3. Class III Malocclusion

Question 1

Define Class III malocclusion - BSI.

Answer 1

Lower incisor edge occludes anterior to the cingulum plateau of upper central incisor.
OJ can be reduced or reversed.

Question 2

What medical conditions are associated with a Class III malocclusion ?

Answer 2

Genetic link.
Cleft lip and palate.
Acromegaly.

Question 3

SKELETAL AETIOLOGICAL FACTORS

What are the skeletal etiological factors contributing to Class III malocclusion ?

Answer 3

Small maxilla - maxillary hypoplasia.
Large maxilla - mandibular prognathism.
Combination of both.

Question 4

SKELETAL AETIOLOGICAL FACTORS

What is the most common AP discrepancy Class III malocclusions are seen on ?

Answer 4

Usually Class III.
Class I.
Occasionally Class II.

Question 5

SKELETAL AETIOLOGICAL FACTORS

What is the most common vertical discrepancy Class III malocclusion is seen with ?

Answer 5

Increased FMPA.

But can be seen with reduced or average FMPA.

Question 6

Why treat a Class III malocclusion ?

Answer 6

Aesthetics.
Dental health - attrition, gingival recession, mandibular displacement.
Function - speech and mastication.

Question 7

What are the four factors which might make a Class III malocclusion difficult to treat ?

Answer 7

Increased number of teeth in anterior cross bite.
Skeletal element in aetiology.
Increased AP discrepancy.
Presence of AOB.

Question 8

What two features can be measured to predict growth status ?

Answer 8

Height and weight charts.
Cervical vertebral maturation on lateral ceph.
(Compare to family members).

Question 9

What can be seen in relation to cervical vertebral maturation on lateral ceph which can help determine growth status ?

Answer 9

Change in shape of bodies of cervical vertebrae C2, C3 and C4.

Question 10

What are the five treatment options for a Class III malocclusion ?

Answer 10

Accept and monitor.
Intercept with URA.
Growth modification.
Camoflague.
Combined orthognathic and orthodontic treatment.

Question 11

DENTAL AETIOLOGICAL FACTORS

What are some dental occlusal anomalies seen with a Class III malocclusion ?

Answer 11

• Class III incisors OR Class I incisors.
• Class III molars.
• Reverse OJ.
• Reduced OB.
• +/- AOB.
• +/- anterior or posterior X-bites.
• Maxillary arch crowding.
• Mandibular arch spacing or well aligned.
• Dentoalveolar compensation - proclined uppers, retroclined lowers.

Question 12

CLASS III TREATMENT OPTIONS

In what circumstances is accept and monitor an appropriate tx option ?

Answer 12

Mild cases where no dental health or aesthetic concern.

Question 13

CLASS III TREATMENT OPTIONS

In what circumstances is interceptive orthodontic treatment with a URA an appropriate tx option to manage a Class III malocclusion ?

Answer 13

Where anterior crossbites - use URA with Z spring with flat posterior bite plane to correct and this can have dento-alveolar compensatory effects.

Question 14

CLASS III TREATMENT OPTIONS

What are some examples of Class III growth modification appliances ?

Answer 14

• Frankel III.
• Modified twin block.
• Chin Cup.
• Protraction head gear with rapid maxillary expansion.

Question 15

CLASS III TREATMENT OPTIONS

What is the aim with growth modification in treating a Class III malocclusion ?

Answer 15

Reduce or redirect growth of mandible and encourage growth of the maxilla.

Question 16

CLASS III TREATMENT OPTIONS

In what circumstances is camoflauge an appropriate management technique for a Class III malocclusion ?

Answer 16

• Growth has stopped.
• Mild-moderate Class III.
• ANB angle not <0 degrees.
• Able to reach edge to edge occlusion.
• Little/no dentoalveolar compensation.

Question 17

CLASS III TREATMENT OPTIONS

What is the aims of using camouflage technique to manage a Class III malocclusion ?

Answer 17

Procline upper, retrocline lowers and correct OJ.
Extract upper 5s, extract lower 4s.

Question 18

CLASS III TREATMENT OPTIONS

When is orthognathic surgery an appropriate management technique for a Class III malocclusion ?

Answer 18

Where severe AP discrepancy.
Once growth has stopped.

Question 19

CLASS III TREATMENT OPTIONS

Explain the orthognathic surgery technique used in treating a Class III malocclusion.

Answer 19

• Maxillary impaction.
• Mandibular sagittal split osteotomy.
• Combination of both.
• With pre-surgical orthodontic treatment - to align and decompensate.
• With post-surgical orthodontic treatment - for fine tuning.