Eruption and Shedding

Question 1

Eruption definition

Answer 1

the movements a tooth makes to attain and maintain its position in the jaw

Question 2

what is the only exception for the directions an erupting tooth will move?

Answer 2

apically

Question 3

what do orthodontists do?

Answer 3

hold structures so that a new periodontal ligament can be established

Question 4

the movements of eruption are a cellular activity involving what structure and what cells types?

Answer 4

PDL

cementoblasts, osteoblasts, osteoclasts and fibroblasts

Question 5

what is the most numerous cell type in the PDL?

Answer 5

fibroblasts

Question 6

what are the fibroblasts role in the PDL?

Answer 6

secrete ECM, lyse ECM (fibroclast) or contractile cell (fibromyocyte)

Question 7

fibromyocyte

Answer 7

also a myofibroblast
-connected to collagen fiber bundles that connect the tooth to alveolar bone, so that when the fibromyocyte contracts the collagen fibers contract and move the tooth

Question 8

where is the osteoclast from?

Answer 8

bone marrow

Question 9

what are the stages of eruption?

Answer 9

1. preemergence (facial)
2. prefunctional (occlusal)
3. functional (mesial)

Question 10

what happens if you take the tooth out of the crypt?

Answer 10

the alveolus will not form and bone will grow into it

Question 11

preemergence stage

Answer 11

dental lamina until the REE and Hertwigs root sheath appearance. Prior to the start of root dentin formation. Moves facially

Question 12

What determines the number of root canals?

Answer 12

the openings in the diaphragm of hertwigs epithelial root sheath (prior to root formation)

Question 13

what physiological event does NOT occur during the preemergence stages?

Answer 13

differentiation of the cementoblasts

Question 14

prefunctional stage

Answer 14

-starts with dentin root formation and ends when the tooth reaches the occlusal plane. The main movement is occlusal

Question 15

beginning of cementogenesis

Answer 15

root sheath breaks up cervically

Question 16

explain the process of the sheath

Answer 16

in the diaphragm stage the number of root canals is determined (tooth erupts occlusally at this level), the sheath elongates and the root dentin outline is determined (with diaphragm roughly at same level) and then the sheath breaks up and cementum is formed to cover the developing root dentin form

Question 17

when do the epithelial rest of Malassez form?

Answer 17

during the prefunctional stage of eruption

Question 18

what is a cyst?

Answer 18

epithelial lined sac

*problems with erosion in the jaw if remnant from hertwigs epithelial root sheath remains in the PDL

Question 19

how is the coronal part of the tooth emerge into the cavity during the prefunctional stage?

Answer 19

the oral epithelium and the REE merge and undergo cell death

**both avascular and get blood supply from the CT

Question 20

what becomes the junctional epithelium in the adult?

Answer 20

the reduced enamel epithelium

Question 21

how many basal laminas of the junctional epithelium?

Answer 21

2

Question 22

functional stage of eruption

Answer 22

starts at the occlusal plane and physiologically continues throughout life: physiologic mesial drift

Question 23

what are the different attachment positions during functional eruption?

Answer 23

attached to enamel only, attached to cementum and enamel and attached to cementum only

Question 24

when does arrangement of the principal fiber bundles of PDL occur?

Answer 24

during the funcitonal stage

**tooth moves in its socket to stimulate the surrounding bone

Question 25

what are changes that can happen during functional eruption?

Answer 25

attrition, dead tracts and tertiary dentin, dentin formation, reduced pulp tissue volume and ectopic mineralization

Question 26

shedding

Answer 26

the physiological elimination of primary teeth caused by the resorptive action of ODONTOCLASTS

Question 27

what do odontoclasts resorb?

Answer 27

the 3 mineralized tissues of the teeth