Aetiology of Malocclusion

Question 1

what are the general aetiological factors of malocclusion

Answer 1

skeletal/muscular/dentoalveolar

Question 2

what are the skeletal factors of malocclusion

Answer 2

size, shape and relative positions of upper and lower jaws

Question 3

what are the muscular factors of malocclusion

Answer 3

form and function of the muscles that surround the teeth

Question 4

what are the dentoalveolar factors of malocclusion

Answer 4

size of teeth in relation to size of jaws

Question 5

why does malocclusion result

Answer 5

due to disharmony between the components of the facial skeleton

Question 6

what type of malocclusion is hereditary

Answer 6

class 3 occlusion

Question 7

what are the possible environmental factors of skeletal variation

Answer 7

masticatory muscles, mouth breathing, head posture

Question 8

what are the 3 views to consider when judging skeletal variation

Answer 8

antero-posterior
vertical
transverse

Question 9

what is the skeletal relationship with a class 1 occlusion

Answer 9

mandible and maxilla related normally so that teeth erupt into class 1

Question 10

how are lateral cephs made reproducible

Answer 10

due to cephalostat

Question 11

what is a lateral ceph

Answer 11

standardised lateral radiograph of the face and base of skull

Question 12

how are lateral cephs analysed

Answer 12

either hand traced onto paper or digitised using a computer

Question 13

what is SNA in eastman analysis

Answer 13

maxilla to anterior cranial base

Question 14

what is SNB in eastman analysis

Answer 14

mandible to anterior cranial base

Question 15

what is ANB in eastman analysis

Answer 15

mandible to maxilla

Question 16

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

Answer 16

mandible placed posteriorly to maxilla

Question 17

what causes the class 2 antero posterior relationship

Answer 17

mandible too small/maxilla too large
normal sized mandible but placed too far back (obtuse cranial base angle)

Question 18

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

Answer 18

mandible placed anteriorly relatively to maxilla

Question 19

what causes the class 3 antero-posterior relationship

Answer 19

maxilla too small/mandible too large or both
normal sized jaw but acute cranial bae angle

Question 20

what is dento-alveolar compensation

Answer 20

when dento-alveolar structures disguise skeletal discrepancies by inclining teeth towards position of soft tissue balance

Question 21

in severe class 3 malocclusion what is the dento-alveolar compensation

Answer 21

proclined upper incisors
retroclined lower incisors

Question 22

what is the frankfurt plane

Answer 22

lower orbital rim to superior border of external auditory meatus

Question 23

what is the mandibular plane

Answer 23

lower border of mandible

Question 24

where do the mandibular and frankfurt plane meet?

Answer 24

external occipital protuberance

Question 25

how do you measure upper anterior face height

Answer 25

brow ridge to base of nose

Question 26

how do you measure lower anterior face height

Answer 26

base of nose to inferior aspect of chin

Question 27

what is the average ratio of lower anterior face height to upper anterior face height

Answer 27

50%

Question 28

what is the average value of frankfurt mandibular plane angle

Answer 28

27 degrees

Question 29

with a long facial type what is the proportion of LAFH to TAFH

Answer 29

>55%

Question 30

what are the features of long facial type

Answer 30

steeply inclined mandibular plane backward mandibular growth rotation anterior open bite

Question 31

what is the proportion of LAFH to TAFH in short facial type

Answer 31

<55%

Question 32

what are the features of short facial type

Answer 32

tendency to parallelism of jaws forward mandibular growth rotation deep overbite tendency

Question 33

what does arch width discrepancies cause

Answer 33

unilateral or bilateral buccal segment cross bites

Question 34

where does mandibular displacement occur

Answer 34

where inter-arch width discrepancy causes upper and lower posterior teeth to meet cusp to cusp

Question 35

what happens to the mandible with mandibular displacement

Answer 35

it deviates to one side to achieve position of inter cuspation

Question 36

what is the dental cause of facial symmetries

Answer 36

displacement of normal mandible due to unilateral cross bite

Question 37

what is true mandibular asymmetry

Answer 37

hemi-mandibular hyperplasia/elongation condylar hyperplasia

Question 38

what is dento-alveolar disproportion

Answer 38

discrepancy between size of teeth and jaws

Question 39

what is crowding caused by

Answer 39

small jaws and normal sized teeth large teeth

Question 40

what is spacing caused by

Answer 40

large jaws and normal sized teeth small teeth