Treatment of Class III Malocclusion Flashcards

1
Q

Correction of class III depends on

A

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

Overbite
- if significant and solved then treatment should last longer

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2
Q

Skeletal pattern - aetiology

A

Increased md length

Anterior placed glenoid fossae = anteriorly placed condylar head

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3
Q

Dento alveolar compensation

A

Upper incisor proclined and lower incisors retroclined

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4
Q

Class III

Increased prominence of chin
Reduced overbite

A

Forward opening rotation

Backwards opening rotation

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5
Q

Mild skeletal class 3

A

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

Accept incisor relationship and direct tx to ARCH ALIGNMENT

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6
Q

Moderate class III skeletal

A

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

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7
Q

Moderate class III skeletal

A

Upper rectangular wire to create torque for motion

Lower round wire

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8
Q

Severe class III skeletal

A

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

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9
Q

timing of treatment for class III

A

Early interception - growth modification

Later - tooth overbite

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10
Q

Skeletal issues - treatment

A

Bring maxilla forward

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11
Q

Bring mandible back

Mechanism

A

Chin cup

  • no evidence that mandible affected
  • retroclines lower incisors
  • rotates mandible down and back
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12
Q

Maxilla forward

A

Protraction face mask (reverse head gear)

Worn 20hrs a day for 4-6 months

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13
Q

Both mandible and maxillary movement

A

Twin block

  • blocks slope in opposite direction
  • push jaw down and maxilla up
  • ineffective as jaw already has limited movement
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14
Q

Frankel 3 appliance

A

Ineffective

Small amount activation possible

Maxillary retrusion common

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15
Q

Interceptive treatment

A

Incisors over the bite

- centrals and laterals

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16
Q

Potential problems

A

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

17
Q

Space required for correction

A

Primary teeth extracted

18
Q

Soft tissue and Dentoalevolar compensation

A

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

19
Q

Dental factors

A

Narrow upper arch and comparatively broad lower arch

20
Q

Occlusal features

A

Lower incisors placed labially = anterior crossbite

21
Q

Normal or increased overbite is an

A

Advantage - provides post treatment stability

22
Q

Main aim of ortho management of class III

A

Increase dento alveolar compensation

23
Q

Crowding occurs

and can be solved by

A

More frequently in upper

Expansion of upper arch

24
Q

Upper arch extractions

A

contraindicated

if essential then extract as far forward in lower arch

25
Q

Interceptive ortho

A

Correction in mixed dentition

Further fwd mandibular growth may be counterbalanced by DA compensation

26
Q

Ortho correction options

A

Proclination of uppers

Retroclination of lowers or BOTH with fixed appliance

27
Q

Lower arch extractions required if

A

Retroclination of lower labial segment requires space

28
Q

Surgery almost always required if

A

Value of ANB angle < -4º

Inclination of lower incisors to md plane < 80º