V4- PLANETS OF ORTHODONTICS- Orthodontic Appliances.pdf

PLANETS OF
ORTHODONTICS
Authors
Dr. Mohammed Almuzian
Specialist Orthodontist (UK)
BDS Hons (UoM), MDS Ortho. (Distinction), MSc.HCA (USA), Doctorate Clin.Dent. Ortho. (Glasgow), Cert.SR
Health (Portsmouth), PGCert.Med.Ed (Dundee), MFDRCSIre., MOrth.RCSEd., FDSRCSEd., MRACDS.Ortho. (Aus-
Dr. Haris Khan
Consultant Orthodontist (Pakistan)
Professor in Orthodontics (CMH Lahore Medical College)
BDS (Pakistan), FCPS Orthodontics (Pakistan), FFDRCS Ortho. (Ire.)
Dr. Ali Raza Jaffery
Specialist Orthodontist(Pakistan)
Associate Professor Orthodontics (Akhtar Saeed Medical and Dental College)
BDS (Pakistan), FCPS Orthodontics (Pakistan), MOrth.RCS (Edin.)
Dr. Farooq Ahmed
Consultant Orthodontist (UK)
BDS. Hons. (Manc.), MDPH (Manc.), MSc (Manc.), MFDS (RCS Ed.), PGCAP, MOrth.RCS (Eng.), FDSRCS
Ortho. (Eng.), FHEA
Volume IV
Orthodontic Appliances
With

Acknowledgments
This book is the sum and distillate of work which would not have been possible without the support of our fam-
ilies and friends.
Additionally, we would like to thank the rest of contributors of this volume for their time and expertise in updat-
ing individual chapters.
Dedication
I would like to dedicate this book to my mother, Muneba, who was my biggest supporter throughout my
life.
She put me on the path to success and I am forever grateful to her.
Dr M. Almuzian

Contributors
Dr. Samer Mheissen/ Specialist Orthodontist (Syria)
Dr. Mark Wertheimer/ Consultant Orthodontist (South Africa)
Dr. Mushriq Abid/ Specialist Orthodontist and Professor in Orthodontics (Iraq/ UK)
Dr. Emad E Alzoubi/ Specialist Orthodontist and Lecturer in Orthodontics (Malta)
Dr. Ahmed M. A. Mohamed/ / Specialist Orthodontist (UK/KSA)
Dr. Abu Bker Reda/ Specialist Orthodontist (Egypt)
Dr. Dalia El-Bokle/ Specialist Orthodontist (Egypt)
Dr Lubna Almuzian/ Specialist Paediatric Dentist (UK)
Dr. Muhammad Qasim Saeed / Specialist Orthodontist and Professor in Orthodontics (Pakistan)
Dr. Asma Rafi Chaudhry / Assistant Professor in Orthodontics (Pakistan)
Dr. Taimoor Khan / Specialist Orthodontist (Pakistan)
Dr. Maham Munir / Postgraduate Trainee in Orthodontics (Pakistan)
Dr. Eesha Najam / Postgraduate Trainee in Orthodontics (Pakistan)
Dr. Farhana Umer / Postgraduate Trainee in Orthodontics (Pakistan)

Copyrights
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 Dr Mohammed Almuzian and Dr Haris Khan who have the exclusive copyright, except in
the case of brief quotations embodied in critical reviews and certain other non-commercial uses permitted by
copyright law.
For permission requests, contact them at info@orthodonticacademy.co.uk
ISBN: 9798430760410

Preface
Questions expose our uncertainty, and uncertainty has been our motive. The authors and contributors have ag-
gregated this book, and the series of books to follow, in answer to questions covering the breadth and depths of
orthodontics.
This volume describes briefly the most common orthodontic appliances and their applications in orthodontics.
The theme of this chapter is Mercury as it has been known for a long time because it is visible to the naked eye.
The writing of the book started with the amalgamation of orthodontic notes and the experience of the main two
authors, Dr Mohammed Almuzian and Dr Haris Khan, it organically grew with input from other authors who
helped in proofreading, summarising the key points of each chapter, and implementing the ‘exam night review’
section. There have been numerous contributors to this book, we seek to acknowledge them, as, without each
contributors efforts, this book would have been nothing more than an interesting idea and a ‘what if’.

Table of Contents
FIXED APPLIANCES IN ORTHODONTICS......... 1
History of orthodontic appliances ...................................... 2
Types of fixed appliances ...................................................... 2
Components of fixed appliances........................................... 2
Classification of the bracket system ..................................... 2
Metal Brackets....................................................................... 3
Stainless steel brackets .......................................................... 3
Titanium brackets................................................................. 4
Cobalt chromium.................................................................. 4
Types of the bracket base....................................................... 4
Bracket base surface area...................................................... 4
Orthodontic brackets recycling............................................ 4
Bracket configurations.......................................................... 5
Bracket prescriptions............................................................ 5
Begg appliance....................................................................... 5
Tip-Edge’ system.................................................................... 6
Self-ligating (SL) appliances.................................................. 6
Factors that have hindered the adoption of self-ligation..... 6
Commonly used SL system................................................... 6
Claimed advantages of SLB .................................................. 6
Disadvantages of SLB ........................................................... 7
Fully-customised brackets..................................................... 7
Aesthetic Brackets ................................................................ 7
Plastic brackets...................................................................... 7
Ceramic brackets................................................................... 7
Disadvantages of ceramic brackets....................................... 8
Types of ceramic brackets..................................................... 8
Polycrystalline brackets......................................................... 8
Monocrystalline brackets...................................................... 8
Table 4: Problems with ceramic brackets.............................. 9
EXAM NIGHT REVIEW...................................................... 10
BEGG ORTHODONTIC MECHANICS................ 13
Begg philosophy.................................................................... 14
Indication of Begg appliance ................................................ 14
Features of Begg appliance.................................................... 14
Begg appliance therapy’s stages and their objectives............ 15
EXAM NIGHT REVIEW ...................................................... 15
REMOVABLE ORTHODONTIC APPLIANCES.... 17
Indications of RAs (Reay and Stephens, 1993)..................... 18
Wires used to construct RAs ................................................ 18
Components of RAs.............................................................. 19
Anchorage component of RAs.............................................. 20
Baseplate................................................................................ 20
Designing RAs....................................................................... 20
Mode of action of RAs........................................................... 21
Checklist while fitting a new RA........................................... 21
Overview Of Clear Aligner Appliances................... 25
General indications of CAT.................................................. 26
General limitations of CAT................................................... 26
Claimed advantages of CAT.................................................. 26
Disadvantages of CAT........................................................... 27
Extraoral appliances ................................................ 31
Classification of Headgear.................................................... 32
Components of the headgear................................................ 32
Types of maxillary retraction headgear................................ 32
Clinical uses of retraction headgear..................................... 32
Factors influencing the effects of the maxillary
retraction headgear............................................................... 33
Fitting of the maxillary retraction headgear........................ 33
Problems and limitations of maxillary retraction
headgear................................................................................. 33
Classification of headgear injury.......................................... 34
Chin cup................................................................................ 34
REVERSE-PULL PROTRACTION FACEMASK
(PFM)..................................................................... 38
Components of PFM............................................................. 39
Types of PFM......................................................................... 39
Indications of PFM................................................................ 39
Effects of PFM........................................................................ 39
Treatment timing for PFM.................................................... 40
Factors influencing the effect of PFM................................... 40
Side effects of PFM therapy .................................................. 41

Predictors of failure of PFM therapy.................................... 41
Skeletal anchorage for maxillary protraction ...................... 41
Instructions to patients wearing PFM ................................. 41
Evidence summary regarding PFM...................................... 42
AUXILIARYARCHES............................................. 45
The Nance appliance.............................................................. 46
The lower lingual arch........................................................... 46
Clinical steps ......................................................................... 46
Indications for transpalatal, Nance and lingual arches........ 46
Applications in vertical direction such as:............................ 47
Common complications........................................................ 47
MOLAR DISTALIZATION APPLIANCES .......... 53
Indications............................................................................. 54
Limitations and contraindications....................................... 54
Decision making.................................................................... 54
Clinical Considerations........................................................ 54
Molar distalization techniques.............................................. 54
Molar distalization techniques.............................................. 58
FINISHING PHASE IN ORTHODONTICS ........ 61
Managing tooth-size discrepancies (TSD) during the
finishing phase ..................................................................... 62
Obtaining an ideal gingival level during the
finishing phase ...................................................................... 62
Assessing the gingival form during the finishing
phase ..................................................................................... 62
Assessing the first order bend during the finishing
phase...................................................................................... 62
Errors in second-order bend during the finishing
phase .................................................................................... 63
Errors in third-order bend during the finishing
phase .................................................................................... 63
Assessing root angulation during the finishing
phase..................................................................................... 63
Control of rebound and posturing during the finishing
phase...................................................................................... 63
Settling of the teeth during the finishing phase.................... 63
EXAM NIGHT REVIEW ...................................................... 63
RETENTION AND STABILITY .......................... 65
Principles of retention........................................................... 66
Factors related to retention................................................... 66
Retention requirements........................................................ 67
Types of orthodontic retainers ............................................. 68
B. Fixed retainers .................................................................. 69
Bonded retainer placement................................................... 70
Retention duration and regimen.......................................... 71
Evidence summary ............................................................... 71
FUNCTIONAL APPLIANCES ................................ 76
History of Functional Appliances......................................... 77
Theories on how functional appliances work....................... 77
Functional appliances and airway......................................... 77
Skeletal modifications by functional appliances.................. 77
Summary of evidence for the effect of functional
appliances.............................................................................. 78
Soft tissue effects of the functional appliance ..................... 78
Indications of a functional appliance ................................... 78
Classification of functional appliances................................. 78
Advantages of removable functional appliances.................. 79
Problems with functional appliances.................................... 79
Class II functional and orthopedic appliances..................... 79
Twin block therapy................................................................ 79
Advantages associated with the twin block ......................... 80
Short-term effects of twin block............................................ 80
Activators appliances............................................................. 80
Activators combined with headgear..................................... 80
Bass appliance........................................................................ 80
Medium opening activator.................................................... 81
Dynamax appliance............................................................... 81
Frankel appliance .................................................................. 81
Herbst Appliance................................................................... 81
Jasper Jumper appliance........................................................ 81
MARA (Mandibular anterior repositioning appliance) ...... 81
Sabbagh universal spring (SUS): .......................................... 82
Twin force bite corrector....................................................... 82
Forsus fatigue resistant device (FRD)................................... 82
Class III correction appliances.............................................. 82
Factors affecting the choice of functional appliances ......... 82
Recommended wear time of removable functional

appliances............................................................................. 83
Timing of intervention using functional appliance therapy
83
Success rates of functional appliances ................................. 83
Stability of treatment secondary to functional appliance
therapy.................................................................................. 83
Early versus late treatment ................................................... 83
Use of functionals in the UK................................................. 84

1
1. History of fixed appliances
2. Types of fixed appliances
3. Components of fixed appliances
4. Classification of the bracket system
5. Bracket base surface area
6. Bracket configurations
7. Standard edgewise and straight wire
8. Bracket prescriptions
9. Begg appliance
10. Tip-Edge’ system
11. Self-ligating (SL) appliances
12. Fully-customised brackets
13. Aesthetic brackets
14. Lingual brackets
15. Problems with ceramic brackets
16. Exam night review
In this chapter
FIXED
APPLIANCES IN
ORTHODONTICS
Written by: Mohammed Almuzian, Haris Khan and Dalia El-
Bokle

fixed appliance in orthodontics
2
Fixed orthodontic appliances are temporarily attached
to the teeth during orthodontic treatment and cannot be
removed by the patient. Fixed appliances apply forces to the
teeth or skeletal structures by interaction with the orthodon-
tic wires and/or auxiliaries.
History of orthodontic appliances
The origin of orthodontic brackets (fixed appliances) can be
matched with the birth of orthodontics and the human de-
sire to align crooked teeth. The first written record correct-
ing crowded or protruded teeth was found 3000 years ago.
Orthodontic appliances to correct malaligned teeth have
been found in Greek, Etruscan and Egyptian artefacts. These
range from crude metal wire loops to metal bands wrapped
around individual teeth in ancient Egyptian mummies.
Pliny the Elder (23-79 AD) was the first to align elongated
teeth mechanically. Pierre Fauchard (1678 –1761), a French
dentist, was the first to make a scientific attempt to align
irregular teeth by an appliance named Bandeau. Edward
Angle introduced a series of fixed appliances like E arch,
Pin and tube appliance, Ribbon arch, and eventually the
Edgewise appliance in 1928 (Angle, 1928). Raymond Begg,
a student of Angle, introduced the Begg appliance in the
1950s. A Straight wire appliance was then introduced by
Larry Andrew (Andrews, 1972). Ronald Roth (1933-2005)
refined Andrew’s straight wire appliance (SWA) in 1976 by
combining extraction and non-extraction series of brackets
to make what is called the “Roth setup.”
The MBT prescription was introduced by Richard McLaugh-
lin, John Bennett and Hugo Trevisi in 1997. The ‘Tip-Edge’
appliance was developed by Peter Kesling (Kesling, 1988)
while the lingual appliance was designed by Kurz in the
1970s (Proffit et al., 2012).
In terms of fixed functional appliances (Herbst appliance)
was first introduced in 1905 (Herbst, 1934) and reintro-
duced in 1979 by Pancherz (Pancherz, 1979). Jasper Jumper
was introduced by James Jasper in 1987.
Table 1 compares removable and fixed orthodontic appli-
ances.
Types of fixed appliances
Fixed appliances can be buccal or lingual. The advantages
and disadvantages of each system are listed in table 2.
Ideal properties of brackets
These include:
• Biocompatible
• Aesthetically pleasing
• Cost-effective
• High modulus of elasticity
• High corrosion resistance
• No magnetic properties
• No friction on bracket/wire interaction
• Correct strength and hardness.
• Resist staining and discoloration in the oral environ-
ment
• Resist plaque accumulation
Table 1: Comparison of fixed and removable appliances
Removable appliances Fixed appliances
Can only produce simple
type of tooth movements
like tipping.
All types of tooth move-
ment in three dimensions
can be achieved.
Root movements cannot be
controlled.
Root movements can be
controlled.
Greater patient compliance
is required.
Less patient compliance is
required.
Oral hygiene is easy to
maintain as the appliance
is removed at the time of
brushing and eating.
Difficult to maintain oral
hygiene.
Good intrinsic anchorage Poor intrinsic anchorage
Low cost Reasonably high cost
Components of fixed appliances
Bracket
Brackets are one of the main components of fixed orth-
odontic appliances that are attached to the crown of teeth,
through which forces are mediated to the teeth by archwires
and auxiliaries to achieve tooth movement.
The most commonly used labial brackets are preadjusted
Edgewise appliances. Customised brackets are primarily
used in lingual bracket system, such as Incognito, but non-
customised brackets like ALIAS by Ormco are also available.
Classification of the bracket system
1. On the basis of material type such as:
• Metal
• Plastic
• Ceramic
• Zirconium
2. On the basis of morphology such as:

fixed appliances in orthodontics 3
Table 2: The advantages and disadvantages of fixed appliance system.
Buccal fixed appliances
Advantages Disadvantages
• Easy access and work for the clinician.
• Reduced chair-side time.
• Excellent finishing and detailing.
• Poor aesthetics.
• Increased chances of visible decalcification.
Lingual fixed appliances
• Good aesthetics (Wiechmann D Nes-
bit L 2007, Russell, 2005).
• Less visible decalcification (Wiech-
mann D Nesbit L 2007, Russell, 2005).
• Upper lingual brackets act as bite
blocks and help in opening the bite
(Singh and Cox, 2011).
• Arch expansion is easier with lingual
appliances.
• Impact on speech
• Difficult to maintain good oral hygiene (Khattab et al., 2013).
• Difficult access for the orthodontist.
• Increased working time.
• Possible soft tissue trauma.
• Short inter-bracket span leading to high force.
• Customised appliances are needed, hence, they are more costly.
• Difficulty in finishing and detailing (Singh and Cox, 2011).
• Mostly do not work well with orthognathic surgical cases.
• Needs indirect bonding.
• Siamese.
• Mini-twin.
• Single-wing e.g., Attract.
• Self-ligating e.g., Damon, In-ovation R, Smartclip.
• Tip-edge.
3. Based on slot size such as:
• 0.018” x 0.028”
• 0.022” x 0.028”
• 0.022” x 0.030”
4. On the basis of method of manufacturing (Matasa,
1992) such as:
• Cast (soft) - may distort on debonding or in deep
bite cases.
• Milled (hard).
• Metal injection moulded (MIM).
• Sintered.
Metal Brackets
These include:
• Stainless steel brackets
• Titanium brackets
• Cobalt chromium brackets
• Precious metal brackets
Stainless steel brackets
Different stainless steel (SS) based orthodontic brackets are
used in contemporary orthodontics including:
1. Austenitic stainless-steel (300 series) is one of the most
popular types of SS alloy used in orthodontics as a bracket
and wire material due to its good corrosion resistance,
excellent formability and low cost compared to other types
of SS. The standard orthodontic twin brackets are usually
manufactured from austenitic type 302, 303SE ,303L ,304
,304L,316 ,316L and 318 with 304 L and 316 L are the mostly
used materials. The L designation refers to lower carbon
contents of steel. The lower carbon contents in SS eliminate
harmful carbide precipitation, thus, decreasing corrosion
susceptibility, but low carbon steel decreases strength. 316
SS and 316-L SS are used where higher corrosion resistance,
especially to chloride, is required. 316 SS is used more
commonly for making base components and, because of
increased corrosion resistance, has been shown to release
less nickel. Austenitic SS is given an AISI number (American

4
Iron and Steel Institute). Low numbers have little additional
alloy metal and are soft in nature. Most brackets are AISI
304 milled, having the following composition, Fe 71%, Ni
8%, Cr 18%, C<0.2%. Some brackets are also made from
AISI 316. These brackets are casted as AISI 316 as it is too
hard to be milled. The main disadvantage of SS is the poten-
tial to cause a nickel allergy (BOS 2012).
2. Super austenitic SS: Super SS is defined as SS with a pit-
ting resistance equivalent value of 40. Super-SS has higher
molybdenum and nitrogen content than conventional SS.
Super SS show good frictional properties, higher resistance
to chloride pitting and crevice corrosion. Super SS has only
been used for in-vitro studies.
3. Precipitation-hardening (PH) martensitic SS (17-4 PH
or S17400): This form of SS has corrosion resistance equal
to austenitic stainless 304 but has better strength than the
latter. 17-4 PH or S17400 precipitation– hardening alloy
type has lower nickel content but poor localised corrosion
resistance. 17-4 PH SS is usually used to manufacture wing
components of brackets or make mini-brackets due to its
higher hardness and strength.
Titanium brackets
Titanium as a metal has excellent biocompatibility and
increased corrosion-resistance. To overcome the release of
nickel from stainless steel brackets which may cause a nickel
allergy in some patients, titanium brackets were introduced
as nickel-free alternatives to SS in the mid-1990s. Con-
temporary titanium brackets are manufactured from alpha
titanium grade 2 and 4 or alpha-beta titanium (Ti-6Al-4V).
Grade 2 CP titanium is usually used to make the base com-
ponent 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 which is more wettable
than SS, so, it has a greater bond strength than SS. Also, ti-
tanium brackets are covered by a layer of titanium to reduce
friction.
Cobalt chromium
Cobalt-based wear-resistant alloys are used presently for
orthodontic brackets manufacturing. In cobalt-based, wear-
resistant alloys, CoCr brackets are made from ASTM F-75
CoCr where ASTM stands for American Society for Testing
and Materials. The amount of nickel in this alloy is kept low
and is up to 0.5 %. In theory, these brackets cause less nickel
sensitivity and less release of nickel. Also, these brackets are
harder but have less friction than SS brackets.
Types of the bracket base
These include:
• Perforated – obsolete
• Mesh- these are further subdivided into:
1. Foil mesh base
2. Gauze or woven mesh base
3. Mini-mesh base
4. Micro-mesh base
5. Optimesh base
6. Ormesh base
7. Laminated mesh base
8. Single mesh base
9. Double mesh base
10. Supermesh base
• Integral bases: Integral bases have furrows, pits and
undercut channels (Dynalok) for retention
• Photo-etched bases - microlock
• Laser structured bases
• Micro-etched bases
• Polymer-coated, e.g., Primekote (TP)
Bracket base surface area
An essential technical specification that affects the bond
strength of an orthodontic bracket is its base surface area.
Most orthodontists presently use twin brackets. The surface
area (Sorel et al., 2002, Haydar et al., 1999) of twin brackets
range from 12.5mm2
to 28.5 mm2
. The greater the retentive
bracket base area, the higher bond strength and vice versa
(Wang et al., 2004). But there are practical limitations of in-
creasing or decreasing the bracket base surface area though
the literature showed no direct relationship between bracket
base area and bond strength (Reynolds IR 1981). Clinically
acceptable bond strength (Reynolds, 1975) is around 5.9 to
7.8 Mpa but bond strength should not exceed than 13.5Mpa
(Retief, 1974) to avoid enamel damage.
Proffit (Proffit et al., 2018) proposed that the width of the
bracket should not be more than half of the width of the
tooth, while MacColl (MacColl et al., 1998) recommended
that bracket base surface area should be around 6.82 mm2
.
Usually, the manufacturers of orthodontic bracket keep
larger base area to give better bond strength and rotational
control.
Orthodontic brackets recycling
Although different commercial companies provide bracket
recycling services, brackets are routinely not recycled in the
UK (BOS 2011 Reuse of orthodontics devices, Coley-Smith
and Rock, 1997). Recycling has a negligible change in slot
size but decreases bond strength in the case of mesh type
brackets. However, in cases of recycling using chemical or
heating, the corrosion resistance of the brackets decreases.

Tooth number 1 2 3 4 5 6 7
TIP
MBT 4 8 8 0 0 5 5
UPPER
LOWER
Roth 5 9 11 0 0 0 0
Andrews 5 9 11 2 2 5 5
Andrews 2 2 5 2 2 2 2
Roth 0 0 6 0 0 -1 -1
MBT 0 0 3 2 2 2 2
TORQUE
UPPER
LOWER
MBT 17 10 -7 -7 -7 -14 -14
Roth 12 8 0 -7 -7 -14 -14
Andrews 7 3 -7 -7 -7 -9 -9
TEETH 1 2 3 4 5 6 7
Andrews -1 -1 -11 -17 -22 -30 -30
Roth -1 -1 -11 -17 -22 -30 -30
MBT -6 -6 -6 -12 -17 - 20 -10
Bracket configurations
Standard Edgewise and Straight wire
Standard edgewise brackets which were introduced by Angle
(Angle, 1928) are rarely used. Nowdays, the most common
appliance system used in the USA is a preadjusted edgewise
appliance (O’Connor, 1993). The philosophy of preadjusted
edgewise system based on Andrew six keys of occlusion
(Andrews, 1976).
Like conventional edgewise, the bracket slot height could be
0.022”, 0.018” or mixed system,. For example, torque control
with 0.018” labially and 022” buccally. The bracket slot depth
is usually 0.028” but it can be in 0.025” or 0.030”. Slot size
and shape vary among the manufacturer because of varia-
tions in the manufacturing processes (Brown et al., 2015).
In 0.018” x 0.028” brackets, the working archwire is 0.016” x
0.022” SS while in 0.022” slot brackets, the working archwire
is 0.019” x 0.025” SS. According to an RCTs (Yassir et al.,
2019a, Yassir et al., 2019b, El-Angbawi et al., 2019), there
is no difference in terms of the effectiveness between 018”
and 022”. Similar findings were made by a systematic review
(Vieira et al., 2018).
In preadjusted edgewise brackets, the molar tubes are usually
convertible and could be single, double, or triple tubes,
with/without HG tubes (Tidy DC & Coley-Smith A, Swartz,
1994).
Bracket prescriptions
In preadjusted edgewise brackets, three-dimensional tooth
movements are built in the brackets, which is called the pre-
scription of the brackets. The prescription of the preadjusted
edgewise brackets has effectively removed the three aspects
of wire bending:
• In - out bend which is also called 1st order bend.
• Tip bend which is also called 2nd order bend.
• Torque bend which is also called 3rd order bend.
A number of brackets prescriptions are available (Table 3)
such as Andrew’s (Andrews, 1976), Roth’s, Alexander and
MBT prescriptions (McLaughlin and Bennett, 1989)
Begg appliance
The Begg appliance was introduced by Dr. Begg and then
modified into ‘Tip-Edge’ appliance (Kesling, 1988). Treat-
ment using Begg appliance involves three stages:
• Stage I: Alignment of teeth, correction of incisor and
molar relationships, relief of crossbite and rotations.
• Stage II: Space closure and maintenance of stage I
corrections.

6
• Stage III: Correct inclinations of teeth.
For more details, please read the chapter on Begg
appliances.
Tip-Edge’ system
The Tip-Edge brackets were introduced by Peter Kesling
(Kesling, 1988) in late 1988. Tip-Edge brackets are a modi-
fication of edgewise brackets using the treatment mechanics
of light wire and differential anchorage of the Begg system.
The Tip-Edge bracket has a dynamic slot, opened and closed
slot. The open slot dimension is 0.028” x 0.028” while the
closed slot dimensions is 0.022” x 0.028”. A modification of
the Tip-Edge bracket was Tip Edge plus by Parkhouse (Park-
house, 2007) in 2007; it contains an auxiliary horizontal slot
beneath the main archwire slot. At the the final stages of the
treatment, round 0.14” superelastic NiTi wire is passed in
the auxiliary slot replacing the sidewinders of the original
Tip Edge brackets.
The tip edge and tip edge plus system allows low friction and
early space closure but they are highly reliant on patients’
compliance and are asscoiated with complex mechanics in
stage III. No significant difference was found between the
preadjusted edgewise and tip-edge appliances in a prospec-
tive study comparing canine retraction rates (Lotzof et al.,
1996), however, there was less anchorage loss in Tip-Edge
patients.
Self-ligating (SL) appliances
Self-ligating brackets have an in-built metal face, which can
be opened and closed. The Russell Lock edgewise attach-
ment described by Stolzenberg in 1935 is an early example
of self-ligating brackets, but they were prone to breakages
and inadvertent opening. The Russell bracket was active
in demand. New designs continue to appear, with at least
twenty-four new brackets since 2000.
Factors that have hindered the adoption of self-ligation
These include:
• Design and manufacture imperfection.
• An inherent conservatism amongst orthodontists
• Lack of evidence of what low friction, secure arch-
wire engagement and light forces can achieve
Commonly used SL system
These include:
1. Passive SLB brackets such as:
• Damon SL brackets
• Damon 2
• Damon MX brackets
• Damon Q brackets
• SmartClip bracket
2. Active SLB brackets such as:
• In-Ovation GAC
• SPEED bracket
• Activa
3. Aesthetic options in SLB such as:
• In-Ovation C
• Damon 3
• Damon Clear
4. Lingual SLB such as:
• Philippe brackets
• Adenta LT brackets
Claimed advantages of SLB
These include:
• Full archwire engagement.
• Less chair-side assistance is required (Turnbull and
Birnie, 2007).
• Less chair-side time is required (Chen et al., 2010).
• Reduced number of appointments (Eberting et al.,
2001).
• Short treatment span (4-6mths) (Harradine, 2001)
though there is no evidence regarding improved effi-
ciency, faster alignment, stable or superior aesthetic
results using Damon (Wright et al., 2011, Dehbi et
al., 2017).
• Minimal incisor proclination when compared to
conventional brackets (Chen et al., 2010).
• Better oral hygiene with minimal accumulation of
S. mutants when compared to conventional brackets
(Longoni et al., 2017, Huang et al., 2018).
• Decreased root resorption (Yi et al., 2016).
• Better torque expression when compared to conven-
tional brackets, however, this benefit was negated by
a Al-Thomali’s systematic review (Al-Thomali et al.,
2017).
• Reduced friction (Pizzoni et al., 1998, Thomas et al.,
1998). However, according to a systematic review
(Ehsani et al., 2009), there might be less friction with
self-ligating brackets on the round wire, but there is
no difference with rectangular wires where friction
has greater implications.
• Better canine retraction when compared to con-
ventional brackets, however, literature showed that

there is no difference between self-ligating brackets
and conventional brackets between canine retrac-
tion and loss of anteroposterior anchorage (Zhou et
al., 2015).
Disadvantages of SLB
These include:
• Requires expertise for better results.
• Clips may get fractured/opened between appoint-
ments.
• Not possible to apply partial ligation.
• Costly.
• No evidence of treatment efficacy compared to con-
ventional ligation (Dehbi et al., 2017).
Fully-customised brackets
Fully adjusted brakcets are specifically designed according to
the situation/patient’s malocclusion. Fully customised brack-
ets such as Incognito are mainly used for lingual orthodon-
tics and are bonded indirectly (Andreiko, 1994, Wiechmann
et al., 2003).
The advantage of a customised brackets system is minimal
chair-side time, good arch coordination and improved fit-
ting of the brackets. The main disadvantage of this system is
increased cost. Also, the patient has to wait for the brackets
to be manufactured, thus, increasing the overall treatment
time.
Aesthetic Brackets
Lingual brackets
Lingual brackets have a long development history, but they
were first reported in 1978 by Kinja Fujita (Fujita, 1978) in
Japan to avoid injury to lips and cheeks by labial brackets for
patients who practised martial arts. Later on, lingual brack-
ets were introduced in United States in1982 by Alexander
(Alexander et al., 1982). In the early 1990s, Craven Kurz
developed his lingual bracket series, the seventh generation.
As the lingual surface of the tooth has more variations in
anatomy, there has been increase in popularity of custom-
ised brackets to account for this variation. Customised lin-
gual brackets uses CAD/CAM technology for the accuracy
of customisation.
Lingual brackets can be either directly bonded, for example,
In-ovation L, (Singh and Cox, 2011, Auluck, 2013) or cus-
tom-made and indirectly bonded, for example, Incognito.
Plastic brackets
The first commercially available plastic brackets were intro-
duced in 1963 by Morton Cohen and Elliott Silverman (Sil-
verman et al., 1979). Plastic brackets are either translucent
or transparent to fulfill aesthetic demand during treatment
and to make the appliance less visible. Plastic brackets are
usually manufactured from plastic injection molding and are
a good alternative to metal brackets for patients with a nickel
allergy. Conventional plastic brackets were made of unfilled
polycarbonate. The drawbacks of plastic brackets
are:
• They undergo water absorption in the oral cavity.
Water absorption has plasticising effects on the brackets
with a resultant decrease in mechanical properties of the
brackets.
• Staining increased bacterial growth over the brack-
ets. A foul odour from the mouth are also reported with
unfilled polycarbonate plastic brackets.
• The unfilled polycarbonate plastic bracket has a
stiffness 60 times less than that of stainless-steel brackets.
This decreased strength is further aggravated by the plas-
ticising effect of water absorption. Applying torque using
rectangular wires engaged in plastic brackets is extremely
difficult if not impossible because deformation or creep of
the bracket slot.
• Wing’s fractures of plastic brackets are common
because of decreased strength and wear -resistance.
• Plastic brackets offer greater friction to wires on
sliding mechanics than SS brackets because of the rough sur-
faces of the bracket slot. Also, the bracket slot is softer than
SS wires, so there are greater ploughing effects on sliding
steel wires.
• Some conventional unfilled plastic brackets need an
application of a special primer for bonding. Plastic brackets
have been reported to have lower shear bond strength than
conventional brackets.
• Polycarbonate plastic brackets are produced by
bisphenol A and phosgene CoCl. There are biocompatibil-
ity issues with polycarbonate brackets due to bisphenol A
release.
To overcome the problems of conventional plastic brack-
ets, different materials were used to manufacture plastic
brackets; these materials include polyoxymethylene, filled
polycarbonate, polyurethane brackets, and hybrid polymers.
Ceramic brackets
Ceramic brackets were introduced in the early 1980s and
extensively marketed in the mid- 1980s as the “invisible
braces”. Ceramic is the third hardest material known and
is harder than stainless steel and enamel. Ceramics are a
broad class of inorganic materials that are neither metallic
nor polymer and includes glasses, clays, precious stones, and
metal oxides. As ceramic brackets are transparent or trans-
lucent, hence, they mask the appearance of fixed appliances.

8
Table 4: Comparison between Monocrystalline and Poly-
crystalline Bracket
Monocrystalline brackets Polycrystalline brackets
Transparent as they contain a single crystal of aluminum oxide. Decreased optical clarity due to the presence of the binder
during the manufacturing process. Also, multiple crystals in
a polycrystalline bracket mean increases in the number of
grain boundaries and decreases in optical clarity.
They resist staining They discolour over time if used with some specific diets.
They are expensive (Scott, 1988) because they require a delicate
process to shape a single crystal into a bracket by cutting tools.
They are inexpensive because the moulding process is sim-
ple, and large quantities of brackets can be manufactured.
They have high tensile strength up to 1800 MPa (Johnson et al.,
2005)
The tensile strength is 380 MP meaning multiple grain
boundaries and less resistance to crack propagation (Flores
et al., 1990, Viazis et al., 1990)
The fracture strength decreases with time (Flores et al., 1990). Bracket strength remains unchanged with time.
They have smoother surfaces than polycrystalline brackets but
have equivalent friction resistance (Cacciafesta et al., 2003)
They have a rough surface compared to monocrystalline
brackets.
The bonding strength of monocrystalline versus polycrystalline brackets are controversial in the literature (Viazis et al., 1990,
Klocke et al., 2003)
Advantages of ceramic brackets
These include:
• High bond strength.
• Superior aesthetic.
• High wear resistance.
• Good colour stability over the plastic brackets.
• Inert and can safely be bonded in patients with nick-
el and chromium allergies.
• Safely used in patients who require multiple MRI
images.
Disadvantages of ceramic brackets
These include:
• Cost.
• Due to increased hardness, there is difficulty in
debonding with high chances of enamel damage and
bracket fracture. Therefore, they are contraindicated
in patients with enamel cracks, restorations or de-
vitalised teeth, hypoplastic teeth and hypocalcified
teeth.
• Discolouration of ceramic brackets in cases with
longer treatment times.
• Being the third hardest material, ceramic is harder
than SS wires. So, they offer greater friction on slid-
ing mechanics. They also cause teeth abrasion when
they contact the opposing teeth.
• Ceramic brackets are radiolucent and so cannot be
detected by x-rays if accidentally aspired or swal-
lowed during debonding.
• Ceramic brackets are made bulkier to resist fracture.
Bulkier brackets are more conspicuous and may
cause soft tissue injury.
Types of ceramic brackets
These include:
• Multiple crystals or polycrystalline brackets.
• Single crystal or Monocrystalline brackets.
• Zirconia brackets.
• Metal reinforced polycrystalline brackets.
Polycrystalline brackets
These are tooth-coloured brackets, e.g., 3M Clarity. Poly-
crystalline brackets are made by ceramic injection moulding
so they can be produced in large quantities, hence, they are
inexpesive compared to other ceramic brackets. However,
polycrystalline brackets are opaque and suffer from structur-
al imperfections, high friction and low fracture toughness.
Monocrystalline brackets
These are transparent brackets, e.g., Inspire Ice. They are
machined by milling from synthetic sapphire and they are
heat-treated to relieve stress, followed by cooling and then
milling. Monocrystalline brackets are clear with fewer im-
perfections, impurities and low friction than polycrystalline
brackets, however, they are expensive with low toughness.
Problems with ceramic brackets and suggested solutions are

listed in table 5.
Table 4: Problems with ceramic brackets
Problems Solutions
Error in bracket placement • Visualise from different angles.
• Coloured adhesives.
• Using transfer gauge.
• Bracket markers, although it can make removing the excess bonding material
more difficult.
• Indirect bonding.
Ligation problems such as:
• Clear and tooth-coloured elastic ligatures tend to discolour.
• Metal ligatures are obvious under clear brackets.
• Ligature’s lockers can fracture the brackets.
• Using Polycrystalline brackets.
• Using Teflon coated ligatures or ‘white’ elastomeric modules.
• Using thin Quickligs must be fully tied in with the twisted tails tucked under
the archwires.
•Using Self-ligating ceramic brackets.
Bracket fracture due to:
• Fracture of tie-wings during ligation.
• Fracture of brackets on debonding (if inhaled, can be problematic
because these are not radio-opaque).
• Careful application of torquing force, e.g., use rectangular.
• Careful ligation using stress relaxing composite ligatures (McKamey and Kusy,
1999).
High friction
• There is increased frictional resistance to sliding mechanics with
ceramic brackets (Tidy, 1989), especially with rectangular NiTi arch-
wires (Frank and Nikolai, 1980).
• Hard ceramic abrades stainless steel wire.
• Using lower friction ceramics e.g., zirconium oxide.
• Using ceramic brackets with metal lined slots.
• Closing loops rather than sliding mechanics for space closure.
• Bypassing premolar teeth during space closure.
Enamel wear
• Ceramic is 7 times harder than enamel.
• Enamel wear/fracture is common with ceramic brackets.
• Increased risk of enamel fracture when debonding.
• It is better to use ceramic brackets in the upper arch only.
• Avoid using ceramic brackets in the lower arch for deep bite cases.
• Using polycarbonate bracket in case of deep overbite.
• Using bite plane to clear the intermaxillary contact
• Procline upper incisors before bonding the lower incisors.
• Using rubber ligatures over tie wing slots of ceramic brackets can prevent con-
tact with the opposing dentition.
• To reduce enamel fracture, avoid using ceramic brackets in periodontally
involved teeth, root treated teeth, large restorations, small teeth, cracked enamel,
and lower incisors with thin labial enamel.
Debonding of ceramic brackets
It is essential to wear safety glasses to protect eyes while debonding
ceramic brackets, especially when debonding mechanically (Bishara
and Trulove, 1990).
There are different methods of debonding ceramic brackets, including:
• Mechanical method: First, remove the composite around the brackets and then
use manufacturer recommended tools to remove the brackets (Stewart et al.,
2014).
• Chemical debonding: Use of peppermint oil or other chemical solvents (75%
ethanol, polyacrylic acid, acetone, acetic acid) that plasticises the composites
• Ultrasonic debonding
• Thermal debonding using hot instruments tips, electrothermal or laser
debonding radiation (Obata et al., 1999)

10
Zirconia brackets
Zirconia brackets are polycrystalline brackets with an
opaque or yellowish tinge. Zirconia brackets are aesthetically
poor but have better fracture resistance and their frictional
properties are similar to alumina brackets (Keith et al.,
1994).
Metal reinforced polycrystalline brackets (MRPB)
MRPB incorporate a metal slot to reduce friction, and weak-
ness is intentionally introduced in the base to allow easy
removal.
Retention of ceramic brackets
The ceramic bracket bases are available in four different
designs to aid retention of adhesive:
• Chemical retention
• Mechanical retention
• Micromechanical retention
• Combination of the above designs
Initially, Vinyl silane coupling was used to increase the bond
strength, but it is associated with increased chances of enam-
el fracture on debonding. Nowadays, primarily mechanical
base retention is used. Other modifications in bonding are
using a weakening bonding agent, metal mesh in the base,
and introducing pre-stressed areas.
Other aesthetic brackets including composite brackets
Composite brackets are made from thermoplastic polyure-
thane and are available with metal slot. Composite brackets
have less staining/discolouration than polyurethane and less
enamel wear than ceramic brackets.
The differences between monocrystalline and polycrystalline
brackets are provided in Table 4.
EXAM NIGHT REVIEW
It is difficult to summarise this chapter; however, below is
the most important evidence for the exam:
• According to an RCT (Yassir et al., 2019a, Yassir et
al., 2019b, El-Angbawi et al., 2019) there is no differ-
ence between 0.018” and .022”. A systematic review
made a similar finding (Vieira et al., 2018).
• According to a systematic review(Chen et al., 2010),
less chairside time is required with SLB. Also, there
is less incisors proclination with the use of SLB when
compared to conventional brackets.
• According to a systematic review (Dehbi et al.,
2017), there is no evidence regarding improved ef-
ficiency of SLB over conventional brackets.
• According to a systematic review (Longoni et al.,
2017), with a low level of evidence, self-ligating me-
tallic brackets accumulate less S. mutants than con-
ventional brackets, improving infection control.
• According to a systematic review(Yi et al., 2016)
there is no evidence for the claim that SLB causes
less root resorption.
• According to a systematic review (Al-Thomali et al.,
2017) there is better torque expression by SLB.
• According to a systematic review (Ehsani et al.,
2009), there might be less friction with self-ligating
brackets on a round wire, but there is no difference
on rectangular wires where friction matters most.
• According to a systematic review (Zhou et al., 2015),
there is no difference between self-ligating brackets
and conventional brackets between canine retrac-
tion and loss of anteroposterior anchorage(Huang et
al., 2018).

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2
1. Begg philosophy
2. Indication of Begg appliance
3. Advantages of Begg appliance
4. Disadvantages of Begg appliance
5. Features of Begg appliance
6. Begg appliance therapy’s stages and their objectives
In this chapter
Begg
orthodontic
mechanics
Written by: Mohammed Almuzian and Haris Khan

BEGG ORTHODONTIC MECHANICS
14
PaulRaymondBegg(1889-1983)isanAustralianorthodon-
tits who studied at Angle school in USA from March 1924
to November 1925. He was trained in using both Ribbon
archwire appliances and Edgewise archwire appliances. Begg
returned to Australia in 1927 and moved away from Angle’s
non-extraction philosophy.
In 1933, Begg modified Angle’s ribbon archwire appliances by
turning the slot of the bracket upside down.
Begg also replaced the heavy 0.010 x 0.020-inch rectangular
gold wire of ribbon arch with 0.016 inches round stainless-
steel wire. therefore his appliance is also called a light wire ap-
pliance. Begg published his appliance and mechanics in 1956
(Begg, 1956).
Begg philosophy
Begg’s light wire appliance used differential anchorage dur-
ing tooth movement. In Begg philosophy, tooth movement
is performed on light wires. Therefore, the appliance had
poor control of root position which require different auxil-
iary springs later in the treatment to correct the root position.
Begg philosophy was based on two points:
1. Tooth extraction: Begg looked at Aborigines’ dentition
and noticed an excessive amount attrition and abrasion had
occurred due to a course diet. He noticed wear occurring in
two planes:
• Occlusal/incisal wear: Wear to the cusps reduces
interdigitation. Consequently, the mandible comes
forward into an ‘edge to edge’ type of occlusion.
• Interproximal wear: The contact points become
broad over time with loss of interproximal enamel
from distal of the second molar to second molar,
this is equivalent to the loss of one premolar in each
quadrant.
2. Differential force technique: The differential force tech-
nique is the key aspect of the Begg appliance approach The
differential force technique is based on the theory that force
required to tip a tooth is less than the force required to bodily
move the tooth. With differential force technique, teeth are
moved in a two-stage process, tipping followed by uprighting
in the final position. .
Indication of Begg appliance
These include:
• Compliant patients who require long appointment
intervals.
• There are no facial concerns regarding orthodontic
iatrogenic retrusion of the facial profile or ‘dishing
in.’
• Class II division I cases with an increased overbite,
full unit II molars, and crowding needing four ex-
tractions is the most common.
• High anchorage demand cases.
• Bimaxillary protrusion (Lew, 1989)
Advantages of Begg appliance
These include:
• Permits all tooth movements to be carried out rap-
idly and over great distances without re-activation
(Begg and Kesling, 1977).
• There is less demand upon anchorage because of the
lack of friction effects with free tipping, light forces,
and differential force. Hence, the extraoral anchor-
age is usually not needed (Begg and Kesling, 1977).
• Minimal post-treatment relapse (Begg and Kesling,
1977).
Disadvantages of Begg appliance
These include:
• Extraction-based technique.
• Requires patient compliance, requires the continu-
ous wear of elastics.
• Oral hygiene problems because of the loops on the
wire.
• Dishing of the face during the first stage of treat-
ment.
• The appliance becomes complicated to manage in
later stages due to the need of accessories.
• Potential for increased root resorption and peri-
odontal problems, due to unlimited tipping and
counter-tipping, especially in mature patients.
• Backward rotation of the mandible due to molar
extrusion can have a detrimental effect on the face,
especially in open-bite cases.
• Bite opening, anchorage loss (especially in the max-
illa), and insufficient maxillary incisor torque were
found in the Begg appliance compared to the edge-
wise appliance (Barton, 1973). However, a systemat-
ic review (Mousoulea et al., 2017) found low-quality
evidence that Begg and modified Begg appliances
show a statistically significant worsening in occlusal
outcomes when assessed with the Peer Assessment
Review (PAR) scores compared to a preadjusted ap-
pliance with Roth prescription.
Features of Begg appliance
These include:
• Gingival opening of the bracket to prevent the an-

BEGG ORTHODONTIC MECHANICS 15
chor bends from being bitten off. Hence, wire is al-
ways placed in gingivally.
• The bracket has minimal mesiodistal width with
single point contact on incisors, canines, and pre-
molars, allowing tipping and rotation. Therefore,
less force is required.
• Molar tubes have a round buccal tube with a hook,
which achieves two-point contacts; this imparts
bodily movement.
• Early Class II elastics.
• Accessory springs and archwire modifications are
used at later stages for apical and rotational tooth
movements.
Begg appliance therapy’s stages and their objectives
Stage I
A. Intra-arch tooth alignment objectives including:
• Relief of crowding
• Overcorrect rotations of all teeth except anchor mo-
lars
• Align impacted and unerupted teeth
• Tooth levelling
• Closure of anterior spacing
B. Transverse correction objectives including:
• Coordinate upper and lower dental arches, achieve
symmetry
• Correct cross-bites of posterior teeth
C. Vertical correction objectives including:
• Overcorrection of overbite to edge to edge
D. AP correction objectives including:
• Overcorrection of overjet to edge to edge
Stage II which aim to:
• Maintain stage I objectives
• Correct centrelines
• Premolars alignment
• Close remaining extraction spaces
Stage III which aim to:
• Maintain space closure
• Correct mesiodistal angulation (tip) using upright-
ing springs
• Correct labio-lingual inclination (torque) using
torquing springs.
• Finishing and retention
References:
EXAM NIGHT REVIEW
Begg published his appliance and mechanics in 1956 (Begg,
1956). Begg philosophy was based on tooth extraction and
differential force technique
Indication of Begg appliance
• Compliant patients
• No facial concerns
• Class II division I with an increased overbite
• High anchorage demand cases
• Bimaxillary protrusion
Advantages
• Movements to be carried out rapidly
• Less demand upon the anchorage
• Minimal post-treatment relapse
Disadvantages
• Extraction based technique
• Requires patient compliance
• Oral hygiene problems
• Dishing of the face
• Potential for increased root resorption and peri-
odontal problems
• Backward rotation of the mandible
• Bite opening, anchorage loss

BEGG ORTHODONTIC MECHANICS
16
Barton, J. J. 1973. A cephalometric comparison of cases treated
with edgewise and begg techniques. Angle Orthod, 43, 119-26.
Begg, P. R. 1956. Differential force in orthodontic treatment. Am J
Orthod 42, 481-510.
Begg, P. R. & Kesling, P. C. 1977. Begg orthodontic theory and
technique, WB Saunders Company.
Lew, K. 1989. Profile changes following orthodontic treatment of
bimaxillary protrusion in adults with the begg appliance. Eur J
Orthod, 11, 375-81.
Mousoulea, S., Papageorgiou, S. N. & Eliades, T. 2017. Treatment
effects of various prescriptions and techniques for fixed orthodon-
tic appliances : A systematic review. J Orofac Orthop, 78, 403-414.

3
1. Advantages of removable appliances (RAs)
2. Disadvantages of RAs
3. Indications of RAs
4. Components of removable appliances
5. Active components of RAs
6. Retentive components of RA
7. Anchorage component of RA
8. Base Plate
9. Mode of action of RAs
10. Checklist for RAs
In this chapter
REMOVABLE
ORTHODONTIC
APPLIANCES

REMOVABLE ORTHODNTIC APPLIANCES
18
Removable appliances (RAs) are orthodontic devices that
can be removed and inserted by the patient. The advantages
and disadvantages of RAs are listed in table 1.
Indications of RAs (Reay and Stephens, 1993)
These include:
1. As an interceptive active appliance for the management of:
• Anterior crossbites correction.
• Posterior crossbites correction.
2. As an interceptive passive appliance for the management
of a habit.
3. As a space maintenance appliance for the management of:
• Early loss of primary teeth.
• The traumatic loss of permanent anterior teeth.
• Permanent tooth extraction awaiting eruption of
impacted teeth.
4. Active orthodontic appliance for:
• Treating retroclined upper incisors in Class 2 Divi-
sion 2 cases (e.g., ELSAA type appliance)
• Treating narrow upper arch
• Maintain the result of the functional appliance, e.g, a
removable appliance with an anterior inclined plane.
• Headgear combination therapy to aid en masse re-
traction, molar distalisation or posterior teeth intru-
sion.
5. As an adjunct appliance to fixed appliance therapy for:
Table 1: The advantages and disadvantages of RAs
• Cost-effective.
• The removable nature of the appliance makes it possible for
the patient to maintain good oral hygiene during treatment.
• Patients can remove damaged appliances.
• Laboratory fabricated rather than directly in the ‘patient’s
mouth, therefore, less chair-side time.
• Allow growth guidance treatment to be carried out more
readily than with fixed appliances
• Less iatrogenic effect than fixed appliances such as decalcifi-
cation, caries under molar bands, and gingivitis.
• They can be used during the mixed dentition for various
interceptive treatments.
• Not effective with an uncooperative pa-
tient.
• Efficient tooth movement in three dimen-
sions is not possible. Traditional RAs are only
capable of tipping movements
• Only certain types of malocclusions can be
corrected.
• They may hinder speech and eating.
• Difficult to tolerate lower appliances.
• Appliances may be lost or broken.
• Residual monomer (greater in self-cure ap-
pliances) may cause allergy and/or irritation.
• Overbite correction
• Open bite correction
• Disengaging the occlusion and removing occlusal
interferences to enhance tooth movement, by incor-
porating bite planes.
• Extruding teeth, such as impacted palatal canines.
• Provide lower posterior attachments for Class 2 in-
ter-arch elastics/traction in Class 2 malocclusions.
6. As a retainer appliance such as:
• U loop labial bow retainer (Hawley).
• Begg retainer.
• Vacuum-formed retainers.
Wires used to construct RAs
The composition of austenitic stainless-steel wires used to
construct RAs is iron 73%, chromium 18%, nickel 8%. This
stainless-steel wire is 18/8 stainless steel (18 refers to the per-
centage of chromium included while 8 refers to the level of
nickel incorporated). For the construction of spring of a re-
movable appliance, hard stainless steel is usually used, but it is
possible to use medium-hard in some situations.
Elgiloy can also be used to construct RAs sporing. Elgiloy
wire consists of iron 14%, chromium 20%, cobalt 40%, nickel
16%, molybdenum 7%, manganese 1.5%. Elgiloy wire is avail-
able in four grades red (resilient), green (semi resilient), yel-
low (ductile) and blue (soft). Elgiloy is generally used in its
soft blue form to construct Southend clasps or other clasp
components for removable appliances. Heat-treating the wire
increases its strength significantly.

REMOVEABLE ORTHODONTIC APPLIANCES 19
Components of RAs
Active components
Active components deliver forces to achieve orthodontic
tooth movement, component types are::
1. Bows are active components that are mainly used for inci-
sor retraction. Types of bows include:
• Short and long labial bows (0.7mm SS). Because of
the high force levels, a labial bow with U loops (0.7
mm SS) are used for minor incisor retraction.
• Labial bow with reverse loops mesial to second pre-
molars (0.8 mm SS).
• Labial bow with large C loops (0.7mm SS)
• Split labial bow (0.7mm SS).
• Reverse labial bow (0.8mm SS).
• High labial bow with apron springs in which the
base arch is made from 1 mm SS, and the apron
spring is made from 0.35-0.4 mm SS).
• Mills retractor.
• Robert’s retractor (0.5 mm SS supported with
0.7mm SS sleeve).
• Self-straightening bows (0.4 mm SS).
2. Bite planes are made of acrylic and are an active compo-
nent. Bite planes can be used for:
• Intrusion of teeth.
• Extrusion of teeth: Teeth not in contact with the bite
plane extrude passively /over-erupt.
• Open the bite in cases of premature contacts, cross-
bite or used to advance or setback the mandible e.g.
Twin block and reverse Twin block.
3. Springs are an active component of RAs used to deliver
tooth movements. Springs can be classified into springs with
helix, spring without helix, spring with loops and self-sup-
ported springs. The ideal properties of springs are that they
should be easy to fabricate, adjustable, easy to clean, engage
with tooth surface without discomfort and extended range of
activation.
Springs are mainly cantilevers in nature, i.e., supported at one
end (also called the tag) and free at the other end to deliver
the force. These include:
• Z spring (0.5mm SS) is mainly used anteriorly to
procline / rotate teeth. It requires good anterior re-
tention and is activated by 3mm through the open-
ing of helixes, at 45 degrees to the base plate.
• T spring (0.6mm SS), mainly used posteriorly to tip
teeth buccally. Capping of the springs is essential for
crossbite correction. A T-spring is activated by 2mm
reduction/compression of T bend.
• Palatal spring (0.5mm SS for central to 2nd premo-
lar, 0.6mm SS for molars) can be used both anterior-
ly and posteriorly to move teeth mesial or distal, and
it is activated by 3mm through opening or closing of
the helix.
• Canine retractor (0.5 / 0.6mm SS) are a specific type
of palatal springs that can also be placed buccally. It
moves canines in a distal direction. Examples are U-
loop canine retractor, helical canine retractor, buccal
and palatal canine retractor.
• Buccal spring / reverse buccal spring (0.7mm SS, if
sleeved 0.5mm SS) are used to move teeth distally.
1mm of activation is required, and this is most read-
ily done by cutting off 1 mm of wire from the free
end and re-forming it to engage the mesial surface of
the tooth. Alternatively, it can be activated by open-
ing the loop by 1 mm.
• Robert’s retractor (0.5 mm SS with SS sleeving) are
used to retract anterior teeth. It consists of a labial
bow connected to two buccal retractors, and it is ac-
tivated by closing the helix by 3mm.
• Coffin spring (1.25mm SS) is used for the maxillary
arch expansion and is activated by pulling the two
halves apart.
The force applied by the springs should be perpendicular to
the long axis of the tooth, and should be as close as possible
to the centre of resistance. The force delivered by the spring
is presented by the following formula: Force ᾳ dr4
/l3
. This
means the force will be lighter with a greater length of wire
in the spring, the reduced radius of the wire and reduced de-
flection. It is recommended that when the wire is activated
from its passive position, the direction of activation should
be in the same direction as planned tooth movement. This is
due to increased steel hardening (Bauschinger effect) which
might fracture while un-winding; hence is why reverse loops
are preferred. Wire flexibility is essential to deliver the de-
sired force for tipping movement. Increasing flexibility is rec-
ommended by increasing the length through incorporating
coils or reducing the diameter, however, this might affect the
spring rigidity. This can be resolved, using a guided wire or
reinforced wire with a tubing sheath.
4. Screw, mostly, a jackscrew is used with RAs, but other
screws can be utilised. Screws can be used for the following
purpose:
• Arch expansion (screws are expanded on slow ex-
pansion protocols, one turn on alternative days or
two turns a week, equating to 0.5-1mm/week).
• Arch contraction.

20
• Space opening.
• Space closing.
• Tooth movement buccally or labially.
Retentive components of RAs
Retentive components help in keeping the appliance in place
and resist displacement. Incorporating specific wire / plas-
tic parts that engage undercuts on the teeth, such as clasps,
which provide retention.
The ideal properties of retentive clasps are:
• Easy to fabricate and offer adequate retention.
• They should not apply any active force that would
cause undesired tooth movement of the anchorage
teeth.
• They should not impinge on the soft tissues/or in-
terfere with normal occlusion.
The types of retentive clasps include:
• Adam’s clasps which are commonly made from 0.7
mm wire for molar teeth and in the case of premolar
teeth a 0.6 mm wire is used. The bridge of an Ad-
ams’ clasp provides a site where the patient can ap-
ply pressure with their fingertips during the removal
and insertion of the RA. Moreover, auxiliary springs,
extraoral traction tubes and hooks can be soldered
to the bridge of the clasp.
• Southend clasps are made from 0.7mm or 0.8-mm
SS wire or Elgiloy wire. These clasps are activated by
bending the U-loop towards the baseplate, which
moves the clasp back into the labial undercut of the
tooth.
• C-clasps is also called a recurved clasp and it is fab-
ricated from 0.7 mm SS wire.
• Ball-ended clasps are made from 0.7 mm wire.
• Plint clasps around molar bands is made from 0.7-
mm SS and engages the undercuts on a maxillary
molar band.
• Acrylate and fitted labial bow (0.7 mm SS).
Anchorage component of RAs
Anchorage should be considered in all three planes of
space. The greater the number of teeth incorporated into
the appliance, the greater the anchorage value of the ap-
pliance. Teeth with larger root surface areas incorporated
within the appliance will also provide more anchorage.
The use of light forces reduces the burden on the anchor-
age components. Intermaxillary anchorage used with
elastics running from the upper to the lower arch may be
used to optimise anchorage. This does, however, increase
the demand on the retentive part of the appliance, and an
operator needs to be confident in the retentive compo-
nent of their appliance.
Baseplate
It is constructed from self-polymerising or heat polymerising
polymethyl methacrylate. The base plate has four functions:
• It acts as a connector of the appliance parts.
• It contributes to anchorage through contact with the
palatal vault and teeth not being moved.
• It may be built up into bite planes to disengage the
occlusion or produce overbite reduction (anterior or
posterior bite plane).
• It provides housing and protection of the URA com-
ponents.
Material of the base plate is contracted via a polymerisation
process of the following:
• Powder or polymer, known as polymethyl methac-
rylate + peroxide initiator + pigment
• Liquid monomer methacrylate + stabiliser hydro-
quinone to prevent polymerisation on storage and a
cross-linking agent.
The polymerising process:
• Heat cured: It has the advantage of not releasing
polymerised monomer, which has been reported to
cause skin and mucosal reactions for technicians,
dentists, and patients.
• Self-cured, cold-cured, auto-polymerizing, or
chemically-activated acrylic is similar to the heat
cure material, except the liquid contains an activa-
tor, such as dimethyl toluidine.
• Light cured
• Dual cured
Designing RAs
Appliance design in conjunction with good diagnosis is the
key to successfully treating an orthodontic problem. No mat-
ter how well made, an inappropriately designed appliance is
unlikely to achieve optimum tooth movement and thus the
desired result. The stages of appliance design are as follows:
• Select the active components required to achieve the
type and direction of tooth movements needed.
• Select the retentive components that enable the ap-
pliance to remain in its desired position and not to
be displaced when the active components are acti-
vated.
• The base plate holding active and retentive compo-

nents together must be designed to have all these
components together. Thought must be given to pa-
tient comfort.
• An estimate of additional anchorage requirements
are considered at this stage, specifically if the base
plate along with the retentive clasps is sufficient
for the type of tooth movements that is desired, or
whether additional anchorage requirements are
indicated, such as the addition of headgear (distal
movement, protraction) or inter-maxillary elastics.
Mode of action of RAs
RAs can carry out limited tooth movement predictably (Ward
and Read, 2004). The predictable movements are listed below:
• Tipping in labio-lingual or mesiodistal directions.
• Reduction of deep overbites in growing individuals
• Space maintenance
More complex movements involving bodily or root changes
are unpredictable due to challenges in creating a force couple.
Aligners are theoretically able to achieve a force couple; how-
ever, the predictability of root movement with aligners is low
(Dai et al., 2019)
Tipping movement (Christiansen and Burstone, 1969): A
force applied as a single point on the crown will tip the tooth
about a fulcrum. Tipping takes place about a fulcrum within
the apical third of the root, the centre of rotation is usually
about 40% of the length of the root from the apex. This means
that while the crown moves in one direction, the apex moves
in the opposite direction (also termed uncontrolled tipping).
The exact level of the fulcrum depends on a variety of factors,
that are not under the orthodontist’s control; these include
root shape, periodontal support and the distribution of fibre
bundles within the periodontal ligament.
Intrusion movement: When a bite plane is incorporated
into an appliance, an intrusive force is applied to the teeth
which contact it. The amount of actual intrusion is small, and
overbite reduction with removable appliances is primarily the
result of the passive eruption of the dentoalveolar segments
not occluding on the bite plane, typically the posterior teeth.
Incisors may tip labially if they do not occlude perpendicu-
lar to the anterior bite plane. Intrusion of teeth may also be
produced unintentionally by the incorrect application of a
spring. For example, when a spring retracts, the canine is ap-
plied to the cuspal incline, the tooth will be intruded as well as
retracted. This most often happens when attempts are made
to retract a partially erupted canine. For the same reason, it
is preferable to avoid moving a tooth until it is fully erupts.
Rotation movement: Rotations are challenging to correct
with RAs becasue of the requirement to generate a force cou-
ple. Some rotations can be rectified by applying simultane-
ous buccal and lingual forces. For example, a rotated upper
central incisor, it may be possible to correct a rotation with a
couple between a labial bow and a palatal spring at the base-
plate, but this requires careful management.
Checklist while fitting a new RA
It is important to undertake a thorough check during the first
and recall visits. The tables below is a checklist for this pur-
pose (Table 2 and 3).
Table 2: Checklist while fitting a new RA
Item Yes/ No
Is it the correct
appliance for the
patient?
Is it the correct
design?
Check for any
sharp areas
Show the ap-
pliance to the
patient
Insert appliance
into the mouth
and assess fit of
the appliance
Adjust the clasps
to generate suf-
ficient retention
Activate and
trim acrylic to
enable the ap-
propriate tooth
movements
Final try in
Inform the pa-
tient of the time
appliance is to
be worn per day
Instruct the pa-
tient on how to
take care of his
appliance, and
provide infor-
mation leaflets
on managing
removable appli-
ances
Arrange a recall
visit

22
Disadvantages of removable orthodontic appliances:
• Not effective with uncooperative patients.
• Mainly tipping movements.
• Limited control of tooth movement.
• Only certain types of malocclusions can be correct-
ed.
• Speech and eating affected.
• Inefficient for multiple tooth movement.
• Lower appliances are poorly tolerated.
• The residual monomer is allergenic.
Indications of removable orthodontic appliance: (Reay and
Stephens, 1993)
A. Interceptive treatment
1. Active
• Correction of anterior crossbites
• Correction of posterior crossbites
2. Passive
• Habit-breaker
3. Space maintenance
• Early loss of primary teeth
• Traumatic loss of incisors.
• After permanent tooth extraction to allow impacted
teeth to eruption
Table 2: Checklist on recall visits
Inquire about any problems Yes/No
Inquire what wear pattern
Assess speech, the quality of speech can be gauged as this indicates if the patient has been wearing
the appliance
Check appliances inside the mouth prior to removal. This allows oral hygiene to be assessed, and
any trauma spots can be identified
Ask the patient to insert/remove the appliance; ease of performing these tasks indicates good
compliance
Recognising unwanted tooth movements at an early stage and undertaking remedial action at this
stage is of the utmost importance
Check springs are correctly positioned and fit of the appliance. If the fit is poor and springs are
displaced, it indicates the patient has been flicking the appliance in and out with their tongue and
has made appliance loose. This can produce fractures of the wire components during treatment
Measure the overjet reduction/relevant tooth movements and note in patients file
Check molar relationships for anchorage loss
The appliance must be adjusted with care and good records need to be kept
Oral hygiene should be carefully monitored and reinforced
EXAM NIGHT REVIEW
Definition:
RA→ can be taken out of the mouth by the patient.
Classification of RA
Active Appliances
Produce tooth movement/growth modification, e.g., Func-
tional appliance, a removable appliance with z springs in
Class II div 2 corrections.
Passive appliances
These are RAs where no active tooth movement is present.
These include retainers space maintainers.
Advantages of removable orthodontic appliances:
• Removable
• Laboratory fabricated, less chair-side time.
• Growth guidance possible
• Good oral hygiene during treatment.
• Less orthodontic risks such as decalcification loss of
attachment.
• Cost-effective.
• It can be used during mixed dentition
• Interceptive treatment possible
• Maintaining space.

B. Removable appliances as an adjunct to fixed or func-
tional appliance therapy.
• Pre-functional appliances to procline incisors in a
Class II Division 2 case and expand the upper arch.
• Enabling distal movement by adding headgear ther-
apy.
• Overbite correction.
• Disengage occlusion with bite planes
C. Removable orthodontic appliance as a retainer:
• ‘’’U’ loop labial bow retainer [Hawley]
• Begg retainer
• Vacuum-formed retainers.
• Material
• Baseplate: Acrylic
• Plastic type appliances: Polypropylene / polyvinyl-
chloride
• Wires: Stainless steel, Elgiloy
• Elastics
Components of removable appliances
Components of RA include
• Active components
• Retentive components
• Anchorage components
• Baseplate
Type of springs in RA
Mostly cantilever springs are used in RA. These include:
• Z spring (0.5mm SS), activated by 3mm opening of
helix
• T spring (0.6mm SS), posterior capping required,
activation 3mm
• Palatal springs (0.5mm / 0.6mm SS anterior / mo-
lars) activated by 3mm through opening or closing
of the helix
• Canine retractor (0.5 / 0.6mm SS)
• Buccal springs (0.7mm SS, if sleeved 0.5mm SS)
• Robert’s retractor (0.5 mm SS with sleeving). Activa-
tion is 3mm through closing the helix.
• Coffin spring (1.25mm SS), Activate by pulling 2
halves apart.
Retentive components of RA (Seel, 1967)
• Adam’s clasp: 0.7 mm SS for molar teeth, 0.5 mm for
premolar teeth.
• Southend clasp: 0.7- or 0.8 mm elgiloy.
• C-clasp: 0.7 mm SS
• Adam’s crib: 0.7 SS / 0.6mm SS permanent / primary
teeth.
• Ball ended clasps: 0.7 mm SS.
• Splint clasp: 0.7 mm SS wire.
Anchorage component of RA
• Teeth
• The base plate
• Extraoral forces

24
References
Christiansen, R. L. & Burstone, C. J. 1969. Centers of rotation
within the periodontal space. Am J Orthod, 55, 353-69.
Dai, F. F., Xu, T. M. & Shu, G. 2019. Comparison of achieved and
predicted tooth movement of maxillary first molars and central
incisors: First premolar extraction treatment with invisalign. Angle
Orthod, 89, 679-687.
Reay, W. J. & Stephens, C. D. 1993. Indications for the use of fixed
and removable orthodontic appliances. Dent Update, 20, 25-6,
28-30, 32.
Seel, D. 1967. A rationalization of some orthodontic clasping prob-
lems. Dent Pract Dent Rec, 17, 188-95.
Ward, S. & Read, M. J. 2004. The contemporary use of removable
orthodontic appliances. Dent Update, 31, 215-8.

4
1. Indication of clear aligner therapy (CAT)
2. Contraindication of CAT
3. Advantages of CAT
4. Disadvantages of CAT
5. Evidence about CAT
6. EXAM NIGHT REVIEW
In this chapter
Overview Of
Clear Aligner
Appliances

clear alligner appliances
26
Sheridan initially described the idea of clear aligner therapy
(CAT) (Sheridan, 1994) by introducing the first vacuum-
formed Essix polyurethane plastic for minor tooth move-
ment. CAT is an orthodontic technique that uses a succes-
sion of clear aligners to position the teeth. The system uses
CAD/CAM stereolithographic (STL) technology to predict
treatment outcomes and create custom aligners from a single
model.
Aligners are used 24/7 (apart from eating,drinking and
brushing) and replaced every 1-2 weeks to move the teeth by
0.2-0.25mm on each aligner. Aligners are provided by many
suppliers and can also be produced locally (in-house align-
ers or IHA). The Invisalign system is one of the popular CAT
systems introduced by Align Technology (Santa Clara, Calif)
in 1998.
The conventional fixed appliance system can explain the
components of CAT. For example, aligners’ attachments, akin
to an orthodontic auxiliaries, permit the force delivery from
the aligner. At the same time, the plastic part (aligner) rep-
resents a wire. So, the aligner’s shape elicits a pushing force
on the teeth. These pushing forces come from the bending/
deformation of the plastic, followed by the aligner returning
to its original shape (shape memory).
General indications of CAT
These include:
• Mild to moderate crowding (1-5 mm).
• Spacing (1-5 mm).
• A mild to moderate degree of anterior open bite
where the overbite is improved by extrusion of the
incisors.
• Mild degree of deep overbite, decreased by intrusion
and proclination of the incisors.
• Narrow arches that can be expanded with tipping
teeth.
General limitations of CAT
These include:
• Crowding over 5 mm.
• Spacing over 5 mm.
• Anterior-posterior discrepancies of more than 3
mm.
• Significant open bite correction.
• Severely rotated teeth more than 20 degrees.
• Severely tipped teeth, more than 45 degrees.
• Teeth with short clinical crowns.
Claimed advantages of CAT
These include:
1. Patients preference due to aesthetic appliance.
2. Less iatrogenic effects: According to a systematic review
(Elhaddaoui et al., 2017), clear aligner therapy delivers
less chance of root resorption than a fixed appliance in
non-extraction cases. Similar results were found by other
systematic reviews and meta-analyses (Fang et al., 2019,
Aldeeri et al., 2018). However, a systematic review by
Gandhi (Gandhi et al., 2021) found a significant differ-
ence in root resorption between the clear aligner and
fixed appliances only on right maxillary lateral incisors
with fixed appliances causing more resorption. Accord-
ing to a systematic review (Cardoso et al., 2020), orth-
odontic patients treated with Invisalign appear to feel
lower pain levels than those treated with fixed appliances
during the first few days of treatment.
3. Less detrimental effects of the periodontal tissue (Ros-
sini, et al. 2015a, Karkhanechi et al., 2013) mainly due
to improved oral hygiene, minimal uncontrolled tipping
teeth, light force system and minimal planned movement
(linear and angular movement in the range of 0.12mm
and 1 degree respectively per aligner). However, it was
found that the concentration of biological markers were
similar for aligners and fixed appliances (Castroflorio, et
al. 2017).
4. Improved efficiency due to longer visit intervals, up to 12
weeks. A systematic review (Zheng et al., 2017)
found that the current evidence on aligners only sup-
ports shortened chair time and treatment duration in
mild-to-moderate cases compared to conventional fixed
appliances. According to a systemic review (Rossini
et al., 2015b), it was concluded that there is low-quality
evidence that aligners treatment is associated with im-
proved periodontal health indices. Similar results were
put forward by another meta-analysis(Jiang et al., 2018).
It was suggested that aligners could be used in orthodon-
tic patients who have a high risk of developing gingivitis.
5. Improving technology development.
6. An acceptable range of tooth movement including:
• Anterior alignment and buccolingual changes are
almost comparable to fixed for anterior (Robertson,
et al. 2020)
• Tipping movement are 77% as accurate as fixed
appliance therapy (Weir 2017), while bodily move-
ment is 36% as accurate as fixed appliance therapy
(Zhou and Guo 2020)
• Obtaining 2.6mm of molar distalisation without the
use of skeletal anchorage (Simon, et al. 2014)

clear alligner appliances 27
• Achieving expansion of 2mm at the canine region.
• Vertical control in high angle and anterior open bite
cases, achieving an average of 3.27mm of overbite
due to a combination of maxillary and mandibular
incisor extrusion and maxillary and mandibular
molar intrusion (Harris, et al. 2020a)
Disadvantages of CAT
These include:
1. Aesthetics of attachments: An eye-tracking technique
compared photos of patients with attachments in different
locations in the mouth, this study showed that laypeople no-
ticed attachments and preferred ceramic brackets over align-
ers with anterior attachments (Thai, et al. 2020).
2. Patient satisfaction with the outcome is below that
achieved with the fixed appliance (Thai, et al. 2020). The
mean accuracy of Invisalign for all tooth movements was es-
timated at 41% in a clinical study (Kravitz et al., 2009). Djeu
et al. (Djeu et al., 2005) made a retrospective comparison of
outcomes of non-extraction Invisalign and fixed appliance
treatments, using the ABO objective grading system (Thomas
Set al 1998), and found a significant difference in the pass rate
of Invisalign compared to Tip-Edge treatment (20.8%, 47.9%,
respectively) and the time for Invisalign at 1.4 years com-
pared to 1.7 years for Tip-Edge treatment. So, Invisalign is
shorter in the duration of treatment but with poor outcomes.
It is shorter in time because it moves the teeth without round-
tripping to the defined final position. Lagravere’s (Lagravère
and Flores-Mir, 2005) systematic review found insufficient
evidence for the treatment effects of Invisalign treatment. The
study concluded that clinicians must rely on their Invisalign
clinical experience when using Invisalign appliances.
3. Except for minor horizontal movements (Robertson, et
al. 2020), almost all movements have poor accuracy and pre-
dictability with CTA, for instance:
• Deep bite reduction is unpredictable, and a maxi-
mum of 1.6mm correction can be achieved (Khos-
ravi, et al. 2017) with around 50% of accuracy (Al-
Balaa, et al. 2021).
• Rotational and vertical movements have poor pre-
dictability (Charalampakis, et al. 2018) with 40% ac-
curacy for the derotation (Simonds and Brock 2014).
• More than 2mm of space closure is difficult to
achieve with CAT (Papadimitriou, 2018)
• The average predictable distalisation is 1.5-2.6mm
• Expansion is achieved mainly via tipping (Houle,
2017; Zhou, 2020)
• 80% of clear aligner cases that were submitted to the
American Board of Orthodontics failed to pass the
criteria compared to 50% failure with fixed appli-
ance (Djeu, 2005).
• According to a systematic review (Rossini et al.,
2015a), clear aligner therapy effectively achieve the
following: level align, anterior intrusion, contro
posterior buccolingual inclination and upper molar
bodily movements of about 1.5 mm. Aligners are
ineffective in anterior extrusion, correction of tooth
rotation, notably round teeth, and controlling ante-
rior buccolingual inclination. The present evidence
was of low quality.
4. Additional refinement is likely in most cases as 50% of
the overall movements is achieved with the first set of align-
ers, with the first refinement accuracy increases to 75%
(Haouili, 2020). Many orthodontists, however, report that
70-80% of patients require case refinement and /or detail-
ing with fixed appliances. Align Technology suggests that
20-30% of patients may require mid-course fixed appliance
orthodontic appliance correction to achieve the predicted
treatment outcome. For adult patients, a systematic review
(Papageorgiou et al., 2020) found that aligners are associ-
ated with worse treatment outcomes than fixed appliances.
EXAM NIGHT REVIEW
History
Sheridan initially described CAT in 1980 and 1990 (Sheri-
dan, 1994)
General indications of CAT
• Mild to moderate crowding
• Mild spacing
• Mild overbite problems
• Narrow arches that can be expanded without tip-
ping the teeth too much.
General limitations of CAT
• Crowding over 5 mm.
• Spacing over 5 mm.
• Anterior-posterior discrepancies of more than 2
mm.
• Significant open bite correction.
• Severely rotated teeth more than 20 degrees.
• Severely tipped teeth, more than 45 degrees.
• Teeth with short clinical crowns.
Claimed advantages of CAT
• Ideal aesthetics
• Less pain, decalcification and OIRR compared to
conventional fixed appliance therapies.

clear alligner appliances
28
References
Aldeeri, A., Alhammad, L., Alduham, A., Ghassan, W., Shafshak, S.
& Fatani, E. 2018. Association of Orthodontic Clear Aligners with
Root Resorption Using Three-dimension Measurements: A System-
atic Review. J Contemp Dent Pract, 19, 1558-1564.
Cardoso, P. C., Espinosa, D. G., Mecenas, P., Flores-Mir, C. &
Normando, D. 2020. Pain level between clear aligners and fixed
appliances: a systematic review. Prog Orthod, 21, 3.
Djeu, G., Shelton, C. & Maganzini, A. 2005. Outcome assessment
of Invisalign and traditional orthodontic treatment compared with
the American Board of Orthodontics objective grading system. Am
J Orthod Dentofacial Orthop, 128, 292-8; discussion 298.
Elhaddaoui, R., Qoraich, H. S., Bahije, L. & Zaoui, F. 2017. Orth-
odontic aligners and root resorption: A systematic review. Int
Orthod, 15, 1-12.
Fang, X., Qi, R. & Liu, C. 2019. Root resorption in orthodontic
treatment with clear aligners: A systematic review and meta-analy-
sis. Orthod Craniofac Res, 22, 259-269.
Gandhi, V., Mehta, S., Gauthier, M., Mu, J., Kuo, C. L., Nanda, R. &
Yadav, S. 2021. Comparison of external apical root resorption with
clear aligners and pre-adjusted edgewise appliances in non-extrac-
tion cases: a systematic review and meta-analysis. Eur J Orthod, 43,
15-24.
Jiang, Q., Li, J., Mei, L., Du, J., Levrini, L., Abbate, G. M. & Li, H.
2018. Periodontal health during orthodontic treatment with clear
aligners and fixed appliances: A meta-analysis. J Am Dent Assoc,
149, 712-720.e12.
Karkhanechi, M., Chow, D., Sipkin, J., Sherman, D., Boylan, R. J.,
Norman, R. G., Craig, R. G. & Cisneros, G. J. 2013. Periodontal
status of adult patients treated with fixed buccal appliances and
removable aligners over one year of active orthodontic therapy.
Angle Orthod, 83, 146-51.
Kravitz, N. D., Kusnoto, B., Begole, E., Obrez, A. & Agran, B. 2009.
How well does Invisalign work? A prospective clinical study evalu-
ating the efficacy of tooth movement with Invisalign. Am J Orthod
Lagravère, M. O. & Flores-Mir, C. 2005. The treatment effects of
Invisalign orthodontic aligners: a systematic review. J Am Dent
Assoc, 136, 1724-9.
Malik, O. H., Mcmullin, A. & Waring, D. T. 2013. Invisible ortho-
dontics part 1: invisalign. Dent Update, 40, 203-4, 207-10, 213-5.
Papageorgiou, S. N., Koletsi, D., Iliadi, A., Peltomaki, T. & Eliades,
T. 2020. Treatment outcome with orthodontic aligners and fixed
appliances: a systematic review with meta-analyses. Eur J Orthod,
42, 331-343.
Rossini, G., Parrini, S., Castroflorio, T., Deregibus, A. & Debernar-
di, C. L. 2015a. Efficacy of clear aligners in controlling orthodontic
tooth movement: a systematic review. Angle Orthod, 85, 881-9.
Rossini, G., Parrini, S., Castroflorio, T., Deregibus, A. & Debernar-
di, C. L. 2015b. Periodontal health during clear aligners treatment:
a systematic review. Eur J Orthod, 37, 539-43.
Sheridan, J. 1994. Essix appliances: minor tooth movement with
• Improved periodontal health (Karkhanechi et al.,
2013).
• Shorter treatment duration
Disadvantages of CAT
• Poor control over root movements
• Not suitable for use in anterior-posterior discrepan-
cies greater than 2-4
• Lack of operator control

clear alligner appliances 29
divots and windows. J Clin Orthod, 28, 659-663.
Zheng, M., Liu, R., Ni, Z. & Yu, Z. 2017. Efficiency, effectiveness
and treatment stability of clear aligners: A systematic review and
meta-analysis. Orthod Craniofac Res, 20, 127-133.

5
1. Classification of Headgear
2. Components of the headgear
3. Types of maxillary retraction headgear
4. Clinical uses of retraction headgear
5. Factors influencing the effects of headgear
6. Fitting of retraction headgear
7. Problems and limitations of headgear
8. Classification of headgear injury
9. Chin cup
10. EXAM NIGHT REVIEW
In this chapter
Extraoral
appliances

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