional (3D) location. PHOTOGRAPHIC ANALYSIS Profile and frontal photographs are taken to evaluate the relationship between the soft tissue and the skeletal supporting structures. In the profile view, the patient’s head is parallel to the Frankfort horizontal (FH) plane in the natural head position, the eyes are focused straight ahead, and the ear is visible. CEPHALOMETRIC ANALYSIS Cephalometric analysis is used to evaluate the formation of the facial skeleton, the relationship of the jaw bases, the axial inclination of the incisors, soft tissue morphology, growth patterns, localization of malocclusion, and treatment limitations. STUDY CAST ANALYSIS The dentition and degree of malocclusion can be analyzed in three dimensions using study cast analysis. Analysis of the arch form can be subdivided into the sum of upper incisor widths, anterior arch width, posterior arch width, anterior arch length, and palatal height. Arch symmetry is evaluated using a perpendicular to the mid-palatal raphe. Space analysis is calculated by subtracting the total amount of tooth structure—or predicted tooth structure if the patient is in the mixed dentition—from the total space available. Incisor inclination, sagittal discrepancies, and depth of the curve of Spee may also influence the space available. Bolton analysis, a ratio of mandibular teeth width sum to maxillary teeth width sum, gives an index to determine how teeth will couple. The overall calculated ratio should be 91%; if the ratio is reduced, the maxillary teeth are relatively too large. The anterior ratio should be 77%. Finally, the occlusion can be studied, classification of the malocclusion can be made, and overjet and overbite relationships can be determined.8–10

2. What is a prioritized problem list? A prioritized problem list places the orthodontic/developmental problems into priority order to help evaluate the interaction, compromise, and cost/benefit of treatment for each of the problems in order to determine the appropriate course of action that maximizes benefit to the patient.9 To create an orthodontic problem list, group all related findings into major categories (Box 6-1). For example, facial convexity, mandibular retrognathism, upper incisal protrusion and proclination, and an excessive overjet may all be manifestations of a skeletal Class II malocclusion.

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CHAPTER 6 • Diagnosis of Orthodontic Problems

BOX 6-1

Orthodontic Problem List

1. Dental Class II division 1 2. Skeletal Class II malocclusion a. Facial convexity b. Maxillary incisal proclination/protrusion c. Overjet 6 mm d. Mandibular retrognathism e. Retrusive AP chin position 3. Posterior crossbite a. Unilateral (right side) b. Deviation of jaw toward affected side c. Presence of CO/CR shift d. Constricted maxillary dental arch relative to mandibular dentition e. Midline off center 4. Mild crowding a. Mandibular arch crowding 5 mm b. Rotated upper and lower incisors 5. Mandibular hypodivergence a. Normal cephalometric MPA b. Anterior deep bite 5 mm AP, Anteroposterior; CO, centric occlusion; CR, centric relation; MPA, mandibular plane angle.

3. What are the orthodontic problems in the three planes of space? ANTEROPOSTERIOR PLANE The anteroposterior (AP) plane passes through the body parallel to the sagittal suture, dividing the head and neck into left and right portions. The AP or sagittal dimension deals with maxillary and mandibular forward growth.8–11 Cephalometric analysis is used to determine if the underlying skeletal bases are in harmony or if there is a significant deviation that warrants consideration. A determination is made about whether a patient is in skeletal Class I, II, or III function. Orthodontic profiles are examined in this plane as well as the dental and skeletal classification of malocclusions. Overjet would also be noted in the dental position. Soft tissue analysis is used to determine the esthetics and facial balance of the patient. TRANSVERSE PLANE The transverse plane passes horizontally through the body, at right angles to the sagittal and vertical planes, dividing the body into upper and lower portions. The transverse dimension is evaluated skeletally by measuring the width of the posterior maxilla. Measurements less than 36 mm from the upper first molar mesiolingual gingival margins may indicate a skeletal discrepancy.8–11 Dental transverse deficiencies are more commonly due to lingually tilted upper bicuspids and molars, or buccally tilted lower bicuspids and molars. The soft tissue is evaluated for deviations in alar base width and overall facial harmony. By looking at the diagnostic rec ords in this plane, one may detect any problem relating to right and left asymmetries. The occlusal views of orthodontic models are in the transverse plane. Dental and skeletal posterior crossbites are noted in this dimension as well as intercanine and intermolar widths.

VERTICAL PLANE The vertical plane passes longitudinally through the body from side to side, dividing the head and neck into front and back parts. Skeletal discrepancies in the vertical dimension may be determined by analysis of a lateral cephalometric radiograph in coordination with a clinical examination. Discrepancies can include increased or decreased facial height, extremely low or high mandibular plane angle (MPA), or skeletal open bite.8–11 Dental analysis can reveal an open bite relationship, a deep impinging overbite, a deep curve of Spee, or non-erupting or ankylosed teeth. (Overbite is listed in the dental portion of the grid.)

4. What is included in the frontal analysis? The frontal analysis allows evaluation of the overall relationship between the face and the dentition. The four main areas of interest when analyzing the face include: (1) midline, (2) lip posture, (3) buccal corridor space, and (4) smile.4,12,13 MIDLINES When evaluating the midline of a patient, it is important to consider both the facial and dental midlines. An evaluation should be made to determine if the dental midlines are coincident with the facial midline and whether they are coincident with one another.13 This is best accomplished by looking face-to-face with the patient in an upright portion. The relation of the contact point of the centrals to the facial midline should be considered to rule out a non-parallel dental-tofacial midline. If a facial midline deviation is determined, such as a deviation of the chin, additional radiographs may be required to establish the cause of the deviation. A posteroanterior cephalometric radiograph or a 3D scan can help determine if the problem is in the condyle, the ramus, or the body of the mandible. One must be careful to separate true skeletal deviations from functional deviations caused by occlusal discrepancies. LIPS The lip posture should be evaluated both at rest and with the lips lightly touching. Watch for evidence of lip strain on closure, which may indicate a need for extraction treatment. Evaluate the upper lip length and the amount of tooth and gum display at rest and on full smile. If no amount of tooth is displayed at rest, the teeth may be dried, utility wax placed at the incisal edges, and the lip length indexed on the wax. The amount of vertical deficiency can then be read from the wax. Excessive gingival display on smiling can be due to short upper lip length, short clinical crowns from excess gum tissue, or vertical maxillary excess. In females, 3 to 4 mm of incisal display should be present at rest; at full smile, the upper lip should reach the height of the centrals or slightly above.4 BUCCAL CORRIDORS Dark buccal corridor spaces can be due to lingually set or lingually tipped premolars. Indiscriminate expansion has questionable long-term stability and can create buccal root dehiscences.14,15 Proper use of expansion requires careful treatment planning.


SMILE LINE The relationship of the upper teeth to the lower lip should be evaluated for parallelism among their curvatures. Treatment should be aimed at keeping or creating parallelism and avoiding a flat or reverse smile line.

5. What is included in the profile view? The profile view is used to evaluate the AP relationship of the maxilla and mandible to the overall face, the nose, lip posture, and vertical discrepancies.8–11 ANTEROPOSTERIOR The relationship of the maxilla and the mandible to the overall face is evaluated. Deviations in midface projection and mandibular projection are noted. NOSE The nose plays an important part in facial balance. Note any morphological variations in shape, and discuss any concerns with the patient. Upturned nasal tips tend to be more youthful in appearance but may require variations in treatment planning if extractions are being considered to eliminate crowding in the dentition. LIPS The lip posture should again be considered at rest and with lips lightly touching. The interlabial gap should be approximately 1 to 3 mm at rest posture. Evaluate the amount of incisor display at rest, as well as the inclination of the incisors in relation to TABLE 6-1

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facial balance. The nasolabial angle is an indication of upper lip inclination. The esthetic-line (E-line) proposed by Ricketts is influenced by the nose and chin but can aid in evaluating lip protrusion or retrusion. VERTICAL The height of the lower face, from subnasale to menton, can be further subdivided. One-third of the distance is measured from subnasale to stomion and two-thirds of the distance is measured from stomion to menton. Deviations from this ratio may indicate vertical maxillary excess, a short upper lip, a skeletal open bite, or an increase in anterior facial height. The normal ratio of the lower facial height to the posterior facial height is 0:69.16 The general characteristics of a long face include increased anterior facial height relative to posterior facial height, steep MPA, possible lip incompetence, and a shallow mentolabial fold.

6. What is the 3D-3 T diagnostic grid, and why is it important as a routine part of an orthodontic patient record? The 3D-3 T diagnostic grid represents a diagnostic summary of the findings in the three tissue categories: skeletal, soft tissue, and dental for the sagittal, transverse, and vertical planes of space (Table 6-1). With its systematic and comprehensive description of examination results, it offers a helpful tool to develop a prioritized problem list and facilitate treatment planning to correct the problems. Orthodontic diagnosis is an objective process, with each practitioner developing the same

3D-3 T Grid with Common Findings

3D-3 T

SAGITTAL (AP) PLANE

TRANSVERSE PLANE

VERTICAL PLANE

Skeletal findings of cephalometric analysis and model analysis

Box 1 • Class I, II, or III skeletal malocclusion • Maxillary prognathism/ retrognathism • Mandibular prognathism/ Retrognathism • Incisal protrusion/retrusion • AP position of chin Box 4 • Facial profile: straight/convex/ concave • Lip protrusion/retrusion • Lip soft tissue thickness • Facial musculature: strong/weak masculatory muscles • Nasolabial angle Box 7 • Angle’s classification of molar relationship: Class I, Class II division 1, Class II division 2, Class III • Incisal proclination/retroclination • Overjet • Anterior crossbite

Box 2 • Constricted/wide maxillary arch • Constricted/wide mandibular arch • Intermolar width • Posterior skeletal crossbite

Box 3 • Posterior skeletal open bite/ deep bite • Posterior facial height • Anterior facial height • Rotation of palatal plane • MPA • Mandibular hyper/hypodivergence Box 6 • Proportion of facial thirds: upper, middle, lower thirds • Lip competence/incompetence • Gummy smile (VME)

Soft tissue findings of clinical examination and photographs

Dental findings of clinical examination and model analysis

Box 5 • Facial asymmetry • Deviation of jaw to one side • Buccal corridors

Box 8 • Asymmetries in the dental arch • Posterior dental crossbites—buccal or lingual • Bolton discrepancies • Congenitally missing teeth • Previous extractions • Blocked out teeth • Rotated teeth • Dental midline

Box 9 • Posterior dental open bite/ deep bite • Occlusal cant • Overbite • Anterior open bite/deep bite

3D, Three-dimensional; 3 T, three tissues; AP, anteroposterior; MPA, mandibular plane angle; VME, vertical maxillary excess.

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measurements for the problem list. Once the list is completed, the treatment planning process begins with prioritized treatment objectives discussed with the patient. Treatment planning is a very subjective process and is individualized for each orthodontic patient.

7. What are the advantages of using the 3D-3 T diagnostic grid in treatment planning? Listing the examination and orthodontic analyses data in this format ensures that all factors and possibilities for a given case are considered before a treatment plan is established. Each box is designated for a specific problem type; thus, completion of the table ensures that all diagnostic records are carefully considered. In addition, the side effects of correcting one problem, which may help or worsen another problem, are more clearly evaluated before a list of objectives and the best possible treatment plan is selected. The immediate insight into the difficulty of a case is another advantage of this methodology. Understandably, cases with abnormalities involving all tissue categories or all three planes of space require more attention than a case having fewer dimensional problems. A malocclusion with problems in all three places of skeletal tissue is very difficult to treat. The end result of such an approach is a comprehensive and effective treatment plan with concise and realistic goals.

8. What are the steps of the 3D-3 T treatment plan method? 1. Creation of the 3D-3 T grid 2. Creation of an orthodontic problem list 3. Listing of treatment objectives 4. Formation of a treatment plan

9. What information is contained within each box? Table 6-1 shows a 3D-3 T grid with some common findings listed in each box. As a general rule, soft tissue problems are detected in the clinical examination and orthodontic photographs. Exceptions are soft tissue cephalometric analyses, which are also useful diagnostic tools for detecting soft tissue problems in all planes of space. Dental tissue findings are observed in the patient examination and by performing an orthodontic model analysis. Skeletal tendencies or problems are sometimes detected during the patient examination but are confirmed with a cephalometric analysis. A 3D-3 T grid with various problems listed in each of the three planes and three tissues is presented (see Table 6-1).

10. What are treatment objectives? After the review of all diagnostic findings and the formation of a problem list, the clinician forms a list of goals and treatment objectives listed in order of importance for each patient.8–11,14 The patient’s chief concern is always given high priority. Failure to accomplish correction of the patient’s chief complaint usually results in the patient being dissatisfied with the overall orthodontic treatment.

Ideally one would like to correct all existing malocclusions, and in many cases, this can be achieved without difficulty. However, there will be cases in which one or more limiting factors will force the clinician to limit the goals to those most beneficial to the patient. For example, when the patient is a non-grower, the complete correction of a skeletal Class II malocclusion is likely only with the assistance of orthognathic surgery. If the patient is opposed to correctional surgery, the only other realistic alternative, aside from no treatment, is an orthodontic treatment plan designed to camouflage the problem. When Class I molar correction is unlikely, a better aim may be to get the cuspids into a Class I relationship. In cases of upper premolar extractions (without extraction in the lower arch), the cuspids are positioned into a Class I relationship while the molars are kept at a full step Class II position. However, to establish an ideal occlusion, the normal molar 14-degree rotation must be corrected to 0 degrees if it is in a Class II molar relationship. Although the treatment goals are made before the treatment plan is created, sometimes they are modified during the process of treatment planning.8–11 Insights coming from closer attention to the case may cause one to switch goals or change their order of importance. At the end, one should be able to break down the treatment plan into the individual components that address each of the goals. An orthodontist should be able to confidently predict the chances of reaching a goal. When the clinician anticipates that a goal will be difficult to achieve, the patient should be made aware of this to avoid false expectations at the end of treatment.

11. How does one form a treatment plan? To form a treatment plan, one takes the treatment objective and then chooses a treatment modality that will achieve that desired result.8–11 In orthodontics, a patient presents with symptoms and problems, the dentist and orthodontist engage in diagnosing these problems, and they finally agree on treatment options to correct the problems. Based on the collective data, one treatment choice may be more effective and advantageous than another. If the patient decides not to choose the ideal option for treatment, alternatives should be presented to meet the patient’s desired needs, realizing it may be a compromised treatment plan. We have to be certain that we listen to what our patients perceive their problems to be and agree on a treatment strategy that is acceptable to both the patient and the orthodontist. At times, an orthodontic tool designed to correct one problem may actually make another problem worse. For example, the correction of a posterior crossbite with a quad helix or “W” appliance, without exceptional control of upper molar eruption, is contraindicated for patients with mandibular hyperdivergence or anterior open bite. In cases like these, it may be better to use a rapid maxillary expander with bonded posterior occlusion to prevent excessive extrusion of the upper molars. Of course, if the patient is a non-grower with a profile that has excessive anterior facial vertical height, one may opt to correct the maxillary constriction at the time of the orthognathic surgical correction of the vertical problem. In order to easily go


from a problem list to a concrete treatment plan, one has to know the many orthodontic treatment modalities, their main functions and side effects, advantages and disadvantages, and indications and contraindications. To more clearly demonstrate how to formulate a treatment plan, refer back to the sample problem list in Box 6-1. Based on knowledge of appropriate treatment timing, one should correct the transverse problem (the posterior crossbite) first. The patient’s posterior crossbite is unilateral and deviates to the right-hand side, causing the jaw to deviate to the affected side. The presence of a centric occlusion (CO)/centric relation (CR) shift reveals that the posterior crossbite is a functional crossbite resulting from a constricted maxillary dental arch. The patient is a growing individual, so one expects to be able to expand his maxillary arch with an expansion appliance without surgical assistance. The extrusion of the upper molars is a side effect of maxillary expansion, but in this case, it will help the patient’s anterior deep bite and mandibular hypodivergence. This same extrusive effect, however, may cause the mandibular plane to rotate clockwise and worsen the patient’s convexity. The patient has a facial convexity with a retrognathic mandible and retrusive chin. He has protrusive and proclined maxillary teeth with a moderate overjet. Because of his age, in late mixed dentition, the patient has an advantageous growth potential. There are a number of appliances designed to correct a skeletal Class II malocclusion in a growing patient: the headgear; the bionator and Twin Block appliance (and other early treatment appliances); and the Herbst appliance, the Mandibular Anterior Repositioning Appliance (MARA), and the Jasper Jumper, just to name a few. Treatment with headgear is eliminated because this appliance is indicated for skeletal Class II malocclusion with maxillary prognathism. All the early treatment appliances are ruled out because they are most effective (if effective at all; see Chapter 3) during the early mixed dentition stage. Now the choices are narrowed to the Herbst, the MARA, and the Twin Block, which are all appliances aimed at growing patients in the late mixed dentition stage. Refining these choices would have to depend on the patient’s motivation and attitude and the doctor’s own clinical skill and experience. For a non-compliant preadolescent male, a fixed Herbst appliance may be a wise choice. Remember, a treatment plan is subjective and will vary among orthodontists based on their expertise! The minor crowding and rotations in this case will readily resolve with the fixed upper and lower orthodontic appliances. The mandibular arch may be stabilized with a fixed intercanine retainer, whereas the upper arch can be retained with a removable maxillary appliance. The following questions further discuss information in the 3D-3 T diagnostic grid. The intention of this section is to encourage the diagnostic and treatment approach using the 3D-3 T grid. It is beyond the scope of this section to encompass all aspects of orthodontic problems. The individual chapters in this book, as well as other orthodontic textbooks recommended in the reference list, provide further insights and knowledge of the related subjects.

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12. What are the problems in the sagittal (anteroposterior) plane of space? AP orthodontic problems of all three tissue types are detected in the sagittal plane of space. A compilation of the data in this plane results in a definitive classification of the patient’s softtissue, dental, and skeletal malocclusion. The clinical examination of the patient’s profile at the start of treatment gives the clinician an immediate impression of the patient’s facial harmony and esthetics as well as the underlying dental and skeletal structure before taking any records. The succeeding orthodontic model analysis gives more insight to the patient’s dental malocclusion, whereas the skeletal component data derived from the cephalometric analysis gives the clinician a complete picture of the sagittal malocclusion. SKELETAL TISSUE IN THE SAGITTAL PLANE Class I, II, or III Skeletal Malocclusion There are numerous cephalometric methods to distinguish the skeletal relationship of the maxilla and the mandible to each other and to the cranial base. In the Steiner’s analysis, the ANB angle (formed between the A-point, nasion, and B-point) indicates the AP position of the maxilla in relation to the AP position of the mandible. A comparison of the SNA and SNB angles from the norm further shows if the problem is a maxillary or mandibular prognathism or retrognathism. The Wits analysis, using the difference between the projections of points A and B to the functional occlusal plane, is another common method to verify the relationship of the maxilla and the mandible. SOFT TISSUE IN THE SAGITTAL PLANE Evaluation of the Facial Profile The soft tissue problems of the AP plane are best seen through a profile analysis of the patient. A proper analysis gives valuable information about the patient’s esthetics and shows whether the jaws are proportionately positioned in this plane of space. With the patient sitting or standing in the upright position and looking at a distant object, an imaginary line connecting the bridge of the nose to the base of the upper lip and extending to the chin is evaluated.8–11 When this line is straight, the soft tissue profile of the patent is harmonious. A disproportion in the size of the jaws, on the other hand, results in a profile convexity or concavity. A convex profile is indicative of a Class II jaw relationship, whereas a concave profile points to a Class III relationship. Since esthetics is a major reason for orthodontic treatment, a severe profile convexity or concavity points to more involved orthodontic treatment and possible orthognathic surgery. The non-harmonious profile by itself does not indicate which jaw is at fault. That information is derived from examining the skeletal tissue in this plane of space. During the clinical examination of the soft tissue profile, it is also helpful to visualize the MPA. This can be accomplished by placing a mirror handle or other instrument along the border of the mandible.9 When the mirror handle is angulated slightly below the ear, the MPA is predicted to be normal. Too steep an inclination indicates a high cephalometric mandibular

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plane value or mandibular hyperdivergence; too flat an inclination indicates a low MPA or hypodivergence. A hyperdivergent mandible is an indicator of a difficult malocclusion of increased vertical dimension. In general, a very steep mandibular angle coincides with a long and narrow face. The facial musculature of a dolichocephalic patient shows masseter muscles that are weak and hypotrophic. Strong hypertrophic masseter muscles are characteristic of a brachycephalic patient with mandibular hypodivergence. The facial form of this patient tends to be short in facial height and square in appearance. Lip Protrusion/Retrusion By looking at the lips’ position in this plane, one gets a quick impression of the underlying dental position, such as maxillary dental protrusion or lack of upper lip support in cases of Class II division 2 malocclusion.14 A determination of lip protrusion or retrusion also helps the clinician decide if extraction treatment is necessary. One way to assess the AP position of the lip is through the Ricketts’ E-line. This line is drawn from the tip of the nose (point Pn) to soft tissue pogonion (Pog). Ideally, the upper lip should be approximately 4 mm behind the line, whereas the lower lip should be about 2 mm behind it. Another way to assess the position of the lips is by looking at the lower facial plane, created by connecting a point at the base of the nose (Subnasale or Sn) to soft tissue pogonion (Pog). The lips should appear relaxed in the repose position. Thin lips respond more readily than thick lips to orthodontic retraction of the incisors. Extractions followed by retraction of incisors behind the Sn-Pog line should be avoided.14 DENTAL TISSUE IN THE SAGITTAL PLANE Interarch Molar and Incisal Relationships Labeling the relationship of the first molars of each case according to Angle’s classification of malocclusions is essential because the establishment of a normal Class I molar relationship is frequently a goal in orthodontics. Overjet is also best studied in this plane. Normal overjet is the horizontal overlap of the upper incisors to the lower incisors. Ideally it is 2 mm. When there is negative overjet, or when the lower incisors are anterior to the upper incisors, the condition is called an anterior crossbite. To determine if this anterior crossbite has a skeletal component and not just a functional expression of a dental malocclusion, the orthodontist looks for the presence of an anterior CO/CR shift. When the malocclusion is a functional one, the incisors show negative overjet in centric occlusion but touch edge to edge in centric relation. An anterior dental crossbite tends to be easier than one with a functional shift or of a skeletal nature. The evaluation of the inclination of the incisors is important to Angle’s molar classification (distinguishing Class II division 1 from division 2) and the identification of an abnormal overjet relation. Excessive incisal proclination is related to crowding. This is further discussed in the section addressing findings of the transverse plane. The upper incisor should be proclined 103° to the sella-nasion (SN) plane, whereas the lower incisor should be proclined 93° to the mandibular plane.

13. What are the problems in the vertical plane of space? The scope of this question is a discussion of the proportions of the face as viewed in the vertical plane as well as posterior crossbite and open bite. SKELETAL TISSUE IN THE VERTICAL PLANE OF SPACE A general strategy of cephalometric analyses used to evaluate vertical problems is to compare the posterior to anterior facial heights. The more equal these measurements are, the more likely it is that the patient will display a short square facial type known as brachyfacial with low MPA, decreased anterior vertical dimension, and a deep bite. On the contrary, when the anterior facial height is excessively long compared with the posterior portion, a long and narrow facial type known as dolichofacial is evident. COMPARISON OF THE POSTERIOR TO ANTERIOR FACIAL HEIGHT In the Steiner’s analysis, the vertical position of the mandible is measured by the relationship between the anterior cranial base (defined by the plane sella to nasion) and the mandibular plane (extending from points gonion to gnathion). The mean value is 32° for SN-MP. An increase in this angle correlates with an increase in anterior facial height.8–11,14 The MPA is helpful in locating the vertical chin. It is formed by the intersection between the FH and the GoGn (goniongnathion) line and relates the cant of the mandibular plane to the FH plane. The mean value for MPA is 25°. SOFT TISSUE IN THE VERTICAL PLANE OF SPACE Proportion of the Facial Thirds A well-proportioned face can be divided into approximately equal vertical thirds, with the upper third extending from point trichion (Tr), at the top of the forehead, to soft tissue glabella (G), which is the most anterior point of the forehead. The second vertical third extends from soft tissue glabella to the subnasale (Sn), or the point at which the columella of the nose merges with the upper lip in the midsagittal plane. The lower third begins with subnasale and ends with soft tissue menton (Me), which is the lowest point on the contour of the soft tissue chin, found by dropping a perpendicular line from a horizontal line through skeletal menton.14 It is important to evaluate middle and lower facial thirds. At the initial evaluation of the patient, a “sunken” appearance of the midface in the middle third may be an indication of a maxillary AP deficiency or maxillary retrognathism associated with skeletal Class III malocclusion. This finding should be confirmed with a cephalometric analysis. The middle third to lower third vertical height of the face should have a 5:6 ratio.14 The upper lip length should make up one-third of the lower facial height and the distance from the lower lip to soft tissue menton should be two-thirds. Aside from facial proportion, one should also examine the lips in this


plane, since their harmonious position is essential to facial esthetics. When the upper and lower lips do not meet at rest, this is known as lip incompetence. When asked to close their lips, these patients may exhibit mentalis strain and display some lip strain. Lip incompetence is an association of an excessive AP discrepancy between the maxilla and mandible or an increased anterior vertical facial height. DENTAL TISSUE IN THE VERTICAL PLANE OF SPACE Overbite, or the vertical overlap of the upper and lower incisors, is normally 2 mm. When it is positive and excessive, an anterior deep bite exists. When there is a negative overbite and the incisors fail to overlap, an anterior open bite exists. Open bites and deep bites are dental malocclusions in the vertical plane of space. Anterior open bites are the result of an undereruption of the anterior teeth or an overeruption of posterior teeth. Likewise, when the posterior teeth are undererupted, the clinical observation is an anterior deep bite. Anterior open bite and deep bite with differing etiologies warrant different treatments. If the anterior open bite is derived from an undereruption of the anterior teeth themselves, this is indicative of a dental open bite due to a tongue or digit habit. The treatment aim is to extrude the anterior teeth. If the open bite is a result of an overeruption of the posterior teeth, this is indicative of a skeletal open bite. The treatment mechanics should be aimed toward intruding these teeth and usually leaving the incisors in their original position. If one sees a greater underlying skeletal cause of the open bite (through a cephalometric analysis), it is more likely that the patient needs a combination of orthodontics and orthognathic surgery to correct the malocclusion. Precision in diagnosis allows the orthodontist the great advantage of treating the abnormal to the normal, ensuring the best chance of getting beautiful, healthy results.

14. What are the problems of the transverse plane of space? Although no face is perfectly symmetrical, the absence of any obvious asymmetry is necessary for good facial esthetics. In order to assess facial symmetry, an imaginary line is drawn through the soft tissue glabella down the center of the face to the midpoint of the chin.14 The maxillary and mandibular dental midlines, also known as upper dental midline (UDML) and lower dental midline (LDML), should be assessed in relation to the facial midline. Some dental factors that may have caused midline shifts include crowding, rotations, and blocked-out teeth, as well as missing and irregularly sized teeth. A facial asymmetry caused by a mandibular lateral displacement may be a sign of a posterior crossbite or of a more complicated skeletal disorder. A deviation of the mandible to one side, accompanied by a cant of the occlusal plane, can be detected as the patient bites on a wooden spatula, with her head positioned so that the projected interpupillary line is parallel to the floor. The parallelism of the wooden spatula is then evaluated to this interpupillary line. A more common malocclusion that may involve a mandibular lateral displacement is a posterior crossbite. Viewing the

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intercuspation of the posterior occlusion in the coronal plane allows the best visualization of this malocclusion, which is described as when the mandibular teeth occlude in buccal version to the maxillary teeth. An infrequent reverse of this malocclusion is a complete lingual version of the posterior mandibular segments, often referred to as a Brodie bite or scissor bite. A posterior crossbite may be bilateral or unilateral and can be dental or skeletal. As in the anterior crossbite, a unilateral dental posterior crossbite can often be distinguished from a skeletal crossbite by the presence of a posterior CO/CR shift. When the posterior crossbite exists in centric occlusion but disappears in centric relation, the bite is functional in nature, and often results from the combination of a constricted maxillary arch and a shift of the mandible to the affected side on closure. To find if the constricted maxilla is caused solely by a constricted dental arch or also a narrow bony palate, one should measure the palatal transversal dimensions of the orthodontic study model. Intercanine and intermolar widths are measured and compared with a chart of norm for the patient’s age and gender. When they are very narrow compared with the norm, most likely the crossbite is skeletal. A stronger skeletal problem mandates more aggressive treatment and is more sensitive to the developmental age of the patient. Table 6-2 is an example of the diagnostic grid (3D-3 T), which includes those areas and measurements that absolutely must be included.

15. What is the discrepancy index used by the American Board of Orthodontics? The American Board of Orthodontics (ABO) discrepancy index is a grading system used to assess the complexity of an orthodontic case.17 There are eleven target disorders evaluated and scored depending on the severity of their manifestation: overjet, overbite, anterior and lateral open bite, crowding, occlusion according to the Angle classification, lingual crossbite or buccal crossbite, ANB angle, SN-MP angle, and U1*-SN angle. Other features may add to the complexity of the case, such as congenitally missing teeth or supernumerary teeth, ectopy or ectopic eruption, transposition, impaction, anomalies of tooth size and shape (e.g., peg lateral incisors), significant skeletal asymmetries that require dental compensation, significant midline discrepancies or CO-CR shifts, and excessive curve of Wilson. Examples of the Discrepancy Index form used by the ABO can be seen on the ABO website http://www.americanboardortho.com/. CASE EXAMPLES It is impossible to list in this chapter all of the orthodontic malocclusions that could exist. Following are some case examples using the 3D-3 T grid for diagnosis and actual treatment. Case 1: Headgear (Fig. 6-1 and Table 6-3)

* U1, Upper incisor.

TABLE 6-2 Diagnostic Grid (3D-3 T) Skeletal Soft tissue Dental

Other considerations

ANTEROPOSTERIOR

TRANSVERSE

VERTICAL

SNA SNB ANB Profile NLA E-line Molar classification OJ 1 to NA 1' to NB 1 to SN 1' to MP Mandibular arch form Discrepancy index Perio status

6' to 6' Width 6' to 6' Width

SN-MP FMA

Buccal corridor

Lips VME

UDML LDML U-ALD L-ALD 3' to 3' Width

OB Curve of Spee Incisor display

3D, Three-dimensional; 3 T, three tissues; E-line, esthetic-line; FMA, Frankfort mandibular angle; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OJ, overjet; SN, sella-nasion; U-ALD, upper arch length discrepancy; UDML, upper dental midline; VME, vertical maxillary excess.

A

D

F

I

C

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G

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J FIG 6-1 Case 1: Headgear. A-H, Composite initial photographs. Facial (A-C) and intraoral (D-H). I, Initial panoramic radiograph. J, Initial cephalometric tracing.


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T FIG 6-1, cont'd K-R, Composite final photographs. Facial (K-M) and intraoral (N-R). S, Final panoramic radiograph. T, Final cephalometric tracing.

16. How does one decide what type of headgear to use? To begin with, one must ask a series of questions. Is the patient a child or an adult? What sort of facial pattern does the patient have; is it hypodivergent or hyperdivergent? What sort of malocclusion exists; is it a dental problem or is it a skeletal problem? What is the soft tissue picture; is it characterized by a flat lip posture, or are the lips full, protrusive, and convex? What are the anchorage requirements of the case once treatment is instituted? What are the treatment objectives for this case?

Is the malocclusion a Class II, and how is it to be corrected? The answers to these questions come only with a complete set of diagnostic records and a thorough understanding of an entire range of subjects.8–11,18 Assume, for the sake of this discussion, that the patient has a Class II division 1 malocclusion with bimaxillary crowding, bimaxillary protrusion, open bite tendency, a high MPA, and a slightly retrognathic mandible. Assume that the treatment requires more than simply minimum anchorage control. If a headgear was the anchorage mechanism of choice, then a decision must be made as to design and how it is to be used. Age

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TABLE 6-3 Diagnostic Summary (3D-3 T): Case 1—Headgear (12 yr:7 mo) Skeletal Soft tissue Dental


ANTEROPOSTERIOR

TRANSVERSE

VERTICAL

SNA = 78° SNB = 74° ANB = 4° Profile = slightly convex NLA = obtuse E-line = −3.4 mm Molar: Class II L, end on R OJ = 4 mm 1 to NA = 3.6 mm 1' to NB = 2.8 mm 1 to SN = 100° 1' to GoGn = 90.2° Mand Arch Form = Ovoid DI = 17 Perio/OH = Good oral hygiene

6' to 6' Width = 29.5 mm 6' to 6' Width = 40.3 mm

SN-GoGn = 35° FMA = 27°

Buccal corridors = narrow

Lips competent Thin upper lip Mesofacial OB = 0.5 mm

UDML = 3 mm R LDML = coincident U-ALD = 2 mm L-ALD = 0 mm 3' to 3' Width = 26.8 mm

PRIORITIZED TREATMENT OBJECTIVES

TREATMENT PLAN

1. Establish Class I molar and cuspid 2. Correct maxillary dental midline 3. Improve facial esthetics 4. Maintain vertical control

1. Deliver cervical-pull headgear 2. Full-time wear until molar correction; then nighttime only 3. Band and bond Mx/Mn 4. Level and align CCS to open space for U2s and shift UDML 5. Detail occlusion 6. Class II elastics prn 7. Retain: Mx wrap Mn 3-3

5. Restrict maxillary growth in AP 6. Close diastema 7. Maintain oral hygiene

3D, Three-dimensional; 3 T, three tissues; AP, anteroposterior; CCS, closed coil spring; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort mandibular angle; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; SN, sella-nasion; U2, upper lateral incisor; U-ALD, upper arch length discrepancy; UDML, upper dental midline.

of the patient certainly plays a major role in these decisions. In the case of an 11-year-old, the treatment might be considerably different than it would be for a 21-year-old. In the first instance, harnessing whatever horizontal growth might be available could help in gaining at least part of the Class II correction.18 In the adult patient, however, growth is not a factor, and Class II correction may have to be accomplished in an entirely different manner. Then again, while a headgear might be appropriate for the child, it may not be for the adult; microimplants might be more advisable. In the Class II adult, treatment options are usually limited to two choices: performing orthognathic surgery to advance the mandible or camouflaging this case with extraction of maxillary first bicuspids, leaving the first molars in a Class II. In either case, if extraction treatment is necessary, anchorage requirements must be established and decisions made relative to Class II molar correction. If, as has been illustrated, the patient presents with a hyperdivergent facial pattern, the headgear of choice might very well be a high pull design.6 If, on the other hand, this hypothetical patient had presented with a hypodivergent facial pattern, the headgear of choice might be a cervical pull design.18 In the end, factors such as anchorage requirements, patient age, facial pattern, and treatment objectives help the orthodontist decide upon the appropriately designed appliance. In this hypothetical example, if the patient was a child and if the molars were in a full-step Class II relationship, the facial pattern were hyperdivergent, the mandibular anchorage requirements were maximum,

and the final treatment objective was to achieve a Class I molar relationship, how many hours of headgear would be required to achieve the goal? Since, in this case, the Class II molar relationship will result without mesial movement of the mandibular molars (maximum anchorage), the Class I molar relationship will be achieved by some distalization of the maxillary molars and forward growth or repositioning of the mandible. Therefore, the number of hours required to wear a headgear to create the desired change—if, in fact, the objective could be reached at all—might be 14 hours/day or more. Of course, it is assumed that molar distalization with high pull headgear is not necessarily an appropriate expectation. In fact, in the case of a hyperdivergent patient, it is understood that distalization of molars could easily increase the anterior facial height as the molars “wedge” the mandible down and back in a clockwise direction.6 This, in and of itself, is a limiting factor in the successful treatment of such a malocclusion. In the adult patient with a similar malocclusion, the treatment of choice might not include headgear; it also might not involve just orthodontics alone. It would be unrealistic to expect the adult to wear a headgear the required number of hours, if at all. In addition, with no growth potential available to help with the correction, microimplants might be a better option in correcting the dental malocclusion. As to the issue of the skeletal discrepancy, surgery might very well be the only choice for the adult.9,10 Case 2: Extraction vs. Non-Extraction (Fig. 6-2 and Table 6-4)


17. What factors can affect the decision to extract teeth when correcting a malocclusion? Facial profile and soft tissue considerations have come to play a much more important role in terms of the method of treatment. A knowledge and understanding of the interplay and interrelationship of the soft tissue response to normal growth

A

F

I

and tooth movement is critical to the success or failure in creating a pleasing soft tissue appearance. Studies have shown that people have difficulty in distinguishing between patients who have or have not had extractions when evaluating posttreatment soft tissue results.19–21 Thus, it may be assumed that a proper diagnosis treatment plan and ultimate treatment approach should result in a patient who has a pleasing soft tissue appearance.

C

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J FIG 6-2 Case 2: Extraction. A-H, Composite initial photographs. Facial (A-C) and intraoral (D-H). I, Initial panoramic radiograph. J, Initial cephalometric tracing. (Continued)

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The degree of dental discrepancy and patient age play important roles in the decision to treat a malocclusion with or without the extraction of permanent teeth. For example, the patient who presents in the mixed dentition may be a candidate for a non-extraction approach if the orthodontist feels that it is possible to take advantage of growth and by developing increased arch length to accommodate the permanent teeth. In certain situations, one must decide if a combination of arch development and air rotor stripping (ARS) is sufficient

to accomplish the treatment objectives.22,23 Some suggest that a significant amount of mesiodistal tooth reduction can, in a significant number of cases, reduce the need for extraction of teeth. In the end, however, a patient who presents in the permanent dentition with a severe enough discrepancy in arch length might very well require extraction treatment. Certain cephalometric findings might also tip the balance toward extraction treatment when these findings are superimposed upon other factors such as those mentioned previously.


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TABLE 6-4 Diagnostic Summary (3D-3 T): Case 2—Extraction (17 yr:7 mo) Skeletal Soft tissue

Dental


ANTEROPOSTERIOR

TRANSVERSE

VERTICAL

SNA = 83° SNB = 79° ANB = 4° Profile = convex NLA = Acute E-line = +7 mm Bi-dentoalveolar protrusion Molar: Class I OJ = 4 mm 1 to NA =11 mm 1' to NB = 15 mm 1 to SN = 112° 1' to GoGn = 106° Mand Arch Form = Tapered DI = 15 Perio/OH = Good oral hygiene


SN-MP = 36° FMA = 29°

Buccal corridors = normal

Lips incompetent Dolichofacial mentalis strain

UDML = on LDML = on U-ALD = −1 mm L-ALD = −1.5 mm 3' to 3' Width = 26.8 mm

OB = 1.5 mm


TREATMENT PLAN

1. Reduce dentoalveolar protrusion 2. Eliminate crowding in Mx/Mn 3. Retract and upright Mx and Mn incisors 4. Improve facial and dental esthetics

1. Extract all first bicuspids 2. Band and bond Mx/Mn 3. Level and align 4. Close extraction spaces Detail occlusion 5. Class II elastics prn 6. Retain: Mx wrap Mn 3-3 7. Crown lengthening UR1

5. Establish ideal OB and OJ with coincident dental midlines 6. Maintain oral hygiene 7. Maintain Class I molar and cuspid

3D, Three-dimensional; 3 T, three tissues; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort mandibular angle; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; SN, sella-nasion; U-ALD, upper arch length discrepancy; UDML, upper dental midline; UR1, upper right central incisor.

In a borderline extraction case, the orthodontist will tend not to extract in a low MPA case but will tend to extract in a high MPA case. For example, when the degree of protrusion, which may be considered a form of crowding, and the amount of retraction are combined with the desired change in soft tissue and the need for decrowding of the dentition, extraction may become the treatment of choice.8–11 Case 3: Maxillary Expansion (Fig. 6-3 and Table 6-5)

18. What is the difference between the treatment approach of the adult or child who requires expansion of the maxillary arch? As is the case in all other situations, a proper diagnosis is required in order to determine the nature of the problem.24–27 If, for example, there is a posterior crossbite and it is determined that the transverse discrepancy is of dental origin, the correction of the malocclusion will be considerably different than if the problem is skeletal in nature. Aside from a clinical evaluation and a routine set of diagnostic records, the addition of an AP cephalogram would be an appropriate diagnostic tool for determining the nature of the problem. If the malocclusion is determined to be of dental origin, the correction may

be similar for either the adult or the child patient in terms of mechanotherapy. If, on the other hand, the transverse discrepancy is due to a maxillary basal bone constriction, the treatment will be considerably different for the adult and the child.28 Let us first consider the treatment of a dental maxillary transverse discrepancy of dental origin in the child patient. In the mixed dentition, spontaneous correction is a possibility if the permanent teeth erupt in a more buccal position relative to the deciduous teeth. Failing that, however, mechanical expansion is likely the treatment of choice. Although certain constraints exist in terms of how much mechanical expansion can be done, this approach is certainly reasonable. If, however, the transverse discrepancy is due to a basal bony problem, the treatment of choice is rapid maxillary expansion. Naturally, an understanding of the timing of mid-palatal suture closure is critical to the diagnosis and treatment planning for the maxillary expansion procedure.9–11 At what age the mid-palatal suture closes can vary from patient to patient, but certain general rules apply. If, however, the young patient has reached an age beyond which the orthodontist feels comfortable attempting a routine expansion, a surgically assisted procedure may be the treatment of choice. In the adult patient who presents with a dental posterior crossbite, mechanical expansion is also an acceptable treatment, as it is in the child, but in adults it is important to include a periodontal evaluation prior to instituting expansion mechanics. In the presence of untreated mild to moderate periodontal disease,

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A

B

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F

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C

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J FIG 6-3 Case 3: Maxillary expansion. A-H, Composite initial photographs. Facial (A-C) and intraoral (D-H). I, Initial panoramic radiograph. J, Initial cephalometric tracing.


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TABLE 6-5 Diagnostic Summary (3D-3 T): Case 3—Maxillary Expansion (15 yr:6 mo) Skeletal Soft tissue


ANTEROPOSTERIOR

TRANSVERSE

VERTICAL

SNA = 82° SNB = 74° ANB = 8° Profile = convex NLA = obtuse E-line = −0.4 mm Molar: Class II end on OJ = 3 mm 1 to NA = 0.5 mm 1' to NB = 3.5 mm 1 to SN = 96° 1' to GoGn = 87° Mand Arch Form = Tapered DI = 34 Perio/OH = Good oral hygiene Crossbite = UR5, UL2

6' to 6' Width = 29 mm 6' to 6' Width = 36.2 mm

SN-MP = 35° FMA = 29°

Buccal corridors = narrow UDML = on LDML = on U-ALD = −12 mm L-ALD = −9 mm 3' to 3' Width = 25 mm

Lips strain on closure Dolichofacial Long lower third OB = 6 mm


TREATMENT PLAN

1. Eliminate ALD in both arches 2. Expand the maxilla transversely 3. Establish Class I molar and cuspid with cuspid and anterior guidance 4. Establish ideal OB and OJ with coincident midlines

1. Extract all first bicuspids 2. Banded RPE to expand approx 9 mm 3. Band and bond Mx/Mn

5. Decrease lip strain 6. Improve dental and facial esthetics 7. Maintain oral hygiene

4. Level and align Close extraction spaces with reverse curve TMA CLAW 5. Detail occlusion with seating elastics 6. Retain: Mx wrap Mn 3-3 7. Refer for extraction of 8’s

3D, Three-dimensional; 3 T, three tissues; ALD, arch length discrepancy; CLAW, closing loop arch wire; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort mandibular angle; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; RPE, rapid palatal expander; SN, sella-nasion; TMA, beta titanium archwire; U-ALD, upper arch length discrepancy; UDML, upper dental midline; UL2, upper left lateral incisor; UR5, premolar.

echanical expansion may be somewhat risky and contraindim cated. If, in the adult patient, the maxillary transverse problem is due to a narrowness of the basal bone, the treatment of choice is a surgically assisted rapid palatal expansion (SARPE) appliance. Similar prerequisites apply in terms of overall periodontal health. In the patient who presents with a hyperdivergent facial pattern, control of the vertical dimension is important when considering any form of posterior expansion therapy, whether it is mechanical or orthopedic in nature. During correction of a posterior crossbite, one might typically expect an increase in the anterior vertical dimension. This usually results as the buccal cusps of the maxillary teeth override the buccal cusps of the mandibular teeth. Under normal circumstances this phenomenon is of a temporary nature, since the cusps achieve a more normal buccolingual relationship. In circumstances in which the patient is a young growing individual, one might have an easier time controlling this problem with the use of various extra-oral appliances (e.g., vertical pull headgears/ vertical pull chin cups) to redirect vertical growth. In the adult patient, however, controlling the vertical may be entirely different. Adult patients who present with these types of malocclusions often exhibit other characteristics of the so-called long face syndrome, such as maxillary vertical excess. In cases like these, the treatment of choice is often orthognathic surgery

with any number of different approaches to correcting the transverse and vertical discrepancies.8–11 Case 4: Impacted Cuspid (Fig. 6-4 and Table 6-6)

19. In what instance(s) might one choose to extract an impacted cuspid rather than bring it into its normal position? The diagnosis and treatment of impacted teeth, especially the maxillary cuspid, present the orthodontist with a particularly difficult problem and a serious challenge.29,30 For the purposes of this brief discussion, this section focuses on the problem as it relates to the maxillary cuspid. There is a logical approach to the diagnosis of this particular problem, but the approach to treatment may not necessarily be so easily determined, and it may not be similar for the child vs. the adult patient. In order to arrive at an appropriate treatment plan, one must understand dental development, retention, biomechanics, mechanotherapy, periodontal considerations, esthetics, functional occlusion, and other topics before making the decision. Although most orthodontists would prefer to bring an impacted maxillary cuspid into its normal position, there are certain circumstances that might preclude that decision.


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J FIG 6-4 Case 4: Impacted cuspid. A-H, Composite initial photographs. Facial (A-C) and intraoral (D-H). I, Initial panoramic radiograph. J, Initial cephalometric tracing. (Continued)

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TABLE 6-6 Diagnostic Summary (3D-3 T): Case 4—Impacted Cuspid (14 yr:10 mo) ANTEROPOSTERIOR Skeletal Soft tissue Dental


TRANSVERSE

SNA = 82° 6' to 6' Width = 38 mm SNB = 78° 6' to 6' Width = 37.5 mm ANB = 5° Profile = convex Buccal corridors = normal NLA = normal E-line = -2 mm Molar: Class I UDML = 3 mm Rt OJ = 3 mm LDML = 2 mm Rt 1 to NA = 4 mm U-ALD = −10.5 mm 1' to NB = 7 mm L-ALD = −9 mm 1 to SN = 107° 3' to 3' Width = 24.5 mm 1' Go-GN = 96° Mand Arch Form = Ovoid DI = 17 Perio/OH = Fair oral hygiene but some decalcification present Maxillary left canine impacted facially

VERTICAL SN-MP = 38° FMA = 30° Lips competent Dolichofacial full lips OB = 2 mm


TREATMENT PLAN

1. Eliminate crowding in Mx/Mn 2. Establish ideal OB/OJ with coincident midlines 3. Improve facial and smile esthetics 4. Improve oral hygiene 5. Establish Class I mutually protected occlusion 6. Restrict maxillary growth

1. Place Nance arch 2. Extract all first bicuspids and ULC 3. Band and bond remaining teeth 4. Close extraction spaces 5. Detail occlusion 6. Retain: Mx wrap Mn 3-3

3D, Three-dimensional; 3 T, three tissues; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort Mandibular Angle; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; SN, sella-nasion; U-ALD, upper arch length discrepancy; UDML, upper dental midline; ULC, upper left canine.

Let’s look at the following example. Assume that the maxillary left cuspid is palatally and somewhat horizontally impacted, that the left buccal occlusion is in Class II dental relationship, and that there is little or no space available for the cuspid in that quadrant. In addition, assume that the case requires extraction of permanent teeth in all four quadrants of the mouth. With a complete understanding of the treatment objective relative to establishing a final occlusion, it is determined that the maxillary left first bicuspid will finish in a Class I relation to the mandibular left cuspid. Thus, the question arises: “Does it make sense to extract the first bicuspid or the cuspid?” The decision to remove the cuspid in this instance may preclude establishing an ideal cuspidguided occlusion in favor of avoiding the risks or uncovering the cuspid and bringing it into place. This decision is predicated upon the orthodontist’s ability to weigh the risk/reward benefits of erupting the cuspid as opposed to extracting the tooth. The inherent risks in the surgical procedure, the possibility of a compromised final p eriodontal situation, the difficulties of mechanotherapy, the discomfort and hygiene problems for the patient, and the chance of failure of the cuspid to erupt are all factors that contribute to the decision of how to treat the problem. A thorough radiographic, cephalometric, and clinical diagnosis coupled with an understanding of the factors just mentioned should lead to an appropriate treatment modality.29

Case 5: Missing Maxillary Laterals (Fig. 6-5 and Table 6-7)

20. The congenitally missing maxillary lateral incisor presents the orthodontist with a true dilemma. What is one to do—implant or canine substitution? There are few entities in orthodontics that challenge one’s diagnostic skills more than that of a unilateral congenitally missing maxillary lateral incisor. The decision as to an appropriate treatment approach encompasses a whole range of options based upon the findings in the diagnostic records. A list of questions that must be answered might include, but are not limited to, any or all of the following: • What is the morphology of the contralateral lateral incisor? • What is the morphology of the cuspid on the side of the missing tooth? • How much space is available in the missing lateral position? • What is the condition of the ridge in the missing lateral area? • What is the buccal occlusion on both sides of the dentition? • What sort of restoration will be planned for the missing tooth? Assume, in just one scenario, that the occlusion on the side of the missing tooth is such that at least half the lateral space has been lost. Further assume that the patient has a high MPA

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J FIG 6-5 Case 5: Missing maxillary laterals. A-H, Composite initial photographs. Facial (A-C) and intraoral (D-H). I, Initial panoramic radiograph. J, Initial cephalometric tracing.


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TABLE 6-7 Diagnostic Summary (3D-3 T): Case 5—Missing Maxillary Laterals (12 yr:3 mo) ANTEROPOSTERIOR Skeletal Soft tissue Dental


TRANSVERSE

SNA = 79° 6' to 6' Width = 30 mm SNB = 83° 6' to 6' Width = 38 mm ANB = −4° Profile = concave Buccal corridors = normal NLA = normal E-line = −2 mm Molar: Class I UDML = 1 mm L OJ = 2 mm LDML = coincident 1 to NA = 8 mm U-ALD = 3 mm 1' to NB = 0 mm L-ALD = 2 mm 1 to SN = 113° 3' to 3' Width = 26 mm 1' Go-GN = 82° Mand Arch Form = Ovoid DI = 17 Perio/OH = Fair oral hygiene but some decalcification present Maxillary left canine impacted facially


TREATMENT PLAN

1. Improve dental and facial esthetics 2. Establish ideal OB/OJ with coincident midlines 3. Correct transposition, rotations, and crowding 4. Obtain Class I molar and cuspid with cuspid guidance 5. Improve oral hygiene 6. Establish Class I mutually protected occlusion 7. Retain

1. Extract UL B, C 2. Band and bond U6-6, L6s 3. Band and bond U3s, L5-5 as available 4. Level and align 5. Place U2 pontics, as possible 6. Detail occlusion 7. Retain: Mx wrap with pontics Mn 3-3 8. Lateral implants upon termination of growth

VERTICAL SN-MP = 26° FMA =19° Lips competent OB = 5 mm

3D, Three-dimensional; 3 T, three tissues; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort mandibular angle; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; SN, sella-nasion; U-ALD, upper arch length discrepancy; UDML, upper dental midline; UL, upper left central incisor.

and little or no overbite. Is it possible, or is it even advisable, to attempt space-opening mechanics by distalizing the buccal segment? Given the difficulties of the scenario, one might decide to forgo the “ideal” plan and “settle for” the space closure in that quadrant, reshape the cuspid, and leave the left buccal occlusion in Class II. Given this situation, the decision must be made as to the disposition of the existing right lateral incisor. Is it desirable to retain the lateral and finish with an asymmetrical situation? Or is it better to remove the contralateral lateral incisor and close the space in order to maintain symmetry? In this particular situation, one must consider the anterior occlusion, the esthetics, the final functional occlusion, and the difficulties that such mechanics might present given that there is little overjet.31 The decision to place osseointegrated implants upon termination of growth was made for this patient. Case 6: Ankylosis (Fig. 6-6 and Table 6-8)

21. How does one treat an ankylosed tooth? The diagnosis of an ankylosed tooth requires a combination of findings. Often the main finding on clinical examination is a tooth below the plane of occlusion of adjacent teeth (infraocclusion) in a patient with a previously level occlusion. The cessation of eruption is known as ankylosis and occurs

when the cementum or dentin of the tooth fuses with alveolar bone. Percussion of the involved tooth may produce a sharp, solid sound, but only when more than 20% of the root is fused to bone.32 The involved tooth may also radiographically show a loss of periodontal ligament (PDL) space in areas where the tooth is fused to alveolar bone. If a determination cannot be made at the examination, an attempt to move the tooth with orthodontic traction will give a definitive answer. When a tooth is determined to be ankylosed, there are three options for treatment, depending on the level of ankylosis and the tooth involved: (1) surgical removal of the tooth, (2) distraction osteogenesis of the tooth-bone segment, or (3) corticotomy of the surrounding bone and luxation of the tooth. Each option has its benefits and drawbacks, and each treatment for an ankylosed tooth should be determined on a case-by-case basis. Mandibular primary first molars are the most common ankylosed teeth, and treatment often involves their surgical removal to allow for eruption of the second premolars or to allow space closure or tooth replacement in cases of congenitally missing lower second premolars. Ankylosed permanent teeth, especially those that were affected by trauma, are likely to require distraction osteogenesis or surgical corticotomy and luxation, with or without the addition of temporary anchorage devices to aid in eruption of the tooth.33,34


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J FIG 6-6 Case 6: Ankylosis. A-H, Composite initial photographs. Facial (A-C) and intraoral (D-H). I, Initial panoramic radiograph. J, Initial cephalometric tracing. (Continued)

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TABLE 6-8 Diagnostic Summary (3D-3 T): Case 6—Ankylosed Tooth (27 yr:10 mo) Skeletal Soft tissue Dental


ANTEROPOSTERIOR

TRANSVERSE

VERTICAL

SNA = 77° SNB = 77° ANB = −1° Profile = straight NLA = normal E-line = 0 mm Molar: Class I OJ = 3 mm 1 to NA = 7 mm 1' to NB = 3 mm 1 to SN = 105° 1' to GoGn = 86° Mand Arch Form = Ovoid DI = 11 Perio/OH = Good oral hygiene

6' to 6' Width = 34 mm 6' to 6' Width = 44.9 mm

SN-MP = 32° FMA = 27°

Buccal corridors = WNL

Lips competent Mesofacial

UDML = coincident LDML = coincident U-ALD = 1 mm L-ALD = 4.5 mm 3' to 3' Width = 25.5 mm

OB = 4 mm


TREATMENT PLAN

1. Improve dental and facial esthetics 2. Establish ideal OB/OJ with coincident midlines 3. Correct crowding, rotations, and crossbite 4. Establish Class I molar and cuspid with cuspid guidance 5. Maintain oral hygiene 6. Retain

1. Band and bond all teeth 2. Determine status of UL1 3. If ankylosed, decorticate or osteotomy 4. Level and align 5. ARS as needed 6. Detail occlusion 7. Retain: Mx 2-2, wrap Mn 3-3

3D, Three-dimensional; 3 T, three tissues; ARS, air rotor stripping; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort Mandibular; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; SN, sella-nasion; U-ALD, upper arch length discrepancy; UDML, upper dental midline; UL, upper left central incisor.

Case 7: Transposition (Fig. 6-7 and Table 6-9)

22. Should a transposition be corrected? Tooth transposition is a unique form of ectopic eruption that requires an intensive exploration of treatment options prior to treatment. Tooth transposition is a relatively rare dental anomaly term applied to extreme cases of ectopic eruptions. All transpositions are a form of ectopic eruptions, but not all ectopic eruptions qualify as transpositions. Transposition can be defined as the “positional interchange of two adjacent teeth, especially their roots, or the development or eruption of a tooth in a position occupied normally by a nonadjacent tooth.”35 Transposition is often accompanied by other dental anomalies. The most frequently reported of these include missing, small or peg-shaped laterals, congenitally missing teeth (excluding third molars), severe rotations or malpositions of adjacent teeth, retention of deciduous teeth, dilacerations of roots, or malformation of teeth. Although many originally thought that canine transposition was caused by over-retention of a deciduous canine, it is now known that canine–first premolar transpositions have an underlying genetic basis.35 Treatment options include alignment of teeth in their transposed positions, extraction of one or both transposed teeth, or orthodontic movement to their proper positions in the arch. If probable transposition is detected early enough, interceptive orthodontics may be used with little disturbance to the supporting structures. Longer treatment time and possible gingival recession are drawbacks to correcting transpositions.36 In cases of

complete transposition, where the roots are parallel, an attempt to move the teeth to their correct position in the arch may be detrimental to the teeth or supporting structures.37 In those cases it may be beneficial to the patient for the orthodontist to consider aligning the teeth in their transposed positions and reshaping their occlusal surfaces to enhance the esthetic outcome.38 In planning the treatment of transposition cases, it is important to consider initial root positions and inclinations and sufficiency of bone in which to move the transposed teeth. Tooth movement should be monitored closely while treatment is rendered. Tooth transpositions can be a challenge to the practitioner. Understanding how teeth can be transposed and the etiology behind the transposition can help the practitioner make an informed decision on treatment options. Transpositions must be carefully evaluated prior to beginning treatment so that the method of treatment will provide the most beneficial outcome to the patient. Case 8: Root Resorption (Fig. 6-8)

23. Which measures should be taken in the orthodontic management of teeth presenting with root resorption or dilacerations? Resorption of a tooth is the dissolution of the root by osteoclasts in response to caries, trauma, crowding, orthodontic tooth movement, or physiological movement in the transition

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TABLE 6-9 Diagnostic Summary (3D-3 T): Case 7—Transposed Teeth (13 yr:10 mo) Skeletal Soft tissue Dental


ANTEROPOSTERIOR

TRANSVERSE

VERTICAL

SNA = 77° SNB = 76° ANB = 0° Profile = slightly concave NLA = normal E-line = −3 mm Molar: Class I OJ = 3 mm 1 to NA = 4 mm 1' to NB = 3 mm 1 to SN = 97° 1' to GoGn = 93° Mand Arch Form = Ovoid DI = 17 Perio/OH = Good oral hygiene


SN-MP = 38° FMA = 28°

Buccal corridors = normal

Lips competent Mesofacial

UDML = 1.5 mm to R LDML = coincident U-ALD = 2.5 mm L-ALD = 4 mm 3' to 3' Width = 25 mm

OB = 3.5 mm


TREATMENT PLAN

1. Improve dental and facial esthetics 2. Establish ideal OB/OJ with coincident midlines 3. Correct transposition, rotations, and crowding

1. Place RPE arch, expand 1× day for 30 days; bond L7-7 2. Band and bond U7-7 3. Replace RPE with TPA soldered with retraction hook to retract UR4 palatally; protract UR3 4. Level and align 5. Detail occlusion 6. Retain: Mx wrap Mn 3-3 7. Evaluate for perio graft UR3

4. Obtain Class I molar and cuspid, with cuspid guidance 5. Maintain oral hygiene 6. Establish Class I mutually protected occlusion

3D, Three-dimensional; 3 T, three tissues; DI, discrepancy index; E-line, esthetic-line; FMA, Frankfort mandibular angle; GoGn, gonion to gnathion; L-ALD, lower arch length discrepancy; LDML, lower dental midline; NLA, nasolabial angle; OB, overbite; OH, oral hygiene; OJ, overjet; RPE, rapid palatal expander; SN, sellanasion; TPA, transpalatal arch; U-ALD, upper arch length discrepancy; UDML, upper dental midline; UR, upper right.

FIG 6-8 Case 8: Root resorption. Root resorption prior to orthodontic treatment on initial panoramic radiograph.

from primary to permanent dentition.39–41 It results in blunting of the root apex and internal loss of dentin from the pulpal part of the root, and it may lead to loss of the affected tooth depending on the severity of the process. If root resorption of a permanent tooth is radiographically detected, the area should be observed for clinical symptoms and the crown-root ratio should be closely monitored. However, root resorption resulting from orthodontic treatment has been found to be more common and more severe in initially resorbed teeth,

but even in these cases it is usually without significant clinical consequences for the patient (see Fig. 6-8). Dilaceration is the severe distortion of the root of a tooth, whereas a sharp curve or twist is termed flexion. The orthodontist should ascertain that dilacerated roots are not causing resorption to adjacent teeth. In the course of orthodontic alignment of the dilacerated roots within the arch, alteration of the crown shape of the corresponding tooth may be necessary to achieve an aesthetically pleasing result.


24. Why are treatment objectives important in treatment planning? “If you aim at nothing, you will hit it every time.” ~ Zig Ziglar

Orthodontic treatment objectives are essential to successful treatment outcomes. Treatment objectives should specify the growth and facial changes planned, as well as the desired positions of the teeth in all three planes of space. Successful orthodontic treatment requires a thorough knowledge of the problems, an understanding of growth and development, and an understanding of the ideal or desired outcome. Specific treatment objectives are derived directly from a complete understanding of the desired outcome. This concept is often referred to as beginning with the end in mind. You may understand the diagnostic problems, but if you fail to set specific treatment objectives you will usually fail to achieve the best result. Without specific treatment objectives, any treatment plan will be essentially aimless, and the outcome equally random.

25. How do you establish specific treatment objectives? Treatment objectives are frequently listed in terms similar to those below: • Ideal facial profile, or improve facial esthetics • Class I molar and canine • Ideal overbite and overjet • Coincident dental midlines • Correct crowding • Ideal occlusion with proper canine guidance and no posterior interferences • Maintain healthy TMJs • Maintain healthy periodontal tissues These objectives are general in nature and are often referred to as “rubber stamp” objectives because they are applicable to virtually every orthodontic patient, but they provide few details specific enough to create a proper treatment plan. Imagine if you were asked for directions to the museum and your response was, “drive the speed limit, stay between the white lines, use your turn signal to change lanes, and stop at the red lights.” All of these are reasonable but reveal little about how to get to the destination. These general objectives don’t require a specialty education in orthodontics to comprehend. They are understood by most graduating dental students. Specific treatment objectives, however, require specialty knowledge and provide the information necessary to design a treatment plan that will give you the best chance of achieving the desired outcome. Specific objectives can be established by starting from the desired outcome and asking a series of questions to achieve the desired outcome (AP, vertical, and transverse): 1. What facial changes are necessary? 2. What must happen to the maxilla? a. Do you need to restrict the maxilla to aid correction of a Class II or protract in the case of a Class III? b. Do you need to control or inhibit vertical maxillary growth? c. Does the maxilla need to be expanded?

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3. What must happen to the mandible? a. Do you expect normal growth? What direction of growth is expected? Will the direction of growth change with treatment? b. Do you need to restrict the vertical growth? 4. What changes are needed for incisor position? a. Do they need to be retracted or advanced? If so, how far? Or do they need to stay close to the pretreatment position? b. What angulation (torque) change is required, and how much? c. Where do the incisors need to be placed vertically, and what movement is needed? 5. What changes are needed in molar position? a. What do you expect from normal growth? b. What direction and amount of change are needed? Table 6-10 is a form designed to aid in the creation of more specific treatment objectives. The format is the same as that required by the ABO. The ABO requires skeletal and dental objectives to be described in the three planes, AP, vertical, and transverse. Each section of Table 6-10 offers choices that might be applicable. These choices are intended to be guides and are not the only possible options for each objective category. Additionally, more than one option may be needed in a specific category. Aimlessly determining a treatment plan without setting specific treatment objectives is a prescription for failure. The key in setting specific treatment objectives is to know the desired outcome and to decide the skeletal and dental changes necessary to achieve that outcome. Both of these must be supported by the available evidence; otherwise the aim is blind.

26. Why are superimpositions necessary? Monitoring treatment progress and outcomes is critical to patient care. Monitoring orthodontic treatment outcomes is just as important as setting specific treatment objectives. Otherwise, what’s the point in setting objectives? The purpose of superimpositions is to aid the orthodontist in determining the skeletal and dental changes that occurred over time. The ABO requires superimpositions to evaluate changes that resulted from treatment and growth. Subtracting the changes expected from normal growth and development from the actual changes allows the orthodontist to determine the treatment effect and to determine whether the specific treatment objectives were met.

27. What superimpositions are required and what is the best method to use? Three superimpositions are required by the ABO: cranial base, maxilla, and mandible. The Structural Method42,43 of superimpositions required by the ABO is based on the use of stable structures described in Melsen’s research of cranial base growth44 as well as Björk and Skieller’s42,45 implant research, which has been subsequently verified.46–48 This method has been shown to be the most reliable except in situations of aberrant growth defects. The standards required for tracings and superimpositions are published on the ABO website (www.americanboardortho.com/professionals/clinicalexam).

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TABLE 6-10 Skeletal, Dental, and Facial Treatment Objectives TREATMENT OBJECTIVES VERTICAL

TRANSVERSE

Max

No change, no growth expected Minimal growth expected Normal growth expected Hold, Restrict Advance _____mm Retract _____mm

No change Expand (______mm) Constrict (_______mm)

Mand

No change, no growth expected Minimal growth expected Normal growth expected (mostly horizontal) Normal growth expected (equal horizontal and vertical) Normal growth expected (mostly vertical) Adv Pg—autorotation by controlling vertical Advance Pg _____mm Set back Pg _____mm

No change, no growth expected Minimal growth expected Normal growth expected Hold Intrude (Post _____mm/Ant _____mm) Downgraft (Post _____mm/Ant _____mm) Correct vertical asymmetry: ________________ No change, no vertical growth expected Minimal vertical growth expected Normal vertical growth expected Excess vertical growth expected Plan to rotate clockwise—increase LFH Plan to rotate counterclockwise—decrease LFH Correct vertical asymmetry ________________

No change expected or planned Expect normal development Hold 6’s—Maximum Hold 6’s—Moderate Intrude 6’s _____mm Extrude 6’s _____mm -----------------No incisor change expected or planned Hold incisors Intrude incisors _____mm Extrude incisors _____mm

No change planned Expand molars ______mm Expand premolars ______mm ----------------Expand canines _______mm Constrict canines ______mm ARCH FORM: Maintain Alter to:____________________

No change expected or planned Expect norm development Hold 6’s—Maximum Hold 6’s—Moderate Intrude 6’s _____mm Extrude 6’s _____mm ----------------No incisor change expected or planned Hold incisors Intrude incisors _____mm Extrude incisors _____mm

No change planned Expand molars ______mm Expand premolars ______mm ---------------Expand canines _______mm Constrict; ______mm ARCH FORM: Maintain Alter to:____________________

Skeletal

Dental

Max Dent

Mand Dent

No change expected or planned Expect normal growth, no anchorage planned Hold 6’s—Maximum Hold 6’s—Moderate (allow mesial 2 to 3 mm) Advance 6’s: UR6 _____mm, UL6 _____mm Tip back/Dist 6’s: UR6 ___mm, UL6____mm ----------------No incisor change expected Hold incisors Advance/flare incisors ____mm _____degrees Retract/ upright incisors ____mm _____degrees Maintain incisor angulation Angulation change, (circle) + or − ,____degrees No change expected or planned Expect normal growth, no anchorage planned Hold 6’s—Maximum Hold 6’s—Moderate (allow mesial 2 to 3 mm) Advance 6’s: UR6 _____mm, UL6 _____mm Tip back/Dist 6’s: UR6 ___mm, UL6____mm ---------------No incisor change expected Hold incisors Advance/flare incisors ____mm _____degrees Retract/upright incisors ____mm _____degrees Maintain incisor angulation Angulation change, (circle) + or − ,____degrees

No change Expand (______mm) Constrict (_______mm)


ANTEROPOSTERIOR

ARCH

TABLE 6-10 Skeletal, Dental, and Facial Treatment Objectives—cont'd TREATMENT OBJECTIVES ARCH Face

ANTEROPOSTERIOR

VERTICAL

TRANSVERSE

No change planned or required Reduce facial convexity Increase facial convexity Hold lips but retract relative to nose/chin, E-line Retract U lip _____mm (estimate actual change) Retract L lip _____mm (estimate actual change) Advance U&L lips relative to E-line Advance U lip _____mm (estimate actual change) Advance L lip _____mm (estimate actual change) Increase chin projection (w/ growth, w/ surgery)

Expect norm increase in facial height No change expected Decrease LFH Reduce lip incompetence Increase LFH Minimize increase in LFH with mechanics Expect significant increase in LFH with growth Incisal display (increase, decrease) Alter smile arc (maintain, increase or decrease) Reduce gingival display

Maintain alar base width Smile esthetics (be specific) _____ ___________________________ __________________________

APPLIANCE/MECHANICS ANTEROPOSTERIOR

VERTICAL

TRANSVERSE

SPACE

Anchorage/Appliance

Maxilla

Open Space

VHA Lip bumper Miniscrews Miniplates

RPE (Hyrax) RPE (RPFM hooks) RPE (Haas type) RPE (McNam type) W-Arch Quad helix Expanded archwire

Open coil (SS) springs _____________________ Open coil (Niti) springs _____________________ TMA sectional opening loop _____________________

Class II

Class II

Surgery

Close Space

Herbst CPHG Combi HG Class II elastics Forsus springs “Distalizing” -Niti spring Other________

HPHG Combi HG Bite block Miniscrews or plates

Surgery assisted RPE Segmental Mx. 2 piece Segmental Mx. 3 piece Segmental Mx. 4 piece

Sliding-retract coils Sliding-power chain Closing arch TMA sectional retractable loop ____________________

Class III

Class III

Mandible

Maintain Space

Class III elastics RPFM Skeletal plates

Chin cup Miniscrews Miniplates Incisors: COS-U/RCOS-L Aux intrusion arch/utility arch J-Hook HG Vertical elastics

Lingual arch Lip bumper Expanded archwire

LLA Nance Bonded ret

Surgery

Surgery

Surgery mandible Advanced Surgical setback Genioplasty

Mx, impact (AP) Mx, impact post only Mx, down Autorotate mandible

Distraction osteogenesis

COS-U, curve of spee upper; CPHG, cervical pull headgear; E-line, esthetic-line; HG, headgear; LFH, lower facial height; LLA, lower lingual arch; Pg, pogion; RCOS-L, reverse curve of spee lower; RPE, rapid palatal expander; RPFM, rapid palatal expander with facemask hooks; TMA, beta titanium arch wire; TPA, transpalatal arch; VHA, vertical holding arch.

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Surgery

Mx. thumb crib Mx. tongue crib Mn. tongue crib Brackets ling 2×2


Anchorage/Appliance Nance TPA LLA/Lip bumper Tweed tip-back Palatal implant Miniscrews Miniplates

HABIT

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28. How do you properly superimpose on the cranial base?

No growth after 7 years of age.

Cranial base superimpositions allow the orthodontist to assess the overall or total changes. The overall changes include the tooth movements that occur within the maxilla and mandible, as well as the displacements of the teeth due to jaw growth or treatment. Accurate superimpositions require the use of structures that do not change or grow over time. Most cranial and cranial base structures grow or remodel; therefore, they cannot be used for superimposition. The posterior cranial base should not be used for superimposing because of growth that occurs throughout childhood and adolescence at the spheno-occipital synchondrosis and remodeling that occurs on the surfaces of the occipital and posterior sphenoid bones, including the posterior wall of sella. The anterior and middle cranial base includes structures that have been shown to exhibit little or no growth after 7 to 8 years of age, which is when the spheno-ethmoidal synchondrosis ceases its growth. After that time a number of structures, especially those associated with neural tissues, remain stable and are reliable for superimposition (Fig. 6-9). Two of the most important structures for cranial base superimposition are the anterior wall of sella turcica below the anterior clinoid processes, which is stable after age 5 to 6, and the cribriform plate, which is stable after approximately 4 to 5 years of age. The planum or jugum sphenoidale shows minimal growth after age 6, but bony apposition can occur in some cases up to 14 years of age. It has also been shown that the ethmoidal crests, which grow only minimally after age 6, are reliable for superimposing, as are the cerebral surfaces of the frontal bone associated with the orbits and the greater wings of the sphenoid, both of which are relatively stable after age 7 (Fig. 6-10). All of these structures can be reliably identified on most lateral cephalograms. It is important to know which structures

Minimal growth after 6 years of age. None after 14 years of age. Ethmoidal crest

Cribriform plate Cerebral surface of the orbital part of the frontal bone

Planum sphenoidal (jugum) Chiasmatic sulcus

Anterior wall of sella

FIG 6-10 Regions of cranial base stability for superimposition.

cross the midline and which ones are bilateral. Start by tracing the radiopaque surface that represents the anterior portion of sella (Fig. 6-11). Using as small a line as possible, carefully trace either the superior or inferior edge of the opaque structure and stay consistent. More inaccuracies occur when tracing the center of the opaque structure. Trace along the anterior wall of sella superiorly until the anterior wall intersects with the anterior clinoid processes. This point, referred to as the Walker point, is stable after 5 to 6 years of age and serves as an important stable landmark for superimposition. As you continue anteriorly along the sphenoid bone, you should note the planum sphendale, which is relatively flat and extends to the greater wings of the sphenoid. The greater wings demarcate the separation of the sphenoid and ethmoid bones. Continuing beyond the planum and past the greater wings of the sphenoid, you should see two radiopaque lines that diverge. One usually diverges superiorly and the other inferiorly. The lower line, which is sometimes continuous with the planum, is difficult to see because it demarcates the cribriform

Jugum sphenoidale: Appositional growth at 4-5 years, plus prepubertal and beyond Anterior sella tercica: Stable after 5-6 years of age

Cribriform plate of ethmoid: Stable after 4-5 years of age

Posterior sella turcica: Resorptive until the teens

Apposition

Greater wing of the sphenoid

Sphenoethmoidal synchondrosis: Stable after 7 years of age

Resorption Resting Spheno-occipital synchondrosis: Initial osseous correction at 12-13 years in girls and 14-15 years in boys Anterior margin of the foramen magnum: Appositional until 16 years of age

FIG 6-9 Cranial base structures and age of growth cessation and stability.


93

FIG 6-11 Cranial base anatomy for superimposition, skull and ceph view.

Primary Secondary

plate. If the cribriform plate is not clearly seen, then the ethmoidal crests should be used. If these structures are not clearly visible, then the planum sphenoidale and cerebral surfaces of the frontal bone should be used. Additionally, the occiput can be used to aid in proper orientation. While the occiput is not a stable structure during growth, it can be used as a rotational reference. You should not consider it as a stable structure for superimposition. But if the final tracing outline is inside the initial tracing outline of the occiput, then you will know the tracings are not correctly oriented. The accurate use of primary and secondary cranial base structures makes it possible to reliably represent the overall changes that take place during treatment or during growth.

29. How do you properly superimpose on the maxilla? FIG 6-12 Primary and secondary structures used for accurate cranial base superimposition.

plate where the olfactory bulbs lie. The more obvious superior line represents the ethmoidal crests. These crests should always be visible. The most superior radiopaque lines visible above the ethmoid bone are the cerebral surfaces of the orbital parts of the frontal bone. They typically appear somewhat disorganized due to their bilateral nature and uneven surface. Certain structures are more important to ensure an accurate sagittal orientation, while others are more important for vertically orienting your cranial base superimposition (Fig. 6-12). The primary structures for sagittal (AP) orientation are, first, the contour of the anterior wall of sella turcica and, second, the greater wings of the sphenoid. The primary structures for vertical orientation are the intersection of the anterior wall of sella and the anterior clinoid process and the cribriform

Determining the AP and vertical changes of the maxillary dentition requires a reliable method of superimposition. Using small implants for superimposition, Björk and Skieller45 showed that the most stable surface of the midface during growth is the zygomatic process. This method has been verified by others.47,48 The most stable aspect of the process is located just above and anterior to key ridge. The lower aspect of the key ridge is not reliable because it models downward and backward with growth. You also cannot rely on the region just below the orbital rim where the zygomatic process and orbital floor meet. The orbital rim and the orbital floor model upward during growth. Consequently, it is the region between the orbital rim and key ridge that should be used for structural superimposition (Fig. 6-13). The second set of structures that help when superimposing the maxilla are the maxillo-zygomatico-temporal sulci. The sulci are the two vertical, or almost vertical, lines located

94


FIG 6-13 Maxillary anatomy required for accurate superimposition.

behind the lateral contour of the orbits that extend below the orbits. Actually, they start just below the cribriform plate on the lateral cephalograms and extend down to the nasal floor, usually to the level of the maxillary molars. Over longer periods of time, the sulci model in a posterior direction and thus are not absolutely stable, but during the normal orthodontic treatment intervals little change occurs. Vertically, focus on the orbital floor and the nasal floor. Orbitale, which is approximately where the lateral contours of the orbits and the orbital floor meet, normally models upward with growth. In contrast, the nasal floor models downward. The result of growth at these structures is an increase in the distance between the orbital and nasal floor. Superimposing on the palatal plane ignores these changes, producing an inaccurate interpretation of the dental changes. The structures that need to be used for proper maxillary superimpositions are the right and left zygomatic processes, the right and left maxilla zygomatico-temporal sulci, orbital floors, and the nasal floor. These structures can all be identified on lateral cephalograms; however, the anterior part of the zygomatic process can be difficult to see on some cephalograms. You should start by tracing the zygomatic process and the zygomatico-temporal sulci. Then trace the superior aspect of the orbital floor and identify orbitale. Remember, these structures are bilateral, so you will have to identify both sides and trace the midline between them. Then trace the nasal floor. Be sure to use small lines, whether hand tracing or using computer software (see Fig. 6-13 and Fig. 6-14). Once you have completed the tracings, you can superimpose them based on the primary and secondary reference structures. The primary structure used to vertically superimpose tracings is the anterior surface or the zygomatic process. If there is any doubt about your tracing or if the process cannot be easily identified, then superimpose on the zygomatico-temporal sulcus. The primary vertical structures are the orbital floor, where bony apposition occurs during growth, and the nasal floor,

FIG 6-14 Primary and secondary structures used for accurate maxillary superimposition.

which resorbs. In order to determine the correct vertical position of the tracing for superimposition, you should slide along the anterior surface of the zygomatic process so that the orbital floor shows apposition of bone and the nasal floor shows resorption of bone. There should be slightly greater apposition of the orbital floor than resorption of the nasal floor. Remember, the distance between the orbital and nasal floors increases during growth. Approximately three-fifths of the increase is due the apposition at orbitale and two-fifths is due to resorption of the nasal floor (Fig. 6-15).


Slide along the anterior surface of the zygomatic process so that the floor of the orbit shows upward growth (apposition) while the floor of the nose shows downward resorption. (The ratio is 3/5 apposition at the floor of the orbit and 2/5 resorption at the floor of the nose.)

95

3/5

2/5

FIG 6-15 Maxillary superimposition requirement.

In summary, first focus on the anterior surface of the zygomatic process as you begin the superimposition. Then slide along the anterior zygomatic process until three-fifths of the increase in the distance between the nasal and orbital floors is due to apposition on the orbital floor. Always verify to be sure that approximately two-fifths of the increase was due to resorption of the nasal floor. The resulting superimposition will reliably demonstrate the AP and vertical dental changes that occurred over time.

FIG 6-16 Areas of mandibular growth and remodeling.

30. How do you properly superimpose on the mandible? The Structural Method42,43 of superimposing the mandible has been shown to be the most reliable.46,48 Due to modeling and remodeling with growth, the mandibular surfaces, mandibular growth, and treatment effects cannot be evaluated by superimposing on the mandibular outline. This is why superimpositions on the lower border are not reliable. Bone is either being added or it is being removed. Except for the periosteal contour of the chin just below pogonion, the entire mandibular outline changes over time (Fig. 6-16). An accurate mandibular superimposition demonstrates the dental changes that resulted from treatment and vertical alveolar growth. In order to accurately superimpose the mandible, you need to be able to rely on structures that do not change over time. There are both primary and secondary stable structures that can be reliably superimposed. The primary structures are the most important, and should be used whenever they can be visualized. Secondary structures are used to support the primary structures, or when the primary structures cannot be clearly seen. Perhaps the most reliable primary structure is the anterior contour of the chin just below pogonion. The inner contour of the cortical plate at the lower border of the symphysis located at the most inferior aspect of the trabecular bone is another primary structure within the symphysis that is stable (Fig. 6-17). Secondarily, the trabecular bone itself can aid superimposition (Fig. 6-18). Posteriorly, the mandible is superimposed on the contours of the alveolar canal, which are stable throughout growth. Remember, as many as four contours, representing the right and left canals, may be visible; try to use the two most anterior or posterior contours. Before root development begins,

Primary Secondary Contours of alveolar canal rd

Anterior-inferior contours of chin just below pogonion

Lower contour of 3 molar bud before root development begins Inner contour of cortical plate at lower border of symphysis

FIG 6-17 Mandibular anatomy required for accurate superimposition.

Primary Secondary

FIG 6-18 Primary and secondary structures used for accurate mandibular superimposition.

96


the lower contour of a mineralized tooth germ can be used for superimposition; however, this is not usable for most patients after treatment of the full permanent dentition. To determine the mandibular superimposition, the tracings are first oriented horizontally on the anterior contour of the chin. Then they are oriented vertically on the inner contour of the cortical plate. Remember, it is the lowest aspect of the contour that should be used. Also, any distinct trabecular structure in the symphysis can be used for superimposition. Posteriorly, the tracings should be superimposed on the mandibular canal. The third molar germ can be used if there is no root development. To verify that the mandibular superimposition is correct, always check the anterior border of the ramus. It usually moves posterior with growth, indicating resorption of bone; it should never move anteriorly with growth. Also, mandibular growth is often rotational with resorption at the inferior border, so the mandibular plane should not be perfectly aligned on the inferior border. If it is, this indicates that the tracings are not properly oriented. The most likely error is selecting different outlines of the inferior alveolar canals on the different tracings. SUMMARY Measuring treatment outcomes is critical to patient care. Poor superimpositions result in a misunderstanding of the treatment effects on the face and the dentition. Accurate superimpositions using the structural method allow orthodontists to effectively evaluate treatment progress and outcomes, and improve the quality of patient care. REFERENCES 1. Hunt Institute for Botanical Documentation, A Research Division of Carnegie Mellon University: Order from chaos: linnaeus disposes (website). Available at http://huntbot.andrew .cmu.edu/HIBD/Exhibitions/OrderFromChaos/pages/intro .shtml. Accessed February 26, 2014. 2. Angle EH: The treatment of malocclusion of the teeth. Angle’s system, ed 6, Philadelphia, 1907, The SS White Dental Manufacturing Company. 3. Magie WF, Carnot S, Clausius R, et al: The second law of thermodynamics; memoirs by Carnot, Clausius, and Thomson, New York, 1899, Harper & Brothers. 4. Nanda R: Patterns of vertical growth in the face, Am J Orthod Dentofacial Orthop 93:103–116, 1988. 5. Pearson LE: Vertical control in fully banded orthodontic treatment, Angle Orthod 56:205–224, 1986. 6. Sankey WL, Buschang PH, English JD, et al: Early treatment of vertical skeletal dysplasia: the hyperdivergent phenotype, Am J Orthod Dentofacial Orthop 118(September):317–327, 2000. 7. Vaden J: Nonsurgical treatment of the patient with vertical discrepancy, Am J Orthod Dentofacial Orthop 113:567–582, 1988. 8. Rakosi T, Jonas I, Graber TM: Color atlas of dental medicine: orthodontic diagnosis, New York, 1993, Thieme Medical Publishers. 9. Proffit WR: Contemporary orthodontics, ed 3, St Louis, 2001, Mosby. 10. Graber TM, Vanarsdall RL, Vig K: Orthodontics: current principles and techniques, ed 4, St Louis, 2005, Elsevier.

11. Riolo ML, Avery JK: Essentials for orthodontic practice, ed 1, Ann Arbor and Grand Haven, MI, 2003, EFOP Press. 12. Nanda R, Ghosh J: Facial soft tissue harmony and growth in orthodontic treatment, Semin Orthod 1(2):67–81, 1995. 13. Arnett GW, Bergman RT: Facial keys to orthodontic diagnosis and treatment planning. Part I, Am J Orthod Dentofacial Orthop 103:299–312, 1993. 14. Reyneke JP: Essentials of orthognathic surgery, Carol Stream, IL, 2003, Quintessence Publishing. 15. Schiffman PH, Tuncay OC: Maxillary expansion: a meta analysis, Clin Orthod Res 4:86–96, 2001. 16. Horn A: Facial height index, Am J Orthod Dentofacial Orthop 102:180, 1992. 17. Cangialosi T, Riolo ML, Owens Jr SE, et al: The ABO discrepancy index: a measure of case complexity, Am J Orthod Dentofacial Orthop 125(3):270–278, 2004. 18. O’Reilly MT, Nanda SK, Close J: Cervical and oblique headgear: a comparison of treatment effects, Am J Orthod Dentofacial Orthop 103(June):504–509, 1993. 19. Chua A, Lim J, Lubit E: The effects of extraction versus nonextraction orthodontic treatment on the growth of the lower anterior face height, Am J Orthod Dentofacial Orthop 104:361–368, 1993. 20. Bowman J, Johnston Jr LE: The esthetic impact of extraction and nonextraction treatments on Caucasian patients, Angle Orthod 70(February):3–10, 2000. 21. Johnson D, Smith R: Smile esthetics after orthodontic treatment with and without extraction of four first premolars, Am J Orthod Dentofacial Orthop 108:162–167, 1995. 22. Sheridan JJ: Air-rotor stripping, J Clin Orthod 19:43–59, 1985. 23. Sheridan JJ: Air-rotor stripping update, J Clin Orthod 21: 781–788, 1987. 24. Haas AJ: The treatment of maxillary deficiency by opening the mid-palatal suture, Angle Orthod 35:200–217, 1965. 25. Haas AJ: Palatal expansion: just the beginning of dentofacial orthopedics, Angle Orthod 57:213–255, 1970. 26. Haas AJ: Long-term post-treatment evaluation of rapid palatal expansion, Angle Orthod 50:189–217, 1980. 27. Wertz RA: Skeletal and dental changes accompanying rapid mid-palatal suture opening, Am J Orthod 58:41–66, 1970. 28. McNamara Jr JA: Early intervention in the transverse dimension: is it worth the effort? Am J Orthod Dentofacial Orthop 121: 572–574, 2002. 29. Bishara S: Impacted maxillary canines: a review, Am J Orthod Dentofacial Orthop 101:159–171, 1992. 30. Kokich VG: Surgical and orthodontic management of impacted maxillary canines, Am J Orthod Dentofacial Orthop 126(Sept):378–383, 2004. 31. Spear FM, Mathews DM, Kokich VG: Interdisciplinary management of single-tooth implants, Semin Orthod 3:45–72, 1997. 32. Damm N, Bouquot A, editors: Abnormalities of teeth. In Oral and maxillofacial pathology, 2 ed., Philadelphia, 2002, WB Saunders. 33. Steiner DR: Timing of extraction of ankylosed teeth to maximize ridge development, J Endod 23:242–245, 1997. 34. Kofod T, Würtz V, Melsen B: Treatment of an ankylosed central incisor by single tooth dento-osseous osteotomy and a simple distraction device, Am J Orthod Dentofacial Orthop 127(1): 72–80, 2005. 35. Peck S, Peck L: Classification of maxillary tooth transpositions, Am J Orthod Dentofacial Orthop 107:505–517, 1995. 36. Kavadia S: A clinical study of maxillary canine transposition and their orthodontic management, Euro J Orthod 25(5):531, 2003. 37. Shapira Y, Kuftinec M: Orthodontic management of mandibular canine – incisor transposition, Am J Orthod Dentofacial Orthop 83(4):271–276, 1983. 38. Shapira Y, Kuftinec M: Intrabony migration of impacted teeth, Angle Orthod 73(6):738–744, 2003.


39. Sameshima GT, Sinclair PM: Predicting and preventing root resorption: parts I and II, Am J Orthod Dentofacial Orthop 119:505–515, 2001. 40. Linge L, Linge BO: Patient characteristics and treatment variables associated with apical root resorption during orthodontic treatment, Am J Orthod Dentofacial Orthop 99:35–43, 1991. 41. Harris EF, Baker WC: Loss of root length and crestal bone height before and during treatment in adolescent and adult orthodontic patients, Am J Orthod Dentofacial Orthop 98:463–469, 1990. 42. Björk 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 5:1–46, 1983. 43. Duterloo HS, Planché P: Handbook of cephalometric superimposition, Hanover Park, IL, 2011, Quintessence Publishing.

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44. Melsen B: The cranial base: the postnatal development of the cranial base studied histologically on human autopsy material, Acta Odontol Scand Suppl 32(62):1–126, 1974. 45. Björk A, Skieller V: Growth of the maxilla in three dimensions as revealed radiographically by the implant method, Br J Orthod 4:53–64, 1977. 46. Buschang PH, LaPalme L, Tanguay R, et al: The technical reliability of superimposition on cranial base and mandibular structures, Eur J Orthod 8:152–156, 1986. 47. Doppel D, Damon W, Joondeph D, et al: An investigation of maxillary superimposition techniques using metallic implants, Am J Orthod Dentofacial Orthop 105:161–168, 1994. 48. Nielsen IL: Maxillary superimposition: a comparison of three methods for cephalometric evaluation of growth and treatment change, Am J Orthod Dentofacial Orthop 95:422–431, 1989.

C H A PT E R

7

Orthodontic Appliances

P. Emile Rossouw

T

he introduction of fixed appliances to the teeth with bands or brackets set a milestone in the discipline of orthodontics. Orthodontic treatment options increased significantly; moreover, three-dimensional (3D) control of tooth movement became a standard goal of orthodontic treatment. Contemporary fixed appliances now have incorporated first-, second-, and third-order prescriptions. Numerous attachments and/or auxiliary appliances can now be attached to the fixed appliance, hence the term fixed-removable for such appliances as the headgear, removable transpalatal arch, and removable lingual arch. Fixed appliances, which encompass the various designs of brackets (directly bonded to enamel or laser-welded to bands and cemented to teeth), tubes, buttons and others, with the activated archwires in place, move teeth into new positions. Orthodontics reached out to industries with requests for “space-age” and biocompatible materials to facilitate and enhance treatment options. It is thus not surprising that the discipline went from the large gold bands and wires of Dr. Angle to the small, esthetic appliances constructed from various materials, including stainless steel, titanium, and ceramic, as well as combinations of the noted materials. In addition, archwires that exhibit amazing memory and heat-activation characteristics have become the order of the day. The amazing bracket designs comparable to classic artwork and the highly developed archwires have changed orthodontic treatment from laborious and time consuming to a very refined, efficient, and reliable practice; this is truly a remarkable ingredient in providing quality of life to millions of patients. The development of the fixed appliance over the past 100 years incorporated sophistication second to none. The purpose of this chapter is to provide insight into these developments and stimulate further study by providing a brief overview of fixed orthodontic appliances.

1. What is a fixed orthodontic appliance? A fixed orthodontic appliance has the capability of being fixed to teeth. Its design dictates either direct fixation by bonding to the enamel surface with composite cement or cemented via a band around the crown of a tooth. The nature of the appliance prevents removal by the patient, except if it is a fixed-removable appliance, such as a headgear. The archwires are then fixed to the brackets or tubes by clips, steel ligatures, or elastomeric o-rings to form the total fixed appliance that, when activated, leads to tooth movement.1 98

2. What characteristics should fixed orthodontic brackets or appliances exhibit? Fixed orthodontic appliances or braces, commonly referred to as orthodontic brackets attached to teeth, should exhibit the following properties2–4: • They should be simple to place and activate; thus they should easily pull, push, and rotate teeth. • They should be fixed in a stable position to the teeth in order to accept the applied forces without failure but could be removed by choice without tissue damage. • Tooth movement must occur efficiently (refer to friction requirements) and the anchorage provided must negate Newton’s third law (for every action there is an equal and opposite reaction). • Braces should be large enough for effective application, but also delicate enough to avoid tissue trauma; however, they must not cause inflammation and soreness. • Braces must be small and inconspicuous and, thus, esthetically acceptable.

3. When and by whom was the edgewise appliance introduced to the discipline of orthodontics? The edgewise appliance was introduced by Dr. Edward Hartley Angle in 1928.2

4. Which appliance preceded the edgewise appliance? The Angle System (Fig. 7-1) by Dr. Edward H. Angle (1887) preceded the edgewise appliance. It consisted of adjustable clamp bands closely adapted to the teeth and held in place by friction. The clamp bands had soldered retraction screws to enable closure of space; moreover, prototype bands on incisors and cuspids had soldered tubes into which rotation springs were inserted. Jackscrews crossed the palate for arch expansion. The expansion arch (E arch) replaced jackscrews; the latter were soldered to the buccal aspects of molar bands. The E arch appliance was used to expand the arches.2

5. Why did Angle develop the pin and tube appliance? Angle realized that the axial inclinations of teeth needed to be corrected. He developed the pin and tube appliance to enable orthodontists to accomplish root movement (Fig. 7-2). The pins had to

Orthodontic Appliances • CHAPTER 7

99

A

FIG 7-1 The Angle System. (From Angle EH: Treatment of malocclusion of the teeth, Philadelphia, 1907, SS White Dental Manufacturing.)

B

FIG 7-3 A and B, Angle’s ribbon arch appliance. Note that the wire is inserted occlusally. (From Steiner CC: Is there one best orthodontic appliance? Angle Orthod 3[4]:277, 1933.)

FIG 7-2 Angle pin and tube appliance. Note that the wire is inserted occlusally. (From Steiner CC: Is there one best or thodontic appliance? Angle Orthod 3[4]:277, 1933.)

be expertly soldered to the archwire, fitted perfectly into the tubes on the bands, removed as the movement progressed, moved along the archwire, soldered again, and fitted once more into the tubes on the bands. This precise and delicate procedure had to be completed at each patient visit, often with activation every few days, which was a laborious and difficult task and not user friendly.2

6. Which appliance did Angle develop in 1915 to replace the cumbersome pin and tube appliance? The ribbon arch appliance (Fig. 7-3) was a much simpler appliance to construct and activate. The brackets, which were soldered to bands, consisted of a vertical slot (in contrast to contemporary edgewise brackets, which have horizontal slots). Brass pins, inserted from the occlusal aspect of the vertical tube, held the archwire in place. The teeth could now freely move along the archwire, similar to a string of beads.2

7. Which modern appliance is based on the ribbon arch appliance? The Begg appliance of Dr. Raymond Begg uses the vertical bracket slot principle; however, the bracket is upside down with the archwire

inserted from the gingival aspect and then held in place with a variety of pins. Each pin fulfills a different function (Fig. 7-4). The Begg light wire technique or appliance uses mostly round archwires with numerous auxiliary springs inserted into the vertical slots to achieve the required tooth movement. The treatment with this appliance consists of different stages: Stage 1 starts with the initial alignment and bite opening, Stage 2 is mostly space closure, and the final Stage 3 is where all the detail of the occlusion is consolidated.2,4,5

8. What is the Tip-Edge bracket? The Tip-Edge bracket or appliance developed by P.C. Kesling6 is basically a combination of the edgewise and Begg bracket. The bracket has been modified to include a specialized slot like an edgewise bracket that has two wedges removed from each side of the slot (Fig. 7-5, A) and to provide a bracket that permits free crown tipping (such as with the Begg bracket) followed by controlled root uprighting (i.e., the Begg bracket with auxiliary spring and edgewise). The initial Tip-Edge bracket had a vertical slot and rotation wings. The Tip-Edge Plus bracket was introduced in 2003 and incorporated the latter as well as a horizontal slot for enhanced tooth movement in the final stages of treatment (see Fig. 7-5, B).

9. How did the edgewise appliance evolve? En masse movement of teeth, particularly in an anteroposterior direction, was extremely difficult with the ribbon arch appliance. Dr. Angle changed the bracket format; he placed the slot in the center of the bracket and fitted the bracket slot in a

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CHAPTER 7 • Orthodontic Appliances box with three walls within the bracket. The new design provided a more efficient mechanism with which to torque teeth.2

11. Who started the first pure edgewise specialty practice? Dr. Charles H. Tweed, a student of Dr. Edward Angle, followed Dr. Angle’s advice that one could only master the edgewise appliance if the practitioner limited the practice solely to the use of this appliance. Tweed, who received the first specialty certificate in Arizona, devoted 42 years to the advancement of the edgewise appliance. The Tweed philosophy has undergone contemporary changes and is still taught at the Tweed Foundation for Orthodontic Research in Tucson, Arizona, where it has developed the reputation as one of the finest basic edgewise courses.2

12. How is the archwire in the edgewise appliance held in place?

FIG 7-4 The Begg appliance in Stage 3; this stage uses vari ous springs. The uprighting springs (as shown) allow for cor rect tooth inclination. Note that these are inserted in the vertical slot of the bracket and the archwire is inserted gingivally. (From Begg PR, Kesling PC: Begg orthodontic theory and technique, ed 2, Philadelphia, 1971, WB Saunders.)

horizontal plane to the band rather than vertically. One could say that the vertical bracket now had its edge in a sidewise position; accordingly, archwire insertion was with the edge on its side, hence the very appropriate term edgewise appliance.2

10. What made the new edgewise bracket different from the original pin and tube vertical bracket? The vertical bracket had two walls and a pin held the archwire in place. The new edgewise bracket, 0.022 × 0.028 inch in dimension with the slot opening horizontally, consisted of a rectangular

Various methods are used, ranging from the original brass wire ligature to delicate stainless steel wire ligatures; however, elastic o-rings are more often used today (Fig. 7-6, A and B). The elastic o-rings are available in various colors, which orthodontic patients often request to provide esthetic themes such as orange and black for Halloween (see Fig. 7-6, C). A significant milestone in contemporary orthodontics is the development of self-ligating brackets (see Fig. 7-6, D), which incorporate a spring or gate mechanism as an integral part of the bracket to secure the archwire in place.2,3

13. Do all self-ligating brackets function in the same manner during active treatment? No. Larger twin (Damonc; In-Ovationb and Timea) and smaller single brackets (SPEEDd) are available. Moreover, active clip (SPEEDd and In-Ovationb) and passive clip (Damonc) mechanisms exist.3,4 American Orthodontics, Sheboygan, Wisconsin; b GAC International, Bohemia, New York; c Ormco Corporation, Glendora, California; d SPEED™ Systems, Strite Industries Ltd, Ontario, Canada a

Remove wedges from two opposite ends of archwire slot

A

B

FIG 7-5 A, Removal of diagonally opposed corners of a conventional edgewise bracket archwire slot to create the basic Tip-Edge bracket. B, The addition of a horizontal tunnel intersects the vertical slot; therefore the bracket profile remains low. The tipping surfaces (T) limit the degree of initial crown tipping, and the uprighting surfaces (U) control final tip and torque angles for a specific tooth. The central ridges (CR) provide vertical control dur ing the noted tooth movements. (Reprinted from Kesling PC: Tip-Edge plus guide, ed 6, La Porte, IN, 2006, TP Orthodontics, Inc. With permission from Dr. Peter C. Kesling.)


A

B

C

D

101

FIG 7-6 Various means of securing archwires into bracket slots. A, Pattern as re quested by a patient. B, Stainless steel ligatures on Siamese or twin brackets; note the tie-wings used as retention for the ligatures. C, Halloween time with power chain to close spaces. D, Self-ligating bracket.

14. What is the difference between full banded versus full direct bonded bracket systems?

tissues during functioning. Direct bonded attachments can be placed in lingual positions to fulfill the “invisible appliance” requirement or individual attachments on the lingual surfaces to facilitate correction of crossbites.4

The banded fixed appliance systems use bands cemented to all teeth with various attachments soldered or laser welded to the bands (Fig. 7-7, A). The fitting of this type of appliance is cumbersome because band space needs to be created in order to fit the bands around tight fitting teeth and even more so in the presence of a malocclusion. Separating elastics, ligatures, or clips are used for this space-gaining exercise. In contrast, the introduction of the acid etch technique revolutionized orthodontic treatment as numerous types of brackets were developed that could be attached directly to enamel by composite/resin or resin-reinforced glass-ionomer cements (see Fig. 7-7, B). Direct bonded appliances are the choice of the majority of clinicians today because they fulfill all the basic requirements of fixed appliance treatment (i.e., an esthetic and stable attachment), which can be efficiently placed with no trauma to the

15. What is meant by the bracket prescription or preadjusted appliance? Tooth movement normally occurs in three dimensions. The dimensions were originally incorporated in the edgewise mechanotherapy by specific adjustments to the archwires, because the first generation of brackets was known as standard edgewise brackets with no prescription. The archwire adjustments are called first-, second-, and third-order bends. First-order bends are the so-called in-out bends, which are represented by the distance of the bracket slot to the tooth surface and is a horizontal adjustment. This accommodates for the differences in the buccal tooth anatomy. Second-order bends refer to the vertical adjustments, up and down or tip bends, to provide correct axial inclination and tooth-root alignment in a mesiodistal

B

A

FIG 7-7 A, Full bands versus part B, which shows direct bonding. B, SPEED bracket multi-piece construction.

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CHAPTER 7 • Orthodontic Appliances

imension. The mesial to distal tip of the bracket slot in respect d to the long axis of the tooth represents this adjustment of the bracket prescription. Third-order or torque adjustments refer to the bucco-palatal or bucco-lingual position of the roots in respect to the crowns of the teeth. All three orders are built into the bracket by the manufacturer and thus represent the prescription of contemporary brackets and in turn meet the requirements of the straight-wire or preadjusted appliance.2

terms are attached close to the middle or center on the buccal enamel surface of the teeth. A variety of tooth movements such as controlled and uncontrolled tipping, translation, root movement and rotation occur when the force or couple is applied at the bracket. To have a specific tooth movement (e.g., controlled tipping), an equivalent force system must be created at the center of resistance of the tooth. Thus, when a force of 100 gm is applied at the bracket of a tooth, which is approximately 10 mm coronal from the center of resistance, a tipping moment of the crown (moment of the force) occurs in the direction of the force (Fig. 7-8, A). The clinician can expect to have both a linear and rotational movement of the tooth in the direction of the applied force vector when an equivalent force system is created at the center of resistance. Thus, a controlled tipping moment of 1000 g-mm (100 gm × 10 mm: magnitude of the force multiplied by the distance from the bracket center to the center of resistance measured in gram millimeters) is the result of the tipping force. Utilizing the same principle, but now applying an equivalent force system with an opposite moment (controlled torque) results in the force vector being displaced to pass through the center of resistance. The resulting force system describes the expected tooth movement at the center of resistance. If this is an equivalent force system, the tooth will translate in the direction of the force vector through the center of resistance (see Fig. 7-8, B). Clinicians manipulate force systems to attain the required tooth movement.7

16. How does tooth movement occur with fixed appliances? Tooth movement occurs when a force is applied to the tooth through the bracket, usually an elastic band, coil spring, or specific types of loops or bends in the archwire. This initiates the resorption of bone on the pressure side and deposition of bone on the tension side of the tooth: the biologic process of tooth movement. A moment is created as a result of the distance of the force application to the center of resistance of the tooth. The center of resistance coincides with the centroid of the root, which in a single-rooted tooth is the geometric center of the root between the apex and alveolar crest. Depending on the significance of the moment, the tooth will translate, tip, or rotate. The latter movements are obviously influenced by the contact of the archwire and the bracket; thus, a full-thickness archwire allows a different type of movement when compared with a thinner dimension and likely more flexible archwire. In most instances several stages of tooth movement occur with fixed appliances. Examples of these stages include the initial level and alignment stage using smaller size wires, which could be a flexible nitinol or supercable of 0.016-inch size for a 0.018 × 0.25–inch bracket slot. The wire rigidity and size dimension increase as treatment progresses, and this allows dental arch form control.2,4

18. How is a direct bonded bracket constructed? Construction of brackets is a complex process, which is executed with infinite precision. Brackets are designed for each tooth individually because 3D prescriptions differ for the different teeth. Moreover, bracket base designs have to include adaptation for the various anatomical configurations of the tooth surfaces. The SPEED bracket is an example of a modern bracket constructed through a complex process; however, it is simple to use (Fig. 7-9). Self-ligation is a popular choice today

17. What is indicated by an equivalent force system in the appliance? In fixed orthodontic appliance therapy, forces or couples (moments, torque) are usually applied at the bracket. These orthodontic brackets (“handles to move teeth”) in general 100 g-mm

C

100 g-mm

100 g

C

100 g

10 mm

100 g

100 g

A

B

FIG 7-8 A, Controlled tipping moment in the direction of the force applied at the crown/ bracket. B, Translation/bodily movement occurs when an equivalent force system is cre ated with an opposite moment to that of the tipping moment in A; the force vector now passes through the center of resistance.


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Gingival SPEED Mushroom hookTM

Lingual

Opening instrument access slot

Micro-Retentive MeshTM bonding base

Archwire slot (.018 or .022")

In-out adapter

“Super-Elastic” spring clipTM

.016" Horizontal Auxiliary slot

Labial WindowTM

Occlusal

Labial (buccal)

FIG 7-9 The different parts of a modern fixed appliance bracket are seen on the SPEED bracket multi-piece con struction. (Courtesy of Strite Industries, Cambridge, Ontario, Canada.)

and the SPEEDd bracket will be described to show the various components of a contemporary self-ligating direct bonded bracket.3

19. What are the components of a direct bonded bracket? The bracket can be a one- or multi-piece bracket. A one-piece bracket is rigid and manufactured usually by injection molding. A multi-piece bracket is usually milled from metal pieces and welded together to form the bracket. Irrespective of construction, there is normally a bracket base, stem with bracket slot, tie-wings to retain the ligatures or o-rings as it secures the archwire into the slot, and some form of hook used for intramaxillary or intermaxillary attachment of elastics or coils. The very popular self-ligating or self-locked brackets also include a passive or active clip to secure the archwire.2–4

20. What is a self-ligating bracket? A self-ligating bracket is defined as “a bracket, which utilizes a permanently installed, moveable component to entrap the archwire.” Self-ligating brackets may be classified into two categories: passive and active.3

21. What is an active self-ligating bracket? Active brackets use a flexible component to entrap the archwire (Fig. 7-10). The active component or flexible clip constrains the archwire in the archwire slot and has the ability to store and release energy through elastic deflection. A continuous light force is imparted on the tooth and its supporting structures, resulting in precise and controlled movement. The skilled clinician will choose the appropriate bracket-archwire combination to allow low or friction-free movement when sliding of the teeth on the archwire is required but use the friction provided by the clip pressing on the archwire when rotational correction is required or when a larger dimension wire is used for 3D control. An example of an active bracket is the SPEEDd self-ligating bracket, which provides this precise control when required.3

Activated

Passive

FIG 7-10 Active spring-clip forces wire into slot. (Courtesy of Strite Industries, Cambridge, Ontario, Canada.)

22. What is active and passive self-ligation? Active indicates that the spring-clip or gate mechanism is always active against the archwire. Irrespective of the wire size or archwire to bracket angulation, the clip mechanism exerts a force on the wire and thus the tooth-bracket-wire combination. Some bracket systems (In-Ovationb and Timea) only exhibit this function. A passive system indicates that the gate mechanism or clip that entraps the archwire in the bracket slot has no active exertions of force on the archwire. Thus the latter combination only moves the tooth through an interaction of the distorted archwire bracket interaction; the archwire engages the bracket where it has contact points and this allows tooth movement (Damonc). A combined system (i.e., active or passive force spring-clip action when required) is also available (SPEEDd). The latter system has a specific bracket slot design that includes a parking ramp upon which the clip rests to prevent interaction when small dimension wires are utilized. The parking ramp enables the spring-clip to be passive during tooth movements utilizing small dimension archwires (especially for sliding) and active when tooth movement (such as torquing) is required. This combined clip action format is also referred to as dual-action bracket spring-clips.8 In addition, the dual action is further enhanced by such characteristics as a nitinol spring-clip (SPEEDd) versus a more rigid steel clip (Damonc, In-Ovationb). A different entrapment method is by a “grabbing mechanism” or clip, also fabricated from nitinol material, which grabs the archwire into the bracket slot (SmartClip Self-Ligating Appliance System, 3 M Unitek, St. Paul, MN).

23. What is a spring-wing bracket? A single bracket provides a larger inter-bracket distance between teeth and theoretically allows a lighter force to act on the teeth compared with a similar dimension wire in a twin or Siamese bracket. The latter is wider and thus closer together when placed on the teeth. However, rotations are believed to be more difficult to correct with a small and narrow single bracket, hence the additions of rotation arms or wings (Fig. 7-11). These were traditionally named the Steiner wings,

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A

B FIG 7-11 The bracket body has wings on each side that ro tate teeth when activated. Note the contrast between the band versus the direct bonded bracket and the steel versus the elas tic o-ring to secure the wire in position. The steel ligature is often used to enhance the force of activation.

Lang antirotation arms, or Lewis spring wings. These wings or arms can be adjusted depending on the rotation and direction of correction required.2

24. What is inter-bracket width? Inter-bracket width refers to the distance between contact points of brackets, also referred to as the distance of archwire between two neighboring teeth. Siamese or twin brackets generally have less inter-bracket space or width compared with single brackets (see Figs. 7-6, B and D). A small inter-bracket width limits the size of stainless steel wire that will be able to fit in the bracket slots of adjacent teeth. The sooner the clinician is able to engage a full-thickness stainless steel archwire in the bracket slot, the sooner 3D control of tooth position is initiated. Not all treatment objectives require this procedure; however, if this is part of the treatment plan, then single brackets with larger inter-bracket width obviously have advantages. Clinicians have added multiple loops into archwires in the past to accommodate more length of wire between brackets in an effort to increase the flexibility of the steel wires. Newer flexible archwires developed from space-age materials (such as nitinol and titanium) plus the addition of heat-sensitive or heat-activated characteristics have, in the majority of instances, overcome this limitation. Thus, instead of multiple loops between teeth, a straight archwire is the order of the day. Moreover, all popular contemporary brackets have become smaller; thus interbracket width has increased, but single brackets still have the advantage in this area.2,4

25. What is a single-, double-, or triple-tube bracket? These terms most frequently apply to the attachments for the first molar teeth. Depending on the type of mechanotherapy, a clinician may use only one archwire per treatment stage and thus require only a single slot or tube. Sometimes an auxiliary appliance is used in addition to the base archwire.

FIG 7-12 A, Flexible wire in auxiliary slot while remainder of arch is kept stable with a rigid base archwire. B, Maxillary molar band illustrating a double tube: one for auxiliary (such as, headgear) application and one for archwire. Mandibular molar illustrates a single tube accommodating only the arch wire. Note the additional hooks on the brackets that are used for retraction coils or elastic traction. (A, Courtesy of Strite Industries, Cambridge, Ontario, Canada.)

Such auxiliaries could be a lip bumper that is often used in the mandibular arch, a utility arch that is used in both arches (introduced as part of the Bioprogressive system in the late 1970s), and headgears (Fig. 7-12, A). If an archwire and one such auxiliary are used, a double tube is required on the molar bracket and similarly a triple tube where a headgear, base archwire, and a utility arch are used. Brackets such as the SPEEDd self-ligating bracket have an auxiliary slot incorporated into the bracket stem and accept an additional wire of up to 0.016 × 0.016–inch dimension to assist with tooth movement where needed (see Fig. 7-12, B). The latter function is especially effective where a malpositioned tooth is aligned after a full-thickness base archwire is already in place. An example of the latter is when an impacted tooth, such as a surgically exposed maxillary canine, is brought into an already aligned and stabilized dental arch.3,4

26. What is the mechanism to secure a direct bonded appliance to tooth enamel? The advent of acid etching revolutionized orthodontic fixed appliance therapy. The enamel surface is usually prepared by etching the surface with 37% phosphoric acid for 15 to 30 seconds, then rinsed with water, dried, and sealed with a lightly filled resin. The bracket is then secured or bonded to this prepared surface by a filled or hybrid composite resin adhesive. The latter is available in an auto-polymerizing or self-cured adhesive, which is often referred to as chemical cure; however, light-polymerized adhesives are the most popular composite adhesives. Curing in contemporary clinical practice is accomplished by light-curing


105

A

B

C

D

FIG 7-13 Scanning electron microscope (SEM) images of different bracket base designs. A, A 150-gauge SuperMesh. B and C, Integral cast showing two patterns. D, A 60 gauge.

using a halogen, argon laser, plasma arc, or light-emitting diode light source. This process of fitting attachments to the enamel has many variants, including using other concentrations of acid, other types of acids, indirect bonding versus direct bonding, moisture-insensitive primers, self-etching primers, acid-resin combinations that are mixed and applied in a single process, and various types of cements that could be resin, glass ionomer, or a combination resin-reinforced glass ionomer. The bonding process evolved, and brackets can be bonded successfully to amalgam, gold, acrylic, or porcelain restorations, provided that the surfaces are correctly prepared. Moreover, manufacturers have included another variable in this process: various bonding bases exist (Fig. 7-13). The latter varies from a conventional mesh base (different gauge mesh [e.g., 60-gauge SPEED, 80-gauge American master series, 150-gauge SuperMesh SE GAC]) to an integral cast base with undercuts (American Time self-ligating bracket). The metal surfaces can also be sandblasted or microetched by the manufacturers, which increases the surface area of the base to enhance bond strength.3,4,9

27. What are tie-wings? Tie-wings are extensions of the conventional bracket (see Figs. 7-6, A-C, and 7-10, A). They are used for their undercuts to secure elastic or stainless steel ligatures, which in turn hold the archwires in place. In addition, tie-wings can be used to secure wire hooks, such as Kobayashi tie hooks for elastic traction (Fig. 7-14), if this is required and the bracket design did not provide for this utility.2–4

FIG 7-14 Kobayashi tie hooks are often used with the con ventional edgewise twin bracket. Note that the wire hook can be adjusted to accommodate various directions of elastic traction. (Courtesy of Strite Industries, Cambridge, Ontario, Canada.)

28. What does the bracket slot dimension indicate? The two most often used dimensions are the 0.018 × 0.025–inch and the 0.022 × 0.028–inch brackets. The main difference is that that the 0.022 slots can accommodate a larger selection of archwire sizes. No evidence exists to prove that one system is superior to the other; American Board of Orthodontics (ABO) quality results have been obtained with both. The selection of

106


either is a matter of preference of the clinician. The first number indicates the width of the bracket slot occlusogingivally, and the second number indicates the depth of the slot. Full-thickness archwires for these two systems are normally 0.017 × 0.025 inch and 0.021 × 0.028 inch, respectively; thus, a rectangular wire of this nature will fill the bracket slot in all dimensions.2–4

29. Friction between bracket and archwire plays an important role during orthodontic tooth movement. How is this factor minimized? Studies have shown that two absolutely smooth surfaces of similar metals brought into contact and slid over each other can initiate a process called cold welding, which literally means that the metals are “fused” together. This obviously increases friction and slows the movement. This also happens between archwires and bracket slots. Ceramic bracket surfaces have also traditionally provided increased friction values—hence the incorporation of metal slot inserts to decrease sliding friction. Therefore, it is imperative to select appropriate combinations of archwires and bracket slot dimensions when teeth have to move or slide along an archwire or when only root or crown movement is required, such as in torquing or third-order movements. When sliding is required, such as during the distal movement of a canine into a space, minimal friction is required. The movement should be accomplished by the use of a smaller diameter wire, which does not bind in the bracket slot. Stainless steel and elastic ligatures increase friction when used to secure archwires into bracket slots; in addition, the friction is increased when any minor bend in the archwire comes in contact with the ligature. Self-ligating brackets have basically eliminated this limitation. Most self-ligating brackets are passive (e.g., Damon appliance); there is no action on the wire except when there is wire bracket contact. The active self-ligation brackets have active clip mechanisms to secure the archwires into the bracket slots. The SPEED bracket clip is unique in that it prevents active contact until full-thickness archwires are used; this characteristic thus provides low friction during sliding and initial alignment when low friction is required, but it increases the friction when full-dimension archwires are used for 3D control and when friction-free sliding is not a factor.3,10,11

30. Is a friction-free appliance ideal? Friction-free is only an advantage when the archwire has to slide. This is most often required during the initial alignment of teeth and when spaces are closed or opened. On the contrary, when corrective movements such as treatment of rotations, movement of severely displaced teeth in only one direction, when teeth are used as anchors, or when torquing movements of teeth are required, then friction is necessary to accomplish the correction. Friction is thus an important factor in attaining successful tooth movements and requires intelligent decision making.4,10

31. How is a bracket constructed? The two major processes are milling and injection molding. Milling indicates that the bracket is milled out of a piece of metal, sometimes in more than one piece, and then followed by

welding together all the pieces to form the bracket for bonding to enamel or welding to a band. Injection molding is a process in which a mold of the bracket is prepared and then filled by a process in which a liquefied metal is poured or injected into the mold; the liquid cools and sets into the bracket form, which is removed and further prepared as a unit for bonding. Brackets are manufactured in stainless steel, titanium, nickel-free alloys, gold plated steel, ceramic, and reinforced polycarbonate materials.2–4

32. What is a convertible tube? In order to provide a tube at the end of the archwire, mostly for ease of wire insertion, a tube is used for the last tooth in the arch, usually the second molar. However, treatment is often initiated prior to the full eruption of the second molar, and the first molar is then used as the end tooth. A tube is fitted that has a removable plate welded over the slot to provide a slot for ease of placement of the archwire as noted. Therefore, when the second molar is provided with an attachment, the first molar tube can be converted into a bracket by removing the plate; hence it is called a convertible tube/bracket.4 In contrast, the SPEED appliance uses a bracket on the mesiobuccal cusp of the maxillary molars, and the active clip can be opened to insert the archwire (see Fig. 7-12, A; note that the plate is in place, securing the archwire in the slot).

33. What is an initial archwire? The initial archwire is usually the first archwire in a sequence of increasing size and wire stiffness, normally a very flexible wire that exerts a low force to the teeth and that is of a small diameter (Fig. 7-15). It is also required to have super elasticity and shape memory, meaning that lots of flexibility is available to allow the wire to engage all the irregularly positioned teeth without a high force caused by the deflection of the wire. Examples of such wires are 0.012-inch stainless steel, 0.014-inch nitinol, or 0.016-inch Supercable archwires. Rectangular archwires of similar characteristics have been introduced recently, and this would be the choice as a starting wire when possible to initiate 3D control from the beginning. The initial archwire first focuses on tooth rotations and alignment of the marginal ridges, which is followed by vertical and then anteroposterior correction of the malocclusion using more rigid archwires, sometimes with intermaxillary mechanotherapy added as needed.2–4

34. What is sliding mechanics? Sliding mechanics literally means that the teeth are sliding on the archwire. A single tooth or en masse movement can be provided. Usually a stainless steel wire of smaller dimension than the bracket slot is used for this movement in order to prevent friction that will slow movement. There are various ways to activate this movement, including power chain, conventional rubber/elastic bands, or coil springs such as the Pletcher coil spring, present day nitinol, and titanium closing coils (Fig. 7-16). This type of movement is in contrast to the traditional closing loop archwire in which the activation of the closing loop allows for the teeth to move and spaces to close where indicated.2–4


A

107

A

B

B

FIG 7-15 Note the flexible initial wire (0.016 supercable) in the crowded dentition (A) versus the rigid rectangular stainless steel wire (0.017 × 0.025 SS) in the aligned dentition (B) where three-dimensional (3D) control is important, such as arch form and crown-root alignment.

35. What is a D-shaped, C-shaped, or dual-dimension archwire? These wires are important when self-ligation appliances are used, in particular the SPEED appliance with its active clip mechanism (Fig. 7-17). For effective use of the energy exerted by the active spring on archwires, it is important that the spring be locked in a secure position. The use of full-thickness archwires facilitates 3D control; thus, when D- or C-shaped archwires are used for this purpose, the D or C rounded side of the archwires allows easy closure of the active clip. The edge of a rectangular or square wire of the same dimension causes difficulty in clip closure; moreover, forceful closure of the clip can damage the clip and negate the energy release for accurate tooth movement.3

36. What are the properties of an ideal orthodontic archwire? The ideal orthodontic archwire is one that has a high elastic limit but is not too brittle to break under loading and exhibits a low load-deflection rate. The latter function is determined by the modulus of elasticity or in simple terms, the rigidity of the wire. Stainless steel, for example, has a modulus of elasticity 1.8 times greater than that of gold. If this example is used for the reactive part of an appliance, which is the part that provides

FIG 7-16 A, Conventional edgewise appliance illustrating o-ring ties to secure archwire in place as well as a nitinol coil spring to retract the anterior teeth into the space. B, Power chain positioned under the archwire in a self-ligating SPEED appliance to enhance space closure in a sliding format. Note also the intramaxillary and intermaxillary elastic traction to fa cilitate correction of the malocclusion.

the anchorage against movement, then stainless steel will be 1.8 times more resistant to deflection compared with a reactive component made from gold wire. Moreover, activations made in a steel wire for tooth movement will produce a loaddeflection rate almost twice that of a similar activation made in an identical dimension gold wire. In addition, the orthodontic alloy should also be resistant to corrosion when exposed to the oral environment, should not fracture to accidental loading in the mouth or during fabrication of an appliance, should be formed in a soft state and then be heat treated to hard temper, and lastly should allow easy soldering of attachments. Manufacturers provide cross-section stiffness (Cs) and material stiffness (Ms) numbers to wires to allow clinicians to compare archwires with different dimensions and alloys with one another. Provided the alloy is the same, a 0.014-inch wire will have a significantly smaller Cs compared with a 0.018-inch wire; the first will be able to deflect more when exposed to a force of the same design.3,4

37. What is the difference between nitinol, beta-titanium, and stainless steel wires? Nickel-titanium (nitinol) and beta-titanium (TMA) are shape memory alloys with low-force high-springback capabilities. Nitinol in particular has a tremendous resistance to permanent deformation. The modulus of elasticity of nitinol is only 0.26 that of stainless steel; thus, a comparison of the Ms shows that a 0.018-inch nitinol wire has the approximate stiffness of

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Anterior - square

A

Posterior - round

FIG 7-18 The keys to a Class I occlusion in the making. Note that the mesiobuccal cusp of the maxillary first molar is occluding in the buccal groove of the mandibular first molar. This allows all the posterior teeth as shown to occlude in cor rect Class I relationships.

B

Rectangular arch wire

Passive

FIG 7-17 A, The dual-dimension wire as shown is the SPEED Hills wire. The anterior section of the archwire is square for torque control, and the posterior section is round to facilitate sliding of the wire. B, The C-wire is shown in comparison to a rectangular wire in the cross-section of the SPEED self-ligating bracket. Note that the C-shape rounding of the edge of the rectangular wire facilitates the active clip to close securely in position. (Courtesy of Strite Industries, Cambridge, Ontario, Canada.)

a 0.013-inch stainless steel wire. Nitinol archwires are particularly useful when low forces and large deflections are required in relatively straight wires, such as in the initial phases of or thodontic treatment when the teeth are too irregularly aligned to use stainless steel wires. Super-elastic nitinol wires are also available that are activated by exposure to mouth temperature; they are very flexible at room temperature and become more rigid at higher mouth temperatures. This property allows the wire to be inserted when teeth are severely displaced (see Fig. 7-15). TMA wires have a modulus of elasticity that falls between that of steel and nitinol wires and can be deflected almost twice as much as steel without permanent deformation. Unlike nitinol, TMA can accommodate some adjustments, and auxiliaries (such as, finger springs) can be welded to the wire. TMA can be used as an active working wire; however, it is often used as a finishing wire because small adjustments can be bent into the wire to secure perfect alignment of teeth.3,4

38. What is a straight wire appliance and who popularized the concept? Dr. Larry F. Andrews published his classic article “The Keys of Normal Occlusion” in 1972.12 He used the six keys to ideal occlusion to develop and introduce the straight wire appliance

to orthodontics, which is basically an appliance with built-in 3D prescription to represent ideal tooth positions (Fig. 7-18). The slots are all aligned parallel to the occlusal plane when the teeth are in ideal occlusion, provided that the brackets are correctly placed on the tooth surface. Andrew’s bracket had a base contoured occlusogingivally and mesiodistally; when fitted correctly, it would avoid any archwire adjustments as reflected in the original no-prescription appliances with the three orders bent into the archwires; hence, the straight wire appliance.2,12

39. Does bracket position on the tooth influence treatment? With the advent of preadjusted, straight wire, or fully programmed appliances, as the plethora of new developments in bracket systems were called, bracket position became very important both occlusogingivally and mesiodistally. The specific heights can be measured using such instruments as an Andersen gauge or a Boone gauge. The skilled clinician can position most of the brackets correctively most of time; however, with efficiency and chair time in the modern orthodontic office at a premium, another technique of bracket placement surfaced. This indirect bonding technique differs from the direct placement in the mouth; a preliminary impression is provided, and the brackets are accurately positioned in the laboratory whereupon a transfer tray allows the brackets to be bonded to the enamel in the conventional manner through acid-etching and resin cements.3,4

40. Why is a power arm attached to a bracket? In order to provide planned tooth movement (i.e., translation versus tipping), the clinician must plan the point of force application on the tooth and the direction of the force in respect to the center of resistance of the tooth (Fig. 7-19). The center of resistance is mostly situated between the root apex and alveolar bone crest. This makes it impossible to apply force to a bracket unless a power arm is attached to the bracket, which allows for the applied force to be closer to the center of resistance. If a force is applied in this way, the clinician has the ability to control the translation or rotation/tipping of a tooth or group of teeth.2–4,13


109

A

B

C

Performed SPEED hooks installed in SPEED brackets

FIG 7-19 A, The center of resistance (black dot in middle of root) and the center of rotation (circle root apex and crown tip) are illustrated. The horizontal arrow indicates the force vec tor; two moments are shown: (1) the moment where the center of rotation is at the root apex and the resultant movement is tipping of the crown; the force application is at the bracket on the crown and the archwire could be a round wire, and (2) the moment where root torque is accomplished with the center of rotation at the crown tip; a rectangular wire could be inserted and the torque prescription is causing the root tip. B, Power arms can be inserted as shown with the SPEED hooks. Bodily movement is encouraged with the power arm, al lowing the force vector through the center of resistance. C, Power arms can be inserted into an auxiliary slot (0.016 × 0.016 inch) as shown with the SPEED hooks. (A, From Graber TM, Vanarsdall RL Jr, Vig KWL: Orthodontics: current principles and techniques, ed 4, St Louis, 2005, Mosby. B, From Smith RJ, Burstone CJ: Mechanics of tooth movement, Am J Orthod 85[4]:294–307, 1984. C, Courtesy of Strite Industries, Cambridge, Ontario, Canada.)

41. What is a ceramic bracket? Orthodontic materials have developed significantly over the past 20 years, resulting in an increasing number of adult patients seeking orthodontic treatment. These patients requested the use of more esthetic appliances. Direct bonded brackets replaced bands, brackets became smaller, lingual appliances became popular, and ceramic (clear or tooth-colored) brackets were introduced (Fig. 7-20). Ceramic brackets were initially

very fragile, but the bonding to the enamel occurred initially through a Silane layer, resulting in a chemical bond of very high bond strength. Not only did the brackets fracture during treatment, but more important, enamel fracture occurred during bracket removal. The ceramic was also more resistant to wear compared with enamel, which resulted in enamel wear if an opposing tooth touched the bracket. A new generation of ceramic bracket was introduced with a lower profile and a mechanical retentive bonding base without these flaws. It is recommended

110

CHAPTER 7 • Orthodontic Appliances also reduced on the lingual surfaces, which limits adjustments. To facilitate treatment, customized brackets are presently produced with accompanying custom archwires using scanning and computerized robotics.3

43. What does Hooke’s law define in respect to orthodontic archwires?

FIG 7-20 Two self-ligating brackets: ceramic In-Ovation in the maxillary arch and stainless steel SPEED in the mandibular arch being used to close an anterior open bite.

to avoid contact of an opposing tooth to a ceramic bracket. High friction between archwire and the ceramic bracket slot was also evaluated, resulting in ceramic brackets with smoother surfaces as well as stainless steel inserts into the slots reducing friction for sliding and thus aiding tooth movement.2–4

42. What is a lingual appliance? Esthetic requirements differ from person to person. Mostly, it is a decision of obtrusiveness. Clear or ceramic appliances may satisfy some, others prefer a small stainless steel selfligating bracket, others prefer the conventional bracket with various colored o-rings to secure wires, and then there is an option of lingual braces. Lingual braces are secured to the lingual surfaces of the teeth (Fig. 7-21). Surprisingly, the problem with lingual braces is not the retention of the attachments on the enamel surfaces, but rather that some pronunciation difficulties occur after insertion. Furthermore, the technique is difficult and time consuming, and the working position is awkward. The interbracket distance is

Hooke’s law refers to load and deflection of wires (Fig. 7-22). If a linear relationship exists between loading and deflection, the deflection will increase when the force exerted on the wire increases. This proportionality is referred to as Hooke’s law. Loaddeflection diagrams differ for different wires. Activation and deactivation curves also provide relevant information as to the load and deflection properties of wires.3

44. How does contamination of the bracket base affect the bonding to enamel? Contamination of the bracket base with substances (such as talc powder, skin oil, laboratory wax, and others) significantly reduces the bond strength of the bracket to the enamel surface and subsequently leads to premature bracket bond failure. It is imperative to follow a meticulous protocol for bonding fixed appliances to the teeth for successful ortho dontic treatment.14

45. What is indicated by the angle of torque? This is the angle, viewed from an occlusogingival perspective, formed between the intersection of the line perpendicular to the tangent of the bracket base surface (tooth-side surface) and a line bisecting the bracket slot. The value is normally expressed as a positive or negative value: positive (+) if the angle is directed occlusally and negative (−) if it is gingivally directed (Fig. 7-23). Torque is represented as in the slot or in the base, and it depends on the manufacturer’s preference when brackets are manufactured.

Load

Elastic range

Pmax

0

FIG 7-21 Lingual appliances fitted by indirect bonding actively aligning the lower teeth.

Plastic range

Pult

Deflection

FIG 7-22 The linear display of the graph from 0 to Pmax rep resents Hooke’s law. (From Graber TM, Vanarsdall RL Jr, Vig KWL: Orthodontics: current principles and techniques, ed 4, St Louis, 2005, Mosby.)


111

46. What is a torquing moment?

Gingival

A torquing moment is a third-order couple creating a moment for faciolingual rotation.15 The moment is equal to the force multiplied by the distance between the two forces of the couple (M = F × D), and this distance is limited to the depth of the bracket slot (Fig. 7-24). Angle of torque directed toward the gingiva (negative value)

Occlusal

FIG 7-23 A negative angle of torque. d

F M=F d F

FIG 7-24 A third-order torquing moment for faciolingual/ faciopalatal movement.

REFERENCES 1. Daskalogiannakis J: Glossary of orthodontic terms, Berlin, 2000, Quintessence Publishing. 2. Vaden JL, Dale JG, Klontz HA: The Tweed-Merrifield Edgewise appliance: philosophy, diagnosis, and treatment. In Graber TM, Vanarsdall RL, Vig WL, editors: Orthodontics: current principles and techniques, ed 2, St Louis, 2012, Mosby. 3. Woodside DG, Berger JL, Hanson GH: Self-ligation orthodontics with the speed appliance. In Graber TM, Vanarsdall RL, Vig WL, editors: Orthodontics: current principles and techniques, ed 2, St Louis, 2005, Mosby, pp 717–752. 4. Proffit WR, Fields HW, Sarver D: Contemporary orthodontics, ed 2, St Louis, 2013, Mosby. 5. Begg PR, Kesling PC: Begg orthodontic theory and technique, ed 2, Philadelphia, 1971, WB Saunders. 6. Kesling PC: Tip-Edge plus guide, ed 6, La Porte, IN, 2006, TP Orthodontics. 7. Nanda R: Biomechanics in clinical orthodontics, Philadelphia, 1997, WB Saunders Company, pp 1–22; 229–245. 8. Smith DV, Rossouw PE, Watson P: Quantified simulation of canine retraction: evaluation of frictional resistance, Semin Orthod 9:262–280, 2003. 9. Sharma-Sayal, Rossouw PE, Kulkarni GV, et al: The influence of orthodontic bracket base design on shear bond strength, Am J Orthod Dentofac Orthop 124(1):74–82, 2003. 10. Rossouw PE: Friction—an overview, Semin Orthod 9(4):218–222, 2003. 11. Rossouw PE, Kamelchuk LS, Kusy RP: A fundamental review of variables associated with low velocity frictional dynamics, Semin Orthod 9(4):223–235, 2003. 12. Andrews LF: The keys of normal occlusion, Am J Orthod 63:296, 1972. 13. Smith RJ, Burstone CJ: Mechanics of tooth movement, Am J Orthod 85(4):294–307, 1985. 14. Rossouw PE, Penuvchev AV, Kulkarni K: The influence of various contaminants on the bonding of orthodontic attachments, Ont Dentist 73(7):15–22, 1996. 15. Isaacson RJ, Rebellato J: Two-couple orthodontic appliance systems: torquing arches, Semin Orthod 1(1):31–36, 1995.

C H A PT E R

8

Biomechanics in Orthodontics

André Haerian • Sunil Kapila

I

n general terms, mechanical principles that govern the be havior of devices that interface with biological tissues are collectively termed biomechanics. At the core of all ortho dontic treatment are the devices or appliances that deliver con trolled forces to the teeth and jaws. Therefore, the mechanics of force delivery is an integral part of orthodontics. The principles of biomechanics are a common thread in all ortho dontic curricula.1 This chapter addresses some of the basic bio mechanical principles that are critical in clinical orthodontics. An understanding of these principles and their appropriate ap plication provides the clinician the ability to achieve consistent and controlled tooth movement.1 Orthodontic appliances—simple or complicated, fixed or removable—are all subject to laws of physics.1 Therefore, the discussion in biomechanics often begins with an introduction to Newtonian mechanics.

1. What is biomechanics? Biomechanics is the research and analysis of the mechanical properties of living tissues and nonliving objects that affect those living tissues. In orthodontics, this analysis of biome chanical properties is used to determine the effect of ortho dontic appliances on oral tissues, particularly teeth and bone. The analysis of the nonliving component simply follows Newtonian mechanical principles. In contrast, the biomechan ical properties of living tissue are more complicated and often not thoroughly understood.2,3

2. What is Newtonian mechanics? Newton’s three Laws of Motion describe the relationship be tween the external forces acting on an object and the motion of that object, which form the basis for classical mechanics. Mechanics is the branch of physics concerned with the behavior of objects when subjected to forces or displacements. These laws were first formulated by Sir Isaac Newton and published in his work Philosophiae Naturalis Principia Mathematica (1687).4,5

3. What are Newton’s three laws of motion? First Law: A body at rest remains at rest, and a body in mo tion continues to move in a straight line with a constant speed unless and until an external unbalanced force acts upon it.4,5 Second Law: The rate of change of momentum of a body is directly proportional to the impressed force and takes place in the direction in which the force acts.4,5 •

•

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Third Law: Whenever A exerts a force on B, B simultane ously exerts a force of the same magnitude and in the oppo site direction on A. This can be stated simply as: “For every action, there is an equal and opposite reaction.”4,5 •

4. What is force in physics? In physics, force is an influence that may cause an object to change its velocity (accelerate). It may be experienced as a lift, a push, or a pull, and it has a magnitude and a direction and hence is mathematically represented by a vector. The actual acceleration of the body is determined by the vector sum of all forces acting on it. Forces can also cause deformation or rotations of an object.6,7

5. What is a vector in physics? A vector is a concept characterized by a magnitude and a direc tion. Force is a vector quantity defined as the rate of change of the momentum of the body that would be induced by that force acting alone. Since momentum is a vector, the force has a direction associated with it6,7 (Fig. 81).

6. What is the difference between a vector and a scalar? A vector is a concept characterized by a magnitude and a di rection. A scalar has only a magnitude. An example of a vec tor is force and examples of scalars are weight and height. Orthodontic forces are described by their magnitude, point of application, and direction. The direction of the force is defined by the line of action and the sense (arrowhead). The magnitude of the force is depicted by the length of the line using an arbi trary scale (e.g., 1 cm represents 100 grams).6,7

7. What are the horizontal and vertical components of an orthodontic force? Any force applied to a tooth can be broken up into its verti cal and horizontal components using the occlusal plane as the horizontal reference of an orthogonal coordinate system. The calculations of magnitude and direction of the components can be carried out geometrically as in Fig. 82 or by using trigo nometric methods.8

8. What is an orthodontic force system? Delivery of physical force to the dentition is achieved by using a combination of force delivery methods. These include orthodon tic wires, springs, elastic chains, and headgears. The force system

Biomechanics in Orthodontics • CHAPTER 8

113

Magnitude

Line of action Sense Direction Point of origin or application

/

/

FIG 8-1 Force vector. F1 R

45°

/

45°

/ F2

/ H

/

F1 and F2 two concurrent forces; R Resultant

FIG 8-3 The resultant (R) for two concurrent forces (F1 and F2) acting on a tooth.

45° F V

/

of the resultant (R). The direction of the resultant relative to any plane (e.g., the occlusal plane) can be determined using a protractor.6,7 /

F Force; H horizontal component of force; V vertical component of force

FIG 8-2 Horizontal and vertical components of a force (F) applied to a tooth.

describes all the forces involved and allows for analysis and calcu lation of resultant forces on a tooth or a group of teeth.2

9. What are two methods to calculate the resultant of two concurrent forces? Concurrent forces depicted as vectors can be added together to calculate the resultant by using the parallelogram method or by addition of their components in a reference system. For the latter method, the horizontal and vertical components of each of the two forces can be added to calculate the resultant as follows: If F1 = h1 + v1 and F2 = h2 + v2, then R = F1 + F2 = (h1 + h2) + (v1 + v2). The parallelogram method used to derive resultant forces entails drawing the two concurrent forces (F1 and F2 in Fig. 8-3) to scale at appropriate angulations. The ends of these lines are joined together with a parallelogram. The diagonal of this par allelogram from the point of force application, when measured and converted using the specified scale, gives the magnitude

10. What is the center of resistance (centroid)? The center of resistance is analogous to the center of mass of a free body or its balance point. In physics, the center of mass of a system of particles is a specific point at which the system’s mass behaves as if it were concentrated. This center of resistance or centroid of the physical object coincides with its center of mass if the object has uniform density, or if the object’s shape and density are symmetric. In orthodontics this centroid or center of resistance of a tooth is a point in the tooth at which a force application results in translational movement. The center of resistance remains constant and is located about one-third to one-fourth of the root length from the cementoe namel junction (CEJ) in a normally sized tooth and normal periodontium.3,8

11. What is the center of rotation? The center of rotation of a tooth is the point around which the tooth rotates. A very small rotational tooth movement can be considered as part of a circle (arc), the center of which is called the center of rotation for that movement. The location of the center of rotation is not constant and is determined by the type of movement that the tooth is undergoing. For example, in

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CHAPTER 8 • Biomechanics in Orthodontics

translational tooth movement, the center of rotation is located at an infinite distance from the center of resistance.9,10

12. What is uncontrolled tipping? Uncontrolled tipping movement results when the tooth crown and root move in opposite directions. It occurs when the net force on a tooth results in a center of rotation that is near the center of resistance of that tooth. Removable appliances usually produce this type of tooth movement (Fig. 8-4).11

13. What is controlled tipping? Controlled tipping movement occurs when the net force on a tooth results in a center of rotation that is near the apex of that tooth. This results in the crown moving in the direction of the force, but the root tip moving minimally. Orthodontic treat ment requires this type of tooth movement in many instances (Fig. 8-5).11

14. What is translational tooth movement? Translational or bodily movement results when the whole tooth (crown and root) moves equidistantly in the same direction. The movement occurs when the net force on a tooth results in a center of rotation that is infinitely far from the center of resistance of that tooth. Tooth translation is essential in major correction during orthodontic treatment. This type of tooth movement is achieved by using a force system that has an equivalent force applied to the center of resistance (Fig. 8-6).11

Cres Crot

FIG 8-5 Controlled tipping movement with the center of rotation located near the root apex.

Cres

Cres

Crot

Crot at infinity

FIG 8-4 Uncontrolled tipping movement showing the location of the center of rotation (Crot) relative to the center of resistance (Cres).

FIG 8-6 Translational tooth movement in which all points on the tooth have moved equally in the same direction and the center of rotation is located at infinity.


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15. What is root torque? Root torque is produced when the root and crown move in the same direction, with the root moving a greater distance than the crown. This type of movement occurs when the net or equivalent force on the tooth results in a center of rotation at the incisal tip of that tooth (Fig. 8-7).11

16. What is the moment of force? In classical mechanics, the moment of force is a quantity that represents the magnitude of a given force applied to a rotational system at a distance from the axis of rotation. The International System of Units (SI) unit for moment is the Newton meter (Nm). The moment of the force (Mf) has both magnitude and direc tion (clockwise or counterclockwise) and is therefore a vector.12,13 Moment of the force = Magnitude of Force × Perpendicular distance to the center of resistance of the tooth

Or Mf = F × D Cres

17. What is the unit of moment of the force? The unit of moment of a force is the unit of force (Newton) and distance (meter), which is designated Nm. Given the dis tance (D) and force (F), you can calculate the moment of force placed on a tooth in three planes of space in Fig. 8-8.12,13

D 10 mm

Crot

FIG 8-7 Root torque is represented by movement in which the root apex moves more than the incisal edge and the center of rotation is located close to the incisal edge of the tooth.

D 10 mm

D 4 mm F Mf D

D

Mf

Mf

D

F

Mf F 10 Nmm

F

Mf F 10 Nmm F Force; Mf moment of the force;

Mf F 4 Nmm Cres

FIG 8-8 Depiction of the moment of force (Mf) in three planes of space that results from the application of the force (F) on the tooth crown.

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18. What is a couple? A couple is composed of two equal but opposite non-coplanar forces acting on an object (Fig. 8-9).11

19. What is the moment of the couple? Moment of the couple is the sum total of the moments created by individual force components of a couple. The magnitude of moment of a couple (Mc) is equivalent to the magnitude of the component forces multiplied by the distance between the two component forces at the point of application. The moment of the couple in fixed appliance orthodontic treatment results from the deflection of the orthodontic wire against the bracket that pro duces the couple (f) on the bracket and the tooth (Fig. 8-10).12,13

f

f

FIG 8-9 Example of a couple produced as a result of bracket wire interaction.

20. Where is the center of rotation for movement created by a couple? A pure moment or a couple applied anywhere on the tooth pro duces a center of rotation around the center of resistance. Although experiments using laser holography show a time-dependent effect where the center of rotation starts off slightly apical to the center of resistance, after a short initial period a couple produces a center of rotation near the center of resistance (see Fig. 8-10).12,13,19

21. How is moment of couple instrumental in creating translational movement? When a force F is applied to a tooth, it produces a moment of the force (Mf), which tends to rotate the tooth in a counter clockwise direction. As the tooth tips and the bracket moves relative to the wire, it engages and deflects the wire, creating a couple whose moment (Mc) equals f × d (where d is the mesio distal dimension of the bracket) in a clockwise direction. As the tip of the bracket relative to the wire increases, the Mc progres sively increases and can eventually become of equal magnitude, but opposite in direction to the moment of the force. The Mf and Mc cancel each other out, resulting in a net effective mo ment of zero. This places the equivalent of the force F through the center of resistance, producing translational tooth move ment (Fig. 8-11).13,14

22. When retracting a cuspid on an archwire, what determines the moment of the couple? The moment of the couple is determined by the magnitude of its component force times the distance between the opposing force’s point of action. In the previous example, the distance between acting component forces is fixed (bracket width), but the magnitude of the component force varies based on the wire bracket interaction. Therefore, it is the amount of force deliv ered by the wire that determines the moment of the couple, and in turn the force delivered by the wire results from the wire’s compositions, its geometry, and amount of deflection.13,14

23. What is static equilibrium? f

d

f

A rigid body is in equilibrium when the external forces acting on it form a system of forces and moments whose sum is equiv alent to zero. Therefore, the requirements for a system to be in equilibrium are that the sum of all of horizontal forces = 0, the sum of all vertical forces = 0, the sum of all transverse forces = 0, and the sum of all moments = 0. An object in mechanical equi librium is neither undergoing linear nor rotational accelera tion; however, it could be translating or rotating at a constant velocity.8,12

24. How does the law of equilibrium apply to orthodontic appliances? Mc Moment of the couple, Mc f d

FIG 8-10 Depiction of the moment of the couple: Mc = f × d.

Application of force on one part of a system leads to an equal and opposite force on another part of the system. For example, extraoral appliances deliver active forces intraorally, while the


Mf

Mc

Mf

f

Mc

Mf

f

F

F

117

F

f f

Uncontrolled tipping

Controlled tipping

Translation

FIG 8-11 Depiction of changes in the types of tooth movements as the moment of the couple increases because of wire deflection or increasing wire stiffness from left to right.

reactive forces are extraoral. Another example is the intermax illary elastics where the active and reactive forces are in the opposite arches. Similarly, the consolidation of spaces in intraarch mechanics results in static equilibrium.8,12

25. Give an example of equilibrium in an orthodontic appliance system In the previous example, the forces F1 and F2 produced by an elastic chain are equal and opposite such that their sum is zero. The moment created by F1 is F1 × D = M1 in a counterclock wise direction, whereas that from F2 is F2 × D in a clockwise direction. Since F1 equals F2 and the distances D are equal, M1 equals M2 but in opposite directions. Therefore, the sum of M1 and M2 is also zero. Because the sum of all forces is zero, and the sum of all moments is also zero, this orthodontic appliance system is in equilibrium (Fig. 8-12).11,15

26. What is a one-couple orthodontic force system? A one-couple orthodontic force system results with an ortho dontic appliance that has two points of action in the system, each with the capability to deliver a force but only one of which generates a couple. An example of a one-couple orthodontic force system is an intrusion arch that applies a point force on an anterior tooth or segment of tooth and is engaged in the molar bracket, as depicted in Fig. 8-13. This arrangement results in the single moment of the couple on the molar and intrusive and extrusive forces on the canine and molar, respectively. The couple on the molar results in a counterclockwise rotation of this tooth. Because the molar extrudes and the incisors intrude,

M1

M2

D

D F1

F2

FIG 8-12 Static equilibrium in a simple orthodontic force system.

the whole system can be thought to have a clockwise rotation (see Fig. 8-13).11,16–18

27. What is a two-couple orthodontic force system? An orthodontic appliance that has two points of action in the system with capability to deliver force at both points that result in separate couples at each of these sites is a two-couple ortho dontic force system. An example of a two-couple orthodontic force system is an intrusion arch that engages brackets both in the anterior and posterior teeth, or a canine bracket intrusion arch in which the wire engages the brackets at both the canine and molar, as shown in Fig. 8-14.11,16–18

118


Mm

FIG 8-13 Example of a one-couple orthodontic force system. The wire bracket interaction produces a couple at only one end of the system, in this case on the molar. Mm, Moment on molar.

Mc

Mm

FIG 8-14 An example of a two-couple orthodontic force system. The wire bracket interaction produces two couples, one at each end of the system, namely, on the canine and on the molar in this case. Mc, Moment on canine; Mm, moment on molar.

28. What is a temporary anchorage device? Temporary anchorage devices (TADs) are biocompatible de vices that are inserted into bone for the purpose of achieving near static anchorage against which to move teeth. The devices

are maintained for a period of time during treatment and are subsequently removed after they have served their purpose. Overall, TADs are primarily used as a means of overcoming anchorage limitations.20


29. How does the use of temporary anchorage devices change the biomechanical principles that define orthodontic tooth movement? The force system and the net force determinations are unaf fected by the use of TADs in the system. However, the bio logical response to the force system is different when a TAD is subjected to any force because TADs do not move as a response to the force systems. It is important to note that biomechanical principles remain the same even though these devices respond differently to applied force than natural teeth (see Fig. 8-14).20,21 REFERENCES 1. Burstone C: Orthodontics as a science: the role of biomechanics, Am J Orthod Dentofacial Orthop 117(5):598–600, 2000. 2. Burstone CJ, Koenig HA: Force systems from an ideal arch, Am J Orthod 65(3):270–289, 1974. 3. Hocevar RA: Understanding, planning, and managing tooth movement: orthodontic force system theory, Am J Orthod 80(5):457–477, 1981. 4. Cohen IB, Smith GE: The Cambridge companion to Newton, Cambridge, UK; New York, 2002, Cambridge University Press. 5. Tait PG: Newton’s laws of motion, London, 1899, A&C Black. 6. Abraham R, Marsden JE: Foundations of mechanics; a mathematical exposition of classical mechanics with an introduction to the qualitative theory of dynamical systems and applications to the three-body problem, New York, 1967, WA Benjamin. 7. Becker RA: Introduction to theoretical mechanics, New York, 1954, McGraw-Hill.

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8. Smith RJ, Burstone CJ: Mechanics of tooth movement, Am J Orthod 85(4):294–307, 1984. 9. Burstone CJ, Pryputniewicz RJ: Holographic determination of centers of rotation produced by orthodontic forces, Am J Orthod 77(4):396–409, 1980. 10. Christiansen RL, Burstone CJ: Centers of rotation within the periodontal space, Am J Orthod 55(4):353–369, 1969. 11. Nanda R: Biomechanics in clinical orthodontics, Philadelphia, 1997, Saunders. 12. Shellhart WC: Equilibrium clarified, Am J Orthod Dentofacial Orthop 108(4):394–401, 1995. 13. Tanne K, Koenig HA, Burstone CJ: Moment to force ratios and the center of rotation, Am J Orthod Dentofacial Orthop 94(5):426–431, 1988. 14. Gjessing P: Controlled retraction of maxillary incisors, Am J Orthod Dentofacial Orthop 101(2):120–131, 1992. 15. Mulligan TF: Common sense mechanics. 3. J Clin Orthod 13(11):762–766, 1979. 16. Nikolai RJ: Rigid-body kinematics and single-tooth displacements, Am J Orthod Dentofacial Orthop 110(1):88–92, 1996. 17. Isaacson RJ, Lindauer SJ, Rubenstein LK: Activating a 2 × 4 appliance, Angle Orthod 63(1):17–24, 1993. 18. Demange C: Equilibrium situations in bend force systems, Am J Orthod Dentofacial Orthop 98(4):333–339, 1990. 19. Pedersen E, Andersen K, Gjessing PE: Electronic determination of centres of rotation produced by orthodontic force systems, Eur J Orthod 12(3):272–280, 1990. 20. Yamaguchi M, Inami T, Ito K, et al.: Mini-implants in the anchorage armamentarium: new paradigms in the orthodontics, Int J Biomater 2012:394121, 2012. 21. Reynders R, Ronchi L, Bipat S: Mini-implants in orthodontics: a systematic review of the literature, Am J Orthod Dentofacial Orthop 135(5):564.e1–564.e19, 2009, discussion 564–565.

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9

Treatment Planning

James L. Vaden • Terry M. Trojan

T

reatment planning is the critical first step in orthodontic treatment. Without an adequate treatment plan, proper treatment cannot be rendered. Indeed, the patient’s destiny is determined by the treatment plan that is devised by the treating clinician. This chapter delves into some of the common areas that should be considered during the treatment planning process.

1. When a treatment plan for a patient is being developed, what should be the goal? The goal during the development of any treatment plan should be to make the decisions that will allow the orthodontist to: • Prioritize objectives—both the patient’s and the orthodontist’s1 • Make decisions that will allow the orthodontist to treat the patient so that the greatest number of attainable objectives is reached For most patients, the objectives are esthetics, health, function, and stability. If a growing child is being treated, an additional objective should be to use forces that act in harmony with growth and development.2,3

2. Is there “room for error” during the treatment planning process? Absolutely not. The orthodontic clinician must use a systematic approach to develop each and every treatment plan. This systematic approach must be based on sound fundamental principles that have been scientifically validated.1,4–6 Treatment plans should not be formulated with the use of anecdotal evidence that is contraindicated by scientific data.7

3. Should patient/parent desires be considered when a treatment plan is developed? Absolutely, but only if the patient/parent desires are1,7–9: • In harmony with the body of scientific evidence • Consistent with what can be reasonably delivered by the competent and caring orthodontic specialist PATIENT/PARENT DESIRES THAT ARE NOT CONSISTENT WITH THE SCIENTIFIC BODY OF EVIDENCE A patient who presents with minor mandibular crowding and a reasonably steep mandibular plane angle wants a “movie star” smile and a great occlusion—but no extractions! Fig. 9-1, A to C, shows the facial photographs of such a patient. Fig. 9-1, D and E, illustrates the occlusal views of the pretreatment casts. 120

The crowding is not severe. Fig. 9-1, F and G, shows the cephalogram, its tracing, and the cephalometric values. The patient was treated—according to the parent’s wishes—with no extractions. Fig. 9-1, H to M, exhibits a comparison of the pretreatment/ progress photographs. Is the face better or worse? Fig. 9-1, N and O, the pretreatment/progress cephalograms and their tracings (see Fig. 9-1, P and Q) confirm the fact that the teeth were not “retracted” as the patient/parent desired. Facial esthetics has been compromised as is evidenced in Fig. 9-1, H to M. What happened? The answer is quite simple. Parent desires were not consistent with the scientific body of evidence in orthodontics— evidence that speaks to expansion orthodontic treatment and facial esthetics. The fact that mandibular incisors must be uprighted in certain skeletal patterns in order to improve facial esthetics was forgotten during formulation of the treatment plan. Simply stated, the patient’s treatment plan and parents’ desires were not consistent with the body of knowledge in orthodontics. It is the clinician’s duty to explain all of these things to a family when the treatment plan is presented. Not to do so can be disastrous. The patient/parent must be made to understand that desires, at times, cannot be achieved unless preferences or wishes—in this case, no extractions—are modified. RESULTS THAT ARE CONSISTENT WITH THE SCIENTIFIC BODY OF EVIDENCE The patient and the parent requested “retreatment.” Four premolars were extracted. Fig. 9-2, A to D, shows the pretreatment/ posttreatment dentition. Fig. 9-2, E to M, illustrates the pretreatment, “progress,” and posttreatment facial esthetics. The cephalometric tracings (see Fig. 9-2, N to P) reflect the tooth movement. Fig. 9-2, Q to S, confirms that the patient has a pleasing smile at the cessation of treatment. These results were “reasonable.”10–12 The altered treatment plan and the patient’s altered expectations became harmonious with the scientific evidence. This patient wanted “straight” teeth and a nice smile that a flawed treatment plan could not deliver, so a scientifically sound plan was initiated.

4. Is there an underlying concept that should be considered when a treatment plan is developed? If so, how can the concept be simply and succinctly explained? A fundamental treatment planning concept that should be considered when every treatment plan is developed is that there is a finite dimension of the dentition.13 This concept has been expressed in various ways. Merrifield14 expressed it best

Treatment Planning • CHAPTER 9

FIG 9-1 Patient with minor mandibular crowding and a reasonably steep mandibular plane angle. A to C, Facial photographs. D and E, Cast occlusal views. F, Cephalogram. G, Tracing and values. Comparison of pretreatment with progress. H to M, Pretreatment (H to J) and progress (K to M) photos. N, Pretreatment cephalogram. O, Progress cephalogram. P, Pretreatment tracing and numbers. Q, Progress tracing and numbers.

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FIG 9-2 “Retreatment” of patient seen in Fig. 9-1. A and B, Pretreatment casts. C and D, Posttreatment casts. Comparison of facial esthetics. E to G, Pretreatment photographs. H to J, Progress photographs. K to M, Posttreatment photographs. Comparison of tracing and numbers: pretreatment (N), progress (O), and posttreatment (P). Q to S, Smiling photographs: pretreatment (Q), progress (R), and posttreatment (S).

when he stated that the dimension of the dentition concept has four premises, provided that the musculature is normal. PREMISE #1—ANTERIOR LIMIT OF THE DENTITION An anterior limit of the dentition exists (Fig. 9-3, A). Teeth must not be pushed forward off basal bone. If the teeth are too far forward, all objectives of treatment are compromised. The facial photographs (see Fig. 9-3, B to G) of this patient provide illustration of this important concept. The pretreatment photographs (see Fig. 9-3, B to D) reflect a mildly protruded facial profile. There was a need for moderate lip retraction. Teeth were pushed forward to eliminate minor crowding. The anterior limit of the dentition was violated.13–15 The lip

rocumbency is worse after treatment (see Fig. 9-3, E to G). p Facial esthetics was compromised because the anterior limit of the dentition was violated. PREMISE #2—POSTERIOR LIMIT OF THE DENTITION A posterior limit of the dentition exists (Fig. 9-4, A). Teeth can be positioned and/or impacted into the area behind the mandibular first molar in the mandibular arch even as they can be moved too far forward off basal bone. Easier than posterior movement of mandibular teeth is posterior movement of maxillary teeth. Maxillary posterior expansion is easy to accomplish but can lead to impaction of the second molars and, more often than not, vertical expansion.13


123

FIG 9-3 A, Anterior limit of the dentition. B to D, Pretreatment photos. E to G, Posttreatment photos.

A

B,C

FIG 9-4 A, Posterior limit of the dentition. B, Pretreatment cephalogram. C, Posttreatment cephalogram. D and E, Pretreatment facial photos. F and G, Posttreatment facial photographs.

A posterior dentition space discrepancy is a common problem. Second molars do not have room to erupt. The pretreatment cephalogram of a patient (see Fig. 9-4, B) exhibits a common problem that is a result of a posterior space

iscrepancy: impaction of the second molars. This patient was d subsequently treated with premolar extraction. The posttreatment cephalogram (see Fig. 9-4, C) and the pretreatment/posttreatment facial photographs (see Fig. 9-4, D to G) illustrate

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the resolution of a posterior discrepancy problem along with maintenance of facial balance and harmony.

5. Is there a way to “simplify” the treatment planning process by analyzing the malocclusion in “components”?

PREMISE #3—LATERAL LIMIT OF THE DENTITION A lateral limit of the dentition exists (Fig. 9-5, A). If the teeth are moved buccally into the masseter and buccinator muscles, relapse over the long term is likely to result. This fact has been repeatedly reported in the scientific literature.16 Most unstable of all lateral expansion is mandibular canine expansion. The mandibular casts (see Fig. 9-5, B to D) of a patient who was treated as a teenager with extraction—but with mandibular canine expansion—graphically illustrate this concept of the lateral limit of the dentition.

One way to analyze the malocclusion in a systematic manner is to examine a patient’s problem by studying: • The face • The skeletal pattern • The teeth By looking at each of these three separate yet related entities, the clinician can compile information that will be invaluable to the formation of a treatment plan.14–18

PREMISE #4—VERTICAL LIMIT OF THE DENTITION A vertical limit of the dentition exists (Fig. 9-6, A). Vertical expansion is harmful to facial balance and harmony in the sagittal plane except in deep bite, hypodivergent patients.17 To allow the maxillary and mandibular molars to extrude during treatment—in the moderate to high mandibular plane angle skeletal pattern—can lead to an unesthetic face. The pretreatment/posttreatment superimpositions of a patient (see Fig. 9-6, B) and the patient’s pretreatment/ posttreatment facial photographs (see Fig. 9-6, C to D) illustrate the point. The posttreatment face has a “stretched” appearance. In summary, orthodontists must recognize the limitations of the dental environment and plan treatment to conform to these dimensions when normal muscle balance exists.

THE FACE

6. What should be considered when a face is evaluated? To answer this question requires books! The orthodontic literature abounds with articles about “the face.” Many authors and investigators have studied the face. To answer this question requires more questions, the answers to which should guide the practitioner to a consideration of what role the face plays in the formulation of a treatment plan. The following questions, and the answers to them, should guide the clinician to make reasonable treatment planning decisions that will maintain a “good face” and, when possible, improve a “poor face.”19–21

7. What are the prerequisites for a “good face?” Prerequisites for a good face22–26 are: • The soft tissue chin should be nicely positioned in the facial profile: A patient who has a weak chin (i.e., a retrognathic mandible due to a serious skeletal convexity [Fig. 9-7, A to D]) cannot have a posttreatment face that has esthetic chin

FIG 9-5 A, Lateral limit of the dentition. B, Pretreatment cast. C, Posttreatment cast. D, “Relapse” cast.


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FIG 9-6 A, Vertical limit of the dentition. B, Superimposition tracing. C, Pretreatment facial photograph. D, Posttreatment photograph.

projection.27–31 A serious skeletal convexity generally predisposes a patient to a recessive chin after orthodontic treatment. • Conversely, a patient who has a Class II malocclusion but who has a fairly “strong” chin can have a more balanced face after orthodontic treatment (see Fig. 9-7, E to H): A patient who has a significant malocclusion but who has no serious skeletal convexity should have an orthognathic profile after proper treatment. • “Weak” lips predispose a patient to compromised facial esthetics: There is nothing an orthodontist can do about this problem, because the patient has inherently poor lip structure32 (Fig. 9-8, A and B). On the other hand, a patient with more lip fullness will always have a more pleasing face if treated properly (see Fig. 9-8, C and D). Additionally, there should be a definite curl, which measures 3 to 5 mm

in depth, to the upper lip. Lower lip form and curl must be in harmony with upper lip form and curl (Fig. 9-9).33

8. What measurements allow the clinician to quantify or measure a good face? There are several ways to quantify a pleasing face. A very simple way is to use the profile line. The profile line starts at soft tissue chin, touches the most prominent lip, and continues past the nose (Fig. 9-10, A and B). If the profile line lies outside the nose, the patient has a protrusion. If the profile line is inside the tip of the nose, the patient generally has pleasing facial balance. Merrifield34 used the profile line and suggested the angle that the profile line made with the Frankfort horizontal, which is called the Z angle, was an excellent way to quantify facial balance.35,36 A normal Z angle for a pleasing face is 72 to 78 degrees (see Fig. 9-10, C and D). Reed Holdway37 developed the Holdway

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FIG 9-7 Patient 1: A and B, Pretreatment photographs; C and D, posttreatment photographs. Patient 2: E and F, Pretreatment photographs; G and H, posttreatment photographs.

FIG 9-8 Patients with more lip fullness will achieve a more pleasing face. Patient 1: A, Pretreatment photograph. B, Posttreatment photograph. Patient 2: C, Pretreatment photograph. D, Posttreatment photograph.

FIG 9-10 A, Profile line to nose, drawing. B, Photograph. C, Z angle, drawing. D, Photograph.

FIG 9-9 Upper lip thickness. Lower lip form and curl.

angle, which he used to quantify facial balance (Fig. 9-11, A). Steiner38 developed a series of angles that he used to quantify facial balance (see Fig. 9-11, B). Ricketts39 used the facial esthetic line. He felt that a Caucasian patient who possessed facial balance had lips that were approximately 4 mm inside a line drawn from soft tissue chin to the tip of the nose (Fig. 9-12).


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FIG 9-11 A, Holdway analysis. B, Steiner analysis.

FIG 9-12 Ricketts analysis.

9. What factors affect facial balance/facial harmony? There are essentially three factors that influence facial balance or the lack thereof14,40–43: 1. The position of the teeth 2. The skeletal pattern 3. The soft tissue overlay

10. How do teeth affect facial balance? Facial balance is affected by marked protrusion and/or crowding of the teeth or, conversely, by retrusion of the teeth. The upper lip rests on the upper two-thirds of the labial surface of the maxillary incisors. The lower lip is supported by the lower one-third of the labial surface of the maxillary incisors; thus, lip protrusion or retrusion is a reflection of the position of maxillary incisors. Maxillary incisor position is directly related to the position of the mandibular incisors. Protruded teeth cause facial imbalance. Reduction of a protrusion improves facial balance (Fig. 9-13, A to D).44–49

11. What does the skeletal pattern have to do with facial balance? The underlying theme that surfaces from all artists and ortho dontic investigators is the concept that there cannot be good balance and harmony of the lower face unless the vertical

FIG 9-13 Reduction of a protrusion to improve facial balance. A and B, Pretreatment photos. C and D, Recall photos.

dimension is within normal limits. The most important prerequisite for facial balance is normal vertical dimension of the lower face. Poulton50 conducted a study on cervical traction and found that large lower anterior facial heights were most often associated with a displeasing face. In their article on soft tissue profile preference, DeSmit and Dermaut51 created three different series of nine profile photographs so that a total of more than 200 profiles could be ranked by graduate dental students. They found that differences in gender and orthodontic knowledge of the students seemed to have no significant influence on their esthetic preference. The results of their study confirmed the importance of anteroposterior deviations but suggested that unesthetic facial profiles that were a result of anteroposterior deviations were completely overshadowed by long-face features—the long-face feature being more unesthetic. Before discussing the abnormal, it is prudent to understand the normal. The “ideal” face is vertically divided onto equal thirds

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12. What part does soft tissue overlay or a maldistribution of soft tissue have on facial balance?

FIG 9-14 Divisions of the face.

by horizontal lines that approximate the hairline, the bridge of the nose, the ala of the nose, and menton (Fig. 9-14). These divisions of the face can be used by the clinician to help diagnose vertical dimension problems. For example, does a patient have a disproportionately long lower facial height because of vertical maxillary excess or because of excessive chin height?52–57 Conversely, is a short facial height caused by vertical maxillary deficiency or by short chin height? When using these accepted proportions as a guide, it is apparent that the patient shown in Fig. 9-15, A, has excessive lower anterior facial height, whereas the patient shown in Fig. 9-15, B, has diminished lower anterior facial height. A careful determination of the vertical proportion of the face is the first step in the diagnosis of a vertical dimension problem.

FIG 9-15 A, Excessive lower anterior facial height. B, Diminished lower anterior facial height.

Facial disharmonies that are not the result of skeletal or dental distortion are generally the result of poor soft tissue distribution.33–58 This problem needs to be identified during differential diagnosis and treatment planning so that needed dental compensations can be planned. The millimetric measurements of total chin thickness and upper lip thickness are essential components in any study of facial balance. Upper lip thickness is measured from the greatest curvature of the labial surface of the maxillary central incisor to the vermilion border of the upper lip. The total chin thickness is measured horizontally from the NB (Nasion-Pt. B) line extended to the soft tissue pogonion (Fig. 9-16). Total chin thickness should equal upper lip thickness. If total chin thickness is less than upper lip thickness, the mandibular anterior teeth must be uprighted further to facilitate a more balanced facial profile because lip retraction follows tooth retraction. THE SKELETAL COMPONENT

13. How does one begin to analyze the skeletal problem and its impact on a malocclusion? For simplicity, the skeletal analysis can be subdivided into three components: vertical, anteroposterior, and transverse. Like the discussion of the “face,” it is prudent to discuss the skeletal component of the treatment planning process. Again, books have been written about the subject. Many combinations of skeletal aberrations can exist.59–61 These may include, but are not limited to, the following: • Maxilla: Maxillary posterior alveolar excess and an inferiorly or superiorly positioned maxilla • Mandible: Mandibular posterior alveolar excess and short/ long mandibular rami Other abnormalities may include a superiorly positioned condylar fossa, an obtuse cranial base angle, and/or condylar resorption. Any of these conditions, with or without aberrant mandibular growth rotation, can be a causative factor in the skeletal discrepancy. It must also be understood that any malocclusion may present with a combination of skeletal problems. For example,

FIG 9-16 Soft-tissue thickness.


a patient with a significantly increased or decreased anterior facial height may have an anteroposterior problem and/or a transverse problem.

THE VERTICAL COMPONENT OF THE SKELETAL PATTERN PUZZLE

14. What factors influence a skeletal pattern in the vertical plane? There are several factors, but the two most significant ones seem to be condylar growth and dentoalveolar development.62–67 The role of “environmental factors” like swallowing and tongue posture continue to be debated.

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15. What does condylar growth have to do with the skeletal pattern and, ultimately, with treatment planning? Mandibular growth and growth rotation can unfavorably impact dentoalveolar development in both the maxilla and mandible.68 Björk and Skieller69 have performed numerous studies that have shown that the most common direction of condylar growth is vertical with some anterior component. Patients with a pronounced short lower anterior facial height (Fig. 9-17, A to C) generally exhibit upward and forward condylar growth. These individuals generally have a deep vertical overbite with a deep mentolabial sulcus and a strong overclosed appearance. In contrast, patients with long anterior facial height (see Fig. 9-17, D to F) have a more posteriorly

FIG 9-17 A to C, Patient with pronounced short lower anterior facial height. Facial photos (A and B) and cephalogram and numbers (C). D to F, Patient with long-face syndrome. Facial photos (D and E) and cephalogram and numbers (F).

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directed growth pattern of the mandibular condyle. These backward growth rotators have increased anterior facial height, a more posterior position of the chin, and, in extreme cases, an anterior open bite.70 Isaacson and colleagues71,72 and Schudy,73 following Björk’s reports, studied jaw rotation caused by vertical condylar growth. A succinct summary of the findings of these investigators is that forward mandibular rotation occurs when vertical condylar growth exceeds the sum of the vertical growth of the maxillary sutures and the maxillary/mandibular alveolar processes. When alveolar process growth exceeds condylar growth, backward rotation occurs, and the face becomes longer. An understanding of the effect of condylar growth on mandibular position is fundamental if the clinician is to adequately and appropriately diagnose a vertical dimension abnormality.

16. What role does dentoalveolar development have in the skeletal pattern scenario? Isaacson and colleagues72 studied dentoalveolar development in three groups of subjects: (1) those with short anterior facial height, (2) those with average anterior facial height, and (3) those with excessive anterior facial height. In patients with long anterior facial height, the mean distance from the occlusal plane to the inferior edge of the palate was 22.50 mm. This distance decreased to 19.6 mm for the average group and 17.1 mm for the group with short anterior facial height (low mandibular plane-sella nasion [MP-SN] angles). This difference of 5.1 mm of dentoalveolar development between the high-angle and low-angle groups has great significance when the vertically compromised skeletal pattern is studied.

17. As one considers skeletal problems during the treatment planning process, is the role of environmental factors clear? How should these factors be assessed? The role of tongue posture, swallowing, and breathing is a subject of debate, argument, and study. Their respective impact on the vertical dimension is in need of continued study and research. MOUTH BREATHING The relationship between mouth breathing, altered mandibular posture, and the development of malocclusion is not as clear cut as the theoretical outcome of shifting to oral respiration might appear at first glance. Airway obstructions that might be a result of large adenoids, tonsils, septum deviations, large conchae, or allergies are frequently observed in high-angle, long anterior facial height patients and may affect mandibular posture by allowing more freedom for posterior tooth eruption. This hypothesis is supported by Linder-Aronson74 who showed closing of the mandibular plane angle and reduction in the anterior face height after removal of adenoids and a tonsillectomy. Recent experimental studies have only partially clarified the situation. Current experimental data for the relationship between malocclusion and mouth breathing are derived from studies of the nasal/oral ratio in normal versus long-face children. The data from the study show that both normal and long-face children

are likely to be predominantly nasal breathers under laboratory conditions.75,76 In conclusion, it appears that mouth breathing may contribute to the development of orthodontic problems, but it is difficult to indict it as a primary etiologic agent. Clinically, most orthodontists should refer mouth breathers to an otolaryngologist for an evaluation. This problem should be evaluated carefully during the diagnosis of a patient with excess vertical dimension. SWALLOWING AND TONGUE POSTURE Many clinicians believe that if a patient has a forward resting tongue posture, the duration of this pressure, even if very light, could affect tooth position vertically or horizontally. Tonguetip protrusion during swallowing is sometimes associated with forward tongue posture.77 Others contend that tongue thrust swallowing has too short a duration to have an impact on tooth position. Pressure by the tongue against the teeth during a typical swallow lasts for approximately 1 second. An individual swallows 800 times per day while awake but has only a few swallows per hour while asleep. The total per day, therefore, is usually under 1000. One thousand seconds of pressure, of course, totals only a few minutes— not nearly enough time, it is argued, to affect the equilibrium. During treatment planning for the patient with a vertical dimension problem, the clinician must understand that condylar growth, sutural lowering of the maxillary complex, dentoalveolar development, dental eruption, and the patient’s oral environment/ habits are interrelated. There is generally not a single causative factor that predisposes the patient to excessive or too little vertical development of lower facial height. To simplify, one might conclude that when vertical condylar growth exceeds tooth eruption (alveolar development), forward mandibular rotation occurs. The result is increased posterior facial height and an increase in the ratio of posterior facial height to anterior facial height. Conversely, if dentoalveolar growth and tooth eruption are greater than vertical condylar growth, the resultant mandibular change is a backward rotation. The anterior facial height/posterior facial height ratio decreases. Environmental factors can play a role, but the role is, at times, difficult to assess and varies from patient to patient. THE ANTEROPOSTERIOR COMPONENT OF THE SKELETAL PATTERN

18. How can anteroposterior skeletal problems be assessed? Several cephalometric values can be used. The most common are: SNA: This angular value gives guidance in determining the relative horizontal position of the maxilla to cranial base. At the end of growth and development78 a range of 80 to 84 degrees is normal (Fig. 9-18). SNB: This value expresses the horizontal relationship of the mandible to the cranial base, and a range of 78 to 82 degrees indicates normal horizontal mandibular position.78 If the value is below 74 degrees, it might indicate that orthognathic surgery would be a valuable adjunct to treatment. The same concern should be accorded a value of over 84 degrees (see Fig. 9-18).


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FIG 9-18 Sella-Nasion-Subspinale (SNA) indicates the relative horizontal position of the maxilla to cranial base. Sella-Nasion-Supramentale (SNB) expresses the horizontal relationship of the mandible to cranial base. FIG 9-20 A to C, Posterior crossbites are seen on these pretreatment casts. D to F, A “Brodie bite” is seen on these pretreatment casts.

A to C). Conversely, a patient who has a very low mandibular plane angle—the hypodivergent patient—will have a bypass bite, commonly referred to as a Brodie bite (see Fig. 9-20, D to F).

FIG 9-19 Subspinale-Nasion-Supramentale (ANB) expresses the horizontal relationship of the mandible to the maxilla. AO-BO quantifies the horizontal relationship of the mandible to the maxilla and is measured along the occlusal plane.

ANB: The normal range is 1 to 5 degrees. This significant value expresses a direct horizontal relationship of the maxilla to the mandible.79 As the Class II malocclusion becomes proportionally more difficult, the higher the ANB. An ANB above 10 degrees usually indicates that orthognathic surgery could be a possible adjunct to treatment. A negative ANB value is perhaps even more indicative of horizontal facial disproportion. For example, if the ANB is −3 degrees or more, and if the mandible is in its true position, careful monitoring with the possibility of surgical assistance for Class III correction could be indicated78,79 (Fig. 9-19). AO/BO: The relationship will verify the horizontal relationship of the maxilla to the mandible. It is perhaps more sensitive to malrelationships than ANB because it is measured along the occlusal plane.80–82 Treatment becomes more difficult if the value is outside the normal range of 0 to 4 mm. Since the measurement is made from a perpendicular to occlusal plane from Point A and Point B, it is affected by the steepness or flatness of the occlusal plane (see Fig. 9-19). THE TRANSVERSE COMPONENT OF THE SKELETAL PATTERN

19. How does the transverse skeletal problem generally manifest—or more simply stated, how is it seen? The transverse skeletal problem is most often seen when the dentition is carefully examined. A patient who has a very high mandibular plane angle (i.e., a hyperdivergent skeletal pattern) will, if a transverse problem exists, exhibit posterior crossbites (Fig. 9-20,

THE DENTITION

20. How can the dentition and space for the teeth, or lack thereof, be evaluated carefully? For most patients, a dental disharmony is manageable. To correctly diagnose the dental problem, a careful total dentition space analysis and a study of occlusal relationships are essential. The dentition can be divided into three areas: anterior, midarch, and posterior. This division is made for two reasons: simplicity in identifying the area of space deficit or space surplus and the possibility of arriving at a more accurate differential diagnosis.14–83 ANTERIOR SPACE ANALYSIS The anterior space analysis includes the difference in millimeters between the space available in the mandibular arch from the distal of the contralateral canines with the mesiodistal widths of all the six anterior teeth. Essentially, the space available is measured (Fig. 9-21, A to C). Space required is measured (see Fig. 9-21, D to I). The difference between these measured values is referred to as a surplus or a deficit. A cephalometric discrepancy, or the calculation of how much space is necessary if mandibular incisor uprighting is necessary, must be added to the anterior space surplus or deficit. Cephalometric discrepancy is a term that originated with Charles Tweed.84 He studied the cephalograms of 37 consecutively treated patients and integrated his findings with those of Brodie, Downs, and B. Holly Broadbent. He found that the patients who exhibited pleasing facial esthetics had a Frankfort mandibular incisor angle (FMIA) between 62 and 70 degrees, no matter what their Frankfort mandibular plan angle (FMA). This led Tweed to propose his formula for cephalometric correction (mandibular incisor uprighting) to arrive at a favorable FMIA for each patient. Tweed’s formula was: • FMA 21 to 29 degrees: FMIA should be 68 degrees. • FMA 30 degrees or greater: FMIA should be 65 degrees.

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FIG 9-22 Calculation of cephalometric discrepancy.

FIG 9-21 Anterior space analysis. A to C, Measurement of anterior space available. D to I, Measurement of space required.

• FMA 20 degrees or less: IMPA (incisor mandibular plane angle) should not exceed the original mandibular incisor inclination. Tweed measured his cephalometric correction on an x-ray by doing the following: • A cephalogram was made of the patient, and the Tweed triangle was drawn on the cephalogram with white ink. A dotted line that originated at the apex of the mandibular incisor was drawn upward to intercept the Frankfort plane at an angle of 65 degrees. The distance between the solid line, which was the existing inclination of the mandibular incisor, and the dotted line, which was the desired incisal inclination (measured at the incisal edge of the mandibular incisor), was the distance in millimeters that the mandibular incisors must be uprighted to satisfy the minimum requirement for an FMIA of 65 degrees. • The number of millimeters from the desired position of the mandibular incisor edge to the actual position of the mandibular incisor edge was multiplied by two because both sides of the arch had to be considered (Fig. 9-22). The sum of the anterior tooth arch surplus or deficit and the cephalometric discrepancy is referred to as the anterior discrepancy. MIDARCH SPACE ANALYSIS The midarch area includes the mandibular first molars, the second premolars, and the first premolars. Careful analysis of this area can show mesially inclined first molars, rotations, spaces, a deep curve of Spee, crossbites, missing teeth, habit abnormalities, blocked-out teeth, and occlusal disharmonies. This is an extremely important area of the dentition because it allows for space management for posterior malocclusion correction. A careful measurement of the space from the distal of the canine to the distal of the first molars should be recorded as available midarch space (Fig. 9-23, A and B). An equally accurate

FIG 9-23 Midarch space analysis. A and B, Midarch space available. C to H, Midarch space required. I, Measurement of depth of curve of Spee.


measurement of the mesiodistal widths of the first premolar, the second premolar, and the first molar should also be recorded (see Fig. 9-23, C to H). The lesser value is subtracted from the greater value. To the space surplus or deficit is added space required to level the curve of Spee. To calculate the amount of space required to level the curve of Spee, the greatest depth of the curve is measured on both sides (see Fig. 9-23, I), the values are summed, and the sum is subsequently divided by two.85 From these space analysis and curve of Spee measurements, one can determine the total space deficit or surplus in the midarch area. Although not a part of the actual midarch space analysis, occlusal disharmony, a Class II or Class III buccal segment relationship, must be measured because an occlusal disharmony adds a great deal to the difficulty of correction of any malocclusion and requires a careful treatment strategy. Occlusal disharmony is measured by articulating the casts and using the maxillary first premolar cusp as a reference.86 The clinician should measure mesially or distally from the maxillary first premolar buccal cusp to the embrasure between the mandibular first and second premolars. This measurement is made on both sides and is then averaged to determine the occlusal disharmony (Fig. 9-24). During the treatment planning process, it must be remembered that movement of the posterior teeth requires space management. POSTERIOR SPACE ANALYSIS This area of the dentition has great importance. Before any measurement of posterior space can be made, it must be understood that there is a posterior limit of the dentition. Rarely are healthy functioning mandibular teeth located posterior to the anterior border of the ramus. Regardless of age, the anterior

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FIG 9-24 A and B, Class II measurement.

border of the ramus appears to be the posterior limit of the dentition. The required space is the sum of the mesiodistal widths of the mandibular second molars and third molars (Fig. 9-25, A to C). The available space is more difficult to ascertain on the immature patient. It is: • A measurement in millimeters of the space distal to the mandibular first molar, along the occlusal plane, to the anterior border of the ramus (see Fig. 9-25, D) • An estimate of posterior arch length increase based on both age and sex A literature study suggests that 3 mm per year of increase occurs until age 14 for girls and until age 16 for boys.87–89 This would be 1.5 mm of increase on each side each year after the full eruption of the mandibular first molars. In mature patients, girls over 14 years old and boys over 16 years old, one can measure from the distal of the first molar to the anterior border of the ramus at the level of the occlusal plane and have a reasonably accurate determination of the space available in the posterior area of the dentition. It is of extreme importance

FIG 9-25 Posterior space analysis. A to C, Posterior dentition required space. D, Posterior space available.

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in diagnosis and treatment planning to know whether there is a space surplus or deficit in this area. The orthodontist should not create severe posterior discrepancies while making adjustments in the midarch and anterior arch deficits.

21. How can information assembled by a careful study of the facial, skeletal, and dental components of a malocclusion be assimilated so that it can be used during the treatment planning process? The answer is simple and yet very complex. First, analyze the face. Does the face need to be changed? If so, why? Is the cause of the problem skeletal, dental, or both? If it is skeletal, can orthodontics alone change it? Probably not. Changing it requires a surgical procedure. Is there a dental protrusion? If the face is protruded but the skeletal pattern is normal and the teeth are crooked and protruded, one can favorably change the face by extracting teeth. Is there dental retrusion? If the skeletal pattern is hypodivergent and the face is “straight,” facial change will be much more difficult or may not be desired. Suffice it to say that as a general rule, a rule to which there are always exceptions, the following concepts are very applicable to treatment planning: • The more hyperdivergent the face and the skeletal pattern, the more the mandibular incisors need to be upright over basal bone in order to achieve facial balance. If there is any crowding at all, teeth must be extracted if a favorable facial change is desired. The amount of crowding, the status of the dentition, the soft tissue overlay, and the amount of anteroposterior problem that exists determine the teeth to be extracted. • The more hypodivergent the skeletal pattern and the face, the more mandibular incisors need to remain in their pretreatment positions. Mandibular incisor uprighting will generally harm facial esthetics of these patients. However, if severe crowding is present, these patients must not be treatment planned so that the mandibular teeth are proclined from their original positions. Proclination of the teeth has deleterious effects on both the face and the stability of the teeth.90–93 Treatment planning is a very complex process. A multiplicity of factors must be considered. For this reason it is essential to organize the process by studying the face, the skeletal pattern, and, finally, the teeth. The interrelationship of these three components must be understood in order for a viable treatment plan to be developed.94–98 REFERENCES 1. Gianelly A: Evidence-based therapy: an orthodontic dilemma, Am J Orthod Dentofacial Orthop 129(5):596–598, 2006. 2. Johnston Jr LE: The value of information and the cost of uncertainty: who pays the bill? Angle Orthod 68(2):101–102, 1998 99. 3. Lee R, MacFarlane T, O’Brien K: Consistency of orthodontic treatment planning decisions, Clin Orthod Res 2(2):79–84, 1999. 4. Curtis DA, Lacy A, Chu R, et al: Treatment planning in the 21st century: what’s new? Calif Dent Assoc 30(7):503–510, 2002.

5. Huang GJ: Making the case for evidence-based orthodontics, Am J Orthod Dentofacial Orthop 125(4):405–406, 2004. 6. Sagehorn EG: Competency—that elusive quality, Am J Orthod 78(3):341–345, 1980. 7. Ackerman M: Evidence based orthodontics for the 21st century, J Am Dent Assoc 135(2):162–167, 2004. 8. Bass NM: From treatment planning to treatment results: the luck of the draw? Am J Orthod Dentofacial Orthop 118(2):142–149, 2000. 9. Graber TM: Pride in orthodontics, Am J Orthod Dentofacial Orthop 117(5):618–620, 2000. 10. Labarrere H: To extract or not to extract: is that the right question? J Clin Orthod 38(2):63–78, 2004. 11. Roberts-Harry D, Sandy J: Orthodontics. Part 4: treatment planning, Br Dent J 195(12):683–685, 2003. 12. Vaden JL, Kiser HE: Straight talk about extraction and non-extraction: a differential diagnostic decision, Am J Orthod Dentofacial Orthop 109(4):445–452, 1996. 13. Merrifield LL: The dimensions of the denture: back to basics, Am J Orthod Dentofacial Orthop 106(ll):535–542, 1994. 14. Merrifield LL: Differential diagnosis, Semin Orthod 2(4): 241–253, 1996. 15. Merrifield LL, Cross JJ: Directional force, Am J Orthod 57(5):435–464, 1970. 16. Joondeph DR: Retention and relapse. In Graber TM, Vanarsda RL, Vig KWL, editors: Orthodontics: current principles and techniques, ed 5, St Louis, 2012, Elsevier. 17. Merrifield LL, Gebeck TR: Orthodontic diagnosis and treatment analysis: concepts and values, part II, Am J Orthod Dentofacial Orthop 107(5):541–547, 1995. 18. Merrifield LL, Klontz HA, Vaden JL: Differential diagnostic analysis systems, Am J Orthod Dentofacial Orthop 106(12): 641–648, 1994. 19. Bowman SJ: Facial aesthetics in orthodontics, Aust Orthod J 17(3):17–26, 2001. 20. Peck S, Peck H: The aesthetically pleasing face: an orthodontic myth, Trans Eur Orthod Soc 47:175–185, 1971. 21. Riggio RF, Widamann KF, Tucker JS, et al: Beauty is more than skin deep: components of attractiveness, Basic Appl Soc Psychol 12(l):423–439, 1991. 22. Angle EH: The treatment of malocclusion of the teeth, ed 7, Philadelphia, 1907, SS White. 23. Langlois JH, Roggman LA, Musselman L: What is average and what is not average about attractive faces, Psychol Sci 5:214–220, 1994. 24. McNamara Jr JA, Brust EW, Riolo ML: Soft tissue evaluation of individuals with an ideal occlusion and a well-balanced face. In McNamara Jr JA, editors: Esthetics and the treatment of facial form, vol 28, Craniofacial growth series, Ann Arbor, 1993, Center for Human Growth and Development, University of Michigan. 25. Olds C: Facial beauty in Western art. In McNamara Jr JA, editors: Esthetics and the treatment of facial form, vol 28, Craniofacial growth series, Ann Arbor, 1993, Center for Human Growth and Development, University of Michigan. 26. Peck H, Peck S: A concept of facial esthetics, Angle Orthod 40:284–317, 1970. 27. Klontz HA: Facial balance and harmony: an attainable objective for the patient with a high mandibular plane angle, Am J Orthod Dentofacial Orthop 114:176–188, 1998. 28. Pearson LE: The management of vertical dimension problems in growing patients, the enigma of the vertical dimension. In McNamara Jr JA, editors: Craniofacial growth series 36, Ann Arbor, 2000, Center for Human Growth and Development, University of Michigan. 29. Tweed CH: Indications for the extraction of teeth in orthodontic procedure, Am J Orthod 30:405–428, 1994. 30. Vaden JL: Alternative nonsurgical strategies to treat complex orthodontic problems, Semin Orthod 2:90–113, 1996.

31. Wylie WL, Johnson EL: Rapid evaluation of facial dysplasia in the vertical plane, Angle Orthod 22(3):165–182, 1952. 32. Satravaha S, Schlegel KD: The significance of the integumentary profile, Am J Orthod Dentofacial Orthop 92:422–426, 1987. 33. Burstone CJ: Lip posture and its significance in treatment planning, Am J Orthod 53:262–284, 1967. 34. Merrifield LL: The profile line as an aid in critically evaluating facial esthetics, Am J Orthod 52:804–821, 1966. 35. Jacobs JD: Vertical lip changes from maxillary incisor retraction, Am J Orthod 74:396–404, 1978. 36. Hulsey CM: An esthetic evaluation of lip-teeth relationships present in the smile, Am J Orthod 57:132–144, 1970. 37. Holdway RA: A soft tissue analysis and its use in orthodontic treatment planning: part I, Am J Orthod 84:1–28, 1983. 38. Steiner C: Cephalometrics in clinical practice, Angle Orthod 29(l):8–29, 1959. 39. Ricketts RM: Perspectives in the clinical application of cephalometrics, Angle Orthod 51(2):115–150, 1981. 40. Czarnecki ST, Nanda R, Currier F: Perceptions of a balanced facial profile, Am J Orthod Dentofacial Orthop 104:180–187, 1993. 41. Herzberg BL: Facial esthetics in relation to orthodontic treatment, Angle Orthod 22(l):3–22, 1952. 42. Ricketts RM: Divine proportions in facial esthetics, Clin Plast Surg 9:401–422, 1982. 43. Steiner CC: Cephalometrics for you and me, Am J Orthod 39:729–755, 1953. 44. Angle EH: The treatment of malocclusion of the teeth and fractures of the maxillae, ed 6, Philadelphia, 1900, SS White. 45. Vaden JL, Dale JG, Klontz HK: The Tweed Merrifield Edgewise Appliance: philosophy, diagnosis and treatment. In Graber TM, Vanarsda RL, Vig KWL, editors: Orthodontics: current principles & techniques, ed 5, St Louis, 2012, Elsevier. 46. Tweed CH: A philosophy of orthodontic treatment, Am J Orthod Oral Surg 31(2):74–103, 1945. 47. Tweed CH: Clinical orthodontics, (vols. 1 and 2), St Louis, 1966, Mosby. 48. Tweed CH: The application of the principles of the edgewise arch in the treatment of Class II, Division 1, Part II, Angle Orthod 6(4):255–257, 1936. 49. Tweed CH: The Frankfort mandibular incisor angle (FMIA) in orthodontic diagnosis, treatment planning and prognosis, Am J Orthod Oral Surg 24:121–169, 1954. 50. Poulton DR: The influence of extraoral traction, Am J Orthod 53:8–18, 1967. 51. DeSmit A, Dermaut L: Soft-tissue profile preference, Am J Orthod 86:67–73, 1984. 52. Fields HW, Proffitt WR, Nixon WL, et al: Facial pattern differences in long face children and adults, Am J Orthod 85:217–223, 1984. 53. Isaacson JR, Isaacson RJ, Speidel TM, et al: Extreme variation in vertical facial growth and associated variation in skeletal and dental relations, Angle Orthod 41:219–229, 1971. 54. Pearson LE: Vertical control in treatment of patients having backward rotational growth tendencies, Angle Orthod 48:132–140, 1978. 55. Pearson LE: Vertical control in fully-banded orthodontic treatment, Angle Orthod 56:205–224, 1986. 56. Peck S, Peck L, Kataja M: The gingival smile line, Angle Orthod 62:91–100, 1992. 57. Schendel SA, Eisenfeld J, Bell WH, et al: The long face syndrome: vertical maxillary excess, Am J Orthod 70:398–408, 1976. 58. Burstone CJ: The integumental contour and extension patterns, Angle Orthod 29:93, 1950. 59. Björk A: Facial growth in man, studied with the aid of metallic implants, Acta Odontol Scand 13:9–34, 1955. 60. Björk A: Variations in the growth pattern of the human mandible: longitudinal radiographic study by the implant method, J Dent Res 42(1) Pt 2, 400–411, 1963.


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61. Sarver D, Proffit W, Ackerman J: Diagnosis and treatment planning in orthodontics. In Graber TM, Vanarsdall RL, editors: Orthodontics: current principles and techniques, ed 5, St Louis, 2012, Elsevier. 62. Björk A: Sutural growth of the upper face studied by the implant method, Acta Odontol Scand 24:109–129, 1966. 63. Björk A: The use of metallic implants in the study of facial growth in children, method and application, Am J Phys Anthropol 29:243–254, 1968. 64. Neilsen IX: Vertical malocclusions: etiology, development, diagnosis and some aspects of treatment, Angle Orthod 48: 130–140, 1978. 65. Schudy FF: Vertical growth vs. anteroposterior growth as related to function and treatment, Angle Orthod 24:75–93, 1964. 66. Skieller V: Cephalometric analysis in the treatment of overbite, Rep Congr Eur Orthod Soc 147–157, 1967. 67. Vaden JL, Pearson LE: Diagnosis of the vertical dimension, Semin Orthod 8(9):120–129, 2002. 68. Björk A: Prediction of mandibular growth rotation, Am J Orthod 55(6):585–599, 1969. 69. Björk 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 5(1):1–46, 1983. 70. Proffit WM: The development of orthodontic problems. In Proffit WM, Fields HW, editors: Contemporary orthodontics, ed 5, St Louis, 2013, Mosby. 71. Isaacson RJ: The geometry of facial growth and its effects on the dental occlusion and facial form, J Charles H Tweed Int Found 9:21–38, 1981. 72. Isaacson JR, Isaacson RJ, Speidel TM, et al: Extreme variation in vertical facial growth and associated variation in skeletal and dental relationships, Angle Orthod 41:219–228, 1971. 73. Schudy FF: The rotation of the mandible resulting from growth: its implications in orthodontic treatment, Angle Orthod 35: 36–50, 1965. 74. Linder-Aronson S: Effects of adenoidectomy on the dentition and facial skeleton over a period of five years. In Cook JT, editor: Transactions of the third international orthodontic congress, St Louis, 1975, Mosby. 75. Vig KWL: Nasal obstruction and facial growth: the strength of evidence for clinical assumptions, Am J Orthod Dentofacial Orthop 113:603–611, 1998. 76. Fields HW, Warren DW, Black K, et al: Relationship between dentofacial morphology and respiration in adolescents, Am J Orthod Dentofacial Orthop 99:147–154, 1991. 77. Ingervall B, Thilander B: Relationship between facial morphology and activity of the masticatory muscles, J Oral Rehabil 1:131–147, 1974. 78. Reidel RA: The relation of maxillary structures to cranium in malocclusions and in normal occlusion, Angle Orthop 22: 140–145, 1952. 79. Riolo ML, Moyers RE, McNamara JA, et al: An atlas of craniofacial growth, vol 2, Ann Arbor, 1974. 80. Jacobson A: Update on the “wits” appraisal, Angle Orthod 58:205–219, 1988. 81. Jacobson A: The “wits” appraisal of jaw disharmony, Am J Orthod Dentofacial Orthop 67:125–138, 1975. 82. Gramling JF: The probability index, Am J Orthod Dentofacial Orthop 107:165–171, 1995. 83. Merrifield LL: Differential diagnosis with total space analysis, J Charles H Tweed Int Found 6:10–15, 1978. 84. Tweed CH: Clinical orthodontics, vol. I, St Louis, 1967, Mosby, pp 252–265. 85. Baldridge D: Leveling the curve of spee: its effect on mandibular arch length, unpublished Master’s thesis, Memphis, June 1960, University of Tennessee. 86. Katz MI: Angle classification revisited 2: a modified angle classification, Am J Orthod Dentofacial Orthop 102(9):277–284, 1995.

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87. Richardson ME: Late lower arch crowding: the role of the transverse dimension, Am J Orthod Dentofacial Orthop 107: 613–617, 1995. 88. Richardson ME: The effect of mandibular first premolar extraction on third molar space, Angle Orthod 59(4):291–294, 1989. 89. Ledyard BC: A study of the mandibular third molar area, Am J Orthod 39:366–373, 1953. 90. Glenn G, Sinclair PM, Alexander RG: Nonextraction orthodontic therapy: posttreatment dental and skeletal stability, Am J Orthod Dentofacial Orthop 92:321–328, 1987. 91. Haruki T, Little RM: Early vs. late treatment in crowded extraction cases: a postretention evaluation of stability and relapse, Angle Orthod 68:61–68, 1998. 92. Little RM, Reidel RA, Artun J: An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention, Am J Orthod Dentofacial Orthop 93:423–428, 1988.

93. Little RM, Reidel RA, Engst ED: Serial extraction of first premolars: postretention evaluation of stability and relapse, Angle Orthod 60:255–262, 1990. 94. Little RM, Wallen TR, Reidel RA: Stability and relapse of mandibular anterior alignment-first premolar extraction cases treated by traditional edgewise orthodontics, Am J Orthod 80:349–365, 1981. 95. Little RM: Stability and relapse of mandibular anterior alignment: University of Washington studies, Semin Orthod 5:191–204, 1999. 96. Nance H: The limitations of orthodontic treatment, Am J Orthod 33:253–300, 1947. 97. Paquette DE, Beattie JR, Johnston LE: A long-term comparison of non-extraction and premolar extraction edgewise therapy in “borderline” class II patients, Am J Orthod Dentofacial Orthop 102:1–14, 1992. 98. Vaden JL, Harris EF, Zeigler Gardner RL: Relapse revisited, Am J Orthod Dentofacial Orthop 111:543–553, 1997.

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10

Burcu Bayirli • Christopher S. Riolo • Michael L. Riolo

A

ll orthodontic appliances produce both desired and undesired tooth movements. The science and art of orthodontics are to balance forces in order to maximize the desired movement and minimize the undesired movement. This balance is achieved through proper decision making in three areas: (1) appliance selection, (2) appliance utilization, and (3) timing of appliance therapy. Appliance selection is critical for successful treatment outcomes. For instance, when selecting a functional appliance, one has to consider that certain functional appliances may lead to undesirably procumbent lower incisors. Proper appliance utilization is critical for minimizing undesired tooth movements, such as flaring of the lower incisors. If lower incisor flaring is a concern, a tissue-borne functional appliance or a tooth-borne appliance (such as a mandibular anterior repositioning appliance [MARA]) used in conjunction with fixed appliances using a full-size lower archwire can minimize lower incisor flaring. In addition, the use of Class II elastics without establishing proper anchorage may lead to extrusion of posterior teeth, anterior open bite, and excessive tipping of the occlusal plane. Although proper appliance selection and utilization are two critical issues in effective orthodontic treatment, successful treatment outcomes may not be achieved without appropriate timing of appliance therapy. Using an orthodontic appliance at an inappropriate time may lead to ineffective treatment and result in undesired tooth movements. For example, the use of a rapid palatal expander (RPE) in a skeletally mature patient may cause excessive tipping of posterior teeth, lingual cusp interferences, anterior open bite, adverse periodontal consequences, and high potential for orthodontic relapse after treatment. Timing of appliance therapy also relates to the sequence of treatment events. Attempting space closure and anterior tooth retraction without proper anchorage preparation may lead to undesired tooth movements that cannot be reversed. Consequently, selection, utilization, and timing of appliance therapy are intertwined and involve a comprehension of tooth movement in the transverse, vertical, and anterior-posterior dimensions. TRANSVERSE DISCREPANCIES

•

1. Under what circumstances should a maxillary expansion appliance be used? Correction of dental and/or skeletal posterior crossbites that are either unilateral or bilateral.1–3

•

•

Correction of anterior crossbites associated with a functional shift or traumatic occlusion. Early expansion sometimes used in conjunction with a protraction facemask or upper fixed appliances on the lateral and central incisors can result in anterior movement of the dental alveolar complex through both dental and skeletal movement.2 Elimination of crowding through an increase in arch length. Correction of axial inclinations of posterior teeth. Mobilization of circumaxillary sutures to make skeletal protraction possible during facemask treatment. • •

2.

What are the different types of expansion appliances?

BANDED EXPANDERS Hyrax Expander The Hyrax expander consists of two bands on the upper first molars and usually two bands on the upper first bicuspids (Fig. 10-1, A). The Hyrax expansion screw located near the midpalate is soldered to the lingual surface of the bands. The expansion screw is usually activated one turn (approximately 0.25 mm) each day. If substantial expansion is required, the expander design should incorporate as many teeth as possible to minimize buccal crown torque (tipping rather than translation) and “hanging” lingual cusps. Excessive buccal crown torque should be avoided, since it can result in adverse periodontal sequelae, relapse of the maxillary constriction, and lingual interferences. Haas Expander The Haas expander is a fixed maxillary expander that uses acrylic pads and heavy lingual wires to apply pressure to both the teeth and the palatal tissue during expansion. This expander is thought to result in less tipping of the buccal tooth segments (see Fig. 10-1, B). The lingual wires are soldered to bands on the first bicuspids and the first molars and extend onto the palate where they are embedded in the acrylic pads. The Haas expander as well as the Hyrax expander moves the palate transversely and increases arch perimeter 0.7 mm for each millimeter of transverse expansion. BONDED RAPID PALATAL EXPANDER A bonded RPE is an alternative to the banded design. It is a fixed appliance that uses posterior acrylic coverage and is directly bonded to the teeth (see Fig. 10-1, C and D). The 137

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A

B

C

D

E

F

FIG 10-1 A, The Hyrax maxillary expander. B, The Haas maxillary expander. C and D, The bonded rapid palatal expander (RPE): palatal view (C) and frontal view (D). E, Removable Schwartz appliance. F, Fixed mandibular expander.

osterior blocks remove occlusal interferences and disocp clude the anterior teeth. Headgear tubes, archwire tubes, and reverse pull hooks for a protraction face mask can all be added as desired. This appliance is typically used when a more rigid appliance is desired to minimize tipping of the

(Continued)

buccal segments. It is preferred in mixed dentition patients who do not yet have their upper first bicuspids, but primary molars are present. In addition, it may be used for its bite block effect (impinging on freeway space) in patients with an open bite tendency.

Treatment Tactics for Problems Related to Dentofacial Discrepancies in Three Planes of Space • CHAPTER 10

G

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H

J I

FIG 10-1, cont'd G, Quadhelix. H, W arch. I, Pendex appliance. J, Lip bumper appliance. (A, B, E to I, Courtesy of AOA Orthodontic Appliances, Sturtevant, WI.)

LOWER SCHWARTZ APPLIANCE (REMOVABLE) The Lower Schwarz appliance (see Fig. 10-1, E) is used for minimal arch expansion in the mandible.4 This appliance is usually only activated once or twice a week, unlike the RPEs described previously.

W ARCH The W arch is similar to the quadhelix without the four helical loops (see Fig. 10-1, H). This appliance will lead to more dental expansion as opposed to skeletal expansion than a Hyrax or Haas maxillary expander.

FIXED MANDIBULAR EXPANDER A fixed mandibular expander is used as an alternative to the removable Schwarz appliance. This fixed metal expander provides lateral expansion in the mandibular arch (see Fig. 10-1, F). The lower fixed expander can be a good option when patient cooperation is an issue.

PENDEX The Pendex is a fixed expansion appliance that is also used to distalize and derotate one or both upper first molars (see Fig. 10-1, I). The Pendex appliance eliminates patient compliance concerns from the distalization treatment objective. A Haas expansion screw is usually incorporated into acrylic pads. This appliance can be designed with bands on the bicuspids and is frequently used in conjunction with wire rests that are bonded to the occlusal surface of bicuspids or primary molars to provide additional anchorage.

QUADHELIX This fixed metal expander is capable of applying forces in numerous directions depending upon how it is activated by the orthodontist (see Fig. 10-1, G). The four helical loops (two in the first bicuspid region and two in the first molar region) can be activated in unison or individually to achieve the desired results. The appliance is soldered to bands on the first molars, and lingual arms run from the bands forward to the cuspids or first bicuspids as desired. In general, the quadhelix is used if dental expansion is primarily desired.

LIP BUMPER A lip bumper (see Fig. 10-1, J) is a large-diameter round wire that extends from the mandibular first molar to first molar and rests in the buccal sulcus. It also has an acrylic pad in the anterior region. It can be used in either arch to distalize the first molars and promote transverse development of the arch

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by removing the pressure of the buccal tissues on the teeth and supporting structures. CONVENTIONAL FIXED APPLIANCES Archwires can be expanded transversely to achieve dental expansion in either the maxilla or the mandible.

3. Which expansion appliance should I use? Factors that influence the selection of an expansion appliance include, but are not limited to, the patient’s age or skeletal maturity, the clinician’s desire for dental versus skeletal expansion, the number of teeth available for anchorage, the expectation for patient compliance, and whether the expander will be used in conjunction with fixed appliances or other appliances, such as a facemask.5 In general, the more skeletally mature the patient, the number of teeth required for adequate anchorage to minimize dental movement increases. In addition, more rigid expansion appliances are generally required in more mature patients to minimize dental tipping of the buccal segments.

4. When should expansion be initiated? Treatment of crossbite with a functional shift should be initiated as soon as it is diagnosed. If not treated, these crossbites may adversely affect growth. If the mandible shifts to one side, growth will be asymmetric, and the chin will deviate to that side. Also, very narrow upper arches should be treated as early as possible. As the patient matures, it is hard to get skeletal expansion. These narrow upper arches are usually associated with significant crowding and are best corrected when the patient is skeletally immature. Expansion in skeletally mature patients may result in undesired dental movement; therefore, the best time to correct these constricted arches is usually in the mixed dentition. ANTEROPOSTERIOR AND VERTICAL DISCREPANCIES

5. How is Class II malocclusion corrected using fixed appliances? Correction of a Class II malocclusion using nonextraction orthodontic treatment with fixed appliances requires the distalization of the maxillary teeth and/or anterior movement of the mandibular teeth. Maxillary teeth can be distalized using extra-oral forces (e.g., J-hook headgear or facebow) or intraoral forces (e.g., Class II elastics or appliances such as the Distal Jet or Pendulum appliance) using the lower arch as anchorage.

6. What type of headgear or facebow should I use? Extra-oral traction can be used to achieve both tooth movement and modification of bone growth. The type of headgear used depends on the patient’s skeletal pattern. The direction of the pull may be adjusted accordingly so that a desirable skeletal and/or dental effect may be achieved and any undesirable effects may be avoided. For instance, a cervical pull headgear should not be used in a patient with hyperdivergent vertical

growth tendency, but it is an excellent choice in a hypodivergent patient. A hyperdivergent pattern is best treated with an occipital or high-pull headgear. Also, one must decide if tipping or bodily movement of teeth is preferred. Forces may be arranged to go through the center of resistance of a molar for bodily movement. For distal tipping, the force vector should be below the center of resistance of a molar.

7. When should extra-oral traction therapy be initiated? Extra-oral traction may be initiated in the mixed dentition, especially if a skeletal effect is desired. It may also be used in patients who are not growing if only tooth movement or anchorage is the goal.

8. What are the indications and contraindications for Class II elastics? INDICATIONS • Class II molar or canine dental relationship • Finishing orthodontic cases to achieve anterior coupling • Excessive overbite (deep bite) • Orthognathic facial profile CONTRAINDICATIONS • Class III skeletal discrepancy • Dental open bite or skeletal open bite tendency • Severe mandibular retrognathia • Insufficient wire dimension to resist extrusion of teeth associated with the use of Class II elastics • Excess lower anterior facial height

9. Under what circumstances should orthodontic extractions be considered? Orthodontic extractions should be considered if there is excessive tooth material for the available arch length. Also, extractions will facilitate the anteroposterior tooth movements needed to attain a Class I canine and molar relationship. In addition, patients with anterior dentoalveolar protrusion as well as patients with a skeletal open bite tendency may benefit from orthodontic extractions. Finally, extractions should be considered in noncompliant patients who refuse to wear headgear or elastics.

10. What are the treatment options to correct crowding problems? There are three basic ways to correct crowding problems: 1. Expansion of the dental arches, including distalization of the posterior segments of the dental arch 2. Extraction of permanent tooth mass 3. Reapproximation to reduce the mesial-distal width of selected teeth Expansion of the dental arches can be achieved with a variety of appliances. There are a number of factors that should be considered when selecting an expansion treatment tactic. For example, is the crowding problem caused by space loss in the dental arch, or is one or more of the dental arches constricted? If the arches are constricted, is the constriction primarily

Treatment Tactics for Problems Related to Dentofacial Discrepancies in Three Planes of Space • CHAPTER 10 ental or skeletal? Crowding as a result of space loss is usually d due to either ectopic eruption of the first molars or early loss of primary teeth. If space is not maintained after the early loss of one or more primary teeth, arch length loss can occur. If there is loss of arch length, the clinician must decide to either regain the lost space or maintain the remaining space. Another option is to defer treatment in anticipation of extracting permanent teeth. If the decision is made to regain the space, it is usually best to proceed with treatment as soon as practical. Regaining space caused by the mesial migration of posterior teeth (primarily the first permanent molars) is more easily accomplished before the eruption of the second permanent molars. Space loss caused by ectopic eruption most commonly involves the maxillary first molars (Fig. 10-2). Ectopic mesial eruption may necessitate the early removal of the second deciduous molars in order to allow full eruption of the permanent first molars before regaining the lost arch perimeter. Fig. 10-2 depicts a panoramic radiograph of ectopic maxillary first permanent molars and early resorption of the roots of the second deciduous molars. The extraction of permanent teeth can be used to correct tooth size/arch length discrepancies. In deciding which permanent teeth to extract, the practitioner needs to consider both anteroposterior and vertical discrepancies. After the crowding problem is resolved, how will an anteroposterior problem be addressed? Is there a facial asymmetry? If so, can an asymmetric extraction pattern facilitate the orthodontic mechanics? Is there an open bite tendency? If so, will extracting teeth more posteriorly help minimize increases in the mandibular plane angle? Usually, the easiest part of the orthodontic treatment is aligning the teeth. It is very important that the orthodontist think ahead about how a functional and stable canine Class I occlusion will be achieved and how the extraction pattern will either facilitate or impede the orthodontic mechanics. Reapproximation is the removal of tooth structure or restorative material from the mesial and distal surfaces of the teeth using abrasive strips or a high-speed handpiece.6 It can be

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used to gain space to mitigate slight or moderate crowding in the dental arch without increasing the procumbency of the anterior teeth. When reapproximation is carried out, care should be taken to maintain the interproximal contour of the teeth in order to avoid flat broad contacts.

11. When should serial extractions be considered? Serial extraction is the selected removal of both deciduous and permanent teeth (usually the first premolars) in order to allow severely crowded teeth to erupt into more desirable positions. It is imperative that patients are carefully followed after serial extractions. Space maintenance and guidance of eruption are usually required to avoid space closure with the molars and/ or canines in a severe Class II or Class III relationship. This sequential removal of primary teeth and permanent teeth is typically followed by comprehensive orthodontic treatment after eruption of permanent teeth has brought about as much improvement as it can on its own. INDICATIONS FOR SERIAL EXTRACTIONS • Minimum 7.0 mm of crowding in the anterior areas per arch • Coincident upper and lower midlines • Bilateral Class I molar relationship • Balanced skeletal pattern in all three planes of space COMPLICATING FACTORS FOR SERIAL EXTRACTIONS • Class III molar relationships • Class II molar relationships • Unbalanced skeletal patterns of any kind (transverse, anteroposterior, or vertical) • Unequal crowding in the maxillary and mandibular arches • Unequal crowding bilaterally in either arch • Midline discrepancies (more than 2 mm) • Open bites or impinging deep bites

12. Under what circumstances should orthodontic extractions not be considered?

FIG 10-2 Panoramic radiograph depicting ectopic maxillary first permanent molars and early resorption of the roots of the maxillary second deciduous molars.

In general, orthodontic tooth extraction should not be considered in Class II division 2 patients for the purpose of anteroposterior correction. An exception can be made in the case of severe crowding. In addition, space closure subsequent to orthodontic extractions can be a problem in patients with an obtuse nasolabial angle. Retraction of upper anterior teeth will increase the nasolabial angle even more and may result in an unpleasant profile in these cases. Moreover, caution should be taken with patients who are more susceptible to having adverse sequelae caused by orthodontic tooth movement. These patients include the following: • Patients who are periodontally compromised • Patients who have external root resorption from previous orthodontic treatment • Patients with short blunted root morphology • Patients with thin alveolar ridges

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Poor oral hygiene is also a problem, especially if oral hygiene deteriorates during treatment and decalcification becomes a serious issue. It is problematic to discontinue treatment until the extraction spaces are closed. Frequently, these spaces are difficult to close because of a generalized lack of cooperation in these patients.

13. Which teeth should be removed in order to facilitate orthodontic tooth movement for the correction of a Class II discrepancy? This question is very complex; therefore only general guidelines will be presented. Permanent teeth may be extracted in order to use anchorage to protract and retract key tooth segments in order to establish a Class I canine and molar relationship.7,8 There are a number of important considerations when contemplating permanent tooth extraction. These considerations include: • The degree of crowding in the dental arches • The proclination of the anterior teeth, periodontal support, and presence of lip competence • The interincisal angle and the palatal morphology immediately lingual to the incisors • The facial profile (orthognathic, retrognathic, prognathic, or excess lower anterior facial height) • Presence of skeletal or dental open bite or an open bite tendency • Thickness of the perioral soft tissue • Molar and canine relationship • Presence of maxillary and mandibular midline discrepancy— may require an asymmetric extraction pattern • Missing teeth • Periodontal condition or history of periodontal disease • History of external root resorption or short thin tapered root morphology • Anticipated level of patient cooperation When considering extractions as part of the orthodontic treatment plan and deciding which permanent teeth to extract, the orthodontist must consider whether or not each of the factors just listed will influence the treatment result if specific teeth are extracted. Most of the orthodontic extractions for the correction of Class II malocclusions involve premolars. Most commonly, maxillary and mandibular first premolars are chosen for extraction; however, in many Class II patients, it is worth considering the extraction of maxillary first premolars and mandibular second premolars so that the correction of the Class II molar relationship may be facilitated. In patients with a Class II molar relationship and minimal mandibular crowding, sometimes only maxillary premolars are selected for extraction. This treatment plan results in final Class II molar and Class I canine occlusal relationship. Moreover, if the Class II malocclusion is characterized by excessive lower anterior facial height and open bite or an open bite tendency, maxillary and mandibular second premolars are often considered for extractions.9 Also, asymmetric extraction patterns involving first premolars on one side and second premolars on the other side or unilateral premolar extraction are

commonly used to maximize mechanical advantage in the correction of asymmetric Class II malocclusions.

14. What types of functional appliances are available? Class II correction using functional appliances is achieved by changing the neuromuscular environment of the dentition to promote mandibular growth and guide both the eruption of the permanent teeth and development of the alveolus.10 There are many different designs, but all functional appliances have two characteristics in common: they disarticulate the teeth and position the mandible forward. Functional appliances can be categorized into two different broad groups with respect to design: tissue- and tooth-borne appliances. In general, tissue-borne appliances (e.g., a Fränkel appliance) (Fig. 10-3, A) produce less dental compensation than toothborne appliances. Tooth-borne appliances (see Fig. 10-3, B and C) can be further categorized into two classes: removable and fixed. Fig. 10-3, A and B, shows a MARA and a Herbst appliance, respectively, which are examples of fixed tooth-borne functional appliances. Fig. 10-3, D, depicts a Bionator, which is a type of removable tooth-borne functional appliance.

15. Which functional appliance should I use? Which functional appliance should I use? Removable or fixed functional appliance? Removable functional appliance

Will fixed appliances be used concurrently with the functional appliance?

Fixed functional appliance

Yes

No

Yes

No

Twin Block (without labial bow) or other similar appliance

Twin Block Bionator Fränkel or other similar appliance

MARA or other similar appliance

Herbst or other similar appliance

16. When should functional appliance therapy be initiated? The timing of an early phase of treatment using a functional appliance is a critical decision for the success of a two-phase treatment plan. It is important that the functional appliance therapy be initiated while substantial growth is remaining. A hand-wrist x-ray may be helpful in assessing whether the patient has substantial growth remaining.11 In addition,

Treatment Tactics for Problems Related to Dentofacial Discrepancies in Three Planes of Space • CHAPTER 10

143

A

B, C

D

FIG 10-3 A, Fränkel appliance. B, Mandibular anterior repositioning appliance (MARA). C, Herbst appliance. D, Bionator appliance. (Courtesy of AOA Orthodontic Appliances, Sturtevant, WI.)

r emovable functional appliances require a high degree of patient compliance. Therefore, the maturity of the patient should be considered before initiating an early phase of treatment using a removable functional appliance. Before the functional appliance can be delivered, the upper anterior teeth may need to be decompensated using fixed appliances on the lateral and central incisors so that the lower arch can be positioned into a Class I molar relationship without anterior occlusal interferences. In addition, the upper arch may require expansion in order to accommodate the lower arch in a Class I molar relationship.

18. Under what circumstances should orthodontic extractions be used for the correction of a Class III anteroposterior discrepancy? • Bimaxillary protrusion (in the absence of generalized spacing) • Anterior open bite or anterior open bite tendency • Either growth is nearing completion or the orthodontist is confident that the treatment plan has a high probability of success

17. When should protraction facemask therapy be initiated?

19. Which teeth should be removed in order to facilitate orthodontic tooth movement for the correction of a Class III discrepancy?

A protraction facemask is best used for a Class III malocclusion with a low to average mandibular plane angle. Young patients from 6 to 9 years of age demonstrate a greater skeletal response, whereas adolescents show a more dental response to protraction facemask wear.

Correction of Class III malocclusions can be achieved by the extraction of permanent teeth.8,12 The space provided by the extraction of permanent teeth is used to differentially p rotract and retract posterior and anterior teeth in the maxillary and mandibular arches to achieve a Class I molar and canine relationship.

144


C

A, B

FIG 10-4 A, Diagnostic setup—right. B, Diagnostic setup—frontal. C, Diagnostic setup—left.

Asymmetric extraction patterns can be used when correcting unilateral Class III malocclusions. Care should be taken if extracting primary teeth in place of missing succedaneous teeth, because closing the space resulting from agenesis of permanent teeth can be very difficult. Space closure by attempting to protract posterior teeth in the absence of substantial crowding can be particularly problematic. Bicuspid extraction allows for maximum correction of the Class III molar and canine relationship. Lower first and upper second bicuspid extraction provides substantial mechanical advantage when the treatment plan calls for correction of both the molar and canine Class III relationships. The extraction of the upper and lower first bicuspids is most desirable when the Class III malocclusion is characterized by a bimaxillary protrusion. Typically, differential anchorage is used to correct the molar and canine Class III relationship while uprighting the upper and lower anterior teeth. Four second bicuspid extractions are sometimes used when the Class III malocclusion is accompanied by a skeletal or dental open bite or a skeletal open bite tendency. In this case, differential anchorage is used to correct the molar and canine Class III relationship. The extraction of second bicuspids encourages protraction of posterior teeth and minimizes the tendency for the mandibular plane angle to increase. Lower first bicuspid extraction alone inevitably leads to a compromised treatment result that should be discussed with the patient before this treatment plan is implemented. As a result of this extraction pattern, a molar Class III and canine Class I relationship, usually characterized by a poor posterior occlusion, is achieved. This result may be an acceptable compromise when a surgical treatment plan is not feasible. A lower incisor extraction can be a good alternative to four bicuspid extraction13,14 especially in cases where: • It is desirable to leave the buccal occlusion intact • A treatment objective is to establish excess overjet for restorative purposes • It is a high priority to minimize treatment time (9 to 12 months) • A Bolton discrepancy exists

A diagnostic setup (Fig. 10-4) is always a good idea when contemplating a lower extraction treatment plan. REFERENCES 1. Hayes JL: Rapid maxillary expansion, Am J Orthod Dentofacial Orthop 130(4):432–433, 2006. 2. Pangrazio-Kulbersh V, Berger JL, Janisse FN, et al: Longterm stability of class III treatment: rapid palatal expansion and protraction facemask vs Lefort I maxillary advancement osteotomy, Am J Orthod Dentofacial Orthop 131(7):709–719, 2007. 3. Salemi G: A photogrammetric technique for the analysis of palatal three-dimensional changes during rapid maxillary expansion, Eur J Orthod 29(1):26–30, 2007. 4. O’Grady PW, McNamara Jr JA , Baccetti T, et al: A long-term evaluation of the mandibular Schwartz appliance and the acrylic splint expander in the early mixed dentition patients, Am J Orthod Dentofacial Orthop 130(2):202–213, 2006. 5. Gottlieb LE, Brazones MM, Malerman A, et al: Early orthodontic treatment. 2, J Clin Orthod 38(3):135–154, 2004. 6. Riolo ML, Avery JK: Essentials for orthodontic practice, Ann Arbor and Grand Haven, Michigan, 2003, EFOP Press. 7. Battagel JM: Profile changes in class II, division 1 malocclusions: a comparison of the effects of Edgewise and Frankel appliance therapy, Eur J Orthod 11(3):243–253, 1989. 8. Russell DM: Extractions in support of orthodontic treatment, NDA J 45(2):15–19, 1994. 9. Ngan P, Fields HW: Open bite: a review of etiology and management, Pediatr Dent 19(2):91–98, 1997. 10. Fränkel R: The theoretical concept underlying the treatment with functional correctors, Rep Congr Eur Orthod Soc 42:233–254, 1966. 11. Uysal T, Ramoglu SI, Basciftci FA, et al: Chronologic age and skeletal maturation of the cervical vertebrae and handwrist: Is there a relationship? Am J Orthod Dentofacial Orthop 130(5):622–628, 2006. 12. Battagel JM, Orton HS: Class III malocclusion: a comparison of extraction and non-extraction techniques, Eur J Orthod 13(3):212–222, 1991. 13. Bahreman AA: Lower incisor extraction in orthodontic treatment, Am J Orthod 72(5):560–567, 1977. 14. Kokich VG, Shapiro PA: Lower incisor extraction in orthodontic treatment. Four clinical reports, Angle Orthod 54:139–153, 1984.

Phase I: Early Treatment

C HA P T ER

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Laurie McNamara • James A. McNamara, Jr.

E

arly treatment, also known as Phase I treatment, represents orthodontic and/or orthopedic therapy that is rendered in the mixed dentition, typically with the expectation of a second phase of orthodontic intervention (Phase II) after the eruption of the permanent teeth.1 The goal of early treatment is to correct existing or developing skeletal, dentoalveolar, and/or muscular imbalances, thereby improving the overall oral environment before the eruption of the permanent dentition is complete. By initiating orthodontic and orthopedic therapy at a younger age, it is anticipated that many future abnormalities in the occlusion (e.g., crowding, excessive overjet, underbite) will be resolved with a relatively straightforward second phase of full fixed appliances in most instances. Thus, the frequency of complex orthodontic treatment involving permanent tooth extraction and/or corrective jaw surgery presumably is reduced. During the past 25 years, there has been increasing interest in early treatment, both within the orthodontic community and among the lay population, with articles on this topic appearing in prominent lay publications, such as the New York Times, the Wall Street Journal, and US News and World Report. Within the dental community, there has been increased attention to intercepting or modifying abnormal orofacial conditions that are recognized early. This growing interest has coincided with a general rise in the level of consciousness concerning preventive dentistry and medicine; parents often seek treatment for their children at a young age, based in part on an esthetics-driven society.

1. What are the contraindications to early treatment? Early orthodontic treatment is not always necessary or appropriate. Certainly not all orthodontic therapy delivered under the guise of “early treatment” is good treatment, as, for example, in instances of young patients being treated for extended periods of time with regimens that have ill-defined goals and unpredictable outcomes. In such situations, early treatment may serve only to increase treatment duration and cost; such intervention may result in patient and parental burnout. Early treatment is not indicated in those instances in which early intervention does not change the environment appreciably for dentofacial development and permanent tooth eruption.

2. Which problems can be treated effectively and efficiently during the mixed dentition? The orthodontist has many treatment options available, all of which have specific indications. The possibilities range from simple space maintenance to a variety of active orthodontic and orthopedic therapies. Experience obtained during the past three decades using early orthodontic and orthopedic intervention has guided our current philosophies regarding the appropriate timing of treatment for various clinical conditions. With the increasing emphasis on evidence-based treatments in both medicine and dentistry, we now are gaining an appreciation for the effects produced by specific protocols in patients of varying maturational levels.

3. What is the purpose of space maintenance? A fundamental concept for both general dentists and specialists to comprehend is the importance of maintaining the so-called leeway space, the space that becomes available during the transition from the second deciduous molars to the second premolars. In many borderline crowding cases, the maintenance of the leeway space may mean the difference between treating a patient with or without the removal of permanent teeth. On average, 2 mm of space per side can be gained in the maxillary arch and 2.5 mm of space per side in the mandibular arch because of the differences in the sizes of the second deciduous molars and the succeeding second premolars.2 To preserve such space, lingual wires attached to bands on the first molars may be placed at the time that the second deciduous molars have become mobile or have significant root resorption as seen on a panoramic radiograph. The major role of these wires in the late mixed dentition is to prevent the mesial migration of the first molars during the transition from the second deciduous molars to the second premolars. In the maxilla, a transpalatal arch (TPA; Fig. 11-1, A) extends from one maxillary first molar along the contour of the palate to the first molar on the opposite side. This appliance is capable of producing molar rotation and changes in root torque and angulation; the TPA may remain in place until the completion of the final comprehensive phase of orthodontic therapy.1 In the mandible, a lingual arch (see Fig. 11-1, B) that extends along the lingual contour of the mandibular dentition

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CHAPTER 11 • Phase I: Early Treatment

5. What is “serial extraction”?

A

B

FIG 11-1 A, The transpalatal arch (TPA) is used to maintain the leeway space during the transition from the mixed to the permanent dentition. It also can be used to rotate the maxillary first molars and to produce buccal root torque as necessary. B, The fixed lower lingual arch is used to maintain the lower leeway space during the transition of the dentition. It also can be used to widen the lower posterior dental arch following rapid expansion of the maxilla. (Illustration © James A. McNamara, Jr.)

from first molar to first molar may be used. The lower lingual arch is used less frequently than the TPA, because many patients undergoing early orthodontic treatment do not require the maintenance of the space in the mandibular second premolar region. Thus, the lower lingual arch is used only in patients in whom maximum anchorage is to be maintained. In contrast to the TPA, the lower lingual arch usually is removed as soon as the mandibular second premolars erupt fully into occlusion.

4. How do you treat patients with crowded teeth? Patients with developing moderate to severe tooth-size/archsize discrepancy problems often are treated effectively and efficiently at 8 or 9 years of age. Normally, this treatment is started after the permanent mandibular central and lateral incisors and the permanent maxillary central incisors have erupted. In many instances, there is insufficient space to allow for the unimpeded eruption of the maxillary lateral incisors. Depending on the size of the permanent teeth, either a serial extraction or an orthopedic expansion protocol can be used.

Serial extraction refers to the sequential removal of deciduous teeth to facilitate the unimpeded eruption of the permanent teeth. Such a procedure often, but not always, results in the extraction of four first premolars. The typical serial extraction protocol is initiated about the time of the appearance of the permanent lateral incisors, which erupt in rotated positions or are initially prevented from eruption by the deciduous canines (Fig. 11-2). In the most commonly used protocol, the first teeth to be removed are the deciduous canines. The removal of these teeth allows for the eruption, posterior movement, and spontaneous improvement in the alignment of the permanent lateral incisors. In about 6 to 12 months, the removal of the four deciduous first molars is undertaken, followed later by the extraction of the first premolars. It is common to observe that the adjacent teeth erupt toward the extraction sites, with the lower incisors often uprighting as well (sometimes too much so). As soon as the second molars near emergence, fixed appliances can be used to align and detail the dentition.

6. When is serial extraction indicated? According to Graber and colleagues,3 serial extraction may be indicated when it is determined “with a fair degree of certainty that there will not be enough space in the jaws to accommodate all the permanent teeth in their proper alignment.” A predicted tooth-size/arch-size discrepancy of 7 to 10 mm (or greater) is an indication for serial extraction.4,5 A primary factor to be evaluated when making a treatment decision concerning serial extraction is the size of the individual teeth. In instances in which tooth sizes are abnormally large, as indicated, for example, by the width of the erupted maxillary central incisors, serial extraction protocols may be appropriate. A central incisor with a mesiodistal width of 10 mm or greater indicates that the patient may have larger than average teeth.2 The presence of gingival recession and alveolar destruction on the labial surface of one or both mandibular central incisors also can indicate the need for this type of treatment regimen.3 An additional indication is the early loss of one deciduous mandibular canine and a resultant asymmetrical midline shift.

7. What are the contraindications for serial extraction? It is well known that serial extraction is not a panacea in all instances of tooth-size/arch-size discrepancy problems, and in fact this protocol is used relatively infrequently in our practice. Care must be taken to avoid lingual tipping of the lower incisors as well as unfavorable changes in the sagittal position of the maxillary and mandibular dentitions. In addition, the initiation of serial extraction procedures may result in unwanted spacing in the dental arches. Routine serial extraction protocols also are not indicated in situations of extreme skeletal imbalance. These protocols are not recommended in instances of full-blown Class II or Class III malocclusions because of the imbalance in the interarch relationship along with the emerging intraarch problem.

Phase I: Early Treatment • CHAPTER 11

A

D

B

147

C

E

FIG 11-2 Serial extraction protocol. A, The removal of the upper and lower deciduous canines (x) allows for an improvement in the alignment of the upper and lower incisors. B, The removal of the deciduous first molars encourages the eruption of the first premolars. Some clinicians choose to remove the first premolars at the same time to allow the lower canines to migrate posteriorly before emergence. C, The removal of the first premolars encourages the eruption and posterior movement of the permanent canines. D, The remaining teeth tend to tip toward the extraction sites. The lower incisors often tip lingually as well. E, After the second molars near emergence, fixed appliances are used to align the teeth and level the occlusal plane.1 (Illustration © James A. McNamara, Jr.)

8. What happens if the dental arches are too small to allow for the normal alignment of the teeth? In instances in which a serial extraction protocol is not appropriate, yet arch space is limited, orthodontic and/or orthopedic expansion may be indicated. Rapid maxillary expansion (RME)6,7 refers to the use of appliances that result in true orthopedic expansion of the maxilla, in that changes are produced primarily in the underlying skeletal structures rather than by the movement of teeth through alveolar bone. RME not only separates the midpalatal suture, but also affects the circumzygomatic and circummaxillary sutural systems. A goal of orthopedic treatment initiated in the mixed dentition is to reduce the need for extractions in the permanent dentition through the elimination of arch length discrepancies as well as the correction of bony base imbalances. The original protocol for RME was two turns per day (0.4 to 0.5 mm

of screw expansion), as advocated by Haas.6 In our practice, a one-turn-per-day (0.20 to 0.25 mm) protocol is used.1 Another alternative is “slow maxillary expansion,” which refers to h aving the expander turned once every second or third day.8

9. What types of rapid maxillary expansion appliances are available? Typically, there are three types of RME devices that are used: the bonded acrylic splint expander in mixed dentition patients and the Haas and Hyrax types for patients in the late mixed or permanent dentition. BONDED ACRYLIC SPLINT EXPANDER The acrylic splint type of appliance (Fig. 11-3) that is made from 3-mm-thick, heat-formed acrylic (splint Biocryl) has the additional advantage of acting as a posterior bite block because of the thickness of the acrylic that covers the occlusal surfaces

148


FIG 11-3 The acrylic splint rapid maxillary expansion (RME) appliance is bonded to the primary molars and permanent first molars. The splint is made from 3-mm-thick Biocryl rather than cold-cure acrylic. Brackets often are placed on the maxillary incisors for alignment of these teeth. (Illustration © James A. McNamara, Jr.)

HYRAX EXPANDER The Hyrax-type expander10 (Fig. 11-5, A) is a tooth-borne appliance that consists of bands on the maxillary first molars and first premolars. The use of bands on the maxillary first premolars is recommended if maximum expansion is desired or if a facial mask is to be attached to this appliance. A jackscrew is incorporated in its metal framework. There is no acrylic component to this appliance, making it the most hygienic style of expander. The Hyrax-type expander is more flexible than the two mentioned previously; its use may result in more tipping of the posteriorly teeth laterally. A variation of the Hyrax appliance is shown in Fig. 11-5, B. In this design, there are lingual bars extending anteriorly to the maxillary first premolars, but no bands are placed on these teeth. This modified design (termed by us a “U6 expander”) allows for the placement of maxillary fixed appliances while the expander is in place, hastening treatment.

of the posterior dentition. The posterior bite block effect of the bonded acrylic splint expander prevents the extrusion of posterior teeth,9 which is helpful in controlling the vertical dimension. HAAS EXPANDER The Haas-type expander6 (Fig. 11-4) is a tooth- and tissueborne style of appliance that consists of bands on the upper first molars and first premolars with a midline jackscrew incorporated in two acrylic pads that closely contact the palatal mucosa. This type of expander is used when maximal skeletal expansion is desired. The purpose of the acrylic pads is to minimize tipping of the posterior teeth. Inflammation of the palatal tissue is an occasional complication with this style of expander.

A

B

FIG 11-4 The Haas-type expander with an expansion screw incorporated in the palatal acrylic. This design is used in the permanent dentition when maximal skeletal expansion is needed. (Illustration © James A. McNamara, Jr.)

FIG 11-5 A, The Hyrax-type expander that is the most commonly used design in the early permanent dentition. B, A modification of this design also can be used in mixed dentition patients with bands around the maxillary first permanent molars and wires extending to the lingual of the maxillary deciduous molars. In this example, premolars instead of deciduous molars are shown. (Illustration © James A. McNamara, Jr.)


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10. What are the indications for maxillary expansion? One obvious indication for the use of RME appliances is the existence of a posterior and/or anterior crossbite. Orthopedic expansion also is used for other purposes, including increasing available arch length as well as correcting the axial inclinations of the upper posterior teeth. RME also can be used in the initial preparation of a patient for functional jaw orthopedics, facial mask therapy, or orthognathic surgery. RME also may have a secondary effect of widening the nasal cavity, thus reducing airway resistance and making it easier for some patients to breathe nasally.11

11. Can the lower jaw be expanded in the same manner? No, because a mid-mandibular suture fuses within the first postnatal year. The mandibular teeth usually erupt, however, with a lingual inclination, especially if the maxilla is narrow. Although orthopedic widening of the mandibular dental arch is not possible without surgical intervention, the teeth can be uprighted orthodontically with a removable lower Schwarz appliance1 (Fig. 11-6), especially if the maxilla subsequently is widened by way of RME.

12. Does a Class III malocclusion warrant early treatment? Class III malocclusions can be treated successfully through early orthodontic and orthopedic intervention. In the instance of a Class III malocclusion that is diagnosed in either the late deciduous or early mixed dentition, the onset of treatment may be earlier than for a Class I patient.12 The optimal time for beginning treatment (e.g., orthopedic facial mask, chin cup, Function Regulator Type 3 (FR-3) appliance of Fränkel) is coincident with the loss of the maxillary deciduous incisors and the eruption of the permanent central incisors. This earlier intervention obviously will result in a longer period of time between the start of the initial phase of treatment and the end of the comprehensive treatment

FIG 11-7 The orthopedic facial mask is attached to hooks on a bonded expander by way of strong elastics that produce up to 600 g of force. (Illustration © James A. McNamara, Jr.)

phase after the permanent dentition has erupted. Early treatment of Class III malocclusions also may be characterized by more than one period of intervention during the mixed dentition. The most commonly used protocol for young Class III patients is the orthopedic facial mask (Fig. 11-7) combined with a bonded (see Fig. 11-3) or banded expander, to which facial mask hooks are attached. This type of appliance combination has been shown to be effective in causing a forward movement of the maxilla while producing a distal force on the mandible, leading to the resolution of the underlying Class III relationship. These patients should be “overcorrected” during Phase I with an overjet of at least 4 to 5 mm achieved.13 Maximizing the vertical overlap of the anterior teeth also is a major treatment objective.

13. Does a Class II malocclusion warrant early treatment? That depends. Both Class II and Class III malocclusions, if they are severe, can lead to significant social problems during childhood. Thus, if a child has what can be termed a socially debilitating Class II malocclusion (i.e., patients who present with severe neuromuscular, skeletal, or dentoalveolar problems), early intervention is warranted. For the routine Class II patient, however, the timing of treatment is later than has been described previously for Class I and Class III malocclusions.

14. Are all Class II patients treated in the same way? FIG 11-6 The removable lower Schwarz appliance is used for mandibular dental decompensation before orthopedic expansion of the maxilla. Because there is no mid-mandibular suture, the appliance produces tooth tipping rather than bodily movement. (Illustration © James A. McNamara, Jr.)

If the Class II problem is related to a deficiency in mandibular development (which is the most common problem), a variety of functional jaw orthopedic appliances can be used to correct the sagittal problem with both skeletal and dentoalveolar

150


adaptations occurring. A delay in the use of functional jaw orthopedics (in patients with Class II malocclusions with mandibular skeletal deficiency) until the late mixed dentition or early permanent dentition period is recommended, because there is a greater growth response with functional appliances when treatment is initiated during the circumpubertal growth period (cervical stage 3 using the cervical vertebra maturation method14). Ideally, functional appliance therapy (e.g., Herbst appliance, Twin Block appliance) will be followed directly by a phase of fixed appliance therapy to align the permanent dentition. We have found that the most predictable and effective orthopedic appliance that can be used for the correction of Class II malocclusions is the Herbst appliance, which is the most widely used functional appliance in the United States today.1 The mandible is brought forward by the Herbst bite-jumping mechanism, bilateral devices that are attached to the maxillary first molars and mandibular first premolars by bands (Fig. 11-8, A)

A

or stainless steel crowns (which are our preference). The Herbst mechanism also can be connected to acrylic splints that cover both dental arches (Fig. 11-8, B).

15. What approach is used if the Class II problem is in the maxilla? If a child has a Class II problem characterized by maxillary skeletal or dentoalveolar protrusion, treatment with extraoral traction devices15,16 may be in order. The most commonly used headgear for such problems is the cervical-pull facebow (Fig. 11-9, A), which is a treatment approach that is highly dependent on adequate patient compliance. The inner bow of the facebow is attached to the maxillary first molars, and the outer bow is attached to elastics or to a retraction spring anchored to the neck pad. This appliance can be used to distalize the maxillary dentition and also as an anchorage device following extraction of two maxillary first premolars. An alternative appliance that is not so dependent on patient cooperation is the Pendex appliance17 (see Fig. 11-9, B). The Pendex appliance is a fixed intraoral appliance that can be used for both RME and to distalize maxillary molars efficiently and effectively. An alternative design of this appliance is the Pendulum, fabricated without the midline jackscrew.

16. Can any other treatments be provided to the Class II patient in the early mixed dentition? In many patients with a Class II malocclusion identified in the 7- to 9-year-old age range, treatment may be initiated at that time to handle any intraarch problems (e.g., crowding, spacing, flaring); interarch discrepancies (i.e., sagittal Class II problems) may be handled at a later time. In other words, the same protocols (e.g., orthopedic expansion, extractions) that can be used for Class I patients may be initiated in Class II patients with arch length discrepancies; however, the attempt to correct the anteroposterior skeletal relationship is best delayed until the late mixed dentition period in patients with mild to moderate problems.

B

FIG 11-8 A, The Herbst appliance with bands on the maxillary and mandibular first premolars and first molars. In other designs, stainless steel crowns are placed on the maxillary first molars and mandibular first premolars. B, The acrylic splint Herbst appliance. The maxillary portion of this type of Herbst appliance can be bonded or removable. The lower splint always is removable. (Illustration © James A. McNamara, Jr.)

17. What do you mean by “spontaneous correction” of Class II malocclusions? An interesting phenomenon occurs in some Class II patients who undergo RME in the early mixed dentition—a spontaneous improvement of the underlying sagittal relationship.18–20 As long as the maxilla is maintained in a widened relationship relative to the mandible during the transition from the mixed to the permanent dentition, it appears that the patient tends to posture the mandible forward to achieve a better dental interdigitation (as if the teeth act as an endogenous functional appliance). In some instances, the Class II relationship improves over time, a phenomenon not observed in untreated Class II individuals. If there is a residual Class II problem at the beginning of Phase II, definitive Class II treatment (e.g., Herbst appliance) is initiated.


151

B A

FIG 11-9 A, Cervical facebow. The inner bow has adjustment loops that also act as stops against the facebow tubes on the upper first molar bands. The outer bow is longer than the inner bow and typically is connected to an elastic neck strap or to elastics that attach to hooks on a cervical pad. B, The Pendex appliance of Hilgers. Locking wires connect the bands on the upper first molars to the acrylic button. These connecting wires are removed after the desired expansion has been achieved. (Illustration © James A. McNamara, Jr.)

18. How effective is early treatment in patients with vertical problems, such as open bite and deep bite? Most orthodontists believe that the vertical dimension is the dimension of the face that is the most difficult to correct therapeutically. From a diagnostic perspective, the clinician must differentiate between problems that are primarily dentoalveolar in nature and those that are more skeletally based. An anterior open bite, for example, may be related to a digital sucking habit. The discontinuation of the habit may resolve the problem with orthodontic treatment progressing smoothly. Vertical problems that have a significant skeletal component are a challenge. In a growing patient, increasing a short lower facial height may be accomplished most effectively with a growth guidance appliance, such as the Twin Block21 (Fig. 11-10) or the Function Regulator Type 2 (FR-2) of Fränkel.22 These types of appliances allow for increased vertical development in the growing patient by opening the bite vertically and allowing eruption of the posterior teeth. In the long-face patient, controlling the vertical dimension has been particularly difficult. For example, the treatment effects of a bonded rapid maxillary expander and vertical-pull chin cup23 (Fig. 11-11) have been shown to exist primarily in the mixed dentition and not as much in the permanent dentition.24

FIG 11-10 View of the modified Twin Block appliance of Clark.19 Bilateral bite blocks are located posteriorly in the maxillary appliance and anteriorly in the mandibular appliance. These acrylic blocks can be trimmed to allow for posterior vertical development. (Illustration © James A. McNamara, Jr.)

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FIG 11-12 Occlusal view of the acrylic maintenance plate that is worn following removal of the rapid maxillary expander to stabilize the achieved result. A labial wire is not used most of the time so that the clinician can determine the relapse potential of the maxillary incisors during the interim period. (Illustration © James A. McNamara, Jr.)

FIG 11-11 Lateral view of the vertical-pull chin cup. The hard acrylic chin cup is attached to the head strap by way of a springloaded connector. (Illustration © James A. McNamara, Jr.)

19. What is the duration of a Phase I treatment? Because treatment is being initiated during a time of skeletal maturation, the provider must have a thorough understanding of craniofacial growth and of the development of the dental arches in order to provide the patient with the most effective and efficient regimen of treatment. Every effort should be made to time the treatment appropriately in order to maximize the treatment benefit in the shortest period of time. Optimally, in the treatment of a mixed dentition patient, there should be a phase of treatment that has a defined duration as well as a predictable outcome. In general terms, an initial phase of treatment usually is approximately 1 year in duration, followed by intermittent observation during the transition from the mixed to the permanent dentition.

20. What happens between Phase I and Phase II? The time between the initial phase of treatment and the second phase of fixed appliances is termed by us the interim period. Patients typically are given a removable palatal plate (Fig. 11-12), usually without a labial wire. Patients are asked to wear this maintenance plate full-time for at least 1 year. They are seen every 4 to 6 months until the end of the transition to the permanent dentition when the second deciduous molars become loose. At that point, a TPA is used in about 90% of the patients; about 30% of patients benefit from a lower lingual arch. Fixed

appliances are placed after all of the permanent teeth (except third molars) are erupted or nearing eruption.

21. What occurs during Phase II? Phase II treatment consists of comprehensive edgewise ortho dontic therapy, which is treatment with full appliances. Phase II records are taken, and the malocclusion of the patient is reassessed. Even though a patient may have undergone RME during Phase I, it is not unusual (approximately 20% of patients) to have a patient undergo a second round of maxillary expansion if needed, usually with a Hyrax or U6 type of RME appliance. The profile of the patient is examined as well to see if the extraction of permanent teeth is needed. In patients who have undergone either RME alone or RME preceded by a lower Schwarz appliance in our practice, we still extract in about 10% of that patient subgroup. If the Class II molar relationship remains at the beginning of Phase II, our appliance of choice is the Herbst appliance combined with fixed appliances and later with Class II elastics. If a residual Class III relationship remains at the beginning of Phase II, facial mask hooks may be added to a Hyrax expander, and facial mask therapy is initiated at night. Following the placement of fixed appliances, Class III elastics are worn fulltime until the Class III relationship is resolved. In the case of a severe Class III malocclusion, the patient may be a candidate for surgical intervention using either Bollard Plates (after the eruption of the mandibular canines) or corrective jaw surgery once facial growth is complete. The typical duration of Phase II treatment is about 18 months, but the situation varies. If the patient requires only mild detailing of the occlusion, treatment may take only a year to complete. On the other hand, if extractions are required, the treatment duration may be 18 to 24 months.


22. What are the risks of delaying early treatment in instances in which it is indicated? In all cases of Class I, Class II, and Class III malocclusions, the loss of growth potential creates a situation in which an otherwise borderline case may be forced into the extraction and/or surgical category. The use of RME, functional appliances, molar distalization, or facial mask therapy is all dependent on the clinician’s ability to take advantage of the growth of a patient. In cases of a tooth size/arch size discrepancy, the greatest risk of delaying treatment is the resultant impaction or ectopic eruption of teeth. In the case of the maxillary canines, an ectopic eruption pattern could lead to loss of the root of the maxillary lateral incisor and/or the need for an exposure to bring the canine into the maxillary arch.

23. Do you have any final comments? The topic of early treatment continues to be controversial in the orthodontic community, with advocates on both sides of the issue. Part of the controversy is being put to rest, however, as new data emerge from both prospective and retrospective controlled studies of the treatment protocols used on young patients. The treatment protocols described in this chapter and elsewhere1 have been used routinely in our practice for over three decades. The protocols have been refined over time, but the basic concepts presented here have remained constant. Perhaps the most significant change in our thinking over time has been the treatment of the Class II patient. As described earlier, the treatment of this condition for most patients is delayed until the circumpubertal growth period. Only in those patients with socially handicapping problems is correction of the underlying sagittal problems attempted in the early or mid-mixed dentition. We still advocate intervention in the early mixed dentition for patients with Class III problems or tooth-size/arch-size discrepancies. When we consider the effects of early treatment, it is obvious that the easiest way for a clinician to alter the growth of the face is in the transverse dimension, orthopedically in the maxilla, and dentally in the mandible.18 Significant success also has been achieved in managing sagittal problems in growing patients. The management of vertical problems of a skeletal nature remains a significant challenge, whether these conditions are treated early or late. REFERENCES 1. McNamara Jr JA, Brudon WL: Orthodontics and dentofacial orthopedics, Ann Arbor, 2001, Needham Press. 2. Moyers RE, van der Linden FPGM, Riolo ML, et al.: Standards of human occlusal development. Monograph 5, Craniofacial growth series, Center for Human Growth and Development, Ann Arbor, 1976, The University of Michigan.

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3. Graber TM, Vanarsdall Jr RL, Vig KWL: Orthodontics: principles and practices, ed 5, St Louis, 2012, Mosby. 4. Ringenberg QM: Serial extraction: stop, look, and be certain, Am J Orthod 50:327–336, 1964. 5. Proffit WR, Fields Jr HW, Sarver DM: Contemporary orthodontics, ed 5, St Louis, 2013, Mosby. 6. Haas AJ: Rapid expansion of the maxillary dental arch and nasal cavity by opening the mid-palatal suture, Angle Orthod 31:73–90, 1961. 7. Haas AJ: The treatment of maxillary deficiency by opening the mid-palatal suture, Angle Orthod 35:200–217, 1965. 8. Hicks EP: Slow maxillary expansion. A clinical study of the skeletal versus dental response to low-magnitude force, Am J Orthod 73:121–141, 1978. 9. Wendling LK, McNamara Jr JA, Franchi L, et al.: Short-term skeletal and dental effects of the acrylic splint rapid maxillary expansion appliance, Angle Orthod 75:7–14, 2005. 10. Biederman W: Rapid correction of Class III malocclusion by midpalatal expansion, Am J Orthod 63:47–55, 1972. 11. Hartgerink DV, Vig PS, Abbott DW: The effect of rapid maxillary expansion on nasal airway resistance, Am J Orthod Dentofacial Orthop 92:381–389, 1987. 12. McNamara Jr JA: An orthopedic approach to the treatment of Class III malocclusion in young patients, J Clin Orthod 21: 598–608, 1987. 13. Westwood PV, McNamara Jr JA, Baccetti T, et al.: Longterm effects of early Class III treatment with rapid maxillary expansion and facial mask therapy, Am J Orthod Dentofacial Orthop 123:306–320, 2003. 14. Baccetti T, Franchi L, McNamara Jr JA: The Cervical Vertebral Maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics, Semin Orthod 11:119–129, 2005. 15. Kloehn SJ: Evaluation of cervical anchorage force in treatment, Angle Orthod 31:91–104, 1961. 16. Watson WG: A computerized appraisal of the high-pull facebow, Am J Orthod 62:561–579, 1972. 17. Hilgers JJ: The pendulum appliance for Class II non-compliance therapy, J Clin Orthod 26:706–714, 1992. 18. McNamara Jr JA: Maxillary transverse deficiency, Am J Orthod Dentofacial Orthop 117:567–570, 2000. 19. McNamara Jr JA, Sigler LM, Franchi L, et al.: Changes in occlusal relationship in mixed dentition patients treated with rapid maxillary expansion: a prospective clinical study, Angle Orthod 80:230–238, 2010. 20. Guest SS, McNamara Jr JA, Baccetti T, et al.: Improving Class II malocclusion as a side-effect of rapid maxillary expansion: a prospective clinical study, Am J Orthod Dentofacial Orthop 138:582–591, 2010. 21. Clark WJ: Twin block functional therapy, London, 1995, MosbyWolfe. 22. Fränkel R, Fränkel C: Orofacial orthopedics with the function regulator, Munich, 1989, S Karger. 23. Pearson LE: The management of vertical problems in growing patients. In McNamara Jr JA, editors: The enigma of the vertical dimension. Monograph 36, Craniofacial growth series, Center for Human Growth and Development, Ann Arbor, 2000, The University of Michigan. 24. Schulz SO, McNamara Jr JA, Baccetti T, et al.: Treatment effects of bonded RME and vertical pull chin cup followed by fixed appliances in patients with increased vertical dimension, Am J Orthod Dentofacial Orthop 128:326–336, 2005.

C H A PT E R

12

The Invisalign System

Orhan C. Tuncay • Jonathan L. Nicozisis • John Morton

A

lign Technology® introduced the Invisalign® System, an image-guided system of moving teeth, which was revolutionary at the time it appeared on the market in 1997. As revolutionary as it was, its clinical components are not all necessarily new. The clinician already knows how to fabricate a suck-down thermoplastic cover over the teeth. It is also known that if the thermoformed plastic does not fit the teeth passively, teeth will move enough to accommodate the fit of the plastic. In fact, many orthodontists, when faced with minor relapse of alignment, will advise their patients to seat and press down the old suck-down retainer to realign the teeth and it works. The reason we refer to this entire process as a “system” is because the Invisalign System is more than an appliance; it’s a mindset. The clinician must treat the patient virtually using the computer images long before touching even a single tooth. This process of predicting what should happen and when required significant clinical experience in the earlier days. Recently, the force systems generated by the aligner are better understood, and consequent novel attachment designs are now routinely offered. The benefit of novel attachment designs and plastic material is that the clinician can now have success in tooth movements that were considered difficult or impossible in the earlier versions of the system. The best cases for the beginner or occasional user of Invisalign are those with spacing problems devoid of any skeletal disparities. The result is consistently predictable and the process is comfortable. Treatment shown in Fig. 12-1 supports this statement. The Invisalign System consists of mindset, software, impressions or scans (instead of bracket placement), working with the computer, understanding physical properties and behavior characteristics of the plastic and ensuing force systems that act on teeth via the attachments, as well as patient management. Just as any other appliance system, Invisalign has many remarkable strengths and some weaknesses. The clinician should know these and plan a treatment strategy accordingly; this strategy includes “treatment objectives.” Clearly, Rome was not built overnight, nor was the edgewise appliance developed overnight—and neither will Invisalign reach its level of perfection overnight. Thus, comparisons of performance to other appliances would be inappropriate. Invisalign is used both for adult and teenage patients. Treatment objectives for these two groups may need to differ. In the adult patient, attrition of the teeth is significant, 154

mutilation is common, and patient desires are not occlusionspecific. None of these elements is conducive to assessing the outcome of treatment by quantitative means. Instead, the Invisalign-treated adult case can be judged only qualitatively. In the teenage patient, however, the more conventional goals and outcomes of treatment are possible.

1. Historically, what appliances preceded Invisalign? Prior to introduction of the Invisalign System, the most widely used appliance was an adjunct to fixed appliances, which was worn once the bands and brackets were removed. The Positioner introduced by Kesling (1945) was originally made out of vulcanite material and aided the settling-in process, but it was also useful in correcting certain tooth positions that could not be finished for one reason or another by fixed appliances.1 Later, latex became the standard material to manufacture. But even earlier, Remmensnyder had introduced the Flex-O-Tite gummassaging appliance in 1926 to aid in the treatment of gingival disease.2 He reported that he was observing tooth movements as a side effect. The first thermoformed plastic sheet to move teeth was invented by Nahoum in 1964.3 He called it the Dental Contour Appliance. Subsequently it was modified by Sheridan (1993) and called the Essix appliance.4 Invisalign (1997) takes the principles behind these appliances and manufactures series of Invisalign aligners to move teeth using the computer-aided design (CAD)/computer-aided manufacturing (CAM) and robotic technology.

2. How are polyvinyl siloxane impressions converted to digital images and subsequently to aligners? What is the difference between scanned impressions and teeth scanned with an intraoral scanner? In the manufacture of aligners, a number of imaging technologies have been used. Initially, a laser scanner manufactured by Cyberware was tested, but the undercuts were hard to capture. To improve the speed of image capture, the earlier Invisalign-branded aligners were created from images generated by the destructive scanning process. In this process, layers of two-dimensional (2D) images are stacked to form a three-dimensional (3D) image. Unfortunately, this technique is lengthy, expensive, and messy. Structured light was a popular method to capture the image of a surface, but it too

The Invisalign System • CHAPTER 12

A

155

B

FIG 12-1 This patient in his early 70s exhibits no gingival tissue bunching in contrast to what might be often seen in fixed appliance and elastic chain mechanics. A, Before. B, After.

was not accurate enough; it did not provide enough detail of undercuts and interproximal gaps. Currently, computed tomography (CT) scanning is used, avoiding the need for impressions to be poured. The benefit of scanning the teeth directly in the patient’s mouth with the intraoral scanner is the loss of slack between the impression material and teeth. It yields better accuracy. The manufactured thermoplastic too, has a noticeably better fit. These benefits are in addition to shortening of turnaround time; it is instantaneous. Rather than waiting for the post to arrive at Align® and hope the impressions will arrive devoid of distortions, the scanned images are sent over the Internet and arrive at Align instantaneously. The downside of scanning patient’s teeth is that it could take longer than polyvinyl siloxane (PVS) impressions. This statement assumes there are no retakes of the impressions. If the technician is not highly skilled in impressions, it could take longer than scanning. The scanning is done in 20 minutes, on average. Some technicians are several minutes faster. An added benefit of scanning is the lack of mess left behind after impressions are taken. It should be noted, inherently, the scanning process is intermittent. The fan that blows air to clear any fogging also makes the mouth very dry. Patients often need to stop to take a sip of water to recover from mouth dryness. A favorable tool built into the intraoral scanner software is the simulation. It looks like ClinCheck™, although it is not, and is designed to line up the crowded teeth. Once the scanning is completed, patients can see their estimated, not predicted, anterior tooth alignment. Until recently, light-cured polymer molds were manufactured from the CT scans of PVS images. This process is known as stereolithography (SLA). This series of molds created for each patient is used to thermoform the plastic sheet. This process is now delegated to 3D printing to print out the polymer molds. Thus, scanning, 3D printing, Optimized Attachments, and the new plastic material, collectively, took Invisalign System performance to a level where tooth movements happen more predictably and reliably. Trimming of the thermoformed plastic is done by robots. It is guided by the level of gingival margins. It is critical, therefore, that the impression or the scanning capture the gingival margins perfectly. Prior to packaging and shipping, Invisalign aligners are disinfected.

3. What is the process and software involved in creating the Invisalign-branded aligners? The CT images of PVS impressions are transferred to a special software called Treat™ software.5 It has a number of components that perform different functions. Initially, imperfections of the impression are smoothed out and then submitted to the ClinCheck technicians. Smoothing has become less laborious or obsolete in the intraoral scanned images. Steps involved in the manufacturing process are: 1. Segmentation: Virtual cutting of the teeth 2. Final setup: The desired end result of orthodontic treatment 3. Staging: How to incrementally get to the final result 4. Design and placement of attachments guided by the software that analyzes the forces transmitted to the (virtual) roots of teeth 5. Review: Inspection of ClinCheck by the clinician 6. Fabrication: Production of SLA models and thermoforming the plastic to fabricate the Invisalign aligner

4. What are the force systems generated in the Invisalign aligner that act on each tooth? This is an area of significant research interest both in fixed appliance systems and with the plastic aligners. Currently, it is not fully understood.6 Certainly, one could measure the force systems active at the time of insertion of archwires or a ligners, but as soon as the appliance is inserted, the measured force systems all change. Practically, our current understanding of orthodontic biomechanics is limited to the first millisecond of tooth movement. Movements of adjacent teeth; the nature of periodontal response to force; precision of brackets, wires, attachments, plastic; and the way the patient handles the hardware all affect the force systems. The recent addition of FEA-generated algorithms into the design of attachments now allows better control of individual root movements. What needs to be resolved, however, is the influence of adjacent teeth. By its nature, software assumes that every tooth and root will be compliant. As the experienced orthodontist knows, it is hard to predict if teeth will move as hoped. They usually don’t. There are many reasons for this stubbornness, but p rincipally they are gingival tissues, bone, medications, occlusion, and adjacent teeth.

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CHAPTER 12 • The Invisalign System

Gingival tissues respond and remodel during tooth movement with the Invisalign aligner most favorably. It must be noted, however, that the thick or thin character of the collagenous structures of gingival tissue affects tooth movement. Bone, too, is compliant except in conditions such as idiopathic osteosclerosis, an obstruction from overgrowth or cystic formations, or lining of the maxillary sinus. Medications or hormonal fluctuations inhibit or accelerate tooth movement in a systematic fashion: all tooth movements are affected. The two principal medications are non-steroidal anti-inflammatories (NSAIDs) and bisphosphonates. NSAIDs interfere with the wound-healing type nature of orthodontic tooth movement, and bisphosphonates block osteoclastic activity.7 The orthodontist also knows teeth move faster when the gingival tissues are inflamed and when the patient is pregnant. The latter is due to the presence of the hormone relaxin in circulation.8 It relaxes the collagenous tissues such as the periodontal ligament and sutures of adjoining bones. The “locking” effect of occlusion is known empirically, which is fine as it is nearly impossible to design a good study to prove the already known fact. Orthodontists know the disarticulated teeth move faster and more predictably. As much as the plastic is a separating medium, tightness of occlusion still is an obstruction. Adjacent teeth influence is a difficult problem to overcome. If the adjacent teeth don’t do what they are supposed to, and get out of the way, the middle tooth does not move much. In the fixed appliance systems, the wires overpower the biology and achieve the movement in the absence of heavy occlusion or other obstructive elements mentioned earlier. The Invisalign System is based on the premise that light intermittent forces move teeth best. This premise promotes gingival tissue compliance to remodel, to eliminate root resorption concerns, but it does not overpower. The new Treat software has corrected the earlier problem of assuming all teeth in the mouth move the same: molars no different from incisors, for example. This is a significant improvement that waits to be perfected. Meanwhile, the orthodontist finds some solution in instructing the patient to wear the aligner longer. Unfortunately, this approach has limited effectiveness. The best clinical tip is not to let teeth ever lose tracking.

5. What are the issues that surround forces generated within the Invisalign aligner over a long duration? Do different plastic materials behave significantly differently? Thermoplastic materials are viscoelastic; thus, their properties are time-dependent. Invisalign aligners stretch and fit over the tooth that is programmed to move. While the stretched aligner is trying to move the tooth, it is held at constant strain. In turn, stress relaxation within the plastic material sets in, and the forces generated by the aligner decrease with time. This process is accelerated in a moist and warm environment.9 The newly introduced thermoplastic material (SmartTrack™) was developed to address this problem. The most significant feature of SmartTrack is its resistance to deformation. This characteristic

maintains lighter and more constant force over a longer period of time because of reduced stress relaxation.

6. Does thicker aligner material (Ex40) yield better tooth movement? Increasing the thickness of the aligner material by 0.010 inch from 0.030 to 0.040 inch increases the stiffness of the aligner by approximately one-third. This concept is not dissimilar to what is seen in the behavior of orthodontic wires. But clinical trials provide no indication that a thicker aligner is better in finishing a case. Also, the increased thickness does not affect the quality of tooth movement during the active treatment phase.10 Certainly, as a retainer material, the thicker 0.040 inch is more robust to hold teeth in place. Meanwhile, SmartTrack appears to be the most suited thermoplastic to move the teeth.

7. Can tipping of teeth be controlled in premolar extraction cases? Tipping of teeth into the extraction space is nearly impossible to avoid, even with fixed appliances. We had attributed the tipping of anchorage teeth during Invisalign treatment to archlength/aligner-length discrepancy.11 Tipping is most notable and exaggerated in the adult. The root apices will simply not move very well, especially if the roots of maxillary buccal teeth are in the maxillary sinus (as viewed in the panoramic radiograph). This is because the lining of maxillary sinus does not remodel readily (Fig. 12-2). There are numerous other conditions that precipitate tipping. To mention a few: depth of overbite, crown-to-root ratio, gingival resistance, sclerotic bone, occlusal contacts, crown morphology, and indifference of the orthodontist to carefully study the ClinCheck images and movements. Complex attachment designs for teeth adjacent to the extraction site help reduce the tipping, but, at present, sectional fixed appliances are necessary almost every time. Another common problem seen after the extraction space is closed is leveling of marginal ridges. First and second molar marginal ridges rarely align properly. The sectional fixed appliance should be fabricated to fix that problem simultaneously as it parallels the roots. The orthodontist is advised to employ prominent attachments to prevent the problem of tipping to the extent possible and consequently worry less about correcting the tipped tooth positions. In premolar extraction cases, tipping of the molars is the most problematic; it should not be allowed (Fig. 12-3). To prevent tipping, the orthodontist may employ long and prominent molar attachments (5 mm long, 1 mm wide, and 1.5 mm prominent) placed as mesially as possible. An aggressive anchorage preservation and prevention of tipping is to use miniscrew implants to immobilize the molar positions. In addition to these prominent attachments, it is advised to avoid any measure to soften the plastic. This may be achieved by 1) not using pontics at the extraction spaces and 2) with the aid of sequential movements rather than en-masse. It is critical that the aligner “cups” the tooth for controlled tooth movement. It is prudent to use segmental mechanics to move


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A A

B

C

FIG 12-2 A, The ClinCheck initial tooth positions. B, The desired ClinCheck end of treatment tooth positions. Note all roots are presumed to finish parallel with the posterior teeth stable. C, Typical appearance of tipped teeth during premolar extraction treatment with Invisalign. Blue is where the ClinCheck teeth were supposed to be. The white teeth are where they mostly end up. The shortened aligner applies equal force on the anterior and posterior teeth. In the absence of measures that prevent tipping of premolars and molars, both upper and lower teeth tip mesially. Experience shows such tipping happens more readily in the mandibular arch, compared to the maxillary.

B

C

FIG 12-4 A, Lower incisor crowding condition planned for extraction treatment. B, Note the teeth are moved “one at a time.” This strategy allows the aligner plastic to “cup” the tooth on all surfaces and prevent tipping. Aligner plastic must be allowed to go in-between adjacent teeth. C, The “cupping action” allows bodily tooth movement.

tooth movements are equally affected (albeit, at opposite ends) by the compliance of surrounding periodontal tissues.

8. What are the advantages of Optimized Attachments and SmartTrack combination in Invisalign performance?

FIG 12-3 Prominent attachments around the extraction sites to minimize tipping of posterior segments.

as few as one tooth at a time. Figure 12-4 is a treatment strategy where following the extraction of one incisor, teeth are moved one at a time to prevent the incisor from tipping. In this scenario the moving tooth is cupped on the mesial, as well as the distal. It must be noted, however, that young teenage patients introduce very few problems with root control. We attribute their favorable response to the willingness of periodontal tissues to remodel readily. Indeed, the biomechanics of young and adult

It is well accepted in orthodontics that if the force systems produced by the appliance are correct for the desired tooth movement, the probability of achieving it is greater. Orthodontists have long known force systems are controlled by the material composition and design of the appliance, but also the activation of the appliance. This relationship, the pairing of a material and activation, holds true in the aligner systems as well. In the SmartTrack material, activations are the stages. Such activation combined with Optimized Attachments yield good control of the force systems delivered to the teeth; better than was previously possible. SmartTrack material was developed specifically for the Invisalign System. It possesses several characteristics that make it an excellent thermoplastic material for aligner treatment. The material exhibits excellent thermoformability, which makes for a better fitting aligner. Closer fit translates into better control


158

MATERIAL STRESS RELAXATION

Smart Track‰

FORCE

Standard Aligner Material

TIME

DAY 14

Forces measured in simulated oral environment

FIG 12-5 SmartTrack material stress relaxation.

of the contact points. Contact points are where the forces are delivered. Intimacy of forces between the plastic and tooth surfaces is the reason for the improved control of tooth movement, better tracking, and better finishing. Periodontal tissues around the teeth respond favorably to light and constant forces. SmartTrack produces more constant force than previous aligner materials. This was accomplished by controlling the stress relaxation of the material. Stress relaxation is a change in the morphology of the plastic while it is stretched; it results in the force level dropping off. A comparison of the force delivered by SmartTrack material and previous aligner material is shown in Fig. 12-5. Note that the force produced by SmartTrack is fairly constant for each stage of treatment throughout the 2 weeks it is used. A third feature of the SmartTrack material is its excellent elasticity. After it is stretched, it returns to its original shape more closely than previous aligner materials. Accordingly, better tracking stage-after-stage throughout treatment may be expected. Less permanent deformation of the aligner material leads to better tooth movement. Practitioners know that for some movements, attachments are required. For movements such as extrusion and rotation, there is not a surface conducive to force application by the aligner. Thus, a surface must be created to receive the force; hence, attachments are fabricated. Attachment shape, position, and number are formulated as a function of tooth movement proposed in the ClinCheck images. The Treat software analyzes these tooth movements required for treatment. Based on the force system required to accomplish the individual movement, the software positions and orients the attachment surface appropriately. The desired outcome is when an aligner is engaged on an optimized attachment, the force system delivered to the tooth should be able to accomplish the movement. Over the past several years, Optimized Attachments to accomplish extrusion, rotation, translation, and root movements have been introduced. Some movements need one attachment and some require two.12 There are some movements that require only a change in the shape of the aligner itself and no attachment. A force system to accomplish anterior torque can be produced by including a Power Ridge™ shape feature in the aligner. Force systems to simultaneously accomplish extrusion, rotation, and

tipping of an upper lateral incisor can be produced by combining an attachment and a slight change in the shape of the aligner. The shape change concentrates the force produced by the aligner and applies that force to the tooth at a pressure point determined by the Treat software. The combination of the biomechanical characteristics of the SmartTrack material, the activation of the appliance by the Treat software, and the design of the Optimized Attachments generate improved control over the force systems delivered to the teeth. This results in better control of tooth movements, closer tracking during treatment, and improved treatment outcomes. In a manner of speaking, it simulates the autopilot concept and intends to eliminate the use of dimple pliers or other attempts to create pressure points that were not in the ClinCheck.

9. What are the weakest elements of aligner treatment? The weakest link and foremost frustration is patient compliance. Even though adults are more cooperative than children, a large percentage of patients do not clock the prescribed number of hours on their aligners. Changing aligners prematurely leads to loss of tracking. It is not good protocol to change before all the built-in kinetic energy in the aligner is exhausted. There are no problems reported because of aligners worn longer than the prescribed hours. Patients who cooperate as prescribed can achieve the ClinCheck movements predictably. This statement has become more powerful since the introduction of Optimized Attachments12 and SmartTrack plastic. Orthodontic tooth movement may be affected by a person’s age, hormonal status, medical conditions, medications, epigenetic factors, or genetic makeup. Aligner performance does not overcome these factors. The second most common performance problem is extrusion of teeth, especially the maxillary lateral incisor. But the most recent evidence suggests that this might be due to delayed movements of adjacent teeth, particularly the canines. If the canines do not move, the aligner won’t fit correctly over the laterals and will give the appearance that they are not extruding (Fig. 12-6). Since the canine is a large-rooted tooth, it is prudent to extend the wear time or to significantly slow down the rate of tooth movement on the canine teeth.13 The third significant weakness has been the problems associated with the aligner’s inability to move the root apex.

FIG 12-6 The pressure-indicator paste reveals the pressure points and also the ill-fitting segments of the aligner.


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The addition of Power Ridges, Optimized Attachments, and SmartTrack made torqueing and translational movements possible—all with the aligner.

11. What are the considerations for interproximal enamel reduction?

10. What are the advantages of the Invisalign System over traditional fixed appliances?

The amount of interproximal reduction (IPR) performed with Invisalign should be about the same as with fixed appliances.17 It is a misconception that one type of appliance needs IPR more than the other.18 Exceptions aside, IPR should be limited to instances of: • Bolton’s discrepancy • Need to simulate physiological tooth attrition • Need to camouflage a skeletal deformity without surgery • Necessity to alter the tooth morphology IPR has not been shown to adversely affect dental or periodontal health. Initial concerns of root proximity, caries risk, and the like have not been shown to be valid. Nonetheless, a good depth of enamel must be present so that some of it could be removed. Anterior teeth with peg-shaped morphology are not good candidates for IPR. In the posterior region, at times, it is a good idea to use separators prior to IPR. Separation allows for better direct vision of the tooth to be reduced. Also, it is best to perform IPR during the course of treatment rather than before the intraoral scan or PVS impressions. To perform good IPR, periapical radiographs are needed, but without such benefit, one may safely remove 0.3 mm from the anterior teeth and 0.6 mm from the posterior.19

• Esthetics: Invisalign aligners are undetectable from a distance of 2 feet. Of course, one can remove them at will in anticipation of close encounters or lisping. • Comfort: Traditional pain or soreness associated with fixed appliances is not experienced with Invisalign. • Bonding problems avoided: In patients with amelogenesis imperfecta or prosthetic crowns with porcelain surfaces or bridges, the clinician does not worry about securing brackets onto such surfaces. Also, with the aligner, even patients with less than perfect oral hygiene do not exhibit white enamel spots or decalcification. • Lack of root resorption: There are no reported studies of noticeable root resorption in patients treated with the Invisalign System. This is probably due to less than 0.25 mm of tooth movement per tray with mild forces. This distance does not obstruct the periodontal ligament (PDL) blood flow and avoids formation of necrotic regions. • Oral hygiene: Compared with fixed appliances and untreated control patients, the periodontal tissue health as measured by papillary bleeding score and periodontal pocket depth improves with use of Invisalign during ortho dontic treatment.14 Tuncay and colleagues15 report remarkably lower plaque and gingival bleeding indices in patients treated with Invisalign Teen. • Chair time: Routine follow-up visits take practically no time.15 Also, the instruments needed on the tray setup are minimal. • No emergencies: Normally, the Invisalign aligners do not break. But even if they do, patients need not call the office to schedule an after-hours emergency visit. They simply move to the next aligner. • Special patients: Musicians or athletes benefit greatly from Invisalign. If the aligner interferes with the wind instrument, it can be removed—just as an athlete would. But in most instances the Invisalign trays may function as mouth guards. • Vertical correction: The Invisalign aligner can intrude the posterior teeth and close the anterior openbite. Conversely, it can effectively intrude the anterior teeth to open the bite. • Bruxism: The aligner is a good substitute for bite splints. It will also reposition the mandible to read the correct centric relation. • Bleaching: The Invisalign tray may be used for bleaching, but it is critical not to bleach if there are attachments present because color will not change to the same extent under the attachments. • ClinCheck is a diagnostic tool: The clinician can create innumerable “what if ” scenarios without messy wax setups and can also fine-tune the desired final tooth positions with overcorrections.16

12. Is Invisalign able to correct openbites, deepbites, and crossbites? What is the essence of planning treatment for a case with Invisalign? Successful treatment with Invisalign is a state of mind. In the process, to translate the language and mechanics of fixed appliances to aligner therapy is a challenge the orthodontist must be willing to face. Clarity of communication with the technician is also essential. The orthodontist knows how teeth should be moved with the aid of fixed appliances, but the orthodontist may be challenged to shift from the fixed to aligner mindset. It is important to know that treatment with aligners does not violate one’s philosophy of treatment. Instead, it only enhances the orthodontist’s control over what teeth to move or not to move. Simply put, treatment with aligners should mimic what the orthodontist might do with fixed appliances. It may seem orthodontics is a language where aligner and fixed appliance treatments merely represent different dialects. OPENBITE CORRECTION No matter the appliance used, anterior openbite corrections (Fig. 12-7, A to I) are always a challenge, not to mention the added challenge of maintaining the result. Nonetheless, it is now clear that control of posterior vertical dimension is a pivotal element of treatment strategy. The advent of miniscrew implants, for example, enabled the orthodontist to treat vertical dimension problems without resorting to surgery; this was a paradigm shift. In a similar vein, aligner treatment has also proved itself to be a viable choice for these patients. It too promotes good stability of the corrected occlusions.19


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A

B

EXTRUSION

C

RETRACTION

THE BROADER SURFACE IS AS PERPENDICULAR AS POSSIBLE TO THE VECTOR OF FORCE

D

E

F

G

H

I

FIG 12-7 Openbite correction. A, Initial right buccal. B, Initial left buccal. C, Force vectors acting upon bevel surface. D, Initial left ClinCheck view. E, Final left ClinCheck view. F, Final right buccal view. G, Final left buccal view. H, Initial cephalogram. I, Final cephalogram. (Courtesy Align Technology, Inc., Parts C-E.)


Intrusion of posterior segments closes the openbite in fixed appliance treatment as it does with aligners. In aligner treatment the orthodontist should instruct the ClinCheck technician to intrude the posterior segments by 2 to 3 mm in both arches. Simultaneously, anterior teeth are extruded. The properly designed ClinCheck to correct an openbite should exhibit a posterior openbite with about 4 to 5 mm of freeway space. This will not tangibly happen in the clinic, because the mandible will rotate forward and take up the room. Whereas ClinCheck images are static, the mouth is dynamic. The dynamic mindset of the orthodontist should envision that aligners might 1) block forces of the tongue on the lingual cingula of upper incisors, and 2) in the posterior segments, coverage of occlusal surfaces by the plastic aids the intrusion of the posterior teeth. These attributes may also be contributing factors to the stability of the corrected occlusions in comparison to fixed appliances. Simply stated, strategies that correct a malocclusion are the same to aid in maintaining it. A protocol that has proven successful to extrude a tooth is the optimized horizontal rectangular attachment with a gingival bevel. The orthodontist should understand that these optimized extrusion attachments are only for anterior teeth, upper and lower, and cuspid to cuspid. If the clinician desires extrusion of posterior teeth, one must specifically ask for horizontal rectangular beveled attachments, where the beveled surface faces the gingiva. To extrude the anterior teeth, however, ClinCheck must be designed to exert a net pushing force against the broad s urface

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of the beveled gingival attachment and tooth’s crown in an effort to avoid pulling down along the long axis of the tooth. Clinically, forces are lingual and extrusive in direction. It is also imperative that more than adequate space is created by separating the adjacent teeth away from the tooth that is being extruded. Any interproximal collision will inhibit the extrusive movement. Once the space is created, the clinician should ask for an equal amount of extrusion to be performed with an equal amount of simultaneous retraction. It also is highly critical that the entire distance of extrusion is completed prior to complete space closure to finish the tooth movements in ClinCheck. OVERBITE CORRECTION Correction of deep overbites with aligners has evolved from thinking it was a clinical impossibility to a clinical challenge with predictable outcomes. In the process, the ClinCheck treatment plan must be set up with some thought, such as in openbite cases (Fig. 12-8, A to D). Moreover, as with any treatment planning, proper understanding of the etiology of the deep overbite is important. Also important is the type of patient: adult versus teenager. Oftentimes, adults exhibit retroclined and overerupted lower anterior teeth. This arrangement creates a two-step occlusal plane from the anterior teeth to the posterior. Many times this is combined with palatally inclined upper anterior teeth as well. Excessive wearing of the incisal edges is frequently seen. In a sense, the treatment goal is to reverse what has gradually

A

B

C

D

FIG 12-8 ClinCheck plan to create a reverse curve of Spee in deepbite correction. A, Left ClinCheck view of planned premolar extrusion. B, Right ClinCheck view of planned premolar extrusion. C, Final ClinCheck view of achieved left premolar extrusion. D, Final ClinCheck view of achieved right premolar extrusion. (Courtesy Align Technology, Inc.)

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happened over time, while being mindful of any restorative procedures that may be involved. Transversely, adult teeth are lingually inclined; therefore, uprighting of crowns will improve the curve of Wilson along with overbite correction. Teens tend to have a deep curve of Spee that can be leveled in a similar fashion as with fixed appliances. Sometimes the teen’s deep bite is also accompanied with lingually inclined upper anterior incisors. Foremost, the luxury of differential growth of the jaws with concomitant increase in the vertical dimension can be used to advantage in the correction of a deep overbite in the teen patient. This is not the case in the adult patient. The communication with the ClinCheck technician must include instructions to level the curve of Spee, such as to intrude the lower incisors and extrude the lower bicuspids with the aid of horizontal beveled gingival attachments on the bicuspids. Simultaneously, it is best to intrude upper anterior teeth while torqueing them with Power Ridges. It is a must to apply 10 to 15 degrees of lingual root torque to the upper anterior during space closure to avoid tipping of upper anterior teeth lingually. Tipping deepens the overbite further, leads to ill-fitting of aligners on the incisal edges, and creates anterior interferences and posterior openbites. This best mimics a slightly curved edgewise wire binding in the slot when a power chain is stretched molar to molar. As a side note, these are some of the small interactions one can take for granted with fixed appliances. At times, orthodontists fail to translate this language of fixed appliances to the lexicon of aligner therapy. In most growing teen patients, overbites can be corrected in under a year. What makes the earlier stated protocol slightly different is the active extrusion of the lower bicuspids in addition to the lower anterior intrusion. Special instructions to create the ClinCheck treatment plan include: • Level curve of Spee by extruding the lower bicuspids for a total of 3 mm and by intruding the lower cuspid to cuspid a total of 4 mm. • Attachments on lower bicuspids: Horizontal rectangular beveled gingival: 4 mm wide, 1.5 mm high, and 1.25 mm thick at the occlusal margin tapering to a thickness of

0.25 mm at the gingival margin. Placed as far occlusally without any interferences from the opposing arch. The orthodontist should visualize a reverse curve archwire placed in the lower arch. Then when it is removed after being in place for a few weeks, it is still convex and the lower arch is still slightly concave. Furthermore, when the wire is removed from the anterior brackets, it goes below the brackets into the vestibule. Is this considered excessive? No. Accordingly, asking for a similar amount of overcorrection in the ClinCheck treatment plan should not be either. Just as a wire has flexibility, so does an aligner (Fig. 12-9, A to F).

13. Why choose Invisalign over fixed appliances in deepbite cases? The advantage that aligners have over fixed appliances is that the orthodontist can start correcting the overbite on both arches from the very beginning. Most typically with fixed appliances, upper anteriors would have to be flared out or intruded to create adequate clearance to place the lower brackets. The use of bite ramps may prove uncomfortable for patients or require extra cleanup at some point in the future. CROSSBITE CORRECTION Principles of orthodontic treatment do not change because of the appliance used. If a dentoalveolar crossbite (Fig. 12-10, A to H) can be corrected with fixed appliances, the same can be done with aligners. The advantage with aligners is the plastic that covers the occlusal surfaces acts as a built-in bite raiser to disarticulate the occlusion during crossbite correction. Compliance is ensured as patients often feel more comfortable with aligners in than out. The disarticulation of temporary interferences makes a difference. Empirically, no patient has ever reported any temporomandibular joint (TMJ) issues during this correction. To help in crossbite correction, sometimes it is beneficial to intrude the offending teeth off the occlusal plane. It eliminates or minimizes any interferences with the opposing dentition, only to extrude it back into occlusion during the refinement process using the aforementioned extrusion protocol.

A,B

C

D,E

F

FIG 12-9 Deepbite correction. A, Initial right buccal view. B, Initial frontal view. C, Initial left buccal view. D, Final right buccal view. E, Final frontal view. F, Final left buccal view.


A,B

163

C

D

E

F,G

H

FIG 12-10 Crossbite correction. A, Initial right buccal. B, Initial frontal. C, Initial left buccal. D, Initial right ClinCheck view. E, Initial right buccal overjet ClinCheck view. F, Final right buccal. G, Final frontal. H, Final left buccal. (Courtesy Align Technology, Inc., Parts D-E.)

REFERENCES 1. Kesling HD: The philosophy of the tooth positioning appliance, Am J Orthod 31:297–304, 1945. 2. Remmensnyder O: A gum-massaging appliance in the treatment of pyorrhea, Dent Cosmos 28:381–384, 1926. 3. Nahoum HI: The vacuum formed dental contour appliance, N Y State Dent J 9:385–390, 1964. 4. Sheridan JJ, LeDoux W, McMinn R: Essix retainers: fabrication and supervision for permanent retention, J Clin Orthod 27:37–45, 1993. 5. Beers A: Invisalign software. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence. 6. Cao H, Duong T: Applications of mechanics with Invisalign. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence. 7. Tuncay OC: Biologic elements of tooth movement. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence. 8. Nicozisis J, Nah HD, Tuncay OC: Relaxin affects the dentofacial sutural tissues, Clin Orthod Res 3:192–2019, 2000. 9. Tricca R, Chunhua L: Properties of aligner material Ex30. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence.

10. Duong T, Derakhshan M: Ex40 material and aligner thickness. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence. 11. Tuncay OC: The iatrogenic crowding caused by aligner length/ arch length discrepancy, Clin Rep Tech 1:3–5, 2005 (Fall 1). 12. Tuncay OC, Morton J: The modern aligner, Orthodontic Products, May, 2011. 13. Nord S: An exploratory study to identify the conditions that induce loss of tracking in tooth movement with the Invisalign system, master’s thesis, 2005, Temple University. 14. Taylor MG, McGorray SP, Durrett S, et al: Effect of Invisalign aligners on periodontal tissues, J Dent Res 82:1483, 2003. 15. Tuncay OC, Bowman SJ, Amy BD, et al: Aligner treatment in the teenage patient, J Clin Orthod 47(2):115–119, 2013. 16. Duong T, Derakhshan M: Advantages of the Invisalign system. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence. 17. Miethke RR, Jost-Brinkmann PG: Interproximal enamel reduction. In Tuncay OC, editor: The Invisalign system, Berlin, 2006, Quintessence. 18. Fillion D, Teil II: Vor- und Nachteile der approximalen Schmelzreduktion, Int Orthod Kieferorthop 27:64–90, 1995. 19. Boyd RL: How successful is Invisalign for treatment of anterior open bite and deep overbite? AAO Annual Session, May 2013. https://www.aaoinfo.org.

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13

Treatment of Class II Malocclusions

Richard Kulbersh • Valmy Pangrazio-Kulbersh

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lass II malocclusion is not a single entity but results from numerous combinations of both skeletal and dental alveolar components. The earliest description, solely a dental description, was provided by Edward Angle when he defined a Class II malocclusion as characterized by the lower molar in distal position relative to the upper 6-year molar. He further subdivided Class II malocclusions into Class II division 1, characterized by the anterior maxillary teeth being protrusive; and Class II division 2, characterized by two or more maxillary anterior teeth being retroclined. The Class II division 1 was later shown to also be characterized by a retrognathic mandible or a prognathic maxilla with variable vertical dimensions. The Class II division 2 patient was shown to exhibit an orthognathic maxilla, a short and retrognathic mandible, brachyfacial growth pattern, retroclined maxillary central incisors, and a relatively prominent chin as well as dental deepbite. In later years, further assessment of the dental Class II provided information regarding the underlying skeletal components.

1. What are the components of a Class II malocclusion? Utilizing cephalometrics and computer-based statistical evaluation, Moyers and colleagues4 determined that Class II patients were divided into six separate horizontal types and five vertical types based on various skeletal and dentoalveolar characteristics. The six horizontal types are described in Table 13-1. The five vertical types were defined by an assessment of the following four facial planes relative to their normal position: 1. The sella-nasion (SN) cranial base plane 2. The palatal plane 3. The functional-occlusal plane 4. The mandibular plane The five vertical Class II types were described as shown in Table 13-2. In the transverse dimension, the buccal segments of Class II patients often appear normal. A 3- to 4-mm transverse discrepancy, however, usually exists at the level of the first molar due to a narrow maxillary arch. This is readily observable if the mandible is moved into the Class I relationship at the molar. Further assessment of components of Class II malocclusion in an adolescent population indicated that in a sample of 277 children with a Class II malocclusion, mandibular skeletal retrusion was the most common characteristic. The maxilla was generally either retrusive or well positioned. 164

2. How can Moyers’ differential diagnosis of Class II horizontal and vertical types be used to help us with treatment planning of Class II patients? Moyers’ differential diagnosis of Class II malocclusions allows us to more easily determine the components of the Class II malocclusion problem.4 It identifies the skeletal problem and the dentoalveolar problem and thus directs our treatment thinking to these specific areas. Treatment planning considerations using Moyers’ differential Class II horizontal analysis can be summarized, at least in part, in Table 13-3. In addition to the preceding horizontal considerations, proper patient treatment also requires assessment of the vertical components. Treatment options for vertical correction in growing patients would include bite blocks and various types of headgear. In non-growing patients, surgical correction options, such as LeFort I maxillary impaction and alveolar procedures, may be required.

3. What is the prevalence of Class II malocclusions? According to the NHANES III Study, 15% of the US population have an overjet of greater than 4 mm, 38% have an overjet between 3 to 4 mm, and one-third (33%) of the population have Class II occlusal discrepancies.4 The same frequency for Class II dental characteristics was found in Caucasians, AfricanAmericans, and Hispanics. According to McNamara, 75% of Class II skeletal discrepancies are the result of mandibular retrognathia.3,5

4. What is the etiology of Class II malocclusion?6–10 Class II malocclusion is usually an aberration of normal development and not caused by a pathologic process. It is usually the result of multiple factors that influence growth and development and not from one specific factor. The development of Class II malocclusion may, however, be related to some specific causes, genetic influences, and environmental factors. Specific causes such as the effect of teratogens on mandibular growth, mandibular deficient syndromes (PierreRobin and Treacher-Collins), fetal molding, trauma to the temporomandibular joint (TMJ) area during the birth process, childhood fractures of the jaw, and mandibular arthritic problems may all contribute to the development of a Class II

Treatment of Class II Malocclusions • CHAPTER 13

TABLE 13-1 The Six Horizontal Class II Types Determined by Moyers and Colleagues DIAGRAMMATIC REPRESENTATION

DESCRIPTION Normal

Type A: Maxillary dental protraction

Type B: Maxillary prognathism, dental protraction

Type C: Maxillary retrognathism with flared or upright incisors; mandibular severe retrognathism with flared lower incisors

Type D: Maxillary retrognathism with dental protraction; severe mandibular retrognathism

Type E: Maxillary prognathism and dental protraction + mandibular dental flaring

Type F: Mandibular retrognathism

Adapted from Moyers RE, Riolo MS, Guire KE, et al: Differential diagnosis of Class II malocclusions, Am J Orthod 78(5):477-494, 1980.

skeletal pattern. Less than 1% of orthodontic patients, however, have a disruption in embryological development that can be attributed as the major cause of malocclusion. Genetic influences have been shown to be associated with Class II malocclusions. Local and environmental factors may also be an issue in the development of Class II malocclusions due to their alteration of the normal physiologic pressures and

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forces associated with craniofacial growth. These pressures and forces may be disrupted or imbalanced by the effects of abnormal function of the soft tissues. Disruption of normal lip balance, such as that associated with lip incompetency, may lead to flaring of the upper incisors from an imbalance of labial and lingual musculature. The need to achieve liptongue contact for an oral seal during swallowing can cause the lip to retrocline lower incisors and the protruding tongue to flare upper incisors, thus increasing overjet. It has also been speculated that mouth-breathing can cause the opening muscles to place a distal force on the mandible, retarding its growth and rotating the mandible clockwise. In addition, it is thought that finger sucking habits can produce a Class II division 1 incisal relationship within a Class II or Class I skeletal pattern (Fig. 13-1 and Fig. 13-2).

5. What treatment protocols are used to correct Class II malocclusions? Treatment for Class II malocclusions may involve the following: • Extra-oral traction • Distalizing appliances • Functional jaw orthopedics (FJO) • Camouflage • Surgery The appropriate protocol for each patient depends on patient desires and doctor assessment of the exact nature of the Class II problem as well as the orthodontist’s treatment protocol preferences.

6. What is extra-oral traction?3,5,11 Extra-oral traction is the application of force to the dentition and maxilla through the use of headgear (cervical, occipital, combination) fitted to the skull and attached facebows through which force is directly applied to the dentition, usually via the permanent maxillary first molars. Headgear wear is required for at least 12 to 14 hours per day for a period of 6 to 18 months at a force level of 12 to 16 ounces per side for skeletal modification. Three types of headgear are commonly used depending on the vertical craniofacial growth pattern: cervical pull headgear for low vertical dimension (FMA ≤ 25), occipital pull headgear (FMA > 30), and combination (combi) headgear for cases where the vector of force application needs to be altered depending on the desired effect for a specific patient. The various types of headgear and attached facebows are useful in applying forces of appropriate magnitude and direction to the maxilla via the maxillary dentition. The effect of the applied force has an orthopedic effect. It modifies maxillary position by altering its normal downward and forward growth pattern, thus normalizing the Class II to a Class I skeletal pattern.

7. What is the distalizing protocol for the correction of Class II?3,5,11,12 Molar distalization is used when the Class II problem is dentoalveolar in nature. Molar distalization corrects a dental Class II by moving the maxillary first molar distally into a Class I relationship. Such treatment has no orthopedic effect. Distalizing

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CHAPTER 13 • Treatment of Class II Malocclusions

TABLE 13-2 The Five Vertical Class II Types Determined by Moyers and Colleagues DIAGRAMMATIC REPRESENTATION

DESCRIPTION Type 1: Mandibular plane steeper than normal, steeper functional occlusal plane, palate tipped somewhat downward, anterior cranial base tipped upward

Vertical type 1

Type 2: Mandibular plane, functional occlusal plane, and palatal plane are all flatter than normal and are nearly parallel

Vertical type 2

Type 3: Palatal plane tipped upward anteriorly

Vertical type 3


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TABLE 13-2 The Five Vertical Class II Types Determined by Moyers and Colleagues—cont'd DIAGRAMMATIC REPRESENTATION

DESCRIPTION Type 4: Mandibular plane, the functional occlusal plane, and the palatal plane are all tipped markedly downward

Vertical type 4

Type 5: Palatal plane is tipped downward; cranial base tipped downward

Vertical type 5 Adapted from Moyers RE, Riolo MS, Guire KE, et al: Differential diagnosis of Class II malocclusions, Am J Orthod 78(5):477-494, 1980.

appliances are usually very effective because they require little, if any, cooperation from the patient. Types of such appliances are (Fig. 13-3): • Plates • Pendulum/pendex • Distal jet • Jones jig • Jasper jumper

8. What is functional jaw orthopedics?5,13–15 FJO is the utilization of appliances that work by forward positioning of the mandible. This results in altering the activity of postural muscles of the craniofacial complex, causing changes in skeletal and dental relationships. The goal is to enhance mandibular growth by allowing the full expression of the genetic potential and encouraging remodeling at the glenoid fossa. The mandible is translated downward and forward by

the appliance with resulting growth at the condyle and posterior surface of the ramus. In animal studies, FJO was shown to increase activity at the lateral pterygoid followed by an adaptive growth response at the condyle. Since the lateral pterygoid activity decreases after 6 to 8 weeks, repeated advancement of the appliance is required. Early correction of Class II dentoskeletal malocclusion with FJO shows favorable and stable results. Typical results from FJO therapy show the following: • Condylar growth during treatment: 1 to 3 mm • Fossa displacement, growth, and adaptation: 3 to 5 mm with a dominant vertical vector • More favorable growth direction: 0.5 to 1.5 mm • Withholding of downward and forward maxillary growth: 1 to 1.5 mm • Differential upward and forward eruption of lower buccal segments: 1.5 to 2.5 mm • Headgear effect: 0.0 to 0.5 mm

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TABLE 13-3 Summary of Moyers’ Differential Class II Horizontal Analysis TYPE

TREATMENT CONSIDERATIONS

Type A

1. Extraction of upper bicuspids + orthodontic retraction and uprighting 2. Distalization of upper dentition into Class I (i.e., headgear, molar distalizers) 3. Surgery: Anterior maxillary alveolar osteotomy setback and uprighting of upper centrals and laterals after extraction of upper bicuspids and orthodontic retraction of canines

Type B

1. Headgear (growing patient) 2. Surgery: Maxillary anterior alveolar setback (non-growing patient) with extractions of upper bicuspids

Type C

1. Complex skeletal and dentoalveolar considerations 2. Extraction of upper and lower bicuspids, orthodontics + functional appliance 3. Extraction of upper 5/lower 4’s, orthodontics to close spaces and upright incisors + surgery: Maxillary and mandibular differential advancement

Type D

1. Orthodontic + functional appliance (growing patient) 2. Surgery: Mandibular advancement (non-growing patient)

Type E

1. Headgear 2. Bimaxillary protrusion-extraction of upper and lower bicuspids 3. Extractions + surgery (non-growing patient)

Type F

1. Functional appliance (growing patient) 2. Surgery: Mandibular advancement (non-growing patient)

Adapted from Moyers RE, Riolo MS, Guire KE, et al: Differential diagnosis of Class II malocclusions, Am J Orthod 78(5):477-494, 1980.

9. When is functional appliance therapy indicated?16,17 The primary indication for FJO is mandibular skeletal retrusion. In addition, abnormal muscular function is also an indication. Functional appliances remove abnormal and restrictive muscular activity that prevents the normal development of the

maxilla and mandible as well as appropriate development of the dental arches. Research has shown that there is an ideal time for functional appliance therapy. Greater mandibular length is obtained when functional appliance treatment is performed during the circumpubertal growth period. Ideally, functional appliance therapy should be started in the late mixed dentition or early


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well as related substances that are in greater quantity during the circumpubertal growth period. In the absence of severe dentoskeletal compensations, functional appliance therapy should be initiated at the beginning of cervical vertebrae maturation stage CS3 to maximize the treatment effects and reduce the need for posttreatment retention.

10. What are the two basic types of functional appliances commonly used today?5,15,17–24 FIG 13-1 Vertical and anteroposterior distortion of maxilla due to thumb sucking habit.

permanent dentition followed by Phase II therapy to align the permanent dentition. For some patients who have severe neuromuscular, skeletal, and dentoalveolar problems, treatment may be initiated in the early mixed dentition. The reason for increased growth response may be related to the synergistic interaction between the change in function, produced by the functional appliance and growth hormone as

A

The two basic types of functional appliances commonly used today are tooth-borne and tissue-borne appliances. The only tissue-borne appliance is the functional regulator or Fränkel II (Fig. 13-4A). All other functional appliances, such as the Herbst, Twin Block, Bionator, and mandibular anterior repositioning appliance (MARA), are considered tooth-borne appliances (13-4B-I). The Fränkel II appliance is considered a tissue-borne appliance because it uses the buccal vestibule as the main support of the appliance. The Fränkel II’s vestibular shields and lower labial pads are used to restrain the buccal and labial musculatures that apply pressure and restrict dental and skeletal

B

C

D

FIG 13-2 Facial distortion due to thumb sucking habit. Headgear treatment of Class II division 1 malocclusion. A to D, Initial photos: Facial photos (A and B), intraoral photo (C), and cephalometric radiograph (D). (Continued)

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E

F

G

H

I

J

FIG 13-2, cont’d E to H, Post-cervical headgear: Facial photos (E and F), intraoral photo (G), and cephalometric radiograph (H). I and J, Post-orthodontic treatment with extractions: Facial photo (I) and cephalometric radiograph (J).

development. The mandibular musculature is stimulated to reposition the mandible to a functionally anterior position by feedback stimulus from the lingual pad, which is lingual to the lower incisors. Since the appliance is tissue-borne, greater flaring of the incisors may be noted. The buccal shields provide spontaneous lateral expansion of the maxillary and mandibular arches due to pressure elimination from the buccal

musculature, thus allowing the tongue to help in arch development. In addition, the vestibular shields stimulate additional appositional growth laterally by causing tension on the alveolar periosteum. The second basic type of functional appliance is the toothborne appliance, which uses the dentition as the primary anchor. In this type of appliance, there are more dentoalveolar


A, B C

D, E

F

G

H

I

J

K

L

M, N

O

FIG 13-3 Pendex distalizing treatment. A to C, Initial photos. D, Pendex appliance. E to F, Note molar distalizaiton. G, Pendex arm cut. H, Bicuspid alignment. I to J, Bicuspid distalization. K to O, Posttreatment photos.

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172


A

B

C

D, E

F

G, H

I

FIG 13-4 Functional appliances. A, Fränkel II appliance. B, Bionator appliance. C, Removable acrylic Herbst appliance. D to F, Twin Block appliance. G to I, Mandibular anterior repositioning appliance (MARA).

effects than with the tissue-borne appliance. Increase in mandibular length is expected as well as the potential for some headgear effect. In addition, the maxillary molars usually move distally, and the mandibular molars move mesially. The maxillary incisors often tip lingually and mandibular incisors tend to procline. The degree of skeletal and dentoalveolar movement may vary with each type of appliance. Tooth-borne appliances can be fixed or removable. Examples of removable

appliances are the Activator, Bionator, and Twin Block. The removable appliances are usually composed of a metal framework with clasps and acrylic. The fixed appliances, on the other hand, such as the MARA and the banded Herbst, are cemented to the teeth, resulting in full-time active forward positioning of the mandible. A modification of the fixed functional appliance is the fixed-removable appliance, the Forsus (3 M Uniteck, Monrovia, CA) (Fig. 13-10).

C

A, B

D, E

F

G

J

H, I

M

K, L

N

FIG 13-5 Twin Block treatment. A to G, Initial photos. H to N, Posttreatment. (Continued)

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O

P

Q, R

S

FIG 13-5, cont’d O to S, Twin Block in place.

11. What situations would require orthodontic treatment prior to starting functional jaw orthopedics?5,6,15 The following four situations usually require orthodontic treatment prior to FJO: 1. Severe maxillary constriction: It is often advantageous to expand the maxilla prior to Class II correction to allow the buccal segments to appropriately interdigitate in the final Class I position. This can be done with a rapid palatal expander (RPE) appliance prior to FJO. 2. Deep impinging bite: In order to allow for forward posturing of the mandible, deep impinging bites should be corrected utilizing a utility arch to intrude, tip, or reposition the incisors. 3. Maxillary incisor retroclination and mandibular incisor proclination and spacing: Over 30% of Class II patients present with maxillary incisors in a retroclined position. This inclination problem must be corrected to allow appropriate mandibular advancement. In addition, flaring as well as spacing of the lower incisors must be corrected to allow for maximum mandibular advancement. 4. Moderate to severe crowding: Space supervision or serial extraction may be required depending on the severity of the upper and lower dental crowding.

12. What is a Twin Block appliance?5,6,15,18 The Twin Block is composed of maxillary and mandibular retainer-like acrylic appliances that fit tightly against the teeth and alveolar structures. The upper and lower appliances have two bite blocks, which gives the appliance the name “Twin Block.” The upper bite block covers the molars and extends partially to the second bicuspids, finishing on the mesial with an inclined plane at 70 degrees to the occlusal plane. The lower bite block usually covers the bicuspids and ends on the distal in a posteriorly directed incline plane just above the second

icuspids. Upon closure, the incline planes contact each other, b thrusting the mandible forward. Three-dimensional (3D) control is accomplished by selective grinding of the blocks, guided dental eruption, and transverse expansion via a mid-palatal jackscrew (Fig. 13-5).

13. What is a Bionator appliance?5,15 The Bionator is a tooth-borne appliance that consists of an interocclusal acrylic block with a labial maxillary bow with or without maxillary or mandibular anterior or posterior occlusal coverage. The interocclusal block may have angled flutes to guide the path of eruption of the posterior teeth. Bionators are classified into the following three categories: Bionators to open, maintain, or close the bite. Bionators that open the bite have eruption grooves in the posterior to allow the dentition to erupt and correct the deep curve of Spee. In addition occlusal acrylic, capping is added to control incisor eruption. Bionators that maintain the bite have acrylic posterior bite blocks that are constructed within the freeway space to prevent tooth eruption. Bionators to close the bite have posterior acrylic bite blocks that impinge into the freeway space to stretch the peri-oral musculature to actively intrude the posterior teeth and allow for vertical ramus growth. The Bionator to close the bite may or may not have lower anterior incisor capping, depending on the absence or presence of an anterior dental openbite. Wax bite registrations for the Bionator vary depending on its specific type. The wax registration for the Bionator to open or maintain the bite is taken with the mandible advanced 4 to 5 mm and with an anterior incisor separation of 2 to 3 mm to allow for the incisal capping. The wax registration for the Bionator to close the bite is taken with the mandible advanced 4 to 5 mm and a posterior tooth separation of 5 mm to allow for impingement on the freeway space. Headgear tubes can be added to the Bionator to control either excessive anterior or vertical maxillary growth (Fig. 13-6 and Fig.13-7).


A, B

175

C

D

E

F, G

H

I

J

FIG 13-6 Bionator treatment to correct Class II and open the bite. A to E, Initial photos. F to H, Bionator appliance intraorally. I to J, Bionator appliance. (Continued)

14. What is a Herbst appliance?5,20 The Herbst appliance design most frequently used today employs two types of attachment mechanisms to anchor the appliance: stainless steel crowns and acrylic splints. The stainless steel crown Herbst features crowns on the maxillary first molars and mandibular first premolars. Pivots soldered to the crowns connect the tube and plunger assembly, with the length of the maxillary tube determining the amount of bite advancement. A lower lingual arch connects the crowns on the mandibular first premolars to bands on the mandibular first molars. In the second type, the acrylic splint Herbst, an acrylic material 2.5 to 3.0 mm thick, is applied over a wire framework. This acrylic splint only covers from the canines to the first molars in the maxillary arch but extends over the complete

entition in the lower arch. As in the banded version, the pivd ots of the Herbst bite jumping mechanism are soldered to the wire framework adjacent to the mandibular first premolars and maxillary first molars. Anchorage for the Herbst is provided by the acrylic splint/dentition contact, with the maxillary and mandibular sections either cemented or removable. In both types of Herbst appliances, a hyrax-type screw may be included to expand the maxilla as the mandible is positioned forward. Step-by-step mandibular advancement is achieved by adding shims to the mandibular part of the bite jumping mechanism. In addition, vertical eruption of the upper and lower second molars is controlled by either acrylic coverage in the splint-type appliance or wire occlusal stops soldered to the 6-year molar bands in the stainless steel crown version. Both types of Herbst appliances are worn for 9 to 12 months, after which full fixed appliances are initiated (Fig. 13-8).

176


K, L

M

N

O

R

P, Q

S

FIG 13-6, cont’d K to S, Post-Bionator results.

15. What is a mandibular anterior repositioning appliance?19,21 The MARA is a tooth-borne functional appliance used to correct Class II malocclusions. There is basically one MARA design. The appliance, however, can be modified to accommodate upper and lower expansion, a transpalatal arch, lower lingual arch, orthodontic appliances, and intrusion mechanics, and it can be used unilaterally in asymmetric cases. The basic MARA design consists of: • Four crowns on the first molars • Arms soldered to the lower crowns

• Archwire tubes for upper and lower arches soldered to all first molar crowns • Elbow tubes soldered to the upper crowns • Upper elbows shimmed to provide the desired advancement • Lower lingual arch soldered to lower crowns • Optional specifications include occlusal holes to assist with crown removal On closure of the mouth, the upper elbow’s vertical legs hit the lower arms and the mandible is forced forward. The MARA is effective in treating patients with Class II malocclusion through dental and skeletal changes in the craniofacial complex. The annualized 5.8-mm Class II molar correction is


177

V

T, U

X

W

AA

Y, Z

BB

FIG 13-6, cont’d T to BB, Post-Bionator and orthodontic results.

obtained by a 47% skeletal change (2.7 mm) and 53% dental change (3.1 mm). The 2.7-mm skeletal change is completely due to growth of the mandible. The MARA produces increases in mandibular length and in posterior and anterior face height but has no headgear effect on the maxilla. The dental changes are mainly due to the distalization of the maxillary molars (2.4 mm), which account for 77% of the total dental correction. Dental changes include distalization of the maxillary molar, slight mesial movement of the mandibular molars, and a slight proclination of the mandibular incisors (Fig. 13-9).

16.

What is a Forsus appliance?32,33

The Forsus (3 M Unitek, Monrovia, CA) is used with fixed appliance therapy and consists of telescoping spring modules that fit on small metal extension push rods, usually positioned on both the right and left sides of the dental arches. In specific cases, the Forsus may also be used unilaterally. The push rods are attached to the maxillary molar headgear tubes and the mandibular archwire, distal to the lower cuspid or first bicuspid brackets. This assembly provides a mesial and intrusive

178


A, B

C

D, E

F

G

H, I

J

K, L

M

FIG 13-7 Bionator treatment to close bite. A to G, Initial photos. H to M, Bionator treatment with headgear.


N, O

179

P

Q

R

U

S, T

V

FIG 13-7, cont’d N to V, Post-Bionator treatment. (Continued)

force on the lower arch and a distal and intrusive force on the maxillary arch (see Fig. 13-10). Treatment time in a growing patient is approximately 6 months and consists of dentoalveolar (66%), skeletal, and occlusal plane changes (see Fig. 13-10).

17. Are there variations in clinical response to functional appliance treatment?6,17 The effectiveness of functional appliance treatment to correct Class II malocclusions is well reported in the literature. The effect of functional appliance therapy on increasing mandibular

size, however, is less well documented. In a systematic review by Cozza and colleagues evaluating mandibular changes produced by functional appliances,17 the amount of supplementary growth of the mandible when compared to untreated Class II controls varied. In the review by Cozza and colleagues, assessment was difficult because only one-third of the studies had any information on skeletal maturity at the time of functional appliance therapy, and it is now a well-known fact that mandibular response is enhanced if functional appliance therapy is carried out during the circumpubertal growth spurt. Tulloch

180


W, X

Y

Z

AA

DD

BB, CC

EE

FIG 13-7, cont’d W to EE, Final results post orthodontics.

has reported that in untreated Class II patients, there is about a 30% chance of favorable change in the Class II relationship, approximately a 50% chance of no change, and a 15% chance the condition will worsen. Functional appliance or headgear treatment has shown a 70% to 80% chance of producing a favorable or highly favorable result and about a 20% chance of no change or a worsening of the Class II. It has also been shown that up to 10% of patients do not respond to functional appliance treatment.

18. Are functional treatment results stable long term? Functional treatment results have been reported to be stable in the long term in a variety of articles. Croft found no significant joint space changes at the end of treatment with the Herbst appliance, thus concluding there would be no relapse due to mandibular posturing and condylar repositioning. Gutler and Uner found that functional appliance treatment results were stable


181

FF, GG

HH

II, JJ

KK

FIG 13-7, cont’d FF to KK, Overall treatment comparisons: initial, post Bionator, post orthodontics.

B

A

C

E

D

F

FIG 13-8 Removable acrylic Herbst treatment. A to B, Initial photos. C, Herbst plus upper intrusion arch to flare and intrude incisors. D to F, Post-Herbst and orthodontic treatment results.

182


A

B

C

D

E

F

FIG 13-9 MARA treatment. A to E, Initial photos. F, Mandibular anterior repositioning appliance (MARA).

and even improved during retention. Pancherz indicated that stability of functional results was dependant on finishing the functional appliance phase with good occlusal intercuspation. Pangrazio-Kulbersh and colleagues21 reported that functional appliance patients continued to grow in a favorable direction even after discontinuance of functional appliance therapy and, in addition, the functional results showed stability over time. Functional appliance therapy when initiated at the appropriate patient developmental growth stage has been shown to be stable and results in the correction of Class II malocclusions (see Fig. 13-10).

19. What is Class II camouflage treatment?6,25 Class II camouflage treatment is usually considered for patients who are either too old for growth modification, have mild to moderate skeletal discrepancies, have reasonably good alignment of teeth, have good vertical proportions, have reasonably good facial esthetics, and have overjet that results more from maxillary protrusion than mandibular retrusion. It is most appropriately used when the patient has a mild Class II skeletal relation with a Class II dental malocclusion. Treatment usually requires the extraction of either upper first bicuspids and lower second bicuspids or only the extraction of upper first bicuspids.


G

183

H

I

J

K

FIG 13-9, cont’d G to J, MARA plus orthodontic treatment final results. K, Posttreatment cephalogram.

20. What is surgical Class II treatment, and when should it be considered?6,25–27 Surgical Class II treatment is usually considered when the severity of the discrepancy is so great that neither growth modification nor camouflage treatment can be done to adequately correct the problem. The ultimate decision for surgical Class II correction must include not only the assessment of the treating orthodontist but also the age, psychological fitness, financial means, and desires of the patient. Surgical Class II treatment requires the combined efforts of the orthodontist and the oral surgeon. An accurate assessment of the components of the dental and skeletal Class II must be appropriately analyzed and the surgical sites appropriately delineated. The sequencing of this treatment requires presurgical orthodontic alignment and decompensation followed by necessary orthognathic surgery with 6 to 9 months of postsurgical finishing. Excellent surgical outcomes require the joint consultation among all the professionals involved.

Since skeletal Class II problems are most often due to mandibular deficiencies or clockwise rotation of the mandible due to excessive vertical growth of the maxilla, surgical treatment usually consists of mandibular advancement (66%), maxillary impaction (15%), or a combination (20%). Larger than 10 mm of overjet in a non-growing patient usually suggests the need for surgical correction. This is especially true if the lower incisors are protrusive relative to the pogonion, the mandible is short, or if the anterior face height is long.

21. What is the appropriate timing for orthognathic surgery during growth?6,26,27 If there is a significant dentofacial deformity, early orthognathic surgery may improve the health of the patient with regard to speech, airway, anatomy, occlusion, esthetics, TMJ function, masticatory function, and psycho-social factors. In the absence of a severe deformity, however, surgical mandibular advancement before the growth spurt is questionable. When the mandibular growth rate is normal, mandibular advancement can

184


A, C

E

B, D

F

FIG 13-10 Forsus treatment. A to B, Initial photos: Facial photos (A), dentition (B). C to D, Forsus appliance in place. E to F, Post-Forsus and orthodontic treatment results: Facial photo (E) and intraoral photo (F).

be stable due to continued normal growth of the mandible in its new position. When there is deficient mandibular growth (i.e., progressively worsening mandibular retrusion), the Class II skeletal and dental pattern can be expected to return after surgery as the maxilla continues its normal growth while the mandible continues its deficient growth. In this case additional surgery may be required. REFERENCES 1. McNamara Jr JA: Components of Class II malocclusion in children 8-10 years of age, Angle Orthod 51(3):177–202, 1981. 2. Baccetti T, Franchi L, McNamara JA, et al: Early dentofacial features of Class II malocclusions: a longitudinal study from the deciduous through the mixed dentition, Am J Orthod Dentofacial Orthop 111(5):502–509, 1997. 3. McNamara J, Brudon WL: Orthodontic and orthopedic treatment in the mixed dentition, Ann Arbor, 1993, Needham Press. 4. Moyers RE, Riolo MS, Guire KE, et al: Differential diagnosis of Class II malocclusions, Am J Orthod 78(5):477–494, 1980. 5. McNamara JA, Brudon WL: Orthodontics and dentofacial orthopedics, Ann Arbor, 2001, Needham Press. 6. Proffit WR, Fields HW: Contemporary orthodontics, ed 3, St Louis, 1993, Mosby. 7. Kjellberg H: Juvenile chronic arthritis. Dentofacial morphology, growth, mandibular function and orthodontic treatment, Swed Dent J Suppl 109:1–56, 1995. 8. Mossey PA: The heritability of malocclusion: part 2. The influence of genetics in malocclusion, Br J Orthod 26(3): 195–203, 1999. 9. Smith RA: The etiology of Angle Class II division 1 malocclusion, Angle Orthod 9:15–19, 1939. 10. Brezniak N, Arad A, Heller M, et al: Pathognomonic cephalometric characteristic Angle Class II division 2 malocclusion, Angle Orthod 72(3):251–257, 2002.

11. Sfondrini MF, Cacciafesta, Sfondrini G: Upper molar distalization: a critical analysis, Orthod Craniofac Res 5(2):114–126, 2002. 12. Bussick TJ, McNamara Jr JA: Dentoalveolar and skeletal changes associated with the pendulum appliance, Am J Orthod Dentofacial Orthop 117(3):333–343, 2000. 13. Shen G, Hägg U, Darendeliler M: Skeletal effects of bite jumping therapy on the mandible—removable vs. fixed functional appliances, Orthod Craniofac Res 8(1):2–10, 2005. 14. Berger JL, Pangrazio-Kulbersh V, George C, et al: Long-term comparison of treatment outcome and stability of Class II patients treated with functional appliances versus bilateral saggital split ramus osteotomy, Am J Orthod Dentofacial Orthop 127(4):451–464, 2005. 15. Graber TM, Vanarsdall Jr RL, Vig KWL: Orthodontics: current principles and techniques, ed 4, Philadelphia, 2005, Mosby. 16. Baccetti T, Franchi L, McNamara JA: The cervical vertebral maturation (CVM) method for the assessment of optimal treatment timing in dentofacial orthopedics, Semin Orthod 11:119–129, 2005. 17. Cozza P, Baccetti T, Franchi L, De Tolffol L, McNamara Jr JA: Mandibular changes produced by functional appliance in Class II malocclusion: a systematic review, Am J Orthod Dentofacial Orthop 129(5):599.e1–599.e12, 2006. 18. Clark WJ: The twin block traction technique, Eur J Orthod 4(2):129–138, 1982. 19. Allen-Noble P: Clinical management of MARA, Allesee Orthodontic Appliances 1–63, February 2002. 20. McNamara Jr JA, Howe RP, Dischinger TG: A comparison of the Herbst and Fränkel appliances in the treatment of Class II malocclusion, Am J Orthod Dentofacial Orthop 98(2):134–144, 1990. 21. Pangrazio-Kulbersh V, Berger JL, Chermak DS, et al: Treatment effects of the mandibular anterior repositioning appliance on patients with Class II malocclusion, Am J Orthod Dentofacial Orthop 123(3):286–295, 2003. 22. Toth LR, McNamara JA: Treatment effects produced by the twinblock appliance and the FR-2 appliance of Fränkel compared with an untreated Class II sample, Am J Orthod Dentofacial Orthop 116(6):587–609, 1999.


23. Heinig N, Goz G: Clinical application and effects of the Forsus spring. A study of a new Herbst hybrid, J Orofac Orthop 62(6):436–450, 2001. 24. 3M US Unitek Forsus™ Resistant Device. Forsus™ Fatigue Resistant Device L-Pin Module. http://solutions.3m.com/wps/portal/3M/ en_US/orthodontics/Unitek/products/intraoral/Forsus. 25. Tulloch JFC, Phillips C, Koch G, Proffitt WR: The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial, Am J Orthod Dentofacial Orthop 111(4):391–400, 1997. 26. Croft RS, Buschang PH, English JD, Meyer R: A cephalometric and tomographic evaluation fo Herbst treatment in the mixed dentition, Am J Orthod Dentofacial Orthop 116(4):435–443, 1999. 27. Uner O, Gültan AS: The changes in othodontic area after retention period in skeletal Class 2 cases treated with activator, Turk Ortodonti Derg 2(1):81–91, 1989 [Article in Turkish]. 28. Pancherz H: The Herbst appliance–its biologic effects and clinical use, Am J Orthod 87(1):1–20, 1985.

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29. Mihalik CA, Proffit WR, Phillips C: Long-term follow-up of Class II adult treated with orthodontic camouflage: a comparison with orthognathic surgery outcomes, Am J Orthod Dentofacial Orthop 123(3):266–278, 2003. 30. Wolford LM, Karras SC, Mehra P: Considerations for orthognathic surgery during growth, part I: mandibular deformities, Am J Orthod Dentofacial Orthop 119(2):95–101, 2001. 31. Proffit WR, White Jr RP, Sarver D: Contemporary treatment of dentofacial deformity, Philadelphia, 2003, Mosby. 32. 3 M Unitek Orthodontic Products: Forsus fatigue resistant device treatment guide (website PDF): http://multimedia.3m.com/ mws/mediawebserver?mwsId=66666UgxGCuNyXTtoXfXL xf_EVtQEcuZgVs6EVs6E666666--&fn=0122641_ForsusFRD_ TreatmentGuide. Accessed March 6, 2014. 33. Heinig N, Göz G: Clinical application and effects of the Forsus spring: a study of a new Herbst hybrid, J Orofac Orthop 62(6):436–450, 2001.

C H A PT E R

14

Class III Correctors

Peter Ngan

T

he skeletal Class III malocclusion is characterized by mandibular prognathism, maxillary deficiency, or a combination of both. These patients may have a retrusive nasomaxillary area and a prominent lower third of the face. Intraorally, patients usually present with a Class III molar relationship and a reverse overjet, depending on the severity of the skeletal discrepancy. Many treatment approaches have been advocated for Class III patients, ranging from early orthopedic intervention to camouflage and definitive surgical intervention. Methods designed to intercept the developing malocclusion have included partial fixed appliance, maxillary expansion and protraction with a facemask, chin cup, and fixed orthodontic appliance therapy. In this chapter, an attempt is made to answer a few frequently asked questions related to the use of these Class III correctors, including the indications for treatment, treatment timing, and the response of these appliances to treatment.

1. What is pseudo Class III malocclusion, and how can these patients benefit from early treatment? Patients with pseudo Class III malocclusion often present with anterior crossbites that are caused by a premature tooth contact or improper inclinations of the maxillary and mandibular incisors (Fig. 14-1). Elimination of the centric occlusion/centric relation discrepancy may avoid abnormal wear and traumatic occlusal forces to the affected teeth, avoid potential adverse growth influences in the maxilla and mandible, and improve maxillary lip posture and facial appearance.1 Correction of one or two anterior teeth in crossbite can be accomplished by using a fixed or removable appliance with an inclined plane, removable appliance with auxiliary spring, and lingual arch with finger springs (Fig. 14-2).2 Corrections of multiple anterior teeth in crossbite is best accomplished by partial fixed appliance. An expansion appliance or maxillary lingual arch in conjunction with partial fixed appliance can be used to correct anterior crossbite in young Class III patients. Fig. 14-3 shows an 8-year-old patient who presented with multiple teeth in anterior crossbite. A Hyrax maxillary expansion appliance was fabricated to create arch length for the alignment of the maxillary incisors. After expansion, a sequence of three archwires (0.012" NiTi, 0.018" NiTi, and 0.018" SS) were used to align the maxillary incisors. A coil spring can be inserted between the maxillary lateral incisors and the 186

first primary molars to help in the correction of crossbite. The correction is usually accomplished within 6 months, and retainers are usually not necessary if overbite is adequate after crossbite correction.

2. What is a Delaire facemask? The Delaire protraction facemask is used in the treatment of patients with Class III malocclusion and a maxillary deficiency.3 Oppenheim4 was the first to suggest that one could not control the growth or anterior displacement of the mandible and suggested moving the maxilla forward in an attempt to counterbalance mandibular protrusion. Petit5 later modified Delaire’s basic concept by increasing the amount of force generated by the appliance, thus decreasing the overall treatment time. The protraction facemask is made of two pads that contact the soft tissue in the forehead and chin region (Fig. 14-4). The pads are connected by a midline framework and are adjustable through the loosening and tightening of a set screw. An adjustable anterior wire with hooks is also connected to the midline framework to accommodate a downward and forward pull on the maxilla with elastics. To minimize the opening of the bite as the maxilla is repositioned, the protraction elastics are attached near the maxillary canines with a downward and forward pull of 30 degrees to the occlusal plane (Fig. 14-5). Maxillary protraction generally requires 300 to 600 g of force per side, depending on the age of the patient. Patients are instructed to wear the facemask for 12 hours a day.

3. When is facemask therapy indicated? The facemask is most effective in the treatment of mild to moderate skeletal Class III malocclusions with a retrusive maxilla and a hypodivergent growth pattern. Patients presenting with some degree of anterior mandibular shift on closure and a moderate overbite have a more favorable prognosis (Fig. 14-6, A to H). The correction of anterior crossbite and mandibular shift results in a downward and backward rotation of the mandible that diminishes its prognathism (see Fig. 14-6, I to P).

4. Is expansion necessary for protraction facemask treatment? Various appliances have been used as anchorage for maxillary protraction, including palatal arches and banded and

Class III Correctors • CHAPTER 14

A,B

187

C

FIG 14-1 A to C, Patients with a pseudo Class III malocclusion can often present with an anterior crossbite (A and B) that can be manipulated back to an end-to-end incisal relationship in centric relation (C).

A,B

C

FIG 14-2 A to C, Correction of an anterior dental crossbite (A) with a fixed lingual arch and finger springs (B). C, Posttreatment photo.

A,B C

D,E F

G

H

FIG 14-3 A to C, Eight-year-old patient with multiple teeth in anterior crossbite corrected with a Hyrax expansion appliance (D) and partial fixed appliance (E). F to H, Posttreatment photos.

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CHAPTER 14 • Class III Correctors require maxillary expansion for protraction. However, in the mixed dentition, the maxillary sutures become more tortuous and start to fuse together. The use of an expansion appliance can help in “disarticulating” the maxilla and initiate cellular response in the circumaxillary sutures, allowing a more p ositive reaction to protraction forces.

5. What is the best treatment timing for facemask therapy?

FIG 14-4 The protraction facemask uses the forehead and chin as anchorage to protract the maxilla forward and downward.

bonded expansion appliances (Fig. 14-7). Several circumaxillary sutures play an important role in the development of the nasomaxillary complex, including the frontomaxillary, nasomaxillary, zygomaticotemporal, zygomaticomaxillary, pterygopalatine, intermaxillary, ethmomaxillary, and lacrimomaxillary sutures (Fig. 14-8).2 These sutures are patent until 8 years of age. Patients in the primary and early mixed dentition do not

The optimal time to intervene in a patient with early Class III malocclusion is at the time of initial eruption of the maxillary central incisors. A positive overjet and overbite at the end of facemask treatment appear to maintain the anterior occlusion after treatment. Studies have shown that better skeletal and dental response can be obtained in the primary and early mixed dentition rather than in the late mixed dentition. The erupted maxillary first molars provide better anchorage for maxillary protraction. Maxillary protraction is effective through puberty, with diminishing skeletal response as the sutures mature.

6. What types of effects can be expected from facemask treatment? Anterior crossbites can be corrected with 3 to 4 months of maxillary protraction, depending on the severity of the malocclusion. Improvement in overbite and molar relationship can be expected with an additional 4 to 6 months of treatment.6 In a prospective clinical trial, overjet correction was found to be the result of forward maxillary movement (31%), backward movement of the mandible (21%), labial movement of the maxillary incisors (28%), and lingual movement

A

B

FIG 14-5 A, Protraction elastics are attached to the intraoral anchorage appliance near the maxillary canines region with a downward and forward pull of 30 degrees to the occlusal plane. B, The force vectors that minimize tilting of the palatal plane.


A

189

B

C

D

E,F

G

H

FIG 14-6 A to H, Eight-year-old patient with a Class III malocclusion and a deficient maxilla treated with maxillary expansion and protraction. A and B, Facial photos. C to G, Intraoral photos. H, Cephalometric radiograph. (Continued)

190

CHAPTER 14 • Class III Correctors

I

J

K

L

M,N

O

P

FIG 14-6, cont’d I to P, Posttreatment photographs showing an improvement in facial profile and correction of the anterior crossbite with 8 months of maxillary protraction. I and J, Facial photos. K to O, Intraoral photos. P, Cephalometric radiograph.


191

7. Are these treatment results stable long term? A

B

FIG 14-7 A and B, Rapid palatal expansion appliance used as anchorage for maxillary protraction.

Prospective clinical trials have shown that the effects on the maxilla remained stable for 2 years after facemask treatment.8 During this growth period, the maxilla and mandible reverted back to the original growth pattern. Long-term studies have shown that treatment is successful in 67% to 75% of the patients.9,10 The malocclusion can be camouflaged by orthodontic treatment. Patients who reverted back to an anterior crossbite will eventually require surgical treatment when growth is completed. Therefore, an overcorrection of the maxilla to 3 to 4 mm of anterior overjet is recommended for patients who are diagnosed with excessive mandibular growth.

8. Are there variations in clinical response to facemask treatment? Clinically, the maxilla can be advanced 2 to 4 mm over an 8to 12-month period of maxillary protraction. The amount of forward maxillary movement is influenced by a number of factors, including age of patient, the use of expansion appliance, the force level, the direction and point of force application, and the treatment time. In a prospective clinical study, individual variation in the forward movement of the maxilla can vary from −3.5 mm to +6 mm, and vertical movement of the maxilla varied from −0.5 mm to +2.0 mm with 8 months of maxillary protraction.11

9. Is retention necessary after facemask treatment? Studies have shown that the use of removable appliances such as a Fränkel III regulator or a mandibular retractor helps in maintaining the sagittal and transverse correction by facemask and allows muscle adaptation to the new position of the maxilla (Fig. 14-9). FIG 14-8 Circumaxillary sutures involved in maxillary protraction. A, Frontomaxillary suture. B, Nasomaxillary suture. C, Zygomaticomaxillary suture. D, Zygomaticotemporal suture. E, Pterygopalatine suture. F, Intermaxillary suture. G, Lacrimomaxillary suture. H, Ethmomaxillary suture.

of the mandibular incisors (20%). Molar relationship was corrected to a Class I or Class II dental relationship by a combination of skeletal movement and differential movement of the maxillary and mandibular molars. Anchorage loss was observed during maxillary protraction with mesial movement of the maxillary molars. Overbite was improved by eruption of the maxillary and mandibular molars. The total face height was increased by inferior movement of the maxilla and downward and backward rotation of the mandible. Treatment with protraction facemask can also improve the facial profile by decreasing the facial concavity, improving the posture of the lips, and decreasing the retrusive nasomaxillary area.7

10. When should a chin cup be used? Skeletal Class III malocclusion with a relatively normal maxilla and a moderately protrusive mandible can be treated with a chin cup (Fig. 14-10). It is also indicated in patients when increases in lower anterior facial height are not desired. The objective of this treatment is to provide mandibular growth inhibition and/or redirection and posterior positioning of the mandible.2

FIG 14-9 Fränkel III Regulator used for retention after protraction facemask treatment.

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A B

FIG 14-10 A and B, Chin cup for treatment of patients with Class III malocclusion and protrusive mandible.

11. What is the force magnitude and direction recommended for chin cup treatment? Chin cups are divided into two types: 1) the occipital-pull that is used for patients with mandibular protrusion and 2) the vertical-pull that is used in patients presenting with a hyperdivergent or long face. An orthopedic force of 600 to 700 g for 12 hours per day is recommended. The orthopedic force is usually directed through the condyle or below the condyle (see Fig. 14-10).

12. What types of effects can be expected from chin cup treatment? The orthopedic effects of a chin cup on a mandible include: 1. Redirection of mandibular growth vertically 2. Backward repositioning (rotation) of the mandible 3. Remodeling of the mandible with closure of the gonial angle To date, there is no agreement on whether chin cup treatment inhibits mandibular growth. Chin cup treatment has been shown to produce a clockwise rotation of the mandible during orthopedic treatment. However, studies have shown that removal of the chin cup prior to completion of pubertal growth may lead to return of the horizontal growth pattern of the mandible.

13. What are the timing and duration of chin cup treatment? Patients with mandibular excess can usually be recognized in the primary dentition despite the fact that the mandible appears retrognathic in the early years for most children. Evidence exists that treatment to reduce mandibular protrusion is more successful when it is started in the primary or early mixed dentition. The treatment varies from 1 year to as long as 4 years, depending on the severity of the malocclusion. Recent studies have shown that removal of the chin

cup before completion of pubertal growth invites treatment relapse because the mandible resumes to a more horizontal Class III growth rate and direction during the pubertal growth period. It is recommended that treatment with the chin cup be continued until completion of the pubertal growth period.

14. What is camouflaged Class III treatment? In young patients with mild to moderate skeletal jaw discrepancies, Class III malocclusions can be camouflaged by early orthopedic treatment to normalize the jaw relationships using appliances such as the facemask or chin cup. In older patients where growth is completed, treatment is limited by camouflaging the underlying jaw differences with proclination of the maxillary incisors or retraction of the mandibular incisors. Fixed appliances with Class III elastics that run from the maxillary molars to the mandibular canines are used to achieve the desired tooth movements. In patients with crowded dentitions or dentoalveolar protrusion, extraction of the mandibular first premolars and maxillary second premolars may be necessary to camouflage the malocclusion (Fig. 14-11).

15. What is surgical Class III treatment? Class III patients with significant anteroposterior jaw discrepancies that cannot be camouflaged with orthodontic tooth movement will have to be treated surgically. This is usually performed after growth is completed. Depending on the diagnosis, the maxilla may be brought forward with a LeFort I surgical osteotomy procedure, and the mandible may be set back with a bilateral sagittal split osteotomy or a combination of both. Presurgical orthodontic treatment is usually necessary to decompensate the dentition and allow maximum jaw movement to obtain optimal facial appearance (Fig. 14-12).


A

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E

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F,G H

FIG 14-11 A to H, Thirteen-year-old patient with a mild Class III malocclusion and crowding treated with extraction of premolars to camouflage the skeletal malocclusion. A and B, Facial photos. C to G, Intraoral photos. H, Cephalometric radiograph. (Continued)

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I

J

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FIG 14-11, cont’d I to P, Posttreatment photographs showing the improvement in facial profile and occlusion. I and J, Facial photos. K to O, Intraoral photos. P, Cephalometric radiograph.


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195

B

C,D

E

F,G H

FIG 14-12 A to H, Eighteen-year-old patient with skeletal Class III malocclusion and mandibular asymmetry treated with surgical maxillary advancement and asymmetric mandibular setback to correct the skeletal problems. A and B, Facial photos. C to G, Intraoral photos. H, Cephalometric radiograph. (Continued)

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FIG 14-12, cont’d I to P, Posttreatment photographs showing the improvement in facial profile and occlusion. I and J, Facial photos. K to O, Intraoral photos. P, Cephalometric radiograph.

REFERENCES 1. Joondeph DR: Early orthodontic treatment, Am J Orthod 104:199–200, 1993. 2. Ngan P: Treatment of Class III malocclusion in the primary and mixed dentition. In Bishara S, editor: Textbook of orthodontics, Philadelphia, 2003, Saunders, pp 375–414. 3. Delaire J: Maxillary development revisited: relevance to the orthopaedic treatment of Class III malocclusions, Eur J Orthod 19:289–311, 1997. 4. Oppenheim A: A possibility for physiologic orthodontic movement, Am J Orthod Oral Surg 30:345–346, 1944. 5. Petit HP: Adaptation following accelerated facial mask therapy. In McNamara Jr JA, Ribbens KA, Howe RP, editors: Clinical alterations of the growing face, Monograph 14. Craniofacial growth series, Ann Arbor, 1983, Center for Human Growth and Development, The University of Michigan. 6. Ngan P, Hagg U, Yiu C, et al: Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction, Semin Orthod 3(4):255–264, 1997.


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7. Ngan P, Hagg U, Merwin D, et al: Soft tissue and dentoskeletal profile changes associated with maxillary expansion and protraction headgear treatment, Am J Orthod Dentofacial Orthop 109:38–49, 1996. 8. Ngan P, Yiu C, Hu A, et al: Cephalometric and occlusal changes following maxillary expansion and protraction, Eur J Orthod 20:237–254, 1998. 9. Westwood PV, McNamara JA, Baccetti T, et al: Long-term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances, Am J Orthod Dentofac Orthop 123:266–278, 2003. 10. Hagg U, Tse A, Bendeus M, et al: Long-term follow-up of early treatment with reverse headgear, Eur J Orthod 25:95–102, 2003. 11. Ngan P, Hagg U, Yiu C, et al: Treatment response to maxillary expansion and protraction, Eur J Orthod 18:151–168, 1996.

C H A PT E R

15

Minor Tooth Movement

G. Fräns Currier

I

solated tooth movement necessitates that other teeth should not be moved (i.e., anchored). These tooth movements can be within either the maxillary or mandibular arch as either lateral (transverse), front-to-back (sagittal or anteroposterior), or between the arches, most noticeably transverse or sagittal. Isolated vertical movement, such as extrusion or intrusion, also necessitates important anchorage considerations so that the adjacent teeth do not move. This tooth movement in the transitional dentition is associated with interceptive orthodontics, whereas in the adult it is adjunctive orthodontics in association with fixed prosthodontics, anterior esthetic restorative dentistry, or restorative implants. The most common tooth movement in the primary dentition should be related to the correction of the quadrant posterior crossbite with mandibular shift caused by a narrow maxillary primary intercanine width. The extraction or discing of selected primary teeth is often related to certain types of isolated tooth movement. Sometimes the extractions themselves can improve or correct problems as seen with mandibular midline discrepancies or moderate clinical crowding in the 8- to 10-year-old patients, unfavorable pathway of eruption of the permanent canine in the 9- to 11-year-old patients, the maxillary midline succedaneous supernumerary tooth in the 7- to 9-year-old patients, and the uprighting of the permanent second molar in the adult. Crossbite malocclusions need to be treated in most cases near the time of recognition because of unfavorable asymmetric patterns, anomalous development, or harmful development to the teeth or jaws, including the periodontium. Anterior openbite cases are addressed with the eruption of the permanent eight incisors. The soft tissue profile and esthetic lines of the face, as well as the skeletal pattern seen with the mandibular plane to Frankfort horizontal, are helpful areas of orientation for proper isolated tooth movement.

1. What does minor tooth movement in orthodontics mean compared with major tooth movement? For some, there is no minor tooth movement. All tooth movement is major. One needs to understand that there is orthodontic tooth movement (and orthodontic force systems, which are lower) compared with orthopedic movement (and orthopedic force systems, which are higher).1 Lower force systems are usually related to apposition/resorption of the alveolar bone 198

around the tooth/teeth being moved. One can compute these in ounces or in grams (28 grams = 1 ounce). The current preferred method for most orthodontic tooth movement is not only on the lighter side but also in the continuous format.1,2 One can actually have orthopedic effects (bones moved more than the teeth) with orthodontic forces. An example of this is the quadhelix appliance in the maxillary arch of preschoolers. However, most orthopedic effects are accomplished with higher, or orthopedic, force systems in which the forces applied to the anchor teeth are manifested in the bones. A better term than minor tooth movement is probably isolated tooth movement, in which there is need for a limited amount of orthodontic movement. This also means that other teeth should not be moved. This brings up the concept of anchorage. One does not wish to move the anchor teeth or else the orthodontic system is compromised. An example of an anchor unit is a canine-to-canine lingual arch that can be used in the uprighting of a mandibular permanent second molar. The common term associated with isolated tooth movement in children is interceptive orthodontics; it is called adjunctive orthodontics when it is associated with adults. It is not associated with first-phase corrective orthodontics where too many tooth movement objectives need to be met. Examples of the first phase (usually 12 to 18 months of active therapy) are early treatment of Class II malocclusions with a headgear or a functional appliance and Class III malocclusions with a rapid palatal expander (RPE) and protraction facemask therapy.2

2. When should we first consider orthodontic treatment? The sequence of maturation of the dentofacial complex is not related to Angle’s dental classification of malocclusion, although that helps in classifying treatment problems.3 That skeletal sequence is the transverse plane (side to side), followed by the sagittal plane (anteroposterior problems), and then the vertical plane (deepbite vs. openbite or short face syndrome vs. long face syndrome).4 In the primary dentition, there is usually no crowding, but there can be shifts of the lower jaw to the left or right as the teeth go into maximum intercuspation of occlusion. The maxillary primary canines can erupt into a constricted intercanine dimension about 15 to 20 months after birth that will not allow the lower arch to fit properly. This usually causes the lower

jaw to shift to one side or the other, with the dental midlines becoming non-coincident.5 If one aligns the midlines of the two arches, it is noticeable that the lower arch cannot fit. Probably the best approach to solve this problem is to expand the maxillary arch. Another approach that does not involve isolated tooth movement can be achieved with an occlusal adjustment of the primary canines (i.e., facial of the lower canines and lingual of the upper canines). However, there will be little effect on the lateral overjet of the primary molars. Expansion of the maxillary arch can be achieved in a variety of ways using either fixed or removable appliances.6 A removable jackscrew appliance with a bite plane has the limitations of only two turns per week, or 0.5 mm of expansion, as well as the issue of patient compliance in wearing the appliance. It has limited or no orthopedic effect—only dentoalveolar tipping. Each turn of the screw is 0.25 mm. A predictable appliance for use in the preschooler is a quadhelix from the primary second molars. This appliance is an improved biomechanical one from the original “W” appliance. The quadhelix is fabricated to fit passively. Prior to insertion, the appliance is expanded approximately 10-mm in the faciallingual dimension of the primary second molar and then cemented. By doing this, the appliance can be evaluated in 3- to 5-week intervals. Intraoral activation laterally of a cemented quadhelix is possible but unpredictable. A 10-mm expansion usually gives 5- to 6-mm expansion within 3 to 4 months. The appliance is left in place for another 4 to 6 months after getting the proper lateral overjet with no quadrant in crossbite. It is not necessary to remove the appliance to place a passive Hawley for retention. The total length of the quadhelix treatment is usually about 6 to 8 months. It is not common to have to remove, reactivate, and recement a properly expanded quadhelix. This is the most common active appliance in the primary dentition, and it has an orthopedic effect, which means the left and right maxillae also move. This effect is positive, since it increases the chance for the permanent molars to erupt properly. Another appliance that can be used in the primary dentition is a two-tooth RPE appliance (fixed appliance with a screw from the primary second molars).2–6 This fixed RPE can be expanded either once or twice a day. Although appreciable results can be obtained from using the two-tooth RPE, the quadhelix is the appliance of choice for the treatment of posterior quadrant crossbites in the early to middle transitional dentition. However, upon the eruption of the maxillary first premolars and the presence of a quadrant posterior crossbite, the use of a more rigid appliance that can produce an orthopedic effect should be considered, such as a four-tooth RPE. The mechanics related to the RPE are more complex with multiple sutural effects.7 The use of coordinated archwires with light forces in the permanent dentition has been reintroduced into corrective orthodontics for adolescent treatment. The greater the expansion in the posterior portion, the more stable the results. Furthermore, the greater the effect in the middle arch, the greater the increase in arch perimeter.7

Minor Tooth Movement • CHAPTER 15

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3. How does one orient the lower arches with posterior crossbites? The mandibular arch is consistently ovoid in shape with a midline suture that fuses shortly after birth or by the first year. In some Class II division 2 malocclusions, the lower arch can be square. There is no orthopedic effect of the left and right mandibular bones used in orthodontics, as the midline fusion occurs so early.2 However, the facial-lingual inclination of the mandibular posterior teeth (along the long axis of the tooth) helps in the understanding of the treatment of the lower arch. If the posterior permanent teeth lean inward with the crowns toward the tongue and the roots too far to the facial while the lateral overjet is minimal, then there is probably a problem with constriction of the maxillary arch (curve of Wilson problem with too much lingual crown torque). If one were to upright the lower buccal segments, the result would be a bilateral posterior quadrant crossbite. It is normal to have a mild progressive movement of the roots of the premolars/permanent molars facial to the crowns. It is not uncommon for orthodontists to consider maxillary orthopedics after a proper analysis and positioning of mandibular posterior teeth. All permanent teeth, except the maxillary incisors, are supposed to have their roots facial, or upright, compared with their tooth crowns. These incisors are supposed to have their roots lingual and crowns facial (lingual root torque). This can occur with the mandibular incisors, but it is more variable. The use in individual permanent molar crossbite is the application of cross-elastics. These elastics, usually from the lingual of the maxillary permanent molar to the facial counterpart, present problems with the collateral effect of extrusion of these teeth with the elastics with resultant worsening of the molar relationship.

4. Where does one treat most posterior crossbites? Crossbites are usually treated in the maxilla. The maxillary arch form can vary by the type of Angle’s classification. The common maxillary arch form is ovoid; however, the Class II division 2 malocclusion can present with a square arch form whereas the Class II division 1 malocclusion can present with a tapered arch form. With this Class II division 1 middle arch constriction, as the mandible shifts forward, a bilateral posterior quadrant crossbite can be presented. Therefore, one must be aware that hidden posterior crossbites can occur when the malocclusion is not Class I.5

5. Is there more than one type of posterior crossbite from the classic one presented with maxilla lingual and mandible facial? Yes. The first one, which is not common, has the lower arch completely within the maxilla. It can manifest on one side or both and is called a Brodie bite. The expansion is usually done in the lower arch with a fixed appliance plus a removable bite plane in the maxillary arch that helps disarticulate the occlusion. This problem needs early treatment.5 This can also be seen in the maxillary arch with it completely within the mandibular arch. This pattern is complex and needs to be analyzed

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CHAPTER 15 • Minor Tooth Movement

on a case-by-case basis with the need for bite plane therapy and maxillary orthopedics. The second problem is usually seen later upon the eruption of the permanent second molars. The more common pattern is with the maxillary permanent second molar facial and the less common mandibular permanent second molar lingual. In the maxilla, because of the rhomboid shape of the permanent first molar and the lack of a vertical stop of the malposed permanent second molar, the second molar often needs to be moved distal first and then aligned. Cross-arch elastics are interarch elastics that can make the extrusion problem worse. Maxillary third molars should not be removed prior to these buccoversions of the maxillary permanent second molars nor should they be removed in Class II molar relationships. The removal of the maxillary permanent second molar may be reserved with the third molar as the replacement. This consideration in the mandibular arch is rare. Both problems are more difficult to treat than the usual crossbite, which is due to maxillary transverse deficiency. This is due to the vertical dimension that is manifested in these problems.

6. What happens to individual tooth crossbites if left untreated? If left untreated, abnormal wear patterns appear on the teeth. There can be adverse periodontal responses around the affected teeth. If the quadrant crossbite is left untreated, the growth of the jaw can also be affected adversely.2 From an orthodontic tooth movement point of view, the issue becomes more complex. Whatever the orthodontic intervention initially proposed, usually involving more tipping than torque movements, the problem now presents as an issue of arch perimeter and crowding in the area of crossbite. It is necessary to regain the room in the arch prior to correction of the crossbite. This might involve interproximal tooth reduction or discing and/or removal of primary teeth. One should not reduce proximal surfaces of permanent teeth in the transitional dentition in the correction of crossbite. The crossbite problem is now a two-step treatment sequence as opposed to an earlier one-step sequence.

7. If anterior and posterior crossbites exist within the same patient, which crossbite comes first in the tooth movement? It is usually the posterior quadrant problem involving primary teeth initially. The problem of anterior crossbite of single primary teeth is as rare as a single primary molar crossbite.8 The anterior quadrant variety of primary incisors is usually a manifestation of a skeletal problem that necessitates a combination of intraoral and extraoral appliances. If there is a combination of a posterior and anterior crossbite with the same patient, one treats the posterior crossbite first, then the anterior. If the anterior crossbite is treated first, its correction will be lost when the posterior crossbite is corrected.8 A removable appliance to assist in correction of the anterior crossbite allows retention of the corrected posterior crossbite. The anterior crossbite problem is usually associated

with lingual eruption of the maxillary permanent incisors. The permanent lateral incisor is usually more common in a crossbite than the permanent central incisor. It is not uncommon for the incisors to erupt lingually in a bilateral expression. The timing of treatment of the permanent incisor crossbite correction is important, and it is related to the stage of eruption and the amount of overbite. Tipping the lingually positioned incisor facially causes the overbite to become more shallow. If the overbite is very shallow initially, the tooth/teeth do not retain well in the corrected position. Therefore, it is more appropriate to treat these incisor crossbites when more overlap is present, so that after the treatment is completed, the occlusion can maintain the correction. Both central incisors or both lateral incisors should be treated at the same time. With increased overbite, there is usually a need for a bite plane to open the bite to allow easier and quicker correction of the crossbite. If there is no anterior slide from centric relation, or restricted contact positions with the incisor crossbite, the prognosis of correction decreases markedly, because a skeletal problem is most likely present. The problem with correction of permanent incisor crossbites using a removable appliance with finger springs and a bite plane, or a fixed lingual arch with a finger spring, is that the maxillary incisors will not be well aligned after correction. Many times placing brackets from primary canine-to-canine, including the permanent incisors, is needed for proper alignment. This malalignment problem that needs bracket positioning is usually not necessary in the mandibular arch because of the contained arch principal and functioning occlusion. The removal of the primary canine to gain space for the correction of a permanent lateral crossbite in the maxilla should be limited and treatment should be redirected toward expansion of the buccal segments, space opening with a coil spring for the lateral incisor, and alignment of the primary canine–permanent incisor segment with bracketing. This approach makes the retention of the corrected crossbite much easier than the natural distal angulation of the corrected incisor into the area of the primary canines.

8. What is the problem with these crossbites? Most early crossbites involve the muscles of mastication and are dental crossbites with shifts, or functional crossbites.2–5 Posterior crossbites manifest themselves with curve of Wilson problems (adverse axial inclination of the buccal segments). The posterior teeth are inclined too far facial in the maxilla or too far lingual in the mandible. These are classic signs for the need of maxillary orthopedics, which should be done early. Because the transverse plane matures the earliest, it is important that it be treated prior to the fusion of the midpalatal suture. The correction of transverse discrepancies later with orthodontics and orthognathic surgery is not as successful or predictable as one would like. The most common abnormal slide from centric relation in children is related to posterior crossbites with lateral slides and then anterior crossbites later.6 The pseudo Class III malocclusion with shift is an anterior crossbite malocclusion with a marked slide of 2 to 3 mm. The normal slide in any direction


horizontally is 1 to 2 mm because of natural skeletal asymmetry, and the normal lateral overjet throughout the occlusion should be about 1 to 2 mm. There is also a pseudo Class III malocclusion that is related to the premature loss of a mandibular primary second molar and the shift of the permanent first molar forward from a Class I molar relationship. Premature loss of maxillary primary second molars allows the permanent first molar to shift to a pseudo Class II relationship. The lack of a slide from centric relation with a crossbite is usually a classic sign of a skeletal problem and should be referred to an orthodontist, especially if the crossbite is in conjunction with a crowding problem; a more complicated intervention is probably needed.

9. What happens if the treatment of crossbite malocclusions does not seem to be working? Tincture of time certainly helps. Crossbite correction is needed in all types of orthodontics and is usually addressed early in the treatment plan.1,2,6 If one has isolated cases of the problem and it is taking too long to treat, one needs to step back and reevaluate the treatment plan. There could be problems with the mechanics, problems with cooperation, or problems with the diagnosis. If the diagnosis is not correct, the treatment will not be successful. Crossbites should to be corrected in about 6 months.2 If treatment time is approaching 1 year, there is a problem.

10. Does one need an orthodontic database for isolated tooth movement? Clinicians need to know where they are going. If not, they do not know where they have been. Selected radiographs, photographs, and models with proper analysis will be helpful to plan and implement care.

11. What about the vertical plane and isolated tooth movement? The vertical plane is the last plane of the face and occlusion to mature and truly manifest itself. It is a complex plane to treat. The posterior vertical face height is determined near the patient’s ear while the anterior vertical face height is determined from the nose to the chin. The anterior portion can be further divided into upper (more height) vs. low below nose to chin. Bite plane therapy to correct deep bites takes a long time and usually is not as successful as one would like. Dental openbite problems are usually related to digit habits.9,10 These problems are usually not treated until the permanent incisors erupt. Some openbite/posterior crossbite problems can be treated earlier with patient cooperation. Habit reminder appliances that are removable or fixed, depending on the specific circumstance, with the use of anterior elastics, are possible in 8- to 10-year-old patients who agree to help stop the habit. Because this appliance attempts to stop an adverse event, it is sometimes considered a mild form of punishment (stopping the habit). For these appliances to work, one needs to also use positive reinforcement (praise) in the process of stopping the habit. Usually the tongue is compensatory to the openbite and

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not the primary etiology. An orthodontic appliance that does not have an active component takes longer to treat with less predictable results. The major mistake made with orthodontic appliances in correction of these openbites is that the habit reminder position at the lingual of the maxillary incisors is too close to the incisors and prevents the future lingual movement of those teeth in the correction of the problem. The presence of diastemata (multiple areas of space vs. diastema for one space) improves the prognosis. Correction of the anterior openbite associated with speech articulation distortion (age 9 years and older) does not mean that the speech problem will self-correct.10 These speech problems need to have evaluation prior to correction of the anterior openbite.

12. What does the orientation of the face have to do with isolated tooth movement? In general, isolated tooth movement is associated with ortho dontic treatment plans that involve no planned removal of permanent teeth, except perhaps the third molars.2,11 Orthodontists should treat to the patient’s face.12 However, the face changes during growth and development. The soft tissue facial profile does not accurately reflect the underlying hard tissue or bony profile.13

13. What are the problems associated with the arches that need to be addressed in the early transitional dentition? There are two common problems that need to be addressed; both are related to ectopic eruption of the permanent incisors and/or the permanent first molars.2 The more common problem is the lingual eruption of the mandibular permanent incisors with mild natural expansion of the mandibular primary intercanine width. Because there is usually an incisor liability problem in the lower arch of approximately 5 mm (4-mm-wide primary incisors vs. 5- or 5.5-mmwide permanent incisors), anterior clinical crowding should be expected in many cases.14,15 Natural realignment of the permanent incisors can occur with either discing or removal of the primary canines. In these circumstances, a lingual arch from the permanent first molars with an ideal anterior arch form is usually needed.16 However, if possible, a lingual arch from the primary second molars can be considered to conserve the enamel of the permanent molars. Lingual arches that are bent to follow the maligned incisors will not allow the natural selfcorrection of the clinical crowding of these teeth. If one mandibular primary canine has exfoliated early, causing a midline shift, removal of the contralateral primary canine (same tooth on the opposite side) with the placement of a lingual arch can allow the lower midline to self-correct. Ectopic eruption of the permanent first molar is present in 2% to 3% of occlusions. It is much more common in the maxillary arch. The normal path of eruption of this molar is in a distal facial pattern. However, the molar can deviate to the mesial and lock itself into the distal surface below the contact of the primary second molar. Conservative intervention is best with limited use of a distalizing orthodontic appliance.

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Separating springs or de-impacting springs should be used initially and then followed with radiopaque elastomeric separators. Appointments to monitor progress are spaced every 3 to 6 weeks. Discing of the distal of the primary second molars should be limited. Removal of the primary second molar and distal movement of the permanent first molar via a fixed or removable orthodontic appliance is difficult because of patient cooperation, stage of permanent tooth eruption, and anchorage considerations. These orthodontic appliances should be used as a last resort.17 After correction of the ectopic permanent first molar, the area near the distal of the primary second molar heals satisfactorily. It usually involved ditching of the root apical to the contact. Only if an endodontic-periodontic problem manifests with the primary second molar because of an infected (parulis) or symptomatic circumstance should the primary second molar be removed. Reevaluation concerning distalization mechanics is dependent on a thorough review of the entire dentofacial complex.17 The ectopic position of the mandibular permanent first molar is much less common. This tooth attempts to erupt with a mesial-lingual angulation. Observation/separating/discing/removal/appliance therapy should be considered in that order. This type of ectopic eruption is usually a sign of crowding in the arches that might also be seen in the anterior portion of the arch.

the case. Because most of these cases have anterior deepbite problems, the brackets on the canines need to be placed more gingivally. Most adults have deepbite problems as compared to openbite problems. The maxillary permanent second molar moves into a position different from that of the mandibular second molar after the loss of the permanent first molar. The maxillary molars rotate more around the larger palatal root with the buccal rotated mesially. Therefore, forces that move the tooth posterior and facial are needed. This means the movement is more of a rotational one as compared with the lower arch. The maxillary arch still should have cross-arch anchorage between the permanent canines. If the permanent canines are too severely angulated to the mesial, a first premolar palatal arch should be considered. Removable orthodontic appliances to create this type of tooth movement are not as efficient as fixed appliances. Uprighted second molars need fixed retention rather than removable retention to maintain the results. Molar uprighting is usually not associated with removable partial dentures. If the patient stops wearing the retainer or the RPD, the teeth will have a tendency to move back to their original positions. The use of implants has reduced the number of cases that need molar uprighting. However, the periodontal status and the accompanying marginal bone heights should be considered in the treatment plan.

14. How do we treat the mesial angulation tipping of the permanent second molar?

15. Is there any isolated orthodontic tooth movement the clinician should consider with permanent canines?

The isolated movements of these teeth would be associated with an occlusion that is normal, except for this problem. If the face or the rest of the occlusion needs to be addressed orthodontically, referral to an orthodontist should be considered.2 Bilateral molar uprighting creates more stress on the anterior anchorage unit. Combined or individualized uprighting should be done depending on the features of the dentofacial complex. The method of uprighting a permanent second molar is not the same for both arches. This problem is usually seen in the lower arch with the loss of the permanent first molar. The permanent second molar is an excellent anchorage unit, so the anterior segment needs to be stabilized to prevent a facialanterior reciprocal movement of the premolars and canines. Even if the permanent second molar is moderately tipped, usually in a lingual-mesial pattern, the need is still present for anterior cross-arch anchorage with a canine-to-canine lingual arch. If the anchorage units move during the uprighting, the case is compromised. The usual result is an anterior facial movement of the permanent canine that is very difficult to move back into position. Active molar uprighting usually takes about 6 to 9 months. However, the tooth needs to be stabilized for a few more months prior to abutment preparations. Restorative preparations are better accomplished on stable, not mobile, teeth. During molar uprighting, one of the collateral movements of the permanent second molar can be extrusion.17 It is common that the teeth need to be adjusted occlusally during the uprighting. No anterior openbite occlusion should occur in

Usually the answer is no. However, all cases of unerupted, permanent canines by the age of 9 to 10 years should be palpated. If these teeth cannot be palpated on the facial, they should be assumed to be on the lingual or palatal, or in an unfavorable position.18 This is a much more common problem in the maxillary arch than the mandibular arch. Most of the time, there does not seem to be a major crowding problem in the arches with these cases. The removal of the maxillary primary canine on the affected side should be considered as a method of redirecting the pathway of the unerupted palatal permanent canine. Unfavorable eruption patterns can sometimes be improved with this approach. There is no need to remove the primary canine if there is congenital absence of the permanent lateral incisor on the affected side. The permanent canine will erupt into the position of the lateral incisor, and the primary canine will be retained distal to the mesially positioned permanent canine. Future corrective orthodontics can address this problem.

16. Is there any one permanent tooth extraction treatment plan for isolated tooth movement? There are almost no orthodontic treatment plans involving extraction of one permanent tooth.19 Third molar removal adjacent to second molar uprighting is an exception. Extracting a single permanent tooth in the maxillary arch creates problems associated with crossbites caused by maxillary arch collapse. Extracting a single permanent tooth in the mandibular arch creates lateral overjet problems and anterior deepbite


roblems. This single extraction sequence results in a toothp size arch-perimeter discrepancy. This is similar to the tooth-size arch-perimeter discrepancy with maxillary peg lateral incisors known as the Bolton discrepancy.20

17. What are the isolated tooth movements related to spacing in the arches? The most common problem is associated with the maxillary midline. There is usually generalized spacing in the maxillary anterior segment between 7 and 10 years of age. This is not true in the lower arch because of the contained arch principle. The maxillary incisor liability problem is usually worse than the mandibular incisor liability problem (7 mm vs. 5 mm). However, the upper arch is not contained unless there is an anterior quadrant crossbite and a generalized facial positioning of the permanent incisor crowns with the roots more lingual as compared with the more upright primary incisors. The discussion of closing the midline diastema is related to the stage of eruption of the permanent incisors. Usually one does not close the diastema before the eruption of the permanent canines. From tissue emergence to occlusion, the process of tooth eruption usually takes 4 to 6 months. After all four permanent maxillary incisors have erupted, one then estimates the spacing. If the midline diastema is 2 mm or less, the space should close on the eruption of the permanent canines. If it is larger, the chances of its closing by itself without orthodontic intervention are small. The one thing a clinician should not do to close this space is to place rubber bands, or elastics, around the two incisors. The elastics will migrate apically, cause loss of the alveolar bone, and may even result in inappropriate loss of these teeth. It is usually more efficient to close this space with a fixed appliance rather than a removable one. The wire needs to be stiff enough to prevent undue tipping of the incisor crowns, yet allow sliding of the teeth together. In the adult, dark triangles can result if the distance from the alveolar bone height to the apical position of the contact is more than 5 mm after space closure. A decision relative to frenectomy and orthodontic space closure in this area is related to tooth movement and retention. It is easier to close the space initially and then prescribe the surgical procedure to remove the fibrous band. If the PA radiograph demonstrates an inverted V between the alveolar bone of the two central incisors (muscular band), there is probably a greater need to do a surgical procedure. The surgical procedure removes tissue that assists in keeping the space closed and prevents the diastema from reopening. The decision to perform a surgical procedure should be discussed prior to orthodontic intervention. To recommend surgical intervention after the isolated movement, without prior information given to the patients and/or parents, is not recommended.

18. What if the permanent incisors erupt in a rotated position? This problem is often related to either a midline supernumerary tooth that prevents the normal eruption of the affected incisors or trauma and displacement of the primary incisor, usually occurring at the time a child falls down at 2 to 3 years of age while learning to walk.1,2

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The cause of the rotated permanent incisor should be removed first (i.e., the supernumerary tooth or the ankylosed/ traumatized primary incisor). After this, an observation period with radiographic follow-up should occur. This usually takes about 4 to 6 months. If the permanent incisor erupts, but is rotated, a fixed orthodontic appliance should be placed with facial and lingual attachments on the rotated tooth. The specific case might need more extensive bracketing and anchorage, depending on the situation. However, it is easier to treat early and then retain with a removable appliance with a possible second corrective orthodontic phase to establish a good position in the arch. Corrected tooth rotations create significant relapse problems in orthodontics. Multiple approaches to address this problem are used, including overcorrection, splinting, and/ or supracrestal gingival fiberotomy.21 The relapse problem is related to transseptal fibers. The fibers near the alveolar bone height need to be resected. This procedure is performed around the affected tooth, except the facial fibers on the tooth, which prevents any possible apical migration of the tissue on the facial of these teeth. A fixed orthodontic appliance needs to be in place and remain in place to act as retention for 4 to 6 months after the surgery. A removable appliance does not effectively maintain a corrected rotated tooth.

19. What about “forced eruption” of a tooth that needs further restorative dentistry? This is usually related to fractures of anterior teeth. The tooth that needs the extrusion can be treated with a more apical positioning of the bracket.1,10 One must consider this extrusion as a reduction of a proper crown-root ratio, with a shorter length of the root in the alveolar bone. The relapse potential after the extrusion is apical, so a temporary restoration to maintain the extrusion prior to completion of the restoration should be considered. The lowest forces in orthodontic tooth movement are related to intrusion at 10 to 15 g per tooth, whereas incisor extrusion is higher so that the bone does not come with the tooth.

20. How does anterior trauma to the dentition affect isolated tooth movement? Most primary teeth are displaced, not fractured.1,2 This frequently occurs at the toddler stage, around 2 to 3 years of age, with the incidence the same for boys and girls. When a permanent tooth is traumatized, the crown is usually fractured. If the tooth is avulsed, it needs immediate replacement and splinting. If possible, bracketing in these cases with a flexible wire positioning the avulsed tooth into position is best. This acts as a semi-rigid splint. Stiff wires can lead to possible ankylosis. If the permanent incisor is intruded, the bracketing and the placement of a flexible wire allow the tooth to reestablish its normal position much better than waiting and attempting to move the tooth at a later time. The use of vacuum material for holding the newly positioned teeth should be considered. If the patient already has an orthodontic appliance in place and the tooth is displaced with a freshly bent wire, the new types of wires can be placed, allowing a gradual return to the proper position without the use of oral anesthesia in many cases.

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21. Does the skeletal pattern of the patient affect isolated orthodontic tooth movement? Yes. There is anterior vertical face height (nasion [N] to menton [Me]) and posterior vertical face height (either articulare [Ar] or condylion [Co] to gonion [Go]). They do not relate well to each other.22 In fact, they are usually inversely related with one long and the other short or vice versa. If the mandibular plane (Go to Me) as it projects posterior toward the back of the head lies outside the skull, or occiput, the case is described as low angle. These cases are strongly oriented toward nonextraction orthodontic treatment plans.1,2,23 The mandibular plane becomes even lower with age. If the mandibular plane is low under 10 years of age, the chances that the case should be nonextraction are excellent. If the mandibular plane intersects inside the skull posteriorly, the case is described as high angle. This type of tooth movement should be viewed as possibly more complex, because the posterior teeth have a greater likelihood of overerupting with tooth movement. The normal or average angle case has the mandibular plane tangent to the skull, or the occiput. It is normal for children under 10 years of age to have a higher value here. In addition to age, the relationship is also affected by race and gender. Higher values are seen in African-Americans and Asians as compared with Caucasians.

22. Does the soft tissue profile of the patient affect isolated tooth movement? Yes. It depends on the age and the race of the patient. The younger the patient, the more full the lip position as related to the nose-chin line.24 If the lips are behind the nose-chin line and the child is 10 years of age or younger, the orientation is toward a nonextraction orthodontic treatment plan. Larger noses or chins allow a more forward position of the lips; this is especially true with a larger chin. The smaller nose projection with a wider face and the positioning of the denture base more anterior usually gives African-Americans a fuller lip position. Orthodontic tooth movement affects lip position more with strained or thinner lips as compared with unstrained or thicker lips. The nasolabial angle (from tip of nose along its base to the upper lip) is normally at about a 90- to 110-degree angle (between the positions of an acute and obtuse angle).25 The more obtuse the angle, the more the case limits the retraction of anterior teeth, so avoid extractions in patients with obtuse nasolabial angles.

23. What happens if one does not wish to perform isolated tooth movement in the practice? Identify the problem, and refer the patient. The relationship between the family dentist and the specialist is symbiotic; the referring doctor needs to be kept informed of the treatment of the patient.

24. How have restorative implants affected orthodontic treatment planning? Restored implants are the equivalent to ankylosed teeth. Ankylosed teeth have a marked, adverse effect on orthodontic tooth movement. The planned, reciprocal effects on natural teeth with their ligaments are negated, which affects the collateral movements of the teeth being moved. Because of the ability to quickly place and restore these implants, orthodontic tooth movement is many times delayed until after the implants are placed. This has a compromising effect in treatment of these particular cases, because the orthodontic results can be disappointing. Treatment planning for orthodontic tooth movement, usually here related to crowding or spacing of the teeth in the arches rather than Angle’s Class II or Class III correction, is essential for proper overall treatment of the patient. Orthodontics precedes restorative implants unless it is a coordinated, planned event between dental practitioners. REFERENCES 1. Currier GF: Orthodontic exam and diagnosis. In Riolo ML, Avery JK, editors: Essentials for orthodontic practice, 2003, EFOP Press, pp 264–301. 2. Currier GF: Differential diagnosis and treatment planning in dentofacial orthopedics and orthodontics: early, middle, and later perspectives. In Third International Symposium, Selcuk University on Aesthetics and Function in Dentistry. 2000, August-September, pp 46–62. 3. Andrews L: The six keys to normal occlusion, Am J Orthod 62:296–309, 1972. 4. Snodell S, Nanda RS, Currier GF: A longitudinal cephalometric study of transverse and vertical craniofacial growth, Am J Orthod Dentofacial Orthop 104(5):471–483, 1993. 5. Herman RJ, Currier GF: A retrospective study of the incidence of posterior crossbite and associated orthodontic parameters in primary, transitional, and permanent dentitions, J Dent Res 81(Spec Iss A):A-194, 2002. 6. Currier GF, Molloy RB: Correction of posterior crossbite in the transitional dentition with the quadhelix appliance, Biol Mech Tooth Mov: 333–341, 2000. 7. Adkins M, Nanda RS, Currier GF: Arch perimeter changes upon rapid palatal expansion, Am J Orthod Dentofac Orthop 97(3):194–199, 1990. 8. Housley J, Currier GF: Anterior crossbite malocclusion: incidence and treatment in the transitional dentition, J Dent Res 78:197, 1999. 9. Bracket R, Currier GF: Anterior openbite malocclusions, J Pediatr Dent Care 10(1):23–26, 2004. 10. Currier GF: The smile, the vertical, and time, J Southeast Soc Pediatr Dent 5(3):36–39, 1999. 11. Nowlin R, Currier GF: Criteria for premolar extraction in orthodontics, J Dent Res 78:197, 1999. 12. Czarnecki T, Nanda RS, Currier GF: Perceptions of a balanced facial profile, Am J Orthod Dentofacial Orthop 104(2):180–187, 1993. 13. Formby W, Nanda RS, Currier GF: Longitudinal changes in the adult facial profile, Am J Orthod Dentofacial Orthop 105(5):464–476, 1994. 14. Revels M, Currier GF, Coury C: Anterior linear and archial analysis in bitemark identification, J Pediatr Dent Care 10(1):12–14, 2004. 15. Stephens S, Currier GF, Nanda RS: Growth of the dental arches: a longitudinal study from 2 to 22 years, J Pediatr Dent Care 10(1):19–22, 2004.

16. Gianelly A: Leeway space and the resolution of crowding in the mixed dentition, Semin Orthod 1:188–194, 1995. 17. Osborn WS, Nanda RS, Currier GF: Mandibular arch perimeter changes with lip bumper treatment, Am J Orthod Dentofacial Orthop 99(6):527–532, 1991. 18. Bishara SE: Impacted maxillary canines: a review, Am J Orthod Dentofacial Orthop 101:159–271, 1992. 19. Hurd A, Currier GF: Space analysis and prediction in the transitional dentition, J Pediatr Dent Care 10(1):33–35, 2004. 20. Bolton WA: The clinical application of a tooth-size analysis, Am J Orthod 48(7):504–529, 1962. 21. Edwards JG: A long-term prospective evaluation of the circumferential supracrestal fiberotomy in alleviating orthodontic relapse, Am J Orthod 93:380–387, 1988.


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22. Bulleigh A, Currier GF, Bursac Z: Vertical tooth-lip positions during growth and development from the frontal and lateral positions, J Dent Res 83(Spec Iss A), 2004. 23. Wyatt W, Currier GF: Incidence and treatment for congenitally absent permanent teeth, J Pediatr Dent Care 10(1):27–29, 2004. 24. Blanchette ME, Nanda RS, Currier GF, et al: Longitudinal growth study of soft tissue facial profile of short and long face subjects, Am J Orthod Dentofacial Orthop 109(2):116–131, 1996. 25. Fitzgerald JP, Nanda RS, Currier GF: An evaluation of the nasolabial angle and the relative inclinations of the nose and upper lip, Am J Orthod Dentofacial Orthop 102(4):328–333, 1992.

C H A PT E R

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Phase II: Nonsurgical Adolescent and Adult Cases Steven D. Marshall • Karin A. Southard • Thomas E. Southard

T

he majority of patients receiving orthodontic treatment are either adolescents or adults, and their conditions can range from single tooth crossbites to severe dentofacial deformities. When a patient first arrives for treatment, identification of all structural and functional jaw and dental problems must be made during the clinical and radiographic examination. These problems occur in all three planes of space and may include significant dental spacing or crowding, dental or skeletal deep bites, anterior or posterior dental or skeletal openbites, anterior or posterior dental or skeletal crossbites, anteroposterior skeletal or dental malrelationships, and asymmetries of the dentition or skeleton. In addition, many patients also have other dental problems, such as mutilated dentitions and periodontal disease. The goal of orthodontic treatment is always to address the patient’s chief complaint through the integration of the best research evidence, the clinician’s expertise, and the patient’s values (evidence-based orthodontics). A problem-oriented treatment approach must be used to provide an optimal level of care contingent on the patient’s desires and resources. Orthodontic treatment of adolescent and adult patients may include the use of either removable or fixed appliances. Treatment may include jaw orthopedics to restrict anteroposterior maxillary or mandibular growth, orthopedics to enhance maxillary anteroposterior growth or to accelerate mandibular growth, extraction of permanent teeth to eliminate substantial crowding or to camouflage (mask) an underlying skeletal imbalance, maxillary skeletal expansion or maxillary/mandibular dental expansion, orthognathic surgery, and treatment coordinated with other dental disciplines, including cosmetic dentistry, prosthodontics, endodontics, and periodontics.

1. What is a “problem-oriented” approach to treatment? Based on a systematic clinical and radiographic examination of the patient, the clinician identifies all structural and functional problems of the jaws and dentition. An exhaustive list of these problems is compiled. From this list and the patient’s chief concerns, the goals for treatment are established. Treatment options are composed that address the patient’s chief complaint and all problems on the list. Problems that cannot be addressed are considered treatment compromises and must be discussed with the patient. 206

2. For any patient with an orthodontic problem, what conditions necessitate referral to an orthodontist? A good general rule is this: if an orthodontic problem exists in a single dimension and can be treated in 9 months or less, it is a problem that generally can be treated in general practice. Such problems include patients in need of space maintenance, single tooth crossbite correction, and Class I mild alignment problems. On the other hand, patients with multi-dimensional malocclusion problems, skeletal imbalances, and problems that take greater than 9 months to treat are generally best referred to an orthodontist. Remember, the goal is to provide the patient with the highest level of care, and orthodontic care provided to the patient must be to the level of the specialist even if that care is provided by a generalist. The diagnosis of an orthodontic patient follows a logical sequence of evaluation of facial symmetry and proportions, relationship of the jaws, dental arch length, and irregularities of tooth development, tooth position, and intraoral soft tissues. The following diagnostic criteria will aid in determining if a patient presents with a single dimension or multidimensional orthodontic problem. FACIAL SYMMETRY AND PROPORTIONS AND RELATIONSHIP OF THE JAWS Facial symmetry is noted in the frontal view, which is seen by looking directly at the patient. Mild variation in symmetry from right to left is normal. Landmarks where marked asymmetry can be noted are the eyes, cheekbones, gonial angles of the mandible, occlusal plane, and midline of the chin. The path of opening of the mandible is also evaluated. Opening paths that are not straight or smooth may foretell mandibular asymmetry or temporomandibular dysfunction. The closing path is evaluated to detect the presence or absence of a functional shift of the mandible into centric occlusion. Marked asymmetry of facial structures or presence of a functional shift signifies referral to a specialist. Vertical and anteroposterior facial proportions are judged in both the frontal and profile views. Significant protrusion or retrusion of the maxilla or mandible is an indication for referral. Vertical proportionality is judged by assessing lip

Phase II: Nonsurgical Adolescent and Adult Cases • CHAPTER 16

competence and the amount of maxillary incisor crown exposure in relaxed pose. Lack of lip competence in a relaxed pose and/or excessive showing of the maxillary incisor are indications for referral. Transverse proportions are judged intraorally by the presence or absence of posterior crossbite and/or midline discrepancies. Posterior crossbite involving more than two contiguous maxillary teeth is generally skeletal in nature and is an indication for referral. The amount of incisor protrusion is judged cephalometrically and by evaluation of lip posture and lip function. The presence of mentalis muscle strain on lip closure is an indication of lip incompetence from incisor protrusion. Excessive lip incompetence and incisor protrusion are indications for referral. IRREGULARITIES OF TOOTH DEVELOPMENT Unusual delay in the eruption of one or more second bicuspids and/or second molars is not an uncommon finding and can lead to significant malocclusion for the patient. These situations should be monitored and referred for evaluation. Missing permanent teeth with retained primary teeth add more complications to the patient’s orthodontic problem list, and a team approach to the appropriate treatment should be sought. Tooth size problems commonly occur that prevent ideal Class I occlusion to be obtained. Patients with abnormal incisor widths (e.g., small maxillary lateral incisors) should be referred for further evaluation. Tooth drift or displacement out of the line of the dental arch signifies eruption path problems. Correction of malposition requires an understanding of the impact on arch form. If malposition is the result of crowding, then correction will require expansion of the arch or gaining space by extraction or selected tooth width reduction. Overexpansion of the dental arch is prone to relapse. Therefore, a diagnosis of tooth malposition must be accompanied by an understanding of the limitations of arch expansion treatment. Cases in which arch expansion will lead to an improper transverse occlusal plane or excessive incisor protrusion should be referred for evaluation by a specialist. Tooth displacement that results in anterior or posterior crossbite or anterior overjet may be a clue to an underlying discrepancy between the bony bases of the dental arches. Further diagnosis requires cephalometric and/or orthodontic study model evaluation of the alveolar bases to discover intermaxillary skeletal discrepancies. ANALYSIS OF ARCH LENGTH AVAILABLE Adolescents still in the late mixed dentition should be evaluated for available leeway space. In general, planned future nonextraction treatment can be facilitated considerably with maintenance of the leeway space in the mandible. There are several published analyses that aid in the determination of arch length available in the late mixed dentition.1,2

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CLASS I MOLAR RELATIONSHIP

3. A Class I adolescent patient in the late mixed dentition presents with mild mandibular anterior crowding. Assuming that the mandibular second premolars are present but unerupted below the primary second molars, how much space can be gained to spontaneously align the mandibular incisors by placing a lower lingual holding arch? What percentage of Class I molar cases, with mandibular incisor crowding, can be corrected by placing a lower lingual holding arch before the primary second molars are exfoliated? What is the drawback of using a lower lingual holding arch? The primary second molars are wider in mesiodistal dimension than their permanent premolar successors. As a result of this size difference, approximately 3.4 to 5 mm of total space can be gained for alignment of the mandibular anterior teeth by placing a lower lingual holding arch (LLHA).3,4 Studies have shown that 76% of patients can be treated without extraction in the mandibular arch if an LLHA is used to save this excess (leeway) space and the clinician is willing to accept no more than 1 mm of arch length expansion.5,6 The drawback of using an LLHA is that the leeway space cannot be used by the mandibular first molars to shift mesially into a Class I molar relationship if they are in an end-on position with the maxillary first molars. Thus, in Class II molar relationship or “end-to-end” molar relationship, the use of the leeway space to improve crowding is limited by the amount of mesial movement of the mandibular first molars to gain a Class I molar relationship.

4. What is interproximal reduction (also termed stripping), and when could it be used in Class I crowded patients? Interproximal reduction is the removal of interproximal enamel to make space to align teeth. In primitive humans whose diets consisted of coarse hard foods, interproximal enamel was naturally worn with chewing over time. In theory, this is due to significant movement of teeth and abrasion at interproximal contact points as a result of this tooth movement. In contrast, modern humans with softer diets experience significantly less wear of interproximal enamel over the average human life span. In fact, there is far more enamel present on the sides of human teeth than will ever be worn away during a lifetime of chewing. Therefore, some of this enamel can be removed without detriment to the long-term health of the teeth. Interproximal reduction is a treatment option for Class I malocclusions with crowding of 1 to 5 mm. However, interproximal reduction requires proper instrumentation and careful technique to maintain adequate tooth enamel and interproximal surface contour. For many years stripping was restricted to anterior teeth. Later, air rotor stripping

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CHAPTER 16 • Phase II: Nonsurgical Adolescent and Adult Cases

(ARS) was introduced to remove interproximal enamel from posterior teeth.7

5. What factors are considered in the decision to extract permanent teeth for a Class I patient? For a Class I patient, the primary consideration for extraction of permanent teeth is the amount of crowding in the dental arch. If there is significant crowding in a dental arch, extraction of permanent teeth is generally considered reasonable. However, other factors must also be considered. In particular, the inclination of the incisors as viewed in the sagittal plane on a cephalometric radiograph, an assessment of the lip posture, and the status of the periodontium should be considered. If the anterior teeth are inclined severely to the labial and the patient’s lips are pushed forward as a result, the option of tooth extraction (even in the presence of less crowding) should be considered. Extraction permits uprighting the anterior teeth and reduction of lip protrusion. Conversely, if the anterior teeth are inclined to the lingual, tipping these teeth to the labial to increase the dental arch length can allow correction of considerable crowding without extraction. In this case, the periodontium of the mandibular anterior teeth must be assessed with regard to thickness of the attached gingival tissue both inciso-gingivally and facio-lingually. Tipping incisors that are invested in thin attached gingival tissue in an anterior direction can result in loss of periodontium.

6. What factors are considered when choosing which teeth to extract? Once a decision to extract teeth has been made, dental arch symmetry is an important consideration when choosing which teeth to extract. Generally, in Class I malocclusions, dental arch asymmetries are not severe. The treatment goal is to place the permanent canines in a symmetric position bilaterally relative to the skeletal midline of the arch. As such, extraction choices for Class I molar malocclusions involve two paired teeth in each arch (i.e., two upper first premolars and two lower first premolars). However, significant dental arch asymmetries may call for an asymmetric extraction choice in order to reach a symmetric finished result. In making this decision, the choice for upper and lower teeth on each side of the arch should be paired to allow maintenance of the Class I relationship during treatment mechanics to close the extraction spaces (e.g., upper and lower right first premolars and upper and lower left second premolars).

7. Does extraction of four second molars instead of four premolars make sense for a crowded Class I patient? Premolars are typically extracted when significant crowding and/or protrusion exists in the anterior of the arch. Extraction of mandibular first premolars provides approximately 14 mm of space, allowing alignment of the anterior teeth and/or reduction of their labial inclination. Mandibular second molar extraction (i.e., second molar extraction/third molar replacement8) results in only 2.7 mm more arch length compared with controls (2.7 mm less late arch crowding after the third molars have

erupted).9 This amount of space gained from extraction is similar in magnitude to that which could be gained by interproximal reduction. Furthermore, success of the second molar extraction approach depends on third molar eruption path and timing, both of which are not as predictable as the amount of arch length to be gained by interproximal reduction for a particular patient. CLASS II MOLAR RELATIONSHIP

8. What factors should be considered when making a decision to treat a patient with a Class II molar malocclusion or to refer the patient to a specialist? The most important factor to consider in a patient with a Class II molar malocclusion is the contribution of intermaxillary jaw position to the interarch Class II relationship of the dentition. Imbalance between the forward growth of the maxilla and the mandible warrants referral to a specialist. Patients who have mild to moderate interjaw imbalance can be treated by the general dentist provided that the practitioner has a thorough understanding of facial growth and the application and treatment outcomes of appliances that modify facial growth.

9. If a patient presents with a Class II molar malocclusion and a marked difference in anteroposterior interjaw relationship, what are the major choices for treatment? On what diagnostic criteria are the choices based? Generally there are only three ways to treat marked anteroposterior differences in interjaw relationships: • Orthopedically modifying jaw growth • Compensating the position of the dentition within the jaws to mask the discrepancy of the jaws • Jaw surgery Orthopedic treatment is an attempt to modify the growth of the jaw(s) by placing forces against a jaw during facial growth. For instance, a headgear applies a force against the maxilla to restrict its downward-forward growth, and a functional appliance for Class II correction applies forces to restrict the downward-forward growth of the maxilla and accelerate the inherent downward-forward growth of the mandible. Placing dental compensations (masking) is an attempt to camouflage the underlying jaw problem without addressing the skeletal problem itself. Various extraction patterns can be used to move the teeth into more acceptable positions (e.g., reduce overjet) and thereby mask the underlying skeletal problem without actually modifying the jaw position. Surgery is generally used to treat moderate to severe jaw size imbalances in patients whose discrepancies are beyond correction that is obtainable with camouflage or growth modification or in patients who have completed growth. The decision to use any of these three approaches is based on many factors, the most important of which are the severity of the jaw imbalance, the severity of the Class II interarch relationship, the growth status of the patient, and the patient’s goals.


10. Are headgear treatment and functional appliance treatment equally effective in correcting Class II malocclusions in children (before comprehensive treatment)? The evidence-based answer to this question is yes. Five prospective randomized clinical trials of Class II malocclusions, containing groups of children treated with both headgear and functional appliances (no comprehensive fixed appliances) in the same trial, support this evidence-based conclusion.10–17 Unequivocal short-term skeletal effects include a small restriction in forward maxillary growth with headgear (SNA angle decreases 0.5 to 3 degrees) and a small forward positioning of B point with functional appliances (1 to 2 degrees); resulting in an ANB angle improvement in Class II patients of about 1 degree with either appliance. A significant portion of the Class II correction is distal maxillary molar movement with headgear and mesial mandibular molar movement (along with mandibular incisor proclination) with functional appliances. The following list summarizes the short-term effects of headgear or functional appliances based on these prospective randomized trials (italic type indicates agreement among all studies; regular type indicates disagreement). • Headgear: Restricts maxillary forward growth slightly (SNA angle decreases 1 to 3 degrees),10–12,16 B point (and SNB angle) does not come forward compared to controls,10–12,16 and the result is a mean reduction in ANB angle of about 1 degree.11,12,16 Maxillary molars are retracted distally by an average of up to 3.7 mm compared to controls1 and improve toward neutrocclusion by 3 mm more than with functional appliances.10,16 Overjet is reduced by approximately 1.5 mm.10–16 Effect on observed mandibular length increase ranges from no difference compared to controls,10 to a small increase compared to controls,11,12 to an increase similar to a Fränkel Function Regulator Type 2 (FR-2) appliance.16 Vertically, a slight increase was found when measured at menton10 and in the sella-nasion–mandibular plane (SN-MP) angle.16 • Headgear with biteplate: Restricts maxillary forward growth slightly (0.50 to 1 degree),15,17 ANB angle decreases approximately 1 degree compared to controls,13–15,17 reduction in overjet is observed,13,14 maxillary incisors are uprighted,17 maxillary molars are moved distally,13,14,17 mandibular molars are moved mesially (2.7 mm compared to controls of 1 mm),17 and mandibular incisors were uprighted 2 degrees.17 No significant change in SNB angle is compared to controls.17 Mandibular length changes ranged from no significant difference compared to controls17 to enhanced mandibular growth greater than controls and comparable to that of a Bionator.13,14 Headgear/biteplate treatment has been reported to increase the mandibular plane angle (1.3 degrees)15 or to produce nonsignificant changes in the mandibular plane angle and lower anterior face height (LAFH).17 It is important to mention that a retrospective cohort study18 examined changes in the Class II subjects treated with headgear from the Tulloch and colleagues11 study

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and headgear/anterior biteplates from the Keeling and colleagues study.13 The biteplate provided no additional benefit when using a headgear for Class II treatment. Changes in SNA, SNB, ANB, and mandibular length were not statistically significantly different among the groups. The maxillary first molars moved posteriorly approximately the same average amount in both groups, and there was no difference in the amount of mesial movement by the mandibular first molars. The authors concluded that headgear/anterior biteplate treatment provides no additional anteroposterior dental or skeletal benefit over headgear treatment alone. • Activator/Bionator/FR-2: Functional appliances demonstrate a small increase in SNB angle of approximately 0.6 degrees annualized compared to controls11,12 for a total increase of approximately 1 to 2 degrees.15–17 This change results in a mean annualized reduction in ANB angle (apical base discrepancy) of slightly less than 1 degree compared to controls11–15 and a total ANB angle reduction of 1 degree.16,17 Mandibular molars move mesially more than controls (3.3 mm vs. 1 mm),17 maxillary incisors were uprighted,16,17 and mandibular incisors were proclined (4.2 degrees).16,17 Functional appliance treatment exhibits a large reduction in overjet (annualized 2.5 mm compared to controls, approximately 4 mm total).11–14,16 The effect on observed restriction of maxillary forward growth ranges from a small mean decrease in SNA of approximately 0.7 mm10 to no restriction of maxillary growth in the greater majority of the studies.11–17 Surprisingly, the effect of functional appliances on mandibular length ranges from no significant change in mandibular length compared to headgear10,16,17 to a small increase13,14 (unit length increase approximately 1.3 mm annualized change).11,12 Maxillary molars have been found to either move distally by an average of nearly 1.2 mm10 or to move mesially.17 Vertical skeletal effects ranged from a slight increase measured at menton,10 to nonsignificant changes in the mandibular plane angle,15 Sella-nasion–gonion gnathion (SN-GoGn) angle and LAFH,17 to a slight decrease of the SN-MP angle.16

11. Is Phase I treatment with headgear or functional appliances equally effective in correcting Class II malocclusions in children when Phase I treatment is followed by Phase II treatment with fixed orthodontic appliances? Headgear and functional appliances used in conjunction with fixed orthodontic appliances can effectively correct Class II malocclusions. But higher levels of evidence to answer the question of whether their effects are equal is missing. The success rate of full Class II correction in children has been reported to exceed 90% with both headgear and functional appliance treatment (followed by fixed appliance treatment).19 However, this study was not a randomized clinical trial, and an evaluation of higher levels of evidence was deemed appropriate.

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Children in the Tulloch and colleagues11 study (initially Class II patients who had been assigned to headgear, Bionator, and control groups) were randomized following those first phase treatments and started on a second phase of treatment when they reached the early permanent dentition. Comprehensive prescription edgewise fixed appliance treatment (22 slot twin, 18 slot twin, or 18 slot single-wing brackets) was performed.12 Records were taken at the completion or discontinuation of comprehensive treatment. By the end of fixed appliance therapy, the advantages gained by previous headgear or Bionator treatment were lost, and there was no significant difference among any of the three groups in terms of anteroposterior, vertical, and dental measures including ANB angle, SNA angle, SNB angle, overjet, and Peer Assessment Rating (PAR) scores. The authors point out that their sample (and therefore their findings) excluded children with facial asymmetries, extremely long faces, or extremely short faces. The weakness of this study was that there were no restrictions on any treatment methods employed during the second phase of treatment.12 One of the advantages of a randomized clinical trial is that its design maximizes the likelihood that the observed effect is due to the intervention (in this case headgear or functional appliance treatment). By permitting any treatment method to be used during the second phase in this study, any earlier headgear or functional appliance effect is combined (or potentially lost) with the unknown second phase treatment effect. A better design would have required all first phase headgear or functional appliance subjects to continue to only use those appliances (in addition to the fixed appliances) during the second phase of treatment. After Phase I treatment in the Keeling and colleagues study,13–15 half of the subjects in the Bionator and headgear/ biteplate groups were randomly assigned to 6 months of retention followed by 6 months of no retention, and the other half of the subjects had no retention for 1 year. The retention protocol consisted of full-time wear of the biteplate and nighttime wear of the headgear on alternate nights for the headgear group and alternate nighttime wear in the Bionator group.20 Records of each patient were reviewed by an average of four orthodontists, and a consensus Phase II treatment plan was formulated. During Phase II, subjects were usually treated with full ortho dontic appliances. By the end of full orthodontic treatment, the skeletal differences in all measurements for all three groups were within 1 degree. When the entire treatment period was considered, the treatment group had no effect. The authors concluded that there is temporary skeletal change as a result of Phase I treatment with both appliances but no detectible skeletal difference between Phase I and Phase II treatment of Class II malocclusion by the end of full orthodontic treatment. Also, there were no significant differences with respect to initial PAR or final PAR among the three treatment protocols.20 Like the Tulloch and colleagues study,11,12 a better design would have required all first phase headgear or functional appliance subjects to continue to use only those appliances (in addition to the fixed appliances) during the second phase of

treatment. Instead, during Phase II, headgear was used more often (42%) in the original observation group subjects and in the original Bionator group subjects (23%) than in the original headgear/biteplate (15%) group subjects. Further, the retention protocol (e.g., alternate nighttime appliance wear for 1 year before starting Phase II) was reported by the authors to be only minimally successful at maintaining dental correction5 and must surely have clouded the intervention effect. Although one can understand the desire to optimize care by choosing a treatment plan immediately prior to (or during) Phase II, such a method shrouds the effect of headgear or functional appliance intervention. Better designed studies are needed, but it is unlikely that funding for another large randomized controlled trial to answer this question will be forthcoming.

12. What are the long-term (post-retention) skeletal effects of treatment for Class II malocclusions in growing individuals using functional appliances? The available evidence, based largely on retrospective nonrandomized studies, suggests that, over the long term, functional appliances do not modify the inherited facial growth pattern significantly. A lasting enhancement of horizontal mandibular growth is not supported for Bionator, headgear-activator, or Herbst appliances, and remains equivocal for the FR-2 appliance. Adaptive changes in condylar growth in animals subjected to altered (protrusive) mandibular position forms the historical basis for the clinical use of functional appliances.22–25 However, functional appliance use in humans has not reproduced the dramatic effects seen in animals. The magnitudes of short-term adaptive mandibular changes in humans were shown to be smaller, and the basis for short-term overall increase in mandibular length was equivocal, being attributed to increased condylar growth,26–29 or the result of altered condylar growth direction without increased condylar growth.13,16,30–32 Long-term adaptive changes were first addressed in 1996, when Dermaut and Aelbers33 reviewed the scientific data on outcomes from treatment with various functional appliances and concluded that “there is so far little scientific evidence to support the idea that they have any permanent orthopedic effect.” Within the next 10 years, evaluation of more recent literature provided more specific support to Dermaut and Aelbers’ conclusion, no clinically significant anteroposterior skeletal effects are demonstrable long term.21,34,35 Additionally, it was suggested that the findings of increased mandibular length from functional appliance use13,16,26–32 may be a result of adaptive change in condylar growth direction rather than condylar growth magnitude.36 The strength of evidence for these conclusions is considered secondary because it is based on a small number of studies. The issue of adaptive changes to functional appliances in the vertical dimension has received less attention. Numerous studies have reported short-term increases in anterior facial height with the use of functional appliances,27,28,37–40 and whether physiologic recovery occurs in the vertical dimension remains poorly understood.


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The few long-term studies on functional appliances that have potential answers to these questions are nonrandomized and retrospective in design, often without a comparison to controls. A summary of the long-term studies for various functional appliances follows.

alone.49–51 The treatment effects of mild restraint of maxillary horizontal growth and adaptive changes in mandibular growth and position appear to revert to an anticipated pattern over the long term. Enlargement of mandibular size or significant treatment effects on vertical dimension remain equivocal.

BIONATOR Although there is a long history of Class II treatment using the Bionator,41 the skeletal treatment effect in humans was poorly understood until characterized by Araujo and colleagues36 in a prospective randomized controlled trial using Björk-type metallic implants. Compared to control Class II subjects, Bionator therapy resulted in altered condylar growth in a more posterior direction but no difference in total condylar growth. More important, Bionator therapy appeared to alter the normal pattern of downward and forward displacement of the mandible by limiting forward mandibular rotation during growth. The assessment of the long-term skeletal effect of Bionator therapy has not been widely studied. A search of Pub-Med for the terms “Class II malocclusion” AND “Bionator” resulted in 75 articles. Including the search query “AND long-term” resulted in eight articles, of which only four report longitudinal results after a retention period or a post-retention period.42–47 Reporting of cephalometric skeletal parameters is not consistent among the studies, with angular measures being the most common. Treatment changes in SNA suggest that the Bionator produces less maxillary retrusion than headgear while having a more protrusive effect on B point when used without edgewise appliance therapy. Bionator therapy followed by edgewise appliance therapy appears to show treatment changes in the SNB angle that is remarkably similar to those found for cervical traction headgear followed by edgewise appliance therapy. Long-term changes appear to be the result of reversion to the expected pattern of growth. The treatment effect on the mandibular plane angle and the recovery after treatment are also similar to those seen in longitudinal cervical headgear studies. One study44 reported a lasting increase in mandibular length and anterior face height compared to matched controls but without a concomitant improvement in mandibular projection as measured by the SNB angle. Independent confirmation of these findings is not yet available. Lasting increases in anterior facial height could negate the desired increase in chin projection sought by functional appliance use.

HEADGEAR-ACTIVATOR APPLIANCE Studies evaluating the short-term effects of treatment with a headgear-activator appliance are controversial, with reports of either mainly skeletal effects52,53 or mainly dentoalveolar effects.10,54,55 A search of Pub-Med for the terms “Class II malocclusion” AND “Activator” OR “Headgear Activator” AND “long-term” resulted in four retrospective studies evaluating skeletal effects posttreatment and after a period of followup.56–59 The results suggest that skeletal effects do not differ markedly from the use of headgear alone and appear to revert to a normal pattern of growth during the posttreatment period.

FRÄNKEL FUNCTION REGULATOR TYPE 2 APPLIANCE Studies evaluating the short-term effects of FR-2 therapy have reported various results including restriction of maxillary growth, enhancement of mandibular growth, increased lower facial height, and occlusal correction resulting from a greater proportion of dentoalveolar compared to skeletal ef fects.27,38,46–48 The assessment of long-term skeletal change comes from a few studies. A search of Pub-Med for the terms “Class II malocclusion” AND “Fränkel” resulted in 97 articles. Including the search query “AND long-term” resulted in five articles, only three of which report longitudinal results after a retention period or a post-retention period for the FR-2 appliance

HERBST APPLIANCE By far, the most studied functional appliance, in terms of long-term effect, is the Herbst appliance. The results of many long term studies suggest that the skeletal effects of the appliance are temporary. Over the long term, facial growth reverts to the inherited pattern with no evidence of enhanced skeletal growth.60–67 Studies also suggest the short-term effect of mandibular protrusion on condylar growth is directed more posteriorly than superiorly, promoting a temporary posterior mandibular rotation,40,42,68,69 which recovers to a more superiorly directed vector during growth recovery after treatment. In summary, there is insufficient evidence to support the belief that functional appliances increase mandibular growth beyond that normally achieved by the patient in the long term. In the short term, functional appliances do accelerate growth of the mandible. In earlier studies, this acceleration of growth was misinterpreted as true growth enhancement. However, later studies support the concept that, following this initial growth acceleration, mandibular growth of patients treated with functional appliances decreased, and control subjects eventually caught up, with no distinguishable differences between treated and control long term.

13. If functional appliances do not cause mandibles to grow more than they would normally grow, then how do they work? In other words, how do functional appliances correct a Class II molar relationship? Functional appliances are effective in moving teeth (dentoalveolar effect).33,70,71 With the use of mandibular propulsive functional appliances such as an Activator, Bionator, Twin Block, or Herbst appliance, the mandible is postured forward, the condylar head is distracted out of the glenoid fossa, and the musculature and other soft tissues are stretched. As the stretched soft tissues try to pull the mandible back, the effect of the functional appliance is to increase the labial inclination of the mandibular incisors, reduce the labial inclination of the maxillary incisors, and move the posterior teeth in the alveolar process

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bone toward an interarch Class I relationship. The increased labial inclination of the mandibular incisors can be of concern, especially if a patient’s mandibular incisors are labially inclined before initiation of functional appliance treatment. In addition, there is some restrictive effect on the forward growth of the maxilla with the use of mandibular propulsive functional appliances.

14. What is the effect of a headgear in correcting a Class II molar relationship? A high-pull headgear (i.e., a headgear with the force vector directed toward the top and back of the head) has the effect of restricting downward and forward growth of the maxilla while the mandible grows forward. Also, the maxillary molars are retracted distally and their eruption is slowed. Both effects will improve an interarch Class II molar relationship toward a Class I molar relationship. A cervical-pull headgear, with the force vector directed from the molar teeth down and back toward the cervical vertebrae, also restricts the forward growth of the maxilla and retracts the maxillary molars distally, which will improve the interarch molar relationship from Class II to Class I.72–74

15. What are the long-term (post-retention) skeletal effects of treatment for Class II malocclusions in growing individuals using cervical traction headgear? The available evidence, based largely on retrospective nonrandomized studies, suggests that reduction of the SNA angle by treatment is largely stable, the SNB angle is largely unaffected by treatment or continued growth, and any increase in mandibular plane angle caused by treatment is recovered during continued facial growth. The question of whether cervical traction causes a clinically significant change in vertical facial proportions remains equivocal. The notion that cervical traction headgear has a direct skeletal treatment effect on the maxilla in humans was suggested by Mitani and Brodie75 and Wieslander,76 and was later confirmed by Melsen77 in an experiment characterizing the cervical traction treatment effect and the “physiologic recovery” in 20 subjects. By using Björk-type implants, serial cephalometry, and superimposition, Melsen identified downward and backward maxillary rotation and a similar indirect effect on the mandible as a direct result of an 8-month application of cervical traction.77 After routine fixed-edgewise treatment, retention, and cessation of skeletal growth, these 20 individuals were again evaluated by cephalometry. The skeletal headgear effect appeared to be temporary, because the subjects exhibited, on average, normal downward and forward maxillary and mandibular growth after being released from the growth alteration dictated by the traction to the maxilla. Also, the dentoalveolar effect of the headgear (distal maxillary first molar movement) was changed during continued treatment and growth. Mesial migration of the maxillary first molars relative to cranial base, similar to migration in untreated controls over the same time period, was accompanied by downward and forward mandibular growth to maintain the Class I molar relationship and preserve the inter-maxillary

dentoalveolar effect.77 Although individual growth patterns appeared to recover from the temporary alteration of maxillary growth, the question of a permanent vertical change in the facial pattern could not be determined from this study. Further evidentiary support for the long-term effects of cervical traction consists largely of nonrandomized retrospective trials. A search of the literature pertaining to human trials in all Entrez databases from 1978 to present, for the terms “Class II malocclusion” AND “headgear” OR “extraoral appliance,” returned 317 articles containing 43 randomized trials, five systematic reviews, and two meta-analyses. The five systematic reviews evaluate treatment effects but do not analyze long-term skeletal effects.78–82 Adding “AND long term” to the query returned 24 articles, including three randomized trials, but no systematic reviews or meta-analyses. The three randomized trials evaluate treatment effects and long-term occlusal and soft tissue effects but do not evaluate post-retention long-term skeletal effects of treatment with headgear.83–85 The remaining 21 articles contain nine retrospective studies evaluating skeletal changes induced by cervical traction longitudinally to a time point after retention. Thus, at present, the evidence for long-term (post-retention) effect from the use of cervical traction headgear is supported by nine retrospective post-retention analyses.86–94 Generally speaking, these studies appear to support the findings of earlier reports. The reduction of the SNA angle by maxillary traction is maintained throughout edgewise treatment. During continued growth, changes in the SNA angle revert to an expected growth pattern. In contrast, the SNB angle shows little change with treatment and continued growth. After a transient increase in mandibular plane angle during treatment, posttreatment change suggests a return to mandibular plane closure during continued growth. When compared to controls, the changes in mandibular position are not significantly different, suggesting the effect of cervical traction on chin projection is, on average, clinically insignificant. In contrast, the behavior of the Y-axis, which tracks the effect of treatment and growth on the vertical position of the chin, is variable. Two studies have reported lower anterior facial height changes are not significantly different from controls, but both studies do not agree for significant change in total face height compared to controls.93,94 One additional study has reported mandibular posterior rotation as a result of cervical traction treatment that did not recover 4 years posttreatment.95 Although retrospective analyses have known weaknesses, particularly sampling bias, lack of blinding, and lack of control groups, it is noteworthy that the cervical traction headgear treatment effects, reported in the lower-quality studies,86–94 are largely supported by results in prospective trials where headgear therapy was randomly assigned.10,15,16

16. What are the long-term (post-retention) skeletal effects of treatment for Class II malocclusions in growing individuals using high-pull or vertical-pull headgear? The immediate skeletal effects of high-pull and vertical-pull headgear are thought to be different from those of cervical traction headgear.72,96–98 However, at present, a similar analysis


of high-pull or vertical-pull headgear is not possible, because no long-term evaluations involving the exclusive use of these treatment modalities with or without edgewise treatment are available.

17. Does growth modification for a Class II patient with mandibular propulsive appliances result in a different profile change compared with growth modification with a headgear appliance? Earlier claims that the profile improvement with mandibular propulsive appliances occurs by greater forward movement of the chin in profile have not been substantiated. Profile outcomes that occur when treating an interjaw discrepancy with growth modification appear to be similar whether mandibular propulsive or headgear type appliances are used.99

18. How are orthodontic elastics used in treating Class II molar malocclusion? With Class II elastics, usually worn from the maxillary canines to the mandibular molars, the maxillary teeth tend to be moved posteriorly, whereas the mandibular teeth tend to move anteriorly. The effect is to change a Class II canine and molar relationship toward a Class I relationship. In addition, Class II elastics tend to tip the patient’s occlusal plane in the sagittal view such that the posterior aspect tips superiorly and the anterior aspect tips inferiorly.

19. What are molar distalizing “noncompliance” appliances? How are they used in Class II molar malocclusions? A problem with using headgears, elastics, and removable functional appliances is the need for patient cooperation. The patient must be motivated to wear these appliances. In an attempt to eliminate the need for patient cooperation, a variety of noncompliance appliances were developed for correction of Class II malocclusions. For the most part, these appliances consist of an acrylic button overlaid on the anterior palate and connected with a rigid wire to the maxillary second premolars. The acrylic button and premolars act as the anchorage unit and offer resistance to springs driving the first molars distally. These appliances (Pendulum, Distal Jet, etc.) do distalize maxillary molars. However, for every action, an equal, but opposite, reaction occurs. With the use of these appliances, as the molars are forced distally, the premolars (and anterior teeth) are driven mesially.100–102 Study after study has pointed to the same problem with these appliances. After the molars are distalized to a Class I relationship, they must be held there while the premolars and anterior teeth (which have been pushed anteriorly) must be gathered and brought back. To accomplish this, headgear or elastics must again be worn—defeating the original purpose of using a “noncompliance” appliance.

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20. An adult Class II patient (Class II molars and canines) presents with a convex profile, excessive overjet, and a moderately retrusive lower jaw. The patient lacks profile concerns and does not wish to consider orthognathic surgery to move the mandible forward and correct the Class II dental relationship. What extraction patterns might be considered to obtain Class I canines, proper overbite and overjet, and a stable interdigitation of the posterior teeth, as well as to mask the underlying skeletal discrepancy? The goal will be to provide space to move the maxillary canines from a Class II relationship to a Class I relationship and to eliminate the patient’s overjet. Extraction of the maxillary permanent first premolars would permit this. In this approach, the anchorage provided by the roots of the permanent maxillary second premolars and molars will be reciprocally pitted against the anchorage provided by the canines and incisors during space closure, allowing distal movement of the canines into Class I interarch relationship and improvement of incisor overjet. An alternative approach is the extraction of the maxillary second premolars. This extraction pattern would be indicated for a relatively mild Class II malocclusion. With extraction of maxillary second premolars, the anchorage provided by the roots of the maxillary permanent molars is pitted against the anchorage provided by the roots of the first premolars, canines, and incisors during space closure. Less distal movement of the maxillary canines and incisors will result. This is often desirable when maximum incisor retraction is not required.

21. What other extraction patterns could be considered in treating an adult Class II patient? If a nongrowing adolescent or adult patient presents with a Class II molar malocclusion and significant lower incisor crowding or labial inclination, other extraction patterns can be considered. If, in addition to extraction of the maxillary first premolars, the mandibular first premolars are also extracted to provide room to retract the mandibular canines and align the mandibular incisors, correction of the Class II canine relationship becomes difficult. In a Class II malocclusion, the maxillary canines are already anterior to the mandibular canines in their interarch relationship. Retracting the mandibular canines will necessitate retracting the maxillary canines even farther distally to gain Class I occlusion. In some instances this will not be possible, and at the end of treatment the patient will still have Class II canines and excess overjet. One alternative approach is to remove two maxillary premolars and one mandibular incisor. This allows retraction of maxillary canines while holding mandibular canines essentially in their pretreatment position in the lower dental arch. The mandibular crowding and/or labial inclination are improved

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by the 5 to 6 mm of space gained by the mandibular incisor extraction.103 This approach reaches the treatment goal of improved (Class I) canine function and leaves the patient with incisor overjet that is improved from the pretreatment condition but is not ideal. Another possible extraction pattern for this type of malocclusion includes maxillary first premolars and mandibular second premolars. This pattern is often considered in patients with a “full step” Class II molar relationship—that is, a molar relationship in which the maxillary molar mesiobuccal cusp is seated interproximally between the mandibular second premolar and first molar. Whereas the goal with extraction solely of maxillary first premolars is to obtain Class I canines and Class II molars, the goal with extraction of maxillary first premolars and mandibular second premolars is to obtain Class I canines and Class I molars. If mandibular second premolars are extracted, space closure in the mandible generally results in retraction of the mandibular canines to the point where the patient may finish treatment with Class II canines and excess overjet. However, an end-on Class II molar relationship may be effectively treated with extraction of mandibular second premolars. CLASS III MOLAR RELATIONSHIP

22. What are the effects of wearing a high-pull chin-cup in a growing Class III patient? A high-pull chin-cup applies a backward and upward force against the chin. This vector of force is useful in growing Class III patients with excessive mandibular growth. The anteroposterior effects include a restriction of forward mandibular growth while simultaneously allowing the maxilla to continue its forward growth. The result is improvement in the abnormal Class III molar and canine relationship. Vertically, the anterior face height is decreased with treatment.104,105

23. What are the effects of wearing a reverse-pull face mask in a growing Class III patient? A reverse-pull face mask applies a forward and downward force to the front of the maxilla. This vector of force is useful in growing Class III patients with deficient maxillary forward growth. The skeletal effects of the reverse-pull face mask include forward maxillary movement plus downward and backward rotation of the mandible. The result is improvement in the abnormal Class III molar and canine relationship. The dental effects include maxillary incisor labial inclination and mandibular incisor lingual inclination. The result is improvement (creation) of overjet.106–108 Timing (age of treatment) can markedly affect the outcome and amount of dental correction, with late correction producing more dental effects (less skeletal change with more incisor labial inclination) and early treatment producing a greater skeletal effect (more skeletal change with less incisor labial inclination). Maintenance of the correction may require a growth modification appliance (chin-cup) until growth is complete.

24. How are orthodontic elastics used in treating Class III molar malocclusion? With Class III elastics, usually worn from the mandibular canines to the maxillary molars, the mandibular teeth tend to move posteriorly while the maxillary teeth tend to move anteriorly. The effect is to change a Class III canine and molar relationship toward a Class I relationship. In addition, Class III elastics tend to tip the patient’s occlusal plane, in the sagittal view, such that the posterior aspect tips inferiorly and the anterior aspect tips superiorly.

25. An adult Class III patient (Class III molars and canines) presents with an underbite and a moderately strong lower jaw. The patient lacks profile concerns and does not wish to consider orthognathic surgery to correct the Class III interarch relationship. What extraction patterns might be considered to obtain Class I canines, proper overbite and overjet, and a stable intercuspation of the posterior teeth, as well as to mask the underlying skeletal discrepancy? In this case, the goal is to provide space to move the mandibular canines back (distally) from a Class III relationship into a Class I relationship and to retract the lower incisors back into a normal overjet relationship. Extraction of the permanent first premolars would permit this; the anchorage provided by the roots of the permanent second premolars and molars will be reciprocally pitted against the anchorage provided by the canines and incisors during space closure. This will generally result in the mandibular canines and incisors moving distally more than the mandibular posterior teeth move mesially, and the goals would be achieved. However, care must be taken not to move the mandibular canine teeth too far distally into a Class II relationship with the maxillary canines. For this reason, extraction of the second premolars should be considered as an option and may offer a better alternative for a relatively mild Class III patient. With extraction of mandibular second premolars, the anchorage provided by the roots of the permanent molars is pitted against the anchorage provided by the roots of the first premolars, canines, and incisors during space closure. Less distal movement of the mandibular canines and incisors will result.109 In the case of a relatively severe Class III patient who may not have profile concerns, camouflage treatment with extraction may not be possible because of the limits of lower incisor retraction in the region of the mandibular symphysis.

26. What other extraction patterns could be considered in treating an adult Class III patient? With extraction of only mandibular premolars, the canines can be corrected to a Class I relationship. However, the molars will still remain Class III. Another extraction pattern option is to extract the maxillary second premolars in addition to the


two mandibular premolars. With this option, the canines can be corrected to a Class I relationship, and the maxillary molars may be moved mesially into a Class I molar relationship. The risk of extracting premolars in the maxillary arch is that, during space closure, the maxillary canines can be retracted distally, making correction of the Class III canine relationship even more difficult. OPENBITES AND CROSSBITES

27. What is the difference between dental and skeletal anterior openbites? What is the difference in how they are treated? An anterior openbite exists when a gap is present between the anterior teeth while in occlusion. A dental (functional) anterior openbite exists when there is an anterior openbite while in occlusion but the vertical proportions of the face and jaws, the skeletal proportions, are normal. The cause of a dental anterior openbite is usually of functional origin, either continued thumb-sucking or habitual posturing of the tongue in the openbite space. The cause is not tongue-thrusting during swallowing, because we do not swallow for long enough periods each day to cause tooth movement.110 A psychological approach should first be attempted in treating an adolescent with a thumb habit. If ineffective, a tongue crib may be fabricated and inserted across the palate to interfere with the habit. An effective means of retraining the tongue in cases of tongue posturing is the use of tongue spurs attached to the anterior of an LLHA. If the tongue or thumb habit can be corrected, the anterior teeth will usually commence erupting until the openbite closes. When the maxilla grows downward more than the mandibular ramus lengthens, the mandible will be rotated downward and backward. The result is a skeletal anterior openbite where only the molars are in contact and the lips must be stretched to close. Treatment of a developing skeletal anterior openbite consists of trying to either decrease the vertical descent of the maxilla or decrease eruption of the molars. High-pull headgear, vertical-pull headgear, biteplates, biteplates with repelling magnets in the posterior, exercises (chewing gum), and even LLHAs can all help reduce or correct a developing skeletal openbite. In adults, surgery (maxillary impaction osteotomy) may be necessary to close a skeletal openbite, although recent case reports have found that intrusion of the posterior teeth using skeletal anchorage screws may be effective.111

28. What is the difference between a posterior dental and skeletal crossbite? What is the difference in how they are treated? A posterior dental crossbite exists when the maxilla and mandible relate properly to each other but the teeth in the opposing arches are tipped buccally or lingually into a crossbite. Usually, if one or two posterior teeth are in crossbite, it is a dental crossbite, but not always. A better way to diagnose a dental crossbite is to ask the question, “If any occlusal shifts are removed, and if the posterior teeth are uprighted, what will happen to the crossbite?” If the answer is that the crossbite is greatly

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improved or eliminated, then the crossbite was a dental crossbite. Treatment of a dental crossbite follows the logic of the diagnosis. Posterior teeth are simply uprighted. Correction of a dental crossbite may necessitate the patient wearing a biteplate in order to provide interarch space for banding or bonding and to permit opposing molar cusps to cross during correction. Depending on the degree of supraeruption of the molars in crossbite, occlusal adjustment may also be necessary if the bite is opened significantly during treatment. A posterior skeletal crossbite exists when the maxilla and mandible do not relate properly in the transverse dimension. In this instance, the posterior teeth may be tipped buccally or lingually in the body’s attempt to compensate for the underlying transverse skeletal discrepancy. However, if any occlusal shifts are removed, and if the posterior teeth are uprighted, the crossbite will worsen in the case of a skeletal crossbite. Skeletal crossbites should be treated by addressing the underlying transverse skeletal problem. Most frequently, the skeletal problem is a narrow maxilla, and the treatment involves increasing the basilar maxillary width by lateral expansion. A Hyrax jackscrew appliance is the most common technique for lateral expansion of the midpalatal suture. The younger the adolescent, the greater the chance for successful maxillary expansion. In older children and in adults, maxillary skeletal expansion may not be possible without surgical assistance to reduce the bony resistance to expansion.112 SPECIAL CONSIDERATIONS

29. What are some indications for extraction of a single mandibular permanent incisor? Case types for extraction of a single mandibular incisor103 include: • Class I with moderate to severe lower anterior crowding without deep bite • Class III tendency with good buccal occlusion, lower incisor crowding without deep bite • Class I with anterior tooth size discrepancy (mandibular anterior excess) • Class II with mandibular anterior crowding and two maxillary teeth extracted • Class I with one mandibular incisor extracted (treat nonextraction); may need to perform interproximal reduction on maxillary teeth • Class I with one mandibular incisor missing with moderate/ severe mandibular anterior crowding (treat with one additional lower incisor extraction and two maxillary extractions)

30. How can a patient with missing maxillary lateral incisors be treated? There are two options. The first would be to open spaces for prosthetic replacement of the maxillary lateral incisors. The second is to close spaces while protracting the posterior teeth and substitute the maxillary canines for laterals and the maxillary first premolars for canines. The ideal situation for prosthetic replacement of the laterals exists when the patient is Class I in both the molars and

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canines and when there is ideal occlusal intercuspation, ideal overbite, and ideal overjet. In this ideal case, orthodontics is not even needed. If everything is ideal but the maxillary canines have erupted into the lateral spaces, the maxillary canines need to be retracted distally into a Class I position as the spaces are opened. The lateral incisors can then be restored as pontics in a fixed partial denture, a removable partial denture, or as implants. The ideal situation for substitution of the maxillary canines as lateral incisors exists when the patient is a full-step Class II at the molars and premolars; there is ideal occlusal intercuspation, overbite, and overjet; both canines have erupted into the missing lateral incisor position; and where both canines look like lateral incisors. In this ideal case, orthodontics is not even needed. If a Class II molar interarch relationship exists but is less than a full-step Class II, the maxillary posterior teeth will usually need to be brought forward into a Class II molar relationship. This may be accomplished with Class III elastics, a reverse-pull headgear, or use of skeletal orthodontic anchorage. Also, if the canines do not resemble lateral incisors, cosmetic dentistry may be required to make them look like laterals.

31. When should teeth be extruded? What is meant by extrusion to extraction? Teeth are extruded for a variety of reasons. For example, in the case of trauma to a maxillary central incisor, the tooth may be fractured below the level of the alveolar crest. Although a crown extension surgical procedure may be performed to provide an adequate biologic width for restoration, the result may be unacceptable esthetically if the patient has a high smile line and the crown extension results in a more apical gingival margin on the fractured central incisor. Crown lengthening can be done using orthodontic extrusion in combination with a supracrestal fiberotomy to extrude the root fragment. Additional gingival and/or osseous surgical procedures may be needed after extrusion. If it is desirable to bring down gingival or osseous tissues, the tooth can be extruded initially without the supracrestal fiberotomy. Later, the fiberotomy procedure can be done to aid in stabilizing the extrusion. In addition, postextrusion surgery may be needed to fine-tune gingival heights and contours. Another reason is to extrude teeth prior to implant placement. This procedure is termed extrusion to extraction. In this instance a tooth may have been deemed hopeless because of periodontic or endodontic status of the tooth. If the tooth is simply extracted, the alveolar process will collapse, making implant placement difficult even with bone grafting. By orthodontically extruding the tooth first, before extraction, both bone and soft tissue are developed in the future implant site with a result of improved prosthetic bone and soft tissue contours for the prosthesis.113,114

32. What is skeletal anchorage, and how is it used in orthodontics? Again, for every action, an equal, but opposite, reaction exists. Newton’s third law poses a problem in orthodontics, where frequently the desired movement of one tooth is pitted against

the undesired movement of other teeth. These latter teeth are termed the anchor teeth. For instance, in a Class II patient, it may be desirable to move the maxillary canines distally following extraction of the maxillary first premolars. However, if a force (e.g., an elastic) is applied from the canine back to the molars, then not only will the canine be moved distally (desirable movement), but also the molars will tend to move mesially (undesirable movement, or anchorage loss). To overcome anchorage loss, headgears (or in some cases elastics) have traditionally been incorporated to restrain this mesial molar movement. However, these appliances require significant patient cooperation. In 1945, the first attempt to eliminate this need for patient compliance through the use of skeletal orthodontic anchorage was made at the University of Iowa.115 Skeletal anchorage consists of attaching surgical mini-screws or implants directly to the mandible, maxilla, or zygomatic arch. With a portion of the plate protruding through the mucosa, it is used as an attachment and for anchorage. As opposed to using teeth as anchorage, these auxiliaries undergo very little reciprocal movement. With temporary anchorage devices acting as skeletal anchorage, teeth may be translated, rotated, extruded, and intruded without undesirable reciprocal effects.116–119

33. In adult patients, orthodontic treatment frequently involves the family dentist, the orthodontist, and other dental specialists. What is the normal sequence of treatment in adults, and what is the most important aspect of treatment? The key to adult multidisciplinary treatment is communication. The family dentist (restorative dentist) is the end point of the patient’s care, and all treatment should be directed toward helping that doctor achieve an excellent result. The family dentist is at the center of the treatment hub, and all communications regarding the patient should be coordinated with that doctor. The dentist, orthodontist, and other dental specialists should work as a team to first diagnose and create a treatment plan for the patient. A diagnostic “wax-up” of the final occlusion should be fabricated to establish the treatment goal. The restorative dentist must answer the question, “Where do I need the patient’s teeth in order to restore them?” The orthodontist must answer the question, “Can I, through dental tooth movement or orthognathic surgery, move the teeth into the requested position?” Disease control should be instituted. The level of caries activity should be assessed and active caries removed. Teeth requiring extensive restorative treatment, such as crowns, should generally receive provisional restorations until orthodontic movement is complete. Active periodontal disease should be assessed and treated. Although periodontal surgery to help control disease can be desirable, bone removal should usually be minimized until orthodontic tooth movement is complete. Hopeless teeth should be extracted unless “extruding to extract” in an effort to save alveolar bone. Teeth requiring endodontic treatment should be treated, if they are to be retained.


During orthodontic treatment, the patient’s level of hygiene should be closely monitored and treated. The patient should receive regular dental check-ups and cleanings from the family dentist, and the orthodontist should provide regular progress updates, especially as the time for removal of braces nears. Once the restorative dentist and orthodontist have determined that the teeth are in the desired position, the braces are removed. Retention must be immediately instituted to maintain the teeth in the corrected position. REFERENCES 1. Moyers RE: Handbook of orthodontics, edition 3, Chicago, 1974, Year Book Medical Publishers, pp 369–379. 2. Staley RN, Kerber RE: A revision of the Hixon and Oldfather mixed-dentition prediction method, Am J Orthod 78:296–302, 1980. 3. Nance H: The limitations of orthodontic treatment. I. Mixed dentition diagnosis and treatment, Am J Orthod Oral Surg 33:177–223, 1947. 4. Brennan M, Gianelly A: The use of the lingual arch in the mixed dentition to resolve incisor crowding, Am J Orthod Dentofacial Orthop 117:81–85, 2000. 5. Gianelly A: Leeway space and the resolution of crowding in the mixed dentition, Semin Orthod 1:188–194, 1995. 6. Moyers RE, van der Linden FPGM, Riolo ML, et al: Standards of Human Occlusal Development, Monograph No. 5, Craniofacial Growth Series, Ann Arbor, MI, 1976, Center for Human Growth and Development, the University of Michigan. 7. Sheridan J: Air rotor stripping update, J Clin Orthod 21(11):781–788, 1987. 8. Witzig J: The clinical management of basic maxillofacial orthopedic appliances, volume 1. Mechanics, Chicago, 1987, Year Book Medical Publishers, p 213. 9. Richardson M, Mills K: Late lower arch crowding: the effect of second molar extraction, Am J Orthod Dentofacial Orthop 98:242–246, 1990. 10. Jakobsson S: Cephalometric evaluation of treatment effect on Class II, division 1 malocclusions, Am J Orthod 53:446–457, 1967. 11. Tulloch C, Phillips C, Koch G, et al: The effect of early intervention on skeletal pattern in Class II malocclusion: a randomized clinical trial, Am J Orthod Dentofacial Orthop 111:391–400, 1997. 12. Tulloch C, Proffit W, Phillips C: Outcomes in a 2-phase randomized clinical trial of early Class II treatment, Am J Orthod Dentofacial Orthop 125:657–667, 2004. 13. Keeling S, Wheeler T, King G, et al: Anteroposterior skeletal and dental changes after early Class II treatment with bionators and headgear, Am J Orthod Dentofacial Orthop 113:40–50, 1998. 14. Wheeler T, McGorray S, Dolce C, et al: Effectiveness of early treatment of Class II malocclusion, Am J Orthod Dentofacial Orthop 121:9–17, 2002. 15. Dolce C, McGorray S, Brazeau L, et al: Timing of Class II treatment: skeletal changes comparing 1-phase and 2-phase treatment, Am J Orthod Dentofacial Orthop 132:481–489, 2007. 16. Ghafari J, Shofer F, Jacobsson-Hunt U, et al: Headgear versus function regulator in the early treatment of Class II, Division 1 malocclusion: a randomized clinical trial, Am J Orthod Dentofacial Orthop 113:51–61, 1998. 17. Almeida-Pedrin R, Almeida M, Almeida R, et al: Treatment effects of headgear biteplane and Bionator appliances, Am J Orthod Dentofacial Orthop 132:191–198, 2007. 18. Thurman M, King G, Ramsay D, et al: The effect of an anterior biteplate on dental and skeletal Class II correction using headgears: a cephalometric study, Orthod Craniofac Res 14:213–221, 2011.

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19. Baccetti T, Franchi L, Stahl F: Comparison of 2 comprehensive Class II treatment protocols including the bonded Herbst and headgear appliances: a double-blind study of consecutively treated patients at puberty, Am J Orthod Dentofacial Orthop 698:e1–698.e10, 2009. 20. King G, McGorray S, Wheeler T, et al: Comparison of peer assessment ratings (PAR) from 1-phase and 2-phase treatment protocols for Class II malocclusions, Am J Orthod Dentofacial Orthop 123:489–496, 2003. 21. Huang G, English J, Ferguson D, et al: Ask Us-Functional appliances and long-term effects on mandibular growth, Am J Orthod Dentofacial Orthop 127:271–272, 2005. 22. Harvold E, Vargervik K: Morphogenetic response to activator treatment, Am J Orthod 60:479–490, 1971. 23. Stockli R, Willert H: Tissue reactions in the temporomandibular joint resulting from anterior displacement of the mandible in the monkey, Am J Orthod 60:141–155, 1971. 24. Woodside DG, Altuna G, Harvold E, et al: Primate experiments in malocclusion and bone induction, Am J Orthod 83:460–468, 1983. 25. McNamara JA, Bryan FA: Long-term mandibular adaptations to protrusive function: an experimental study in Macaca mulatta, Am J Orthod Dentofacial Orthop 92:98–108, 1987. 26. Op Heij DG, Callaert H, Opdebeeck HM: The effect of the amount of protrusion built into the Bionator on condylar growth and displacement: a clinical study, Am J Orthod Dentofacial Orthop 95(5):401–409, 1989. 27. McNamara Jr JA, Howe RP, Dischinger TG: A comparison of the Herbst and Fränkel appliances in the treatment of Class II malocclusion, Am J Orthod Dentofacial Orthop 98:134–144, 1990. 28. Mills JRE: The effect of functional appliances on the skeletal pattern, Br J Orthod 18:267–275, 1991. 29. Nelson C, Harkness M, Herbison P: Mandibular changes during functional appliance treatment, Am J Orthod Dentofacial Orthop 104:153–161, 1993. 30. Illing HM, Morris DO, Lee RT: A prospective evaluation of Bass, Bionator and twin block appliances. Part I-the hard tissues, Eur J Orthod 20:501–516, 1998. 31. Toth LR, McNamara Jr JA: Treatment effects produced by the twin block appliance and the FR-2 appliance of Fränkel compared with an untreated class II sample, Am J Orthod Dentofacial Orthop 116:597–609, 1999. 32. Almeida MR, Henriques JFC, Ursi W: Comparative study of Fränkel (FR-2) and Bionator appliances in the treatment of Class II malocclusion, Am J Orthod Dentofacial Orthop 121:458–466, 2002. 33. Dermaut L, Aelbers C: Orthopedics in orthodontics: fiction or reality. A review of the literature-Part II, Am J Orthod Dentofacial Orthop 110:667–671, 1996. 34. Johnston LE: If wishes were horses: functional appliances and growth modification, Prog Orthod 6(1):36–47, 2005. 35. Johnston LE: Commentary on “Mandibular changes produced by functional appliances in Class II malocclusion: a systematic review,” Am J Orthod Dentofacial Orthop 129:e1–e4, 2006. 36. Araujo AM, Buschang PH, Melo AC: Adaptive condylar growth and mandibular remodeling changes with Bionator therapy-an implant study, Eur J Orthod 26:515–522, 2004. 37. Righellis EG: Treatment effects of Fränkel, activator and extraoral traction appliances, Angle Orthod 53:107–121, 1983. 38. Nielsen IL: Facial growth during treatment with the functional regulator appliance, Am J Orthod 85:401, 1984. 39. Pancherz H, Haag U: Dentofacial orthopedics in relation to somatic maturation, Am J Orthod 88:273–287, 1985. 40. Croft RS, Buschang PH, English JD, et al: A cephalometric and tomographic evaluation of Herbst treatment in the mixed dentition, Am J Orthod Dentofacial Orthop 116:435–443, 1999. 41. Ascher F: The Bionator. In Graber T, Neumann B, editors: Removable orthodontic appliances, Philadelphia, 1977, WB Saunders.

218


42. Rudzki-Janson I, Noachtar R: Functional appliance therapy with the Bionator, Semin Orthod 4:33–45, 1998. 43. Faltin KJ, Faltin RM, Baccetti T, et al: Long-term effectiveness and treatment timing for Bionator therapy, Angle Orthod 73:221–230, 2003. 44. Malta LA, Baccetti T, Franchi L, et al: Long-term dentoskeletal effects and facial profile changes induced by Bionator therapy, Angle Orthod 80:10–17, 2010. 45. Kochel J, Meyer-Marcotty P, Witt E, et al: Effectiveness of Bionator therapy for class II malocclusions, J Orofac Orthop 73:91–103, 2012. 46. Owen 3rd. AH: Morphologic changes in the sagittal dimension using the Fränkel appliance, Am J Orthod 80:573–603, 1981. 47. Janson GR, Toruño JL, Martins DR, et al: Class II treatment effects of the Fränkel appliance, Eur J Orthod 25:301–309, 2003. 48. Perillo L, Cannavale R, Ferro F, et al: Meta-analysis of skeletal mandibular changes during Fränkel appliance treatment, Eur J Orthod 33(1):84–92, 2011 Feb. 49. Perillo L, Johnston Jr LE, Ferro A: Permanence of skeletal changes after function regulator (FR-2) treatment of patients with retrusive Class II malocclusions, Am J Orthod Dentofacial Orthop 109:132–139, 1996. 50. Perillo L, Castaldo MI, Cannavale R, et al: Evaluation of longterm effects in patients treated with Fränkel-2 appliance, Eur J Paediatr Dent 12(4):261–266, 2011. 51. Freeman DC, McNamara JA, Baccetti T, et al: Long-term treatment effects of the FR-2 appliance of Fränkel, Am J Orthod Dentofacial Orthop 135:570.e1–570.e6, 2009. 52. Sari Z, Goyenc Y, Doruk C, et al: Comparative evaluation of a new removable Jasper Jumper functional appliance vs an activator-headgear combination, Angle Orthod 73:286–293, 2003. 53. Cozza P, De Toffol L, Iacopini L: An analysis of the corrective contribution in activator treatment, Angle Orthod 74:741–748, 2004. 54. Wieslander L, Lagerström L: The effect of activator treatment on Class II malocclusions, Am J Orthod 75:20–26, 1979. 55. Cura N, Saraç M, Öztürk Y, Sürmeli N: Orthodontic and orthopedic effects of activator, activator-HG combination, and Bass appliances: a comparative study, Am J Orthod Dentofacial Orthop 110:36–45, 1996. 56. Janson G, Caffer DC, Henriques JFC, et al: Stability of Class II division 1 treatment with the headgear-activator combination followed by the edgewise appliance, Angle Orthod 74:594–604, 2004. 57. Hänggi MP, Teuscher UM, Roos M, et al: Long-term changes in pharyngeal airway dimensions following activator-headgear and fixed appliance treatment, Eur J Orthod 30:598–605, 2008. 58. Lerstol M, Torget O, Vandevska-Radunovic V: Long-term stability of dentoalveolar and skeletal changes after activatorheadgear treatment, Eur J Orthod 32:28–35, 2010. 59. Phan KLD, Bendeus M, Hägg U, et al: Comparison of the headgear activator and Herbst appliance-effects and posttreatment changes, Eur J Orthod 28:594–604, 2006. 60. Pancherz H, Fackel U: The skeletofacial growth pattern preand post-dentofacial orthopaedics: a long-term study of Class 11 malocclusions treated with the Herbst appliance, Eur J Orthod 12:209–218, 1990. 61. Hansen K, Pancherz H: Long-term effects of Herbst treatment in relation to normal growth development: a cephalometric study, Eur J Orthod 14:285–295, 1992. 62. Pancherz H, Anchus-Pancherz M: The headgear effect of the Herbst appliance: a cephalometric long-term study, Am J Orthod Dentofacial Orthop 103:510–520, 1993. 63. Hansen K, Pancherz H, Flagg U: Long-term effects of the Herbst appliance in relation to the treatment growth period: a cephalometric study, Eur J Orthod 13:471–481, 1991. 64. Omblus J, Malmgren O, Pancherz H, et al: Long-term effects of Class II correction in Herbst and Bass therapy, Eur J Orthod 19(2):185–193, 1997.

65. Pancherz H: The effects, limitations, and long-term dentofacial adaptations to treatment with the Herbst appliance, Semin Orthod 3(4):232–243, 1997. 66. Pancherz H, Ruf S, Kohlhas P: “Effective condylar growth” and chin position changes in Herbst treatment: a cephalometric roentgenographic long-term study, Am J Orthod Dentofacial Orthop 114(4):437–446, 1998 Oct. 67. Pancherz H, Fischer S: Amount and direction of temporo mandibular joint growth changes in Herbst treatment: a cephalometric long-term investigation, Angle Orthod 73(5):493–501, 2003. 68. Ruf S, Pancherz H: The effect of Herbst appliance treatment on the mandibular plane angle: a cephalometric roentgenographic study, Am J Orthod Dentofacial Orthop 110:225–229, 1996. 69. Nelson B, Hagg U, Hansen K, et al: A long-term follow-up study of Class II malocclusion correction after treatment with Class II elastics or fixed functional appliances, Am J Orthod Dentofacial Orthop 132:499–503, 2007. 70. Aelbers C, Dermaut L: Orthopedics in orthodontics. I. Fiction or reality-a review of the literature, Am J Orthod Dentofacial Orthop 110:513–519, 1996. 71. Pancherz H: The Herbst appliance: a powerful Class II corrector. In Nanda R, editor: Biomechanics in clinical orthodontics, Philadelphia, 1997, WB Saunders. 72. Firouz M, Zernik J, Nanda R: Dental and orthopedic effects of high-pull headgear in treatment of Class II, Division 1 malocclusion, Am J Orthod Dentofacial Orthop 102:197–205, 1992. 73. Baumrind S, Korn D, Isaacson RJ, et al: Quantitative analysis of the orthodontic and orthopedic effects of maxillary traction, Am J Orthod 83:384–398, 1983. 74. Kirjavainen M, Kirjavainen T, Hurmerinta K, et al: Orthopedic cervical headgear with an expanded inner bow in Class II correction, Angle Orthod 70:317–325, 2000. 75. Mitani H, Brodie AG: Three plane analysis of tooth movement, growth and angular changes with cervical traction, Angle Orthod 40:80, 1970. 76. Wieslander L: The effect of force on crania-facial development, Am J Orthod 65:531–538, 1974. 77. Melsen B: Effect of cervical anchorage during and after treatment: an implant study, Am J Orthod 73:526–540, 1978. 78. Harrison JE, O'Brien KD, Worthington HV: Orthodontic treatment for prominent upper front teeth in children, Cochrane Database Syst Rev 18(3):2007, CD003452. 79. Hans MG, Teng CM, Liao CC, et al: An evidence-based approach to treatment of open bite and deep bite: case reports, World J Orthod 8(1):45–64, 2007. 80. Millett DT, Cunningham SJ, O'Brien KD, et al: Orthodontic treatment for deep bite and retroclined upper front teeth in children, Cochrane Database Syst Rev (4):2006, CD005972. 81. Bondemark L, Karlsson I: Extraoral vs intraoral appliance for distal movement of maxillary first molars: a randomized controlled trial, Angle Orthod 75(5):699–706, 2005. 82. Tulloch JF, Medland W, Tuncay OC: Methods used to evaluate growth modification in Class II malocclusion, Am J Orthod Dentofacial Orthop 98(4):340–347, 1990. 83. Virkkula T, Kantomaa T, Julku J, et al: Long-term softtissue response to orthodontic treatment with early cervical headgear-a randomized study, Am J Orthod Dentofacial Orthop 135(5):586–596, 2009. 84. Krusinskiene V, Kiuttu P, Julku J, et al: A randomized controlled study of early headgear treatment on occlusal stability-a 13 year follow-up, Eur J Orthod 30(4):418–424, 2008. 85. Pirttiniemi P, Kantomaa T, Mäntysaari R, et al: The effects of early headgear treatment on dental arches and craniofacial morphology: an 8 year report of a randomized study, Eur J Orthod 27(5):429–436, 2005.


86. Glenn G, Sinclair PM, Alexander RG: Nonextraction orthodontic therapy: posttreatment dental and skeletal stability, Am J Orthod Dentofacial Orthop 92:321–328, 1987. 87. Fidler BC, Årtun J, Joondeph RD, et al: Long-term stability of Angle Class II, Division 1 malocclusions with successful occlusal results at end of active treatment, Am J Orthod Dentofacial Orthop 107:276–285, 1995. 88. Elms TN, Buschang PH, Alexander RG: Long-term stability of Class II, Division 1, nonextraction cervical face-bow therapy: II. Cephalometric analysis, Am J Orthod Dentofacial Orthop 109:386–392, 1996. 89. Lima Filho RMA, Lima AL, de Oliveira Ruellas AC: Mandibular changes in skeletal Class II patients treated with Kloehn cervical headgear, Am J Orthod Dentofacial Orthop 124:83–90, 2003. 90. Lima Filho RMA, Lima AL, de Oliveira Ruellas AC: Longitudinal study of anteroposterior and vertical maxillary changes in skeletal Class II patients treated with Kloehn cervical headgear, Angle Orthod 73:187–193, 2003. 91. Ciger S, Aksu M, Germec D: Evaluation of posttreatment changes in Class II Division 1 patients after nonextraction orthodontic treatment: cephalometric and model analysis, Am J Orthod Dentofacial Orthop 127:219–223, 2005. 92. Tortop T, Yuksel S: Treatment and posttreatment changes with combined headgear therapy, Angle Orthod 77:857–863, 2007. 93. Phan XL, Schneider BJ, Sadowsky C, et al: Effects of orthodontic treatment on mandibular rotation and displacement in Angle Class II Division 1 malocclusions, Angle Orthod 74:174–183, 2004. 94. Kim KR, Muhl ZF: Changes in mandibular growth direction during and after cervical headgear treatment, Am J Orthod Dentofacial Orthop 119:522–530, 2001. 95. Ryan MJ, Schneider BJ, BeGole EA, et al: Opening rotations of the mandible during and after treatment, Am J Orthod Dentofacial Orthop 114:142–149, 1998. 96. Caldwell SF, Hymas TA, Timm TA: Maxillary traction splint: a cephalometric evaluation, Am J Orthod 85:376–384, 1984. 97. Uner O, Yucel-Eroglu E: Effects of a modified maxillary orthopaedic splint: a cephalometric evaluation, Eur J Orthod 18:269–286, 1996. 98. Iscan HN, Dincer M, Gultan A, et al: Effects of vertical chincap therapy on the mandibular morphology in open-bite patients, Am J Orthod Dentofacial Orthop 122:506–511, 2002. 99. Erin AC, Sloss E, Southard K, et al: Comparison of soft-tissue profiles after treatment with headgear or Herbst appliance, Am J Orthod Dentofacial Orthop 133:509–514, 2008. 100. Ghosh J, Nanda R: Evaluation of an intraoral maxillary molar distalization technique, Am J Orthod Dentofacial Orthop 110:639–646, 1996. 101. Chaqués-Asensi J, Kalra V: Effects of the pendulum appliance on the dentofacial complex, J Clin Orthod 35(4):254–257, 2001. 102. Ngantung V, Nanda R, Bowman S: Post treatment evaluation of the distal jet appliance, Am J Orthod Dentofacial Orthop 120:178–185, 2001.

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103. Kokich V, Shapiro P: Lower incisor extraction in orthodontic treatment, Angle Orthod 59(2):139–153, 1984. 104. Deguchi T, Kuroda T, Minoshima Y, et al: Craniofacial features of patients with Class III abnormalities: growth-related changes and effects of short-term and long-term chin cup therapy, Am J Orthod Dentofacial Orthop 121:84–92, 2002. 105. Wendell PD, Nanda R, Sakamoto T, et al: The effects of chin cup therapy on the mandible: a longitudinal study, Am J Orthod 87:265, 1985. 106. Ngan P: Biomechanics of maxillary expansion and protraction in Class III patients, Am J Orthod Dentofacial Orthop 121: 582–583, 2002. 107. Ngan P, Hagg Yiu C, Wei S: Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction, Semin Orthod 3:255–264, 1997. 108. MacDonald K, Kapust A, Turley P: Cephalometric changes after the correction of Class III malocclusion with maxillary expansion/facemask therapy, Am J Orthod Dentofacial Orthop 116:13–24, 1999. 109. Kim T, Kim J, Mah J, et al: First or second premolar extraction effects on facial vertical dimension, Angle Orthod 75:177–182, 2005. 110. Proffit W, Mason R: Myofunctional therapy for tonguethrusting: background and recommendations, J Am Dent Assoc 90:403–411, 1975. 111. Kuroda S, Katayama A, Takano-Yamamoto T: Severe anterior open-bite case treated using titanium screw anchorage, Angle Orthod 74:558–567, 2004. 112. Marshall S, Southard K, Southard T: Early transverse correction, Semin Orthod 11(3):130–139, 2005. 113. Mantzikos T, Shamus I: Forced eruption and implant site development: soft tissue response, Am J Orthod Dentofacial Orthop 112(6):596–606, 1997. 114. Mantzikos T, Shamus I: Case report: forced eruption and implant site development, Angle Orthod 68(2):179–186, 1998. 115. Gainsforth BL, Higley LB: A study of orthodontic anchorage possibilities in basal bone, Am J Orthod Oral Surg 31:106–117, 1945. 116. Roberts WE, Nelson CL, Goodacre CJ: Rigid implant anchorage to close a mandibular first molar extraction site, J Clin Orthod 28:693–704, 1994. 117. Southard T, Buckley M, Spivey J, et al: Intrusion anchorage potential of teeth versus rigid endosseous implants: a clinical and radiographic evaluation, Am J Orthod Dentofacial Orthop 107:115–120, 1995. 118. Liou E, Pai B, Lin J: Do mini-screws remain stationary under orthodontic forces? Am J Orthod Dentofacial Orthop 126:42–47, 2004. 119. Miyawaki S, Koyama I, Inoie M, et al: Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage, Am J Orthod Dentofacial Orthop 124:373–378, 2003.

C H A PT E R

17

Adult Interdisciplinary Orthodontic Treatment Valmy Pangrazio-Kulbersh

I

ncreased awareness of the importance and benefits of a healthy dentition and a pleasant smile are motivating adults to seek orthodontic treatment more so now than in the past. Presently, the amount of orthodontic treatment rendered to adults comprises 30% of the orthodontic practice. The desire for a better smile is not only being patient generated, but general dentists are also becoming more knowledgeable about the possibilities of adult tooth movement to facilitate the establishment of function and health to the different components of the stomatognathic system. Interdisciplinary treatment is calling for more orthodontic interaction with the other specialties to obtain more optimum results in the restoration of often broken-down adult dentitions. The advent of new technology, such as esthetic brackets, invisible braces, new orthodontic wire alloys, and better brackets designed to reduce friction and speed up tooth movement, are also an incentive to attract more adults to seek orthodontic treatment.

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2. What are the goals of adult orthodontic treatment? The objectives of adult orthodontic treatment are: • To achieve improved function, stability, and esthetics1 • To eliminate occlusal interferences and trauma to reduce tooth mobility and promote periodontal healing1 • To obtain better bone and gingival architecture 2,3 • To establish proper tooth position and improve the plane of occlusion for prosthodontic rehabilitation3 • To achieve harmony between teeth and TMJ function7 • To address the patient’s chief complaint, which is usually related to dental and facial esthetics7

1. What are the major differences between adult and adolescent treatment? These differences are as follows: • Adult orthodontic treatment is usually initiated by the general dentist requesting the establishment of occlusal harmony (Fig. 17-1, A and B).1,2 • The lack of craniofacial growth offers no advantage or disadvantage to the orthodontic treatment.1,2 • Periodontal disease is present in about 80% to 90% of the adult patients (see Fig. 17-1, C to E).1,2 • There is a high incidence of missing permanent teeth.3 • Increased tooth mobility is a consequence of a change in occlusal scheme and loading as a result of the uncontrolled dental shifting caused by the mutilated dentitions and/or periodontal disease.3,5 • The lack of long-term stability resulting from periodontal problems requires a different approach to retention.3,5,6 • The increased prevalence and incidence of temporomandibular joint (TMJ) disorders requires a careful approach to the change in occlusal scheme.3,5 • The use of segmental orthodontic treatment mechanics and differential forces should be considered when the crown-toroot ratio is unfavorable.3 • Most adults are concerned with esthetics and the appearance of braces. The use of less conspicuous orthodontic appliances like ceramic brackets, lingual orthodontics, and Invisalign should be considered.5 220

Motivation for treatment in adults comes from the pursuit of esthetic changes or to restore a broken-down dentition or alleviate functional problems (e.g., TMJ dysfunction). The psychological response to treatment varies with the initial motivation. Those patients seeking treatment to improve function are more likely to have a better psychological response than those who are expecting an impact in others by their perceived change in facial appearance.4 Most adults require a multidisciplinary treatment plan to adequately restore esthetics and function.5

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3. What are the contraindications for adult orthodontic treatment? The presence of advanced local and/or systemic diseases (such as, bone, metabolic, or endocrine and renal disorders) could adversely affect tooth movement and bone turnover. The use of bisphosphonates, calcitonin, and ibuprofen has a negative effect on the rate of tooth movement.8–10 The presence of active periodontal disease contraindicates orthodontic tooth movement, because it could accelerate the process of periodontal problems and concomitant tooth loss.11,12 Patients with significant root resorption and poor crownto-root ratio may not benefit from orthodontic treatment.7 When patient compliance with long-term retention and follow-up prosthetic rehabilitation is not present, orthodontic treatment should not be initiated.7 Because of the high incidence of osteopenia and osteoporosis in adults over 50 years of age, a bone mass density test could be prescribed to screen for bone disorders that can lead to alveolar bone loss and loss of teeth.9,10

Adult Interdisciplinary Orthodontic Treatment • CHAPTER 17

A

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B

C, D

E

FIG 17-1 Adult patient seeking orthodontic treatment. Note the complexity of the malocclusion. A and B, Pretreatment facial photos depicting the skeletal imbalance. C to E, Intraoral photos show the dental and periodontal problems in this adult patient.

4. What are the effects of orthodontic treatment on the periodontal tissues? The elimination and control of inflammation before and throughout orthodontic treatment is imperative to ensure the health of the supporting tissues. Clinical studies have demonstrated that teeth with reduced periodontal support, in the absence of inflammation, can undergo tooth movement without compromising the periodontal status.13 • Reduction of pocket depth and probing in orthodontically moved teeth in adults, as well as maintenance of a minimal band of attached gingiva, can be accomplished with ortho dontic treatment.14,15 • A free gingival graft is recommended when a minimum amount of attached gingiva is present and when the tooth movement is directed toward the thin gingival tissue. When tooth movement is confined to the alveolar support, no harmful effects on the surrounding tissues are to be expected.16,17 • Adults have an increased prevalence of root resorption during orthodontic treatment. The use of light forces is recommended to avoid the formation of hyalinized areas and to expedite tooth movement.13,17

5. What kind of periodontal therapy should be instituted before, during, and after adult orthodontic tooth movement is initiated? The elimination of inflammation that rapidly deteriorates the periodontium is essential prior to the initiation of tooth movement. Plaque and inflammation control should continue throughout orthodontic therapy and afterward.18

• Scaling, root planing, open flap surgery, and gingival grafting should be done prior to the commencement of ortho dontic treatment.18 • Recontouring osseous surgery should be postponed until after orthodontic treatment. The architecture of the bone changes with the tooth movement, and possibly less bone recontouring may be necessary after orthodontic treatment.18 • Bone grafting procedures to increase alveolar width and height in an edentulous area, through which tooth movement is to occur, should be done prior to orthodontic treatment. Bone grafting for implant placement could be done 6 months prior to debanding or postponed until treatment completion.18 • Equilibration of occlusal interferences that may arise during treatment should be done at each appointment as necessary to avoid periodontal breakdown and excessive tooth mobility from occlusal trauma.18

6. Which orthodontic records are necessary for proper diagnosis and treatment planning of the adult orthodontic patient? Because of the complexity of factors among which the malocclusion is included, a careful evaluation of the patient, including a thorough medical history, chief complaint, and psychological evaluation, is necessary to properly integrate those factors with the ones related to the actual dental treatment. The standard orthodontic record consists of: • Facial photographs (frontal with lips in repose, frontal smiling, and profile with lips in repose): This will provide important information about the soft tissue drape of the face, such as lip length and competency, soft tissue chin

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CHAPTER 17 • Adult Interdisciplinary Orthodontic Treatment

prominence, nose prominence and slope, amount of gingival display, midline deviations, and overall facial proportionality. 19,20 Lateral and frontal cephalograms.19,20 Panoramic x-rays and full mouth periapical surveys to evaluate for bony, dental, and periodontal pathologies as well as anatomy of the roots.19,20 Submental x-ray and TMJ tomograms may be necessary to diagnose skeletal asymmetries and TMJ pathology.20,21 Models mounted in centric relation will help to detect a centric occlusion–centric relation (CO-CR) slide, which is imperative before the commencement of orthodontic treatment. Roth has suggested that even in the absence of obvious signs or symptoms of TMJ dysfunction, adult patients, specifically those with mutilated dentitions, should undergo splint therapy to eliminate muscle splinting and to avoid treatment planning from a false mandibular position.20,21

7. What is the sequence of adult orthodontic treatment? Once the diagnosis and treatment plan have been established, a treatment sequence should be considered as follows22: 1. Emergency relief of pain (This step, in many instances, will precede the gathering of orthodontic records and follow-up diagnosis.) 2. Therapy of soft tissue lesions • Hygiene instructions • Scaling and root planning • Correction of inadequate restoration • Root resection and endodontic treatment 3. Treatment of the lesions of the attachment • Flap surgery and root planning • Guided tissue regeneration • Autogenous keratinized mucosal or connective tissue grafts • Orthodontic therapy • Occlusal adjustment • Myofunctional therapy 4. Provisional stabilization and retention 5. Reevaluation for further therapy (e.g., extraction of nonrestorable teeth) 6. Completion of periodontal treatment 7. Final occlusal adjustment 8. Restorative prosthetic dentistry 9. Continued periodontal care

8. What are the treatment options for adult patients? Limited tooth movement and comprehensive orthodontic treatment can be considered when doing treatment planning for an adult orthodontic case. The severity of the malocclusion and treatment goals should be considered when selecting the treatment. Limited tooth movement is carried out either with removable or partial fixed orthodontic appliances and is aimed at specific treatment goals. In most instances, limited tooth

ovement is considered as an adjunct to the overall oral rem habilitation of the patient. Comprehensive orthodontic treatment aims to the correction of malocclusion as a whole and has the potential to modify the complete occlusal scheme as required.23

9. What are the specific problems that can benefit from limited tooth movement treatment? Limited tooth movement is indicated to reposition the dental units in a specific quadrant to facilitate prosthetic replacements of missing teeth and to improve periodontal health and dental esthetics. Molar uprighting to improve parallelism of the abutments, to create appropriate pontic space, or to facilitate implant replacement of missing teeth can be accomplished with limited orthodontic treatment. Forced eruption to facilitate preparation of the root for crown placement or to create bone through the occlusal movement of the tooth for implant placement can also be accomplished with partial orthodontic treatment. Correction of spacing, crowding, rotations, and dental crossbites can be accomplished with either fixed or removable orthodontic appliances.24

10. What are the diagnostic considerations when treatment planning for molar uprighting? A thorough evaluation of the occlusion and skeletal characteristics of the patient is indicated. Molar uprighting is best accomplished with limited treatment when an acceptable occlusion with anterior guidance and cuspid rise is present and in patients with a normal vertical dimension. Patients with dolichocephalic faces are not good candidates for molar uprighting, which necessitates distalization of the molar crown. This type of tooth movement further increases the vertical dimension, with concomitant development of a dental openbite.25

11. What are the types of tooth movements that could be considered for molar uprighting? Molar uprighting can be accomplished by: • Distalization of the crown • Mesialization of the root • A combination of both In many instances, mesial movement of the bicuspids that have drifted distally into the edentulous area may be necessary. When indicated, complete space closure of the edentulous space using temporary anchorage devices also should be considered. When only a single tooth is to be uprighted, the clinician has the option of choosing between removable or fixed orthodontic appliances. A removable appliance with a finger spring mesial to the tooth to be uprighted will tip the tooth distally without vertical or transverse control. Because of this limitation as well as the dependence on patient cooperation, removable appliances are not widely prescribed. Partial fixed orthodontic appliances are more effective in controlling tooth movement in three planes of space (Fig. 17-2).


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Another important treatment consideration is the disposition of the third molar. The presence of an antagonist, the occlusion, and type of tooth movement planned will dictate the fate of the third molar. The demand for anchorage would be part of the appliance design and selection. A lingual cuspid-to-cuspid fixed retainer or temporary anchorage devices (temporary implants) could be used when stabilization of the anchoring teeth is necessary (Fig. 17-3).26–28

12. What is the retention protocol after molar uprighting?

FIG 17-2 Typical appliance assembly for molar uprighting. Note auxiliary spring to aid in the uprighting.

When uprighting a molar, standard brackets can be used on the anchoring teeth (cuspids and bicuspids) and a double buccal tube placed on the molar to be uprighted. The double buccal tube allows for the placement of an auxiliary uprighting spring when necessary. Periodic occlusal adjustment and root planing of the tooth being uprighted is recommended to avoid trauma from occlusion, excessive tooth mobility, and pain as well as to promote periodontal healing.

The uprighted teeth should be retained until the placement of the prosthetic device. The retention can be accomplished with an intracoronal stabilization bar or a rigid stainless steel wire bonded to the teeth neighboring the edentulous area. The preparation for the bridge or the placement of the implant should be postponed until the reappearance of the lamina dura around the uprighted tooth. This usually takes place 8 to 12 weeks after the tooth has reached its final position.25,26

13. What is forced eruption? Forced eruption is defined as the orthodontic tooth movement in the coronal direction through the application of continuous forces to create changes in the architecture of the soft tissue and bone. This procedure facilitates the conservative management

A, B

C

D, E

F

H

G

FIG 17-3 Bilateral lower molar uprighting. A to D, Pretreatment intraoral photos. E to H, Posttreatment intraoral photos. Note the extraction of the lower right third molar to facilitate distal crown movement.

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of non-restorable teeth. Forced eruption helps restore the biological width, allowing the restoration to be placed away from the epithelial attachment, thus preventing periodontal inflammation and breakdown. To maintain a healthy periodontium, 3 to 4 mm of tooth length is needed occlusal to the alveolar crest.29

will have a longer taper from the occlusal to the gingival margin due to the smaller dimension of the root surface being exposed. Careful attention should be given to the contour of the restoration to obtain good esthetics and gingival health (Fig. 17-4 and Fig. 17-5).30

14. How is forced eruption accomplished?

15. What are the orthodontic considerations for the correction of dental alignment?

Forced eruption can be done slowly to promote bone remodeling in periodontally compromised teeth or to protect the integrity of the pulpal tissues and avoid root damage. The coronal movement of the tooth elicits bone formation and soft tissue recontouring. This improves the overall esthetics of the final restoration, even when crown lengthening with osseous surgery is needed for placement of the crown. Endodontically treated teeth can be extruded with heavier forces and more rapidly. Bone recontouring does not take place as readily, obviating in some cases the need for osseous surgery, especially when the forced eruption is combined with circumferential sulcus fiberotomy before and weekly during the tooth movement.29 The retention period after forced eruption is approximately 2 to 6 weeks to allow for the rearrangement of the principal fibers of the periodontal ligament. The healing of the periodontal tissues dictates the time of placement of the final restoration. The practitioner should be aware that the restoration

The correction of crowding, spacing, rotations, crossbites, and tipped teeth is indicated not only for esthetic reasons, but also to facilitate restorative procedures and maintain oral health. Crowding and rotations are the result of tooth size/arch length discrepancies. The creation of spaces in the dental arches to correct these problems can be obtained through flaring of the anterior teeth, transverse expansion of the dental arches, interproximal enamel reduction, or extractions. Approximately 0.5 mm of enamel can be removed from the mesial and distal surfaces of the upper anteriors for a total of 4 to 5 mm. Because of the smaller diameter of the lower anterior teeth, less reduction is possible.31–33 Before embarking on the closure of excessive maxillary or mandibular anterior spacing, a careful evaluation of the etiologic factors should be considered. Arch length/tooth size discrepancies, loss of teeth, presence of CO-CR discrepancies produced by posterior interferences, periodontal disease, abnormal labial frenum or abnormal interseptal bone architecture, presence of

A

B

C

FIG 17-4 Forced eruption of the upper right central to facilitate crown preparation. A, Pretreatment periapical radiograph. B, Posttreatment periapical radiograph. C, Posttreatment intraoral photo.


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A B

C

FIG 17-5 Forced eruption of upper left lateral to eliminate vertical bony defect. A, Pretreatment periapical radiograph; note bony defect. B, Progress photo. Note bend in archwire to slowly extrude tooth. Periodontal probe is used to determine pocket depth. C, Posttreatment periapical radiograph shows elimination of vertical bony pocket.

supernumerary teeth, and habits like tongue thrust or nailbiting could be involved in the etiology of this malocclusion. The recognition and elimination of the etiologic factors are essential to select the appropriate mechanotherapy. The correction of crowding, rotations, spacing, crossbites, and tipped teeth in the presence of an acceptable occlusion can be accomplished with partial fixed orthodontic treatment or with Invisalign treatment.

16. When is comprehensive orthodontic treatment indicated for the adult patient? Adults with mutilated dentitions and/or periodontal disease have a history of dental neglect that has contributed to the malocclusion. Dental and functional compensations that have taken place during a prolonged period usually result in a complex malocclusion. The elimination of the structural and functional malocclusions often requires the use of full ortho dontic appliances. The use of osseous integrated implants and temporary anchorage devices is rapidly expanding the scope of orthodontic treatment for adults. Comprehensive orthodontic treatment, designed to change the entire occlusal scheme of the

adult patient, can be performed successfully because of innovations in orthodontic appliance design, orthodontic wires made with new alloys that deliver lighter and more continuous forces, and periodontal, prosthetic, and surgical advances that give the adult patient excellent esthetic and functional results.22,32,34 The ultimate goal of comprehensive adult orthodontic treatment should be the attainment of Andrews’35 six keys to normal occlusion and to restore health and harmony of the different components of the stomatognathic system.

17. What are the retention considerations after adult orthodontic treatment? Permanent splinting of periodontally compromised teeth is advisable after adult tooth movement. The replacement of missing teeth should be done 3 to 6 months after the removal of the fixed orthodontic appliances. Delaying their replacement can cause the loss of tooth alignment and bite collapse. The retainers should be designed to maintain tooth position in three planes of space. In partially edentulous patients, an acrylic bite block should be incorporated into the extraction site to maintain the edentulous space and prevent extrusion of the opposite

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tooth. Invisible plastic retainers offer increased esthetics and comfort as well as protection against parafunctional habits.36,37

18. When should orthognathic surgery be considered for the adult patient? Adult patients with severe skeletal deformities in any of the three planes of space should be considered for combined ortho dontic and surgical treatment (Fig. 17-6).

A

The indication for surgery is also determined by the lack of availability for growth modification treatment, the effect of tooth movement on facial esthetics and periodontal health, anatomy of the palate and the symphysis, other functional and anatomical limitations, as well as patient cooperation and length of treatment. The role of the orthodontist is to remove the dental compensations caused by the skeletal deformity and to coordinate the upper and lower dental arches

B

C, D

E

F, G

H

I

J

FIG 17-6 Orthognathic surgical treatment of a severe dentoskeletal Class II malocclusion characterized by maxillary vertical excess, mandibular retrognathia, and maxillary constriction. A to E, Pretreatment photos. F to J, Presurgical preparation.


K

227

L

M, N

O

P

Q

FIG 17-6, cont’d K to O, Posttreatment results after LeFort I maxillary impaction, mandibular sagittal split advancement, and advancement genioplasty. P and Q, Comparisons of pretreatment and posttreatment cephalograms.

to facilitate the surgical coordination of the skeletal bases. Rigid fixation has made the surgical procedures stabler and more acceptable to patients. The success of orthognathic surgery is dependent on knowledge of basic orthodontic and surgical principles as well as the interaction and communication among all practitioners involved in the final restoration of the esthetic function and psychological well-being of the patient.38,39

19. What are the orthodontic considerations that relate to the patient’s dental esthetics? Over the past decade, advances in dental materials have expanded the restorative procedures available to today’s clinicians, especially in regard to esthetic dentistry. Orthodontists are in a unique position to participate in the “smile design” of the adult patient by properly positioning the anterior teeth to facilitate the placement of esthetic restorations (Fig. 17-7).

The relationship between extraoral and intraoral structures is essential to dental esthetics. The three structures that compose the smile—the lips, the gingiva, and the teeth—must have a harmonious relationship for an acceptable esthetic appearance. If excessive maxillary spacing is present because of tooth size discrepancy, orthodontic treatment to redistribute the space is indicated. Consideration for space allocation needed for the proper restorative sizing of the incisors is essential. The esthetic success of the final restorations will be totally dependent on the prerestorative orthodontic dental repositioning. In cases in which the excessive spacing is due to dental shifting into an edentulous space (e.g., missing maxillary lateral incisor), orthodontic repositioning should be done to open the appropriate amount of space as well as to obtain root parallelism to facilitate implant placement (Fig. 17-8). The minimum amount of space needed for the placement of an implant to

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A, B

C

D, E

F

G, H

I

J

K, L

M

FIG 17-7 Comprehensive orthodontic treatment to intrude the upper and lower incisors and to obtain clearance for crown restorations on severely abraded anterior teeth. A to F, Pretreatment presentation. G to I, Postorthodontic occlusion prior to restorations. J, Occlusal view of lower arch. Note abrasion of lower dentition. K to M, Final result.

replace a maxillary lateral incisor is 6 mm at the root level. This allows for a minimum of 1-mm space mesial and distal to the implant. The presence of a black triangle between the anterior teeth, specifically the central incisors, is considered to be esthetically

unpleasant to many patients (Fig. 17-9). This space usually appears after the correction of overlapped incisors, where the dental papillae did not develop. Interproximal reduction of the mesial surface of the central incisors is recommended to reduce the triangular space. Also, reducing the distal tip of the

A, B

C

D

E

F

G

FIG 17-8 Orthodontic preparation for implant replacement of upper lateral incisors. A to C, Pretreatment intraoral photos. D and E, Postorthodontic preparation. Note root positioning to facilitate implant placement. F and G, Postimplant placement results.

A, B C

D

F

E

G

FIG 17-9 Orthodontic treatment to facilitate space redistribution after extraction of the severely decayed upper right central incisor. The lateral incisor was moved into the central space. Esthetic restoration would reshape the lateral as a central incisor. A, Pretreatment radiograph. B and C, Orthodontic preparation. Extraction of the upper left decayed first molar and space closure was also accomplished. D to G, Final results.

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roots of the central incisors will approximate the crowns gingivally, decreasing the size of the space. When this is done, recontouring of their incisal edges may be necessary. Extrusion and intrusion of teeth, especially in the anterior region of the upper arch, could be considered for leveling of the gingival margins. Intrusion will produce apical migration of the gingival border, and extrusion will bring the level of the gingival tissue toward the occlusal plane. Adjustment of the incisal edges either with equilibration or veneers is recommended when considering these types of tooth movements. Recently, high gingivectomy with lasers has been used for this purpose (Fig. 17-10).40–49

20. Have temporary anchorage devices changed the paradigm in the adult orthodontic treatment? The advent of temporary anchorage devices (TADs) has faci litated the mechanics utilized in the treatment of adults with periodontally compromised and mutilated dentitions. Their utilization as absolute anchorage has allowed the orthodontists to accomplish challenging orthodontic tooth movements. Single or multiple teeth intrusion (Fig. 17-11 and Fig. 17-12), space closure of edentulous spaces through a narrow alveolar ridge (Fig. 17-13), anterior en masse retraction, distalization into posterior edentulous spaces (Fig. 17-14), and any other types of tooth movements where anchorage considerations are critical can be now managed with more predictable results.50–55

A

B

C

FIG 17-10 Excessive gingival display corrected with high gingivectomy to improve the “gummy” smile. A, Pretreatment intraoral photo. B, Gingival markings to guide in contouring of tissue. C, 3 weeks postsurgical result.

B

A

D

C

FIG 17-11 Upper first molar intrusion to facilitate implant replacement of the lower first molar. A, Pretreatment malocclusion. Note lack of vertical clearance for lower tooth replacement. B and C, Buccal and palatal implants used for intrusion. D, Final occlusion.

A

B

D

C

E

F

G

I

H

FIG 17-12 Maxillary buccal segment intrusion to decrease lower anterior face height and close openbite. A and B, Initial malocclusion. C to E, Implant location. F and G, Final occlusion. H and I, Initial and final cephalograms. Note change in angulation of the occlusal plane due to posterior buccal segment intrusion. When this mechanics is used, the arc of closure of the mandible has to be taken into consideration to determine the overjet after the counterclockwise rotation of the mandible.

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A,B

C

F

D,E

G,H

I

J,K

L

FIG 17-13 Class II division 1, periodontally compromised and compensated malocclusion. Missing lower right first molar, buccally displaced lower left second bicuspid, and significant mesial tipping of the lower molars. A to C, Initial malocclusion. D to F, Final occlusion after extractions of the upper first bicuspids and lower left second bicuspid. G to I, Initial, progress, and final panorexes. Note placement of temporary anchorage devices (TADs) in the middle of the extraction sites to close spaces by mesialization of the molars half way into the edentulous area with direct anchorage from the TADs and distalization of the anterior segment into the remaining spaces with direct anchorage from the TADs. J to L, Initial, progress, and final cephalograms. Note significant retraction of the upper and lower anterior segments.


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A, B

C

D, E

F

I

G, H

K

J

FIG 17-14 Severely periodontally compromised malocclusion. Excessive mandibular crowding and significant proclination of the upper incisors. A to C, Initial malocclusion. D to F, Occlusion after distalization of the upper right buccal segment with the aid of a temporary anchorage device (TAD) and space closure of the extraction sites of the upper left and lower first bicuspids. A distally extended arch wire anchored on the TAD by a vertical arm was used on the right side as anchorage. A coil spring was attached to the distal extension and hooked mesially to the cuspid to distalize the right buccal segment into a Class I cuspid occlusion. G to I, Final occlusion. J and K, Progress and final panorexes. Note distal placement of the TAD to allow for sufficient space for distalization of the bicuspids.

REFERENCES 1. Kuhlberg A, Glynn E: Treatment planning considerations for the adult patients, Dent Clin North Am 41(1):17–27, 1997. 2. Matthews DP, Kokich VG: Managing treatment of the orthodontic patient with periodontal problems, Semin Orthod 3(1):21–38, 1997. 3. Roberts EW, Hartsfield Jr JK: Primary management of congenital and acquired compensated malocclusions: diagnosis, etiology and treatment planning, IDA J Summer 1996. 4. Phillips C, Bennett ME, Broader HL: Dentofacial disharmony: psychological status of patients seeking a treatment consultation, Angle Orthod 68(6):547–556, 1998. 5. Barrer G: The adult orthodontic patient, Am J Orthod 72: 617–640, 1977. 6. Boyd RL, Leggott PJ, Quinn RS, et al: Periodontal implications of orthodontic treatment in adults with reduced or normal

periodontal tissues versus those of adolescents, Am J Orthod 96(3):191–198, 1989. 7. Thilander B: Indications for orthodontic treatment in adults. In Thilander B, Ronning O, editors: Introduction to orthodontics, Stockholm, 1985, Tandlakarforlaget. 8. Chanavaz M: Screening and medical evaluation of adults, absolute and relative contraindications for invasive dental procedures, J Indiana Dent Assoc 78(3):10–17, 1999. 9. Roberts WE, Garetto LP, Arbuckle GR, et al: What are the risk factors of osteoporosis? Assessing bone health, J Am Dent Assoc 122(2):59–61, 1991. 10. Payne JB, Reinhardt RA, Nummikoski PV, et al: Longitudinal alveolar bone loss in post-menopausal osteoporotic/osteopenic women, Osteoporos Int 10(1):34–40, 1999. 11. Zachrisson BU: Clinical implications of recent orthodonticperiodontic research findings, Semin Orthod 2(1):4–12, 1996.

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12. Ong MA, Wang HL, Smith FN: Interrelationship between periodontics and adult orthodontics, J Clin Periodontol 25(4):271–277, 1998. 13. Artun J, Urbye K: The effect of orthodontic treatment on periodontal bone support in patients with advanced loss of marginal periodontium, Am J Orthod Dentofacial Orthop 93(2):143–148, 1988. 14. Polson A, Caton J, Polson AP, et al: Periodontal response after tooth movement into infrabony defects, J Periodontol 55(4): 197–202, 1984. 15. Melsen B, Agerback N, Eriksen J, et al: New attachment through periodontal treatment and orthodontic intrusion, Am J Orthod Dentofacial Orthop 94(2):104–116, 1988. 16. Zachrisson BU: Periodontal changes during orthodontic treatment. In McNamara Jr JA, Ribbens KA, editors: Malocclusion and the periodontium, Michigan Growth Series, Center for Human Growth and Development, Ann Arbor, 1989, University of Michigan, pp 43–66. 17. Dorfman HS: Mucogingival changes resulting from mandibular incisor tooth movement, Am J Orthod 74:258–277, 1978. 18. Wennstrom JL, Stokland BL, Nyman S, et al: Periodontal tissue response to orthodontic movement of teeth with infrabony pockets, Am J Orthod Dentofacial Orthop 103(4):313–319, 1993. 19. Pangrazio-Kulbersh V: Adult orthodontic treatment. In Riolo ML, Avery JK, editors: Essentials for orthodontic practice, 1 ed., Grand Haven, MI, 2003, EEOP, pp 510–532. 20. Roth RH: Functional occlusion for the orthodontist. Part I, J Clin Orthod 15(1):32–51, 1981. 21. Roth RH, Rolfs DA: Functional occlusion for the orthodontist. Part II, J Clin Orthod 15(2):100–123, 1981. 22. Vanarsdall RL, Musich DR: Adult orthodontics: diagnosis and treatment. In Graber TM, Vanarsdall RL, editors: Orthodontics: current principles and practice, 5 ed., St Louis, 2012, CV Mosby. 23. Roberts WE: Adjunctive orthodontic therapy in adults over 50 years of age, clinical management of compensated, partially edentulous malocclusions, J Indiana Dent Assoc 76(2):33–41, 1997. 24. Roberts WE, Hartsfield JK: Multidisciplinary management of congenital and acquired compensated malocclusions, J Indiana Dent Assoc 76(2):42–51, 1997. 25. Tulloch JF: Uprighting molars as an adjunct to restorative and periodontal treatment in adults, Br J Orthod 9(3):122–128, 1982. 26. Roberts WW, Chacker FM, Burstone CJ: A segmental approach to mandibular molar uprighting, Am J Orthod 81(3):177–184, 1982. 27. Hom B, Turley P: The effects of space closure of the mandibular first molar area in adults, Am J Orthod 85(6):457–469, 1984. 28. Tuncay OC, Biggerstaff RH, Cutcliffe JC, et al: Molar uprighting with T-loop springs, J Am Dent Assoc 100(6):863–866, 1980. 29. Pontonero R, Celenza F, Ricci G, et al: Rapid extrusion with fiber resection: a combined orthodontic-periodontic treatment modality, Int J Periodontics Restorative Dent 7(5):31–34, 1987. 30. Stevens B, Levine RA: Forced eruption: a multidisciplinary approach for form, function and biologic predictability, Compend Contin Educ Dent 19(10):994–1004, 1998. 31. Hohlt WE, Hovijitra S: Multidisciplinary treatment of anterior spacing by orthodontic and prosthodontic management, J Indiana Dent Assoc 76(3):18–23, 1999. 32. Gianelly AA: Bidimensional technique theory and practice, Rapid City, SD, 2000, Fenwyn Press, pp 229–256. 33. Sheridan JJ, Ledoux PM: Air-rotor stripping and proximal sealants, J Clin Orthod 23(12):790–794, 1989.

34. Bishara SE: Textbook of orthodontics, Philadelphia, 2001, WB Saunders pp 494–531. 35. Andrews LF: The six keys to normal occlusion, Am J Orthod 62(3):296–309, 1972. 36. Bishara SE, Treder JE, Damon P, et al: Changes in the dental arches and dentition between 25 and 45 years of age, Angle Orthod 66(6):417–422, 1996. 37. Zachrisson BU: Third generation mandibular bonded lingual 3-3 retainer, J Clin Orthod 19(9):562–583, 1997. 38. Epker BN, Fish L: Dentofacial deformities: integrated orthodontic surgical correction, St Louis, 1983, CV Mosby. 39. Proffit WR, Fields Jr H: Contemporary orthodontics, ed 5, St Louis, 2013, CV Mosby. 40. Spear FM, Matthezus DM, Kokich VG: Interdisciplinary management of single tooth implants, Semin Orthod 3(1):45–72, 1997. 41. Roberts WE, Baldwin JJ: Pre-prosthetic alignment of a compensated Class II malocclusion in a partially edentulous adult case, Stud Orthod 3(1):1–6, 2000. 42. Kokich VG: Esthetics: the orthodontic-periodontic restorative connection, Semin Orthod 2(1):21–30, 1996. 43. Salama N, Salama M: The role of orthodontic extrusive remodeling in the enhancement of the soft and hard tissue profiles prior to implant placement: a systematic approach to the management of extraction site defects, Int J Periodontics Restorative Dent 13(4):312–333, 1993. 44. Chu SJ, Karabin S, Mistry S: Short tooth syndrome: diagnosis, etiology, and treatment management, J Calif Dent Assoc 32(2):143–152, 2004. 45. Spear FM: Interdisciplinary esthetic management of anterior gingival embrasures, Adv Esth Interdisc Dent 2(1):20–28, 2006. 46. Kokich VG, Spear FM, Kokich VO: Maximizing anterior esthetics: an interdisciplinary approach. In McNamara Jr JA, editors: Frontiers in dental and facial esthetics, Ann Arbor, 2001, Needham Press, pp 1–18. 47. Kokich V: Esthetics and anterior tooth position: an orthodontic perspective, Part III: Mediolateral relationships, J Esth Dent 5(5):200–207, 1993. 48. Kokich V: Esthetics and anterior tooth position: an orthodontic perspective, Part II: Vertical position, J Esth Dent 5(4):174–178, 1993. 49. Kokich VG: Maxillary lateral incisor implants: planning with the aid of orthodontics, J Oral Maxillofac Surg 62:48–56, 2004. 50. Kokich VG: Managing complex orthodontic problems: the use of implants for anchorage, Semin Orthod 2:153–160, 1996. 51. Park JC, Kim DH, Jee SH: Intrusion of posterior teeth using mini screw implants, Am J Orthod Dentofacial Orthop 123:690–694, 2003. 52. Yao CC, Lee JJ, Chen HY, et al: Maxillary molar intrusion with fixed appliances and mini implant anchorage studied in three dimensions, Angle Orthod 75:754–760, 2005. 53. Roberts WE, Marshall KJ, Mozsary PG: Rigid endosseous implant utilized as anchorage to protract molars and close an atrophic extraction site, Angle Orthod 60:135–152, 1990. 54. Park HS, Bae SM, Kyung HM, et al: Microimplant anchorage for treatment of skeletal class I bi alveolar protrusion, J Clin Orthod 32:435–441, 2002. 55. McNamara Jr JA, editor: Implants, microimplants, onplants and transplants: new answers to old questions in orthodontics. In Dept. of Orthodontics and Pediatric Dentistry and Center for Human Growth and Development, 2005, University of Michigan. Craniofacial Growth Series, Vol. 42.

Skeletal Anchorage in Orthodontics

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Onur Kadioglu • Brody J. Hildebrand • Marc Schätzle

O

rthodontics, as one of the oldest specialties in dentistry, has experienced several periods of transformation. New theories, new methods of treatment, new devices, and new materials have dramatically changed and improved the way orthodontists move teeth and/or jaws. From expansion arches (E arches),1 banding all teeth, conventional ligation, stainless steel to edgewise slots, bonding, self-ligation brackets, β-titanium and NiTi wires, and all the way through LeFort osteotomies with rigid fixation and distraction osteogenesis, the world of orthodontics is now quite different from what the founding fathers of our specialty created. Anchorage is still one of the limiting factors in orthodontics, and its control is essential for successful orthodontic treatment. The term orthodontic anchorage, whether extraoral or intraoral, was first introduced by Angle.1 Orthodontic anchorage can simply be explained as resistance to unwanted movement. Although all of Newton’s Three Laws of Motion (1687) affect orthodontic tooth movement, the Third Law, which states that for every action there is an equal and opposite reaction, has the most impact. In orthodontic treatment, both reciprocal and collateral effects should be controlled. The goal is to maximize desired tooth movements and minimize the unwanted ones. Frequently, minimizing the unwanted ones may require greater effort. Each tooth has its own anchorage potential. We know that when teeth are used as anchorage, with or without conventional auxiliary appliances, they move. These unwanted movements of the anchoring units may result in prolonged treatment time and unpredictable or less than ideal outcomes, thus decreasing treatment efficiency. The anchorage potential of each tooth, or groups of teeth, is dependent on many factors including the area of the root surfaces, health of the periodontal attachment, density and structure of the alveolar bone, turnover rates of the periodontal tissues, facial type, muscular activity, occlusal forces, and the nature of the tooth movement planned for the intended correction.2 To maximize tooth-related anchorage, techniques such as differential torque,3 placement of roots against cortical bone,4 and distal tipping of the molars5,6 have been utilized. If the periodontal anchorage is not adequate, additional intraoral and/or extraoral anchorage may be needed by incorporating structures, such as the palate, the lingual mandibular alveolar bone, the occipital bone, and the head/neck. However, extraoral and some intraoral applications are not esthetic and usually require patient compliance. Furthermore,

if these interventions are not planned correctly, they may have undesirable effects, such as tipping of the occlusal plane, proclination of mandibular incisors, and extrusion of teeth. Similar to ankylosed teeth, implants and mini-screws are in direct contact with bone as they do not possess a normal periodontal ligament. Consequently, they do not move when orthodontic forces are applied7 and, therefore, can be used as a significant anchorage source that is independent of the patient’s compliance. Restorative implants can be used as anchors in selected cases; however, they require careful planning prior to orthodontic treatment. On the other hand, orthodontic implants, mini-plates, and mini-screws offer greater flexibility for clinicians. The aim of this chapter is to explore the use of restorative implants and temporary anchorage devices (TADs), which include orthodontic implants and mini-screws, and discuss their place in contemporary orthodontic mechanotherapy.

1. What is the history of implants in dentistry? The history of implants in the oral cavity goes back several millennia. There are reports of implanting seashells, precious stones, ivory, and bone as well as wealthy individuals purchasing teeth from less fortunate citizens to be used as transplants during the Middle Ages.8 More recent implantable materials include vitallium, zirconia, ceramics, stainless steel, pure titanium, and titanium alloys. In the mid-1960s, Brånemark reported on the body’s ability to accept and bond to titanium, a process still referred as osseointegration.9 Andre Schroeder was another pioneer in the modification of surface properties and design for increased predictability of the dental implants.10 These changes shortened the healing time from 6 months to several weeks, effectively allowing for the possibility of their use in orthodontics.11,12 Currently, the most predictable and acceptable implant material is commercial pure titanium with some type of subtractive surface treatment (Fig. 18-1).13

2. What is the history of implants in orthodontics? Although a few unsuccessful attempts can be traced back to the early 1900s, the first known attempt to achieve skeletal anchorage was made in 1945 by Gainsforth and Higley.14 They placed vitallium screws in the ramus of dog mandibles and then immediately applied elastics from the screw to the maxillary archwire to tip or retract the canines (Fig. 18-2). Tooth movement 235

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CHAPTER 18 • Skeletal Anchorage in Orthodontics

A,B

C

FIG 18-1 A, Scanning electron microscope (SEM) image showing the implant surface. B, SEM image showing the roughened surface implant. C, SEM image of macro and micro roughness of stereolithography (SLA) treated implant surface at higher magnification. This provides the architecture for the bone to be directly laid down on the implant surface.

FIG 18-2 Skull of a dog with orthodontic appliance using vitallium screw anchorage. Force is applied through the elastic connecting two hooks. The archwire is welded to the canine band and slides freely in the perforated buccal flange of the molar overlay. (From Gainsforth BL, Higley LB: A study of orthodontic anchorage possibilities in basal bone, Am J Orthod Oral Surg 31:406-416, 1945.)

was successfully accomplished in two of the animals, but an effective force could not be maintained longer than 1 month in any case. This was related to infection and probably the immediate loading of the screw. Linkow also attempted skeletal anchorage with his blade implants; however, long-term results were not presented.15 Later, skeletal anchorage systems followed two different pathways. One originated from dental implants, which had a sound scientific base of clinical, biochemical, and histological studies, while the other evolved from fixation screws used in oral and maxillofacial surgery.

Roberts and colleagues,16–18 Gray and colleagues,19 Shapiro and Kokich,20 and Turley and colleagues,21 in the 1980s, followed the success of the restorative titanium implants, and this resulted in a rise in their use in orthodontics. The first mention of a palatal osseous anchorage was by Triaca and colleagues22 in 1992. The Straumann and Brånemark companies later developed the only two available palatal implants in the United States. The other group evolved from the surgical screws and was very practical in their application. Although they first appeared in the United States, they quickly expanded into various Asian countries, probably due to the greater need for maximum anchorage. The initial clinical report on the use of a TAD appeared in 1983, when Creekmore and Eklund23 used a vitallium bone screw to treat a patient with a deep overbite. The screw was inserted into the anterior nasal spine and was then used to intrude the upper incisors by an elastic thread following a 10-day rest period. It was Kanomi’s24 work that initiated the concept of modern mini-screws that were specially designed for orthodontic use. Many clinicians and researchers prefer the name temporary anchorage devices, or TADs, for this second group.

3. What is the definition of a temporary anchorage device? A TAD is a device that is placed into bone in order to enhance orthodontic anchorage. TADs can either support the anchor teeth, which would be referred to as the indirect application, or they can act as the reactive unit by being directly attached to teeth that the clinician wants to move; this is called direct application. All are temporary and are subsequently removed after use. They can be located on the surface of the bone (transosteal), under the periosteum (subperiosteal), or inside the bone (endosteal) and can be fixed to the bone either mechanically (cortically stabilized, biointegration) or biologically

Skeletal Anchorage in Orthodontics • CHAPTER 18

(osseointegration). Restorative implants, on the other hand, are not considered TADs because a removal is not planned following orthodontic treatment. Nevertheless, incorporation of dental implants and TADs into orthodontic treatment minimizes or eliminates anchorage loss.

4. How does one classify skeletal anchorage? Currently available skeletal anchorage devices can be classified as either biointegrating or osseointegrating. TADs can be further subclassified based on the nature of mechanical retention to the bone, such as fixation wires,25 fixation screws,23 or fixation screws in combination with mini-plates26 and mini-screws.24 The second group would be the osseointegrating endosseous prosthetic implants20,27 (Fig. 18-3). Since orthodontic patients do not usually present with edentulous alveolar bony ridges for the insertion of implants, special implants for orthodontic purposes were developed for the retromolar18 and palatal areas.22 From a clinical standpoint, it is important to determine how the implants are to be utilized. Whether they will be used as TADs or serve as prosthetic abutments in the future, both require careful planning and vary in insertion sites, implant types, dimensions, and orthodontic anchorage, as well as more specific pre-insertion preparation. Furthermore, the fact that these devices may have to be placed in a growing patient has particular importance. Another device, the Onplant,28 which is placed subperiosteally, is a smooth titanium disc with a hydroxyapatite-coated surface that is treated for osseointegration. Unfortunately, due to the submerged nature, the monitoring of the healing process is not practical and their osseointegration questioned.29

5. What are the advantages of using implants or temporary anchorage devices in orthodontics? Implants and TADs are useful in orthodontic treatment when the anchorage needs are maximum. They may lessen the need for extra oral anchorage and decrease or eliminate unwanted movements including round tripping, by allowing clinicians to overcome various biomechanically challenging situations, such Biocompatible TADs Osseointegration

Dental implant

Palatal onplant

Mechanical retention

Fixation screws

Fixation wires

Palatal implant

Retromolar implant

Fixation screws w/ plates

Mini screw implants

FIG 18-3 Classification of skeletal anchorage. (From Cope JB: Temporary anchorage devices in orthodontics: A paradigm shift, Semin Orthod 11:3-9, 2005.)

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as vertical movements. Although long-term data are lacking, they can assist in difficult treatment objectives, including but not limited to nonsurgical treatment of openbites as well as asymmetries. Their compatibility and flexibility may help generate close to ideal force vectors, resulting in greater efficiency and shortened treatment times.

6. What are the disadvantages of using implants or temporary anchorage devices in orthodontics? The main disadvantage is that placement of implants requires surgery. The mini-screw-type TADs are less invasive and require minor surgical intervention, but orthodontic implants require extensive surgery for both placement and removal, which increases the cost of the treatment. Most TADs are small and can be placed into various areas in the oral cavity. However, complications may arise if critical anatomical structures are damaged during placement or during orthodontic tooth movement.

7. What are one’s considerations in regard to specific treatment mechanics? Orthodontic implants allow for effective use of the center of resistance when moving a particular tooth or groups of teeth. However, planning and sound execution of all force vectors are paramount. This is especially true for direct applications. In orthodontics, forces can be described as vectors and are linear, but the moments they generate are circular. Couples are force systems separated by a distance and have equal and opposite vectors. What makes the direct applications of implants and TADs challenging is the absence of conventional reciprocal moments that would normally be cancelling each other, allowing linear movements along an archwire or bodily movements through segmental mechanics. Basic biomechanical considerations, however, still apply; what is different is where the equal and opposite reactive forces (Newton’s Third Law) will occur.30 All reactive forces with implants or TADs dissipate in the skeleton. One example is the distalization of canines into the extraction spaces with sliding mechanics. When this is accomplished with direct skeletal anchorage, the compensating moments that normally cancel each other out are not present, which results in unsolved rotational moments on the canines. This leads to a narrowing of the buccal segments, possibly creating posterior crossbites. Palatal auxiliaries, such as transpalatal bars, should be considered in these situations.31 Additionally, various lever arms can control points of force application and achieve desired intrusive or extrusive effects during retraction.32,33 For example, when attempting to retract anterior teeth, the initial vertical and horizontal position of the anterior teeth needs to be considered. If the maxillary anterior teeth present with a deepbite, retraction and intrusion with a mini-screw placed higher in the buccal vestibule would be appropriate, as would attachment of the retraction force close to the bracket of the teeth to be retracted. This would provide not only a posterior force vector but also a vertical force vector. The creation of counterclockwise rotational forces around the center of rotation of the anterior segment would intrude the maxillary

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anterior segment as it is being retracted.34 Conversely, if the maxillary anterior teeth present with a shallow or openbite, retraction from a mini-screw placed closer to the gingival margin of the teeth would be appropriate as would the attachment of the retraction force to a hook extending from the wire. This places the retraction force higher into the vestibule, thus retracting in a more horizontal vector to help correct the openbite.33 With palatal implants, the teeth themselves can either be moved with the use of activation from the implant or locked down as anchors to move adjacent teeth with traditional mechanics. Both of these applications should take the couples created in the bracket-wire interface into account and be should be carefully planned. Cornelis and De Clerck31 and De Clerck and colleagues35,36 used mini-plates and presented the use of the frictional forces in correcting the overjet in the early stages of canine retraction, thus reducing overall treatment time. This approach can be accomplished by utilizing the disadvantage of the unresolved moments that are described earlier to one’s advantage.

8. Where can we place the implants or temporary anchorage devices? The introduction of small temporary orthodontic anchorage devices, such as mini-screws (<2 mm) in various lengths24,37 and titanium pins,38 or L-shaped mini-plates with the long arm exposed into the oral cavity26 and the zygomatic anchors,39 both fixed by bone screws, offers additional insertion sites, such as the interradicular septum, the supra-apical and infrazygomatic area, and the mandibular symphysis. These seem to be well accepted by the patients.40 Aside from the previously mentioned facial interradicular spaces and retromolar areas of both the mandible and the maxilla, the palate offers a relatively safe placement for many implant applications.41 However, incomplete interdigitation of the median palatal suture during childhood and early adolescence prevents placement of orthodontic implants into the mid-sagittal region due to possible developmental disturbances of the palatal suture. Therefore, the paramedian insertion site is a better alternative in young patients. Furthermore, the exact site chosen for palatal implants needs to be evaluated to avoid perforations of the inferior nasal turbinate.37 A cone beam computed tomography (CT) study42 indicated that the thickest bone with an average thickness of 4 to 8 mm was found in the anterior part of the palate, in both the median and the paramedian areas of the suture. The posterior region was also shown to be suitable with the selection of appropriate screw diameters and lengths. Bernhart and colleagues43 found the greatest mean of about 6 to 9 mm posterior to the incisal foramen in the midsagittal plane. To avoid the midpalatal suture, the suitable area for implant placement is located 6 to 9 mm posterior to the foramen incisivum and 3 to 6 mm paramedian. If the suitable bone volume for an insertion of implants is defined as 4 mm or more, they found that 95% of the patients in their study had enough bone vertically for accommodating palatal implants with a length of 4 mm. Analysis of panoramic radiographs and CT images suggested that adequate bone for mini-screw placement exists

primarily at the mesial of the permanent first molars in the maxilla and mesial and distal of permanent first molars in the mandible. Typically, adequate interradicular bone distances were found more than halfway down the root lengths, which are likely covered by unattached mucosa.44,45 The inability to place mini-screws in attached gingiva may necessitate design modification or oblique insertion direction to decrease softtissue irritation.44,45 The absence of keratinized mucosa around mini-screws has been shown to significantly increase the risk of infection resulting in failure. Poggio and colleagues46 have presented the safe zones for placement of TADs using cone beam CT images on patients with well-aligned roots. No matter what type of skeletal anchorage is used, preplaning the root and/ or crown angulations in advance and positioning the attachments to improve these safe zones for insertion free of roots is essential.

9. How can implants or temporary anchorage devices benefit orthodontics beyond traditional mechanotherapy? Implants may release some of the constraints that Newton’s Third Law holds on the orthodontist when working with tooth-borne anchorage. Implants also allow the orthodontist to treat patients who may have an inadequate number of teeth to act as anchors. At times these patients are those in considerable need of ortho dontic intervention, usually with a need to save existing teeth and prepare the mouth appropriately for restorative modalities.47 Implants give the practitioner the opportunity to treat patients who might not otherwise be capable or compliant with patient-dependent auxiliaries. Treatment of patients with compromised dentitions with multiple missing teeth can be accomplished with proper planning for implants and the possibility of the use of restorative implants following orthodontic treatment.

10. What kinds of imaging techniques are needed prior to implant or temporary anchorage device placement? For TADs, a panoramic radiograph, normally available from pretreatment diagnostic records, is usually sufficient for establishing the accuracy needed for the identification of locations in the interradicular spaces. Many auxiliaries have been utilized over the years with various degrees of success. These include acrylic or putty-based templates,25 adjustable surgical guides,48 the use of a surgical stents,49 or the surgical indeces.50,51 All of these have assisted the clinicians, but the general consensus is the ease and availability of the panoramic imaging along with the experience of the clinician are sufficient for most situations. In recent years the increasing popularity and availability of the cone beam CT helps increase the accuracy of the placement. Aside from TADs, this is especially helpful in palatal implants. The use of the lateral cephalometric images for determining the vertical height of the palatal bone is being replaced by the use of the cone beam. The overestimation problem with the lateral cephalometric images has left the cone


beam CT as the better, more accurate tool for measuring the vertical bone volume at this site. However, a preoperative diagnostic evaluation is recommended in order to avoid perforation of the inferior nasal turbinate.

11. What are the surgical considerations related to implants and temporary anchorage devices? Restorative implants require definitive knowledge of ridge anatomy, augmentation protocols, and sinus structures, as well as neurovascular considerations. The surgical procedure includes local anesthesia, preferably with sedation. Each implant system has its own predetermined drill sequence that should be followed, depending on the implant size placed. The placement of these implants can be done by experienced prosthodontists, periodontists, or oral surgeons. The surgical procedure for placing a palatal implant is similar to that of placing a dental implant, although less demanding. Without root structures, sinus cavities, nerve bundles, and large blood vessels to avoid, the midpalatal suture is almost ideal for placement of implants. The major consideration when placing the palatal implant is to avoid use in the midpalate of young children. If treatment with a palatal implant is necessary, a paramedian placement should suffice. In unusual instances, two palatal implants can be considered. Local anesthesia is necessary for the palate. The drill sequence includes a tissue punch, a round bur, and the single site preparation drill. A controlled-torque surgical handpiece is recommended to prepare the site. The implant is placed and then left to osseointegrate for 6 to 12 weeks. Following treatment, removal is accomplished with an implant trephine. The surgical process of placing most TADs is less invasive than placing implants. Many placement procedures can be completed with a strong topical anesthetic. A common compound anesthetic cream is composed of 20% lidocaine, 4% tetracaine, and 2% phenylephrine. Local anesthesia is needed when the mucosa is thick or highly keratinized. Orthodontists should at the very least be equipped to provide local anesthetic when it is warranted. It is important to note that unattached soft tissue poses a significantly higher risk of failure and infection for mini-implants. Each individual TAD system has its own drill set. Various systems call for a tissue puncture if the location is planned on the unattached mucosa. Most TAD systems are drill-free. However, when dealing with a highly dense bone, a pilot drill that usually is 0.2 mm smaller than the diameter of the TAD can be utilized. Removal, without any topical or local anesthesia, is typically accomplished by reversing the driver. TADs do not integrate as completely as dental implants, making removal less of a problem. If the TAD does integrate, the risk of fracture is present, especially with smaller diameter implants. The minimum recommended diameter for TADs is the commonly available 1.6 mm. Breakage with this size is rare, but if breakage happens, a trephine is necessary to fully remove the TAD. Surgical procedures for orthodontic plates almost exclusively require a soft tissue flap. Local anesthesia and knowledge

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of suturing protocols are required. Plates are attached with the desired number of small screws, depending on the shape, size, design, and location. Most of these screws do not need pilot drills for placement. Removal requires a flap to be raised to gain access and reversing the torque on the screw heads, holding the surgical plate in place. The surgeon sutures the flap for healing after removal. There is the chance that some bone could grow over parts of the plates, but removal is usually not considered difficult.

12. What are the clinical procedures and loading times for mini-screw temporary anchorage devices and palatal implants? The TADs are ideally inserted into areas that are not blocked by the roots. There are situations, although rare, where isolated tooth movements can be done to create adequate space to facilitate their insertion between the roots. As described earlier, these can be achieved by proper bracket positioning. The mucosa can be cleaned with chlorhexidine. Topical anesthesia is usually adequate to anesthetize the soft tissue, because a profound anesthesia of the bone or the periodontal ligament is not recommended. A periodontal probe to measure the mucosal thickness can help determine the appropriate length of the TADs at the intended placement site. The selected appropriate length should allow the thickest diameter of the conical TAD to reside in the cortical bone. When a self-drilling TAD is being placed, the insertion is done directly through the mucosa. With the insertion of a self-tapping TAD, a purchase point and a perforation of the cortical bone are accomplished with a lowspeed contra-angle handpiece under saline solution irrigation followed by the TAD installation. The burs can be kept in the refrigerator for additional heat control, because the irrigation will not reach into the bone surface. The TAD is then inserted manually with its driver or a hand-driver with a torque gauge. Following insertion, the head of the TAD remains outside of the mucosa, with the base of the head or the collar resting against the mucosa creating a gentle seal. If the intended installation site for the mini-screw is in the unattached mucosa, a tissue punch that closely proximates the TAD’s diameter is needed to prevent soft-tissue bunching around the drill or the TAD, which results in postinsertion pain and inflammation later. For palatal implant applications, the palatal mucosa is perforated to the cortical bone using a mucosal punch and removed with an elevator or a curette. After smoothing the exposed bone surface to prevent the profile drill from slipping, the center of the implant site is marked with a round bur. The implant bed is then prepared to the required width and depth using a series of pilot and twist drills. The drilling axis perpendicular to the bone surface is defined based on the pre-surgical analysis from the radiographic images. While the insertion site is prepared, intermediate drilling and cooling of the channel with pre-cooled physiological saline, or Ringer’s solution, should be carried along. The implant is then hand-installed as far into the site as possible and followed by the use of a ratchet to tighten the implant into its final position.


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The implant is covered with the healing cap to prevent the inner screw well from clogging or covered by hyperplastic, mucosal tissue. The palatal Orthosystem implant is allowed to heal in situ for 12 weeks during which it should not be loaded.

13. When can the implants or temporary anchorage devices be loaded? Primary stability is key for any implant or TAD procedure. Insufficient stability affects osseointegration and causes inappropriate healing with possible premature loss of the implant.52 Following the placement of an endosseous implant, primary mechanical stability is gradually replaced by biological, secondary stability (Fig. 18-4). The transition from primary mechanical stability, which is provided by the implant d esign, to biological stability provided by newly formed bone as osseointegration, occurs during early wound healing.53 There is a period of time during healing in which osteoclastic activity has decreased the initial mechanical stability of the i mplant with new bone formation not yet occurring to the level required to maintain implant stability. The placement of an implant in orthodontic treatment as an absolute anchorage device facilitates mechanotherapy.54,55 The inactive waiting time of at least 3 months following insertion should not be seen as a delay in treatment because the advantages outweigh this delay. Even though there are several studies that have reported a successful outcome of early or immediate loaded conventional dental implants placed in the alveolar ridge,55,56 there is a lack of reliable data on adequate healing times for the palatal region, with a commonly accepted healing time of 12 weeks.57 Whether direct or indirect, the general consensus on the timing for loading of TADs is that immediate loading is successful using a variety of forces ranging from 150 to 500 g.58–60 Although some still wait for healing of the peri-TAD tissues, increased failure rates due to immediate loading have not been recently reported.

Primary stability (old bone)

Stability (%)

100

Secondary stability (new bone)

75 50 25 0

1

2

3

4

5

6

7

8

Time (wks)

FIG 18-4 Transition from primary stability at the time of implant placement to secondary stability established by deposition of new bone (osseointegration). (From Raghavendra S, Wood MC, Taylor TD: Early wound healing around endosseous implants: a review of the literature, Int J Oral Maxillofac Implants 20(3):425-431, 2005.)

14. How can the implants or temporary anchorage devices be loaded? The mechanics used in relation to the application of TADs depend on whether the mini-screw is being used as direct or indirect anchorage. For direct anchorage, the line of action of the force has to pass through the mini-screw. If the line of action of the force does not pass through the mini-screw, as would be the case with a power arm, a force away from the mini-screw long axis would be generated. Since these mini-screws are not osseointegrated, a shearing force of this sort would likely lead to screw loosening and failure. For indirect anchorage, the mini-screw can be ligated to a tooth or a group of teeth, via a larger rectangular stainless steel wire. The tooth or group of teeth stabilized with the mini-screw can then be used as absolute anchorage.25 Palatal implants can also be loaded either indirectly or directly, depending on the clinical situation and the orthodontic treatment plan. TADs with indirect loading41 mean that the teeth act as an anchorage unit or are indirectly stabilized by the palatal implant to avoid anchorage loss. This can be achieved with a transpalatal arch (TPA; Fig. 18-5, A). In direct anchorage, the force systems act directly between the teeth to be moved and the implant61 (see Fig. 18-5, B).

15. What are the advantages and disadvantages of skeletal anchorage in orthodontics? Restorative implants have been proven to be effective in pros thodontics (Fig. 18-6). The advantage in orthodontics is excellent modality to enhance anchorage when other anchorage modalities are either not available or less effective. Restorative implants bonded to the bone through osseointegration (Fig. 18-7) serve as the ultimate anchor to resist forces when moving teeth.62 The obvious advantage is that reciprocal movements are minimal with force distribution concentrated on the teeth requiring movement. The main disadvantages of restorative implants are the cost and the surgical procedure. Restorative implants are relatively expensive and even more expensive to place. Surgical placement also necessitates a sound edentulous ridge that can hold a relatively large-size titanium screw traditionally at least 4 mm in diameter. As a general rule, 1 mm of bone should be present on the buccal, lingual, mesial, and distal of the implant. Usually these implants are placed with the intention of being restored after orthodontic treatment. Care should be given to ensure that the implant will be in the correct position for proper crown shape and size for the prosthodontist or the restorative dentist (Fig. 18-8); this requires detailed planning and teamwork. They are not commonly used and should be limited to selected cases. When an edentulous site is not available, viable options are the retromolar pad or the ascending ramus (Fig. 18-9). These sites are often difficult to access surgically and can leave the implant fixture in a less than ideal position and/or angulation. The clinician is also somewhat limited in the ability to use this anchor for maxillary movements.

B

A

FIG 18-5 A, Indirect anchorage. B, Direct anchorage. (A, From Wehrbein H, Merz BR, Diedrich P, et al: The use of palatal implants for orthodontic anchorage. Design and clinical application of the orthosystem, Clin Oral Implants Res 7:410-416, 1996. B, From Büchter A, Wiechmann D, Gaertner C, et al: Load-related bone modeling at the interface of ortho dontic micro-implants, Clin Oral Implants Res 17:714-722, 2006.)

FIG 18-6 Conventional implant.

FIG 18-7 Histological section of osseointegrated ortho dontic implant surface. Close and complete adaptation of the bone to the implant surface allows for a stable anchorage point to resist forces required to move other teeth.

A

B

FIG 18-8 A, Dental implants placed prior to the completion of orthodontic treatment are not recommended. B, They may interfere with the final alignment of the dentition, the restorability of the implant, and possibly the survival of the tooth.

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A

C

B

FIG 18-9 A and B, Dental implants placed in the retromolar area can assist in retraction, intrusion, and leveling the arches without losing any anchorage. In this case, the left second molar needed to be distalized, which was later converted to an anchor in an indirect fashion to help facilitate space closure and shifting the midline in the mandible. C, Radiographic view of the implant.

FIG 18-10 Palatal implant.

Unlike dental implants, the palatal implants are not restricted by the availability of edentulous sites or the ascending ramus (Fig. 18-10).41 The palate is a fine location with sound bone and the minimal limiting anatomy. The force vectors can be easily adjusted during treatment, which makes them suitable in correcting openbites and Class II, Class III, and debilitated dentitions. A single palatal implant can be used for

intrusion, retraction, or midline rotations where numerous mini-implants may be required (Fig. 18-11).63 Palatal implants are excellent for controlling movement of maxillary teeth. However, their effects are minimal on mandibular teeth. Although the surgical placement of a palatal implant is relatively less technique sensitive than that of a restorative implant, the need for local infiltration anesthetic is inevitable. These implants also require careful planning as well as the use of guides, preferably with three-dimensional (3D) imaging modalities and an impression of the implant followed by a lab procedure (Fig. 18-12). TADs are widely used due to their simplicity. It is this fact alone that has propelled them to the forefront of the skeletal anchorage in orthodontics. They are versatile and small, require little hardware, and are easily removed. TADs can help to retract, protrude, intrude, and extrude single teeth or entire segments of teeth. They can be used in place of restorative and palatal implants64 (Fig. 18-13). However, there can be problems. They may fail to provide anchorage for extended periods of time, their proximity to root structures can result in failure,65 and they are not capable of resisting forces in different directions once they are placed. In addition, more than one TAD may be needed for more complex movements, such as intrusion or bilateral retraction. Unfortunately, often the failure of a TAD in a strategic site may stall treatment until the bone has healed enough to place another66 or may result in major changes in treatment plan.


A

B

C

D

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FIG 18-11 A, Palatal implant to stabilize the maxillary arch and serve as anchor for movement of anterior teeth. B, Palatal implant to serving as anchor for leveling, intrusion, and retraction of maxillary anterior teeth. C, Palatal implant first utilized to distalize the second molar and later to act as anchor for retraction of maxillary arch. D, Palatal implant utilized to intrude maxillary premolars and molars in an openbite patient.

Canalis incisivus

Crista nasalis

FIG 18-12 Most palatal implants can be placed with the entry into the cortical bone at the anteroposterior level of the maxillary first and second premolars and perpendicular to the palatal surface. (From Männchen R, Schätzle M: Success rates of palatal orthodontic implants. a retrospective longitudinal study, Clin Oral Implants Res 19:665-669, 2008.)

FIG 18-13 Mini-screw temporary anchorage device (TAD).

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Surgical plates have been used for orthodontic treatment to avoid anatomical and strategic contraindications of the TADs. Their advantage is the ability to provide anchorage while avoiding the roots, unattached gingival tissues, and sinus cavities.31,35,39,40 Surgical plates can be placed in the buccal mucosa of the maxilla and the mandible. Many systems use the maxillary zygomatic buttress as the attachment site.26 Some of the disadvantages with the surgical plates are related to the surgical procedure. Obviously, with this type of skeletal anchorage, a full-thickness flap and sutures would be required after surgical plate placement. Palatal applications or lingual placement in the mandible are not viable options. Force vectors would need to be carefully considered because most of the surgical plate attachment heads are deeper in the buccal vestibules. Removal also requires a surgical flap coupled with sutures.

16. Do implants or temporary anchorage devices remain stable under orthodontic loading? Osseointegration was first defined on a histologic basis only as direct contact between an implant surface and bone without interposed soft tissue at light microscopic level.67 However, complete (100%) bone connection to the implant may not occur. Instead of the histologic definition of osseointegration, a stability-based definition has been proposed. Osseointegration was then defined as a process whereby a clinically asymptomatic, rigid fixation of alloplastic material is achieved and maintained in bone during functional loading.68 Implants, whether used in the alveolar ridge or in the palate, must stay positionally stable under orthodontic loading in order to serve as absolute anchorage, because their stability relies on the osseointegration. Histologic examination of the bone specimens around explanted human palatal orthodontic implants has revealed that osseointegration is maintained during long-term orthodontic loading. The percentage of implant-to-bone contact in the removed implants has reported an average of 75% with a range from 34% to 93%,69 showing comparable results as osseointegrated prosthetic endosseous implants that yield at least 60% of bone to implant contact.70 Although the vertical interrupted nature of occlusal loading and the continuous horizontal orthodontic forces are quite different, implants should withstand the stress and strain applied during orthodontic treatment. The applied forces should not have a negative impact on the peri-implant bone and should, therefore, not impair the long-term prognosis as a prosthetic abutment. In a study by Melsen and Lang,71 specially designed oral implants were inserted in monkeys and, after healing, subjected to well-defined continuous loading. This study supports the theory that apposition of bone around an oral implant is the biological response to a mechanical stress below a certain threshold, whereas loss of marginal bone or complete loss of osseointegration may be the result of mechanical stress exceeding a certain force magnitude. Furthermore, early loading for endosseous implants is still a possibility.72 Similar to implants, TADs also should remain stable under orthodontic loading. The concept of primary stability has

greater importance, because TADs do not have the potential to become stabler over time due to their polished surfaces. One investigation studied the stability of TADs.73 In 7 out of 16 examined patients, although their dimensions were uncommonly long, the TADs tipped, were extruded, and did not remain stable under orthodontic loading. In an animal study, mini-screws with as little as 5% bone contact at the bone-implant interface successfully resisted orthodontic force.74 Despite the fact that miniscrew TADs increased anchorage, they did not remain absolutely stationary throughout orthodontic loading. Placement torques should be used with caution because they may result in excessive stress on the insertion hole, which may lead to loosening and failure.75 Integration of the TAD threads with the cortical bone is the main anchor of the TAD bone interface.

17. What is the success rate of palatal implants? Even though palatal implants have been used in orthodontic treatment for more than 10 years,41 only one prospective study of nine patients exists to demonstrate successful osseointegration and stability in all patients.41 More recently a subjective report of 40 Orthosystem palatal implants was published76 and indicated a 92% success rate of osseointegration. A recent clinical study77 reported that only 3 out of the 70 successfully osseointegrated palatal implants that were loaded actively and/or passively for approximately 19 months failed, mainly due to a lack of primary stability, which suggests a success rate of 95.7%. In the literature, the general consensus on the success rate of TADs is approximately 90%.63,74 Aside from the previously mentioned biologic reasons, most investigations agree that the success rate is highly correlated with the experience of the clinician placing the TADs.

18. What are some complications related to implants or temporary anchorage devices? When considering the palatal applications, one should consider the vertical and transverse growth changes in the maxilla that take place during adolescence. With normal growth, there is maxillary expansion as a result of two processes, with appositional remodeling at the alveolar processes and growth in the midpalatal suture. It has been estimated that growth in the maxillary width is an average of 3 mm between ages 10 and 18 years.78 The restricting effect of the implants on the transverse growth of the maxilla, when placed in the median palatal suture, has been presented in an animal model.79 Deficient transverse maxillary growth may result in maxillary arch length discrepancies that may lead to various orthodontic problems, such as crowding or impactions. Furthermore, placement of implants in the midpalatal suture in growing patients should not be recommended because of the questionable quality of bone in that area. In order to avoid these problems, paramedian placement should be considered. Another consideration is the vertical growth of the maxilla and possible effects of the palatal implants. The most important


vertical growth changes occur through displacement and cortical drift. By implant placement in the palate, the sutural lowering of the maxillary complex as well as the apposition at the orbital floor and at the infrazygomatic crest should not be affected; however, the resorptive lowering of the nasal floor and the increase of the alveolar bone height of the maxilla can be influenced. Björk and Skieller78 measured the mean degree of growth from the age of 4 years to adulthood. During this time the nasal floor drifted 4.6 mm inferiorly, and the height of the maxillary alveolar bone increased 14.6 mm. Assuming that about one-third of these growth changes take place from the age of 12 years to adulthood, that implies a residual vertical growth of about 1.5 mm in the palate and about 5 mm in the alveolar bone, both by drift. As discussed before, osseointegrated implants are in direct contact with bone, do not possess a periodontal ligament, and behave like ankylosed teeth. Therefore, a palatal implant would remain an average 1.5 mm behind its surrounding bone whereas an implant placed in the alveolar bone would produce an infraocclusion of 5 mm during the same period. Consequently, a palatal implant directly or indirectly attached to teeth may lead to infraeruption of a single tooth, several teeth, or the whole maxillary dentition. Finally, one should keep in mind that the palatal implants, as TADs, remain 1 to 2 years in situ. Thus, potential vertical growth impairment is likely to be limited to values less than 1 mm. Complications with TADs have been classified by Kravitz and Kusnoto.80 According to their classification, complications can occur during four different times: (1) during insertion, which includes periodontal damage to the root surface, damage to important anatomy, slippage, and breakage; (2) during loading, which includes loosening and migration of the TADs; (3) soft tissue complications during treatment, which would include ulcers, soft tissue coverage, inflammation, and periimplantitis; and last (4), during removal, which would include fracture of the TADs possibly due to partial osseointegration. Of these complications, the one that is most likely to occur, and hence has been the greatest topic of interest, is the damage to the root surface and periodontal ligament. Kadioglu and colleagues81 intentionally contacted TADs with two maxillary first premolars in ten orthodontic patients who were scheduled to have these teeth extracted as a part of their orthodontic treatment. Half the experimental teeth had contact with the screws for 4 weeks to create mild resorption, and the other half had contact with the screws for 8 weeks for severe resorption. In five patients, the screws were removed, and in the other five the tipping springs were removed to allow the root to relapse. Finally, the roots were allowed to recover for 4 or 8 weeks before extraction. The authors noted no apparent denuded dentin surfaces after either of the healing periods under the scanning electron microscope. Repair was taking place, even with the shorter waiting period (Fig. 18-14). A similar study was later presented, this time by using histologic sections and reported the same results, with most healing taking place within 4 to 8 weeks.82

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19. How does one remove implants or temporary anchorage devices when the orthodontic treatment is complete? Both palatal implants and TADs are removed after completion of the orthodontic treatment. Implants require a systemcompatible trephine that separates the bone from the device. Then the implant may be explanted together with the surrounding bone by rotational movements using an extraction forceps. Sometimes, turning the ratchet counterclockwise for seating the implant may be used to break the implant-bone contact. Clinicians should check for possible oral-nasal communication following the removal and treat it if necessary. Full recovery at the original anchorage site may be observed 3 to 4 weeks after removal. The removal procedure for TADs, on the other hand, is usually uneventful and accomplished with no numbing agent. The custom-made screwdriver that is utilized for placement of the TAD is used to unscrew the mini-screw. In some cases, the TADs may present partial osseointegration, which may complicate the removal. If it happens, a trephine can be utilized similar to that of the implants. No soft tissue closure is necessary.

20. What are some of the legal implications when using skeletal anchorage in an orthodontic practice? An overlooked item in relation to the application of implants in orthodontics is the legal implication. In a litigious society, one cannot dismiss or ignore this aspect. When complications arise, there will be times when the qualifications of practitioners and their ability to handle complications will be reviewed and questioned. Even orthodontists that only use TADs are not immune from inclusion in legal entanglements. Orthodontists should be certain that they have insurance protection for these specific procedures by either their malpractice carriers or through the coverage offered by the institutions where they are performing such procedures. Basic knowledge of many of the surgical aspects of this area of dentistry should be reviewed, including anesthesia, anatomical considerations, and proper preoperative and postoperative precautions. Informed consents that are specific to skeletal anchorage are needed and can be obtained from the clinician’s national organization. In the United States, the American Association of Orthodontists (www.aaoinfo.org) provides not only patient consent forms but also application-specific evidence-based publications that each clinician should be familiar with prior to utilization of these auxiliaries.

21. Will skeletal anchorage in orthodontic treatment become a standard of care? Implants and TADs are considered to be ancillary appliances. It is not likely that they will become a standard of care for cases with a need for maximum anchorage. This is similar to other auxiliaries like palatal expanders and headgear. Additionally, one should use caution when labeling any approach in ortho-


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A

B

C

D

E

F

FIG 18-14 A, Intraoral photograph of the experimental design. B, Periapical radiograph of the contact area after 8 weeks. C, Extracted tooth and demonstration of the contact. D, Scanning electron microscope (SEM) image following screw removal and 8 weeks of repair. Apparent fiber reorganization starting from the bottom of the resorption lacunae. E, SEM image at a higher magnification. Notice the fiber reorganization taking place. F, SEM evaluation. New fibers are present in the resorption lacunae.

dontics as a “standard of care.” There are many options and techniques available to orthodontists for various types of treatments specific to each patient’s needs. This includes the choice of anchorage modality. There are well over 3000 articles published relating to skeletal anchorage in orthodontics. However, none of those is a randomized clinical trial. A recent systematic review clearly shows that a skeletal anchorage system is by no means the most effective anchor system in orthodontics.83 This is due to the lack of controlled trials. Skeletal anchorage will become much more common in orthodontic practices due to their advantages. Implants and TADs hold great promise for the future of new and young orthodontic generations and will likely change the scope of our understanding and application of orthodontic mechanotherapy in ways we cannot foresee even today.

22. What are some of the future developments that we shall see with regard to skeletal anchorage in orthodontics? Implants will continue to develop for orthodontic use, but design changes will most likely be limited to small specific areas, especially with TADs. Dental implants will likely not change in response to orthodontic usage. Although the Onplant is rarely used today, the palatal implant’s shape will remain fairly consistent over time. A larger palatal implant is necessary for attachments. This size difference also can give rise to increased surface areas and thus greater strength. As for TADs, thread pitch, intraoral head configuration, and surface treatments are dominating most of the advancements.84


FIG 18-15 Mini-screw temporary anchorage device (TAD), future concept design. (Courtesy of Dr. Peter Buschang.)

Survival rates of these implants may be greatly enhanced with roughened and/or coated bioactive surfaces. Some feel a greater amount of osseointegration is a disadvantage for removal, but this may be more of a concern only with the small size TADs because of the possibility of fracture. One should also expect to see smaller lengths and larger diameters since the main anchorage is established at the cortical bone level85,86 (Fig. 18-15). The composition of the titanium alloy for the TADs may change, but implant history has continually shown that commercially pure titanium is the most biocompatible and successful material to date.87

23. What is the future of skeletal anchorage in orthodontics? The use of skeletal anchorage will most likely increase in the years to come. Almost all orthodontic graduate/residency programs have adopted skeletal anchorage into their didactic, clinical, and research curricula. This is an indication that the number of clinicians with greater comfort and experience will become higher in the profession with time. This in turn will result in higher success rates and better patient acceptance. Implants are not the panacea for all orthodontic challenges, but they do offer the clinician the ability to treat more complicated, uncooperative, and anchorage-challenged patients with greater ease. Nevertheless, like every aspect of orthodontic treatment, careful planning and sound application that rely on the best available evidence should be accomplished. REFERENCES 1. Angle EH: Treatment of malocclusion of teeth, ed 7, Philadelphia, 1907, SS White Dental Manufacturing. 2. Diedrich P: Different orthodontic anchorage systems. A critical examination, Fortschr Kieferorthop 54:156–171, 1993. 3. Burstone CJ: The segmented arch approach to space closure, Am J Orthod 82:361–378, 1982.

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4. Ricketts RM: Bioprogressive therapy as an answer to orthodontic needs. Part II, Am J Orthod 70:359–397, 1976. 5. Begg PR, Kesling PC: The differential force method of orthodontic treatment, Am J Orthod 71:1–39, 1977. 6. Tweed CH: The applications of the principles of the edgewise arch in the treatment of malocclusions, Angle Orthod 11:12–67, 1941. 7. Melsen B, Lang NP: Biological reactions of alveolar bone to orthodontic loading of oral implants, Clin Oral Implants Res 12:144–152, 2001. 8. Ring ME: A thousand years of dental implants: a definitive history—part 1, Compend Contin Educ Dent (10):1995 1060, 1062, 1064 passim. 9. Brånemark PI, Adell R, Breine U, et al: Intra-osseous anchorage of dental prostheses. I Experimental studies, Scand J Plast Reconstr Surg 3(2):81–100, 1969. 10. Schroeder A, Pohler O, Sutter F: Tissue reaction to an implant of a titanium hollow cylinder with a titanium surface spray layer, SSO Schweiz Monatsschr Zahnheilkd 86(7):713–727, 1976. 11. Thomas KA, Cook SD: An evaluation of variables influencing implant fixation by direct bone apposition, J Biomed Mater Res 19(8):875–901, 1985. 12. Brunski JB: Biomechanical factors affecting the bone-dental implant interface, Clin Mater 10(3):153–201, 1992. 13. Cochran DL, Schenk RK, Lussi A, et al: Bone response to unloaded and loaded titanium implants with a sandblasted and acid-etched surface: a histometric study in the canine mandible, J Biomed Mater Res 40(1):1–11, 1998. 14. Gainsforth BL, Higley LB: A study of orthodontic anchorage possibilities in basal bone, Am J Orthod Oral Surg 31:406–416, 1945. 15. Linkow LI: The endosseous blade implant and its use in orthodontics, Int J Orthod 7:149–154, 1969. 16. Roberts WE, Smith RK, Zilberman Y, et al: Osseous adaptation to continuous loading of rigid endosseous implants, Am J Orthod 86(2):95–111, 1984. 17. Roberts WE, Helm FR, Marshall KJ, Gongloff RK: Rigid endosseous implants for orthodontic and orthopedic anchorage, Angle Orthod 59(4):247–256, 1989. 18. Roberts WE, Marshall KJ, Mozsary PG: Rigid endosseous implant utilized as anchorage to protract molars and close an atrophic extraction site, Angle Orthod 60:135–152, 1990. 19. Gray JB, Steen ME, King GJ, et al: Studies on the efficacy of implants as orthodontic anchorage, Am J Orthod 83(4):311–317, 1983. 20. Shapiro PA, Kokich VG: Uses of implants in orthodontics, Dent Clin North Am 32(3):539–550, 1988. 21. Turley PK, Kean C, Schur J, et al: Orthodontic force application to titanium endosseous implants, Angle Orthod 58(2):151–162, 1988. 22. Triaca A, Antonini M, Wintermantel E: Ein neues TitanFlachschrauben-Implantat zur orthodontischen Verankerung am anterioren Gaumen, Inf Orthod Kieferorthop 24:251–257, 1992. 23. Creekmore TD, Eklund MK: The possibility of skeletal anchorage, J Clin Orthod 17:266–269, 1993. 24. Kanomi R: Mini-implant for orthodontic anchorage, J Clin Orthod 31:763–767, 1997. 25. Melsen B, Petersen JK, Costa A: Zygoma ligatures: an alternative form of maxillary anchorage, J Clin Orthod 32:154–158, 1998. 26. Umemori M, Sugawara J, Mitani H, et al: Skeletal anchorage system for open-bite correction, Am J Orthod Dentofacial Orthop 115:166–174, 1999. 27. Ödman J, Lekholm U, Jemt T, et al: Osseointegrated titanium implants-a new approach in orthodontic treatment, Eur J Orthod 10:98–105, 1988. 28. Block MS, Hoffman DR: A new device for absolute anchorage for orthodontics, Am J Orthod Dentofacial Orthop 3:251–258, 1995. 29. Celenza F, Hochman MN: Absolute anchorage in orthodontics: direct and indirect implant-assisted modalities, J Clin Orthod 34:397–402, 2000.

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30. Keim RG: The biomechanics of TADs, J Clin Orthod 42:261–262, 2008. 31. Cornelis MA, De Clerck HJ: Biomechanics of skeletal anchorage Part 1: Class II extraction treatment, J Clin Orthod 40:261–269, 2006. 32. Park HS, Bae SM, Kyung HM, et al: Simultaneous incisor retraction and distal molar movement with microimplant anchorage, World J Orthod 5:164–171, 2004. 33. Park HS, Kwon TG, Kwon OW: Treatment of open bite with microscrew implant anchorage, Am J Orthod Dentofacial Orthop 126:627–636, 2004. 34. Kim TW, Kim H, Lee SJ: Correction of deep overbite and gummy smile by using a mini-implant with a segmented wire in a growing Class II Division 2 patient, Am J Orthod Dentofacial Orthop 130:676–685, 2006. 35. De Clerck HJ, Cornelis MA: Biomechanics of skeletal anchorage Part 2: Class II nonextraction treatment, J Clin Orthod 40: 290–298, 2006. 36. De Clerck HJ, Timmerman HM, Cornelis MA: Biomechanics of skeletal anchorage Part 3: Intrusion, J Clin Orthod 42:270–278, 2008. 37. Costa A, Raffaini M, Melsen B: Miniscrews as orthodontic anchorage: a preliminary report, Int J Adult Orthodon Orthognath Surg 13:201–209, 1998. 38. Bousquet F, Bousquet P, Mauran G, et al: Use of an impacted post for anchorage, J Clin Orthod 30:261–265, 1996. 39. De Clerck H, Geerinckx V, Siciliano S: The Zygoma Anchorage System, J Clin Orthod 36:455–459, 2002. 40. Cornelis MA, Scheffler NR, Nyssen-Behets C, et al: Patients’ and orthodontists’ perceptions of miniplates used for temporary skeletal anchorage: a prospective study, Am J Orthod Dentofacial Orthop 133(1):18–24, 2008. 41. Wehrbein H, Merz BR, Diedrich P, et al: The use of palatal implants for orthodontic anchorage. Design and clinical application of the orthosystem, Clin Oral Implants Res 7: 410–416, 1996. 42. Graco A, Lombardo L, Cozzani M, et al: Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement, Am J Orthod Dentofacial Orthop 134:361–369, 2008. 43. Bernhart T, Vollgruber A, Gahleitner A, et al: Alternative to the median region of the palate for placement of an orthodontic implant, Clin Oral Implants Res 11:595–601, 2000. 44. Schnelle MA, Beck FM, Jaynes RM, et al: A radiographic evaluation of the availability of bone for placement of miniscrews, Angle Orthod 74:832–837, 2004. 45. Deguchi T, Nasu M, Murakami K, et al: Quantitative evaluation of cortical bone thickness with computed tomographic scanning for orthodontic implants, Am J Orthod Dentofacial Orthop 129:e712–e721, 2006. 46. Poggio PM, Incorvati C, Velo S, et al: Safe zones: a guide for miniscrew positioning in the maxillary and mandibular arch, Angle Orthod 76(2):191–197, 2006. 47. Ödman J, Lekholm U, Jemt T, et al: Osseointegrated implants as orthodontic anchorage in the treatment of partially edentulous adult patients, Eur J Orthod 16:187–201, 1994. 48. Suzuki EY, Buranastidporn B: An adjustable surgical guide for miniscrew placement, J Clin Orthod 39:588–590, 2005. 49. Cousley RR, Parberry DJ: Surgical stents for accurate miniscrew insertion, J Clin Orthod 40:412–417, 2006. 50. Bae SM, Park HS, Kyung HM, et al: Clinical application of micro-implant anchorage, J Clin Orthod 36:298–302, 2002. 51. Maino BG, Bednar J, Pagin P, et al: The spider screw for skeletal anchorage, J Clin Orthod 37:90–97, 2003. 52. Lioubavina-Hack N, Lang NP, Karring T: Significance of primary stability for osseointegration of dental implants, Clin Oral Implants Res 17:244–250, 2006. 53. Berglundh T, Abrahamsson I, Lang NP, et al: De novo alveolar bone formation adjacent to endosseous implants, Clin Oral Implants Res 14:251–262, 2003.

54. Trisi P, Rebaudi A: Progressive bone adaptation of titanium implants during and after orthodontic load in humans, Int J Periodontics Restorative Dent 22:31–43, 2003. 55. Bischof M, Nedir R, Szmukler-Moncler S, et al: Implant stability measurement of delayed and immediately loaded implants during healing, Clin Oral Implants Res 15:529–539, 2004. 56. Gallucci GO, Bernard JP, Bertosa M, et al: Immediate loading with fixed screw retained provisional restorations in edentulous jaws: the pickup technique, Int J Oral Maxillofac Implants 19:524–533, 2004. 57. Crismani AG, Bernhart T, Schwarz K, et al: Ninety percent success in palatal implants loaded 1 week after placement: a clinical evaluation by resonance frequency analysis, Clin Oral Implants Res 17:445–450, 2006. 58. Ohashi E, Pecho OE, Moron M, et al: Implant vs. screw loading protocols in orthodontics, Angle Orthod 76:721–727, 2006. 59. Büchter A, Wiechmann D, Koerdt S, et al: Load-related implant reaction of mini-implants used for orthodontic anchorage, Clin Oral Implants Res 16:473–479, 2005. 60. Büchter A, Wiechmann D, Gaertner C, et al: Load-related bone modeling at the interface of orthodontic micro-implants, Clin Oral Implants Res 17:714–722, 2006. 61. Melsen B, Verna C: Miniscrew implants: the Aarhus Anchorage System, Semin Orthod 11:24–31, 2005. 62. Brunski JB, Moccia Jr. AF, Pollack SR, et al: The influence of functional use of endosseous dental implants on the tissueimplant interface. I Histological aspects, J Dent Res 58: 1953–1969, 1979. 63. Wehrbein H, Merz BR: Aspects of the use of endosseous palatal implants in orthodontic therapy, J Esthet Dent 10(6):315–324, 1998. 64. Cornelis MA, Scheffler NR, Clerck HJ, et al: Systematic review of the experimental use of temporary skeletal anchorage devices in orthodontics, Am J Orthod Dentofacial Orthop 131:52–58, 2007. 65. Kuroda S, Yamada K, Deguchi T, et al: Root proximity is a major factor for screw failure in orthodontic anchorage, Am J Orthod Dentofacial Orthop 131:68–73, 2007. 66. Papadopoulos MA, Tarawneh F: The use of miniscrew implants for temporary skeletal anchorage in orthodontics: a comprehensive review, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 103(5):e6–e15, 2007. 67. Albrektsson T, Brånemark PI, Hansson HA, et al: Osseointegrated titanium implants. Requirements for ensuring a long-lasting, direct bone-to-implant anchorage in man, Acta Orthop Scand 52:155–170, 1991. 68. Zarb GA, Albrektsson T: Osseointegration: a requiem for periodontal ligament? Int J Period Restor Dent 11:88–91, 1991. 69. Wehrbein H, Merz BR, Hämmerle CH, et al: Bone-to-implant contact of orthodontic implants in humans subjected to horizontal loading, Clin Oral Implants Res 9:348–353, 1998. 70. Nyström E, Kahnberg KE, Gunne J: Bone grafts and Brånemark implants in the treatment of the severely resorbed maxilla: a 2-year longitudinal study, Int J Oral Maxillofac Implants 8:45–53, 1993. 71. Melsen B, Lang NP: Biological reactions of alveolar bone to orthodontic loading of oral implants, Clin Oral Implants Res 12:144–152, 2001. 72. Yavuz U, Kirtiloglu T, Acikgoz G, et al: Bone response to early orthodontic loading of endosseous implants, J Oral Implantol 37:87–95, 2011. 73. Liou EJW, Pai BCJ, Lin JCY: Do miniscrews remain stationary under orthodontic forces? Am J Orthod Dentofacial Orthop 126:42–47, 2004. 74. Deguchi T, Takano-Yamamoto T, Kanomi R, et al: The use of small titanium screws for orthodontic anchorage, J Dent Res 82:377–381, 2003. 75. Chen Y, Kyung HM, Zhao WT, et al: Critical factors for the success of orthodontic mini-implants: a systematic review, Am J Orthod Dentofacial Orthop 135:284–291, 2009.


76. Bantleon HP, Bernhart T, Crismani AG, et al: Stable orthodontic anchorage with palatal osseointegrated implants, World J Orthod 3:109–116, 2002. 77. Männchen R, Schätzle M: Success rates of palatal orthodontic implants. A retrospective longitudinal study, Clin Oral Implants Res 19:665–669, 2008. 78. Björk A, Skieller V: Growth of the maxilla in three dimensions as revealed radiographically by the implant method, Br J Orthod 4:53–64, 1997. 79. Asscherickx K, Hanssens JL, Wehrbein H, et al: Orthodontic anchorage implants inserted in the median palatal suture and normal transverse maxillary growth in growing dogs: a biometric and radiographic study, Angle Orthod 75:826–831, 2005. 80. Kravitz ND, Kusnoto B: Risks and complications of orthodontic miniscrews, Am J Orthod Dentofacial Orthop 131:43–51, 2007. 81. Kadioglu O, Buyukyilmaz T, Zachrisson BU, et al: Contact damage to root surfaces of premolars touching miniscrews during orthodontic treatment, Am J Orthod Dentofacial Orthop 134:353–360, 2008.

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82. Ahmed KSV, Rooban T, Krishnaswamy NR, et al: Root damage and repair in patients with temporary skeletal anchorage devices, Am J Orthod Dentofacial Orthop 141:547–555, 2012. 83. Tsui WK, Chua HD, Cheung LK: Bone anchor systems for orthodontic application: a systematic review, Int J Oral Maxillofac Surg 41(11):1427–1438, 2012. 84. Behrens A, Wiechmann D, Dempf R: Mini- and micro-screws for temporary skeletal anchorage in orthodontic therapy, J Orofac Orthop 67:450–458, 2006. 85. Cheng SJ, Tseng IY, Lee JJ, et al: A prospective study of the risk factors associated with failure of mini-implants used for orthodontic anchorage, Int J Oral Maxillofac Implants 19: 100–106, 2004. 86. Wiechmann D, Meyer U, Buchter A: Success rate of mini- and micro-implants used for orthodontic anchorage: a prospective clinical study, Clin Oral Implants Res 18:263–267, 2007. 87. Morais LS, Serra GG, Muller CA, et al: Titanium alloy miniimplants for orthodontic anchorage: immediate loading and metalion release, Acta Biomater 3(3):331–339, 2007.

C H A PT E R

19

Vertical Dimension and Anterior Open Bite Thomas J. Cangialosi

F

rom the time of Edward Angle, the focus in diagnosis and treatment planning has been on the sagittal relationship of the maxilla and mandible and the dental arches, both to the cranial base and to each other. This was a result of the adoption of the Angle classification of malocclusion1 by the orthodontic community, which depends on the anterior-posterior relationship of the maxillary and mandibular molars to one another. In fact, the cases that are often most difficult to treat and have the least favorable prognosis are those that involve a discrepancy in vertical dimension. This may be manifested in the extreme, either as a long face open bite tendency or a short face deep overbite tendency. In this chapter, the focus is mainly on the high angle or long face patient. Patients with a narrow, tapering, long face are generally referred to as being dolichocephalic or dolichofacial, whereas those with a short, wide face are referred to as brachycephalic or brachyfacial. Reviewing the literature, there was little mention of vertical discrepancy until 1931 when Milo Hellman conducted a study on treated and untreated patients with anterior open bite.2 At that time, the predominant thought was that anterior open bite was caused mainly by tongue thrust or thumbor finger-sucking habits.3–7 He found that the percentage of successfully treated cases was approximately the same as the spontaneous corrections in the untreated group. Based on this, he suggested that there could also be a skeletal component to anterior open bite. In the ensuing 40 years, a number of studies8–11 confirmed that concept, culminating with a definitive study by Worms, Meskin, and Isaacson in 1971 in which they divided 1408 Navajo children into 7-to-9-year and 10-to-12-year age groups.12 They found that there was 80% less open bite in the older group, which could account for the spontaneous corrections in the Hellman study. In the late 1960s and early 1970s, Dr. Melvin Moss and Dr. Letty Salentijn proposed the functional matrix hypothesis of craniofacial growth, which presented a clearer picture of how functional issues interacted with genetics in determining a patient’s skeletal development.13 They proposed the theory of gnomonic growth, that is, that there is change in size but no change in form during craniofacial growth. They stated that the mandible grows on a logarithmic spiral (Fig. 19-1), on which are located the foramen ovale, the mandibular foramen, and the mental foramen. This is very common in

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the plant and animal worlds as is manifested in a nautilus shell and in plant life as seen in Fig. 19-2 and Fig. 19-3. They further stated that in high vertical discrepancy patients, the foramen ovale is located lower down on the logarithmic spiral and suggested that this could lead to early diagnosis of anterior open bite. At the time, location of the foramen ovale on a cephalometric radiograph was unreliable; however, with cone beam computed tomography (CT) and threedimensional (3D) imaging, it is now possible to measure its position accurately.

1. What is the etiology of vertical discrepancy and anterior open bite? It appears that the etiology of vertical discrepancy and anterior open bite is multifactorial. Certainly, tongue thrust and fingersucking habits could be the primary cause; however, evidence has shown that the patient’s skeletal pattern and facial type are also major factors. In effect, there are two types of anterior open bites, one being primarily dentoalveolar in nature and caused by habits and the other related to skeletal morphology. The latter may be caused either by the tipping upward of the palatal plane or by a downward tipping of the mandibular plane due to dentoalveolar growth exceeding condylar growth, causing a backward and downward rotation of the mandible. It has also been postulated that this may be as a result of the interaction of the suprahyoid and infrahyoid muscles with the muscles of mastication creating an envelope of function with the resultant force directed through the antegonial notch area, causing the mandible to actually bend at the antegonial notch as shown in Fig. 19-4. This shows one mandibular plane coming off the gonial angle and the other coming off the antegonial notch. One of the characteristics of a hyperdivergent mandible is a deep antegonial notch.

2. How can skeletal anterior open bite be distinguished from dentoalveolar anterior open bite? In the 1970s, a number of articles14–17 appeared in the literature, which indicated that in general, patients with anterior open bite had more extreme vertical cephalometric measurements than patients with a normal overbite relationship. A vertical cephalometric analysis (VCA) was suggested to help differentiate between skeletal anterior open bite and dentoalveolar open

Vertical Dimension and Anterior Open Bite • CHAPTER 19

251

FIG 19-1 Logarithmic spiral. FIG 19-4 Resultant force created by interaction of muscles of mastication and suprahyoid muscles showing bending down of the mandibular plane.

BOX 19-1 1. 2. 3. 4. 5. 6.

Measurements Used in Study: Vertical Cephalometric Analysis

PFH/AFH ratio UAFH/LAFH ratio SN-GoGn (°) Gonial angle (°) SN-PP (°) PP-GoGn (°)

AFH, Anterior face height; GoGn, gonion-gnathion; LAFH, lower anterior face height; PFH, posterior face height; SN, sella-nasion; PP, palatal plane; UAFH, upper anterior face height.

FIG 19-2 Nautilus shell—example of gnomonic growth.

S

N

PNS

ANS

Go

Me Gn

FIG 19-5 Landmarks and planes used in the study.18

FIG 19-3 Example of gnomonic growth in plant life.

bite. The measurements used in these studies were the following: sella-nasion to gonion-gnathion (SN-GoGn), sella-nasion to palatal plane (SN-PP), palatal plane to gonion-gnathion (PP-GoGn), gonial angle, posterior to anterior face height (PFH/AFH) ratio, and upper to lower anterior face height (UAFH/LAFH) ratio (Box 19-1 and Fig. 19-5).

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CHAPTER 19 • Vertical Dimension and Anterior Open Bite

These measurements were made on a sample of 60 open bite patients and were compared to a control group of 60 normal patients.18–20 The VCA for the control group is shown in Box 19-2 and for the open bite group in Box 19-3. The open bite sample was then separated into those cases with extreme vertical measurements, which were identified as skeletal (Fig. 19-6 and Box 19-5), and those that were close to the normal sample measurements, which were then identified as dentoalveolar or habitual (Box 19-4). In this latter group, the etiology is frequently a habit (such as tongue thrust or thumb sucking) and elimination of that habit along with orthodontic intervention will generally lead to resolution of the anterior open bite.

BOX 19-4 Dentoalveolar Open Bite Subjects 1. 2. 3. 4. 5. 6.

PFH/AFH: 0.650 UAFH/LAFH: 0.761 SN-GoGn: 31.4 Gonial angle: 126.5 SN-PP: 7.41 PP-GoGn: 25.3


BOX 19-5 Skeletal Open Bite Subjects BOX 19-2 Normal Subjects 1. 2. 3. 4. 5. 6.

PFH/AFH: 0.669 S.D. +/− 0.044 UAFH/LAFH: 0.812 S.D. +/− 0.082 SN-GoGn: 29.8 S.D. +/− 5.5 Gonial angle: 123.9 S.D. +/− 5.4 SN-PP: 8.2 S.D. +/− 3.3 PP-GoGn: 21.9 S.D. +/− 5.6

AFH, Anterior face height; GoGn, gonion-gnathion; LAFH, lower anterior face height; PFH, posterior face height; S.D., standard deviation; SN, sella-nasion; PP, palatal plane; UAFH, upper anterior face height.

BOX 19-3 Open Bite Subjects 1. 2. 3. 4. 5. 6.



FIG 19-6 Typical skeletal open bite pattern.

1. 2. 3. 4. 5. 6.



3. How can dentoalveolar or habitual open bite be treated? Since there is not a skeletal component to this type of anterior open bite; treatment should focus on correction of the habit. In some cases, habit correction will lead to spontaneous resolution of the open bite; however, in most cases, habit correction will need to be supplemented with fixed or removable appliance therapy. In these cases the incisors are often under-erupted, so they will need to be extruded using vertical elastics to close the bite. If there is a mild skeletal component to the open bite in addition to the habit, prevention of or restraining molar extrusion may also be necessary. This can be accomplished in several ways, including occlusal coverage of the posterior teeth, use of high pull extraoral force, and incorporating certain bends into the archwires on fixed appliances. A tongue guard or crib may be soldered to a maxillary or mandibular lingual arch to help control persistent tongue thrusting and reverse swallow. In more pernicious habits, tongue spurs may be used instead of cribs. The use of such appliances may be also accompanied by myofunctional therapy, which teaches the patient the proper positioning of the tongue during swallowing and also teaches proper tongue posture. However, in cases of severe skeletal open bite, myofunctional therapy will not be effective unless the skeletal imbalance is corrected first. In other words, it is not possible for the patient to swallow correctly until the anatomic pattern is close to normal. Fig. 19-7, A, shows a 9-year-old patient’s open bite that was due to a thumb-sucking habit and a slight constriction of the maxilla. An occlusal coverage appliance with a tongue crib and an expansion screw (see Fig. 19-7, B) was placed, and the patient was instructed to wear it full time. This phase


A

253

A

B B

C

C

FIG 19-7 A, Open bite due to thumb sucking. B, Removable expansion appliance with tongue crib for Phase I treatment. C, Open bite closed in 10 months.

FIG 19-8 A, Open bite due to tongue thrust. B, Fixed tongue crib and vertical elastics. C, Bite closed in 4 months.

of treatment lasted 8 months, after which the patient’s occlusion was essentially normal for her age (see Fig. 19-7, C). The expansion screw was activated slowly and resulted in approximately 4 mm of expansion over this time. Fig. 19-8, A, shows a 12-year-old patient’s open bite that was due to a tongue thrusting habit. He was treated with fixed appliances and a fixed tongue crib to control the habit and vertical elastics to close the bite. See the progress photo in Fig. 19-8, B, and Fig. 19-8, C.

the prognosis becomes. Especially important is the ratio of UAFH/LAFH, which should be approximately 0.82. When this ratio drops below 0.65, it is an indication that there is an extreme vertical skeletal discrepancy, characterized by a long lower face height; this generally requires surgical intervention combined with orthodontic treatment to be resolved. In such cases, the probability of establishing adequate function, acceptable esthetics, and reasonable stability with orthodontic treatment alone, is very low. Also, as the deviation from normal becomes greater (e.g., 3, 4, or more S.D.), the prognosis for treating the case with orthodontics alone also becomes worse. Generally, the use of anterior vertical elastics is contraindicated in skeletal open bites because often both the maxillary and mandibular incisors are over-erupted as opposed to being under-erupted in habitual open bite. Extrusion of incisors in these cases will lead to an unstable and unaesthetic result, as well as the possibility of significant root resorption if vertical elastics are used for an unduly long period of time.

4. How can skeletal open bite be identified? In the study referred to previously,18 the skeletal open bite patients were identified by the extreme cephalometric measurements noted when using the vertical analysis (VCA). In general, when one or more measurements exceed two standard deviations from normal, it is likely that there is a skeletal component to the open bite, which affects the prognosis of the case, making it less favorable. The greater the number of measurements beyond two standard deviations, the worse

254


5. Does gnomonic growth actually occur? In an attempt to answer this question, another sample of 60 anterior open bite patients was divided into 30 mixed dentition cases and 30 adult cases and measured using the VCA measurements.21 The results indicated that there were close similarity and no significant differences in measurements between these groups (Table 19-1). This is in accord with the concept of change in size but not change in form as a result of the growth process. A change was made in the VCA because of this finding, replacing the gonial angle with the Y axis angle, which was found to be more predictable for vertical discrepancy.

6. How can skeletal open bite be treated? As stated earlier, cases with extreme vertical skeletal discrepancy may require a combination of orthodontic treatment and orthognathic surgery to resolve. When the skeletal discrepancy is less severe, there are a number of treatment modalities that may be utilized for treatment, such as: • Anterior vertical elastics • Posterior bite blocks • High pull headgear • Magnets to intrude molars • Extraction of teeth to close the “wedge” • Vertical pull chin cup • NiTi wire and vertical elastics • Multiple loop arches and vertical elastics • Functional appliances • Temporary anchorage devices (TADs) to intrude molars Anterior open bite tendency is often associated with constriction of the maxillary arch in conjunction with a dolichocephalic facial pattern. In these cases, use of a bonded rapid maxillary expansion appliance with occlusal coverage rather than a banded appliance will be helpful in limiting molar extrusion during expansion. The choice of treatment plans and modalities will depend on where specifically the vertical problem is located and how much of a discrepancy exists. One must also remember that in skeletal open bite, tongue thrust as well as tongue posture can be a factor that determines the ultimate prognosis. Although not the primary etiologic factor, in the presence of the anatomically incorrect dental and skeletal TABLE 19-1 Comparison between Mixed and Permanent Dentition Open Bite Values MIXED DENTITION SAMPLE

PERMANENT DENTITION SAMPLE

PFH/AFH: ratio 0.607 UFH/LFH: ratio 0.720 SN-GoGn angle: 37.3˚ Gonial angle: 132.9˚ SN-PP angle: 6.4˚ PP-GoGn angle: 31.3˚

PFH/AFH: 0.598 UFH/LFH: 0.760 SN-GoGn angle: 39.2˚ Gonial angle: 132.1˚ SN-PP angle 7.8˚ PP-GoGn angle: 30.1˚

AFH, Anterior face height; GoGn, gonion-gnathion; LFH, lower face height; PFH, posterior face height; SN, sella-nasion; PP, palatal plane; UFH, upper face height.

form, it is n ecessary for the tongue to come forward (thrust) in order to create a seal during the swallowing process. This is called reverse swallow. It has been estimated that a normal individual swallows approximately 1200 to 2000 times a day, so the potential for correcting the open bite and maintaining the correction can be greatly affected even if there is surgical intervention. In many instances, correction of the anatomic imbalance will lead to spontaneous elimination of tongue thrust and reverse swallow; however, it is often necessary to use a habit appliance to prevent the tongue from obstructing the correction if the habit is pernicious. In these cases, restraining the tongue will generally be necessary into the retention phase of treatment. CASE STUDIES Many of the appliance systems listed earlier attempt to close the bite by intrusion of the posterior teeth. One method introduced by Young Kim22 is the use of rectangular archwires with a series of vertical loops bent into them for flexibility with vertical elastics to close the bite anteriorly. In 2000, it was suggested that NiTi wire be used rather than looped rectangular archwires, because it does not require the orthodontist to bend all the loops because it is already flexible.23 In this system, the wires are modified by placing accentuated curve of Spee into the maxillary arch and reverse curve of Spee into the mandibular arch and heavy anterior vertical elastics are used. They are used to counter and overcome the intrusive forces placed on the anterior teeth and to keep an intrusive force on the posterior teeth to possibly intrude them or, at least, limit their eruption (Fig. 19-9, A and B). The patient in Fig. 19-9 has an anterior open bite with both habitual and skeletal origins and has been treated with this modality. Note in the superimpositions (Fig. 9-9, C), that the incisors have extruded while the molars have been held in place to maintain vertical dimension. Extraction of premolars or molars has also been advocated to attempt to “close the wedge” and to control vertical dimension.24 This is somewhat controversial when attempting to close a frank open bite but may be effective in hyperdivergent cases with moderate crowding (Fig. 19-10, Fig. 19-11, and Box 19-6).18 The patient, a 19-year-old male with somewhat high v ertical measurements, was treated with the extraction of the four first premolars and the placement of a transpalatal arch (TPA) to help control vertical dimension. Although he has a Class I molar relationship, his ANB angle is 4.6 degrees, indicating a Class II skeletal relationship, and it appears that his mandible is somewhat retrusive. Attempting to treat him without extracting premolars could lead to relapse of crowding and loss of vertical control with a tendency for the bite to open anteriorly. In looking at his posttreatment VCA, (Fig. 19-12 and Box 19-7), it can be noted that his vertical dimension was not only controlled by the treatment but that all vertical measurements actually improved. In addition, his ANB angle difference also decreased significantly from 4.6 degrees to 2.6 degrees. This

A

B1

C

B2

FIG 19-9 A, Anterior open bite of both dentoalveolar and skeletal origin. B, Accentuated upper and reverse lower curve and vertical elastics. Progress after 4 months. C, Superimpositions showing extrusion of incisors and molars held in place.

FIG 19-10 Class I crowded with anterior open bite.

256


FIG 19-11 Pretreatment cephalometric radiograph.

BOX 19-6 Pretreatment Vertical Cephalometric Analysis and Anteroposterior Measurements ANTEROPOSTERIOR RELATIONSHIP • SNA angle (°) • SNB angle (°) • ANB angle (°)

85.3 81.0 82.7 78.0 4.6 3.0 Class II

VERTICAL RELATIONSHIP (VCA) • • • • • •

SN-GoGn (°) Y-Axis (SGn-SN) (°) PFH/AFH ratio (%) PP-GoGn (°) UAFH/LAFH ratio (%) SN-PP (°)

38.2 69.1 59.7 32.7 68.1 4.4

32.0 67.0 67.0 22.0 81.0 8.2

Hyperdivergent tendency Short posterior face height Divergent dental bases Long lower face PP tipped upward


BOX 19-7

Posttreatment Cephalometric Values

ANTEROPOSTERIOR RELATIONSHIP • SNA angle (°) • SNB angle (°) • ANB angle (°)

85.3 80.7 4.6

84.7 82.2 2.6


SN-GoGn (°) Y-Axis (SGn-SN) (°) PFH/AFH ratio (%) PP-GoGn (°) UAFH/LAFH ratio (%) SN-PP (°)

38.2 69.1 59.7 32.7 68.1 4.4

34.7 69.3 59.8 29.4 68.5 5.3


could indicate that he grew forward during treatment, rather than down the Y axis, as would have been expected (Fig. 19-13 and Fig. 19-14). How would he have grown if attempts to control his vertical dimension were not initiated or if he had been treated without extracting teeth?

FIG 19-12 Posttreatment cephalometric radiograph.

The patient in Fig. 19-15 has indications of both vertical discrepancy as well as a Class III tendency with an extremely flat profile and a negative ANB angle (Fig. 19-16 and Box 19-8). She has an edge-to-edge incisor relationship and an impacted maxillary left canine. Her hand-wrist radiograph indicated that growth was at or near completion (Fig. 19-17). It was determined that extraction of premolars would have been detrimental to her facial esthetics. Her mandibular incisors were retroclined in typical compensation for a Class III tendency; however, it was decided to treat her nonextraction and nonsurgically. Rapid palatal expansion was ruled out because of a repaired midpalatal cleft. The maxillary arch was treated first so as not to advance the mandibular incisors into a crossbite relationship. A TPA was attached to the maxillary first molars to help with vertical control, and the impacted canine was exposed and brought into the arch. This caused some a dditional flaring of the maxillary incisors, creating some room to advance the mandibular incisors along with some interproximal reduction. Her vertical analysis indicates that vertical dimension has been controlled (Box 19-9 and Fig. 19-18) and her facial profile has been maintained (Fig. 19-19). Fig. 19-20 shows a patient with a large anterior open bite and extreme vertical measurements. All vertical measurements are greater than two standard deviations from normal. In addition, an ANB angle of 7 degrees indicates a sagittal skeletal Class II relationship (Fig. 19-21). The maxillary left second premolar was congenitally missing. A combined orthodontic and orthognathic surgery treatment plan was chosen for this patient. The surgical treatment plan chosen required a three segment LeFort I osteotomy, autorotation of the mandible, and an advancement genioplasty. The maxilla was expanded, impacted 3 mm, advanced 1 mm, and rotated clockwise 3 degrees. A mandibular advancement was initially considered, but because the mandible autorotated into an ideal incisor relationship, it was decided to do an advancement genioplasty instead. In the presurgical phase of orthodontic treatment, the maxillary incisors were leveled segmentally so as not to extrude them, which could have built in a tendency for the open bite to relapse. Note in the final result that the left p osterior


257

FIG 19-13 Posttreatment result.

FIG 19-14 Pretreatment and posttreatment profile.

segment was finished in a Class II molar relationship due to the missing maxillary second premolar (Fig. 19-22 and Fig. 19-23). Recently, TADs have been used to intrude posterior teeth in lieu of maxillary surgery.25 In the case shown in Fig. 1924, the bite is open from first molar to first molar. TADs have been placed between the maxillary second premolars and first molars, a TPA has been placed (Fig. 19-25), and NiTi coil springs have been placed from the TADs around

the archwire back to the TADs to place an intrusive force on the posterior segment (Fig. 19-26 and Fig. 19-27). The open bite is largely resolved after 3 months (Fig. 19-28). Some studies have shown a t endency for the bite to reopen within 2 years, and it has been recommended that cases treated with this mechanism be retained with posterior bite blocks in addition to traditional retainers to maintain intrusion of the posterior teeth. In this brief review of vertical discrepancy and anterior open bite, the etiology, diagnosis, and treatment of different types of vertical problems has been discussed. It is important to understand that not all open bites are the same and should not all be treated in the same way. Each case shown was different with regard to its cause and severity, and an individualized treatment plan was formulated for each patient based on the functional and skeletal requirements. In general, when it comes to poor prognosis for successful treatment of anterior open bite cases, some of the warning signals involve those open bites that extend beyond the anterior teeth to the posterior segments, one or more vertical measurements beyond two standard deviations from normal, and upper to lower anterior face height ratios below 0.70.

258


FIG 19-15 Pretreatment gallery photos.

BOX 19-8 Pretreatment Anteroposterior and Vertical Measurements ANTEROPOSTERIOR RELATIONSHIP • SNA angle (°) 76 • SNB angle (°) 77 • ANB angle (°) 1


FIG 19-16 Pretreatment cephalometric radiograph.

PFH/AFH (%) UAFH/LAFH ratio (%) Sn-Go-Gn (°) Y-Axis (°) SN-PP (°) PP-GoGn (°)

0.598 0.760 39.5 71.6 11.5 28.5



259

BOX 19-9 Posttreatment Anteroposterior and Vertical Measurements ANTEROPOSTERIOR RELATIONSHIP • SNA angle (°) 75 • SNB angle (°) 76.5 • ANB angle (°) 1.5

VERTICAL RELATIONSHIP (VCA) • PFH/AFH • UAFH/LAFH ratio (%) • Sn-Go-Gn (°) • Y-Axis (°) • SN-PP (°) • PP-GoGn (°)

FIG 19-17 Hand-wrist film showing growth is near completion.

0.598 0.760 39.3 71.6 11.5 27.8


FIG 19-18 Posttreatment cepholometric radiograph.

FIG 19-19 Posttreatment result.

FIG 19-20 Severe skeletal vertical discrepancy resulting in open bite.


FIG 19-21 Extreme vertical and sagittal measurements.

FIG 19-22 Presurgery and postsurgery.

FIG 19-23 Final occlusion.

FIG 19-24 Open bite from left to right first molar.

FIG 19-25 Transpalatal arch (TPA) in place.

261

262


FIG 19-26 Temporary anchorage devices (TADs) in place.

FIG 19-27 NiTi coils from archwire to temporary anchorage devices (TADs).

FIG 19-28 Progress after 3 months of treatment.

REFERENCES 1. Angle EH: Malocclusion of the teeth and fractures of the maxillae, ed 6, 1900, SS White Publishing Co, pp. 23-34. 2. Hellman M: Open bite, Int J Orthod 17(5):421–444, 1931. 3. Swinehart E: A clinical study of open bite, Am J Orthod Oral Surg 28:18–34, 1942. 4. Straub WJ: Malfunction of the tongue. Part 1. The abnormal swallowing habit: its causes, effects, and results in relation to orthodontic treatment and speech therapy, Am J Orthod 46(6):404–424, 1960. 5. Subtelny JD: Oral habits—studies in form, function, and therapy, Angle Orthod 43(4):349–383, 1973. 6. Fletcher SG, Casteel RL, Bradley DP: Tongue thrust swallow, speech articulation, and age, J Speech Hear Disord 26:201–208, 1961. 7. Watson WG: Open-bite—a multifactorial event, Am J Orthod 80(4):443–446, 1981. 8. Shudy FF: Vertical growth versus anterior-posterior growth as related to function and treatment, Angle Orthod 34:75–93, 1964. 9. Hapak FN: Cephalometric appraisal of the open bite case, Angle Orthod 34:65–72, 1964. 10. Richardson AR: Skeletal features in anterior open-bite and deep overbite, Am J Orthod 56(2):114–127, 1969. 11. Richardson AR: Dento-alveolar factors in anterior open bite and deep overbite, Dent Pract Dent Rec 21(2):53–57, 1970. 12. Worms FW, Meskin LH, Isaacson RJ: Open-bite, Am J Orthod 59(6):589–595, 1971. 13. Moss ML, Salentijn L: Differences between the functional matrices in anterior open bite and deep overbite, Am J Orthod 60(3):264–280, 1971.

14. Nahoum HI: Vertical proportions and the palatal plane in anterior open bite, Am J Orthod 59(3):273–282, 1971. 15. Nahoum HI, Horowitz SL, Benedicto EA: Varieties of anterior open-bite, Am J Orthod 61(5):486–492, 1971. 16. Nahoum HI: Anterior open-bite: a cephalometric analysis and suggested treatment procedures, Am J Orthod 67(5):513–521, 1975. 17. Nahoum HI: Vertical proportions: a guide for prognosis and treatment in anterior open-bite, Am J Orthod 72(2):128–146, 1977. 18. Cangialosi TJ: Skeletal morphologic features of anterior open bite, Am J Orthod 85(1):28–36, 1984. 19. Cangialosi TJ, Meistrell ME, Leung MA, et al: A cephalometric appraisal of edgewise Class II nonextraction treatment with extraoral force, Am J Orthod Dentofacial Orthop 93(4):315–324, 1988. 20. Chilton NW: Design and analysis in dental and oral research, Philadelphia, 1967, JB Lippincott Company. 21. Moss ML, Salentijn L: The unitary logarithmic curve descriptive of human mandibular growth, Acta Anat (Basel) 78(4):532–542, 1971. 22. Kim Y: Anterior open bite and its treatment with multiloop edgewise archwire, Angle Orthod 57(4):289–321, 1987. 23. Kücükkeles N, Acar A, Demirkaya AA, et al: Cephalometric evaluation of open bite treatment with NiTi arch wires and anterior elastics, Am J Orthod Dentofacial Orthop 116(5):555–562, 1999. 24. de Freitas MR, Beltrão RT, Janson G, et al: Long term stability of open bite extraction treatment in the permanent dentition, Am J Orthod Dentofacial Orthop 125(1):78–87, 2004. 25. Umemori M, Sugawara J, Mitani H, et al: Skeletal anchorage system for open-bite correction, Am J Orthod Dentofacial Orthop 115(2):166–174, 1999.

Oral Hygiene: Possible Problems and Complications

C HA P T ER

20

David A. Covell, Jr. • Winthrop B. Carter • Frank Tsung-Ju Hsieh

“F

irst, do no harm” is a fundamental guiding philosophy in medicine and dentistry. All too often orthodontists are confronted with having to consider this principle with a patient who develops poor oral hygiene partway through his or her orthodontic treatment. Clearly the presence of orthodontic brackets, wires, and other hardware creates a challenging environment for maintaining good oral hygiene. While there are measures that can be used to maintain or improve a patient’s hygiene, these are often ineffective for reasons usually related to patient compliance. For example, a study of patient compliance in a periodontal private practice found that only 16% of patients were totally compliant, whereas 52% showed erratic compliance and 32% were noncompliant.1 In a second study with the same private practice, total compliance was increased to 32% by implementing several communication changes,2 but attaining 100% compliance is seemingly an unattainable goal. When compliance with oral hygiene requirements remains less than ideal, the accumulation of bacterial plaque often leads to demineralization of enamel and the appearance of white spot lesions, which is an early sign of caries formation. In addition, bacterial accumulations on teeth and orthodontic appliances cause inflammation of the gingival tissues, resulting in enlargement or overgrowth of interdental gingival papillae and gingival margins. Although gingivitis related to placement of orthodontic appliances is reversible in most individuals, there are situations when patients are particularly prone to gingival overgrowth (e.g., caused by genetic variations in the response of gingival tissue or side effects of medications needed for systemic health). For these patients, restoration of good oral hygiene practices may be inadequate, making periodontal therapeutic procedures necessary to restore normal gingival architecture. Similarly, with increasing numbers of adults seeking orthodontic treatment, more patients will have had or will need periodontal treatment prior to orthodontics. Thus, orthodontists will be confronted with coordinating the timing of orthodontic treatment following periodontal therapy. The questions that follow relate to areas briefly alluded to earlier, and the accompanying explanations provide insights into a variety of relationships between orthodontics and periodontics.

1. What are evidence-based recommendations regarding the most effective means of preventing white spot lesions in orthodontic patients? Systematic reviews have concluded that with adequate tooth brushing, toothpastes with fluoride concentrations of 1500 to 5000 ppm demonstrate greater preventive effects for white spot lesion formation than those with a concentration of 1000 ppm.3,4 In addition, supplemental use of a brush-on gel with 5000 ppm fluoride once a day has more of a preventive effect than conventional fluoride toothpaste alone.5 All else being equal, variations in the formulation of toothpastes and mouthrinses have a relatively mild impact on white spot lesion formation.6 The use of polymeric tooth coatings or sealants on the tooth surface around the brackets has been shown to have no, or at best limited, impact on preventing enamel demineralization.7–12 In recent years, bracket-bonding adhesives that release fluoride and other minerals have shown a promising potential for reducing or eliminating white spot lesion formation13–16; however, clinical investigations of such adhesives remain sparse. MI Paste Plus®, containing casein phosphopeptide-amorphous calcium phosphate, is a relatively new homecare product aimed at remineralization of white spot lesions, but studies have shown mixed success. A prospective randomized controlled trial with orthodontic patients in mid-treatment found that when MI Paste Plus was delivered daily using fluoride trays, no new white spot lesions appeared and preexisting lesions decreased by over 50% relative to a placebo group (using toothpaste) over a 3-month period.17 This result contrasts with a study on use of MI Paste Plus to treat white spot lesions following orthodontic treatment in that no difference was found between MI Paste Plus, fluoride varnish, and control groups in a 2-month clinical trial.18 The latter study is also consistent with results from a recent in vitro investigation of the effects of MI Paste Plus on the esthetics of experimentally created white spot lesions where there was little evidence to show improvement in the appearance of the lesions.19 It is possible that MI Paste Plus has greater efficacy on newly formed (active) white spot lesions relative to more longstanding (arrested) lesions, but more investigation is needed. 263

264

CHAPTER 20 • Oral Hygiene: Possible Problems and Complications

2. Do mouthrinses impact gingivitis? A number of oral rinses and dentifrices have been tested in clinical trials, with results varying depending on the product.20 A standard that attests to the efficacy of products aimed at treatment of gingivitis has been implemented by the American Dental Association (ADA) Council on Dental Therapeutics. If the ADA Seal of Acceptance is not on a product, it means either that the product was not tested by the ADA Council or that the product has been tested but did not produce the results claimed by the manufacturer. The ADA Seal of Acceptance is given to a product that reduces plaque and demonstrates effective reduction of gingival inflammation over a period of at least 6 months. The agent must also be safe and not induce adverse side effects. Several products have been given the ADA Seal of Acceptance for the control of gingivitis. In one of the products, the active ingredients are thymol, menthol, eucalyptol, and methyl salicylate.21 This product is available over the counter without a prescription. Active ingredients in other products include chlorhexidine digluconate and triclosan.21 Side effects of chlorhexidine digluconate include tooth and tongue staining, increased calculus deposits, bitter taste, mouth and throat irritation, mouth sores (ulcers), coated tongue, and changes in taste of food and beverages. Chlorhexidine digluconate products require a prescription for the patient to purchase. If properly used, the addition of a topical antiplaque agent to a gingivitis treatment regimen for patients with deficient plaque control will likely result in the reduction of gingivitis.22 However, experimental evidence indicates that penetration of topically applied agents into the gingival crevice is minimal.23 Therefore, these agents are useful for the control of supragingival, but not subgingival, plaque. For individuals who demonstrate less than excellent oral hygiene, supragingival irrigation with or without medicaments may reduce gingival inflammation beyond that normally achieved by tooth brushing alone. This effect is likely due in part to the flushing out of subgingival bacteria.24 Mouthrinses containing essential oils and other natural compounds have shown variable effects with orthodontic patients. A prospective clinical trial has shown that a mouthrinse (Listerine) containing an essential oil had significant, positive effects on periodontal bleeding and gingival and plaque indices.25 Short-term studies have shown plaque and gingival inflammation reductions averaging 35%, and long-term studies have shown plaque reduction averaging 25% and gingival inflammation reduction averaging 29% when using Listerine.26,27 These findings contrast with those of other investigations where similar indices were used and only the periodontal bleeding index improved with a mouthrinse containing an essential oil.28 The study also found a positive effect on the bleeding index (but not on other periodontal indices) with use of a different mouthrinse, one containing the natural ingredient fructus mume.28 Additional clinical trials of mouthrinses containing natural, bioactive compounds are needed to investigate their potential for helping maintain periodontal health during orthodontic treatment.

3. Is oral hygiene better using a power toothbrush compared with a manual toothbrush? Powered brushes have been defined as toothbrushes with a mechanical movement of the brush head. Powered brushes have been divided into six groups depending on their mode of action29: 1. Side-to-side action: Brush head moves laterally with a sideto-side motion. 2. Circular: Brush head rotates in one direction only. 3. Rotation oscillation: Brush head rotates in one direction and then the other. 4. Counter oscillation: Adjacent tufts of bristles (usually 6 to 10) rotate in one direction and then the other, independently. Each tuft rotates in the opposite direction to that adjacent to it. 5. Ultrasonic: Brush bristles vibrate at ultrasonic frequencies (i.e., above 20 kHz). 6. Unknown action: Indicates a brush action that the reviewers were unable to establish from either the trial report or the manufacturers. While numerous clinical trials have compared manual and powered toothbrushes for their effectiveness in improving oral health, the results are often conflicting.29 Systematic reviews by the Cochrane Oral Health Group have summarized results and provided unbiased conclusions.30,31 Powered brushes reduced plaque and gingivitis at least as effectively as manual brushing. Rotation-oscillation powered brushes show statistically significant reductions of plaque and gingivitis in both the short32 and long term.30–33 No differences in efficacy have been demonstrated for sonic brushes versus other powered toothbrushes.34 The systematic reviews described earlier involved general populations and were not orthodontic specific.30,32 From existing studies, it can be concluded that compared with a manual toothbrush, orthodontic patients using a powered toothbrush will show a mild, statistically significant reduction for bleeding on probing35 and plaque accumulation.36 A recent investigation of a rotation-oscillation powered toothbrush found that a compact, orthodontic-specific brush head was more effective than a larger, regular-use brush head.36 A need remains for long-term trials on the efficacy of powered brushes in ortho dontic patients.

4. Which oral prophylaxis technique is better for orthodontic patients: and air-powder polishing system or a rubber cup and pumice technique? The conventional rubber cup prophylaxis (RCP) and the airpowder polishing (APP) system (Prophy Jet) are both effective professional techniques for plaque and stain removal without detrimental effects on tooth structure and gingival tissues when used correctly.37–39 The APP system uses a jet formed by a mixture of air, powder, and water to remove dental plaque, soft deposits, and surface stains from pits, grooves, interproximal spaces, and smooth surfaces of the teeth. Barnes and associates40

Oral Hygiene: Possible Problems and Complications • CHAPTER 20

showed that the use of the APP system in orthodontic patients neither affected the composite resin or zinc-phosphate cement used to secure brackets and bands nor caused any damage to archwires or other appliances. Ramaglia and colleagues41 used a split-mouth experimental design to compare the efficacy and efficiency of the APP system with the RCP technique. Significant reductions in the plaque index were found after either APP or RCP. APP was somewhat more efficient, requiring significantly less time to remove dental plaque and staining.

5. Are there ways to prevent periodontal complications during orthodontic treatment? When oral hygiene is marginal to poor, use of steel rather than elastic ligatures has been recommended on brackets, including tooth-colored (“esthetic”) brackets, because elastomeric ligatures attract significantly more plaque than steel ligatures.42 In theory, use of self-ligating brackets may have a similar effect as steel ligatures. Studies comparing self-ligating to elastomeric ligated brackets show that during the first 3 months of comprehensive orthodontic treatment, teeth with self-ligating brackets have less plaque accumulation,43 whereas after 1 year of treatment, no difference in plaque accumulation was found when comparing the two wire ligation methods.44 Because oral hygiene often tends to be better at the start relative to later in treatment, these results suggest that with good oral hygiene practices, self-ligation is advantageous relative to use of elastomeric ligatures, whereas with less ideal hygiene practices, the type of ligation employed makes no difference with regard to plaque accumulation.44 In addition to ligation considerations, bonded brackets are preferable to bands as demonstrated during orthodontic treatment of adults where molars having bonded brackets show less plaque accumulation, gingivitis, or loss of attachment interproximally compared to molars having bands.42,45–47 It is evident that in adults with a reduced but healthy periodontium, orthodontic tooth movement can be performed without further periodontal deterioration.48–50 After 4 to 6 months’ observation following periodontal treatment (such as scaling and root planing), a careful clinical examination and recording of the periodontal status is necessary before orthodontic treatment is initiated. Professional scaling may be indicated especially during active intrusion of elongated maxillary incisors when new attachment is desired,51,52 because orthodontic intrusion may shift supragingival plaque to a subgingival location.53,54 Should efforts aimed at maintaining excellent to good oral hygiene prove unsuccessful once orthodontic treatment has been initiated, termination of treatment (appliance removal) has been recommended.55

6. When can orthodontic treatment be started on a patient who has been treated for periodontitis? Following active periodontal treatment, patients in the maintenance phase of periodontal therapy traditionally are typically observed for 4 to 6 months before initiating orthodontic

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t reatment. This provides time for full expression of the benefits of the periodontal therapy and for monitoring of the patient’s oral hygiene and motivation.56 Once orthodontic treatment is started, periodontal maintenance should be scheduled at shorter intervals, in many instances with the patient being seen as frequently for periodontal maintenance as for orthodontic appliance adjustments (i.e., every 4 to 6 weeks).57

7. Are patients who have been previously treated for periodontal disease more likely to lose periodontal attachment if they receive orthodontic treatment? Tooth movement in adults with reduced but healthy periodontium does not result in further significant loss of attachment.58 However, adults with teeth that do not have healthy periodontal tissues may experience further breakdown and tooth loss because of abscesses during orthodontic treatment.58 In patients (mostly adults) with active periodontitis (that is, plaque-infected deep pockets evidenced by bleeding on probing), orthodontic tooth movement may accelerate the disease process, even when good oral hygiene is practiced.59–63 It should be noted that a systematic review, excluding patients who had any teeth banded, found that patients who had received ortho dontic treatment when compared with no-treatment subjects were associated with slight yet statistically significant gingival recession (0.03 mm) and alveolar bone loss (0.13 mm).64 Presumably similar associations may be found with patients who have orthodontic treatment with a healthy periodontium following periodontal therapy.

8. Is orthodontic treatment a risk factor for gingival recession? Gingival recession is frequently seen in teeth that are positioned facially relative to the supporting alveolus, irrespective of a history of orthodontic treatment. The most important etiologic factor in gingival recession relates to the reduced thickness of the soft tissue and bone, especially on the facial surface of labially prominent teeth.65–69 This thin soft tissue and/or bone is a predisposing factor for gingival recession.66 In fact, vertical loss of buccal or labial bone (dehiscence) is a prerequisite for recession.66 Other common factors in the development of recession are age and trauma, the latter caused, for example, by improper tooth brushing or gingival lesions associated with bacterial plaque.67 As found with non-orthodontic samples, mild facial gingival recession observed over time after orthodontic treatment is a normal development with increasing age, with some teeth being more prone to greater amounts of recession than others.70,71 In addition to the importance of tooth brushing in maintaining periodontal health, as discussed above, use of dental floss during orthodontic treatment has been shown to result in reduced signs of gingivitis and periodontal breakdown relative to when floss is not used.72 Of factors associated with gingival recession, there is evidence to suggest that the “zone” or apico-coronal height of keratinized tissue is not related to gingival recession, whereas the thickness of the keratinized tissue is an important factor.

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A long-term study of a non-orthodontic population has shown that the incidence of recession in areas without keratinized tissue is no greater than that found in areas with a wide expanse of keratinized tissue.69 In contrast, orthodontic tooth movement in a facial direction in areas of thin facial tissue can result in bone dehiscence, creating an environment in which plaque and/or toothbrush trauma may cause sudden recession.73–79 If thick gingival tissue is present in these areas, gingival recession is less likely to occur.73,74,77–79 Thus, there is general agreement that with thin labial tissue, gingival tissue should be augmented before tooth movement is made in a labial direction.73,74,77–79 Conversely, for facially positioned teeth and with root dehiscence, bone may form and gingival thickness may increase when the teeth are moved lingually.80–83 With regard to the relationship between rapid maxillary expansion procedures and gingival recession, Graber and Vanarsdall73 have discussed that if the maxillary expansion is performed after the mid-palatal suture begins to fuse (after approximately 14 to 16 years of age), there is a greater risk later in life of recession of the buccal gingival tissue of the maxillary premolars and molars.

9. What is the best way to manage patients predisposed to gingival overgrowth during orthodontic treatment? Gingival enlargement or gingival overgrowth is the preferred term for all medication-related gingival lesions previously termed gingival hyperplasia or gingival hypertrophy.83 The terms gingival enlargement or gingival overgrowth reflect more of the clinical description of what is observed, whereas gingival hyperplasia and gingival hypertrophy reflect a histologic description of the clinical observation. Although the terms are defined from a medication-related context, the terms are also suitable for use in describing clinical observations of affected gingival tissue during orthodontic therapy, as well as for other etiologic reasons as mentioned later. In many patients, proper oral hygiene is sufficient to achieve normal, healthy gingiva. In some situations, however, gingival overgrowth is drug induced or can be a manifestation of a genetic disorder. The latter may exist as an isolated abnormality or as part of a syndrome. If orthodontic treatment is needed in patients with gingival overgrowth, both orthodontic and periodontal factors should be considered. For example, in a case report of extreme hereditary gingival fibromatosis, the patient was treated periodontally prior to orthodontic treatment by removal of all gingival excess using flaps and gingivectomies.84 After a follow-up period, orthodontic treatment was started with fixed appliances. Monthly periodontal check-ups (scaling and polishing) were scheduled to control the gingival inflammation. After the orthodontic treatment, permanent retention was applied, followed again by a complete gingivectomy in both the maxilla and mandible. Gingival overgrowth occurs in about 50% of persons taking phenytoin (Dilantin).85–89 Lesions may involve the interproximal spaces and become so extensive that the teeth become displaced and their crowns covered. Gingival enlargement is also seen in several blood dyscrasias. This form of gingival dysplasia

is seen in acute monocytic, lymphocytic, or myelocytic leukemia. Thrombocytopenia and thrombocytopathy can also cause gingival enlargement and spontaneous bleeding. In some individuals, gingival enlargement progresses rapidly into destructive periodontal disease as a result of an altered immune response of the gingiva to the bacterial plaque. A slowly progressive fibrous enlargement of the maxillary and mandibular gingiva is a feature of idiopathic fibrous hyperplasia of the gingiva. Characteristically, this massive gingival enlargement may cover the tooth surfaces and displace the teeth, and although the cause of the disease is unknown, there appears to be a genetic predisposition.90,91 Depending on home care and the relationship between the gingival tissue and the crown of the tooth, gingival hyperplasia is frequently reversible, especially after orthodontic appliances have been removed.62 Alternatively, Graber and Vanarsdall73 suggest that some patients may benefit from the removal of excessive gingival tissue around the crowns of the teeth, and this may add to the stability of the orthodontic correction.

10. What is the relationship of periodontal regeneration procedures and orthodontic tooth movement? Regeneration refers to the reproduction or reconstitution of a lost or injured part. Periodontal regeneration is defined histologically as regeneration of the tooth’s supporting structures, including alveolar bone, periodontal ligament, and cementum over a previously diseased root surface.92 Guided tissue regeneration (GTR) is one of two techniques, the other technique being osseous grafting with the most histologic documentation of periodontal regeneration.93,94 Therapeutic outcomes of GTR are not always achieved, and GTR is therefore still considered unpredictable despite conclusive evidence that some regeneration may occur following regenerative procedures.95–97 Complete regeneration is considered to be an unrealistic goal for many situations due to the complexity of biological events, factors, and cells involved with successful periodontal regeneration. Barriers (either resorbable or non-resorbable) with or without bone grafting are utilized in GTR procedures.92 Because GTR is defined histologically, clinically the interpretation of successful GTR procedures is determined by 1) when resistance to probing is encountered and decreased probe depth is recorded; and 2) increased radiodensity as observed in radiographic images if the sites where the procedures were completed can be imaged. The impact of GTR on the potential for orthodontic tooth movement and the ideal timing of tooth movement following GTR procedures have been important areas of clinical investigation. Treatment of Class II furcation lesions in dog animal models demonstrated that a 60-day delay in orthodontic movement did not interfere with healing or adversely impact the amount of bone regenerated by the regenerative periodontal techniques.98–101 It should be noted that the bone remodeling cycle (sigma) in dogs is 3 months, whereas it is 4.25 months for humans102; thus healing to a comparable level will likely take longer in humans. Clinically, several case presentations have demonstrated that, following repair of osseous defects with GTR, o rthodontic


tooth movement can be accomplished without adverse effects on periodontal support.103–106 Similarly, a review of the literature in 2010 found low levels of evidence that teeth can be successfully moved into bone grafts of various types and there were no deleterious effects on tooth roots.107 Consistent with the findings of the tooth movement studies, developing teeth have been shown to be capable of erupting uneventfully through bone grafts.107 When managing intrabony defects, case reports have shown that GTR in combination with orthodontic tooth extrusion108 or space closure109 results in improved periodontal outcomes compared with either procedure alone. Similarly, in a prospective clinical trial, either GTR using bone grafts or orthodontic tooth extrusion was found to be helpful in treating two- and three-wall infrabony defects; moreover combining the two procedures was the most successful for treatment of two-wall defects, but did not improve the outcomes for threewall defects.110 With regard to timing of tooth movement following GTR surgery, studies using dog models found that orthodontic tooth movement can be started as early as 60 days following GTR.98 This delay (the shortest time investigated) was thought necessary to prevent mechanical tooth movement from interfering with the healing process of the periodontal tissues, such as accelerating membrane absorption.98 Previous animal studies evaluating periodontal regeneration from 60 to 90 days after treatment found advanced healing of the periodontal tissues after 60 days.98,99,111,112 In several clinical reports related to GTR, encouraging results were obtained when tooth movement was initiated after radiographic confirmation that the defects had been filled with bone at 5 to more than 11 months following surgery.104–106 In contrast, Attia and colleagues,113 using a prospective clinical investigation, found that when measurements were made 1 year after GTR surgery, better periodontal results were obtained in groups of patients where orthodontic tooth movement was initiated immediately following bone grafting surgery, relative to groups when movement was delayed for 2 months or when there was no tooth movement. Improvements were found in measurements of pocket depths, clinical attachment levels, bone density, and bone fill.113 Thus, when dealing with infrabony defects, delaying orthodontic tooth movement for approximately 60 days following GTR has been recommended based on a number of reports; however, recent clinical evidence suggests that it may be advantageous to initiate orthodontic tooth movement as early as immediately following the GTR procedure. Additional research is needed to help sort out the various recommendations. It can be concluded that in a healthy environment, ortho dontic tooth movement does not adversely impact periodontal results achieved with GTR. Additional research is needed to improve our knowledge regarding advantages or disadvantages related to delaying versus immediate tooth movement following GTR. Extrapolations from animal studies support delaying tooth movement by 3 to 4 months, similar to recommended delays following other periodontal surgical procedures, whereas recent clinical studies suggest that such a delay may be unnecessary or even contraindicated.

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REFERENCES 1. Wilson TG: Compliance: a review of the literature with possible applications to periodontics, J Periodontol 58:706–714, 1987. 2. Wilson TG: The results of efforts to improve compliance with supportive periodontal treatment in a private practice, J Periodontol 64:311–314, 1993. 3. Derks A, Katsarosa C, Frencken JE, et al: Caries-inhibiting effect of preventive measures during orthodontic treatment with fixed appliances, Caries Res 38:413–420, 2004. 4. D'Agostino RB, Cancro LP, Fischman S: Effects of anticaries dentifrices on orthodontic subjects, Comp Con Educ Dent 11:S384–S389, 1988. 5. Alexander SA, Ripa LW: Effects of self-applied topical fluoride preparations in orthodontic patients, Angle Orthod 70:424–430, 2000. 6. Ogaard B, Alm AA, Larsson E, et al: A prospective, randomized clinical study on the effects of an amine fluoride/stannous fluoride toothpaste/mouthrinse on plaque, gingivitis and initial caries lesion development in orthodontic patients, Eur J Orthod 28:8–12, 2006. 7. Fornell AC, Sköld-Larsson K, Hallgren A, et al: Effect of a hydrophobic tooth coating on gingival health, mutans streptococci, and enamel demineralization in adolescents with fixed orthodontic appliances, Acta Odontol Scand 60:37–41, 2002. 8. Wenderoth CJ, Weinstein M, Borislow AJ: Effectiveness of a fluoride-releasing sealant in reducing decalcification during orthodontic treatment, Am J Orthod Dentofacial Orthop 116:629–634, 1999. 9. O'Reilly MT, De Jesus Vinas J, Hatch JP: Effectiveness of a sealant compared with no sealant in preventing enamel demineralization in patients with fixed orthodontic appliances: a prospective clinical trial, Am J Orthod Dentofacial Orthop 143:837–844, 2013. 10. Leizer C, Weinstein M, Borislow AJ, et al: Efficacy of a filledresin sealant in preventing decalcification during orthodontic treatment, Am J Orthod Dentofacial Orthop 137:796–800, 2010. 11. Uysal T, Amasyali M, Ozcan S, et al: Effect of anti-bacterial monomer-containing adhesive on demineralization around orthodontic brackets, Am J Orthod Dentofacial Orthop 139: 650–656, 2011. 12. Farhadian N, Miresmaeli A, Eslami B, et al: Effect of fluoride varnish on enamel demineralization around brackets: an in-vivo study, Am J Orthod Dentofacial Orthop 133(Suppl):S95–S98, 2008. 13. Cain K, Hicks J, English J, et al: In vitro enamel lesion formation and orthodontic bonding agents, Am J Dent 19: 187–192, 2006. 14. Pratt K, Hicks J, English J, et al: Fluoride-releasing orthodontic adhesives and topical fluoride effect on enamel caries formation: an in vitro study, Am J Dent 23:179–184, 2010. 15. Manfred L, Covell DA, Crowe JJ, et al: A novel biomimetic orthodontic bonding agent for prevention of white spot lesions: an in vitro study of surface microhardness changes adjacent to orthodontic brackets, Angle Orthod 83:97–103, 2013. 16. Rogers S, Chadwick B, Treasure E: Fluoride-containing orthodontic adhesives and decalcification in patients with fixed appliances: a systematic review, Am J Orthod Dentofacial Orthop 138:390.e1–390.e8, 2010. 17. Robertson MA, Kau CH, English JD, et al: MI Paste Plus to prevent demineralization in orthodontic patients: a prospective randomized controlled trial, Am J Orthod Dentofacial Orthop 140:660–668, 2011. 18. Huang GJ, Roloff-Chiang B, Mills BE, et al: Effectiveness of MI Paste Plus and PreviDent fluoride varnish for treatment of white spot lesions: a randomized controlled trial, Am J Orthod Dentofacial Orthop 143:31–41, 2013.

268


19. Ballard RW, Hagan JL, Phaup AN, et al: Evaluation of 3 commercially available materials for resolution of white spot lesions, Am J Orthod Dentofacial Orthop 143:S78–S84, 2013. 20. Hancock EB: Prevention, Ann Periodontol 1:223–249, 1996. 21. Mandel ID: Antimicrobial mouthrinses: overview and update, J Am Dent Assoc 125(Suppl 2):2S–10S, 1994. 22. Brecx M, Brownstone E, MacDonald L, et al: Efficacy of Listerine, Meridol, and chlorhexidine as supplements to regular tooth-cleaning measures, J Clin Periodontol 19:202–207, 1992. 23. Pitcher GR, Newman HN, Strahan JD: Access to subgingival plaque by disclosing agents using mouthrinsing and direct irrigation, J Clin Periodontol 7:300–308, 1980. 24. The American Academy of Periodontology: The role of supraand subgingival irrigation in the treatment of periodontal diseases (position paper), Chicago, April 1995, The American Academy of Periodontology. 25. Tufekci E, Casagrande ZA, Lindauer SJ, et al: Effectiveness of an essential oil mouthrinse in improving oral health in orthodontic patients, Angle Orthod 78:294–298, 2008. 26. Lamster IB, Alfano MC, Seiger MC: The effect of Listerine antiseptic on reduction of existing plaque and gingivitis, Clin Prevent Dent 5:12–14, 1983. 27. Gordon JM, Lamster IB, Seiger MC: Efficacy of Listerine antiseptic in inhibiting development of plaque and gingivitis, J Clin Periodontol 12:697–699, 1985. 28. Ogaard B, Alm AA, Larsson E, et al: A prospective, randomized clinical study on the effects of an amine fluoride/stannous fluoride toothpaste/mouthrinse on plaque, gingivitis and initial caries lesion development in orthodontic patients, Eur J Orthod 28:8–12, 2006. 29. Davies RM: Manual versus powered toothbrushes: what is the evidence? Dent Update 33:159–162, 2006. 30. Deery C, Heanue M, Deacon S, et al: The effectiveness of manual versus powered toothbrushes for dental health: a systematic review, J Dent Res 32:197–211, 2004. 31. Deacon SA, Glenny AM, Deery C, et al: Different powered toothbrushes for plaque control and gingival health, Evid Based Child Health 6:2275–2321, 2011. 32. Sicilia A, Arregui I, Gallego M, et al: A systematic review of powered vs manual toothbrushes in periodontal cause-related therapy, J Clin Periodontol 29(Suppl 3):39–54, 2002. 33. Robinson PG, Deacon SA, Deery C, et al: Manual versus powered toothbrushing for oral health, Cochrane Database Syst Rev (2):2005, CD002281. 34. Williams K, Rapley K, Haun J, et al: Comparison of rotation/ oscillation and sonice power toothbrushes on plaque and gingivitis for 10 weeks, Am J Dent 22:345–349, 2009. 35. Sicilia A, Arregui I, Gallego M, et al: Home oral hygiene revisited. Options and evidence, Oral Health Prev Dent 1 (Suppl 1):407–422, 2003. 36. Erbe C, Klukowska M, Tsaknaki I, et al: Efficacy of 3 toothbrush treatments on plaque removal in orthodontic patients assessed with digital plaque imaging: a randomized controlled trial, Am J Orthod Dentofacial Orthop 143:760–766, 2013. 37. Willmann DE, Norling BK, Johnson WN: A new prophylaxis instrument: effect on enamel alterations, J Am Dent Assoc 101:923–925, 1980. 38. Weaks LM, Lescher NB, Barnes CM, et al: Clinical evaluation of the Prophy-Jet as an instrument for routine removal of tooth stain and plaque, J Periodontol 55:486–488, 1984. 39. Mishkin DJ, Engler WO, Javed T, et al: Clinical comparison of the effect on the gingiva of the Prophy-Jet and the rubber cup and paste techniques, J Periodontol 57:151–154, 1986. 40. Barnes CM, Russell CM, Gerbo LR, et al: Effects of an airpowder polishing system on orthodontically bracketed and banded teeth, Am J Orthod Dentofacial Orthop 97:74–81, 1990. 41. Ramaglia L, Sbordone L, Ciaglia RN, et al: A clinical comparison of the efficacy and efficiency of two professional

42.

43.

44.

45. 46. 47. 48.

49.

50.

51. 52.

53.

54. 55. 56. 57. 58.

59.

prophylaxis procedures in orthodontic patients, Eur J Orthod 21:423–428, 1999. Forsberg CM, Brattstrom V, Malmberg E, et al: Ligature wires and elastomeric rings: two methods of ligation, and their association with microbial colonization of Streptococcus mutans and lactobacilli, Eur J Orthod 17:417–420, 1991. Pellegrini P, Sauerwein R, Finlayson T, et al: Plaque retention by self-ligating versus elastomeric orthodontic brackets: quantitative comparison of oral bacteria and detection using ATP-driven bioluminescence, Am J Orthod Dentofac Orthop 135:e426–e427, 2009. Buck T, Pellegrini P, Sauerwein R, et al: Elastomeric-ligated vs. self-ligating appliances: a pilot study examining microbial colonization and white spot lesion formation after 1 year of orthodontic treatment, Orthodontics 12:108–121, 2011. Zachrisson BU: Bonding in orthodontics. In Graber TM, Vanarsdall Jr RL, editors: Orthodontics: current principles and techniques, 5 ed., St Louis, 2012, Mosby. Boyd RL, Baumrind S: Periodontal considerations in the use of bonds or bands on molars in adolescents and adults, Angle Orthod 62:117–126, 1992. Erbe C, Hornikel S, Schmidtmann I, et al: Quantity and distribution of plaque in orthodontic patients treated with molar bands, J Orofac Orthop 72:13–20, 2011. Boyd RL, Leggott PJ, Quinn RS, et al: Periodontal implications of orthodontic treatment in adults with reduced or normal periodontal tissues versus those of adolescents, Am J Orthod Dentofacial Orthop 96:191–199, 1989. Zachrisson BU: Periodontal changes during orthodontic treatment. In McNamara Jr JA, Ribbens KA, editors: Orthodontic treatment and the periodontium, Monograph 15, Craniofacial growth series, Ann Arbor, 1984, Center for Human Growth and Development, The University of Michigan, pp 43–65. Artun J, Urbye KS: The effect of orthodontic treatment on periodontal bone support in patients with advanced loss of marginal periodontium, Am J Orthod Dentofacial Orthop 93:143–148, 1988. Melsen B, Agerbaek N, Eriksen J, et al: New attachment through periodontal treatment and orthodontic intrusion, Am J Orthod Dentofacial Orthop 94:104–116, 1988. Melsen B, Kragskov J: Tissue reaction to intrusion of periodontally involved teeth. In Davidovitch Z, editor: The biological mechanisms of tooth movement and craniofacial adaptation, Columbus, OH, 1992, The Ohio State University, College of Dentistry, pp 423–430. Ericsson I, Thilander B, Lindhe J, et al: The effect of orthodontic tilting movements on the periodontal tissues of infected and non-infected dentitions in the dog, J Clin Periodontol 4:115–127, 1977. Ericsson I, Thilander B, Lindhe J: Periodontal condition after orthodontic tooth movements in the dog, Angle Orthod 48:210–218, 1978. Machen DE: Periodontal evaluation and updates: don’t abdicate your duty to diagnose and supervise, Am J Orthod Dentofacial Orthop 98:84–85, 1990. Zachrisson BU: Clinical implications of recent orthodonticperiodontic research findings, Semin Orthod 2:4–12, 1996. Proffit WR, Fields Jr. HW: Special considerations in comprehensive treatment of adults. In Rudolph P, editor: Contemporary orthodontics, ed 5, St Louis, 2013, Mosby. Boyd RL, Leggott PJ, Quinn RS, et al: Periodontal implications of orthodontic treatment in adults with reduced or normal periodontal tissues versus those of adolescents, Am J Orthod Dentofacial Orthop 96:191–198, 1989. Artun J, Osterberg SK: Periodontal status of teeth facing extraction sites long-term after orthodontic treatment, J Periodontol 58:24–29, 1987.


60. Thilander B: Infrabony pockets and reduced alveolar bone height in relation to orthodontic therapy, Semin Orthod 2:55–61, 1996. 61. Ericsson I, Thilander B, Lindhe J: Periodontal condition after orthodontic tooth movements in the dog, Angle Orthod 48:210–218, 1978. 62. Ericsson I, Thilander B, Lindhe J, et al: The effect of orthodontic tilting movements on the periodontal tissues of infected and non-infected dentitions in dogs, J Clin Periodontol 4:278–293, 1977. 63. 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 43:402–411, 1973. 64. Bollen A-M, Cunha-Cruz J, Bakko DW, et al: The effects of orthodontic therapy on periodontal health. A systematic review of controlled evidence, J Am Dent Assoc 139:413–422, 2008. 65. Bernimoulin JP, Curiloviec Z: Gingival recession and tooth mobility, J Clin Periodontol 4:107–114, 1977. 66. Maynard JG, Ochsenbein LD: Mucogingival problems, prevalence and therapy in children, J Periodontol 46:543–552, 1975. 67. Vanarsdall RL, Corn H: Soft-tissue management of labially positioned unerupted teeth, Am J Orthod 72:53–64, 1977. 68. Wennström JL: The significance of the width and thickness of the gingiva in orthodontic treatment, Dtsch Zahnarztl Z 45:136–141, 1990. 69. Wennström JL: Mucogingival surgery. In Lang NP, Karring T, editors: Proceedings of the 1st European workshop on clinical periodontology, Berlin, 1994, Quintessence, pp 113–209. 70. Thomson WM: Orthodontic treatment outcomes in the long term: findings from a longitudinal study of New Zealanders, Angle Orthod 72:449–455, 2002. 71. Renkema AM, Fudalej PS, Remkema A, et al: Development of labial gingival recessions in orthodontically treated patients, Am J Orthod Dentofacial Orthop 143:206–212, 2013. 72. Zanatta FB, Cunha Moreira CH, Rösing CK: Association between dental floss use and gingival conditions in orthodontic patients, Am J Orthod Dentofacial Orthop 140:812–821, 2011. 73. Graber TM, Vanarsdall RL: Orthodontics: current principles and techniques, ed 5, St Louis, 2012, Mosby. 74. Wennström JL: Mucogingival considerations in orthodontic treatment, Semin Orthod 2:46–54, 1996. 75. Årtun J, Osterberg SK, Kokich VG: Long-term effect of thin interdental alveolar bone on periodontal health after orthodontic treatment, J Periodontol 57:341–346, 1986. 76. Årtun J, Krogstad O: Periodontal status of mandibular incisors following excessive proclination: a study in adults with surgically treated mandibular prognathism, Am J Orthod Dentofacial Orthop 91:225–232, 1997. 77. Coatoam GW, Behrents RG, Bissada NF: The width of keratinized gingiva during orthodontic treatment: its significance and impact on periodontal status, J Periodontol 52:307–313, 1981. 78. Foushee DG, Moriarty JD, Simpson DM: Effects of mandibular orthognathic treatment on mucogingival tissue, J Periodontol 56:727–733, 1985. 79. Maynard JG: The rationale for mucogingival therapy in the child and adolescent, Int J Period Restor Dent 7:37–51, 1987. 80. Karring T, Numan S, Thilander B, et al: Bone regeneration in orthodontically produced alveolar bone dehiscences, J Periodont Res 17:309–315, 1982. 81. Steiner GG, Pearson JK, Ainamo J: Changes of the marginal periodontium as a result of labial tooth movement in monkeys, J Periodontol 52:314–320, 1981. 82. Wennstrom JL, Lindhe J, Sinclair F, et al: Some periodontal tissue reactions to orthodontic tooth movement in monkeys, J Clin Periodontol 14:121–129, 1987.

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83. American Academy of Periodontology informational paper, drugassociated gingival enlargement, J Periodontol 75:1424–1431, 2004. 84. Clocheret K, Dekeyser C, Carels C, et al: Idiopathic gingival hyperplasia and orthodontic treatment: a case report, J Orthod 30:13–19, 2003. 85. Stinnett E, Rodu B, Grizzle WE: New developments in understanding phenytoin-induced gingival hyperplasia, J Am Dent Assoc 114:814–816, 1987. 86. Dooley G, Vasan N: Dilantin hyperplasia: a review of the literature, J N Z Soc Periodontol 68:19–21, 1989. 87. Hall WB: Dilantin hyperplasia: a preventable lesion, Compendium (Suppl 14):S502–S505, 1990. 88. Hassell TM, Hefti AF: Drug-induced gingival overgrowth: old problem, new problem, Crit Rev Oral Biol Med 2:103–137, 1991. 89. Hancock RH, Swan RH: Nifedipine-induced gingival overgrowth. Report of a case treated by controlling plaque, J Clin Periodontol 19:12–14, 1992. 90. Salinas CF: Orodental findings and genetic disorders, Birth Defects 18:79–120, 1982. 91. Shapiro SD, Jorgenson RJ: Heterogeneity in genetic disorders that affect the orifices, Birth Defects 19:155–166, 1983. 92. American Academy of Periodontology: Glossary of periodontal terms, Chicago, 2001, American Academy of Periodontology. 93. Bowers GM, Chadroff B, Carnevale R, et al: Histologic evaluation of new attachment apparatus formation in humans. Part II, J Periodontol 60:675–682, 1989. 94. Bowers GM, Chadroff B, Carnevale R, et al: Histologic evaluation of new attachment apparatus formation in humans. Part III, J Periodontol 60:683–693, 1989. 95. Cole RT, Crigger M, Bogle G, et al: Connective tissue regeneration to periodontally diseased teeth. A histological study, J Periodontol Res 15:1–9, 1980. 96. Bowers GM, Chadroff B, Carnevale R, et al: Histologic evaluation of new attachment apparatus formation in humans. Part I, J Periodontol 60:664–674, 1989. 97. Consensus report. Periodontal regeneration around natural teeth, Ann Periodontol 1:667–670, 1996. 98. da Silva VC, Cirelli CC, Ribeiro FS, et al: Orthodontic movement after periodontal regeneration of class II furcation: a pilot study in dogs, J Clin Periodontol 33:440–448, 2006. 99. Cirelli JA, Marcantonio Jr. E, Adriana R, et al: Evaluation of anionic collagen membranes in the treatment of class II furcation lesions: a histometric analysis in dogs, Biomaterials 18:1227–1234, 1997. 100. Machtei EE, Schallhorn RG: Successful regeneration of mandibular class II furcation defects, Intl J Period Rest Dent 15:146–167, 1995. 101. Houser BE, Mellonig JT, Brunsvold MA, et al: Clinical evaluation of an organic bovine bone xenograft with a bioabsorbable collagen barrier in the treatment of molar furcation defects, Intl J Period Rest Dent 21:161–169, 2001. 102. Roberts WE, Turley PK, Brezniak N, et al: Bone physiology and metabolism, CA Dent Assoc J 15:54–61, 1987. 103. Diedrich PR: Guided tissue regeneration associated with orthodontic therapy, Semin Orthod 2:39–45, 1996. 104. Nemcovsky CE, Zubery Y, Artzi Z, et al: Orthodontic tooth movement following guided tissue regeneration: report of three cases, Int J Adult Orthod Orthognath Surg 11:347–355, 1996. 105. Stelzel MJ, Flores-de-Jacoby L: Guided tissue regeneration in a combined periodontal and orthodontic treatment: a case report, Int J Periodontics Restor Dent 18:189–195, 1998. 106. Aguirre-Zorzano LA, Bayona JM, Remolina A, et al: Postorthodontic stability of the new attachment achieved by guided tissue regeneration following orthodontic movement: report of 2 cases, Quintessence Int 30:769–774, 1999. 107. Reichert C, Götz W, Smeets R, et al: The impact of nonautogenous bone graft on orthodontic treatment, Quintessence Int 41:665–672, 2010.

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108. Ogihara S, Marks MH: Enhancing the regenerative potential of guided tissue regeneration to treat intrabony defect and adjacent ridge deformity by orthodontic extrusive force, J Periodontol 77:2093–2100, 2006. 109. Pinheiro ML, Moreira TC, Feres-Filho EJ: Guided bone regeneration of pronounced gingiva-alveolar cleft due to orthodontic space closure, J Periodontol 77:1091–1095, 2006. 110. Ogihara S, Want HL: Periodontal regeneration with or without limited orthodontics for the treatment of 2- or 3-wall infrabony defects, J Periodontol 81:1734–1742, 2010.

111. Caffesse RG, Dominguez LE, Nasjleti CE, et al: Furcation defects in dogs treated by guided tissue regeneration (GTR), J Periodontol 61:45–50, 1990. 112. Araujo MG, Carmagnola D, Berglundh T, et al: Orthodontic movement in bone defects augmented with Bio-Oss. An experimental study in dogs, J Clin Periodontol 28:73–80, 2001. 113. Attia MS, Shoreibah EA, Ibrahim SA, et al: Regenerative therapy of osseious defects combined with orthodontic tooth movement, J Int Acad Periodontol 14:17–25, 2012.

Orthodontics and Craniofacial Deformities

C HA P T ER

21

Kirt E. Simmons

T

he provision of orthodontic treatment to cleft/ craniofacial-affected patients, although being among the most challenging to treat, provides the most rewarding experience. Although these patients can benefit greatly from orthodontic/craniofacial orthopedic treatment, this requires a specialized knowledge of the unique features of these patients. Their anatomy, function, growth patterns, and concomitant systemic medical issues differentiate them from the typical orthodontic patient and treatment of same. Of course, although these patients may share generalities based on their craniofacial condition/syndrome, it is important when treating a particular patient to remember that he or she will have a unique presentation due to individual differences. The intent of this chapter is to introduce the reader to the typical presentation and treatment of these patients and perhaps entice a few to obtain fellowship training in this recognized subspecialty of orthodontics.

1. What is the most common craniofacial deformity? The most common craniofacial deformity is orofacial clefting, which affects all populations. Approximately 1 in 500 to 700 births will have some form of orofacial clefting: cleft of the lip, palate, or some combination of both.1 These clefts may be complete or incomplete, involve one or both sides, be isolated (i.e., nonsyndromic), or part of a more general syndrome (in about 20% of cases), and are variable in their distortions of the affected tissues and subsequent clinical presentations.

2. What are the common types of facial clefts? The common types of facial clefts are: • Cleft lip only, which may be unilateral or bilateral and may or may not involve the maxillary alveolus • Cleft palate only, which can vary from a submucous cleft of the palate (overtly it appears intact but the muscle and/or bone of the palate are deficient) to a complete cleft of the palate even involving the alveolus • Unilateral cleft lip and palate • Bilateral cleft lip and palate Each of these clefts of the lip and palate can be further subdivided into complete (in which the cleft extends completely through the lip and/or palate) or incomplete (in which some portion of the structures are not cleft).

3. When might cleft-affected patients be treated orthodontically/orthopedically? Effective orthodontic/orthopedic treatment requires a specialized knowledge of these patients’ unique features and typically involves several periods of time at various ages. Because of the intensive nature of orthodontic/orthopedic therapy, performing it in stages is preferable to long-term continuous treatment. The potential treatment stages to be considered are based on four developmental stages: infancy, primary dentition, mixed dentition, and permanent dentition. Orthodontic/orthopedic treatment is often provided at several of these developmental stages.

4. What is “presurgical orthopedics”? Orthopedic treatment of cleft-affected infants provided prior to any surgical lip or palate procedures, or “presurgical orthopedics,” was once routinely accepted as a necessary practice because of the dramatically distorted appearance of the maxilla common at birth (Fig. 21-1, A to C). Orthopedic alignment of maxillary segments, followed by bone grafting at the time of lip and/or palate closure, was proposed to allow normal function, growth, and development.2 However, this early bone graft surgery was consequently shown to affect future growth and development negatively,3,4 as compared with the relatively normal development observed in untreated subjects with clefts.5 Classically, this presurgical orthopedic treatment aimed to address the excessive maxillary distortion, especially in cases of bilateral clefts, in preparation for the surgical procedures to close the lip and palatal clefts. Pin- or screw-retained “jackscrew”-type or spring-loaded appliances (Fig. 21-2, A to B) are used to expand the posterior segments. Retraction of the premaxillary segments can be achieved with an additional screw component, elastic bands between the premaxillary segment and the posterior portion, or extraoral elastic traction across the premaxilla (see Fig. 21-2, C), either alone, or in conjunction with an active posterior expansion appliance or passive posterior “molding” appliance. At some craniofacial centers, preliminary surgical procedures are done (which can be following expansion), including lip adhesion, wherein elastic force of the healing lip retracts the premaxilla prior to the definitive lip/palate repair. There has been a revival of early orthopedic treatment at some centers recently with modifications of the appliances and primary alveolar bone grafting or alveolar periosteoplasty 271

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A

orthopedics is a modification of these earlier techniques to include a nasal stent and taping to mold the cleft nose and columella, known as nasal alveolar molding or the NAM technique.9 Immediate surgical results are quite positive, leading to its increased popularity among surgeons/centers. The technique is still somewhat controversial in terms of benefits versus expense/ risks; the long-term cost and effects are being evaluated with both positive and negative reports currently in the literature.10–13 In the future three-dimensional (3D) scanning and “printing” or prototyping may be used to produce these appliances—as one group in China has demonstrated, greatly decreasing the clinician’s time, appointments for adjustment, and potentially improving outcomes.14,15

5. What orthodontic treatment may be indicated for cleft-affected patients in the primary dentition?

B

C

FIG 21-1 Unrepaired complete clefts of the lip and palate. A and B, Bilateral; note the posterior arch collapse, protrusive premaxilla, short columella, and separation of the lip segments. C, Unilateral; note the distorted alveolar segments.

surgeries done at the same time as lip closure. The centers that advocate this early orthopedic/surgical treatment feel that it provides several potential benefits, including a better arch form, fewer fistulae, a decreased need for secondary alveolar bone grafting, and better surgical outcomes. Treatment choice must be determined by balancing the potential iatrogenic risks of presurgical expansion (e.g., damage to tooth buds, aspiration of materials, anesthetic and surgical procedural risks) and the additional treatment load against the positive benefits of treatment outcomes.5–8 The most recent addition to p resurgical

Depending on developmental and speech milestones, surgical closure of the palate is done between 9 and 18 months of age, leaving a cleft of the maxillary alveolus with buccal and/or lingual fistulae. Orthodontic treatment during this phase is relatively rare, usually involving treatment of deleterious habits, functional shifts, or space maintenance after premature tooth loss. Fixed or removable habit appliances can be used to address digit habits and/or to correct dental crossbites (Fig. 21-3). Crossbite interference should be eliminated when possible to prevent consequent unfavorable jaw growth, particularly if the patient has a functional shift of the mandible for intercuspation. Often, selective reduction of the interfering teeth suffices, but some cases require orthodontic expansion, which may involve anterior and/or posterior expansion. Unlike noncleft children, if the maxilla has no bony continuity across the palate or alveolus, the corrected crossbite should be retained passively with long-term retention until secondary bone grafting provides that bony continuity. Patients should be monitored for dental and overall development during this phase. In short-statured patients especially, delayed dental development may be an indication of growth hormone deficiency, since clefting is often associated with other midline defects, including pituitary and cardiovascular anomalies. These patients, if identified, should be referred to rule out a general growth disorder so that medical treatment can commence as soon as possible to allow the patient to reach their ideal height.

6. What orthodontic treatment may be indicated for cleft patients in the mixed dentition? EVALUATION OF NEEDS/TREATMENT PLANNING Orthodontic evaluation and the development of long-term treatment objectives are indicated at the start of this phase because of the relatively rapid changes in dental and facial growth and development, as well as the developing social and self-awareness of the patient at this time.16 Assessment will involve standard orthodontic records, as well as selected periapical, occlusal, and/or cone beam computed tomograpy (CBCT) radiographs to

Orthodontics and Craniofacial Deformities • CHAPTER 21

273

A

C

B

FIG 21-2 A, An infant orthopedic expansion appliance utilizing a midpalatal screw (jackscrew) and posterior hinge to expand the anterior portion of the lateral palatal shelves to allow retraction of the premaxilla. B, Palatal side of appliance. Note the stainless steel “staples” that are driven into the palate to maintain the appliance. C, An extraoral elastic traction band placed across the premaxilla to provide retraction following expansion of the posterior segments.

FIG 21-3 An example of a digit-sucking appliance in a cleftaffected patient. FIG 21-4 Patient with repaired bilateral cleft lip and palate exhibiting severe arch collapse of the posterior segments.

assess missing, supernumerary, and/or ectopically erupting teeth and/or bone quantity and anatomy in the cleft site. Most patients with cleft alveoli have a posterior crossbite and missing/malaligned maxillary incisors at this stage. The collapse of the maxillary segments, especially in bilateral cases, can be severe (Fig. 21-4). These patients will need expansion of the collapsed maxillary segment(s) and/or elimination of traumatic occlusion in preparation for alveolar bone grafting. Bone grafting is ideally performed when root formation of the erupting adjacent lateral incisor or canine is one-half to two-thirds complete17,18 so that complete eruption of the adjacent tooth, with its accompanying periodontal attachment, will inhibit further bone resorption of the graft.17,19 This timing is tricky because bone can only be grafted when there is bone on both sides of the cleft, yet erupting teeth resorb bone over

the follicle so this must be taken into account. If the adjacent tooth has resorbed the alveolar bone on one side of the cleft, then one must await eruption of that tooth to graft the area. Although these adjacent teeth generally erupt spontaneously, it is occasionally necessary to uncover them surgically and induce eruption via orthodontic traction, particularly for canines.17 ELIMINATION OF TRAUMATIC OCCLUSION A stable maxilla is necessary for bone graft healing. Thus, traumatic occlusion of teeth in the cleft region should be eliminated, when possible, through alignment of the offending (usually maxillary incisor) teeth. Great care must be used to prevent moving the roots into the cleft site prior to the


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graft, and adequate retention is recommended to allow re formation of the cortical bone along the root prior to surgical exposure. It is often best to delay orthodontic alignment until after the graft, because commonly there is only a thin layer of bone along the cleft side of the roots of adjacent teeth (Fig. 21-5, A). Denudation of roots during grafting can result in periodontal defects, ankylosis, root resorption, and/ or decreased alveolar bone mass on healing. If traumatic occlusion cannot be eliminated prior to graft placement, a fulltime bite splint can prevent traumatic occlusion while the graft heals.

A

B

C

FIG 21-5 Examples of expansion appliances in cleftaffected patients. A, Radiograph of a W-arch—note the thin layer of bone on the lateral aspect of the central incisor in the cleft edge. B, Removable maxillary expansion appliance; note the lingual shelf of acrylic on the side of the greater segment to utilize the lower arch to reinforce anchorage and provide greater expansion of the lesser segment. Inverted W stainless steel wire spring provides for expansion anteriorly. C, Bonded “fan” appliance in a patient with bilateral cleft lip and palate. The appliance utilizes posterior occlusal coverage to prevent traumatic occlusion of the incisors, because the premaxilla is flared by the lingual wires. Note that this appliance preferentially expands the anterior portion of the collapsed palatal shelves.

PRE-GRAFT EXPANSION The amount and timing of pre-graft expansion should be planned in consultation with the surgeon. Whereas expansion is valuable before bone grafting to optimize surgical access, segments must not be expanded beyond the limits of surgical closure. The ideal expansion would provide coordinated maxillary and mandibular arch forms. If this interferes with the graft prognosis, three options are posed: 1) delay the graft until adolescence and unite the segments with orthognathic or distraction surgery, 2) perform the graft with little or no expansion and attempt expansion later (which may require surgical assistance), or 3) accept the crossbite. If the patient is expected to need orthognathic maxillary advancement later, less expansion is indicated. Delaying the graft until adolescence may negatively affect the eruption or orthodontic movement of adjacent teeth, which could cause periodontal defects, caries, and social stigmata. In unilateral cleft-affected patients, further expansion is fairly predictable after alveolar bone grafting, although arch form may be compromised. However, post-graft expansion is less predictable in the bilateral situation, with the increased scarring and lack of a functional maxillary midline suture. There are several appliance designs that can be used for expansion: fixed-spring appliances (e.g., quad-helix, W-arch, or combinations; see Fig. 21-5, A), removable appliances with jackscrew devices or wire springs (see Fig. 21-5, B), or fixed jackscrew devices (e.g., “fan” appliance; see Fig. 21-5, C). Bilateral clefts with a posteriorly displaced premaxilla may require a separate appliance first to buccalize the premaxilla (Fig. 21-6), followed by the expander (see Fig. 21-5, C). The selection of appliances is based on several variables: the direction and extent of expansion needed, the teeth present, the expected resistance, access to the cleft area needed by the surgeon, and the compliance anticipated by the patient. Removable appliances are preferred for optimal hygiene, but they lend themselves to compliance problems and loss. Fixed appliances cause fewer such problems, but they cause greater hygiene problems that may lead to decalcification and caries. Spring appliances apply lighter forces, under the control of the orthodontist, and the quad-helix provides lighter forces over a greater range than

FIG 21-6 A “trombone”-style appliance utilizes elastic chain to advance the premaxilla out of crossbite. A separate expansion appliance is then utilized posteriorly followed by alveolar ridge bone grafting.


the W-arch. They also can be activated to expand segments differentially, which is quite useful because the lesser segment (or posterior segments in a bilateral cleft) is generally collapsed more anteriorly than posteriorly. However, repeated reactivation of spring-loaded appliances may be necessary to achieve the desired expansion. Jackscrew appliances are very rigid and generate high forces, resulting in rapid movement, but they require activation by the patient or a parent. They provide a specific amount and direction of expansion. Any fistulae present (including those unknown to the patient and/or clinician) tend to be enlarged during the expansion. Such fistulae are generally closed at the time of the alveolar bone graft. Ideally, the appliance should allow unimpeded surgical access, unless it is in a position to interfere with surgery; then the appliance can be modified beforehand or removed and replaced in the operating room. The appliance should be conducive to good oral hygiene, so as not to cause bone graft failure.20 For proper graft healing, expansion should be maintained for 4 to 6 months after surgery, either by retaining the passive expansion appliance or by replacing it with a removable acrylic retainer or fixed lingual arch (Fig. 21-7, A to B). With complete bilateral clefting, it is important to stabilize a mobile premaxilla through the time that the graft is incorporated into the host bone.20 This requires 6 weeks to 6 months, depending on graft size, tissue stretch and/or scarring, occlusal stability, and individual bone and soft tissue healing capacity. A full-time maxillary splint or heavy labial or lingual fixed appliance can provide this stability.

A

B

FIG 21-7 A fixed lingual arch maintains expansion after placing an alveolar bone graft and incorporating two finger springs to flare the central incisors. A modified W or lingual arch maintains the expansion obtained while allowing surgical access for the alveolar bone graft.

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An alternative approach advocates alveolar bone grafting at a younger age (5 to 7 years) followed by orthodontic stimulation of the graft by rapid expansion with a fixed-expansion (e.g., jackscrew type) appliance (see Fig. 21-5, C).21 Proponents of this method claim shorter orthodontic treatment time and prevention of maxillary horizontal hypoplasia. In theory, rapid expansion could elicit an effect similar to distraction osteogenesis at the cleft site. Initial maxillary incisor alignment can be done with fixed orthodontic appliances immediately after the graft. Generally, the patient then takes a break from active treatment and is placed in retention. If necessary, missing or unerupted teeth may be masked with a removable acrylic retainer with plastic pontics, and a temporary bonded lingual retainer (0.0175-inch multi-strand archwire) can be used to retain spaced incisors until comprehensive orthodontic treatment is begun. MAXILLARY PROTRACTION Following graft stabilization and initial incisor alignment, an orthodontic assessment is indicated to evaluate the patient’s pattern of maxillary and mandibular growth. Discordant monozygotic twin studies have revealed differences based on the type and severity of the cleft.22 Growth is essentially unaffected in patients with clefts of only the lip and alveolus. Cleft palate only can result in a shorter posterior face height, a steeper mandibular plane angle, and retrognathia. Complete unilateral cleft lip and palate can lead to failure of anterior maxillary growth, resulting in posterior and inferior displacement. Patients with very flat profiles, increased face heights, and/or Class III skeletal relationships generally exhibit a worsening of their condition with further growth. Significant skeletal deformities are often best treated with combined orthodontics and surgery, possibly in multiple stages. Young (approximately 8 years23–25) patients with mild maxillary deficient clefts may benefit from orthopedic forces for maxillary protraction via bonded full occlusal coverage acrylic splints19 or fixed banded23,24 intraoral appliances, with extraoral protraction force applied via elastic force to a facial mask. These masks differ in their various pads, bands, and frame styles, and they even include an American football-style helmet.23–26 This treatment can effectively correct anterior crossbites and improve the prognathic profile through a limited maxillary skeletal advancement (1 to 3 mm), maxillary dental advancement, and counterclockwise or posterior rotation of the mandible.23–25 The latest update to this technique uses the expansion appliance alternately to expand and constrict the maxilla repeatedly in rapid succession, followed by protraction of the lateral segments in wide bilateral clefts, to reduce the cleft gap and enhance maxillary advancement.26 Orthognathic surgery or distraction osteogenesis is indicated for patients with true mandibular prognathism, severe mandibular retrognathism, skeletal openbite, moderate to severe maxillary deficiency, or limited or no remaining craniofacial growth. BILATERAL CLEFT LIP AND PALATE: UNIQUE FEATURES Patients with complete bilateral cleft lip and palate may pose a number of challenges for the orthodontist: minimal coverage of

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A

FIG 21-8 A primary canine erupted through the facial skin in a patient with repaired bilateral cleft lip and palate. Teeth in the cleft margin can also erupt into the nasal cavity.

the maxillary incisors by the upper lip, a shallow maxillary labial vestibule, a short and tight upper lip with protrusive lower lip, large fistulae, palatal webs over the maxillary molar area, missing maxillary lateral incisors, ectopically erupting teeth (Fig. 21-8), and hypoplastic or missing central incisors. These individuals also suffer from scar contracture and oral and nasal dysfunction. At this stage, patients may exhibit a protrusive and mobile premaxilla, which usually contains two central incisors. Anterior crossbites are frequently observed, as are severe discrepancies between the three maxillary segments. The ideal vertical premaxillary position is difficult to assess because of common hypoplasia of the nose and/or upper lips, which can appear as vertical overdevelopment. Pre-graft orthopedic movement can usually correct a truly malpositioned premaxilla.26 The premaxilla may be repositioned laterally or intruded with a special jackscrew-type appliance,26 or rarely it may be necessary to surgically reposition it at the time of bone grafting, although this requires great care to prevent loss of perfusion.27 From age 4 years to maturity, forward premaxillary growth is half that of non-cleft patients, whereas mandibular growth is essentially the same.28 Owing to initial protrusion of the premaxilla, this growth differential usually ends with an acceptable maxillary/mandibular relationship by adolescence.28,29

7. What orthodontic treatment may be indicated for cleft patients in the permanent dentition? The most common problems at this point include missing, supernumerary and/or malformed teeth adjacent to the cleft area, residual maxillary constriction, displaced maxillary dental midline, frenal or periodontal abnormalities in the cleft, delayed dental development, and altered eruption patterns. Most patients with mild to moderate retrognathia can be treated with orthodontics alone, but a prognathic pattern or a severe retrognathic pattern (Fig. 21-9, A to B) requires orthognathic surgery or distraction osteogenesis.30 An important treatment planning consideration for many of these patients involves missing teeth, usually the lateral incisor(s). If the maxillary dental midline is on or off to the non-cleft side, the canine is mesially erupted with reasonable root position and is fairly small and white, both premolars are

B

FIG 21-9 Bilateral cleft-affected patient exhibiting severe maxillary hypoplasia. A, Facial profile. B, Occlusion.

present on the affected side, and the molar/canine relationships are Class II, canine substitution can be an excellent choice. Prosthetic replacement is best when the maxillary canine is Class I or has a mesially displaced crown, but the root is still positioned distally, the maxillary midline is cleft-sided, incisors are retroclined, there are other missing teeth, and the molars are bilaterally Class I. With skeletal Class III patients, the choice also depends on whether orthognathic surgical procedures are planned. If interdental osteotomies are planned or insufficient bone exists preoperatively, some space should be left for the surgeon to close. Prosthetic replacement of lateral incisors can be accomplished through removable prostheses, fixed partial dentures, or osseointegrated dental implants (placed following active vertical facial growth and ideally with a minimum of 7-mm space). Children with skeletal problems (true mandibular prognathism, severe mandibular retrognathism, skeletal openbite, moderate to severe maxillary deficiency, or poor facial profiles), who will require orthognathic surgery in the long term, would not begin their comprehensive orthodontic treatment until 1 to 11⁄2 years prior to orthognathic surgery (ideally at the completion of active craniofacial growth). This is typically at 14 to 16 years of age for females and 16 to 18 years of age for males. Growth must be followed with serial lateral cephalometric radiographs at 6- to 12-month intervals. Limited treatment can address crowding, functional issues, and psychosocial issues, and/or eliminate or prevent traumatic occlusion, although the


benefits of such treatment must be realistically weighed against the risks of “burnout,” decalcification, root resorption, and periodontal problems.

8. What orthodontic treatment may be indicated for cleft-affected patients with significant skeletal discrepancies? Cleft-affected patients commonly need maxillary skeletal augmentation, which may involve skeletal advancement, expansion, and vertical displacement. If there is an openbite or mandibular asymmetry, protrusion, or retrusion, the surgery may also include the mandible. The effect of these procedures on facial esthetics and functional abilities to breathe and speak must be considered, with appropriate input from respective specialists. Preoperative orthodontic treatment involves full fixed appliances, but results in apparent “worsening” of the malocclusion due to the removal of natural dental compensations to align the teeth properly with respect to skeletal components. Errors on the side of excessive decompensation are preferred because they allow more aggressive surgical correction. This allows minor skeletal relapses that might occur postoperatively to be managed orthodontically. Preoperative orthodontic establishment of the mandibular arch form should occur early, which will involve reversal of existing dental compensations by expansion of upright, lingually tipped molar crowns, and the flaring and leveling of mandibular incisors. Extractions for crowding should be carefully assessed, and actively closing or deepening the bite preoperatively should not be done for patients who originally presented with an openbite or minimal overbite. Instead, the openbite should be allowed to persist or even open further, because the surgeon will close the bite skeletally. Extrusive posterior tooth movements should be performed preoperatively to minimize the prospect of openbite recurrence. All surgical plans should be approved by the patient’s orthodontist. Cleft-affected orthognathic surgery patients are at greater risk for maxillary relapse. To minimize this risk, the following measures should be explored: rigid fixation, overadvancement to weak Class I relationships, maxillary overexpansion, maintenance of a large (0.040 inch) expanded buccal wire postoperatively, bone grafting, postoperative extraoral traction, and maxillary strut fixation. Posteroanterior relapse should be monitored during the first 3 postoperative months via molar, canine, and incisor relationships. If relapse is present, it should be addressed with Class III elastics and/or reverse-pull headgear. The use of Class III elastics can open the bite by extruding the posterior maxillary teeth in conjunction with a verticalpull chin cup, straight vertical-pull headgear, and/or thick posterior bite blocks. Final lip and/or nose revisions are often best accomplished after orthodontic and orthognathic surgical procedures.

9. What syndromes are associated with clefting? There are many syndromes for which orofacial clefting is one finding. The most common of these include amnion rupture sequence, cerebro-costo-mandibular syndrome,

277

e ctrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, frontonasal dysplasia (median cleft face syndrome), Kabuki syndrome, Larsen syndrome, Stickler syndrome, Van der Woude syndrome, and velocardiofacial syndrome. For a complete listing, see Syndromes of the Head and Neck by Hennekam and colleagues.31

10. What are some other relatively common craniofacial deformities that an orthodontist may be called upon to treat? Some other relatively common craniofacial deformities are: • Craniosynostosis syndromes (craniofacial dysostosis syndromes), including Apert syndrome, Crouzon syndrome, Pfeiffer syndrome, Saethre-Chotzen syndrome, and Carpenter syndrome • Branchial arch and oral-acral syndromes, including oculo-auriculo-vertebral spectrum (hemifacial microsomia, Goldenhar syndrome), mandibulofacial dysostosis (Treacher Collins syndrome), acrofacial dysostosis (Nager acrofacial dysostosis, Nager syndrome) • Turner syndrome and the similar Noonan syndrome and cardio-facio-cutaneous (CFC) syndrome • Trisomy 21 syndrome (Down syndrome) • Alcohol embryopathy (fetal alcohol syndrome), as well as embryopathies from many other common drugs (cocaine, hydantoin, retinoic acid, thalidomide, valproate, and warfarin, to name a few) • Achondroplasia • Cleidocranial dysplasia • Marfan syndrome • Silver-Russell syndrome • Beckwith-Wiedemann syndrome (exomphalos-macroglossiagigantism syndrome) • Sturge-Weber syndrome • Prader-Willi syndrome • Peutz-Jeghers syndrome • Ehlers-Danlos syndrome • Neurofibromatosis • Ectodermal dysplasias

11. What deformities are common in the oculo-auriculo-vertebral spectrum of conditions, and what orthodontic treatment may be indicated? The most common of these are hemifacial microsomia and the more involved Goldenhar syndrome. Hemifacial microsomia, as the name suggests, involves a variable, progressive, and asymmetric deficiency, or absence, of portions of the face (Fig. 21-10, A to C). This spectrum of disorders is extremely heterogeneous with Goldenhar’s syndrome, which displays similar facial deficiencies, plus epibulbar dermoids and vertebral anomalies at the severe end of the spectrum. The first and second branchial arch derivatives are affected, including the bone and neuromuscular and soft tissues. The ears may be small to nonexistent, as may be the mandibular ramus and associated muscles, often with an aberrant or missing temporomandibular joint (TMJ). The occlusal plane is tilted superiorly

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A

B

C

FIG 21-10 Young patient with an oculo-auriculo-vertebral disorder affecting her right side. A and B, Note the dysplastic and severely displaced ear. C, Note the dysplastic ramus and condyle on the affected side.

on the affected side, and the ear and orbit are typically displaced inferiorly. Due to the wide variability of expression in these conditions, they have been grouped into types and subtypes by various authors (ranging from I-III to I-V), based on the extent of the mandibular deformity, with the higher number generally indicating increased deficiencies of the ramus.32–35 The one significant aberration from this generality is the Harvold Type III, which indicates an ankylosis or syndesmosis of the TMJ. Jaw function and opening are often adequate, except in ankylosed/syndesmotic cases. In these severe cases, surgical treatment is indicated as soon as is practical, to release the ankylosis and allow growth of the mandible to occur (Fig. 21-11, A to B). In addition, some of these children will have had tracheostomies, and release of the ankylosis and/or advancement of the mandible are indicated to decannulate these children prior to school age. Ideally primary teeth will be present to allow the placement of an appliance to protract the mandible and provide for physiotherapy (i.e., opening exercises with assistance) to prevent re-ankylosis and loss of function. A later surgery to reconstruct the ramus and TMJ, potentially including distraction osteogenesis, will be likely.

In the more common non-ankylosed types, treatment is also complex and involves many years of integrated therapy, best provided by a craniofacial team approach. The treatment timing and indications are dependent on the phenotypic presentations of the case. For an excellent detailed review of treatment, the reader is referred to Vargervik and Kaban.36 In short, in cases where the TMJ is small, but functional, a Bionator-type functional appliance is indicated in the mixed dentition. This asymmetric appliance advances and lowers the mandible while allowing for maxillary dental eruption on the affected side. The goals of this appliance are to relieve the occlusal cant on the affected side and stimulate downward and forward growth of the mandible on the affected side, to match that of the unaffected side. In addition, the orthodontist should manage the dental crowding and impactions often seen on the affected side. In certain cases, this treatment can eliminate the need for surgery, although good cooperation and long-term treatment are necessary. In the permanent dentition stage, orthodontic treatment will be indicated for many of these patients to prepare them for surgical correction. Alignment of the teeth and coordination of arch forms are the goals of treatment at


A

279

B

FIG 21-11 A, Young patient with severe retrogenia due to ankylosis of the temporomandibular joints (TMJs). B, Same patient after advancement of mandibular corpus and surgical reconstruction of ramus and joint.

this time. If the occlusal plane is still canted, another period of an intraoral splint, to allow active extrusion of the maxillary teeth on the affected side and leveling of the maxillary occlusal plane, can be done if maxillary surgery is not desired or is contraindicated. In patients having a severely aberrant condylar process, the treatment protocol is essentially the same, with surgical correction indicated for the mandible, and maxilla, if necessary. Surgical correction of the mandible, depending on the expertise and preference of the surgeon involved, can take many forms, including rib grafts, distraction, iliac crest grafts, calvarial grafts, and so on. Timing of surgery is somewhat controversial, with some surgeons advocating early surgery in the mixed dentition and others later in adolescence. For review of the types and timing of surgeries for these conditions, the reader is referred to Kearns and colleagues.37 If presurgical maxillary leveling is inadequate or not possible, postsurgical extrusion of the maxillary teeth will be indicated. The vertical correction of the mandibular ramus on the affected side results in an openbite, which must be supported by a postsurgical splint, regardless of the surgical technique. The openbite is closed by progressive reduction of the postsurgical splint on the maxillary side, allowing eruption of the maxillary molar into occlusion first, followed by the premolars. In the more severe cases, those lacking any condylar process and those also lacking a coronoid process, a first stage of reconstruction occurs in the mixed dentition, typically at 6 to 10 years of age. Since these patients lack a glenoid fossa and TMJ, they require construction of a fossa and pseudo-TMJ, plus construction of a condyle and ramus. Ideally the location of the new pseudo-TMJ will be as lateral and posterior as possible, and the lower borders of the mandible will be level at the time of this surgery. This results in an openbite on the affected side, to be managed as described earlier with a postsurgical splint and extrusion. These patients typically require a second phase of orthodontic treatment in adolescence, followed by orthognathic surgery and/or distraction osteogenesis, as well as soft tissue augmentation (Fig. 21-12).

12. What deformities are common in the craniosynostosis syndromes, and what orthodontic treatment may be indicated? Of the craniosynostosis (craniofacial dysostosis) syndromes, the most common are Apert syndrome and Crouzon syndrome. These syndromes, due to similar defects in the fibroblast growth factor receptor genes, not surprisingly share some phenotypic expressions and autosomal dominant transmission. They are both characterized by craniosynostosis and some degree of mid-facial hypoplasia with resultant relative mandibular prognathism. Apert syndrome also has symmetric syndactyly (fusing of digits) of the hands and feet, proptosis (bulging eyes), lateral palatal swellings, severe maxillary dental crowding with V-shaped arch and displaced teeth, anterior openbite, and anterior and posterior crossbites (Fig. 21-13).31 Crouzon syndrome is similar, but it is characterized by shallow orbits and severe ocular proptosis. It has a more variable expression

FIG 21-12 Extraoral distractor applied to a patient affected by hemifacial microsomia.

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B

A

C

FIG 21-13 A patient with Apert syndrome. A and B, Note the midface deficiency, (C) palatal swellings, V-shaped arch, and severe crowding.

than Apert syndrome. Palatal swellings are often present but less pronounced, although the maxillary hypoplasia with dental crowding, ectopic eruption, anterior openbite, and anterior and posterior crossbites is similar. Both syndromes can exhibit a reverse curve of Spee in the lower arch. These patients typically undergo at least three stages of reconstructive surgery: release of involved cranial sutures with advancement and reshaping of the supraorbital rim within the first year; Le Fort III, monobloc, or facial bipartition advancements typically at 4 to 8 years; and, last, a Le Fort I osteotomy advancement with or without genioplasty, rhinoplasty, contour bone grafting, and/or canthoplasties.38 Orthodontic treatment usually commences following the second stage of reconstructive surgery in the mixed dentition and involves management of the dental crowding, often with extractions. Although the relative mandibular prognathism may be much improved after this second reconstructive procedure, it is important to prepare the patient and parents for its predictable return, as the mandible continues to complete its growth while the maxilla stays essentially unchanged. The orthodontist should monitor facial growth with yearly cephalometric films or 3D computed tomographies (CTs) and begin the final stage of orthodontic

preparation in anticipation of the completion of facial growth, at which time the final maxillary advancement will be performed to correct the maxillary hypoplasia. These orthodontic procedures are typical of preparation for orthognathic surgery, common to maxillary deficient patients, including alignment and coordination of arches.

13. What deformities are common in mandibulofacial dysostosis (Treacher Collins syndrome), and what orthodontic treatment may be indicated? This syndrome, with autosomal dominant inheritance and variable expressivity, involves the derivatives of the first and second pharyngeal arch, groove, and pouch.31 The deformities are bilateral, but not necessarily symmetric, and include ear deformities, malar hypoplasia, and mandibular hypoplasia (Fig. 21-14). The clinical presentation is characteristic and includes malformed pinnae, often accompanied by conductive hearing loss, hypoplastic supraorbital rims and zygomas with downslanting palpebral fissures and sunken cheekbones, and a hypoplastic mandible deficient in the ramus and body. In addition, the mandible exhibits a steep mandibular plane angle, a


A

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B

C

FIG 21-14 A patient with mandibulofacial dysostosis. A and B, Note the downslanting palpebral fissures, hearing aids, lack of cheekbones, relatively protrusive nose, and (C) anterior openbite and crowding.

reverse curve of Spee, retrogenia, obtuse gonial angle, and condylar cartilage of the hyaline type rather than fibrocartilage.31 There is no articular eminence, limited opening, and the maxilla is often small with an anterior openbite skeletal pattern and posterior vertical deficiency. Dental crowding can be severe, and cleft palate and palatopharyngeal incompetence are fairly common, as is macrostomia. Treatment may involve early mandibular distraction to prevent tracheostomy due to severe airway difficulties or to allow decannulation in those patients already tracheostomized. This should be reserved for these cases, due to the significant potential morbidity of this technique at an early age.39 The goals of orthodontic treatment should be to manage the crowding and eruption problems as indicated during the mixed dentition, but comprehensive orthodontic treatment should be delayed until facial skeletal growth is nearing completion. At that time orthodontic treatment should commence, in preparation for two-jaw orthognathic and/or distraction procedures.

14. What are some other common syndromes of interest to orthodontists? Turner syndrome is a chromosomal disorder, with classically affected individuals having only a single X chromosome.

These patients are phenotypically female, are of short sta ture with sexual infantilism, and have variable expression of somatic abnormalities. The classic somatic abnormalities include a webbed neck, epicanthal folds, shield neck, cardiovascular abnormalities, abnormal ears, and low hairline (Fig. 21-15, A and B).31 Dental and facial abnormalities include advanced dental age, small teeth, short roots, lateral palatal bulges, a short cranial base, and maxillary and mandibular retrognathia (Fig. 21-15, C).40 From an orthodontic viewpoint, this syndrome is of interest because in mild form, these patients are often not diagnosed until puberty, when they fail to go through menarche. An astute orthodontist may be able to refer these patients at an earlier age, allowing an early diagnosis. In addition, when treating these patients, it is wise to keep in mind the high proportion with cardiovascular anomalies and the tendency for short roots and root resorption. Currently most of these patients undergo growth hormone therapy once diagnosed and eventually sex hormone therapy as well, which can have definite effects on craniofacial growth. For this reason it is wise to consult with the patient’s endocrinologist regarding treatment timing and to consider the differential effect of sex and growth hormones on mandibular versus maxillary growth.

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A

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C

FIG 21-15 A patient with Turner syndrome. A and B, Note the low-set unusual ears, webbed neck, low hairline, retrognathia, and (C) lateral palatal bulges.

Another chromosomal disorder, trisomy 21 (Down) syndrome, is the most common malformation syndrome, having an incidence of about 1 in 650 live births.31 These patients are typically short, with hypotonia, upslanting palpebral fissures, short neck, and mental retardation (Fig. 21-16, A). Orofacially these patients have a flat facial profile due to midface hypoplasia, a characteristic open mouth posture with protruding tongue, hypoplastic sinuses, and delayed and irregular dental eruption (see Fig. 21-16, B). They also commonly have cardiovascular anomalies, a high incidence of periodontal disease (purportedly due to immune system compromises and oral respiration) and sleep apnea, fissures of the tongue, missing teeth, and anomalous teeth.41 An anterior openbite, posterior crossbite, and spaced mandibular incisors with reverse overjet are often manifest, secondary to the midface hypoplasia and anterior tongue posture. Early (6 months of age ideally) functional therapy, consisting of manual therapy, in conjunction with removable or fixed appliances, which contain acrylic bumps on the facial to stimulate the upper lip and an oval midline “bead” for the tongue to “play” with, has been advocated to improve the hypotonia of the lips and tongue and prevent some of the typical sequelae of the chronic open mouth posture.42 Due to their constellation of facial and dental problems, these patients are clearly candidates for orthodontic care. Although access to orthodontic care for these patients is often difficult for a variety of reasons, including financial and transportation,

rthodontists should not arbitrarily preclude these patients o from their practice.43 Although the basic treatment goals of these patients should not be altered, provision of care should involve some modifications specific to these individuals. Staged or multiphase treatment is often beneficial, as are shorter, morning appointments with limited procedures and additional time set aside, because these patients require extra patience on the part of the orthodontist and assistant. Parents and/or siblings can often be very helpful in attaining compliance, and it is imperative to actively involve them in home care of the appliances. The high incidence of cardiovascular problems, sleep apnea, and periodontal disease must be taken into account when deciding on treatment therapies. Sleep apnea therapies may be contraconducive to certain orthodontic treatments (such as oral-nasal positive airway pressure masks and reverse-pull headgear), whereas certain orthodontic/orthognathic therapies (such as maxillary expansion and maxillo-mandibular advancement) may have a positive effect on sleep apnea. Therefore it is important to identify these patients, refer them for an evaluation if sleep apnea is suspected but has not been diagnosed, and consult with the physician treating them to develop a coordinated treatment plan. In the office, all procedures should be carefully explained to the patient and parent and demonstrated to them. Every effort should be made to become “friends” with the patient first and develop a trusting relationship prior to instituting treatment. In addition, keeping appointments and procedures


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A B

FIG 21-16 A young man with trisomy 21 (Down) syndrome. A, Note the open mouth posture and hypotonia; (B) classic anterior openbite, marginal gingivitis, and retained food.

A B

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D

FIG 21-17 Cleidocranial dysplasia. A, Note the midface deficiency and broad face; (B) unerupted incisors bonded with pads and gold chains; (C) fixed eruptive appliance supported by first molars and primary molars with openings for chain to pass through. Elastic thread is tied to chains to apply eruptive force; (D) chains on upper unerupted incisors with hooks bent onto the chains to allow interarch elastics to be placed.

“fun” and providing rewards is important. These patients generally have a happy, friendly demeanor once their trust is gained and can make very good patients, although they can be obstinate at times and easily distracted (not always a liability). Finally, cleidocranial dysplasia (dysostosis) is an interesting syndrome with autosomal dominant inheritance. These

patients are short with a broad skull, pronounced biparietal and frontal bossing, depressed nasal bridge, hypertelorism (wide-set eyes), hypoplasia of the maxilla and zygomas with a short cranial base, and deficiency of the clavicles (allowing many patients to approximate their shoulders and resulting in a drooped shoulder appearance) (Fig. 21-17, A).31 Orally they

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FIG 21-18 Panoramic film of a patient with cleidocranial dysplasia. Note the failure of eruption and multiple, tightly packed supernumerary teeth.

present with a high arched palate, deficient premaxilla with relative prognathism due to normal mandibular length, multiple supernumerary teeth, multiple crown deformities, and lack of eruption of the permanent teeth.31 The primary teeth erupt normally, but often resorb poorly, and the permanent molars usually erupt, as well as occasionally the incisors, but the premolars and canines rarely erupt.44 Eruption of the permanent teeth is not induced by simple extraction of the primary teeth.45 Supernumerary teeth are common, especially in the maxillary incisor and canine regions as well as in the mandibular premolar regions, and these teeth are often dysplastic with dilacerated and deformed roots (possibly due to severe spatial restrictions in the alveolus).46 Assisted eruption of the unerupted teeth should be planned carefully in stages, utilizing the remaining primary teeth and erupted permanent teeth as anchorage, if possible.47 A typical plan would involve extraction of any remaining primary incisors with uncovering and bonding of traction hooks or chains to the unerupted incisors (see Fig. 21-17, B). Fixed appliances on the remaining primary posterior teeth and permanent first molars can be utilized to place eruptive archwires (see Fig. 21-17, C). Alternatively, a reciprocal anchorage concept can be employed, with the patient placing elastics between the maxillary and mandibular teeth (see Fig. 21-17, D). Once the permanent incisors are erupted roughly into contact, they can be bonded with fixed appliances, the primary molars and canines extracted, supernumerary teeth removed, and traction hooks or chains placed on the permanent premolars and canines. The permanent molars and incisors can then support the eruptive archwires to these teeth, although it may still be helpful to employ interarch vertical elastics. Due to the great number of supernumerary teeth present and close proximity of some of the teeth (Fig. 21-18) that are desirable to keep, this stage may require more than one surgical uncovering and placement of traction appliances. Second molars may also benefit from uncovering and placement of eruptive forces. Once all the permanent teeth are erupted, they are aligned, the arches coordinated, and a maxillary Le Fort I advancement and inferior displacement will be necessary for many of these patients. This complex treatment often requires a long duration with multiple surgeries

and challenges in eating/speech during the treatment. It is a disservice to the patient and families involved not to ensure they are comfortable with and willing to undergo these challenges prior to initiation of treatment. REFERENCES 1. World Health Organization: Human genetics programme: international collaborative research on craniofacial anomalies (website): www.who.int/genomics/anomalies/en/. Accessed March 18, 2014. 2. Latham RA: Orthopedic advancement of the cleft maxillary segment: a preliminary report, Cleft Palate J 17:227–233, 1980. 3. Graber TM: Craniofacial morphology in cleft palate and cleft lip deformities, Surg Gynecol Obstet 88:359–369, 1949. 4. Berkowitz S: Timing of cleft palate closure—age should not be the sole determinant, J Cranio Genet Dev Biol (Suppl 1):69–83, 1985. 5. Mestre JC, DeJesus J, Subtelny JD: Unoperated oral clefts at maturation, Angle Orthod 30:78–85, 1960. 6. Millard DR, Berkowitz S, Latham RA, et al: A discussion of presurgical orthodontics in patients with clefts, Cleft Palate J 25:403–412, 1988. 7. Huddart AG: An evaluation of pre-surgical treatment, Br J Orthod 1:21–25, 1973. 8. Subtelny JD: Orthodontic principles in treatment of cleft lip and palate. In Bardach J, Morris HL, editors: Multidisciplinary management of cleft lip and palate, Philadelphia, 1990, WB Saunders, pp 615–636. 9. Grayson BH, Cutting CB: Presurgical nasoalveolar orthopedic molding in primary correction of the nose, lip, and alveolus of infants born with unilateral and bilateral clefts, Cleft Palate Craniofac J 38(3):193–198, 2001. 10. Garfinkle JS, King TW, Grayson BH, et al: A 12-year anthropometric evaluation of the nose in bilateral cleft lip-cleft palate patients following nasoalveolar molding and cutting bilateral cleft lip and nose reconstruction, Plast Reconstr Surg 127(4):1659–1667, 2011. 11. Clark SL, Teichgraeber JF, Fleshman RG, et al: Long-term treatment outcome of presurgical nasoalveolar molding in patients with unilateral cleft lip and palate, J Craniofac Surg 22(1):333–336, 2011. 12. Uzel A, Alparslan ZN: Long-term effects of presurgical infant orthopedics in patients with cleft lip and palate: a systematic review, Cleft Palate Craniofac J 48(5):587–595, 2011. 13. van der Heijden P, Dijkstra PU, Stellingsma C, et al: Limited evidence for the effect of presurgical nasoalveolar molding in


unilateral cleft on nasal symmetry: a call for unified research, Plast Reconstr Surg 131(1):62e–71e, 2013. 14. Yu Q, Gong X, Wang GM, et al: A novel technique for presurgical nasoalveolar molding using computer-aided reverse engineering and rapid prototyping, J Craniofac Surg 22(1):142–146, 2011. 15. Gong X, Yu Q: Correction of maxillary deformity in infants with bilateral cleft lip and palate using computer-assisted design, Oral Surg Oral Med Oral Pathol Oral Radiol 114(5 Suppl):S74–S78, 2012. 16. Moore RN: Orthodontic management of the patient with cleft lip and palate, Ear Nose Throat J 65:46–58, 1986. 17. El Deeb M, Messer LB, Lehnert MW, et al: Canine eruption into grafted bone in maxillary alveolar cleft defects, Cleft Palate J 19:9–16, 1982. 18. Hall HD, Werther JR: Conventional alveolar cleft bone grafting, Oral Maxillofac Surg Clin North Am 3:609–616, 1991. 19. Bergland O, Semb G, Abyholm FE: Elimination of residual alveolar cleft by secondary bone grafting and subsequent orthodontic treatment, Cleft Palate J 23:175–205, 1986. 20. Vig KWL, Turvey TA: Orthodontic-surgical interaction in the management of cleft lip and palate, Clin Plas Surg 12:735–748, 1985. 21. Boyne PJ: Bone grafting in the osseous reconstruction of alveolar and palatal clefts, Oral Maxillofac Surg Clin North Am 3:589–597, 1991. 22. Simmons KE, Johnston MC: Craniofacial morphology of monozygotic twins discordant for clefts of the lip and/or palate. Presentation to ACPA Meeting, St. Louis, Missouri, 1990. 23. Verdon P: Utilisation raisonnée du masque orthopédique facial, Orthodontie, Tours, 1989. 24. Tindlund RS, Rygh P, Boe OE: Orthopedic protraction of the upper jaw in cleft lip and palate patients during the deciduous and mixed dentition periods in comparison with normal growth and development, Cleft Palate Craniofac J 30:182–194, 1993. 25. Tindlund RS, Rygh P: Maxillary protraction: different effects on facial morphology in unilateral and bilateral cleft lip and palate patients, Cleft Palate Craniofac J 30:208–221, 1993. 26. Buschang PH, Porter C, Genecov E, et al: Face mask therapy of preadolescents with unilateral cleft lip and palate, Angle Orthod 64:145–150, 1994. 27. Vig KWL, Turvey TA, Fonseca RJ: Orthodontic and surgical considerations in bone grafting in the cleft maxilla and palate. In Turvey TA, Vig KWL, Fonseca RJ, editors: Facial clefts and craniosynostosis. Principles and management, Philadelphia, 1996, WB Saunders, pp 396–440. 28. Vargervik K: Growth characteristics of the premaxilla and orthodontic treatment principles in bilateral cleft lip and palate, Cleft Palate J 20:289–302, 1983. 29. Friede H, Pruzansky S: Longitudinal study of growth in bilateral cleft lip and palate from infancy to adolescence, Plast Reconstr Surg 49:392–403, 1972.

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30. Ross RB: Treatment variables affecting facial growth in complete unilateral cleft lip and palate, Cleft Palate J 24:3–77, 1987. 31. Hennekam RCM, Allanson J, Krantz I, editors: Oxford monographs on medical genetics: no. 58 Syndromes of the head and neck, ed 5, New York, 2010, Oxford University Press. 32. Pruzansky S: Not all dwarfed mandibles are alike, Birth Defects 1:120–129, 1969. 33. Harvold EP, Vargervik K, Chierici G, editors: Treatment of hemifacial microsomia, New York, 1983, Alan R. Liss. 34. Kaban LB, Mulliken JB, Murray JE: Three-dimensional approach to analysis and treatment of hemifacial microsomia, Cleft Palate J 18:90–99, 1986. 35. Kaban LB, Moses ML, Mulliken JB: Surgical correction of hemifacial microsomia in the growing child, Plast Reconstruct Surg 82:9–19, 1988. 36. Vargervik K, Kaban LB: Hemifacial microsomia I. Diagnosis and management. In Bell WH, editor: Modern practice in orthognathic and reconstructive surgery, vol 2, Philadelphia, 1992, WB Saunders, pp 1533–1560. 37. Kearns G, Padwa BL, Kaban LB: Hemifacial microsomia: the disorder and its surgical management. In Booth PW, Schendel SA, Hausemen JE, editors: Maxillofacial surgery, ed 2, vol 2, Philadelphia, 2007, Elsevier Ltd, pp 918–946. 38. Posnick JC, Mühling J: Surgical treatment of craniofacial dysostosis syndrome and single-suture synostosis. In Booth PW, Schendel SA, Hausemen JE, editors: Maxillofacial surgery, ed 2, vol 2, Philadelphia, 2007, Elsevier Ltd, pp 876–900. 39. Koppel DA, Moos KF: Treacher Collins syndrome. In Booth PW, Schendel SA, Hausemen JE, editors: Maxillofacial surgery, ed 2, vol 2, Philadelphia, 2007, Elsevier Ltd, pp 947–958. 40. Simmons KE: Growth hormone and craniofacial changes: preliminary data from studies in Turner’s syndrome, Pediatrics 104(Suppl):1021–1024, 1999. 41. Pilcher ES: Dental care for the patient with Down syndrome, Down Synd Res Pract 5:111–116, 1998. 42. Hoyer H, Limbrock GJ: Orofacial regulation therapy in children with Down syndrome, using the methods and appliances of Castillo-Morales, ASDC J Dent Child 57:442–444, 1990. 43. Musich DR: Orthodontic intervention and patients with Down syndrome. The role of inclusion, technology and leadership, Angle Orthod 76:734–735, 2006. 44. Jensen BL, Kreiborg S: Development of the dentition in cleidocranial dysplasia, J Oral Pathol 19:89–93, 1990. 45. Winter GR: Dental conditions in cleidocranial dysostosis, Am J Orthodont 29:61–89, 1943. 46. Richardson A, Deussen FF: Facial and dental anomalies in cleidocranial dysplasia: a study of 17 cases, Int J Paediatr Dent 4:225–231, 1994. 47. Daskalogiannakis J, Piedade L, Lindholm TC, et al: Cleidocranial dysplasia: 2 generations of management, J Can Dent Assoc 72:337–342, 2006.

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Temporomandibular Disorders

Peter M. Greco

T

emporomandibular disorders (TMDs) involve musculoskeletal pain and functional disharmony of the masticatory system. TMD is one subcategory of orofacial pain that includes intracranial pain, headache, neuropathic pain, intraoral pain, and all other pains associated with the head and neck.1 The preliminary role of the dental practitioner is to discern whether the patient’s clinical presentation reveals a diagnosis of pathology or dysfunction that is within the realm of dental treatment and/or if the clinical diagnosis requires allied medical collaboration for effective management. Once the problem has been verified to be within the realm of dental therapy, the clinician must identify the source of the problem and treat accordingly. Often the originating source and symptomatic site of the pain are incongruous, which differs from conventional dental diagnosis. Unless the primary site from which the pain emanates is addressed by therapy, control of the problem will remain elusive.2 Hence, history and examination are critical to diagnosis, but also unlike most dental diagnoses, the importance of the patient’s history of the disorder is far more indicative than presenting signs. Keen diagnostic skills in the treatment of TMD are the key to successful management, as TMD is often a combination of etiologies rather than a single anatomical or functional disharmony. Combination of etiologies often complicates successful treatment and can frustrate the clinician and patient. Many diagnostic systems and algorithms of TMD have been proposed since otolaryngologist James Costen first published his findings in 1934. Costen3 described a small group of patients with ear/sinus symptoms in conjunction with functional disturbance of the temporomandibular joints (TMJs). Okeson2 has emphasized the importance of determining whether the presenting signs or symptoms are truly emanating from the region of complaint or whether the symptoms originate from a distant site by virtue of interaction of nerve fibers that coalesce in the upper spinal cord and brainstem. He applied the terms primary pain and secondary or heterotopic pain to these two phenomena, respectively. Successful delineation of primary and secondary pain can mean the difference between treatment success and failure, since quality treatment can unequivocally fail if applied to the incorrect site or misdiagnosed clinical situation. Consider a patient experiencing left-sided mandibular pain as a result of a myocardial infarction who is treated via delivery of a maxillary splint, which provides a perfect mutually protected occlusal scheme. The infarct remains of fatal potential despite apparent harmony of the masticatory system. 286

TMDs can be classified into several subcategories2: • Masticatory disorders, including protective co-contraction, persistent local muscular soreness, myofascial or triggerpoint pain, myospasm, chronic myositis, and fibromyalgia: These disorders predominate in frequency and are each managed differently. • Dysfunction of the joint complex itself, including disc displacements, disc/condyle/fossa incompatibilities including adhesions, and subluxation/dislocation: These problems may require surgical co-therapy and can often be anatomically documented by modern imaging techniques. • Inflammatory conditions, including capsulitis, synovitis, retrodiscitis, arthroses, and posttraumatic sequelae: Many are self-resolving and require little therapeutic management if diagnosed correctly. • Hypomobility, including ankylosis, muscle dysfunction, and anatomic impedance, ranging in need from continued surveillance to initiation of collaborative care with multiple co-therapists. • Growth disorders, including congenital bone and muscle disorders. Accurate diagnosis and classification are critical to proper management to determine therapeutic modalities and to assess the need for involvement of allied specialists. For example, as chronicity of TMD increases, so do the number of therapists needed for effective management given increasing difficulty in management. In general, dental practitioners are most effective at managing acute muscle problems but require increased collaboration to provide effective care as joint involvement and chronicity increase. The intent of this chapter is to address the most common questions pertaining to TMD that arise in dental practice. Hence, the approach to these questions is intended to be practical and applicable to routine care delivery.

1. When is treatment indicated for temporomandibular disorder? The presence of joint sounds is insufficient reason to implement therapy. Consequently, the persistence of joint sounds alone is an inadequate criterion for success or failure of therapy. Pain and/or loss of function are the hallmarks of need for treatment.2 As other weight-bearing joints of the body emit joint sounds during function, the TMJs are no exception. Thus, signs and symptoms of TMJ dysfunction are common but well tolerated and are often ignored by the patient.

Temporomandibular Disorders • CHAPTER 22

Although statistics vary, Dolwick and Dimitriulis4 report that 60% to 70% of the population display at least one sign of TMD and 25% display at least one symptom. It is more often seen in females than males. Furthermore, TMD is a phenomenon most commonly noted during the patient’s reproductive years with peak frequency between the ages of 25 and 44 years, and only 0.7% by age 65. Hence, it is logical to infer that signs and symptoms self-resolve without or in spite of therapy. This phenomenon has been termed regression to the means and occurs frequently in nature.2 Disc position is also not critically related to the success or failure of treatment. A recent study has shown that although approximately 75% of those who have undergone arthroscopic surgery for difficulties in opening may have improvement with significant pain reduction, subsequent magnetic resonance imaging (MRI) of the joints of these patients has demonstrated no true change in disc position.5 Condylar position and occlusion may not be highly correlated. A recent investigation has revealed that there is a significant difference in the occlusal position of asymptomatic patients when comparing maximum intercuspation to condylar-dictated occlusion within the same patient.6

2. What is the role of occlusal factors in temporomandibular disorder? There is scarce clinical-based evidence to address this question. The database comprising signs and symptoms of TMD is often confounded by difficulties in study design. Seligman and Pullinger, Seligman, and Gorbein8 listed the following factors that confound the determination of whether occlusal factors affect the prevalence of TMD7: 1. Symptoms are not always disease: Isolated symptoms may not be pathologic. For example, a joint adhesion heralded by an opening click that is noted on awakening may not be pathology, but may be included within an investigation’s database as a symptom of anterior disk dislocation with reduction. 2. Lack of differential diagnosis: Subjects may be grouped within data without assignment of a differential diagnosis. For example, all patients with joint sounds may be combined into a single data category, but the data do not reflect whether the joint sounds are due to adherences, adhesions, late reducing disks, or non-reducing disks. 3. Unrepresentative samples: Age, gender, and other characteristics of compared populations may not be matched. For example, comparisons between pre-adolescent patients and post-posttraumatic adults with mandibular dysfunction can confound data. 4. Lack of factor definition: Different components of a malocclusion may not have the same impact on the results. For example, ranking a posterior crossbite with equal impact as an anterior openbite in relation to TMD onset may induce error into the conclusions. 5. Multifactorial analysis is not used: Combination of factors may interact to affect investigational findings, and thus should be studied together. Several occlusal factors may interact and affect the conclusions gleaned from the analysis.

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For example, an impinging deepbite relationship and bruxing may be related, and these should not be studied in isolation from one another. 6. Inappropriate grouping of data: Provisions for those variables that consistently appear over the entire period of observation should be considered in the data analysis. For example, if closing muscles remain symptomatic throughout a period of observation, the number of such muscles must be recorded, because this finding may be pertinent to the results. Additionally, the transformation of real data to non-validated severity scales should be avoided. If one sign or symptom is considered to be more important than another, this should be validated rather than assigned an arbitrarily weighted value. In summary, the assessment of occlusal factors in relation to TMD is extremely complex and prone to study errors with potentially erroneous conclusions. Further difficulties in exploring the topic abound. Most studies are retrospective rather than prospective, and many are viewpoint in nature rather than evidence based. Despite the difficulties in data assessment, there has been one non-treated clinical population that may have a predisposed profile for TMD. Pullinger, Seligman, and Gorbein8 observed that there was a significantly high probability of nonreducing disc displacement in growing patients with unilateral posterior crossbite. These authors attributed this tendency toward adaptation of mandibular position, which may account for the condylar displacement. Thilander9 also recommended early correction of posterior crossbite to resolve facial asymmetry, normalize muscle activity, and avoid disc displacement resulting from asymmetric skeletal form. A later study10 using a small subject size determined that pretreatment asymmetric joint spaces and asymmetric mandibles resolved by maxillary expansion, thus supporting early correction of posterior crossbite. Okeson2 has introduced the term orthopedic stability to describe the simultaneous relationship between condyles that are seated in a musculoskeletally stable position because the teeth are in maximum intercuspation. If the position of the teeth prevents superior-anterior seating of the condyles and the complex is loaded by trauma or parafunction, the loading occurs in an unstable joint relationship. This is called orthopedic instability. The joints, muscles, or teeth are adversely affected. Although many patients demonstrate orthopedic instability, the key factors in the development of symptoms are loading and host susceptibility. There are multiple methods of loading unstable joints inclusive of trauma and parafunction. Host susceptibility remains an elusive factor but may include gender, history, or emotional factors.

3. When are occlusal splints indicated in therapy, and when are alternative forms of management of temporomandibular disorder appropriate? Some authors advocate the use of splints to diagnostically determine the position of the condyle prior to orthodontic correction or prosthetic rehabilitation.11–14 The additional intent

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CHAPTER 22 • Temporomandibular Disorders

A

B

FIG 22-1 A, Patient with orthopedic instability and joint pain with local muscle soreness. B, Patient after 2 months of maxillary splint wear with condyles now seated properly.

A

B

FIG 22-2 A, Patient with temporomandibular disorder (TMD) secondary to a habitual intercuspal position that distracted condyles from the fossa. B, Patient after 6 weeks of splint therapy, which allowed the musculature to provide condylar seating.

is to induce muscle relaxation to allow condylar seating in a physiologic position regardless of the occlusion (Fig. 22-1 and Fig. 22-2). Okeson2 recommends occlusal splints to address symptoms of orthopedic instability. Orthopedic instability is the lack of simultaneous superior-anterior condylar seating with the teeth in maximum intercuspation, concurrent with relaxation of the closing musculature. The intent of splint therapy is to provide a functional occlusion that is reversible or modifiable, and to concurrently interrupt destructive force patterns on the muscles and joints. Muscular symptoms are more prevalent than intracapsular disharmonies, and they often surface when an unstable musculoskeletal system is loaded by parafunction resulting from emotional stress, habitual bruxing, or deep pain input. Multiple authors have substantiated the efficacy of splint therapy for the reduction of muscular symptoms.15–18 Occlusal splints may also have a role in therapy when the overwhelming symptomatology and final diagnosis is that of intracapsular dysfunction without predominance of muscle symptoms.19 The design of the splint should provide orthopedic stability, albeit artificial. Efficacy of the full-coverage repositioning splint that reproduces a mutually protected occlusal scheme has been supported by evidence-based investigation. Although a number of splint designs are available, the clinician should choose the design that best suits clinical objectives. Thus, if the goal of splint therapy is to provide posterior contact with anterior disclusion in excursions, the superior repositioning splint or stabilization splint is appropriate. Supportive therapy

(such as physical therapy, pharmacologic management, thermal therapy, and other less conventional modalities) are also used effectively, but precise diagnosis is necessary for appropriate therapeutic prescription.

4. What is the role of occlusal adjustment in the treatment of temporomandibular disorder? In an effort to determine an evidence-based answer to this question, several systematic reviews have confirmed that there is little beneficial value in occlusal adjustment unless a single tooth is the etiology of an acute malocclusion.8,10,20 Although some clinicians have reported that occlusal adjustment seems to have a positive effect on TMD symptomatology, the variabilities of case selection, placebo effect, and spontaneous regression to the mean cannot be excluded as contributing to the apparent success of occlusal adjustment. There do not appear to be any studies of sufficient investigational precision to conclude that occlusal adjustment is effective therapy for TMD symptomatology.20

5. What are the commonly used pharmacologic modalities for management of temporomandibular disorder? Pharmacologic intervention for the treatment of TMD can be categorized into seven broad categories: 1. Centrally acting muscle relaxants: These drugs are actually interneuronal blocking agents acting at the spinal cord

level and brainstem. They decrease muscular activity by inhibiting neurotransmission and are usually administered at bedtime to decrease the possibility of interference with patient lifestyle because of undesirable side effects, such as vertigo or drowsiness. They may also be helpful in inducing effective stages of sleep, which is critical to management of TMD. Examples include chlorzoxazone (Parafon Forte), carisoprodol (Soma), and cyclobenzaprine (Flexeril). 2. Anxiolytics: Most commonly used are benzodiazepines, which provide an antianxiety effect but are often incorrectly prescribed for muscle relaxation. They are helpful in management of insomnia associated with TMD, but studies have shown that their effect on skeletal muscle relaxation is no greater than that of a placebo. Hence, these agents are helpful as an adjunct to skeletal muscle relaxation. Examples are diazepam (Valium), clonazepam (Klonopin), alprazolam (Xanax), hydroxyzine pamoate (Vistaril), and lorazepam (Ativan). 3. Barbiturates: These are often combined with analgesics to enhance pain relief in conjunction with the anxiolytic/ muscle relaxant effect of the barbiturate. They are useful for tension-type headache. Barbiturates have serious side effects including general depression, as well as decreased excitability of cardiovascular, respiratory, and gastrointestinal systems. Sleep disturbances can occur with barbiturate use, and drug disposition tolerance can also develop as increased hepatic metabolism leads to the need of increased quantity of the drug to maintain tissue concentrations. Drug dependence, paradoxical reactions (especially in the elderly), and other physical side effects can occur. A commonly prescribed barbiturate is butalbital, which is combined with caffeine and acetaminophen in Fioricet. The clinician needs to be very careful in prescribing this class of medications for TMD. 4. Tricyclic antidepressants: These are used in doses that are lower than those used for treatment of depression. They act by inhibiting the reuptake of serotonin and norepinephrine. An example is amitriptyline (Elavil) administered in doses of 10 to 20 mg/day at bedtime, compared with 75 to 150 mg for depression. Side effects include drowsiness, xerostomia, urinary retention, blurred vision, ventricular arrhythmias, and/or postural hypotension. 5. Opiate and non-opiate analgesics: Non-opiate analgesics include non-steroidal anti-inflammatory (NSAID) drugs and acetaminophen, the latter of which has no anti-inflammatory properties and does not affect platelet aggregation. An effective regimen of NSAID dosage is 600 mg of ibuprofen three times a day at mealtimes for 1 week. This drug carries very little abuse potential but has many contraindications that are often overlooked. In the case of NSAIDs, such contraindications include intolerance in asthmatics. Non-opiates should be used with caution or avoided in allergic patients; those with hepatic or renal dysfunction, anemia, bleeding tendencies, cardiac failure, pregnancy; the elderly; or those with gastrointestinal (GI) ulceration. Cyclooxygenase-2 (COX-2) inhibitors are contraindicated in patients with sulfonamide


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allergies. Drug interactions include anticoagulants, alpha and beta blockers, thiazide and furosemide diuretics, angiotensin converting enzyme (ACE) inhibitors, fluconazole (antifungal preparations), lithium, and methotrexate. 6. Corticosteroids: Used only locally via injection rather than systemically because of significant side effects. Corticosteroids can be destructive to joints when used repeatedly. 7. Local anesthetics: These are applied either diagnostically or therapeutically. Regional blocks are helpful to determine if pain is primary or secondary. Trigger point injections can be effective in the control of myofascial pain. Both short- and long-acting agents are available. 8. Botulinum toxin: Botulinum toxin type A (Botox) is a neurotoxin that prevents the release of acetylcholine at the motor end plates.21 The toxin is injected into muscles undergoing refractory myospasm in order to produce muscle paralysis of approximately 3 months. Given the temporary nature of such therapy, the use of botulinum toxin is considered to be palliative rather than definitive, but it remains a treatment option should other therapeutic measures fail. The clinician should thoroughly understand the pharmacologic properties of prescribed/administered medications and inform the patient of their possible side effects.

6. What are the contemporary imaging modalities used in temporomandibular disorder diagnosis? Many articles have been written regarding imaging protocol. In patients without medical contraindication, nondynamic evaluation of soft tissue structures (such as the disc) is best accomplished by MRI evaluation, whereas hard structures (such as bone and cartilage) are best visualized by radiographic techniques.22 Panoramic radiographs or conventional radiographs do not contribute to diagnostic accuracy beyond the diagnosis gleaned from history and physical examination alone.23 Arthrography is reserved for observation of disc form, location, and joint dynamics as inferred by observation of contrast injection into the upper and/or lower joint spaces.2 New modalities of cone beam computerized technology are effective in assessment of size, morphology, and position of the condyles but are inadequate for evaluation of musculature or disc morphology.24–27 Imaging is therefore not indicated in suspected masticatory muscle disorders or in short-term inflammatory disease, such as synovitis, capsulitis, or retrodiscitis.

7. What is the role of surgery in temporomandibular disorder management? According to Dolwick and Dimitriulis,4 surgery is unequivocally the therapy of choice to address the less common TMJ disorders, such as ankylosis, neoplasm, growth disorders, and unmanageable dislocation. When the clinical evaluation and patient’s response to conservative therapy (pharmacologic management, splint therapy, physical therapy, etc.) is unsuccessful, surgery should be considered based on presenting levels

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of pain and dysfunction. It is absolutely essential to verify that the TMJ is the primary site of pain rather than a heterotopic site as defined previously by Okeson.2 Although open joint surgery may still have application in the surgeon’s armamentarium, the overwhelming majority of surgery now appears to be arthrocentesis (joint lavage) and arthroscopy (lavage, adhesion release, and visualization). The latter allows tissue reduction procedures (partial or complete diskectomy, arthrotomy, and condylectomy) during arthroscopy if indicated. Numerous recent studies have demonstrated the efficacy of arthrocentesis for conditions of closed lock and osteoarthritic joints.28–32 The reported success rate of surgery varies, but it is well established that the success rate decreases as the number of previous surgeries rises.4 It has been reported that a near zero prognosis of successful surgery is expected if the patient has undergone two or more previous unsuccessful surgeries. As is true of treatment of TMD in general, there is no question that case selection is as important as clinical technique in TMJ surgery.

8. What is the relationship between orthodontic therapy and temporomandibular disorder? This question has been extensively investigated by an evidencebased approach as summarized in an excellent review article by McNamara.33 Twenty-one papers spanning 1980 through 1995 were reviewed, with sample sizes ranging from 22 to 462 patients per study. In summary of the multiple articles reviewed, there is little basis that orthodontic treatment affects the prognosis of TMD either positively or negatively, except in the possible case of unilateral posterior crossbite in the growing patient as previously mentioned in this chapter. It has been stated that an elevated host susceptibility and orthopedic instability in conjunction with joint loading, especially during parafunction, can initiate or exacerbate TMD.2 Orthodontic patients with a previous history of TMD may also be at higher risk for recurrence during treatment, especially in patients undergoing active orthodontic therapy where occlusal interferences emerge during the course of correction.34 The presiding consensus is that orthodontic treatment is not an effective primary treatment modality for patients with TMD, nor does orthodontic therapy predispose patients to TMD.35–37 As Okeson aptly states: “The clinician who only evaluates the occlusion is likely missing as much as the clinician who never evaluates the occlusion.”2

9. What is the currently accepted “standard of care” for temporomandibular disorder patients? The American Association for Dental Research issued its TMD statement revision on March 3, 2010, based on review of the current literature. The policy acknowledges that temporomandibular dysfunction is a diverse, multisystem affliction involving varied etiologies and therapies, often associated with involvement of other systems. Evidence-based, reversible, and conservative care are the watchwords for both diagnosis

and therapy. The ancient adage primum non nocere—Latin for “first do no harm”—should guide TMD therapy and all of our actions on behalf of our patients. The text of the statement is as follows: The AADR recognizes that temporomandibular disorders (TMDs) encompass a group of musculoskeletal and neuromuscular conditions that involve the temporomandibular joints (TMJs), the masticatory muscles, and all associated tissues. The signs and symptoms associated with these disorders are diverse, and may include difficulties with chewing, speaking, and other orofacial functions. They also are frequently associated with acute or persistent pain, and the patients often suffer from other painful disorders (comorbidities). The chronic forms of TMD pain may lead to absence from or impairment of work or social interactions, resulting in an overall reduction in the quality of life.* Based on the evidence from clinical trials as well as experimental and epidemiologic studies: 1. It is recommended that the differential diagnosis of TMDs or related orofacial pain conditions should be based primarily on information obtained from the patient’s history, clinical examination, and (when indicated) TMJ radiology or other imaging procedures. The choice of adjunctive diagnostic procedures should be based on published, peer-reviewed data showing diagnostic efficacy and safety. However, the consensus of recent scientific literature about currently available technological diagnostic devices for TMDs is that, except for various imaging modalities, none of them shows the sensitivity and specificity required to separate normal subjects from TMD patients or to distinguish among TMD subgroups. Currently, standard medical diagnostic or laboratory tests that are used for evaluating similar orthopedic, rheumatologic, and neurologic disorders may also be utilized when indicated with TMD patients. In addition, various standardized and validated psychometric tests may be used to assess the psychosocial dimensions of each patient’s TMD problem. 2. It is strongly recommended that, unless there are specific and justifiable indications to the contrary, treatment of TMD patients initially should be based on the use of conservative, reversible, and evidence-based therapeutic modalities. Studies of the natural history of many TMDs suggest that they tend to improve or resolve over time. Although no specific therapies have been proven to be uniformly effective, many of the conservative modalities have proven to be at least as effective in providing symptomatic relief as most forms of invasive treatment. Because those modalities do not produce irreversible changes, they present much less risk of producing harm. Professional treatment should be augmented with a home care program, in which patients are taught about their disorder and how to manage their symptoms.

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AADR TMD Policy Statement Revision approved by AADR Council 3/3/2010.38


CONCLUSION The identification and treatment of TMD can be as rewarding as it can be frustrating. Careful diagnosis gleaned via history and confirmed by clinical examination with imaging when indicated is key to successful treatment. This approach also indicates the need for allied specialty collaboration. Diagnosis and treatment should always begin conservatively and involve a clear, succinct yet informative explanation of the patient’s condition and treatment plan to enlist involvement of the patient in his or her rehabilitation. ACKNOWLEDGMENT Special thanks to Dr. Jeffrey P. Okeson for his review of sections of this manuscript as well as for his special role in guidance and instruction of the principles of management of TMD. His contributions to dentistry and to the specialty of orthodontics have been invaluable. REFERENCES 1. Okeson JP: Diagnostic classification of orofacial pain disorders. In Orofacial pain: guidelines for assessment, diagnosis, and management, Chicago, 1996, Quintessence Publishing. 2. Okeson JP: Functional neuroanatomy and physiology of the masticatory system. In Management of temporomandibular disorders and occlusion, St Louis, 2006, Mosby. 3. Costen JB: Syndrome of ear and sinus symptoms dependent upon disturbed function of the temporomandibular joint, Ann Otol Rhinol Laryngol 43:1, 1934. 4. Dolwick MF, Dimitriulis G: Is there a role for temporomandibular surgery? Br J Oral Maxillofac Surg 3:307–313, 1994. 5. Ohnuki T, Fukuda M, Iino M, et al: Magnetic resonance evaluation of the disk before and after arthroscopic surgery for TM disorders, Oral Surg Oral Med Oral Path 96(Aug):141–148, 2003. 6. Cordray FE: Three-dimensional analysis of models articulated in the seated condylar position from a deprogrammed asymptomatic population: a prospective study. Part I, Am J Orthod Dentofacial Orthop 129:619–630, 2006. 7. McNamara J, Seligman D, Okeson J: Occlusion, orthodontic treatment and temporomandibular disorders: a review, J Orofac Pain 9(1):73–89, 1995. 8. Pullinger AG, Seligman DA, Gorbein A: A multiple regression analysis of the risk and relative odds of temporomandibular disorders as a function of common occlusal features, J Dent Res 72:968–979, 1993. 9. Thilander B: Temporomandibular joint problems in children. In Carlson DS, McNamara JA, Ribbens KA, editors: Developmental aspects of temporomandibular disorders, Ann Arbor, 1985, University of Michigan Press. 10. Tsukiyama Y, Baba K, Clark GT: An evidence-based assessment of occlusal adjustment as a treatment for TM disorders, J Pros Dent 86(July):57–66, 2001. 11. Roth RH: Functional occlusion for the orthodontist, J Clin Orthop XV(1):32–51, 1981. 12. Roth RH: Functional occlusion for the orthodontist—part II, J Clin Orthop XV(2):100–121, 1981. 13. Williamson EH, Evans DL, Barton WA, et al: The effect of biteplane use on terminal hinge axis location, Angle Orthod 47:25–33, 1977.

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14. Williamson EH, Steinke RM, Morse PK, et al: Centric relation: a comparison of muscle determined position and operator guidance, Am J Orthod 77:133–145, 1980. 15. Kuttila M, Le Bell Y, Savolainen-Niemi E, et al: Efficiency of occlusal appliance therapy in secondary otalgia and TM disorders, Acta Odontol Scand 60(4):248–254, 2002. 16. Ekberg E, Vallon D, Nilner M: The efficacy of appliance a therapy in patients with TM disorders of mainly myogenic origin: a randomized, controlled short term trial, J Orofac Pain 17(2): 133–139, 2003. 17. Roark AL, Glaros AG, O'Mahoney M: Effects of interocclusal appliances on EMG activity during parafunctional tooth contact, J Rehabil 30:573–577, 2003. 18. Greco PM, Vanarsdall RL: An evaluation of anterior temporalis and masseter muscle activity in appliance therapy, Angle Orthod 69:141–146, 1999. 19. Schmitter M, Zahran M, Duc JM, et al: Conservative therapy in patients with anterior disc displacement without reduction using 2 common splints: a randomized clinical trial, J Oral Maxillofac Surg 63:1295–1303, 2005. 20. Huang G: Occlusal adjustment for treating and preventing temporomandibular disorders, Am J Orthod Dentofacial Orthop 126(2):138–139, 2004. 21. Jankovic J, Brin MF: Therapeutic uses of botulinum toxin, N Engl J Med 324:1186–1194, 1991. 22. Styles C, Whyte A: MRI assessment in the assessment of internal derangement of pain within the TM joint: a pictorial essay, Br J Oral Maxillofac Surg 40:220–228, 2002. 23. Epstein JB, Caldwell J, Black G: The utility of panoramic imaging of the TMJ in patients with TM disorders, Oral Surg Oral Med Oral Path 92:236–239, 2001. 24. Brooks SL, Brand JW, Gibbs SJ, et al: Imaging of the temporomandibular joint: position paper of the American Academy of Oral and Maxillofacial Radiology, Oral Surg Oral Med Oral Path 83(5):609–618, 1997. 25. Cevidanes LHS, Styner MA, Proffit WR: Image analysis in superimposition of 3-dimensional cone-beam computed tomography models, Am J Orthod Dentofacial Orthop 129(5):611–618, 2006. 26. Chirani RA, Jacq JJ, Meriot P, et al: Temporomandibular joint: a methodology of magnetic resonance imaging 3-D reconstruction, Oral Surg Oral Med Oral Path 97:756–761, 2004. 27. Kawamata A, Fujishita M, Kuniteru N, et al: Three dimensional computed tomography of postsurgical condylar displacement after mandibular osteotomy, Oral Surg Oral Med Oral Path 85:371–376, 1998. 28. Nitzan DW, Price A: The use of arthrocentesis for the treatment of osteoarthritic TMJ’s, J Oral Maxillofac Surg 59(10):1154–1159, 2001. 29. Yura S, Totsuka Y, Yoshikawa T, et al: Can arthrocentesis release intracapsular adhesions? Arthroscopic Findings before and after irrigation under sufficient hydraulic pressure, J Oral Maxillofac Surg 61:1253–1256, 2003. 30. Nitzan DW: TMJ “open lock” versus condylar dislocation: signs and symptoms, imaging treatment and pathogenesis, J Oral Maxillofac Surg 60(May):506–511, 2002. 31. Emshoff R, Rudisch A, Bosch R, et al: Prognostic indicators of the outcome of arthrocentesis; a short term follow-up study, Oral Surg Oral Med Oral Path 96(July):12–18, 2003. 32. Gesch D, Bernhardt O, Mack F, et al: Association of malocclusion and functional occlusion with subjective symptoms of TMD in adult: results of the study of health in Pomerania (SHIP), Angle Orthod 75(2):183–190, 2005. 33. McNamara J: Orthodontic treatment and temporomandibular disorders, Oral Surg Oral Med Oral Path 83(1):107–117, 1997.

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34. Le Bell Y, Niemi PM, Jamsa T, et al: Subjective reactions to intervention with artificial interferences in subjects with and without a history of temporomandibular disorders, Acta Odontol Scand 64(1):59–63, 2006. 35. Conti A, Freitas M, Conti P, et al: Relationship between signs and symptoms of TM disorders and orthodontic treatment: a cross sectional study, Angle Orthod 73(4):411–417, 2003. 36. Greene C, Stockstill J, Rinchuse D, et al: Orthodontics and temporomandibular disorders: a curriculum proposal for

postgraduate programs, Am J Orthod Dentofacial Orthop 142(1):18–24, 2012. 37. Michelotti A, Iodice G: The role of orthodontics in temporomandibular disorders, J Oral Rehabil 37:411–429, 2010. 38. American Association for Dental Research: Policy statements: temporomandibular disorders (TMD) (website): http://www .aadronline.org/i4a/pages/index.cfm?pageid=3465. Accessed March 19, 2014.

Retention and Relapse in Orthodontics

C HA P T ER

23

Sercan Akyalcin • Hitesh Kapadia • Jeryl D. English

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omprehensive orthodontic therapy requires that treatment goals be established during the time of treatment planning. Begin treatment with the end in mind. These goals should include patient esthetics, improved occlusal function, and long-term retention. Little and colleagues1 state that the only way to ensure continued satisfactory alignment after treatment is by the use of fixed or removable retention for life. Therefore, instability or a tendency toward relapse should be anticipated. Patients should be advised of the potential for relapse prior to treatment and of the need to stay in long-term retention. Orthodontists should work to produce an occlusion that is functionally efficient, esthetic, and healthy. Long-term retention helps to ensure stability of the dentition. Interdigitation of the posterior occlusion plays a significant role in the control of anteroposterior and vertical facial growth and is an important factor in jaw relationships.2 Numerous authors have stated that good intercuspation and occlusal contacts may be the key to a stable orthodontic result.3–8 Many of the current concepts in occlusion are derived from a benchmark study by Andrews9 to determine the keys to normal occlusion. Criteria for inclusion of these non-orthodontic patients in the study were a pleasing appearance, straight teeth, and a good bite that would not benefit from orthodontic treatment. In these individuals, Andrews found six keys in their normal occlusions: 1. Molar relationships 2. Crown angulation 3. Crown inclination 4. No rotations 5. No spaces 6. Flat occlusal plane It has long been the goal of orthodontists to treat their patients using these six keys as guides for establishing a normal occlusion that is esthetic and with good occlusal function. Many of these keys were included in the Objective Grading System (OGS) developed by the American Board of Orthodontics (ABO) in the mid-1990s. In an effort to enhance the reliability of the ABO examiners and provide the candidates with a tool to assess the adequacy of their finished orthodontic results, the Board has established an OGS to evaluate the final dental casts and panoramic radiographs.10 The directors of the ABO developed this grading system for assessing occlusal and radiographic results of orthodontic treatment. Using this system, orthodontists can grade

their treated cases to determine if they are producing excellent clinical results.

1. What is retention? Retention is the last phase of orthodontic treatment and one of the most important, where teeth are held in an esthetic and functional position.11,12 Retention of the corrected malocclusion is just as important as the diagnosis, treatment plan, and actual orthodontic treatment. Planning for retention should be carried out prior to the clinical intervention and should be a part of the individual treatment plan.

2. Why is retention necessary? Teeth that have been moved with orthodontic appliances have an inherent tendency to return to their original malocclusion positions. Without maintained stability, esthetic and functional orthodontic outcomes will be prone to relapse. Therefore, retention plays a pivotal role to maintain the stability of the occlusion achieved by the orthodontist and patient.13

3. What are the general factors affecting stability? Orthodontic literature highlighted many factors concerning the stability of orthodontic treatment outcome.14,15 Among those, three factors are consistently mentioned as to why retention is necessary to maintain the treatment results: 1. The time needed for the gingival and periodontal ligament fibers to reorganize. 2. Remaining growth, especially in the mandible, may alter occlusal relationships. 3. Pressure from soft tissues surrounding the dentition may lead to a relapse tendency.

4. Why is growth a consideration in retention? The nature and duration of retention depend on the patient’s maturational status and on anticipated future growth.16 Growth produces occlusal changes in all three skeletal dimensions. The transverse dimension is completed first and has a lesser effect on the occlusion than the vertical and anteroposterior dimensions. However, if a patient has had transverse expansion, there is a degree of rebound even in the transverse dimension. Ideally, an adolescent patient should wear orthodontic retainers indefinitely; however, at a minimum, the retainers must be worn until growth is completed in adulthood. Even adults show some craniofacial remodeling that can cause alteration 293

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of the occlusion. In orthodontics, we are dealing with a living, dynamic system of growth. Throughout our life, orthodontic retention helps to minimize the changes in our occlusion. Therefore, retention should be considered for life if the occlusal alignment is to be maintained.

5. What are retention considerations in extraction and non-extraction cases? There is not a specific retention philosophy for extraction cases and another for non-extraction cases. The orthodontist decides on the individual’s retention plan at the beginning of treatment when the diagnostic records are used to establish the patient’s treatment plan. By following this plan, it will be possible to achieve an esthetic and functional occlusion. Many orthodontists prefer use of a wrap-around Hawley retainer with soldered arms on the clasps to help preserve the orthodontic space closure in extraction cases. Additionally, Edwards16 has shown that in extraction cases, excess gingival tissue forms as the adjacent teeth are moved toward one another in closing the extraction site. This excess gingival tissue should be surgically removed to prevent relapse.

6. What are retention considerations in Class II cases?

often requires orthognathic surgical correction. A gnathologic positioner is a useful retainer in mild Class III malocclusions. Use of chin caps to restrict mandibular growth is not very effective.

8. What are retention considerations in openbite cases? An openbite malocclusion may be dental or skeletal in nature. A dental openbite may be caused by depression of the incisors because of a habit, such as thumb- or finger-sucking or poor tongue posture. A good cephalometric judgment to differentiate between a dental and skeletal openbite can be made by measuring incision-stomion distance, which represents the extent of maxillary central incisor crown display when the lips are in a relaxed position; dental openbites have less maxillary incisor display, whereas skeletal openbites have a normal incisor position. In cases with skeletal openbites, due to the fact that incisors are in a good position, posterior teeth that have elongated and posterior alveolar segments show more vertical development. Controlling for the vertical plane changes must be a part of the treatment mechanics. Eruption of the maxillary molar with a high-pull headgear and a transpalatal bar with a midline acrylic palatal button 4 mm off of the palate, for instance, is useful to control for excessive extrusion of posterior segments. If correction of severe openbite is not started in the mixed dentition, it will most likely require orthognathic surgery in late adolescence or adulthood. The skeletal openbite phenotype is easily diagnosed in the early mixed dentition.

Skeletal Class II malocclusions are commonly corrected in two ways: 1) restricting maxillary growth with headgear appliances or 2) using a functional appliance, such as a Herbst or Twin Block. Class II elastics are also used to supplement the bite correction, but this may cause more pronounced dental side effects like proclining and flaring of the lower incisors. If proclined, the lower incisor will upright and crowd, because the equilibrium between lower lip, tongue, and periodontal ligament will be altered again once retention is removed. To overcome these relapse tendencies, Class II elastic use should be discontinued at least 2 months prior to debonding. Additionally, overcorrection of the Class II treatment may be feasible in cases where expected remaining growth has potential to cause long-term relapse. This relapse tendency can be controlled by continuing to wear a headgear at night to help restrain forward shift of the maxillary teeth or using a functional appliance (such as a Bionator) to hold the occlusal relationship.15 Obviously, this type of retention is for the patients with severe skeletal problems initially.

Deepbites are common in certain malocclusions, such as Class II division 2, and are caused by overeruption of the maxillary incisors, mandibular incisors, or a combination of both. Once the deepbite is corrected, there is a tendency for relapse.19,20 Relapse of deepbite cases can be prevented using precautionary measures. For instance, if the retention is accomplished using a maxillary removable retainer that incorporates a bite plate, the lower incisors and cuspids will have a contact surface to stop the bite from deepening. However, this appliance should not cause the posterior teeth to disocclude. This retainer should be worn at night until the late teens or early 20s to maintain occlusal stability.

7. What are retention considerations in Class III cases?

10. What are the indications for bonded lingual retainers?

Early correction of skeletal Class III malocclusions in the mixed dentition using a palatal expander and protraction facemask is useful for altering the skeletal components.17,18 It is more successful in deepbite cases than in openbite cases, because the mandibular plane angle and anterior facial length will increase as a result of backward mandibular rotation. Retaining the correction can be frustrating because of continued mandibular growth, which is difficult to control. Correction of true Class III malocclusions in adults caused by maxillary hypoplasia, mandibular prognathism, or a combination of the two most

Fixed orthodontic retainers are usually wires bonded to the lingual surface of the mandible anterior teeth for esthetics and prolonged retention.21,22 These may be fabricated directly in the mouth or indirectly from an accurate stone model. The bonded retainer is placed in the patient’s mouth and secured with a lightcured composite resin. The fixed retainer is useful to retain the mandibular canine-to-canine region, and a bonded retainer is more esthetic than a banded retainer. The fixed bonded retainer is also used to maintain corrected midline diastema and to maintain pontic or implant space. It is also useful for maintaining the

9. What are the considerations in deepbite cases?

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A

FIG 23-2 Maxillary Hawley retainer. (Courtesy of AOA Orthodontic Appliances, Sturtevant, WI.)

B

FIG 23-1 Mandibular bonded retainer. A, Cuspid to cuspid. B, Bonded to every tooth.

vertical position of teeth extruded into the arch, such as palatally impacted cuspids. In most instances the retainer wire is bonded to the terminal teeth (canines) of the retainers (Fig. 23-1, A) and not bonded to every tooth. Fixed retainers make interproximal hygiene procedures more difficult. However, with good flossing procedures, these fixed bonded retainers could be left in place until adulthood or indefinitely if needed. It is important that the general dentist not remove the bonded lingual retainer without consultation with the orthodontist, because the teeth may relapse. Today more orthodontists are bonding a 0.0195-twisted wire to every tooth from cuspid to cuspid (see Fig. 23-1, B). This increases stability and is possible because of improvements in the composite material.

11. What are the indications for removable retainers? Removable retainers are effective for retention against intraarch relapse. These retainers are made of stainless steel wire and acrylic (Fig. 23-2). The four basic components are the clasps, the anterior retainer wire, the acrylic body, and any auxiliaries added to the retainer. They should be fabricated from an accurate stone cast. The labial bow provides the orthodontist the ability to control the anterior teeth. Retention clasps are necessary for the retainer to stay firmly in place. The Hawley retainer is the most common removable retainer and the type of retainer used to control a deepbite because a bite plane is easily added. A lower Hawley retainer is much more difficult to insert because of undercuts in the premolar and molar region. A bonded lingual retainer is more suitable for the mandibular arch.

FIG 23-3 Maxillary wrap-around retainer. (Courtesy of AOA Orthodontic Appliances, Sturtevant, WI.)

A second major removable retainer is the wrap-around retainer (Fig. 23-3). It firmly holds each tooth in position and is excellent for maintaining space closure after extractions. There are no wires across the occlusion, so there are no occlusal interferences. Wrap-around retainers are more difficult to fabricate and are therefore more expensive than regular Hawley retainers.

12. What are the indications for vacuumformed retainers? With the development of clear, thin thermoplastic materials, vacuum-formed retainers have become very popular with many orthodontists in the past few years.23 Vacuum-formed retainers have many advantages over wire and acrylic for many orthodontic patients requiring removable retainers. These retainers are fabricated on a dental study cast in approximately 30 minutes with a relatively inexpensive material. The retainers are comfortable and rarely interfere with speech, they require no adjustments, and they are esthetic because of their almost-invisible appearance. The retainer is typically inserted on the day the braces are removed. These retainers are easily cleaned and provide good stability of the occlusion, especially in the maxillary arch. Possible disadvantages are that they do not allow the settling of the occlusion, and since they cover

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the occlusal surfaces, masticatory forces can cause wear and require the retainer to be remade. Some have advocated using a sectional vacuum-formed retainer from cuspid to cuspid. Unfortunately, this type of retention over the long term would allow extrusion of the premolars and molars, potentially opening the bite. This retainer is simple, esthetic, and comfortable, and it has received an enthusiastic reception from both patients and orthodontists. In addition, the vacuumforced retainer offers a perfect vehicle for transporting bleach to patients’ teeth after completion of orthodontic treatment.

13. Are there indications for combining removable and fixed retainers? In adult cases with generalized spacing, a palatal bonded retainer may be necessary to avoid reopening of spaces. In cases with large diastemata, a bonded palatal retainer may be required to maintain the closure. In cases with a palatally impacted canine, a bonded retainer may be necessary to prevent vertical relapse. In each of the three examples, a vacuum-forced retainer could be used over the bonded retainer to help prevent breakage of the bonded retainer caused by occlusal interference or contact during biting. It is important for the orthodontist to evaluate the patient’s overbite and overjet and to place the bonded retainer as gingival as possible to avoid interference with bite closure. When a properly placed lingual-bond retainer is combined with a vacuum-forced retainer, the bonded retainer can remain in place for a long time.

14. What are the long-term retention considerations? Orthodontic retention should be continued until craniofacial growth is essentially completed in the early 20s.24 Late mandibular growth is the greatest contributor to mandibular incisor crowding; therefore, retention is certainly a requirement for all orthodontic patients. It is commonly recommended that all

atients have a retention maintenance phase for at least 1 year. p After that, the patient will be seen only if there are difficulties with the retainer (e.g., if it is broken, bent, or lost). It is important that the orthodontist establish a retention protocol for each patient during the initial diagnosis and treatment planning phase. Most orthodontists use a removable retainer in the maxillary arch. As most of the relapse occurs in the first 6 months following bracket removal, the maxillary retainer is worn full time for 6 months. After the first 6 months, the patient can go to night wear only and gradually reduce this if no pressure areas are noted when seating the retainer. Eventually, the maxillary retainer may not be needed. The lower retainer is usually a bonded-lingual retainer, which should be left in place at least until early adulthood. Removal of this retainer should be done only after the orthodontist is consulted. Some retainers may stay for a lifetime. The answer to the question of long-term stability is long-term retention.

15. When are positioners used as retainers? A tooth positioner is an excellent retainer in certain malocclusions, although it is more commonly used as a finishing appliance25,26 (Fig. 23-4). It has the advantages of massaging the gingival tissues, and it is not subject to breakage as acrylic retainers are. It is bulky and typically is worn 2 to 4 hours per day. Positioners do not retain rotations or incisor irregularities as well as standard retainers. Positioners maintain the occlusal relationship as well as the intra-arch tooth positions. They are excellent retainers for Class II and Class III malocclusions as well as for openbite malocclusions. The optimum positioner is one that has an articulator mounting that records the patient’s hinge axis. This gnathologic positioner is more expensive, but it will prevent the posterior openbite that results when a positioner is made to an incorrect hinge axis. A tooth positioner is not appropriate for every orthodontic patient, but for selected patients, it can be an excellent finishing appliance and retainer.

FIG 23-4 Silicone tooth positioner. (Courtesy of AOA Orthodontic Appliances, Sturtevant, WI.)


16. Are spring retainers useful for retreatment of mandibular incisor crowding? Recrowding of mandibular incisors is the indication for a spring aligner to correct incisor position. If late mandibular growth is the cause of the crowding, it may be necessary to reduce the interproximal width of the incisors. The interproximal enamel can be removed with thin discs in a handpiece called air rotor stripping (ARS) or with abrasive strips. This enamel reduction must be performed cautiously to remove only 0.25 mm per side on the incisors. If the recrowding is only 2 to 3 mm, this can be corrected with the spring retainer. First, the interproximal reduction is completed followed by topical fluoride, and then an impression is taken for a study cast. The anterior teeth are sectioned and reset into proper alignment. The spring aligner is fabricated and seated in the patient’s mouth. Once the teeth move into alignment, the “active” spring retainer now becomes a passive retainer. Most orthodontists find that it is actually much faster and easier to replace brackets on the anterior teeth and realign rather than using a spring retainer.

17. What are the indications for circumferential supracrestal fiberotomy? Circumferential supracrestal fiberotomy (CSF) is a surgical excision of the free gingival fibers and transseptal fibers to reduce rotational relapse. Surgery to cut the supracrestal elastic fibers is necessary, because rotational relapse is caused by the network of elastic supracrestal gingival fibers returning to their original position. This surgical technique was developed by Edwards and includes infiltration with a local anesthetic followed by a circumferential incision around the tooth to the crest of alveolar bone.27–31 These surgical cuts are made after a previously rotated tooth is orthodontically moved to its ideal position within the arch. There is minor discomfort after the procedure, but no periodontal pack is necessary. In most cases, it is done by the orthodontist near the end of the finishing phase of treatment. The most important consideration is to retain the tooth in its ideal position while gingival healing occurs. Some orthodontists prefer to perform the CSF after the braces have been removed, but retainers must be inserted immediately to prevent the tooth from rotating back to its original position. This procedure is indicated for a severely rotated tooth, and it is not appropriate for crowding of teeth without rotations.

18. What are the indications for a frenectomy? A frenectomy is the surgical removal or repositioning of a frenum and is performed to enhance the stability of a corrected diastema.32 A maxillary midline diastema is caused by insertion of the labial frenum, which is a band of heavy fibrous tissues between the central incisors. When the cause of the diastema is a prominent labial frenum, the frenectomy should be performed after orthodontic alignment and space closure but prior to the removal of the orthodontic appliances. The major point in a frenectomy being successful is removal of the interdental fibrous tissue. It is not necessary to remove a large

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portion of the frenum itself. The scar tissue stabilizes the teeth and helps to prevent the diastema from returning. This procedure should not be performed until the diastema is closed, or the scar tissue will prevent closure. It is difficult to maintain space closure after correcting a diastema, so a lingual-bonded retainer is indicated to keep the space closed. In addition, many children in middle to late mixed dentition demonstrate diastemas of approximately 2 mm. This diastema will normally close with the eruption of the maxillary canines and does not require a frenectomy.

19. What is relapse? Relapse is the change in tooth position toward the former location following active orthodontic treatment. Teeth are in a stable position because of the equilibrium of forces of chewing, swallowing, tongue, and cheek movements. There is a balance between the internal and external oral musculature. If a tooth is moved, this equilibrium is altered, and it must be reestablished to prevent relapse. New fiber and hard tissue formation is dependent on retention. The gingival fiber networks must reorganize to accommodate the new tooth positions. Immediately after orthodontic appliances are removed, the teeth are unstable to occlusal and soft tissue pressures.13 This is the reason every patient must be placed in orthodontic retainers for a minimum of 6 months to reestablish the equilibrium. Very few cases require minimal or no retention. If the posttreatment dentition starts developing mandibular incisor irregularities, reduction of the incisor width by slenderizing can certainly help. Usually, only minimal tooth structure has to be removed if the incisor root apices have been adequately spaced. Routine cases require retention appliances until the decision to extract or retain the third molars is determined, and the growth process is nearly completed in the early 20s.

20. What is the role of the third molars and relapse? It is unclear what role the third molars play in the severity of late mandibular crowding. The etiology of late crowding of the mandibular arch is multifactorial and is associated with the amount and direction of late mandibular growth. There is a controversy of the relative merits of extraction of third molars to alleviate mandibular anterior crowding.33,34 Most authors feel that the extraction of third molars for the purpose of preventing mandibular anterior relapse is not justified.

21. What is the Objective Grading System used by the American Board of Orthodontics? In the mid-1990s, the ABO began investigating methods of making the clinical examination more objective. Because a major emphasis has always been placed on the final occlusion, the first efforts were directed at developing an objective method of evaluating the dental casts and intraoral radiographs. At the 1995 ABO Clinical Examination, 100 cases were evaluated. A series of 15 criteria were measured on each of the final dental casts and panoramic radiographs. The data showed that the majority of the inadequacies in the final results occurred in 7

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of the 15 criteria (alignment, marginal ridges, buccolingual inclination, overjet, occlusal relationships, occlusal contacts, and root angulation). The following year in another field test, 300 sets of final dental casts and panoramic radiographs were evaluated by a subcommittee of four directors. Again, the majority of the inadequacies in the final results occurred in the same seven categories, but the committee had difficulty establishing adequate interexaminer reliability. Therefore, the subcommittee recommended that a measuring instrument be developed to make the measuring process more reliable. In 1997, a third field test was performed with the modified scoring system and the addition of an instrument to measure the various criteria more accurately. Based on the collective and cumulative results of extensive field tests, the Board decided to officially initiate the use of this OGS for candidates for the Clinical Examination.10 Today, the OGS is called the Cast Radiograph Evaluation (CRE). The seven criteria are: 1. Alignment: In the anterior region, the incisal edges and lingual surfaces of the axillary anterior teeth and the incisal edges and labial-incisal surfaces of the mandibular anterior teeth were chosen as the guide to assess anterior alignment. In the maxillary posterior region, the mesiodistal central groove of the premolars and molars is used to assess adequacy of alignment. 2. Marginal ridges: Marginal ridges are used to assess proper vertical positioning of the posterior teeth. Based on the four field tests, the most common mistakes in marginal ridge alignment occurred between the maxillary first and second molars. The second most common problem area was between the mandibular first and second molars. 3. Buccolingual inclination: In order to establish proper occlusion in maximum intercuspation and avoid balancing interferences, there should not be a significant difference between the heights of the buccal and lingual cusps of the maxillary and mandibular molars and premolars. 4. Occlusal relationship: Occlusal contacts are measured to assess the adequacy of the posterior occlusion. Again, a major objective of orthodontic treatment is to establish maximum intercuspation of opposing teeth. Therefore, the functioning cusps are used to assess the adequacy of this criterion (i.e., the buccal cusps of the mandibular molars and premolars and the lingual cusps of the maxillary molars and premolars). 5. Overjet: Overjet is used to assess the relative transverse relationship of the posterior teeth and the anteroposterior relationship of the anterior teeth. 6. Interproximal contacts: Interproximal contacts are used to determine if all spaces within the dental arch have been closed. Persistent spaces between teeth after orthodontic therapy are not only unesthetic but also can lead to food impaction. 7. Root angulation: Root angulation is used to assess how well the roots of the teeth have been positioned relative to one another. Although the panoramic radiograph is not the perfect record for evaluating root angulation, it is probably the best means possible for making this assessment. The Directors of the ABO spent countless hours developing this system for assessing the occlusal and radiographic results of

orthodontic treatment. The usefulness of this system depends not only on its objectivity, but more importantly on the validity and reliability of the measurements. After repeated comparison of both objective and subjective systems, the Directors are confident that the cut-off score to pass this portion of the clinical examination is valid. Today, candidates must grade their own results before the clinical examination. Candidates will know if their results will pass the CRE portion of the clinical examination. Furthermore, diplomates may use this scoring system at any time in their orthodontic career to determine if they are producing Board-quality results. The Board hopes that this method of self-evaluation will help to improve the quality of orthodontic care in the future.

22. Is there a difference between the relapse tendency of extraction and non-extraction cases? Orthodontic mechanotherapy is the main reason for relapse, irrespective of teeth extractions.35 Comparisons36–38 of extraction versus non-extraction cases have shown no significant difference between the two at the postretention phase with regard to the incisor irregularity. Therefore, the extraction decision must be based on the individual’s treatment needs. It was shown that early treatment of crowding with extractions might potentially decrease the amount of relapse.35,39 However, with both treatment approaches, it is essential to maintain the arch form while avoiding excessive expansion of the dental arch and advancement of the incisors in the mandible.

23. How does the extraction pattern affect the relapse in Class II cases? Treatment of Class II malocclusions with two maxillary premolar extractions or four premolar extractions has similar long-term occlusal stability.40 In reality, there is no evidencebased obligation to finish the molars in Class I relationship concerning either temporomandibular joint (TMJ) health or long-term stability. Furthermore, a case-control study indicated that treatment efficiency was greater with the extractions of two maxillary premolars and finishing in Class II molar relationship as compared to non-extraction treatment of the malocclusion.41 It was later shown that finishing Class II malocclusion treatment with the molars in a Class II relationship had similar long-term occlusal results as finishing with the molars in a Class I relationship.42

24. What are the factors that affect the long-term success of comprehensive Class II correction? Evidence from a randomized controlled study43 of early headgear treatment on occlusal stability suggests that treatment timing is not critical. However, remaining growth plays a pivotal role for most of the posttreatment changes in Class II cases. Favorable downward and forward mandibular growth both during and after treatment is the key to successful long-term results.44–46 In the orthodontic correction of Class II malocclusion, a significant amount of relapse in molar relationship occurs during the posttreatment period, and this change could


be ascribed to the mesial movement of the upper molars.47 However, forward mandibular displacement compensates for the relapse of molar correction by making up for the mesial tipping and transposition of the maxillary molar in adolescents.48 The posttreatment changes in dental and skeletal structures in adults are very limited. Therefore, adults show a similar degree of relapse in sagittal molar correction to adolescents.48

25. What contributes to the posttreatment occlusal stability in Class III cases? Orthodontic treatment of mild to moderate Class III cases requires maxillary protraction (facemask therapy) with or without maxillary expansion. Careful patient selection, treatment timing, and overcorrection appear to be the predominant factors that contribute to the long-term success of this approach. Maxillary deficient individuals with a flatter gonial angle and less vertical growth pattern benefit from facemask therapy the most.49,50 It is suggested to start the treatment between early to mid mixed dentition period to induce more favorable craniofacial adaptations.51,52 It is reported that up to age 10, which is the time at which facemask therapy begins, does not appear to be a major factor in long-term success in maintaining positive overjet.53 Patients treated with rapid maxillary expansion and facemask therapy in the late mixed dentition will still benefit from the treatment, but to a lesser degree and possibly by having more significant dental changes.54 Due to horizontally directed and often late mandibular growth, 25% to 30% of Class III cases relapse into reverse overjet.53 Extending the treatment of Class III skeletal malocclusion, perhaps to a degree that an aggressive overcorrection presents with Class II molar and positive overbite and overjet relationships, is advised for the longterm stability of the treatment outcome.55

26. What are the main reasons of relapse in openbite cases? Openbite malocclusion has a poor long-term stability rate. Relapse may occur due to a number of reasons including tongue posture and activity, respiratory problems, prolonged habits, and unfavorable growth.56–61 However, it is extremely difficult to predict the nature of openbite correction and stability either at posttreatment or follow-up periods.62 Relapse frequency of anterior openbite in nonsurgical orthodontic cases is reported to be somewhere between 23% and 38% depending on the treatment mechanics utilized and follow-up time.63–66 In surgical cases, the success rate is a little higher and is predicted to be around 20%.66

27. How stable is it to level the curve of Spee? Individuals with Class II malocclusions have significantly deeper pretreatment curve of Spee measurements than individuals presenting with Class I molar relationships.67 Leveling of the curve of Spee is, nevertheless, a relatively stable treatment objective that involves uprighting the molars, extruding the premolars, and intruding and/or flaring the incisors. Extraction and non-extraction treatment approaches do not affect the amount of relapse in leveling.67 Relapse of curve of Spee in the long term is not correlated with the amount of

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c orrection at posttreatment.68 However, there seems to be a link between the relapse of the curve of Spee and the relapse of both the irregularity index and overbite measurements.67,68 From a clinical point of view, it may be advisable to completely level the initial curve of Spee to counteract with relapse if any. It was shown that the pretreatment curve of Spee that is not completely level post treatment has a higher incidence of relapse than one that is completely level post treatment.69 In summary, relapse in the curve of Spee is minimal and should be maintained at a high level once corrected properly.

28. What are the main factors affiliated with the relapse in deepbite cases? According to a recent systematic review, about 71% of deepbite correction can successfully be retained, and the amount of follow-up does not appear to be related to the amount of relapse.70 Patients with upright pretreatment maxillary and mandibular incisors tend to have deeper initial overbite and a tendency to return to their original relationship throughout the postretention follow-up. In other words, initial severity of the overbite is associated with long-term changes in overbite measurement.20,70 Extraction and non-extraction patients tend to have fairy similar relapse tendencies following the correction of their deepbites.70–75 However, growth pattern of the individual seems to affect the long-term retention of overbite correction, and high-angle subjects tend to display less relapse than low-angle and normal-angle subjects.75

29. What is the relation between other occlusal characteristics and incisal changes in the long term? About half of the relapse, as evaluated by the peer assessment rating (PAR), occurs in the first 2 years following retention therapy.76 Adolescents display significantly greater posttreatment increases of mandibular incisor irregularity and the PAR index than adults.77 However, it appears that long-term posttreatment incisal changes and long-term changes occurring in the occlusion are not directly related, as reflected in the weighted PAR score.78 Despite the presence of excellent occlusal relationships, maintaining the stability of incisors is a highly variable and independent challenge.79 Buccal segment occlusal correction usually remains very stable and may even improve because of settling following active orthodontic mechanotherapy.80,81 The CRE component of the ABO when utilized to compare posttreatment and postretention phases in a random study sample revealed that mean scores for occlusal contacts, marginal ridges, occlusal relationships, overjet, and buccolingual inclinations all improved after treatment, with alignment being the only criterion to actually worsen after treatment.81 In light of these findings, it can be concluded that establishment of perfect occlusal results will not necessarily ensure stability.

30. Is there a sound scientific approach to retainer selection for mandibular incisor stability? The etiology of relapse is not fully understood, and there is a paucity of high-quality evidence on which to base our clinical

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practice of orthodontic retention.82 Limited studies with fixed lingual retainers bonded canine-to-canine demonstrate sufficient evidence for acceptable incisor alignment and fairly good periodontal health in the long-term follow-up.83–85 Therefore, they are still the standard of care. These retainers can be bonded on all the teeth or just on the canines; they can be made of stainless steel or flexible wires. There are clinical challenges with each application and a need for annual check-up exists throughout their use. In some individuals a mild to moderate increase in incisor irregularity may still be observed despite their effectiveness.84,85 However, for a clinical procedure that is an accepted standard of care in orthodontics, it is unfortunate that insufficient evidence is available on which to base the clinical practice guidelines on orthodontic retention.86 REFERENCES 1. Little RM, Riedel RA, Artun J: An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention, Am J Orthod Dentofacial Orthop 93:423, 1988. 2. Ostyn JM, Maltha JC, van't Hof MA, et al: The role of interdigitation in the sagittal growth of the maxillo-mandibular complex of Macaca fascicularis, Am J Orthod Dentofacial Orthop 109:71–78, 1996. 3. Tweed CS: Indications for the extraction of teeth in orthodontic procedures, Am J Orthod 30:405–428, 1944. 4. Huckaba GW: The physiologic basis of relapse, Am J Orthod 38:335–350, 1952. 5. Schudy GF: Posttreatment craniofacial growth: its implications in orthodontic treatment, Am J Orthod 65:39–57, 1974. 6. Fotis B, Melsen B, Williams S: Posttreatment changes of skeletal morphology following treatment aimed at restriction of maxillary growth, Am J Orthod 88:288–296, 1985. 7. Harris EF, Vaden JL, Dunn KL, et al: Effects of patient age on postorthodontic stability of the mandibular arch, Eur J Orthod 105:25–34, 1994. 8. Parkinson CE, Buschang PH, Behrents RG, et al: A new method of evaluating posterior occlusion and relation to posttreatment occlusal changes, Am J Orthod Dentofacial Orthop 120:503–512, 2001. 9. Andrews LF: The six keys to normal occlusion, Am J Orthod 62:296–309, 1972. 10. Casko JS, Vaden JL, Kokick VG, et al: Objective grading system for dental casts and panoramic radiographs. American Board of Orthodontics, Am J Orthod Dentofacial Orthop 114(5):589–599, 1998. 11. Blake M, Bibby K: Retention and stability: a review of the literature, Am J Orthod Dentofacial Orthop 114:299–306, 1998. 12. Kaplan H: The logic of modern retention appliances, Am J Orthod Dentofacial Orthop 93:325–337, 1988. 13. Sandowsky C: Long-term stability following orthodontic therapy. In Burstone CJ, Nanda R, editors: Retention and stability in orthodontics, Philadelphia, 1993, WB Saunders, pp 107–113. 14. Reitan K: Principles of retention and avoidance of treatment relapse, Am J Orthod 55:776–790, 1969. 15. Nanda RS, Nanda SK: Considerations of dentofacial growth in long-term retention and stability: is active retention needed? Am J Orthod Dentofacial Orthop 101:297–302, 1992. 16. Edwards J: The prevention of relapse in extraction cases, Am J Orthod 160:128–140, 1971. 17. McNamara JA: An orthopedic approach to the treatment of Class III malocclusion in young patients, J Clin Orthod 21:598–608, 1987. 18. Kulbersh VP, Berger J, Kersten G: Effects of protraction mechanics on the midface, Am J Orthod Dentofacial Orthop 114:484–491, 1998.

19. Lewis P: Correction of deep overbite: a report of three cases, Am J Orthod 91:342–345, 1987. 20. Kim TW, Little RM: Postretention assessment of deep overbite correction in Class II division 2 malocclusion, Angle Orthod 69(2):175–186, 1999. 21. Espen HD, Zachrisson BU: Long-term experience with direct bonded lingual retainers, J Clin Orthod 10:619–630, 1991. 22. Orchin JD: Permanent lingual bonded retainer, J Clin Orthod 24:229–231, 1991. 23. Sheridan JJ, LeDoux W, McMinn R: Essix retainers: fabrication and supervision for permanent retention, J Clin Orthod 27: 37–45, 1993. 24. Zachrisson BU: Important aspects of long-term stability, J Clin Orthod 9:563–583, 1971. 25. Kesling HD: The philosophy of the tooth positioning appliance, Am J Orthod 31:297–304, 1945. 26. Carano A, Bowman SJ: Short-term intensive use of the tooth positioner in case finishing, J Clin Orthod 36(4):216–219, 2002. 27. Edwards J: A surgical procedure to eliminate rotational relapse, Am J Orthod 57:35–40, 1970. 28. Edward J: A long-term prospective evaluation of the circumferential supracrestal fiberotomy alleviating orthodontic relapse, Am J Orthod 93:380–387, 1988. 29. Edwards J: The prevention of relapse in extraction cases, Am J Orthod 60(2):128–140, 1970. 30. Boose L: Fiberotomy and reproximation without lower retention, nine years in retrospect: part I, Angle Orthod 50:88–97, 1980. 31. Boose L: Fiberotomy and reproximation without lower retention, nine years in retrospect: part II, Angle Orthod 50:169–178, 1980. 32. Edwards JG: The diastema, the frenum, the frenectomy: a clinical study, Am J Orthod 71:489–508, 1977. 33. Richardson ME: The role of the third molar in the cause of lower arch crowding: a review, Am J Orthod Dentofacial Orthop 95(1):79–83, 1989. 34. Ades A, Joondeph D: A long-term study of the relationship of third molars to mandibular dental arch changes, Am J Orthod Dentofacial Orthop 97:323–335, 1990. 35. Woodside DG, Rossouw PE, Shearer D: Postretention mandibular incisor stability after premolar serial extractions, Semin Orthod 5(3):181–190, 1999. 36. Rossouw PE, Preston CB, Lombard C: A longitudinal evaluation of extraction versus nonextraction treatment with special reference to the posttreatment irregularity of the lower incisors, Semin Orthod 5(3):160–170, 1999. 37. Erdinc AE, Nanda RS, Işiksal E: Relapse of anterior crowding in patients treated with extraction and nonextraction of premolars, Am J Orthod Dentofacial Orthop 129(6):775–784, 2006. 38. Quaglio CL, de Freitas KM, de Freitas MR, et al: Stability and relapse of maxillary anterior crowding treatment in class I and class II Division 1 malocclusions, Am J Orthod Dentofacial Orthop 138(1):16–22, 2010. 39. Haruki T, Little RM: Early versus late treatment of crowded first premolar extraction cases: postretention evaluation of stability and relapse, Angle Orthod 68(1):61–68, 1998. 40. Janson G, Leon-Salazar V, Leon-Salazar R, et al: Long-term stability of Class II malocclusion treated with 2- and 4-premolar extraction protocols, Am J Orthod Dentofacial Orthop 136(2):154.e1–154.e10, 2009. 41. Janson G, Barros SE, de Freitas MR, et al: Class II treatment efficiency in maxillary premolar extraction and nonextraction protocols, Am J Orthod Dentofacial Orthop 132(4):490–498, 2007. 42. Janson G, Camardella LT, Araki JD, et al: Treatment stability in patients with Class II malocclusion treated with 2 maxillary premolar extractions or without extractions, Am J Orthod Dentofacial Orthop 138(1):16–22, 2010. 43. Krusinskiene V, Kiuttu P, Julku J, et al: A randomized controlled study of early headgear treatment on occlusal stability: a 13 year follow-up, Eur J Orthod 30(4):418–424, 2008.


44. Fidler BC, Artun J, Joondeph DR, et al: Long-term stability of Angle Class II, division 1 malocclusions with successful occlusal results at end of active treatment, Am J Orthod Dentofacial Orthop 107(3):276–285, 1995. 45. Elms TN, Buschang PH, Alexander RG: Long-term stability of Class II, division 1, nonextraction cervical face-bow therapy: I. Model analysis, Am J Orthod Dentofacial Orthop 109(3):271–276, 1996. 46. Elms TN, Buschang PH, Alexander RG: Long-term stability of Class II, division 1, nonextraction cervical face-bow therapy: II. Cephalometric analysis, Am J Orthod Dentofacial Orthop 109(4):386–392, 1996. 47. Franchi L, Baccetti T, McNamara Jr JA: Treatment and posttreatment effects of acrylic splint Herbst appliance therapy, Am J Orthod Dentofacial Orthop 115(4):429–438, 1999. 48. Harris EF, Vaden JL, Dunn KL, et al: Effects of patient age on postorthodontic stability in Class II, division 1 malocclusions, Am J Orthod Dentofacial Orthop 105(1):25–34, 1994. 49. Macdonald KE, Kapust AJ, Turley PK: Cephalometric changes after the correction of class III malocclusion with maxillary expansion/facemask therapy, Am J Orthod Dentofacial Orthop 116(1):13–24, 1999. 50. Moon YM, Ahn SJ, Chang YI: Cephalometric predictors of long-term stability in the early treatment of Class III malocclusion, Angle Orthod 75(5):747–753, 2005. 51. Baccetti T, Franchi L, McNamara Jr JA: Treatment and posttreatment craniofacial changes after rapid maxillary expansion and facemask therapy, Am J Orthod Dentofacial Orthop 118(4):404–413, 2000. 52. Lee DY, Kim ES, Lim YK, et al: Skeletal changes of maxillary protraction without rapid maxillary expansion, Angle Orthod 80(4):504–510, 2010. 53. Wells AP, Sarver DM, Proffit WR: Long-term efficacy of reverse pull headgear therapy, Angle Orthod 76(6):915–922, 2006. 54. Franchi L, Baccetti T, McNamara JA: Postpubertal assessment of treatment timing for maxillary expansion and protraction therapy followed by fixed appliances, Am J Orthod Dentofacial Orthop 5:555–568, 2004. 55. Westwood PV, McNamara Jr JA, Baccetti T, et al: Long-term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances, Am J Orthod Dentofacial Orthop 123(3):306–320, 2003. 56. Huang GJ, Justus R, Kennedy DB, et al: Stability of anterior openbite treated with crib therapy, Angle Orthod 60:17–24, 1990. 57. Vig KW: Nasal obstruction and facial growth: the strength of evidence for clinical assumptions, Am J Orthod Dentofacial Orthop 113(6):603–611, 1998. 58. Yashiro K, Takada K: Tongue muscle activity after orthodontic treatment of anterior open bite: a case report, Am J Orthod Dentofacial Orthop 115(6):660–666, 1999. 59. Burford D, Noar JH: The causes, diagnosis and treatment of anterior open bite, Dent Update 30(5):235–241, 2003. 60. Zuroff JP, Chen SH, Shapiro PA, et al: Orthodontic treatment of anterior open-bite malocclusion: stability 10 years postretention, Am J Orthod Dentofacial Orthop 137(3):302.e1–302.e8, 2010. 61. Smithpeter J, Covell Jr D: Relapse of anterior open bites treated with orthodontic appliances with and without orofacial myofunctional therapy, Am J Orthod Dentofacial Orthop 137(5):605–614, 2010. 62. Remmers D, Van't Hullenaar RW, Bronkhorst EM, et al: Treatment results and long-term stability of anterior open bite malocclusion, Orthod Craniofac Res 11(1):32–42, 2008. 63. Janson G, Valarelli FP, Beltrão RT, et al: Stability of anterior open-bite extraction and nonextraction treatment in the permanent dentition, Am J Orthod Dentofacial Orthop 129(6):768–774, 2006.

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64. Janson G, Crepaldi MV, Freitas KM, et al: Stability of anterior open-bite treatment with occlusal adjustment, Am J Orthod Dentofacial Orthop 138(1):14.e1–14.e7, 2010. 65. Baek MS, Choi YJ, Yu HS, et al: Long-term stability of anterior open-bite treatment by intrusion of maxillary posterior teeth, Am J Orthod Dentofacial Orthop 138(4):396.e1–396.e9, 2010. 66. Greenlee GM, Huang GJ, Chen SS, et al: Stability of treatment for anterior open-bite malocclusion: a meta-analysis, Am J Orthod Dentofacial Orthop 139(2):154–169, 2011. 67. Shannon KR, Nanda RS: Changes in the curve of Spee with treatment and at 2 years posttreatment, Am J Orthod Dentofacial Orthop 125(5):589–596, 2004. 68. De Praeter J, Dermaut L, Martens G, et al: Long-term stability of the leveling of the curve of Spee, Am J Orthod Dentofacial Orthop 121(3):266–272, 2002. 69. Preston CB, Maggard MB, Lampasso J, et al: Long-term effectiveness of the continuous and the sectional archwire techniques in leveling the curve of Spee, Am J Orthod Dentofacial Orthop 133(4):550–555, 2008. 70. Huang GJ, Bates SB, Ehlert AA, et al: Stability of deep-bite correction: a systematic review, J World Fed Orthod 1(3):e89–e86, 2012. 71. Simons ME, Joondeph DR: Change in overbite: a ten-year postretention study, Am J Orthod 64(4):349–367, 1973. 72. Harris EF, Vaden JL: Posttreatment stability in adult and adolescent orthodontic patients: a cast analysis, Int J Adult Orthodon Orthognath Surg 9(1):19–29, 1994. 73. Sadowsky C, Schneider BJ, BeGole EA, et al: Long-term stability after orthodontic treatment: nonextraction with prolonged retention, Am J Orthod Dentofacial Orthop 106(3):243–249, 1994. 74. Millett DT, Cunningham SJ, O'Brien KD, et al: Orthodontic treatment for deep bite and retroclined upper front teeth in children, Cochrane Database Syst Rev 18(4):2006, CD005972. 75. Pollard D, Akyalcin S, Wiltshire WA, et al: Relapse of orthodontically corrected deepbites in accordance with growth pattern, Am J Orthod Dentofacial Orthop 141(4):477–483, 2012. 76. Al Yami EA, Kuijpers-Jagtman AM, van 't Hof MA: Stability of orthodontic treatment outcome: follow-up until 10 years postretention, Am J Orthod Dentofacial Orthop 115:300–304, 1999. 77. Park H, Boley JC, Alexander RA, et al: Age-related longterm posttreatment occlusal and arch changes, Angle Orthod 80(2):247–253, 2010. 78. Lenz GJ, Woods MG: Incisal changes and orthodontic stability, Angle Orthod 69(5):424–432, 1999. 79. Artun J, Garol JD, Little RM: Long-term stability of mandibular incisors following successful treatment of Class II, Division 1, malocclusions, Angle Orthod 66(3):229–238, 1996. 80. Nett BC, Huang GJ: Long-term posttreatment changes measured by the American Board of Orthodontics objective grading system, Am J Orthod Dentofacial Orthop 127(4):444–450, 2005. 81. Dyer KC, Vaden JL, Harris EF: Relapse revisited-again, Am J Orthod Dentofacial Orthop 142(2):221–227, 2012. 82. Littlewood SJ, Millett DT, Doubleday B, et al: Orthodontic retention: a systematic review, J Orthod 33(3):205–212, 2006. 83. Booth FA, Edelman JM, Proffit WR: Twenty-year follow-up of patients with permanently bonded mandibular canine-to-canine retainers, Am J Orthod Dentofacial Orthop 133(1):70–76, 2008. 84. Renkema AM, Al-Assad S, Bronkhorst E, et al: Effectiveness of lingual retainers bonded to the canines in preventing mandibular incisor relapse, Am J Orthod Dentofacial Orthop 134(2): 179e1–179e8, 2008. 85. Renkema AM, Renkema A, Bronkhorst E, et al: Long-term effectiveness of canine-to-canine bonded flexible spiral wire lingual retainers, Am J Orthod Dentofacial Orthop 139(5): 614–621, 2011. 86. Vig K: Fixed lingual retainers prevent relapse of lower incisor alignment, J Evid Based Dent Pract 9(4):215–216, 2009.

C H A PT E R

24

Soft Tissue Diode Laser Surgery in Orthodontics Kathleen R. McGrory • Sam A. Winkelmann • Angela Marie Tran

A

s customized treatment plans and an increased focus on personal esthetics in orthodontics take hold, laser technology has risen to the forefront of adjunct care by creating the opportunity for the most esthetic result possible in conjunction with orthodontic treatment. In recent years, the use of laser technology in many aspects of general dentistry has given rise to greater access to laser education, thereby increasing the number of orthodontists who use laser technology to enhance or facilitate treatment outcomes. In the past, orthodontists were limited by the types and cost of lasers available on the dental market. With the advent of affordable diode lasers that limit tissue removal to soft tissue, orthodontists can now comfortably embrace lasers in the orthodontic field. The diode laser is of particular interest to orthodontists due to its tissue specificity and patient friendliness. Several advantages of the diode laser include ease of use, ability to maintain a hemostatic environment, minimal discomfort to the patient with use of topical anesthetic, soft tissue specificity, and no requirement for sutures. Slowly erupting teeth and gingival overgrowth no longer delay treatment completion when the orthodontist can turn to the diode laser for quick, easy removal of soft tissue covering the crowns of teeth. Unesthetic gingival contours and margins, along with gingival hyperplasia, can now be managed in coordination with incisal recontouring to produce the most esthetic treatment outcome. Several soft tissue laser procedures along with their indications and methods will be addressed in this chapter.

1. What soft tissue procedures using a laser should an orthodontist consider? Orthodontists want the best functional and esthetic treatment results for their patients and are constantly striving to find methods to enhance treatment results and reduce treatment time. The advent of soft tissue lasers has given the orthodontist more control over factors that previously could impede treatment time and compromise treatment results. Clinical instances where the use of a soft tissue laser would benefit both the orthodontist and the patient include gingival recontouring, removal of hypertrophic tissue, aphthous ulcer management, facilitation of tooth eruption, operculum removal, and frenectomies.1–5 GINGIVAL RECONTOURING Gingival reshaping can improve tooth proportions, and improving a gummy smile can greatly enhance the esthetic treatment outcome. The ideal position of the gingival 302

margins of the upper anterior teeth is at or near the inferior border of the upper lip during a full smile.5 Gingival recontouring is indicated in patients with poor hygiene where inflamed gingiva, pseudopockets, and difficulty brushing and flossing are present3,4 (Fig. 24-1). Excessive gingival tissue may also prevent the orthodontist from placing brackets in their ideal position. The removal of this excess gingival tissue permits the orthodontist to bond a bracket to the tooth in the desired position in a timely manner3,4 (Fig. 24-2, Fig. 24-3, and Fig. 24-4). APHTHOUS ULCER MANAGEMENT Aphthous ulcers are uncomfortable and often painful for the patient. Traditionally, salt water rinses, topical anesthetic, and tetracycline would be prescribed to alleviate the symptoms.3 With a diode laser, the orthodontist has the ability to lase the aphthous ulcer, relieving the patient of pain and speeding the healing of the lesion. The diode laser is activated for 30 seconds at a very low wattage or with a non-activated tip, and kept at a distance of 1 to 2 mm away from the lesion.3,4 Aphthous ulcers generally take up to 14 days to heal, but with laser treatment, the ulcers may heal within 1 day after treatment. The laser wound that replaces the ulcer is not painful and allows the patient to have a faster and more comfortable recovery.3,4 TOOTH EXPOSURE Soft tissues sometimes cover a tooth and impede its eruption into the arch. Delayed tooth eruption or gingival tissue in the way of proper bond positioning can extend treatment time. The diode laser can be used to remove the overlying tissue so that the orthodontist can bond a bracket and begin moving the tooth immediately.3,4 Many months can be saved in cases with labially placed high cuspids that are taking a long time to erupt through excessively tough gum tissue (Fig. 24-5, Fig. 24-6, Fig. 24-7, and Fig. 24-8). Unerupted teeth should be palpated, visualized, and localized by radiographic images to determine if laser uncovering is warranted. OPERCULUM REMOVAL Orthodontists sometimes find themselves waiting to band or bond second molars when an operculum is present. The diode laser can remove the operculum, allowing immediate placement of a band or bond on the desired tooth to keep treatment on track for timely completion.4

Soft Tissue Diode Laser Surgery in Orthodontics • CHAPTER 24

FIG 24-1 Gingival hyperplasia from inadequate oral hygiene.

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FIG 24-6 Archwire traction placed on delayed cuspids.

FIG 24-7 Cuspid exposed with diode laser and bonded. FIG 24-2 Excessive gingival tissue inhibiting proper bracket placement.

FIG 24-8 Cuspid seated into occlusion. FIG 24-3 Cuspid engaged in proper position.

FIG 24-4 Delayed passive eruption.

FRENECTOMIES Patients who have a large central diastema often have a low frenum that contributes to the excessive spacing. After orthodontically closing the space, or sometimes before space closure, it may be recommended to perform a frenectomy to help stabilize the space closure long term. The laser can also be used for the release of a tight lingual frenum for the treatment of tongue-tie or on any frenum that is causing a traumatic force on the gingival margin of a tooth (Fig. 24-9, Fig. 24-10, and Fig. 24-11). The soft tissue laser makes frenectomy procedures easier to manage than a traditional scalpel approach, minimal in discomfort, and hemostatic.

2. What type of laser should be used in orthodontics?

FIG 24-5 Delayed cuspid eruption.

Four main types of lasers are used in dentistry: the CO2 laser, the Nd:YAG laser, the erbium lasers (Er:YAG and Er, Cr:YSGG), and the diode laser. The CO2 laser can be difficult to use due to technique sensitivity because the tip does not directly contact the surgical site; instead, it must be used at a slight distance and a delay is present from the time the incision is made to when the incision can be seen.2 The erbium laser has a very

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CHAPTER 24 • Soft Tissue Diode Laser Surgery in Orthodontics

FIG 24-9 Normal lingual frenum.

FIG 24-10 Lingual frenum with excessive tongue tie.

of aluminum, gallium, arsenide, or indium, has a wavelength of roughly 810 nm to 980 nm. This wavelength is readily a bsorbed by melanin and hemoglobin, and poorly absorbed by tooth structure and metal, making diode lasers ideal for soft tissue surgeries. The diode laser works by energy, via an electrical current, being supplied to the laser system and moved through the active medium contained in an optical resonator that amplifies the photons. The photons are then delivered to the target tissue by way of a fiber optic cable with a protective outer coating. The outer coating must be removed prior to tip initiation before the laser can be used for tissue ablation. The laser cuts the tissue through ablation, where the energy is absorbed in the target cells and is immediately subjected to heating, welding, coagulation, protein denaturation, drying vaporization, and carbonization.2 It is recommended that the laser deliver its energy in a pulsed mode, which allows intermittent cooling, less tissue damage, and less discomfort.2 Most procedures can be performed at a setting of 1 to 1.2 watts. Areas with dense tissue may require settings closer to 2 watts. The American Academy of Laser Dentistry recommends using the lowest power setting that can effectively remove the tissue to help prevent collateral thermal damage of adjacent tissue.

4. What is the indication and technique for soft tissue laser surgery for gingival recontouring?

FIG 24-11 Lingual frenum causing gingival recession.

high wavelength and is effective in soft tissue removal; however, it does not control bleeding well and also cuts hard tissue.2 The diode laser, where the light energy is absorbed by the melanin pigment found within the cells,2 allows exceptional control of bleeding at the surgical site. The laser tip gently contacts the surgical site, allowing the operator to have tactile feedback during ablation.2 Other advantages of the diode that make it ideal for use in orthodontics include its manageable size for portability, its specificity to cut only soft tissues and not hard tissues, its relatively low cost compared to other dental lasers, and the fact that procedures typically require only a topical anesthetic for pain management.2

3. How does a diode laser work? A laser is made up of three main components: an energy source, an active medium, and an optical cavity or resonator. The wavelength of a laser is determined by the composition of the active medium. The diode laser, which uses an active medium

The principles of cosmetic dentistry must be incorporated into orthodontic treatment in order to optimize the esthetic results.1 Orthodontists routinely evaluate the smile line, smile arc, and tooth and gingival proportions. The orthodontist should understand the esthetic concepts of tooth proportions, contacts, embrasures, and gingival characteristics before using laser surgery for gingival removal. The ideal maxillary central incisor should be approximately 66% to 80% width compared with height.1 It is important to assess if a tooth disproportion is due to a short clinical crown height, gingival overgrowth, or delayed passive eruption.1 Depending on the cause of disproportion, waiting for eruption, gingival recontouring, or dental restoration of lost tooth structure may be the optimal solution.1 Other important esthetic concepts include the placement of contact points and embrasures. Assessing teeth from the midline to posterior, contact points between teeth should progress apically and embrasures should become larger.1 Gingival esthetics play an important role in the overall success of a treatment outcome. The gingival shape (the curvature of the gingival margin of the tooth) of the mandibular incisors and maxillary laterals should have a symmetrical half-oval or half-circular shape; therefore, their gingival zenith should be located within their longitudinal axis.1 The gingival shape of the maxillary centrals and canines is elliptical with a gingival zenith that is distal to the longitudinal axis.1 The orthodontist can find numerous occasions to use gingival recontouring to improve treatment results. When initially evaluating a patient for orthodontic care, the orthodontist carefully evaluates the casts and patient to determine


ideal bracket placement. Most orthodontists will use the incisal edge of the teeth to determine bracket placement height. Orthodontists find that they may be unable to place a bracket in an ideal location because of gingival overgrowth or delayed passive eruption. In these instances, it would be very helpful for the orthodontist to be able to remove any excess gingival tissue in order to place the brackets in an ideal position rather than waiting for eruption or referring the patient to a periodontist to have the teeth uncovered.3,4 Gingival recontouring can also be helpful in aiding patients with poor oral hygiene. Patients with marginal to poor oral hygiene can cause inflammation and pseudopocket formation of their gingiva. These pseudopockets can exacerbate the inflammatory process by impeding the patient’s ability to thoroughly brush and floss around the teeth and gums.3,4 Gingival recontouring can help to reduce this inflammation and allow the patient to access more areas to keep the gingivitis under control. Closing large extraction spaces can sometimes cause redundant tissue to appear, especially in conjunction with poor oral hygiene.3 Removal of this tissue allows the patient to keep these areas under hygienic control and allows for more effective space closure. Gingival recontouring is extremely useful in finishing a case to a best esthetic outcome. Patients may have uneven gingival margins, gingival inflammation, or poor crown height-towidth ratios that result in less than optimal treatment results. The soft tissue laser allows orthodontists to improve tooth proportionality and gingival shape and contour in accordance to the smile arc and smile line of the individual patient.1,2,4 When performing a gingivectomy, apply topical anesthetic and use a probe to mark height guides, leaving 1 mm of sulcus when finished to preserve the biologic width. Bleeding points or laser points can be used to mark the new gingival contour. With the laser set at 1.2 watts, hold the laser tip perpendicular to the tissue at the gingival margin, and in a smooth, continuous fashion, cleanly remove the excess gum tissue. After the ideal contours are achieved, clean the area with a microbrush or cotton roll with 3% hydrogen peroxide6 (Fig. 24-12, Fig. 24-13, Fig. 24-14, Fig. 24-15, Fig. 24-16, and Fig. 24-17).

5. What are the indication and technique for soft tissue laser surgery for a frenectomy? Patients who have a large diastema often have a low frenum attachment that can contribute to the excessive spacing. Orthodontists treat the diastema by closing the space and then stabilizing it with fixed or removable retention in addition to a frenectomy. The soft tissue laser makes performing a frenectomy more comfortable for the patient. The healing process is less painful, no sutures or dressings are needed, and bleeding is highly controlled. The technique for performing a frenectomy includes first placing topical anesthetic at the surgical site. Hold the upper lip and lightly pull the lip forward until the frenum is taut. With the laser set at 1.0 watts, lase the frenum horizontally approximately 3 mm from the frenum base, and use light, continuous strokes until the lip is released from tension, leaving a V-shaped

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A

B

C

FIG 24-12 A, Uneven gingival architecture detracts from finished orthodontic case. B, Diode laser used to sculpt proper architecture. C, Enhanced esthetic result after diode laser recontouring and healing.

A

B

FIG 24-13 A, Central incisors lack proper proportion. B, Enhanced esthetics from proper height-to-width ratio of centrals.

wound approximately 1 cm wide. Continue to lase any deeper fibrous attachments to prevent reattachment. Then, lasing parallel to the gingiva, smooth the remaining tissue at the base of the frenum. Clean the surgical site with 3% hydrogen peroxide on a cotton roll or cotton-tipped applicator.6 Another


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A A

B

B C

FIG 24-16 A, Uneven gingival architecture. B, Immediately after diode laser therapy. C, Enhanced symmetry after healing.

C

FIG 24-14 A, Low, rolled gingival tissue in anterior. B, Immediately post tissue removal with diode laser. C, Esthetic crown height-to-width ratio after healing.

A

A

B B

C C

FIG 24-15 A, Gingival hyperplasia from a lack of proper oral hygiene technique. B, Immediately post diode laser tissue removal. C, Tissue response after healing for 2 weeks.

FIG 24-17 A, Patient unhappy with gums when smiling. B, Immediately after diode laser therapy. C, Patient happy with increased esthetics of smile.


A

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A

B B

C C

FIG 24-18 A, Strong frenum pull and gingival hyperplasia. B, Immediately after excess tissue removal and release of frenum tension. C, Gingival tissues healed and no excessive pull from frenum.

FIG 24-20 A, Bilateral impacted maxillary cuspids. B, Cuspids uncovered and brackets bonded. C, Cuspids engaged with archwire to help erupt teeth into position.

A A

B

B

C

C

FIG 24-19 A, Cuspid bulge evident, but tooth has not erupted. B, Diode laser used to open small access window. C, Bracket bonded and elastic force used to help erupt tooth into position.

FIG 24-21 A, Delayed eruption of cuspid. B, TAC 20% topical anesthetic applied to numb the gingiva where laser will be used. C, Cuspid uncovered and ready for bracket to be bonded.

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technique, the diamond-release frenectomy, involves pulling the upper lip taut, lasing the sides of the V-shaped frenum, and then lasing the base of the frenum, which creates a diamondshaped surgical site (Fig. 24-18).

6. What is the indication and procedure used with a soft tissue laser to uncover impacted teeth? Orthodontic treatment can sometimes be slowed dramatically by waiting on a soft tissue impacted tooth to erupt.3 Traditionally, patients would be referred to a periodontist for the tooth to be exposed and a bond and chain could be placed for orthodontic traction; however, thick tissue covering the tooth can still impede the tooth from finally erupting into the arch, especially palatal tissue. The soft tissue laser can be used to remove thick tissue so that the tooth can continue to be moved into the arch without hindrance. Sometimes the impacted tooth is nearly erupted into the mouth with just a thin layer of tissue still covering its surface.3 In these cases, the laser can be used to remove the overlying tissue so that the orthodontist can bond an attachment to the tooth and begin moving it into the arch immediately.3 When lasing tissue overlying a tooth, the operator must adjust the power as needed according to the tissue thickness. After applying topical anesthetic, probe the surgical site to locate the tooth, confirm there is no bone covering the tooth, and mark the attached tissue. Starting with the laser set at 1.2 watts and

adjusting as needed according to tissue density, carefully remove the tissue with light, continuous strokes until the underlying tooth is exposed. After exposure, wipe the area with 3% hydrogen peroxide with a microbrush or cotton roll. A bond can be placed immediately after tissue removal6 (Fig. 24-19, Fig. 24-20, and Fig. 24-21). REFERENCES 1. Sarver DM: Principles of cosmetic dentistry in orthodontics: part 1. Shape and proportionality of anterior teeth, Am J Orthod Dentofacial Orthop 126:749–753, 2004. 2. Sarver DM, Yanosky MR: Principles of cosmetic dentistry in orthodontics: part 2. Soft tissue laser technology and cosmetic gingival contouring, Am J Orthod Dentofacial Orthop 127:85–90, 2005. 3. Sarver DM, Yanosky MR: Principles of cosmetic dentistry in orthodontics: part 3. Laser treatments for tooth eruption and soft tissue problems, Am J Orthod Dentofacial Orthop 127:262–264, 2005. 4. Yanosky MR: The soft tissue laser: managing treatment and enhancing aesthetics, orthodontic Products (website): http:// www.orthodonticproductsonline.com/2006/08/the-soft-tissuelaser-2006-08-05/. Accessed March 20, 2014. 5. Tracey S: Lasers in orthodontics, Academy of Dental Therapeutics, (website): http://www.ineedce.com/courses/2028/PDF/1103cei_ laser_ortho_web3.pdf. Accesses July 9, 2014. 6. Denmat Lasers. Orthodontic laser procedure guide. Available at: https://d2jos99evcoum8.Cloudfront.net/orchestraCMS/ a2S80000000foGzEAI.pdf. Accessed July 9, 2014.

Secrets in Computer-Aided Surgical Simulation for Complex Craniomaxillofacial Surgery

C HA P T ER

25

James J. Xia • Jaime Gateno • John F. Teichgraeber • David M. Alfi

C

raniomaxillofacial (CMF) surgery is an encompassing term that involves the treatment of diseases, injuries, and deformities of the skull and face. CMF deformities can occur in utero and are present at birth, while others are acquired later in life. They result from many causes: genetic abnormalities, deformations, intrauterine disruptions, diseases, injuries, or abnormal function. Because of the complex anatomy of the skull and face, the treatment of these deformities requires extensive presurgical planning

1. How many patients with craniomaxillofacial deformities are in the United States? In the United States, it is estimated that 17 million individuals aged 12 to 50 years (18% of the population) have malocclusions that are severe enough to warrant surgical correction.1–4 In addition, congenital anomalies of the CMF skeleton affect a large number of children. The most common congenital anomalies include cleft lip and palate (0.3 to 3.6 per 1000 live births depending on ethnicity5), craniosynostosis (343 to 476 per 1 million live births6), and hemifacial microsomia (1 per 5600 live births5). A majority of these patients require surgery. Additional CMF deformities also occur after tumor ablation and trauma. Treatment for head and neck tumors often results in significant deformities that require reconstruction.7,8 The incidence of head and neck cancer is 9.7 per 100,000 Americans. This translates into 28,000 new patients every year, a figure that does not include an even larger number of patients with benign tumors who may also require surgery.9 It is reported that nonfatal injuries from trauma affect 28 million Americans (10% of the population) annually10 with 37% suffering injuries involving the head and face.11 A significant number of these patients also require surgical treatment. Finally, 5% to 15% of the population is reported to have symptoms of temporomandibular joint (TMJ) disorders with peak prevalence in young adults (20 to 40 years of age).12,13 Although the majority of these patients does not need surgical treatment, patients with TMJ ankylosis, severe rheumatoid arthritis, or osteoarthritis may require TMJ reconstruction. It is estimated that about 3000 prosthetic joint replacements are performed each year,14 as well as a similar number of autogenous reconstructions.

2. What are the current planning methods for craniomaxillofacial surgery? CMF surgery requires extensive presurgical planning because of the complex anatomy of the skull and face. The current

methods used to plan CMF surgery vary according to the type of surgery being planned but are not much different from the methods that are used to plan orthognathic surgery. In general, current surgical planning methods for complex CMF deformities involve the following steps. The first step is to gather data from many difference sources, including physical examination, photographs, imaging studies (e.g., cephalograms, computed tomography [CT], and so on), and plaster dental models. The second step is to simulate the surgery, including prediction tracings, dental model surgery, or CT-based physical model surgery. The last step in surgical planning is to create a way of transferring the surgical plan to the patient at the time of the surgery. This is usually done by creating surgical splints, templates, measurements of the bone movements, and visual “clues.”

3. Why are the current planning methods often not adequate for planning complex craniomaxillofacial surgery? ISSUES WITH TWO-DIMENSIONAL PREDICTION TRACINGS CMF surgery is usually simulated using prediction tracings. These tracings are made on a cephalogram by outlining the bones and soft tissues onto an acetate paper.15,16 The outlines of the bones to be moved are drawn on additional sheets of acetate paper. The surgical simulation is completed by moving the bone tracings to the desired position. Similar prediction tracings can also be completed using computerized software. A significant drawback of prediction tracing is that it is twodimensional (2D).17–20 The patient’s three-dimensional (3D) anatomic structures are compressed into a 2D cephalometric radiograph, creating an overlap of structures. Prediction tracings may be clinically acceptable if the patient only has anteroposterior (AP) or vertical deformities. However, with this technique, it is impossible to simulate surgery in three dimensions, which is essential in patients with 3D problems (i.e., asymmetries).21,22 Another problem with prediction tracings is that they portray the dentition as a 2D image.21,23 For this reason, surgeries that involve the dentition should also be simulated on plaster dental models that have been mounted on an articulator.15,16,24 ISSUES WITH COMPUTED TOMOGRAPHY MODELS Three-dimensional (3D) CT scans have been successfully used to visualize and to quantify the patient’s condition. However, they have not been successfully used for surgical simulation 309

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because of two major reasons. First, the CT does not render the teeth with the accuracy that is necessary for surgical simulation.21,23 Raw CT data are presented by a sequence of 2D cross-sectional images of the volume of interest, layer by layer. During 3D reconstruction, the missing data between adjacent layers are reconstructed by mathematical algorithms (e.g., Marching Cubes25). Currently, the most precise 3D CT scanners scan at a minimum slice thickness of 0.625 mm. This thickness, while adequate for bony structures, is not capable of accurately rendering the teeth to the degree that is necessary for surgical planning. The occlusion between maxillary and mandibular teeth requires a high degree of precision. Even a 0.5-mm error may cause malocclusion. Furthermore, it is very difficult, if not impossible, to remove artifacts, which is the scattering caused by orthodontic brackets or dental metallic restorations. Because of these limitations, surgeries that involve the teeth are still simulated on plaster dental models to fabricate surgical splints.15,16,24 With the rapid development of cone beam computed tomography (CBCT) technology, the scanning slice thickness is reduced to 0.2 mm. It also has a better control of artifacts. Radiation exposure to the patient has been significantly reduced. The CBCT scanner has become a useful tool for orthodontists and dentists. However, in the treatment of complex CMF deformities, surgeons need to see the “true” replica of the skeleton. Images from CBCT have very low contrast compared with regular medical CT images. This makes the segmentation process—to separate the bones from soft tissue on the CT image—rather difficult. After 3D reconstruction, it is common to observe that the anterior walls of the maxillary sinus or orbital floors are “mystically” missing on the 3D model. Although the artifacts produced by CBCT are minimal, the rendition of the teeth is still inappropriate for simulating the final occlusion or for making the surgical splints. ISSUES WITH COMPUTED TOMOGRAPHY–BASED PHYSICAL MODELS Another means of simulating surgery is to use CT-based physical models produced by rapid prototyping techniques (e.g., stereolithography [SLA] apparatus models). Even though these models are useful, they have a number of disadvantages. One disadvantage is that in cases involving the occlusion, the teeth are not accurate enough for precise surgical simulation. This is because the CT image data, from which the models are built, are unable to accurately render the teeth and are also subject to artifacts. Additional plaster dental model surgery is still necessary to establish a new dental occlusion and to fabricate surgical splints. Another disadvantage is that it is impossible to simulate different surgeries on a single model. Once the model is cut, the cut is irreversible. ISSUES WITH PLASTER DENTAL MODEL SURGERY Surgeries that involve the teeth are also simulated on plaster dental models.15,16,24 The purpose of this step is to establish a new dental occlusion and to fabricate surgical splints. The

splint helps the surgeon establish the desired relationship between maxilla and mandible. A drawback of plaster dental models is that they do not depict the surrounding bony structures.23,26 Therefore, it is impossible for the surgeon to visualize the skeletal change that occurs during model surgery, which is critical in the treatment of complex CMF deformities. Finally, there are two major issues regarding the use of plaster dental model surgery. Issues with Face-Bow Transfer The ability of the surgeon to transfer the desired surgical plan to the patient during orthognathic surgery depends mainly on the accuracy of the surgical splint. The fabrication of an accurate splint requires that the models be mounted to replicate the position of the patient’s dentition. However, Ellis and colleagues24 demonstrated a significant difference between the inclination of the occlusal plane on the mounted models and the actual occlusal plane as measured on the cephalograms. Another study27 confirms these findings, showing that the average occlusal plane inclination obtained by using the SAM Anatomical Face-Bow is 7.8 ± 4.2 degrees greater than the actual. The advantage of using models that are accurately oriented to the horizontal plane becomes evident once the implications of using inaccurately mounted models are understood. Fig. 25-1 illustrates the results of using inaccurate models to fabricate an intermediate splint. Fig. 25-1, A, depicts the cephalometric tracing of a hypothetical patient with mandibular prognathism and maxillary hypoplasia. The surgical plan for this patient calls for a 10-mm maxillary advancement and a 4-mm mandibular setback. In this case, the axis-orbital plane (face-bow) is 12 degrees off the horizontal. Fig. 25-1, B, depicts the articulator on which the models have been mounted using the conventional system. The occlusal plane inclination of the mounted models (see Fig. 25-1, B) is 12 degrees greater than that on the cephalometric tracing (see Fig. 25-1, A). Fig. 25-1, C, depicts the maxillary model that has been advanced 10 mm forward, and the intermediate splint has been fabricated. Fig. 25-1, D, depicts the planned position for the maxilla and the actual position of the maxilla at the time of surgery. In this hypothetical case, the position of the maxilla at surgery is 1.5 mm behind the planned position, producing a maxillary advancement of only 8.5 mm, or 15% less than desired. In order to solve this problem, researchers and clinicians have developed various techniques. Ellis and colleagues24 developed a modified mounting technique used with the Hanau articulator. In addition, Gateno and colleagues27 developed a face-bow transferring technique used with the SAM articulator, which is a technique that takes into consideration the individual anatomic variations among subjects. Issues with the Transfer of the Surgical Plan to the Patient at the Time of the Surgery The last step in surgical planning is to transfer the surgical plan to the operating room. In cases involving the jaws, this is done using dental splints.15,16 These splints help the surgeon place the jaws in the desired position. However, for craniofacial operations

Secrets in Computer-Aided Surgical Simulation for Complex Craniomaxillofacial Surgery • CHAPTER 25

A

B

C

D

311

FIG 25-1 Face-bow transfer of a hypothetical patient. A, Prediction tracing of a hypothetical patient. The horizontal black line is Frankfort horizontal. The red line is the axis-orbital plane, which is 12 degrees off Frankfort horizontal. The plan calls for a 10-mm maxillary advancement (blue line). B, The models are mounted on an articulator. Note that the occlusal plane inclination of the mounted models is 12 degrees steeper than the actual occlusal plane. C, Model surgery. The maxillary model has been advanced 10 mm, and the intermediate splint (red) has been fabricated. D, The maxillary position at surgery. The blue outline represents the desired position for the maxilla. The red outline represents the actual position at surgery. Note that the actual position is 1.5 mm behind the desired position.

not involving the dentition (e.g., orbital osteotomies, cranial vault reshaping), surgeons currently do not have an accurate method of transferring the plan to the operating room. Certain measurements taken during the planning process can be used to guide surgery, but most commonly, the placement of the bones in the desired position is more of an art than a science. HOW TO SOLVE THESE ISSUES The success of CMF surgery depends not only on the surgical techniques, but also on an accurate surgical plan. Each one of the problems mentioned earlier can result in a less than ideal surgical outcome. In isolation, these problems may be minor, but when added together the results can be devastating.22,23,28–30 Moreover, the whole planning process is time consuming.31 An experienced surgeon frequently spends 4 to 6 hours to complete the surgical plan and to fabricate the splints. Finally, the cost of planning a complex case, both in time and in resources, can be fairly high.31

The need to improve the current surgical planning methods has led researchers to develop a more sophisticated planning method for CMF surgery (i.e., computer-aided surgical simulation [CASS]). CASS has wide applications in maxillofacial surgery,19,32–37 craniofacial surgery,20,38 trauma, and distraction osteogenesis.20,39–43 Using CASS, surgeons can perform “virtual surgery” and create a 3D prediction of the patient’s surgical outcomes as if they are performing surgery in the operating room.

4. What are the basic steps of computeraided surgical simulation clinical protocol to plan a craniomaxillofacial surgery? There are four major steps in the CASS protocol.30,44 The first step of the CASS protocol involves the collection of the preoperative records. The records include direct anthropometric measurements, clinical photographs, stone dental models, a patient-specific bite jig, a neutral head posture (NHP) recording, and a CT scan of the face.

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The second step of the protocol involves data processing. This entails the creation of a composite skull model that displays an accurate rendition of the skeleton, soft tissues, and teeth (the details will be described in the next question); reorientation of the composite skull model to NHP; establishment of a unique 3D coordinate system for the 3D models; and digitization of cephalometric landmarks. The third step of the CASS protocol is to plan and simulate the surgery in the computer. 3D cephalometric analysis is performed. Guided by real-time cephalometric measurements and clinical measurements, the surgeon plans the surgery by moving and rotating the digitally osteomized bony segments until the desired outcome is achieved. The final step of the protocol is to fabricate surgical splints and templates. These are generated in the computer and fabricated using a rapid prototyping machine. Chin templates for the genioplasty and other bone graft/ostectomy templates are also fabricated as needed. Splints and templates are used to transfer the computerized plan to the patient at the time of the surgery.

5. How do you create a computer model that is adequate for planning a craniomaxillofacial surgery? If the surgery does not involve teeth, a conventional 3D CT model can be used for surgical planning. However, if the surgery involves teeth, as mentioned previously, a conventional CT model does not present the teeth accurately to the degree that is necessary for surgical planning. Therefore, a composite skull model17,21,45 is required. This model simultaneously displays an accurate rendition of both the bony structures and the teeth. It is done by merging two separate digital data sets: the digital dental models and the 3D CT. The merger of separate data sets is done by utilizing common reference points between the two sets. Our approach utilizes fiducial markers for this purpose. In

our system, the fiducial markers are spheres that are part of a plastic face-bow. The face-bow is attached to a bite registration that is placed in the patient and on the dental models before they are scanned (Fig. 25-2, A). In order to create a composite skull model, it is necessary to create a patient-specific bite jig using self-curing low-shrinkage bite registration material (e.g., LuxaBite [DMG America, Englewood, NJ]). The bite registration material is first placed on the bite jig and an impression is taken on the occlusal surfaces of the maxillary teeth. After the bite registration material has hardened, additional material is placed in the mandibular side of the jig, and the mandibular bite registration is captured in centric relation (CR). Once the bite registration is created, a face-bow with a set of fiducial markers (Medical Modeling Inc., Golden, CO) is attached to the bite jig. These markers serve as points of reference to register the digital dental models to the 3D CT. A CT scan of the patient’s craniofacial skeleton is then obtained while the patient is biting on the bite jig (see Fig. 25-2, B). The CT scan can be completed using either a spiral multi-slice CT scanner (using the standard scanning algorithm, matrix of 512 × 512 at 0.625 to 1.25 mm slice thickness, 25 cm or lesser field of view, 0° gantry tilt and 1:1 pitch), or a CBCT scanner (with 0.4-mm isotropic voxel). After segmentation, three separate but correlated computer models are generated: a midface model, a mandibular model, and a fiducial-marker model (see Fig. 25-2, C). The digital dental models are then created by scanning the plaster dental models, the bite jig, and the face-bow (see Fig. 25-2, D). This can be done with a 3D surface scanner (res olution: 0.1-mm or higher), a calibrated CBCT scanner (with 0.125- to 0.2-mm isotropic voxel), or a micro-CT scanner (resolution: 7 μm to 75 μm). This generates three separate but correlated computer models: a maxillary digital dental model, a mandibular digital dental model, and a fiducial-marker model (see Fig. 25-2, E).

FIG 25-2 Creation of the computerized composite skull model. A, Face-bow with fiducial markers is attached to the bite jig. B, The patient is biting on the bite jig and facebow during computed tomography (CT) scan. C, Three separate but correlated computer models are reconstructed: a midface model, a mandibular model, and a fiducial-marker model. D, The bite jig and face-bow are placed between the upper and lower plaster dental models during the scanning process. E, Three separate but correlated computer models are also reconstructed: an upper digital dental model, a lower digital dental model, and a fiducial-marker model. F, By aligning the fiducial markers, the digital dental models are incorporated into the three-dimensional (3D) CT skull model. The computerized composite skull model is thus created. It simultaneously displays an accurate rendition of both the bony structures and the teeth.


313

FIG 25-3 Orientation of the composite skull model to the neutral head posture (NHP) using the laser scanner method. A, The surface geometry of the facial soft tissue is captured while the patient is sitting on a calibrated chair at the center of the laser scanner. B, Captured surface geometry (scanned image) of the facial soft tissue. C, In the computer, a soft tissues model is rendered, and the composite model is “glued” to the soft tissue model. D, The soft tissue model is aligned to the NHP by matching it to the scanned image. E, Both soft tissue and composite skull models are thus oriented to the NHP. F, The composite skull model is in the NHP after the soft tissue is hidden.

After the 3D CT models and the digital dental models are obtained, the teeth of the CT skull model are removed, leaving the fiducial markers in place. The maxillary and the mandibular digital dental models with their corresponding fiducial markers are imported into the CT skull model. By aligning the fiducial markers, the digital dental models are incorporated into the 3D CT skull model. The fiducial markers are then hidden. This results in a computerized composite skull model, which simultaneously displays an accurate rendition of the bones and the teeth (see Fig. 25-2, F).17,21,29,30

6. How is the composite skull model reoriented to neutral head posture? Because many patients with CMF deformities have significant asymmetries, common cephalometric landmarks and planes cannot be used to orient the composite skull model. The use of the NHP obviates the need for internal landmarks and provides a reproducible reference framework. The NHP is a head position where the human head is not flexed, extended, tilted, or rotated. There are two methods to attain NHP: self-balanced position or physician-manipulated position. A self-balanced NHP is usually established by the patient flexing and extending her/his head and then balancing in a position of comfort while looking straight ahead to a blank wall without specific focus. A physician-manipulated position is usually used when the patient has a tendency to tilt or rotate away from neutral alignment. Our laboratory has developed two techniques to orient the composite model to the NHP: the first one utilizes a 3D calibrated laser surface scanner and the second utilizes a digital orientation sensor. With the laser surface scanner method, the surface geometry of the facial soft tissues is captured while the patient is in the NHP. During the scanning, the patient is sitting on a calibrated chair at the center of the scanner. The scanner creates a correctly oriented 3D image of the face. The soft tissues of the

composite model are then rendered, and the model is aligned to the NHP by matching its soft tissues to the scanned image (Fig. 25-3).17,29 The digital orientation sensor technique is the one we are currently using in our clinical practice. In this technique, a digital orientation sensor is attached to the same face-bow. With the patient in the NHP, the pitch, roll, and yaw of the face are recorded.46,47 The recorded pitch, roll, and yaw are then used to reorient the composite skull model. In the computer, a digital replica (computer-aided design [CAD] model) of the digital orientation sensor is registered to the composite skull model via the fiducial markers, and the two objects are attached to each other. Afterward, the recorded pitch, roll, and yaw are applied to the digital oriental sensor replica reorienting the composite skull model to the NHP (Fig. 25-4). The advantages of the digital orientation sensor technique are cost and convenience. The digital orientation sensor costs a hundred times less than the laser scanner, it is portable, and requires little maintenance. In addition to the methods described earlier, other methods may be used to record the NHP. They include the use of a 3D digitizer48 and photographs. In the latter method, lateral and frontal photos are taken orthogonally using a camera that is calibrated to the true vertical plane (Fig. 25-5).

7. How do you perform a three-dimensional cephalometric analysis? Two basic problems are associated with traditional 2D cephalometry. First, many important parameters cannot be measured on plain cephalograms, and second, most 2D cephalometric measurements are distorted in the presence of facial asymmetry. 3D cephalometry, which has been facilitated by the introduction of CBCT scans, can solve these problems. Unfortunately, 3D cephalometry is much more complex than just adding the third dimension (width) to a

314


FIG 25-4 Orientation of the composite skull model to the neutral head posture (NHP) using the digital orientation sensor method. A, A digital orientation sensor is attached to the bite jig and face-bow. B, The pitch, roll, and yaw of the sensor are recorded. C, In the computer, a digital replica (computer-aided design [CAD] model) of the digital orientation sensor is registered to the composite skull model (via the fiducial markers), and the two objects are attached to each other. D, The recorded pitch, roll, and yaw are applied to the sensor replica reorienting the composite skull model to the NHP. E, After the composite skull model is orientated to the NHP, the digital orientation sensor replica is marked hidden.

FIG 25-5 Orientation of the composite skull model to the neutral head posture (NHP) using the photographic method. The photographic method utilizes a calibrated camera to take orthogonal lateral and frontal photos when the patient is in the NHP. The recorded NHP is then transferred to the three-dimensional (3D) composite model in the computer.


lateral analysis.30 There are several important problems with 3D cephalometry. These include the reference systems, the way in which angles and distances are measured in 3D, and the assessment of symmetry. In addition, facial asymmetry affects 3D and 2D cephalometric measurements.49 These fundamental problems must be solved before a 3D cephalometry can be realized. To this end, we have developed a prototype of a new 3D cephalometric analysis that uses different geometric approaches to solve the fundamental problems previously mentioned.50 This analysis allows the accurate measurement of the size, shape, position, and orientation of the different facial units and incorporates a novel method to measure asymmetry. The goal of our new 3D cephalometric analysis is to maintain all of the positive aspects of conventional 2D analysis while addressing its negative aspects. All cephalometric measurements are classified into four different groups (size, shape, position, and orientation) according to the parameter they measure. In our new analysis, size is measured as a linear distance in 3D space. Shape is measured by projecting the involved landmarks onto the midsagittal plane of the local coordinate system⁎ for each facial unit. Position is measured differently depending on the direction of the measurements. The transverse position is measured as a linear distance between the involved landmark and the midsagittal plane of the world coordinate system. The AP and vertical positions are measured after all the involved landmarks have been projected onto the midsagittal plane of the world coordinate system. Finally, orientation is measured as separate pitch, roll, and yaw for each facial unit. This is done by comparing the orientations of the local and world coordinate systems. Finally, our 3D cephalometric analysis is divided into six components: symmetry, transverse, vertical, pitch, AP, and shape (Fig. 25-6). The order of these sections mimics the ideal order in which a 3D surgical plan should be developed. The symmetry analysis is novel, whereas the other five components incorporate time-proven measurements. The new analysis also incorporates data gathered during the physical examination. The concept behind this analysis is to have all of the necessary information needed to plan a surgery in a single report. Finally, this analysis is meant to be modular. The important aspects of the analysis are its concepts and structure.

⁎

A local coordinate system is a local Cartesian frame of reference of a given object, whereas the world coordinate system is global Cartesian frame of reference of the space around us. A simple way of envisioning the difference between the two systems is to imagine a room with a toppled chair. In this scenario, the world coordinate system is the frame of reference of the room: roof is up, floor is down, and walls are East, West, North, and South. Yet, the toppled chair, lying in the middle of the room, has its own internal (local) frame of reference. It has a top, a bottom, a front, a back, and sides. The object’s features define the local coordinate system, which is a frame of reference that is independent of spatial position or orientation. The world and local coordinate systems may be aligned with each other; however, as in this example where the top of the chair is sideways, they may not. The same is true in 3D cephalometry. The maxilla, mandible, chin, and so on of a head are individual objects. They have their own local coordinate systems, while the whole head is aligned with the world coordinate system.

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8. How do you plan surgery using computeraided surgical simulation techniques? The composite skull model is initially prepared (precut) to simulate various osteotomies. As an example, they may include a Le Fort I osteotomy, a sagittal split osteotomy, an inverted “L” osteotomy, or a genioplasty. After the model is prepared, the surgeon is able to move the bony segments to the desired position and rotate each bony segment around a pivot point according to quantitative guidance and the surgeon’s visual judgment. Once the bony segments are in the desired location, the simulated outcomes and surgical movements are recorded. Using CASS, the surgeon is able to simulate a number of different surgical treatments in order to create the most appropriate surgical plan.

9. How do you transfer the computerized surgical plan to the patient at the time of the surgery? The final step of the CASS is to transfer the computer surgical plan to the patient. In order to accomplish this, surgical dental splints and templates are created using computer-aided designing/computer-aided manufacturing (CAD/CAM) techniques.17,45,51 In surgeries that involve the teeth (e.g., Le Fort I osteotomy, mandibular ramus osteotomy), surgical dental splints are created by a computational process after inserting a digital wafer between the maxillary and mandibular dental arches (Fig. 25-7, A). In surgeries that do not involve the teeth (e.g., genioplasty), digital templates can be created (Fig. 25-8, A and B). They are used during surgery to help the surgeons achieve the desired results. The templates record the 3D surface geometry of the area of interest so that the template fits on the bone in a unique position. The digital splints and templates are then sent to a rapid prototyping machine to fabricate physical splints and templates (see Fig. 25-7, C, and Fig. 25-8, C). They can then be sterilized and used at the time of the surgery (see Fig. 25-7, C; and Fig. 25-8, D and E). In facial asymmetry, a computerized mirror-imaging technique is used to assess final symmetry after all facial units have been repositioned. In this technique, a mirrored image from the healthy side is superimposed over the defect side (Fig. 25-9, A). Then the difference of geometries between the two sides is computed, resulting in a digital template (see Fig. 25-9, B). This template can be printed using rapid prototyping machines (see Fig. 25-9, C) and can be used during surgery to guide resection or augmentation (see Fig. 25-9, D and E). If desired, the digital templates can also be used to directly fabricate facial implants. Finally, when advantageous, a physical model with the planned outcome can be fabricated to pre-bend the bone plates that are used in the surgery (Fig. 25-10). This not only improves the accuracy of the operation but also reduces the total operative time by eliminating the need to bend these plates at the time of the surgery.

10. What can happen if the bite jig is not fabricated accurately? In CASS, the importance of an accurate bite jig cannot be overemphasized.44 In the CASS protocol, the bite jig serves three

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CHAPTER 25 • Secrets in Computer-Aided Surgical Simulation for Complex Craniomaxillofacial Surgery Internal Reference Plane Assessment Parameter FH-Axial Plane, Angle

Patient

SN-Axial Plane, Angle

Whole Face Parameter

Patient

Maxilla Norm

Parameter

Patient

Mandible Norm

Parameter

Norm 0° 7°

Chin

Patient

Norm

Parameter

Patient Norm

Symmetry Intrinsic Symmetry

Dental Arch

Dental Arch

0°

Basal Bone

0°

0 mm

LIE to MSP

0 mm

Pg to MSP

0 mm

Dental Arch Yaw Basal Yaw

0° 0°

Chin Yaw

0°

Dental Arch Roll

0°

Basal Roll

0°

Chin Roll

0°

Holdaway Ratio [(L1E-NB)/(P-NB)]

1:1

0°

Symmetric Alignment

Midlines (transverse)

UIE to MSP

Yaw

Dental Arch Yaw

0°

Roll

Dental Arch Roll

0°

Transverse (Width) Upper Intermolar Width (UR6-UL6 at central fossae) Width of the alar base (Ral-Lal) Intercanthal Width (Ren-Len)

Lower Intermolar M: 46.72.6mm Width (LR6-LL6 F: 43.94.2mm at centroids)

M: 43.02.3mm F: 41.72.3mm

M: 34.92.1mm F: 31.42.0mm M: 33.32.7mm F: 31.82.3mm

Vertical Forehead Height [(Tr-G’)/(Tr-Me’)]

1/3

Upper Lip Length

Midface Height [(G’-Sn)/(Tr-Me’)]

1/3

Incisal Show at Rest

Lower Face Height [(Sn-Me’)/(Tr-Me’)]

1/3

Gingival Smiling Line

Interlabial gap Upper lip to lower lip-chin height ratio (Sn-ULS /LLS-Me’)

2-5 mm

M: 2.63.2mm Incisal Attrition F: 3.32.9mm 1:2

M: 23.42.5mm Overbite F: 21.22.4mm

M: 2.51.4mm F: 3.21.1mm

Lower Facial Height (ANS-Xi-PM)

474°§ (Ricketts norm)

M: -0.82.4 mm F: 0.72.1 mm 0 mm

Delayed Passive Eruption

0 mm

Pitch U1 to AxP

M: 117.06.9° † MPto AxP F: 110.59.1° †

Maxillary Occlusal Plane to AxP

9.33.8° †‡

M: 21.65.7° † F: 23.15.0° †

L1 to MP

M: 90.69.1° F: 90.86.8°

Interincisal Angle (U1-L1)

M: 130.811.4° F: 136.011.1°

Anteroposterior SNA (S-N-A)

M: 81.64.6° F: 80.5°3.3°

SNB (S-N-B)

M: 79.94.8° F: 77.83.5°

Maxillary Depth (N-Point A to AxP)

M: 91.93.0° † F: 91.63.2° †

Facial Angle (N-Pg to AxP)

M: 91.84.8° † F: 90.53.1° †

Nasolabial Angle (Cm-Sn-Ls)

M: 105.58.4 F: 111.69.5°

Posterior Airway Space

11.01.0mm*

Maxillomandibular Discrepancy Parameter

Patient

Norm

Wits Appraisal

M: -2.93.5mm F: -2.53.2 mm

ANB (A-N-B)

M: 2.51.6° F: 3.01.8°

Convexity of Point A (Point A to N-Pg)

M: 0.33.6 mm F: 1.23.0 mm

Overjet

M: 3.72.1 mm F: 2.90.9 mm

Shape Right Gonial Angle (Right Co-Go-Me)

M: 121.45.6° ¶ F: 123.75.0° ¶

Left Gonial Angle (Left Co-Go-Me)

M: 121.45.6° ¶ F: 123.75.0° ¶

FIG 25-6 See figure legend in opposite page


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FIG 25-7 Surgical dental splints are created using computer-aided designing/computer aided manufacturing (CAD/CAM) technique. A, Digital surgical splint. B, Physical surgical splint. C, The use of physical surgical splint at the time of the surgery.

FIG 25-6 A new three-dimensional (3D) cephalometric analysis for orthognathic surgery. All of the norms were established for Caucasian subjects with normal facial appearance. All of the norms for symmetry analyses were based on the authors’ opinion. The hard tissue norms were established by Bhatia and Leighton for 20-year-old subjects71 with the exception of the following: Ricketts norms were established by Ricketts for 9-year-old subjects72–74; maxillary occlusal plane inclination was established by Downs75,76; and Holdaway ratio was based on Holdaway’s opinion.77–80 The soft tissue norms were established by Farkas for 20- to 26-year-old subjects81 with the exception of the following: Incisal show was based on the authors’ opinion; lip measurements were established by Peck and colleagues for 15 1⁄2-year-old subjects who were either in orthodontic treatment or posttreatment82,83; and posterior airway space was established by Riley and colleagues for male subjects.84 The dental arch norms were established by Moyers and colleagues for 18-year-old subjects.85 Note: A shadowed space indicates input from clinical examination. §: This is the original Ricketts norm established for 9-year-old subjects. No age adjustment is required. †: The norm is calculated for Frankfort horizontal (FH) plane. Please use with caution. ‡: This is the original Downs norm established for “Occlusal Plane to FH” (“Cant of Occlusal Plane” in Downs’s original manuscript75). The occlusal plane was defined as a line bisecting the occluded mesiobuccal cusps of the upper and lowers first molars and the incisal overbite. Please use with caution. ¶: The gonial angle is measured by projecting the landmarks, articulare, gonion, and menton, to the mandibular local midsagittal plane. *: Posterior airway space should be measured as the shortest distance between the tongue base and the posterior pharyngeal wall. The norm was established by Riley for measuring the distance between the two landmarks: Tongue base (TB; the intersection point of a line from point B through gonion and the base of the tongue), and posterior pharyngeal wall (PPWB; the intersection point of a line from point B through gonion and the base of the posterior pharyngeal wall). Please use with caution. Abbreviations: M, male; F, female; MSP, midsagittal plane; UIE, upper central incisal embrasure; LIE, lower central incisal embrasure; Pg, pogonion (the most anterior point on the mandibular symphysis); UR6, mesiobuccal cusp of maxillary right first molars; UL6, mesiobuccal cusp of maxillary left first molar; LR6, mesiobuccal cusp of mandibular right first molars; LL6, mesiobuccal cusp of mandibular left first molar; Ral, right alar; Lal, left alar (the most lateral points on the right and left alar contour); Ren, right endocanthion; Len: left endocanthion (a point at the inner canthus of the eyelids); Tr, trichion (the point on the hairline in the midsagittal plane of the forehead); G’, soft tissue glabella (the most prominent or anterior point in the midsagittal plane of the forehead at the level of the superior orbital ridges); Sn, subnasale (a point located at the junction between the columella of the nose and the skin of the upper lip at the midsagittal plane); Me’, soft tissue menton (the most inferior point on the midline of the soft tissue chin); ULS, upper lip stomion (the most inferior point of the midline of the upper lip vermilion); LLS, lower lip stomion (the most superior point of the midline of the lower lip vermilion); ANS, anterior nasal spine (the tip of the anterior nasal spine); Xi, Ricketts Xi landmark (the midpoint of the right and left inferior alveolar nerve foramens); PM, suprapogonion (a point at which the shape of the symphysis metalis changes from convex to concave—also known as protuberance menti); U1, long axis of maxillary central incisors (a line connects the upper central incisal embrasure and the midpoint of right and left upper central incisal apices); AxP, axial plane (the true horizontal plane); Go, gonion (the midpoint at the mandibular angle); ME, menton (the lowest point on the lower border of the mandibular symphysis); MP, mandibular plane (a plane constructed by the landmarks Me, right Go, and left Go); L1, long axis of mandibular central incisors (a line connects the lower central incisal embrasure and the midpoint of right and left lower central incisal apices); S, sella (the center of sella turcica); N, nasion (the most anterior point on the frontonasal suture); A, point A (the deepest point on the concave outline of the upper labial alveolar process extending from the anterior nasal spine to prosthion); B, point B (the deepest point on the bony curvature between the crest of the alveolus [infradentale] and pogonion); Cm, columella (the most anterior point on the columella of the nose); Ls, laberale superius (a point located at the maximum convexity of the vermilion border most prominent in the midsagittal plane); Co, condylion (the most posterosuperior point of the mandibular condyle).

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B

A

C

D

E

FIG 25-8 Surgical templates are created using computer-aided designing/computeraided manufacturing (CAD/CAM) technique. Chin template includes a set of two surgical guides. The first guide is used to predefine the screw holes prior to the osteotomy. The second guide is used to bring the chin segment to the planned position and orientation using predrilled screw holes. Both guides use the mandibular dentition as a reference to predrill the screw holes and to position the chin segment. A, Computer model of the first guide to define the screw holes. B, A computer model of the second guide to bring the chin segment to the desired position. C, Physical chin template set; the first guide is on the left and the second guide is on the right. D, The use of the first guide at the time of surgery. E, The use of the second guide at the time of surgery.

purposes: 1) to register the digital dental models to the CT; 2) to capture CR; and 3) to record the NHP. If the bite jig is not correctly fabricated, the error is carried over to the following steps. The bite jig should not be too thick (unnecessarily large autorotation) or too thin (fragile). The occlusal indentations on the bite jig should be deep enough to lock the teeth but also shallow enough to avoid undercuts. The authors recommend a

three-layer approach for bite jig fabrication. In this approach, the first layer of bite registration material is added to the top of the bite jig, and it is used to capture the maxillary teeth. Before the material gets completely hard, the bite jig is gently removed and repositioned a few times to eliminate possible undercuts. After the material completely hardens, any undercuts are further eliminated by grinding the bite jig to the appropriate thickness. The second layer records CR. The bite jig is


A

319

B

C E D

FIG 25-9 Surgical planning of onlay bone grafting. A, A mirror image of the unaffected side was created. It was superimposed over the affected side. B, A digital template that depicted the differences between the mirror image and the affected side was created. C, A physical form of the same template was fabricated. D, Autogenous bone was harvested and sculpted according to the shape of the template. E, The sculpted autogenous bone graft precisely replaced the missing bone. (From Gateno J, Xia JJ, Teichgraeber JF, et al: J Oral Maxillofac Surg 2007;65(4):728-734.)

A

B

FIG 25-10 A physical model of the planned outcome is fabricated and used to prebend the bone plates that will be used in the surgery. A, Pre-bend the bone plates based on a physical model of planned outcome and bone graft. B, Adopt the pre-bent bone plates at the time of the surgery. (From Gateno J, Xia JJ, Teichgraeber JF, et al: J Oral Maxillofac Surg 2007;65(4):728-734.)

placed back on the maxillary teeth. Afterward, the mandible is manipulated into CR and rotated closed until the mandibular teeth make initial gentle contact with the jig. This maneuver is repeated a few times to ensure correctness. A second layer of the material is then added to the bite jig on the labiobuccal side of the mandibular teeth while the mandible is still at CR. Once the material is set, the mandible is opened and closed in CR to test the adequacy of the CR recording. Finally, a third layer is added on the bottom side of the bite jig to capture the mandibular occlusal surfaces. The second layer of material, at

the labiobuccal region, guides the mandible into CR. Before the last layer of material is set, the mandible should be gently swung open and closed to eliminate any possible undercuts. Finally, the mandibular side of the bite jig is ground to the appropriate thickness. It is necessary to also cross-check the fitting of the bite jig on the stone models. If the bite jig does not fit the stone models, either the stone models (dental impressions) are distorted or the bite jig has undercuts. Surgeons should correct the problem accordingly before proceeding with the CASS protocol.

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A

B

C

D

FIG 25-11 Unwanted bimaxillary retrusion was caused by a combination of incorrect recording of central relation and the maxillary surgery first. A, In this unilateral bimaxillary retrusion patient, the midline was shifted to one side (>2 mm). B, From the preoperative computed tomography (CT) model, the condyle appeared in the central relation. C, From the postoperative CT model, the condyle also appeared in the central relation. D, When the two models were registered, it clearly demonstrated that the preoperative condyle (yellow) was protruded and then the postoperative condyle (blue).

In a recent prospective clinical study evaluating the accuracy of the CASS protocol in orthognathic surgery, 3 of 65 patients had large discrepancies between their planned and actual outcomes.44 Their maxillomandibular advancement was less than predicted (>4 mm). Two of them also ended with a large maxillary dental midline deviations (>2 mm). Post hoc analysis demonstrated that these discrepancies were caused by one or both condyles not being in CR during CT scan acquisition (Fig. 25-11). This finding demonstrates the importance of an accurate bite jig,

11. What is the accuracy of the computeraided surgical simulation method in orthognathic surgery? A recent published study evaluated the accuracy of CASS in the treatment of patients who had dentofacial deformities requiring double-jaw orthognathic surgery.44 The accuracy of the CASS protocol was assessed by comparing the planned and postoperative outcomes of 65 consecutive patients. Computergenerated occlusal splints were used for all patients. For the genioplasty, one center utilized computer-generated chin templates to reposition the chin segment of patients with asymmetry. For the remaining patients, standard intraop erative measurements were utilized. The primary outcome measurements were positional. Orientation differences for the maxilla, mandible, and chin (planned and postoperative

models) were registered at the cranium. Secondary outcome measurements were maxillary dental midline difference between the planned and postoperative positions and positional and orientational differences of the chin segment between the groups with and without the use of the template. The latter was measured when the planned and postoperative models were registered at the mandibular body. Statistical analyses were performed, and the accuracy was reported using root mean square deviation (RMSD) and Bland and Altman’s method for assessing measurement agreement.52 In the primary outcome measurements, there was no statistically significant difference among the three centers for the maxilla and mandible. The largest RMSD was 1.0 mm and 1.5 degrees for the maxilla and 1.1 mm and 1.8 degrees for the mandible. For the chin, there was a statistically significant difference between the groups with and without the use of the chin template. The chin template group showed excellent accuracy with the largest positional RMSD of 1.0 mm and the largest orientational RSMD of 2.2 degrees. However, larger variances were observed in the group not using the chin template (3.5 mm in positional difference and 5.8 degrees for orientation; Table 25-1). Positional differences were significant in the AP and superoinferior directions. Orientation differences were significant in pitch and yaw. The results of Bland and Altman’s method for assessing measurement agreement are presented in Table 25-2.


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TABLE 25-1 Accuracy (Root Mean Square Deviation) of Positional and Orientational Differences between the Planned and Postoperative Outcomes (Models Registered at the Cranium) ORIENTATIONAL DIFFERENCE

POSITIONAL DIFFERENCE Maxilla

Mediolateral Anteroposterior Superoinferior

0.8 mm 1.0 mm 0.6 mm

Pitch Roll Yaw

1.5° 0.9° 1.3°

0.8 mm 1.1 mm 0.6 mm

Pitch Roll Yaw

1.8° 1.0° 1.7°

Intraoperative Measurements Mediolateral Anteroposterior Superoinferior

1.7 mm 3.5 mm 2.5 mm

Pitch Roll Yaw

5.8° 3.0° 3.9°

Template Mediolateral Anteroposterior Superoinferior

0.8 mm 1.0 mm 0.6 mm

Pitch Roll Yaw

2.2° 1.8° 1.9°

0.8 mm 1.0 mm 0.6 mm

Pitch Roll Yaw

1.5° 0.9° 1.3°

0.8 mm 1.1 mm 0.6 mm

Pitch Roll Yaw

1.8° 1.0° 1.7°


1.7 mm 3.5 mm 2.5 mm

Pitch Roll Yaw

5.8° 3.0° 3.9°


0.8 mm 1.0 mm 0.6 mm

Pitch Roll Yaw

2.2° 1.8° 1.9°

Mandible


Chin

Maxilla


Mandible


Chin

TABLE 25-2 Accuracy (Bland and Altman Upper and Lower Limits) of Positional and Orientational Differences between the Planned and the Postoperative Outcomes (Models Registered at the Cranium) POSITION DIFFERENCE (95% CI)

ORIENTATIONAL DIFFERENCE (95% CI) UPPER LIMIT LOWER LIMIT

LOWER LIMIT

UPPER LIMIT


−1.7 mm (−2.0 to −1.4) −0.7 mm (−0.9 to −0.4) −0.8 mm (−1.0 to −0.6)

1.4 mm (1.0 to 1.7) 1.6 mm (1.4 to 1.9) 0.9 mm (0.7 to 1.0)

Pitch Roll Yaw

−2.3° (−2.9 to −1.7) −1.8° (−3.2 to −1.4) −2.7° (−3.2 to −2.1)

3.4° (2.8 to 4.0) 1.8° (1.4 to 2.1) 2.3° (1.7 to 2.8)


−1.4 mm (−1.5 to −1.0) −0.9 mm (−1.1 to −0.6) −0.8 mm (−1.0 to −0.6)

1.0 mm (0.8 to 1.3) 1.5 mm (1.3 to 1.8) 0.7 mm (0.6 to 0.9)

Pitch Roll Yaw

−3.7° (−4.5 to −2.9) −2.0° (−2.4 to −1.6) −3.3° (−4.0 to −2.6)

3.6° (2.8 to 4.3) 1.8° (1.4 to 2.2) 3.3° (2.6 to 4.0)


−2.9 mm (−4.9 to −0.1) −6.2 mm (−10.1 to −2.2) −5.3 mm (−8.2 to −2.5)

3.9 mm (2.0 to 5.8) 7.8 mm (3.8 to 11.7) 4.6 mm (1.8 to 7.4)

Pitch Roll Yaw

−9.4° (−15.6 to −3.2) −5.8° (−9.3 to −2.4) −7.1° (−11.5 to −2.8)

12.9° (6.6 to 19.1) 6.3° (2.9 to 9.7) 8.4° (4.1 to 12.8)


−1.7 mm (−2.6 to −0.7) −2.1 mm (−3.3 to −1.0) −1.4 mm (−2.1 to −0.8)

1.8 mm (0.8 to 2.8) 2.0 mm (0.8 to 3.2) 1.0 mm (0.3 to 1.6)

Pitch Roll Yaw

−4.1° (−6.5 to −1.7) −4.0° (−6.1 to −2.0) −4.0° (−6.2 to −1.9)

4.9° (2.5 to 7.3) 3.7° (1.6 to 5.7) 4.1° (1.9 to 6.2)

CI, Confidence Interval.

322


In the secondary outcome measurements, the RMSD of maxillary dental midline position was 0.9 mm, with a Bland and Altman’s limit of −1.3 mm and 1.1 mm. When registered at the body of the mandible, the positional and orientational differences of the chin segment between the groups with and without the use of the chin template were consistent with the results found in the primary outcome measurements (1.1 mm versus 2.0 mm in positional difference, and 1.6 degrees versus 5.0 degrees in orientational difference, respectively; Table 25-3). The results of Bland and Altman’s method for assessing measurement agreement are presented in Table 25-4.

12. What is the surgical outcome achieved with computer-aided surgical simulation compared to the outcome achieved with the traditional planning methods? A recent published study evaluated whether the surgical outcomes achieved with CASS are better than those achieved with traditional methods.53 In this study, a total of twelve consecutive

patients with CMF deformities were enrolled. Following the CASS clinical protocol,30 a 3D computer composite skull model for each patient was generated and reoriented to the NHP. These models underwent two virtual surgeries: one was based on CASS (experimental group) and the other was based on traditional methods (control group). Once both virtual surgeries were completed, two experienced CMF surgeons at two different settings evaluated both surgical outcomes. They were blinded to the planning method used on the virtual models and to each other’s evaluation results. The primary outcome was overall CMF skeletal harmony. The secondary outcomes were individual maxillary, mandibular, and chin harmonies. Finally, statistical analyses were performed. The results showed that the overall CMF skeletal harmony achieved with CASS was statistically better than that achieved with traditional methods. In addition, the maxillary and mandibular surgical outcomes achieved with the CASS method were also statistically better. Furthermore, although not included in the statistical model, the chin symmetry achieved by

TABLE 25-3 Accuracy (Root Mean Square Deviation) of Chin Position and Orientation for Genioplasties Done with Intraoperative Measurements versus Those Done with Chin Templates (Models Registered at the Body of the Mandible) ORIENTATION DIFFERENCE

POSITIONAL DIFFERENCE Chin


1.4 mm 2.0 mm 1.5 mm

Pitch Roll Yaw

5.0° 2.6° 2.9°


0.6 mm 1.1 mm 0.5 mm

Pitch Roll Yaw

1.1° 1.6° 1.6°

TABLE 25-4 Accuracy (Bland and Altman Upper and Lower Limits) of Chin Position and Orientation for Genioplasties Done with Intraoperative Measurements versus Those Done with Chin Templates (Models Registered at the Body of the Mandible) POSITION DIFFERENCE (95% CI) LOWER LIMIT

ORIENTATION DIFFERENCE (95% CI) UPPER LIMIT

LOWER LIMIT

UPPER LIMIT

−9.7 (−12.8 to −4.9) −5.5 (−7.2 to −3.1) −4.3 (−4.9 to −0.9)

10.4 (1.2 to 9.1) 5.0 (0.2 to 4.3) 6.6 (2.2 to 6.2)

−1.7 (−2.9 to −0.6) −3.5 (−5.3 to −1.7) −3.5 (−5.2 to −1.7)

2.6 (1.4 to 3.7) 3.3 (1.5 to 5.2) 3.1 (1.3 to 4.8)

Chin

Intraoperative Measurement Mediolateral −2.9 (−4.5 to −1.2) Anteroposterior −4.1 (−6.4 to −1.8) Superoinferior −3.4 (−5.1 to −1.7) Template Mediolateral Anteroposterior Superoinferior CI, Confidence Interval.

−1.2 (−2.0 to −0.5) −2.1 (−3.4 to −0.8) −1.1 (−1.7 to −0.6)

2.9 (1.3 to 4.6) 4.0 (1.7 to 6.2) 2.7 (1.0 to 4.4)

Pitch

1.4 (0.7 to 2.1) 2.4 (1.1 to 3.7) 0.9 (0.4 to 1.5)

Pitch

Roll Yaw

Roll Yaw


CASS tended to be better. Finally, the study discovered that the most critical step in achieving better overall CMF skeletal harmony was to restore mandibular symmetry.53

13. What is the cost-effectiveness of using the computer-aided surgical simulation? A published study compared the costs and benefits between using CASS and the current surgical planning methods for complex CMF surgery.31 The comparison of methods applies to all CMF surgeries where the patient’s condition is severe enough to require a CT scan and a rapid prototyping model. The study shows that CASS has lower costs in terms of surgeon time, patient time, and material costs. Specifically, total surgeon hours spent in planning are 5.25 hours compared to 9.75 for current standard methods. Material and scanning costs are $1900 for CASS compared to about $3510 for standard methods. Patient time for planning is reduced from 4.75 hours to 2.25 hours with CASS. The reduction in both time and other costs remains when the up-front costs of CASS are added to the variable costs. Amortized across the 600 patients per year (1800 for the assumed 3-year life of the training and software), this adds only a few dollars and a fraction of an hour per surgery. Even in the case of a small clinic when the cost is amortized for six patients Pre-OP

Post-OP

Pre-OP

323

per year (18 patients for the assumed 3-year life of the training and software), the presurgical costs (9.65 hours and $2456) will still favor CASS. In the same study, the authors hypothesized that the maximum potential cost savings of CASS could be best realized when a single planning facility serves multiple surgeons, in multiple clinics, and in multiple cities. Further efficiencies can be achieved by centralized specialization where the surgeon’s time is replaced with the less expensive technician’s time. Recent reports also demonstrated the cost-effectiveness of using CASS planning over the traditional planning method for routine orthognathic surgery.30,54 The initial CASS records appointment (dental impressions, bite jig creation, clinical examination, anthropometric measurements, recording NHP) takes about 60 minutes.30,54 It takes another 5 to 10 minutes to set the final occlusions on the plaster dental models. After the patient’s CT scan is completed, the preparation of the computer data, including dental model scanning, segmentation of CT images, 3D model reconstruction, composite skull model creation, landmark digitization, and virtual osteotomies are completed by a centralized service facility. Once the computer data are prepared, they are electronically transmitted to the surgeon. The surgeon only spends time on examining the cephalometric analysis results, Planned

Actual Post-OP

FIG 25-12 Comparison chart of a patient’s preoperative, planned, and postoperative outcomes. The patient suffered temporomandibular joint (TMJ) ankylosis due to a left ear infection at the age of 5. He was treated by arthroplasty and costochondral graft. Although the arthroplasty was successful, the costochondral graft and the left face failed to grow. The patient was planned following the CASS clinical protocol. The computer-generated surgical splints and templates were used to transfer the computerized surgical plan to the patient at the time of the surgery. The osteotomized maxilla was positioned using the computer-generated intermediate splint. The mandible and chin were then osteotomized and fixated by mini plates. The chin was also positioned using the computer-generated chin template. Finally, bone grafts were harvested and carved according to the planned size and shape. Six-week postoperative CT scans showed that the surgical plans were precisely reproduced in the operating room and the deformities were corrected as planned. (From Gateno J, Xia JJ, Teichgraeber JF, et al: Clinical feasibility of computer-aided surgical simulation [CASS] in the treatment of complex cranio-maxillofacial deformities, J Oral Maxillofac Surg 65[4]:728-734, 2007.)

324


formulating a surgical plan, and testing the plan with the virtual surgical movements. Although there is a learning curve in this process, once it is fulfilled, it usually takes 10 to 20 minutes to plan a routine case and up to an hour for a complex one. After the plan is finalized, based on the surgeon’s request (which jaw is operated first), the service facility designs the surgical splints and templates and fabricates them using a rapid prototyping machine. CASS may further save the surgeon’s time during the operation. This is because the 3D nature of computer planning allows the surgeon to anticipate potential complications and pitfalls, which may not be readily apparent during traditional plaster model surgery. Currently at the service center, the entire process takes around 4 hours and costs up to $1000.55 This is slightly above the amount that is now reimbursed by insurance companies for the fabrication of an oral surgical splint (CPT code 21085). Ultimately, in this entire CASS planning process, the total surgeon’s time is reduced to 70 to 100 minutes per case in comparison to 9.75 hours31 in the traditional planning process.

“best possible” intercuspation in the computer. More importantly, it is almost impossible to be certain that what is seen in the computer represents the best possible intercuspation. We have not been able to rely on this computerized dental alignment to treat real patients, because a small deviation in occlusion can cause significant problems. To ensure that the digital final occlusion is at its correct MI, we scan the plaster models while they are physically positioned in MI (final occlusion). The scanned models are incorporated into the composite skull model to guide the placement of the distal mandible into MI. Meanwhile, the authors are developing a method of automated digital dental articulation. Some progress has been made already.56–58 Once this method is completely developed and validated, the need of plaster dental models will be eliminated.

14. Do you still need plaster dental models in the computer-aided surgical simulation planning system?

Surgical navigation is an alternative tool to transfer the computerized surgical plan to the patient at the time of the surgery.17,59–64 The navigation system is similar to a car global positioning system (GPS). It consists of a computer, a monitor, a set of cameras (like the satellites), and a series of navigated instruments (like the GPS handheld). The navigated instruments include a patient tracker (Fig. 25-13, A), a navigation pointer (see Fig. 25-13, B), an instrument tracker (see Fig. 25-13, C), and a calibration station (see Fig. 25-13, D). The navigated instrument (i.e., a patient tracker mounted on the patient’s skull) emits infrared signals of the x, y, and z coordinates to the cameras. Once the cameras receive these signals and send them to the computer, a unique link is established between the camera and the instrument (Fig. 25-14). Therefore, the position of the patient’s head can be tracked down by the patient tracker. Equally, the position of both surgical instrument and

In the future, plaster dental models will not be necessary for CMF planning. However, at this time we are still using them to establish the final dental occlusion in maximum intercuspation (MI). Using a set of plaster dental models, an experienced operator can determine the final occlusion in a matter of seconds. The same is not true in the virtual world where the dental arches are represented by two 3D images that lack collision constraints. The computer system does not stop the images from moving through each other once the model surfaces have made contact. In addition, the operator has no tactile feedback when articulating the models. Because of these difficulties, it usually takes close to an hour to achieve the

15. What other method can be used to transfer the computerized plan to the patient at the time of the surgery?

A

D

B C

FIG 25-13 Navigation emitters consist of patient tracker (A), navigation pointer (B), instrument tracker (C), and calibration station (D).


325

Detector

FIG 25-14 A unique link is generated between the detector and the emitters after the registration process.

FIG 25-15 The navigation monitor displays the sagittal, coronal, axial, and three dimensional (3D) views of the computed tomography (CT) image and the location and trajectory of the navigated surgical instruments. The resection margins have also been recorded in the navigation computer, forming a computerized surgical plan.

pointer can be tracked by the instrument tracker. The calibration station (see Fig. 25-13, D) is a special type of the emitter. It calibrates the position of the instrument’s tip to the instrument tracker. Virtually any kind of surgical instrument can be calibrated by the calibration station and instrument tracker. Finally, the monitor displays the sagittal, coronal, axial, and 3D

views of the CT image and the location of the navigated surgical instruments (Fig. 25-15). This technology has been proven accurate, with a precision ranging from 0.2 to 1.1 mm.40,65–67 Surgical navigation also offers an improved spatial representation of complex surgical environments, helping the surgeon to avoid vessels, nerves, or

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other important structures.41,68,69 However, navigation technology requires the installation of cameras and sensors followed by registration. This extra step may prolong the surgery in comparison to the use of surgical splints and templates. Another disadvantage is the cost of the navigation system. An additional staff member is also required during the surgery for the manipulation of the computer. Therefore, the indication for using surgical navigation technology is limited. The authors reserve this technology to surgeries in which the use of surgical splints and templates is not feasible. These surgeries usually involve areas with minimal surface geometry or limited surgical exposure (e.g., reconstruction of complex posttraumatic deformities of the midface38,59 or TMJ ankylosis17,60,70). REFERENCES 1. National Center for Health Statistics: Third national health and nutrition examination survey (NHANES III, 1988–1994), Hyattsville, MD, 1996, National Center for Health Statistics. 2. Proffit WR, Fields Jr. HW, Ackerman JL, et al: Contemporary orthodontics, ed 3, St Louis, 2000, Mosby. 3. Proffit WR, Phillips C, Dann CT: Who seeks surgical-orthodontic treatment? Int J Adult Orthodon Orthognath Surg 5:153–160, 1990. 4. Severt TR, Proffit WR: The prevalence of facial asymmetry in the dentofacial deformities population at the University of North Carolina, Int J Adult Orthodon Orthognath Surg 12:171–176, 1997. 5. Gorlin RJ, Cohen MM, Hennekam RCM, editors: Syndromes of the head and neck, ed 4, New York, 2001, Oxford University Press. 6. Cohen MM, MacLean RE: Craniosynostosis: diagnosis, evaluation, and management, ed 2, New York, 2000, Oxford University Press. 7. National Center for Health Statistics: National hospital discharge survey: annual summary with detailed diagnosis and procedure data. Vital and health statistics series 13 number 151. DHHS publication No.(PHS)2001-1722, Hyattsville, MD, 1999, National Center for Health Statistics. 8. American Society of Plastic Surgeons: National plastic surgery statistics: cosmetic and reconstructive patient trends (2000/2001/2002), 2000/2001/2002, American Society of Plastic Surgeons. 9. Cancer Statistics Branch: Surveillance research program, National Cancer Insitute SEER*Stat Software (www.seer.cancer.gov/seerstat) version 5.0.20, Bethesda, MD, 2003, National Cancer Institute. 10. WISQARS: Overall all injury causes nonfatal injuries and rates per 100,000 (2001–2002, United States), Altanta, GA, 2003, National Center for Injury Prevention and Control. 11. Ticknon L: Trauma statistics, Minneapolis, MN, 2003, Trauma Registry, Hennepin County Medical Center. 12. NIH Office of Medical Application of Research: National Institutes of Health Technology Assessment Conference on Management of Temporomandibular Disorders. Bethesda, Maryland, April 29-May 1, 1996. Proceedings, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 83:49–183, 1997 (pp. 179). 13. National Institutes of Health: Management of temporo mandibular disorders. National Institutes of Health Technology Assessment Conference Statement, J Am Dent Assoc 127:1595– 1606, 1996. 14. Cowley T: Numbers of patient undergo TMJ reconstruction annually (Personal Communication), Milwaukee, WI, 2003, President of The Board of Directors, The TMJ Association, LTD. 15. Bell WH, editor: Surgical correction of dentofacial deformities, Philadelphia, 1980, WB Saunders.

16. Bell WH, editor: Modern practice in orthognathic and reconstructive surgery, Philadelphia, 1992, WB Saunders. 17. Xia JJ, Gateno J, Teichgraeber JF: Three-dimensional computeraided surgical simulation for maxillofacial surgery, Atlas Oral Maxillofac Surg Clin North Am 13:25–39, 2005. 18. Papadopoulos MA, Christou PK, Athanasiou AE, et al: Threedimensional craniofacial reconstruction imaging, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 93:382–393, 2002. 19. Xia J, Ip HH, Samman N, et al: Computer-assisted threedimensional surgical planning and simulation: 3D virtual osteotomy, Int J Oral Maxillofac Surg 29:11–17, 2000. 20. Gateno J, Teichgraeber JF, Xia JJ: Three-dimensional surgical planning for maxillary and midface distraction osteogenesis, J Craniofac Surg 14:833–839, 2003. 21. Gateno J, Xia J, Teichgraeber JF, et al: A new technique for the creation of a computerized composite skull model, J Oral Maxillofac Surg 61:222–227, 2003. 22. Santler G: 3-D COSMOS: a new 3-D model based computerised operation simulation and navigation system, J Maxillofac Surg 28:287–293, 2000. 23. Santler G: The Graz hemisphere splint: a new precise, noninvasive method of replacing the dental arch of 3D-models by plaster models, J Craniomaxillofac Surg 26:169–173, 1998. 24. Ellis 3rd E, Tharanon W, Gambrell K: Accuracy of face-bow transfer: effect on surgical prediction and postsurgical result, J Oral Maxillofac Surg 50:562–567, 1992. 25. Lorensen WE, Cline HE: Marching cubes: a high resolution 3D surface construction algorithm, Comput Graphics 21:163–169, 1987. 26. Lambrecht JT: 3D modeling technology in oral and maxillofacial surgery, Chicago, IL, 1995, Quintessence. 27. Gateno J, Forrest KK, Camp B: A comparison of 3 methods of face-bow transfer recording: implications for orthognathic surgery, J Oral Maxillofac Surg 59:635–640, 2001, discussion 640–631. 28. Bell WH, Guerrero CA: Distraction osteogenesis of the facial skeleton, ed 1, 2006, BC Decker, Inc. 29. Gateno J, Xia JJ, Teichgraeber JF, et al: Clinical feasibility of computer-aided surgical simulation (CASS) in the treatment of complex cranio-maxillofacial deformities, J Oral Maxillofac Surg 65(4):728–734, 2007. 30. Xia JJ, Gateno J, Teichgraeber JF: New clinical protocol to evaluate craniomaxillofacial deformity and plan surgical correction, J Oral Maxillofac Surg 67:2093–2106, 2009. 31. Xia JJ, Phillips CV, Gateno J, et al: Cost-effectiveness analysis for computer-aided surgical simulation in complex craniomaxillofacial surgery, J Oral Maxillofac Surg 64:1780–1784, 2006. 32. Altobelli DE, Kikinis R, Mulliken JB, et al: Computer-assisted three-dimensional planning in craniofacial surgery, Plast Reconstr Surg 92:576–585, 1993, discussion 586–587. 33. Vannier MW, Marsh JL, Warren JO: Three dimensional CT reconstruction images for craniofacial surgical planning and evaluation, Radiology 150:179–184, 1984. 34. Marsh JL, Vannier MW: The “third” dimension in craniofacial surgery, Plast Reconstr Surg 71:759–767, 1983. 35. Xia J, Samman N, Yeung RW, et al: Three-dimensional virtual reality surgical planning and simulation workbench for orthognathic surgery, Int J Adult Orthodon Orthognath Surg 15:265–282, 2000. 36. Xia J, Samman N, Yeung RW, et al: Computer-assisted threedimensional surgical planing and simulation. 3D soft tissue planning and prediction, Int J Oral Maxillofac Surg 29:250–258, 2000. 37. Xia J, Ip HH, Samman N, et al: Three-dimensional virtual-reality surgical planning and soft-tissue prediction for orthognathic surgery, IEEE Trans Inf Technol Biomed 5:97–107, 2001.


38. Westendorff C, Gulicher D, Dammann F, et al: Computerassisted surgical treatment of orbitozygomatic fractures, J Craniofac Surg 17:837–842, 2006. 39. Schicho K, Figl M, Seemann R, et al: Accuracy of treatment planning based on stereolithography in computer assisted surgery, Med Phys 33:3408–3417, 2006. 40. Klug C, Schicho K, Ploder O, et al: Point-to-point computerassisted navigation for precise transfer of planned zygoma osteotomies from the stereolithographic model into reality, J Oral Maxillofac Surg 64:550–559, 2006. 41. Heiland M, Habermann CR, Schmelzle R: Indications and limitations of intraoperative navigation in maxillofacial surgery, J Oral Maxillofac Surg 62:1059–1063, 2004. 42. Gateno J, Teichgraeber JF, Aguilar E: Computer planning for distraction osteogenesis, Plast Reconstr Surg 105:873–882, 2000. 43. Gateno J, Allen ME, Teichgraeber JF, et al: An in vitro study of the accuracy of a new protocol for planning distraction osteogenesis of the mandible, J Oral Maxillofac Surg 58:985–990, 2000, discussion 990–991. 44. Hsu SS, Gateno J, Bell RB, et al: Accuracy of a computeraided surgical simulation protocol for orthognathic surgery: a prospective multicenter study, J Oral Maxillofac Surg 71:128–142, 2013. 45. Gateno J, Teichgraeber JF, Xia J: Method and apparatus for fabricating orthognathic surgical splints (US Patent 6,671,539). In USPTO Patent Full-Text and Image Database, U.S.A, 2003, US Patent and Trademark Office. 46. Xia JJ, McGrory JK, Gateno J, et al: A new method to orient 3-dimensional computed tomography models to the natural head position: a clinical feasibility study, J Oral Maxillofac Surg 69:584–591, 2011. 47. Schatz EC, Xia JJ, Gateno J, et al: Development of a technique for recording and transferring natural head position in 3 dimensions, J Craniofac Surg 21:1452–1455, 2010. 48. Ferrario VF, Sforza C, Serrao G, et al: A direct in vivo measurement of the three-dimensional orientation of the occlusal plane and of the sagittal discrepancy of the jaws, Clin Orthod Res 3:15–22, 2000. 49. Gateno J, Xia JJ, Teichgraeber JF: Effect of facial asymmetry on 2-dimensional and 3-dimensional cephalometric measurements, J Oral Maxillofac Surg 69:655–662, 2011. 50. Gateno J, Xia JJ, Teichgraeber JF: New 3-dimensional cephalometric analysis for orthognathic surgery, J Oral Maxillofac Surg 69:606–622, 2011. 51. Gateno J, Xia J, Teichgraeber JF, et al: The precision of computergenerated surgical splints, J Oral Maxillofac Surg 61:814–817, 2003. 52. Bland JM, Altman DG: Statistical methods for assessing agreement between two methods of clinical measurement, Lancet 1:307–310, 1986. 53. Xia JJ, Shevchenko L, Gateno J, et al: Outcome study of computer-aided surgical simulation in the treatment of patients with craniomaxillofacial deformities, J Oral Maxillofac Surg 69:2014–2024, 2011. 54. McCormick SU, Drew SJ: Virtual model surgery for efficient planning and surgical performance, J Oral Maxillofac Surg 69:638–644, 2011. 55. Christensen AM: Cost and time spent on the computer data preparation and splint fabrication for computer-aided surgical simulation for orthognathic surgery (Xia JJ, Teichgraeber JF, editors), 3/25/2009: Golden, CO (AMC), and Houston, TX (JJX and JFT). 56. Chang YB, Xia JJ, Gateno J, et al: In vitro evaluation of new approach to digital dental model articulation, J Oral Maxillofac Surg 70:952–962, 2012. 57. Xia JJ, Chang YB, Gateno J, et al: Automated digital dental articulation, Med Image Comput Comput Assist Interv Int Conf Med Image Comput Comput Assist Interv 13:278–286, 2010.

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58. Chang YB, Xia JJ, Gateno J, et al: An automatic and robust algorithm of reestablishment of digital dental occlusion, IEEE Trans Med Imaging 29:1652–1663, 2010. 59. Xia JJ, Gateno J, Teichgraeber JF: A new paradigm for complex midface reconstruction: a reversed approach, J Oral Maxillofac Surg 67:693–703, 2009. 60. Malis D, Xia JJ, Gateno J, et al: New protocol for one-stage treatment of TMJ ankylosis using surgical navigation, J Oral Maxillofac Surg 65,2006, In-press. 61. Bell RB: Computer planning and intraoperative navigation in orthognathic surgery, J Oral Maxillofac Surg 69:592–605, 2011. 62. Bell RB, Weimer KA, Dierks EJ, et al: Computer planning and intraoperative navigation for palatomaxillary and mandibular reconstruction with fibular free flaps, J Oral Maxillofac Surg 69:724–732, 2011. 63. Bell RB: Computer planning and intraoperative navigation in cranio-maxillofacial surgery, Oral Maxillofac Surg Clin North Am 22:135–156, 2010. 64. Bell RB, Markiewicz MR: Computer-assisted planning, stereolithographic modeling, and intraoperative navigation for complex orbital reconstruction: a descriptive study in a preliminary cohort, J Oral Maxillofac Surg 67:2559–2570, 2009. 65. Marmulla R, Hilbert M, Niederdellmann H: Inherent precision of mechanical, infrared and laser-guided navigation systems for computer-assisted surgery, J Craniomaxillofac Surg 25:192–197, 1997. 66. Hassfeld S, Muhling J: Navigation in maxillofacial and craniofacial surgery, Comput Aided Surg 3:183–187, 1998. 67. Husstedt H, Heermann R, Becker H: Contribution of low-dose CT-scan protocols to the total positioning error in computerassisted surgery, Comput Aided Surg 4:275–280, 1999. 68. Gellrich NC, Schramm A, Hammer B, et al: Computer-assisted secondary reconstruction of unilateral posttraumatic orbital deformity, Plast Reconstr Surg 110:1417–1429, 2002. 69. Smith JA, Sandler NA, Ozaki WH, et al: Subjective and objective assessment of the temporalis myofascial flap in previously operated temporomandibular joints, J Oral Maxillofac Surg 57:1058–1065, 1999, discussion 1065–1067. 70. Baumann A, Schicho K, Klug C, et al: Computer-assisted navigational surgery in oral and maxillofacial surgery, Atlas Oral Maxillofac Surg Clin North Am 13:41–49, 2005. 71. Bhatia SN, Leighton BC: A manual of facial growth: a computer analysis of longitudinal. cephalometric growth data, ed 1, New York, 1993, Oxford University Press. 72. Athanasiou AE: Orthodontic cephalometry, St Louis, 1995, Mosby-Wolfe. 73. Ricketts RM: Perspectives in the clinical application of cephalometrics. The first fifty years, Angle Orthod 51:115–150, 1981. 74. Ricketts RM, Roth RH, Chaconas SJ, et al: Orthodontic diagnosis and planning: their roles in preventive and rehabilitative dentistry, 1982, Rocky Mountain Orthodontics. 75. Downs WB: Variations in facial relationships: their significance in treatment and prognosis, Am J Orthod 34:812–840, 1948. 76. Downs WB: The role of cephalometrics in orthodontic case analysis and diagnosis, Am J Orthod 38:162–182, 1952. 77. Holdaway RA: The relationship of the bony chin and the lower incisor to the line NB (in a postgraduate course, University of California), 1955. 78. Holdaway RA: A consideration of the soft tissue outline for diagnosis and treatment planning. In Angle Society conference, 1957, Pasadena, CA. 79. Freeman RB: Are Class II elastics necessary? Am J Orthod 49:165–185, 1963. 80. Steiner CC: The use of cephalometrics as an aid to planning and assessing orthodontic treatment, Am J Orthod 46:721–735, 1960.

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81. Farkas LG, editor: Anthropometry of the head and face, ed 2, New York, 1994, Ravan Press. 82. Peck S, Peck L, Kataja M: Some vertical lineaments of lip position, Am J Orthod Dentofacial Orthop 101:519–524, 1992. 83. Peck S, Peck L, Kataja M: The gingival smile line, Angle Orthod 62:91–100, 1992, discussion 101–102.

84. Riley R, Guilleminault C, Herran J, et al: Cephalometric analyses and flow-volume loops in obstructive sleep apnea patients, Sleep 6:303–311, 1983. 85. Moyers RE, van der Linden FPGM, Riolo ML, et al: Standards of human occlusal development, Ann Arbor, 1976, Center for Human Growth and Development, The University of Michigan.

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Sercan Akyalcin

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oon after the rise of the information age, our offices have inevitably welcomed the “digital revolution.” Over the past several years, orthodontists have witnessed a tremendous increase in the number of technological innovations related to the clinical practice. Paperless charts and practice management solutions, virtual three-dimensional (3D) patient records, digital treatment planning, and customized appliances are here to stay. These changes may not be easy to adapt at once and may require further training of the practicing clinicians and the staff members. However, as we strive for clinical excellence and efficiency in patient care, we also need to be aware of technological advancements and use them wisely. There are many ways to correct the skeletal deformity and dental imbalance in an individual. However, there is only one diagnosis. The main goal of orthodontic diagnosis and treatment planning is to ensure that strategized mechanics and long-term retention goals can actually address the individual’s unique needs. Accurate diagnosis of an orthodontic patient requires high-quality records. According to the American Association of Orthodontists (AAO), pretreatment and posttreatment records should include extraoral and intraoral photographs, dental models, intraoral and/or panoramic radiographs, and cephalometric radiographs as well as any additional indicated tests or procedures.1 With today’s technology, it is possible to have all this information from 3D digital sources. 3D technologies include the use of laser scanning, structural light, stereophotogrammetry, magnetic resonance imaging (MRI) and surface scanning, computed tomography (CT), and cone beam computed tomography (CBCT). Perhaps most sophisticated among these is the CBCT, which permits the visualization of craniofacial anatomy in three dimensions. CBCT involves the use of a cone-shaped x-ray beam and a pair of source-detector devices that rotate around the patient’s head and create a series of two-dimensional (2D) images. Eventually a 3D data set will be formed based on the reconstruction of these images through computer software (Fig. 26-1). Additionally, it is possible to synthesize 2D and segmented 3D images from a single CBCT scan, which will allow the clinician to retrieve diagnostic information that can be obtained from all the conventional methods together. There is no doubt that those individuals that require the investigation of the maxillofacial structures in all three dimensions of the space, as usually is the case in orthodontics and maxillofacial surgery, will benefit from CBCT imaging. However, there are certain limits with the use of this technology.

The aim of this chapter is to address some of the key clinical issues that have been answered with the use of CBCT through recent research efforts and clinical trials. On reviewing this chapter, clinicians who are new to this technology will have a better understanding of the information offered with CBCT examinations in the field of orthodontics.

1. Can cone beam computed tomography be the standard of care in orthodontic diagnosis? The current answer to this question seems to be mostly negative. A 3D radiographic examination of the craniofacial skeleton with CBCT is indicated for a number of clinical conditions. However, like any x-ray exposure, CBCT scans also expose the patient to certain biologic risks of radiation. As the indications for CBCT imaging become more universal, so does the concern for radiation safety related to dental and orthodontic procedures.2–4 There are certain guidelines that should be reviewed by all clinicians who work in the area of craniofacial disorders before making a conclusive action in routinely prescribing CBCT examinations.5–7 Present guidelines are not compulsory, and clinical justification is the right answer in most situations. The American Dental Association Council on Scientific Affairs5 recommends that CBCT should only be considered as an adjunct to standard oral imaging modalities. During the clinical decision-making process, CBCT may supplement or replace conventional (2D or panoramic) dental radiography for the diagnosis, monitoring, and treatment of oral disease or the management of oral conditions when it is determined that structures of interest may not be captured adequately by means of conventional radiography.5

2. Why should we be concerned about the radiation exposure affiliated with the cone beam computed tomography scans? In diagnostic imaging, exposure to x-ray radiation must be accompanied by a related benefit that outweighs the associated risks for the use of that radiation. Orthodontists, as practicing health care providers, must remain cognizant of the risks if CBCT imaging is to become a more integral part of standard orthodontic practice. If so, it is important to know what the radiation doses are for orthodontic-indicated CBCT scans. There are already advocates for the universal use of CBCT scans to replace conventional radiographs. Their claim is based on the premise that the radiation doses from CBCT are lower than 329

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CHAPTER 26 • Three-Dimensional Update on Clinical Orthodontic Issues

FIG 26-1 Three-dimensional (3D) reconstruction of the dentofacial structures with the use of cone beam computed tomography (CBCT).

the combined radiation dose of a lateral cephalogram, panoramic radiograph, and a full series of periapical radiographs.8 However, there is no conclusive evidence to fully support these views.

3. What is the radiation dose for cone beam computed tomography? Radiation exposure puts the patient at risk of getting a radiation-induced cancer or heritable mutation (i.e., stochastic effect). To assess the patient risk from a radiationprotection perspective, the effective dose unit of measurement is regarded as the most suitable dose index.7 Effective dose takes into account the types of tissues being exposed and the amount of radiation dose to each tissue. Although methods to calculate the effective dose have been established, these methods depend heavily on the ability to estimate the dose to radiosensitive organs from the imaging procedure. This process is intended to broadly match the risk of an actual, generally nonuniform, irradiation to a hypothetic uniform whole-body irradiation of a standard person represented by an anthropomorphic head/body phantom.9,10 However, in reality every individual has unique shape, size, and attenuation. A large fraction of the current literature misuses the term effective dose by implying that it is both a precise and an accurate indicator of an individual patient’s risk.11 Depending on the unit and the operation mode, resulting effective dose may range between 30 to 1000 microsieverts (μSv) in CBCT examinations.12,13 Each CBCT scanner has different settings and energy levels. Use of continuous versus pulsed x-ray beam exposure, altering kV, mA, scanning time, and field of view (FOV) are the main reasons for the wide range of reported radiation doses. Grünheid and colleagues14 determined that effective doses from

a conventional digital cephalometric and panoramic imaging unit are 4.5 and 21.5 μSv, respectively. There is no argument that a CBCT examination will expose the patient to a higher level of radiation when compared with conventional methods. When obtaining CBCT scans, use of thyroid collars and leaded glasses reduces the effective organ doses to the radiosensitive tissues. Additionally, combination low kV and moderate mA settings should suffice in obtaining decent quality images in the average individual.15 The mA setting of the unit does not need to be adjusted to a higher level unless the size and attenuation of the subject increase. It is always a good practice to focus on the specific imaging need of the patient by reducing the scan FOV to only include the immediate region of interest in CBCT scans (Fig. 26-2).

4. Can cone beam computed tomography data be used to replace traditional cephalometry? The human face provides a difficult challenge for quantification for its individual complexity. Although 2D cephalometrics has been adapted in our field to study the face, 3D cephalometry offers more accurate information free of magnification, distortion, superimposition, and misinterpretation of structures. The most common problems affiliated with measuring 3D anatomy on 2D projections are the limited number of parameters and the presence of facial asymmetry. A 3D cephalometric analysis is generated digitally and viewed on a computer monitor superimposed on a virtual 3D head and face. Anatomic points and landmarks can easily be identified because images can be examined from different perspectives (Fig. 26-3). Quantification of the data is possible by measuring x, y, and z coordinates, distances between landmarks, and angles between planes and/or by using volumetric calculations.16

Three-Dimensional Update on Clinical Orthodontic Issues • CHAPTER 26

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FIG 26-2 In a clinical case, where both the second primary molar and second permanent premolar are impacted, immediate regions of interest can be viewed in different angles and aspects using a scan size of 5 × 5 cm for the affected area. Reducing the size of the field of view (FOV) reduces the radiation dose to the patient accordingly.

FIG 26-3 Landmark identification in three-dimensional (3D) cephalometry can be done from different perspectives.

Comparison of cephalometric measurements from 3D reconstructed images with conventional 2D images seems to yield contradictory results. Although some authors17–20 report good similarity between the measurements taken with conventional cephalograms and those obtained three-dimensionally with the CBCT, others21,22 signify the difference between the two methods and suggest that 3D tracings should not be used

as a follow-up to previous 2D data. The same trend seems to exist in the comparison of CBCT-generated cephalograms to conventional radiographs.23,24 Differences in projection techniques, software packages, study samples, and cephalometric analyses used in these studies do not allow for a sound comparison between the 2D and 3D methods. It is concluded that computer-aided 3D cephalometric measurements are more

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accurate25 and easier26 to interpret. However, generation of the cephalometric information from a CBCT scan requires a full-size FOV, thereby exposing the patient to higher risk of radiation. Orthodontic literature can benefit from well-designed studies investigating how much the diagnosis and treatment planning of the individual would actually differ with the use of 3D methods as compared to conventional cephalograms.24

5. What are the incidental findings in cone beam computed tomography examinations? According to a systematic review,27 incidental findings in CBCT scans of the head and neck region may range between 1.3 and 2.9 findings per examination. Frequency of the scans with incidental findings is 24.6% to 93.4%. These numbers suggest a

high but also considerably variable rate of additional findings in CBCT examinations. Most of the incidental findings that are reported in the literature are non-dental pathologies and/ or abnormalities in the head and neck region, such as airway, temporomandibular joint (TMJ), bone problems, and soft tissue calcifications.28–31 Although a CBCT scan may really be worthwhile to investigate, based on the additional information it provides compared to panoramic and full-mouth periapical radiography, the majority of the incidental findings are not directly related to orthodontic treatment planning.32 Most dental problems can easily be detected using conventional radiography with very few exceptions (Fig. 26-4, A and B). The high incidence of additional findings on CBCT scans requires the need for a thorough and proper review of the entire image, regardless of immediate region of interests by adequately trained

A

B

FIG 26-4 A, Conventional two-dimensional (2D) radiographs of an orthodontic patient. B, Cone beam computed tomography (CBCT) scan of the same patient revealing the presence of a mesiodens that was not very clear in the 2D radiographs.


clinicians. Orthodontists, because of their affiliations with the treatment and long-term follow-up, may need to pay special attention to cleft lip and palate (CLP) patients. Compared with regular orthodontic patients, CLP patients present with more dental, ear, and nasal problems. Incidental findings in this group of orthodontic patients are present in 95.1% of the examined CBCTs.31

6. Can dental models and measurements be accurately derived from cone beam computed tomography scans? Accuracy of linear and diagnostic dental measurements in CBCT images were thoroughly investigated using dry skulls,33 maxillae,34 mandibles,35 cadavers,36–38 porcine heads,39 and even artificial polydimethylsiloxane polymer models.40 All of these efforts contributed to our knowledge that accurate diagnosis can be made using CBCT technology without the need for another source (e.g., radiographs and dental models). This is not to say that a CBCT scan should be obtained to replace all of these. In other words, use of ionizing radiation to substitute for other methods for merely performing dental measurements is not acceptable at any rate. However, preexistence of a CBCT scan for other reasons will even allow for generation of 3D digital dental models. This requires the segmentation of the maxillary and mandibular dentoalveolar structures using specific software and conversion of the resultant image into a stereolithography (SLA) file (Fig. 26-5). Studies demonstrate that dental measurements made on CBCT-generated dental models as compared to caliper measurements and other digital dental model systems reveal reliable results for linear measurements41,42 and other diagnostic measures.43,44 However, study model analysis using CBCTgenerated study models is not always valid and requires more time to perform when compared with plaster models.45 This becomes more obvious when comprehensive statistical evaluations are considered along with test-retest measures. There is a similar pattern of systematic errors with the use of CBCTgenerated models44 and/or CBCT scans46 versus the use of other

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digital methods when each is compared with manual caliper measurements. However, CBCT-based measurements always display higher mean bias and agreement limits. Additionally, when evaluated for the differences in the surface areas, a high surface overlap match does not exist in the comparisons of CBCT-generated models with the other digital model systems until a 1- to 1.5-mm difference between the surface areas is tolerated.42,44 This finding suggests that the surface areas of the CBCT-generated models are lacking fine details, such as occlusal pits and fissures. The lack of detail in CBCT-generated models can even be observed with the naked eye in some instances (Fig. 26-6). This is partly due to the segmentation process of maxillary and mandibular teeth during the construction phase of the CBCT-generated models. Digital models synthesized from CBCT images are constructed from scans with the patient’s teeth in occlusion. This inevitably leads to overlapping of the images and makes the segmentation process arduous and time consuming.47,48 Second, spatial resolution might play an important role in the accuracy of 3D teeth reconstructions. A high level of accuracy as well as high-quality image detail is required before CBCT-generated models can generally be accepted.

FIG 26-6 Occlusal view of cone beam computed tomography (CBCT)-generated models.

FIG 26-5 Cone beam computed tomography (CBCT) scans can be segmented and converted to generate three-dimensional (3D) digital dental models.

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7. What did we learn from cone beam computed tomography scans regarding the placement of temporary anchorage devices? In just a short time since their introduction, temporary anchorage devices (TADs) have been used in various applications and orthodontic mechanics setups such that the possibilities for treatment of simple and complex cases with their aid are virtually limitless.49,50 Perhaps the most important feature that should exist in an orthodontic TAD application is the presence of “stability” following the implantation procedure. Soft tissue and bone thicknesses, bone density, as well as contact with the adjacent roots may affect the stability of TADs. There is no question that CBCT scans will allow for ideal visualization of the TAD placement site by presenting the entire volume as opposed to a 2D projection of it. However, no scientific evidence suggests that obtaining a CBCT scan will actually prevent the clinician from damaging the roots and/or increase the stability of the application. On the other hand, CBCT studies have been very helpful in understanding the differences between maxillary and mandibular TAD placement sites as well as the quantity of bone in these sites. According to a retrospective evaluation51 following the placement of TADs, inter-root distance made from the outline of the roots at the level of mini-screws was significantly higher in the mandible than in the maxilla (Fig. 26-7). Of the TADs placed, 65.2% were in contact with the periodontal ligament (PDL). Calculations based on using 7-mm-length screws revealed that 76.6% and 65.7% of the screw section was embedded in the alveolar bone of the maxilla and mandible, respectively. In the maxilla, the paramedian palate is a very suitable location to place short screws. The paramedian area 3 to 6 mm

posterior to and 2 to 9 mm lateral to the incisive foramen is identified as the best site for TAD placement.52 At 4 mm distal and 3 mm lateral to the incisive foramen, more than 90% of boys and girls have sufficient vertical bone depth to host a 3-mm implant.53 Although suggested locations to place the TADs in both jaws primarily point out to the interradicular area between the first and second molars either on the buccal or lingual aspects of the alveolar bone,51 it is also reported that there is good quality of bone between the second premolar and the first molar in the maxilla and between the first premolar and the first molar in the mandible buccally.54

8. What are the benefits of using cone beam computed tomography examinations in the identification of airway problems? Because changes in normal airway function may affect the facial development and contribute to the orthodontic problem, clinical examination requires a careful evaluation of the patient in this regard. However, the relationship between the airway and overall facial growth is a controversial topic in orthodontics. Many studies using conventional techniques have attempted to identify the link. Perhaps the controversy arises from examining a 3D complex structure on the 2D projections of it. Studies that compare the lateral cephalometric radiographs with CBCT scans for the measurement of airways present weak correlations.55–57 Measurements of airway volume made on CBCT scans show far more variability than the measurements of corresponding airway area performed on lateral head radiographs.56,57 Additionally, 3D images of the airway allow for a better view and improved evaluation of the obstruction sites.58 Therefore, evaluation of the airways in individuals with severe skeletal and craniofacial anomalies with comorbidities

FIG 26-7 Axial slices displaying the distance between the adjacent roots at the level of the temporary anchorage devices (TADs) in both jaws.


(such as obstructive sleep apnea) should not be made on 2D radiographs. CBCT scans enhance the diagnosis and treatment planning. Additionally, 3D registration techniques may be worthwhile to investigate the postoperative changes that occur in the airway dimensions following surgical procedures.

9. Does cone beam computed tomography offer a better evaluation in facial asymmetry? Although perfect symmetry does not exist in the human face, alteration from the normal range of symmetry brings about social as well as esthetic concerns for the individual. Facial asymmetries can arise from genetic, congenital, developmental, acquired, and, in some cases, unidentified factors. Regardless of the cause, it is important to understand the nature of facial asymmetry, which presents itself in dental, skeletal, and functional forms. Additionally, asymmetry can affect the whole face in a generalized form or can be limited in nature (e.g., mandibular asymmetry). Because all human beings are slightly asymmetric, it is important to cut the line between clinically significant and normal asymmetry. Unfortunately, common radiographic procedures included in the orthodontic diagnosis can only provide limited information. Cephalometric measurements are distorted when the patient has an underlying skeletal asymmetry. Detailed comparison of structures is not possible on panoramic radiography. Although various methods were proposed to evaluate the symmetry on posteroanterior (PA) cephalometric images, a comparison of direct measurements with PA images and CBCT images demonstrated the relative weakness of the 2D method.59 In another study, PA cephalograms were shown to have less reliability in determining the mandibular body length asymmetry when compared with the CBCT images.60 In theory, 3D cephalometry can eliminate the shortcomings of the 2D studies, especially in patients with facial asymmetries. However, it was shown that depending on the types of evaluations in the areas of size, position, shape, and orientation both the 2D and 3D measurements are affected by roll and yaw asymmetries.61

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The primary problem when diagnosing facial asymmetry is the establishment of reference planes. Without bilateral symmetry, a patient lacks a midsagittal plane. For patients with a minor and/or local asymmetry limited to a single area of the face, the normal facial tissues can be used as a reference for the correction of the asymmetry, and the use of a computer-generated midsagittal plane is feasible. However, in cases of generalized asymmetry (Fig. 26-8), it is harder to identify a reference plane. Even in normal individuals, construction of a midsagittal plane may be problematic and may show clinically relevant deviation from the true plane of symmetry. A true plane of symmetry in living subjects can be constructed using morphometrics methods.62 With morphometrics, a mirror image is created for each subject, and the original and mirror image are prealigned and translated together until the center points are superimposed. The computer then rotates the image to the best-fit landmark configuration. Construction of the midsagittal plane is then formed by splitting the individual symmetric configuration. Recently, mirroring with cranial base registration is also suggested. Studies showed that mirroring using a midsagittal plane and using a registration-based approach provided similar quantification of mandibular asymmetry for most areas.63,64 However, there are certain problematic issues with the application of mirroring techniques to facial asymmetry because computer modeling of a midsagittal plane in subjects with gross deformities will be highly inaccurate. A good clinical example is the presence of a cleft palate deformity that affects the midline structures. In some cases the cranial base itself may also be asymmetric. Orthodontic literature will benefit from studies that provide normative data on facial symmetry in all dimensions of the space using 3D images.

10. What is the role of cone beam computed tomography scans in the detection of root resorption? Root resorption is an undesirable complication of orthodontic treatment as orthodontic forces often trigger this clinical problem.65,66 Respectively, 2% and 5% of adolescents and adults develop root resorption of 5 mm and more in at least

FIG 26-8 Identification of the midsagittal plane is much harder in individuals with generalized asymmetry. Treatment planning of these cases benefits from establishment of threedimensional (3D) normative values in all dimensions of the space. (Photo courtesy of Drs. Xia and Gateno, Houston, TX.)

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one tooth during their active treatment.67,68 However, the incidence of resorption among orthodontically treated individuals differs among different studies because of the variability69 and potential shortcomings of the evaluation techniques. A striking CBCT investigation70 on 152 patients with Class I malocclusion revealed that practically all patients and up to 91% of all teeth showed some degree of root shortening on completion of the orthodontic treatment. It is suggested that patients at risk of severe apical root resorption can be identified according to the amount of resorption during the initial phases of the treatment using conventional 2D radiography adjusted for projection errors.68 Regardless of the projection geometry, conventional radiographs are not good means of quantitative evaluation and demonstration of the actual root resorption pattern. Scientific studies that compare the use of 2D radiographs to 3D evaluations agree that root resorption following orthodontic treatment is underestimated when evaluated with conventional radiography.66,71,72 As an alternative, CBCT offers a 3D evaluation of the roots free of projection errors in vivo. Studies that involved the use of CBCT indicated a high level of reproducibility,73 effectiveness in detecting even minimal degrees of resorption,74 and the potential for diagnosing slanted root resorption.70 The mean difference in length determinations between direct physical and CBCT measurements made on a dry skull was reported as 0.05 mm.73 Although clinically significant root resorption was well documented at the end of the ortho dontic treatment in a CBCT report, no correlations were found either with the resorption seen after 6 months or with the length of treatment.75 In another report,76 the CBCT method showed high accuracy of volumetric measurement of teeth in vivo as compared to micro-CT measurements in vitro. In light of this information, CBCT has the potential to sensitively detect the changes occurring on the roots of the teeth as a result of root resorption. CBCT scans with small FOVs that are only limited to the dentoalveolar region, obtained not so early after the start of treatment, may be very helpful for the detection of this treatment complexity in high-risk individuals. However, more studies are needed to confirm this statement and to further evaluate the sensitivity of the CBCT method in the diagnosis of different forms of root resorption.

11. How did cone beam computed tomography contribute to our knowledge in rapid maxillary expansion applications? Rapid maxillary expansion (RME) appliances have been commonly used by orthodontists to treat maxillary constriction and, in some cases, to resolve arch-length discrepancy. Although many types of palatal expanders and their effects on facial structures have extensively been documented, recent CBCT reports have been useful to support, refute, or to expand on the original findings. Perhaps the most important outcome that is expected from an RME application is the achievement of true orthopedic changes via skeletal expansion. Orthopedic expansion is not only limited to the midpalatal suture. The network of sutures around the maxillary and zygomatic bones is also affected. In most orthodontic maxillary expansion applications dental tipping and related alveolar changes occur and, in some

cases, may exceed the desired levels. Marginal bone loss, buccal fenestrations, and gingival problems may occur as a consequence.77,78 The periodontal consequences of RME in the permanent dentition emphasize the importance of early intervention. RME produces a greater orthopedic effect in the deciduous and mixed dentition. Despite the possibility of periodontal involvement, the future eruption of teeth will be followed by new alveolar bone, reestablishing the integrity of the area.79 It is also reported that heavy buccally directed forces produce significantly more resorption than light forces.80,81 Because RME therapy relies on the transmission of heavy forces to the maxilla by the anchor teeth, root resorption of these teeth is a well-documented finding in histologic investigations.82–84 Conventional radiographs, such as cephalometric and panoramic radiographs, are not appropriate for examining buccal bone or periodontal changes during and after RME therapy (Fig. 26-9). These techniques are based on a 2D representation of a 3D object and do not allow the clinician to reasonably evaluate the presence of buccal bone, dental and alveolar inclination changes, root resorption, bone density, limits of absolute skeletal expansion, and related airway and sinus changes. All of the characteristics mentioned earlier can be evaluated with CBCT. Based on the conclusions of a systematic review85 that investigated the effects of RME using 3D methods, skeletal expansion equals 20% to 50% of the screw expansion. However, no consistent evidence is present whether the suture opening is parallel or triangular. Although our classic knowledge of triangular pattern of skeletal expansion with a wider base in the anterior region is confirmed,86 parallel opening of the midpalatal suture is also documented.87 Additionally, it is confirmed that structures that are closely located to the maxilla show more width and/or displacement changes than those of distant structures.85 Greatest width increase is reported in the midpalatal suture followed by basal bone and nasal cavity.87 Nasal width increases between 17% and 33% of the total screw expansion.85,86,88 Although a subsequent decrease in maxillary sinus width is also reported,86 total maxillary sinus volume appears to remain virtually stable.88 RME has no effect on the nasopharynx volume.89 Additionally, there is no evidence to support the hypothesis that RME could increase the airway volume in individuals with narrow oropharyngeal airways.89–91 Several authors indicated the importance of buccal tipping of the anchored teeth and alveolar bending,87,92,93 particularly in banded RME applications as compared to bonded the RME devices.93 These changes led to the observation of an immediate decrease in buccal bone thickness and buccal marginal bone levels.78,92,94,95 However, changes related to the buccal bone thickness were generally reversible after the completion of orthodontic treatment in the long term with no evident deleterious effects on the alveolar buccal bone.78 A successful RME application requires careful monitoring of the patient’s age and initial buccal bone thickness so as not to compromise the periodontal status of the individual. Additionally, it was recently shown that slow maxillary expansion as opposed to rapid expansion causes significantly more vertical and horizontal bone losses.96


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FIG 26-9 Cone beam computed tomography (CBCT) scan of a young adult displays the absence of buccal bone on the maxillary first molar. This type evaluation is not possible with conventional two-dimensional (2D) radiographs.

FIG 26-10 Transposition of the mandibular right canine with the lateral incisor, viewed with cone beam computed tomography (CBCT) with a limited field of view (FOV).

12. Is cone beam computed tomography a better tool for treatment planning of localized dental problems as opposed to conventional radiographs? Localized dental problems (such as impacted, supernumerary, and transposed teeth) are commonly diagnosed with 2D

radiographs. The fundamental question is whether supplementing this evaluation with CBCT scans provides a better treatment/surgical outcome or not. Without any doubt a CBCT scan with only a small volume provides more information on the proper location of the problem, relationship with neighboring teeth, potential presence of root resorption, and treatment planning (Fig. 26-10). It is indicated that there is

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i ncreased precision in the localization of the impacted canines, associated root resorption, and the improved estimation of the space conditions in the dental arches with CBCT scans.97,98 Accordingly, it is suggested that CBCT scan with a limited or small FOV may be justified to supplement conventional x-rays when canine inclination in the panoramic radiograph exceeds 30 degrees, root resorption is an evident finding, and there is a difficulty in visualizing the root apex on the panoramic radiographs.99 CBCT scans are very helpful in the assessment of the relationship between impacted mandibular third molars and the mandibular canal, given the appearance of common artifacts in this region with the use of traditional panoramic radiographs.100 Although a randomized controlled clinical trial demonstrated that a CBCT buccolingual view can accurately confirm the number of roots and root morphology of the third molar better than a panoramic radiograph, the CBCT method was not any better than panoramic radiography in predicting postoperative complications.101 Furthermore, a recent systematic review102 suggested that there is only limited evidence for the diagnostic efficacy of utilizing CBCT for impacted teeth and associated features. Orthodontic literature can benefit from studies with strong methodologies for evaluating both the diagnostic, operative, and postoperative efficacy of CBCT in the management of localized dental problems. REFERENCES 1. Peluso MJ, Josell SD, Levine SW, et al: Digital models: an introduction, Semin Orthod 10:226–238, 2004. 2. Scholz RP: The radiology decision, Semin Orthod 17:15–19, 2011. 3. Baumrind S: The road to three-dimensional imaging in orthodontics, Semin Orthod 17:2–12, 2011. 4. Halazonetis DJ: Cone-beam computed tomography is not the imaging technique of choice for comprehensive orthodontic assessment, Am J Orthod Dentofacial Orthop 141:403–411, 2012. 5. The American Dental Association Council on Scientific Affairs: The use of cone-beam computed tomography in dentistry: an advisory statement from the American Dental Association Council on Scientific Affairs, J Am Dent Assoc 143:899–902, 2012. 6. SEDENTEXCT project: Radiation protection: cone beam CT for dental and maxillofacial radiology. Evidence based guidelines 2011 (website): http://www.sedentexct.eu/files/guidelines_final .pdf. Accessed on March 20, 2014. 7. Pauwels R, Beinsberger J, Collaert B, et al: SEDENTEXCT Project Consortium: effective dose range for dental cone beam computed tomography scanners, Eur J Radiol 81:267–271, 2012. 8. Larson BE: Cone-beam computed tomography is the imaging technique of choice for comprehensive orthodontic assessment, Am J Orthod Dentofacial Orthop 141:402–410, 2012. 9. Bauhs JA, Vrieze TJ, Primak AN, et al: CT dosimetry: comparison of measurement techniques and devices, Radiographics 28:245–253, 2008. 10. Balter S, Zanzonico P, Reiss GR, et al: Radiation is not the only risk, Am J Roentgenol 196:762–767, 2011. 11. Borrás C, Huda W, Orton CG: Point/counterpoint. The use of effective dose for medical procedures is inappropriate, Med Phys 37:3497–5300, 2010. 12. Qu XM, Li G, Ludlow JB, et al: Effective radiation dose of ProMax 3D cone-beam computerized tomography scanner with different dental protocols, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 110:770–776, 2010.

13. Ludlow JB, Ivanovic M: Comparative dosimetry of dental CBCT devices and 64-slice CT for oral and maxillofacial radiology, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 106:106–114, 2008. 14. Grünheid T, Kolbeck Schieck JR, Pliska BT, et al: Dosimetry of a cone-beam computed tomography machine compared with a digital x-ray machine in orthodontic imaging, Am J Orthod Dentofacial Orthop 141:436–443, 2012. 15. Gamache CS, English JD, Salas AM, et al: Assesment of image quality in maxillofacial CBCT imaging, J Dent Res 92(SIA), 2013, ABS #3645. 16. Jacobson A, Jacobson RL: Radiographic cephalometry—from basics to 3-D imaging, ed 2, 2006, Quintessence Publishing Co., Inc. IL. 17. Zamora N, Llamas JM, Cibrián R, et al: Cephalometric measurements from 3D reconstructed images compared with conventional 2D images, Angle Orthod 81:856–864, 2011. 18. Shaw K, McIntyre G, Mossey P, et al: Validation of conventional 2D lateral cephalometry using 3D cone beam CT, J Orthod 40:22–28, 2013. 19. Oz U, Orhan K, Abe N: Comparison of linear and angular measurements using two-dimensional conventional methods and three-dimensional cone beam CT images reconstructed from a volumetric rendering program in vivo, Dentomaxillofac Radiol 40:492–500, 2011. 20. Yitschaky O, Redlich M, Abed Y, et al: Comparison of common hard tissue cephalometric measurements between computed tomography 3D reconstruction and conventional 2D cephalometric images, Angle Orthod 81:11–16, 2011. 21. van Vlijmen OJ, Maal TJ, Bergé SJ, et al: A comparison between two-dimensional and three-dimensional cephalometry on frontal radiographs and on cone beam computed tomography scans of human skulls, Eur J Oral Sci 117:300–305, 2009. 22. van Vlijmen OJ, Maal TJ, Bergé SJ, et al: A comparison between 2D and 3D cephalometry on CBCT scans of human skulls, Int J Oral Maxillofac Surg 39:156–160, 2010. 23. Rossini G, Cavallini C, Cassetta M, et al: 3D cephalometric analysis obtained from computed tomography. Review of the literature, Ann Stomatol (Roma) 2:31–39, 2011. 24. van Vlijmen OJ, Kuijpers MA, Bergé SJ, et al: Evidence supporting the use of cone-beam computed tomography in orthodontics, J Am Dent Assoc 143:241–252, 2012. 25. Olmez H, Gorgulu S, Akin E, et al: Measurement accuracy of a computer-assisted three-dimensional analysis and a conventional two-dimensional method, Angle Orthod 81: 375–382, 2011. 26. Farronato G, Garagiola U, Dominici A, et al: “Ten-point” 3D cephalometric analysis using low-dosage cone beam computed tomography, Prog Orthod 11:2–12, 2010. 27. Edwards R, Altalibi M, Flores-Mir C: The frequency and nature of incidental findings in cone-beam computed tomographic scans of the head and neck region: a systematic review, J Am Dent Assoc 144:161–170, 2013. 28. Price JB, Thaw KL, Tyndall DA, et al: Incidental findings from cone beam computed tomography of the maxillofacial region: a descriptive retrospective study, Clin Oral Implants Res 23: 1261–1268, 2012. 29. Cağlayan F, Tozoğlu U: Incidental findings in the maxillofacial region detected by cone beam CT, Diagn Interv Radiol 18:159–163, 2012. 30. Allareddy V, Vincent SD, Hellstein JW, et al: Incidental findings on cone beam computed tomography images, Int J Dent 2012:871532, 2012. 31. Kuijpers MA, Pazera A, Admiraal RJ, et al: Incidental findings on cone beam computed tomography scans in cleft lip and palate patients, Clin Oral Investig, 2013 Aug 27, Epub ahead of print.


32. Drage N, Rogers S, Greenall C, et al: Incidental findings on cone beam computed tomography in orthodontic patients, J Orthod 40:29–37, 2013. 33. Baumgaertel S, Palomo JM, Palomo L, et al: Reliability and accuracy of cone-beam computed tomography dental measurements, Am J Orthod Dentofacial Orthop 136:19–25, 2009. 34. Veyre-Goulet S, Fortin T, Thierry A: Accuracy of linear measurement provided by cone beam computed tomography to assess bone quantity in the posterior maxilla: a human cadaver study, Clin Implant Dent Relat Res 10:226–230, 2008. 35. Damstra J, Fourie Z, Huddleston Slater JJ, et al: Accuracy of linear measurements from cone-beam computed tomographyderived surface models of different voxel sizes, Am J Orthod Dentofacial Orthop 137(16):e1–e6, 2010. 36. Ganguly R, Ruprecht A, Vincent S, et al: Accuracy of linear measurement in the Galileos cone beam computed tomography under simulated clinical conditions, Dentomaxillofac Radiol 40:299–305, 2011. 37. Patcas R, Müller L, Ullrich O, et al: Accuracy of cone-beam computed tomography at different resolutions assessed on the bony covering of the mandibular anterior teeth, Am J Orthod Dentofacial Orthop 141:41–50, 2012. 38. Benninger B, Peterson A, Cook V: Assessing validity of actual tooth height and width from cone beam images of cadavers with subsequent dissection to aid oral surgery, J Oral Maxillofac Surg 70:302–306, 2012. 39. Sherrard JF, Rossouw PE, Benson BW, et al: Accuracy and reliability of tooth and root lengths measured on cone-beam computed tomographs, Am J Orthod Dentofacial Orthop 137:S100–S108, 2010. 40. Nguyen E, Boychuk D, Orellana M: Accuracy of cone-beam computed tomography in predicting the diameter of unerupted teeth, Am J Orthod Dentofacial Orthop 140:e59–e66, 2011. 41. Creed B, Kau CH, English JD, et al: A comparison of the accuracy of linear measurements obtained from cone beam computerized tomography images and digital models, Semin Orthod 17:49–56, 2011. 42. Lightheart KG, English JD, Kau CH, et al: Surface analysis of study models generated from OrthoCAD and cone-beam computed tomography imaging, Am J Orthod Dentofacial Orthop 141:686–693, 2012. 43. Kau CH, Littlefield J, Rainy N, et al: Evaluation of CBCT digital models and traditional models using the Little's Index, Angle Orthod 80:435–439, 2010. 44. Akyalcin S, Dyer D, English JD, et al: A comparison of 3-D dental models obtained from different sources: diagnostic accuracy and surface registration analysis, Am J Orthod Dentofacial Orthop 144:831–837, 2013. 45. Luu NS, Mandich MA, Flores-Mir C, et al: The validity, reliability, and time requirement of study model analysis using cone-beam computed tomography-generated virtual study models, Orthod Craniofac Res, 2013 Apr 17, doi: (Epub ahead of print). 46. Akyalcin S, Cozad BE, English JD, et al: Diagnostic accuracy of impression-free digital models, Am J Orthod Dentofacial Orthop 144:916–922, 2013. 47. Al-Rawi B, Hassan B, Vandenberge B, et al: Accuracy assessment of three-dimensional surface reconstructions of teeth from cone beam computed tomography scans, J Oral Rehabil 37(5):352–358, 2010. 48. Fourie Z, Damstra J, Rutger HS, et al: Segmentation process significantly influences the accuracy of 3D surface models derived from cone beam computed tomography, Eur J Radiol 81:e542–e530, 2012. 49. Chung KR, Choo HR, Kim SH, et al: Timely relocation of miniimplants for uninterrupted full-arch distalization, Am J Orthod Dentofacial Orthop 138:839–849, 2010.

339

50. Hyde JD, King GJ: Survey of orthodontists’ attitudes and experiences regarding miniscrew implants, J Clin Orthod 44:481–486, 2010. 51. Kau CH, English JD, Muller-Delgado MG, et al: Retrospective cone-beam computed tomography evaluation of temporary anchorage devices, Am J Orthod Dentofacial Orthop 137(166):e1–e5, 2010. 52. AlSamak S, Gkantidis N, Bitsanis E, et al: Assessment of potential orthodontic mini-implant insertion sites based on anatomical hard tissue parameters: a systematic review, Int J Oral Maxillofac Implants 27:875–887, 2012. 53. King KS, Lam EW, Faulkner MG, et al: Vertical bone volume in the paramedian palate of adolescents: a computed tomography study, Am J Orthod Dentofacial Orthop 132:783–788, 2007. 54. Park J, Cho HJ: Three-dimensional evaluation of interradicular spaces and cortical bone thickness for the placement and initial stability of microimplants in adults, Am J Orthod Dentofacial Orthop 136(3), 2009, 314.e1-12. 55. Sears CR, Miller AJ, Chang MK, et al: Comparison of pharyngeal airway changes on plain radiography and conebeam computed tomography after orthognathic surgery, J Oral Maxillofac Surg 69:e385–e394, 2011. 56. Aboudara CA, Hatcher D, Nielsen IL, et al: A three-dimensional evaluation of the upper airway in adolescents, Orthod Craniofac Res 6:173–175, 2003. 57. Aboudara C, Nielsen I, Huang JC, et al: Comparison of airway space with conventional lateral headfilms and 3-dimensional reconstruction from cone-beam computed tomography, Am J Orthod Dentofacial Orthop 135:468–479, 2009. 58. Grauer D, Cevidanes LS, Styner MA, et al: Pharyngeal airway volume and shape from cone-beam computed tomography: relationship to facial morphology, Am J Orthod Dentofacial Orthop 136:805–814, 2009. 59. de Moraes ME, Hollender LG, Chen CS, et al: Evaluating craniofacial asymmetry with digital cephalometric images and cone-beam computed tomography, Am J Orthod Dentofacial Orthop 139:e523–e531, 2011. 60. Damstra J, Fourie Z, Ren Y: Evaluation and comparison of postero-anterior cephalograms and cone-beam computed tomography images for the detection of mandibular asymmetry, Eur J Orthod 35:45–50, 2013. 61. Gateno J, Xia JJ, Teichgraeber JF: Effect of facial asymmetry on 2-dimensional and 3-dimensional cephalometric measurements, J Oral Maxillofac Surg 69:655–662, 2011. 62. Damstra J, Fourie Z, De Wit M, et al: A three-dimensional comparison of a morphometric and conventional cephalometric midsagittal planes for craniofacial asymmetry, Clin Oral Investig 16:285–294, 2012. 63. AlHadidi A, Cevidanes LH, Mol A, et al: Comparison of two methods for quantitative assessment of mandibular asymmetry using cone beam computed tomography image volumes, Dentomaxillofac Radiol 40:351–357, 2011. 64. Cevidanes LH, Alhadidi A, Paniagua B, et al: Three-dimensional quantification of mandibular asymmetry through cone-beam computerized tomography, Oral Surg Oral Med Oral Pathol Oral Radiol Endod 111:757–770, 2011. 65. Weltman B, Vig KW, Fields HW, et al: Root resorption associated with orthodontic tooth movement: a systematic review, Am J Orthod Dentofacial Orthop 137(4):462–476, 2010, discussion 12A. 66. Dudic A, Giannopoulou C, Leuzinger M, et al: Detection of apical root resorption after orthodontic treatment by using panoramic radiography and cone-beam computed tomography of super-high resolution, Am J Orthod Dentofacial Orthop 135:434–437, 2009. 67. Linge BO, Linge L: Apical root resorption in upper anterior teeth, Eur J Orthod 5:173–183, 1983.

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68. Artun J: Van 't Hullenaar R, Doppel D, et al: Identification of orthodontic patients at risk of severe apical root resorption, Am J Orthod Dentofacial Orthop 135:448–455, 2009. 69. Lund H, Gröndahl K, Gröndahl HG: Cone beam computed tomography evaluations of marginal alveolar bone before and after orthodontic treatment combined with premolar extractions, Eur J Oral Sci 120:201–211, 2012. 70. Lund H, Gröndahl K, Hansen K, et al: Apical root resorption during orthodontic treatment. A prospective study using cone beam CT, Angle Orthod 82:480–487, 2012. 71. Dudic A, Giannopoulou C, Martinez M, et al: Diagnostic accuracy of digitized periapical radiographs validated against micro-computed tomography scanning in evaluating orthodontically induced apical root resorption, Eur J Oral Sci 116:467–472, 2008. 72. Alqerban A, Jacobs R, Fieuws S, et al: Comparison of two cone beam computed tomographic systems versus panoramic imaging for localization of impacted maxillary canines and detection of root resorption, Eur J Orthod 33:93–102, 2011. 73. Lund H, Gröndahl K, Gröndahl HG: Cone beam computed tomography for assessment of root length and marginal bone level during orthodontic treatment, Angle Orthod 80:466–473, 2010. 74. Castro IO, Alencar AH, Valladares-Neto J, et al: Apical root resorption due to orthodontic treatment detected by cone beam computed tomography, Angle Orthod 83:196–203, 2013. 75. Makedonas D, Lund H, Hansen K: Root resorption diagnosed with cone beam computed tomography after 6 months and at the end of orthodontic treatment with fixed appliances, Angle Orthod 83:389–393, 2013. 76. Wang Y, He S, Yu L, et al: Accuracy of volumetric measurement of teeth in vivo based on cone beam computer tomography, Orthod Craniofac Res 14:206–212, 2011. 77. Rungcharassaeng K, Caruso JM, Kan JY, et al: Factors affecting buccal bone changes of maxillary posterior teeth after rapid maxillary expansion, Am J Orthod Dentofacial Orthop 132(428):e1–e8, 2007. 78. Akyalcin S, Schaefer JS, English JD, et al: A cone-beam computed tomography evaluation of buccal bone thickness following maxillary expansion, Imaging Sci Dent 43:85–90, 2013. 79. Garib DG, Henriques JF, Janson G, et al: Periodontal effects of rapid maxillary expansion with tooth-tissue-borne and toothborne expanders: a computed tomography evaluation, Am J Orthod Dentofacial Orthop 129:749–758, 2006. 80. Paetyangkul A, Türk T, Elekdağ-Türk S, et al: Physical properties of root cementum: part 14. The amount of root resorption after force application for 12 weeks on maxillary and mandibular premolars: a microcomputed-tomography study, Am J Orthod Dentofacial Orthop 136(492):e1–e9, 2009. 81. Oh C, Türk T, Elekdağ-Türk S, et al: Physical properties of root cementum: Part 19. Comparison of the amounts of root resorption between the right and left first premolars after application of buccally directed heavy orthodontic tipping forces, Am J Orthod Dentofacial Orthop 140:e49–e52, 2011. 82. Langford SR: Root resorption extremes resulting from clinical RME, Am J Orthod 81:371–377, 1982. 83. Langford SR, Sims MR: Root surface resorption, repair, and periodontal attachment following rapid maxillary expansion in man, Am J Orthod 81:108–115, 1982. 84. Odenrick L, Karlander EL, Pierce A, et al: Surface resorption following two forms of rapid maxillary expansion, Eur J Orthod 13:264–270, 1991. 85. Bazargani F, Feldmann I, Bondemark L: Three-dimensional analysis of effects of rapid maxillary expansion on facial sutures and bones, Angle Orthod, 2013 Jun 7 (Epub ahead of print).

86. Garrett BJ, Caruso JM, Rungcharassaeng K, et al: Skeletal effects to the maxilla after rapid maxillary expansion assessed with cone-beam computed tomography, Am J Orthod Dentofacial Orthop 134:8–9, 2008. 87. Christie KF, Boucher N, Chung CH: Effects of bonded rapid palatal expansion on the transverse dimensions of the maxilla: a cone-beam computed tomography study, Am J Orthod Dentofacial Orthop 137:S79–S85, 2010. 88. Darsey DM, English JD, Kau CH, et al: Does hyrax expansion therapy affect maxillary sinus volume? A cone-beam computed tomography report, Imaging Sci Dent 42:83–88, 2012. 89. Ribeiro AN, de Paiva JB, Rino-Neto J, et al: Upper airway expansion after rapid maxillary expansion evaluated with cone beam computed tomography, Angle Orthod 82:458–463, 2012. 90. Zhao Y, Nguyen M, Gohl E, et al: Oropharyngeal airway changes after rapid palatal expansion evaluated with conebeam computed tomography, Am J Orthod Dentofacial Orthop 137:S71–S78, 2010. 91. Zeng J, Gao X: A prospective CBCT study of upper airway changes after rapid maxillary expansion, Int J Pediatr Otorhinolaryngol, 2013 Sep 4, pii: S0165-5876(13)00362-5. 92. Domann CE, Kau CH, English JD, et al: Cone beam computed tomography analysis of dentoalveolar changes immediately after maxillary expansion, Orthodontics (Chic) 12:202–209, 2011. 93. Pangrazio-Kulbersh V, Wine P, Haughey M, et al: Cone beam computed tomography evaluation of changes in the nasomaxillary complex associated with two types of maxillary expanders, Angle Orthod 82:448–457, 2012. 94. Rungcharassaeng K, Caruso JM, Kan JY, et al: Factors affecting buccal bone changes of maxillary posterior teeth after rapid maxillary expansion, Am J Orthod Dentofacial Orthop 132(428):e1–e8, 2007. 95. Pangrazio-Kulbersh V, Jezdimir B, de Deus Haughey M, et al: CBCT assessment of alveolar buccal bone level after RME, Angle Orthod 83:110–116, 2013. 96. Brunetto M, Andriani Jda S, Ribeiro GL, et al: Threedimensional assessment of buccal alveolar bone after rapid and slow maxillary expansion: a clinical trial study, Am J Orthod Dentofacial Orthop 143:633–644, 2013. 97. Botticelli S, Verna C, Cattaneo PM, et al: Two- versus threedimensional imaging in subjects with unerupted maxillary canines, Eur J Orthod 33:344–349, 2011. 98. Oberoi S, Knueppel S: Three-dimensional assessment of impacted canines and root resorption using cone beam computed tomography, Oral Surg Oral Med Oral Pathol Oral Radiol 113:260–267, 2012. 99. Wriedt S, Jaklin J, Al-Nawas B, et al: Impacted upper canines: examination and treatment proposal based on 3D versus 2D diagnosis, J Oral Rehabil 38:208–216, 2011. 100. Neves FS, Souza TC, Almeida SM, et al: Correlation of panoramic radiography and cone beam CT findings in the assessment of the relationship between impacted mandibular third molars and the mandibular canal, Dentomaxillofac Radiol 41:553–557, 2012. 101. Guerrero ME, Botetano R, Beltran J, et al: Can preoperative imaging help to predict postoperative outcome after wisdom tooth removal? A randomized controlled trial using panoramic radiography versus cone-beam CT, Clin Oral Investig, 2013 Mar 15 (Epub ahead of print). 102. Guerrero ME, Shahbazian M, Elsiena Bekkering G, et al: The diagnostic efficacy of cone beam CT for impacted teeth and associated features: a systematic review, J Oral Rehabil 38: 208–216, 2011.

Index A AAO. See American Association of Orthodontists (AAO) ABO. See American Board of Orthodontics (ABO) ACE. See Angiotensin converting enzyme (ACE) inhibitors Acetaminophen, 289 Achondroplasia, 277 Acrofacial dysostosis, 277 Activator appliance, 169–170, 209, 211–212 Active self-ligating bracket, 103 ADA. See American Dental Association (ADA) Adjunctive orthodontics, 198 Adolescent interdisciplinary orthodontic treatment for, 220 maxillary arch expansion in, 73–76 Phase II treatment for, 137, 206–219. (See also Class III malocclusions treatment; Class II malocclusions treatment; Class I malocclusions treatment) crossbites, 215 defined, 24 open bites, 215 orthodontist referral for, 206–207 “problem-oriented” approach to, 206 special considerations, 215–217 Adult/adulthood interdisciplinary orthodontic treatment, 220–234 adolescent vs. 220, 221f contraindications for, 220 dental alignment, 224–225 dental esthetics and, 227–230, 228f, 229f, 230f eruption, forced, 223–224, 224f, 225f goals of, 220 indications for, 225 for molar uprighting, 222–223, 223f options for, 222 orthodontic records for diagnosis and, 221–222 periodontal tissue, effects of, 221 retention considerations for, 225–226 sequence of, 222 surgery as, 226–227, 226f temporary anchorage devices and, 230, 230f, 231f, 232f, 233f tooth movement and, 221, 222 lips, length and thickness of, 10 maxillary arch expansion in, 73–76 nose growth during, 10 Phase II treatment for, 137, 206–219. (See also Class III malocclusions treatment; Class II malocclusions treatment; Class I malocclusions treatment) crossbites, 215 defined, 24 open bites, 215 orthodontist referral for, 206–207 “problem-oriented” approach to, 206 special considerations, 215–217 soft-tissue facial profile for, 10

Age clinical evaluation, considerations for, 37–38 malocclusions treatment, for early, 24 minor tooth movement, for considering, 198–199 peak height velocity and, 2 Agenesis of teeth, 21 Air powder polishing (APP) system, 264–265 Air rotor stripping (ARS), 72, 297 Airway, 56, 334–335 Alcohol embryopathy, 277 Alignment, 224–225, 298 Align Technology, 154 Alpha blockers, 289 Alprazolam (Xanax), 289 Altman’s method for assessing measurement agreement, 320, 322 Alveolar bone destruction of, 137–138 heights/volume assessment of, 56 procedures for, 164 American Academy of Laser Dentistry, 304 American Association for Dental Research, 290 American Association of Orthodontists (AAO), 245, 329 American Board of Orthodontics (ABO), 67, 89, 105–106 Clinical Examination, 297–298 Objective Grading System of, 293, 297–298 Structural Method of, 89, 95 American Dental Association (ADA) Council on Dental Therapeutics, 264 Council on Scientific Affairs, 329 Seal of Acceptance, 264 American Time self-ligating bracket, 104–105 Amitriptyline (Elavil), 289 Amnion rupture sequence, 277 Analysis anterior space, 131–132 Bolton, 40–41 cast, 39 cephalometric, 44–45 ANB angle for, 46, 210, 254–256 cone beam computed tomography and, 330–332 diagnostic database and, 61 essentials of, 45–46 landmarks, 44–45 facial profile, 47 frontal, 62–63 functional, 61 midarch space, 132–133 of photographs, 61 posterior space, 133–134 predictive, 46–47 Steiner’s, 65 study cast, 61 for three-dimensional imaging, 57 Anatomic landmarks, 44 Anatomic reference planes, 45 ANB angle, 46, 210, 254–256

Anchorage, 235. See also Skeletal anchorage Anchor teeth, 216 Andersen gauge, 108 Andrews, Larry F., 108 Angiotensin converting enzyme (ACE) inhibitors, 289 Angle, Edward Hartley, 60, 98, 100, 250 occlusion development, classification of, 16 orthodontic models, dental classification for, 41, 42f Angle of torque, 110, 111f Angles ANB, 46, 210, 254–256 gonial, 250–251 Holdway, 116 low, 204 mandibular plane, 62 sella-nasion to gonion-gnathion, 209, 250–251 SNA, 45, 46, 65, 210, 212 SNB, 45, 46, 65, 210, 212 Z, 116 Angle System, 98, 99f Angular values for space, 45–46 Ankylosis, 10, 20f, 82–85 Anodontia, 21 ANS. See Anterior nasal spine (ANS) Anterior cranial base, 45 Anterior crossbites, 24, 188–191, 200 Anterior crowding, timing for, 28–31 Anterior facial height, 66 Anterior limit of dentition, 122 Anterior nasal spine (ANS), 44 Anterior open bites dental, 215 dentoalveolar, 250–253 habitual, 252–253 skeletal, 215, 250–252, 253, 254–257 Anterior space analysis, 131–132, 132f Anterior trauma, 203 Anterior vertical face height, 204 Anteroposterior component of skeletal pattern, 130–131 Anteroposterior discrepancies, 140–144 Class II malocclusion elastics, 140 fixed appliances for correcting, 140 tooth movement for correction of discrepancy in, 142, 143–144 crowding, treatment options for correcting, 140–141 extraction circumstances for considering, 140, 141–142 for Class III anteroposterior discrepancy, 143 serial, 141 extra-oral traction therapy, 140 functional appliances for, 142–143 headgear and facebow, 140 protection facemask therapy for, 143 Anteroposterior interjaw, 208 Anteroposterior maxillomandibular relationship, 8 Anteroposterior planes of space, 62

Note: Page numbers followed by f indicate figures, t indicate tables and b indicate boxes. 341

342

INDEX

Anteroposterior profile view, 63 Anteroposterior skeletal measurements, 45–46 Anticoagulants, 289 Anxiolytics, 289 Apert syndrome, 277, 279–280 Aphthous ulcer management, 302 “A” point (A), 44 APP. See Air powder polishing (APP) system Appliances. See also specific types of Activator, 169–170, 209, 211–212 Begg, 99 Bionator, 169–170, 174, 209, 210, 211–212, 294 for Class II malocclusions treatment, 174 Dental Contour, 154 distalizing, 165 edgewise, 98, 99–100 archwire in, 100 Dr. Charles H. Tweed and, 100 evolution of, 99–100 pin and tube vertical bracket vs., 100 Essix, 154 fixed, 98 characteristics of, 98 Invisalign® System vs., 159, 162 tooth movement with, 102 fixed-removable, 98 Flex-O-Tite gum-massaging, 154 Forsus, 169–170, 177–179 friction-free, 106 functional for anteroposterior discrepancies, 142–143 for Class II malocclusions treatment, 169–172 clinical response to, variations in, 179–180 stability of, long-term, 180–182 therapy using, 168–169 Headgear Activator, 211 Herbst, 65, 140, 165, 142, 169, 175, 211–212 Hyrax jackscrew, 215 Invisalign® System, preceding of, 154 lingual, 110 Lower Schwartz, 139, 140 mandibular anterior repositioning, 65, 120, 142, 169–170, 176–177 molar distalizing “noncompliance,” 213 Pendex, 139 Pendulum, 140, 213 Positioner, 154 rapid palatal expander, 24–25, 137, 174, 198 fixed, 199 four-tooth, 199 two-tooth, 199 surgically-assisted rapid palatal expansion, 73–76 Twin Block, 65, 149–150, 151, 169–170, 174, 211–212 W, 199 Arches circumference discrepancy in, 39 depth of, 5, 5f diagnostic, 39 expansion, 235 length of, 18–19, 39, 207 limited, 147 lingual, 145–146 lower, 199 lower lingual holding, 207, 215

Arches (Continued) minor tooth movement, problems with, 201–202 perimeter of, 4f perimeter of, untreated, 4 ribbon, 99 spacing in, 203 transpalatal, 145–146, 240, 254–256 W, 139 width of, changes in, 19 Archwire cold welding of, 106 C-shaped, 107, 108f cuspid retraction on, 116 D-shaped, 107, 108f dual-dimension, 107, 108f in edgewise, 100 Hooke's law and, 110, 110f initial, 106, 107f properties of ideal, 107 ARS. See Air rotor stripping (ARS) Arthrography, 289 Articulare (Ar), 45 Articulator orthodontic models, 43 Ascending ramus, 240 Asymmetric extraction, 144 Asymmetric occlusal relationships, 41–42 Average faces, 53–54

B Balance of face, factors affecting, 127–128 Band expanders, 137, 149 Banding of teeth, 235 Barbiturates, 289 Beckwith-Wiedemann syndrome, 277 Begg, Raymond, 99 Begg appliance, 99, 100f Behavioral clinical evaluation, 37 Bell stage, 1 Bends, 101–102 Beta blockers, 289 Beta-titanium (TMA), 107–108 Beta-titanium wires, 107–108 Bicuspid extraction, 144 Bilateral cleft lip and palate, 271 Bilateral hard tissue landmarks, 44–45 Bilateral posterior crossbite without a functional shift, timing for, 27 Biological width, 223–224 Biomechanics, 112–119 center of resistance, 113 center of rotation, 113–114 controlled tipping, 114, 114f couple center of rotation for movement created by, 116 defined, 116, 116f moment of, 116, 117f defined, 112 equilibrium, 116–117, 117f force concurrent, 113, 113f defined in physics, 112 horizontal and vertical components of, 112, 113f moment of, 115, 115f, 116f one-couple, 117, 118f system of, 112–113 two-couple, 117, 118f

Biomechanics (Continued) Newtonian mechanics, 112 Newton's three Laws of Motion, 112 root torque, 115f temporary anchorage device, 118, 119 translational tooth movement, 114, 114f uncontrolled tipping, 114, 114f vector, 112 Bionator appliance, 169–170, 174, 209, 210, 211–212, 294 for Class II malocclusions treatment, 174 Bisphosphonates, 156 Bite Brodie, 67, 199–200 deep, 162, 174, 299 open, 31f, 215 anterior, 215 posterior, 215 relapse in, 299 registration of, 320 scissor, 67 Sunday, 37 Biteplate, headgear with, 209 Bit jig, fabrication of, 315–320 Björk-type dental implants, 211, 212 Black triangle, 228–230 Blade implants, 235–236 Bleaching, 159 Blockers, 289 Bollard plates, 140 Bolton analysis, 40–41 Bolton’s discrepancy, 23, 159, 202–203 Bonded acrylic splint expander, 147–148, 148f Bonded expander, 149 Bonded lingual retainers, 294–295 Bonded rapid maxillary expander, 151 Bonded rapid palatal expander, 137–138 Bonding, 110, 159, 235 Bone grafting procedures, 221 Bony chin, 9 Boone gauge, 108 Botulinum toxin, 289 “B” point (B), 44 Brachycephalic, 250 Brachyfacial, 66, 250 Bracket double-tube, 104f single-tube, 104f triple-tube, 104f Brackets ceramic, 109–110, 110f characteristics of, 98 cold welding of, 106 contamination of, impact on bonding to enamel, 110 convertible, 106 Damon, 100, 103 direct bonded components of, 103 construction of, 102–103 mechanism for securing to tooth enamel, 104–105 double-tube, 104 elastomeric ligated, 265 In-Ovation, 100, 103 ligated, elastomeric, 265 pin and tube vertical, 100

INDEX

Brackets (Continued) position of, influence on treatment, 108 power arm attached to, 108, 109f prescription, 101–102 self-ligating, 100 active, 103 defined, 103 passive, 103 single-tube, 104 slot dimension, 105–106 SPEED, 100, 102–103, 104–105, 106 spring-wing, 103–104 systems, full banded vs. full direct bonded, 101 Time, 100, 103 Tip-Edge, 99 tooth-colored (“esthetic”), 265 triple-tube, 104 Bracket spring-clips, dual-action, 103 Branchial arch syndrome, 277 Brodie bite, 67, 199–200 Bruxism, 159 B-titanium wires, 235 Buccal corridors, 47, 62 Buccolingual inclination, 298 Buccoversion, 38 Butalbital, 289

C CAD. See Computer-aided design (CAD) CAM. See Computer-aided manufacturing (CAM) Camouflaged Class III malocclusions treatment, 192 Canines permanent, 202 substitution vs. implant, 79–82 upper, problems with, 20 Cap stage, 1 Cardio-facio-cutaneous (CFC) syndrome, 277 Carisoprodol (Soma), 288–289 Carpenter syndrome, 277 Case history, 61 CASS. See Computer-aided surgical simulation (CASS) Cast analysis, 39, 41f Cast Radiograph Evaluation (CRE), 297–298 Caucasians, craniofacial growth and development of, 8 CBCT. See Cone beam computed tomography (CBCT) CEJ. See Cementoenamel junction (CEJ) Cementoenamel junction (CEJ), 113 Center of resistance, 113 Center of rotation, 113–114, 116 Centrally acting muscle relaxants, 288–289 Centric occlusion (CO), 65, 67, 222 Centric relation (CR), 65, 67, 222 Centroid, 113 Cephalograms, 222 Cephalometry/cephalometric analysis, 44–45, 45t ANB angle for, 46, 210, 254–256 cone beam computed tomography and, 330–332 diagnostic database and, 61 essentials of, 45–46 anteroposterior skeletal measurements, 45–46 incisor measurements, 46 soft tissue measurements, 46 vertical skeletal measurements, 46

Cephalometry/cephalometric analysis (Continued) landmarks, 44–45, 44f hard tissue, 44–45 reference planes connecting, 45–46, 45f soft tissue, 45 serial, 212 three-dimensional (3D), 313–315, 317f Ceramic bracket, 109–110 Ceramics, 235 Cerebro-costo-mandibular syndrome, 277 Cervical-pull facebow, 139 Cervical traction, 212 CFC. See Cardio-facio-cutaneous (CFC) syndrome Chaos theory, 60 Chemical cure, 104–105 Child/children. See Adolescent Chin, bony, 9 Chin cup duration of, 192 effects of, 192 force magnitude and direction for, 192 high-pull, 214 indications for, 191 timing for, 192 Chlorhexidine digluconate, 264 Chlorzoxazone (Parafon Forte), 288–289 Circular toothbrush, 264 Circumference discrepancy in arch, 39 Circumferential supracrestal fiberotomy (CSF), 297 Class III malocclusions treatment, 186–197, 214–215 camouflaged, 192, 193f chin cup for duration of, 192 effects of, 192 force magnitude and direction for, 192, 192f high-pull, 214 indications for, 191, 192f timing for, 192 early, 149 elastics for, 214 extraction for, 143, 214–215 facemask therapy for, 186, 189f clinical response to, 191 Delaire, 186, 188f effects of, 188–191 expansion for protraction of, 186–188, 191f retention and, 191, 191f reverse-pull, 214 skeletal discrepancy and, 214 timing for, 188 with overbite, 214 with overjet, 214 posttreatment occlusal stability in, 299 pseudo, benefits of, 186, 187f stability of, long-term, 191 surgical, 192, 195f with underbite, 214 Class II malocclusions treatment, 41, 164–185, 208–214 anteroposterior interjaw and, relationship between, 208 Bionator appliance for, 174, 178f, 181f components of, 164, 165t, 166t with convex profile, 213

343

Class II malocclusions treatment (Continued) of discrepancies anteroposterior, 140 tooth movement for correction of, 142, 143–144, 144f early, 149–150 in early mixed dentition, 150 in maxilla, 150 “spontaneous correction” of, 150 elastics for, 140, 213 etiology of, 164–165, 169f with excessive overjet, 213 extraction patterns for, 213–214 extra-oral traction and, 165, 171f facemask therapy for, 213 fixed orthodontic appliances for, 209–210 Forsus appliance for, 177–179, 184f functional appliances used for, 169–172, 173f, 209–210 Bionator, 211 clinical response to, variations in, 179–180 Fränkel Function Regulator type 2 (FR-2) appliance, 211 Headgear-Activator appliance, 211 Herbst appliance, 211 long-term skeletal effects of, 210–211 process for, 211–212 stability of, long-term, 180–182 therapy using, 168–169 functional jaw orthopedics and, 167, 174 headgear for, 209–210 cervical traction, 212 effects of, 212 high-pull, 212–213 mandibular propulsive profile change and growth modification with, 213 vertical-pull, 212–213 Herbst appliance for, 175, 182f impact on pattern of, 298 long-term success of, factors affecting, 298–299 mandibular anterior repositioning appliance for, 176–177 with moderately retrusive lower jaw, 213 molar distalizing “noncompliance” appliances for, 213 Moyers' differential diagnosis of horizontal/ vertical, 164, 168t prevalence of, 164 protocols for, 165–167, 172f referral for, 208 surgical, 183–184 Twin Block appliance for, 174, 175f Class I malocclusions treatment, 207–208 crowding extraction of second molars vs. premolars for, 208 interproximal reduction for, 207–208 mandibular anterior, 207 mandibular incisor, 207 extraction and, 208 lower lingual holding arch, 207 Cleft lip and palate (CLP), 271, 332–333 Cleft lip only, 271 Cleft palate only, 271 Clefts/clefting, 271, 277. See also Facial clefts Cleidocranial dysplasia (dysostosis), 277, 283–284 ClinCheck™, 155, 156, 158, 159, 161, 162

344

INDEX

Clinical evaluation, 36–38 age considerations for, 37–38 aspects of, 36 of jaw and occlusal function, 36–37 of malposition of teeth, 38 medical/dental history, key points clarified in, 36 of physical growth and maturation status, 38 social/behavioral, 37 of temporomandibular joint function, 37 of tooth anomalies, 38 Clinical examination, 61 Clinical Examination of ABO, 297–298 Clinical setting for three-dimensional imaging, 58 Clonazepam (Klonopin), 289 CLP. See Cleft lip and palate (CLP) CMF. See Craniomaxillofacial surgery (CMF) CO. See Centric occlusion (CO) Cochrane Oral Health Group, 264 Cold welding, 106 Complete cleft, 271 Composite skull model for craniomaxillofacial surgery, 313 Computed tomography-based physical models, 310 Computed tomography models, 309–310 Computer-aided design (CAD), 154, 317f, 318f Computer-aided manufacturing (CAM), 154, 317f, 318f Computer-aided surgical simulation (CASS), 311, 312 accuracy of, 320–322, 321t, 322t clinical protocol for, 311–312 cost-effectiveness of, 323–324 outcome of, 322–323 plaster dental models for, 311f, 324 techniques for, 315 Concrescent teeth, 38 Concurrent force, 113 Condylar growth, 129–130 Condylion, 8–9 Cone beam computed tomography (CBCT), 329–340, 330f for airway, 56, 334–335 for alveolar bone heights/volume assessment, 56 cephalometry and, 330–332, 331f dental models/measurements, derived from, 333, 333f for facial asymmetry, evaluation of, 335, 335f incidental findings in, 332–333, 332f limitations of, 58 oral abnormalities and, 56 radiation from, 329–330, 331f radiography vs., 337–338, 337f rapid maxillary expansion and, 336, 337f for root resorption detection, 335–336 as standard of care, 329 temporary anchorage devices, placement of, 334, 334f Conservative care, 290 Controlled tipping, 114 Conventional fixed appliances, 140 Conventional ligation, 235 Conventional radiographs, 289 Convertible tube/bracket, 106 Convex profile, 213 Corticosteroids, 289 Council on Dental Therapeutics, 264 Council on Scientific Affairs, 329

Couple center of rotation for movement created by, 116 defined, 116 moment of, 116 COX-2. See Cyclooxygenase-2 (COX-2) inhibitors CR. See Centric relation (CR) Cranial base, superimposition on, 92–93 Craniofacial deformities, 271–285 in craniosynostoses syndromes, 279–280 facial clefts mixed dentition and, 272–276 orthodontic/orthopedic treatment for, 271 permanent dentition and, 276–277 primary dentition and, 272 skeletal discrepancies and, 277 types of, 271 in mandibulofacial dysostosis, 280–281 in oculo-auriculo-vertebral spectrum of conditions, 277–279 orofacial clefting and, 271, 277 presurgical orthopedics and, 271–272 in Trisomy 21 syndrome, 282–283 in Turner syndrome, 281 types of, 277 Craniofacial dysostosis, 277, 279–280 Craniofacial growth and development, 1–13 of arch, 4, 4f, 5, 5f of bony chin, 9 in Caucasians, 8 ceasing of, 10 of condylion, 8–9 of craniofacial sutures, closing of, 9, 9t crowding and horizontal/vertical mandibular growth and, 4 incisor, prevalence of, 3 third molars and, 3–4 differences in relative, 6, 7f equilibrium theory of tooth position and, 2–3 eruption and, 4 facial heights, sex differences in, 6, 7f of glenoid fossa, 8 of gonion, 8–9 growth spurt and, 2, 7–8 of hyperdivergent patients, morphology of, 6 of intercanines, 5–6, 6f of intermolara, 4, 5f of lip, length and thickness of, 9–10 malocclusion and class II, 3 class III, 3 of mandible, 6, 8f, 10 of nose, 10 peak height velocity and, 2, 2f of soft-tissue facial profile, 10 transverse rotation and, 8 Craniofacial sutures, closing of, 9 Craniomaxillofacial deformities, population statistics for, 309 Craniomaxillofacial surgery (CMF), 309–328 bit jig, fabrication of, 315–320 composite skull model for, reorientation to neutral head posture and, 313 craniomaxillofacial deformities, population statistics for, 309 planning methods for, 309–311. (See also Computer-aided surgical simulation (CASS)) computed tomography and, 309–310 computer for, 312–313, 312f, 315, 324–326

Craniomaxillofacial surgery (CMF) (Continued) plaster dental model surgery, 310–311 two-dimensional prediction tracings, 309 three-dimensional cephalometric analysis and, 313–315 Craniosynostoses syndrome, 277, 279–280 CRE. See Cast Radiograph Evaluation (CRE) Crossbites anterior, 25f, 26f, 188–191 Invisalign® System, correction with, 162 Phase II treatment for, 215 posterior anterior vs., treatment of, 200 bilateral, without a functional shift, 27, 30f with lateral functional shift, timing for, 27, 30f lower arch and, 199 maxilla, treatment for, 199 with maxilla lingual and mandible facial, 199–200 problems with, 200–201 unsuccessful correction of, 201 untreated, 200 Crouzon syndrome, 277, 279–280 Crowding anterior, 33f anterior, timing for, 28–31 anteroposterior discrepancies and, treatment options for correcting, 140–141, 141f early treatment for, 146 extraction for, 208 of incisors, 3, 207 interproximal reduction for, 207–208 late, 10 of mandible, 4, 207 physiological, 5–6 secondary, 10 third molars and, 3–4 CSF. See Circumferential supracrestal fiberotomy (CSF) C-shaped archwire, 107 Curve of Spee, 162, 174, 299 Cuspids impacted, 76–79 retraction of, on archwire, 116 Cyberware, 154–155 Cyclobenzaprine (Flexeril), 288–289 Cyclooxygenase-2 (COX-2) inhibitors, 289

D Damon bracket, 100, 103 DAP. See Dental anomaly patterns (DAP) Deep bite, 162, 174, 299 Deformities craniofacial, 271–285. (See also Facial clefts) in craniosynostoses syndromes, 279–280 in mandibulofacial dysostosis, 280–281 in oculo-auriculo-vertebral spectrum of conditions, 277–279 orofacial clefting and, 271, 277 presurgical orthopedics and, 271–272 in Trisomy 21 syndrome, 282–283 in Turner syndrome, 281 types of, 277 craniomaxillofacial, population statistics for, 309 Delaire protraction facemask, 186 Dens evaginatus, 38 Dens in dente, 38 Dens invaginatus, 38 Dental anomalies, association with hypodontia, 22 Dental anomaly patterns (DAP), 22

INDEX

Dental Contour appliance, 154 Dental history, key points clarified in, 36 Dental tissue, 67 Dentist/dentistry family, 216 implants in, 235 restorative, 203, 216 Dentition. See also Teeth/tooth mixed, 4 early, 145, 150 facial clefts and, 272–276 permanent, 276–277 Dentoalveolar anterior open bites, 250–253 Dentoalveolar development, 130 Dentofacial discrepancies in planes of space, treatment tactics for, 137–144 anteroposterior/vertical discrepancies, 140–144 Class II malocclusion, 140, 142, 143–144 crowding, treatment options for correcting, 140–141 extraction, 140, 141–142, 143. (See also Serial extraction) extra-oral traction therapy, 140 facebow, 140 functional appliances for, 142–143 headgear, 140 protection facemask therapy for, 143 transverse discrepancies, 137–140. (See also Maxillary expansion appliance) Depths of arch, 5 Derived landmarks, 44 Diagnosis of orthodontic problems, 60–97. See also Diagnostic database Diagnostic arch, 39 Diagnostic database, 61–96 composition of, 61 case history, 61 cephalometric analysis, 61 clinical examination, 61 functional analysis, 61 photographic analysis, 61 radiologic examination, 61 study cast analysis, 61 discrepancy index of ABO, 67 case examples of, 67 frontal analysis, 62–63 buccal corridors, 62 lips, 62 midlines, 62 smile line, 63 planes of space, 62 anteroposterior plane, 62 sagittal, 65–66 transverse, 62, 67 vertical, 62, 66–67 prioritized problem list, 61, 62b profile view, 63 anteroposterior, 63 lips, 63 nose, 63 vertical, 63 superimposition on cranial base, 92–93, 92f, 93f on mandible, 95–96, 95f on maxilla, 93–95, 94f, 95f methods for, 89 necessity of, 89 required, 89

Diagnostic database (Continued) 3D-3T diagnostic grid, 63t, 68t advantages of, 64 defined, 63–64 information contained in, 64 patient record, importance in, 63–64 steps of, 64 treatment objectives, 64, 89 treatment plan, 64–65, 89 Diagnostic set-up, usefulness of, 42 Diagnostic “wax-up,” 216 Diazepam (Valium), 289 Differential diagnosis, 60 Moyers', 164 Digital models vs. plaster of Paris models for diagnosis, 42 Digit-sucking habit, 32f Digit-sucking habit, time for, 28 Dilaceration, 85–88 Direct application, 236–237 Direct bonded brackets components of, 103 construction of, 102–103, 103f full banded vs., 101f tooth enamel, mechanism for securing to, 104–105, 105f Discrepancy index of ABO, 67 case examples of, 67 ankylosis, 82, 83f, 85t extraction vs. non-extraction, 70, 71f, 73t headgear, 67, 68f, 70t impacted cuspid, 76, 77f, 79t maxillary arch expansion, 73, 74f, 76t missing maxillary lateral incisors, 79, 80f, 82t root resorption, 85, 88f transposition, 85, 86f, 88t Distalizing appliances, 165 Distal Jet, 140, 213 Distoversion, 38 Dolichofacial, 66 Dolicocephalic, 250 Dolicofacial, 250 Double-tube bracket, 104 Down syndrome, 277, 282–283 D-shaped archwire, 107 Dual-action bracket spring-clips, 103 Dual-dimension archwire, 107 Dysfunction of the joint complex, 286 Dysostosis acrofacial, 277 cleidocranial, 277, 283–284 craniofacial, 277, 279–280 mandibulofacial, 277, 280–281 Dysplasia cleidocranial, 277, 283–284 ectodermal, 21, 277 frontonasal, 277

E Early ankylosis, 10 Early mixed dentition, 150 Early treatment, 145–153 of arches, limited, 147 for Class III malocclusion, 149, 149f for Class II malocclusion, 149–150, 150f in early mixed dentition, 150 in maxilla, 150, 151f “spontaneous correction” of, 150

345

Early treatment (Continued) contraindications to, 145 for crowding, 146 duration of, 152 interim period after, 152 during mixed dentition, 145 rapid maxillary expansion and, 147 appliances for, 147–148 indications for, 149 of lower jaw, 149, 149f risks of delaying, 153 second phase following, 152, 152f serial extraction contraindications for, 146 defined, 146 indications for, 146 space maintenance, purpose of, 145–146 for vertical problems (open/deep bite), 151, 151f, 152f Ectodermal dysplasia, 21, 277 Ectopic eruption, 20, 201–202 Ectrodactyly-ectodermal dysplasia-clefting (EEC) syndrome, 277 Edgewise appliance, 98, 99–100 archwire in, 100, 101f Dr. Charles H. Tweed and, 100 evolution of, 99–100 pin and tube vertical bracket vs., 100 Edgewise brackets, 101–102 Edgewise slots, stainless steel to, 235 EEC. See Ectrodactyly-ectodermal dysplasiaclefting (EEC) syndrome Ehlers-Danlos syndrome, 277 Elastics, 140, 213, 214 Elastomeric ligated brackets, 265 Embryopathy, 277 Enamel, 104–105, 110 Enamel organ, 1 Enlargement of gingivitis/gingival, 266 Entropy, 60 Environmental factors, 130 E plane, 46 Equilibration of occlusal interference, 221 Equilibrium example of, 117 law of, 116–117 static, 116 tooth position, theory of, 2–3 Equivalent force system, 102, 102f Eruption delay in, 207 ectopic, 20, 20f, 201–202 forced, 203, 223–224 of incisors, maxillary/mandibular, 4 lingual, 201 of molars, 4 permanent incisors and, rotation of, 203 of permanent teeth, 16–17 changes following, 19 second molars, problems with, 20–21 upper canines, problems with, 20 primary failure of tooth, 10 reasons for interference in, 19 sequence of, importance of, 15t, 17f, 17t, 18 stages of, 14, 15f timing of, 14–15, 15t, 16–17, 17f, 17t Essix appliance, 154 Esthetic line, 46 Esthetics, 159, 227–230

346

INDEX

Ethmomaxillary sutures, 186–188 Evaluation of needs, 272–273 Evidence-based care, 290 Evidence-based treatments, 145 Excessive overjet, 213 Expanders, 149 Expansion arches, 235 maxillary arch, 73 adult vs. child, difference between, 73–76 Hyrax, 186 for protraction, 186–188 slow maxillary, 139 Extraction asymmetric, 144 bicuspid, 144 circumstances for considering, 140, 141–142 for Class III malocclusions, 143, 214–215 for Class II malocclusions, 213–214 for Class I malocclusions, 208 extrusion to, 216 impacted cuspid and, 76–79 lower first bicuspid, 144 lower incisor, 144 permanent teeth, treatment plan for, 202–203 of premolars, 208 relapse and, 298 of second molars, 208 serial, 141 complicating factors for, 141 indications for, 141 for single mandibular permanent incisor, 215 vs. non-extraction, 70, 71–73 Extra-oral forces, 140 Extra-oral traction, 139, 140, 165 Extrusion to extraction, 216

F Facebow, 139, 140, 310 Face/facial, 124 asymmetry of, evaluation of, 335 average, 53–54 balance and harmony of, factors affecting, 127, 127f, 128f bipartition advancements in, 280 evaluation of, 124 good, 124–126, 126f, 127f growth of, 21, 53 heights of, 6, 209 jaws, symmetry/proportions and relationship of, 206–207 musculature of, 65–66 orientation of, 201 photographs of, 221–222 profile analysis of, 47, 65–66 Facemask therapy, 186 for Class II malocclusions treatment, 213 clinical response to, 191 Delaire protraction, 186 effects of, 188–191 expansion for protraction of, 186–188 protection, 143 protraction, 198 retention and, 191 timing for, 188 Facial clefts, 272–276 mixed dentition and, 272–276 bilateral cleft lip and palate, 275–276

Facial clefts (Continued) evaluation of needs, 272–273 maxillary protraction, 275 pre-graft expansion, 274–275 traumatic occlusion, elimination of, 273–274 treatment planning for, 272–273 orthodontic/orthopedic treatment for, 271 permanent dentition and, 276–277 primary dentition and, 272 skeletal discrepancies and, 277 types of, 271 Facial/facemask, 149, 186 Facial plane, lower, 66 Facial thirds, proportion of, 66–67 Family dentist, 216 Fetal alcohol syndrome, 277 FH. See Frankfort horizontal (FH) plane Fiberotomy, 203, 297 Field of view (FOV), 330, 331–332 Fioricet, 289 First-order bends, 101–102 Fixed mandibular expander, 138f, 139 Fixed orthodontic appliances, 98 characteristics of, 98 for Class II malocclusions treatment, 209–210 conventional, 140 Invisalign® System vs., 159, 162 tooth movement with, 102 Fixed rapid palatal expander, 199 Fixed-removable appliances, 98 Fixed retainers, 296 FJO. See Functional jaw orthopedics (FJO) Flexion, 85–88 Flex-O-Tite gum-massaging appliance, 154 Fluconazole, 289 Force concurrent, 113 extra-oral, 140 horizontal components of, 112 intraoral, 140 one-couple, 117 physics, defined in, 112 system of, 112–113 two-couple, 117 vertical components of, 112 Forced eruption, 203, 223–224 Force magnitude, 192 Forsus appliance, 169–170, 177–179 Four-tooth rapid palatal expander, 199 FOV. See Field of view (FOV) FR-2. See Function Regulator Type 2 (FR-2) of Fränkel FR-3. See Function Regulator Type 3 (FR-3) appliance Frankfort horizontal (FH) plane, 45, 61 Frenectomy, 297, 303 Friction-free appliance, 106 Frontal analysis, 62–63 buccal corridors, 62 lips, 62 midlines, 62 smile line, 63 Frontal cephalograms, 222 Frontal orthodontic photographs, 47 Frontomaxillary sutures, 186–188 Frontonasal dysplasia, 277 Full mouth periapical surveys, 222 Functional analysis, 61

Functional appliances for anteroposterior discrepancies, 142–143 for Class II malocclusions treatment, 169–172, 209–210 Bionator, 211 Fränkel Function Regulator type 2 appliance, 211 Headgear-Activator appliance, 211 Herbst appliance, 211 long-term skeletal effects of, 210–211 process for, 211–212 clinical response to, variations in, 179–180 stability of, long-term, 180–182 therapy using, 168–169 therapy using, initiation of, 142–143 types of, 142, 142f, 143f Functional jaw orthopedics (FJO), 165, 167, 174 Functional-occlusal plane, 164 Functional regulator, 169 Functional shift, timing for, 24 Function Regulator Type 2 (FR-2) of Fränkel, 151, 169–170, 209, 211 Function Regulator Type 3 (FR-3) appliance, 140, 191 Furosemide diuretics, 289

G Gemination, 38 Gingivitis/gingival enlargement of, 266 graft/grafting for, 221 hyperplasia and, 266 hypertrophy and, 266 mouthrinse and, 264 overgrowth, management of, 266 recession of, 137–138, 265–266 recontouring of, 302, 304–305 Glabella (Gla), 45 Glenoid fossa, 8 Global positioning system (GPS), 324–325 Gnathion (Gn), 44 Gnomonic growth, 254 Goldenhar syndrome, 277–278 Gonial angle, 250–251 Gonion (Go), 8–9, 45 Good face, 124–126 GPS. See Global positioning system (GPS) Graft/grafting for gingivitis/gingival, 221 Growth disorders, 286 Growth modification with headgear, 213 Growth spurt, 2, 7–8 GTR. See Guided tissue regeneration (GTR) Guided tissue regeneration (GTR), 266–267

H Haas expander, 137, 148, 148f Habitual anterior open bites, 252–253 Hard tissue imaging, 56–57 for airway analysis, 56 of alveolar bone heights/volume assessment, 56 of impacted teeth, 56 of oral abnormalities, 56 of temporomandibular joint morphology, 56–57 Hard tissue landmarks, 44–45 Harmony of face, factors affecting, 127 Harvold Type III, 277–278

INDEX

Headgear, 67, 140 anteroposterior discrepancies and, 140 with biteplate, 209 for Class II malocclusions treatment, 209–210 cervical traction, 212 effects of, 212 high-pull, 212–213 mandibular propulsive profile change and growth modification with, 213 vertical-pull, 212–213 J-hook, 140 types of, 69–70 Headgear-Activator appliances, 211 Height assessment of alveolar bone, 56 Hellman, Milo, 250 Herbst appliance, 65, 134, 140, 142, 169, 211–212 for Class II malocclusions treatment, 175 Heterotopic pain, 286 High-pull chin cup, 214 High-pull headgear, 212–213 Holdway, Reed, 116 Holdway angle, 116 Hooke’s law, 110 Horizontal components of force, 112 Horizontal mandibular growth, 4 Hydroxyzine pamoate (Vistaril), 289 Hyperdivergent patients, morphology of, 6 Hyperdontia, 21, 22f Hyperplasia, 266 Hypertrophy, 266 Hypodontia, 21 commonality of, 22 dental anomalies, association with, 22 teeth most affected by, 21–22 Hypomobility, 286 Hyrax arch expansion, 186 Hyrax expander, 137, 138f, 148, 148f Hyrax jackscrew appliance, 215 Hyrax rapid maxillary expansion, 140, 186

I Imaging hard tissue, 56–57, 56f airway analysis, 56 alveolar bone heights and volume assessment, 56, 57f impacted teeth, 56, 57f oral abnormalities, 56, 57f temporomandibular joint morphology, 56–57, 57f for implants vs. temporary anchorage devices, techniques for, 238–239 surface, 53–54, 54t average faces, 53–54, 55f facial growth, 53, 54f superimposition, 53–54, 55f surgical evaluations, 54, 55f of temporomandibular disorders, 289 three-dimensional, 53–59 analysis for, 57 classification system for, 53 clinical applications for, 53–57 clinical setting for, 58 costs of, 58 defined, 53 devices for, 53 future of, 58

Imaging (Continued) limitations of, 58 medicolegal issues with, 58 obtaining, 53 revolutionization of, 57–58 techniques for, 53 of virtual patient, 58, 58f Impaction of cuspid, 76–79 hard tissue imaging of, 56 LeFort I osteotomy and, 164 soft-tissue diode laser surgery for, 308 of teeth, 32, 34f Implants Björk-type, 211, 212 blade, 235–236 canine substitution vs., 79–82 in dentistry, 235, 236f legal implications of, 245 materials for, 235 mechanics of, 237–238 occlusion development, adverse effects of, 21 in orthodontics, 235–236, 236f Orthosystem palatal, 244 osseointegrated, 245 palatal, 239, 242, 244, 245 partial, clinical procedures and loading times for, 239–240 restorative, 204, 239, 240 restorative titanium, 236 temporary anchorage devices vs., 237 benefits of, 238 complications related to, 244–245, 246f disadvantages of, 237 imaging techniques for, 238–239 loading of, 240, 240f, 241f, 244 mini-screw, clinical procedures and loading times for, 239–240 placement of, 238 removing, 245 surgical considerations for, 239 Incisors crowding, prevalence of, 3 crowding of, 3f extraction of lower, 144 mandible and, 4, 174 maxilla and, 4, 79–82 measurements of, 46 permanent, 17, 203 proclination of, 66 sagittal planes of space, relationships with, 66 Incomplete cleft, 271 Indirect application, 236–237 Infraocclusion, 10 Infraversion, 38 Initial archwire, 106 Initiation stage, 1 In-out bends, 101–102 In-Ovation bracket, 100, 103 Instability of orthopedics, 287 Interarch molar, 66 Inter-bracket width, 104 Intercanines malocclusions treatment for, 5–6 mandible and, 5 maxilla and, 5 width of, 6f widths of, 5–6

347

Interceptive orthodontics, 198 Interim period after early treatment, 152 Intermaxillary sutures, 186–188 Intermolars width of, 5f Intermolar widths, 4 International System of Units (SI), 115 Interproximal contacts, 298 Interproximal reduction (IPR), 159, 207–208 Intraoral forces, 140 Intraoral periapical orthodontic radiographs, 43 Invisalign® System, 154–163, 155f appliances preceding, 154 for crossbite correction, 162, 163f fixed appliances vs. advantages of, 159 for deep bite, 162 interproximal enamel reduction (IPR), 159 intraoral scanner, scanned impressions vs. teeth scanned with, 154–155 Invisalign-branded aligners force systems generated in, 155–156 plastic materials for, 156 process and software involved in creating, 155 tooth movement and thicker, 156 weakest elements of, 158–159, 158f for open bite correction, 159–161, 160f Optimized Attachments and SmartTrack combination in, 157–158, 158f for overbite correction, 161–162, 161f, 162f planning treatment for, 159–162 polyvinyl siloxane impressions, conversion to digital images/aligners, 154–155 tipping of teeth and premolar extraction, 156–157, 157f IPR. See Interproximal reduction (IPR) Irregularities of tooth development, 207 Isolated tooth movement. See also Minor tooth movement anterior trauma and, impact of, 203 arches and, spacing in, 203 face orientation and, 201 orthodontic database for, 201 permanent canines and, 202 permanent tooth extraction treatment plan for, 202–203 referral and, 204 skeletal pattern, impact on, 204 soft tissue profile and, impact of, 204 vertical plane and, 201

J Jasper Jumper, 65 Jaws clinical evaluation of, 36–37, 37f face/facial, symmetry/proportions and relationship of, 206–207 moderately retrusive lower, 213 J-hook headgear, 140 Joint complex, dysfunction of the, 286

K Kabuki syndrome, 277 Keratinized tissue, 265–266 Kesling, P.C., 99 Key to occlusion, 41 Kim, Young, 254

348

INDEX

King’s College School of Medicine and Dentistry, 8 Kobayashi tie hooks, 105

L Labioversion, 38 Lacrimomaxillary sutures, 186–188 LAFH. See Lower anterior face height (LAFH) Landmarks anatomic, 44 cephalometric, 44–45 hard tissue, 44–45 reference planes connecting, 45–46 soft tissue, 45 derived, 44 Lang antirotation arms, 103–104 Larsen syndrome, 277 Lasers for soft-tissue diode laser surgery, 303–304 Late ankylosis, 10 Late crowding, 10 Late primary dentition, 4 Lateral cephalograms, 222 Lateral cephalometric orthodontic radiographs, 44 Lateral functional shift, timing for, 27 Lateral limit of dentition, 124 Laterocclusion, 41–42 Laterognathy, 41–42 Laws of entropy, 60 of equilibrium, 116–117 Hooke’s, 110 of motion, 112 of thermodynamics, 60 LDML. See Lower dental midline (LDML) Leeway space, 6, 18, 145 LeFort III osteotomy, 280 LeFort I osteotomy, 164, 192, 235, 315 Length discrepancy in arch, 39 Lewis spring wings, 103–104 Ligated brackets, elastomeric, 265 Ligation, conventional, 235 Limited arches, 147 Linear values for space, 45–46 Lingual appliances, 110, 110f Lingual arch, 145–146 Lingual eruption, 201 Linguoverted tooth, 38 Linnaeus, Carolus, 60 Lip bumper, 138f, 139–140 Lips frontal analysis of, 62 length and thickness of, 9–10 profile view, 63 protrusion of, 66 retrusion of, 66 weak, 125 Listerine, 264 Lithium, 289 LLHA. See Lower lingual holding arch (LLHA) L1-MP (lower incisor to mandibular plane), 46 L1-NB (lower incisor to NB line), 46 Loading of implants vs. temporary anchorage devices process of, 240 stability during, 244 timing for, 240

Local anesthetics, 289 “Locking” effect of occlusion, 156 Lorazepam (Ativan), 289 Loss of function, 286–287 Low angle, 204 Lower anterior face height (LAFH), 209 Lower arch, 199 Lower dental midline (LDML), 67 Lower facial plane, 66 Lower first bicuspid extraction, 144 Lower incisor extraction, 144 Lower lingual holding arch (LLHA), 207, 215 Lower Schwartz appliance, 138f, 139, 140

M Magnetic resonance imaging (MRI), 289 Major vs. minor tooth movement, 198 Malocclusion treatment, 24–35, 124, 134 age for early, 24 for anterior crossbite with a functional shift, timing for, 24 for anterior crowding, timing for, 28–31 for bilateral posterior crossbite without a functional shift, timing for, 27 Class I, 207–208 crowding and, 207–208 extraction and, 208 lower lingual holding arch, 207 Class II, 5–6, 41, 164–185, 208–214 anteroposterior interjaw and, relationship between, 208 Bionator appliance for, 174 components of, 164 with convex profile, 213 craniofacial growth/development and, 3 elastics for, 213 etiology of, 164–165 with excessive overjet, 213 extraction patterns for, 213–214 extra-oral traction and, 165 facemask therapy for, 213 fixed orthodontic appliances for, 209–210 Forsus appliance for, 177–179 functional appliances used for, 169–172 functional appliance treatment for, 209–210 functional jaw orthopedics and, 167, 174 headgear for, 209–210 Herbst appliance for, 175 mandibular anterior repositioning appliance for, 176–177 with moderately retrusive lower jaw, 213 molar distalizing “noncompliance” appliances for, 213 Moyers' differential diagnosis of horizontal/ vertical, 164 prevalence of, 164 protocols for, 165–167 referral for, 208 surgical, 183–184 timing for, 25–27, 29f Twin Block appliance for, 174 Class III, 186–197, 214–215 camouflaged, 192 chin cup for, 191, 192 craniofacial growth and development and, 3 elastics for, 214 extraction for, 214–215 facemask therapy for, 186

Malocclusion treatment (Continued) mandibulra growth and, 3 maxillary growth and, 3 with overbite, 214 with overjet, 214 pseudo, benefits of, 186 stability of, long-term, 191 surgical, 192 timing for, 24–25, 27f, 28f with underbite, 214 dentition evaluation for, 131–134 anterior space analysis, 131–132 midarch space analysis, 132–133 posterior space analysis, 133–134 of digit-sucking habit, time for, 28 face, 124 balance and harmony of, factors affecting, 127 evaluation of, 124 good, 124–126 for impacted teeth, 32 intercanine, 5–6 for orthognathic surgery, 34–35 of posterior crossbite with lateral functional shift, timing for, 27 skeletal component of, 128–129 for skeletal open bite, 27–28 skeletal pattern and anteroposterior component of, 130–131 transverse component of, 131 vertical component of, 129–130 space-regaining procedures and, in mixed dentition, 32–34 for supernumerary teeth, 32 Malposition of teeth, 38, 39f Mandible arch depths and, 5 crowding and, 207 facial posterior crossbite and, 199–200 growth of, 3, 4 growth spurt and, 7–8 incisors and, 4, 174, 207, 299–300 intercanines and, 5 length of, 209 position of, 6 rotation of, 10 sex differences in, 6 size of, 6 spacing of, 174 superimposition on, 95–96 vertical position of the, 66 Mandibular anterior repositioning appliance (MARA), 65, 120, 142, 169–170 for Class II malocclusions treatment, 176–177 Mandibular plane (MP), 45, 164, 204 Mandibular plane angle (MPA), 62 Mandibular propulsive profile change, 213 Mandibular retractor, 191 Mandibulofacial dysostosis, 277, 280–281 MARA. See Mandibular anterior repositioning appliance (MARA) Marfan syndrome, 277 Marginal ridges, 298 Masticatory disorders, 286 Maturation status, clinical evaluation of, 38 Maxilla arch depths and, 5 Class III malocclusions treatment and, 3 Class II malocclusions treatment and, 150

INDEX

Maxilla (Continued) growth spurt and, 7–8 incisors and, 4 intercanines and, 5 LeFort I impaction and, 164 lingual posterior crossbite and, 199–200 posterior crossbite, treatment for, 199 superimposition on, 93–95 Maxillary arch expansion, 73–76, 186 Maxillary expansion appliance, 137 initiation of, 140 types of, 137–140 band expanders, 137 bonded rapid palatal expander, 137–138 conventional fixed appliances, 140 fixed mandibular expander, 139 lip bumper, 139–140 Lower Schwartz appliance (removable), 139 Pendex, 139 quadhelix, 139 W arch, 139 Maxillary lateral incisors, missing, 79–82 Maxillomandibular relationship, anteroposterior, 8 Maximum entropy production (MEP), 60 Maximum intercuspation (MI), 324–325 Measurements Altman’s method for assessing, 320, 322 anteroposterior skeletal, 45–46 cone beam computed tomography, derived from, 333 good face, for quantifying or measuring, 125–126 of incisors, 46 skeletal, 45–46 soft tissue, 46 vertical skeletal, 46 Mechanotherapy, 60, 238 Median cleft face syndrome, 277 Medical history, key points clarified in, 36 Menton (Me), 44 MEP. See Maximum entropy production (MEP) Mesial angulation tipping, of permanent second molar, 202 Mesiodens, 22 Methotrexate, 289 Mf. See Moment of force (Mf) MI. See Maximum intercuspation (MI) Midarch space analysis, 132–133, 132f, 133f Mid-childhood growth spurt, 2 Midline diastema, 6 frontal analysis of, 62 lower dental, 67 upper dental, 67 Midsagittal hard tissue landmarks, 44 Milling and injection molding, 106 Mineralization of permanent teeth, 17 Mini-screw implants vs. temporary anchorage devices, 239–240 Minor tooth movement, 198–205. See also Isolated tooth movement age for considering, 198–199 arches and, problems with, 201–202 crossbites posterior, 199–200 problems with, 200–201 unsuccessful correction of, 201 untreated, 200

Minor tooth movement (Continued) eruption and, 203 major vs., 198 mesial angulation tipping, of permanent second molar, 202 restorative implants and, 204 MI Paste Plus®, 263 Missing maxillary lateral incisors, 79–82, 215–216 Missing permanent teeth, 207 Mixed dentition, 4 early, 145, 150 facial clefts and, 272–276 bilateral cleft lip and palate, 275–276 evaluation of needs, 272–273 maxillary protraction, 275 pre-graft expansion, 274–275 traumatic occlusion, elimination of, 273–274 treatment planning for, 272–273 space-regaining procedures in, 34f Models derived from CBCT, 333 Moderately retrusive lower jaw, 213 Molars distalizing “noncompliance” appliances for, 213 eruption of, 4 interarch, 66 second, 20–21, 202 6-year, 4 Molar uprighting, 202 diagnostic considerations for, 222 retention protocol after, 223 tooth movement for, types of, 222–223 types of, 222–223 Moment of couple, 116 Moment of force (Mf), 115 Monobloc, 280 Moss, Melvin, 250 Motion, laws of, 112 Mouth breathing, 130 Mouthrinse, 264 Moyers' differential diagnosis, 164 MP. See Mandibular plane (MP) MPA. See Mandibular plane angle (MPA) MRI. See Magnetic resonance imaging (MRI) Muscle relaxants, centrally acting, 288–289

N NAM technique. See Nasal alveolar molding (NAM technique) Nasal alveolar molding (NAM technique), 271–272 Nasion (N), 44 Nasolabial angle (NLA), 47, 204 Nasomaxillary sutures, 186–188 National Health and Nutrition Examination Survey (NHANES) III, 3–4, 41, 164 National Health Survey, 3 National Institutes of Health (NIH), 3–4 Natural/neutral head position (NHP), 45, 311, 312, 313, 313f, 314f Needs, evaluation of, 272–273 Neurofibromatosis, 277 Newton, Isaac, 112 Newtonian mechanics, 112 Newton meter (Nm), 115 Newton’s Three Laws of Motion, 112, 235, 237 New York Times, 137 NHANES. See National Health and Nutrition Examination Survey (NHANES) III

349

NHP. See Natural/neutral head position (NHP) Nickel-titanium, 107–108 NIH. See National Institutes of Health (NIH) Nitinol, 107–108 Nitinol wires, 107–108 NiTi wire, 235, 254 NLA. See Nasolabial angle (NLA) Nm. See Newton meter (Nm) Non-extraction vs. extraction, 70, 71–73, 298 Non-opiate analgesics, 289 Non-steroidal anti-inflammatories (NSAIDs), 156, 289 Nonsuccedaneous teeth, space/spacing of, 18 Noonan syndrome, 277 Nose, 10, 63 NSAIDs. See Non-steroidal anti-inflammatories (NSAIDs)

O Objective Grading System (OGS), 293, 297–298 Occlusal adjustment, 288 Occlusal factors, 287 Occlusal function, 36–37 Occlusal interference, equilibration of, 221 Occlusal loading, 244 Occlusal relationship, 41–42, 42f, 298 Occlusal splints, 287–288 Occlusal stability, 299 Occlusion, 14–23 Angle's classification of, 16 ankylosis and, 19–20 of arches, 18–19 centric, 65, 67, 222 eruption and ectopic, 20 of permanent teeth, 16–17, 19, 20–21 reasons for interference in, 19 sequence of, importance of, 18 stages of, 14 timing of, 14–15, 16–17 facial growth and, relationship between, 21 hypodontia and commonality of, 22 dental anomalies, association with, 22 teeth most affected by, 21–22 implants and, adverse effects of, 21, 22f key to, 41 “locking” effect of, 156 space/spacing and anterior, 18 deficit in, 17–18 leeway, 18 of nonsuccedaneous teeth, 18 of teeth/tooth development of, 14 permanent, 17 position and, 21 primary, 15–16, 17 size and, impact on, 23 variations in number of, 21 wisdom, 19 terminal plane and of permanent molars, 16 of primary dentition, 15–16 of primary second molars, 16 Oculo-auriculo-vertebral spectrum of conditions, 277–279 OGS. See Objective Grading System (OGS)

350

INDEX

Okeson, Jeffrey P., 291 Oligodontia, 21 One-couple force, 117 Onplant, 237 Open bites, 215 anterior, 215 posterior, 215 relapse in, 299 skeletal, 6, 27–28, 62 Open flap surgery, 221 Operculum removal, 302 Opiate analgesics, 289 Optimized Attachments, 155, 157, 158 Oral abnormalities, 56 Oral-acral syndromes, 277 Oral hygiene, 159, 263–270 gingivitis and, 265–266 mouthrinse for, 264 periodontitis and periodontal attachment and, 265 prevention methods for, 265 regeneration procedure and, 266–267 treatment for, 265 prophylaxis technique for, 264–265 toothbrush for, power vs. manual, 264 tooth movement and, relationship between, 266–267 white spot lesions and, 263 Orbitale (Or), 44 Orofacial clefting, 271, 277 OrthoCAD, 42 Orthodontic anchorage, 235 Orthodontic appliances, 98–111. See also specific types of angle of torque, 110 Angle System, 98 archwire cold welding of, 106 C-shaped, 107 D-shaped, 107 dual-dimension, 107 Hooke's law and, 110 initial, 106 properties of ideal, 107 Begg, 99 beta-titanium wires, 107–108 brackets ceramic, 109–110 cold welding of, 106 contamination of, impact on bonding to enamel, 110 direct bonded, 102–103, 104–105 double-tube, 104 full banded vs. full direct bonded, 101 position of, influence on treatment, 108 power arm attached to, 108 prescription, 101–102 self-ligating, 100, 103 single-tube, 104 slot dimension, 105–106 spring-wing, 103–104 Tip-Edge, 99 triple-tube, 104 convertible tube, 106 edgewise, 98 archwire in, 100 Dr. Charles H. Tweed and, 100

Orthodontic appliances (Continued) evolution of, 99–100 pin and tube vertical bracket vs., 100 equivalent force system in, 102 fixed, 98 brackets/appliances, characteristics of, 98 tooth movement with, 102 friction-free, 106 inter-bracket width, 104 lingual, 110 milling and injection molding, 106 nitinol wires, 107–108 pin and tube, 98–99 preadjusted, 101–102 ribbon arch, 99 sliding mechanics, 106 stainless steel wires, 107–108 straight wire, 108 tie-wings, 105 torquing moment, 111 Orthodontic casts, 43 Orthodontic database, 201 Orthodontic models, 39–43 Angle's dental classification, 41 articulator, 43 asymmetric occlusal relationships, classification of, 41–42 Bolton analysis, 40–41 cast analysis, 39 diagnostic set-up, usefulness of, 42 digital models vs. plaster of Paris models for diagnosis, 42 Orthodontic photographs, 47 facial profile analysis, 47 frontal, 47 views captured in, 47 Orthodontic plates, 239 Orthodontic radiographs, 43–47. See also Cephalometry/cephalometric analysis lateral cephalometric, 44 panoramic vs. series of intraoral periapical, 43 posteroanterior cephalometric film, primary rationale for taking, 43 predictive analysis, 46–47 superimposition of serial cephalograms, 47 supplemental intraoral periapical films for, 43 Orthodontic records and case evaluation, 36–52, 37b adult interdisciplinary orthodontic treatment and, 221–222 clinical evaluation, 36–38 age considerations for, 37–38 aspects of, 36 of jaw and occlusal function, 36–37 of malposition of teeth, 38 medical/dental history, key points clarified in, 36 of physical growth and maturation status, 38 social/behavioral, 37 of temporomandibular joint function, 37 of tooth anomalies, 38 orthodontic models, 39–43 Angle's dental classification, 41 asymmetric occlusal relationships, classification of, 41–42 Bolton analysis, 40–41 cast analysis, 39 diagnostic set-up, usefulness of, 42

Orthodontic records and case evaluation (Continued) digital models vs. plaster of Paris models for diagnosis, 42 orthodontic casts on articulator, indications for mounting, 43 orthodontic photographs, 47 facial profile analysis, 47 frontal, 47 views captured in, 47 orthodontic radiographs, 43–47. (See also Cephalometry/cephalometric analysis) lateral cephalometric, 44 panoramic vs. series of intraoral periapical, 43 posteroanterior cephalometric film, primary rationale for taking, 43 predictive analysis, 46–47 superimposition of serial cephalograms, 47 supplemental intraoral periapical films for, 43 Orthodontics, 236 adjunctive, 198 facial clefts, treatment for, 271 implants in, 235–236 interceptive, 198 Orthodontic therapy, 290 Orthodontic treatment, sequence of normal, 216–217 Orthodontist referral, 206–207 arch length analysis, 207 facial symmetry/proportions and relationship of jaws, 206–207 irregularities of tooth development, 207 Orthognathic surgery, 34–35 Orthopedics facial clefts, treatment for, 271 functional jaw, 165, 167, 174 instability of, 287 presurgical, 271–272 stability of, 287 Orthosystem palatal implants, 244 Osseointegrated implants, 245 Osseointegration, 235, 244 Osteotomy LeFort I, 192, 235, 315 Le Fort III, 280 LeFort III, 280 Overbite, 214 Overgrowth of gingivitis/gingival, management of, 266 Overjet, 66, 210, 298 Class III malocclusions treatment with, 214 excessive, 213

P Pain, 286–287 Palatal auxiliaries, 237 Palatal implants, 239, 242, 244, 245 Palatal plane (PP), 45, 164 Palatal plane to gonion-gnathion (PP-GoGn), 250–251 Panoramic radiographs, 43, 289 Panoramic x-rays, 222 PAR. See Peer assessment rating (PAR) Parallax technique, 56 Partial implants, clinical procedures and loading times for, 239–240 Passive self-ligating bracket, 103 Patient record, importance in, 63–64 PDL. See Periodontal ligament (PDL)

INDEX

Peak height velocity (PHV), 2f age and, 2 skeletal indicators associated with, 2 timing of, 1 Peer assessment rating (PAR), 210, 299 Pendex appliance, 138f, 139 Pendulum appliance, 140, 213 Periapical surveys, full mouth, 222 Perimeter of arch, 4 Periodontal attachment, 265 Periodontal ligament (PDL), 43, 82, 334 Periodontal regeneration procedure, 266–267 Periodontal tissue, 221 Periodontitis periodontal attachment and, 265 prevention methods for, 265 treatment for, 265 Permanent canines, 202 Permanent dentition, 276–277 Permanent incisors, rotation of, 203 Permanent second molar, 202 Permanent teeth eruption of, 16–17 changes following, 19 second molars, problems with, 20–21 upper canines, problems with, 20 extraction treatment plan for, 202–203 incisors, initial location and size of, 17 mineralization of, 17 missing, 207 Peutz-Jeghers syndrome, 277 PFE. See Primary failure of tooth eruption (PFE) Pfeiffer syndrome, 277 PFH/AFH. See Posterior to anterior face height (PFH/AFH) ratio Pharmacologic modalities for TMDs, 288–289 Phase II treatment, 137, 206–219. See also Class III malocclusions treatment; Class II malocclusions treatment; Class I malocclusions treatment crossbites, 215 defined, 24 open bites, 215 anterior, 215 posterior, 215 orthodontist referral for, 206–207 arch length analysis, 207 facial symmetry/proportions and relationship of jaws, 206–207 irregularities of tooth development, 207 “problem-oriented” approach to, 206 special considerations, 215–217 extraction, 215, 216 missing maxillary lateral incisors, 215–216 orthodontic treatment, sequence of normal, 216–217 skeletal anchorage, 216 Phase I treatment, 24, 137. See also Early treatment Phenytoin (Dilantin), 266 Philadelphia Center for Research in Child Growth, 8 Philosophiae Naturalis Principia Mathematica (Newton), 112 Photographs analysis of, 61 facial, 221–222 orthodontic, 47, 48f, 50f

PHV. See Peak height velocity (PHV) Physical growth, clinical evaluation of, 38 Physical models, computed tomography-based, 310 Physics, force defined in, 112 Physiological crowding, 5–6 Pierre-Robin syndrome, 164–165 Pin and tube, 98–99, 99f Pin and tube vertical bracket, 100 Planes E, 46 facial, 66 Frankfort horizontal, 45, 61 functional-occlusal, 164 lower facial, 66 mandibular, 45, 164, 204 reference, 45 anatomic, 45 linear and angular values for space in, 45–46 sella-nasion cranial base, 164 vertical, 129, 201 Planes of space, 62 anteroposterior, 62 sagittal, 65–66 dental tissue in, 66 skeletal issues in, 65 soft tissue in, 65–66 transverse, 62, 67 vertical, 62, 66–67 dental tissue in, 67 posterior/anterior facial height in, 66 skeletal tissue in, 66 soft tissue in, 66–67 Planning methods for craniomaxillofacial surgery, 309–311. See also Computer-aided surgical simulation (CASS) computed tomography-based physical models, 310 computed tomography models, 309–310 computerized, transfer to patient, 315, 324–326 computer model for, process for creating, 312–313 plaster dental model surgery, 310–311 face-bow transfer, 310 transfer of plan to patient at time of, 310–311 two-dimensional prediction tracings, 309 Plaster dental models for CASS, 324 Plaster dental model surgery, 310–311 Plaster of Paris models for diagnosis, 42 Plates Bollard, 140 orthodontic, 239 surgical, 244 PNS. See Posterior nasal spine (PNS) Pocket depth, 221 Pog-NB (pogonion to NB line), 46 Pogonion (Pog), 44 Polyvinyl siloxane (PVS) impressions, 155, 159 Porion (P), 44 Positioner appliance, 154 Positioners as retainers, 296 Postemergent spurt, 2 Posterior crossbite anterior vs., treatment of, 200 bilateral, without a functional shift, timing for, 27 with lateral functional shift, timing for, 27 lower arch and, 199 maxilla, treatment for, 199 with maxilla lingual and mandible facial, 199–200

351

Posterior facial height, 66 Posterior limit of dentition, 122–124 Posterior nasal spine (PNS), 44 Posterior open bites, dental vs. skeletal, 215 Posterior space analysis, 133–134, 133f Posterior to anterior face height (PFH/AFH) ratio, 250–251 Posteroanterior cephalometric film, 43 Posttreatment occlusal stability, 299 Power arm attached to bracket, 108 Power Ridge™, 158–159, 162 Power vs. manual toothbrush, 264 PP. See Palatal plane (PP) PP-GoGn. See Palatal plane to gonion-gnathion (PP-GoGn) Prader-Willi syndrome, 277 Preadjusted, 101–102 Predictive analysis, 46–47 Prescription bracket, 101–102 Presurgical orthopedics, 271–272 Primary dentition/teeth facial clefts and, 272 features of, 15, 15f initial location and size of, 17 late, 4 terminal plane and, 15–16, 16f Primary failure of tooth eruption (PFE), 10 Primary pain, 286 Primate spaces, 15 Primum non nocere, 290 Prioritized problem list, 61 Probing, 221 “Problem-oriented” approach, 206 Profile view, 63 anteroposterior, 63 lips, 63 nose, 63 vertical, 63 Prophy Jet, 264–265 Prophylaxis technique, 264–265 Prosthodontics, 240 Protection facemask therapy, 143 Protraction facemask therapy, 198 Pseudo Class III malocclusions, 186 Pterygopalatine sutures, 186–188 Pure titanium, 235 PVS. See Polyvinyl siloxane (PVS) impressions

Q Quadhelix, 138f, 139

R Radiation, 329–330 Radiographs/radiography cone beam computed tomography vs., 337–338 conventional, 289 examination using, 61 intraoral periapical orthodontic, 43 orthodontic, 43–47, 48f lateral cephalometric, 44 panoramic vs. series of intraoral periapical, 43 posteroanterior cephalometric film, primary rationale for taking, 43, 44f predictive analysis, 46–47 superimposition of serial cephalograms, 47 supplemental intraoral periapical films for, 43 panoramic, 43, 43f, 289

352

INDEX

Rapid maxillary expansion (RME), 139 appliances for, 147–148 bonded acrylic splint expander, 147–148 Haas expander, 148 Hyrax expander, 148 bonded, 151 cone beam computed tomography and, 336 Hyrax, 140 indications for, 149 of lower jaw, 149 protocol for, 139 U6 type of, 140 Rapid palatal expander (RPE), 24–25, 137, 174, 198, 199 RCP. See Rubber cup prophylaxis (RCP) Reapproximation, 129 Recession of gingivitis/gingival, 137–138, 265–266 Recontouring osseous surgery, 221 Reference planes, 45–46 Referral for Class II malocclusions treatment, 208 isolated tooth movement and, 204 orthodontist, 206–207 arch length analysis, 207 facial symmetry/proportions and relationship of jaws, 206–207 irregularities of tooth development, 207 Regeneration defined, 266 guided tissue, 266–267 periodontal, 266–267 Regression to the means, 286–287 Relapse in deep bite, 299 defined, 297 extraction vs. non-extraction and, 298 Class III malocclusion, 299 Class II malocclusion, 298–299 incisal changes, relationship to, 299 occlusal characteristics of, 299 in open bite, 299 third molars and, 297 Removable retainers, 295, 296 Reorientation to neutral head posture, 313 Resistance, center of, 113 Restorative dentist/dentistry, 203, 216 Restorative implants, 204, 239, 240 Restorative titanium implants, 236 Retainers bonded lingual, 294–295, 295f fixed, 296 positioners as, 296, 296f removable, 295, 295f, 296 scientific approach to, for mandibular incisor stability, 299–300 spring, 297 vacuum-formed, 295–296 Retention adult interdisciplinary orthodontic treatment, considerations for, 225–226 in Class III malocclusions, 294 in Class II malocclusions, 294 in deep bite, 294 defined, 293 extraction/non-extraction and, 294 facemask therapy and, 191 growth and, 293–294

Retention (Continued) long-term, 296 molar uprighting, protocol after, 223 necessity of, 293 in open bite, 294 Retraction, 116, 191 Retromolar pad, 240 Reverse-pull facemask therapy, 214 Reverse swallow, 254 Reversible care, 290 Ribbon arch, 99, 99f Ricketts’ E-line, 66 RME. See Rapid maxillary expansion (RME) RMSD. See Root mean square deviation (RMSD) Robotic technology, 154 “Room for error” during treatment plan/ planning, 120 Root angulation, 298 Root mean square deviation (RMSD), 320, 322 Root planing, 221 Root resorption, 85, 159 cone beam computed tomography, detection with, 335–336 delacerations and, measures for management of, 85–88 prevalence of, 221 Root torque, 115 Rotation center of, 113–114 of mandible, 10 of permanent incisors, 203 transverse, 8 Rotation oscillation toothbrush, 264 Rubber cup prophylaxis (RCP), 264–265 Rule of Fifths, 47 Rule of Thirds, 47

S Saethre-Chotzen syndrome, 277 Sagittal planes of space, 65–66 dental tissue in, 66 skeletal issues in, 65 soft tissue in, 65–66 Salentijn, Letty, 250 SAM Anatomical Face-Bow, 310 SARPE. See Surgically-assisted rapid palatal expansion (SARPE) appliance Scalar, 112 Scaling, 221 Schroeder, Andre, 235 Scientific body of evidence, 120 Scissor bite, 67 Seal of Acceptance of ADA, 264 Secondary crowding, 10 Secondary pain, 286 Second molars, 20–21, 202 Second-order bends, 101–102 Second phase following early treatment, 152. See also Phase II treatment Self-ligating bracket, 100, 235, 265 active, 103, 103f American Time, 104–105 defined, 103 passive, 103 Self-ligation, 102–103 Sella (S), 44 Sella-nasion (SN), 45, 164

Sella-nasion-gonion gnathion (SN-GoGn) angle, 209, 250–251 Sella-nasion to palatal plane (SN-PP), 250–251 Serial cephalometry, 47, 212 Serial extraction contraindications for, 146 defined, 146, 147f indications for, 146 Sex differences, 6 SGn-FH (Y-axis), 46 SI. See International System of Units (SI) Side-to-side action toothbrush, 264 Silver-Russell syndrome, 277 Single-tube bracket, 104 6-year molars, 4 Skeletal anchorage, 216, 235–249. See also Implants advantages of, 240–244, 241f, 242f, 243f defined, 237, 237f disadvantages of, 240–244, 241f, 242f, 243f future of, 246–247, 247f as standard of care, 245–246 temporary anchorage device and, 236–237, 240f Skeletal anterior open bites, 250–252, 253, 254–257 Skeletal discrepancies, 214, 277 Skeletal indicators associated with peak height velocity, 2 Skeletal issues in sagittal planes of space, 65 Skeletal measurements, anteroposterior, 45–46 Skeletal open bite, 6, 27–28, 62 Skeletal pattern anteroposterior component of, 130–131, 131f balance and harmony of face, factors affecting, 127–128 isolated tooth movement, impact on, 204 vertical component of, 129–130 condylar growth and, 129–130, 129f dentoalveolar development and, 130 environmental factors and, 130 in vertical plane, 129 Skeletal tissue, 66 Skull model for craniomaxillofacial surgery, 313 SLA. See Stereolithography (SLA) Sleep apnea, 282–283 Sliding mechanics, 106, 107f Slot dimension, 105–106 Slow maxillary expansion, 139 SmartClip Self-Ligating Appliance System, 103 SmartTrack™, 156, 157, 158 Smile, structures composing, 227 “Smile design,” 227 Smile line, 63 SN. See Sella-nasion (SN) SNA angle, 45, 46, 65, 210, 212 SNB angle, 45, 46, 65, 210, 212 SN-GoGn. See Sella-nasion-gonion gnathion (SN-GoGn) angle SN-MP, 46 SN-PP. See Sella-nasion to palatal plane (SN-PP) Social clinical evaluation, 37 Soft tissue balance and harmony of face, factors affecting, 128 cephalometric landmarks and, 45 facial profile and, 10, 65–66 lip protrusion/retrusion and, 66 measurements for, 46 profile and, impact of, 204 in sagittal planes of space, 65–66 in vertical planes of space, 66–67

INDEX

Soft-tissue diode laser surgery, 302–308 frenectomy and, 305–308 lasers for, 303–304 procedures for, 302–303 aphthous ulcer management, 302 frenectomy, 303, 305–308 gingival recontouring, 302, 304–305 impacted teeth, 308 operculum removal, 302 tooth exposure, 302 Space-regaining procedures, 32–34 Space/spacing angular values for, 45–46 anterior, 18 in arch, 203 deficit in, 17–18 leeway, 18 linear values for, 45–46 maintenance of, purpose of, 145–146, 146f of mandible, 174 of nonsuccedaneous teeth, 18 planes of, 62 anteroposterior plane, 62 sagittal, 65–66 transverse, 62, 67 vertical, 62, 66–67 primate, 15 SPEED bracket, 100, 102–103, 104–105, 106 Splint Biocryl, 139–140 Splints, occlusal, 287–288 “Spontaneous correction” of Class II malocclusions treatment, 150 Spring retainers, 297 Spring-wing bracket, 103–104, 104f Stability of Class III malocclusions, treatment of, 191 curve of Spee, 299 factors affecting, 293 of functional appliances, 180–182 during loading of implants vs. temporary anchorage devices, 244 occlusal, 299 of orthopedics, 287 Stainless steel, 235 Stainless steel to edgewise slots, 235 Stainless steel wires, 107–108 Standard edgewise brackets, 101–102 Standard of care, 245–246, 290, 329 Static equilibrium, 116 Steiner’s analysis, 65 Steiner wings, 103–104 Stereolithography (SLA), 155, 333 Stickler syndrome, 277 Stomion (St), 45 Straight wire, 108, 108f Structural Method of ABO, 89, 95 Study cast analysis, 61 Sturge-Weber syndrome, 277 Submental x-ray, 222 Subnasale (Sn), 45 Subspinale, 44 Sunday bite, 37 Superimposition, 212 on cranial base, 92–93 on mandible, 95–96 on maxilla, 93–95 methods for, 89 necessity of, 89

Superimposition (Continued) required, 89 of serial cephalograms, 47 surface imaging of, 53–54 Supernumerary teeth, 32 Supplemental intraoral periapical films, 43 Supportive therapy, 288 Supracrestal gingival fiberotomy, 203 Supraeruption, 38 Supramentale (B), 44 Surface imaging, 53–54 of average faces, 53–54 of facial growth, 53 of superimposition, 53–54 of surgical evaluations, 54 Surgery as adult interdisciplinary orthodontic treatment, 226–227 for Class III malocclusions treatment, 192 for Class II malocclusions treatment, 183–184 open flap, 221 orthognathic, 34–35 plaster dental model, 310–311 recontouring osseous, 221 surface imaging and, 54 for temporary anchorage devices vs. implants, 239 for temporomandibular disorders, 289–290 Surgically-assisted rapid palatal expansion (SARPE) appliance, 73–76 Surgical plates, 244 Sutures, 9, 186–188 Swallowing, 130 Syndromes Apert, 277, 279–280 Beckwith-Wiedemann, 277 branchial arch, 277 cardio-facio-cutaneous, 277 Carpenter, 277 cerebro-costo-mandibular, 277 craniofacial dysostosis, 277 craniosynostoses, 277, 279–280 Crouzon, 277, 279–280 Down, 277, 282–283 ectrodactyly-ectodermal dysplasia-clefting, 277 Ehlers-Danlos, 277 Goldenhar, 277–278 Kabuki, 277 Larsen, 277 Marfan, 277 median cleft face, 277 Noonan, 277 oral-acral, 277 Peutz-Jeghers, 277 Pfeiffer, 277 Pierre-Robin, 164–165 Prader-Willi, 277 Saethre-Chotzen, 277 Silver-Russell, 277 Stickler, 277 Sturge-Weber, 277 Turner, 277, 281 Van der Woude, 277 velocardiofacial, 277 System of force, 112–113

T TAD. See Temporary anchorage device (TAD) Taurodontia, 38

353

Teeth/tooth. See also Dentition agenesis of, 21 anchor, 216 ankylosis of, 19–20 balance and harmony of face, factors affecting, 127 banding of, 235 clinical evaluation of anomalies, 38, 40f concrescent, 38 development of, 14, 207 displacement of, 207 drifting, 207 enamel of, 104–105 exposure of, 302 hypodontia, most affected by, 21–22 impacted, 32 linguoverted, 38 malposition of, 38 missing permanent, 207 nonsuccedaneous, 18 permanent extraction treatment plan for, 202–203 incisors, initial location and size of, 17 mineralization of, 17 missing, 207 position of, 2–3, 21 primary features of, 15 initial location and size of, 17 terminal plane and, 15–16 size of, 23, 40–41, 137–138, 207 supernumerary, 32 transposition of, 85 wisdom, 19 Temporary anchorage device (TAD) adult interdisciplinary orthodontic treatment and, 230 cone beam computed tomography, placement of, 334 defined, 118 implants vs., 237 benefits of, 238 complications related to, 244–245 disadvantages of, 237 imaging techniques for, 238–239 loading of, 240, 244 mini-screw, clinical procedures and loading times for, 239–240 placement of, 238 removing, 245 surgical considerations for, 239 skeletal anchorage and, 236–237 tooth movement and, changes in, 119 Temporomandibular disorders (TMDs), 286–292 alternative forms of management for, 287–288 imaging modalities for, 289 indications for, 286–287 occlusal adjustment and, 288 occlusal factors in, 287 occlusal splints for, 287–288, 288f orthodontic therapy and, relationship between, 290 pharmacologic modalities for, 288–289 standard of care for, 290 surgery for, 289–290 Temporomandibular joint, 37, 56–57

354

INDEX

Terminal plane of permanent molars, 16 of primary dentition, 15–16 of primary second molars, 16 of primary teeth, 15–16 Therapy functional appliances, initiation of, 142–143 orthodontic, 290 supportive, 288 using functional appliances, 168–169 Thermodynamics, law of, 60 Thiazide diuretics, 289 Third molars, 3–4, 297 Third-order bends, 101–102 Three-dimensional (3D) cephalometric analysis, 313–315 Three-dimensional (3D) technology, 53 Three-dimensional imaging, 53–59 analysis for, 57 classification system for, 53 clinical applications for, 53–57 hard tissue imaging, 56–57 surface imaging, 53–54 clinical setting for, 58 costs of, 58 defined, 53 devices for, 53 future of, 58 limitations of, 58 medicolegal issues with, 58 obtaining, 53 revolutionization of, 57–58 techniques for, 53 of virtual patient, 58 3D-3T diagnostic grid advantages of, 64 defined, 63–64 information contained in, 64 patient record, importance in, 63–64 steps of, 64 Thrombocytopathy, 266 Thrombocytopenia, 266 Tie-wings, 105, 105f Time bracket, 100, 103 Time self-ligating bracket, American, 104–105 Time/timing of chin cup, 192 of Class III malocclusions treatment, 24–25 of Class II malocclusions treatment, 25–27 for digit-sucking habit, 28 of eruption, 14–15, 16–17 of facemask therapy, 188 for loading of implants vs. temporary anchorage devices, 240 of peak height velocity, 1 Tip-Edge bracket, 99, 100f Tip-Edge Plus bracket, 99 Titanium alloys, 235 TMA. See Beta-titanium (TMA) TMDs. See Temporomandibular disorders (TMDs) TMJ tomograms, 222 Tongue posture, 130 Toothbrush circular, 264 manual, 264 power, 264 rotation oscillation, 264

Toothbrush (Continued) side-to-side action, 264 ultrasonic, 264 unknown action, 264 Tooth-colored (“esthetic”) brackets, 265 Tooth movement adult interdisciplinary orthodontic treatment and initiation of, 221 limited, benefits of, 222 with fixed appliances, 102 isolated (See also Minor tooth movement) anterior trauma and, impact of, 203 arches and, spacing in, 203 face orientation and, 201 orthodontic database for, 201 permanent canines and, 202 permanent tooth extraction treatment plan for, 202–203 referral and, 204 skeletal pattern, impact on, 204 soft tissue profile and, impact of, 204 vertical plane and, 201 molar uprighting, types of, 222–223 periodontal regeneration procedure and, relationship between, 266–267 translational, 114 Torquing moment, 111, 111f Torsiversion, 38 TPA. See Transpalatal arch (TPA) Traction cervical, 212 extraoral, 139, 140, 165 Tranpalatal bars, 237 Translational movement , creation of, 116 Translational tooth movement, 114 Transpalatal arch (TPA), 145–146, 240, 254–256 Transposition, 38, 85 Transverse component of skeletal pattern, 131, 131f Transverse discrepancies, 137–140. See also Maxillary expansion appliance Transverse planes of space, 62, 67 Transverse rotation, 8 Transversion, 38 Trauma, anterior, 203 Treacher Collins syndrome, 164–165, 277, 280–281 Treatment. See also Class III malocclusions treatment; Class II malocclusions treatment; Early treatment. See also specific types of for ankylosis, 82–85 of anterior open bites dentoalveolar, 252–253 habitual, 252–253 skeletal, 254–257 during early mixed dentition, 145 objectives of, 64, 89 orthodontic, sequence of normal, 216–217 for periodontitis, 265 Phase I, 24, 137. (See also Early treatment) Treatment plan/planning, 64–65, 120–136. See also Malocclusion treatment concept of, 120–124 anterior limit of dentition, 122, 123f lateral limit of dentition, 124, 124f posterior limit of dentition, 122–124, 123f vertical limit of dentition, 124, 125f

Treatment plan/planning (Continued) evidence-based, 145 for extraction, 202–203 goal of, 120 importance of, 89 patients desires and, consideration of, 120, 121f, 122f “room for error” during, 120 Treat software, 156, 158 Tricyclic antidepressants, 289 Triple-tube bracket, 104 Trisomy 21 (Down) syndrome, 277, 282–283 Tubes convertible, 106 pin and, 98–99 shift method for, 56 Turner syndrome, 277, 281 Tweed, Charles H., 100 Tweed Foundation for Orthodontic Research, 100 Twin Block appliance, 65, 149–150, 151, 169–170, 211–212 for Class II malocclusions treatment, 174 Twinning, 38 Two-couple force, 117 Two-dimensional prediction tracings, 309 Two-tooth rapid palatal expander, 199

U UDML. See Upper dental midline (UDML) UFH/LFH. See Upper to lower face height (UFH/LFH) Ugly duckling, 6 U1-L1 (interincisal angle), 46 Ultrasonic toothbrush, 264 U1-NA (upper incisor to NA line), 46 Uncontrolled tipping, 114 Underbite, 214 Unilateral cleft lip and palate, 271 University of Iowa, 216 University of Michigan, 8 University School Growth Study, 5 Unknown action toothbrush, 264 Untreated crossbites, 200 Upper canines, problems with, 20 Upper dental midline (UDML), 67 Upper to lower face height (UFH/LFH), 250–251, 253 U1-SN (upper incisor to SN), 46 US News and World Report, 137 U6 type of rapid maxillary expansion, 140

V Vacuum-formed retainers, 295–296 Van der Woude syndrome, 277 VCA. See Vertical cephalometric analysis (VCA) Vector, 112 Velocardiofacial syndrome, 277 Vertical cephalometric analysis (VCA), 250–251, 252, 253, 254 Vertical components of force, 112 Vertical dimension, 250–262 anterior open bite and, 250–253 etiology of, 250 gnomonic growth, 254 Vertical discrepancies, 140–144 Class II, 140, 142, 143–144 crowding, treatment options for correcting, 140–141

INDEX

Vertical discrepancies (Continued) extraction and circumstances for considering, 140, 141–142 for Class III anteroposterior discrepancy, 143 serial, 141 extra-oral traction therapy and, 140 facebow for, 140 functional appliances for, 142–143 headgear for, 140 protection facemask therapy for, 143 Vertical face height, 204 Vertical limit of dentition, 124 Vertical mandibular growth, 4 Vertical plane, 129, 201 Vertical planes of space, 62, 66–67 anterior facial height in, 66 dental tissue in, 67 posterior facial height in, 66 skeletal tissue in, 66 soft tissue in, 66–67

Vertical position of the mandible, 66 Vertical problems, 151 Vertical profile view, 63 Vertical-pull chin cup, 151 Vertical-pull headgear, 212–213 Vertical skeletal measurements, 46 Views captured in orthodontic photographs, 47 Virtual patient, three-dimensional imaging of, 58 Visual treatment objective (VTO), 46–47 Vitallium, 235 Volume assessment of alveolar bone, 56 VTO. See Visual treatment objective (VTO)

W Walker point, 92 Wall Street Journal, The, 137 W appliance, 199 W arch, 138f, 139 Weak lips, 125 White spot lesions, 263

Wires beta-titanium, 107–108 β-titanium, 235 NiTi, 235, 254 nitinol, 107–108 stainless steel, 107–108 straight, 108 Wisdom teeth, 19

X X-ray, 222

Y Y-Axis, 45

Z Z angle, 116 Zirconia, 235 Zygomaticomaxillary sutures, 186–188 Zygomaticotemporal sutures, 186–188

355

Mosbys Orthodontic Review 2e

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