Guy’s, King’s andSt Thomas’ Schoolsof Medicine,Dentistry andBiomedical Sciences

GKT Dental Institute University of London

BDSGKT Programme

Year 4 & 52003 / 2004

Orthodontics

Course organisers:

Professor F McDonald

Student Name

N.B. A charge of £6 will be levied for replacement of these notes

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LIST OF CONTENTS

OUTLINE OF THE ORTHODONTI DEPARTMENT COURSE 3

Aims & Objectives of the Undergraduate Orthodontic Course 3

Year 4 3

Year 5 3

GDC REGULATIONS FOR ORTHODONTICS 4

ORTHODONTIC COURSE TIMETABLE 5

Year 4 Spring & Summer 5Year 5 Summer, Autumn & Spring 5Internal assessment for Year 5 5

LECTURE LIST (Year 4 and 5) 6

ORTHODONTIC UNDERGRADUATE TEACING TIMETABLEAT GUY’S CAMPUS 7

TEXT BOOKS 7

THE ORTHODONTIC DIAGNOSTIC FORM 8Initial Details 8

1. Reason for Attendance 8

2. Past Medical History 8

3. Family History 8

4. Past Dental History 9

5. Skeletal Patterns 9

6. Soft Tissue Patterns 9

7. Oral Examination 10

8. Report of Radiographs 12

9. Attitude of Parents 12

10. Conclusions 12

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INFORMATION HANDOUTS AVAILABLE IN THE DEPARTMENT TO GIVE TO PATIENTS

Handout 1 - A Guide to Orthodontic Treatment 14

CEPHALOMETRIC RADIOGRAPHY 16

Basic Cephalometric Analysis 17

Cephalometric Landmarks 21

REVISION NOTES Appendix Pages

Classification of Occlusion and Malocclusion 1

Development of Dentition and Occlusion 2

Aetiology of Malocclusion: Skeletal and Soft Tissue Factors 3

Aetiology of Malocclusions: Local Factors 5

Orthodontic Diagnosis and Treatment Planning 8

Class I Malocclusions 10

Class II Division 1 Malocclusions 12

Class II Division 2 Malocclusions 14

Class III Malocclusions 16

Removable Appliances 17

Fixed and Functional Appliances 19

Facial Growth and Orthodontics 20

Tooth Movement and Retention 22

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Aims of course

To provide a comprehensive course giving the undergraduate student a sound foundation inorthodontic diagnosis and treatment planning to enable the qualified student to recognise a developingmalocclusion and be confident to deal with it or refer for appropriate specialist treatment at the correcttime.

Year 4

Each student attends once a fortnight for a clinical teaching session consisting of a tutorial and clinicalexercises and a clinical patient session. All patients are seen by the whole group each session andstudents work in groups of 2 or 3 to carry out diagnosis and treatment planning for patients andappropriate appliance demonstration treatment patients are seen.

At the end of the year 4, students should know the basics of aetiology, diagnosis and treatmentplanning for all malocclusions, and the use and adjustment of specific removable appliances.

Requirements for year 4 are:-

a) attendance at clinical sessions and participation in diagnosis and treatment planning.b) able to take impressions, insert, adjust and be familiar with specific removable appliance

designs. c) obtain pass mark in year 4 written exam.

Year 5

Students attend clinical teaching sessions consisting of a tutorial (for which the topic and essay planshave been prepared and reading material is given in advance of each tutorial and full participation isexpected) and clinical exercises and a clinical patient session. The clinical patient session will be newpatients for diagnosis and treatment planning. Again all patients are seen by the whole group eachsession and students work in groups of 3 to carryout diagnosis and treatment planning.In addition, during the spring term students should also observe and become familiar withcontemporary treatment techniques by observing postgraduate patients undergoing specific fixedappliance treatments under consultant supervision.At the end of year 5, students should have a comprehensive knowledge of aetiology, diagnosis andtreatment planning and be aware of the possible range of modern orthodontic techniques available andspecifically know what and when to refer for specialist advice and treatment.

Requirements for year 5 are:-

a) attendance at clinical sessions and participation in diagnosis and treatment planning.b) participation in tutorials for prepared topics.

c) observation of fixed appliance techniques, bonding, placement and adjustment of archwires,retainer placement and adjustment, making safe broken appliances.

d) obtain pass mark in year 5 written exam and clinical viva.

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At the completion of the course each student should have fulfilled the current GDC regulations(‘The First Five Years’, second edition 2002) :-

1). ORTHODONTICS

a) be competent at carrying out an orthodontic assessment including an indication of treatmentneed

b) be competent at managing appropriately all forms of orthodontic emergency including referralwhen necessary.

c) be competent at making appropriate referrals based on assessmentd) have the knowledge to be able to explain and discuss treatments with patients and their parentse) have the knowledge to be able to design, insert and adjust space maintainersf) have the knowledge to design, insert and adjust active removable appliances to move a single

tooth or correct a crossbiteg) be familiar with contemporary treatment techniquesh) be familiar with the limitations of orthodontic treatment

2). ORTHODONTICS

Orthodontics is concerned with the development and growth of the face and occlusion the extent ofnormal variation in the form and function of both the hard and soft tissues of the mouth and face, andparticularly the ways in which such variation produces differences in occlusion. The study of thesefactors should emphasise their inter-relationship with the general and psychosocial development of theindividual. Changing patterns of orthodontic care have been influenced by changes in the perception ofsimple orthodontic treatment by both patients and practitioners. Most orthodontic treatment is nowdelivered by specialists. Students should be able to:-a) Carry out orthodontic assessment.b) Identify treatment needs.

c) Understand the role of orthodontics in overall patient care.d) Recognise and describe developing and manifest malocclusions.e) Understand the appropriate timing of interventions and what these interventions are likely to

be.f) See and assist in the delivery of all forms of orthodontic treatment.g) Make safe all forms of orthodontic appliances.h) Know when and how to refer for specialist advice.i) Recognise and manage those problems of the mixed dentition where interceptive treatment is

indicated, including space maintenance.

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Orthodontic Course TimetableYear 4.

Clinical timetable. Students attend once a fortnight for a clinical teaching session.

Spring term clinical teaching sessions

1) Clinical diagnosis.2) Radiographic assessment – use of radiographs – lateral ceph.3) Treatment planning and appliance design exercises.4 & 5) Treatment planning exercise with models and radiographs for class I. (Crowding and spacing)6 & 7) Treatment planning exercise with models and radiographs for class II div. 1 and class II div. 2.

Summer term clinical teaching sessions

8 & 9) Treatment planning exercise with models and radiographs for class III and crossbite.

Internal assessment for year 4.

(50% of total internal orthodontic assessment)(10% BDS)1 hour short question answer paper at end of summer term.

Year 5.

Summer term clinical teaching sessions.

10) Treatment planning exercises with models and radiographs for anterior open bite.11) Extra oral traction. – Clinical aspects, theory and uses.12) Functional appliances. – Clinical aspects theory and uses.

Autumn term clinical teaching sessions.

13) Soft tissues.14) The unerupted maxillary canine.15) Fixed versus removable appliances.16) Referral to specialist and I O T N.17) Timing of treatment, interceptive, adult.18) Tooth movement, retention and stability.19) Revision.

Spring term

1). Clinical competency diagnostic exam and 2) retake exam if required.(3 sessions attachments to postgraduates)

Internal assessment for year 5.

(50% of total internal orthodontic assessment)(5% +5% of BDS).1). 1¼ hours (2 out of 3 essay questions) written exam in December.2). Clinical competency diagnostic exam. 10 minute viva following a 20 minute examination of apatient with appropriate x-rays in January/February.

Lecture list

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Year 4 (Spring and summer term)

Introduction to orthodontics, classification of malocclusionIntroduction to removable appliance designTreatment planning: choice of extractions and appliance therapyDevelopment of dentitionAetiology of malocclusion – skeletal and soft tissues, habitsAetiology of malocclusion – local and dental factorsClass I malocclusionClass II div. 1 malocclusionClass II div. 2 malocclusionClass III malocclusionCrossbitesFunctional appliancesAnchorage and extra-oral tractionFacial growth and timing of treatmentHistology of tooth movement, stability and retentionReferral to specialist and IOTN

Prof. McDonald.Dr. Derringer.Dr. Derringer.Dr. Derringer.Dr. Hill.Miss Padhani.Prof. McDonald.Miss Padhani.Miss Padhani.Prof. McDonald.Dr. Derringer.Dr. Derringer.Dr. Hill.Prof. McDonald.Dr. HillMiss Padhani.

Year 5

Cleft lip and palate – topic teaching with OS

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Orthodontic undergraduate teaching

at Guy’s campus:-

Monday Tuesday Wednesday Thursday Fridayam Year 4 / 5

Miss PadhaniYear 4Mr Thom

Year 4 / 5Dr. Derringer

Year 5Dr. Derringer

Year 4 / 5Mrs Dowsett

pm Year 4 / 5Mrs Dowsett

Year 4Miss Gibilaro

Year 4 / 5Dr. Hill

Year 5Mrs Dowsett

Year 4 / 5Dr. Derringer

Text Books

F.McD & A.J.I = Diagnosis of the Orthodontic Patient (1998)(Available from Floor 22, Guy’s campus Tower).

W.H.O.N. = Walther and Houston's Orthodontic Notes (5th edition)

H S & T = Textbook of Orthodontics, Houston, Stephens and Tulley (2nd edition)

C.D.S. = Companion to Dental Studies, Volume 3, Clinical Dentistry

L.M. = An Introduction to Orthodontics, Laura Mitchell (1996)

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THE ORTHODONTIC DIAGNOSTIC FORMIntroduction (A copy of the form is shown above).This sheet will be used by students with patients presenting for orthodontic diagnosis. The completedform will be discussed at a Teaching Clinic when the assessment is modified as necessary. Althoughthe information as detailed is retained for record purposes, the main purpose of the form is as an aid tolearning and teaching, thus students should not hesitate to complete the details to the best of theirability.

Any important medical history is normally revealed prior to orthodontic consideration but this ischecked and confirmed during this investigation.

The following notes indicate the order in which the various points are determined and recorded in eachsection of the chart.

Initial DetailsThese are generally self-evident -Clinic Name and date of Teaching Clinic on which patient is presented.

Referred by - The TYPE of practice from which the patient has been referred e.g. G.D.P. - GeneralDental Practitioner, C.D.S - Community Dental Service or another department in the hospital.

1. Reason for Attendance

This is to establish whether the patient and parents know why they have been referred and whetherthey have engineered the consultation of their own initiative. Replies help in assessing likely co-operation.

2. Past Medical History

The medical history should be taken as for all patients seeking general dental treatment with thespecial aim of establishing any unusual medical history that may provide -

a - Contra-indication to prolonged treatmentb - Possible difficulties associated with extractionsc - High risk patients e.g. Hepatitis B and HIV positive patients

3. Family History

a) Note any similar dental irregularities (e.g. diastema) or familial skeletal discrepancy (e.g. Class III tendency).

b) History of prior orthodontic treatment for other members of family - will help to assess

co-operation.

c) Observe if parent(s) possess own teeth or dentures.

4. Past Dental History

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i. Any information on previous extractions and methods of anaesthesia. Patients rarely give you aclear history of how many teeth have been extracted and when.

ii Traumatic incidents to the mouth should be recorded with dates eg. fractured incisors.

iii Determine the frequency of previous dental inspections.

iv Note nature and length of any previous orthodontic treatment.

HabitsNote the presence of digit-sucking habits or dates at which such habit ceased (often if stated to berelatively recent, habit may in fact be continuing, though intermittently). For the avid thumb-sucker, determine how many hours a day the digit is in the mouth.

4. Skeletal PatternsClinical Assessment of the External Facial Appearance

a) Antero-posteriorNote should be made of the sagittal relationship of the tooth bearing areas of the mandible andmaxilla. The 'A' and 'B' points are assessed clinically and any obvious discrepancy noted usingthe shorthand Skeletal I, II or III.

b) VerticalA most important aspect of mandibular form is whether the Mandibular Plane (obtained byplacing a straight edge along the lower border of the mandible) subtends a high, median or lowangle to the Frankfort Plane (formed by linking the lower border of the orbit and the supra-tragalnotch). The average is 27°. A very high angle will mean that the extended mandibular planepasses through the occipital bone; a low angle occurs when the two planes are near to parallel.

c) LateralA general appraisal of the child in full face should be made, noting any gross asymmetry. (Mostchildren have slightly asymmetrical faces and this should only be noted when there is obviousasymmetry).

It is also important to note the maxillary and mandibular form, deciding whether they vary fromtheir expected widths. This may be shown by a high vault to the palate, posterior lateralcrossbite or fanning of the incisors.

6. Soft Tissue PatternsA - LIPSa) At rest - A general appraisal should be made of the shape of the lips and their posture at rest. Noteparticularly whether the upper lip is really short from the columella to the vermilion border (redmargin). It should almost cover the upper incisor teeth. Note the thickness of the lips.

If the lips do not form an anterior oral seal at rest they are described as 'incompetent' unless they aremerely separated by proclined upper incisors and are of sufficient length to come together when thedental interference is removed. Such lips are described as 'potentially competent'. Only rarely are lipswhich are sufficiently long to be competent, habitually apart through enforced mouth-breathing due tonasal congestion.

It is most important to note at rest the position of the inner border of the lower lip in relation to thelabial surface of the maxillary incisors. This will affect the prognosis for stability of the upperlabial segment following overjet reduction.

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b) The lips in function - Note should be made of any excessive circumoral contraction duringswallowing and any particular habit. If the lower lip is very taut in expressive behaviour in ClassII cases, special note should be made of this. It is useful to run a finger round the labial sulci toget some idea of the tautness of the labial musculature.

c) The type of anterior oral seal should be determined i.e. lip to lip with or without circumoralcontraction, lower lip to palate, lower lip to tongue, lips together and mandibular posture.

B - TONGUEa) At rest - It is difficult to make an accurate description of tongue size but an obvious disparity in

size of mouth and size of tongue should be noted. It is again difficult to assess tongue restingposture but special note should be made if it is constantly resting forward against the lower lipbetween the teeth.

b) Function - Special note should be made if the tongue not only rests forward but thrusts forwardsto contribute to the anterior oral seal in swallowing and is placed interdentally during 's' sounds.

C - MANDIBULAR PATH OF CLOSURENormally this should be from its resting position by a simple hinge movement with a rotation ofthe condylar head in the glenoid cavity to a position of maximal cuspal interdigitation.

Certain Class II division 1 and division 2 cases habitually posture their mandibles in a forwardposition - thus closure initially appears to require an upward and back movement (mandibular'deviation'). True distal 'displacement' of the mandible following an initial contact is rarely seen.

In patients showing lateral narrowness of the maxillary arch and in Class III type incisorrelationships, it may be possible to demonstrate an initial contact of the cheek or incisor teethfollowed by a lateral and/or forward mandibular ‘displacement’. This must be excluded or notedin all cases where teeth are in crossbite.

D - SPEECHIt may be possible to demonstrate an anterior air escape as with some lisping speech (anteriorsigmatism) especially during the 's' sound. In Class II division 1 types a lateral air escape may benoted.

7. Oral ExaminationA thorough examination is made of the teeth and intra-oral soft tissues. It is particularly important toestimate the prognosis of teeth which have been heavily restored or which require restoration. Thiswill perhaps point to the most desirable teeth to be extracted where extractions are required as part ofthe plan of treatment. Any dubious teeth must be checked for vitality. Using the dental chart: -

a) Note teeth present in the mouth (watch for supplemental maxillary laterals and missing lowerincisors).

b) Caries - Mention when necessary the quality of the previous conservation and identify the rateof onset of caries.

c) Report on oral hygiene and periodontal condition, noting areas of plaque retention or any excessive mobility or pocketing.

d) Lower archLabial Segment.

L.L.S. - Lower Labial Segment

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Note the inclinations of the upper incisors to the Frankfort Plane (approx. 108º ideal) and thelowers to the Mandibular Plane (approx. 90° ideal). Crowding/Spacing and rotations should beidentified. For rotations, describe the direction e.g. mesio-palatal, disto-buccal etc. and thedegrees that the tooth is rotated from the line of the arch. (Rotations are described by theapproximal surface that is furthest from the line of the arch).

e) Upper archULS - Upper Labial SegmentsUBS - Upper Buccal SegmentsNote individual rotations, tilting or drifting. Observe the presence of crowding or spacing.

Relationships of Labial Segments

f) O.J. - OverjetIt is necessary to assess whether the antero-posterior incisor overjet is within normal limits(2-4 mm), increased, decreased, edge-to-edge or reversed (which is also described as an anteriorcrossbite).

g) O.B. - OverbiteNote should be taken as to whether the vertical incisor overbite is normal (normal being that theupper incisors overlap the lowers by one-third to one-half of their clinical crowns). The overbitemay be increased, decreased, edge-to-edge or there may be a frank anterior open bite. When apositive overbite exists but there is no contact by the lower incisors onto teeth or palate, this isan incomplete overbite - contact produces a complete overbite. With a greatly increasedoverbite there may be contact of the lower incisors with the palatal gingivae or the upper incisorswith the lower labial gingivae (traumatic overbite).

h) C.L. - Centre LinesNote should be made as to whether the upper and lower centrelines are coincident with eachother and whether this is in the centre of face or off to one side. If the centrelines are notcoincident then record which one is incorrect and in which direction it is incorrect.

i) 6s - (Buccal Segment Relationships)6's - Classify the relationship of the first permanent molars in occlusion. If these are missing,or when the malocclusion is complex, then use the premolar or refer to the canine relationship.Angles classification of Class I, II or III is used. Intermediate occlusal positions may be referredto as half way towards the next 'full' relationship (e.g. half-unit Class II first molar relationship -one unit equals width of a premolar).

j) B.S. OCCLUSIONBuccal Segment Occlusion. The bucco-lingual relationship of the cheek teeth may be disturbed.Crossbites will be noted where one or all of the teeth in the lower buccal segment occlude buccalto the buccal cusps of the upper counterparts. The condition may be unilateral or bilateral. Inrare instances the lower buccal segments may occlude completely palatal or buccal to theirantagonists (scissor bite). Always check for a mandibular displacement (see note 3C) whenevera posterior crossbite is present.

Special In-course assessments

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a) Dental - Vitality tests and further procedures to determine the prognosis for the long-termretention of decayed or well filled teeth (may need further information from patient's dentalpractitioner for this).

b) Advisability of reference for opinion of Speech Therapist, Physician, ENT Surgeon.

8 Report of Radiographs

As a routine, radiographs should be taken of all areas where teeth are unerupted, together with anocclusal view of the anterior part of the upper arch. The main objective of radiographs taken priorto the formulation of a treatment plan are to ascertain -

a) Whether the full complement of permanent teeth is developing (especially looking for missing5's, 2/2 and 8's).

b) The position, angulation and form of unerupted teeth e.g. upper canines, lateral incisors havingdeep cingulum pits and dilacerated teeth.

c) Presence of a wide maxillary midline sutural space and possible patent interpremaxillary suture.

d) Presence of active or recurrent caries and/or any periapical lesions.

e) Other conditions - with special reference to unerupted supernumeraries in the maxillary incisorregion.

f) Cephalometric analysis.

At present the routine is to take a DPT though in general dental practice, with a routine dental x-raymachine, it is possible to produce a standard occlusal of the upper incisor region and rotated obliquelateral jaw films (bimolars) which should show the 8 - 4 in each quadrant.

9 Attitude of Parentsa) To establish whether parents comprehend the nature of orthodontic treatment and whether they

want it for their child and are likely to see it through.

b) Attitude of patient and whether he/she wants orthodontic treatment.

10 ConclusionsA Case Description

or SUMMARY - A short description of the case type, mentioning -

i Angles incisor classification - Class I, Class II division 1, Class II division 2, Class III - If theseare not suitable then describe more fully in terms of overjet and overbite.

ii Skeletal pattern - Skeletal I, II or III - Include the vertical dimension if this varies greatly fromthe average figures.

iii Crowding if present and site.iv Any obvious local factors e.g. missing teeth etc.

B Aetiology or FACTORS - which have contributed to the malocclusion; i.e.

a) Dental Base Relationships - In any of the three spatial planes.

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b) Soft Tissues - Noting to what extent these have either contributed to or compensated for themalocclusion.

c) Dento-alveolar disproportion (Disproportion between arch sizes and number of teeth) - It isimportant to assess whether there is potential crowding or spacing. Few patients are able toaccommodate all 32 teeth in good alignment.

Assessment of potential crowding can be helped by deciding whether there is good length ofjaw. Crowding is primarily due to anterior-posterior shortness of the jaw. If there has beenany premature loss of deciduous teeth the degree of space closure by mesial movement ofposterior teeth and some migration round the arch of anterior teeth, will give any indication ofthe degree of potential crowding present. Although it may be helpful to measure spacesagainst the width of successional teeth, such is the variation in tooth size that this is of dubiousvalue.

d) Local Factors - e.g. supernumeraries, habits etc.

C Aims of Treatment (Theoretical) - Main objectives of treatment such as -

a) Limit treatment to deal with crowding only

b) Retraction of maxillary incisors within lower lip activity

c) Tilting of proclined incisors to compensate for a skeletal discrepancy.

d) Tilting of normally inclined teeth would be unacceptable.

D Treatment

1 Decide if an extraction or non-extraction case.

2 Enumerate stages of treatment - if necessary give the various lines of treatment that may beconsidered.

3 Give details of types of appliances.

E Prognosis

As accurate as possible a forecast of the ultimate effects of treatment and some opinion as to thefinal stability of the case and factors which might affect it e.g. upper incisors within control of thelower lip following reduction of the overjet.

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INFORMATION HANDOUTS AVAILABLE IN THEDEPARTMENT TO GIVE TO PATIENTS

Handout 1 - A GUIDE TO ORTHODONTIC TREATMENTRef:HOT/UGO/STO/90/5

When necessary, orthodontics aims to improve the position and appearance of the teeth and face. Thetreatment also helps to ensure the long-term health of the teeth and gums. The treatment is rarely verysimple or quick and perfectly straight teeth are not necessarily obtainable, though considerableimprovement is the usual outcome of the treatment. The following notes will help to give you someidea of what is involved in a course of orthodontic treatment. They are general and if you need furtherdetails, please do not hesitate to ask.N.B. Due to current NHS arrangements, not all referred patients can be accepted for Hospitalorthodontic treatment.

Treatment Timing

Active treatment is usually first considered at about the ages of 10 to 12, since by then most of theadult teeth are present. In some cases earlier treatment may be needed. Adults can also have treatmentalthough the objectives will be different and progress may be slower.

Planning Treatment

Consideration of possible orthodontic treatment cannot begin without first obtaining detailedinformation. At an initial appointment we generally take radiographs, photographs and dentalimpressions (to make a mould of the teeth). A further appointment will be made to be seen on a'Consultant Clinic' when the full assessment is completed and any necessary treatment will beexplained to you.

Duration of Treatment

The time taken for orthodontic treatment is variable. Although some very simple treatment may lastonly a short while, routine treatment could take between one to three years. During treatment you willgenerally be required to attend appointments regularly once a month, and return between appointmentsif the brace breaks or cannot be worn.

At the end of treatment it is likely that simple 'retaining' appliances will be inserted, to allow the teethto settle well in their new positions. The necessary check appointments at that stage are not as frequentas during active treatment.

Requirements

Success of orthodontic treatment does not depend solely on the skill of the dentist, but also on theparents, and especially the patient who has to carry out the dentist's instructions. Without bothencouragement and enthusiastic co-operation, a good result is unlikely.

The requirements of routine orthodontic visits will involve loss of time from school or work. Beforedeciding on treatment you will need to make arrangements for regular leave of absence from school orwork throughout the full course of treatment. Bear in mind that the appointments will occur eachmonth, on the same day of the week, during normal working hours, Monday to Friday.

Waiting ListsOnce you decide to accept treatment, the commencement will be delayed until your name reaches thetop of our treatment waiting lists.

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Extraction of Permanent Teeth

It may be necessary to have certain permanent teeth extracted as part of the treatment. This is usuallybecause the jaws are not large enough to hold all the teeth. The space created by their loss will allowthe remaining teeth to be straightened. Usually the extractions are carried out by your own dentist, butin certain cases an overnight stay in hospital may be needed.

Appliances

Treatment will usually involve the wearing of an orthodontic appliance (brace) inside the mouth.The brace may be fixed to the teeth and only removed by the dentist at the end of treatment.Alternatively a removable brace is provided, which is worn day and night but only removed forcleaning.

When wearing an appliance it will be important to carry out all instructions, particularly thoseconcerning cleaning of the teeth and gums.

As well as needing to attend by appointment for the regular visits when the brace is adjusted, you willalso have to return swiftly between appointments, during the working hours of 9.30 - 12 or 2 - 4,Monday to Friday, should the brace break or cause serious discomfort.

Treatment is generally provided free of charge. If, however, an appliance is carelessly damaged orlost, a charge may be made for its replacement.

Appointments

It is necessary to be on time for your appointments as the dentist carrying out your treatment works to aclose appointment system. On our part, we shall do our best not to keep you waiting.

When under Treatment

At each visit a further appointment will be given to you. This will represent the appropriate period oftime that the appliance may be left safely, before further adjustments must be made. When it is notpossible to keep an appointment you will need to contact and inform your orthodontist, as soon aspossible, to re-arrange the next visit.

Remember it is most important, if problems occur, to return between appointments for corrections to becarried out.

General Dental Treatment

If you have been sent by your dentist for orthodontic treatment, it is essential that you continue toattend your own dentist at regular intervals for routine inspections and any necessary fillings, etc.Alternatively, please remind us regularly, if your general dental care is also under our supervision.

ORTHODONTIC DEPARTMENTFLOOR 22, GUY’S CAMPUS TOWER

LONDON BRIDGE SE1 9RT0207 955 4037

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CEPHALOMETRIC RADIOGRAPHY

Cephalometric radiography is one of the standard diagnostic tools in orthodontics, it is used:-

1) To help PLAN certain treatments

2) To EVALUATE treatment changes

3) As a tool for RESEARCH AND COMMUNICATION between clinicians.

Clinically, cephalometric analysis is of value in:-

(a) helping to assess facial form (especially the dental base relationships),

(b) as an aid to treatment planning,

(c) to evaluate the extent to which any changes that occur are due to growth or treatment.

Cephalometric radiography was described in simultaneous publications by Broadbent and Hofrath in1931. It involves radiographs being taken under standardised conditions, so that the measurementsrecorded can be compared between different patients and between the same patient at different times.

The patient's head is held in position with specially constructed ‘ear posts’ in apparatus termed a'Cephalostat'. Each time a patient is seated in the apparatus, the x-ray tube, the mid- sagittal plane ofthe patient's head and the film are held at fixed distances. The central ray from the x-ray tube isthrough the ear posts, which have been constructed to incorporate two radio-opaque circles of differentdiameter. If the patient's head is correctly positioned within the Cephalostat, on the resultingradiograph the ear posts will show as concentric circles.

There is no manufacturer's agreement on the exact distances between x-ray tube, mid-sagittal plane andfilm. Thus the degree to which the image has been magnified during this type of radiographic processmust be determined if there is a need to compare films taken on different machines.

When the patient is positioned within the cephalostat, it is therefore important that:-

1) The ear posts are not deflected and lie completely within the ear canals.

2) The patient's Frankfort plane is viewed as being horizontal i.e. parallel to the floor.

3) The teeth are generally held in the intercuspal position. [Where a mandibular displacement hasbeen previously recorded, a request can be made for the mandible to be also positioned in centricrelation, to record the teeth in their initial contact position.]

4) The lips should be in a relaxed, habitual position.

Figure 1 shows the general relationship of film, patient's head and tube for cephalometric radiography.

BASIC CEPHALOMETRIC ANALYSIS

Cephalostat

Central RayTube

Film

Figure 1

5ft 1ft

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It is conventional to trace the lateral cephalogram with the patient's head facing to the right. Theradiograph should show both hard tissue detail and the soft tissue profile. (The shadows of the metalrings within the ear posts should appear as concentric circles.)

TRACING

The film is placed on a viewing box and, once satisfactorily orientated, it is secured with sellotape.The film is then covered with tracing paper which is also secured with sellotape. Various hard tissuestructures and the soft tissue profile are traced. These include:-

1) The outlines of the mandible and maxilla

2) The outlines of the most prominent upper and lower incisors and first permanent molars

3) The base of the skull (sella turcica, nasal and frontal bones)

4) The lower border of the orbit and external auditory meatus (or the porion as identified from theposition of the ear posts)

The face is often not perfectly symmetrical and there is usually some discrepancy in the magnificationbetween the two sides of the head, producing two sets of outlines for the mandibular border and orbit.

When two shadows of a structure are seen, (such as the left and right aspects of the lower border of themandible) then both are traced, and any landmark, (e.g. gonion) is taken as midway between the twopoints.

The cephalometric landmarks to be used later in an analysis of the radiograph are identified on thetracing. It is bad practice to mark these locations on a radiograph since this will bias any subsequentrepeat measurements. The commonly used landmarks that have been agreed are a compromisebetween the tracer's ability to reproduce them repeatedly and accurately, and the validity of theanatomical sites chosen. However, rigid definition of the landmarks are essential if the results are to bevalidly reproducible between different tracers.

Commonly used landmarks are shown with their definitions printed in Appendix I at the end of thesenotes.

There are many different cephalometric analyses, some of which have received internationalacknowledgement. Such an analysis is a collection of measurements, ideally associated with a set ofnormal values, which aims to compress the cephalogram information into a form that can be used forevaluating clinical assessment and treatment planning.

It is not meant to provide a set of figures as an objective for treatment.

ANALYSIS

1. Antero-Posterior Dental Base Relationship (Skeletal Pattern)

There are many ways of determining the skeletal pattern. One of the simplest is to measure theangles SNA/SNB.SNA/SNB Difference (sometimes referred to incorrectly as Down's Analysis)

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Points A and B have been taken as the anterior limit of the dental bases. The relationship of theseto the anterior cranial base (S-N line) can be determined. Thus the angles SNA and SNB willmeasure the position of the maxilla and mandible relative to the anterior cranial base. Thedifference between these angles (ANB) indicates the jaw relationship:

Angle ANB 5º or > Skeletal base II 2-4º Skeletal base I 1º or < Skeletal base III

Figure 3 SNA/SNB

The ANB assessment is quick and simple but has the disadvantage that the angle ANB can varywith vertical or horizontal positioning of sella or nasion in the skull.

Thus the further that the patient's SNA angles varies from 82º (+ 3º) the more inaccurate becomesthe interpretation of the values of the ANB angle! As a crude rule of thumb, if SNA departs from82º, a correction (termed the Eastman correction) can be applied. [N.B. For every degree that SNAis above 82º, subtract ½º from the angle ANB. For every degree below 82º add ½º to ANB. Thiscompensation becomes less valid as SNA departs greatly from 82º.]

The mandibular plane is drawn between menton and gonion.

The lines of the maxillary and mandibular planes should be extended on the tracing paper until theymeet, and the angle between them (MMPA) measured. The average is 27º ± 4º.

It is interesting to note that if this angle is significantly greater than 32º, the anterior lower facialheight is usually increased. Similarly if the angle is reduced below 23º, the lower facial height isoften also reduced.

2) Dental Relations:If the lateral cephalogram has been taken correctly then the incisors will be in their habitualintercuspal position. The relationship between the upper and lower incisors is noted.

N

S

A

B

19

The incisor relationship is defined as the relationship between the incisal edge of the lower incisorsand the cingulum plateau of the upper. If the lower incisor edge lies on the cingulum plateau of theupper incisors it is Class I. If it lies posterior to the cingulum, it is Class II and if anterior, Class III. (Figure 3)

Figure 3

The degree of overjet and overbite present is assessed clinically, but can be corroborated from thelateral cephalogram.

In a normal or Class I malocclusion - THE OVERJET should be between 2-4mm (as measured fromthe incisal edge of the most prominent upper incisor to the labial surface of the corresponding lowerincisor ) and the OVERBITE between 30-50% (as measured by the amount of vertical overlap ofthe lower incisors by the upper incisors.

The next step is to assess the angulation of the incisors to their dental bases. This is done bymeasuring the angles between the long axes of the most prominent upper and lower incisors andtheir respective maxillary or mandibular planes. The upper incisors should make an angle of 109º±5º to the maxillary plane and the lower incisors 92º ± 4º to the mandibular plane.

If the angles are greatly increased, the teeth are proclined. If reduced, retroclined. When theincisors are in a Class I relationship the interincisal angle formed by the intersection of the longaxes of the upper and lower incisors should be 130º ± 5º.

BALLARD'S CONVERSIONAnother method of determining the skeletal pattern involves a geometrical formula and is termed aBallard "Conversion Tracing”. This uses the maxillary plane, the mandibular plane and theshadows of the most prominent upper and lower central incisors.

Lines are drawn through the long axes of these incisors and extended to their respective basalplanes (Maxillary and Mandibular planes). The angles made by these teeth are noted.

On a superimposed second tracing the upper incisor is then tipped to its ideal inclination of 109º, bymoving this tooth about a point on its long axis, that is one-third of its length from the root apex.

The lower incisor is similarly tipped about a point one-third of its length from the root apex. [Itsexact angulation will vary inversely with the value of the maxillary-mandibular planes angle(MMPA). The lower incisor to mandibular plane and the MMPA need to total 120º and knowingthis one can calculate the value for the angle of the lower incisor to the mandibular plane]. Thelong axis of the lower incisor in its new 'ideal' position is adjusted as discussed and then projecteduntil it meets the upper incisor. These theoretical geometrical procedures have removed any dentalcompensatory inclination from the teeth. The relationship of the line through the lower incisors andprecisely where it meets the upper incisor long axis indicates the skeletal relationship (see Figures 2and 3).

11 1 111

20

3) Vertical Dental Base Relationship:

The Frankfort plane is taken as a line through orbitale and porion (porion is often identified by theear post position!) Since both orbitale and porion can be difficult to identify, the maxillary plane(ANS-PNS) is commonly used instead to represent the inclination of the maxilla. [The Frankfortand maxillary planes were assumed to be approximately parallel but there is in fact a markedindividual variation and the maxillary-mandibular planes angle needs to be measured accuratelyeach time]

INTERPRETATION OF THE ANALYSIS

As a result of the above, we have established:

SNA 82º ± 3º ]SNB 78º ± 3º ] This gives the anterior/posterior skeletal base relationshipANB 3º ± 2º ]

MMPA 27º ± 4º ] Maxillary/Mandibular Planes Angle gives the vertical skeletal relationship

1 Mx Pl 109º ± 6º ] The degree of proclination / retroclination will indicate the type of tooth1Md Pl 92º ± 6º ] movement that treatment should involve

1 to 1 130º ± 5º ] The interincisal angle should ideally be around 130º ± 5º at the end of treatment for stability of the incisor relationship.

Figure 4

Ballard’s conversion tracingshowing a Class II division 1incisor relationship on aSkeletal I dental base

(The shaded teeth have been “corrected” to their ideal angle -shown by the dotted lines)

21

Cephalometric LandmarksS - Sella turcica. The midpoint of the pituitary fossa as determined by inspection.

N - Nasion. The most antero-inferior point on the frontal bone at the nasofrontal suture.

ANS - Anterior nasal spine. The tip of the anterior nasal spine as seen in the lateral skull radiograph.

A - A point (sub-spinale). The deepest point on the curvature of the surface of the maxillary bonebetween ANS and the alveolar crest of the upper central incisor.

B - B point (supra-mentale). The deepest point on the curvature of the anterior border of themandible between pogonion and the alveolar crest of the lower central incisor.

Po - Pogonion. The most anterior point on the bony chin in the midline.

Me - Menton. The most inferior point on the mandible at the symphysis.

Go - Gonion. The lowest point on the curvature of the angle of the mandible where the body of themandible meets the ramus. Where bilateral images of the mandible occur, a mid-point betweenthe right and left images should be constructed.

PNS - Posterior nasal spine. The tip of the posterior spine of the palatine bone in the hard palate.

P - or Porion. The highest point on the bony external auditory meatus. If both sides are visible, themidpoint is taken.

Or - Orbitale. The most inferior point on the margin of the orbit. If two orbital shadows are visible,the midpoint is taken.

Frankfort Plane (Porion-Orbitale). This plane is described as being horizontal when the head is in afree postural position. There is, in fact, considerable individual variation and its defining pointsare difficult to identify. For this reason it is more conventional to use the:

Maxillary Plane. This plane is constructed by drawing a line from the anterior to posterior nasalspines. This plane is not usually parallel to the Frankfort plane.

Mandibular Plane (Gonion-Menton). A variety of mandibular planes have been described but one ofthe most commonly used is the line from gonion to menton. It requires the construction ofgonion.

Functional Occlusal Plane (FOP). A line passing through the occlusion of the premolars (ordeciduous molars) and the first permanent molars. The cuspal outlines of these teeth may beunclear and this plane may be difficult to define, particularly in the mixed dentition.

Appendix Page 1

Classification of Occlusion and MalocclusionIDEAL OCCLUSIONRarely exists in contemporary populations.However for the purposes of diagnosis, defining treatment goals and for evaluating treatment outcome, an appreciation of the features of ideal occlusion is

required.1. The line of occlusion passes through the central fossae and along the cingulae of the maxillary teeth and through the buccal cusps and incisal edges of the

lower teeth.2. Approximal tooth contacts are tight, with level marginal ridges, and there are no rotations.3. The distobuccal cusp of the maxillary first permanent molar occludes with embrasure between the mandibular first and second permanent molars.4. There is a flat occlusal plane or slight curve of Spee.5. The long axes of the teeth, except the mandibular incisors, have a slight mesial inclination (i.e. the crowns are more mesial than the roots).6. The crowns of the posterior teeth (canine to molars) have a lingual inclination).

COMMONLY USED CLASSIFICATIONS AND INDICESAngle’s classification• Only internationally recognised classification of malocclusion• Based on the premise that the first permanent molars erupted into a constant position with the facial skeleton. This is incorrect.• 3 groups according to the anteroposterior relationship of the dental arches. Vertical and transverse malrelationships not included.Angle’s Classification:Class I or neutrocclusion - the mesiobuccal cusp of the upper first molar occludes with the mesiobuccal groove of the lower first molar.Class II or distocclusion - the lower first molar occludes distal to the Class I position. Postnormal relationship.Class III or mesiocclusion - the lower first molar occludes mesial to the Class I position. Prenormal relationship.

British Standards Institute classificationBased upon the incisor relationshipClass I. The lower incisor edges occlude with or lie immediately below the cingulum plateau of the upper central incisors. Overjet = 2- 4 mm.Class II. The lower incisor edges lie posteriorly to the cingulum plateau of the upper central incisors. There are 2 subdivisions.

Division 1. The upper incisors are proclined or of an average inclination and there is an increase in overjet. i.e. 5 mm or more.Division 2. The upper central incisors are retroclined. There may or may not be an increase in overjet. i.e. maybe 2-4 mm or 5 mm or more.

Class III. The incisal edges of the lower incisor lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed. i.e. 1 mm or lessincluding negative values.

INDICES OF MALOCCLUSIONNeither Angle’s nor the incisor classification provide a measure of the severity of malocclusion.Different methods are required for estimating (i) prevalence of malocclusion in a population, (ii) treatment priority (iii) treatment success and (iv) investigating

the relationship between malocclusion and various aspects of dental health.The World Health Organisation (1977) proposed requirements for an ideal index:

(i) reliable and reproducible, i.e. does the index give the same result when recorded on two different occasions and by different examiners?(ii) valid, does it measure what it is supposed to measure?(iii) Should be acceptable to professionals and public.(iv) Should require a minimum of judgement to apply it successfully(v) Should be administratively simple.

However few orthodontic indices have been thoroughly tested.

Quantitative Assessment of MalocclusionIndices are used and two separate approaches can be employed. Either

1) Each feature of the malocclusion is given a score, or2) The worst feature of a malocclusion is recorded (e.g. the Index of Orthodontic Treatment Need).

Indices of MalocclusionSummers occlusal Index- develop in 1960s for research. Good reproducibilityThe index scores 9 parameters including overbite overjet, posterior crossbite, median diastema, absent upper incisors, tooth displacement.Index of Orthodontic Treatment Need (IOTN) - used to determine the impact of a malocclusion on an individual’s dental health and psychosocial well being It

comprises 2 elements.Dental health component and Aesthetic component.

Indices of Treatment NeedAim is to rank occlusal disharmonies according to their severity. The index can be used for epidemiological purposes and to establish priorities of treatment.Examples are the Handicapping Malocclusion Assessment Record (HMAR; Salzmann, 1968), and the Occlusal Index (OI; Summers, 1971).The HMAR allocates points for dental irregularities and arch malrelationships, which are multiplied by a weighting factor before the total score is assigned. This

can be done either from orthodontic models or clinically with the patient.The OI scores dental age, molar relationships, overbite, overjet, posterior crossbite, tooth displacement, missing upper lateral incisors. More complicated than

HMAR but more reliable.

Index of Orthodontic Treatment NeedDental Health Component- The single worst feature of a malocclusion is noted (the index is not cumulative) and categorised into one of five grades reflecting

need for treatment. Grade 1-no need, Grade 2- little need, Grade 3 -moderate need, Grade 4 -great need, Grade 5 - very great need.Aesthetic component- developed in an attempt to assess the aesthetic handicap posed by a malocclusion and thus the likely psychosocial impact upon the

patient. The aesthetic component comprises a set of ten standard photographs which also grade from score 1, the most aesthetically pleasing to score 10, theleast aesthetically pleasing. Score 1 or 2-none, 3 or 4 slight, 5,6, or 7 moderate, 8,9,10 - definite. Disadvantage- subjective and no Class III or open bitephotographs.

Indices of Treatment ChangeTo evaluate the quality of treatment provided. The OI has been used and gives reliable and valid results.The Peer Assessment Rating Index (PAR) was developed for use in the British National Health Service (Richmond et al., 1990).Scores are listed for a number of parameters before and at the end of treatment, using study models. Unlike IOTN, the scores are cumulative and a weighting is

applied to each component to reflect current opinion in the UK as to their relative importance.By applying pre and post treatment scores to a nomogram three categories of judgement can be obtained for all types of malocclusion (i) great improvement; (ii)

moderate improvement; (iii) no change.

Appendix Page 2

Development of the Dentition and OcclusionNormal Dental Development - normal means average rather than ideal. A knowledge of what constitutes the range of normal dental development is

essential.A knowledge of both calcification and eruption times is essential for determining (i) dental as opposed to chronological age and (ii) whether a tooth not present

on radiographic examination can be considered absent.

Development of the deciduous dentitionThe neonate is without teeth for 6 months and at birth the lower gum pad lies distal to the upper to a variable degree. During the first year the gum pads and

dental arches widen to accommodate all the teeth.Deciduous incisors are smaller and whiter than their successors. They erupt upright and spaced - a lack of spacing indicates that the permanent successors will

be crowded. The overbite is increased but reduces over the next 4 years until the incisors are edge to edge which may result in marked attrition.Deciduous dentition is complete by ~3 yrs. No increase in lateral or anteroposterior arch dimensions over the next 3 yrs. Absence of lower arch crowding in the

permanent dentition can only be assured if the deciduous dentition is spaced by more than 6 mm.

Transition from the deciduous to the mixed dentitionClassically the mixed dentition begins with the eruption of either the first permanent molars or the lower central incisors at ~ 6yrs.The first permanent molars may be guided into a cusp-to-cusp relationship by the distal surfaces of the deciduous second molars if they are flush at this stage or

into full intercuspation if the lower arch has moved forwards.Growth in maxillary length is necessary to allow eruption of the first permanent molars which develop in the maxillary tuberosity and face buccally, distally and

occlusally.The mandibular molars develop under the anterior border of the ascending ramus of the mandible and growth in mandibular length is required for these teeth to

erupt.The replacement of deciduous teeth by their successors in the buccal segments may commence as early as 7 yrs of age and is not always complete by 12 yrs.There is a discrepancy in the total space occupied by the deciduous cheek teeth compared with that required for their successors (permanent canine, first and

second premolars).The combined width of the deciduous canine, first molar, and second molar is greater than that of their permanent successors, The surplus space or leeway space

as it is known, is greater in the lower arch. On average this space is 1-1.5 mm in the maxilla and 2- 2.5 mm in the mandible.This means that if the deciduous buccal segment teeth are retained until their normal exfoliation time, there will be sufficient space for the permanent canine and

premolars.Teeth in the upper labial segment develop on the palatal aspect of the roots of their predecessors and erupt down, out and forwards.Except in crowded cases, when the upper central incisors erupt, a midline diastema is normally present. The upper lateral incisors develop in a more palatal

position than the central incisors.Treatment is not indicated for the diastema which will gradually close as the upper lateral incisors and canines erupt.The lateral incisors are distally inclined due to pressure from the crowns of the unerupted canines. As development proceeds, the canines move buccally and

should be palpable high in the buccal sulcus and this allows the lateral incisors to become more upright.The upper labial frenum should no longer be attached to the crest of the alveolar process but to its labial surface. A low attachment will interfere with space

closure.The lower permanent incisors erupt before their counterparts in the upper arch.The permanent incisors are larger than their predecessors. Space is made available by:Deciduous incisors are spaced.Permanent incisors erupt more proclined.Increase in the intercanine width at this time ~ 3 mm.Lower incisors in particular, may erupt rotated and crowded as but will spontaneously align if space is made available.The permanent incisors develop behind the roots of their predecessors with the lateral incisors more lingually placed.

Transition from the mixed to the permanent dentitionThe second deciduous molars usually erupt with their distal surfaces flush anteroposteriorly. The transition to the stepped Class I molar relationship occurs when

all the deciduous teeth have been replaced and the upper first permanent molar moves mesially to a lesser extent than the lower first permanent molar.Sequence of eruption is variable. In the lower buccal segment the first tooth to erupt is either the canine or first premolar. The second premolar sometimes

erupts after the second permanent molar.In the upper arch the first premolar usually erupts before the canine.The upper canine erupts into a wider arc in the same manner as the upper incisors and any remaining space between the incisors should close at this time.The second molars erupt at 12-14 yrs and third molars at 16-20 yrs.

Development of the Dental ArchesIntercanine width is measured across the cusps of the canines. During the primary dentition an increase of about 1-2 mm is seen. In the mixed dentition an

increase of about 3 mm occurs which is complete by 9 yrs. A small decrease in labial segment crowding may occur before 9 yrs.Arch width is measured across the arch between the lingual cusps of the second deciduous molars or second premolars. An increase of 2-3 mm occurs between

3 an 14 yrs of age.Arch circumference is determined by measuring around the buccal cusps and incisal edges of the teeth to the distal aspect of the second deciduous molars orsecond premolars. In the maxilla there is little change but in the mandibular arch, the circumference decreases ~ 4mm because of the leeway space.

Late changes in the permanent dentitionMaybe an increase in incisor crowding particularly in the lower arch.Increase in the interincisal angle.Slight increase in mandibular prognathism.Factors contributing to late incisor crowdingPrognathism.Mandibular growth rotations.Soft tissue influences.Mesial migration of the buccal teeth

Appendix Page 3

AETIOLOGY OF MALOCCLUSIONSKELETAL AND SOFT TISSUE FACTORS

INTRODUCTIONMalocclusion can occur as a result of genetically determined factors which are inherited, or environmental factors, or more commonly a combination of both.! Studies from twins indicate that skeletal pattern and tooth size and number are largely genetically determined.! General factors affecting occlusal development include:

Skeletal factors. The size, shape and relative positions of the upper and lower jaws. Soft tissue or muscle factors. The form and function of the muscles which surround the teeth, i.e. the muscles of the lips, cheek and tongue. Dental factors. Size of the dentition in relation to the jaw size.

SKELETAL FACTORS AND OCCLUSAL DEVELOPMENT Any pathological condition affecting growth of the jaws is likely to affect the occlusion of the teeth. e.g. Inherited and acquired congenital malformation, traumaor infection. Uncommon.! Concerned primarily with normal variation, which is frequent and wide ranging.! As the teeth are set in the jaws, the relationship of the jaws to each other will have a large influence on the dental arches.! Skeletal relationship can be considered under 3 headings:

(1) Jaws in relation to the Anterior Cranial Base (2) Jaws in relation to each other (3) Alveolar bone in relation to basal bone

Jaws in relation to the anterior cranial base: The jaws are part of the total structure of the head, and it is possible for each jaw to vary in its positionalrelationship to other structures of the head i.e.vertical, sagittal, and transverse.• Should relate the jaw positions to the anterior cranial base. Jaws in relation to each other: This can occur in all 3 planes.• Sagittal skeletal relationship: The antero-posterior relationship (APR) of the basal parts of the jaws to each other with the teeth in occlusion is known as the

or skeletal pattern. In common use, viz. Skeletal Class I - The jaws are in their ideal APR in occlusion.

Skeletal Class II - The lower jaw in occlusion is positioned more posteriorly than in SkCl I.Skeletal Class III -The lower jaw in occlusion is forward of SkCl I

There is a range of severity of Sk CL II & CL III. Variation in SK relationship can be due to:

(a) variation in size of jaws; (b) variation in the position of jaws in relation to the cranial base

• Transverse skeletal relationship: The relative sizes of the jaws in the lateral dimension also has an effect on occlusion. If the lower jaw is wider, buccal

crossbite arises. If the upper jaw is too wide, lingual occlusion of the lower teeth arises. Crossbites may be unilateral or bilateral. • Vertical skeletal relationship: The vertical relationships of the upper and lower jaws also affects occlusion. The mandible with a high gonial angle tends

to produce a longer vertical dimension of the face, and in severe cases an anterior open bite. The mandible with a low gonial angle tends to produce a shortervertical dimension of the face.

Alveolar bone in relation to basal bone. The term SK relationship refers to the basal bone of the jaws. The relationship between the upper and loweralveolar bones may not necessarily be the same as that between the upper and lower basal bones. Alveolar bone supports teeth and will match tooth positionrather than basal bone position. However the alveolar bone and tooth positions can only differ from the basal relationship within a limited range. This is a veryimportant factor in orthodontic treatment. The reason for the possibility of difference between alveolar and basal bone is that tooth position is not governedentirely by jaw position (see later). However it the basal bone relationship or the skeletal pattern that is the most important in occlusal development. Skeletal Relationship in Orthodontic Treatment• SK rel. is important in occlusal development and orthodontic treatment. Orthodontic treatment which is confined to tooth movement has little effect on the

size, shape or relative positions of the basal parts of the jaws. Its only direct effect is on tooth position and alveolar bone position and form. As teeth must bepositioned on basal bones, the SK relationship limits the amount of orthodontic tooth movement in all 3 planes of space. It may not be possible to correct CLII or CL III incisor relationships if they are based on severe SK II or SK III bases.

• In practical terms, it is easy to alter the inclination of incisor teeth producing little change in their apical positions. Treatment techniques are also availablewhich can produce apical tooth movement but because they are limited in their scope, severe SK discrepancy remains a limiting factor to orthodontictreatment. For example it would be difficult to reduce an overjet of 8mm where the teeth are in the correct inclination. The aetiology of the OJ is the severityof SK II relationship.

Soft Tissues and Occlusal Development• The muscles of the tongue, lips and cheeks are of importance in guiding teeth into their final positions.• Variation in muscle form and function can affect the position and occlusion of the teeth.• These muscles have their main origin on the basal parts of the jaws and so the position of the jaws will influence muscle action. Therefore the muscles should

not be considered in isolation to the jaws.• The Lips and occlusal development: consider their size, form and function. The form and function can be considered in two planes, vertical and sagittal (AP). Lip contour or form: If the lips are everted, the underlying teeth may be proclined and if the lips are vertical with no outward curve at the red margin the

underlying teeth may be retroclined. The average lies between these two extremes. Lip seal: In the vertical dimension considerable variation occurs in the resting lip form. In many individuals the lips do not meet in the rest position, referred to as “labial incompetence”. The reason may be due to the shape of the jaws e.g. when a

high mandibular gonial angle places the origin of the lower lip too far down in relation to the upper lip. In most cases the source of the discrepancy lies in thelips themselves which are too short in the vertical dimension or the wrong shape to meet at rest. Patients with mild lip incompetence unconsciously hold theirlips together by slight circumoral contraction for a significant part of the time.

Appendix Page 4

Lip incompetence is of greatest significance in Cl II Div 1 mal., because the ultimate stability of the corrected incisor overjet depends on a lip seal being

achieved. The desire to maintain a lip seal increases until the late teens. However cases with marked lip incompetence should be given a guarded prognosis. The importance of discrepancies in vertical size of the lips lies in the fact that the lips are usually brought together during swallowing and speech movements. If

they are of sufficient size then lip closure will not place extra forces on the teeth. If the lips at rest are apart then muscular contraction will be required to bringthem together during speech and swallowing, which will impose extra forces on the underlying teeth. Some people whose lips don’t meet at rest, maintain aconscious lip closure, again imposing muscular forces on the teeth. The effect depends on the sagittal relationship of the lips (see below).

LIP LINE: The level at which the lips meet together in normal function is usually called the ‘lip line’. It is applied only to the relationship of the lower lip to

the upper central incisors. In ideal incisor occlusion the resting lower lip covers between a third and a half of the labial surface of the upper central incisors. In CL II Div 1 incisor relationship the lip line will be lower and often fail to control the upper incisors whilst in a CL II Div 2 incisor relationship the lower lip

may cover the entire labial surface of the crown. In SK II relationships the lower lip may function partly or completely behind the upper incisors. If the skeletal discrepancy is not severe, the lip may procline

the upper incisors so that the occlusal relationship is more severely CL II than the SK relationship. If the SK relationship is severe the lower lip may functionbehind the upper incisors without causing them to be proclined.

In other cases of SK II the lower lip functions entirely in front of the upper incisors causing them to be retroclined into CL II Div 2. It is equally possible for lipactivity to produce CL II or CL III incisal relationships on a SK I base. It is also possible for lip activity to produce either a CL I incisal relationship on eithera SK II or SK III base.

The sagittal relationship of the lips is determined by the relationship of the basal bone of the jaws to which they are attached. The lower lip is further back in SkClass II and further forward in SK Class III. This may cause the lower lip to modify the eruptive path of the incisors and alter the primary effect of the SKrelationship on the occlusal relationship, either increasing or decreasing the effect of any skeletal discrepancy.

Tongue position and size are important in determining the occlusion of the teeth. Where the lips are incompetent the tongue will be used to

produce an anterior oral seal during swallowing. This adaptive lip-tongue-alveolar process seal is used because it requires less effort. It tends to disappear as dental development proceeds. Not to much

importance should be attached to an adaptive tongue thrust, however it may produce an incomplete overbite, or more severely an anterior open bite. It is seenmore commonly in CL II Div 1 where the upper incisors make a lip seal more difficult.

Unfortunately about 1% of individuals have a swallowing activity accompanied by tongue thrusting (endogenous tongue thrust). These individuals should beidentified as orthodontic treatment will relapse.

Signs: lisp, reverse curve of Spee in both arches, presence of tongue between the anterior teeth, proclined U/L incisors, tongue thrust associated with lipcompetence.

If the tongue is too large it may prevent the full eruption of the buccal or incisal teeth resulting in open bites or incomplete overbites. HABITS AND OCCLUSION Lip and tongue sucking and pencil biting are of no significance to occlusal development. Digit sucking is of relevance. Considered as normal in infancy as 67% of children suck either a digit or dummy. Probably innate until 2 yrs. Prolongation after

infancy due to learning. The effects on the dentition depends on the persistence of the habit and partly on the favourability of the soft tissues.• Commonly the presence of a thumb between the erupting teeth causes either an incomplete overbite or an anterior open bite which is usually

asymmetrical.• There is often an increase in the overjet due to proclination of the upper incisors.• The upper arch is narrowed by pressure from the cheeks on the buccal teeth. As both arches are of equal width, there is often a lateral displacement of the

mandible into the position of maximum occlusion causing a unilateral crossbite. These defects will disappear if the habit ceases by 7-8 yrs and it is the sole causative factor. Should not underestimate the effects of prolonged and persistent sucking habits. The degree of disturbance in the incisor region is in proportion to the time,

force and manner in which the digit is sucked. Management of digit sucking: Attempts to stop thumb or finger sucking usually fail unless the child wishes to stop, in which case the fitting of any appliance after 8 yrs is usually sufficient.

• Parents should be discouraged from nagging as it is counterproductive.• Drastic measures to break the habit are inappropriate.• Few children persist in the habit to the point where the behaviour justifies psychological investigation.• Dummy sucking causes mild AOB of primary dentition and is transient.

NEUTRAL ZONE AND OCCLUSION Once the teeth have erupted, all the forces acting upon them are equalised to maintain them in a stable position known as occlusion. The muscular forces acting directly on the teeth, that is the muscles of the lips, cheeks and tongue must be in balance if the teeth are to remain in a position of

stability. The fact that the lips and cheeks function outside and the tongue within the dental arches has led to the concept of a ‘neutral zone’ existing between the inner and

outer perimeters of the dental arches, where the forces of the lips and cheeks are balanced by those of the tongue and within which the teeth are positioned. The Neutral Zone, must be considered not only in relation to muscle forces but also in relation to intra-oral pressures which are induced by mandibular positions,

and to occlusal contacts and the integrity of the periodontal ligament. As muscle form and function is to a large extent genetically determined, alteration of muscle activity at a subconscious level by education is difficult. Therefore

not only are the teeth positioned in a neutral zone of the oral environment as a result of development, but they must also be in a neutral zone at the end oforthodontic treatment, otherwise they will move to take up other positions.

This neutral zone has been called a position of ‘muscle balance’ but it probably involves more than muscle pressures. Changes during growth can affect the muscular environment of the teeth as well as the size and relationship of the jaws. If the lips do not meet at rest there is a tendency for them to remain apart during childhood but to be held together by muscular activity progressively more as the

child grows. This puts more pressure on the incisor teeth.

Appendix Page 5

AETIOLOGY OF MALOCCLUSION

LOCAL FACTORS Introduction General factors are considered to be determined genetically and cannot be intercepted to any great extent. Local factors produce a local disturbance in dental

development that becomes more severe the longer it continues to operate. Local factors are much less frequent than general factors however they aresuperimposed on general factors and may provide additional complications to occlusal development. Alternatively, a local abnormality may be the onlymodifying feature present in an individual, the effect of the general factors being favourable.

CLASSIFICATION OF LOCAL FACTORS• Variation in tooth number.• Variation in tooth form.• Aberrant developmental position of individual teeth.• Local abnormalities of soft tissue.• Local pathology.

! VARIATION IN NUMBER OF TEETH1) Supernumerary teeth: one that is additional to the normal series. Occurs in the permanent dentition in 1-2% of the population and in the primary

dentition in < 1%. A supernumerary in the primary dentition is often followed by a supernumerary in the permanent dentition. Result from excessive butorganised growth of the dental lamina. Most frequent in the upper incisor region and are more common in males. Appear to be an inherited feature. Thereare 3 main types of supernumerary teeth in the permanent dentition• Supplemental teeth: extra teeth of normal form and occurs at the end of a tooth series, the most common being the lateral incisor. It is less common to

find supplemental premolars and molars, except in Asian and African populations.• Conical teeth: the typical conical supernumerary occurs in the premaxilla, near the midline, and is often called a mesiodens. It may occur singly or in

pairs. It is sometimes inverted, in which case it does not erupt.• Tuberculate: this type also occurs in the premaxilla, but is different from the conical tooth in form, position, behaviour and time of development. It is a

later development than the conical tooth, its root developing later than the permanent upper central incisor. It appears on the palatal aspect of centralincisors and does not normally erupt in childhood. It may be uni or bilateral and classically it prevents eruption of a permanent tooth.

• Odontome: Rare. Both complex and compound forms.

Effects of supernumerary teeth and their managementI. Failure of eruption: The presence of a supernumerary tooth is the most common reason for the failure of eruption of a maxillary permanent incisor.

However, failure of any tooth in either arch can be due to a supernumeray tooth. Management involves removing the supernumeray and ensuring thatthere is sufficient space to accommodate the unerupted tooth. It is advisable to bond a gold chain to the unerupted tooth at the time of removing thesupernumerary so that traction can be applied to the unerupted tooth if necessary.

II. Displacement: Can cause displacement or rotation of an erupted tooth. Management involves removal of the supernumerary and fixed appliances. Aconical supernumerary may also cause a median diastema. Treatment involves removal of the supernumerary and localised tooth movement.

III. Crowding: This is caused by the supplemental tooth and is treated by removing the most poorly formed or displaced tooth.IV. No Effect: Occasionally a supernumerary tooth (conical) is found as a chance finding on a radiograph. Usually symptomless and can be left in situ

under radiographic examination if they are inaccessible. They are removed if there are signs of enlargement of the follicle, with potential cysticformation around the crown and also if orthodontic tooth movement is required.

2) Gemination: Gemination of permanent teeth is not very common.Usually upper or lower incisors are affected. Treatment depends on the degree of crowding caused.

• Where there are a normal number of incisors and gemination appears to be the merging of 2 of these teeth, no treatment may be required.• An increase in the number of incisor crowns caused by a true gemination will usually cause crowding. This can present a difficult aesthetic problem.

May need to extract the tooth and provide a prosthetic replacement.

3) Hypodontia: Developmental absence of one or more teeth from the dentition, is not common occurring in about 6% of European populations. Total anodontia is rare.

Hypodontia is inherited.

MISSING UPPER LATERAL INCISORS. Incidence 2%.If one is absent the other may be of normal size but is often small and conical.Of importance is the effect of the absence of this tooth on the eruptive path of the maxillary canine, which frequently becomes displaced palatally.The local problem caused by a missing lateral incisor varies according to the arch size and relationship.• In a crowded arch the permanent canine may erupt into contact with the central incisor. If the canine is not too pointed, a reasonable aesthetic result may

be obtained by reducing its tip. • In the average to large arch spacing can be dealt with in several ways.

a) Minimal spacing may be acceptable to the patient. b) Sufficient space for a bridge can be made by retracting the canine.

c) Sometimes the space is too small to accommodate a reasonably sized pontic. The options available are:- i) Create space by distal movement of the upper buccal segments or extract a premolar tooth ii) Closure of the anterior spacing by forward movement of posterior teeth.

• Where there is a CL III incisor relationship and missing upper lateral incisors, advancement of the upper labial segment tends to open up space further sothat a pontic may be necessary.

• In crowded cases serious consideration should be given to transplanting the premolar tooth into the site of the missing incisor.

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MISSING LOWER CENTRAL INCISORS- Uncommon. Incidence 0.5%. Management:• In uncrowded cases an acid etch retained bridge can provide a satisfactory solution.• In crowded cases space can close although a fixed appliance will be required. Absence of lower incisors can have an adverse secondary effect on the upper labial segment because of the difficulty of arranging 6 upper teeth around 5 or

4 lower teeth. Crowding will appear in the upper labial segment unless there is an increased overjet or the upper lateral incisors are diminutive. In othercases it will be necessary to accept a disruption in the buccal occlusion to maintain incisor alignment.

MISSING PREMOLARS- Incidence 5 % lower and 2% upper.• The fact that lower second premolars and less frequently upper second premolars may be missing makes it essential to take radiographs before extracting

permanent teeth to relieve crowding.• Lower premolars can develop late and should not be assumed to missing until 9 yrs.• If the arch is of ample size the second deciduous molars that are not resorbing may remain in place until 30-40 yrs unless they are submerging or are of

poor quality. MISSING LOWER THIRD MOLARS- absence of these teeth has little adverse effect on the developing occlusion and may be of some benefit as

impactions are common and there may be less chance of later deterioration in incisor alignment.• Second molars should not be extracted before the presence of third molars has been confirmed. Third molar development is variable 7-14 yrs.

TEETH OF ABNORMAL FORM DENS-IN-DENTE (tooth within a tooth)- where the lateral incisors are small and conical it is important to check radiographically whether this

abnormality, produced by a coronal invagination, is present. The deep cingulum pit leads into a cavity with a deficient enamel lining, which enablesbacteria to gain access to the pulp.

DILACERATION-this term describes an abnormal angulation between the crown and the root or within the root. The site of deformation depends on the

timing of the disturbance during the tooths development. Usually due to trauma to the deciduous tooth, but sometimes there is no history. Treatment,extract or align if mild.

ABERRANT DEVELOPMENTAL POSITION OF INDIVIDUAL TEETH

The developmental position of any tooth, before it erupts into the mouth, may be such that it cannot erupt into its correct position Teeth most commonlyaffected are the upper canines, lower third molars, upper central incisors and lower lateral incisors. Maybe the result of crowding, trauma or unknownaetiology.

! Trauma affecting developmental position- Upper central incisors are most commonly affected. History of trauma to deciduous incisors at 4-6 yrs. When there is no history of trauma and there is no

dilaceration, the tooth may be congenitally displaced.! Ectopic upper canines• The upper canine is particularly liable to develop ectopically due to its long path of eruption from under the orbital floor.• Prevalence is about 2%.• The tooth commonly becomes deflected palatally, and the deciduous canine is retained. More rarely it becomes grossly displaced lying horizontally

near the floor of the nose.• There is an association between small or absent lateral incisors and ectopic eruption of canines. If the canine crown isn’t detected as a bulge high in

the buccal sulcus it is probably in an ectopic position.• Position confirmed radiographically using two intraoral views with different tube positions. The tooth furthest from the tube moves in the same

direction as the tube according to the parallax principle. It does not deal with the canine that is high. Use a DPT and standard occlusal radiographusing parallax principle.

Treatment:-i. Remove the deciduous canine. This will help to bring the permanent canine back to a normal course of eruption.ii. Note whether there is any root resorption of either the lateral or central incisor. Maybe well advanced by 12 yrs but rarely starts after 14 yrs.

The affected incisor(s) may be symptomless and remain vital and firm even with only half a root.Treatment where the canine is not markedly displaced

i. Insufficient space for the canine, either distalize the buccal segments or extract the upper first premolar. If the canine is in the line of the archno appliance treatment may be necessary.

Treatment Options For Displaced Canines: Is the patient prepared to accept treatment which will be prolonged.1) Leave, review radiographically to see if crypt enlarges with cystic formation.2) Extract especially if deciduous canine crown and root are good or if the first premolar contacts the lateral incisor.3) If the deciduous canine needs to be extracted then an extra 2 mm of space will be needed to accommodate the permanent canine. Either by

approximating spaced anterior teeth or distalizing buccal teeth.

Treatment Of Established Palatal Canine1) Provide adequate space as in 3) above or extract a premolar in crowded cases. In some cases the canine tooth will erupt.2) In most cases surgical exposure is needed with or without attachment of a gold chain so an appliance can be used to align the tooth.3) Surgical transplantation:- canine is surgically accessible and there is sufficient space within the arch. Splinting for 2-3 weeks to

allow formation of a normal periodontal attachment. Vitality of the transplanted canine is less important in the assessment of success than viability. If the tooth is firm with no radiological signs of apical rarefaction or root resoption then endodontic treatment should not be instituted for the tooth that shows no response to vitality testing. After 2 yrs a degree of root resorption is present in 50% of cases. Teeth with patent apices achieve a new pulpal blood supply more readily and have a higher chance of success.

ABNORMAL POSITION OF CRYPTSThe crypt of any tooth may be displaced or rotated. Lower second premolar can show tipping of its developing crown which usually corrects in later

development. The third molar shows a wide range of crown orientation which may improve during development. There is little that early intervention cando except in the case of the developing maxillary canine.

Appendix Page 7

PREMATURE LOSS OF DECIDUOUS TEETHBalancing extraction is the removal of the contralateral tooth. Compensating extraction is the removal of the equivalent opposing tooth.

The major effect of early loss of a primary tooth is localisation of pre-existing crowding although this will not occur in uncrowded cases. Where there iscrowding the adjacent teeth will drift/tilt into the extraction site. This will depend on the site, degree of crowding and age of the patient. There is a greatertendency for mesial drift in the maxilla; the younger the patient is; and the more crowded dentitions. With regard to the site consider tooth types:

Deciduous incisor: little impact as shed early.Deciduous canine: in a crowded mouth there will be a centre line shift to the affected side. Should be balanced even in mild crowding cases.Deciduous first molar: may result in centre line shift. Kept under review and balanced if necessary. The second deciduous molar and first permanent molar

drift forwards without rotation or tilting and the anterior teeth spread around the arch. In the upper arch the first premolar usually erupts into the arch butthe canine is outlocked. In the lower arch the effect is more variable and sometimes the canine erupts first and the first premolar is short of space.

Deciduous second molar: if the second deciduous molar is extracted before eruption of the first permanent molar, the latter tooth will erupt in a more anteriorposition and total space loss may occur. With later extraction, the upper first permanent molar tips mesially with some rotation. The upper secondpremolar usually erupts into the palate and the lower erupts lingually or with later extraction may impact vertically between the lower first molar and firstpremolar. Should try and preserve second deciduous molars until the permanent tooth has erupted. In most cases balancing or compensating extractions ofother sound second deciduous molars is not required.

Space maintenance and balancing or compensating extractionsMany children have potentially crowded arches and will require extraction of permanent teeth so the use of space maintainers is rarely essential. Spacemaintenance may be advantageous where there is acceptable alignment of teeth but with a tendency to mild crowding. In such a case, early loss may produce alocalised malocclusion for which it is difficult to plan simple treatment.

• Disadvantages of space maintenance 1) May need prolonged wear and there is no guarantee that this will avoid the need for later orthodontic treatment. 2) May hinder plaque control and precipitate an increase in caries. 3) Removable space maintainers fail if not worn and fixed ones need regular inspection.

• The natural tooth forms the ideal space maintainer and attempts should be made to conserve the single carious deciduous molar by pulp treatment ifrequired.

• Where extractions have to be carried out under GA, balancing and compensating extractions should be considered. Where contralateral and opposing teethare of poor prognosis there is no difficulty in applying the principles of balancing and compensating extractions. Balancing extractions are designed toeliminate centre line discrepancies that will require fixed appliances for their correction. Compensating extractions are a means of preserving interarchrelationships by allowing the posterior teeth to drift forward

! General rules for balancing and compensating extractions

In CL I cases with mild crowding: if a first deciduous molar has to be extracted on one side in the upper arch the contralateral tooth should be extracted topreserve the centre line and allow some temporary improvement in incisor crowding. This is a balancing extraction. If one deciduous molar has to beextracted in the lower arch it may be desirable to balance this with the contralateral tooth. This may signal the need for compensating extractions in theupper arch particularly if the teeth are of poor quality.

In CL II cases with crowding and a deep overbite treatment will be required later. In the lower arch should not balance or compensate the loss of a deciduousmolar. The reverse is true in the upper arch.

It used to be thought that loss of second deciduous molars should not be balanced or compensated because the effect on the centre line was minimal. Recentevidence suggests that centre line shifts occur when these teeth are removed prior to the eruption of crowded permanent incisors.

! THE UPPER LABIAL FRAENUM

This occasionally modifies the position of the teeth. In infancy the labial fraenum is frequently attached to the crest of the alveolar ridge in the midlinebetween the upper central incisors. With normal dento-alveolar growth, the upper alveolar process grows down and the frenal attachment becomes higherwith no influence on tooth position. Occasionally the low attachment persists and the fraenum causes a midline space ‘median diastema’ between thecentral incisors. Factors which may indicate that this is the case include:-the anterior teeth may be crowded; radiographically a notch can be seen at thecrest of the interdental bone between the upper central incisors and when the fraenum is placed under tension there is blanching of the incisive papilla.

Management Wait until the permanent canines erupt to see if the space closes. If not resect the fraenum (frenectomy) and institute appliance treatment to close the space.

! There are other causes of median diastema.

• Median diastema: prevalence 98% of 6 yr-olds, 49% of 11 yr-olds and 7% of 12-18 yr-olds.• Aetiology: physiological (normal dental development).• Hypodontia, especially missing upper lateral incisors.• Small teeth in large jaws (spaced dentition).• Presence of midline supernumerary tooth/teeth.• Proclined upper incisors.

Management Periapical radiograph to exclude the presence of supernumeraries. If the diastema is larger than 3 mm and the lateral incisors are present it may be necessary to approximate the central incisors to provide space for the

canines to erupt. Care should be taken to ensure that the roots of the teeth being moved are not pressed against any unerupted crowns as this can lead toroot resorption.

Diastemas have a high tendency to relapse following closure so permanent retention will be required. INDICATIONS FOR THE EXTRACTION OF DECIDUOUS CANINES

• In a crowded upper arch the lateral incisors may be forced palatally. In a CL I case this will result in a crossbite and the apex of the tooth will be forcedpalatally making correction difficult.

• In a crowded lower arch one incisor may be forced through the labial plate of bone, resulting in a dehiscence, compromising the periodontal attachment.Relief of crowding by extracting the lower deciduous canines usually resolves the situation.

• Extraction of lower deciduous canines can be advantageous in CL III cases.• To provide space for appliance therapy in the upper arch, for example correction of an instanding lateral incisor or to facilitate the eruption of an incisor

prevented from erupting by a supernumerary tooth.• To improve the position of a displaced permanent canine.

Appendix Page 8

ORTHODONTIC DIAGNOSIS AND TREATMENT PLANNING

Orthodontic Assessment Purpose of the orthodontic assessment is to evaluate and record the features of a malocclusion in preparation for planning treatment.! A thorough and logical approach should be adopted.! History: (1) Medical- epilepsy, blood dyscrasias, mental & physical handicap, aphthous ulceration. (2) Dental- irregular attendance, oral hygiene, caries. (3) Social - parents and childs opinion, live.! Extra-oral examination! Skeletal pattern-

• antero-posterior:-CL I, II or III, • vertical:- Lower face height / Frankfort mandibular plane angle • transverse : facial asymmetry & arch widths.

! SOFT TISSUES! Form of lips and tongue of greatest importance. Activity less so. LIPS - form, tonicity and fullness competence, if not how is an anterior oral seal achieved? lower lip relative to upper incisors. TONGUE- tongue thrusts are usually adaptive i.e. the tongue is postured between the teeth to achieve an anterior oral seal during swallowing. Ceases once thepatient can achieve a lip-to-lip contact. Endogenous tongue thrust- rare, neuromuscular defect.! HABITS- thumb or finger sucking.! Intra-oral examination! Orthodontic records - study models and radiographs. Dental examination: chart all erupted teeth, note teeth of poor prognosis and untreated caries, oral hygiene, abnormal teeth, trauma to anteriors. Lower arch-always assessed first. Treatment is based on the lower arch since if their is an occlusal discrepancy in this arch it will not be possible to correct theupper teeth.! Labial segment• 1) angulation relative to mandibular base 90o.• 2) general alignment-spacing or mild, moderate, severe crowding• 3) Rotations or displaced teeth.• 4) Inclination of the canines.! Buccal segments 1) general alignment, rotations, crowding, spacing.! Upper arch- as above.! Examination of the teeth in occlusion Path of closure- patient’s position of maximum intercuspation and path of closure from the rest position should be assessed. Displacement on closure- prematurecontact leads to either an anterior or lateral displacement on closure. Deviation on closure seen in CL2 Div I cases where the patient postures forward to maskthe underlying problem. ! Incisor occlusion-• Overjet. labial surface of the lower incisor to the labial surface of the upper recorded in millimetres.• Overbite. overlap of the lower incisors by the uppers. Increased = more than 4 mm, average or reduced = less than 3 mm. Complete i.e. the lower incisor tips touch opposing tooth or mucosa (traumatic if signs of ulceration or gingival recession) or incomplete.• Presence of anterior crossbites• Centre lines coincident and with centre of face.! Canine occlusion- CL I , II or III ! Buccal occlusion- Molar relationship and presence of crossbites.! Radiographic examination common views are:• 1) DPT orthopantomogram• 2) Lateral cephalometric radiograph-indicated for skeletal discrepancies or where movement of incisors is required.• 3) A view of the upper incisors-periapicals or upper anterior occlusal. Useful prior to starting treatment to check for supernumerary teeth, root resorption or root fracture.

! Radiographs checked as follows:• 1) check clinical charting, presence of unerupted or missing teeth, supernumeraries.• 2) Assess position and degree of development of unerupted teeth.• 3) Teeth with large restorations, untreated caries and alveolar bone levels.• 4) Root resorption, root fractures, apical pathology.

! TREATMENT PLANNING! Principles of treatment planning Stability is a primary requirement. Cannot procline the lower incisors or expand the arches transversely to relieve crowding. The result should be functionallyacceptable. No premature contacts, non-working side contacts in lateral excursion and other potential causes of occlusal dysfunction. Aesthetics apply to the alignment and relationship of the labial segments. ! Timing of treatment! Usually the early permanent dentition 10-14 yrs. Reasons• Active tooth movement cannot begin until after eruption.• Growth can be used for overbite reduction, anteroposteior arch correction and spontaneous tooth movement.• Patient co-operation best around early teens.• Bone remodelling in response to orthodontic forces are more rapid in children.

Appendix Page 9

! Aims of treatment Appliances and/or extractions are only embarked upon when a significant improvement in dental health or aesthetics will arise. Determine whether the

objective should be an ideal or compromise. Lower arch - the lower labial segment lies in a zone of balance between the tongue and the cheeks. This precept has the advantage of providing a starting

point around which treatment planning can be based. Assess degree of crowding. Intercanine width stable at 9 yrs. Measure arch circumference from mesial of the first permanent molars around the arch through

the contact points and compare with the widths of the teeth. If the overbite is increased space will be required to level the curve of Spee. An average curveof Spee will require about 2 mm.

Upper arch - Mentally reposition the maxillary canine into a CL I relationship with lower canine. This will give an indication as to whether space has to bemade and the type of movement required. If the aim of treatment is to produce a CL I incisor and canine relationship then in crowding cases it is usual toextract the same teeth in each arch. The exceptions occur where extractions are planned to aid dento-alveolar compensation.

! Correction of incisor relationship If tipping movements of the upper labial segment alone suffice removable appliances can be considered. fixed appliances are required for bodily, intrusion

and apical root torque. ! The buccal segments

If no extractions are planned, or matched extractions in both arches are indicated, the molar rel. at the end of treatment should be CL I. If extractions arecarried out in the upper arch only the molar rel will be CL II; conversely if extractions are planned only in the lower arch the molar rel will be CL III.

! Extractions! Factors governing choice of teeth for extraction are:• Prognosis• Position• Amount of space required. Provided that relief of crowding only is indicated, the following is a general rule: 1-2 mm per quadrant, second premolars, 3-5mm per quadrant first premolar extractions; more than 5 mm per quadrant extractions and space maintenance.• Incisor relationship• Anchorage requirements• Appliances to be used and patients profile

! Incisors and canines! Extraction of a lower incisor results in:• decrease in intercanine width• lingual tilting of lower labial segment• reappearance of crowding in the remaining lower incisors.• the upper intercanine width is buttressed by the lower arch and so secondary reduction in upper intercanine width and incisor crowding.! Lower incisors may be extracted if• 1 Lower incisor is of poor prognosis (trauma, caries, gingival recession).• 2 Labial segment is fanned with distal inclination of the canines.• 3 Previous orthodontic treatment involving extraction of upper premolars has left a well aligned upper arch and a Cl I buccal occlusion

with crowding in the lower labial segment.• 4 A mild CL III incisor relationship with acceptable upper arch.! Upper incisors are rarely extracted. Only where trauma or morphology have reduced their prognosis or grossly displaced.! Canines:- only if severely displaced/crowded.

! First premolars:- teeth of choice for moderate to severe crowding. Best chance of spontaneous occurrence of acceptable alignment. Space closure occursmost rapidly during the first 6 months following extraction. In the upper arch the first premolar usually erupts before the canine so if space is required thenthe first premolar should be extracted just prior to canine eruption.

! Second premolars: indications for extraction when there is crowding.• mild to moderate crowding (2 mm per quadrant)• severe displacement of the premolar• hypoplasia of premolar• congenital absence of premolar• space closure by forward movement of the molars rather than retraction of the labial segment. ! First permanent molars- never first choice as little space is provided anteriorly for the relief of crowding or correction of the incisor relationship unless

appliances are used. Indicated if prognosis compromised. Patients in whom enforced extraction of the first molars is required are often the least able tosupport complicated treatment.

! The following should be assessed before extracting first molars:• Presence of all permanent teeth.• Not indicated in the uncrowded dentition.• Tendency for mesial drift is greater in the upper arch so timing of the extraction not so critical.• In the lower arch a good spontaneous result is more likely if:• a) the lower second molar has developed as far as its bifurcation• b) the angle between the long axis of the crypt of the lower second permanent molar and the first permanent molar is between 15 and 30 degrees.• c) the crypt of the 2nd molar overlaps the root of the 1st molar

! Extraction of 1st molars will relieve buccal segment crowding but will have little effect on incisor crowding.• If space is required in the upper arch to relieve labial segment crowding or reduce an overjet then extraction of upper 1st molars should be delayed until the

2nd molar has erupted.! Consider extracting the upper 1st molar should extraction of a lower 1st molar be necessary.! A compensating extraction in the lower arch should be avoided if the upper 1st molar is extracted as a good spontaneous result is less likely.! Second permanent molars! Indications include• a) facilitating distal movement of the upper buccal segments.• b) relief of mild lower premolar crowding• c) provision of space for third permanent molars reducing impaction chances.• d) prevention of lower labial segment crowding.

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CLASS I MALOCCLUSION ! CL I malocclusions include all those anomalies where the anteroposterior relationship is within normal limits. SKELETAL PATTERN:! This is usually CL I, but it can also be CL II or III with the incisor inclination compensating for the skeletal discrepancy. There may be transverse (i.e

crossbites) or vertical sk discrepancies (i.e.AOB). SOFT TISSUES:! Soft tissues are usually favourable. The exception is bimaxillary proclination where the lips are full and everted. This is a major factor in determining tooth

position. DENTAL FACTORS! In the majority of CL I malocclusions the underlying problem will be one of tooth/arch size discrepancy, leading to crowding or less frequently spacing.! Environmental or local factors can also contribute to crowding or spacing e.g. premature loss of deciduous/permanent teeth.! Local factors also include displaced and impacted teeth, anomalies in number and size of teeth. CROWDING! Approx. 60% of caucasian children exhibit crowding.! relief of crowding cannot be achieved by either expansion of the lower intercanine width or labial movement of the lower incisors.! Crowding is relieved either by extractions or distal movement of the upper buccal segments which gives limited space.! In a CL I case with mild crowding (1 mm/quadrant)-accepted.! In cases with moderate crowding (3-5 mm/quadrant)-extract 4’s.! In severe crowding cases (>5mm/quadrant)-space maintenance +4’s ! After relief of crowding a degree of spontaneous tooth movement will occur. Greater under the following circumstances:

! growing child! extractions carried out prior to the eruption of adjacent teeth.! where adjacent teeth are favourably positioned to upright if space is made i.e. mesially inclined canines more favourable than distal ones! no occlusal interferences with anticipated movement! most spontaneous movement occurs in the first six months.

! Mild crowding cases can be accepted as premolar extractions will provide a large amount of excess space, the closure of which will require fixed appliances.The alternative of extracting teeth at the back of the arch does nothing to relieve anterior crowding unless EOT is used.

LATE LOWER INCISOR CROWDING! Intercanine width increases up to 9 years of age and this is followed by gradual diminution throughout adult life! Most noticeable during mid to late teens. This results in an increase in labial crowding.! Aetiology of late lower incisor crowding! Forward growth of mandible in conjunction with soft tissue pressures! Mesial migration of the posterior teeth.! Erupting third molars

SPACING - aetiology1) small teeth in relation to the size of arches2) teeth are missing3) a combination of 1) and 2)! Complete space closure may be difficult and permanent retention is usually required. It may be necessary to concentrate the spaces posteriorly in the arch and

fit bridges as necessary. Missing upper incisors! Upper central incisors are rarely congenitally absent.! Can be lost as a result of trauma or extracted because of dilaceration! Upper lateral incisors are absent in 2% of Caucasian. Can also be lost due to trauma. Both can occur unilaterally or bilaterally. Management! 1) Close space.! 2) Open space and placement of a denture/ bridge.! The choice for a particular patient depends on a number of factors

! Skeletal rel; if SK pattern is CL III space closure in the upper labial segment may compromise the incisor relationship; conversely for a Cl 2 Div 1pattern space closure may be preferable as it will aid overjet reduction.

! Presence of crowding or spacing! Colour and form of adjacent teeth; if permanent canines are much darker than the incisors and or particularly caniniform in shape, modification to

make them resemble lateral incisors will be difficult! Also if a lateral incisor is to be brought forward to resemble a missing central incisor an aesthetically pleasing result will only be obtained where the

lateral incisor is large and has a good gingival circumference.! The inclination of adjacent teeth as this will influence whether it is easier to open or close space! The desired buccal segment occlusion at the end of treatment; for example if the lower arch is well aligned and the buccal segment is Cl I, space

opening may be preferable.! The patient’s wishes and ability to co-operate with complex treatment.

DISPLACED TEETH- aetiology

Appendix Page 11

1) Abnormal position of tooth germs; canines and premolars most common. Management involves

a) Extraction of primary tooth and space maintenance b) Exposure and application of orthodontic traction c) Extraction if severely displaced

2) Crowding: lack of space for a permanent tooth to erupt. Those teeth that erupt last in segment, e.g. lateral incisors, upper canines, 2nd premolars, 3rdmolars are most commonly affected.

Management involves: a) Relief of crowding followed by active tooth movement b) If severe it may be prudent to extract the tooth.

3) Retention of a deciduous tooth; management involves extracting the deciduous tooth as soon as possible4) Secondary to the presence of a supernumerary tooth/teeth. Management: extract the supernumerary tooth and align.5) Secondary to pathology e.g. a dentigerous cyst- least common.

BIMAXILLARY PROCLINATION can occur in CL 1, CL II Div 1 or CL III mal.! Term used to describe occlusions where both the upper and lower incisors are proclined.! This may be a feature of CL II Div 1 mal, but quite often the incisor relationship is CL I which may be mistakenly diagnosed as CL 2 Div I because of a an

increased overjet.! Important to make the distinction as the overjet cannot be reduced in CL I cases unless the lower incisors are also retracted.! The underlying aetiology is the soft tissue pattern. Management involves retroclining both the upper and lower labial segments with fixed appliances.! It is sometimes suggested that bimaxillary proclination should not be treated because of its instability. However sometimes the soft tissues can adapt to the

new incisor positions. If the lips are incompetent but have a good muscle tone the chances of obtaining a stable result are good.! Where the lips are competent or grossly incompetent the result is likely to be unstable and permanent retention will be required.

Appendix Page 12

CLASS II DIVISION 1 MALOCCLUSION Definition CL II DIV 1: British Standards Institute Classification: The lower incisor edges lie posterior to the cingulum plateau of the upper incisors, there is anincreased overjet and the upper central incisors are usually proclined.! Children with overjets of > 9 mm are twice as likely to have suffered trauma involving the upper incisors. ! AETIOLOGY

1) Skeletal pattern: usually SK 2 with a retrognathic mandible. However may have a CL I SK rel with proclined upper incisors and retroclined lower incisorsdue to a habit or soft tissues. Found in association with a range of vertical SK patterns.

2) Soft tissues: The influence of the soft tissues on CL II Div 1 mal. are mainly mediated by the SK pattern. The lips areincompetent due to the prominence of the upper incisors and/or SK pattern. If the lips are incompetent the patient will try to achieve an anterior oral seal inone of the following ways:

1) circumoral muscular activity to achieve a lip-to-lip seal. 2) mandible is postured forwards to allow lips to meet at rest 3) Lower lip is drawn up behind the upper incisors. 4) tongue placed forwards between the incisors to contact the lower lip resulting in an incomplete overbite. 5) combination of these.

• Where the patient achieves either 1) or 2) above then the influence of soft tissues moderates the underlying SK pattern by dento-alveolar compensation.• More commonly situation 3) prevails, and the lower lip retroclines the lower incisors and proclines the upper incisors so that the incisor rel is more severe

than the SK relationship.• If 4) prevails then the tongue may procline the lower incisors compensating for the SK pattern.• Infrequently a CL II Div 1 incisor reoccurs due to retroclination of the lower incisors by an active lower lip.! Dental factors: May occur in the presence of crowding/spacing.! Habits: Persistent digit sucking habit (more than 2 hrs/day) acts as an orthodontic force.

Severity of the effects will depend upon the duration and intensity of the habit but commonly causes: 1) proclination ofupper incisors } increased2 retroclination of the lower incisors } overjet3) incomplete overbite or anterior open bite 4) narrowing of the upper arch- tongue assumes lower posture in the mouth and negative pressure generated as well as pressure from buccinator muscles.

! Occlusal Features• Overjet increased, upper incisors may be proclined• Overbite often increased. If incomplete due to adaptive tongue swallow.• Molar relationship often reflects SK pattern. ! Assessment and Treatment planning Patients age- important in relation to facial growth. In the average child, forward growth of the mandible occurs during the pubertal growth spurt and early teens.Advantageous in CL II mal. In the adult, lack of growth reduces complexity of CL II cases that are Rx.! Sk pattern is major determinant in treatment both AP and vertical dimension.! Stability of overjet reduction: Soft tissues major determinant. Ideally at the end of Rx the lower lip should act on the incisal one third of the upper incisors

and should be able to achieve a competent lip seal.! Patients facial appearance In the child with a retrusive mandible a functional appliance may be preferable to distal movement of the upper buccal segments with headgear. ! Practical treatment planning:• 1) reduce the overbite• 2) reduce the overjet• Overbite reduction requires space in the lower arch, about 2 mm per quadrant. If extractions are required in the lower arch both spontaneous and active

tooth movement are facilitated by removing the corresponding tooth in the upper arch. ! Where the lower arch is well aligned and molar relationship is CL II space for OJ reduction either by distal movement or extraction of 4/4.• Molar relationship at end of treatment will be CL II. Distal movement only if molar rel is <half unit Cl 2 at outset of Rx.• If prognosis for a stable reduction in OJ is guarded then use headgear rather than extractions. ! Early Treatment! Due to possibility of trauma to the incisors, early treatment is tempting, however there are a number of drawbacks:• 1) Lips often incompetent, thus reducing the chance of stability• 2) May not be able to reduce the OJ fully, thus increasing the chance of relapse• 3) If maxillary incisors retracted before the canines erupt, risk of root resorption or deflecting canines• 4) Further treatment often required in permanent dentition.• 5) Treatment with a functional appliance can be considered. ! Management of increased overjet associated with CL I or mild SK II pattern.! Fixed appliances give the best result. If fixed appliances are not indicated and the overjet can be reduced by tilting the upper incisors, a URA can be used where the SK pattern is Cl I. Can assessupper incisor angulation from a lateral cephalogram before treatment.! If extractions are required in the lower arch, better spontaneous alignment of the lower arch will occur in growing child.! functional appliance used in child with well aligned arches and moderate SK II pattern.

Appendix Page 13

! Management of increased overjet associated with moderate to severe CL II SK pattern.• 1) Growth modification-only small changes can be produced and the extent depends on favourable growth pattern of the jaws

a) Restrain maxillary growth- EOT-used to restrain horiz or vert. growth of the maxilla depending on direction of force application.b) Encourage mandibular growth- functional appliancec) combination of a) and b)

♦ Prolonged retention until growth is complete is required ! 2) Orthodontic camouflage• a) use fixed appliances to retract upper incisors bodily. This is limited by amount of cortical bone palatal to incisor roots and patients profile.• b) procline lower incisors. Usually unstable. Only stable in very small number of instances where lower incisors have been trapped lingually by habit, lip

trap or increased overbite.! 3) Combination of 1) and 2)! 4) Surgical correction

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CLASS II DIVISION 2 MALOCCLUSION

! Definition of CL II DIV 2: The lower incisor edges occlude posterior to the cingulum plateau of the upper incisors. The upper incisors are retroclined.! Aetiology

1) Skeletal: commonly a mild SK II pattern but maybe SK I or SK III. Where the SK pattern is more severely CL II the upper incisors lie outside the control of the lower lip resulting in a CL 2 Div I mal. except where the lower

lip line is high relative to the upper incisors a CL II div 2 mal. arises. Vertical dimension is usually reduced. Reduced lower face height in conjunction with a SK II jaw relationship results in the absence of an occlusal stop to

the lower incisors which continue to erupt leading to an increased overbite. Reduced lower face height is associated with a forward growth rotation of the mandible which means that the mandible becomes more prognathic with

growth. This pattern of growth reduces the severity of the SK II pattern but it also increases the overbite.

2)Soft Tissues: Influence of the soft tissues is usually mediated by the SK pattern. If the lower face height is reduced the lower lip line will be higher and cover more than one third of the crowns of the upper central incisors, resulting in

their retroclination. In some cases the lateral incisors which have a shorter clinical crown will escape from the action of the lip. CL II Div 2 incisor rel may also result from bimaxillary retroclination caused by active lips irrespective of the SK rel.

3) Dental factors: Crowding is common due to retroclination of the labial segment(s) resulting in narrower arcs. Lack of space for upper lateral incisors which are usually rotated mesiolabially. Lower incisors crowded due to retroclination. Lack of an occlusal stop for the lower incisors may result in their continued development, giving rise to an increased overbite. This may be due to the SK II

pattern and/or retroclination of the upper incisors leading to an increased inter-incisal angle. Occlusal features

Upper central incisors retroclined, lateral incisors average inclination or proclined depending on their position relative to the lower lip. Where lower lip line is very high the lower incisors are retroclined. The overbite is increased. The lower incisors may occlude on the palatal mucosa and cause ulceration. The upper incisors may occlude on the labial gingivae

and cause stripping. The overbite is then described as traumatic. Such cases are rare. Management : 2 possibilities

Either (1) accept or (2) correct the incisor relationship. (1) Accept where the problem is mild, the incisors occlude with tooth tissue and no other occlusal anomalies such as crowding. (2) Stable correction of CL II Div 2 mal. is difficult. Correct overbite and interincisal angle to 135° to create an effective occlusal stop.

Correction of the interincisal angle:- a) torque the upper incisor roots palatally with fixed appliance. b) Procline lower incisors. Only stable if the incisors have been trapped behind the upper incisors. c) Procline upper labial segment followed by functional appliance to reduce the resultant increased overjet. d) combination of these.

Treatment option depends on patients profile, compliance, crowding and aetiology of the malocclusion. If the lower arch is crowded and extractions are required to relieve this, then try and prevent lingual movement of the lower incisors during residual space

closure with fixed appliances. Reduction of overbites

a) Intrusion of the incisors: Difficult to achieve. Use fixed appliances. The intrusion of the incisors is achieved using the buccal segments for verticalanchorage. However as it is easier to move molars occlusally than intrude incisors and canines, the former usually predominates. In practice the effectsachieved are relative intrusion where the incisors are held stationary whilst vertical growth of the face occurs around them including extrusion of the molars.

b) Eruption of the molars: Use an anterior bite plane on a URA to free the occlusion of the buccal segments. This prevents the lower incisors erupting whilstallowing the lower molars to erupt. Requires a growing patient to accommodate the increase in vertical dimension otherwise the molars will intrude underthe forces of occlusion once the appliance is withdrawn.

c) Extrusion of the molars: Achieved with fixed appliances during incisor intrusion. Need growing patient for stable result. d) Surgery: Adults with severe overbite-combined with orthodontic treatment.

Practical management• Mild cases: accept incisor relationship.• If crowding is marked in the lower arch extract either first or second (usually) premolars but use fixed appliances to prevent the lower labial segment from

moving lingually.• Space for alignment of the upper arch can be created by extractions or by distal movement of the upper buccal segments.• If premolars are extracted in the lower arch then extract in the upper arch usually first premolars.• If the lower arch is treated non-extraction, the upper arch can either be treated with distal movement of the upper buccal segments (i.e if half a unit Cl 2

molar relationship pretreatment) or by extraction of upper first premolars. If distal movement is to be considered it may be necessary to extract the uppersecond molars (only if third molars present radiographically and of a good size).

• Correction of incisor relationship certainly indicated where the overbite is complete to soft tissues.

1)Fixed appliances• Interincisal angle can be corrected by palatal root torque to the upper incisors and/or proclination of the lower incisors.• Palatal root torque is dependent upon the presence of sufficient cortical bone palatal to the upper incisor roots and is more likely to cause root resorption

than other forms of tooth movement.• Proclination of the lower segment may not be stable so permanent retention may be required.• Space for correction of the incisal relationship can be gained by extractions in the upper arch or by distal movement of the upper buccal segments.• On completion of treatment retain with an upper removable appliance incorporating a bite plane until growth is complete to prevent overbite relapse.

Appendix Page 15

2) Functional appliance.• Utilised in growing patients with mild to moderate SK II pattern and well aligned lower arch. A prefunctional phase to procline any retroclined upper

incisors and expand the upper buccal segments with a URA is needed. Reduction of the interincisal angle is achieved by proclination of the upper incisorsprimarily but also lower incisors.

• Finally fixed appliances may be required to detail the occlusion. 3) Surgery• A stable aesthetic orthodontic correction may not be possible in patients with an unfavourable AP or vertical SK pattern. In these cases surgery will be

necessary.• A phase of presurgical orthodontics is required to align teeth. However arch levelling is usually not attempted until after surgery when it is easier.• Where the overbite is very severe, the lower labial segment may have to be set down surgically.

Appendix Page 16

CLASS III MALOCCLUSION

Definition of CL III (BSI): lower incisor edge occludes anterior to the cingulum plateau of the upper incisors. 3% of caucasians. Aetiology (1) Skeletal pattern: most important factor in the aetiology of CL III malocclusion.

Majority of CL III incisal rel. are associated with a SK III dental base. Compared with CL I occlusions, CL III malocclusions exhibit:

a) increased mandibular length. b) a more anteriorly placed glenoid fossa so that condylar head is positioned anteriorly leading to mandibular prognathism. c) reduced maxillary length. d) more retrude position of the maxilla leading to maxillary retrusion

Cl 3 malocclusion occur in association with a range of vertical SK proportions i.e. both increased and reduced lower ant. face heights.

(2) Soft tissues: These do not play a major role. In contrast to CL II mal. the soft tissues tend to reduce the severity of the Skeletal discrepancy by dento-alveolar compensation.

This dentoalveolar compensation occurs in CL III mal. because an anterior oral seal can often be achieved by lip contact. Exception occurs in patients withincreased vertical SK proportions where the lips are more likely to be competent and an anterior oral seal is achieved by tongue to lip contact.

(3) Dental Factors: Usually have a narrow upper arch and broad lower arch. Upper arch crowded and lower well aligned or spaced.

Occlusal features: Anterior crossbite of one or more incisors is common. Check for displacement of the mandible from a premature contact into maximal interdigitation. If the

patient can achieve edge-to-edge incisor relationship the prognosis for correction of the incisor rel. is more favourable. Buccal crossbite which is usually due to a discrepancy in the relative widths of the arches. This occurs because the lower arch is positioned relatively more

anteriorly in CL III and is often well developed whilst the maxilla is narrow. Exhibit dentoalveolar compensation of incisors.

Treatment Planning! Patient’s opinion regarding occlusion and facial appearance! Severity of SK pattern both AP and vertically is most important.! Expected pattern of future growth both AP and vertically. Average growth will tend to worsen the relationship and should growth be unfavourable a

significant deterioration will ensue. Patients age, sex, and facial pattern should be considered. Children with increased vertical SK proportions often continueto exhibit a vertical pattern of growth which will reduce the incisor overbite.

! In CL III malocc. a normal or increased overbite is an advantage, as vertical overlap of the upper and lower incisors post-Rx is essential.! Degree of crowding should be assessed in each arch.! Prognosis for correction of the incisor rel. increased if:! a) mild CL III SK relationship.! b) patient can achieve edge-to-edge incisor relationship.! c) lower incisors proclined and upper incisors retroclined.! d) normal or increased overbite. Although the maxilla is frequently crowded one should resist extracting teeth only in this arch, as this will lead to a worsening of the incisal relationship. Ifextractions are necessary in the upper arch, it is advisable to extract at least as far forwards in the lower arch. Correction of the incisor rel. can be achieved by proclination of the upper incisors, retroclination of the lower incisors or a combination.! If the lower arch is crowded extract lower first premolars to allow the lower incisors to drop lingually.! Space for the relief of crowding in the upper arch can often be gained by expansion of the arch both anteriorly and/or bucco-lingually to correct buccal

crossbites. Expansion of the upper arch to correct a buccal crossbite will reduce the overbite.! Do not distalize the upper buccal segments with headgear in CL III mal as this will restrain maxillary growth.! Treatment options

1) Accept mild CL III incisal rel. Simply relieve crowding and align teeth2) Procline upper incisors. This depends on the presence of the prognostic factors mentioned earlier.

Best carried out in the mixed dentition when the canines are unerupted and high above the roots of the upper lateral incisors.Extraction of the lower deciduous canines may allow the lower incisors to drop lingually and assist in the correction of the reverse overjet.Early correction of the incisal rel. has the additional advantage that further forward mandibular growth may be counter balanced by dentoalveolar

compensation.Later in the mixed dentition, when the developing permanent canines drop down into a buccal position relative to the lateral incisor roots there may be a

risk of root resorption if the lateral incisors are moved labially. Defer until the permanent dentition.Where the upper labial segment is crowded, permanent extractions should be delayed until after the incisor relationship is corrected as proclination of the

upper incisors will provide additional space.Proclination of the upper and retroclination of the lower incisors can be achieved with a removable appliance in the early mixed dentition.Fixed appliances can be used in the permanent dentition.

3) In those cases with mild to moderate SK III pattern or where there is insufficient overbite a combination of proclination of the upper incisors andretroclination of the lower incisors will often achieve correction of the incisal rel. The incisors are changed around in the zone of soft tissue balanceand provided that there is an adequate overbite and further growth is not unfavourable the end result should be stable.

Although removable and functional appliances can be used for this purpose, fixed appliances are more efficient.Space is required in the lower arch for retroclination of the lower incisors, and extractions are required unless the arch is naturally spaced.

4)SurgerySevere CL III Sk pattern and/or reduced overbite/anterior open bite precludes ortho. alone and surgery is required to correct the underlying skeletal

problem. Required if ANB angle is < -4 degrees and lower incisor inclination is <83 degrees to mandibleCephalometric findings should be considered in conjunction with the patients facial appearance.Surgical approach should be explored before any extractions are undertaken. The reason for this is that management of Cl 3 mal. by orthodontics alone

involves dento-alveolar compensation for the underlying skeletal discrepancy whilst a surgical approach relies on removing the existing dentoalveolarcompensation first with presurgical orthodontics followed by surgical correction of the jaws.

Some patients with SK 3 dental base relationships are unwilling to undergo presurgical orthodontics. Management by surgery alone is unsatisfactory asthe occlusion will be severely disrupted.

Appendix Page 17

REMOVABLE APPLIANCESIndications for use of removable appliances1. Treatment of simple malocclusions where teeth have to be tipped about a fulcrum close to the middle of the root.2. Application of extra-oral traction to blocks of teeth, or an entire arch, to help achieve distal movement or intrusion.3. Arch expansion.4. Adjunct to fixed appliance treatment.5. Flat anterior bite plane to reduce deep overbites.6. Posterior bite capping to free the occlusion with the lower arch.7. Retaining appliance following fixed treatment.8. Lower removable appliances are poorly tolerated by patients.

Design4 requirements : Active, retentive, anchorage, baseplate (ARAB). Some components may contribute to more than one function.

1. Active components: springs, bows, screws, and elastics.a) Springs - most common active component. Expression of force F delivered by a spring is:

F a dr4

L3

F=force, d=deflection of wire, r=radius of wire and L= spring length.

Force used for tipping a tooth is 25-50 grams.Convenient to have a spring deflection of 2-4 mm so that the appliance is self-activating when inserted and the force does not drop off as the tooth

moves.Most important factor in spring design is the diameter of the wire. 0.5-0.7 mm wire is used.However 0.5 mm spring requires an activation of about 3 mm whilst 0.7 mm requires only 1 mm.The stability of the spring should be considered also, not a problem if protected by the baseplate or supported by a stiffer component but if the spring

needs to be self-supporting as in certain designs of buccal canine retractor there may need to be compromise between stability and stiffness.

b) Screws - Less versatile than springs, bulky and expensive. Used when the teeth to be moved are also required for retention with clasps.Two types of screw. Most common type consists of two halves on a threaded central cylinder turned by means of a key which separates the two

halves by a predetermined distance, 0.2 mm for each quarter turn.The other type is the spring loaded piston screw which is activated by moving the whole screw assembly by means of a screw driver.Activation of screw is limited by width of the periodontal ligament as to exceed this limit would crush the periodontal ligament.

c) Elastics - special intra-oral elastics are manufactured for orthodontic use. Classified by their size and range from 1/8 inch to5/8 inch.

Commonly used componentsLabial movement of incisors.

1. Z-spring (0.5 mm). Anterior retention required to prevent displacement of the appliance. Activated by pulling 1-2 mm away from the baseplate so that thespring is not caught by incisal edge as inserted.

2. Double cantilever spring- moving more than one incisor 0.7 mm.3. Screw appliance- useful when retention is limited, as the incisors to be moved can also be used for retention.

Palatal movement of incisors1. Split Labial bow (0.7 mm Stainless Steel wire).2. Roberts retractor 0.5 mm sheathed with tubing distal to the coils. Activated by bending the arms of the spring towards the incisors.

Mesial/distal movement of incisors, premolars and canines.1. Palatal finger spring- (0.5 mm) spring should lie at the level of gingival margin and point of application on tooth should be at right angles to the intended

direction of movement. Activated half a tooth width to give optimal force.2. Buccal canine retractor- 0.5 mm tubed. Used where a canine needs to be moved palatally and distally. Activation by winding up the coil.3. Buccal canine retractor-0.7 mm. Activated by cutting the end and bending the wire in again.

Screw appliance-used to move premolars and or molars distally. Screw is positioned to open anteroposteriorly.

En masse appliance - Used for distal movement of upper buccal segments with headgear. Need EOT and screw for transverse expansion as the teeth are moveddistally.

Buccal movement of premolars and molars.T-spring- Used for movement of single premolar or molar. Good retention required to prevent displacement. Activated by pulling the spring away from the

acrylic at angle of 45 degrees.Screw - used to move more than one tooth e.g. correct crossbite. Patient should turn the screw one quarter turn every third or fourth day.

2. Retaining the appliance.Adams Clasp - engages undercuts at the junction of the mesial and distal surfaces with the buccal aspect. (0.7 mm). Used primarily on first permanent molar

tooth but can be used on any tooth.Versatile as EOT tubes, labial bows, hooks or buccal springs can be soldered to the bridge of the clasp and coils can be incorporated.

Southend Clasp - utilised to engage the undercut beneath the contact point between the two incisors. (0.7 mm)Ball ended clasps - engage undercuts interproximally.

Appendix Page 18

Labial bows - Anterior retention especially if mesial/distal movement of anterior teeth is required as it will guide tooth movement along the arch. Also usedin retaining appliances.

3. BaseplateOther components of removable appliance are connected by acrylic baseplate which can be an active or passive component of the appliance.a) Anterior bite-plane - increasing the thickness of acrylic behind the upper incisors forms a bite-plane onto which the lower incisors occlude. Used when the

overbite needs to be reduced by allowing the buccal segment teeth to erupt or for eliminating occlusal interferences. Need to inform the technician how farposteriorly the bite-plane should extend and the depth of the bite plane.

b) Buccal capping- used when occlusal interferences need to be eliminated and when reduction of the overbite is contra-indicated.Buccal capping is produced by carrying the acrylic over the occlusal surface of the buccal teeth and props the incisor teeth open. Used to move a palatally

positioned incisor over the bite. If the capping fractures away the posterior teeth may overerupt which can be deleterious.

ANCHORAGEDefinition: source of resistance to the forces generated in reaction to the active components of an appliance or as Newton’s third law of motion which states that

there is an equal and opposite reaction to the force(s) applied by the active components. This reaction force is dissipated over the teeth which are contacted bythe appliance. The importance of anchorage is appreciated when it has been neglected at the treatment planning stage.

Types of anchorage1. Simple anchorage: active movement of one tooth versus several anchor teeth.2. Compound: teeth of greater resistance to movement are utilised as anchorage for the translation of teeth which have less resistance.3. Reciprocal anchorage- two groups of teeth are pitted against each other resulting in reciprocal movement of both. e.g. expansion of upper arch or

movement of 4 incisors labially will result in a distal force being exerted on the posterior teeth.Extra-oral anchorage (EOA) Achieved by the patient wearing headgear. Patients head used for anchorage. Designed to prevent forward movement of

the anchor (upper buccal) teeth.Extra-oral traction is a method of achieving tooth movement in the distally direction usually. Similar to EOA the only difference being the magnitude of

force applied and duration of wear.EOA force 200-250 g for 10-12 hrs per night.EOT 400-500 g 14-16 hrs per night.The direction of headgear force also needs to be considered.A direction of force below the occlusal plane (cervical pull )extrudes the upper molars and increases the vertical dimension of the lower face. Acceptable

in patients with reduced lower anterior face heights but not in those with increased face heights.A direction of pull above the occlusal plane (High pull headgear) should be used in patients with increased vertical proportions. This will intrude the

upper buccal segments and restrain vertical maxillary development. This direction of force should also be used with removable appliances to aidretention of the appliance.

Components of headgear- 3 partsa) Attachment to the teeth: Facebow slots into tubes soldered onto the bridge of a removable appliance crib.b) Headcap or neckstrap- for cervical pull use a neckstrap and for high pull use a headcap.c) Elastic component or spring mechanism- this connects the other two elements and controls the magnitude of the force applied. Elastic force - applied by

an elastic strap or extra-oral elastics. Spring incorporated into the headcap provides the spring component.d) Headgear safety- cases of ocular injury including blindness have been reported due to accidents with headgear. Occurred with facebows used in

conjunction with an elastic force where the facebow has been pulled out and recoiled in to the patients eye.

Monitoring Progress with removable appliancesPatients seen every 4 weeks for re-activation.Compliance with wear- how much are you wearing the appliance?Lack of compliance - no wear and tear on appliance, patients lisps, frequent breakages, and no marks around palatal mucosa.

Check list for each visit:Check treatment plan, oral hygiene, loss of anchorage by recording overjet and molar relationship, tooth movement achieved, retention of appliance, and

whether appliance needs activation or bite planes altered.

Common problemsa) Slow rate of tooth movement (average 1 mm/month): Poor wear, incorrect activation or positioning of springs, obstruction of tooth movement by acrylic

or occlusion.b) Frequent breakages- appliance not being worn, patient flicks appliance in and out, inappropriate foods being eaten.c) Appliance becomes loose quickly as patient flicks it in and out.d) Excessive tilting of teeth being moved- point of contact of spring too far away from gingival margin and/or excessive force.e) Anchorage Loss: Part-time wear, forces exerted by active components exceed anchorage resistance.f) Palatal inflammation -(i) poor oral hygiene, resulting in fungal infection and angular cheilitis. May need to prescribe nystatin cream to fitting surface

4x/day and miconazole cream for angular cheilitis. (ii) Entrapment of palatal mucosa behind upper incisors during overjet reductiong) Lack of overbite reduction- not actively growing e.g. adults or patients with horizontal direction of mandibular growth.

Advantages of Removable AppliancesCan be removed for tooth brushing.Palatal coverage increases anchorage.Easy to adjust.Can be used for overbite reduction in growing child.Posterior bite capping can be incorporated to free the occlusion Used as retainer or space maintainer.Can be used to transmit forces to blocks of teeth.

Disadvantages of removable appliancesAppliance left out.Only tilting movements possible, limited to simple treatment.Good technician required.Affects speech initially.Lower removable appliances difficult to tolerate.Inefficient for multiple tooth movements.

Appendix Page 19

FIXED AND FUNCTIONAL APPLIANCESFIXED APPLIANCESAttached to teeth and therefore greater range of tooth movement possible. Rotational, vertical, tilting and apical movements possible.

Indications for use of fixed appliances1. Correction of mild to moderate skeletal discrepancies.2. Intrusion and extrusion of teeth. e.g. overbite reduction.3. Correction of rotations.4. Multiple tooth movements required.5. Active closure of extraction spaces due to hypodontia.

Components of fixed appliancesBands - rings encircling teeth, usually placed on molar teeth and cemented with glass ionomer.Bonds - brackets are bonded onto teeth by composite resin. Adhesion of composite to brackets by mechanical interlocking and to enamel by acid-etching.Brackets and bands have a horizontal slot in which the archwire is placed.Slot dimensions in an edgewise system are either 0.018 width or height x 0.025 depth or 0.022 x 0.032.Auxiliaries- elastomeric modules or wire ligatures secure the archwire into the archwire slot.

Arch wiresAmount and type of force applied can be controlled by varying the cross-sectional diameter and form of the archwire, and / or the material of its construction.The first stage of treatment involves the alignment of the teeth i.e. correction of rotations and crowding. A wire that is flexible with good resistance to permanent

deformation is desirable, so that teeth can be aligned without the application of excessive forces. Use multistrand or twistflex stainless steel wire whichcomprises 3 or more strands of fine stainless steel wire twisted together. Alternatively can use nickel titanium wire which is more flexible and has a greaterresistance to deformation, but it is more expensive.

The second stage involves the levelling of the curve of Spee. This is achieved with stiffer stainless steel wire.The third stage involves overjet reduction and space closure which is achieved with stiff stainless steel wire usually by sliding the teeth along the archwires with

intra-oral elastics or springs.

FUNCTIONAL APPLIANCESUnique in that they have no active components but utilise the forces generated by the masticatory and facial muscles. These forces are delivered primarily to the

teeth, with a posterior force direct to the upper arch and an anterior force directed to the lower arch.Achieved by constructing the appliance so that the mandible is in a postured position away from the position of rest with the condyles displaced from the

glenoid fossa.Most effective during growth. Aim of functional appliances is to correct the anteroposterior occlusion without correcting dental irregularities.Effects of a functional appliance used to treat a CL II malocclusion:

(i) Dento-alveolar: upper teeth moved posteriorly, lower teeth moved anteriorly.(ii) Maxillary growth: restricts forward growth similar to EOT. However possible relapse afterwards.(iii) Mandibular growth: may induce on average an extra 1-2 mm of growth of the mandible.(iv) Glenoid fossa: remodelling of the fossa more anteriorly may happen in humans. The mandible will be repositioned more anteriorly.

Indications for functional appliances 1. The patient must be growing, preferably at a rapid growth phase. 2. Favourable growth pattern. 3. Well motivated patient. 4. Timing of treatment - dental development does not necessarily correlate with skeletal growth and the pubertal growth spurt. Do not want a protracted course

of treatment. Ideally the appliances should be used just before the pubertal growth spurt.

Use of functional appliancesMost effective in the treatment of Class II arch malrelationships in children in the mixed dentition. Limited use where facial growth is almost complete. If there

is crowding this can treated with fixed appliances following the functional appliance. The upper arch has to be expanded transversely to a small extent inorder to conform to the lower. This expansion can either be incorporated into the appliance or an initial phase of removable appliance treatment canaccomplish this objective.

If a Cl 2 Div 2 mal is to be corrected then the upper incisors can be proclined with a removable appliance prior to registering the postured bite with wax.The Class III malocclusions that can be treated with functional appliances are mild and these can be treated with an upper removable appliance.Examples of functional appliancesThe Andresen appliance- upper and lower baseplates sealed together.The bionator -similar to the Andresen appliance but less bulky.The twin block appliance- described by Clark 1982. Made and worn as two independent parts (upper and lower removable appliances with inclined bite

platforms which induce a forward posturing of the mandible.All the above appliances can be used in the treatment of either CL II Div 1 or CL II Div II malocclusion.

Appendix Page 20

FACIAL GROWTH AND ORTHODONTICSPOSTNATAL GROWTH OF THE SKULL AND JAWSIntroduction:Most orthodontic treatment is carried out during the growth period, between the ages of 10 and 15 years.The occlusion and position of the teeth is also established during the growth period.Patterns of growth of the jaws and development of the occlusion, which vary between individuals may have a bearing on the need for orthodontic treatment and

its timing.A knowledge of previous growth changes may be important in planning treatment.The timing of treatment in relation to growth may facilitate the progress of treatment.

MECHANISMS OF BONE GROWTHBone grows either by replacement of cartilage (endochondral ossification) or by periosteal activity (intramembranous ossification).• Endochondral ossification- this process is seen in both the epihyseal plates of long bones and the synchondroses of the cranial base. This form of bone

growth is under tight intrinsic control (genetic).• Intramembranous ossification- bone is laid down and resorbed by the investing periosteum and endosteum. These processes of resorption and formation

constitute bone remodelling. Periosteal remodelling is also needed to maintain the overall shape of the bone as it grows - thus a growing bone always hasareas of deposition and resoption. The bones of the skull and face articulate at sutures, and growth at the sutures is regarded as a special form of periostealremodelling.

• Growth which causes the mass of bone to be moved relative to its neighbours is known as displacement of the bone e.g. forward and downward movementof the maxillary complex.

• The change in the position of a bony structure owing to remodelling of that structure is called drift e.g. palate, where bone is deposited on the inferiorsurface and resorbed from its superior surface.

Growth Patterns• Growth of the face involves many growth processes in the mandible, mid-face, cranial base etc. The overall pattern of growth results from the interplay

between them. They must harmonise if a normal facial form is to result. Different systems have different growth patterns in terms of rate and timing andsmall deviations from a harmonious facial growth pattern will cause discrepancies of major significance to the orthodontist.

• Growth is fairly rapid in the early years of life but slows in the prepubertal period. The pubertal growth spurt is a period of very rapid growth which isfollowed by further slower growth. The pubertal growth spurt occurs on average at 12yrs in girls and 14 yrs in boys.

• The different parts of the skull follow different growth patterns, with the much of the growth of the face occurring later than the growth of the cranium. Asa result the proportions of the face to cranium change during growth and the face of the child represents a much smaller proportion of the skull than in theadult.

The cranial vault or calvarium Complete by 7 yrs. Its growth consists of a combination of drift and displacement. Drift occurs because the intracranial aspects of the bones are resorbed whilebone is laid down on the external surfaces. There is displacement as the bones are separated by the growing brain, with fill-in bone growth occurring at thesutures to maintain continuity of the cranial vault. Cranial Base As in the calvarium there is both sutural infilling and remodelling as the brain enlarges, but there are also primary cartilaginous growth sites in this region- thesynchondroses.• The spheno-occipital synchondrosis makes a contribution to growth of the cranial base until 15 yrs; it fuses at 20 yrs.• Thus, the middle cranial fossa enlarges both by AP growth and remodelling. • The anterior cranial fossa enlarges and increases in AP length by remodelling, with resorption intracranially and extracranial deposition.• The SOS is anterior to the TMJ but posterior to the anterior cranial fossa and its growth influences the facial skeletal pattern.• Growth at the SOS increases the length of the cranial base, and since the maxilla and mandible are both relate to this structure, the latter plays an important

part in how the 2 jaws relate to each other.• The shape of the cranial base also affects jaw relationship.• A small cranial base angle tends to cause a CL III skeletal pattern whilst a larger cranial base angle is more likely to be associated with a CL 2 SK pattern.

THE FACIAL SKELETON The facial skeleton serves a variety of functional requirements: vision, respiration, olfaction, mastication and speech etc. and growth is integrated so that none ofthese functions is compromised. The maxillary complex• Growth occurs by displacement with fill-in growth at the sutures and in part by drift and periosteal remodelling.• The maxilla enlarges AP by deposition of bone posterioly at the tuberosities which enlarge the dental arches. Anterior displacement occurs as bone is laid

down on its posterior aspect.• Downward growth occurs by development of the alveolar process and dental eruption, and also by inferior drift of the hard palate.• Lateral growth in the mid-face occurs by displacement apart of the 2 halves of the maxilla, with deposition of bone at the midline suture.• Maxillary growth ceases at 15 yrs (girls) and 17 yrs (boys).

The Mandible• Growth of the condylar cartilage elongates the mandible.• Most mandibular growth occurs as a result of periosteal activity which maintains the shape.• Bone is laid down on the posterior aspect of the vertical ramus and resorbed on the anterior margin. This drift lengthens the dental arch.• Vertical ramus increases in height to accommodate the increase in the vertical dimension of the alveolar process.• Remodelling also increases the width of the mandible.• Growth ceases at 17 yrs in girls and 19 yrs in boys.

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Growth Rotations• On average the face grows downwards and forwards away from the cranial base.• However Bjork has shown that the direction of facial growth is curved, giving a rotational effect. These rotations have their greatest effect on the mandible.

Mandibular growth rotations arise due to the effect of the growth of a number of structures which together determine the ratio between the posterior andanterior face heights.

• Posterior face height is determined by direction of growth at the condyles and SOS.• Anterior face height is determined by eruption of the teeth and vertical growth of soft tissues.• Marked forward growth rotation tends to result in a reduced anterior vertical facial proportion and an increased overbite.• Conversely a marked backward growth rotation will produce increased anterior vertical facial proportions and a reduced overbite or skeletal open bite.• There are also AP effects. e.g. the correction of a CL II mal. will be assisted by a forward growth rotation but made more difficult by a backward growth

rotation.• Growth rotations also have an effect on the lower labial segment with a forward growth rotation causing retroclination of the lower incisors and crowding.• Growth rotations play an important part in the aetiology of certain malocclusions.• They can be assessed by determining the anterior face height and the FMPA. Also the shape of the lower border of the mandible gives some indication:

concave lower border and marked antegonial notch signifies a backward growth rotation whilst a convex lower border is associated with a forward rotation. Control of Facial Growth• There is an interaction between genetic and environmental factors.• Significant environmental component- clinician may alter growth pattern with appliances?• Genetic control is significant in facial growth due to similarities in family members.• Two theories- (1) Growth of the primary cartilages is under tight genetic control and cannot be influenced by external factors to any great extent. However

the condylar cartilage is not a primary growth centre.• 2nd theory- bone growth is under loose genetic control and takes place in response to growth of the surrounding soft tissues- the functional matrix which

invests the bone. For example the calvarium and orbits develop intramembranously and enlarge in response to growth of the orbits and brain. However thistheory cannot explain growth of the facial skeleton as there are a no expanding structures in the face. this theory suggests that orthodontic treatment shouldbe able to alter the course of facial growth.

• Current practice indicates that the impact of orthodontic treatment on facial growth is small and there is considerable variation in response to individualpatients.

Influence of growth on orthodontic treatment• Tooth movement - active tooth movement is more readily achieved during periods of growth than after it has ceased, especially in the vertical plane e.g.

reduction of overbites.• Relative tooth movement- the general direction of developmental movement of the dentition in relation to the skull base is down and forward. An

orthodontic force applied to groups of teeth in the opposite direction has a double effect during the growth phase. The force not only tends to move the teethbut also restricts the normal forward and downward movement of growth. This relative movement plays an important part in the apparent distal movementachieved with EOT and functional appliances.

Timing of orthodontic treatment• Interceptive measures such as correction of mandibular displacements can be undertaken prior to the pubertal growth spurt• The pubertal growth spurt is the most favourable time for active treatment although this may not coincide with dental development. Until growth ceases,

tooth positions achieved by active treatment may not be stable. Effect of orthodontic treatment on growth• EOT and functional appliances produce the heaviest and most prolonged forces. Debatable whether they can induce orthopaedic changes i.e. alterations to

the basal parts of the jaws.

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TOOTH MOVEMENT AND RETENTION Histological basis of tooth movement Single point force application to crown of tooth- tilting of tooth about an axis at apical third and coronal two-thirds of the root.! Force concentrated at the coronal one-third of the socket wall and the root apex in the opposite direction.! Continuos optimal force- cell proliferation occurs in the PL in areas of compression and osteoclasts migrate via blood vessels.! Direct resorption of bone of the socket wall in areas of compression in a few days.! On the tension side PL fibres are stretched and there is proliferation of fibroblasts and osteoblasts.

Osteoid is deposited on the tension side, which becomes mineralised and called woven bone which is remodelled into mature lamella bone. Tooth movesunder the applied force.

! A force that exceeds capillary blood pressure and reduces blood flow will not produce optimal tooth movement.! Tooth movement occurs with a force duration for only 6 hrs/day Excessive force! No direct resorption of bone! Compression of blood vessels! This results in sterile necrosis of cells (known as hyalinization because of the structureless appearance under the microscope.! No tooth movement initially.! Delay of 2-3 weeks then there is undermining resorption outwards from the marrow spaces of the adjacent alveolar bone. The optimum force for tooth movement is 25 g/cm2 of root surface area. The size of force is determined by surface area of the root and the type of movement i.etipping < force than bodily movement.! Excessive forces results in:-

a) delay in tooth movement b)discomfort to patient c) tooth mobility d) root resorption e) excessive force dispersed over anchor teeth, threshold exceeded

! RETENTION! Retention: maintenance of intra-arch alignment and both static and dynamic inter-arch relationships.! Relapse: return following correction, of the original features malocclusion.Why retain? To permit osteoid/bone maturation

Reorganisation of the periodontal ligament fibres (PLF)Allows for seating of the occlusionTeeth will rebound and they are mobile

Planning retention:Soft tissues: teeth should be in a position of soft tissue balance following treatment. Labial competence important in stability of CL 2: Div I mal.Facial growth: considered at the outset of treatment. Especially important in SK III and the extremes of vertical range i.e. AOB and deep overbites. These cases

may need retention until growth has ceased. Late lower incisor crowding is multifactorial, but facial growth is one cause.Supporting tissues: PLF are placed under tension during orthodontic treatment. If force is removed, tension in PLF may lead to relapse. The turnover of

different PLF varies.Patient with periodontal disease i.e. loss of periodontal attachment, The loss of PL support means that soft tissue pressures may result in movement of the teeth

whereby permanent retention is required.The PLF within the socket are remodelled during tooth movement however the supracrestal PLF may take 6 months or longer to remodel.De-rotation of teeth is prone to relapse due to the slow turnover of free gingival fibres which can remain under tension for years. Pericision/ circumferential

supracrestal fiberotomy indicated.Midline diastema- if still present after the upper canines have erupted then it is likely to re-open after orthodontic treatment. This may be due to the discontinuity

of the transeptal fibres between the central incisors. If a low fraenal attachment is the cause then a fraenectomy during space closure is indicated.

Retention regimes: Immediately following active ortho. treatment1. If active treatment involved removable appliance then retain with a removable appliance for 3 months full-time and 3 months night-time wear.2. If active treatment involved treatment with fixed appliances then removable Hawley retainers are worn for 6 months full-time then 6 months at night.3. De-rotation and closure of mid-line diastemas require permanent retention with bonded retainers.

Relapse problems• rotations• maxillary expansion-transverse• lower incisor proclination• median diastema and general spacing Adjuncts to retention• overtreatment- 110% correction• frenectomy for median diastema if indicated• pericision of rotated teeth• interproximal stripping- keystoning or slenderising• occlusal adjustment- cuspid protection or group function eliminate non-working side contacts.