Class III Malocclusion

Question 1

Class III

Answer 1

Lower incisor edges are anterior to the cingulum plateau of the upper incisors

Question 2

Significance

Answer 2

Poor dental appearances
May be associated with an anterior mandibular displacement
Facial profile often poor
Growth usually unfavourable ie mandible grows forward more than maxilla

Question 3

Incidence

Answer 3

3-5% UK

Question 4

Aetiology

Answer 4

Genetic - skeletal pattern
AP skeletal discrepancy (mandibular excess, maxillary hypoplasia)
may be the result of mandibular displacement
CLP pts

Question 5

Genetic background class III

Answer 5

13% pts have affected sibling
13% have class III mother
20% have class III father

Question 6

Cepthalometric

Answer 6

ANB <2

Question 7

Skeletal features

Answer 7

> 70% have a skeletal III pattern (ANB <2)
Skeletal pattern may be as a result of small maxilla and large mandible
Maxilla is often narrow –> crossbite

Question 8

Dental features

Answer 8

Class III incisors (mild cases are edge-edge, severe cases may have large reverse overjet)
Dentoalveolar compensation (upper incisors proclined and lowers retroclined)
Upper arch often narrow and crowded –> crossbites

Question 9

Tx of class III

Answer 9

Improve dentofacial appearance
Psychosocial teasing
Eliminate mandibular forward displacement if present

Question 10

Tx aims

Answer 10

Produce a positive overjet
Relieve crowding and align arches
Improve facial profile
Produce a stable result

Question 11

Tx options

Answer 11

Accept incisor relationship
Procline upper incisors
Retrocline lower incisors
Orthogathnic surgery

Question 12

Skeletal discrepancies and tx

Answer 12

None/mild: orthodontic appliances only
Moderate: orthognathic surgery
Severe: Orthognathic surgery

Question 13

Timing of tx

Answer 13

Growth - often unfavourable and lasts longer in class III cases
Displacements can often be treated early using appliances to procline the upper incisors
Appliance treatment usually carried out at a later age than in other types of malocclusion - age 15/16 when growth has stopped

Question 14

Favourable factors for tx

Answer 14

Pre-tx overbite
Ability to bite edge to edge
Anterior displacement
Small/no skeletal discrepancy

Question 15

Tx with fixed appliances

Answer 15

Mild to moderate skeletal discrepancies with acceptable facial profile
Crowded lower arches
Aim to produce dentoalveolar compensation
Extract lower premolars to allow retroclination of lower incisors

Question 16

Tx with surgery

Answer 16

Severe skeletal discrepancies and poor facial profile/appearance
Vertical problems and AOB
Fixed appliances to align individual arches and produce decompensation
Surgical mandibular set back and/or maxillary advancement