Malocclusion Class 2 Div 1 Flashcards
Class 2 div 1
-Lower incisors lies above cingulum plateau of upper central incisors.
- upper central incisors are at normal inclination or proclined
- increased Overjet
Incidence
20%
Aetiology of class 2 div 1
- Skeletal factors
- soft tissue factors
- Dento alveolar factors
- habits
Skeletal pattern class 2 div 1
- sk Class 2 div 1 76%
- sk Class 2 div 2 15%
- sk class 1 Less than 30%
- sk class 3 less than 5 %
Sk Factor - AP
- large maxilla
- small mandible
- posterior articulation of mandible with glenoid fossa
Sk Factors vertical and lateral.
-All types ( Average, increased , reduced face height)
- facial asymmetry possible
Soft tissues factors
-lip morphology - length or tone
- lip competence definition : ( lower lip resting height)- short upper lip or low lower lip
- anterior oral seal
- tongue
Lip competency definition
Lips together at rest without muscular activity
Lip competency describe?
-Resting height of lower lip should ideally cover Incisal third upper 21-12
- lip competence seems to improve with age due to growth and social acceptability.
Habitual competency
Contraction of mentalis muscle alllow lips to meet.
Why do lips matter in tx?
- Markedly incompetent lips may cause Relapse of overjet
- Ditto a low lower lip line.
- short upper lip may give an un attractive smile.
Anterior oral seal
- Tongue to lower lip
- lower lip to palate
Why do we need AOS?
Swallowing
Dento alveolar factors
Crowding
Does not cause CLASS 2 div 1
Habit
Digit sucking