Tx Class III Malocclusion

Question 1

Class III incisors?

Answer 1

The edge of lower incisor tip lies anterior to cingulum plateau of the upper incisor

Question 2

Aetiology of class III incisors?

Answer 2

Maxillary retrusion 34%
Mandibular protrusion 40%
Both 26%

Question 3

Skeletal pattern of class III?

Answer 3

Have dento-alveolar compensation - maxilla set back compared mandible
Compensation: proclined uppers and lowers retroclined/ upright
Pt can achieve edge-edge - displacement between ICP and RCP

Question 4

How to tx reverse overbite in class III?

Answer 4

Procline upper sto reduce overbite

Question 5

Tx approach if normal overbite and mild skeletal class III

Answer 5

Can be tx

If no crowding lower arch then upper XLA should be avoid

Question 6

Tx approach normal overbite and moderate skeletal class III?

Answer 6

Upper and lower fixed appliance
Loss overbite - poor prognosis stability
Consider XLA lower arch

Question 7

Tx approach normal overbite and severe skeletal class III?

Answer 7

Orthognathic surgery

Question 8

Tx approach if reduced overbite and mild skeletal class III?

Answer 8

Accept incisor relationship and align teeth only

Question 9

Tx approach if reduced overbite and moderate-severe skeletal class III?

Answer 9

Poor prognosis for stable tx
Align teeth and accept incisor relationship
Orthognathic surgery

Question 10

Tx to bring mandible back?

Answer 10

Use chin-cup (unsuccessful?)
Worn like headgear
Prevent forward growth mandible

Question 11

Tx to bring maxilla forwards?

Answer 11

Face mask - worn full time (12-14 hours for 6-9 months)
Uses elastics
Dependent on compliance

Question 12

Example of functional appliance used in class III?

Answer 12

Class III twin block
Blocks slope opposite direction
Condyle already in glenoid fossa - can’t push back much further

Question 13

Problems functional appliance used in class III?

Answer 13

Only small amount activation possible
Maxillary retrusion common
Timing of fitting - if fit early age still have growth period (10-13 depend gender)

Question 14

What simple interceptive tx could be used for tooth-over-bite (anterior cross bite)

Answer 14

URA

Can add posterior bite block - prevent occlusal interference

Question 15

List potential problems tx class III?

Answer 15

Class III skeletal patterm
Overbite
Space
Interference primary canines
Position of permanent canines (wait for perm. erupt before correction)
Growth

Question 16

Problem caused class III skeletal pattern?

Answer 16

If severe - upper incisors will be over-proclined

Ensure pt can meet edge-edge w/o large vertical space between posterior teeth

Question 17

Why can overbite be a problem?

Answer 17

Need to retain overbite

Question 18

Problem with space?

Answer 18

Should be enough space between C–>C to allow forward movement of incisors
If not XLA both C’s

Question 19

Why can deciduous canine relationship be issue?

Answer 19

Abnormal relationship may maintain forward displacement after incisor correction
Grind or XLA C’s

Question 20

Why can position unerupted permanent canines be an issue?

Answer 20

If close root of lateral - can cause resorption
Risk esp in narrow arch - canine often develop forward position (buccal to lateral)
Can be better to wait for eruption of canine in these cases