Eruption and Shedding

Question 1

eruption

Answer 1

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

Question 2

what direction is a tooth not moved physiologically to attain and maintain its position in the jaw

Answer 2

apically

Question 3

is tooth movement that occurs throughout life normal?

Answer 3

yes

Question 4

what different cell types of the periodontal ligament are involved in movements of eruption?

Answer 4

cementoblasts, osteoblasts, osteoclasts, and fibroblasts

Question 5

what is the most numerous cell type in periodontal ligament?

Answer 5

fibroblast

Question 6

what are the roles of fibroblast within the pdl?

Answer 6

secretes extracellular substance
lysis the extracellular substance
may become a contracting cell called fibromyocyte myofibroblast- cell connected to principal collagen fiber bundles that connect the tooth to alveolar bone, when it contracts, the collagen fibers contracts, moving the tooth

Question 7

what are the 3 stages of eruption?

Answer 7

1. preemergence
2. prefunctional
3. functional

Question 8

what is the main direction of movement in the preemergence stage?

Answer 8

facial

Question 9

what is the main direction of movement in the prefunctional stage?

Answer 9

occlusal

Question 10

what is the main direction of movement in the functional stage?

Answer 10

mesial

Question 11

what does the preemergence stages consist of?

Answer 11

appearance of dental lamina and continues to the appearance of reduced enamel epithelium and hertwig’s root sheath, just prior to start of root dentin formation

Question 12

what is the fate of cervical loop?

Answer 12

outer and inner layers coming together forming hertwig’s epithelial root sheath
sheath 2 functions:
determines number of root canals of tooth- apical end continues as diaphragm
determine root dentin outline

Question 13

physiologic event during the preemergence stage

Answer 13

start of odontogenesis: epithelial stages and tooth germ appearances
differentiation of ameloblasts, odontoblasts and fibroblasts
appearance of crown dentin
enamel formation begins and is maturing
appearance of pulp chamber
establishment of dej
enamel organ over the enamel becomes the reduced enamel epithelium that is attached to the enamel by a basal lamina
the outer and inner layers of enamel organ come together at cervical loop to form: hertwig’s epithelial root sheath
number of root canals a tooth will have is determined at this stage
bone crypts (undergoes remodeling, becoming alveolar process)

Question 14

what happens in the prefunctional stage of eruption?

Answer 14

starts with root dentin formation break up hertwig’s epithelial root sheath
appearance of epithelial rest of malassez
differentiation of cementoblasts
cementogenesis
formation of periodontal ligament and alveolar process- maturing dental follicle part of the tooth germ
collagen fiber bundles of pdl are not functionally arranged in group: arranged obliquely
merging of reduced enamel epithelium with oral epithelium
emergence into oral cavity
reduced enamel epithelium becomes the junctional epithelium of free gingiva- junctional peithelium attached to tooth surfface by basal lamina
ends when tooth reaches the occlusa plane

Question 15

what is are the fates of hertwig’s epithelial root sheath cells

Answer 15

daphragm stage- number of root canals determined: tooth erupts occlusially from this level
sheath elongates: determines root dentin outline
diaphragm remains at relatively same level
root dentin forms: sheath breaks up- cementum forms on exposed dentin- this sequence continues apically until root dentin is completed

Question 16

what is epithelial rest of malassez?

Answer 16

remnants of epithelial cells from hertwig’s root sheath in the periodontal ligament

appear in the prefunctional stage of eruption

Question 17

functional stage of eruption

Answer 17

starts at the occlusial plane and physiologically continues throughout life

Question 18

what are the position changes during functional eruption?

Answer 18

a. attached to enamel
b. attached to enamel and cementum
c. attached to cementum

Question 19

what happens to pdl during functional stage of eruption?

Answer 19

functional arrangement of principal fiber bundles of pdl

Question 20

what changes occur during functional eruption?

Answer 20

attrition, dead tracts, reparative (Tertiary) dentin

continued dentin formation, reduced pulp tissue volume, ectopic mineralization

Question 21

physiologic events occurring during functional stage?

Answer 21

starts at occlusial plane and physiologically continues throughout life
functional arrangement of the principal fiber bundles of pdl
maintenance (preservation) of alveolar process
continued dentin (secondary and tertiary) and cementum formation
physiological mesial drift
junctional epithelium moves from its attachment to just enamel. to enamel and cementum, then to just cementum (physiologic passive eruption)
reciprocal induction occurs between the junctional epithelium and adjacent connective tissue (lamina propria)
age changes: unique changes of each tooth tissue

Question 22

what stage is primary teeth seen in?

Answer 22

functional stage of eruption

Question 23

what stage is permanent teeth seen in?

Answer 23

preemergence or prefunctional stages of eruption

Question 24

shedding

Answer 24

the physiologic elimination of primary teeth caused by resorptive action of odontoclasts
odontoclasts like the osteoclast originates in the bone marrow and conveyed to the site of activity by blood vessels