Class III malocclusion Flashcards
Class 3 incisor relationship BSI definition
lower incisors edges occlude anterior to the cingulum plateau of the upper central incisors
overjet is reduced or reversed
Class 3 incisor relationship - incidence
uk 3-7%
higher incidence in Asia
Class iii aetiology
strong genetic link
- Habsburg family
environmental factors
- cleft lip and palate
acromegaly
Class 3 incisor relationship - skeletal features
usually present with a class 3 skeletal base
can present with a class 1 and rarely a class 2 skeletal base
the greater the a-p discrepancy the more difficult treatment is
Class 3 dental features
tendency to reverse overjet
class 3 molar relationship (not always)
reduced overbite
- anterior open bite may be present
crossbites
- anterior
- buccal
alignment
- mandible often aligned or spaced
- maxilla often crowded
dentoalveolar compensation
- proclined upper incisors
- retroclined lower incisors
tendency for displacement on closing
Reasons for treating a class 3
aesthetics
- dental
- profile concerns
dental health reasons
- attrition
- gingival recession
- mandibular displacement
function
- speech
- mastication
Factors which affect the difficulty of treating a class 3 malocclusion
number of teeth in anterior cross bite
skeletal element in aetiology
the degree of ap discrepancy
presence of an anterior open bite
Why does facial growth make treating a class 3 malocclusion more difficult?
tends to be unfavourable
- mandibular growth continues for longer
- potential for class 3 to become worse
When would you accept and monitor a class 3 occlusion
no patient concerns
no dental health indications
- no displacements
- no attrition
mild cases
When would interceptive treatment be suitable for treatment of a developing class 3 malocclusion and why?
suitable if class 3 incisors have developed due to early contact on permanent incisors (i.e mandibular displacement)
- correction of anterior crossbite in mixed dentition has the advantage that further forward mandibular growth may be counter balanced by some dento-alveolar compensation
- only suitable for correcting a lateral incisor crossbite if permanent canines are high above lateral roots
interceptive treatment for class 3
URA to procline incisors over the bite
Class 3 growth modification indications and aims
indications = growing patient
aims
- reducing and/or redirecting mandibular growth
- encouraging maxillary growth
class 3 growth modification appliances - give examples
functional appliances
- chin cup
- reverse twin block
- Frankel III
protraction headgear +/- rapid maxillary expansion
bollard implants (late mixed and permanent dentition)
Chin cup features
mainly historic treatment form
lingual tipping of lower incisors
rotates mandible down and backwards
Frankel III features
pellotes (shields) placed labial to upper incisors to hold lip away
palatal arch to proline upper incisor
Lower labial bow to retrocline lower incisors
protraction headgear indications, use and features
co-operative patient
worn for 14 hours a day
400g force per side
best results in early mixed dentition (8-10 years)
+/- rapid maxillary expansion
- disrups circus-maxillary sutures
orthodontic camouflage aims
accept underlying skeletal base relationship
- aim for class 1 incisor relationship by:
- procline upper incisors
- retrocline lower incisors
- correct overjet
Orthodontic camouflage for class 3 - indications
growth stopped
mild to moderate class 3
- ANB >0 degrees
average or increased overbite
able to reach edge to edge incisor relationship
little or no dentoalveolar compensation
class 3 orthodontic camouflage extraction pattern
extract further back in upper arch
extract further forward in lower arch
classic pattern
upper 5s, lower 4s
not always possible as dental health may dictate extraction pattern
orthognathic treatment indications
patient has aesthetic or functional concerns
growth completed
moderate to severe skeletal discrepancy
orthognathic surgical treatment requirements
careful planning
multidisciplinary team approach
- orthodontist
- maxilofacial surgeon
- technician
- psychologist
prediction planning software
orthognathic treatments steps
pre surgical orthodontics to level, align, co-ordinate and decompensate (18 months)
- uppers 109 degrees
- lower incisors 90 degree inclination
orthognathic surgery to reposition the jaws
- mandible
- mandible and maxilla
post surgical
GDP role in treatment for class 3
identify class iii malocclusion
refer to hospital service or specialist practitioner
URA treatment
- anterior crossbite correction
