Eruption and Shedding Flashcards
eruption
the movements a tooth makes to attain and maintain its position in the jaw
what direction is a tooth not moved physiologically to attain and maintain its position in the jaw
apically
is tooth movement that occurs throughout life normal?
yes
what different cell types of the periodontal ligament are involved in movements of eruption?
cementoblasts, osteoblasts, osteoclasts, and fibroblasts
what is the most numerous cell type in periodontal ligament?
fibroblast
what are the roles of fibroblast within the pdl?
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
what are the 3 stages of eruption?
- preemergence
- prefunctional
- functional
what is the main direction of movement in the preemergence stage?
facial
what is the main direction of movement in the prefunctional stage?
occlusal
what is the main direction of movement in the functional stage?
mesial
what does the preemergence stages consist of?
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
what is the fate of cervical loop?
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
physiologic event during the preemergence stage
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)
what happens in the prefunctional stage of eruption?
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
what is are the fates of hertwig’s epithelial root sheath cells
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
what is epithelial rest of malassez?
remnants of epithelial cells from hertwig’s root sheath in the periodontal ligament
appear in the prefunctional stage of eruption
functional stage of eruption
starts at the occlusial plane and physiologically continues throughout life
what are the position changes during functional eruption?
a. attached to enamel
b. attached to enamel and cementum
c. attached to cementum
what happens to pdl during functional stage of eruption?
functional arrangement of principal fiber bundles of pdl
what changes occur during functional eruption?
attrition, dead tracts, reparative (Tertiary) dentin
continued dentin formation, reduced pulp tissue volume, ectopic mineralization
physiologic events occurring during functional stage?
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
what stage is primary teeth seen in?
functional stage of eruption
what stage is permanent teeth seen in?
preemergence or prefunctional stages of eruption
shedding
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
