59095527 ortho lecture manual 2011 latest1

Dr. Choo Yew On & Dr. Ling Chern Chern

SECOND

EDITION ORTHODONTIC LECTURE MANUAL

ORTHODONTIC LECTURE MANUAL BY Dr. YEW ON & Dr. CHERN CHERN This book is not for sale.

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Acknowledgements We would like to thank OMF Cambodia for supporting this project to provide educational material to the Orthodontic Department at the Faculty of Odontostomatology, University of Health Sciences. Most of all we would like to thank the LORD for the opportunity to serve and to teach at the Faculty of Odontostomatology since 1996. In this new edition of Orthodontic Lecture Manual, more photos, pictures and tables have been included to make it more readable. We are thankful to the staff and postgraduate students at the Orthodontic Department for providing us with many of the clinical photos that are used as illustrations in this book. Most of the content of the book is compiled from various Orthodontic books as listed in the reference section. We hope that this book would be a useful resource to the Cambodian dental undergraduate students in their understanding and learning of orthodontics.

Drs. Choo Yew On & Ling Chern Chern


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CONTENTS

Topic Page 1. INTRODUCTION TO ORTHODONTICS 1

2. DEVELOPMENT OF NORMAL OCCLUSION 7

3. MALOCCLUSION 17

4. LOCAL FACTORS IN THE AETIOLOGY OF MALOCCLUSION 26

a. Anomalies in Number of teeth 27

b. Anomalies in Size and Form of teeth 40

c. Anomalies in Position of teeth 44

d. Habits and Others 52

5. INTERCEPTIVE ORTHODONTICS 58

6. CRANIOFACIAL GROWTH 67

7. CEPHALOMETRIC ANALYSIS 77

8. ORTHODONTIC ASSESSMENT AND DIAGNOSIS 86

9. ORTHODONTIC TREATMENT PLANNING 98

10. SPACE ANALYSIS 103

11. REMOVABLE APPLIANCES 110

12. ANCHORAGE 129

13. FUNCTIONAL APPLIANCES 136

14. INTRODUCTION TO FIXED APPLIANCES 144

15. CLASS 1 MALOCCLUSION 154

16. CLASS II DIVISION 1 MALOCCLUSION 159

17. CLASS II DIVISION 2 MALOCCLUSION 168

18. CLASS 3 MALOCCLUSION 174

19. TISSUE CHANGES WITH TOOTH MOVEMENT 182

20. RETENTION 194

21. RISKS OF ORTHODONTIC TREATMENT 201

22. LOWER INCLINED PLANE 211

23. EXAMPLES OF ORTHODONTIC TREATMENT 213


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Chapter 1 INTRODUCTION TO ORTHODONTICS

Orthodontic treatment can improve the appearance, mastication and speech, as well as overall health, comfort, and self-esteem.

1.1 Definition of Orthodontics. Orthodontics is the area of dentistry concerned with study of the craniofacial growth, development of the dentition and occlusion, and with the diagnosis, interception, and treatment of dentofacial anomalies.

1.2 Ideal Occlusion It is a hypothetical concept based on the anatomy of the teeth. It provides a standard by which all other occlusions may be judged. It is rarely found in nature.

1.3 Normal Occlusion ( Fig. 1.1)

is an occlusion within the accepted deviation of the ideal.

minor variation in the alignment of the teeth which are not of aesthetic or functional importance might be considered as normal occlusion.

Molar relationship: Class 1 occlusion (Angle classification) The mesiobuccal cusp of the maxillary first permanent molar occluding with the buccal groove of the opposing mandibular first permanent molar.

Incisors relationship: Class 1 (British Standards Incisor [BSI] classification) The lower incisors occlude with or lie immediately below the cingulum plateau of the upper incisors.

No rotation

No spaces (for permanent dentition)

Flat of mildly increased (≤ 1.5mm) curve of Spee

Fig.1.1 Normal occlusion


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1.4 Malocclusion (Fig. 1.2)

1.4.1 Definition: An unacceptable deviation – aesthetically and/or functionally – from the „ideal‟ occlusion.

1.4.2 Introduction: Not all malocclusion has to be treated. Only if the patient will benefit aesthetically or

functionally and only if patients are suitable (e.g. have good oral hygiene and good cooperation) and willing to undergo treatment (e.g. wear the appliances) should orthodontic treatment be considered.

Decision to treat malocclusion depends on: Benefits of treatment versus Risk i) Improved function Worsening of dental health (eg. traumatic

bite) ii) Improved aesthetic Failure to achieve aims of treatment

Fig. 1.2 The photographs above show two examples of malocclusion

1.5 Reasons for orthodontic treatment Three main reasons for doing orthodontic treatment:

1. To improve dento-facial appearance

2. To correct the occlusal function of the teeth

3. To eliminate occlusion that could damage the long-term health of the teeth and periodontium


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1.6 The Scope and Aims of Orthodontic Treatment

The improvement of facial and dental aesthetics This can have a positive effect on the psychosocial well-being and self-esteem of an individual.

The alignment of the teeth to eliminate stagnation areas. Mal-alignment of teeth may reduce the potential natural tooth-cleansing and increase the risk of caries.

The elimination of premature contacts which give rise to mandibular displacements and may contribute to muscle or temporomandibular joint pain.

The elimination of traumatic occlusion/ irregularities of the teeth. (Fig. 1.3)

The alignment of prominent teeth which are at risk of being traumatised (eg. severe overjet) (Fig. 1.4)

The alignment of irregular teeth prior to bridgework, crowns or partial dentures.

The alignment of periodontally involved teeth prior to splinting.

The alignment and planned positioning of teeth in the jaws prior to orthognathic surgery.

To assist the eruption and alignment of displaced teeth.

Fig. 1.3 Traumatic bite- gum recession on 1 Fig. 1.4 Large overjet – higher risk to trauma


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1.7 Orthodontic Treatment Options There are six basic treatment approaches to management and treatment of malocclusion:

1. No treatment. Patient accepts the mild irregularity of the teeth. Clinician has to consider the long term stability & retention, and benefit versus the risk of orthodontic treatment.

2. Extraction only For cases where the degree and position of crowding, and the local tooth angulations are favourable. In a growing patient, extraction of teeth will allow spontaneous movement and may provide an acceptable result in a limited number of cases. Example: Extraction of retained deciduous tooth or supernumeraries. 3. Removable appliance treatment (Fig. 1.5) To use for simple cases when simple tipping movements of few teeth are needed, and where tooth position, inclination & angulations are favorable. Example: To tip upper incisor forward in anterior crossbite in a Pseudo Class III. 4. Fixed appliance (Fig. 1.6) To use for more complex malocclusion cases as it can correct all teeth in three planes (antero-posterior, vertical and lateral) of space.

5. Functional appliances (Fig. 1.7) They are best used for growing patients with retrusive mandibular teeth and jaw (Class II). 6. Orthognathic surgery For patients with severe discrepancies/ malrelationship of the jaws. The treatment involves the combination of both fixed appliances and surgery to the jaws.

Fig. 1.5 Removable appliance Fig. 1.6 Fixed appliance

Fig. 1.7 Functional appliance to correct skeletal Class II


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1.8 The timing of orthodontic treatment

1.8.1 The deciduous dentition

Treatment at this stage is hardly ever indicated.

Examples of possible exceptions are i) where a malpositioned tooth or premature contact may give rise to marked mandibular

displacement leading to unilateral posterior crossbite. (Fig. 1.8) ii) where a supernumerary tooth is creating a localized problem.

It is important to identify and refer those patients with significant jaw discrepancy of facial asymmetry during early stages of growth to be managed by orthodontists.

1.8.2 The early mixed dentition

The aim is either to eliminate or reduce the severity of a developing malocclusion.

Orthodontic treatment may include: a) the planned extraction of intensively carious first permanent molars (8½ -10 years old) b) balancing extractions of deciduous teeth c) serial extractions d) Space maintainers may be fitted. (Fig. 1.9) e) simple orthodontic treatment to correct in-standing incisor or to eliminate a mandibular

displacement f) Reverse headgear to correct retrognathic maxilla in Skeletal Class III

Only treatment which can be completed rapidly and which will be stable should be attempted (not longer than between 3 and 6 months).

Fig. 1.8 Premature contact of C causing displacement of mandible & unilateral crossbite . C C


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Fig. 1.9 Lingual arch as space maintainer

1.8.3 The late mixed and early permanent dentition (10-13 years old)

Most of the orthodontic treatment is carried out at this stage.

Most of the permanent teeth have erupted and there is little further growth in arch width, thus crowding can be reliably estimated.

In the majority of children the jaw relationship changes only to a limited extent after the age of 10 years.

Functional appliance is best suited at this stage as there is growth.

1.8.4 The late permanent dentition (> 16 years old)

Treatment planning and mechanics will usually require modification from that which is appropriate in the growing child.

Normally it is more difficult to treat adult cases and treatment time may take longer than growing child.

Orthognathic surgery is indicated for severe skeletal discrepancy and when patient has stopped growing.


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Chapter 2. DEVELOPMENT OF NORMAL OCCLUSION

2.1 Introduction At birth -----> deciduous dentition -----> mixed dentition ------> permanent dentition 6 months old 6 years old 12 years old onwards Occlusal development may be divided into five stages: Stage 1. Birth to establishment of deciduous dentition. Stage 2. Deciduous dentition to early mixed dentition. Stage 3. Early mixed dentition to late mixed dentition. Stage 4. Late mixed dentition to permanent dentition. Stage 5. Permanent dentition. However, occlusal development should be considered a continuous process.

2.2 Stage 1. Birth to the establishment of deciduous dentition. (Fig. 2.1)

2.2.1 At birth

The maxillary and mandibular gum pads have 20 segmented elevations corresponding to the unerupted deciduous teeth.

The upper arch is horseshoe-shaped and the vault of the palate is very shallow.

The lower arch is U-shaped and the gum pad on the anterior is slightly everted labially.

With the mandible in its physiological rest position the gum pads are parted, with the tongue filling the space between them and projecting against the lips anteriorly.

The maxillary gum pad overlaps the mandibular both buccally and labially, corresponding to the occlusal relationship of the teeth.

1Fig. 2.1 Relationship between maxilla & mandible in infant

1 Picture taken from a lecture given by Dr. Jon Hammond, University of Edinburgh.


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2.2.2 The deciduous dentition (Table 2.1)

Eruption of the lower incisors begins at about 6 months of age.

The timing of eruption may vary at a range of 6 months earlier or later compared to the time of eruption on the chart.

Usually by the age of 2½ years all the deciduous teeth have erupted.

The incisors are more vertical than their permanent successors and they are often spaced (Fig. 2.2a). Lack of spacing strongly suggests that the permanent incisors will be crowded (Fig 2.2b).

There may be spacing distal to the lower canines and mesial to the upper canines (known as „primate spacings‟) (Fig. 2.3a, b)

The distal surfaces of the second deciduous molars usually end in line with each other (termed the „flush terminal plane‟) (Fig. 2.4, 2.5)

By age 5-6 years, an edge-to-edge occlusion with incisor attrition is common.

Table 2.1 Typical ages of eruption, mesiodistal widths and calcification of the deciduous teeth

Time of eruption Mesiodistal width Calcification commences (months) (mm) (weeks in utero)

Maxillary teeth Central incisor 8 6.5 12-16 Lateral incisor 9 5.0 13-16 Canine 18 6.5 15-18 First molar 14 7.0 14-17 Second molar 24 8.5 16-23 Mandibular teeth Central incisor 6 4.0 12-16 Lateral incisor 7 4.5 13-16 Canine 16 5.5 15-18 First molar 12 8.0 14-17 Second molar 20 9.5 16-23

Notes:

1. Eruption times vary considerably - up to 6 months earlier or later than the times given is not unusual.

2. Mesiodistal widths vary up to 20 % of the figures given. 3. Root formation is complete between 12 to 18 months after eruption. 4. There is usually a difference of a few weeks between tooth eruption on the left and right sides. 5. Usually the lower teeth erupt ahead of their upper counterpart. 6. Calcification of first permanent molars begins at birth


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a. b. Fig. 2.2 a) Spacing between deciduous incisors. b) Lack of adequate spacing.

a. b2

Fig 2.3a,b Primate spaces between the B & C, and between the C & D (shown by red arrows in the photos above). The crowns of permanent incisors lie lingual to the deciduous incisors.

3Fig. 2.4 Flush terminal plane distal of Es

2 Picture taken from Contemporary Orthodontics, 3

rd edition by William Profitt

3 Picture taken from a lecture given by Dr. Jon Hammond, University of Edinburgh.


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4Fig. 2.5 At approximately 5 years old. Note the flush terminal on the distal surface of the Es. The

permanent incisors are positioned lingual/palatal to the roots of the deciduous incisors.

2.3 Stage 2. Deciduous dentition to early mixed dentition (Fig. 2.6)

Lower first molars or lower central incisors are usually the first to erupt- at the age of 6 years. Mild incisor crowding is common but tends to resolve by 9 years with an increase in intercanine width.

Eruption times of permanent teeth may vary at a range of 18 months earlier or later compared to the time of eruption on the chart.

Note: Teeth presence in early mixed dentition (at 6 to 8 years) are 6EDC21 12CDE6 6EDC21 12CDE6

4 Photo taken from Reynolds and Abraham McMinn’s Interactive Clinical Anatomy: Head and Neck: 1997

Mosby International.


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Table 2.2 Typical ages of eruption, mesiodistal widths and calcification of the permanent teeth

Time of eruption Mesiodistal width Calcification commences (years) (mm) (months)

Maxillary teeth Central incisor 7.5 8.5 3-4 Lateral incisor 8.5 6.5 10-12 Canine 11.5 8.0 4-5 First premolar 10.0 7.0 18-21 Second premolar 11.0 6.5 24-27 First molar 6.0 10.0 Around birth Second molar 12.0 9.5 30-36 Mandibular teeth Central incisor 6.5 5.5 3-4 Lateral incisor 7.5 6.0 3-4 Canine 10.0 7.0 4-5 First premolar 10.5 7.0 21-24 Second premolar 11.0 7.0 27-30 First molar 6.0 11.0 Around birth Second molar 12.0 10.5 30-36

Notes: 1. The figures given both for the eruption times and for mesiodistal widths commonly vary up to 20%

on either side of the figure given. 2. The permanent teeth usually erupt when ¾ of their roots are formed. 3. Root formation is normally completed 2-3 years after eruption.

Fig. 2.6 Desirable eruption sequence for the permanent eruption

2.3.1 The permanent incisors 1. The permanent incisors develop lingual/palatal to the roots of the deciduous incisors (Fig.

2.5)


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2. Space for the permanent incisors teeth (which are larger than their deciduous predecessors) is provided by: a) Utilization of existing spacing between the deciduous incisors. b) A growth increase in intercanine width. This takes place during the eruption of the

incisors. (The intercanine growth is mostly completed by 9 years with some minimal increase up to age 13 years. After this time a gradual decrease is the norm)

Upper inter-canine width increase by about 3.5 mm

Lower inter-canine width increase by about 3.0 mm c) The upper permanent incisors are more proclined and thus form a larger arch than the

deciduous incisors. Notes: [i] If the deciduous incisors root is not resorbed normally, the permanent incisors may be deflected lingually or labially or distally. (Fig. 2.7). [ii] When the upper incisors erupt they are frequently distally inclined so that there is a median diastema. (Fig. 2.8) This is the ‘ugly duckling’ stage. It is due to 3 3 migrate and press on the roots of 2 2; causing their crowns & to a lesser extent those of 1 1 to flare distally (Fig. 2.9). When the 3 3 erupt the median diastema (physiological spacing) will usually close spontaneously.

This is a natural developmental stage and treatment should not be undertaken to close the diastema before the permanent canines erupt.

Note: Other causes of median diastema could be due to:

large fibrous fraenum

supernumerary

missing or small lateral incisors

generalised spacing

dilaceration of a central incisor

cyst

Fig. 2.7 Retained B causing deflection of 2 distally.


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At 7 years At 11 years Fig. 2.8 Spontaneous closure of median diastema (Ugly duckling) of the same patient.

Fig. 2.9 About 8 years old. Upper canines pressings on the roots of lateral incisors

causing their crowns and the central incisor crowns to flare distally.

2.3.2 The permanent first molars

In a normal occlusal relationship the flush terminal plane of the second deciduous molars brings the first permanent molars into cusp-to-cusp contact (Fig. 2.10)

There is usually a small growth spurt associated with the eruption of the 1st permanent molars leading to an increase in face height, and in a growth in inter-canine width to accommodate the larger incisor teeth.

5Fig. 2.10 1

st permanent molars at cusp-to-cusp contact during early mixed dentition.

5 Picture taken from Handbok of Orhodontics by Martyn T. Cobourne and Andrew T. DiBiase


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2.4 Stage 3. Early mixed dentition to late mixed dentition (about 9-10 years old) No permanent teeth erupt at this stage.

2.5 Stage 4. Late mixed dentition to permanent dentition.

(≥ 11 years old) a) The mandibular canines and maxillary first premolars are usually the first to erupt at this

stage. b) During this phase the remaining deciduous teeth (C, D, E) are shed and replaced by their

permanent successors (3, 4, 5), and the 2nd & 3rd molars erupt. c) Space for the permanent canines and the premolars (3, 4, 5s) is provided by slightly

greater width of the deciduous canines and molars (C, D, Es). d) The discrepancy between the combined mesiodistal width of the C, D, E and that of the

3,4,5 is called the ‘leeway space’. (Fig. 2.11) e) In normal occlusion, Class 1 molar relationship is established due to:

Greater leeway space in the mandible (about 2-2.5mm) than in the maxilla (about 1-1.5mm) allows the lower permanent molar to move forward further than the upper molar- when C, D, Es are replaced by 3,4,5s.

Forward growth of the mandible f) The second upper permanent molars are guided directly into occlusion by the distal

surface of the first permanent molars. g) Growth posteriorly at the back of the arch provides space for the permanent molars. h) Alveolar bone growth maintains occlusal contact as the face grows vertically.

6Fig 2.11 Leeway space ( )

6 Picture adapted & taken from An Introduction to Orthodontics, 3rd edition by Laura Mitchell


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2.6 Stage 5. Permanent dentition (Fig. 2.12)

2.6.1 Features of normal occlusion in the permanent dentition (Static occlusal relations)

The mesiobuccal cusp of the upper first permanent occludes with the midbuccal groove of the lower first permanent molar.

The upper canine occludes in the embrasure between the lower canine and the lower first premolar.

The overjet is 2 to 3 mm.

There is complete overbite = 1/3 of the lower incisor clinical crown (20% to 30%)

The arches are regular in form.

All teeth must be present, are of normal form and in correct alignment.

There should be tight contact points between each of the teeth.

2.6.2 Andrew Six Keys

1. Correct molar relationship:

The distal surface of the distal marginal ridge of the upper 1st molar occludes with the mesial surface of the mesial marginal ridge of the lower 2nd molar.

The mesiobuccal cusp of the upper 1st molar occludes with the groove between the mesiobuccal & middle cusps of the lower 1st molars.

2. Correct crown angulation (tip) 3. Correct crown inclination (torque) 4. No rotations 5. No spaces: tight contact points 6. Flat occlusal plane: Curve of Spee ≤ 1.5mm

Fig. 2.12 Normal occlusion (Frontal view) (Lateral view)


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2.6.3 Functional occlusal relation Centric relation (CR) should coincide with centric occlusion (CO)

On lateral excursions, canine guidance or group-function on the working side, with no contact on the non-working side.

During protrusion only incisors contact.

2.7 Maturation changes in the occlusion

a) Increase in the lower incisor crowding. This is a noticeable natural change which

occurs in the permanent occlusion between the ages of 15 and 20 years. An increase in the incisor crowding

This is largely due to a slight retro-inclination of the lower incisors which occur during the later stages of facial maturation due to mandibular growth rotations.

Mesial drift of buccal teeth may contribute to this late crowding. The following explanations have been offered:

i) It is a natural growth tendency in human. ii) Crowded teeth, particularly third molars, may exert a forward pressure on the other

teeth. iii) The anterior component of force: due to the upper and lower incisors are slightly

mesially inclined. Vertical occlusal loading produces an intrusive force and a small anterior component of force which could be responsible for mesial drift

b) Slightly increase in the interincisal angle with incisor uprighting.

c) Slight increase in mandibular prognathism.


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Chapter 3. MALOCCLUSION 3.1 Definition Malocclusion is an irregularity of the teeth beyond the accepted range of normal occlusion (aesthetically and/or functionally) or a malrelationship of the dental arches in any of the three planes of space - sagittal (antero-posterior), vertical or lateral (transverse).

3.2 Prevalence According to a small research done by Dr. Paul Smith & Dr. Jon Hammond in 2003 on 70 (11-13 years-old) Khmer school children, there were 51% Class 1, 19% Class II division 1, 1% Class II division 2 and 29% Class III malocclusion amongst the students.

3.3 Malocclusion Malocclusion may be associated with one or more of the following:

a) malposition of individual teeth. b) malrelationship of the dental arches.

3.3.1 Malposition of individual teeth (Fig. 3.1) A tooth may occupy a position other than normal by being:

1. Tipped: The tooth apex is normally placed but the crown incorrectly positioned. Example:

Proclined [labially inclined]

Retroclined [lingually inclined]

Mesially or distally inclined

2. Displaced: Both the apex and crown are incorrectly positioned.

3. Rotated: The tooth is rotated around its long axis. Rotations are described by the approximal surface which is furthest from the line of the arch and the direction in which it faces: for example, a rotated upper lateral incisor is described as mesio-labially rotated if the mesial aspect is out of the line of the arch (Fig. 3.2)

4. In infra-occlusion: The tooth has not reached the occlusal level.

5. In supra-occlusion: The tooth has erupted past the occlusal level.

6. Transposed: Two teeth have reversed their positions, for example an upper canine exchanged position with the first premolar.


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Fig. 3.1 Malposition of teeth in a patient with Class II division 2 malocclusion.

Fig. 3.2 Upper right lateral incisors is mesio-labially rotated. Upper canines are buccally displaced.

3.4 Classification of malocclusion

1. Angle‟s classification

2. British Standard Incisor classification

3.4.1 Angle’s classification

is based on the arch relationship in the antero-posterior (sagittal) plane.

the key relationship in Angle‟s classification is that of the first permanent molars.

in normal occlusions, the anterior buccal groove of the lower first permanent molar occlude with the mesio-buccal cusp of the upper first permanent molar.

Class I. (Normal or neutro-occlusion) (Fig 3.3)

Mesiobuccal cusp of 6 occludes in the buccal grove of 6.

Discrepancies of ≤ ½ a cusp width were also regarded as Class 1.

Retroclined

Rotated

Bucally displaced & distally inclined

Proclined


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Class II. (Disto-occlusion) (Fig. 3.4, 3.5)

Mesiobuccal cusp of 6 occludes anterior to the buccal groove of 6 Class III. ( Mesio-occlusion) (Fig. 3.6)

Mesiobuccal cusp of 6 occludes posterior to the buccal groove of 6 ( Note: In Class I cases, the upper permanent canine occlude into the embrasure between the lower canine and first premolar)

Fig. 3.3 Class I molar & incisor Fig. 3.4 Class II molar/ Class II division 1 Relationship. incisor relationship.

Fig. 3.5 Class II molar/ Class II div 2 Fig. 3.6 Class III molar & incisor incisor relationship. relationship.

3.4.2 British Standard Incisor classification (BSI) Class I

The lower incisor edges occlude with or lie immediately below the cingulum plateau (middle part of the palatal surface) of the upper central incisors. (Fig. 3.7a)

Class II

The lower incisor edges lie posterior to the cingulum plateau of the upper incisors. There are two divisions to Class II malocclusion: (i) Division 1.

The upper incisors are proclined or of average inclination and there is an increased overjet. (Fig. 3.7b)


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(ii) Division II. The upper central incisors are retroclined . The overjet is usually minimal but may be increased. (Fig. 3.7c) Class III

The lower incisor edges lie anterior to the cingulum plateau of the upper incisors. The overjet may be reduced or reversed. (Fig. 3.7d)

In clinical practice the Incisor classification is usually found to be more useful than the Angle‟s classification.

7Fig. 3.5 British Standard Incisor classification: a, Class I; b, Class II Division 1;

c, Class II Division 2; d, Class III

3.5 The aetiology of malocclusion (Fig. 3.8)

Malocclusion can occur as a result of genetic factors which are inherited, or

environment factors, or more commonly a combination of both inherited and environment factors acting together.

Genetics tend to influence skeletal pattern, environment influences tooth position, but both act synergistically to create malocclusion.

Aetiology of malocclusion can be categorized into General factors and Local factors.

7 Figure taken from Walther & Houston’s Orthodontic Notes by ML Jones & RG Oliver


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8Fig. 3.8 The aetiology of malocclusion. Factors most responsive to interceptive orthodontics are in

capital letters

3.5.1 General factors (genetic influence)

include variations in the skeletal relationship (Skeletal pattern), disproportion between the tooth and arch size (causing spacing or crowding), and soft tissue factors (e.g. muscular dystrophy).

malocclusion may be associated with a number of genetic and developmental disorders such as Down syndrome/mongolism (Fig. 3.9), cleft lip and palate, and Cleidocranial dystosis (Fig. 3.10, 3.11).

9 Fig. 3.9 Down syndrome patient.

10 Fig. 3.10 Cleidocranial dystosis

8 Adapted from Interceptive Orthodontics by Andrew Richardson

9 Photo taken from http://www.genetic-diseases.net/down-syndrome/

10 Photo taken from http://www.doctorpedi.net/fordoctor/casereports/cleidocranial_dysplasia.asp

MALPOSITION

AND

MALOCCLUSION

Skeletal Pattern

LOCAL FACTORS

SPACE DEFICIENCY and

excess

Soft tissues

http://www.genetic-diseases.net/down-syndrome/

http://www.doctorpedi.net/fordoctor/casereports/cleidocranial_dysplasia.asp


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Fig. 3.11 Dental panoramic radiograph showing the oral manifestations of cleidocranial dysplasia. There is retention of the primary dentition, delayed eruption of the secondary dentition and the presence of multiple supernumerary teeth (arrowed)

3.5.1a Down Syndrome:

The primary skeletal abnormality affecting the orofacial structures is an underdevelopment or hypoplasia of the midfacial region. The bridge of the nose, bones of the midface and maxilla are relatively smaller in size. This causes a prognathic Class III occlusal relationship which contributes to an open bite.

A reduced degree of muscle tone is generally found in Down syndrome. This affects the musculature of the head and oral cavity as well as the large skeletal muscles. The reduced muscle tone in the lips and cheeks contribute to an imbalance of forces on the teeth with the force of the tongue being a greater influence. This contributes to the open bite often seen in Down syndrome.

3.5.1b Cleft lip & palate: Patient may have supernumerary and/or missing teeth. Patient who had cleft palate repaired tends to have a retrognathic maxilla and constricted maxilla.

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Photo taken from Fleming P. S. et al. Revisiting the supernumerary: the epidemiological and molecular basis

of extra teeth. BDJ 2010; 208: 25-30


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3.5.1c Cleidocranial dysostosis (Fig. 3.11)

It is a genetic disorder characterized by hypoplasia or aplasia of the clavicles, patent fontaneles, and a short stature. Teeth problem associated with this syndrome are:

primary teeth do not fall out at the expected time delayed eruption and impaction of permanent teeth extra teeth (supernumerary teeth) peg teeth

3.5.2 Local factors (environment influence) (Fig. 3.12) - include habits and anomalies in number, form and developmental positions of the teeth, retained deciduous tooth and pathology Note: more information on the local factors in the etiology of malocclusion is found in Chapter 4.

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Fig. 3.10 Local factors in the aetiology of malocclusion

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Adapted from Interceptive Orthodontics by Andrew Richardson

MALPOSITION AND

MALOCCLUSION

Teeth of abnormal form or size

Supernumerary teeth

Premature loss of deciduous teeth

Trauma

Transposition

Impaction

Ectopic position of tooth germ

Loss of permanent teeth

Prolonged retention of deciduous teeth

Missing teeth

Large labial fraenum

Habits

Pathology


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3.6 An alternative way of categorizing aetiology of malocclusion

HARD TISSUE SOFT TISSUE

i) Dental

Local e.g. tooth number/size/shape ectopic eruption (3) early/delayed loss deciduous tooth.

General e.g. size of arch/tooth

extensive hypodontia or hyperdontia

ii) Skeletal

Local e.g. alveolar insufficiency

General e.g. genetics: cranial base length, saddle angle

Pathology e.g excessive growth hormone

Head & Neck syndrome e.g. Crouzon syndrome

i) Local

Digit sucking

Lip habit (Fig. 3.11)

Tongue habit (Fig. 3.12)

Fraenum

Pathology e.g. scarring ii) General

Genetic

Lip morphology

Respiration (mouth breather)

Pathology e.g. cleft lip

Fig. 3.11 Patient with lip trap on I1. At rest. When smiling. Note the proclination of I1

` Fig. 3.12 Open bite due to tongue thrust


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3.7 Summary of aetiology of malocclusion

13Aetiological associations for intra-arch variation Intra-arch variation Dentoaveolar factors Skeletal factors Neuromuscular

factors General crowding irregularities

Large teeth Small jaw capacity Restricted development of arch circumference

Local crowding irregularities

Premature extraction of deciduous teeth. Retained deciduous teeth; supernumerary teeth Local variation in tooth size or shape.

Impacted teeth As for general and local crowding

Ectopic teeth As for general and local crowding. Trauma to deciduous predecessor.

Late lower incisor crowding

Mesial migration of posterior teeth during vertical growth.

Late mandibular rotation.

Increased lower lip tone.

General spacing Small teeth Large jaw capacity Large tongue; everted lips.

Local spacing Tooth extraction, hypodontia, abnormal fraenal attachment; interrupted trans-septal fibre system; supernumerary teeth. Cysts, tumors.

Compensatory maxillary incisor proclination in Class III skeletal pattern.

Digit sucking.

14Aetiological associations for inter-arch variation

Inter-arch variation Dentoaveolar factors Skeletal factors Neuromuscular factors Class II division 1 incisor relationship

Class II skeletal pattern Digit sucking Lack of lower lip coverage

Class II division 2 incisor relationship

Underdeveloped incisal cingulae

Class II skeletal pattern (often mild). Decreased lower face height.

High lower lip line. Overclosure and undereruption of posterior teeth related to lack of interincisal contact.

Class III incisor relationship

Class II skeletal pattern. Anterior forced bite from premature contact

Partial anterior crossbite Lingual deflection of maxillary incisor, e.g. retained deciduous tooth, crowding.

Class III skeletal pattern (mild)

Anterior forced bite from premature contact

Bimaxillary proclination Protrusive maxilla and mandible.

Large tongue, everted lips

Increased overbite Skeletal relationships preventing interincisal contact (as in Class II divisions 1 and 2 and Class III incisal relationships; reduced lower face height

Overclosure and under-eruption of posterior teeth related to lack of interincisal contact

Anterior openbite Increased lower face height Digit sucking, obstructed nasal airway. Tongue position.

Centre line discrepancy Asymmetry in the number of developed teeth or in the pattern of extractions.

Skeletal asymmetry Lateral forced bite position from premature contact.

Class II molar relationship

Loss or absence of mesial teeth in maxilla

Class II skeletal pattern

Class III molar relationship

Loss or absence of mesial teeth in mandible

Class III skeletal pattern Anterior force bite

Posterior crossbite Localized deflection of teeth e.g. retained deciduous tooth, crowding

Discrepancy in maxillomandibular width

Lateral forced bite (in unilateral crossbite)

Lateral open bite Localized failure of eruption Increased curve of Spee as compensation for Class III skeletal pattern.

Tongue position

13

Table taken from Orthodontics and Occlusal Management by W.C. Shaw 14

Table taken from Orthodontics and Occlusal Management by W.C. Shaw


26

Chapter 4. LOCAL FACTORS IN THE AETIOLOGY OF MALOCCLUSION

The local factors can be divided into: 4.1 Anomalies in Number of Teeth 4.1.1 Developmentally missing teeth 4.1.2 Supernumerary (extra teeth) 4.1.3 Early loss of deciduous teeth 4.1.4 Retained deciduous teeth 4.1.5 Loss of permanent teeth 4.2 Anomalies in Size and Form of Teeth 4.2.1 Size

4.2.1a Macrodontia 4.2.1b Microdontia

4.2.2 Form

4.2.2a Peg lateral incisor 4.2.2b Dilaceration 4.2.2c Twin teeth (germination/ fusion)

4.2.2d Dens evaginatus

4.3 Anomalies in Position of Teeth 4.3.1 Ectopic 4.3.2 Transposition 4.3.3 Impaction 4.4 Habits 4.4.1 Finger sucking 4.4.2 Tongue thrusting

4.5 Others 4.5.1 Fraenum 4.5.2 Trauma 4.5.3 Pathology 4.5.4 Bad restoration


27

4.1 Anomalies in Number of Teeth

4.1.1 Developmentally Missing Teeth 4.1.1a Anodontia

failure to develop all teeth

is a rare condition due to aplasia of the dental lamina.

is often related to Ectodermal Dysplasia (a hereditary condition in which there is dry coarse skin, sparse hair and absence of sweat glands)

4.1.1b Hypodontia

failure in the development of 1 tooth or several teeth.

Incidence:

less than 6% of population (not including missing 8s)

teeth most commonly missing are third molars, upper lateral incisors, lower second premolars and upper second premolars.

is often due to hereditary, sometimes related to Ectodermal Dysplasia (Fig 4.1a, b). The teeth are often conical shaped and small size. Patient will need bridge, partial dentures or implants.

a15. b

16.

Fig. 4.1 Ectodermal dysplasia

4.1.1c Missing Upper and Lower 8s (third molars)

doesn‟t give much problem except when 7s need to be extracted

make sure that 8 is present & normal before extracting 7

avoid extraction of 7 for distal movement of buccal segment

15

Photo a. taken from www.wsahs.nsw.gov.au/services/dental/paediatric/paed_dent_research.htm 16

Photo b, taken from www.arquivosdeorl.org.br/conteudo/acervo_eng.asp?id=388

http://www.wsahs.nsw.gov.au/services/dental/paediatric/paed_dent_research.htm

http://www.arquivosdeorl.org.br/conteudo/acervo_eng.asp?id=388


28

4.1.1d Missing Upper 2s (lateral incisors) (Fig. 4.2)

Missing upper 2s usually cause aesthetic problem

Fig. 4.2 Missing left 2 causing spacing Two treatment options:

1) to reopen the space and replace the missing teeth 2) to close the space

The decisions of treatment options depend on:

the patient‟s opinion and co-operation

antero-posterior and vertical skeletal relationships

colour, size, shape and inclination of canine and incisor teeth

whether the arches are spaced or crowded

the occlusion of the buccal segments. Note: Do a Kesling (diagnostic) set-up on duplicated study models to help in deciding the treatment options. Option 1: Open the space to replace the 2s with bridge or partial denture or implants (Fig. 4.3a, b) Indication:

Class I uncrowded arch or

Class III with little maxillary arch crowding

a. b. 17

Fig. 4.3 Missing 2s After orthodontic treatment & resin bonded bridge

17

Photos taken from Orthodontics and Paediatric Dentistry by D Millett & R. Welbury

Resin bonded bridge


29

Option 2: Close the space and change the shape of 3s to look like 2s (Fig.4.4) Indication:

if there is crowding, or

Class II problem that might otherwise require tooth loss for its correction Management: Extract Cs early to facilitate mesial drift of posterior teeth; use fixed appliance to align & approximate 31 13 followed by fixed retainer and reshaping of 3s to look like 2s. Advantages:

- no need for prosthesis - preserves the overall dento-alveolar height at the upper 2 area

Disadvantages:

- morphology and color of upper 3 may not resemble upper 2 - loss of cuspal protection occlusion

Fig. 4.4 Upper canines reshaped & replaced missing lateral incisors (after orthodontic treatment)

4.1.1e Missing 5s (second premolars) Check with radiograph whether tooth 5 is present or not, before extracting other teeth for orthodontic treatment. Two treatment options: Option 1: Preserve E (2nd deciduous molar). The tooth may be remained till the patient is 30-40 years old. Tooth might shed by itself. Sometimes E might submerge. If the E starts to submerge, place an occlusal onlay either with composite or cast inlay. Follow-up & observe the patient (Fig. 4.5). Indication:

no crowding and good alignment of the dentition

good prognosis of E: not carious or having only a small restoration and well-formed roots.


30

Fig. 4.5 Patient has missing lower right 5. Lower E built up with composite onlay. Lower E starts to submerge. To follow up patient.

Option 2: Extract E and close the space between teeth 4 and 6. Indications:

poor prognosis of E (large restorations or large caries)

roots of E already resorbed

there is crowding in the arch

there is increased of overjet in the upper arch (use the space to reduce overjet)

E is submerged (ankylosed) below gingival level and 6 is tilted mesially. Extract E and treat with fixed appliance.

4.1.1f Missing lower incisors

A fixed appliance is required to close the space in a crowded arch or to open space in an uncrowded arch prior to prosthetic replacement of the incisors.

4.1.2 Supernumerary Supernumerary is a name given to extra teeth and it is formed during the time prior to birth or as late as 10 to 12 years old. 4.1.2a Incidence

0.8% in deciduous dentition

1.6% in permanent dentition

Down‟s syndrome, cleidocranial dysplasia and cleft palate and cleft lip patients. Cleft patients have a higher tendency of having supernumeraries at the cleft areas.

more commonly in males than females

4.1.2b Location

can happen anywhere in the arch

occurs more frequently at the premaxilla ( ≥ 80% ). Fig. 4.6 4.1.2c Aetiology

an offshoot of the dental lamina or

a tertiary dentition


31

4.1.2d General Effects

causes crowding (Fig. 4.7)

rotation of teeth (Fig. 4.7)

root resorption of the existing teeth

displacement of teeth (Fig. 4.7)

obstruction to the eruption of permanent teeth

occasionally no effect, if it‟s in the bone. Observe and follow-up.

Fig. 4.6 Occlusal film showing 2 supernumeraries

Fig 4.7 Supernumerary causing displacement of 1 1 & rotation of left 1


32

4.1.2e Types of supernumeraries i) Supplemental (Fig. 4.7, 4.10)

tooth looks like the normal series

e.g. additional of lateral incisor, 2nd premolar, or 4th molar

tooth chosen for extraction is the tooth that is most malpositioned and has a bad prognosis .

ii) Mesiodens (Fig. 4.9)

found in the midline

can be conical or tuberculate in shape

can cause displacement of incisors

can cause median diastema

Fig. 4.8 Supplemental supernumerary Fig. 4.9 Mesioden tuberculate/barrel-shaped

Fig. 4.10 Note the 4

th upper molars and conical supernumerary between 1 1


33

iii) Paramolars (Fig. 4.11)

found in the molar region

usually peg shaped (may be fused to a permanent molar)

18

Fig. 4.11 Paramolar

19

Fig. 4.11 Paramolar

iv) Odontome (Fig. 4.12)

Is rare

Maybe compound or complex forms

20

Fig. 4.12 Odontome compound

4.1.2f Treatment of supernumeraries:

Extraction - if it is pathological or - if it causes problems to the occlusion. May need orthodontic treatment. (Fig. 4.13)

Radiographic observation – if it is in the bone and not causing problem. But if there are any pathological changes, remove it.

18

Photo taken from www.sanedentist.com/abnormalities-you-should-know-in-the-number-of-teeth.html 19

Photo taken from http://www.sanedentist.com/abnormalities-you-should-know-in-the-number-of-teeth.html 20

Photo taken from www.lecourrierdudentiste.com/conseil-plus/diagnostic-differentiel-des-radio-opacites-des-

maxillaires.html

Fig 4.13a. Before treatment. Patient has supernumerary and instanding 22

Fig 4.13b. Mesioden extracted and patient treated with fixed appliance.

http://www.sanedentist.com/abnormalities-you-should-know-in-the-number-of-teeth.html

http://www.sanedentist.com/abnormalities-you-should-know-in-the-number-of-teeth.html

http://www.lecourrierdudentiste.com/conseil-plus/diagnostic-differentiel-des-radio-opacites-des-maxillaires.html

http://www.lecourrierdudentiste.com/conseil-plus/diagnostic-differentiel-des-radio-opacites-des-maxillaires.html


34

4.1.3 Early loss of deciduous teeth 4.1.3a Effects of premature loss of deciduous teeth The effects depend on i) the tooth lost

ii) age when tooth was lost iii) teeth crowding

Premature loss of deciduous teeth may

cause crowding and/or

cause midline shift i) The Tooth Lost A, B:

Generally no effect on the development of occlusion, except in very severe crowding cases.

If deciduous incisor is intruded by a blow/ fall, displacement or dilacerations of the successor may occur.

C:

Early loss of C (particularly in lower arch), might be due to the result of resorption of its root by a crowded permanent lateral incisors.

Unilateral loss causes midline shift to the side of loss/extraction

In cases where there is an early loss of C on one side, do balancing extraction on the opposite side of C in the same arch to prevent midline shift.

Note: May need to put a lingual arch for the lower arch to prevent lower incisors from tilting lingually (causing further loss of space and deepening OB), especially if patient has active lower lip muscular activity.

D:

Early loss of D will result in loss of space for the premolars, partly through forward drift of E and partly as a result of relieve of incisors crowding.

Unilateral loss may cause midline shift to the side of loss/extraction

Observe the midline. If there is midline shift, extract the opposite D on the same arch

Fig. 4.13 c. Space between upper two central incisors is closed. 22 is aligned into the arch

Balancing and compensating extractions

1. Balancing extraction is the removal of the contralateral tooth - to avoid midline/ centerline shift.

2. Compensating extraction is the removal of the equivalent opposing tooth – to help maintain occlusal relationships between the arches.


35

E:

If E is extracted the 6 will drift mesially and encroach on the space for premolars. There will be loss of space in the arch for the premolars to erupt (Fig. 4.14).

Space loss is usually more severe in the upper arch & if E is lost before 6 erupts. Therefore try to preserve E until 6 has erupted.

Unless the extraction is very early, loss of E has little effect on the midline so that balancing and compensating extraction are rarely necessary.

Fig. 4.14 Early loss of upper Es cause buccal crowding and 5s erupted palatally. ii) Age when tooth was lost Generally, the earlier the tooth is lost, the loss of space will be faster and more severe. iii) Teeth crowding

If the arch shows potential crowding, the early loss of deciduous teeth would cause crowding especially in the buccal segment.

If there is generalized spacing in the arches, the early loss of deciduous teeth doesn‟t affect the occlusion of the permanent dentition.

4.1.3b Treatment of early loss of deciduous teeth

1. Balanced extraction is needed if C is missing unilaterally.

2. Unilateral loss of D:

Unilateral loss of D may result in centerline shift.

In most cases an automatic balancing extraction is not necessary, but centerline should be kept observed

If there is centerline shift, extract D on the opposite side of the same arch (balancing extraction)


36

3. Loss of E:

Balancing and compensating extraction are usually not necessary

Space maintainer might be used if preservation of space for a permanent successor will avoid or simplify subsequent orthodontic treatment.

4.1.4 Retained deciduous teeth Deciduous teeth may be retained if the successor is congenitally missing Retained deciduous teeth can cause the permanent successor to be impacted or deviate from the normal path of eruption. If contralateral tooth has been shed more than 6 months earlier, investigate (e.g. using radiograph) to find out why the tooth has not erupt yet. 4.1.4a Retained deciduous incisors (A, B)

can deflect the eruption of 1, 2 (Fig 4.15)

Fig. 4.15 Retained right B, causing right 2 to be deflected distally.

Space maintainers Indications:

Where there is just sufficient room for all the permanent teeth, or

In severely crowded case, where the extraction of one permanent tooth from each quadrant will provide just enough space.

Contraindications:

For patient with spacing (where space loss will not occur anyway)

In moderate crowding (where extraction of permanent teeth and orthodontic treatment will be needed)


37

Treatment: a] Extract A, B before 1, 2 reaches the occlusal level. 1, 2 will move to the normal position. b] If 1,2 are already palatally erupted and there is an anterior crossbite,

treat with a removable appliance with Z-spring (Fig. 4.16), or

use a wooden spatula or ice-cream stick to prop the tooth to the front (Fig. 4.17). Ask patient to bite on the spatula for 10-15 minutes, 3 to 6 times a day for 2 to 3 weeks, or

use a lower inclined plane (Fig. 4.18)

Fig. 4.16 Removable appliance Fig. 4.17 Patient biting on tongue spatula with Z-spring & Posterior Biteplane

Fig. 4.18 Lower inclined plane

4.1.4b Retained deciduous canines (C) If it is retained, it may be a sign that 3 may be in an ectopic position.

Palpate buccally and palatally to locate whether 3 is present from 9 years.

If 3 is not palpable in the buccal sulcus, its position should be investigated radiographically.

The C should be removed if 3 is found to be palatally placed.

If the unerupted palatal 3 overlaps less than half of the breath of the root of lateral incisor, 91% of it will normalized if C is extracted by age of 10-13 years.


38

4.1.4c Retained deciduous molars (D, E)

may be retained due to congenitally missing successors.

a] If the prognosis of the tooth is good, keep the tooth. Observe the teeth in case they submerge. b] If the successors are present, the retained D, E will cause the eruption of 4, 5 to be deflected or impacted. (Fig. 4.19) Treatment: extract the deciduous teeth.

Fig. 4.19 Retained E causing deflection of 5

4.1.5 Loss of Permanent teeth Incidence:

6 (first molars) are usually extracted due to caries

1 or 2 (central or lateral incisors)- usually loss due to trauma. Effect: drifting and tilting of adjacent teeth and loss of space. 4.1.5a Loss of 1st Molar (6)

First permanent molars are rarely the first tooth of choice for extraction for orthodontic treatment

Sometimes 6 have to be extracted due to large caries and/or hypoplasia. If 6 have to be extracted the time of extraction is very important, especially for lower arch. i) The best (optimal) timing for extraction of 6 is: (Fig. 4.20)

before 5 & 7 erupt

when the roots at the bifurcation of 7s are forming

about age 9 to 10 years old


39

Effect of extraction of 6 at the optimal time:

7 erupts mesially and 5 erupts distally and there is usually fair contact between 5 & 7.

this will relieve crowding in the premolar & canine region and mild & moderate incisors crowding may improve.

(a) (b)

Fig. 4.20 Before (a) and after timely extraction (b) of upper & lower left 1st molars. Note that the

5s and 7s have good contact spontaneously.

ii) If 6 is removed before the age of 8 years old: Effect:

The unerupted 5 can drift distally and tip from its position below the apices of E.

The lower labial segment can retrocline, resulting in increased overbite

iii) Extraction of 6 at the permanent dentition stage (after 7 has erupted): Effect:

7 will tip forward and rotate mesiolingually

Spacing or poor contact between 5 & 7 causing food impaction

Usually needs fixed appliance to achieve good contact

Treatment planning for the loss of 1st molars

a) In Class I Malocclusion

In minimal incisor or moderate premolar crowding - aim for extraction at the optimal time for good spontaneous eruption of 7, relief of crowding and spontaneous space closure.

In moderate severe crowding (especially in the incisor regions) - either delay extraction until 7s have erupted and use the extraction space for tooth alignment with fixed appliance; or - extract at optimal time for spontaneous space closure and treat the crowding once the permanent dentition is established. However, if premolar extractions (in addition to the extraction of 6s) are likely to be required, 8s should be present and of good morphology.


40

b) In Class II Division 1 Malocclusion

Space will be required to relieve crowding and to reduce overjet. Timing of 6s extraction is important because of the need for overjet reduction.

Extract 6s after 7s have erupted and use the space for overjet reduction with fixed appliances.

Extract 6s at the optimal time and correct sagittal discrepancy early with functional appliance, or with a removal appliance and headgear. Fixed appliance can then be used to detail the occlusion.

c) In Class II division 2 Malocclusion

Requirements are similar to those for a Class 2 division 1, space being required to relieve crowding and correct the incisor relationship.

However, overbite reduction can be difficult if large extraction spaces need to be closed in the mandibular arch and these should be avoided. If lower 6s need to be extracted this should be done at the optimal time to avoid spacing associated with the erupted lower 7s, even if this may result in some worsening of the overbite.

d) In Class III Malooclusion

Extract 6s after 7s have erupted so that space can be used to relieve the crowding in maxillary arch and for incisor retraction in the mandible.

4.1.5b Loss of upper 1, 2 Main reason of loss is due to trauma (usually in Class II div I incisor relationship). Sometimes the incisors have to be extracted due to gross caries.

i) Due to trauma

If the tooth is fractured in a trauma, try to preserve the tooth by filling the tooth and doing root canal treatment, if necessary.

If tooth is avulsed, reimplant the tooth, if possible.

If the tooth has to be extracted, maintain the space with a denture to prevent midline shift (consider bridge or implant at a later stage) or

If case is suitable, do orthodontic treatment by using the space to relieve crowding or reduce an overjet.

ii) Due to Gross Caries

Extract carious teeth and replace tooth with denture, bridge or implant, or

Extract carious teeth and do orthodontic treatment and reshaped the teeth (Fig. 4.21)


41

a) Gross caries on upper central incisors. b) Near completion of orthodontic treatment

c) At the end of treatment. Upper lateral incisors shaped into central incisors and canines into lateral incisors.

Fig. 4.21 Patient with gross carious upper central incisors that were extracted and treated with fixed appliance and reshaping of upper lateral incisors and canines.

4.2 Anomalies in Size and Form of Teeth

4.2.1 Size

4.2.1a Macrodontia (Fig.4.22) - causes crowding 4.2.1b Microdontia (Fig. 4.23) - may causes spacing

Note: Anomalies in size affect the function and esthetics of teeth.

21

Fig. 4.22 Macrodontia of right 1 Fig. 4.23 Microdontia of 2s

21

Photo taken from http://32teethonline.com/pediatric-dentistry-teeth-dental%202.htm

http://32teethonline.com/pediatric-dentistry-teeth-dental%202.htm


42

4.2.2 Form/ Shape 4.2.2a Peg Lateral Incisors (Fig. 4.23)

may cause excessive space at the anterior maxillary segment due to its small size and shape.

Management:

Closed the space between central incisors (if there is spacing) with orthodontic treatment.

Reshaped peg incisor with composite or veneer or porcelain crown

4.2.2b Dilaceration Definition: It is a distortion or bend in the root of a tooth. It usually causes failure in eruption. Aetiology:

a) Developmental (Fig. 4.24):

this usually affects an isolated central incisor & occurs in female more than males.

The crown of the affected tooth is turned upward and labially and no disturbance of enamel and dentine is seen.

b) Trauma (Fig. 4.25):

intrusion of a deciduous incisor leads to displacement of the underlying developing permanent tooth germ.

This causes the developing permanent tooth crown to be deflected palatally, and the enamel & dentine forming at the time of injury are disturbed, giving rise to hypoplasia.

Management:

If dilaceration is severe, remove the tooth.

If dilacerations is mild, it may be treated by exposing the crown surgically and apply traction to align the tooth with orthodontic treatment.

Fig 4.24. Dilaceration of root

22Fig. 4.25 Extracted dilacerated tooth

22

Photo taken from Orthodontics and Paediatric Dentistry by D. millet & R. Welbury


43

4.2.2c Twin teeth

a) Fusion (Fig. 4.26)

less in the number of teeth as two teeth are being replaced by one abnormally formed fused teeth.

may cause spacing.

b) Germination (Fig. 4.27)

normal in the number of teeth but with one tooth being replaced by an abnormally formed one.

may cause crowding

germination of two deciduous teeth is usually followed by absence of a permanent tooth.

Fig. 4.26 Fusion of lower right 3 and 2 Fig. 4.27 Germination of lower lateral incisor 4.2.2d Dens evaginatus

a) Talon cusp (Fig. 4.28)

is prominent additional cusp

commonly found on the palatal surface of permanent incisor, buccal surface of Ds and the palatal surface of Es.

often caused malocclusion and may require removal of the talon cusp and elective root treatment once root is fully formed.

b) Leong’s premolar (Fig. 4.29)

Incidence:

commonly found among Mongoloid origin

more common on mandibular premolars than upper premolars Management:

fracture or wear of the tubercle can lead to death of the tooth and periapical abscess.

Therefore protect the tubercle (horn) with GIC or composite as early as possible as the turbercle is easily facture.

If all other teeth are in good condition, extract this tooth if extraction is needed for orthodontic treatment.


44

Fig. 4.28 Talon cusp

Fig. 4.29 Leong’s premolar Radiograph showing Leong’s premolar

4.3 Anomalies in Position of Teeth

a) Ectopic Position

b) Transposition

c) Impacted 4.3a Ectopic Position Definition: position of tooth away from normal or away from where it should be. Incidence:

often involve the upper permanent canine. Can involve other teeth. (Fig. 4.30)

about 2% of Caucasian population have ectopic 3s (15% buccal; 85% palatal)

Leong’s

premolar

(tubercle)

Tooth

filled up

to protect

tubercle

from

fracture


45

Fig. 4.30 Ectopic eruption of 1

Ectopic Eruption of Upper Canines Aetiology: mutifactorial

long path of eruption (especially for upper canines)

ectopic position of the tooth germ

crowded arch

small or developmentally absent of 2s (42.6%)

Cs resistant to resorption

Polygenic inheritance

palatal impacted 3 (genetic)

buccal displaced 3 (inadequate arch space)

Investigation: If canine not palpable buccally (just distal to the root of lateral incisor around its apical third) at 9-10 years then investigate.

(i) Observe: bulge, inclination & color of adjacent teeth (ii) Palpation: of canine crown, mobility of C and 2 (iii) Radiographs: to establish Presence

Position Pathology

OPG radiograph is useful for initial assessment (Fig. 4.31)

If the 3 cannot be palpated buccally, take two periapical radiographs for horizontal parallax view or an anterior maxillary occlusal view radiograph and OPG for vertical parallax view (Fig. 4.32) to locate the position of the tooth. The clinician can also use Cone Beam Computed Tomography (CBCT) to locate the position of the 3.

Clinical signs of palatally impacted 3:

Delayed eruption of 3 or prolonged retention of C

Absence of normal labial 3 bulge or presence of a palatal bulge in the 3 region

Delayed eruption, distal tipping of 2

Loss of vitality and increased mobility of 2, 1 If 3 is palatally impacted, it may cause resorption of the root of adjacent 2.


46

Fig. 4.31 OPG showing ectopic eruption of lower right canine

Fig. 4.32 Anterior Occlusal View showing palatally impacted canine

Choice of treatment depends on: - patient‟s age - position of canine - whether there is malocclusion or not Management of ectopic upper canine:

a) Just leave it:

if the tooth is deeply embedded, symptom free and no orthodontic treatment movement of adjacent teeth is planned.

if occlusion is acceptable without it

take radiograph 6 monthly to screen for pathological changes (cyst formation or root resorption of 2)


47

b) Extract:

If canine is very displaced

occlusion is acceptable without 3

there is good contact between 2 & 4 (Fig. 4.33)

Fig. 4.33 Buccally displaced 3. 4 & 2 in good contact

c) Orthodontic treatment:

i) Buccal canine

In crowded arch, remove 4 as 3 starts to erupt to allow spontaneous alignment (Fig. 4.34).

If 3 is mesially inclined, may be able to treat with Buccal Canine Retractor on a removable appliance

Fixed appliance is required if 3 is upright or distally inclined.

If eruption of 3 is delayed and the position favourable for alignment, exposed the tooth with an apically repositioned flap; use bonded attachment to facilitate alignment.

Fig. 4.34 4s extracted to allow spontaneous eruption of 3s. Photo taken just

before starting fixed appliance on upper arch.


48

ii) Upper Palatal Canine

a) Remove C: in mixed dentition, if the arch is uncrowded and 3 is mildly displaced. Extraction of C may allow successful eruption of 3.

b) Retain C and review the position of 3 radiographically to ensure no pathological changes or resorption of adjacent teeth.

c) Exposure and traction of 3 with orthodontic treatment. (Fig. 4.35). Indications:

Cooperative patient and good oral hygiene

3 should overlap not more than the mesial aspect of 2 root & not higher than apical third of the root of 2

Root apex of 3 should not be distal to 5 & its long axis to mid-sagittal plane should be ≤ 55°

The arch is spaced or space could be created for 3

23

Fig. 4.35 The prognosis for successful alignment of a palatally impacted 3 is influenced by its position. The red bold arrows show that as the height of 3 crown increases or

the distance towards the dental midline reduces or the angle of 3 to the mid-sagittal plane increases beyond 55°, the prognosis worsen.

d) Removal of 3:

If patient is not keen for orthodontic therapy

2 and 4 are in good contact, or

There is good root length of C & the aesthetics of C are acceptable, or

If the position of 3 is not favourable for orthodontic treatment, surgically remove 3 and retain C (may need to reshape C with composite to mimic 3)

23

Picture taken from Handbook of Orthodontics, by Martyn T. Cobourne and Andrew T. DiBiase


49

e) Autotransplantation:

Indications:

If prognosis for the alignment of 3 is hopeless

There is adequate space in the arch for the 3

There is adequate buccal & palatal bone

The prognosis is improved if 3 root is ⅔ formed (open apex at 13-14 years).

Management:

Surgical removal of 3 should be as atraumatic as possible

The autotransplanted 3 should be kept out of occlusion and semi-rigidly splinted for a maximum duration of 3 weeks.

Once the splint is removed, the 3 should be root canal treated to reduce the risk of subsequent external resorption.

Disadvantages:

The autotransplanted tooth can be susceptible to subsequent ankylosis or external root resorption

Reduced long-term prognosis compared to canines aligned orthodontic traction.

f) No treatment but observe the impacted 3:

3 is deeply impacted and there is no pathological changes, or

When patient is unsure of treatment but may choose to do alignment of 3 later.

Monitor the status of 3 and the incisor roots annually through radiographic examination.

4.3b Transposition (Fig. 4.36) Definition: The change in position of a tooth with an adjacent tooth or erupting into a position normally occupied by a non-adjacent tooth Incidence:

upper 3 transpose with upper 4 (71% - most common)

upper 3 transpose with upper 2 (20%)

lower 3 transpose with lower 2 Aetiology: primary genetic. Treatment:

no treatment if occlusion is acceptable

accept the transposition, extract the most displaced tooth or

align the arch with orthodontic treatment


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Fig. 4.36 a) Transposition of left 3 & 2 b) Transposition of 3s and 4s

4.3c Impacted teeth Definition: Impacted tooth is tooth that is obstructed from erupting. Incidence: 8s (most common), 5s, 6s

i) Impaction of 6s (also known as ectopic eruption of 1st molars)

Around 2-6% of children have impaction of 6s against Es. More commonly occur in upper arch.

Spontaneous disimpaction may occur, but this is rare after 8 years old. Aetiology:

Crowding

Large crown of 6

Eruption path of 6 too mesial

Management:

i) Mild impaction a) Tighten a soft brass separating wire (0.5-0.7 mm) or use a orthodontic metal or elastic

separator around the contact point between 6 & E for about 2 months (Fig. 4. 37) or b) Using a Modified Halterman appliance (Fig. 4.38) or c) Removable appliance with finger spring and bonded button or composite on the

occlusal surface of 6.

ii) In more severe cases, keep the impaction under observation. Extract E if it becomes abscessed or when 6 becomes carious due to poor access.


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24

Fig. 4.37 Brass wire placed. After dis-impaction with brass wire.

25

Fig.4.38 Modified Halterman appliance After 4 months

ii) Impacted third molars Aetiology:

Crowded arch

Etopic position Indication for removal of impacted 3rd molars:

Recurrent pericoronitis

Caries

Root resorption of 2nd molar

Cysts, tumors

Destruction of adjacent teeth and bone If 2nd molars need to be extracted (e.g. due to gross caries), 3rd molars may erupt into good or acceptable position if:

Extraction of 2nd molars took place at full crown formation of 3rd molars

Inclination of 3rd molar < 30° to long axis of 1st molar

24

Photos taken from www.aapd.org/upload/articles/Kupietzky-22-05.pdf 25

Photos taken from www.aapd.org/upload/articles/327-9.pdf

http://www.aapd.org/upload/articles/Kupietzky-22-05.pdf

http://www.aapd.org/upload/articles/327-9.pdf


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4.4 Habits 4.4.1 Habitual Finger or Thumb Sucking (Fig. 4.39)

Finger sucking is normal in babies and children. There is no need to stop them at this stage. If sucking is continued until mixed dentition period, malocclusion will occur. The severity of the malocclusion will depend on:

Positioning of the finger(s) or thumb

Frequency and intensity of the sucking

Duration of the habit Effects:

Limited to the tooth and alveolar process.

When this habit is stopped at the right age the dento-alveolar segment will grow to its normal position in the right occlusion.

Malocclusion caused by finger/ thumb sucking: (Fig.4.40)

21/12 proclined and 21/12 retroclined

decreased overbite or incomplete overbite

upper arch narrowed, unilateral crossbite in posterior segment*.

if the overbite is incomplete, there is a tendency of tongue thrust. *(This occurs due to the negative intra-oral pressure developed by the sucking, together with a lower tongue position and increased buccinators activity)

26Fig.4.39 Thumb sucking Fig. 4.40 Effects of thumb sucking

If the child stops thumb sucking before 7 years, the malocclusion will usually resolve spontaneously.

26

Photo taken from http://www.freeprintablebehaviorcharts.com/thumbsucking.htm

http://www.freeprintablebehaviorcharts.com/thumbsucking.htm


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Management: The child should be gently persuaded to stop the habit before 6 years old. There are two treatment options:

1. Behavior modification, including reward therapy

2. Behavior modification + appliance therapy 1. Behavior therapy, including reminder and reward therapy

find out which finger/thumb that the child sucks and why he sucks. If the child is sucking due to anxiety or distress, address the cause(s).

the patient should be shown models and photographs demonstrating the detrimental effects of thumb-sucking.

ask questions such as whether the child would suck his thumb in the midst of his friends? When is he going to stop sucking his thumb permanently? Tell the child, “You are not going to suck your thumb for the rest of your life so why don‟t you stop today?”

Should the child wish to stop sucking his thumb, then proceed with the treatment. There are various methods of treatment should the child desire to stop the habit.

i) An adhesive bandage may be taped to the offending finger as a reminder.

ii) Use a reward chart as an incentive to help him stop sucking. Praise the child whenever he stops sucking his thumb.

iii) Use a clean sock to cover the child‟s hand during the night iv) Tying or pining a child‟s hand onto his pajamas. v) Use a thumb/ digit guard (Fig. 4.41)

vi) Place bad tasting compounds on the offending thumb.

27

Fig 4.41 Patient wearing a Thumb guard

27

Photo taken from http://www.thingamababy.com/baby/2005/12/antithumb_sucki.html

http://www.thingamababy.com/baby/2005/12/antithumb_sucki.html


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2. Behavior modification + appliance therapy

Use either fixed appliance (Fig. 4.42) or a „goalpost‟ Removable appliance. This appliance should be left in the mouth for 6 months.

28Fig. 4.42 A Fixed appliance used to deter thumb sucking and to expand constricted maxillary arch

4.4.2 Tongue thrusting (Fig. 4.43)

The swallowing pattern of an infant is with the jaws separated and the tongue protruded.

The normal swallowing behavior in an adult is with the teeth together, the tongue contained within the dental arches and little or no contraction of the circumoral musculature.

Nearly all young children exhibit a swallowing pattern involving tongue protrusion, but by the age of six most have switched to a normal swallowing pattern.

Types:

Adaptive tongue thrust (typical) – when there is open bite or increased overjet due to skeletal discrepancy or thumb sucking habit and incompetent lip, the tongue will protrude forward to form an anterior oral seal during swallowing.

Endogenous tongue thrust (atypical) Fig. 4.44 –it is an inborn atypical pattern of neuromuscular activity of infantile swallowing pattern that has been retained by an individual. The tongue pushes actively during swallowing. This is an involuntary, subconscious habit that is difficult to correct.

Effects:

Reduction of overbite or anterior openbite

Anterior teeth may be spaced out

Increased overjet

28

Photo taken from

http://www.zimbio.com/member/dentoclub/articles/4gZZa7xuDzS/Single+Appliance+Correction+Digit+sucking

http://www.zimbio.com/member/dentoclub/articles/4gZZa7xuDzS/Single+Appliance+Correction+Digit+sucking


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29

Fig. 4.43 Tongue thrust Fig. 4.44 Openbite and incisors spacing due to endogenous tongue thrust

Treatment:

For adaptive tongue thrust: treat malocclusion with orthodontics. Tongue function usually improves after orthodontic treatment

For endogenous tongue thrust: patient may need to have myofunctional therapy to train the tongue and have fixed retention after orthodontic treatment.

Give patient a tongue habit appliance to wear (Fig. 4.45)

In a young child, wearing a myofunctional appliance (e.g. Trainer) might help to train the tongue and help to reduce or eliminate the malocclusion.

30Fig. 4.45 Blue Grass Roller Tongue habit appliance

4.5 Others

4.5.1 Abnormally large upper labial fraenum

In infants the upper labial fraenum starts from the inner surface of the upper lip across the alveolar process and ends at the incisive foramen on the palate.

As the deciduous incisors erupt, this continuity is lost and the fraenum becomes attached to the labial surface of the alveolar process.

Occasionally, the fraenum persists and this may be associated with a median diastema.

An abnormally thick and fleshy fraenum can cause median diastema

29

Photo taken from http://www.bracesquestions.com/considering-braces/straight-teeth/adult-orthodontic-

problems/ 30

Photos taken from http://parortholab.com/habit.aspx

http://www.bracesquestions.com/considering-braces/straight-teeth/adult-orthodontic-problems/

http://www.bracesquestions.com/considering-braces/straight-teeth/adult-orthodontic-problems/

http://parortholab.com/habit.aspx


56

Management: If the fraenum is associated with median diastema:

The palatine papilla will blanch if the lip is pulled forward (Fig. 4.46)

There will be notching between 1 1 in a periapical radiograph (Fig. 4.47)

Take an anterior occlusal radiograph to exclude other causes of diastema mentioned below.

Treatment of abnormal fraenum:

Generally, wait for 3 3 to erupt, the median diastema (ugly duckling stage) may close on its own.

If the median diastema is caused by abnormal labial faenum, frenectomy is indicated followed by appliance to close the space. Place a bonded fixed retainer.

Fig. 4.46 Abnormally large and fibrous upper anterior labial fraenum causing diastema.

The incisive papilla blanches when the upper lip is pulled up.

Fig. 4.47 Radiograph showing a V-notch of the interdental bone between central incisors


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Median diastema is rarely caused by labial fraenum, more often it is caused by other factors like:

a) physiological spacing during the ugly duckling stage

b) congenitally missing 2/2

c) 2/2 peg shaped and small in size

d) proclined incisors

e) mesiodens

f) general spacing in the arch

g) median cyst (seldom)

4.5.2 Trauma

Trauma on the deciduous incisors may cause deformity in the permanent incisors or dilaceration. This causes esthetic problems and abnormal eruption to the permanent teeth.

4.5.3 Pathology

Cysts, tumors and odontomes may interfere with the eruption of teeth or cause displacement of teeth

4.5.4 Bad Restoration

Improper dental restoration:

under-contoured restoration (too little contact) of deciduous teeth can cause migration of teeth, resulting in crowding of the permanent dentition.

over-contoured restoration, e.g. on the distal of E may cause 6 to be impacted.


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Chapter 5 INTERCEPTIVE ORTHODONTICS

5.1 Definition Interceptive orthodontics is an orthodontic procedure that eliminates or lessens the severity of a developing malocclusion.

5.2 Need Developing problems in deciduous or mixed dentition could be fully corrected with

relatively simple interceptive treatment in 15% of orthodontic cases.

5.3 Objective To reduce the severity of malocclusion, therefore may reduce further treatment

time/duration or make future orthodontic treatment simpler.

To encourage the eruption of the teeth to the normal position.

To prevent trauma (eg. in patients with severe overjet or traumatic bite)

5.4 Routine screening During clinical examination, monitor developing dentition and look for abnormalities

Take radiograph- only if clinically justified

5.5 Timing for Interceptive Orthodontic Treatment

1. During deciduous dentition

usually no treatment required except for posterior crossbites with displacement.

2. During mixed dentition

elimination of local factors e.g. supernumeraries, habits

where there is direct trauma to soft tissue

crossbites with displacement – anterior and posterior

skeletal Class II discrepancy with retrognathic mandible.

(Note: Many of the condition and treatment mentioned under chapter 4, “Local Factors of Orthodontics” comes under Interceptive Orthodontics topic too.)


59

5.6 Some examples of Interceptive orthodontics

5.6.1 Crossbites 5.6.1a Anterior crossbites These anomalies are best treated at an early stage because

the upper incisor and lower incisors may undergo wear (abrasion) due to traumatic bite.

the periodontal support of the incisors may suffer as a result of occlusal trauma

it may cause the patient to develop into a Class III malocclusion. Treatment: 1. Extract any retained A or B when the successive permanent incisor is erupting. 2. If the permanent incisors are still erupting, the overbite is still shallow and there is only

one incisor in lingual occlusion, the tooth may be moved by using a tongue spatula /ice-cream stick. The tongue spatula is placed vertically and the child should bite on it 3 to 4 periods of 15 minutes each day. (Fig. 5.2)

3. If the overbite is more established or more than one incisor is involved , a] use an upper removable appliance with Z-spring in 0.5 mm wire or screw, incorporating the posterior bite plane. (Fig. 5.3, 5.4, 5.6) b] use the lower inclined plane, if there are a lot of missing upper posterior teeth which makes it difficult to make an removable appliance. Don‟t wear more than 2 months.

(Fig. 5.5)

Indications:

1. Class I or mild Class III skeletal discrepancy. If the patient can bite the incisor teeth at edge to edge in centric relation (pseudo-Class III) [Fig. 5.1], the prognosis of treatment is good.

2. The overbite at the end of treatment should be sufficient to maintain the corrected incisor relationship

Fig. 5.1 Edge to edge at Centric Relation Patient occluding at Centric Occlusion


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Fig. 5.2 Using of an ice-cream stick to prop Fig. 5.3 Removal Appliance with Z-spring the upper incisor across the bite. and Posterior Biteplane (palatal view)

Fig. 5.4 Removable appliance with screw Fig. 5.5 Lower inclined plane cemented to procline the incisors. To correct crossbite on 2

a. b. Fig. 5.6 Patient before (a) and after 4 months of treatment (b) with removable appliance


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5.6.1b Posterior crossbite If there is lateral deviation of the mandible with unilateral posterior crossbite in a young child, it should be treated. Treatment:

Early treatment is recommended. It can help in the development of normal occlusion.

Grind off occlusal interference.

Use appliance such as:

1. Removable appliance with screw (Fig. 5.7); or with T- spring if only one tooth is involved, or

2. Fixed appliance with quadhelix: for molar & premolar crossbites (Fig. 5.8)

Fig. 5.7 Removable appliance with Fig. 5.8 Quadhelix expansion screw.

5.6.2. Increased Overjet (Fig. 5.9)

Early treatment is indicated when:

there is moderate/severe overjet- increase risk of trauma to upper incisors.

there is presence of tooth fracture (indicates patient has a past history of a fall or accident).

there is trauma at the palatal mucosa by the lower incisors. Types of treatment: i ] Functional appliance (Fig. 5.10) - it is useful in reducing an overjet during the mixed dentition. - it is suitable for Class II division 1 on a mild to moderate Class II skeletal with

retrognathic mandible. - the upper and lower arches are in good alignment or at least not crowded ii] Appliance with extra-oral traction (Fig. 5.11) iii] Removable appliance (Fig. 5.12) iv] Fixed appliance


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Fig. 5.9 Patient with large overjet Fig. 5.10 Twin Block appliance

before treatment.

Patient after Functional appliance before fixed appliance treatment

Fig. 5.11 A high angle patient wearing a high-pull headgear with functional appliance.

a. b. Fig. 5.12 Patient with mild overjet and spacing on upper arch treated with removable appliance.

(a) Before treatment (b) After treatment


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5.6.3. The treatment of crowding

Crowding of the teeth is caused by a faulty relationship between the jaw size, arch perimeter and tooth size. Chronologically, crowding may become manifested at

7 years of age on eruption of the incisors

10 to 12 years on eruption of the canines, premolars and second molars 5.6.3.1 Types of treatment: a] extraction with / without appliances b] disking of deciduous teeth 5.6.3.1a Extraction with/ without appliances Before any extraction procedures, check the: a] tooth prognosis b] area of crowding c] tooth alignment - rotation, tipping etc d] permanent teeth that are present e] space needed for alignment f] choices of appliances Types of extractions:

1. Timely extraction

2. Serial extraction

3. Extraction of deciduous canines

4. Extraction of first permanent molars

1. Timely extraction

Definition: Extraction of teeth done in order to

a) relief crowding temporarily or

b) to eliminate the source of deflection / interference of eruption. Example: i) extraction of supernumerary tooth that prevents the permanent tooth from erupting.

ii) extraction of retained deciduous teeth for the succeeding permanent teeth to erupt into alignment.


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2. Serial Extraction

It was first advocated in 1948 as a solution to a shortage of orthodontists.

It involves the timed extraction of deciduous, and ultimately, permanent teeth to relieve severe crowding.

Indications

Patient age 8-9 years and the incisors substantially crowded.

Skeletal Class I arch relationship.

Overbite normal or reduced.

All permanent teeth are present in good positions.

The first permanent molars have a good prognosis.

The first premolars should be more close to eruption than the canines.

Class I molar relationship.

Large arch perimeter deficiency (10mm or more) - severe crowding Contraindications

Skeletal Class II or skeletal III jaw relationships

Face is unduly long or short (where a tight lower lip would retrocline lower incisors)

Facial profile is substantially concave The procedure consists of three steps:

a) Extraction of Cs as the permanent laterals are erupting in a crowded positions b) Extraction of Ds when its roots are ½ resorbed, to promote early eruption of 1st

premolars (usually 6 to 12 months before Ds normal exfoliation, at the point when the underlying premolars have ½ to ⅔ of their roots formed)

c) Extraction of the permanent first premolars before eruption of the permanent canines Most of these patients still need some appliance therapy which will be shorter duration and simpler than if crowding had been allowed to develop before orthodontic intervention.

Disadvantages

It involves putting the child through several sequences of extractions

3. Extractions of deciduous canines Timely extractions of Cs may avoid more complicated treatment in the future. Indications:

Lateral incisors erupting into a crowded upper arch in Class I malocclusion.

In a crowded lower labial segment one incisor may be pushed through the labial plate of bone, resulting in a compromised labial periodontal attachment.

Extraction of lower Cs in Class III malocclusion can be advantages as it allows lower incisors to move/tip lingually.

To provide space for appliance therapy in the upper arch, e.g. correction of an instanding lateral incisors

To improve the position of a displaced permanent canine.


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4. Extractions of first permanent molars First permanent molar extraction is done when the prognosis of the teeth is poor. Indications for elective extraction of all 4 permanent 1st molars: 1. The child should be aged 9-10 years (lower second molar bifurcation beginning to form,

angle between long axis of 6 & crypts of 7 is 15-30°) 2. Class I malocclusion. 3. Mild or moderate crowding 4. The overbite is normal or reduced. 5. All the permanent teeth should be present. 6. The 1st permanent molars are carious. 7. The unerupted lower second premolar should not be distally inclined or spaced from the

first premolar or outside the control of the E roots. Note:

If the first permanent molar is removed too early (before 8 years old), there is a tendency for the second premolar to erupt distally and become impacted against the second molar.

Extraction of upper 6s should be delayed until the 7s erupt when it is intended that the extraction space be used to treat an increased overjet or crowded upper incisors.

If a lower 6 must be extracted, the opposing 6 should be extracted (compensatory extraction) in mildly crowded Class I cases. This is to prevent over-eruption of upper 6 following extraction of lower 6. Over-eruption of upper 6 can lead to premature contacts and impaired closure of lower extraction space.

If an upper 6 must be extracted, no need to do compensatory extraction of lower 6 as less tendency for lower 6 to over-erupt in a Class 1 malocclusion.

5.6.3.1b Disking of deciduous teeth Disking of deciduous teeth is indicated when there is mild crowding /impaction

Example: disking of C to align the irregular permanent incisors

5.7 Screening at 9 years old Do further investigation if any of these clinical findings are found:

Delayed eruption in comparison with contralateral side or abnormal sequence.

Crowding – overlapping teeth or lateral incisors almost in contact with Ds.

Overjet ≥ 4 mm.

Crossbites

Submerged deciduous molars

Caries of 1st molars

Early loss of Cs or deciduous molars

Deep overbite or open bite Note: Palpate for unerupted 3s, when patient is 9-10 years old. If you cannot palpate the 3s, do a radiographic investigation. Take parallax radiographs to check the position of the impacted 3s.


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5.831 THE DOs and DON’Ts OF INTERCEPTIVE ORTHODONTICS

Do Age Don’t Encourage general & local caries prevention

Birth- 2 yrs

Worry about seemingly abnormal relationships of gum pads

Encourage caries prevention 3-6 yrs Worry about spaced incisors or primate spacings

Look for the early signs of malocclusion Worry about distal surfaces of Es in vertical line Expect crowded permanent incisors if no

spaces exist

Discourage habits.

Treat abnormal closure path or displacement

Encourage caries prevention 7-9 yrs Worry about “ugly duckling” stage.

Investigate delayed eruption Worry about slight anterior open bite.

Refer Skeletal Class III to orthodontist

Observe or use Leeway space in minimal crowding

If crowding is greater, consider serial extraction or extraction of 6s if carious/ poor prognosis

Maintain space if appropriate

Extract retained deciduous & supernumerary teeth that cause malocclusion

Strongly discourage habits

Observe or treat impacted upper 6s

Consider extraction of transposed teeth.

Treat incisors in anterior crossbites

Treat pathology early

Palpate canines starting from 9 years old extract upper Cs when 3s are ectopically placed.

Watch for crowding & consider extraction of 4s or 7s

11-12 yrs Worry about buccal segment crowding if deciduous canine & molars are still present

Extract deciduous teeth deflecting permanent successors

Worry about rotated premolars when they first erupt

Excise very large fraena where there is an upper midline diastema

Worry about minor submergence of deciduous molars

Strongly discourage habits.

Extract upper Cs when 3s are ectopically placed

Treat incisors in lingual occlusion urgently

Consider Functional appliance for Skeletal Class II

31

Adopted from Interceptive Orthodontics by Andrew Richardson


67

Chapter 6. CRANIOFACIAL GROWTH

6.1 Introduction Definition:

i) Growth is an increase in size by natural development as a result of cellular

proliferation and differentiation.

ii) Growth site is the location at which growth occurs.

iii) Growth centre is the location at which independent, or genetically controlled

growth, occurs.

Growth can affect the severity of the malocclusion (improving or worsening it as

growth continues), the progress and outcome of orthodontic treatment, and the

stability of the orthodontic result.

Orthodontic treatment may also have an effect on facial growth - e.g. functional

appliance and headgear.

Growth is initiated mainly by growth hormone (somatotrophin hormone) released from

the pituitary gland.

6.2 The extent and timing of growth The extent and timing of growth is controlled by 2 main factors:

A) Genetic control

Homeobox genes provide the genetic “blue print” for growth and development

Gives rise to family resemblances – a disturbance of these genes can cause

chromosome defects such as Trisomy 21 (Down‟s syndrome)

B) Environmental factors

Psychological stress in emotionally deprived children inhibits the release of

growth hormone. Therefore retarding the growth of those children.

Moss’s Functional Matrix theory states that “growth of the face occurs as a

response to functional needs and is mediated by the soft tissue in which the

jaws are embedded”. Example, the orbit growth is a result of eye growth and

brain growth causes increase in the cranium size.

6.3 Mechanism of bone growth

The process by which new mineralized bone is formed is termed ossification.

Ossification can occur: a) by membrane activity (Intramembranous ossification) or

b) by bony replacement of a cartilaginous model (Endochondral ossification).


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6.3.a Intramembranous Ossification (Fig. 6.1, 6.2)

During the embryonic development the mesenchymal cells transform directly into

osteoblasts. Bone is formed directly by secretion of bone matrix by osteoblasts within

connective tissue. Intramembranous ossification occurs in sheet-like osteogenic

membranes.

Intramembranous ossification occurs in the bones of the calvaria, the facial bones and

the mandible.

Intramembranous bones grow as a result of periosteal remodeling.

6.3.b Endochondral ossification (Fig. 6.1, 6.2)

It the process by which the general bone shape is laid down first by a cartilage

scaffold followed by progressive replacement of bone.

Occurs in the bones of the cranial base.

Endochrondral bone growth occurs through cartilaginous replacement. The cartilage is

transformed into bone.

Growth centre at synchondroses:

spheno-occipital synchondrosis, fronto-ethmodial synchondrosis & spheno-ethmoidal synchondrosis

32

Fig. 6.1 Medial view of intramembranous ossification (red color), endochrondral ossification (dark blue color)

32

Photo taken from http://embryology.med.unsw.edu.au/wwwhuman/Hum12wk/Hum12wk.htm

http://embryology.med.unsw.edu.au/wwwhuman/Hum12wk/Hum12wk.htm


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33 Fig. 6.2 Types of ossification of the skull & face.

6.4 Growth of face and skull

Overall, bone grows through remodeling (resorption and deposition of new bone) and displacement/transposition.

a) Skull

The skull develops from a combination of endochrondral and intramembranous

ossification.

i) Cranial vault

The bone of the cranial vault develop in the membranes covering the brain in the

embryo through intramembranous ossification

Centre of ossifications appear and the bones expand so that by birth they are

related to one another at sutures, although some areas- the fontanelles, still have

a membranous covering (Fig. 6.3).

Growth consists of a combination of displacement due to the expanding brain and

osteogenesis at sutural margins, and remodeling to increase thickness and

change shape.

ii) Cranial base

The cranial base comprises of the bones that develop from cartilaginous

chondrocranium (endochondral ossification) of the embryo.

At birth, cartilage remains at sites where growth can occur: the synchondroses.

The spheno-ethmoidal and spheno-occipital synchondroses are responsible for

growth in length of the cranial base (Fig. 6.4).

Spheno-ethmoidal synchondroses fuse at about 6-7 years old. Therefore, after the

age of 7 years, the anterior cranial base may be used as a stable reference

structure upon which sequential lateral skull radiographs may be superimposed to

analyze changes in facial form due to growth and orthodontic treatment.

33

Picture taken from The Johns Hopkins Hospital Central for Craniofacial Development & Disorder website


70

Growth of spheno-occipital synchondroses increases the length of the cranial base

(continues till age 20 years), thus has an influence on how the mandible and

maxilla relate to each other.

The length of the cranial base has an influence on jaw relationships due to the

upper facial skeleton (maxillary complex) is related to the anterior cranial fossa,

while the mandible is related to the middle cranial fossa (Fig. 6.5). The spheno-

occipital synchodrosis is anterior to temporo-mandibular joints, but posterior to

anterior cranial base.

Class II skeletal facial pattern is often associated with the presence of a long

cranial base which causes the mandible to be set back relative to the maxilla.

The overall shape of the cranial base also affects the jaw relationship. A smaller

cranial base angle tends to cause a Class II skeletal pattern, while a larger cranial

base angle is more likely to be associated with a Class II skeletal pattern (Fig. 6.6).

Growth of cranial base is not influence by orthodontic means and is probably

under fairly tight genetic control.

34Fig. 6.3 Cranial vault: sutures & fontanelles

35

Fig. 6.4 Synchondroses of the cranial base

34

Picture taken from Contemporary Orthodontics by W. Proffitt 35

Picture taken from Contemporary Orthodontics by W. Proffitt


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36

Fig. 6.5 Anteroposterior growth at the spheno-occipital synchondrosis affects the anteroposterior relationship of the maxilla and mandible.

37Fig 6.6. View (i) Low cranial base angle associated with Class III skeletal pattern.

View (ii) Large cranial base angle associated with a Class II skeletal pattern

36

Picture taken from An Introduction to Orthodontics by Laura Mitchell 37

Picture taken from An Introduction to Orthodontics by Laura Mitchell


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b) Naso-maxillary complex

The maxilla is derived from the 1st pharyngeal arch and ossification of the maxillary

complex is intramembranous except for the nasal cartilage.

Growth occurs by apposition at circum-maxillary sutures with extensive surface

apposition and remodeling of bone, and alveolar development to allow eruption of

teeth

Primary growth-promoting forces in the naso-maxillary complex are the growth of

the nasal septum and of the eyeballs.

The maxilla grows downwards and forwards from the anterior cranial base (Fig

6.7).

Heavy forces applied to maxillary teeth by orthodontic appliances can, according

to the direction of traction, reduce or accelerate growth at the maxillary sutures.

For example, reverse headgear can be used to protract the maxilla.

38

Fig. 6.7 Forward and downward displacement of maxillary complex associated with deposition of bone at the sutures.

c) Mandible

The mandible is derived from the 1st pharyngeal arch and ossifies

intramembranously.

It ossifies laterally to the Meckel‟s cartilage. Ossification extends forwards,

backwards and upwards to form the body, alveolar processes and ramus (Fig.

6.8).

Growth occurs by apposition at sutures and remodeling due to the „functional

matrices‟ of attached muscles (respiratory, eating and head posture)

Increase in ramus height by condylar growth

Increase in body height due to alveolar development to allow eruption of teeth

The mandible is translated downward and forwards from its articulation with the

middle cranial fossa (Fig. 6.9)

Mandibular growth slows to adult levels later than maxillary growth. It ceases to

grow at about 17 years in girls and 19 years in boys, although it may continue for

longer.

38



73

39

Fig. 6.8 Bone formation begins just lateral to Meckel’s cartilage and spreads posteriorly along it without any direct replacement of the cartilage by the newly forming bone of the mandible.

40

Fig 6.9 Growth of mandible

6.5 Growth pattern Different tissues have different growth patterns (curves) in terms of rate and

timing.

Neural and somatic (general) growth patterns are the most relevant to craniofacial

growth.

6.5.1 Neural growth is determined by growth of the brain, with the calvarium following this

pattern.

39

Picture taken from Contemporary Orthtodontics by W. Proffit 40

Picture taken from Contemporary Orthtodontics by W. Proffit

B


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6.5.2 Somatic (general) growth is that which is followed by most structures, like long bones and is the pattern followed by increase in body height.

The pubertal growth spurt is a time of very rapid growth.

Pubertal growth spurt occur at about 12 ± 2 years in girls and 14 ± 2 years in boys.

The maxilla and mandible follow a pattern of growth that is intermediate between

neural and somatic (general) growth.

The mandiblular growth follows the somatic (general) curve more closely than the

maxilla, which has a more neural growth pattern (Fig. 6.10)

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Fig. 6.10 Postnatal growth patterns of neural, somatic (general), maxilla and mandible shown as percentages of total increase.

Table 6.1 Age of decline of growth to adult levels Dimension Female Male

Transverse (intercanine width)

12 years (maxilla) 9 years (mandible)

12 years (maxilla) 9 years (mandible)

Anteroposterior 2-3 years after the first menstruation 14-15 years (maxilla) 16-17 years (mandible)

4 years after sexual maturity 17 years (maxilla) 19 years (mandible)

Vertical 17-18 years Early 20‟s

41

Graph taken from Contemporary Orthodontics by W. Proffit


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6.6 Growth rotation (Fig. 6.11)42

Growth rotation in the mandible can affect (i) the vertical dimension, (ii)

anteroposterior relationship of the jaws and cause (iii) crowding of lower incisors.

A marked forward growth rotation tends to result in reduced anterior vertical facial

proportions and increased overbite. The more severe the forward rotation the more

difficult it will be to reduce the overbite.

A more backward rotation will tend to produce increased anterior vertical facial

proportions and a reduced overbite or anterior open bite.

Class II malocclusion will be helped with a forward growth rotation but made more

difficult by a backward rotation

A forward growth rotation tends to cause retroclination of the lower labial segment

which is often associated with shortening of the dental arch anteriorly and

crowding of the lower incisors.

42

Photo taken from lecture given by Prof. Kelvin Foong of National University of Singapore.

Fig. 6.11 Backward growth rotation and (b) Forward growth rotation of mandible

(a) (b)


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6.7 Relevance of growth to orthodontic treatment

Orthodontic treatment is usually quicker if growth is present.

Growth helps to facilitate:

i. overbite reduction ii. distal movement of posterior teeth iii. space closure iv. functional appliance treatment vi. use of Rapid Maxillary Expansion

Residual growth in corrected skeletal discrepancy cases may result in relapse of

overjet & overbite. May need retention with Functional Appliance during growth

period.

Functional appliance for skeletal Class II is best used during pubertal growth spurt

Extraction-only treatment should be timed with a period of maximal growth

(pubertal growth spurt) in order to obtain maximum spontaneous space closure

Direction of growth rotation influences the development & treatment of a

malocclusion

Mandibular growth continues after maxillary growth- orthodontic treatment for

moderate or severe Class III cases should be delayed until the pubertal growth

spurt has ceased.

Bone can be induced to grow at surgically-created sites by distraction

osteogenesis method


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Chapter 7 CEPHALOMETRIC ANALYSIS

7.1 Definition Evaluation and interpretation of both lateral and posteroanterior (PA) radiographs of the head (mainly use for lateral cephalometric radiograph)

7.2 Objective of cephalometric analysis to compare the patient to normal population standards appropriate for his/her racial

group

to identify any differences between patient and normal population

7.3 Indications when anteroposterior and/or vertical skeletal discrepancies are present and/or

when anteroposterior incisor movement is planned

7.4 Uses of cephalometric radiograph i) To aid diagnosis: to assess the dental and skeletal characteristics of a malocclusion.

Cephalometric analysis is helpful in assessing the probable aetiology of a malocclusion and in planning treatment.

It allows assessment of:

a) Skeletal pattern

anterior-posterior relationship

vertical relationship

b) Dental base length

c) Soft tissue profile

d) Incisors positions and angulations

e) Detection of unerupted displaced teeth and other pathology

In small proportion of patients it may be helpful to monitor growth to aid planning and timing of treatment by taking serial cephalometric radiographs over time

ii) As a pre-treatment record

It is useful in providing a baseline record prior to the placement of appliances, particularly where movement of upper and lower incisors is planned.

iii) To monitor treatment progress during fixed or functional appliance treatments.

Lateral cephalometric is taken during treatment to monitor the incisor inclinations and anchorage requirements.

It is useful in monitoring the movement and position of unerupted teeth

It provides an accurate view for assessing upper incisor root resorption if this is felt to be a significant risk during treatment*.

*Upper incisor root resorption can now be assessed more accurately by using Cone Beam Computed Tomography (CBCT) radiograph.


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iv) To assess treatment and growth changes by superimposing radiographs or tracings on stable areas:

Anterior Cranial base

Anterior vault of the palate

Bjork‟s structures in the mandible v) Research purposes

In the past, information of growth and development was obtained by longitudinal studies which involved taking serial cephalometric radiographs from birth to late teens or beyond.

The effect of growth and treatment can be assessed by comparing pre-treatment, during and post-treatment records.

7.5 Landmarks of lateral cephalometric (Fig. 7.1)

1) Sella point (S) - The midpoint of the sella turcica

2) Nasion (N) - The anterior point of the frontonasal suture

3) „A‟ point (A) - The deepest point on the maxillary profile between the anterior nasal spine and the alveolar crest

4) „B‟ Point (B) - The deepest point on the concavity of the mandibular profile between the point of the chin and the alveolar crest.

5) Anterior nasal spine (ANS) - Tip of the bony anterior nasal spine of the maxilla

6) Posterior nasal spine (PNS) – Tip of the posterior nasal spine of the maxilla

7) Gonion (Go) - The most posterior, inferior point on the angle of the mandible

8) Menton (Me) - The lowermost point on the mandible symphysis 9) Porion (Po) - The highest point on the bony external acoustic meatus 10) Orbitale (Or) - The most inferior point on the margin of the orbit 11) Pogonion (Pog) - The most anterior point of the bony chin


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7.6 Reference planes and line (Fig. 7.1) Maxillary plane (Mx) - Represented by a line drawn through ANS and

PNS. This indicates the orientation of the palate.

Mandibular plane (Mn) - Represented by a line drawn from Me and Go This indicate the orientation of the body of mandible.

Sella-Nasion plane (S-N) – Represents the antero-posterior extent of the anterior cranial base

Frankfort Horizontal plane - Represented by a line connecting the Po - Or

Functional Occlusal plane (FOP) - Represented by the line following the occlusion of the molar and premolar teeth.

Upper face height (UFH) - Line that is perpendicular to the Mx from the N

Lower face height (LFH) - Line that is perpendicular to the Mx from Me

7.7 Cephalometric Value for selected Groups Caucasian **Chinese

SKELETAL

1 SNA 81 ± 3 83 ± 3

2 SNB 78 ± 3 80 ± 3

3 ANB 3 ± 2 3 ± 2

4 Max./Mand. Plane (MMPA) 27º ± 4 26° ± 5

5 LFH/TFH % (Facial proportion) 55 ± 2 50 - 55

6 Maxillary protrusion***

(mm from point A to Nasion perpendicular-Frankfort plane)

1 mm behind the vertical line

1 mm behind the vertical line

7 Mandibular protrusion***

(mm from Pogonion to Nasion perpendicular-Frankfort plane)

2 - 4 mm behind vertical line

5 - 7 mm behind vertical line

DENTAL

8 UI - SN 111° ± 7

9 UI/ Max. plane 109 ± 6 118 ± 6

10 LI/ Mand. plane * 93* ± 6 97 ± 7

11 UI/ LI 135° ± 10 118° ± 9

12 LI – APog (mm) 1 ± 2 5 ± 2

SOFT TISSUE

13 Lower lip – E line (mm) -2+ 2 4 ± 2

14 Upper lip – E line (mm) 3 ± 2

15 Nasolabial angle 95 ± 3


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Note:

* Corrected LI/ Mand. plane =120º - MMPA

Caucasian norm (Eastman Standard)

** Chinese norm (Cooke and Wei 1988) - this cephalometric value can be used for Cambodians until there is research done for Cambodian norms because many of the patients seen at the Orthodontic Department at the Faculty of Odontostomatology are of mixed Khmer- Chinese origin.

***McNamara analysis (John Wu, Urban Hägg and A. Bakr M. Rabie 2007)

43Fig. 7.1 Commonly used cephalometric points and planes

7.8 Interpretation of Cephlometric analysis

7.8.1 Antero-posterior skeletal pattern

a) Angle ANB (Fig. 7.2)

ANB Skeletal pattern

2 - 4 Class I

greater than 4 Class II

less than 2 Class III Mill‟s Eastman correction

If SNA < or > 81º and SN/Max. plane is within 5º to 11º, correct ANB as follows:

For every ºSNA > 81º, subtract 0.5º from ANB value

For every ºSNA < 81º, add 0.5º to ANB value

Note: If the SN/Max. plane is not within 5º -11º range, this correction is not applicable

43



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44Fig. 7.2 Assessment of skeletal pattern using angles SNA, SNB and ANB

b) Maxillary protrusion and Mandibular protrusion using McNamara analysis (Fig. 7.3)

Fig. 7.3 Assessment of skeletal pattern using McNamara analysis ( )

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Picture taken from Contemporary Orthodontics by William Proffit


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7.8.2 Vertical skeletal pattern The commonly used ways of assessing vertical skeletal pattern are:

The Maxillary-Mandibular Planes Angle (MMPA) [Fig. 7.4]

The Facial Proportion/ percentage of Lower face height (Fig. 7.5)

45Fig. 7.4 Assessment of vertical skeletal pattern using MMPA

46Fig. 7.5 Assessment of facial proportion

Facial proportion= A x 100%

A+ B

45

Picture adapted from An Introduction to Orthodontics by Laura Mitchell 46

Picture adapted from An Introduction to Orthodontics by Laura Mitchell

A

B

MMPA


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7.8.3 Incisor position (Fig. 7.6)

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Fig. 7.6 Dental analysis

There is a relationship between MMPA and the lower incisor angle. As the MMPA increases, the lower incisors become more retroclined and vice-versa.

An alternative way of deriving the „average‟ lower incisor angulation for an individual (Caucasian) is to subtract MMPA from 120°.

Lower incisor angle = 120°- MMPA

7.8.4 Soft tissue analysis (Fig. 7.7)

This is particularly important in diagnosing and planning for orthognathic surgery

The commonly used analysis is Rickett‟s E-plane. This line joins the soft tissue chin and the tip of the nose.

In a balanced face the lower lip would lie 2mm (± 2mm) anterior to the Rickett‟s E-line with the upper lip positioned a little further posteriorly to this line.

47

Picture adapted from An Introduction to Orthodontics by Laura Mitchell

UI/Max.

plane

UI/LI

LI/ Mand.

plane


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48Fig. 7.7 Soft tissue analysis

7.9 Prognosis tracing To assess if overjet reduction is possible by bodily (Fig. 7.8a) or tipping (Fig. 7.8b)

movement, do a prognosis tracing or

For every 1 mm of overjet reduction subtract 2.5º (point of rotation about one-third from apex of root) from 1 inclination

49

Fig 7.8a. Prognosis tracing. In this picture, bodily movement of the upper incisors to reduce this patient’s overjet would not be feasible as it would penetrate the palate. Therefore surgical approach is recommended.

48

Picture taken from An Introduction to Orthodontics by Laura Mitchell 49



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50Fig 7.8b Prognosis tracing. Overjet reduction by tipping movement is unacceptable in this

patient as the root would penetrate the labial alveolar bone.

50

Picture taken from Orthodontics and Paediatric Dentistry by D. Millet and R. Welbury


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Chapter 8 ORTHODONTIC ASSESSMENT

AND DIAGNOSIS

8.1 Introduction The purpose of an orthodontic assessment is to record information that describes the nature of malocclusion and from this to determine the underlying cause (etiology) in preparation for treatment planning.

8.2 Equipment

8.2.1 Instrument Mouth mirror, probe, and stainless steel orthodontic ruler

8.2.2 Study models They are important as pre-treatment record

Helpful in assessing malocclusion

8.3 Introduction and History

8.3.1 Age and sex Provide useful information regarding growth status of the patient and timing of eruption. Patient with skeletal discrepancy may need treatment to be timed to coincide with pubertal growth spurt.

8.3.2 Reason for attendance / Chief complaint: The objective is to find out which features of the occlusion is the patient concerned about.

Are they concern about their dental and/or facial aesthetic, or occlusal function?

Ask patient question such as “Tell me what bothers you about your teeth or face”.

8.3.3 Medical History:

Epilepsy: if not under control, may not be advisable to do removable appliance due to risk of injury to the mouth caused by broken appliance during an epileptic attack.

Bleeding disorder: be careful during extraction or sub-gingival scaling. Patient must maintain a high standard of oral hygiene. At each appointment, make sure there are no wires or sharp surfaces that traumatize the soft tissues.

Rheumatic fever or cardiac anomalies: Please refer to recommendation by American Heart Association on the use of antibiotic prophylaxis.

Antibiotic prophylaxis with dental procedures that may cause bleeding is recommended only for patients with cardiac conditions associated with the highest risk of adverse outcomes from endocarditis, including: prosthetic cardiac valve, previous endocarditis, congenital heart disease

Diabetes - periodontal breakdown might be accentuated by orthodontic forces. Patient must maintain excellent oral hygiene and have regular periodontal maintenance.


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Kidney disease, hepatitis: be careful when giving medications, may need lower dosages or medications that do not have adverse effects on kidneys/ liver.

Bisphosphonates administered intravenously: orthodontic treatment and extraction are contraindicated due to risk of osteonecrosis.

Adults being treated for arthritis or osteoporosis: If they are taking high doses of prostaglandin inhibitors or resorption-inhibitors agents, orthodontic tooth movement may be impeded (slowed down).

Airway obstruction: these patients tend to be mouth breathers leading to constricted maxilla, Class II relationship, high MMPA and openbite. Patient should be referred to ENT specialists before starting orthodontic treatment.

Asthma: regular use of steroid-based inhalers can result in oral candida infections on the palate, which can be made worse by the use of palate-covering removable appliance. Patients with autoimmune and hyper-allergenic conditions can also be more prone to root resorption during orthodontic treatment.

8.3.4 Dental history:

Patient must have regular dental care and good oral health before orthodontic treatment.

Trauma to the teeth- may affect the development of occlusion (e.g. dilaceration) - increase the possibility of root resorption during orthodontic

treatment.

Trauma to the jaw may lead to ankylosis of the TMJ leading to facial asymmetry.

8.3.5 Family, Social history:

Patient‟s skeletal pattern may be due to hereditary

Does patient understand what orthodontic treatment involves?

How far do they live?

Can they come regularly?

8.3.6 Behavior / altitude of patient: Evaluate the interest and co-operation of patient and parents towards the treatment.

8.4 Extra-oral Examination 8.4.1 Skeletal pattern

The patient should be comfortably seated upright with his Frankfort plane in line with true horizontal.

The teeth should be together in Centric Relation.

The skeletal pattern should be assessed in all three planes: a) Anteroposterior b) Vertical c) Transverse


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8.4.1.a Anteroposterior (Fig. 8.1) Note the relationship between two lines, one dropped from the bridge of the nose to the base of the upper lip, and a second one extending from that point downward to the chin. Is it convex (Skeletal Class II), straight (Class I) or concave (Class III)?

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i) Convex (Skeletal Class II) ii) Straight (Class I) iii) Concave (Class III)

Fig. 8.1 Assessment of anteroposterior skeletal pattern

8.4.1.b Vertical facial proportions and mandibular plane

Lower face height With the face in profile and the teeth in occlusion, an estimate should be made of the lower face height. Does the lower part of the face appear excessively long or short? - Usually reduced face height is associated with deep overbites. - Excessive lower face height may be the cause of anterior open bite.

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A well-proportion face can be divided into vertical thirds as below (Fig. 8.2)

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Fig. 8.2 Assessment of lower face height. In an averagely proportioned face X=Y

Frankfort mandibular planes angle (FMPA) (Fig. 8.3) The inclination of the mandibular plane to the true horizontal or Frankfort plane should be noted. - a steep mandibular plane angle correlates with long anterior facial vertical dimensions and anterior open bite malocclusion. - a flat mandibular plane angle correlates with short anterior facial height and deep bite malocclusion. The mandibular plane is visualized readily by placing a finger or mirror handle along the lower border of the mandible against the Frankfort plane (external auditory meatus to the lower border of the orbital margin). In an average FMPA, these two planes will intersect approximately at the back of the head (Fig 8.3c).

a) Average FMPA (Average angle) b) Decreased FMPA (Low angle) c) Increased FMPA (High angle)

Fig. 8.3 Assessment of FMPA.

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52


X

Y


90

8.4.1.c Transverse

Check whether the face is symmetry or asymmetry (Fig. 8.4). Any marked asymmetry should be noted.

Check whether there is any canting of the occlusal plane by asking patient to bite onto a tongue spatula or the orthodontic ruler (Fig. 8.5)

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Fig. 8.4 Check for facial symmetry Patient with facial asymmetry, chin shifted to the right

Fig. 8.5 Patient with canting of the occlusal plane

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53



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8.4.2 Soft tissue 8.4.2.a Lips

The form, tonicity and fullness of lips.

Hyperactive lip can cause incisor to be retroclined.

An everted lips may be associated with proclined incisors

Lip competence: Is it competent or incompetent (Fig. 8.6)

Smile aesthetics: Smile showing more than interproximal gingival area are unaesthetic (Fig. 8.7)

Lower lip line position relative to the upper incisors:

Ideally, at rest the lower lip covers between ⅓ and ½ of the labial surface of the upper central incisors.

A high lower lip line is often one of the aetiological factors in Class II division 2 malocclusions (Fig. 8.8)

Lip posture: normal, protrusive or retrusive

Lip trap: Lip trap can cause proclination of upper incisors (Fig. 8.9)

Fig. 8.6 Patient with incompetent lip Fig. 8.7 Unaesthetic smile (gummy smile)

Fig. 8.8 A patient with high lip line. High lower lip line relative to the upper central incisors resulted in retroclination of the upper incisors. Lip trap causing proclination of upper left lateral incisor.


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Fig. 8.9 Patient with lip trap on upper incisors. Note the increase overjet.

8.4.2.b Tongue

Size; large tongue can cause openbite (Fig. 8.10)

Position: High position of tongue may be associated with scissor bite; low position of tongue may be associated with crossbite

Swallowing behavior: adaptive (typical) or endogenous (atypical). Note: Tongue thrust is usually adaptive: the tongue is placed between the teeth to help achieve an anterior oral seal during swallowing. Adaptive tongue thrust will cease following treatment when a lip-to-lip contact can be achieved, whereas an atypical tongue thrust will not cease and this often leads to relapse.

Fig. 8.10 Huge large causing anterior and posterior open bite

8.4.3 Temporomandibular joints (TMJ)

Ask patient if he has any TMJ symptoms (e.g. pain, clicking)

Palpate the TMJ. Record any clicks, crepitus and locking, mandibular path of closure.

8.4.4 Habits

Enquire and check about finger or thumb-sucking habits

Check also for any lip-sucking habits


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8.5 Intraoral Examination

Do a general intra-oral examination of the oral health to rule out any pathology (Fig. 8.11)

8.5.1 Dental examination (i) Teeth present:

erupted and unerupted;

missing teeth

extra teeth;

ectopic teeth and pathological conditions

(i) Oral hygiene: good, average or poor (iii) Condition of teeth:

caries

damaged teeth/malformed teeth

non-vital discoloration

hypoplastic or unusual form or size

condition of filling

(iv) Periodontal condition: any recession or reduced width of attached gingival

Inadequate attached gingival around crowded incisors indicates the possibility of tissue dehiscence developing when the teeth are aligned, especially with nonextraction (arch expansion) treatment

Fig. 8.11 Enlargement of buccal bone on the right side of maxilla

8.5.2 Mandibular path of closure See whether there are any displacements on closure.

Record if there is any lateral or anterior displacement of the mandible on closure (Fig. 8.12 a, b).

Where a displacement exists, the occlusion should be assessed in maximum inter-cuspation and the direction and amount of displacement recorded


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i) ii) Fig. 8.12a Patient with forward displacement of mandible due to premature contact. (i) At Centric Relation and (ii) At Centric Occlusion

i) ii) Fig. 8.11b Patient with lateral displacement of mandible due to maxilla smaller than mandible. (i)At Centric Relation and (ii) At Centric Occlusion

8.5.3 Position and relationship of teeth 8.5.3.a Labial segment: (i) Incisor relationship: Class I / Class II division 1 / Class II division 2 / Class III

overjet = +/- ? mm)

overbite = ? (% or in mm); anterior open bite / complete / incomplete

centre line: any midline shift?

any displacement on closure (Fig. 8.12a)

(ii) Upper and lower arch

general alignment and symmetry

proclined / average / retroclined

crowding / spacing

well-aligned?

median diastema, gingival recession, fraenum

rotations / crossbites / tilted

missing / impacted / supernumeraries


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8.5.3.b Buccal segment: (i) Angle Classification: Left molar = Class I / II / III Right molar = Class I / II / III Left canine = Class I / II / III Right canine = Class I / II / III (ii) Upper and lower arch:

Angulation of canines : mesially inclined / upright / distally inclined

crowding / spacing

rotations

impactions

bilateral / unilateral crossbite

posterior open bite

8.6 Radiograph Examination

OPG: alveolar bone height, teeth present or missing teeth, position of teeth, ectopic eruption, impacted teeth, supernumeraries, pathology, condyles etc. (Fig. 8.13)

Lateral cephalometric: skeletal discrepancies

Periapical radiograph: periodontal bone destruction, impaction, supernumeries, periapical pathology, root morphology (Fig. 8.14)

Upper anterior occlusal: location of impacted teeth, supernumeraries or pathology

Bitewing: inter-proximal caries, quality of restoration, periodontal disease The radiographs taken should be examined as below:

Check the clinical charting and record the presence of any unerupted teeth. Any missing teeth should be noted.

Assess the position and degree of development of any unerupted teeth. Also record any abnormalities (e.g. dilaceration)

Note any teeth with large restorations or untreated caries

Check to see any root resorption and apical pathology

Do cephalometric tracing


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Fig. 8.13 OPG showing dilacerated 1 and grossly carious ED DE

Fig. 8.14 Periapical showing impacted canine with large radiolucent lesion


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8.7 Diagnosis Only important clinical characteristics need to be mentioned. Example: Patient is aged 12 years and is concerned about his upper teeth sticking out. He has a Class II division 1 incisor relationship on a mild Class II skeletal pattern with decreased lower face height. Overjet = 7 mm Overbite = 50%, complete He has a well aligned lower arch. There is a median diastema between 1 1

8.8 Aetiology Write down the causes of malocclusion. Treat according to the causes (factors). Example:

Aetiology of increase overjet - skeletal factor? (treat with functional appliance?) - dental factor?

- soft tissue factor? - habit? (stop habit)

Aetiology of crowding - imbalance between the size of teeth and the size of arch? - premature loss of deciduous tooth/teeth

8.9 Summary History

Clinical

Examination

Analysis of Diagnostic Records:

Study models

Radiographs

Photos

Database of Information

Analysis of Information

Diagnosis (Problem List)

Pathological Problems E.g. caries, periodontal disease

Orthodontic problems

- Patient‟s concern - Facial & dental aesthetic - Alignment & symmetry in each arch - Skeletal & dental problems in each plane: transverse, anteroposterior & vertical.

Creating a problem list in orthodontics (taken from An Introduction to Orthodontics by Laura Mitchell)


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Chapter 9 ORTHODONTIC TREATMENT PLANNING

9.1 Introduction Areas that need to be considered during orthodontic treatment planning:

Dental health- should not compromise dental health

Function- promote good function

Aesthetics- ensure good facial and dental aesthetic result

Stability- produce as stable a result as possible

Co-operation of the patient and parents

9.2 Treatment planning Treatment planning can be divided into two sections:

1) Treatment Aims 2) Treatment Plan

9.2.1 Treatment Aims

Improved dental health- e.g. elimination of traumatic bite or premature contact

Improved facial and soft tissues aesthetics

Relieve crowding or closing of spaces

Leveling and aligning the dental arches

Correcting the incisor relationship (overbite & overjet)

Correct the buccal occlusion

9.2.2 Treatment Plan The treatment plan should be considered as follows:

Oral health

Lower arch

Upper arch

Buccal occlusion

Anchorage

Choose and design the appliance

Retention

9.2.2.a Oral health

Oral hygiene instruction (tooth brushing) and diet advice must be given.

Restoration of all carious teeth- except those that need to be extracted.

Periodontal problems must be treated and controlled- scaling, prophylaxis

Manage/treat any pathology.

Teeth that need endodontic treatment must be treated endodontically. Wait at least 3 months before beginning orthodontic treatment.

Note: Restorative and periodontal treatment must be carried out before orthodontic treatment. Patient must maintain good oral health.


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9.2.2.b Lower arch

Plan the lower arch first, especially the lower labial segment.

The size and form of lower arch should generally be accepted.

Excessive expansion of the buccal region and excessive movement of lower labial segment would increase the risk of relapse.

In most cases it is advisable to maintain the current sagittal position of the lower labial segment due to its inherent stability.

In certain situations, treatment plan maybe to procline the lower incisors, for example:

a) Cases presenting with very mild incisor crowding. b) Treatment of deep overbites, particularly in Class II division 2 cases c) Lower incisors has been retroclined due to either digit-sucking or in Class II

division 2 cases d) To prevent unfavorable profile changes in reduction of large overjet when

surgery is not indicated or declined (e.g. camouflage Class II division 1 cases).

The lower incisors can also be retroclined to camouflage a Class III malocclusion, or in treatment of bimaxillary dental protrusion.

In the correction of mild crowding (less than 4 mm), slight proclination of lower incisors and expansion of lower premolar region may be acceptable.

9.2.2.c Upper arch

Plan the upper arch around the lower arch in order to obtain a Class I incisor relationship.

The key to achieving a Class I incisor relationship is to get the canines into a Class I relationship.

Anticipate the lower canine position once the lower labial segment has been aligned. This gives the clinician an idea of: a) how much space will be required b) how far the upper canines need to be moved c) indication of the type of movement and type of appliance required d) the anchorage requirement

If no extractions are carried out in the lower arch the space for upper arch alignment may come from either distal movement of the upper buccal segments or, extractions of upper premolars.

As the degree of crowding and overjet increase, then the space requirement will also increase.

9.2.2.d Plan the buccal segments/occlusion

The aim is usually to obtain a Class I canine relationship but it is not necessary to always have a Class I molar relationship.

Whether extractions are needed or not will depend on the space requirement of each arch. Space analysis (see Chapter 10) is done to know how much space is required to correct a malocclusion.

If lower arch is crowded, space may be created by extraction of two lower premolars. This is then matched by upper premolar extractions and the molar must be Class I at the end of treatment to allow the arches to fit together.


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If lower arch is well aligned, space to align the upper arch can be created by either upper premolars extractions or by distal movements of the upper buccal segments. The choice depends on how much space is required and what the molar relationship is at the start of treatment.

If teeth are extracted in the upper arch, but not in the lower arch, the molars will be in Class II relationship.

9.2.2.e Planning anchorage

Anchorage is about resisting unwanted tooth movement. Anchorage is the resistance to the reactive forces generated by active components of the appliance.

When planning a case, it is important to decide how to limit the movement of teeth that do not need to move.

Generally, 60% of the space provided by extraction of upper 1st premolar is used by distal movement of anterior teeth and 40% by mesial movement of the posterior teeth.

Anchorage must be planned correctly for a treatment plan to work well. 9.2.2.f Choose and design the appliance

An appropriate appliance should be selected.

It may involve using a removable appliance, fixed or functional appliances with addition of anchorage or extra-oral traction.

Please refer section 9.3 for removable appliance design 9.2.2.g Retention

At the end of orthodontic treatment almost every case needs to be retained to prevent relapse back to original malocclusion.

Patient should be informed before orthodontic treatment begins, that they would need to wear retainers at the end of treatment.

Usually patient is advised to wear 6 months full-time wear follow by 6 months night-time only. This is necessary for the collagenous fiber networks within the gingiva to complete reorganization.

Long term retention (usually with a bonded retainer) will be needed: (a) after correction of tooth rotations and median diastema as the supracrestal

fibers remodel extremely slowly and can still exert forces capable of displacing a tooth a year after removal of an orthodontic appliance.

(b) where orthodontic treatment has been carried out to re-align periodontally involved teeth.

(c) where lower incisors have been proclined during treatment.

Little if any retention will be needed following correction of anterior crossbite if there is positive overbite at the end of treatment.

Retention may not be required when the tooth alignment has been achieved by spontaneous improvement, for example: (a) reduction of overjet following cessation of a finger-sucking habit.

(b) spontaneous lower arch alignment after first premolar extractions.


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Note: Major causes of relapse after orthodontic treatment include:

Elastic recoil of gingival fibers

Cheek/lip/tongue pressure

Differential jaw growth

9.3 Removable appliance design Before designing the appliance, list the required tooth movements and the order in which these movements are to be carried out.

9.3.1 General principles

1. For reasons of anchorage, only two single rooted teeth should be moved at any time.

2. Two active components per appliance are best. Four should only be included in exceptional circumstances.

3. Where only just sufficient space exists to carry out the required tooth movement, reinforce the anchorage with headgear.

4. Active components in decreasing order of preference are: (i) palatal springs (ii) buccal springs (iii) screws (iv) elastics.

5. There should only be one wire crossing each contact point.

6. Soldered joints should be avoided if at all possible.

7. Lower removable appliances are of very limited use. They are mainly used in: a] the retraction of mesially inclined mandibular canines. b] the unilateral distal movement of a molar.

South-end clasp

(Retentive component)

Buccal canine

retractor

(Active component)

Adam clasp

(Retentive component)

Baseplate


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9.3.2 Steps in appliance design

Step 1 Choose the active component for the first tooth movement (up to a maximum of two) using the preference list given above. (general principles no. 4)

E.g. palatal springs to move canines distally Step 2 Plan posterior retention.

E.g. Adams clasps on the first molars. Step 3 Plan anterior retention.

E.g. Adams clasps / labial bows / Southend clasp Steps 4 Outline the baseplate and add any bite plates required.

E.g. Anterior biteplane/ posterior biteplane Steps 5 Plan the anchorage. If in doubt add molar tubes to the bridges of the molar Adams clasps so that the anchorage can be reinforced with headgear later if necessary. Note: Remember the acronym ARAB during design. Anchorage Retentive components Active components Baseplate


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Chapter 10 SPACE ANALYSIS

10.1 Introduction Space analysis is a process that allows an estimation of the space required in each

arch.

It involves assessment of the space required and methods of creating this space.

It helps to determine whether the treatment aims are feasible, as well as assisting with the planning of treatment mechanics and anchorage control.

Space analysis requires a comparison between the amount of space available for the alignment of teeth and the amount of space required to align them properly.

10.2 Method for space analysis (when permanent second premolar have

erupted)

10.2.1 Total arch length (Amount of space available) To establish the available arch length from the mesial contact point of the

permanent first molar to the mesial contact point of the contralateral permanent first molar

Divide the dental arch into 4 straight line segments. Then measure each segment individually with a divider. (Fig. 10.1)

Sum up the measurement of each segment to get the amount of space available.

Fig. 10.1 Space available can be measured by dividing the arch into 4 straight line segments. Each segment is then measured individually with a sharp divider.


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10.2.2 Total teeth width (Amount of space required) (Fig. 10.2)

Measure the size of teeth from the distal surface of the permanent second premolar to the distal surface of the contralateral second premolar.

Note down the mesio-distal measurement of each tooth.

Sum up the measurements taken to get the amount of space required to align the teeth properly.

Fig. 10.2 Use a divider to measure the size of each teeth.

Crowding/Spacing = Total arch length – Total teeth width

A negative value indicates the presence of crowding, and a positive value indicates spacing in the dental arch.

10.3 Mixed dentition analysis (for mixed dentition only)

Based the Tanaka-Johnston prediction values:

a) Estimated width of mandibular 3, 4 & 5 in one quadrant is Half of the sum of mandibular incisor width + 10.5mm: ________ (mm)

b) Estimated width of maxilla 3, 4 & 5 in one quadrant is

Half of the sum of mandibular incisor width + 11.0mm: ________ (mm)


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10.4 Calculating the space requirements (see Table 10.2)

Space is required to correct the following:

Crowding

Incisor anteroposterior change (usually achieving a normal overjet of 2 mm)

Leveling of curve of Spee.

Arch contraction (expansion will create space)

Correction of upper incisor angulation (mesiodistal tip)

Correction of upper incisor angulation (torque) The space requirements to correct incisor angulation and inclination are usually minimal.

i) Crowding (Fig. 10.3)

Crowding/Spacing = Total arch length – Total teeth width

The amount of crowding is classified as: a) Mild (< 4 mm) b) Moderate (4 to 8 mm) c) Severe (> 8 mm)

ii) Incisor anteroposterior change

The treatment aim is to achieve an overjet of 2 mm at the end of treatment.

Every millimeter of incisor overjet reduction requires 2 mm of space in the dental arch.

For every millimeter of incisor overjet increase, 2 mm space are created in the dental arch.

iii) Leveling curve of Spee (Fig. 10.4a, b)

Space is required to level a curve of Spee (a curvature in the arch in an anteroposterior direction).

The aim of treatment is to create a flat curve of Spee

Estimation space requirement to flatten a curve of Spee can be seen in Table 10.1

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Fig. 10.3 Upper and lower dental arch crowding

54

Photo taken from Handbook of Orthodontics by Martyn T. Cobourne and Andrew T. DiBiase


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Fig. 10.4a Curve of Spee before treatment. Fig. 10.4b A flatten curve of Spee after treatment.

Table 10.1 Approximate space requirement to flatten a curve of Spee

Depth of curve (mm) Space requirement (mm)

3 or less 1

4 1.5

5 or more 2

Table 10.2 Example for calculating space requirement.

Patient has an overjet of 7mm and a curve of Spee of 3 mm in the lower arch. Upper arch

spacing 2mm and crowding at lower arch 5mm.

To reduce overjet to a normal 2mm (7mm-2mm=5mm), requires 5mm x 2= 10 mm space

(a negative score shows a space gain, a positive score shows space requirement)

Upper arch Lower arch

1) Crowding/spacing -2mm 5mm

2) Leveling curve of Spee 0 1mm

3) Anteroposterior movement of incisors 10mm 0

TOTAL 8mm 6mm

From the above calculation, this patient requires 8mm of space in the upper arch, and 6mm of

space in the lower arch.


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10.5 Creating space Space can be created by one or more of the following:

Extractions

Distal movement of molars

Enamel stripping

Expansion

Proclination of incisors

A combination of any or all of the above

10.5.1 Extractions

Before planning extractions of any permanent teeth, it is important to ensure that all

remaining teeth are present and developing appropriately.

Factors that affect the choice of teeth for extraction are as follows:

Prognosis

Position

Amount of space required and where

Incisor relationship

Anchorage requirements

Appliances to be used

Patient‟s profile and treatment aims

Usually tooth with poor prognosis or compromised periodontal support is the choice for

extraction.

First premolars are often the teeth of choice to be extracted when space requirement is

moderate or severe.

10.5.2 Distal movement of molars

Distal movement of upper molars can be achieved with headgear or mini-implant.

By using headgear, the upper molars can be moved distally 2-3 mm per side

(creating 4-6 mm space in total).

Therefore distalizing upper molars with headgear is used when there is a mild

space requirement where extractions may produce too much space.

Examples of when headgear can be used to distalize upper molars:

Class I incisor relationship with mild crowding in the upper arch

Class II division 1 incisor relationship with minimally increased overjet and molar

relationship of less than half a unit Class II

Where extractions of first premolars does not give sufficient space to complete

alignment

Where unilateral loss of a deciduous molar has resulted in mesial drift of first

permanent molar


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10.5.3 Enamel stripping

Enamel interproximal stripping is the removal of a small amount of enamel on the

mesial and distal aspect of teeth.

On anterior teeth approximately 0.5 mm can be removed on each tooth (0.25 mm from

the mesial and distal)

Enamel can be carefully removed with an abrasive strip (Fig. 10.5). The teeth are

treated with fluoride following the enamel stripping.

55Fig. 10.5 Interproximal stripping using abrasive strip

10.5.4 Expansion

Space can be created by expanding the upper arch laterally.

For every 1 mm of posterior arch expansion, approximately 0.5 mm is created.

Expansion is usually done when there is a posterior crossbite.

Expansion without a crossbite increases the risk of instability and the risk of

perforation of buccal plate.

Any significant expansion in the lower arch, particularly at the intercanine width, is

likely to be unstable. (Fig. 10.6)

10.5.5 Proclination of upper incisors

Space can be created by proclining the incisors teeth, but this is dictated by the aims

of treatment.

Each mm of incisor advancement creates approximately 2 mm of space within the

dental arch.

55

Photo taken from http://wikisites.mcgill.ca/Dentalpedia/index.php/Interproximal_reduction_IPR and

http://www.jco-online.com/product-news/?pnid=66

http://wikisites.mcgill.ca/Dentalpedia/index.php/Interproximal_reduction_IPR

http://www.jco-online.com/product-news/?pnid=66


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56

Fig. 10.6 Picture showing the maximum of mm that can be

expanded for stability in the lower arch. The data suggest that moving

lower incisors forward more than 2 mm is problematic for stability.

Expansion of canines are not stable.

56

Picture taken from Contemporary Orthodontics 3rd

edition by W. R. Proffit and H. W. Fields, Jr.


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Chapter 11 REMOVABLE APPLIANCES

Definition Removable appliances are not orthodontic appliances consisting mainly of wires and acrylic components that can be inserted and removed by patient.

11.1 Indications: 1. simple tipping movements 2. overbite reduction 3. elimination of occlusal interference 4. as space maintainers 5. to help transmit forces to groups of teeth 6. minor de-rotation of incisor teeth 7. simple extrusion and rotation in conjunction with a fixed attachment 8. retainer

11.1.1 Simple tipping movement (Fig.11:1; 11.2a, b; 11.3; 11.4)

Teeth tip at a point approximately at 40% of the root from its apex, which means the root apex will move in the opposite direction to the crown. Removable appliances are particularly good at correcting incisor crossbites, provided that the tooth or teeth in crossbite are not already proclined, and there is adequate overbite. Note:

Proclination of an incisor will reduce the overbite, and

A positive overbite at the end of treatment is essential for stability. Indication for tipping movement (when moving tooth distally)

tooth that is mesially-tipped before treatment

tooth that is in upright position, provided that some distal tipping is acceptable at the end of treatment.

Contraindication for tipping movement (when moving tooth distally)

tooth that is distally-tipped (need to be treated by fixed appliance for bodily movement).


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Fig. 11.1 Tipping movement. The fulcrum of rotation is approximately 40% of the length of the root from the apex.

A B ( Broken line: before movement. Continuous line: after movement )

Remember that if distal movement of mandibular canine is intended, then the maxillary canine will have to be moved further distally to achieve or maintain a Class I relationship.

57

Picture taken from Removable Orthodontic Appliances by K.G Isaacson, J.D. Muir & R.T. Reed

Fig 11.2 A, Favorable tipping of a tooth. The canine crown is mesially placed and when tipped distally, lies favorably in the space available

Fig 11.2 B, Unfavorable tipping of a tooth. The canine crown is distally placed and when tipped distally into the space available increases an already unfavorable inclination


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Fig. 11.3 Buccal canine retractor to move bucally-erupted upper canine distally and palatally.

Fig. 11.4 Palatal springs to retract canines in the line of arch distally.

11.1.2 Overbite reduction (Fig. 11.5, 11.6)

In a growing child, the incorporation of an anterior bite plane helps to reduce the overbite through the eruption of the lower buccal segment teeth.

Anterior bite plane should not be used to reduce the overbite in bimaxillary proclination cases, as the effect will be to procline the mandibular incisors further.

Fig. 11.5 Anterior bite plane used to reduce overbite and to eliminate occlusal interferences to allow upper canine to move distally by using palatal spring.


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11.1.3 Elimination of occlusal interference (Fig. 11.5, 11.7)

Anterior or posterior bite planes will efficiently eliminate occlusal interferences during crossbite correction.

Lower removable appliances with bite planes may also be used to assist a maxillary fixed appliance which is attempting anterior crossbite correction.

Fig. 11.7 Posterior bite plane to eliminate occlusal interferences in anterior segment to enable the proclination of upper central incisors in anterior crossbite

11.1.4 Space maintainer (Fig. 11.8) Keeping space in the dental arch for unerupted teeth can be achieved with a removable appliance. The advantages of a removable appliance as space-maintainer are:

it can incorporate an anterior bite plane to reduce overbite.

it is easy to attach a prosthetic tooth to the baseplate to act as a space maintenance and also helps to enhance aesthetics in cases such as congenital absence of a maxillary incisor.

Fig. 11.8 Removable appliance used to maintain space to allow upper canines to erupt.

Posterior bite plane


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11.1.5 To help transmit forces to groups of teeth Examples:

for arch expansion (Fig. 11.9), or

distal movement of buccal segment (Fig. 11.10)

Fig. 11.9 Removable appliance with screw for upper arch expansion

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Fig. 11.10 An En Masse appliance for distal movement of the upper buccal segments. Note the midline screw to expand the buccal teeth as they move distally, and

Adam clasps on 6s and 4s to assist retention.

11.1.6 Minor de-rotations of incisor teeth (Fig. 11.11)

A force couple, i.e. two wires acting in opposite directions on the opposed corners of the incisor tooth, will cause de-rotation. This is only possible if the rotated tooth is upright.

A rotated incisor occupies less space in the arch, so more space will be required for de-rotation.

58

Photo taken from Walther & Houston Orthodontic Notes by M.L. Jones & R.G. Oliver


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Fig. 11.11 To rotate 1l. Z spring is active on the distopalatal corner and the labial bow is active on the mesiobuccal corner of the crown of the tooth.

11.1.7 Simple extrusion and de-rotation of teeth in conjunction with a fixed attachment (Fixed removable appliance )

a) The wide palatal coverage of a removable appliance provides excellent resistance to the reactive forces generated by extrusive mechanics. This is particularly helpful when straightforward vertical movement of a tooth is necessary ((Fig. 11.12). i.e. A free-ended spring, with a coil for additional flexibility constructed in 0.5 mm wire, hooks over a suitable attachment on the tooth.

60

Fig. 11.12 A Begg bracket has been directly bonded to the labial surface of the crown, and a free-

ended wire spur in 0.6 mm hard stainless steel wire has been soldered on to the Adams clasp on the first molar. The spur is adjusted to lie below the level of the incisal edge of the lateral incisor, and is lifted up and placed in the vertical slot of the Begg bracket. This tooth was successfully extruded in 3 months.

59

Photo taken from Walther & Houston Orthodontic Notes by M.L. Jones & R.G. Oliver 60



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b) Where one or two incisors are rotated, a whip spring and bonded attachment may be effective when used in conjunction with a labial bow from a removable appliance (Fig. 11.13)

. 61

Fig. 11.13 A whip spring on the upper lateral incisor with a directly bonded Edgewise bracket. The whip which is made from 0.5 mm wire. It clips over the wings of the bracket and is held in place by a ligature twisted through the loops in the wire. The free end of the whip clips over the labial bow and a rotational couple is applied to the tooth. The patient can take out the removable appliance for cleaning.

11.1.8 As a retainer (Fig. 11.14)

A passive removable appliance is frequently used as a retainer following removable or fixed appliance treatment.

Fig. 11.14 Upper and lower soldered Hawley labial bow as removable retainers.

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11.2 Case selection for removable appliance

11.2.1 Indications:

Skeletal Class I, mild Class II (< ANB 4 - 6),

Pseudo Class III (< ANB 1 or 0 )

When upper and lower orthodontic treatment can be done separately.

The teeth apices are not displaced.

Teeth need tipping movement only.

Unilateral posterior crossbite with mandibular displacement.

One or two rotated tooth that has less than 45 rotation.

11.2.2 Contraindications:

Severe imbalance skeletal pattern i.e. severe Class II or severe Class III.

The tooth apex is displaced / severe rotation / more than 2 rotated teeth.

Teeth need bodily movements.

Very deep overbite, openbite.

11.3 Advantages and disadvantages of removable appliances

Advantages Disadvantages Can be removed for tooth brushing

Appliance can be left outside the mouth and be lost

Palatal coverage increases anchorage

Only tipping movements possible

Easy to adjust

Good laboratory work needed

Less risk of iatrogenic damage (e.g. root resorption) than fixed appliances

Affects speech

Acrylic can be thickened to form anterior bite-plane or posterior bite-plane

Intermaxillary traction not practical

Useful as passive retainer or space maintainer

Lower appliances are difficult to tolerate

Can be used to transmit forces to blocks of teeth

Inefficient for multiple individual tooth movements

11.4 Components of removable appliance

The components of removable appliances are:

1. Active components

2. Retentive components

3. Anchorage components

4. Baseplate


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11.4.1 Active components (Fig. 11.15)

Function: to apply force to the teeth in order to move the teeth. Types of active component:

a) Springs

b) Labial Bow (active)

c) Screws

d) Elastic 11.4.1a Springs

is made from spring hard stainless steel wire.

most commonly used active component.

it is desirable to deliver a light (physiological) force over a long activation range

incorporating a coil into the design of a spring increases the length of wire, therefore results in the application of a smaller force for a given deflection.

For 0.5 mm wire, an activation of about 3mm = 30-50 g of force (optimum for tipping movements)

For 0.7 mm wire, an activation of 1mm = the optimum force for tipping movements.

TYPES WIRE SIZE (mm) FUNCTION

Palatal finger spring 0.5 or 0.6 to move a tooth in the dental arch mesially or distally

Buccal canine retractor 0.7 to move a buccally erupted canine palatally and distally

Z-spring/Double helical 0.5 or 0.6 to procline one or a group of anterior teeth

T-spring 0.5 to move premolar or canine buccally; or to procline an upper incisor.


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Z- spring Palatal finger springs on canines

62

T-spring Use only orthodontic spring hard stainless steel wires. Fig. 11.15 Various kinds of springs shown above.

11.4.1b Labial bows (Fig.11.16) Function: to retract the upper incisors.

Types Wire size

i) Hawley Labial Bow ( U-loop Labial Bow) 0.7 mm

ii) Reversed Loop Labial Bow 0.7mm

iii) Robert‟s Retractor 0.5 mm (in stainless steel tube)

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Photo taken from An Introduction to Orthodontics by Laura Mitchell


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i) Soldered Hawley labial bow to retract ii) Reversed loop labial bow upper incisors (to reduce overjet)

63

iii) Robert’s retractor

Fig. 11.16 Various kinds of labial bows shown above.

11.4.1c Screws Functions:

To move one or a group of anterior teeth labially

To expand the upper arch transversely(Fig. 11.17)

To move one or a group of teeth distally (Fig. 11.18). Disadvantage: bulky and more expensive compared to springs

63

Photo taken from Orthodontics and Paediatric Dentistry by Declan Millet, Richard Welbury


121

Fig. 11.17 Screw to procline upper anterior incisors

64Fig. 11.18 Screws to distalize 6s to create space for 5s to erupt

11.4.2 Retentive Components Is made from spring hard stainless steel wires.

Function: to keep the appliance in position. The various types of retentive component are: a] Adams Clasp (for anterior or posterior teeth) [Fig. 11.19] b] South-end Clasp (for anterior) [Fig. 11.20] c] Labial Bow (passive stage)

64

Photo taken from http://www.dynaflex.com/labpages/lab_cat10.html

http://www.dynaflex.com/labpages/lab_cat10.html


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Fig. 11.20 South-end clasp (0.7mm) on upper central incisors

11.4.3 Anchorage (For Removable appliances)

Anchorage is the resistance to the reactive forces generated by active components of the appliance.

Anchorage is provided by the sites which resist the forces of reaction generated by the active components of the appliance.

The main sources of intra-oral anchorage are the teeth which are to be not moved and to which the appliance is attached by the retentive components.

The contact between the baseplate with the palate and teeth also provide additional anchorage.

Note: Remember to use only light forces to move tooth in order to avoid loss of anchorage.

Fig. 11.19a Adam clasps on 6 (0.7mm) & 4 (0.6mm/ 0.7mm)

Fig. 11.19b Double anterior Adam clasp (0.7mm) on central incisors


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For removable appliances, anchorage may be preserved by:

Placements of clasps or bows on teeth which are not being moved. Incorporate as many teeth as possible into the anchorage.

Contact of the baseplate with other teeth not being moved

Contact of the baseplate with the vertical part of the palate in the area of the rugae (for distal movement of teeth)

Use light forces to move teeth

Only one buccal tooth on each side should be moved at a time. Canines should be moved separately from incisors.

Extra-oral traction: with headgear (Fig. 11.21a, b)

Fig. 11.21a Removable appliance with headgear tube soldered on Adam clasps. Patient needs to wear headgear due to great anchorage demand (large overjet).

Fig. 11.21b Removable appliance with facebow inserted into the headgear tube.


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11.4.4 Baseplate

Functions:

supports the wire or screw components

contributes to anchorage by contacting teeth not to be moved and the palate.

prevents unwanted drift of teeth

Anterior bite planes or posterior bite planes

protect palatal springs 11.4.4a Anterior bite planes (ABP) Fig. 11.22 Functions: a] to reduce a deep overbite. b] if patient has posterior crossbite together with an increase in overjet, ABP can be used to relieve the occlusion when correcting the crossbite and at the same time reducing the overbite (for growing patient).

Fig. 11.22 Anterior bite-plane. It is flat and lengthened to the posterior just long enough for the lower incisors to occlude with it.

Thickness: a] If the function is to relieve the occlusion, the ABP is made just thick enough to relieve the occlusion of the posterior teeth. b] If the function is to reduce the overbite, the ABP must have enough thickness to open the molar occlusion as much as 2-3 mm for actively growing patients, and 1-2 mm for adult patients. (Fig.11.23) Note: Overbite reduction that can be obtained by using anterior bite plane in adult is less than that for a child patient, it takes time to achieve overbite reduction and it may not remain stable.


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65

Fig.11.23 An anterior bite plane allows vertical eruption of the posterior teeth. The bite plane should be thick enough to separate the posterior teeth by 2-3mm and long enough to engage the lower incisors when the mandible is retruded.

Trimming of anterior bite plane to allow reduction of overjet (in Class II malocclusion) [Fig. 11.24, 11.25]

66 Fig. 11.24 Trimming of anterior bite plane to allow overjet reduction.

The fitting surface is progressively trimmed away to allow the upper incisors to be retracted while the lower incisors are still in contact with the bite plane.

65

Picture taken from Removable Orthodontic Appliances by K.G. Isaacson, J.D. Muir, R.T. Reed 66

Picture taken from Removable Orthodontic Appliances by K.G. Isaacson, J.D. Muir, R.T. Reed


126

Fig. 11.25 Trimming an anterior bite plane to allow incisor retractions.

The ABP must not be trimmed back too far, so that the lower incisors will still occlude with it. Then it is undermined to clear well away from the palatal surface of the upper incisors.

11.4.4b Posterior bite planes Functions: a] to relieve the cuspal lock when correcting the anterior crossbite. (Fig. 11.26) b] to relieve the occlusion when correcting the unilateral posterior crossbite (Fig. 11.27, 11.28) Thickness: Just thick enough to clear the occlusion.

Fig. 11.26 Appliance to correct anterior crossbite with posterior bite-plane


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Fig. 11.27 Appliance to correct unilateral posterior crossbite with posterior bite-plane

67

Fig. 11.28a, Unilateral crossbite with midline shift pre-treatment. b, Unilateral crossbite corrected by expansion of upper arch with screw, and posterior bite plane to remove occlusal interference.

67

Picture taken from A Clinical Guide to Orthodontics by D. Robert-Harry and J.R. Sandy

a

b


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11.5 Removable appliance design and planned teeth movement 1. Plan which tooth/teeth that need(s) to be moved. 2. Plan the number of appliances that are needed and their functions. Example: In the case of Class II division I, overjet 7 mm , overbite 70% . Lower arch in good alignment Treatment plan: (Fig. 11.29) 1. Extract 4 / 4 2. 1st appliance : a) retract 3 / 3 with finger spring,

b) reduce overbite with anterior bite plane.

3. 2nd appliance: a) reduce overjet with labial bow b) maintain overbite with anterior bite plane,

c) maintain 3 / 3 position with a stop (wire). 3. 3rd appliance: Retainer

1st appliance 2nd appliance

3rd appliance

68Fig. 11.29

68



129

Chapter 12 ANCHORAGE

12.1 Definition Anchorage is the resistance to the reactive forces generated by active components of

the appliance.

12.2 Introduction

According to Newton‟s 3rd law of motion, whenever tooth movement is attempted there will be an equal and opposite reaction of the force(s) applied by the active component. This reaction force is spread over the teeth that are in contact with the appliance (Fig. 12.1).

Anchorage is required to prevent unwanted tooth movements.

Anchorage loss may result in unsuccessful result because inappropriate movement of anchor teeth results in insufficient space remaining to achieve the intended tooth movements. For example, anchorage loss during retraction of canines for a Class II malocclusion will cause forward movement of the anchor teeth, which result in an increase of overjet.

Unwanted tooth movements during orthodontic treatment can occur in anteroposterior (sagittal), vertical and transverse dimensions. Therefore, it is necessary to plan anchorage in sagittal, vertical and transverse planes.

69

Fig. 12.1 Diagram showing the effect upon the anchor teeth while retracting upper canines with a fixed appliance.

69

Diagram taken from An Introduction to Orthodontics by Laura Mitchell


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12.3 Assessing anchorage requirements

The amount of anchorage required will depend on the factors below: a) The number of teeth to be moved

When more teeth are to be moved the anchorage demand is greater.

b) The distance the teeth need to be moved The greater the distance the teeth are to be moved, the greater the anchorage demand is. The final position of the teeth needs to be anticipated. (Fig. 12.2)

Fig. 12.2 Due to severe lower arch crowding the lower canines need to be moved distally, thus the upper canines need to be moved further distally to achieve a Class I relationship.

c) Forced applied Bodily movement is more anchorage demanding than tipping movement. For example, less force would be required to tip a mesially inclined 3 back into a Class I occlusion compared to retracting a distally inclined 3, which requires bodily movement and uprighting the root. (Fig. 12.3)

Fig. 12.3 The distally inclined canines need to be moved bodily.

This places a high demand on anchorage.


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d) Root surface area(RSA) of the teeth used for anchorage Teeth with a larger RSA or a block of teeth with a larger RSA will resist anchorage loss more than those with a smaller RSA. Thus molar teeth are more suitable to provide anchorage compared to incisors.

e) Tendency for tooth movement in the arch

Anchorage loss is more rapid in the maxillary arch as the upper teeth have a greater tendency for mesial drift.

f) Skeletal pattern

In patients with increased vertical skeletal dimension (increased Frankfurt Mandibular Plane Angle) and a backward growth rotation, mesial movement and anchorage loss seems to occur more readily compared to reduced vertical skeletal proportions and a forward pattern of growth rotation.

g) Occlusal interdigitation

Good buccal interdigitation may act to resist tooth movement.

12.4 Types of anchorage

12.4.1 Intramaxillary: where the teeth within the same arch are used as anchorage.

a] Simple anchorage Where teeth of greater resistance are used as anchorage for movement of a tooth /teeth of lesser resistance. Examples:

first molars as anchor teeth when proclining an upper incisor labially in anterior crossbite. (Fig. 12.4)

active movement of one tooth versus several anchor teeth. b] Reciprocal anchorage When equal and opposite tooth movements are carried out on both sides, e.g. transverse arch expansion. (Fig. 12.5)

Fig. 12.4 Anchorage provided by 6|6 and I1. Fig. 12.5 An expansion appliance, showing the

use of reciprocal anchorage.


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12.4.2 Intermaxillary: where opposing arch is used for anchorage.

This is commonly used with fixed-appliances in which elastics are used by using Class II or Class III intermaxillary traction.

12.4.3 Extra-oral anchorage, where headgear is used to provide or reinforce anchorage.

(Fig. 12.6).

Fig. 12.6 Cervical-pull headgear High-pull headgear attached to a face-bow.

12.5 To minimize anchorage loss (Fig. 12.7 a, b, c)

Use force as light as possible for the intended tooth movement (30-50g for tipping

movement; 150-250g for bodily movement)

Move the minimum number of teeth at one time

Increase the resistance of the anchor teeth


133

c) When 4s & 3s are retracted, there are fewer teeth available for anchorage

and a greater number of teeth to be moved. There will be loss of anchorage

resulting in increase of overjet.

70

Fig. 12.7 Anchorage considerations in relation to tooth movement

12.6 To reinforce anchorage

a) Intra-oral reinforcement of anchorage

Anchorage can be preserved intra-orally during treatment as below:

i) Increasing the number of teeth in the anchor unit.

ii) Making movement of the anchor teeth more difficult.

In fixed appliance it is possible to ensure that the anchor teeth move only bodily. As bodily

movement requires greater forces, the resistance of the anchorage unit is increased.

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a) When moving a single tooth, the other teeth in the arch and palate provide favourable anchorage.

b) When retracting 3s the reaction to the movement results in slight forward movement of the anchor teeth


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iii) Intermaxillary anchorage

The anchorage available in one arch can be reinforced if the patient wears elastic traction

to the opposing arch.

For example, using Class II elastic traction in a Class II malocclusion (Fig. 12.8) or Class

III elastic traction in a Class III malocclusion (Fig. 12.9).

Fig. 12.8 A Class II elastic traction. Fig. 12.9 A Class III elastic traction

iv) Palatal and lingual arches (Fig. 12.10a, b)

An arch which connects contralateral molars either across the palatal vault or around the

lingual aspect of the lower arch will help to prevent movement of the molars and thus

reinforce anchorage.

Fig. 12. 10a Palatal arch. Fig 12.10b Lingual arch

v) Choice of appliance

Upper removable appliance provides more anchorage than fixed appliance due to its

palatal coverage by the baseplate.

vi) Implants

This includes onplant, implant and mini-implant (mini-screws). (Fig. 12.11)


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Fig. 12.11 Mini-implant placed to reinforce anchorage.

b) Extra-oral anchorage and traction (Fig. 12.6, 12.12)

Extra-oral anchorage for reinforcement of anchorage (200-250g for 10-12 hours/day).

Extra-oral traction for distalizing buccal teeth (400-500g for 14-16+ hours/day).

Fig. 12.12 A combination pull headgear.


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Chapter 13 FUNCTIONAL APPLIANCES

13.1 Definition An appliance that utilize, eliminate, or guide the forces of muscle function, tooth eruption and growth to correct a malocclusion.

13.2 Introduction Functional appliances utilize the forces of the oral-facial musculature to move the

teeth

Most functional appliances work by the principle of posturing the mandible forwards in growing patients.

They are most effective at changing the anteroposterior occlusion between the upper and lower arches, usually in patient with a mild to moderate Class II skeletal discrepancy. (Fig. 13.1, 13.2)

They are not effective at correcting tooth irregularities and improving arch alignment. Therefore patient may need to have fixed appliance following treatment by functional appliance.

13.3 Timing of treatment Functional appliance should be used in actively growing patient.

The best timing for treatment with functional appliance is during the pubertal growth spurt of the patient (around 10-12 years for girls, 12-14 years in boys); during the late mixed dentition.

Fig. 13.1 Before treatment. Large overjet in After treatment with function appliance.

well-aligned arches.


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Fig. 13.2a Patient with retrusive mandible (before treatment). Fig 13.2b Patient profile after treatment with Functional appliance.

13.4 Indications for Functional Appliance (FA) Therapy

1. Increased overjet and Class II buccal segment relationship

2. Active Growth FA are best used when the patient is still growing actively, if possible, coincide with the pubertal spurt (10-11 years for girls and 11-12 for boys). It is most effective for patient with mild-to-moderate skeletal Class II discrepancy with retrognathic (short) mandible.

3. Late mixed dentition

4. Well aligned arches Functional appliance can be used alone to treat Class II division 1 malocclusions (due to skeletal discrepancy) if the arches are well-aligned. For arches which are not well aligned (with crowding, rotations etc.), functional appliance is usually followed by a second phase of treatment by fixed appliance.

5. Average or reduced lower face height/ Frankfurt Mandibular Plane Angle (FMPA)

6. Upright or slightly retroclined lower incisors

7. Active retention FA is used as retention appliances for growing patient who had undergone skeletal growth modification with functional appliance or headgear. It is worn at night. This can help to limit adverse late growth changes.


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13.5 How functional appliances work

The mode of action of functional appliances is not completely understood.

Forces are developed by posturing the mandible (downward & forward in Class II cases; downward & backward for Class III cases).

When the mandible is postured, pressures are created by stretching of the muscles and soft-tissues. These pressures are then transmitted to the dental arches and skeletal structures.

The functional appliances produce mainly dento-alveolar effects, with small skeletal changes.

13.5.1 Effects of functional appliances i) Skeletal

It restrains forward maxillary growth in the same way (though perhaps not to the same extent) as headgear.

Mandibular growth can be accelerated and perhaps even stimulated to attain its potential size.

Lower face height increases.

ii) Dental

Retroclination of upper incisors/ proclination of lower incisors

Inhibition of lower incisor eruption

Mesial and upwards eruption of lower posterior teeth

Prevention of eruption and mesial movement of upper posterior teeth

Arch expansion in some cases (e.g. when used with screw)

13.6 Types of functional appliances (Fig. 13.3)

There are many different types of functional appliances

They can be tissue-borne (e.g Frankel) or tooth-borne (e.g. Twin-block), and may be removable or fixed (e.g. Herbst)

Examples of Functional Appliances are:

a) Monobloc (Andresen appliance)

b) Bionator appliance

c) Frankel appliance

d) Clark‟s Twin Block appliance


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Twin Block appliance

71Bionator

72

Frankel II Appliance Herbts (Fixed Functional appliance) Fig. 13.3 Different types of functional appliances shown above.

13.7 Practical management

For skeletal Class II discrepancy, wax bite registration is taken with the mandible postured downwards and forwards 5-7 mm or at edge-to-edge with 5mm vertical opening at the premolar area.

Functional appliance should be worn for at least 14 hours per day.

Review 1-2 weeks after issuing appliance and then review patient at 6-8 weeks intervals.

Record the overjet with mandible at maximum retrusion at each review visit.

It is advisable to slightly over-correct the occlusion, and then the appliance should be worn as retainer at night only until growth has reduced to adult levels or until second phase of treatment with fixed appliance starts.

If there is no progress in the first 6 months, stop treatment and reassess.

71

Photo taken from Orthodontics and Paediatric Dentistry by D. Millet and R. Welbury 72

Photo taken from Orthodontics and Paediatric Dentistry by D. Millet and R. Welbury


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Example of a patient treated by using Twin block appliance

Case 1

a) Before treatment. Patient with skeletal Class II and short mandible. Large overjet and deep bite.

Lateral profile. Frontal view (Intra-oral)

Lateral view (Intra-oral)

Case1. Before treatment. Patient with skeletal Class II and short mandible. Large overjet and deep bite.


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b) Start of treatment (March 06)

Twin block appliance. Side view Occlusal view. Note the screw use to expand the maxilla.

c) During treatment (Dec 06)

Note the reduced overbite and overjet. There is vertical gap between the premolars and 1st molar

(normal for Twin block appliance).


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d) The Support Phase

Patient wears a removable appliance with a steep anterior inclined guide plane to allow lower posterior teeth to erupt to close the posterior open bites. The anterior inclined plane also helps the mandible to bite in the corrected forward position preventing relapse.

Case 2. Combination of Functional Appliance and High Pull Headgear

Is usually used in patient with high-angle (large MMPA)

Case 2. Patient with high angle and large overjet. (Before treatment)


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Case 2. After Functional appliance (FA) treatment. Note the lateral openbite and much reduced

overjet & overbite. After FA, patient was treated with fixed appliance.

Note: Patient was treated with Fixed appliance at Phase 2 treatment.

Functional appliance with face bow Patient wearing high-pull headgear with functional appliance.


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Chapter 14 INTRODUCTION TO FIXED APPLIANCE

14.1 Definition An appliance fixed to teeth by attachments through which force application is by archwires

or auxiliaries.

Fixed appliances are capable of producing tooth movement in all three planes of

space (sagittal, lateral and vertical).

14.2 Components

i) Brackets and bands: (Fig. 14.1)

Brackets are generally bonded to teeth by acid etch and composites.

Brackets allow the teeth to be directed by active components (archwires and/or

accessories.

Width of edgewise bracket slot is either 0.018 or 0.022 inch.

A narrow bracket (single wing) results in greater span of archwire between the

brackets which increases the flexibility of the archwires (increased inter-

bracket space).

A wider bracket (double wing) reduces the interbracket archwire span, but is

more efficient for de-rotation and mesiodistal control (reduced inter-bracket

space).

Bands are usually cemented to molars with glass ionomer cement (GIC).

ii) Archwires:

The archwires may be round or rectangular.

Usually the round wire (NiTi or Stainless steel) is used initially (Fig. 14.2).

With round wire only tipping movements in a mesial-distal and buccolingual

direction is possible.

Rectangular wire is used to provide torque (buccolingual apical movements)

later in the treatment (Fig. 14.1)

iii) Auxiliaries: (Fig. 14.3, 14.4)

Elastics or elastomeric modules/chain/thread. E.g. power chain to retract teeth

Springs. E.g. coil springs


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Fig. 14.1 Fixed appliances near finishing stage.

Fig. 14.2 Initial alignment with Nickel Titanium (NiTi) round wires.

Fig. 14.3 Auxiliaries. Open coil springs to open space and power chain to retract teeth.

Rectangular

archwire

Brackets

tied with

elastomerics

modules

Band

Coil

springs

Power

chains

Ligating teeth

together to

enhance

anchorage


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Fig. 14.4 Auxiliaries. Closing NiTi coil-spring (lower arch)

and elastomeric power chain (upper arch).

14.3 Indications for fixed appliances

Correction of mild to moderate skeletal discrepancies: as fixed appliances can be

used to achieve bodily movement

Intrusion or extrusion of teeth

Correction of rotations

Overbite reduction by intrusion of incisors

Alignment of grossly misplaced teeth

Closing spaces

Multiple tooth movements

14.4 Anchorage control

Bodily movement places greater strain on the anchorage compared to tipping

movements.

Anchorage can be reinforced by bonding on more teeth and ligating them together

(Fig 14.1); transpalatal arch of Nance (Fig. 14.5), lingual arches; intermaxillary

traction; extraoral traction (headgears); implants.


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Fig. 14.5 Anchorage reinforced by using Nance

14.5 Appliance management

Patient must be willing to:

maintain excellent oral hygiene

co-operate fully in wearing elastic or headgear traction, if required.

attend appointments regularly at 4-6 weeks interval to have appliance adjusted

avoid hard or sticky foods and the consumption of sugar-containing foodstuffs

between meals.

14.6 Fixed Appliance systems

I) Pre-adjusted appliances

It is also known as straight wire appliance.

Individual tooth positions (tip & torque) are built into the brackets.

Example of bracket prescription is Roth & MBT (Fig. 14.6) system.

Treatment using pre-adjusted systems usually involves six steps:

Alignment

Overbite reduction

Overjet correction

Space closure

Finishing- usually needs to place small bends in the archwires for fine

detail of tooth position and occlusion.

Retention


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a) Start of treatment. Alignment stage b) 2

nd visit. Teeth almost aligned.

c) 3

rd visit. Teeth have been aligned. d) 5

th visit. Start of space closure in the upper

arch. Leveling at lower arch.

e) 6

th visit. Overbite & overjet reduction f) 8

th visit. Complete overbite reduction.

Continuing overjet reduction and space

closure

g) Completion of treatment.

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Fig. 14.6 Patient treated with pre-adjusted appliance (MBT system)

73

Photos taken from a lecture by Dr. Jon Hammond, University of Edinburgh.


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II) The Tip Edge appliance

It was developed from the Begg appliance.

The Tip edge brackets (Fig. 14.7) allows tipping of the tooth in the initial stages

of treatment when round archwires are used.

In the later stages, the full-sized rectangular archwires are used. The built-in

pre-adjustments in the brackets help to give a better control of the final tooth

positioning.

Treatment usually involves three stages (Fig. 14.8, 14.9).

Fig. 14.7 A Tip Edge bracket


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Stage 1

Stage 2

Stage 3

Completed 74

Fig. 14.8 A Class II div 1 case treated with Tip-Edge system

74

Photos taken from http://www.tipedge.com/tipedgesystem.aspx#


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a

Fig. 14.9a Stage 1 of Tip Edge treatment

Objectives: Align anterior teeth to eliminate crowding or spacing

Vertical correction of deep or anterior open bites

Horizontal correction of anterior overjet or reverse overjet

b

Fig. 14.9b Stage II of Tip Edge

Objectives: Close posterior space

Midline correction

Correct molar relationship, if necessary

c

Fig. 14.9c Stage 3 of Tip Edge

Objective: Uprighting & Torqueing of roots

Lock in bite (Finishing)


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II) Self-ligating system

Brackets have their own clips, so modules and ligatures are un-necessary

Less friction at initial arch wires

Chair-time is reduced and less incisor proclination

Examples are Damon, Smartclip and In-Ovation (Fig. 14.10, 14.11)

75 Fig. 14.10 In-Ovation self-ligating brackets

76Damon bracket

Fig. 14.11 In-Ovation self-ligating system

75

Picture taken from http://www.gacintl.com/UserFiles/Image/group.jpg 76

Picture taken from http://www.simonorthodontics.com/Portals/0/DQ_Bracket_Wire.jpg

http://www.gacintl.com/UserFiles/Image/group.jpg

http://www.simonorthodontics.com/Portals/0/DQ_Bracket_Wire.jpg


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14.7 Decalcification, gingivitis and fixed appliance

Plaque gets accumulated much easier in the presence of a fixed attachment.

Demineralization of enamel surface can occur if patient has poor oral hygiene and

consumes diet rich in sugar/ refined carbohydrate.

Patients with poor oral hygiene can also have gingivitis (Fig. 14.12).

To avoid or reduce the incidence of decalcification during fixed appliance treatment:

a) Select patients who have good oral hygiene and are able to maintain good

oral hygiene.

b) Use fluoride mouth rinse for the duration of orthodontic treatment.

c) Use fluoride-release cements and bonding adhesive (e.g. glass ionomer

cements), if possible.

Fig. 14.12 Accumulation of plague and severe gingivitis

due to poor oral hygiene


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Chapter 15 CLASS I MALOCCLUSION

15.1 Incidence

This is the most common malocclusion.

50-55% of Caucasian have Class I malocclusion

15.2 Aetiology

15.2.1 Skeletal

The skeletal pattern is usually Skeletal Class I (Fig. 15.1), but it can also be Class II or Class III with inclination of the incisors compensating for the underlying skeletal discrepancy.

There may be mild transverse skeletal discrepancy

There may be increased vertical proportions (lower face height) and anterior open bite.

Fig. 15.1 Skeletal 1

77

A Class I malocclusion associated with a Class I skeletal pattern.

77

Picture taken from Walther & Houston’s Orthodontic Notes


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15.2.2 Soft Tissues In most cases of Class I malocclusion, soft tissues is not an aetiological factor,

Except in bimaxillary protrusion, where the upper and lower teeth are proclined due to pressure from the tongue in the presence of the lack of lip tone.

15.2.3 Dental Factors Dental factors are the main aetiological cause in Class I malocclusion.

The most common are tooth/arch size discrepancies, leading to crowding or spacing.

Early loss of deciduous teeth, displaced or impacted teeth, and anomalies in size, number & form can cause a localized malocclusion.

15.3 Occlusal features

Class I incisor relationship

Molar relationship varies. Extraction of teeth mesial to the molars will cause mesial drift of the molars.

Crowding usually occur in 3s, 5s areas because they are the last teeth to erupt

Occasional crossbite with associated mandibular displacement and centreline shift.

15.4 Treatment aims 1. To improve the aesthetics of the teeth and the function of the teeth and jaws. 2. To relieve crowding and produce alignment of the teeth within the arches. 3. If necessary, to reduce a deep overbite and improve the interincisal angle.

15.5 Treatment planning

Treatment of the upper and lower arches must be coordinated.

Plan treatment of the lower arch first, then plan the treatment of the upper arch in relation to the lower arch.

To have a stable result at the end of the treatment, usually the original size and the form of the lower arch must not be changed.

As a general rule in Class I cases, if extractions are necessary in the lower arch, matching teeth should be extracted from the upper arch.


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15.6 Treatment options

15.6.1 No treatment Many mild malocclusions can and should be accepted. (Fig. 15.2)

Fig. 15.2 Spacing on upper incisors can be filled with composites or veneers.

15.6.2 Extractions

In moderate crowding, where teeth are favourably inclined, e.g. mesially inclined canines that are erupting, extraction of first premolars will create space for the spontaneous erupting of the canines.

Similarly, loss of lower first premolars will relieve the vertical impaction of the second premolars and they should erupt into occlusion.

Note: There can be no guarantee that this spontaneous change will occur in all cases. The patient should be reviewed regularly.

Approximately 9 months after the extractions most of the spontaneous movement of teeth would have taken place. A decision will need to be taken regarding further active treatment, if spontaneous alignment is not fully achieved.

15.6.3 Removable appliances For teeth that are favourably tipped, upper removable appliance can be used to tip teeth

mesiodistally or labiopalatally.

Lower removable appliances are seldom used as they are difficult to fit, constrict the tongue space and have limited space for the active components.

15.6.4 Single arch fixed appliances The „2 x 4‟ single arch fixed- bands on the molars (the „2‟) and bonded brackets on the

incisors (the „4‟) can be used to produce alignment of the anterior teeth.

This appliance may be placed on the upper or lower arches.

This is particularly useful if there are incisor rotations. Note : A full single arch fixed gives better control of all the teeth compared to 2 X 4.


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15.6.5 Upper and lower arch fixed appliances (Fig. 15.3) This appliance gives the best control of all the teeth and a high standard of result.

In the severely crowded mouth with anterior and/or posterior rotations, this is the treatment of choice. (Fig. 15.4)

Fig. 15.3 Severe crowding in the lower arch and distally inclined canines.

This case need to be treated with fixed appliance.

Before treatment. Near finishing with fixed appliance.

At the completion of fixed orthodontic treatment.

Fig. 15.4 A Class I malocclusion treated by fixed appliance


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15.7 Post-treatment stability

Correction of rotations is one of the major problems of post-treatment stability. The various method to enhance stability are: a] Over-correction Over-derotation of the rotated tooth will allow the tooth to settle in its correct position. b] Pericision

In pericision the supracretal periodontal fibers that run between the tooth and gingiva are “cut”.

The amount of relapse is reduced in the derotated teeth which have had pericision. c] Long-term retention

Full-time retention for more than 9 months. Part of this may be achieved by correcting rotations early in treatment.

Use a bonded retainer on the derotated tooth and its adjacent teeth (Fig. 15.6) d] Combined treatment Any of the above combinations.

Fig. 15.6 A bonded retainer


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Chapter 16 CLASS II DIVISION 1 MALOCCLUSION

16.1 Incidence For Caucasians, Class II division 1 is the second most common malocclusion,

accounting for about 15-20% of all malocclusions.

16.2 Aetiology

16.2.1 Skeletal (Fig. 16.1, 16.2) Usually Class II (in Caucasian, mostly due to a retrognathic mandible)

May be Class I or mild Class III

Anterior vertical facial proportion varies (low/ normal/ high angle)

Fig. 16.1 A Class II division 1 incisor relationship on a Class II Skeletal pattern

with retrognathic mandible and incompetent lips.

78

Fig. 16.2 A Class II Division 1 malocclusion associated with a Class II skeletal pattern

78



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16.2.2 Soft tissues i) Lips

Lips are normally incompetent due to the proclination of the upper incisors and/or Class II skeletal pattern

In patients with reduced lower face height the lower lip may be drawn behind the upper incisors in order to achieve anterior oral seal (also known as lip trap). This can result in the proclination of upper incisors and/or retroclination of the lower incisors, which worsen the increased overjet (Fig. 16.3).

A hyperactive lower lip (increased mentalis activity) can cause retroclination of the lower incisors which results in an increase of overjet.

a) b)

c) Fig. 16.3 (a )In this patient, the lower lip lies behind the upper incisors (also known as lower lip

trap) which has been proclined. (b) Intra-oral side-view showing upper incisors being proclined. (c)Intra-oral front view showing upper incisor proclination and increased overjet.

ii) Tongue

In patient with increased lower face height and/or grossly incompetent lips, the tongue usually comes forward to contact the lower lip in order to achieve anterior oral seal. The tongue may procline the lower incisors, helping to compensate for the Class II skeletal pattern.

16.2.3 Dental factors In crowded arches, the upper incisors may be proclined due to the lack of

space in the anterior segment.


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16.2.4 Habits

Habitual digit sucking (Fig. 16.4) can cause:

Proclination of upper incisors

Retroclination of lower incisors

Incomplete overbite or a localized anterior open bite

Narrowing of upper arch

Fig. 16.4 Malocclusion due to fingers sucking

16.3 Occlusal and dento-alveolar features

The lower incisor edges lie posterior to the cingulum plateau of the upper incisor (Fig. 16.5).

Overjet is increased with possible trauma to gingival palatal to 1 1

Upper incisors may be proclined or upright

Overbite varies – increased/ normal/ incomplete/ open bite (Fig. 16.5, 16.6).

Molars are usually Class II unless there is mesial drift due to early loss of deciduous teeth.

If lips are grossly incompetent, drying of upper labial gingivae may worsen pre-existing gingivitis.

Fig. 16.5 Class II division 1 malocclusion with increased overjet and at risk of trauma.


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Fig. 16.6 Class II division 1 malocclusion with anterior open bite.

16.4 Treatment aims

to improve the esthetics of the teeth and the function of the teeth and jaws.

to relieve crowding and produce alignment of the teeth within the dental arches.

to reduce the overjet but not at the expense of worsening the upper lip contour.

to reduce the overbite and achieve a stable inter-incisal angle.

to achieve a good intercuspation between upper and lower buccal teeth. This would usually be Class I, but could be Class II in appropriate cases.

16.5 Treatment planning During treatment planning, the clinician needs to consider: i) Patient’s age

Functional appliance can be used during pubertal growth spurt for patients with retrognathic mandibles.

It is easier to reduce overbite in a growing patient.

In adult patients, a lack of growth will limit the choice of treatment options.

ii) Skeletal pattern

It is difficult to treat patients who has marked antero-posterior discrepancy and/or significant increased or reduced vertical skeletal proportions

Overjet reduction will unlikely be stable in patients with increased vertical skeletal proportions and marked incompetent lips. This is because the upper incisors would not be controlled by lower lip at the end of treatment. Prolonged retention is needed.

Severe skeletal pattern will need to be treated by orthognathic surgery


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iii) Pattern of mandibular growth

Correction of incisor relationship in a child with increased vertical skeletal proportions and a backward rotational growth pattern has a poorer prognosis for stability.

iv) Space requirement. Refer to chapter 10.

16.5.1 The lower arch

The lower arch should be planned first.

Usually the original form of the lower arch must not be changed.

Proclination of the lower incisors is only acceptable if they are in a retroclined position.

Space will also be required in the lower arch in order to level the curve of Spee.

If there is crowding, teeth usually have to be extracted.

16.5.2 The upper arch

Extraction may be required to relieve crowding and to reduce the overjet.

If lower extractions are required, then the upper extractions will be necessary.


16.6.1 No treatment A mild Class II division 1 incisor relationship may be acceptable.

16.6.2 In Class I or mild Class II skeletal pattern a) Upper Removable appliance

Indications:

The patient is growing. This helps the overbite reduction.

FMPA slightly reduced/ average

Lower arch is acceptably aligned and not crowded, or is moderately crowded with 3 3 mesially inclined and no incisor rotations

3 3 mesially inclined

21 12 aligned and proclined Contraindication:

Patient has severe overjet (Fig. 16.7)


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Typically, treatment of Class II division 1 using removable appliance will involve the following stages:

Extraction of 4 / 4 Lower 1st premolars may be extracted if the lower arch is crowded. In a growing child, spontaneous space closure will likely to occur if canines are mesially angulated.

First Upper removable appliance with: - Adams clasps on 6 / 6 ; Southend clasps on 1 / 1 - Finger springs or buccal canine retractor on 3 / 3

- Anterior bite plane for overbite reduction.

once the canines have been moved distally into a Class I relationship with the lower canines, a Second appliance for overjet reduction and maintenance of overbite reduction will be needed as follows:

- Adams clasps on 6 / 6 - Guard wire at mesial of 3 / 3 - Labial bow to reduce overjet - Anterior bite plane to maintain overbite reduction.

The acrylic should be trimmed progressively from behind the upper incisors to provide space for their palatal movement. The guard wire mesial to the canines will have to be removed in the later stages of treatment to allow contact between canine and lateral incisor.

Once overjet reduction is complete the same appliance with a passive labial bow may be used as a retainer. If it is unsuitable, a Third appliance will be necessary.

The usual design for a retainer is as follows: - Adams clasps on 6 / 6 - Hawley bow (labial bow) This should be worn full time for 6 months followed by 6 months at night-time.

79

Fig. 16.7 When the overjet is large and if the upper incisor angle is normal (not increased), retraction with a removable appliance will produce a Class II division 2 incisor relationship.

This is not an acceptable treatment option.

79



165

b) Fixed appliances (Fig 16.8) Indications:

the angulation of the canines is unsuitable for simple tipping movement

the upper incisors are already at their correct inclination to the maxillary plane

there are anterior and/or posterior rotations

the lower incisors are proclined or retroclined

controlled space closure of residual space in the extraction site is required

there is an increased and complete overbite in an adult

Before treatment (April 2005). Fixed appliance (Jan 2006)

Treatment completed (December 2006)

Fig. 16.8 A Class II div 1 malocclusion treated with fixed appliance.

16.6.3 Moderate to severe Class II skeletal pattern

a) Growth modification

Indicate for patient during pre-pubertal and pubertal growth spurt

Use functional appliance (Fig. 16.9) or headgear, or both


166

Before treatment with Functional appliance After treatment (slightly “over-treated”)

Facial profile. Before treatment. After treatment with Functional appliance.

Fig. 16.9 Patient treated with a Functional appliance

b) Orthodontic camouflage

This usually involves premolar extractions and fixed appliance to bodily retract the upper incisors.

The amount of bodily movement of the upper incisors that can be retracted by fixed appliance is limited by the availability of cortical bone palatal to the upper incisors and by patient‟s facial profile.

c) Orthognathic surgery

Indicated for very severe skeletal discrepancies – anteroposterior/ vertical/ transverse


167

16.7 Post-treatment stability

The aim of treatment is to bring the upper incisors under the control of the lower lip. This usually means that the lower lip should overlap the incisal third of the upper incisors. (Fig. 16.11a, b)

Prognosis is good if upper incisors can be retracted to a position of soft tissue balance and are controlled by the lower lip.

If this lip control cannot be achieved, some form of permanent retention may be necessary after a “normal period” of retention (6 months full time followed by 6 months night only):

1] Hawley retainer worn on alternate nights (Fig. 16.12) 2] A bonded lingual retainer.

80 Fig. 16.11 a, An adaptive anterior oral seal with contact between the tongue and lower lip.

b, Following retraction of the upper incisors, an anterior seal will be obtained by lip contact. The lower lip covers the incisal third of the upper incisors and this will ensure stability of the overjet reduction.

Fig. 16.12 Hawley retainers

80


a b


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Chapter 17 CLASS II DIVISION 2 MALOCCLUSIONS

17.1 Incidence It occurs in approximately 10% of Caucasians.

17.2 Aetiology

17.2.1 Skeletal pattern (Fig. 17.1) Usually mild Class II but may be Class I or mild Class III skeletal pattern

Usually a reduced FMPA and increased overbite

17.2.2 Soft tissues Lips are usually competent with a high lower lip line. This tends to retrocline

the upper incisors.(Fig. 17.2)

Active muscular lips can cause bimaxillary retroclination of upper and lower incisors.

17.2.3 Dental Crowding is commonly seen due to retroclination of the incisors.

Lack of an effective occlusal stop to the eruption of the lower incisors may result in increased overbite and increased inter-incisal angle

Upper incisors may have a more acute crown and root angulation.

Fig. 17.2 A high lower lip line causing retroclination of the upper central incisors and lip trap causing proclination of 2|

17.2.4 Occlusal features

Lower incisors occlude posterior to the cingulum plateau of upper incisors. Typically: 1 1 retroclined; 2 2 proclined and mesiolabially rotated; overbite is deep

and complete; overjet is minimal or slightly increased (Fig. 17.3)

Occasionally 21 12 and 21 12 are retroclined with 3 | 3 erupting bucally

Overbite may be traumatic in severe Class II skeletal pattern

Mild Class II buccal segment relationship

In a more severe Class II skeletal pattern there may be scissor bite of first or second premolars due to the relative position and widths of the arches (Fig. 17.4).


169

Fig. 17.3 Typical features of Class II division 2 malocclusion

Fig. 17.4 Lingual crossbite (scissor-bite) at premolar region.


170

81

Fig. 17.5 A Class II Division 2 malocclusion associated with a moderate Class II skeletal pattern.

17.3 Treatment aims

To improve the esthetics and the function of the teeth and jaws, but not to jeopardize the lip and facial profile.

To relieve crowding and produce alignment of the teeth within the arches.

To reduce excessive overbite. If overbite is to be reduced, the interincisal angle must also be reduced by torquing back the upper incisor apices with a fixed appliance.

To reduce the overjet, if the overjet is increased.

17.4 Treatment planning

Assess the lower arch to estimate the space requirements, especially in relation to crowding, overbite reduction and flattening the curve of Spee.

To obtain a nice profile and a good finishing interincisal angle, the incisors may on occasion need to be proclined as part of the treatment plan.

Stable correction of Class II division 2 incisor relationship is difficult. It requires a reduction of the overbite and reduction of the interincisal angle to between 125° and 135°

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There are several ways to reduce the inter-incisal angle in Class II division 2 malocclusion:

Torqueing the incisor roots palatally/ lingually with a fixed appliance.

Proclination of lower labial segments (only if they are trapped lingually by the upper labial segment)

Proclination of the upper labial segments followed by the use of functional appliance in a growing child with well-aligned lower arch.

A combination of the above methods.

Orthognathic surgery for patients with severe Class II skeletal pattern and/or reduced vertical skeletal proportions.


17.5.1 No treatment In mild Class II division 2 malocclusions where the facial appearance and overbite is acceptable, and the incisors are neither too retroclined nor too crowded.

17.5.2 Class I or mild Class II skeletal pattern

a) Where overbite and retroclination of 1 | 1 or 21 | 12 are acceptable and space requirement is mild:

Confine treatment to relief of upper arch crowding and upper labial segment alignment.

Treatment may be performed using upper removable appliance:

First, retraction of the upper buccal segments distally (e.g. using en masse appliance) is performed. [The pretreatment upper 1st permanent molars must not be inclined distally. Extraction of upper 2nd permanent molars may be indicated if 3rd molars are present and of good size/ position.] Second, use a removable appliance with a labial spring to tuck a single proclined lateral incisor into the arch. b) If the lower arch is acceptable, upper arch is mildly crowded with ≤ ½ a unit Class II molar relationship

Move the upper buccal segment distally with headgear (may require extraction of 7|7), followed by upper canines retraction to provide space to align the upper incisors.

If patient does not cooperate in wearing the headgear, extract 5 | 5 and treat with fixed appliance.

If buccal segment relationship is a full unit Class II, or extraction of 5 | 5 is required to relief crowding, extraction of 4 | 4 is usually indicated.


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c) Where overbite and retroclination of 1 | 1 or 21 | 12 are to be corrected.

This is indicated where the overbite is deep and complete on gingival or palatal tissue with existing or potential trauma.

Use fixed appliances to reduce overbite and to reduce the inter-incisal angle by proclining the incisors or in combination with palatal/lingual root torque (Fig. 17.6)

Extractions is required if lower arch crowding is severe.

Space for correction of the incisal relationship and for relief of crowding can be obtained by upper arch extractions or by distal movement of the buccal segment (using headgear)

For stability of overbite correction, reduce the inter-incisal angle to between 125° to 135°.

Before treatment. May 2005 With fixed appliance.

Completed. June 2007

Fig. 17.6 A Class II div 2 malocclusion treated with fixed appliance.

17.5.3 Moderate or severe Class II skeletal discrepancy

a) Growth modification

This is indicated in growing patients with mild to moderate Class II skeletal pattern.

If upper incisors are retroclined, it may be helpful i. to have a pre-functional phase to procline them by using a removable appliance or

use a sectional-fixed appliance on the upper incisors, ii. if using Twin block appliance, to incorporate a Z-spring into the appliance to

procline the upper incisors Note: May need to include a screw to expand the upper arch


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After the anteroposterior correction by functional appliance, fixed appliance may be required to detail the occlusion.

Pretreatment Jun 2010 Dec 2010

Fig. 17.7 Upper incisors proclined with 2 x4 appliance, prior to functional appliance

b) Orthognathic surgery In the more severe forms of malocclusion where the facial profile is poor and the overbite is very deep and traumatic, a combination of orthodontics and jaw surgery is the best approach.

17.6 Retention phase The retention phase in Class II division 2 malocclusion is particularly important in

order to prevent relapse.

De-rotation of the upper lateral incisors and overbite reduction are prone to relapse.

Use bonded retainer on the upper lateral incisors (to prevent rotation)

Flat anterior bite plane on upper removable appliance retainer is recommended until growth is complete to promote overbite stability (to prevent an increase in overbite).


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Chapter 18 CLASS III MALOCCLUSIONS

18.1 Incidence Class III malocclusion is found in about 3% of the Caucasians population.

18.2 Aetiology

18.2.1 Skeletal pattern (Fig. 18.1) i) Class III is usually associated with:

a long mandible

a forward position of the glenoid fossae on the skull base, so that the mandible is more anteriorly positioned than normal.

a short maxilla

more retruded position of the maxilla leading to maxillary retrusion

short anterior cranial base

or a combination of the above factors. ii) FMPA may be reduced/ average/ increased iii) May have transverse discrepancy with a narrow maxilla and wide mandible

18.2.2 Soft tissues

Where lips are competent, dento-alveolar compensation (proclination of upper incisors & retroclination of lower incisors) usually occurs naturally. This will mask the severity of the Class III skeletal pattern.

If the vertical skeletal proportions (FMPA) is increased and lips are incompetent with anterior open bite, the lower incisors may be proclined.

18.2.3 Dental (Fig. 18.2a, b)

The maxilla is often narrow and short, resulting in crowding

The mandible is usually broad. Therefore the lower arch is usually well aligned or evenly spaced.

. maxilla and a long mandible.

Fig. 18.1 A high angle Class III patient with a normal maxillary and long mandibular length

A high angle Class III patient with a retruded (short) maxilla and long mandibular length


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a) b) Fig. 18.2a Class III malocclusion with Fig. 18.2b A Class III malocclusion with crowded anterior and buccal crossbite. maxillary arch and anterior crossbite.

18.2.4 Occlusal features (Fig. 18.2a, b)

Class III incisor relationship.

the lower incisor edges occlude anterior to the cingulum plateau of the upper incisors. a] Labial segments

The upper incisors are often crowded and they are usually proclined.

The lower incisors - may be slightly crowded but they are often spaced. - are frequently retroclined.

There may be a reverse overjet b] Buccal segments

There may be a unilateral or bilateral crossbite in the buccal segments.

A unilateral crossbite is usually associated with lateral displacement of the mandible to obtain maximal intercuspation.

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Fig. 18.3 A Class III malocclusion associated with a Class III skeletal pattern.

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There are two types of Class III malocclusion: 1. True Class III (also known as Skeletal Class III or True mesio-occlusion)

2. Pseudo Class III (also known as Neuromuscular Class III or Pseudo mesio-occlusion) [Fig. 18.4]

For Pseudo Class III, when the mandible is in centric relation, the incisors would meet edge-to-edge (with the posterior teeth out of occlusion). But, in order to obtain a position of maximal occlusion, there is a forward displacement of the mandible. Thus creating a reverse overjet. Patient has Class I skeletal pattern, upper incisors are retroclined while lower incisors are proclined.

Fig. 18.4 Patient can achieve edge-to-edge Reverse overjet during centric occlusion. in centric relation.

18.3 Treatment Planning Factors that need to be considered during treatment planning: i) The patient’s opinion regarding their facial appearance and occlusion.

Is the facial profile acceptable or is orthognathic surgery needed to correct the skeletal pattern? ii) The severity of the skeletal pattern both anteroposteriorly and vertically.

For patients who have an anterior open bite or cannot obtain an edge-to-edge occlusion of the incisors by retracting the mandible, the prognosis for correction of the reverse overjet is poor (may need surgery to correct).

iii) A normal or increased overbite is important for stability.

Would there be an overbite following correction of the reverse overjet? If not, correction of the overjet will not be stable. iv) If patient can achieve edge-to-edge incisor contact where incisors have minimal dento-alveolar compensation, there will be a better prognosis in correcting the incisor relationship. v) The pre-existing incisor angulations.

If there is already an increased dento-alveolar compensation, treatment by proclining the upper incisors and/or retroclining the lower incisors may not be possible or stable.

If the upper incisors are already proclined, it may not be possible to tip them further forwards as this may promote periodontal breakdown.

The limit of acceptable compromise is an upper incisor angle of 120° to the maxillary plane and a lower incisor of 80° to the mandibular plane.

vi) Take into consideration of the degree of crowding in the upper and lower arch.


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18.4 Prognosis of treatment The prognosis is more favourable in patient who has:

Skeletal pattern is Class I or mildly Class III

Average or low FMPA

Average or deep overbite

Upper arch crowding

Proclined lower incisors

Ability to achieve edge-to-edge incisor relationship

18.5 Treatment

18.5.1 Accept

When the skeletal pattern is mildly Class III and/or incisor relationship is acceptable with minimal crowding and no mandibular displacement.

18.5.2 In Class I or mild Class III skeletal pattern

i) If overbite is minimal

Accept incisor relationship and align teeth (may need extractions). ii) If ovebite is normal or increased and upper incisors are upright, treat by proclining the upper incisors.

This is best done during the early mixed dentition when the upper canines are still high above the roots of the upper lateral incisors.

Treatment options: 1) Removable appliances

Only anterior crossbite associated with Pseudo Class III can be treated with removable appliances. a] Upper arch Removable appliances can be used to procline the upper incisors if they are retroclined or of average inclination. Active components : Z - spring or screw . Bite plane: Posterior bite plane b] Lower arch

Usually no treatment is needed.

If lower incisors are proclined and spaced, they may have to be retracted by using a lower removable appliance with labial bow (Fig. 18.5)


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2) Mandibular inclined plane.

Mandibular inclined plane is normally used for patients aged 7 - 9 years old who have anterior crossbite with deep overbite.

Don‟t wear it for more than 6 weeks.

3) Single arch fixed appliance

A 2 X 4 upper fixed appliance may be used to correct the Pseudo Class III anterior crossbite during the mixed dentition (Fig. 18.6).

a. b. a) Start of treatment b) Six months later

Fig. 18.5 Pseudo Class III with lower incisor spacing treated with a lower removable appliance.

Before treatment Start of treatment

Six months later. Start of full mouth fixed appliance to correct malocclusion. Fig. 18.6 A mild Class III case treated initially with 2 X 4 fixed appliance.


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18.5.3 In mild to moderate Class III Skeletal pattern When overbite is average or increased, patient‟s maxilla is retrusive, treat with:

1. Growth modification

By using a Reverse-pull headgear attached to a maxillary splint (Fig. 18.7 & 18.8).

It can advance the position of the maxilla in patient around 8-10 years old.

The reverse-pull headgear causes some downward and backward rotation of the mandible, which helps in reducing the severity of anteroposterior skeletal Class III pattern.

2. Orthodontic camouflage

By using fixed appliance (Fig. 18.8)

Correct the incisor relationship by retroclination of the lower incisors and/or proclination of the upper incisors.

Extraction of lower first premolars are usually required to allow retroclination of lower incisors.

Intermaxillary Class III elastic traction can be used to help move the upper arch forwards and lower arch backwards (Be careful not to extrude the molars as this will reduce the overbite).

Fig. 18.7 A maxillary splint and elastics

Reverse-pull headgear


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Before treatment. Centric Occlusion Centric Relation (July 2007)

Patient wore the occlusal splint and reverse head gear (July 2007)

After wearing reverse headgear (Nov 2007). End of treatment after fixed appliance (Apr 09)

a) Before treatment. b) After wearing reverse headgear. c) End of treatment.

Fig. 18.8. A ten year old girl with a retrusive maxilla was treated with a reverse headgear and

fixed appliance.


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18.5.4 In severe Class III skeletal pattern

Either just align the arches and accept the Class III incisor relationship or

Treat with orthognathic surgery with orthodontic decompensation

18.6 Post-treatment stability Stability of overjet correction depends on an adequate overbite and on a favorable facial growth. Note:

The true Class III is most difficult to treat.

Pseudo Class III is usually easy to treat when treated early in a young patient.

Anterior crossbites should be treated early.


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Chapter 19 TISSUE CHANGES WITH TOOTH MOVEMENT

19.1 Introduction

Orthodontic tooth movement involves two interrelated processes: the bending of alveolar bone and remodelling of the periodontal tissues.

A periodontal ligament placed under pressure will result in bone resorption whereas a periodontal ligament under tension results in bone formation.

19.2 TYPES OF TOOTH MOVEMENT

a) Tipping movement (Fig. 19.1) This is produced by removable appliances. With light forces the fulcrum is at a point about 40% of the length of the root from the apex. With tipping movements, areas of maximum pressure and tension are concentrated at the apical and cervical regions of the root.

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Figure 19.1. The effects of tipping force. A, areas of bone deposition. B, areas of resorption

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Compression

areas

Tension areas


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b) Bodily movement and Rotation This is produced by fixed appliance. With bodily movements, the force is distributed reasonably evenly along the root axis. More force is needed to produce bodily movement.

c) Extrusion and intrusion This is usually produced by fixed appliance. Less force is needed to intrude a tooth as the force is being concentrated at the small apical area.

19.3 TISSUE CHANGES

1. The tissue changes produced depend mainly on the amount (magnitude) and duration of the force used.

2. Orthodontic movement is possible because cementum is more resistant to resorption than bone. Both vital & non-vital teeth can be moved.

3. Within the first 24 hours after the application of the force, the tooth moves some way through the periodontal space, setting up areas of tension and compression within the periodontium.

19.3.1 Areas of pressure

1. Light Pressures (e.g. 30g [1 oz] per single tooth for tipping movement ) - The periodontal ligament is compressed but not crushed. - The blood vessels are still patent. - Within 24-48 hours osteoclasts appear along the bone surface and direct bone resorption proceeds. This process is known as frontal resorption (Fig. 19.2). - Within the cancellous spaces, deposition of osteoid (new bone) takes place. **For tipping movement a very light force should be applied initially and this can be increased to about 30g (1oz) for a single rooted tooth. Heavier forces may be used for bodily tooth movement as the force is more evenly distributed throughout the periodontal ligament.

2. Heavy Forces

Heavy forces lead to pain.

The periodontal ligament is crushed between the tooth and the socket wall.

The blood vessels are occluded thus the blood flow is totally cut off in that area. Therefore differentiation of osteoclast is not possible

The periodontal ligament becomes acellular and hyaline in appearance (known as hyalinization). (Fig. 19.3)

These hyalinized areas are often fairly localized, and adjacent to them and within the cancellous spaces of the underlying bone osteoclasts appear.


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After several days, the osteoclast in the marrow spaces adjacent to a cell-free zone (necrotic) in the periodontal ligament area begins to remove the cortical bone of the alveolar wall. This process in known as undermining resorption. The osteoclasts also removed the hyalinized areas and attack the cementum area of the root. (Fig. 19.4)

Hyalinization and undermining resorption cause delay in tooth movement. This is because there is a delay in stimulating differentiation of cells within the marrow spaces and, a considerable thickness of bone and necrotic tissues need to be removed from the underside before any tooth movement can occur. This causes a delay of 10-14 days before tooth movement can continue.

When excessive force is used, it is very likely that the anchor teeth may move as the amount of force applied is heavy enough to encourage movement of larger rooted teeth. On the other hand, the tooth that is desired to move will often move very little due to loss of anchorage.

When excessive force is used, there is more problem of root resorption (especially at the apical area).

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Fig 19.2 Pressure site of a tooth being moved by light forces. Frontal resorption by osteoclasts.

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Picture taken from http://www.nature.com/bdj/journal/v196/n7/fig_tab/4811129a_F1.html

Blood vessels Osteoclasts Alveolar bone

Tooth

http://www.nature.com/bdj/journal/v196/n7/fig_tab/4811129a_F1.html


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85Fig. 19.3 Hyaline (H) areas (pink color) in the periodontal ligament formed due to use of

continuous heavy forces

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Fig. 19.4 Photo showing undermining resorption. Focal hyalinization of the periodontal ligament at the pressure side which a heavy force was applied for seven days. T indicates tooth; B, bone; H, hyalinization. Undermining resorption of alveolar bone by osteoclasts from the marrow spaces (arrow )

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Picture taken from

http://www.scielo.br/scielo.php?pid=S217694512010000100003&script=sci_arttext&tlng=en 86

Picture taken from Murray C. Meikle. The tissue, cellular, and molecular regulation of orthodontic

tooth movement: 100 years after Carl Sandstedt. European Journal of Orthodontics 28 (2006) 221–240

http://www.scielo.br/scielo.php?pid=S217694512010000100003&script=sci_arttext&tlng=en


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19.3.2 Areas of tension

Initially there is a proliferation of fibroblasts and preosteoblasts & the periodontal fibers become elongated.

The preosteoblasts migrate toward the alveolar bone surface, along the stretched Sharpey‟s fibers. Simultaneously, PDL fibroblasts in tension zones begin multiplying and remodeling their surrounding matrix.(Fig. 19.5)

Osteoid tissue is deposited along the bone surface in spicules by osteoblasts, lying in the direction of the stretched periodontal fibers (Fig. 19.6, 19.7). The osteoid tissue is progressively replaced by bundle bone.

Where heavy forces have been used, the periodontal fibers on the tension side may be torn and blood vessels ruptured.

When the tooth is being moved labially or palatally, modelling resorption and deposition on the external alveolar surface, particularly in the marginal region, will maintain the thickness and contour of the alveolar plates.

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Fig. 19.5 Photomicrograph showing osteoblasts (OB) covering the bone surface at the tension side to which a force was applied for 20 days. Alkaline phosphatase staining.

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Picture taken from Martina Von Böhl, etal. Changes in the Periodontal Ligament After Experimental Tooth

Movement Using High and Low Continuous Forces in Beagle Dogs. Angle Orthod 2004; 74:16–25.


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Fig. 19.6 At tension side. New bony trabeculae ( ) extending into the periodontal ligament (P) space. (R) is root; (B) is the aveolar bone

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Fig. 19.7 Tension side. View under electro-microscope at day five.

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Photo taken from G.E. Wise and G.J. King. Mechanisms of Tooth Eruption and Orthodontic Tooth Movement.

J Dent Res 87(5):414-434, 2008

New bone spicules formed.


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19.4 89Physiologic Response to Sustained Pressure against a tooth

TIME

Light pressure

Heavy pressure

Event

<1 sec

PDL fluid incompressible, alveolar bone bends, piezoelectric signal generated.

1-2 sec PDL fluid expressed, tooth moves within PDL spaces

3-5 sec Blood vessel within PDL partially compressed on pressure side, dilated on tension side; PDL fibers and cells mechanically distorted.

Minutes Blood flow altered, oxygen tension begins to change; prostaglandins & cytokines released.

Hours Metabolic changes occurring; Chemical messengers affect cellular activity, enzymes levels change

~4 hours Increased cAMP levels detectable; cellular differentiation begins within PDL

~ 2 days Tooth movement beginning as osteoclasts/osteoblast remodel bony socket.

3-5 sec Blood vessels within PDL occluded on pressure side.

Minutes Blood flow cut off at compressed PDL area.

Hours Cell death in compressed area.

3-5 days Cell differentiation in adjacent marrow spaces, undermining resorption begins.

7-14 days

Undermining resorption removes lamina dura adjacent to the compressed PDL; tooth movement occurs.

PDL = periodontal ligament

19.5 THEORIES OF ORTHODONTIC TOOTH MOVEMENT Orthodontic tooth movement is made possible by the application of prolonged forces. Prolonged force, even at low magnitude, produces remodeling of the adjacent bone.

19.5.1 Bioelectric theory When alveolar bone flexes and bends, it produces stress-generated electric signals which cause changes in bone metabolism and tooth movement. i) Piezoelectric effect

The application of force causes distortion of the collagen and bone which produces a flow of electric current as electrons are displaced from one part of the crystal lattice to another. (Bending flow of electrons current)

These electric potentials are short-lived and very small. Therefore probably play little or no active role in tooth movement.

The stress-generated signals are important in the maintenance of normal skeletal function (skeletal regeneration and repair). Without such signals, bone mineral is lost and general skeletal atrophy will occur.

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Table taken from Contemporary Orthodontics by W.R. Proffit etal.


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The signals generated by the bending of alveolar bone during normal chewing are important for the maintenance of bone around the teeth, but it probably has little to do with the response to orthodontic tooth movement.

ii) Bioelectric potential at cell membrane level

Bioelectric potential can be observed in bone that is not being stressed.

Metabolically active bone or connective tissue cells (in area of active growth and remodeling) produce electronegative charges that are generally proportional to how active they are.

Although the purpose of bioelectric potential is not known, cellular activity can be modified by adding the exogenous electric signals.

Animal and human experiments have shown that: - when an exogenous electrical currents (low voltage) is applied to the alveolar bone in conjunction with orthodontic forces, it enhances cellular activities in the PDL and alveolar bone, as well as faster tooth movement. - a pulsed electromagnetic field increased tooth movement by affecting the cell membrane potentials and permeability, and thereby triggers changes in cellular activity.

19.5.2 Pressure-Tension theory

When a sustained pressure (force) is applied to a tooth, it causes the tooth to shift position within the PDL space, compressing the ligament in pressure areas while stretching it in tension areas.

Pressure and tension within the PDL alters the blood flow. - Pressure reduces the diameter of blood vessels whereas tension increases the

diameter of blood vessels. Thus alters the blood flow. Alterations in the blood flow quickly create and release chemical messengers such as

prostaglandin and cytokines. - These chemical changes, acting either directly or by stimulating the release of

other biologically active agents, then would stimulate cellular differentiation and activity which ultimately causes tooth movement.

This theory of tooth movement can be shown in 3 stages: i) alterations of blood flow ii) formation and/or release of chemical messengers iii) activation of cells

Note: both bioelectric theory and pressure-tension theory may play a part in the biologic control of tooth movement.

19.5.3 Mechanobiology of tooth movement theory (Henneman et al. 2008) The theoretical model describes four stages in the induction of tooth movement. These stages are as follows: (1) Matrix strain and fluid flow ( Fig. 19.8a ). Immediately after the application of an external force, strain in the matrix of the PDL and the alveolar bone results in fluid flow in both tissues. (2) Cell strain ( Fig. 19.8b ). As a result of matrix strain and fluid flow, the cells are deformed. (3) Cell activation and differentiation ( Fig. 19.8c ). In response to the deformation, fibroblasts and osteoblasts in the PDL as well as osteocytes in the bone are activated. They produce cytokines and other mediators which lead to remodeling of PDL and alveolar bone. (4) Remodelling ( Fig. 19.8d ). A combination of PDL remodelling and the localized apposition and resorption of alveolar bone enable the tooth to move.


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90

Figure 19.8. A theoretical model of tooth movement. The model describes 4 different stages in the induction of tooth movement. Frame (a) represents matrix strain and fluid flow, (b) cell strain, (c)

cell activation and differentiation, and (d) remodeling of periodontal ligament (PDL) and bone. (ECM = extra cellular matrix)

90

S. Henneman , J. W. Von den Hoff and J. C. Maltha (2008). Mechanobiology of tooth movement. European

Journal of Orthodontics 30: 299–306


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19.6 The rate of tooth movement

19.6.1 Rate

About 1mm per month may be regarded as an acceptable rate of tooth movement.

19.6.2 Factors that affect the rate of tooth movement

Differences in bone metabolic capacity, bone density, morphological differences, and genetic factors could influence the remodeling process and subsequent tooth movement.

a] Age Tooth movement in adult is slower than in children. In the adult the periodontal ligament is much less cellular than in the child. In addition, the alveolar bone in children is less dense than in older patients. b] The force applied Both light and heavy forces will result in orthodontic movement. However it is generally felt that if light forces are used, minimizing hyalinization of the periodontal ligament, the rate of tooth movement will be greater. c] Individual variations In some individuals, (i) the alveolar bone is loose and cancellous with large marrow spaces, whereas (ii) in others it is dense lamellated bone with few marrow spaces. Tooth movement will be much slower in the (ii) case.

19.7 Drugs effects on the response of orthodontic forces Some drugs can have effect on orthodontic tooth movement.

19.7.1 Drugs that can enhance tooth movement are: Vitamin D3 is a bone resorption-promoting agent because of its stimulatory effects on

osteoclasts.

Prostaglandin. - Direct injection of low concentration of prostaglandin into the periodontal ligament

can increase the rate of tooth movement but it is quite painful and not very practical. Higher concentration leads to root resorption.

Corticosteroid, parathyroid hormone, and thyroxin

Osteocalcin enhance the osteogenesis (stimulate the appearance of osteoclasts) at the pressure side of the alveolar bone surface

Cytokines

Leucotrines stimulates bone resorption.


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19.7.2 Drugs that can inhibit or reduce the rate of tooth movement are:

Bisphosphonates (used in the treatment of osteoporosis). Example alendronate, risedronate. They act as specific inhibitors of osteoclast-mediated bone resorption.

Prostaglandin inhibitors - NSAIDs (especially the more potent drugs like indomethacin) or large doses (like

Ibuprofen) inhibit the conversion of arachidonic acid, blocks production of primary and/or secondary messengers.

- Long-term use of aspirin decrease bone resorption by inhibition of prostagladin synthesis and may effect differentiation of osteoclasts from their precursors.

Calcitonin inhibits bone resorption by direct action on osteoclasts decreasing their ruffled surface which forms contact with resorptive pit. It also stimulates the activity of osteoblasts.

19.8 Harmful effects of orthodontic tooth movement

19.8.1 Pulp Death This can result from the application of heavy forces, particularly if the apex of the tooth is closed.

19.8.2 Root Resorption Some minimal (less than 1mm) apical root resorption during orthodontic treatment

may occur

Some predisposing factors for root resorption are: - Abnormal root morphology: Teeth with conical roots and pointed apices,

dilacerations - Prolonged treatment time: Excessive, prolonged orthodontic forces - Genetic predisposition - History of trauma - Contact with cortical plates. It‟s the most common cause of iatrogenic root

resorption.

Severe root resorption is most often seen in maxillary incisors.

If root resorption is observed during treatment, the tooth movement should be stopped for some months to allow repair by secondary cementum.

For this reason radiograph is recommended before orthodontic treatment is started. If root resorption is observed before treatment, the dentist should be cautious to undertake the treatment.


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19.9 Optimum force for different tooth movement

Optimum force levels for orthodontic tooth movement should be just high enough to stimulate cellular activity without completely occluding blood vessels in the PDL.

Type of tooth movement Optimal Forces (g)

Tipping 25-60

Bodily 50-120

Extrusion 35-60

Intrusion 10-20

Root uprighting 50-100

Rotation 35-60


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Chapter 20 RETENTION

20.1 Introduction

Orthodontic treatment results are potentially unstable and retention is necessary for three major reasons:

i) Gingival, periodontal and supporting bone tissues change during orthodontic treatment and require a period of time for re-organization after the appliances are removed. ii) Teeth are inherently in an unstable position after the treatment, so they are easily

affected by unbalanced soft tissue pressure. iii) Continual growth of the jaws and alveolar processes affect the orthodontic result.

Retention is necessary in order to maintain the results achieved at the end of orthodontic treatment.

Retention will help to prevent or minimize relapse.

During the initial treatment plan, the retention phase needs to be planned and explained to the patient.

20.2 Aetiology of relapse (Fig. 20.1) Four possible reasons for relapse are:

a) Gingival and periodontal factors b) Occlusal factors c) Soft tissue factors d) Growth factors – continual growth of the jaws and alveolar process e) Age changes

Fig. 20.1 Aetiology of relapse

a) Gingival and periodontal factors When teeth are moved the periodontal ligament and associated alveolar bone

remodels.

Until the periodontium adapts to a new position, there is a tendency for the stretched periodontal fibers to pull the tooth back to its original position.

The alveolar bones remodel within a month

The principal fibers rearrange in 3-4 months

The collagen fibers in the gingivae complete their reorganization after 4-6 months

Gingival &

periodontal factors Occlusal factors

Aetiology of relapse

Soft tissue factors Growth factors

Age changes


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The supracrestal fibers (elastic fibers in the dento-gingival and interdental fibers) take more than 12 months to remodel. Therefore there is a tendency for rotated teeth or diastema to relapse.

Teeth will tend to move back in the direction from which they were from, primarily because of elastic recoil of gingival fibers and also due to unbalanced tongue-lip forces.

In retention phase, teeth need to be held long enough to allow the periodontal fibers to remodel to their new position.

Retention for teeth that are rotated or in diastema needs to be longer so as to allow the supracrestal fibers to remodel to their new position.

To minimize relapse in rotated teeth and diastema: i) correct them as early as possible during treatment ii) over-correct the rotated teeth iii) cut the supracrestal fibers that are above the alveolar bone at or just before

the removal of appliance. This is known as pericision. (Fig. 20.2) iv) Frenectomy of large fibrous fraenum for diastema in between the central

incisors (Fig. 20.3)

91Fig. 20.2 Pericision technique. (a) crest of alveolar ridge identified. (b) incision to alveolar crest

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Fig. 20.3 Frenectomy. (a) Before frenectomy. (b) After frenectomy

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Photo taken from http://www.aso.org.au/members/NSW%20Brighter%20Futures/Brighter_Futures_002.pdf 92

Photo taken from http://www.aso.org.au/members/NSW%20Brighter%20Futures/Brighter_Futures_002.pdf

http://www.aso.org.au/members/NSW%20Brighter%20Futures/Brighter_Futures_002.pdf

http://www.aso.org.au/members/NSW%20Brighter%20Futures/Brighter_Futures_002.pdf


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b) Occlusal factors

For deep bite correction: - Stability is increased if at the end of treatment, the lower incisor edge lies 0-

2mm anterior to the mid-point (centroid) of the root axis of the upper incisor. (Fig. 20.4)

- Achieve an inter-incisal angle close to 135°, to produce a strong occlusal stop and prevent incisors erupting past each other. (Fig. 20.5)

- For growing patient, using anterior bite plate on a retainer is useful to prevent lower incisors from over-erupting. Because vertical growth continues into the late teens, the patient may need to wear the retainer for a few years after completion of fixed appliance treatment.

Usually a retainer is not required when a labial crossbite is corrected as the overbite achieved will help to prevent relapse.

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Fig. 20.4 Overbite reduction will be more stable if upper incisor centroid lies palatal to the lower incisors edge.

94Fig. 20.5 Good inter-incisal angle after overbite correction ensures stability

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Picture taken from Introduction to Orthodontics by Laura Mitchell 94

Picture taken from Introduction to Orthodontics by Laura Mitchell


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c) Soft tissues

Teeth lie in an area of balance between the tongue, cheeks and lips known as the neutral zone.

The forces from the tongue are greater than those from the lips and cheeks, but provided the periodontal ligament is healthy, the teeth will maintain in a position of equilibrium.

Teeth should be in the neutral zone at the end of orthodontic treatment.

For Class II division 1: To reduce the risk of relapse the upper incisors need to be retracted so that they can be controlled by the lower lip at the end of treatment.

If lower incisors are proclined or retroclined excessively beyond the neutral zone, they will most likely relapse.

Where possible the original lower arch form is maintained throughout treatment, and the upper archform is then planned around the lower archform.

Changes in a patient‟s intercanine width is unstable

d) Growth Majority of a patient‟s growth is complete by end of puberty, but there are small age

changes occurring throughout life anteroposteriorly and vertically.

Late facial growth can give rise to late lower incisal crowding.

Controlling the eruption of upper molars during retention phase is very important for anterior open bite patients. In a growing patient, give him/her a retainer with posterior bite blocks to wear at night and conventional retainer to wear during the day.

For Class II treatment, overcorrection of occlusal relationships can help to lessen the risk of relapse

For moderate skeletal Class II problem: - If original growth pattern continues, treatment that involved growth modification

will most likely result in loss of at least some correction. - Use either

i) headgear at night and conventional retainer during the day to hold the teeth in alignment or ii) a “passive” functional appliance (activator-bionator) at night to hold tooth position and occlusal relationship, and conventional (Hawley) retainers during the day (continue for 12-24 months). Bite registration is taken in Centric Relation, so appliance is “passive” Patients most likely to require “passive” functional appliance treatments:

1) The younger the patient at the end of treatment 2) The greater the initial Class II problem

e) Age changes Changes in the soft tissue environment with age and late facial growth changes might

cause relapse.


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20.3 Types of Retainers a) Removable retainers b) Fixed retainers c) Active retainers

a) Removable retainers i) Hawley appliance (Fig. 20.6)

is the most common removable retainer

Adam clasps on molars, palatal coverage, and labial bow with adjustment loops

can incorporate anterior biteplate for deep bite patients

it allows more rapid vertical settling of teeth than vacuum-formed retainers

Fig. 20. 6 A Soldered Hawley retainer. A Hawley retainer.

ii) Vaccum-formed retainers (Fig. 20.7)

Advantages: good esthetics, less interference with speech, good retention of lower incisors, minimal bulk

Contraindicated for patient with poor oral hygiene.

Fig. 20.7 An Essix retaine


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b) Fixed retainers (Fig. 20.8) They are usually attached to the palatal/lingual aspect of the upper or lower anterior

segment.

Multistrand wire is the bonded retainer of choice. Usually the 0.0175” diameter is used.

Indications: - closure of spaced dentition (including median diastema) - following correction of severely rotated teeth - where there have been substantial movement of lower incisors - in reduced periodontal support teeth - as maintenance of lower incisor position during late growth - to keep extraction spaces closed in adults

Fig. 20.8 Multi-strand bonded retainer.

c) Active retainer (Fig. 20.9) Modified functional appliance: to manage relapse potential in Class II or Class III

cases

Example: If an adolescent (growing patient) slips back 2-3 mm into Class II after early correction, a Bionator functional appliance can be used to recover proper occlusion

- can only be used if no more than 3mm correction is needed - Goal: Hold maxillary posterior segment and allow for eruption of mandibular

posterior segment anteriorly

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Fig. 20.9 A Bionator as active retainer

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Photo taken from Orthodontics and Paediatric Dentistry by D. Millet and R. Welbury


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20.4 Period of Retention

The initial 6-month post-treatment is important, as it may take 4 to 6 months for the periodontal ligament and supporting bone to complete re-organization.

Patient is usually advised to wear removable retainer for 6 months full-time followed by 6 months of night-time wear; except during contact sports.

Continued on a part-time basis for at least 12 months, to allow time for remodeling of gingival tissues. After that, to reduce risk of relapse it is advisable to wear retainers on alternate night-time for as long as possible.

If significant growth remains, continue wearing retainers part-time until completion of growth.

Retainers need to be reviewed on a regular basis.

Long-term retention and monitoring are recommended to reduce the risk of relapse.


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Chapter 21 RISKS OF ORTHODONTIC TREATMENT

21.1 Introduction

It is important to assess the risks of treatment as well as the potential gain before deciding to treat a malocclusion.

Patient selection is important in minimizing risk of orthodontic treatment.

Patient must have good oral hygiene and be cooperative.

Clinicians should be vigilant in assessing and monitoring every aspect of the patient‟s orthodontic treatment during and after treatment to achieve an uneventful and successful final result.

The risks of orthodontic treatment may involve:

Oral structures

Tooth movement

Appliance

Others

21.1.1 Oral structures 1. Enamel demineralisation or caries

orthodontic treatment should not be started if patient has bad oral hygiene. Aetiology

Poor oral hygiene and frequent intake of sugary food can cause enamel demineralization or caries.

Prevention a) Before orthodontic treatment, the following steps must be taken:

Teach the patient how to take care of his oral hygiene and dietary counselling.

Do scaling and prophylaxis

Select only patient with good oral hygiene for orthodontic treatment. b) During orthodontic treatment, the following steps are taken:

Show the patient how to take care of the appliance

Instruct patient to clean his appliances after meal.

Tell the patient to brush his teeth carefully.

Daily rinsing with 0.05% sodium fluoride can reduce the risk of demineralization or caries.

Check the patient‟s oral hygiene. If patient develops bad oral hygiene, advise and warn the patient.

Treatment/Management:

Teach patient concerning oral hygiene instruction and dietary counseling again

Daily rinsing with 0.05% fluoride mouth rinse or apply topical fluoride to help in remineralisation.

Restore carious tooth


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If patient is not cooperative and not committed to maintain good oral hygiene, warn the patient. May need to ask patient to stop wearing appliance to prevent further damage to teeth and gingivae due to poor oral hygiene.

For more severe cases of demineralization, treatment involving an acid/pumice micro-abrasion technique might be used, but should be performed at least 3 months after debond to allow initial remineralisation.

Fig. 21.1 Patient with very poor oral hygiene and severe gingivitis.

2. Physical damages on enamel

Enamel damage most commonly arise from occlusal contacts with orthodontic brackets; especially with ceramic brackets.

Careless use of an orthodontic band seater or band remover can result in enamel fracture.

Debonding of brackets may also result in enamel fracture.

Carbonated drinks and pure juices are the most common causes of erosion, they should be avoided in patients with fixed appliances

3. Gingivitis (Fig. 21.1, 21.2)

Gingival recession and loss of alveolar bone have been reported as a result of teeth being moved in the presence of inflammation.

Plaque retention is increased with appliances and plaque composition may also be altered. There is an increase in anaerobic organisms and a reduction in facultative anaerobes around bands, which are therefore periopathogenic.

Aetiology: Bad oral hygiene Treatment/Management: Oral hygiene instruction, using interproximal brush (for fixed orthodontics), scaling and prophylaxis.


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Fig. 21.2 Gingivitis due to poor oral hygiene while wearing of removable appliance.

4. Hyperplasia of the palate (Fig. 21.3) Aetiology Poor oral hygiene and/or ill-fitting baseplates. Treatment/Management:

Make sure that the baseplate contact nicely with the oral mucosa.

Give oral hygiene instruction again

If it is due to candida albicans infection, apply Nystatin cream at the fitting-surface of the baseplate.

Fig. 21.3 Hyperplasia of gums due to poor oral hygiene and ill-fitting appliance.


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5. Trauma from the appliance (Fig. 21.4)

Causing laceration or ulcers

Aetiology:

Sharp part of the acrylic components

Sharp part of the wire components

Accidentally disengagement of headgear whiskers eg. during play or while sleeping. This can lead to laceration or injury to the mucosa of the lip, palate, tongue; skin or eye. Prevention Use only safety headgear products. Treatment/Management:

Trim the sharp part of the acrylic.

Make sure that the tip of the wire is rounded and not over-extended.

Position the wire components correctly.

Change the design, if necessary.

Fig. 21.4 Loop position too far out, Loop adjusted to the correct position can cause ulcer

6. Gingival stripping (Fig. 21.5) Aetiology:

The wire or elastic components entered too deep into the gingival sulcus.

Traumatic occlusion, e.g. In Class II division 2 cases with very deep overbite, there may be gingival stripping at the labial of the lower incisors and palatal stripping at the palatal of aspect of the upper incisors.


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Treatment/Management:

Make sure the wire or elastic components are designed correctly and appliance fitted properly without injuring the mucosa.

Orthodontic treatment to reduce overbite and correct inter-incisal angle in Class II division 2 malocclusion that has traumatic occlusion

Fig. 21.5 Stripping of gingivae due to wrong position of labial bow

7. Abnormal tooth mobility Aetiology:

Usage of too much force.

Appliance not worn full-time

Traumatic occlusion

Abnormal resorption of the root e.g. in periodontal disease Treatment/Management:

Treat the causes

Always use optimum forces and not excessive forces 8) Pain in the tooth Aetiology:

Undetected caries

The application of light continuous force to the crown of a tooth will produce a mild and reversible transient inflammatory response within the pulp.

Too much force being used will cause pain and may cause pulp necrosis.

There may be an increase in pulpitis in teeth previously traumatised. With traumatised teeth, only light forces should be applied and vitality should be monitored every 3 months.

Tenderness from the periodontal ligament Management: Check the cause and treat it.


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8) Pulp death (Fig. 21.6) Aetiology:

Usage of too much force

Pulp could be non-vital before orthodontic treatment (due to previous trauma)

Undetected deep caries or undetected caries in dens-in-dente. Treatment/Management:

Treat with root canal therapy

After root canal treatment, wait at least 3 months before continuing with active orthodontic treatment.

Fig. 21.6 Non-vital I . Note the fistula

9) Root resorption

Orthodontic treatment can cause very minor root resorption. This area is usually repaired by deposition of secondary cementum.

The mechanism of tooth resorption during orthodontic treatment remains unclear. According to one theory, excessive force and hyalinization of the periodontal ligament results in excessive activity of cementoclasts and osteoclasts.

The risk factors associated with severe resorption are: - Shorter than average roots - Previously traumatised teeth - Teeth lacking vitality after root treatment; - Application of excessive forces to teeth - Combining orthodontic and orthognathic procedures.

If there is a lot of tooth resorption: a] stop activating appliance for at least 6 to 8 weeks. b] use a lighter force to move the teeth c] if there is periodontal disease, treat it first. d] check whether patient is having any systemic disease

e.g. hyper-parathyroidism.


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21.1.2 Tooth Movement

1. Tooth movement lesser than expected Normally, the tooth will move about 1 mm in a month if the removable appliance is worn full-time. Causes of lesser tooth movement or no movement are:

Obstruction from the components of the acrylic or wire

Too much activation (usage of too much force)

Too little activation (usage of too little force)

Active component placed at the wrong position

Patient not wearing the appliance full-time

Obstruction from occlusion

2. Overbite reduction lesser than expected Aetiology:

In adult patients, overbite reduction is much slower

Patient is not wearing the appliance full-time

3. Tooth more mobile Causes and treatment: a] Traumatised tooth or non-vital tooth

If a tooth is non-vital, it must be treated with root canal therapy before orthodontic treatment.

Severe root resorption of a patient

treated by fixed appliance


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Check with periapical radiograph for any signs of fracture of the root. - if fracture at apical 1/3 of the root, do apicectomy. - if fracture at middle third of the root, splint with metal post or extract it. Note: Traumatised tooth/ root canal treated tooth should not be moved orthodontically during the initial 3 months.

b] Periodontal disease

Orthodontic treatment should not be started until the periodontal disease has been treated and patient can maintain good oral hygiene. If not, there will be loss of bone support.

Use a lighter force to move the tooth that has been treated for periodontal disease.

21.1.3 Appliance

1. Not fitting well Aetiology

Failure to block-out undercut area

Shrinkage or distortion of baseplate

Impression is not accurate or distorted

Teeth have moved after impression has been taken due to delay in issuing appliance Treatment/Management:

Make sure the impression is accurately taken

Pour the model as soon as possible

Appliance must be issued not more than 2 weeks after impression is taken.

2. Appliance no longer fit well during wear. Aetiology

Patient didn‟t wear the appliance for a while

Deciduous tooth being replaced by new permanent tooth

Distortion of wire Treatment/Management:

Advise patient to wear it if he has not been wearing.

Make a new appliance if the patient‟s appliance does not fit anymore.

3. Poor retention Aetiology

Not enough retentive components

Retentive components not bent correctly


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Management:

Make sure there are enough retentive components.

Bend retentive components properly.

Make sure that the arrow –heads of Adams claps are engaging in the undercut area.

4. Poor tolerance to appliance When patient wears the removable appliance for the first time, he will experience:

i) more salivation ii) more difficulty in chewing his food iii) more difficulty in talking

Management:

Inform the patient that it will take 1 or 2 weeks for him to get used to it.

Make sure that the appliance is not too bulky or extend too far backwards into the soft palate area.

5. Broken wire or acrylic components. Management:

If any wire is broken, replace it.

If the baseplate is broken, repair it.

21.1.4 Others risks of orthodontic treatment 1. Allergy

Leaching of materials from appliances is responsible for hypersensitivity reactions and may involve the release of known allergens such as nickel, chromium, and cobalt.

Other allergens can include bonding materials, cold curing acrylics, or in latex components.

2. Infection control

Spread of infection between patients, between operator and patient, and by third parties should be prevented by adequate infection control procedures throughout the clinic.

Use of gloves, masks, sterilized instruments, and „clean‟ working areas.

Give patients an eye goggle to wear .

Patients at risk of endocarditis should be treated in accordance with appropriate guidelines and in consultation with a cardiologist.

Clinicians and assistants should have Hepatitis B vaccination.

3. Swallowing/inhalation of small parts

Orthodontic appliances are composed of very small parts connected together. They can be accidentally swallowed, aspirated, and they can irritate or damage oral tissues.


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21.15 Summary 96

Table 21.1 List of some possible complications related to orthodontic treatment.

CROWNS Decalcification

Caries

Enamel fracture from debonding

ROOT Resorption

PULP Pulpitis

PERIODONTAL Gingivitis

Periodontitis

Recession

Dark triangle spaces

BONE Crestal bone resorption

SOFT TISSUES Direct trauma

Mucosal ulcerations due to appliances

Trauma from headgear whisker

TEMPORAL MANDIBULAR JOINT

Temporomandibular joint dysfunction

FACE Skin trauma from displaced headgear whisker

Eye trauma from displaced headgear whisker

Chemical burn from etchant

Allergy/sensitivity to nickel

Thermal burns from overheated handpiece

HEART Infective endocarditis

CROSS-INFECTION Operator to patient

Patient to operator

GASTRO-INTESTINAL or RESPIRATORY TRACT

Swallowing or aspiration of small parts

GROWTH Unfavourable growth

TREATMENT RESULT Unfavourable results

Unable to complete treatment

Failed treatment

96

Adapted from Paul Yun-Wah Lau, Ricky Wing-Kit Wong. Risks and complications in orthodontic treatment.

Hong Kong Dental Journal 2006;3:15-22


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Chapter 22 THE LOWER INCLINED PLANE

22.1 Introduction The lower inclined plane is an appliance used for the treatment of an incorrect biting relationship of upper and lower incisors when one or a number of upper incisors bite lingually to the lower incisors (anterior crossbite).

22.2 Indications and contra-indications for the use of Lower inclined plane

22.2.1 Indications

the incisor teeth are at an early stage of eruption

in cases where many deciduous teeth have been removed. The construction of upper removable appliance with posterior bite plane is difficult in these cases.

22.2.2 Contra-indications

patient's mandible is very prognathic.

very minimal overbite.

22.3 Design and Construction of the Lower Inclined Plane

1. The appliance is made of acrylic resin plate inclined at about 45 to the occlusal plane.

2. It is placed on the lower incisors in such a way that the upper incisor(s) bite on the plane and are guided into their correct position labially to the lower incisors. ( Fig. 22.1)

3. The inclined plane is built-up, capping the lower incisor and canine teeth, and the appliance is made of clear acrylic material.

4. The inclined plane is cemented to the teeth (Fig. 22.2) for not longer than 6 weeks because posterior teeth may erupt due to absence of contact, leading to loss of overbite. If there is no improvement, check the diagnosis of the case.


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Fig. 22.1 The lower inclined plane caps the lower incisors and is inclined at about 45 to the occlusal plane. On closing the upper incisors, which formerly bit behind the lower incisors, bite on the plane and the pressure of bite (P) develops a component at angles to the plane F and a component along the plane D. The pressure (F) proclines the upper incisors

Fig. 22.2 Front view. Lateral view


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Chapter 23 Examples of orthodontic treatment with removable appliances

23.1 Management of buccally erupted canine 23.1.1 Aetiology

malrelationship between jaw size and teeth size (crowding) or

forward drift of the buccal segments due to early loss of deciduous molars

23.1.2 Treatment

1) Treatment by extraction alone

In the absence of gross decay of other teeth, extraction of first premolar is usually indicated. Indications

mesially inclined canines

canines are at their active eruption phase ( 10 - 12 years old )

enough space ( the space from distal of lateral incisors to the mesial of 2nd premolar must be greater than the width of the canine )

Note: the canines will drift distally to the extraction sites on the 1st premolar Contra-indications

distally inclined canines

poor prognosis of canines - grossly carious or hypoplastic ( extract canine instead )

grossly displaced canines ; good contact between lateral incisor & 1st premolar (extract canine)

Class III incisor relationship

2) Treatment with removable appliance

Advantages

more reliable than without using an appliance Indications

mesially inclined or upright canines

10 - 16 years old Contra-indication

distally inclined canines


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23.1.3 Design of Buccal canine retractor (Fig. 23.1) Active components : buccal canine retractor ( 0.7 mm ) Retention : Adams clasps on 6/6 ( 0.7 mm ). If extra retention is needed, Double Adams clasps or South-end clasps can be added on 1/1. Baseplate : contact on all the teeth except on 1st premolars area. Activation : between 1 to 2 mm per month.

Fig. 23.1 Buccal canine retractor


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23.2 Management of anterior crossbite

23.2.1 Aetiology - retained upper deciduous incisors deflect the permanent incisors so that it erupts in lingual occlusion with the lower incisors.

23.2.2 Treatment

1) Prevention

- extract the over-retained deciduous incisors when the permanent incisors started to erupt.

2) Use tongue spatula or ice-cream stick

- 2 to 6 times of 15 minutes each day for 2 to 3 weeks. Indications

only one incisor in lingual occlusion

overbite is still shallow

the upper permanent incisor is still erupting

3) Appliance

Indications

one or more than one incisors are involved

overbite is more established

3a) Upper removable appliance Active component: Boxed Z-spring ( 0.5 mm or 0.6 mm ) / screw. Retention: Adams clasps on 6/6 ( 0.7 mm ) ; 4/4 or D/D ( 0.6 mm ) Baseplate : with posterior bite plane 3b) Lower inclined plane

is indicated where upper first permanent molars are missing and retention of an upper removable appliance would be a problem.

Please refer to chapter 22 for more information.


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BIBLIOGRAPHY/ Reference

1. An Introduction to Orthodontics, 3rd Edition by Laura Mitchell

2. Contemporary Orthodontics, 4th Edition by Willam R. Proffit, Henry W. Fields, JR and David M. Sarver.

3. Interceptive Orthodontics, 4th Edition by Andrew Richardson.

4. Orthodontics and Paediatric Dentistry by Declan Millet, Richard Welbury.

5. Walters & Houston’s Orthodontic Notes, 5th Edition by M.L

Jones, R.G Oliver.

6. Removable Orthodontic Appliances, by K.G. Isaacson, J.D. Muir, R.T. Reed

7. Handbook of Orthodontics, by Martyn T. Cobourne and Andrew T. DiBiase

8. Postgraduate Notes in Orthodontics MSc/MOrtho Programme by University of Bristol

59095527 ortho lecture manual 2011 latest1

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