1 - Class 2 div 1 malocclusion Flashcards
What is the BSI definition of a class 2 div 1 malocclusion?
The lower incisor edges lie posterior to the cingulum plateau of the upper incisors, there is an increased overjet, and the upper central incisors are proclined or of average inclination
What percentage of the population have a class 2 div 1 malocclusion?
15-20%
What are the reasons for treating a class 2 div 1 malocclusion?
- aesthetic concerns
- trauma risk due to incompetent lips
Describe the skeletal patterns associated with class 2 div 1 malocclusion.
A/P
- typically class 2 skeletal base
- commonly have retrognathic mandible
- can be seen on class 1 base, if uppers +++ proclined
Vertical
- found with a range of vertical patterns
Transverse
- not associated with transverse problems
- can have narrow maxilla due to thumb sucking
What is the normal SNA value?
81 +/- 3
What is the normal SNB value?
78 +/- 3
What is the normal ANB value?
3 +/- 2
What is the normal MxP/MnP value?
27 +/- 4
What is the normal Ui/MxP value?
109 +/- 6
What is the normal Li/MnP value?
93 +/- 6
What is the SNA value?
Sella turcica to soft tissue point A
What is the SNB value?
Sella turcica to soft tissue point B
What is the ANB value?
Angle between soft tissue point A and B
What is the MxP/MnP value?
Angle between the maxillary and mandibular planes
What is the Ui/MxP value?
Angulation of upper incisors to maxillary plane
What is the Li/MnP value?
Angulation of lower incisors to mandibular plane
What is the normal LAFH/TAFH value?
55%
How do soft tissues influence class 2 div 1 malocclusion?
- lips become incompetent due to proclination of upper incisors
- lip trap can further procline the upper incisors