Class 3 Flashcards
1
Q
What is Class 3?
A
- lower incisors occlude anterior to the cingulum plateau of upper central incisor
- OJ is reduced/ reversed
2
Q
Incidence
A
- geographical variation
- UK 3-7 %
- higher incidence in Asia
3
Q
Aetiology
A
- strong genetic link
- Habsburg family
- pattern of transmission
Environment factors
- cleft lip and palate
- acromegaly
- skeletal
- dental
- ST
4
Q
Skeletal A/P
A
- small maxilla
- large mandible
- combination of both
- usually present with class 3 skeletal base
- can present as class 1/ class 2
- greater A/P discrepancy, more complex the malocclusion is
5
Q
Vertical Sk
A
- increase FMPA and anterior Openbite is more complex to treat
6
Q
Transverse relationship
A
- retrusive maxilla sits on wider part of mandible
- bilateral CB
7
Q
Dental features of Class 3
A
- class 3 incisor relationship
- class 3 molar relationship
- tendency to reverse OJ
- reduced overbite, anterior openbite
- crossbite (anterior/ buccal)
- maxilla often crowded
- mandible often aligned/ spaces
- proclined upper incisors
- retroclined lower incisors
- tendency for displacements on closing
8
Q
Soft tissues
A
- not usually involved in aetiology
- encourage dentoalveolar compensation
- tongue will procline upper incisors, and lip trap will retrocline lowe incisors
9
Q
Why treat?
A
- aesthetics
- dental health reasons due to attrition and gingival recession, mandibular displacement
- function, ie: speech and mastication
10
Q
Factors which make tx more difficult?
A
- number of teeth in anterior crossbite
- sk element in aetiology
- higher the A/P discrepancy
- presence of anterior openbite
11
Q
Facial growth for class 3
A
- mandibular growth tends to continue longer
- potential for class 3 to get worse
- tends to be unfavourable
12
Q
Class 3 management options
A
- accept/ monitor - mild class 3/ unsure how growth and development will progress
- intercept early with URA- early correction of incisor relationship
- growth modification - functional appliance/ head gear/ TADs
- Camouflage - accept underlying sk, correct incisors to class 1
- combined orthognathic and ortho- functional/ masticatory/ profile concerns
13
Q
Accept and monitor
A
- no concerns
- no dental health indications
- no displacements
- no attrition
- mild cases
14
Q
Interceptive tx
A
- suitable if class 3 incisors have developed due to early contact on permanent incisors
- correction of anterior CB in mixed dentition has the advantage that further forward mandibular growth may be counter balanced by dento-alveolar compensation
- only suitable for correcting lateral incisor CB if permanent canine are higher above lateral roots; if drop down to buccal position then risk of RR
15
Q
What to use in interceptive tx?
A
- URA to procline incisors over bite
- good overbite will maintain stability
18
Q
Chin cup
A
- lingual tipping of lower incisors
- rotates mandible down and back
19
Q
Frankel 3
A
- shields labial to upper incisors to hold lip away
- palatal arch to rpocline upper incisors
- lower labial bow to retrocline lower incisors
20
Q
Reverse twinblock
A
