development of normal occlusion 2

Question 1

retrognathic mandible and anterior open bite are anomalies of which developmental stage/?

how are they self corrected?

Answer 1

they are characteristic of the gum pad stage

-retrognathic mandible is corrected by differential growth of mandible

-anterior open bite is corrected by eruption of primary incisor

Question 2

anomalies of deciduous period and how they are corrected :

Answer 2

-anterior deep bite(overjet)
=corrected by eruption of primary molars and attrition of incisal edges

-flush terminal plane
=corrected by early and late mesial shift , eruption of 1st molar

-spacing
=corrected by eruption of 1st permanent molars

Question 3

anomalies of mixed dentition and how they are corrected :

Answer 3

-mandibular anterior crowding
=corrected by tongue pressure increasing inter-canine width

-ugly duckling stage
=maxillary canine eruption

-edge-edge occlusion
=eruption and late shift of 1st permanent molar

Question 4

describe late teen crowding :

Answer 4

as the mandible continues to grow outwards, the mandibular incisors get caught behind the maxillary incisors . the growing forces then cause the mandibular incisors to tip lingually, resulting in the decreased parameter of the lower arch

-mostly seen in boys

Question 5

arch width is measured between which teeth?

Answer 5

either from canine to canine (intercanine width)

or from molar to molar ( intermolar width)

Question 6

the maxillary intercanine width increases by 5mm from ages 3-14. what is responsible for this change in arch width?

Answer 6

primary incisors are wider than deciduous ones so when they are eventually replaced they result in the increasing of upper arch width. they also tend to erupt more labially which also contributes to the 5mm increase

less increase in width is observed in intermolar width for both arches

-ARCH length is also increased from 6-10 years

Question 7

after the initial increase in intermaxillary width from ages 3-14, what is the next important event to occur regarding arch width and why does it happen?

Answer 7

at around 10 years leeway space causes arch parameter to decrease after shedding of deciduous molars

Question 8

arch perimeter is measured from :

Answer 8

mesial surface of first permanent molar to mesial surface of opposite permanent molar

Question 9

line of occlusion falls on :

Answer 9

upper
-molar: central fossa
-anterior : cingulum

lower
-molar: buccal cusps
-anterior : incisal edges

Question 10

curve of spee is on the ____ plane

Answer 10

saggital plane

Question 11

function of curve of spee:

Answer 11

allows normal functional and protrusive movement of mandible

Question 12

the curve of wilson will be straight in case of :

Answer 12

attrition (worn dentition)

Question 13

importance of curve of Wilson :

Answer 13

allows exquisite movements which are used in chewing

Question 14

3-dimentional combination of curves od spee and wilson :

Answer 14

curve of monsoon

Question 15

interarch relationship regarding upper first molar that is needed for correct occlusion according to andrews 6 keys of normal occlusion.

Answer 15

mesiobuccal cusp of upper first molar—> (occludes) between mesial and middle buccal cusps of lower first molar

distal marginal ridge of upper first molar occludes with mesial marginal ridge of lower 2nd molar

Question 16

describe the ideal mesio-distal crown angulation for all teeth :

Answer 16

gingival portion should be (+ve) or distally angulated –> mesiodistal tip

Question 17

describe the proper inclination (labio-lingually of teeth:

Answer 17

maxillary incisors:
-gingival aspect is more lingual than the incisal aspect (+ve)

all other teeth :
opposite(-ve). in order to prevent biting of check

Question 18

according to the 6th key of occlusion , curve of spee should not exceed:

Answer 18

1.5mm

Question 19

factors influencing tooth position and occlusion :

Answer 19

muscle factors

periodontal health and masticatory forces

skeletal factors

dental factors (proximal contact , occlusal contact , premature contacts )

trajectories of forces

buccinator mechanism

Question 20

describe the neutral zone in the oral cavity

Answer 20

tooth position is maintained by equal micro-forces from facial muscles and tongue movement .

if facial muscle exertion overpowers the tongue then arch collapse can be seen. if increased tongue forces are present then arch expansion may be observed

Question 21

in the direction of function stresses , what happens to spongy bone?

Answer 21

converts to compact bone (ridges and pillers), these ridges are stress baring areas called trajectory lines

Question 22

most trajectory lines pass:

Answer 22

upwards and towards the base of the cranium

Question 23

what is wolf’s law of bone transformation / remodeling ?

Answer 23

bone in healthy person will adapt to loads under which it is placed (reversible process)