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Orthodontics Flashcards

1
Q

What are general factors in the aetiology of malocclusion? (4)

A
  1. Skeletal pattern
    > A/P relation
    > Vertical facial proportion
    > Lateral facial symmetry

2) Crowding/spacing

3) Tooth size

4) Soft tissues
> lips/cheeks
> tongue

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2
Q

What are local factors in the aetiology of molocclusion?

A

1) Abnormalities in tooth position e.g. transposition

2) Abnormalities of soft tissues e.g. franum (median diastema)

3) Local pathology e.g. cysts, germination, fusion

4) Habits e.g. digit sucking

5) Variation in tooth number
> supernumerary (extra teeth)
> hypodontia (missing teeth)

6) Variation in tooth size
> macrodontia (big teeth)
> microdontia (small teeth)

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3
Q

What is skeletal pattern and its three dimensions?

A

The relationship of the maxilla to the mandible.

a. Anterior-posterior relationship
b. Vertical relationship
c. Transverse

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4
Q

Is skeletal pattern the same as skeletal class?

A

NO!
Skeletal class is the classification of anterio-posterior relationship of the dental bases which support the teeth and alveolar processes.

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5
Q

What is skeletal class?

A

The classification of the antero-posterior relationship of the maxilla and mandible

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6
Q

What is skeletal class 1?

A

Maxilla lies 2-3mm anterior to the mandible when in occlusion

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7
Q

What is skeletal class 2?

A

Maxilla lies >3mm anterior to mandible when in occlusion

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8
Q

What can cause skeletal class 2?

A

Retrognathic mandible
Prognathic maxilla
Combination

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9
Q

What is skeletal class 3?

A

Maxilla is <2mm anterior to the mandible when in occlusion

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10
Q

What are causes of skeletal class 3?

A

Retrognathic maxilla
Prognathic mandible
Combination

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11
Q

What cranial base angle is associated with Class III skeletal pattern?

A

Low cranial base angle

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12
Q

What cranial base angle is associated with class II skeletal pattern?

A

Large cranial base angle

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13
Q

What is dentoalveolar compensation?

A

When AP jaw relationship is II or III, but soft tissues are favourable, the lips and tongue can compensate.

This may mean that the teeth are more or less proclined or retroclined than normal to achieve incisal contact

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14
Q

What can be used to determine the patient’s true skeletal class?

A

Lateral ceph

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15
Q

How do you calculate ANB and what is the value for different skeletal classes?

A

ANB = SNA-SNB
SNA (sella-nasion to A point) and SNB (sella-nasion to B point). It is obtained using the equation: ANB = SNA - SNB. Calculate angle

  • Class I = 2<x>4</x>
  • Class II = >4
  • Class III = <2

(check the exact values)

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16
Q

What can incorrect skeletal class diagnosis cause?

A

Failure to achieve desired occlusion
Poor dental aesthetics
Poor facial aesthetics
Instability of end treatment

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17
Q

How can you assess vertical relationship (facial proportions)

A

Upper vs lower facial height

Maxillary-mandibular angle

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18
Q

What are the ideals for vertical relationship?

A

Upper facial height = lower facial height
A/B = 50-55%

Maxillary-mandibular angle = 27+-5

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19
Q

What does increased lower facial height cause? angle?

A

Angle MMA >32 degrees

Reduced overbite or anterior open bits occlusal tendencies

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20
Q

What does lower facial height cause? angle?

A

MMA <22 degrees

Prominent chin and lips cover teeth completely
Increased overbite occlusal tendency, very difficult to correct.

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21
Q

What can you assess transverely in skeletal pattern?

A

Centre-line discrepancy

Facial symmetry

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22
Q

What should you look for if there is a centreline discrepancy?

A

Posterior crossbite (premolar crowding usually)

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23
Q

What can crowding be caused by?

A

Small arches
Big teeth
Combination of both

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24
Q

What is the chance of permanent dentition crowding abed off of deciduous teeth status at 5 years?

A

Crowded = 100%

Less than 3mm spacing = 50%

More than 6mm spacing = 0%

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25
Q

What is the aetiology of crowding? and where do teeth tend to erupt?

A

In a crowded mouth, upper laterals tend to erupt palatally, lower laterals erupt lingually.

Early loss of deciduous molars modified presentation of crowding.
> Early loss of Ds = premolar crowding as Cs erupt into Ds space
Premolar crowding always due to loss of deciduous molars.

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26
Q

How can you treat crowding? (3)

A
  1. Create space for alignment by extracting teeth
  2. Create space by expansion of arch laterally (palatal expander)
    3) Create space by expansion antero-posteriorly (headgear)
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27
Q

What are causes and treatment of spacing?

A

Causes:
> teeth too small for arch size
> arch too large for normal sized teeth

Treated by closing spaces (fixed appliance) or re-distribution of space and fill prosthetically.

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28
Q

What does the soft tissues determine the position of compared to hard tissues?
Evidence for this? (4)

A

Soft tissues (lip, cheeks, tongue) determine the position of tooth crowns.

Dental bases determine position of teeth apices/roots

1) Spontaneous alignment of crowded teeth into neutral zone post XLA
2) Partial overjet reduction less stable
3) Everted lips associated with proclined incisors
4) Correlation between size of tongue and angle of incior proclination

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29
Q

What causes dentoalveolar compensation?

A

Soft tissue factors

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30
Q

What is lip competence?

A

Lips meet together at rest without any muscular activity (mentalis muscle)

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31
Q

What is marked incisal incompetence?

A

Half-crown height visible at rest

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32
Q

What does growth do to lip competence?

A

Growth increases lip competence and reduces overjet

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33
Q

What is lip line and what does it influence?

A

Related to lower lip
Influences the positioning of the upper incisors, normally overlaps 3-6mm of crown height

  • High lip line causes retroclined upper incisors
  • Low lip line causes proclination of upper incisors, causes unstable overjet reduction (high chance of relapse to previous malocclusion post tx)
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34
Q

What does a high lip line cause?

A

Retroclined upper incisors

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35
Q

What does a low lip line cause?

A

Proclination of upper incisors, causes unstable overjet reduction (high chance of relapse to previous malocclusion post tx)

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36
Q

What does upper lip length influence?

A

Incisor visibility (aesthetic concern for pt)

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37
Q

What can increased cheek forces cause and when does this normally occur?

A

Increased cheek forces (digit sucking habit) can narrow the upper arch and cause a crossbite

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38
Q

What can an endogenous tongue through cause and which patients it is commonly present in?

A

Can cause bimaxillary proclination and anterior open bite presence.

Present in Down syndrome patients

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39
Q

What can a large tongue cause?

A

Increased mandibular arch width

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40
Q

What classification is used for cleft lip and palate?

A

LAHSAL classification based upon the striped Y diagram
Lip, alveolus, hard palate, soft palate, alveolus, lip

Cleft palate (CP)
Unilateral Cleft lip and palate (UCLP)
Bilateral Cleft tip and palate (BCLP)

LAHSAL indicates a complete cleft lip and palate.

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41
Q

What is the epidemiology of cleft lip and palate?

A

Common craniofacial malformation
1:700 live births in the UK
Male prevalence>female
Associated with other syndromes:
> Sticklers, Vander Woude, Pierre Robin Sequence, Di George

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42
Q

What is the treatment of cleft lip and palate?

A
  1. Diagnosis at birth
    > Specialist nursing contact within 24 hrs
    > Use of special soft bottles, traditional feeding not possible
    > Pre-surgical orthopaedics
  2. Surgery at 3/12
    > Correct muscle layer
    > Restore functionality
  3. Surgery at 6/12
    > Close hard palate
    > Restore velopharyngeal competence (ONF closed)
    > Allow speech
  4. Furlow Palatoplasty to aid with speech
  5. Alveolar bone graft surgery due to alveolar clefts
    > Pre-bone graft ortho = expand upper arch laterally
    > Corect anterior crossbite
  6. Orthodontics with orthognathic surgery
    > Pts are skeletal class III due to improper maxilla formation
    > Ortho tx to decompensate incisors
    > Treat when growth complete
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43
Q

What is IOTN?

A

An index used by GDPs to refer paediatric pts to orthodontics by assessing the perceived need for the patient to orthodontic treatment to correct a malocclusion

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44
Q

What are the 2 components of Index of Orthodontic Treatment Need (IOTN)

A
  1. Dental health component (DHC), a 5-point scale

2). Aesthetic component (AC), a 10-point scale

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45
Q

What is the Dental Health Component of IOTN?

A

It looks for the single most detrimental occlusal feature in relation to dental health and function.
5 point scale

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46
Q

What is the aesthetic component of the IOTN?

A

Aesthetic component assesses impact of psychosocial wellbeing
10 point scale

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47
Q

What IOTN qualifies for NHS dental tx

A

Pt must be under 18

DHC grade 4 or 5
or
DHC 3 with AC of 6 or more

Therefore need to IOTN of 3.6 of higher

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48
Q

What are limitations of IOTN?

A

DHC evidence is incomplete
IOTN scores being higher don’t necessarily correlate to treatment complexity.
AC is very subjective, often many borderline cases

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49
Q

What do these letters correspond to on IOTN?

A

a = overjet
h = hypodontia
i = impacted
d = displacement (contact point displacement or crowding)
s = submerged deciduous teeth
m = missing teeth

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50
Q

What are the IOTN scores of DHC = 5?

A

5i. Impeded eruption of teeth (except for third molars) due to crowding, displacement, the presence of supernumerary teeth, retained deciduous teeth or
any pathological cause

5h. Extensive hypodontia with restorative implications (>1 tooth missing in any
quadrant) requiring pre-restorative orthodontics

5a. Increased overjet >9mm

5m. Reverse overjet >3.5mm with reported masticatory and speech difficulties

5p. Defects of cleft lip and palate and other craniofacial anomalies

5s. Submerged deciduous teeth

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51
Q

IOTN tricky points

A
  • If space for unerupted tooth is <4mm then it is defined as impacted rather than crowded (5i), therefore goes under missing teeth bracket.
  • Spacing and crowding is not measured unless the tooth deviates from the line of the arch
  • Submerged teeth not recorded unless only 2 cusps are visible or significant tipping of adjacent tipping of adjacent teeth
  • Overjet is measure to the most prominent point of the incisors
  • All 4 incisors must be in lingual occlusion to be recorded as reverse overjet
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52
Q

What is the hierarchal scale of severity MOCDO?

A

M = missing teeth (most severe)
O = overjet
C = crossbites
D = displacement of contact points
O = overbite including open bite (least severe)

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53
Q

What is the peer assessment rating index (PAR)?

A

Measure of overall occlusal irregularity, used to assess quality of occlusal outcome compared to initial malocclusion.

PAR ruler used to speed assessment. Score specific features and add them up.

Pre-tx and post-tx models are recorded to give two PAR scores.
PAR nomogram used to compare scores.

Used to assess the overall quality of occlusal improvements of orthodontists across the UK.

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54
Q

What are 3 tooth positioning variables controlled by straight wire system in fixed appliances?

A

1st order = in/out labio-lingual position
2nd order = mesio-distal dip
3rd order = tooth inclination or torque

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55
Q

How is 1st order incorporated into a fixed appliance?

A

in/out control (labio-lingual) is incorporated into the bracket by variations in bracket base thickness, considering the varying bucco-lingual thickness of the dentition

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56
Q

How is 2nd order incorporated into fixed appliances?

A

Tooth angulation (mesio-distal tip) is controlled by the angulation of the arch wire slot. It considers the optimal mesio-distal angulation of each tooth relative to the occlusal plane.

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57
Q

How is 3rd order incorporated into the fixed appliance system?

A

Torque incorporated in the bracket by the angle the bracket base makes with the slot

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58
Q

Where is the coloured marking on a bracket placed to ensure the correct orientation?

A

Disto-gingival aspect

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59
Q

What is important to ensure when bonding brackets?

A

Check no plaque on the teeth, remove if necessary.
Cheek retractor (labial sulcus cotton wool rolls)
Moisture control is vital before, during and after etching.
Place all the brackets in one visit

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60
Q

What 3 things do you need to think about when placing the bracket?

A

Correct height (LA point)
Correct angulation
Correct mesio-distal position

> Centre of the bracket base must be positioned approximately over the midpoint of the long axis of the clinical crown (LA point)

> Bracket must be in middle of anatomical labial face of the tooth.

> Errors of mesio-distal positioning lead to rotational errors of tooth position

Each bracket must be at the same distance from the incisal edge or cusp tip as its contralateral tooth.

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61
Q

What is the eruption pattern of deciduous teeth?

A
  1. Lower As
  2. Upper ABs and lower Bs
  3. Ds
  4. Cs.
  5. Es.
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62
Q

What is the eruption pattern of permanent teeth?

A

1.Upper and lower 6s
2. Lower 1s
3. Upper 1s, lower 2s.
4. Upper 2s
5. Lower 3s
6. Upper 4s
7. Lower 4s
8 Upper and lower 5s
9. Upper 3s
10. Upper and lower 7s
11. Upper and lower 8s.

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63
Q

What are the eruption dates of A&Bs?

A

6-9 moths

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64
Q

What are the eruption dates of Cs?

A

16-18 months

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65
Q

What are the eruption dates of Ds?

A

12-14 months

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66
Q

What are the eruption dates of Es?

A

20-30 months

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67
Q

What are the eruption dates of upper 1s?

A

7-9 years

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68
Q

What are the eruption dates of lower 1s?

A

6-8 years

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69
Q

What are the eruption dates of upper 2s?

A

7-9 years

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70
Q

What are the eruption dates of lower 2s?

A

6-8 years

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71
Q

What are the eruption dates of upper 3s?

A

11-12 years

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72
Q

What are the eruption dates of lower 3s?

A

9-10 years

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73
Q

What are the eruption dates of upper 4s?

A

10-11

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74
Q

What are the eruption dates of lower 4s?

A

10-12 years

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75
Q

What are the eruption dates of upper 5s?

A

10-12 years

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76
Q

What are the eruptions dates of lower 5s?

A

11-12

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77
Q

What are the eruption dates of upper 6s?

A

6-7 years

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78
Q

What are the eruption dates of lower 6s?

A

6-7 years

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79
Q

What are the eruption dates of upper 7s?

A

11-13 years

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80
Q

What are the eruption dates of lower 7s?

A

11-13 years

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81
Q

What are the eruption dates of upper 8s?

A

17-21 years

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82
Q

What are the eruption dates of lower 8s?

A

17-21 years

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83
Q

For the primary dentition what is normal development? (Quick reference guide to orthodontic assessment and referral)

A
  • Normal eruption pattern (see overleaf)
  • Spacing is normal (primate spaces)
  • Encourage cessation of thumb/finger/dummy
    sucking before 5 years old
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84
Q

What are indications for referral in primary dentition (QRGTOAAR)

A
  • Severe skeletal discrepancies
  • Severely delayed dental development
  • Missing/ supplemental teeth
  • History of head and neck radiotherapy +/- chemotherapy
  • Advice for balancing/ compensating extractions
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85
Q

For the mixed dentition, what is normal development (QRGTOAAR)

A
  • Normal eruption pattern (see overleaf)
  • Contralateral teeth should erupt within 6/12
  • Midline (median) diastema normal
  • Maxillary canines palpable at 10 years old
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86
Q

What are indication for referral in the mixed dentition (QRGTOAAR)?

A
  • Severe skeletal patterns where early treatment may be appropriate e.g. developing class II/III
  • Dental anomalies e.g. double teeth, dens-in-dente, talon cusps
  • Developmentally missing permanent teeth
  • Supernumerary teeth
  • Teeth in unfavourable positions e.g. canines
  • Impacted first permanent molars
  • Infraoccluded teeth
  • Crossbites
  • Extraction advice where severe crowding evident or first molars have poor prognosis
  • Advice following trauma to permanent teeth
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87
Q

In the permanent dentition, what is normal development? (QRGTOAAR)

A
  • Skeletal base acceptable
  • All permanent teeth present
  • Class I incisors
  • Class I molar relationship
  • Average overjet 2-4mm
  • Average overbite (1/3rd – ½ lower inc coverage)
  • Well aligned arches
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88
Q

In the permanent dentition, what are the indications for referral? (QRGTOAAR)

A
  • Clear-cut IOTN eligible for NHS treatment?
    > YES (IOTN 3/6 and above)
    Refer to NHS orthodontic provider

> NO (below IOTN 3/6)
Discuss private referral to orthodontic provider

  • Borderline cases (Grade 3 below 3/6) can be referred for NHS
    assessment as these cases can be difficult toevaluate
  • Remember, every patient has the right to a secondopinion
  • Adults may qualify for NHS treatment e.g. if they require
    complex multidisciplinary care. Otherwise, please refer them to an orthodontic provider for private treatment
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89
Q

When may an adult qualify for NHS treatment?

A

If they require complex multidisciplinary care.

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90
Q

What is the definition of Class 1 malocclusion?

A

The tip of the lower incisors occludes with the middle third of the upper central incisor.

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91
Q

What is the A/P relationship, ANB and occurence rate of Class I malocclusion?

A

A/P relationship: usually skeletal Class 1
ANB = 3.4 (SNA-SBA) ??
Occurence rate 60%

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92
Q

What is Class 1 molar relationship?

A

The mesiobuccal cusp of the maxillary first permanent molar occludes with the mesiobuccal groove of the mandibular first permanent molar.

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93
Q

What is dento-alveolar compensation?

A

A mechanism through which the soft tissues produce a more Class 1 incisor relationship when the A-P skeletal pattern is more Class II or Class III.

94
Q

What can cause facial asymmetry?

A

Biological variation
Pathological: condylar hyperplasia
Centre line-discrepancies
Posterior cross bites and mandibular displacements

95
Q

What are features that may require orthodontics?

A

Crowding
Spacing
Local factors: variation in tooth number and form, soft tissue and pathology
Abnormalities in position: transposition and ectopic teeth
Anterior open-bite: due to increased lower face height
Posterior cross-bite

96
Q

What is mandibular displacement?

A

When there is significant movement (>1mm) of the mandible between initial contact in RCP and final position in ICP.

RCP = retruded contact position (CR)
ICP = intercuspal position (CO)

Can be either forward or lateral displacement.

97
Q

What are 3 causes of posterior crossbite?

A
  1. Digit sucking habit
  2. Narrow maxilla
  3. Local problem (often crowding)
98
Q

What is the definition of Class II div 1 malocclusion?

A

The tip of the lower incisors occludes posterior to the cingulum plateau of the upper incisors.

Upper central incisors are either normal inclination or proclined.

99
Q

What dental features may Class II div 1 have? Occurrence rate?

A

Increased overjet
Occurrence rate 22%?

100
Q

Why treat Class II div 1?

A

Aesthetic considerations
Functional considerations
Dental health (trauma) considerations

101
Q

What is the risk of overjet >9mm?

A

Increased risk of trauma, incidence of 44%

102
Q

What is common aetiology for class II div 1?

A

Usually a small mandible.
Vertical and lateral relationships are often normal.
Soft tissue causes:
> markedly incompetent lips and a low lower lip resting height
> digit sucking, may cause proclination of upper +/- retroclination of lowers.

103
Q

What dental impacts may digit sucking have?

A
  • anterior open bite (unilateral)
  • Proclined uppers +/- retroclined lowers
  • (unilateral) posterior crossbite
104
Q

What are treatment aims for Class II div 1?

A

Reduce the overbite
Reduce the overjet
(relieve crowding and align teeth)

105
Q

Can upper removable appliances be used in Class II div 1 cases?

A

URAs tip teeth only.

Used for cases then the patient has a minimal overjet and proclined upper labial segment.

Because URA retrocline upper incisors, this can lead to pt developing Class II div 2 malocclusion.

Due to this URAs are rarely in indicated (unable to bodily move teeth), as well as multiple other conditions often associated with pts that URAs cannot fix.

106
Q

How do functional appliances work?

A

Removable appliances that harness force from orofacial tissues created by the mandible being in a postured position.

107
Q

What treatment is common with Class II div 1?

A

Commonly two stage treatment: functional appliance W fixed appliance.

  • One stage Tx only indicated in well aligned arches with Class II molar relationship.
108
Q

What can fixed appliances do in Class II div 1 cases?

A

Torque control of upper incisors to prevent retroclination.

Irregular arch alignment.

Rotation

Space closure.

109
Q

What is the definition of Class II div 2 malocclusion?

A

The tip of the lower incisors occludes posterior to the cingulum plateau of the upper central incisors, with the upper central incisors retroclined.

110
Q

What are features of Class II div 2?

A

Occurrence rate 4.5%
Sagittal view (AP relationship) = often mild skeletal class II
Vertical relationship = reduced lower facial height
Maxillary base much broader than mandible (can cause premolar scissor bite)
Well developed chin

111
Q

What is the general facial appearance for someone with Class II div 2?

A
  • Chin well developed in relation to mandible
  • Often retrusive lips compared to the nose and chin - normally competent.
  • Reduced lower facial height common
112
Q

Why may Class II div 2 pts seek treatment?

A

Aesthetics: dont like appearance of retroclined incisors.
Sometimes there is proclination of upper laterals due to lower lip trap?

Dental: traumatic overbites require treatment

113
Q

What is the aim of treatment in class II div 2?

A

Either accept incisor relationship and overbite (partial)
or
Correct incisor relationship to Class I including correction of overbite.

114
Q

What does treatment of Class II div 2 involve? (general aim needed to achieve tx)

A

Change in the inter-incisor (I-I) angle.
- Lower incisal edge to upper root centroid relationship.
- Procline upper and lower incisors to form an occlusal stop.

Upper incisor torque needs a fixed appliance and rectangular wire.

Extractions often indicated less (or more distal) as we want to keep incisors labially inclined to keep the interincisal angle low and reduce the overbite.

115
Q

What appliances may be used in Class II div 2 tx?

A

Headgear (EOT) can be used to make the upper buccal segment teeth more distal

Can also convert pt to II/1 with a functional appliance (often a twin block) and then use a fixed appliance to finish the case.

Orthognathic surgery very uncommon because skeletal pattern usually mild class II.

116
Q

What is the definition of Class III malocclusion? Occurrence rate?

A

The tip of the lower incisors occludes anterior to the cingulum plateau of the upper incisors.

Occurrence rate 3%?

117
Q

What are skeletal features of Class III malocclusions?

A

AP relationship usually Class III, with small maxilla or large mandible.
Short anterior cranial base
Vertical skeletal feature can be any of average, increased or reduced.
Laterally often a narrow maxilla arch or broad mandile, with crossbites often a consequence.

118
Q

What does dento-alveolar compensation result in, in a sk class III pt?

A

Upper proclined and lowers retroclined

119
Q

What is a common features for Class III malocclusion pts?

A

Tendency to have anterior and posterior crossbites due to skeletal features.
Anterior crossbite due to Class III incisors.
Posterior crossbite due to AP relationship = lower arch broadest parts contacting narrow upper arch parts.

Both may be associated with mandibular displacement.

120
Q

What are common occlusal features for Class III malocclusion pts?

A

Forward displacement of mandible in ICP can cause wear on labial incisors.
Gingival recession on lower incisors
Narrow upper arch = crowding

121
Q

What is the stat for growing more skeletal class III? Implications for tx?

A

On average people grow 2mm more skeletal class III after the age of 11.

Because of this treat pts as late as possible to minimise growth potential.

122
Q

What are 3 treatment options for Class III malocclusion?

A

Mild: procline upper incisors using URA
Moderate: procline uppers and retrocline lowers
Marked: orthodontic and orthognathic tx

123
Q

Facts about canines? (3)

A
  1. Canines are the cornerstone of the dental arch, vital for aesthetics and function.
  2. Long roots, meaning good long-term periodontal prognosis
  3. Difficult to replace prosthetically (canine guidance)
124
Q

What percentage of maxillary and mandibular canines become ectopic and in what direction?

A

2-3% of maxillary canines become ectopic. (85% palatally displaced), with 12% associated with lateral incisor root resorption.

0.3% mandibular canines are ectopic.

125
Q

What is the normal canine development?

A

Crown development begins at age 4-5 months high in the maxilla.

Crown calcified at 6-7 years

Canines migrate down and forward distal to the root of the lateral incisor

Palpable in buccal sulcus aged 10

Erupts 11-12 years old

126
Q

What is the aetiology of an ectopic maxillary canine? (4)

A
  1. Displacement of dental crypt (space in the alveolar process of a tooth)
  2. Long path of eruption
  3. Diminutive or missing 2
  4. Crowding
127
Q

What is the main issue with ectopic canines?

A

Resorption of 2s roots (12%)

128
Q

What are clinical signs of possible ectopic canines? (7)

A
  1. Not palpable in the buccal sulcus aged 10
  2. Cs not mobile
  3. Ped shaped lateral incisors
  4. Missing lateral incisors
  5. Labially inclined lateral incisors (ectopic canines may be placed buccally)
  6. Asymmetric loss of Cs
  7. Unerupted 3 after 6 months of contralateral 3.
129
Q

How can you determine the position of the ectopic C?

A

Horizontal or vertical Parallax technique using SLOB
- Same Lingual, Opposite Buccal

  • Parallax = relative movement of the canine in relation to other adjacent teeth when two radiographs are taken with an angle between them
130
Q

What can be used for horizontal parallax?

A
  1. 2 x PAs at different angulations
  2. Upper occlusal + periapical at different angulation
131
Q

What can be used for vertical parallax?

A

1) PA and upper standard occlusal

2) DPT and USO

132
Q

What is the purpose of the interceptive extraction of C/C?

A

Extraction C/C to create space and balance to maintain centre-line.

Ericson and Kurol (1988) found that interceptive C/C extractions in 10-13 year olds will improve 78% of the time if no crowding.

133
Q

When do interceptive extractions of C/C work better for tx of ectopic canines?

A

If the 3 only overlaps 2 roots rather than 1 as well.
Space is available
If pt <14 years old.

134
Q

When is immediate active treatment indicated for ectopic canines?

A

patient aged >13 years at diagnosis.
Significant crowding
If the canine does not improve after 6/12 post XLA of C/C.

135
Q

What dictates the prognosis of ectopic canines?

A
  1. Height - worse if crown tip of canine at or above the apical third or incisor roots.
  2. Mesio-distal position - worse if canine more than halfway across the upper incisor roots. Worse closer to the midline.
  3. Angulation - the more horizontal the canine the worse the prognosis.
136
Q

What are treatment options for ectopic canines? (4) (general names)

A
  1. Leave and review
  2. Extraction of 3 and orthodontics
  3. Exposure and align (open or closed exposure)
  4. Create space and replace restoratively: replace with denture, bridge or implant.
137
Q

Ectopic canines: leave and review:

A

> canine hopeless prognosis
C root morphology adequate
Patient doesn’t want treatment
Increased risk of surgery in that pt

Negatives: ectopic canines become cystic, resorption of Cs, space if Cs exfoliate.

138
Q

Why might we chose to leave and review ectopic canines? (4)

A
  1. Canines hopeless prognosis (very high, close to midline, horizontal angulation)
  2. C root morphology adequate
  3. Increased risk of surgery in that pt.
  4. Pt might not want treatment.
139
Q

What are negative of leaving and reviewing ectopic canines? (3)

A

Ectopic canine becomes cystic.

Resorption of Cs.

Space if Cs exfoliate.

140
Q

When may we choose to extract 3s and then orthodontics?

A

Age, co-operation, oral hygiene and MH must be considered.

Used if pt very overcrowded, with good 4-2 contact (reshape 4)

Poor prognosis for alignment or lateral resorption risk high.

141
Q

Why may we choose to expose and align ectopic canines?

A

Canines in favourable position.
Sufficient space is available.

142
Q

What methods can you use to expose and align ectopic canines?

A

Expose crown and leave to erupt for 8-12 weeks before applying fixed orthodontic appliance (traction)
- Require thick 19-25 wire to provide anchorage to align exposed canine.

Open exposure: remove palatal mucosa and bone, expose tooth and then CoePak (two component material for wound dressing, to cover stitches or to stabilise loose teeth) and suture placed in hole in palate.

Closed exposure: especially for buried teeth, canine is exposed, and gold chain attached to bracket on chain, mucosa then grows back over.

If canine buccal then need to avoid pulling canine through non-keratinised mucosa.
–> either bone bracket and gold chain or use an apically-repositioned flap.

143
Q

What restorative options do you have if you decide to orthodontically create a space for 3s?

A

Replace with denture, bridge or implant.

Bridges to replace 3 are avoided ideally, poor prognosis.

144
Q

What are reasons for orthodontic extractions? (3)

A

Space for relief of crowding

Space for correction of incisor relationship, mainly for overjet patients.

Provision of anchorage to move teeth.

(Extractions permit relief of crowding without arch expansion or incisor proclination)

145
Q

What may ortho extractions to create space prevent you from doing and why are they good?

A

Arch expansion

Incisor proclination

  • Favouarble to avoid as they both take teeth out of the soft tissue neutral zone.
  • Upper incisor retraction stable, lower incisor proclination tends to relapse.
  • Premolar extractions make space for incisor retraction.
  • Often keep pt in class II molar relationship.
146
Q

What factors influence choice of orthodontic extraction?

A
  1. Health and form of individual teeth
  2. To increase stability
    > usually avoid anterior lower incisor A-P position
    > Aim to not expand arches laterally to accommodate crowding (except crossbites), as arch expansion not very stable and likely to replase.
  3. Amount of space and anchorage required.
    –> Extracting teeth nearer to the problem created more space and anchorage.
    –> XLA 4s relieve anterior crowding better than 5s
147
Q

What are advantages of premolar extractions?

A
  1. Space near the front teeth, means good anchorage
  2. Some spontaneous alignment of crowded incisors
  3. Residual space dentally healthy if treatment relapses.
  4. Good occlusal fit
148
Q

In what situations are 4s more favourable to extract?

A

If more anterior crowding or bigger overjet.

149
Q

What is the average width of the permanent dentition?

A

Central incisor ~9mm
Lateral incisor ~7mm
Canine ~8mm
Premolar ~4mm
Molar ~11mm

150
Q

How do you plan extractions? (check tx answers)

A
  1. Plan the lower arch first
    > Mild crowding may not need extractions
    > Moderate (5-9mm) remove 4s or 5s.
    > Severe (9+mm) remove 4s
  2. Assess tie-break factors
    > Canine angulation, retroclined 3s need more anchorage to upright
    > Lip prominence, upright incisors need more anchorage
    > Incisor inclination
  3. Upper arch to fit round lower
    > Upper arch needs more anchorage normally
    > Due to upper teeth being larger and overjet reduction normally indicated
  4. If lower arch is non-extractino
    > if upper 4s and XLA and no lower XLA then pt will finish Class II.
151
Q

What are causes of median diastema? (8)

A
  1. Pathology
  2. Microdontia
  3. Macrognathia
  4. Missing laterals
  5. Peg laterals
  6. Extracted teeth causing spacing in arch
  7. Mesiodens supernumerary
  8. Large labial frenum
152
Q

Why is XLA of first premolars not ideal ?

A

Because space is so far from the front of the arch.

Means that anchorage is very difficult, 5s most always migrate distally.

153
Q

How can timing Xtn of 6s be beneficial?

A

Allow 7s to migrate into 6s spaces when 7s start to bifurate.

154
Q

What are indications of poor prognosis 6s that leat to early extraction? (5)

A
  1. Gross caries and pulpal involvement.
  2. Hypoplastic or hypomineralised
  3. Large restorations
  4. Recurrent caries
  5. Lingual or buccal caries.
155
Q

What do successful interceptive 6s extractions depend on? (4) (general names)

A
  1. Timing
  2. Degree of crowding
  3. Mandibular vs Maxillary arch extractions
  4. Molar relationship
156
Q

What is the best time to extract 6s?

A

When bifuration of 7 roots forming, normally around age 10.

157
Q

What is the risk of XLA 6s too early?

A

Risk of the 5 migrating distally from beneath the E.

158
Q

What is the risk of Extn 6s too late?

A

Space closure will be incomplete, may cause tipping of 7s.

159
Q

How does degree of crowding affect success of interceptive 6s extractions?

A

No crowding - spontaneous closure will not occur.

If small amount of premolar crowding present = good prognosis.

160
Q

How do mandibular vs maxillary arch extractions affect the success of interceptive 6s extractions?

A

Lower arch harder to get final 5-7 contact

Upper arch easier due to natural distal angulation of 7

Lower molars converge, upper molars diverge.

161
Q

What does balancing extractions mean?

A

Balancing = extractions of a tooth on the opposite side of the same arch, to prevent centre-line discrepancies

162
Q

What does compensation extractions mean?

A

Extraction of the same tooth in the opposite arch, to preserve buccal segment relationships (molar relationship) and prevent over-eruption.

163
Q

Do you need to balance 6s?

A

No! loss of a 6 is too far from the midline

164
Q

Do you need to compensate 6s?

A

Yes! - compensating is required if over eruption of opposite 6 likely and help maintain molar relationship.

165
Q

If lower 6s are extracted early, do upper 6s need to be extracted?

A

Yes, as no occlusal stop, as upper 6s lie posterior to lower 6s.
Upper 6s with over erupt more than lowers.

166
Q

What are problems with interceptive extractions of 6s?

A

Lower 7s tip mesially and roll lingually.

Upper 7s rotate around palatal root.

Poor contacts if incomplete closure

Stagnation areas

Spacing

Necking of the alveolar bone

167
Q

Why do we do interceptive extractions in primary teeth?

A

Extractions undertaken to minimise or eliminate the severity of the developing malocclusion or eliminate potentially harmful occlusion before damage occurs.

  1. To guide the eruption of permanent successors
  2. To encourage space closure in hypodontia
  3. To reduce localised gingival recession
  4. Preserving symmetry and molar relationship
  5. Impacted 6s
168
Q

How do interceptive extractions of primary teeth help guide the eruption of permanent successors?

A

> Unerupted upper incisors (ensure its not a differential diagnosis), extract delayed exfoliating deciduous incisors.

> Palatally erupted upper 2: if anterior dentition very crowded then XLA C/C before the 2s reach the occlusal level (moves crowding to the C region)

> Unerupted lingual lower incisors: normally due to retained deciduous incisors (XLA of deciduous incisors)

> Ectopic canines, XLA of Cs

> Submerged tooth: infra-occluded deciduous teeth, normally due to absent permanent successor

169
Q

How does interceptive extractions of primary teeth encourage space closure in hypodontia?

A

Common if 2 or 5 missing

170
Q

How do interceptive extractions of primary teeth help reduce localised gingival recession?

A

> XLA C/C if crowding and gingival recession of one lower incisor present.
Soft tissue moves the incisors into the neutral zone.
Gingival recession in the crowded dentition due to teeth erupting outside the neutral zone.

171
Q

How do interceptive extractions of primary teeth help preserve symmetry and molar relationship?

A

> Lower incisor crowding can cause a 2 root to resorb a C, resulting in premature exfoliation.
This can result in a centreline shift to the affected side.
To prevent this happening a balancing extraction of the contralateral C must be done.

> only ever needs to be one balancing extraction in every arch.
The further from the midline the smaller the effect on the centre line
The further from the midline the greater the effect on molar relationship

172
Q

How do interceptive extractions of primary teeth help impacted 6s?

A

May require XLA of D or E to allow the impacted 6s to upright naturally.

173
Q

What are submerged/infraoccluded teeth?
Most common teeth?

A

Teeth that fail to maintain their occlusal relationship with opposing or adjacent teeth.
Most commonly affects the deciduous mandibular molars (8-14%)

174
Q

What is Grade 1 infraocclusion?

A

The occlusal surface of the tooth is above the contact point of the adjacent tooth.

175
Q

What is Grade 2 infraocclusion?

A

The occlusal surface of the tooth is at the contact point of the adjacent tooth

176
Q

What is Grade 3 infraocclusion?

A

The occlusal surface of the tooth is below the contact point of the adjacent tooth

177
Q

When do you extract deciduous infraoccluded teeth?

A
  • Permanent success absent (ortho tx), to allow teeth to align spontaneously
  • Severe submergence, approaching gingival level
  • Adjacent teeth tipping above the tooth
178
Q

What can you do to a submerged tooth to get in back into occlusion?

A

Can potentially build up with onlays if patient is older and submergence has stopped.

179
Q

What is a force couple?

A

When there are equal forces in opposite directions

180
Q

What are the mechanical principles of ortho appliances? (3)

A
  1. Applies mechanical force couple to the crown
    > Tipping movement = removable appliance
    i. achieves tipping movement of tooth around the centroid
    ii. Centroid = centre of resistance.
    > Bodily movement = fixed appliance
    i. overcomes tendency to tip - tooth moves bodily by the force couple.
    > Rotation movements
    i. force couple applied on the centre of resistance in horizontal plane
    ii. achieves controlled tooth movement such as derotation.
  2. Allows precise control over nature and direction of forces applied.
  3. Forces are applied through interactions between components such as arch wires, brackets and auxilliaries.
181
Q

What are the functional components of fixed appliances?

A
  • Archwires: multiple metals (nickel titanim), either round or rectangular
    > pre-formed shape, then this shape either accepted or adapted.
  • Brackets: twin or self-ligating
    > identifying marker is distal and gingival
  • Auxiliaries
    > Niti springs
    > Power chains
    > Elastic bands
182
Q

What are different types of movements that can be achieved by fixed appliances?

A

Derotation
Torque movements - require rectangular wire to grip bracket slot and apply force couple
Bodily movements

  • Centreline correction
  • Controlled space closure
  • Overjet reduction
183
Q

What are the 5 fixed treatment phases?

A
  1. Levelling and alignment
    - archwire small diameter, flexible, high elastic limit
    - nicket titanium
    - 0.012 or 0.014
    - if brackets correctly positioned a flat archwire will align teeth correctly
  2. Overbite reduction
    - rigid archwire of large dimensions
    - stainless steel
    - round or rectangular
    - 0.019 x 0.025
  3. Overjet reduction
    - Rigid archwire of large dimensions
    - stainless steel, rectangular
    - 0.019 x 0.025
    - provides bodily control in all planes
  4. Space closure
    - Rigid archwire of large dimensions
    - stainless steel, rectangular 0.019 x 0.025
    - provides bodily control in all planes
    - need to prevent teeth tipping into the space
  5. Finishing procedures
    - Small diameter archwires, thin, round stainless steel.
184
Q

What are problems with fixed appliances?
appliance related (4) and pt related issues (5)

A

Appliance related issues:
1. gingival inflammation
2. decalcification
3. root resorption
4. soft tissue trauma

Patient related issue
1. breakages
2. attendance
3. poor oral hygiene
4. caries
5. staining

185
Q

What are functional appliances? how do they work?

A

They utilise forces generated by soft tissues to move teeth

  • They posture the mandible away from rest position
  • Forces are therefore generated by the resulting soft tissue stretch
  • They increase growth potential
186
Q

When are functional appliances commonly used?

A

Mainly treat pts with Class II div 1 incisor relationship, with or without crowding, on a moderate to severe skeletal class II base

Can use it for Class II div 2 pts but must convert to class II div 1 first to treat

187
Q

What is the classification for functional appliances?

A
  1. Myodynamic
    > Forces are generated by stimulation of the masticatory muscles
    > Twin block or Bionator
  2. Myotonic
    > Elastic recoil within the stretched forces generates force
    > Harvoid
188
Q

How are the dentoalveolar effect of functional appliances due to stretched tissues applying force to the teeth?

A
  • Retraction of upper incisors (palatal tipping)
  • Distal movement of the upper buccal segment (molar relationship correction)
  • Proclination of lower incisors
  • Overbite reduction by reducing lower incisor eruption while permitting buccal segment
    tooth eruption
  • Mesial movement of lower buccal segment
189
Q

What are the skeletal effects of functional appliances?

A

Mandibular growth enhanced by 1mm average
Maxillary growth inhibited by 1mm average
- Wide variation of these effects

3 theories as to the location of change in skeletal effects

  1. More actual mandible growth
  2. Change in position of the glenoid fossa
  3. Change in direction of growth
190
Q

What are the soft tissue effects of functional appliances?

A

Frankel has proposed that a functional appliance + lip exercises = alter lip and cheek position.
Soft tissue encourage to be correctly positioned, with normal function.

191
Q

At what age are functional appliances used?

A

Growing patient, as they are better tolerated in younger patients.
Late mixed/early permanent dentition, but can be used at later stage.
Girls 10-12, boys 12-14 as can influence growth a little more when pt growing rapidly.

192
Q

what are 4 types of functional appliance?

A
  1. Clark Twin Block
    > Two-part appliance
    > Well tolerate
  2. Bionator
    > Single piece
    > not retentive (relies on pt biting to maintain position
    > used for mixed dentition mainly
  3. Frankel
    > Single piece
    > not well tolerate
    > expensive and v fragile
  4. Harvoid
    > Less A-P posture, more vertical effects
    > Not retentive and not well tolerated.
193
Q

What advice can be given with functional appliances?

A
  • Patient can eat with the appliances. That even increased the speed of appliance work
  • Initial soft diet of eggs, soup and boiled vegetables suggested.
  • Increased salivation at the beginning of wear
  • Suggested to be worn at least 18 hrs. a day especially during sleep.
  • Brush the appliance at least once a day with water and soft toothbrush
194
Q

What do you need for construction of functional appliance?

A

Upper and lower impressions
Bite record

195
Q

How can you monitor if the functional appliance is being worn?

A
  • Do they come in wearing it?
  • Is speech normal?
  • Does it look worn?
  • Slight gingival inflammation may be present?
  • Can they insert and remove it with ease?
  • Lateral open bites appear often?
  • Are the active components more passive?
  • Has progress been made?
    > Check overjet, as should reduce by > 1mm per month
    > Molar relationship should improve
    > Lateral open bites appear often
    > Radiographs alongside specialist training to identify success or failure
196
Q

When does intercanine growth stop?

A

No intercanine growth above 10 years old, therefore spontaneous resolving of anterior crowding not possible after this.

197
Q

How does the skeletal pattern change with growth? ANB angle

A

Mandible grows more compared to maxilla on average
> AP skeletal pattern measured by ANB angle

ANB angle gets smaller by 1 degree from 11 to 20.
However there is a standard deviation of 2.5 degrees.
- 15% grow more class III by >3.5 degrees
- 15% grow more class II by > 3.5 degrees

MOST PEOPLE HAVE A JAW RELATIONSHIP WHICH STAYS THE SAME WITH GROWTH

198
Q

What are the 2 types of gone growth?

A
  1. Cartilage replacement
    - Cranial bases synchondroses
    - Mandibular condyles
    - resistant to the effects or applied forces, working entirely genetically.
  2. Membranous growth
    - Periosteal activity at surface and at sutures
    - All other cranial and facial growth
    - Influenced by pressure and tnesion, like periodontal remodelling in response to orthodontic forces.
199
Q

How can clinicians control growth?

A

> Headgear and functional appliances restrain maxillary growth (membranous growth)

> Traction to skeletal anchorage can increase midface growth
- These include bollard mini plates and Class III elastics
- Average enhancement = 4mm

> Mandible less amenable to growth modification
- FA enhance growth of mandible by 1-2mm in growing patient

200
Q

What can excessive vertical growth lead to (a malocclusion)

A

anterior open bite

201
Q

when should you treat class III and II pts?

A
  • Class III patients treated late as growth unfavourable
  • Class II patients treated earlier as growth favourable
202
Q

When only can you carry out orthognathic surgery and dental implants?

A

After growth stopped

Orthognathic surgery + 4 yrs. after growth has stopped.

Implant surgery at around 23 yrs. old

203
Q

When is the average growth spurt? (girl vs boy)

A

Girls - 10-12. Growth stops age 16

Boys - 12-14. Growth stops age 18

204
Q

Orthodontic tx planning: read

A
  1. Do you need to treat the patient?
  2. The patients wish list, what do they want from the treatment?
  3. Occlusal relationship aims — usually Class I incisors and molars
  4. Where in the face should occlusion be put?
    • Usually try not to move lower incisors substantially forwards or backwards
    • Try not to expand the arches very much
    • Both changes make stability less likely
  5. Choice of appliance depends on clinical and patient factors
  6. Extractions: need and choice of extraction

Collection of data –> Problem List –> Treatment aims and means
1. Gathering data
2. Compiling a problem list
3. Deciding treatment AIMS
4. Deciding treatment MEANS

205
Q

What is lip competence and what is it particularly important for?

A

= if the lips meet at rest without muscular activity

  • important for stability of overjet reduction
  • if they are incompetent, then overjet reduction more unstable.
206
Q

How is crowding classified?

A

Mild = 1-4mm
Moderate = 5-8mm
Severe = 8+mm

Labial and buccal segment crowding.
Crowding mesial to canine is labial, distal is buccal.

207
Q

How can you classify incisor relationship? (4)

A
  • Incisor classification
  • Overjet
  • Overbite
    > normal, increased, reduced AOB
    > incomplete or complete overbite
  • Centre-line discrepancies
208
Q

How can you classify molar relationship?

A
  • Class I = MB cusp of first molar lies in the buccal groove of the lower first molar
  • Class II = MB cusp U6 lies anterior to the buccal groove of L6
  • Class III = MB cusp lies posterior to the buccal groove of L6

Units in terms of premolars. full unit, 1/2 unit, 1/4 unit?

209
Q

What is orthognathic treatment?

A

Combined orthodontic and surgical treatment, due to the problem being so severe that orthodontics alone cannot provide solution

Treatment carried out when facial growth is complete or almost complete

Plan the procedure by cephalometric planning and treatment simulation

> Superimposition of bony segments over original lat-ceph
Computer prediction from digital lat-ceph radiographs
Superimpose both the profiles on top of each other, analysing planned changes

210
Q

What are 4 types of orthognathic treatment?

A
  1. Correction of antero-posterior relationships
    • Mandible can be moved both forwards and backwards to correct
    • Maxilla can only be moved forwards due to posterior skeletal interference
    • Retrognathic mandible corrected by sagittal split osteotomy surgery
  2. Correction of vertical relationship
    • Long lower face height associated with AOB
    • Short lower face height associated with deep traumatic overbite
    • Maxilla movement: intrusion successful, extrusion unpredictable
    • Mandible can be moved up or down anteriorly
    • Downward movement of mandible at the gonial angle unstable
  3. Correction of transverse relationship
    • Surgical expansion of the maxilla possible
    • Difficult in the mandible due to temporo mandibular articulation
  4. Genioplasty
    The chin can be moved in all 3 planes
    • Aesthetically better results if the bony movement increases soft tissue support
    • Inferior border osteotomy to correct protrusive mental bone
211
Q

What are the stages of orthognathic + orthodontic tx?

A
  1. Presurgical orthodontic treatment (orthodontic decompensation)
    • Arch alignment
    • Normal inclinations of upper and lower labial segments
    • Upper arch expansion (co-ordination of arch widths post-surgery)
    • Once orthodontic decompensation has been achieved the malocclusion will often appear substantially worse, reflecting underlying skeletal discrepancy
  2. Surgical management
    • 2-3-hour op, in hospital 1-3 days post-op and then 2-3 weeks home recovery
  3. Post-surgical orthodontic treatment
    • 3-8 months
  4. Orthodontic retention
212
Q

Andrews 6 keys to normal occlusion

A
  1. Correct molar relationship (Class I)
  2. Correct crown angulation
  3. Correct crown inclination
  4. No rotations
  5. Flat occlusal plane
  6. Tight interproximal contacts (no spaces)
213
Q

What is the definition of orthodontic anchorage?

A

Resistance which prevents unwanted reciprocal tooth movement

(Tooth moving forces create equal and opposite forces, reciprocal forces must be resisted to minimise unwanted reciprocal tooth movement)

214
Q

What 5 different sources of orthodontic anchorage?

A
  1. Teeth in the same arch
  2. Oral mucosa and underlying bone
  3. Opposing teeth (intermaxillary traction)
  4. Extra-oral anchorage
  5. Temporary Anchorage Device (TADs)
215
Q

Anchorage advice: read

A
  • Ways to just move anterior teeth, preventing loss of space by posteriors moving mesially
    1. Move few teeth at once
    2. Keep active forces minimal
    3. Make anchorage root area as large as possible (XLA of 4s and incorporate 7s in unit)

Teeth bodily moved require more anchorage, than teeth being tipped as bone must be resorbed over a much larger surface area

Teeth free to tip move very easily due to the small root surface area and minimal force needed

  • Bodily movement requires much more anchorage than tipping
  • Due to bodily movements needing to resorb bone over large surface area
  • Intermaxillary elastics provide anchorage (traction) for space closure

Extra-oral anchorage: force resisted by the bones of the head, a very large anchorage
- Headgear used as extra-oral anchorage
- Used when there is not enough intra-oral anchorage or to move all teeth distally

TADs: a potentially infinite anchorage source
- Avoids the spring pushing the upper front teeth forwards (loss of anchorage) They contain no PDL, meaning that forces applied on them do not invoke a cellular response to move a tooth

216
Q

What are the 3 Ps for ortho radiography?

A

Presence
Position
Pathology

217
Q

What view does a lateral cephalogram take? Reasons for a lateral ceph?

A

A standardized lateral view of the facial bones, base of skull, soft tissues and cervical spine.

  • 2D assessment of upper and lower jaws relative to cranial base
  • Assessment of tooth inclinations
  • Identification of ectopic teeth
  • Implant planning
  • Baseline for monitoring growth
218
Q

Radiographic locations
ANS, PNS, N, S, ME, GO

A

ANS –anterior nasal spine

PNS – posterior nasal spine

Maxillary-mandibular planes angle

N – Nasion, most anterior point on frontonasal suture

S — Sella, midpoint of Sella turcica, the saddle shaped depression in the sphenoid bone

ME – Menton, lowest point on mandibular symphysis

GO — Gonian, the most inferior point on the angle of the mandible

219
Q

What can removable appliances be used for?

A

Removable appliances can only tip teeth, they are unable to perform bodily movements

Current uses of removable appliances
- Simple tooth movements
- Space maintenance
- Retainers for post-orthodontic treatment
Functional appliances

220
Q

What are the elements of a removable appliance?

A

ARAB
1. Active component
i. springs
ii. labial bows
iii. screws
iv. z springs?

  1. Retentive component
    i. adams clasps (0.7mm ss wire posteriorly)
    ii. southend clasp (0.7mm ss wire anteriorly)
  2. Anchorage
  3. Baseplate
    i. holds appliance together
    ii. provides anchorage from vault of palate
    iii. can provide anterior and posterior bite planes
221
Q

What factors determine the applied force in removable appliances?

A

i. length of spring (increased length = greater force)

ii. elastic modulus of wire (decreased elasticity = greater force)

iii. thickness of the wire (increased thickness = greater force)

222
Q

What can labial bows be used for?

A

Reverse looped bow in 0.8mm ss wire
Can be used as a retainer
- Or split in two and used as a retractor

223
Q

What are screws used for?

A

Used for unilateral and bilateral distal movement Used for arch expansion
Turn once or twice a week for optimal results

224
Q

What is orthodontic relapse?

A

Relapse: return of the original malocclusion following correction

225
Q

What is orthodontic stability?

A

Stability: the dentition existing in a state of equilibrium between forces imparted by soft tissues of the lips, cheeks and tongue

226
Q

What is orthodontic retention?

A

> Retention: the phase following active orthodontic treatment, aimed at stabilization of
the orthodontic correction

227
Q

What can cause orthodontic relapse?

A

Soft tissue
Occlusal factors
Facial growth
Supporting tissues

228
Q

How can soft tissue factors affect relapse?

A

> Teeth not in neutral zone unstable, only stable if new balance found
Reducing overjet in Class II div 1, stable if lower lip in front of upper incisors post Tx
Unstable if short lips present, whereby lower lip doesn’t cover the upper incisors

229
Q

How can occlusal factors affect relapse?

A

> Adequate overbite must be reached in Class III cases
Appropriate inter-incisal angle in Class II div 1 cases (133 degrees)
Good intercuspation must be achieved in all cases

230
Q

How can facial growth affect relapse?

A

> Class III skeletal pattern growth may worsen with facial growth
Over-correction in Class II and III patients
- Lower incisor crowding
- Anterior open bites may worsen with backward growth rotation
- Deep bites may worsen with forward growth rotation

231
Q

How can supporting tissues affect relapse?

A

Bone
> Newly formed osteoid and immature woven bone more susceptible to remodelling, has critical period of 3 months

Periodontal ligament
> Avoid ‘spring back’ post-treatment
Sharpey fibres between cementum and bone require 1-2 months to re-organise

Gingiva
> Supra-crestal fibres require 6 months to re-organise
> Free gingival fibres require 12 months to re-organise
> Derotation during orthodontics most prone to relapse (prevented by circumferential supracrestal fiberotomy)

232
Q

What are types of orthodontic retainers?

A

Fixed: wire attached to the teeth with composite, used in more unstable situations

Removable: vacuum formed retainers (VFRs) and Hawley type retainers

Revision big doc (8 decks)

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