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23 Cards in this Set

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Exfoliation
Progressive and discontinuous resorption of the deciduous roots by odontoclasts in the absence of inflammation
Why is exfoliation necessary?
Because adults cannot effectively masticate with tiny baby teeth, therefore they must be shed to allow for larger teeth to come it
What dictates the pattern of root resorption?
Dictated by pressure exerted by the erupting sucedaneous totth
What is exfoliation characterized by?
Alternating cycles of resorption and healing, leading to a net loss of root structure

Odontoclasts resorb way more tissue than needed to relieve the pressure

Immature Cellular cementoid is deposited with patchy spots of mineralization
What is the pattern of root resorption in anterior teeth?
Resorption begins at the lingual edge of the primary root

Some root structure remains at the time of exfoliation

Resorption never reaches CEJ

Only cementum and dentin are resorbed

Odontoclasts DO NOT migrate into pulp cavity

Pulp and dentin are left un-touched
Where does resorption begin in anterior teeth?
Lingual edge of the primary root
How far does resorption reach in anterior teeth?
Never reaches CEJ

Only cementum and dentin are resorbed

Enamel is left un-touched

Does not migrate into pulp cavity therefore pulp and dentin left un-touched
What are patterns of root resorption in posterior teeth?
Resorption begins on primary lingual root so secondary tooth can move underneath in between the roots during pre-eruptive phase

Second phase is when resorption occurs on inner edges of all roots

No root structure remains at time of exfoliation

Resorption can reach past the CEJ, resorbing cementum, dentin and some enamel

Odontoclasts often migrate into pulp cavity to eat tooth from inside out, leaving shell of enamel at time of exfoliation
How far does resorption reach in posterior teeth?
Reaches past the CEJ resorbing cementum, dentin and some enamel

Odontoclasts also migrate into pulp cavity to eat tooth away from the inside out
Where does resorption begin in posterior teeth?
First on lingual root of primary tooth to allow for secondary tooth to move underneath

Then resorption on inner edges of all roots to adjust for the secondary crown
What is the pattern of root resorption during excessive masticatory forces?
Masticatory forces are too much for retained primary tooth

Pressure on the roots of primary tooth causes resorption of its roots

Leads to exfoliation
What are some resorption trends
Mandibular teeth exfoliate before maxillary teeth

Girls exfoliate before boys

Dentin resorbs the fastest because it has tubules increasing surface area

Enamel resorbs the slowest because it's comprised mainly of minerals taking the longest to dissolve
Which tissue is fastest to resorb?
Dentin resorbs the fastest
Which arch exfoliates first?
Mandibular exfoliates before maxillary teeth
Which tissue is slowest to resorb?
Enamel because it's comprised mainly of minerals taking the longest to dissolve
What are some clinical abnormalities during exfoliation?
Retained primary teeth because of absence of secondary tooth underneath

Retained roots doe to piece of primary root that never experience resorptive pressures. This leads to ankylosis in alveolar bone
What are the molecular signals that induce clast activity?
Pressure on root/bone stimulate dental follicle cells to secrete Epidermal Growth Factor (EGF) which affects Stellate Reticulum to upregulate production of IL-1a and TGF-B1
TGF-B1
Stellate Reticulum is stimulated by EGF to produce TGF-B1

It upregulates production of IL-1a

It upregulates dental follcle cells' expression of IL-1a receptors

It recruits monocytes into the area through chemotactic factorsr
IL-1a
Stellate Retciulum is stimulated by EGF to produce IL-1a

It stimulates the dental follicle cells to produce Colony Stimulating Factor-1 to make even more CSF-1 (autocrine function) and recruit macrophages to clump and form osteoclasts/odontoclasts (paracrine function)
What is the function of Colony Stimulating Factor-1
It is produced by the dental follicle by stimulation from IL-1a

It has a paracrine function to recruit macrophages to clump and form osteoclasts and odontoclasts

Also has a autocrine function to make even more CSF-1
What is the function of Epidermal Growth Factor?
It is secreted by dental follicle cells in response to pressure on the root

It directly affects IL-1a production by stimulating Stellate Reticulum to produce more

It indirectly affects IL-1a by stimulating stellate reticulum to upregulate production of TGF-B1, which also upregulates production IL-1a
Characteristics of Clast Cells
Huge

Multi-nucleated

Phagocytic

Comprised of 50+ fused Macrophages

Ruffled border and apical cisterna increaes resorptive capacity

Tons of lysozomes in acidic cytoplasm
What is the sequence of Clastic Resorption?
1. Clast begins resorption by creating Howship's Lacunae sealing off acidic environment

2. Lysozomes release protons and acid phosphatase to dissolve inorganic crystals first

3. Demineralization exposes the protein scaffold that HAP gets deposited on

4. Lysozomes release proteases/collagenases to break protein components

5. Clast cell phagocytizes bits of collagen to complete collagen break down

6. HAP crystals get dissolved, but are not phagocytized