Aetiology of Malocclusion 1

Question 1

what are general aetiological factors of malocclusion?

Answer 1

skeletal: size, shape, relative position of U+L jaw

muscular: form and function of muscles that surrounds teeth

dentoalveolar: size of teeth in relation to size of the jaws

Question 2

what are the reasons for skeletal variation?

Answer 2

• environmental - head posture, mouth breathing, masticatory muscles
• genetics

Question 3

why is lateral cephalometry used in ortho?

Answer 3

• standardised radiographs of face and base of skull
• reproducible (can be used to directly compare, distance and scale all kept constant)

Question 4

how can you analyse a lateral cephalogram of a ortho pt?

Answer 4

• hand trace over a lightbox
• computer digitisation

Question 5

what is the antero-posterior relationship in a class 1?

Answer 5

• mandible related normally to maxilla
• jaws correctly sized

Question 6

what is the antero-posterior relationship in a class 2?

Answer 6

• mandible placed posteriorly relative to maxilla
• mandible too small (most commonly), maxilla too large, or combination of both
• mandible & maxilla normal sized but just placed too far back [Larger CRANIAL BASE ANGLE]

Question 7

what is the antero-posterior relationship in a class 3?

Answer 7

• mandible placed anteriorly relative to maxilla
• maxilla too small (most common), mandible too large, or combination of both
• normal sized jaw but mandible positioned too far forwards [Smaller CRANIAL BASE ANGLE]

Question 8

what is the antero-posterior relationship in a class 3?

Answer 8

• mandible placed anteriorly relative to maxilla
• maxilla too small (most common), mandible too large, or combination of both
• normal sized jaw but mandible positioned too far forwards [Smaller CRANIAL BASE ANGLE]

Question 9

what do the letters S, N, A, B stand for in cephalometrics?

Answer 9

S - sella turcica (bony depression in sphenoid)
N - naison
A - A plane (Maxilla)
B - B plane (Mandible)

Question 10

what is the frankfurt plane?

Answer 10

lower orbital rim to superior border of external auditory meatus

Question 11

what is the mandibular plane?

Answer 11

lower border of mandible

Question 12

what should the average ratio of your upper anterior face height be to your lower anterior face height?

Answer 12

equal, so 50%

Question 13

where is ur upper and lower anterior face height measured from?

Answer 13

Upper - brow ridge to base of nose
Lower - base of nose to inferior aspect of chin

Question 14

what can happen when a patient has arch width discrepancies?

Answer 14

cause unilateral or bilateral buccal segment cross-bites