Class III Malocclusion

Question 1

What is the definition of a class III malocclusion?

Answer 1

Lower incise edges occlude anterior to the cingulum plateau of upper incisors.

The overjet is reduced or reversed.

Question 2

What are the etiological factors that result in a class III malocclusion?

Answer 2

Genetics
Acromegaly
Cleft lip and palate- narrow upper arch

Question 3

What are the skeletal A-P features of a class 3 malocclusion?

Answer 3

Skeletal class 3- mandible is less than 2-3mm posterior to the maxilla.
But some can present as skeletal class 1.

The greater the A-P discrepancy, the harder it is to correct.

Question 4

Why might a skeletal class 3 have occurred?

Answer 4

Small maxilla (most common)
Large mandible
Combination of both

Question 5

What are the skeletal vertical features of a class 3 malocclusion?

Answer 5

Patient may have average, increased or reduced vertical proportions.

FMPA
Facial height proportions
Lateral cephalometry.

Question 6

What are the skeletal transverse features of a class 2 malocclusion?

Answer 6

Retrusive maxilla sits on a wider part of the madible
- end up with a bilateral crossbite.

Question 7

Summarise the key skeletal features of a class 3 malocclusion?

Answer 7

Skeletal class 3 but can be a class 1.
May have average, increased or decreased facial height proportions/FMPA.
Bilateral crossbites.

Question 8

What are the dental features of a class 3 malocclusion?

Answer 8

Maxilla often crowded- caused by maxillary hypoplasia.
Mandible often spaced or well aligned
Proclined upper incisors
Retroclined lower incisors
- as a result of dent-alveolar compensation.
Displacements on closing.

Question 9

What are the soft tissue features of a class 3 malocclusion?

Answer 9

Usually not involved in the malocclusion but involved in dento-alveolar compensation.
- tongue prolines the upperr incisors
Lower lip retroclines the lower incisors.

Question 10

Why would you want to treat a class 3 malocclusion?

Answer 10

Aesthetics
Attrition of teeth
Gingival recession
Mandibular displacement
Speech
Mastication

Question 11

What factors make a class 3 malocclusion more difficult to treat?

Answer 11

Skeletal discrepancy in the aetiology
Greater the A-P discrepancy
AOB
More teeth in anterior cross bite

Question 12

How does mandibular growth affect the class 3 malocclusion?

Answer 12

Mandibular growth occurs for longer than maxillary growth
- possibility that the malocclusion could get worse.

Question 13

How could you tell if a patient is still growing?

Answer 13

Has their shoe size increased?
Have you noticed if you have increased in height?

Question 14

What are the management options for a class 3 malocclusion?

Answer 14

Accept and monitor
Interceptive orthodontics
Growth modification
Camouflage
Orthognathic surgery

Question 15

Why might you want to accept and monitor a class 3 malocclusion?

Answer 15

No concerns
No dental health implications- no attrition, no displacement
Mild cases

Question 16

Why might a URA be a good treatment option?

Answer 16

If class 3 has developed due to early contact on permanent incisors.

Only a suitable option if the upper canines are high above the roots of the laterals.

Question 17

What features are good prognostic indicators that a patient can be treated with a URA?

Answer 17

Can achieve edge to edge incisor relationship.
Deep overbite at start of treatment.

Question 18

What is the goal of growth modification in a class 3 patient?

Answer 18

Promote maxillary growth and reduce and/or redirect mandibular growth.

Question 19

What appliances may be employed for growth modification treatment in patients with a class 3?

Answer 19

Chin cup
Frankel III
Reverse twin block
Protraction headgear

Question 20

What is a Frankel III?

Answer 20

Pellotes labial to upper incisors to hold the lip away
Palatal arch to procline the upper incisors
Labial bow to retrocline the lower incisors.

Question 21

What is the goal of a reverse twin block?

Answer 21

Restrict mandibular growth and promote maxillary growth.
Tip upper incisors forwards.

Question 22

What are bollard implants used for?

Answer 22

Applied to the infrazygomatic crest and lower canine region.

Elastics added to them to promote movement of the maxilla forwards and restricts movement of the mandible.

Question 22

With regards to class 3 malocclusion, what is orthodontic camouflage?

Answer 22

Accept the underlying skeletal discrepancy and aim for class 1 incisors.

Question 23

When is orthodontic camouflage favourable in a class 3 malocclusion?

Answer 23

Growth has stopped
Mild to moderate class 3 skeletal base- ANB not less than 0
Average to increased overbite
Able to reach edge to edge incisor relationship
Little or no dentoalveolar compensation

Question 24

What are the aims of orthodontic camouflage in a class 3 malocclusion?

Answer 24

Procline upper incisors
Retrocline lower incisors
Correct the overjet

Question 25

What is the ideal extraction pattern for orthodontic camouflage in class 3 patients?

Answer 25

Extract further back in the upper arch
Extract further forward in the lower arch

Question 26

What is orthognathic/orthodontic approach?

Answer 26

Surgical manipulation of the mandible and/or maxilla to produce optimal dent-facial aesthetics and function.

Question 27

Why might orthognathic surgery be considered an option?

Answer 27

Patient has aesthetic or functional concerns
Growth completed
Moderate/severe skeletal discrepancy.