ORTHODONTIC BRACKETS SELECTION, PLACEMENT AND DEBONDING
Dr. Haris Khan B.D.S., F.C.P.S,F.F.D RCSI
Assistant Professor Orthodontics The University Of Lahore Lahore Pakistan
ORTHODONTIC BRACKETS SELECTION, PLACEMENT AND DEBONDING
Dr. Haris Khan B.D.S., F.C.P.S,F.F.D RCSI
Assistant Professor Orthodontics The University Of Lahore Lahore Pakistan
COPYRIGHT
All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law. For permission requests, write to the publisher, or contact at
[email protected] PUBLICATION DATA
ISBN-13: 978-1508936275 978-1508936275 ISBN-10: 1508936277 Library of Congress Control Number: 2015905934 CreateSpace Independent Publishing Platform, North Charleston, SC DEDICATION
This book is dedicated to my supervisors Dr. M. Waheed ul Hamid and Dr. Irfan ul Haq
ACKNOWLEDGEMENT
I highly acknowledge the efforts and inspiration made by Dr. Ateeq ul Reham to write this book. I am thankful to Dr. Fayyaz Ahmad and Dr. Munawer Manzoor for providing me the technical guidance on various aspects of brackets. I am also thankful thankful to Dr. Erum Bashir for doing the proofreading, proofreading, Dr. Dr. lubna batool for provided used brackets from her clinical practice and practice and Mr Jahanzeb for doing the composing of this book.
CONTRIBUTOR, EDITOR AND AUTHOR Dr. Haris Khan B.D.S , F.C.P.S,F.F.D RCSI
Assistant Professor Orthodontics UOL, Pakistan
In this era of pre-adjusted brackets, the existing literature on orthodontics limits itself to wire bending treatment practices. Since contemporary authors were not trained on the pre-adjusted bracket mechanics, hence they were handicapped to broach on the subject at the relevant point in time. In present day orthodontics, many orthodontists still resort to wire bending methods to to close extraction spaces or to correct three dimensional dimensional positions positions of the teeth. Chapters on orthodontic brackets in various books either focus on theoretical perspective or are devoid of essential correlation of brackets,vis-a-vis their intended clinical use. Some authors have depicted fancy graphics to demonstrate clinical use of brackets. To address such obvious lacunae, I started working on orthodontic brackets in the year 2012 by collecting the brackets which were debonded during my clinical practice.This took me through the entire literature on orthodontic brackets as presented in various journals and manufacturer catalogues. This provided me an access to real time pictures of brackets using special micro lenses and portable microscopes. This book was authored to cater for all aspects of orthodontic brackets. The focus being to provide students with real time pictures of different brackets available in the market and to determine their behaviour in oral cavity and their appearance after debonding. The main emphasis being on three vital aspects viz; the selection, placement and debonding,this book has accordingly been designed to comprise these three sections. Real times of new and used brackets have been specifically included to provide the students a realistic insight of brackets.Care has has been taken to ensure correlation of clinical situation and various bracket selection criterions. This book has materialized after an enormous effort of two years in data collection and a year further in arranging the data in a convenient book form. I deeply acknowledge the help and encouragement provided my colleagues in consummating this endeavor endeavor.. I earnestly hope that this effort would go a long way in providing ready help to students. Haris Khan
Table of Contents Historical Perspective of Orthodontic Brackets
1
Material Perspective of Orthodontic Brackets
13
Selection of Bracket Base
41
Selection of Bracket Slot
61
Selection of Auxiliary and Convenience features
77
Selection of Bracket Prescription
83
Placement of Orthodontic Brackets
153
Bonding in Orthodontics
189
Debonding of Orthodontic Brackets
203
Adhesive Remnants Removal
239
Recycling of Orthodontic Brackets
255
R E T P A H C
1
Historical Perspective of Orthodontic Brackets In this Chapter
History
Begg Appliance
Pierre Fauchard
Other Appliances
Modifications of bandeau appliance
Modification of Standard Edgewise Appliance
Development of edgewise appliance
Self ligating brackets
E Arch
Light wire Appliances
Pin and Tube Appliance
Lingual brackets
Ribbon Arch Appliance
Customized labial brackets
Edgewise Appliance
Orthodontic brackets are important part of fixed appliances which are temporarily attached to the teeth during the course of orthodontic treatment. They are used to deliver forces from the wires or other power modules to the teeth. Before going into the details of orthodontic brackets a historic preview on the evolution of brackets is given. History
The origin of orthodontic brackets can well be coined with the origin of orthodontics and the human desire to align crooked teeth. The first 1 written record to correct crowded or protruded teeth is found 3000 years ago. Orthodontic appliances to correct maligned teeth have been found in Greek, Etruscan and Egyptian artifacts 2 .These ranges from crude metal wire loupes to metal bands wrapped around individual teeth in 3 ancient Egyptian mummies . Pliny the Elder 1
(23-79 AD) was the first to mechanically align 4 elongated teeth . Pierre Fauchard
Pierre Fauchard (1678 –1761) a French dentist was the first to make a scientific attempt to align irregular teeth by an appliance named Bandeau (Figure 1.1 & 1.2).This appliance was made of precious metal and it was shaped like a horse shoe to align teeth by arch expansion. Fauchard also used to reposition irregular teeth with his Pelican forceps and then ligate them with neighboring teeth until healing took place. Fauchard published his work in 1728 in his landmark book entitled The Surgeon Dentist: A Treatise on the Teeth.
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1
another French dentist used swelling threads and wooden wedges to separate crowded teeth. Horace H. Hayden (1769-1844) invented bands with soldered knobs to correct tooth rotation.
Figure 1.1
Pierre Fauchard
In 1803, Joseph Fox invented a modified version of bandeau appliance that consisted of silver or gold rim. Silk thread was used as mode of attachment and force transfer between the rim and teeth. These silk threads were adjusted after every three weeks (Figure 1.3a). Blocks of ivory were used to disocclude the occlusion and to prevent interference with tooth movement. J. M. A. Schange (1841) a French dentist wrote the first book exclusively on orthodontics. He modified bandeau appliance and took anchorage by skeletal cribs attached to molars (Figure 1.3 b). He also invented an appliance to move malposed teeth within the arch (Figure 1.3 c).Harris in 1850 attached metal caps to molar and took anchorage from palate in his expansion appliance (Figure 1.3d) Development of edgewise appliance
Norman W. Kingsley (1825-1896) and Calvin S. Case (1847-1923) advocated extraction for orthodontic purpose. Though Norman W. Kingsley later abandoned his extraction philosophy. This extraction philosophy later influenced the basic design of orthodontics braces. 5
Figure 1.2
BandeauAppliance
Modifications of bandeau appliance
Fauchard's bandeau appliance was further refined by another fellow French dentist Etienne Bourdet (1722-1789) who was a dentist to the King of France in his time. Etienne Bourdet was also the pioneer of lingual orthodontics by expanding the arch by metal framework placed on the lingual side. Christophe François Delabarre (1787-1862)
Edward Hartley Angle (1855-1930) was the most dominant and influential figure in orthodontics and is regarded as the “Father of Modern Orthodontics.” (Figure 1.4). Because of Edward Angle, orthodontics was recognized 6 as a distant and separate science from general dentistry. In his initial days of orthodontic practice Angle advocated extraction in orthodontics .But latter on the basis of Wolff's law that “bone in a healthy person will adapt to applied load” Angle abandoned extraction treatment. Also another reason to abandon extraction treatment was failure to get satisfactory result after extracting 1st maxillary 2
R E T P A H C
2
Material Perspective of Orthodontic Brackets In this Chapter
Introduction
Plastic Brackets
Manufacturing Techniques
Plastic Polyoxymethylene brackets
Casting
Polyurethane brackets
Milling
Composite plastic brackets
Sintering Metal injection molding (MIM)
Ceramics Brackets Aluminum oxide or Alumina (Al2O3) brackets
Ceramic injection molding (CIM)
Monocrystalline brackets
Plastic injection molding (PIM)
Polycrystalline brackets
Brazing Cold working
Zirconia brackets Calcium phosphate ceramic brackets
Metal Brackets Stainless steel brackets Cobalt chromium brackets Titanium brackets Precious metal brackets
Introduction
Contemporary orthodontic brackets are modification of a standard edgewise brackets developed by Edward H Angle. At the time of edgewise brackets invention stainless steel alloy although invented was in the phase of evolution and orthodontic brackets soldered to bands were largely made of 14 karat or 18 karat 1 gold. Rudolf Schwarz was the first to use 13
stainless steel in edgewise appliances. Ernest Sheldon Friel (1888-1970) a pupil of the Angle (Angle School, 1909) used stainless orthodontic bands for the first time in 1935.Apart from stainless steel different other materials have also been introduced with time to meet the orthodontists and patient's need. Modern orthodontic brackets are made up of three different types of materials which are as follow :
Selection of Stainless steel brackets
Stainless steel brackets with good corrosion resistance should be selected. Good corrosion resistance of a bracket is more important than its nickel contents. Ideally SS brackets should not be used for nickel sensitive patients. Conventional SS brackets with softer base component and harder slot/wings component should be preffered.17-4 PH MIM brackets are a good choice for proper torque expression. New bracket should always be the first choice by orthodontists to avoid corrosion.
Cobalt chromium brackets were introduced in mid 1990s as a low nickel alternative to stainless steel. Cobalt chromium brackets are fabricated from casting or metal injection molding. Type and Composition of Cobalt based alloys
Cobalt based alloys can be divided into three categories .These are: 1. Cobalt based wear resistant alloys 2. Cobalt based high temperature alloys 3. Cobalt based corrosion resistant alloys In these alloys cobalt based wear resistant alloys 29 are used presently for orthodontic brackets manufacturing .In cobalt based wear resistant alloys CoCr brackets are made from ASTM F75 CoCr where ASTM stands for American Society for Testing and Materials. The amount 29 of nickel in this alloy is kept low and is up to 0.5 %. Composition of cobalt based wear resistant alloys is given in table 2.3. A cobalt chromium bracket is shown in figure 2.19.
Table 2.3 Cobalt-Base Wear-Resistant Alloys
Cr 25-30% Mo 7% max W 2-15% C 0.25-3.3% Fe 3% max Ni 0.5%max Si 2% Mn 1% Co Balanced Where Cr=Chromium, Mo=Molybdenum, W = Tungsten, C =Carbon, Fe = Iron, Ni=Nickel, Si = Silicon
Properties of Cobalt Chromium Brackets Friction Resistance
In terms of friction resistance cobalt chromium 30, 31 brackets show comparable but slightly less amount of friction than that of stainless steel brackets when used with stainless steel wires. But CoCr brackets offer more friction than 30 titanium brackets with both stainless steel and beta titanium wires. Corrosion Resistance
Because of increase chromium contents there is 32 less chance of corrosion of cobalt chromium brackets.
Figure 2.19 Nu- Edge® Mini Cobalt Chromium Brackets by TP orthodontics with 0.5 % nickel.
27
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Selection
Cobalt chromium alloys have good corrosion resistance and have a highly polished surface. But due to less favorable friction properties with different types of wires, selection of CoCr brackets over titanium and steel brackets is a matter of personal choice than logical basis. Titanium Brackets
Titanium metal has excellent biocompatibility 18, 33, 34 and increased corrosion resistance so it has wide ranging surgical application from artificial heart valves and hip joints to dental implants. In orthodontics to overcome the release of nickel from stainless steel brackets which may cause nickel allergy in some patients, titanium 35, 36 brackets have been introduced as nickel free alternatives to stainless steel in mid 1990s. Types of Titanium
From material science perspective titanium has the following three types:
2
4 CP titanium, which offers highest strength and moderate formability. Composition of different grades of CP titanium is given in table 2.5. 21, 37
Contemporary titanium brackets are either manufactured from alpha titanium grade 2 and 4 or alpha-beta titanium (Ti-6Al-4V).Grade 2 CP titanium is usually used to make base component of brackets due to its decreased strength while the wing component is made from much harder titanium alloy, the alpha -beta titanium Ti-6Al -4V.Both these components are laser welded to make a single unit of bracket. As explained before for stainless brackets combination of harder slot/wings part and softer base part has clinical importance. The softer base part will allow easy mechanical debonding while harder slot/wings part will allow expression of torque. 37
Due to release of vanadium from titanium alloy Ti-6Al-4V which may have biological hazardous effects some manufacturer make single unit milled or metal injection molded bracket from grade 4 CP titanium.
Characteristics of Titanium brackets 1. αTitanium Corrosion Resistance
2. β titanium 3. α &β Titanium Alpha titanium is commercially pure (CP) unalloyed titanium while the other two types are titanium alloys.β titanium include Ti-15V-3Cr3Sn-3Al alloy while α-β titanium included Ti6Al-4V alloy. Alloyed titanium has greater strength than unalloyed titanium. Chemical composition of various types of titanium is given in table 2.4. Commercially pure (CP) titanium is further classified into four grades depending upon degree of impurity, primary oxygen within the unalloyed titanium. Grade 1CP titanium has the lowest strength but highest purity, corrosion resistance and formability as compared to grade
Titanium and titanium alloy brackets have greater corrosion resistance than stainless steel brackets. This is due to the presence of thin passive protective layer of titanium dioxide over the titanium. This layer of titanium dioxide 23 is more stable than its counterpart layer of chromium oxide on stainless steel. The composition of titanium dioxide layer which is also called rutile is given in table 2.6. Brackets in which two parts are joined toge ther by welding have greater chances of galvanic corrosion than one piece milled or MIM brackets. A titanium bracket is shown in figure 2.20.
28
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than conventional ceramic brackets and these brackets don't cause enamel damage.
2
Vivo: Aging and Related Phenomena. New York, NY: Quintessence; 2003:141–156. 8. Brockhurst PJ, Pham HL. Orthodontic silver brazing alloys.
Selection of ceramic brackets
Ceramic brackets are usually selected for patients who have aesthetic concerns. Due to iatrogenic damages associated with ceramic brackets they should only be selected when clinicians have proper knowledge of mechanics and proper instrumentation for debonding is available. Monocrystalline brackets give better aesthetic than polycrystalline brackets but are more expensive and fracture easily and more with time. Zirconia brackets are rarely used in contemporary orthodontics. Calcium phosphate ceramics is manufactured by only one company and not much is known about these brackets so selection of these brackets is a personal preference.
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R E T P A H C
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Selection of Bracket Base In this Chapter
Bracket Base Retention Design Stainless steel Brackets Mechanical Retention Perforated bases Mesh type bases Integral bases Photoetched bases Microetced bases Metal sintered bases Laser structured bases Plasma coated brackets
Chemical Retention Stainless steel brackets and Cross infection
Plastic Brackets Chemical Retention Mechanical Retention Combination of chemical and mechanical retention
Ceramic Brackets Chemical Retention Mechanical Retention Micromechanical retention Ceramic brackets with prestressed base Combination of different retention designs
Bracket base surface area Bracket base shape
Titanium Brackets
Bracket identification marks
Cobalt Chromium Brackets
Torque in the Base
The base component of orthodontic brackets makes possible the attachment of a bracket to the tooth. This attachment must be strong enough to transfer orthodontic forces from the wires to the teeth, withstand masticatory loads and should easily be removed at the end of treatment.
41
Precious metal Brackets
Bracket Base Retention Design
Orthodontic brackets are attached to teeth or other supporting structures of porcelain, metal, composite and acrylic through various commercially available adhesives. To increase retention of bracket bases to adhesives various chemical, mechanical or combination of both retention designs have been added to the bracket base. Though the exact manufacturing details
CHAPTER e s a B t e k c a r B f o n o i t c e l e S
are not provided from the manufacturer some basic informations are available. 1) Stainless steel Brackets
Most orthodontic brackets used in contemporary orthodontics are made of stainless steel which mostly uses mechanical retention because stainless steel doesn't form any chemical union with adhesives. Stainless steel bracket base is either integral part of the bracket or is made separately and then joined to the main body of the bracket by brazing or welding (Figure 3.1).Different types of stainless steel bracket bases are given in the following text. 1. Perforated bases
Brackets with perforated bases are one of the oldest bracket designs for mechanical 1 retention (Figure 3.2). The original metal pad consists of one row of peripheral perforation. The basic idea was to allow greater penetration and free flow of adhesive cement through the bracket base to increase the bond strength. But unfortunately excessive adhesive coming out of the holes of bracket base was potential plaque retention area which get discolored with time so raised esthetic concerns by the patients and don't provide superior retention as compared to other 2,3,4,5,6 designs . Because of these disadvantages perforated bracket bases went into disuse. 2. Mesh type bases
Mesh type bases have replaced perforated bases and are most popular type used in contemporary orthodontics. Following different terms are used for mesh based bases in literature and by manufacturer owing to slight variation in mesh design.
3
a) Foil mesh base b) Gauze or woven mesh base c) Mini mesh base d) Micro mesh base e) Optimesh base f) Ormesh base g) Laminated mesh base h) Single mesh base I) Double mesh base j) Supermesh base Description of some important mesh designs is as follows. a) Foil mesh base
In orthodontic literature the term foil mesh base is used interchangeably with gauze or woven mesh base. But there are slight differences in the manufacturing design between foil mesh and woven mesh base (Figure 3.3) .Foil mesh bases are more esthetic and hygienic than perforated bases because of their smooth 2, 3, 7, 8 covered surface . Foil and woven mesh bases provide superior retention than perforated bases and many other b r a c k e t b a s e d e s i g n s u s e d i n 4, 7, 9 contemporary orthodontics . Foil mesh bases can be simple or microetched, photoetched or plasma coated by the manufacturer. The foil mesh is either brazed or welded on to the bracket base. The spot welding of foil mesh to bracket base results in decreased base surface 2, 4, 10 areas and so bond strength therefore spot welding have been taken over by 11 silver based laser welding . Foil mesh bases can be single mesh or double mesh. 42
CHAPTER e s a B t e k c a r B f o n o i t c e l e S
3
lower bond strength than high filled adhesives. Another alternative is to use glass ionomer or 41 resin modified glass ionomer cements (RMGIC) with ceramic brackets as glass ionomer cements have shown to have 42,43 decreased but clinically acceptable bond 32, 44, 46 strength than composite resins . Though bond failure of glass ionomer cement is present at enamel adhesive interference but 44, 45 no enamel damage is reported with this adhesive cement because RMGIC has lower bond strength. Glass ionomer cement also has the added advantage of fluoride release and so it pre vents ena mel decalc if ic ati on and formation of white spot lesions during orthodontic treatment. Selection of ceramic bracket base
Ceramic bracket base using only chemical retention is neither marketed nowadays nor should be used due to risk associated with enamel damage. All other commercially available ceramic brackets are acceptable for orthodontic purpose as long as suitable or recommended debonded techniques are used. My personal recommendation after going through all the available literature and personal experience is that ceramic brackets with plastic base or prestressed base should be used as it debond safer than other base types. Bracket base surface area
An important technical specification that affects the bond strength of orthodontic bracket is its base surface area. Most orthodontists presently 26,47 use twin brackets. The surface area of these 2 2 brackets range from 12.5mm to 28.5 mm . Greater the retentive bracket base area greater would be the bond strength and vice versa (Figure 3.27). But there is practical limitations
Greater the retentive bracket base surface Figure 3.27 area greater would be the bond strength.If the base surface area is not retentive then no matter how much wider is the bracket the bond strength will remain minimum or bracket will fail to bond. The above brackets have manufactur ing faults which have increased the surface area but area is not retentive. So instead of favoring bond strength the area can act as p laque reservoir and may lead to development of white spot lesion under the bracket base.
of increasing or decreasing the bracket base 48 surface area. Proffit purposed that width of the bracket shouldn't be more than half of the 49 width of the tooth while MacColl recommended that bracket base surface area 2 should be around 6.82 mm . Usually the manufacturer of brackets keep a larger base area to give better bond strength and rotational control .
Clinical implication of Bracket base surface area Increase Bracket base surface area Advantages
This has the following advantages: 1. Increased bond strength. This is helpful especially in case of plastic brackets which offer less bond strength than other type of brackets. Clinically acceptable bond 50 strength is around 5.9 to 7.8 Mpa but bond 51 strength shouldn't exceed than 13.5Mpa to avoid enamel damage. 56
R E T P A H C
4
Selection of Bracket Slot In this Chapter
Introduction
Bidemensional mechanics
Type of bends for 3 dimensional tooth movements
Morphology of the brackets
Dimensions of Edgewise slot Accessary slots Tip edge brackets
Gingival offset brackets Slot modifications to reduce friction Ligation: The fourth wall of Bracket slot Tie Wings of the brackets
Advantages of 0.018” slot Advantages of 0.022” slot
Introduction
Slot is part of the bracket in which the wire is engaged to express the builtin prescription of the bracket. The slot of the bracket has seen much evolution with time. It started from occlusal opening slot in Angle ribbon arch appliance to gingival opening slot in Begg appliance and front opening slot in Angle edgewise system. In contemporary orthodontics edgewise slot is universally accepted .Vertical slots are still used in some bracket series but usually as an accessary slot. When bracket slot was first introduced they were simple openings in which a bended wire incorporating all the necessary tooth movements was inserted. The brackets having such passive slots were called standard brackets. With time 1st, 2nd and 3rd order bends 61
were incorporated in brackets to produce 1 respective tooth movements . Before going into the details of slot a brief description of these bends and associated movements are given. Type of bends for 3 dimensional tooth movements First order bends (In or out bends)
First order bends are given to accomplish first order tooth movements which are in a labiolingual or buccopalatal direction. 1st order bends can be made in horizontal direction in the wires such as the step bends, or are accommodated in the brackets (Figure 4.1). As different teeth in the arch have different width these bends made in the wire or built into the bracket are used to accommodate different tooth width. Vertical step bends that don't change the
CHAPTER t o l S t e k c a r B f o n o i t c e l e S
4
angulation of the teeth are also considered as 1st order bends. First order bends in brackets are incorporated by increasing the prominence of the bracket.
A
B
C Figure 4.1 A. A line showing different prominence of the teeth in natural dentition due to difference in width of the teeth. B. Wire bending done to compensate 1st order tooth movement. This type of wire bending is usually done in conventional edgewise system. C. First order bends built within the bracket. This is evident with different prominence of the brackets in upper arch.
Clinical Notes
The clinician should always use same companie's brackets. If a bracket is debonded either the bracket should be recycled and reused or a new bracket of same company should be used. Different companies have different prominence of the brackets(Figure 4.2). So using different companie's brackets will result in first order tooth position problems in a finished case.
Maxillary lateral incisor brackets from two Figure 4.2 different manufacturers having same builtin prescription. The height or prominence of these brackets is different.
Second Order Bends (Tip or Angulation bends)
These bends are made in vertical plane in the wire to accommodate tooth angulation and root parallelism. Second order bends can also be incorporated in the brackets by placing the slot at an angle to the base (Figure 4.3).
Clinical Notes
Different bracket prescription have different builtin tip. An experienced clinician can use combination of brackets from different prescription provided that they have the same prominence. It is a good pra cti ce to use br acket s of si ng le manufacturer while altering the prescription. 62
R E T P A H C
5
Selection of Auxiliary and convenience features In this Chapter
Auxiliary features Power arms Accessary slots Convenience features Vertical Mid Scribe line Shape of brackets Bracket identification
Many auxiliary and convenience features are added to the brackets and tubes to make treatment mechanics easier and convenient.
Auxiliary features Power arms
Power arms are added to the brackets on its gingival side to control root position during translation of the teeth. The reason for making power arms on gingival side is to bring the force application closer to the center of resistance of 1 the teeth. Andrew proposed that for effective control of root position during translation, the mesiodistal length of bracket plus height of power arm should be equal to distance from the slot point to tooth center of resistance (Figure 5.1). As root of canine is longer than other teeth so power arm of canine tooth would also be 77
longer than other teeth. But there are practical limitations in increasing the width of bracket and height of power arm. A wider bracket will decrease interbracket distance so increasing the wire stiffness and thus greater time would be needed in alignment and leveling. Also a wider bracket will be more noticeable, thus increasing aesthetic concerns of the patients. The height of power arm is limited by soft tissue present around the tooth as long power arm will impinge on the gingiva either making ideal bracket placement difficult or leading to gingival hyperplasia due to soft tissue impingement. Advantages of power arm
1. Power arm makes the application of force delivery system such as springs, power chains, and elastics much easier and close to
R E T P A H C
6
Selection of Bracket Prescription In this Chapter
Introduction Andrew Prescription Key I: Interarch Relationship Key II: Crown Angulation or Mesiodistal Crown tip
Different Bracket prescriptions Roth Prescription Limitations of Roth Prescription MBT Prescription Alteration of prescription
Key III: Crown inclination or Torque Key IV: Absence of Rotations Key V: Tight Contact points Key VI: Flat Occlusal plane or Curve of Spee Limitations of Andrew prescription
Introduction
Angle introduced edgewise brackets to have a better control on three dimensional positions of the teeth. But the problem in these brackets was that complex wire bending was required to 1,2 control the tooth position. Andrew modified the standard edgewise brackets developed by Angle by introducing tip, torque and in& outs in his preadjusted edgewise brackets .The amount of tip torque and in & outs built within preadjusted brackets were called prescription of the brackets. After Andrew a lot of orthodontists introduced their versions of bracket prescription sometimes based on studies and many times based on clinical experience. Each clinician 83
who advocated a specific prescription also advocated specific mechanics during the course of treatment for expression of the prescription. In medicine to treat a disease properly, the right diagnosis should be made. That helps the physician to advise the right prescription of drug .Same is true in orthodontics. After making a right diagnosis and treatment planning of a malocclusion the right prescription should be used. Using the right prescription, simplify the treatment mechanics which will save considerable chairside time. In most cases there would be minimal or no need of wire bending during the course of orthodontic treatment.
CHAPTER n o i t p i r c s e r P t e k c a r B f o n o i t c e l e S
A detailed description on evolution of different types of orthodontic prescriptions is given in this chapter. Main focus is given to the development of Andrew prescription because all other prescriptions are either variations or based on Andrew's data. Andrew Prescription 1
Lawrence F. Andrew introduced the first preadjusted brackets where all the bending's needed in archwire in standard edgewise bracket system were built within the brackets. It was proposed that this appliance does not require wire bending during treatment hence the name Straight wire appliance (SWA) was given to it. Andrew after a study on 120 non-orthodontic ideal occlusion dental casts concluded that in order to attain ideal occlusion some characteristics must be present within the occlusion. These characteristics were divided into six keys. Based on these 6 keys Andrew developed his prescription of brackets, so that using this bracket prescription no wire bending would be required during treatment and at the end of treatment, all the six keys to normal occlusion would be attained. Andrew apart from studying these nonorthodontic ideal occlusion dental casts also studied 1150 orthodontic treated cases so that his prescription could also address some of the problems not found in ideal occlusion e.g. Extraction cases where molar relation may deviate from class I relationship. Most of the modern preadjusted brackets are minor modification of Andrew straight wire appliance. To give a better understanding of prescription so that clinician can make an easy selection of brackets a complete description of Andrew six keys to normal occlusion and how prescription components evolve from each key is given. Details on how a prescription in bracket is transferred to a tooth are also given
6
with each key so that the readers can have a clear knowledge of effects and limitations of a prescription. Key I: Interarch Relationship 1
Key I as originally proposed by Andrew was 2 molar relationship. But in 1989 Andrew changed the key from molar relationship to interarch relationship. Interarch relationship is broader and more definite description of occlusal relationship than relying on molar 1 relations only. Interarch relationship as key is considered in this text because it will clear the reader's mind about the basis and need of prescription. 2
Key I have seven parts which are given below: Part 1
The mesiobuccal cusp of the maxillary first permanent molar fits in the groove between the mesial and middle buccal cusps of the mandibular first permanent molar. Part 2
The distal marginal ridge of maxillary 1st molar occludes with mesial marginal ridge of the nd mandibular 2 molar. 1
Previously this relation was. "The distal st surface of the distobuccal cusp of maxillary 1 molar made contact and occluded with the mesial surface of the mesiobuccal cusp of the mandibular second molar." The closer these two surfaces of maxillary 1st and mandibular nd 2 molar contact and occlude , the better would be the opportunity for normal occlusion. Part 3 st
The mesiolingual cusp of the maxillary 1 permanent molar occludes in the central fossa of mandibular 1st permanent molar.
84
Part 4
The buccal cusp of the maxillary premolars have cusp embrasure relationship with nd mandibular premolars. The maxillary 2 premolar buccal cusp lies between embrasure of mandibular 1st molar and mandibular 2nd premolar. Buccal cusp of maxillary 1st premolar lies in the embrasure between mandibular 1st and 2nd premolars. Clinical Notes
To check if a case has attained Key I, always judge from buccal aspect clinically and both from buccal and lingual aspects on the dental cast. Part 5
The lingual cusp of the maxillary premolars has a cusp fossa relationship with mandibular premolars. Part 6
The maxillary canine tip lies slight mesial to the embrasure between mandibular canine and 1st premolar. Part 7
The maxillary incisors overlap the mandibular incisor with their dental midlines coinciding. A description of key I is given in figure 6.1.
A Figure 6.1
85
Incorporating key I into bracket prescription
Key I is interrelated with next 5 keys to normal occlusion. Key I will only be achieved when the rest of the keys have been achieved too. To attain key I, a preadjusted bracket should st nd rd have built in 1 , 2 and 3 order bends and brackets should be optimally placed on the tooth. Only description of 1st order bends and how and why they are included in the prescription would be given here. The rest would be discussed in their respective keys. To incorporate the right amount of 1st order 2 bends with in his prescription Andrew measured the facial prominence of each tooth within the arch of an ideal occlusion case .This was done by measuring the distance from the embrasure line to most prominent facial point of each tooth, where embrasure line is imaginary line at crown mid transverse plane that connects the facial portion of contact areas of a single crown or all the crowns in an arch when the crowns are optimally placed. Figure 6.2 and table 6.1. From the figure 6.2 and table 6.1 it is clear that in maxillary arch lateral incisors have least facial prominence while in mandibular arch both central and lateral incisors have least facial prominence. These values were built within the base or stem of the brackets so that at the end of leveling and alignment all the brackets slots
B An ideal occlusion case meeting all the criteria of key I . A .Buccal aspects . B. Lingual aspects
S e l e c t i o n o f B r a c k e t P r e s c r i p t i o n
CHAPTER n o i t p i r c s e r P t e k c a r B f o n o i t c e l e S
6
have same level of prominence while all the teeth have the prominence value found in table 6.1. How it works?
To build the right amount of prominence within the brackets, Andrew incooperated a simple rule that the distance between most prominent facial point of the crown and the embrasure line is inversely proportional to the distance between slot point and most prominent facial point of crown in mid transverse plane.(Figure 6.3A) . This means that if a tooth has less facial prominence of crown it would have increased bracket prominence (Figure 6.3B&C). The slot point is the mid of the bracket slot in all three planes of space. For the ease of simplicity since we are viewing the tooth from lateral side so base of the slot instead of slot point would be used in this text.
A
So in maxillary arch lateral incisor bracket would be the most prominent bracket in mid transverse plane. When such a bracket is placed on the tooth a palatal force is expressed by the flexible wire on this tooth as compared to neighboring teeth which absorb reactionary labial or buccal force because less prominent brackets are placed on them . So eventually on heavy wires maxillary lateral incisor crowns are found to be less prominent than central incisors and canine crowns while all the brackets slot point or slot bases are at same level of prominence .
B Facial prominence of teeth in the arch Figure 6.2 .The distance between embrasure line and most prominent facial point of each tooth is the prominence of the tooth. A. Average maxillary arch crown prominence. B. Average mandibular arch crown prominence. These prominence values are incorporated into the brackets by varying the distance from base of slot to base of brackets.
In Andrew's prescription (table 6.2) of fully programmed standard brackets, maxillary
Table 6.1.Crown prominence in maxillary and mandibular arch
Teeth
st
nd
st
nd
Canine
1 premolar
2 premolar
1 Molar
2 Molar
Maxillary Arch
Central Lateral incisors incisors 2.1mm 1.65mm
2.5mm
2.4mm
2.4mm
2.9mm
2.9mm
Mandibular arch
1.2mm
1.9mm
2.35mm
2.35mm
2.5mm
2.5mm
1.2mm
86
CHAPTER n o i t p i r c s e r P t e k c a r B f o n o i t c e l e S
6
A
B Figure 6.43 . A. Improper tip of central incisors and lack of torque in lateral incisors. To compensate it canine was moved forward leaving poor contact point between canine and premolar. B. A case with good occlusal results and proper contact points due to proper tip, torque, prominence and lack of rotation characteristics.
A
B
Figure 6.44 A. increased curve of spee. If curve of spee is increased or deep, there would be less space for upper incisor. Occlusion would be disturbed both anteriorly and posteriorly. B. Reverse curve of spee. If the curve of spee is decreased or reversed in lower arch than there would be excessive space in the upper arch.
increased at the end of treatment. Clinical implication of Key VI
Nothing is built within bracket prescription to accommodate key VI because it is more related with position of the brackets on the teeth. Accomplishing this key is very important for a good occlusal outcome. Andrew found that nonorthodontic dentition has flat to slight curve of spee and preposition of flat curve of spee was given to accommodate natural tendency of curve of spee to increase with age due to growth of lower jaw and its growth rotation. Banding or
bonding the second molars also help in leveling of curve of spee .Usually leveling 1mm of curve 37 of spee require less than 1mm of space. A description of curve of spee is given in the figure 6.44. Limitations of Andrew prescription Large inventory
In Andrew system to deal with different types of arch discrepancies there are 12 maxillary and 11 mandibular sets, which are combination of five different types of brackets .These are 118
S – Standard Brackets T1 – Minimum Translation Brackets T2 – Medium Translation Brackets T3 – Maximum Translation Brackets T4 – Maxillary Molar tubes or bands for Class II&III Andrew gave such a big inventory to make the treatment more individualized. But unfortunately this became one of the biggest limitations of his prescription. Making so many different types of brackets means that there is need for more machinery, more space, more work force and so more finances needed for the manufacturer. Also when there are so many different types of brackets, more time and education is needed for the orthodontist to get a better understanding for making the right choice in each case. So when there is no Magic formula available, orthodontics will remain only for professional orthodontists. This means loss of valuable clientage for the manufacturers. Unfortunately the problem in orthodontics is that if the orthodontist is customizing treatment
by bracket prescription or by wire bending he is wasting his time but if the manufacturer is customizing brackets it's an innovation and you have to pay for that innovation. For the orthodontist keeping a large inventory at orthodontic office means there is need for mor e financial resources and more office space. This is obviously against the core rules of good office financial management. So unfortunately the very benefit of Andrew prescription to provide individualized treatment to some extent became the most limiting factor of its wide acceptance. Tip and Torque
Both tip and torque values placed in Andrew prescription are slight different from Andrew 2 original findings of normal occlusion . Tip in Andrew Straight wire appliance and actual tip from his study are given in table 6.12. There is overall increased in tip in SWA as compared to Andrew original findings. For change in tip values it is generally presumed that Andrew made the changes to accommodate wagon wheel effects. There are some questi ons in this regard that for the time being have no
Table 6.12
answers. Do we need to accommodate wagon wheel effect in class I incisor torque as it is natural position of the incisors within the arch? If wagon wheel effects occur due to anatomy of area and our treatment mechanics, why not the tip is decreased in the prescription in case of class II incisor torque and increased in case of class III incisor torque? 119
Torque values were also changed by Andrew to some extent than original norms (table 6.13).Overall there is decrease in torque values in SWA as compared to original findings. After going through Andrew work my understanding is that Andrew changed the upper incisor torque values to incorporate finding of his unpublished 100 cases cephalometric study. For example in
S e l e c t i o n o f B r a c k e t P r e s c r i p t i o n
CHAPTER n o i t p i r c s e r P t e k c a r B f o n o i t c e l e S
6
Table 6.13
original Andrew's norms the maxillary central incisor class I torque was 6.11° while the lateral incisor torque was 4.42°.In cephalometric study Andrew found that there is always 4° difference between maxillary central and lateral incisor torque. So I presume that he changed the torque of central to 7° and lateral to 3° to make that study count. Other values were changed either to incorporate clinical experience or to round off values for ease of standardization.
Apart from this, Andrew also didn't take in consideration various factors that affect the expression of tip and torque especially the play of the wire. This is because Andrew advocated full dimension wires at the end of treatment for expression of entire builtin tip and torque. Because of their increased stiffness use of full dimension wires have been abandoned and so the problem started with expression of the prescription. Counter-rotation
Andrew incorporation of counter rotation into the slot was also not appreciated by many. Though effective during space closure but if the orthodontist remain on a heavier wire for long time using effective ligation of wire to consolidate tooth position or torque correction after space closure the teeth having counter rotation brackets will become rotated due to expression of prescription . So Andrew prescription presents a dilemma for clinician in extraction cases. Moving to heavier
wire for better tip and torque expression as Andrew didn't accommodated wire play in his prescription but such wire will cause counter rotation expression. Many clinicians who favors counter rotation in brackets for extraction cases and also have included counter rotation in their own prescription advocate that as relapse is inevitable so the rotation is part of over correction and it will eventually be relapsed during the settling phase. But the practical problem a young orthodontist face today is that he has to display his finished case in exam and complete the settling phase with elastics or wire bending than going on natural settling with retainers. It is difficult to settle teeth into occlusion when they are rotated. Correction of rotation will leave space in the arch and there are many different retainers of modern day such as fix retainers and vacuum formed retainers that don't allow settling to the extent as Hawley retainers do. So orthodontists are left with two choices when using counter rotation brackets at the end of treatment. Replace bracket with standard brackets or resort to wire bending. Limitations in Mechanics
As expression of bracket prescription depend upon what mechanics one uses, many clinicians who later made their own prescription pointed out some mechanics flaws present in Andrew philosophy for case treatment. These were 1) Anchorage loss 120
As tip built into Andrew appliance was more than what Andrew found in his original research so this increased tip put strain on posterior anchorage and also cause anterior anchorage loss at the initial stages of treatment. Anchorage control was also difficult in extraction case. 2) Leveling Curve of Spee
Many clinicians also didn't agree with Andrew philosophy of leveling curve of spee with compensatory curves in wires in maxillary arch and reverse curves in wire in mandibular arch. 3) Roller coaster effects
In early years of SWA class II elastics were used for sliding mechanics. In order to overcome friction heavy forces were used. Increased anterior tip, vertical component of elastics and heavy forces resulted in deepening of anterior bite and opening of lateral bite. This effect was called Roller Coaster Effect (Figure 6.45).
32
of variation between long axis of clinical crown and long axis of the tooth. Placing the bracket just by keeping in mind the long axis of clinical crown will result in poor root parallelism in many cases. Also due to increase tip built into Andrew prescription there are chance of root approximation of teeth especially between maxillary canines and premolars. 5) Bracket Height
Andrew advocated bracket placement at mid of long axis or facial axis of clinical crown also called LA point(long axis point) or FA point(facial axis point). Judging the FA point or LA point on a tooth was a matter of clinical 3, 38 experience. Some clinicians didn't agree with validity of placing bracket at the FA 39, 40 point to get an ideal occlusion while others advocated that there are greater chances of error in placing bracket on FA point and gave fixed distance from incisor edge and suggested using special gauges for bracket placement. Effects of change in height on bracket prescription have been discussed before. Because of these limitations different types of bracket prescription were put forward with time. Whether these new bracket prescriptions solved any practical limitation of Andrew prescription is still debatable but there is a general consensus that they solved the problem of manufacturers and general dentists in the form of “A Single Fairytale Bracket Set for All Types of Malocclusion”. Different Bracket prescriptions
Roller coaster effects and anterior deep bite Figure 6.45 and lateral open bite.
4) Root parallelism
Andrew measured tip values by using long axis or facial axis of clinical crown and not the whole tooth. There is always some degree 121
With time so many clinicians put forward their own prescriptions of brackets .For effective use of these prescriptions many of them also advocated their own treatment mechanics and bracket position on teeth. Even some clinician went to the extent to recommend certain commercial brands of wires for effective
S e l e c t i o n o f B r a c k e t P r e s c r i p t i o n
Table 6.15 Mandibular Arch
Mandibular arch values of different prescriptions
Central incisor
Lateral incisor
Torque° Tip°
Torque°
Tip°
Canine
1 st Premolar
Torque° Tip°
Torque°
Tip°
2 nd Premolar
1 st Molar
Torque°
Torque° Tip°
Tip°
2nd Molar
Offset°
Torque° Tip ° offset
-5
+2
+5
+6
–7
+6
–7
0
–9
0
–10
0
0
0
0
5
Begg
0
0
0
0
0
0
0
0
0
0
0
0
6
0
0
6
Burstone
–1
0
–1
0
– 11
+6
–17
0
–22
0
– 27
0
5
–27
+2
6
Damon
-3
2
-3
+4
+7
+5
-12
+4
+4
-28
+2
2
-10
0
5
Hasund
0
0
0
+5
0
+5
–10
+2
–15
+2
-22
+4
0
– 25
+2
6
Hilgers
–1
0
–1
0
+7
+6
–11
0
–17
0
–25
0
7
–25
0
6
Ricketts® –
0
0
0
0
+7
+5
0
0
0
0
+7
+5
0
0
0
0
0°
0
0
0
0
0
Alexander
-17
(standard torque)
0°
-7 ex -14 nex
0
–22°
–5
12
–27
0
16
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0/6
0
0/6
-7ex 0 nex
IV. Dimension Ricketts® Standard Standard Edgewise Tweed
diminution of force. III. Leveling of curve of spee to some extent by placing anterior brackets more incisal. IV. More torque in anterior brackets to accommodate torque loss by wire play. V. Super torque brackets for rapid correction of torque in class II div2 cases. VI. Roth proposed a new archform called TruArch to be used with his prescription. Roth advocated selection of archwire is important as it effects the rotational position of teeth. Wider the archform more positive torque would be expressed and vice versa. Roth archform was most prominent and wide at mesiobuccal cusp of the first molars. VII. Different translation philosophy. According to Roth tipping of the teeth to some extent is accepted on round wires. 123
VIII. Many auxiliary features were added to
0
brackets such as double and triple tubes, addition of hooks for ease of mechanics. How Roth Made this Prescription? 42
Dr. Andrew in one of his articles commented on origin of Roth prescription. According to Andrew, Dr. Roth found that a high percentage of his cases can be treated by using Andrews' class III incisor torque brackets for maxillary arch and class I incisor torque brackets for mandibular arch. For buccal segment Roth used Series 1-C and Series II-Classic. Where series st 1-C was given in all 1 premolar extraction cases where both maxillary and mandibular canines are given maximum translation series nd brackets and both arches 2 premolars are given minimum translation series brackets while molars are given standard SWA. Series IIClassic brackets were used in case of extraction st nd of maxillary 1 and mandibular 2 premolars because of class II molar relationship. In this series maxillary canines and lower posterior
S e l e c t i o n o f B r a c k e t P r e s c r i p t i o n
CHAPTER n o i t p i r c s e r P t e k c a r B f o n o i t c e l e S
Table 6.16.
Teeth
Roth Prescription
Central incisors
Lateral incisors
1st & 2nd Premolar
Canine
Torque Tip Torque Tip Torque Tip° ° ° ° ° °
Maxillary Arch
+12
Mandibul ar arch
-1
6
+5
+8
+9
-2
+13
1st &2nd Molar
Rotatio Torque Tip Rotation Tip Torq n° ° ° ° ° ue°
2MR
-7
0
2 MR
0
Rotation°
-14 14DR/0° Class II
+2
-1
+2
-11
+7
2 DR
-17 P1&
-1
4DR
-1
-30
4DR
-22 P2
Where MR=Mesial Rotation to counter distal translation. DR= Distal rotation to counter mesial st nd translation. P1 = 1 Premolar P2 =2 Premolar , Class II= Molar Class II in cases where st nd only upper 1 or 2 premolars are extracted .Reference for above Table 3, 40. are given maximum translation series brackets and lower canine and upper posterior are given minimum translation series brackets.
Roth prescription is given in table 6.16. These comments by Andrew about Roth prescription were made in 1976 and in the same 43 year Roth wrote an article about his 5 year practice changing experience with Andrew prescription. Unfortunately he didn't reveal anything about his specific selection of brackets 3 from Andrew's work. It was in 1987, that Roth published his prescription and given justification for it. That prescription is far different from Andrew's comments. The only comment true is about maxillary and mandibular incisor tip and torque. A personal review of literature by this author couldn't find a prescription by name of Roth that matches Andrew's comments. The first published Roth prescription is given in table 6.16.
An evaluation of origin of this prescription is given. Maxillary Arch.
Canines
The maxillary canine tip is taken from minimum translation series brackets made for distal translation. Canine torque was Roth personal calculation of torque to accommodate wire play. Canine counter rotation feature was also taken from Andrew distal translation group in minimum translation series brackets. Premolars st
nd
Both 1 and 2 premolar tip was taken from minimum translation series brackets requiring mesial translation. Premolar torque was taken from Andrew standard SWA. Counter rotation feature was taken from minimum translation series brackets for distal translation. Molars st
nd
Both 1 and 2 maxillary tip was selected from Andrew Class II molar tip. Torque of molars was selected from Andrew medium translation series brackets. Counter rotation values for molars were taken from medium translation series for mesial translation. 124
Controversy
mesial translation.
In maxillary arch both canine and premolars brackets have minimum translation features builtin. If one tooth need to be minimally translated in extraction space in most of the cases than the other tooth need to be maximally translated to close the extraction space. Premolars have counter rotation feature for distal translation. It's a common finding that in most of our cases premolars needed to be translated mesially than distally. Also premolar counter rotation feature don't correlate well nd with molar except in 2 premolar extraction cases where molar need mesial translation and 1st premolar need distal traction.
Controversy
In mandibular arch canine is given minimum translation series counter rotation feature and tip values while molars and premolars have medium translation series values. Second st molar torque was made equal to 1 molar. Giving less torque on second molar increase their chances of coming in cross bite as it's a nd common finding that 2 molars are usually st present slightly buccally as compared to 1 molar in finished cases using Roth prescription. Roth Justification for his prescription 3
The molar tip is meant for class II relationship while offset is meant for class I molar relationship. Mandibular Arch Canines
Canine tip is taken from minimum translation series brackets for mesial translation while torque is taken from Andrew standard SWA. Counter rotation feature for canine is taken from minimum translation series for mesial translation. Premolars
Premolars tip correlate with Andrew medium translation series brackets. Torque values remain similar to standard SWA while counter rotation feature values are from medium translation series for mesial translation. Molars
Molars have tip of medium translation series st for mesial translation. 1 mandibular molar torque remain same as that of standard SWA nd st while 2 molar torque was made equal to 1 molar. Counter rotation feature were also taken from medium translation series brackets for 125
Roth while giving his prescription gave some justification for the specific selection. Maxillary Arch
Roth3 justified his prescription by explaining that 5° extra torque was added to maxillary incisors keeping is line with his treatment p h i l o s o p h y o f o v e r c o r r e c t i o n a n d accommodating torque loss by wire play. So without moving to full dimension wires the clinician can attain natural inclination of incisors. For canines, Roth used -2° torque which was 5° less than Andrew prescription. This was done to avoid reactionary effect of building more positive torque into the incisors brackets. This is explained in the figure 6.46. The final torque of canine would be -7° due to reactionary forces from the wire and because of wire play. If no wire play is present the final torque of the canine would be -2°. Also canine tip was increased by +2° to accommodate tip loss in extraction cases as distal translation of canine take place and it is also helpful to get better canine guidance. Canines was also given 2° rotation to mesial so that when it is translated distal, mesial builtin rotation compensate the effect of distal
S e l e c t i o n o f B r a c k e t P r e s c r i p t i o n
CHAPTER n o i t p i r c s e r P t e k c a r B f o n o i t c e l e S
6
A
B
C
Figure 6.46 A .A rectangular wire passed through maxillary incisors and canine brackets. The slots opening of the maxillary incisors is facing downward causing the wire to rotate clockwise on exiting the lateral incisor bracket. This clockwise rotated wire when passes through canine bracket whose slot o pening is facing upward will cause the canine bracket to rotate clockwise while canine bracket slot will cause the wire and so the incisor brackets to rotate counterclockwise. So positive torque would be expressed on incisors and negative torque would be expressed on canine. If the incisors have more positive torque, than reactionary forces of wire leaving from incisors will cause more negative torque on canine. This only happen when wire play is present. If no wire play is present all the torque built within the bracket would be expressed. B. Wire exiting lateral incisor in a clockwise fashion. C. Wire engaging canine bracket clockwise at an angle thus negative torque expression in canine.
rotation that occur during distal translation of canine. Premolar torque was kept the same while the tip was decreased. Though there was no justification given for using minimum translation angulation in both premolars nor does there is any logical basis of decreasing tip after giving 2° mesial offset for counter rotation. This decreased tip can accommodate increased tip on canine but the roots of these teeth come close to each other at end of treatment. Also 2° mesial rotation was added to premolar brackets. The justification was that this was done to counter the of effect distal traction of these teeth. As Roth favored headgears in his mechanotherapy this addition seems logical. st
nd
On 1 and 2 molars buccal root torque was increased from -9° to -14°.The increased torque
A
B According to Roth -14° torque should be Figure 6.47 given to maxillary molar to counter the effect of palatal cusp hanging during translation. A. Palatal cusp hanging in maxillary molar after translation. B. No cusp hanging.
126
R E T P A H C
7
Placement of orthodontic brackets In this Chapter
Mesiodistal position of brackets Checking mesiodistal position of the brackets Modifications in mesiodistal position of the bracket Axial or long axis position of the brackets
Importance of vertical position of brackets Bracket positioning gauges Parts of gauges Position of the gauge during bracket placement
Importance of axial position of brackets
Bracket placement by wire guidance
Checking axial position of brackets
Position of clinician during brackets placement
Modifications in axial position of brackets Vertical position of brackets Modifications in Vertical position of the brackets
Prescriptions in preadjusted edgewise brackets are built after taking prescription values from a certain point or area on labial surface of the tooth. The prescription built into the bracket will work best if the brackets are placed at that specific area. Mostly that specific area where the brackets needed to be placed is also pinpointed by the inventor of the prescription. During orthodontic bonding of preadjusted brackets the orthodontist must place brackets accurately in vertical, mesiodistal and axial planes as advocated for that prescription or based on his clinical experience. These 153
accurately placed brackets will give better control on three dimension position of the teeth during treatment. An accurately placed bracket will also result in better expression of its builtin prescription and orthodontist will need less wire bending and complex mechanics during the course of treatment. Mesiodistal position of brackets
It is a general saying in orthodontics that brackets should be placed at mesiodistal center of the teeth. This statement is partially correct as this rule can't be applied to all the teeth. A more
CHAPTER
s t e k c a r b c i t n o d o h t r o f o t n e m e c a l P
7
clear description for right mesiodistal position 1 of brackets was given by Andrew that brackets should ideally be placed at the mid developmental ridge of the teeth. The correct mesiodistal position of brackets on different teeth is given as under. Maxillary and mandibular incisors Bracket should ideally be placed at mesiodistal center of maxillary and mandibular incisors. The mid developmental ridge of these teeth is also present at their mesiodistal center of the labial surface (Figure 7.1).
Figure 7.2 The vertical lines on maxillary and mandibular canines indicate the mid developmental ridge of the canines and ideally the middle of the brackets should coincide with this line.
Mandibular Premolars 2
Vertical lines showing mesiodistal center of Figure 7.1 the upper and lower incisors. Brackets should be placed at the recommended height on this line.
Maxillary and mandibular Canines
Placing brackets at the mesiodistal center of the canines will result in contact point error and slight rotation of the teeth as the mid developmental ridge of upper and lower canines lies slightly mesial to the mesiodistal center of the teeth and is more mesial in case of lower canines. So bracket is placed slightly off center and toward mesial, in case of canines (Figure 7.2).
Roth purposed that premolars brackets should be placed at area of maximum convexity which is usually the mesiodistal center of the teeth and mid developmental ridge also lies in this area. Sometimes the area of maximum convexity lies slightly mesial to the mesiodistal center but degree of mesial deviation is less than that of canines. The difference between bracket placement on premolars and anterior teeth is presence of a lingual cusp on premolars which must be taken into consideration while placing the brackets. In mandibular premolars the buccal and lingual cusps lies at the same level in the mesiodistal perspective. So when placing lower premolars brackets the scribe line of the bracket should coincide with line connecting the buccal and lingual cusps (Figure 7.3). 154
R E T P A H C
8
Bonding in Orthodontics In this Chapter
Tooth Cleaning Enamel Roughening or acid Etching Sealing the etched enamel surface Bonding Bonding in special circumstances Indirect bonding
Historically orthodontic brackets were soldered to bands and eventually banded to teeth. As bands need space between the contact points at time of their placement and leave spaces between teeth at end of treatment so they were not a preferred method. With the introduction of acid etching by 1 Buonocore in 1955 banding of teeth was eventually abandoned with time and is now only used on molars in cases requiring special mechanics like headgears. Extensive details about bonding are given in almost all the text books of orthodontics so only a brief review on this topic would be given here. Bonding of brackets can be done either directly or indirectly. Steps in direct bonding of bracket are given. 1. Tooth cleaning 189
2. Enamel roughening of labial or lingual surface of tooth by acid etching 3. Sealing of etched surface 4. Bonding 1) Tooth Cleaning
This step is only done in patients in whom there is plaque or thick pellicle layer over the enamel surface at the time of bonding. If only pellicle is present then pumicing of teeth alone is sufficient but if plaque or calculus is also present over the enamel surface then scaling is done which is followed by pumicing (Figure 8.1).
CHAPTER
8
s c i t n o d o h t r O n i g n i d n o B
Pumicing teeth with a polishing paste and Figure 8.1 pumice powder.
A
Clinical Notes 2-4
Pumicing before etching is controversial if conventional etching is done but clinician 5-7 should do pumicing if self-etching primer is used. 2) Enamel Roughening or acid Etching
Enamel roughening or acid etching is done to create retention areas for the adhesive on the enamel surface. Moisture control is important during this step and rest of the steps that follows. Good moisture control is provided by using cheek/lip retractors and high volume section. This arrangement of moisture control is usually sufficient in majority of the cases but in some cases where patients have increased salivary flow, special gadgets are available that combine lip/ cheek retractors, saliva ejectors and tongue guards (Figure 8.2). Cotton rolls are also used to increase moisture control. Some clinician also uses antisialogogue like atropine sulphate to create a dry field for brackets bonding. Antisialogogues can be used on patients having excessive salivary 8 flow but evidence doesn't support their routine use during orthodontic bonding. Before going for enamel conditioning enamel surface should be dried with oil free air. Enamel conditioning is conventionally
B A Nola dry field system combining all the Figure 8.2 necessary gadgets for good moisture control during enamel conditioning. This system is especially helpful in indirect bonding.
done with 35 - 37% phosphoric acid. Enamel roughening by sandblasting has also been proposed but sandblasted enamel yield lower 9-13 bond strength than acid etched enamel. Sandblasting first followed by conventional etching have also been proposed but bond strength of brackets with this combination 14, 15 technique is controversial than doing conventional acid etching alone. Lasers have 16-19 also been advocated for enamel etching 20 either alone or in combination with acid etching. But due to high cost of lasers and more safer application of conventional etching the use of laser for enamel roughing is still a novel approach in orthodontics. In enamel etching with 37% phosphoric acid the acid is available in both liquid and gel form. The liquid form of the acid has 190
10
R E T P A H C
Adhesive Remnants Removal In this Chapter
Hand instrumentation for adhesive removal Adhesive removing pliers Ligature wire cutters Hand Scalers
Discs Finishing and polishing auxiliaries Ultrasonic scalers Sandblasting or air abrasion Adhesive remnants removal by Lasers
Rotatory instruments Burs Carbide burs Diamond burs Steel burs Brown and green stones Composite burs
After orthodontic brackets removal, adhesive remnants needed to be removed from the tooth so that enamel can be returned to its pretreatment condition. These residual adhesive if remained attached to the teeth will be a potential plaque retentive area and may get discolored with time. The amount of these adhesive remnants depends upon the type of bond failure. If bond failure during debonding occurs at bracket adhesive interference, more adhesive needed to be removed as compared to a bond failure at enamel adhesive interference (Figure 10.1). 239
Removal of these adhesive remnants should be done without causing any damage to enamel.
Adhesive remnants on the tooth after Figure 10.1 debonding. Bond failure occur at the bracket adhesive interference. Such bond failure require more time to clean adhesive from the tooth enamel.
R E T P A H C
11
Recycling of orthodontic brackets In this Chapter
Introduction
Chemical Method
Recycling of orthodontic brackets
Sandblasting
Ultrasonic Cleaning
Laser Recycling
Electropolishing Adhesion Enhancement Silane coupling Agents Adhesion Boosters Rotatory instruments Flame Method Buchman modiifed flame method Modified Buchman method ,The Acid Bath Limitations of flame method Lew and Djeng Method
255
Introduction
these circumstances are as follow.
Recycling or reconditioning are different terms used for reusing orthodontic brackets which were once bonded in clinical practice and were latter debonded accidently by the patient or intentionally by the clinician. 5% to 7% of brackets bonded with light cured or chemical1, 2 cured composite resins debond in clinical practice under different circumstances. Some of
1. Bracket debonded by patients
This usually occurs while masticating hard food, aggressive tooth brushing or by traumatic forces especially in children while playing sports. Some externally motivated patients also intentionally debond the brackets to show their unwillingness towards treatment.
A Abfraction, 229 Access bevel, 82 Accessary slots, 61,65,77,79 Accessory tube, 82 Acetone, 222,264 Active ligatures, 134,235 Active self ligating brackets,72,73,264 Adhesion boosters, 255,260,261,273 Adhesion enhancement, 255,257,260
Bracket identification marks ,58,80
CP titanium,28-30
Bracket prominence,63,86,87,113,
Cracked teeth ,209
Bracket removing plier ,210,215,249
Crown Angulation ,92-94
Bracket sitting area,171
Crown inclination,99
Bracket stem,18,100,208,212,259,
Crown morphology,136,161
Brazing,13-21,38,42,209,260,
Crown remover,226
Bristle brush,240,249
Curve of Spee,117, 118,121,123,129, 132,
Broussard bracket,8
165,166, 173
Brown and green stones,243,246
D
Brown part,16 Buccal groove,88,93,97,127,128,133 Bunsen flame,262
Debonding plier,205,206,208,210-230
Adhesive precoated brackets,193,196
Debracketing, 203
Adhesive remnants,210,261,265,268
C
Adhesive removing plier 203,214,240 AISI 21,24,25
Deligation saddle,82 Dentinogenesis imperfect,194,209, 226, 256
Differential anchorage ,6,10
All Bond 2, 261
Calcium phosphate ceramics,36-38
All Bond 3, 261
Canine tie backs ,134
Alumina Brackets,36
Carbide burs,195,227,243-253
Amelogenesis imperfect,229
Casting,14,,15,18,23,27,43,47,51.260
Andrew plane,165
Central fossa,84
Antirotation,98,116
Ceramic injection molding ,18,36
Antisialagogues,190
Ceramic reinforced plastic,216,217
Aperture diameter,45,46
Chamfered slot walls,70,72
ASTM,27
Chemical Retention ,50-57,218,220
Attrition,33,34,160,161,178,229
Chromium oxide,22,26,28,
Austenitic stainless steel,24,25,32,263
Chromophores,231
Auxiliary features,77,123,
CO2 laser 234,235,252,270
Auxiliary procedures,257
Cobalt Chromium Brackets,27,50,259
Auxiliary spring ,6,65,67,
Cold working,20,23
E arch,3,4
Axial position,114,160,161,184,194
Collapsible base ,219,220,222
Edge bevel,107,108
Composite burs , 243,246,247
Edgewise appliance,7,13,64,104
Composite plastic brackets ,32,216
Elastic ligatures,72,82
Composite resin ,56,194,223,227,241
Elastic modules tie backs,132,134
Compound contoured base,57,59,104
Electrolytic solution ,259
Computer numerated milling ,16
Electromagnetic spectrum,230,231, 233, 234
Connectors,94,160,161,164
Electropolishing
Contact angle ,30,46,66,69,102
Electrothermal debonder , 229
Contact po ints,117,118,189,256
Embrasure,91,92,94,155,160,161,164
Contact sports,256
Embrasure line,85-90
Continuous mode ,234
Enhance polisher,249
Convenience features ,79-82
Er,Cr:YSGG lasers ,270
Corrosion resistance,17,19,21,24-
Er:YAGlasers,195,233,252,270,271
28,111,260
Erosion ,229
Counter buccolingual tip,102
Esmadent,259,271,272
Counter rotation ,116,117, 120,122 ,124-
Ethanol ,53,222
126,130,131,157
Excimer lasers ,232,233
B Band removing plier ,214,241 Bandeau appliance,1,2,3 Base method, 19,203,205,207.209,257 Begg appliance,5,6,61,172 Big Jane machine,272 Bis GMA ,227,228,235,260 Black triangle,94,161,162,164 Bleaching ,195 Bonding base shape ,57 Bracket base surface area,56,57,59,266 Bracket identification
(I)
Direct bonding ,169,171,189,256 Distal offset ,88-90,134,137 Distal translation ,95,96,117,124-126 Double mesh base,42,44,269 Dougherty gauges,181 Duplex stainless steel,26 Dust confinement chamber,266 Duplex stainless steel,26 Dust confinement chamber,266
E
F
L
Microetched bases,42 Microleakage,192 Microretention,47,48,195,240 Mid-developmental ridge,92,93,154,156,158,165
FA point,58,121,165,171,
LA point,121,165
FACC,92,93,97,99,105,165
LACC,92,93,99,105,159,165
Facial point ,85-87
Laminated mesh base,42
Facial prominence ,85,86,88,90
Lang brackets,8
FDA,257
Laser structured bases,48,50,54,267,268
Feedstock,16
LED curing light,192,195,199
Ferritic stainless steel,25
Lewis brackets,7,8
Fiber reinforced ,246,247
Lift off debonding plier,199,212,213
Filling adhesive ,194
Ligature cutter,82,210,211,221,242
First order bend,61,62,163
Light wire appliance,6,9,10,172
Flame gun ,229,262,264
Line pressure,47,197,260,263,266-269
Flame method ,19,48,50,70,257,258, 262-
Lingual brackets,10,111,214,215
265,270,273
Long axis position,93,158,160,161,184
Flamepyrolytic method,260
Luting adhesive,50,53,194
Milling,14-18,20,21,37,47,194 Mini mesh base,42 Minimum Translation series,95,96,102,123-125
Flash ,22,168,193,196,218,222-227,
Moisture insensitive primer,192 Molar offset,88,90-93,98,127 Moment arm,66,69 Monobond plus,261 Monocrystalline brackets,35,37,38,55, 232,233,235,265
N Nd:YAG,35,48,233,252 Nickel allergy,19,20,22,28,30,31,33
242,266
M
Foil mesh base ,42,43,47
Non vital teeth,220,221 Notching,205,223
Free play,107 Frequency,224,231,251,271
Magnetostrictive scaler,224,240
Friction resistance,16-18,27,29,31,32,
Manufacturer tolerance,99,108
37,70-73
Marginal ridges,166-173
Gated pulse mode ,234
Martensitic stainless steel,25,26
Gauze or woven mesh base,42,43,46, 50
Maximum translation series,95,96,102,123,124
Gingival hyperplasia,77,209
Meccaca Monkey,228
Gold plated carbide bur,261
Mechanical Retention,42,46-48,50-
Green part ,16
52,54,55,218
Hand scaler,240,243
Mechanotherapy,107,109,126,130
Hard tissue lasers,231
Medium translation,95,96,102,119,124,125,137
Headgear tube,82
Mesh diameter,44,45
HEMA,227,228
Mesh gauge,44
Horizontal slot,5,10,65,80
Mesh number,44-46,50,267
Howe plier,208,212
Mesh type bases,48,50
Hybrid copolymer,32
Mesial offset,90,122,126
Hydrofluoric acid,195
Mesial translation,95,96,124,125
Implants,28,34,161,162
Mesiobuccal cusp,84,88,91,92,97,98,123,127,156
Impulse debonding,205,226,227
Mesiobuccal groove,88,91,92
brackets,10,72,73,109,264
In and out bends,8,9
Mesiodens,161,162
Pellicle,189
Indirect bonding,169,190,195,198,256
Mesiodistal Crown tip,92
Peppermint oil,222
Integral bases,47
Mesiodistal position,153,154,156,157,183-186,194
Perforated bases,42,43
Interarch relationship,84
Mesiolingual cusp,84,91,92,127
Phosphoric acid,190,195,240
Isopropyl alcohol,264
Metal injection molding,14-18,27,47
Photoablation,232,235
Kinetic energy,227
Metal sintered bases,48
Photoetched bases,42,47
Kobayashi hook,78
Metallic luster,263
Photon,231
KrF Lasers,270
Micro mesh base,42
Piezoelectric scaler,224,240
(II)
O Occlusal plane,92,93,9799,105,106,112,117,127,129,133,135, 136,162,166,182 Open area percentage,46,47 Optimesh base,42 Ormesh base,42 Ortho bonding,271,272 Ortho Solo,261 Orthotronics,271,272
P Passive self ligating