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BDS4 CDS Ortho > Class III > Flashcards

Class III Flashcards

1
Q

all malocclusions are classed by

A

incisor relationship

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2
Q

definition of class III malocclusion

A

lower incisor edge occludes anterior to the cingulum plateau of the upper central incisor

3 presentations of class III,Not necessary for reverse OJ or ant Xbite

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3
Q

incidence of class III

A

Geographical variation

UK 3-5%
* Higher incidence in west of Scotland
* Higher incidence in Asia

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4
Q

aetiology of class III

A

**Strong genetic link **
* Patter of transmission controversial (unknown)
* Run in families

Environmental factors
* Cleft lip and palate - Restricted growth of maxilla due to cleft surgery
* Acromegaly - Inc production of growth hormone from pit gland will inc size mandible

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5
Q

3 aspects to consider when assessing malocclusion

features

A

skeletal
dental
soft tissues

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6
Q

skeletal - consider in

A

3 planes
* antero-posterior
* vertical
* transverse

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7
Q

antero-posterior skeletal relationship for class III

A

*All have class III incisor relationship
Left is class I skeletal
Middle is moderate class III
Right is class III skeletal with OB *

Aetiology could be due to
* Small maxilla
* Large mandible
* Combination of both (most)

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8
Q

vertical class III skeletal relationship

A

may be associated with average, increased or reduced vertical proportions
* Frankfort Mandibular Planes Angle
* Facial Height proportions
* Lateral Cephalometry

↑FMPA and anterior open bite more complex to treat –* likely need orthognathic*

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9
Q

transverse relationship of class III

A

A-P and transverse relationship linked

Retrusive maxilla sits on wider part of mandible
* Bilateral Crossbites - Narrow maxilla against wide mandible

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10
Q

dental features of class III

8

A

Vary

  • Class III incisor relationship
  • Class III molar relationship (not always)
  • Tendency to reverse overjet
  • Reduced overbite, anterior open bite may be present
  • Crossbites sometimes: Anterior or Buccal

Alignment
* Maxilla often crowded common;
* Mandible often aligned or spaced

Dentoalveolar compensation
* Proclined upper inicors
* Retroclined lower incisors
* teeth erupt towards despite underlying skeletal discrepancy

Tendency for displacements on closing
* Mandible displacement to achieve posterior teeth contact

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11
Q

alignment in class III

A
  • Maxilla often crowded common;
  • Mandible often aligned or spaced
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12
Q

dentoalveolar compensation in class III

A

Proclined upper inicors
Retroclined lower incisors

teeth erupt towards despite underlying skeletal discrepancy

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13
Q

tendency for displacement on closing for class III

A

Mandible displacement to achieve posterior teeth contact

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14
Q

in general tx difficulty for class III malocclusion

estimate

A

.> number of teeth in anterior crossbite (more than 1-2)
Skeletal element in aetiology
.> the A-P discrepancy (vertical issues e.g. AOB)
Presence of anterior open bite

= more complex case

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15
Q

soft tissues in class III

A

Not usually involved in aetiology

Do encourage dentoalveolar compensation
* Tongue proclines the upper incisors
* Lower lip retroclines lower incisors

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16
Q

why tx class III malocclusions

3

A

aesthetics

dental health reasons

function

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17
Q

tx class III malocclusion for aeshtetics

A

dental
profile concerns

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18
Q

tx class III malocclusion for dental health reasons

A

attrition - wear on labial of UI and lingual face of LI
gingival recession - occlude healvily on LI, press root through buccal plate
mandibular displacement

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19
Q

tx class III malocclusion for function

A

speech - warn improve malocclusion, won’t necessarily alter speech
mastication

20
Q

facial growth for class III malocclusions

A

Tends to be unfavourable

Mandibular growth continues for longer

Potential for Class III to get worse

Do not do anything irreversible until growth has stopped
* Could affect future treatment if surgery required

20
Q

facial growth for class III malocclusions

A

Tends to be unfavourable

Mandibular growth continues for longer

Potential for Class III to get worse

Do not do anything irreversible until growth has stopped
* Could affect future treatment if surgery required

21
Q

how to predict growth status

A

Difficult to predict

Height and weight charts
* ? Cervical vertebral maturation (CVM) on lateral ceph
* Evaluates the shape changes in the bodies of cervical vertebrae C2, C3 and C4 – already taking lat ceph to assess skeletal pattern
* difficult to reproduce, poor reliability and valid

DONT USE - Hand wrist radiographs - low reliability and risks of repeated radiography so not justified

Individual variation - If in doubt watch and wait

onset of pubertal growht spurs coincides with spurt in growth

22
Q

class III management guide

5 options

A

accept and monitor
intercept early with URA
growth modification
camouflage
combined orthognathic/orthodontic tx

23
Q

when to accept and monitor class III

A

no concerns

no dental heatlh indicatins - displacements/attrtion

mild cases

24
Q

interceptive tx for class III malocclusion

when

A

Suitable if Class III incisors have developed due to early contact on permanent incisors (i.e. mandibular displacement)

Correction of anterior crossbite in mixed dentition has the advantage that further forward mandibular growth may be counter-balanced by some dento-alveolar compensation.
* Can achieve edge to edge, but displacing into anterior crossbite
* If pt continues to grow, mandible grows, dentoalveolar compensation teeth adapt to new position

Only suitable for correcting a lateral incisor crossbite if permanent canines are high above lateral roots
* Delay if canines have dropped down into buccal position as risk of resorption to lateral incisor

25
Q

URA for interceptive ortho tx

A

URA procline incisors over the bite
* Z spring
* Screw section
* Need to disclose occlusion – molar capping over buccal segments

Good OB will maintain stability

26
Q

growth modification for class III

when and options (4)

A

growing pt
* Aimed at reducing and / or redirecting mandibular growth and encourage maxillary growth

Functional appliances
* Chin cup
* Reverse Twin Block
* Frankel III
* Protraction headgear ± Rapid Maxillary Expansion

27
Q

chin cup

A

doesn’t have large skeletal effect

Mainly historic form of treatment

Lingual tipping of lower incisors

Rotates mandible down and back

28
Q

frankel III

A

Outdated now – sometimes used
* One piece appliance – hard to wear all the time
* Acrylic heavy - buccal flange, labial culottes - trauma and break easily
* Largely dentoalveolar effect

Pellotes (Shields) labial to upper incisors to hold lip away
Palatal arch to procline the upper incisors
Lower labial bow to retrocline the lower incisors

29
Q

reverse twin block

A

Slope the opposite way to twin block

Hard to get pt to bite into wax correctly
* Need mandible in most retruded position

Best in pt who can have edge to edge at start of tx

Mainly dentoalveolar

30
Q

protraction headgear

A

Co-operative patient

14 hour/day protraction facemask wear

400g/side – large force

Best results when used in early mixed dentition ( 8-10 years)
* Young pt – co-operation needed

± Rapid maxillary Expansion
* Pt needs to turn screw 2x daily – split mid palatal suture
* Attach to head gear – theory is disrupts circum-maxillary sutures as well

31
Q

bollard implants

A

Used in late mixed and permanent dentition

Infrazygomatic crest and lower canine region
* Mucoperiosteal flaps need to be raised for insertion and removal
* GA maybe needed

Can be used in conjunction with facemask

32
Q

what is orthodontic camoflauge for class III

A

accept underlying skeletal base relationship, aim for class 1 incisors

33
Q

3 aims of camoflauge ortho tx

A

procline upper incisors
retrocline lower incisors
correct OJ

aim for class 1 incisors

34
Q

favourable features for camoflage tx

5

A

Growth stopped

Mild to moderate Class III Skeletal base ANB not <0o

Average or inc OB

Able to reach edge to edge incisor relationship (Ask pt)

Little or no dentoalveolar compensation
* Don’t want pt to start tx with UI proclined and LI retroclined

35
Q

extractions pattern for camoflage tx of class III

A

Extract further back in the upper arch

Extract further forward in the lower arch

Classic pattern - Upper 5’s , lower 4’s
* However not always possible
* Dental health may dictate extraction pattern

36
Q

example tx plan for class III camoflage

A
  1. XLA all first permanent molars
  2. Surgically remove LL8 and LR8
  3. Upper and lower fixed appliances to treat to Class I
  4. Life long retention
37
Q

what is good to have pre tx for retention of movement post camo tx (class III)

A

good overbite proportion

38
Q

if pt still growing

A

do not embark on full correction - can get worse, pt undo results due to growth
* Cannot predict growth changes
* Consider upper arch alignment only - Keep pt happy until able to deal with underlying jaw relationship

Do not XLA in lower arch as this could affect future treatment options
* Risk reopen extraction sites in lower arch -> need pros tx

39
Q

orthognathic surgery

def

A

surgical manipulation of the mandibule and/or maxilla to produce optimal dentofacial aesthetics and function

40
Q

when would orthognathic/ortho tx approach be taken for class III

3

A

pt has aesthetic or functional concerns

growth completed

moderate/severe skeletal discrepanacy
* A-P
* transverse
* vertical

41
Q

orthognathic surgical tx planning

A

Careful planning

Multidisciplinary team approach
* Orthodontist
* Maxillofacial surgeon
* Orthognathic Technician
* Psychologist

Prediction planning software
* Make image up of what pt is expected to look like post surgery

42
Q

3 stages in orthognathic/orthodontic tx for class III

A

Presurgical orthodontics (approx. 18 months)
* Level, align, co-ordinate and decompensate
* Rid of curve of spee - want teeth to interdigitate when move jaws, as will make lateral OB
* Un-rorate teeth
* Coordinate width of arches- avoid lateral discrepancies
Uppers 109˚
Lowers 90˚

Orthognathic surgery to reposition the jaws
* Mandible
* Mandible ± Maxilla

Post surgical Orthodontics (approx. 6 months)
* settle bite in, with full time intermaxillary elastics usually

sometimes sugery first - want interdigitation after surgeryA

43
Q

GDP role in class III management

A

identify class III malocclusion - refer to hosp or specialist

URA tx? - anterior cross bite correction

44
Q

summary of class III malocclusion management

A

Challenging malocclusion to treat

Complicated by unpredictable growth

Careful assessment of aetiology important
* Purely dental? Or skeletal involvement?
* Is it treatable with orthodontics only?

BDS4 CDS Ortho (9 decks)

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