aetiology of malocclusion: dental alveolar factors

Question 1

most common reason for malocclusion

Answer 1

crowding

Question 2

3 causes of crowding

Answer 2

small teeth
big arches
combination

Question 3

distribution / inheritance of tooth sizes

Answer 3

bell shaped curve of distribution

polygenetic inheritance

Question 4

how tooth size distribution compares to dental crowding distribution

Answer 4

both normal distribution

curve shifted towards crowding rather than severe spacing

Question 5

Raymond Begg theory on crowding based on aboriginies

Answer 5

aboriginies had to eat raw food –> more tooth wear –> less mesiodistal width of teeth –> less crowding
teeth erupt –> muscles try to intrude –> teeth are worn –> teeth erupt more –> face height constant

Question 6

compare aboriginie tooth wear to modern man

Answer 6

modern man: teeth try to erupt –> muscles weaken –> teeth not worn –> face height increases –> overjet increases –> crowding increases

Question 7

describe relevance of face height growth

Answer 7

face height continues to grow after the rest of the body has stopped
BUT crowding presents before inc face height/

Question 8

why can raymond beggs theory not be the only reason for inc crowding in modern man

Answer 8

rapid rise in malocclusion has only occurred in the last 500 years. tudor skulls show inc attrition compared to modern man but no crowding, and not enough time for genetic change in last 500 years

Question 9

% thought to be accounted for by

a. inherited factors
b. evironmental factors

Answer 9

a. inherited factors: 60%

b. evironmental factors: 40%

Question 10

most common occlusion for incisors and %

why this is relevant

Answer 10

class I (93.5%)
60% of people have malocclusion, so the cause is normally not due to incisor occlusion

Question 11

3 hypotheses about environmental factors in dento-facial variation

Answer 11

• dietary: bottle feeding, soft foods, lack of vitamins
• speech: incorrect positioning of tongue
• allergies: nasal blockage –> mouth breathing–> low jaw, inc eruption of teeth, lower tongue posture

Question 12

chance of crowding in permanent dentition with deciduous

a. crowding
b. 6mm spacing

Answer 12

a. crowding: 100%

b. 6mm spacing: 0%

Question 13

what dictates how permanent teeth will erupt

Answer 13

pre eruptive position

Question 14

which teeth erupt palatally/ lingually in a crowded dentition

Answer 14

2nd incisors

2nd premolars

Question 15

when is crowding usually first seen

Answer 15

when permanent dentition erupts (incisors first)

Question 16

where does crowding usually occur

Answer 16

incisor and molar regions

Question 17

what causes crowding in the premolar region

Answer 17

early loss of deciduous molars (due to caries) –> molars move distally, incisors/ canines move mesially

Question 18

2 tx options for crowding

Answer 18

• creating space for alignment by extracting teeth

- creating space by expansion laterally and antero-posteriorly

Question 19

3 situations in which extraction rather than expansion would be needed

Answer 19

• severe crowding –> lots of arch expansion needed
• anterior open bite –> tilting incisors forward would worsen open bite
• instability

Question 20

3 tx options for spacing

Answer 20

• closing the spaces
• re-distributing the space
• re-distributing the space and fill prosthetically

Question 21

3 main causes of malocclusion

Answer 21

• skeletal factors
• soft tissues
• dento-alveolar factors

Question 22

examples of local factors 8

Answer 22

missing teeth
extra teeth
funny teeth
ectopic teeth
cysts
labial frena
digit habits
trauma