tx of class III Flashcards
What is class III incisor relationship?
Lower incisor occludes in front of upper incisor cingulum plateau
What three things need to be considered before treating class III?
SKELETAL PATTERN (degree of dento-alveolar compensation, can they achieve edge to edge? do they have forward displacement on closure?)
OVERBITE (normal/reduced? If proclining uppers, the OB will be reduced)
POTENTIAL GROWTH (ortho will be done in vain if jaws are still growing during/after tx)
What is dento alveolar compensation?
Class III skeletal pattern= maxillary retrusion/mandibular protrusion
If the teeth were placed normally in these jaws, there would be almost zero occlusion
So the soft tissues tip the teeth naturally to allow contact
Procline uppers/retrocline lowers
What is forward displacement on closure?
If when the patient bites down, the mandible displaces forward
It’s a good thing
As it shows that the class III seems worse than it actually is
So check for edge to edge
What is edge to edge?
If the pt can achieve edge to edge incisors it shows that the skeletal pattern is not severe and they are more suitable for ortho
Should you extract teeth for space in the upper arch if there is no crowding in the lower (mild scenario)?
No
Will result in small upper arch compared to lower
Procline the teeth in cross bite- will create space
What are some useful mechanics in correcting a class III?
Upper rectangular archwire- proclines incisors by expressing torque
Lower round archwire- keeps lower incisors back
Box elastics- settle bite by bringing teeth together (sloped can help)
If the skeletal pattern is severe how do you treat?
Orthodontics + orthognathic surgery
1. Ortho- Aim to decompensate arches by upright proclined uppers and procline lowers so there’s the correct inclination (pre-surgery)
2. Surgery- the step above would help to move the jaws to the correct position (only carried out when growth is complete)
Need to warn pt that their occlusion will be worse before it gets better
If there is a mild class III but there is a reduced over bite how would you tx?
Accept the skeletal pattern and align the teeth
There would be a lack of stability
If there is a moderate/severe class III w reduced OB how would you tx?
Orthognathic surgery + ortho
When should you tx class III?
Early interception- growth modification of skeletal pattern, correct incisor crossbite that’s causing class III (central/lateral)
Later tx
What are some growth modifications?
Bring maxilla forwards (face mask)
Push mandible back (chin-cup)
Or both (class III functional appliance eg twin block, functional regulator)
What is a chin cup?
No evidence that it affects mandible
But it may retrocline the lower incisors
Possible TMJ problems
What is a face mask?
For 10 years or younger
Part time wear (compliance!)
-12-14hrs a day
For 4-6 months
Brings maxilla forward
Proclines upper incisors
Downwards and backwards rotation of mandible
Retroclines lower incisors
What is a class III twin block functional appliance?
Similar to class II twin block but blocks slope in opposite direction
