Tooth Development Flashcards
What week does tooth development start?
Week 4-5
What is the first event in tooth development?
Condensation of mesenchymal tissue in the alveolar ridge (internal surfaces to each other) - lamina
What forms from ectoderm?
enamel
What forms from ectomesenchymal tissues
Dentine/pulp, PDL, Alveolar bone
Where does ectoderm come from?
Germ layer on the outer surface of the embryo. superior layer when invagination of neural fold (has neural crest as last loss of other layer).
What are the 4 stages of tooth development?
- Bud 2. Cap (cap and late cap) 3, Bell (bell and late bell) 4. root formation
What occurs in Bud stage?
-20 downgrowths of dental lamina from lamina into underlying mesenchymal tissue (from neural crest)
What does the ectomsenchymal tissue form from?
neural crest cells where ectoderm cells migrate through the neural fold.
What occurs in Cap stage?
-Early cap: papilla forms enamel organ and primary enamel knot -Late cap: interior ectomsenchymal cells condense and the enamel organ fills with mucopolysaccharide acid
What occurs in early Bell Stage?
Week 10 -water influx into enamel organ causing cells to spread out but stay connected by demsomosmes (stallate reticulum). -Cellular differentiation, lamina breakdown, crown shape from IEE forms -3 layers form: 1. IEE (glycogen and columnar) 2. OEE (cuboidal from enamel organ. 3. stratum intermediate between columnar and stallate which flattens. -OEE/IEE junction at cervical loop, BM forms creating enamel organ and dental papilla
What occurs in late Bell Stage?
-IEE continues until mitosis stops with columnar cells at tip is laid. -polarity of cells occurs towards IEE (TGF-B) -Acellular zone: basal lamina removed, reciprocal induction when contact occurs and organ collage matrix is laid down (predentine) by odontogenic processes -IEE polarized amealoblasts = pre-enamel - Cells use glycogen until stellate reticulum collapses allowing blood vessel nutrients
What occurs in root formation stage?
-HERS of IEE/OEE grows downwards and around papilla (open at apex). -epi contact inducts odontoblastic differentiation -HERS breaks down (rests of Malessaz in PDL)
What stage does Amelogenesis occur?
Bell Stage
What are the 5 stages of Amelogenesis?
- Presecretory phase (morpho/cytodifferentiation) 2. Secretory (Rod/Prism - Rodless/Prismless) 3. Transitional 4. Maturation (ruffled/smooth) 5. Post Maturation (Protective/Desmolytic)
What occurs in the Presecretory phase of Amelogenesis?
-IEE are pre-ameloblast, odontoblasts form collagen bundles. rER have free ribosomes, vesicles in cytoplasm. linked at proximal end and distal end by terminal bar (dental papilla). -TGFB controlled, enzymes exocytosis degrade BL and absorbs the products > contact / DSPP release -enamel proteins through diffusion = crystalisation. -crystal lengthen, cell bodies move away. Aprismatic with no tomes and polarity reverses, organelles move
What occurs in Secretory phase of Amelogenesis?
-Columnar ameloblasts with tomes processes (mercocrine glands) = prismatic -Tomes create honeycomb structure (1 rob = 4 ameloblasts) -moves away from dentine as hydroxyappetite spindle like (50um) and is perpendicular to the CEJ (aprismatic) -Ca from blood enters enamel organ and rER. -New enamel 30% protein, 1% when mature -Proteins released to help growth
What are the 5 proteinatious enamel formers?
Enamelin (crystal growth) Enameysin (MMP20) Tufflin(Cell signaling) Ameloblastin (protein) - structure/function role, crystal growth Amelogens (90%) (mineral binding and crystal growth)
What happens in the transitional phase of amelogenesis?
-High water and low mineral content > maturation -50% of ameolblasts undergo apoptosis and secretion finishes -remaining reduce in size and redistribute their organelles and amelogins are removed -enamel organ invaginates, BV and microvilli form and basal lamina with hemidesmosomes form -Cell for ion spread, crystal growth, TRAP and enamel at CEJ
What happens in maturation phase of amelogenesis?
-enamel thickness increases (65% h20/20% organic) > increase crystal growth, size and width. -organic matrix removed between crystals to <1% (amelogens squeeze out and CaPO4 influx and tomes lost) -ruffled or smooth(5+ changes), ruffled tight and secrete CAPO4, smooth lose junctions and organic molecules move out. -from cusp to cervical.
What happens in protective phase?
-Ameloblasts flatten into fissures and amorpheous layer of protein forms (primary enamel cuticle) -reduced enamel epithelium (serres), degrade while eruption occurs = desmelytic stage.
At What stage does dentiogensis occur?
Bell stage
How is dentinogenesis intiated?
repricocal induction when BM is broken down to allow contact between preameolblasts of IEE and OEE.
Whenn induction occurs and polarity shifts they release GF = preodonotblasts
undergoes mitosis (1 daughter, 1 odontoblast)
controlled by SHH, BMP, IGF, Wnt.
accellular zone is invaded by increase in size and cell polaristion away from the IEE (gogi and ER increase in size)
What are some products expressed in early odontigenesis?
Fibronectin (binds to collagen), actin, vinculin, restin, cytokataylin
What are the 3 main stages of dentinogenesis?
- Deposition
2 Secretion
- Mineralisation
