Orthodontics at a Glance

Orthodontics at a GlanceDaljit S. Gill

BDS (Hons), BSc (Hons), MSc, FDSRCS (Eng), MOrth, FDS (Orth), RCS (Eng)

Consultant Orthodontist/Honorary Senior Lecturer Eastman Dental Hospital (UCLH NHS Foundation Trust)/UCL Eastman Dental Institute, London, UK

Honorary Consultant Orthodontist Great Ormond Street Hospital, London, UK

This edition first published 2008© 2008 Daljit S. Gill

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ISBN: 9781405127882

Library of Congress Cataloging-in-Publication DataGill, Daljit S.

Orthodontics at a glance / Daljit S. Gill.p. ; cm. – (At a glance series)

Includes index.ISBN-13: 978-1-4051-2788-2 (pbk. : alk. paper)ISBN-10: 1-4051-2788-0 (pbk. : alk. paper) 1. Orthodontics. I. Title. II. Series: At a glance series(Oxford, England)[DNLM: 1. Orthodontics–methods–Handbooks. WU 49 G475o 2008]

RK521.G55 2008617.6′43–dc22 2007042412

A catalogue record for this book is available from the British Library.

1 2008

v

Contents

Acknowledgements and dedication vii

1 Introduction 2

Craniofacial growth and development2 An introduction to facial growth and development 63 Growth and development of the neurocranium 84 Growth and development of the naso-maxillary complex 105 Growth and development of the mandible 126 Growth and development of the soft tissues 147 Development of the dentition 16

Diagnosis and treatment planning8 The aetiology of malocclusion: (i) skeletal and

soft tissue factors 209 The aetiology of malocclusion: (ii) locals factors and habits 22

10 Classification of malocclusion 2411 Principles of orthodontic treatment planning 2612 Risks and benefits of orthodontic treatment 2813 History 3014 Extra-oral examination: skeletal pattern 3215 Extra-oral examination: soft tissues 3416 Intra-oral examination 3617 Smile analysis 3818 Space analysis 4019 Orthodontic records 4220 Cephalometric analysis 44

The management of malocclusion21 Class I malocclusion 4822 Class II division 1 malocclusion 50

23 Class II division 2 malocclusion 5224 Class III malocclusion 5425 Asymmetries 5626 Open bite malocclusion 5827 Deep bite malocclusion 6028 Interceptive orthodontics 6229 Poor prognosis first permanent molars 6430 Crossbites 6631 Impacted teeth 6832 Impacted maxillary canines 7033 Hypodontia 7234 Supernumerary teeth 74

Treatment techniques35 The biology of tooth movement 7836 Biomechanics of tooth movement 8037 Anchorage management 8238 Removable appliances 8439 Functional appliances 8640 Fixed appliances 8841 Stability and retention 9042 Adult orthodontics 9243 Orthognathic surgery 9444 Cleft lip and palate 96

Appendix 1 The Index of Orthodontic Treatment need (IOTN) 98

Appendix 2 Commonly used cephalometric points and reference lines 100

Glossary of orthodontic terms 101Index 104

vii

Acknowledgements and dedication

(Evans, R. & Shaw, W. Preliminary evaluation of an illustrated scale for rating dental attractiveness. European Journal of Orthodontics1987;9:314–318).

Dental Update for Figure 17.1B.

Dr Robin Richards (Department of Medical Physics and Bioengineering,University College London, London) for Figure 19.1D.

Finally, I would also like to acknowledge and thank Katrina Chandlerand all the production team at Wiley-Blackwell for their enthusiasm,support and hard work throughout this project.

DedicationI would like to dedicate this text to my parents and grandparents for theopportunities they have given me, their love, kindness and encourage-ment throughout my life.

I would like to acknowledge the following people for permission toreprint figures used within the text:

Staff at the Eastman Dental Hospital (University College LondonHospital NHS Foundation Trust, London)/University College LondonEastman Dental Institute, London, and Farhad Naini (ConsultantOrthodontist, St George’s and Kingston Hospital), for providing someof the photographs used in this book.

Don Enlow and Mark Hans for Figures 3.1A, 4.1A, 4.1B and 4.1C.

Elsevier for Figures 5.1B and 35.1C (from Proffit, W.R. ContemporaryOrthodontics).

Orthocare for permission to reprint the Dental Health and Aestheticcomponents of the Index of Orthodontic Treatment Need. The SCANscale was first published in 1987 by the European Orthodontic Society

2 Introduction

1 Introduction

Figure 1.1 The scope of orthodontic treatment. Orthodonticscan be used for (A) the correction of malocclusion, (B) tofacilitate restorative treatment, (C) to aid surgical correctionof severe skeletal discrepancies, (D) to facilitate thetreatment of cleft lip and palate, and (E) for the comprehensivemanagement of craniofacial deformity as in this patient withSturge–Weber syndrome.

AB

C D

E

Figure 1.2 A risk–benefit analysis should be undertaken before commencing orthodontictreatment. Only if the benefits outweigh the risks should treatment be undertaken.

Risks

DecalcificationRoot resorptionPeriodontal damagePoor satisfaction

Benefits

PsychologicalDental health

Introduction 3

Orthodontics is the specialty of dentistry concerned with growth anddevelopment of the face and dentition, and the diagnosis, preventionand correction of dental and facial irregularities. The word orthodonticscomes from the Greek words ortho meaning straight and odons meaningtooth.

The scope of orthodontic treatmentOrthodontic treatment is commonly undertaken for the management of malocclusion. Malocclusion is any deviation from normal or idealocclusion. It should not be considered as a disease but a variation of normal. When such a deviation impacts on an individual’s psychologicalor dental health one should consider orthodontic treatment.

Besides the management of malocclusion, orthodontics is increas-ingly being undertaken to enhance the results of other forms of dentaland surgical treatment (multidisciplinary care, Figure 1.1A–E). Forexample, orthodontics can be used to facilitate:• restorative treatment;• the management of severe skeletal discrepancies in combination withorthognathic surgery;• management of cleft lip and palate;• management of severe craniofacial deformity;• management of obstructive sleep apnoea.

The demand and need for orthodontictreatmentThe patient’s perception of the need for treatment does not necessarilyalways correspond with the professional’s viewpoint. Often patientswill request treatment when there is very little need on dental healthgrounds. In other cases, patients may not want to pursue treatment even when there would be a clear dental health benefit. A risk–benefitanalysis is a useful method of determining whether to undertake treatment. This involves weighing up the risks and benefits of treatmentand only undertaking care if the risks are clearly outweighed by thebenefits (Figure 1.2).

The need for orthodontic treatment, based on professional criteria, is dependent on the population studied. The treatment need in the UK,on the basis of the Index of Orthodontic Treatment Need (IOTN, seeAppendix 1), is estimated to be approximately 45% in 12-year-olds and35% in 15-year-olds (IOTN Dental Health Component 4 and 5). Theuptake of treatment among females is greater than among males even

though the need is equal. In the USA, the treatment need is estimated tobe 42% in white adolescents and 30% in black adolescents aged 12–17years. These figures assume that patients who had already receivedtreatment at the time of survey had a definite need for treatment.

Where is orthodontic treatment provided?The majority of orthodontic treatment is undertaken within specialistorthodontic practices by orthodontic specialists or dentists with a specialinterest in orthodontics. The latter are not specialists but have under-gone some training in orthodontics in addition to training at the undergraduate level. Hospital services provide treatment for thosepatients requiring complex multidisciplinary care and management ofthose malocclusions that are of value for the purposes of teaching andtraining. In the UK, the community dental services also provide care for people from disadvantaged groups for whom access to treatment isotherwise difficult.

How is orthodontic treatment provided?The majority of orthodontic treatment is provided with the use of fixedorthodontic appliances. There has been a steady increase in the numberof patients treated with fixed appliances over time (Table 1.1). The proportion of patients treated with removable appliances has reduced.The quality of the final occlusal result is significantly improved whenfixed appliances are used instead of removable appliances. Removableappliances (e.g. functional appliances) are a useful adjunct to simplify-ing later fixed appliance treatment. The use of fixed appliances shouldnot be attempted without undergoing comprehensive training.

Table 1.1 Types of appliance worn by 12-year-olds (15-year-olds) atthe time of survey in 1993 and 2003 (data taken from UK Child DentalHealth Survey).

Percentage of 12(15)-year-olds wearing orthodontic appliances

1993 2003

Fixed 49% (68%) 72% (83%)Removable 50% (37%) 28% (18%)