Treatment of Class III Malocclusion Flashcards
Correction of class III depends on
Skeletal pattern
Dento alveolar compensation
Can pt achieve edge-to-edge incisors
Overbite
- if significant and solved then treatment should last longer
Skeletal pattern - aetiology
Increased md length
Anterior placed glenoid fossae = anteriorly placed condylar head
Dento alveolar compensation
Upper incisor proclined and lower incisors retroclined
Class III
Increased prominence of chin
Reduced overbite
Forward opening rotation
Backwards opening rotation
Mild skeletal class 3
Normal overbite
No lower arch extractions
Do not extract in upper arch
Accept incisor relationship and direct tx to ARCH ALIGNMENT
Moderate class III skeletal
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
Moderate class III skeletal
Upper rectangular wire to create torque for motion
Lower round wire
Severe class III skeletal
Pre-Surgical ortho - remove compensations which may have occurred e.g proclination of incisors
Orthognathic surgery
timing of treatment for class III
Early interception - growth modification
Later - tooth overbite
Skeletal issues - treatment
Bring maxilla forward
Bring mandible back
Mechanism
Chin cup
- no evidence that mandible affected
- retroclines lower incisors
- rotates mandible down and back
Maxilla forward
Protraction face mask (reverse head gear)
Worn 20hrs a day for 4-6 months
Both mandible and maxillary movement
Twin block
- blocks slope in opposite direction
- push jaw down and maxilla up
- ineffective as jaw already has limited movement
Frankel 3 appliance
Ineffective
Small amount activation possible
Maxillary retrusion common
Interceptive treatment
Incisors over the bite
- centrals and laterals
Potential problems
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
Space required for correction
Primary teeth extracted
Soft tissue and Dentoalevolar compensation
Tend to tilt upper and lower incisors towards each other to meet
Dental factors
Narrow upper arch and comparatively broad lower arch
Occlusal features
Lower incisors placed labially = anterior crossbite
Normal or increased overbite is an
Advantage - provides post treatment stability
Main aim of ortho management of class III
Increase dento alveolar compensation
Crowding occurs
and can be solved by
More frequently in upper
Expansion of upper arch
Upper arch extractions
contraindicated
if essential then extract as far forward in lower arch
Interceptive ortho
Correction in mixed dentition
Further fwd mandibular growth may be counterbalanced by DA compensation
Ortho correction options
Proclination of uppers
Retroclination of lowers or BOTH with fixed appliance
Lower arch extractions required if
Retroclination of lower labial segment requires space
Surgery almost always required if
Value of ANB angle < -4º
Inclination of lower incisors to md plane < 80º
