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Oral pathology > Tooth Development > Flashcards

Tooth Development Flashcards

1
Q

What week does tooth development start?

A

Week 4-5

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2
Q

What is the first event in tooth development?

A

Condensation of mesenchymal tissue in the alveolar ridge (internal surfaces to each other) - lamina

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3
Q

What forms from ectoderm?

A

enamel

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4
Q

What forms from ectomesenchymal tissues

A

Dentine/pulp, PDL, Alveolar bone

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5
Q

Where does ectoderm come from?

A

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).

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6
Q

What are the 4 stages of tooth development?

A
  1. Bud 2. Cap (cap and late cap) 3, Bell (bell and late bell) 4. root formation
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7
Q

What occurs in Bud stage?

A

-20 downgrowths of dental lamina from lamina into underlying mesenchymal tissue (from neural crest)

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8
Q

What does the ectomsenchymal tissue form from?

A

neural crest cells where ectoderm cells migrate through the neural fold.

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9
Q

What occurs in Cap stage?

A

-Early cap: papilla forms enamel organ and primary enamel knot -Late cap: interior ectomsenchymal cells condense and the enamel organ fills with mucopolysaccharide acid

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10
Q

What occurs in early Bell Stage?

A

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

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11
Q

What occurs in late Bell Stage?

A

-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

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12
Q

What occurs in root formation stage?

A

-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)

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13
Q

What stage does Amelogenesis occur?

A

Bell Stage

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14
Q

What are the 5 stages of Amelogenesis?

A
  1. Presecretory phase (morpho/cytodifferentiation) 2. Secretory (Rod/Prism - Rodless/Prismless) 3. Transitional 4. Maturation (ruffled/smooth) 5. Post Maturation (Protective/Desmolytic)
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15
Q

What occurs in the Presecretory phase of Amelogenesis?

A

-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

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16
Q

What occurs in Secretory phase of Amelogenesis?

A

-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

17
Q

What are the 5 proteinatious enamel formers?

A

Enamelin (crystal growth) Enameysin (MMP20) Tufflin(Cell signaling) Ameloblastin (protein) - structure/function role, crystal growth Amelogens (90%) (mineral binding and crystal growth)

18
Q

What happens in the transitional phase of amelogenesis?

A

-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

19
Q

What happens in maturation phase of amelogenesis?

A

-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.

20
Q

What happens in protective phase?

A

-Ameloblasts flatten into fissures and amorpheous layer of protein forms (primary enamel cuticle) -reduced enamel epithelium (serres), degrade while eruption occurs = desmelytic stage.

21
Q

At What stage does dentiogensis occur?

A

Bell stage

22
Q

How is dentinogenesis intiated?

A

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)

23
Q

What are some products expressed in early odontigenesis?

A

Fibronectin (binds to collagen), actin, vinculin, restin, cytokataylin

24
Q

What are the 3 main stages of dentinogenesis?

A
  1. Deposition

2 Secretion

  1. Mineralisation
25
Q

What occurs in depoistion of dentinogenesis?

A

Predentine is deposited as cusp tips

-Er has collgane 1 precurseres and PPDSP

= mantle dentine (1, 3, 5, in ground substance)

26
Q

What occurs in the secretory phase of odontogenesis?

A
  • odonoblast process extends (if into enamel creates spindle)
  • move away from IEE as they secrete from Toms processes (1 per cell) - regular bulk dentine laid
  • collagen 1 + PPDSP =non collagenous proteins
  • mineralisation front (collagenous/noncollageous proteins meet aka mantle dentine/regular
27
Q

What occurs in mineralisation phase of dentinogenesis?

A
  • active trasport of Ca+ by odontoblasts
  • pulp = fibroblasts (III) von Kolff (fibrnectin for adhesion)
  • two patterns of mineralisation
    1. Globular
    2. linear

vesicles bud off, mineral spreads from single hyrdoappatite crystal (seeding). clusters fuse and non collegenous matrix protein continues on long axis of fibres and osteoblast bodies retreat.

28
Q

What is globular mineralisation?

A

Pattern of dentine mineralisation

-rpaid crystal growth in circular patterns that fuse together . increase in size and faster spread

29
Q

What is linear mineralisation

A

Pattern of dentine mineralisation

-occurs more slowly and more evenly and occurs parrellel to the DEJ

30
Q

What occurs in root dentine formation?

A

same as crown but slower with less mineral

structurally and comparitable different from crpwn, von korff fibrills parralel to DEJ

31
Q

What are the 3 types of post eruptive dentine?

A
  1. Peritubular dentine
  2. secondary dentine
  3. tertiary dentine

Pertiubular = odontblasts and plasma proteins (pysiological repsonse)

Secondary = post apoptosis duen to blood flow change

Teritary = protective barrier, if mild irritant odontoblasts are alive but if severe new odontoblasts form from poietogenic in pulp.

32
Q

When does pulpal development being?

A

Bud stage as densly packed mesenchymal cells around enamel organ (1st phargeal arch - neural crest origin)

  • cells on outer layer of germ become PDL
  • at bell stage: poioneer vessels for vasculaisation with antigen presenting dendritic cells and odontoblasts form dentine/pulp complex
  • cells expand, organelle synthesis -> collagen fibril into amorphous ground substance
  • Glyocosaminoglycans high in active phase. mature pulp includes macrophages, dendritic cells, pericytes, lymphocytes
33
Q

What is the pulp shape and size determined by?

A

HERS

34
Q

Where does our information on tooth development come from?

A

Human - extracted teeth (histology, ground section, PCR, CT, MRI, mRNA (tufellin and ameogen specific)

Mice (klein O 2013)

35
Q

Have we identified all pathways currently?

A

No,

  • Tooth type determination not proven. Two therories BUTLER and OSBOURNE. Clone theory (all the same triggered in sequence). Regional theory: morphogenic field. signal triggers
  • Odontoblast trigger (Baldin 2017) many factors identified as being involved. TGF, TWist, Wnt, Runx, runx3, Dux, EGF
  • Tooth eruption initiator (Kjaer 2014) master gene, gingiva, follicle or external?
36
Q

What do errors in Bud and Cap stage cause?

A

odontomes (trubecular, conical, supernumary, odontome), extra lamina budding

-genetical conditions with anaplasia, hypo and hyperplasia (Wnt errors also)

If error with Shh mutation: epitherlial initiation will not occur for lamina - holocephaopathy

37
Q

What errors can occur in Bell stage?

A

Morpho and cytological differentiation. 16th weeks errors

  • Amelogensis, dentinogeneis, (Wnt 10 disorders)
  • hypophosphosphatasia, if in secondary teeth can ifluenced by childhoog cancer tx (chemo/radiation)
38
Q

What errors can occur with erruption?

A

Dentigerous cysts (REE), eruption cysts, OKC serres

Periondontal lateral cysts later - Hers/malessez

39
Q
A

Oral pathology (11 decks)

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