Aetiology Flashcards
How to describe class 2 div 1 malocclusion soft tissues and what can happen
“Depends on patients attempt to achieve anterior oral seal”
- lower lip trap (lower incisors retrocline, upper incisors procline)
- tongue goes in between upper and lower incisors to contact lower lip (can have incomplete overbite + lower incisors proclination)
- Circumoral musculature contracting to create seal. Can help with dentoalveolar compensation, can make underlying skeletal look less severe
Class 2 div 2 aetiology - soft tissues
- strap strong lips can retrocline upper and lower incisors
- with reduced vertical dimension, your lower lip can sit higher than normal (normal is lower lip rests on incisal third of uppers). So if lower lip sitting higher, can retrocline upper incisors.
Lateral incisors can escape this action and become proclined/mesiobuccal rotations as your centrals become retroclined = lack of space
Soft tissue in relation to skeletal pattern
Soft tissues often follow skeletal pattern
Class 2 div 2: skeletal
AP: Often class 1 or mild class 2 skeletal. Could be mild class 3
Forward rotational growth pattern
Often decreased lower facial height
List aetiologies types
Skeletal
Soft tissue
Dental
Habit
Class 3 skeletal
Class 3 malocclusion in majority of cases is gonna be on class 3 skeletal base
Prognathic and retrognathia = position of condyle in glenoid fossa
Length = plastic. Often increased length in class 3, or prognathic mandible in class 3
Increased mandibular length, and prognathism (usually not an issue with maxilla)
VERTICAL: (varies)
Downwards !!!! and backwards growth rotation of mandible
- therefore usually increased lower facial height for this pattern (but ranges depending on growth pattern), reduced overbite
Or Could have forward growth pattern (eg mandible being long, getting reverse overjet), mandible sticks out = prominence of chin
Class 3 soft tissues
Soft tissues don’t play a MASSIVE role in this but:
They may actually help? When trying to achieve anterior oral seal if incomplete overbite, circumoral musculature contraction Can help tilt upper and lower incisors toward each other = masking severity and causing dento-alveolar compensation eg trying to get seal.
But if lips incompetent bc of increased lower facial height and you stick your tongue forward to seal (proclination of lower incisor), it will make malocclusion worse (propping bite open even more, further incomplete overbite or AOB)
Class 3 aetiology: dental
Because of skeletal factors eg hypoPLASTIC maxilla (small/reduced size) or big mandible THEREFORE:
- upper arch usually more crowded, but lower arch may be more spaced or well aligned bc larger)
- can get crossbites as a feature (not aetiology) eg anterior crossbite
If you have to extract, would prefer to XLA 5s in upper and 4s in lower
But often upper arch is crowded so may have to XLA (but ideally not)
Class 3 aetiology : habits
Not rlly relevant
Class 2 div 1 : habits
Main habit is thumb sucking
- can cause incomplete OB or anterior OB
- can procline uppers and retrocline lowers
- can cause narrow palate (-ve pressure from sucking, tongue going lower, cheeks coming in, palate narrowing)
Class 2 div 1 dental
- Crowding may lead to class 2 div 1 (anterior incisors being labially displaced)
- or ectopic eruptions of upper incisors labially
Class 1 : dental
- crowding may be due to early loss of primary molars
- supernumerary
- tooth-arch size discrepancy
Dental is the main issue in class 1
Don’t rlly have habit impact
Class 1 soft tissue
May have lack of Tonicity of lips = bimaxillary proclination
Class 2 div 2 dental
Lack of occlusion stop
Increased inter incisal angle
Deep overbite
