Class III Malocclusions

Question 1

what is the BSI of class 3 malocclusion?

Answer 1

Lower incisor edge occludes ANTERIOR to cingulum plateau of upper central incisor

Overjet is reduced OR reversed

Question 2

what is the aetiology of class 3 malocclusion?

Answer 2

Strong genetic link

Environmental factors:
- Cleft lip & palate
- Acromegaly

Question 3

what are the antero posterior skeletal features of a pt with class 3 malocclusion?

Answer 3

small maxilla
OR
large mandible
OR
combination of both

Question 4

what are the VERTICAL skeletal features of a pt with a class 3 malocclusion?

Answer 4

may be associated with average, increased or reduced vertical proportions (not fixed to one)

• FMPA Angle
• Facial Height
• Lateral Ceph

Question 5

what are the TRANSVERSE features of a pt with class 3 malocclusion?

Answer 5

Retrusive maxilla sits on WIDER part of mandible
- BILATERAL CROSSBITE

Question 6

What are the dental features of a class 3 malocclusion?

Answer 6

can vary
- class 3 incisor
- class 3 molar (not always)
- tendency to reverse overjet
- reduced overbite, AOB may be present
- crossbites

Question 7

what are the dental health reasons for treating class 3 malocclusion?

Answer 7

• attrition
• gingival recession
• mandibular displacement

Question 8

what are the functional issues of why u would tx class 3?

Answer 8

• speech and mastrication

Question 9

what factors make a class 3 malocclusion more difficult to treat?

Answer 9

large AP discrepancy
presence of anterior open bite
lots of teeth in anterior crossbite

Question 10

what are the orthodontic tx options for managing a pt with class 3?

Answer 10

• accept/monitor
• intercept early with URA
• growth modifications
• camouflage
• combined orthognathic & orthodontic tx

Question 12

when is growth modification is effective for a pt with class 3?

+

What would be done?

Answer 12

• a growing pt

aimed at reducing mandibular growth + encourage maxilla growth.

Question 12

what tx could you do with a URA for a pt with class 3 malocclusion?

Answer 12

URA to procline incisors over the bite

Question 12

names of growth modification equipment for a pt with class 3?

Answer 12

Reverse twinblock
protraction headgear

Question 13

how would orthodontic camouflage be carried out in a pt with class 3?

Answer 13

accept skeletal base relationship and AIM for class 1 incisors

XLA further back in upper arch (5s)
XLA further forward in lower arch (4s)

PROCLINE upper incisors
RETROCLINE lower incisors
CORRECT OVERJET

Question 14

when would orthognathic tx be appropriate for a pt with class 3 malocclusion?

Answer 14

moderate/severe skeletal discrepancy

pt has functional/aesthetic concerns

completed their growth

Question 15

whats the GDP role for a class 3 malocclusion?

Answer 15

to identify it
refer to hospital/specialist

URA treatment (for anterior cross bite)