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ortho year 4 > Class III Malocclusion > Flashcards

Class III Malocclusion Flashcards

1
Q

The diagnosis of class III malocclusion is based on

A

The incisor relationship

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2
Q

What is the definition of class III malocclusion

A

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

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3
Q

What is the significance of class III malocclusion?

Appearance?
Associated with?

A

 Poor dental appearance
 May be associated with an anterior mandibular displacement

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4
Q

Class III

Facial profile?
Growth?

A

Facial profile often poor

Growth usually unfavourable (i.e. Mandible grows forward more than maxilla)

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5
Q

What is the incidence of class III malocclusion?

A

relatively uncommon malocclusion
 3-5% (UK)
Relatively common in some ethnic groups

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6
Q

Aetiology of class III malocclusion

A

 Genetic – due to skeletal pattern

 Most are due to an AP skeletal discrepancy
(mandibular excess, maxillary hypoplasia or
both)

 May be a result of a mandibular
displacement

  • Cleft lip and palate patients
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7
Q

Skeletal Class III: maxillary hypoplasia would look like…

A

Mandible in normal position and maxilla looks retruded

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8
Q

Skeletal class III mandibular excess would look like

A

Maxilla in normal position and mandible protruded

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9
Q

Class III mandibular displacement- describe

A

Patient initially bites edge to edge then displaces forwards

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10
Q

Genetic background of class III mandibular displacement?
Mother?
Father?
Siblings?

A

 13% of patients have an affected sibling
 13% have a Class III mother
 20% have a Class III father

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11
Q

Family history can be useful in

A

Helping to predict future growth patterns for skeletal class III

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12
Q

Ceph tracing… what is the ANB

A

<2 degrees

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13
Q

What is the percentage of class III patients with a skeletal III pattern? (<2 degrees)?

A

> 70% have a skeletal III pattern (ANB < 2
degrees)

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14
Q

Skeletal pattern may be the result of

A

Small maxilla and/or large mandible

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15
Q

The maxilla is often … resulting in …

A

Narrow
Crossbite

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16
Q

Dental features of class III
Incisors?
…
Arch
Arch

A

 Class III incisors (mild cases are edge-edge,
severe cases may have a large reverse
overjet)

 Dentoalveolar compensation (i.e. upper
incisors proclined & lowers retroclined)

 Upper arch often narrow & crowded,
crossbites

  • Mandibular arch may be spaced
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17
Q

Why treat class III?

A

 Improve dentofacial appearance
 Psychosocial - teasing
 Eliminate mandibular forward displacement if present

18
Q

Treatment of class III- aims? (4)

A

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

19
Q

Treatment options?

A

 Accept the incisor relationship
 Procline the upper incisors
 Retrocline the lower incisors
 Orthognathic Surgery (correct skeletal problems)

20
Q

Class III Skeletal Discrepancy and
Treatment

None/mild
Moderate
Severe

A

 None / Mild: Orthodontic appliances only
 Moderate: +/- Orthognathic Surgery
 Severe: Orthognathic Surgery

21
Q

Timing of treatment-
Growth?

A

Is often unfavourable and lasts longer in Class III cases (ie. Class III tends to get worse

22
Q

Timing of treatment- displacements?

A

can often be treated early using appliances to procline the upper incisors, often in the mixed dentition

23
Q

Timing of treatment-

Appliance treatment is…

A

usually carried out at a later age than in other types of malocclusion

Age 15-16 when growth has stopped

24
Q

Favourable factors for patients suitable for appliance treatment only?

A

pre-treatment overbite

ability to bite edge-edge

anterior displacement

Small or no skeletal discrepancy

25
Q

Favourable factors for patients suitable for appliance treatment only?
(4)

A

pre-treatment overbite

ability to bite edge-edge

anterior displacement

Small or no skeletal discrepancy

26
Q

Favourable factors for treatment with fixed appliances? (2)

A

Mild to moderate skeletal discrepancies with
acceptable facial profile

 Crowded lower (and/or upper) arches

27
Q

Fixed appliance treatment - the aim is …

A

To produce dentoalveolar compensation

28
Q

Dentoalveolar compensation provided by fixed appliance treatment for class III is done by …

A

Extracting lower premolars to allow retroclination of lower incisors

29
Q

What other appliance can you have?

A

Class III elastics

30
Q

Surgery for class III?
Patients suitable

A

 severe skeletal discrepancies and poor
facial profile / appearance

 Vertical problems and anterior open bites

31
Q

Class III surgery- clinical procedure-

A
  • Fixed appliances to align individual arches &
    produce “decompensation”
     Surgical mandibular setback and / or Maxillary advancement
32
Q

What is the prognosis of class III?
Growth?

A

Is often unfavourable and continues longer. Incisor relationship often gets worse
during teens

33
Q

Prognosis of class III
Stability?

A

of incisor correction depends on the
presence of a positive overbite
 Surgically treated cases are usually stable

34
Q

Aim for treatment of class III is

A

positive overjet and acceptable facial profile

35
Q

Mild cases may be treated with

A

early with URA – to
eliminate displacements and push upper incisors
“over the bite”

36
Q

Most cases are treated with

A

fixed appliance treatment which is often carried out later than Class II or Class I
cases

37
Q

What are NOT used in treatment of class III?

A

Functional appliances

38
Q

What is common with class III

A

Displacements (Forwards)

39
Q

What is favourable for treating with appliances only in class III?

A

Pre- treatment presence of a positive
overbite and the ability to bite edge-edge

40
Q

What is unfavourable for treating in class III

A

The pre-treatment presence of dentoalveolar
compensation or a skeletal problem

41
Q

What is often a problem in treating class III

A

Growth

ortho year 4 (11 decks)

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