Treatment of Class III Malocclusion

Question 1

Correction of class III depends on

Answer 1

Skeletal pattern
Dento alveolar compensation
Can pt achieve edge-to-edge incisors

Overbite
- if significant and solved then treatment should last longer

Question 2

Skeletal pattern - aetiology

Answer 2

Increased md length

Anterior placed glenoid fossae = anteriorly placed condylar head

Question 3

Dento alveolar compensation

Answer 3

Upper incisor proclined and lower incisors retroclined

Question 4

Class III

Increased prominence of chin
Reduced overbite

Answer 4

Forward opening rotation

Backwards opening rotation

Question 5

Mild skeletal class 3

Answer 5

Normal overbite
No lower arch extractions
Do not extract in upper arch

Accept incisor relationship and direct tx to ARCH ALIGNMENT

Question 6

Moderate class III skeletal

Answer 6

Loss of overbite
Poor prognosis for stability
Needs upper and lower fixed appliances
Consider extractions in lower arch e.g premolar which allows space for lower incisors to move back to recreate overbite

Question 7

Moderate class III skeletal

Answer 7

Upper rectangular wire to create torque for motion

Lower round wire

Question 8

Severe class III skeletal

Answer 8

Pre-Surgical ortho - remove compensations which may have occurred e.g proclination of incisors
Orthognathic surgery

Question 9

timing of treatment for class III

Answer 9

Early interception - growth modification

Later - tooth overbite

Question 10

Skeletal issues - treatment

Answer 10

Bring maxilla forward

Question 11

Bring mandible back

Mechanism

Answer 11

Chin cup

• no evidence that mandible affected
• retroclines lower incisors
• rotates mandible down and back

Question 12

Maxilla forward

Answer 12

Protraction face mask (reverse head gear)

Worn 20hrs a day for 4-6 months

Question 13

Both mandible and maxillary movement

Answer 13

Twin block

• blocks slope in opposite direction
• push jaw down and maxilla up
• ineffective as jaw already has limited movement

Question 14

Frankel 3 appliance

Answer 14

Ineffective

Small amount activation possible

Maxillary retrusion common

Question 15

Interceptive treatment

Answer 15

Incisors over the bite

- centrals and laterals

Question 16

Potential problems

Answer 16

Class III

Over bite - need enough to retain correction

Space

Interference from primary canines - should be extracted

Position of permanent canine - may prevent movement and resorb lateral if moved

Do not over proline incisors

Warn about relapse

Question 17

Space required for correction

Answer 17

Primary teeth extracted

Question 18

Soft tissue and Dentoalevolar compensation

Answer 18

Tend to tilt upper and lower incisors towards each other to meet

Question 19

Dental factors

Answer 19

Narrow upper arch and comparatively broad lower arch

Question 20

Occlusal features

Answer 20

Lower incisors placed labially = anterior crossbite

Question 21

Normal or increased overbite is an

Answer 21

Advantage - provides post treatment stability

Question 22

Main aim of ortho management of class III

Answer 22

Increase dento alveolar compensation

Question 23

Crowding occurs

and can be solved by

Answer 23

More frequently in upper

Expansion of upper arch

Question 24

Upper arch extractions

Answer 24

contraindicated

if essential then extract as far forward in lower arch

Question 25

Interceptive ortho

Answer 25

Correction in mixed dentition

Further fwd mandibular growth may be counterbalanced by DA compensation

Question 26

Ortho correction options

Answer 26

Proclination of uppers

Retroclination of lowers or BOTH with fixed appliance

Question 27

Lower arch extractions required if

Answer 27

Retroclination of lower labial segment requires space

Question 28

Surgery almost always required if

Answer 28

Value of ANB angle < -4º

Inclination of lower incisors to md plane < 80º