Class III Flashcards
what is definition of Class III?
Lower incisor edge occludes anterior to the cingulumplateau of the upper central incisor
The overjet is reduced or reversed
1) what could skeletal aetiology of class II be due to?
1) Small maxilla
Large mandible
Combination of
both
2) what are skeletal features of class III
2) Usually present with a Class 3 skeletal base
relationship
Can present with a Class 1 and rarely a Class 2 skeletal base relationship
The greater the A-P discrepancy the more complex the malocclusion is to treat
What do you use for vertical relationships and what is more complex to treat?
May be associated with average, increased or reduced
vertical proportions
- Frankfort Mandibular Planes Angle
- Facial Height proportions
- Lateral Cephalometry
increase FMPA and anterior open bite more complex to treat
what is this measuring?
FMPA
what is this measuring?
facial height proportions
what is transverse relationship of Class III?
A-P and transverse relationship linked
Retrusive maxilla sits on wider part of mandible
- Bilateral Crossbites
what are dental features of class III?
Vary
- Class III incisor relationship
- Tendency to reverse overjet
- Reduced overbite, anterior open bite may be present
- anterior Crossbites
- Maxilla often crowded
- Mandible often aligned or spaced
- proclined uppers
- retroclined lowers
what are soft tissue features of Class III?
- Tongue proclines the upper
incisors - Lower lip retroclines lower
incisors
why treat a class III?
Aesthetics
- Dental
- Profile concerns
Dental health reasons
- Attrition
- Gingival recession
- Mandibular Displacement Function
- Speech
- Mastication
what are factors of Class III which make treatment more difficult? and in regards to facial growth?
number of teeth in anterior crossbite
Presence of anterior open bite
Mandibular growth continues for longer
Potential for Class III to get worse
what are class III management options?
Accept/ Monitor - Mild Class III/ or unsure how growth and development will progress
Intercept early with URA - Early correction of incisor relationship
Growth Modification - Functional appliance/ Head Gear/ TAD’s
Camouflage - Accept underlying skeletal relationship. Correct incisors to Class I
Combined Orthognathic/ Orthodontic Tx - Functional/Masticatory/ or profile concerns
1) when to accept and monitor?
1) No concerns
No dental health indications
No Displacements
No attrition
Mild cases
2) When to use interceptive tx? what does it do?
- if class III incisors developed to early contact permanent incisors
*mandibular displacement - fix anterior crossbite in mix dentition
*forward mandibular growth countered by dento-alveolar comp - only able correct lateral incisor crossbite if canine high abover lateral roots
*delay if canine drop to buccal position cause risk resorption lateral - URA procline incisors over bit
*good OB maintain stability
1) when to use growth modification?
2) types of functional appliances?
3) aim of it?
1) Growing patient
2) Functional appliances
Chin cup
Reverse Twin Block Frankel III
Protraction headgear ± Rapid Maxillary Expansion
3) Aimed at reducing and / or redirecting mandibular growth and encourage maxillary growth
what is this and what does it do?
Frankel III
Pellotes (Shields) labial to upper incisors to hold lip away
Palatal arch to procline the upper incisors
Lower labial bow to retrocline the lower incisors
what is this?
reverse twin block
what is this and explain it?
Protraction Headgear
Co-operative patient
14 hour/day protraction facemask wear
400g/side
Best results when used in early mixed dentition ( 8-10
years)
± Rapid maxillary Expansion
- Disrupts circum-maxillary sutures
what are bollard implants?
Used in late mixed and permanent dentition
Infrazygomatic crest and lower canine region
Mucoperiosteal flaps need to be raised for
insertion and removal
what would treatment plan be for class III? camouflage
- XLA all first permanent molars
- SR LL8 and LR8
- Upper and lower fixed appliances to treat to Class I
- Life long retention
what do you do in terms of treatment for patients that are still growing?
Do not embark on full correction if still growing
- Can not predict growth changes
- Consider upper arch alignment only
- Do not XLA in lower arch as this could affect future
treatment options
1) what is idea of orthodontic camouflage?
2) what are favourable features for it?
3) What do you actually do?
4) What are aims?
1) Accept underlying skeletal base relationship
- Aim for class 1 incisors
2) Growth stopped
Mild to moderate Class III Skeletal base ANB not <0˚
Average or increased overbite
Able to reach edge to edge incisor relationship
Little or no dentoalveolar compensation
3)Extraction pattern
- Extract further back in the upper arch
- Extract further forward in the lower arch
- Classic pattern - Upper 5’s , lower 4’s
However not always possible
- Dental health may dictate extraction pattern
4) Procline upper incisors
Retrocline lower incisors
Correct overjet
what is purpose of orthognathic surgery approach?
Orthognathic surgery is surgical manipulation of the mandible and / or maxilla to produce optimal
dentofacial aesthetics and function
camouflage
3) What do you actually do?
4) What are aims?
3)Extraction pattern
- Extract further back in the upper arch
- Extract further forward in the lower arch
- Classic pattern - Upper 5’s , lower 4’s
However not always possible
- Dental health may dictate extraction pattern
4) Procline upper incisors
Retrocline lower incisors
Correct overjet
1) when do you do orthognathic surgery treatment?
2) who is part of mdt for it?
1) Pt usually has aesthetic or functional concerns
Growth completed
Moderate/Severe skeletal discrepancy
- A-P
- Transverse
- Vertical
2) Orthodontist
Maxillofacial surgeon
Technician
Psychologist
what is treatment for orthognathic surgery?
Presurgical orthodontics (approx. 18 months)
- Level, align, co-ordinate and decompensate
* Uppers 109˚
* Lowers 90˚
Orthognathic surgery to reposition the jaws
- Mandible
- Mandible ± Maxilla
Post surgical Orthodontics (approx. 6 months)
what is GDP role of class III?
GDP role
Identify Class III malocclusion
Refer to hospital service or specialist practitioner
URA Treatment ?
Anterior cross-bite correction
