Treatment of class III malocclusions Flashcards
Class III malocclusion aetiology (definition)
The edge of the lower incisor lies anterior to the cingulum plateau of the upper incisor
Prognosis for treatment depends on
Skeletal pattern -dento-alveolar compensation -can pt achieve edge-to edge incisors? Amount of overbite Growth -can be unfavourable, particularly in boys
Class III skeletal pattern - aetiology
- Mandibular protrusion?
- 40% - Maxillary retrusion?
- 34% - Both
- 26%
Dento-alveolar compensation
Upper incisors proclined
Lower incisors upright or retroclined
-so you can contact on more teeth
-makes treatment harder
Overbite in class III
Loss of overbite as tooth preoclined
Must retain tooth at end of treatment???
Class III treatment
Normal overbite & reduced overbite –> skeletal pattern (mild, moderate or severe)
Normal overbite: mild skeletal III
Can be treated
No lower arch extractions
Do not extract in upper arch if there is no crowding in the lower arch
Moderate skeletal III: normal overbite
Needs U and L fixed appliances
Loss of overbite
Poor prognosis for stability
Consider extractions in lower arch
Rectangular upper arch wires
Helping us with torque
Round will not introduce torque
Severe skeletal III: normal overbite
Pre-surgical orthdontics
Orthognathic surgery
Mild skeletal III: reduced overbite
May accept class III incisal relationship and align teeth only
Moderate to severe skeletal III: reduced overbite
Poor prognosis for stable treatment
Can align teeth and accept incisor relationship or perform orthognathic surgery when pt is older
Timing of treatment for class III malocclusion
Early interception
-growth moedification
Later treatment
-tooth over the bite
Skeletal problem treatment
Bring maxilla forwards most of the time
Mandible back
Chin-cup Doesn't really work -no evidence that mandible affected -retroclines lower incisors -possible TMD problems
Maxilla forward
Face mask (reverse headgear)
9-11 yo
-worn full-time (20 hours per day) for 4-6 months
Both mandible and maxilla movement
Functional appliance Logic? -blocks slope in opposite direction -reverse twin block design Frankel 3 appliance -proclines uppers, retroclines lowers
Class III problems with functional appliances
Only small amount activation possible
Maxillary retrusion common
Continued growth
Interceptive treatment
Incisor over the bite
- central
- laterals
Potential problems: check list
Class III skeletal pattern Overbite -need enough to retain correction Space -extract Cs? Interference from primary canines Position of permanent canine? -prevents movement of lateral incisor Growth
Overbite
Need enough overbite to retain correction
Do not overly procline upper incisors
Position of permanent canine
May prevent movement
Resorb lateral if moved
Wait for canine eruption before correction
Effect of growth
Complicating factor with class III malocclusions Mandible may continue to grow throughout teens this worsening class III Prediction of growth uncertain
Extractions in class III cases
Space is gained as upper anterior teeth are moved forward
-requires careful assessment of upper space requirements
No extractions in upper arch if you have not extracted in lower teeth
Removable appliances: class III cases -patient selection
Only select cases with class I or very mild class III skeletal pattern, and normal OB
If pt can achieve edge-to-edge bite on posturing forward, may be suitable (if mild skeletal pattern)
-not always the case as upper teeth may already be proclined and cannot be moved labially any more MOST COMMON SITUATIONS:
Moving incisor over bite
Correcting anterior X-bite of incisors
Moving incisor over bite: check list
Often considered simple procedure well suited by GDP but there are several potential pitfalls
- skeletal class III
- sufficient OB to retain correction
- Enough space between Cs to allow forward movement of incisors (if not, XLA Cs)
- Deciduous canine relationship?
- Position of unerupted 3s (when moving 2s over the bite)
Moving incisor over bite: skeletal class III?
If this is severe, the upper incisor will be overproclined. Test that the patient can achieve an
edge-to-edge bite without producing a large
vertical space between the posterior teeth
Moving incisor over bite: deciduous canine relationship
An abnormal relationship of the deciduous canines may maintain a forward displacement after incisor correction. Grind or extract the deciduous canines in this case
Moving incisor over bite: position of unerupted permanent canine? When moving lateral incisors over the bite
Check by palpation and radiographs. If it is close
to the root of the lateral incisor, it may cause
resorption. This is a particular danger in narrow
arches where the canine often develops in a forward position buccal to the lateral. It is better to wait for the eruption of the permanent canine in these case
