Eruption and Shedding Flashcards
Eruption definition
the movements a tooth makes to attain and maintain its position in the jaw
what is the only exception for the directions an erupting tooth will move?
apically
what do orthodontists do?
hold structures so that a new periodontal ligament can be established
the movements of eruption are a cellular activity involving what structure and what cells types?
PDL
cementoblasts, osteoblasts, osteoclasts and fibroblasts
what is the most numerous cell type in the PDL?
fibroblasts
what are the fibroblasts role in the PDL?
secrete ECM, lyse ECM (fibroclast) or contractile cell (fibromyocyte)
fibromyocyte
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
where is the osteoclast from?
bone marrow
what are the stages of eruption?
- preemergence (facial)
- prefunctional (occlusal)
- functional (mesial)
what happens if you take the tooth out of the crypt?
the alveolus will not form and bone will grow into it
preemergence stage
dental lamina until the REE and Hertwigs root sheath appearance. Prior to the start of root dentin formation. Moves facially
What determines the number of root canals?
the openings in the diaphragm of hertwigs epithelial root sheath (prior to root formation)
what physiological event does NOT occur during the preemergence stages?
differentiation of the cementoblasts
prefunctional stage
-starts with dentin root formation and ends when the tooth reaches the occlusal plane. The main movement is occlusal
beginning of cementogenesis
root sheath breaks up cervically
explain the process of the sheath
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
when do the epithelial rest of Malassez form?
during the prefunctional stage of eruption
what is a cyst?
epithelial lined sac
*problems with erosion in the jaw if remnant from hertwigs epithelial root sheath remains in the PDL
how is the coronal part of the tooth emerge into the cavity during the prefunctional stage?
the oral epithelium and the REE merge and undergo cell death
**both avascular and get blood supply from the CT
what becomes the junctional epithelium in the adult?
the reduced enamel epithelium
how many basal laminas of the junctional epithelium?
2
functional stage of eruption
starts at the occlusal plane and physiologically continues throughout life: physiologic mesial drift
what are the different attachment positions during functional eruption?
attached to enamel only, attached to cementum and enamel and attached to cementum only
when does arrangement of the principal fiber bundles of PDL occur?
during the funcitonal stage
**tooth moves in its socket to stimulate the surrounding bone
