Class III Malocclusion Flashcards
What is the definition of a class III malocclusion?
Lower incise edges occlude anterior to the cingulum plateau of upper incisors.
The overjet is reduced or reversed.
What are the etiological factors that result in a class III malocclusion?
Genetics
Acromegaly
Cleft lip and palate- narrow upper arch
What are the skeletal A-P features of a class 3 malocclusion?
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.
Why might a skeletal class 3 have occurred?
Small maxilla (most common)
Large mandible
Combination of both
What are the skeletal vertical features of a class 3 malocclusion?
Patient may have average, increased or reduced vertical proportions.
FMPA
Facial height proportions
Lateral cephalometry.
What are the skeletal transverse features of a class 2 malocclusion?
Retrusive maxilla sits on a wider part of the madible
- end up with a bilateral crossbite.
Summarise the key skeletal features of a class 3 malocclusion?
Skeletal class 3 but can be a class 1.
May have average, increased or decreased facial height proportions/FMPA.
Bilateral crossbites.
What are the dental features of a class 3 malocclusion?
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.
What are the soft tissue features of a class 3 malocclusion?
Usually not involved in the malocclusion but involved in dento-alveolar compensation.
- tongue prolines the upperr incisors
Lower lip retroclines the lower incisors.
Why would you want to treat a class 3 malocclusion?
Aesthetics
Attrition of teeth
Gingival recession
Mandibular displacement
Speech
Mastication
What factors make a class 3 malocclusion more difficult to treat?
Skeletal discrepancy in the aetiology
Greater the A-P discrepancy
AOB
More teeth in anterior cross bite
How does mandibular growth affect the class 3 malocclusion?
Mandibular growth occurs for longer than maxillary growth
- possibility that the malocclusion could get worse.
How could you tell if a patient is still growing?
Has their shoe size increased?
Have you noticed if you have increased in height?
What are the management options for a class 3 malocclusion?
Accept and monitor
Interceptive orthodontics
Growth modification
Camouflage
Orthognathic surgery
Why might you want to accept and monitor a class 3 malocclusion?
No concerns
No dental health implications- no attrition, no displacement
Mild cases
Why might a URA be a good treatment option?
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.
What features are good prognostic indicators that a patient can be treated with a URA?
Can achieve edge to edge incisor relationship.
Deep overbite at start of treatment.
What is the goal of growth modification in a class 3 patient?
Promote maxillary growth and reduce and/or redirect mandibular growth.
What appliances may be employed for growth modification treatment in patients with a class 3?
Chin cup
Frankel III
Reverse twin block
Protraction headgear
What is a Frankel III?
Pellotes labial to upper incisors to hold the lip away
Palatal arch to procline the upper incisors
Labial bow to retrocline the lower incisors.
What is the goal of a reverse twin block?
Restrict mandibular growth and promote maxillary growth.
Tip upper incisors forwards.
What are bollard implants used for?
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.
With regards to class 3 malocclusion, what is orthodontic camouflage?
Accept the underlying skeletal discrepancy and aim for class 1 incisors.
When is orthodontic camouflage favourable in a class 3 malocclusion?
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
What are the aims of orthodontic camouflage in a class 3 malocclusion?
Procline upper incisors
Retrocline lower incisors
Correct the overjet
What is the ideal extraction pattern for orthodontic camouflage in class 3 patients?
Extract further back in the upper arch
Extract further forward in the lower arch
What is orthognathic/orthodontic approach?
Surgical manipulation of the mandible and/or maxilla to produce optimal dent-facial aesthetics and function.
Why might orthognathic surgery be considered an option?
Patient has aesthetic or functional concerns
Growth completed
Moderate/severe skeletal discrepancy.
