Aeitology Of Malocclusion

Question 1

What skeletal classification can be hereditary

Answer 1

Class III

Question 2

Possible environmental factors of skeletal variation

Answer 2

Masticatory muscles
Mouth breathing
Head posture

Question 3

How to measure A-P jaw relationship

Answer 3

Palpation

Question 4

Why are lateral cephalograms used in orthodontics

Answer 4

Reproducible- pt. In cephalostat at a set distance from cone and film
Monitor growth

Question 5

How is pt positioned during LC

Answer 5

Pt positioned via ear post
FRANKFURT PLANE HORIZONTAL

Question 6

How are LCs analysed

Answer 6

Computer digitisation: Eastman Analysis (red values)

Question 7

SNA vs SNB

Answer 7

SNA: maxilla to anterior cranial base
average value 81 deg +/-3
SNB: mandible to anterior cranial base
average value 78 deg +/-2
Angle between gives you ANB avg 3 deg

Question 8

Class II causes and cranial base angle

Answer 8

Mandible post to maxilla
Mandible too small, maxilla to large, or both
Mandible norm but too far back due to >CBA
Normally obtuse CBA

Question 9

Class II cephalometrics

Answer 9

SNA usually average
SNB decreased
ANB > 5

Question 10

Class III causes and CBA

Answer 10

Mandible anterior to maxilla
Maxilla too small, mandible too large, combination
Normal sized jaws but mandible too far forward due to acute CBA
ACUTE CBA

Question 11

Class III cephalometrics

Answer 11

SNA decreased if maxilla deficient
SNB average
ANB <1 or negative

Question 12

Dento-alveolar compensation

Answer 12

May disguise underlying skeletal discrepancies
Forces from lips, cheeks and tongue tend to incline teeth towards a position of soft tissue balance

Question 13

Dento-alveolar compensation in class III malocclusion

Answer 13

Proclined upper incisors
Retroclined lowers