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Oral biology > OB D3- Tooth development > Flashcards

OB D3- Tooth development Flashcards

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1
Q

what do the dental papilla cells mature into?

A

Odontoblasts

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2
Q

what do inner enamel epithelium mature into?

A

ameloblasts

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3
Q

Describe what happens in the bell and crown stages.

A 
Cervical loop cells divide :
-Signal DP-IEE: IEE cells mature:
◦ Elongate and polarise
-Signal IEE-DP: DP cells mature
◦ DP cells invade acellular zone
-Signal DP-IEE: IEE cell mature
-DP cells mature into Odontoblasts 
◦ Form predentine then dentine
-IEE cells mature into Ameloblasts 
◦ Form Enamel
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4
Q

what happens during the bell stage?

A

-Cells of IEE are more columnar and nucleus is towards the stratum intermedium-cells staring to differentiate into pre-ameloblasts. Also interacting with DP cells causing differentiation to pre- odontoblasts.
Some evidence IEE cells are synthesising Enamel proteins

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5
Q

In the bell stage , where is the first place that pre-dentine laid down?

A
  • the cusp
  • Probably close to enamel knot so there are more growth factors etc. Differentiation always starts in cusp- maybe due to GF of EK.
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6
Q

what happens in the crown stage?

A

Once dentine made- there is a signal for ameloblast to become secretory and lay down enamel.
There is no such thing as pre-enamel- once made is mineralised and the proteins broken-down.
Note: nucleus near Stratum Intermedium

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7
Q

Is there a root is the crown stage?

A

There is no root

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8
Q

what is a cervical loop?

A
  • Most cervical portion of the enamel organ that is responsible for root development.
  • Cells found here are the Inner Enamel Epithelium and ecto-mesenchyme cells (which are yet to differentiate).
  • Signal from the ecto-mesenchyme induces the limited proliferation of IEE.
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9
Q

what is this signal?

A

BMP, WNT and FGF family proteins

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10
Q

Describe the cervical loop proliferation.

A
  • Signal: DP to IEE - control number of cell divisions
  • Signal: IEE to DP - induce papilla cells to mature
  • Signal: DP to IEE- induce IEE cells to mature
  • Signal: dentine to IEE -appearance of dentine signals start of enamel secretion
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11
Q

what do cells of the cervical loop go on to form?

A
  • some of these cells will go on to form root
  • the rest will start to differentiate
  • IEE start to differentiate into ameloblasts
  • ameloblasts of IEE then signal to condensing mesenchyme and these will start to differentiate into odontoblasts
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12
Q

Describe the maturation of odontoblasts interaction between ameloblast and odontoblast.

A

1) Ameloblast starts to differentiate first
2) Peripheral ectomesenchyme cells
divide some migrate under
odontoblast layer.
3) On signal from ameloblast, pre-
odontoblasts differentiate
4) Synthetic organelles increase
5) Nucleus move basally and
odontoblast processes form
6) Cell retreats as matrix laid down
leaving one process
7) Once first layer of dentine laid down
ameloblast lays down matrix

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13
Q

Describe odontoblast differentiation.

A

-All cells become columnar in shape-obvious protein secreting cells-lots of Rough ER and Golgi.
-Forming cells produce processes-
Matrix produced by cells mainly collagen.
-A lag phase before mineralisation of matrix- therefore we have pre-dentine and then dentine.
-Dentine formed throughout life
-Dentine varied structure producing regions such as mantle, granular and hyaline layers

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14
Q

Describe the lifecycle of an ameloblast.

A

1) IEE start to differentiate
2) Reverse polarity – nucleus as far away from Dentine as possible
3) Initial enamel secreting cells- component of enamel-dentine junction
4) A) high nucleus in major secretory phase-as slows more in low nucleus (b)
5) Maturation seen by irregular morphology although ones at enamel surface remain smooth (b)
6) Once matured cells regress in height-protect enamel surface.

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15
Q

what is the pre-secretory stage of life as an ameloblast?

A

Cytodifferentiation, morphodifferentiation, resorption of basal lamina, Epi-Mes Interaction

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16
Q

what is the secretory stage of life as an ameloblast?

A

Initial layer of aprismatic enamel formed, develop Tomes processes, Matrix secretion to final thickness, Initiation and mineralisation, crystallite elongation, matrix degradation, development of prismatic structure

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17
Q

what is the transition stage of life as an ameloblast?

A

Ameloblasts shorten-50% die, Vascular invagination, reformation of basal layer, Cessation of matrix secretion, matrix degradation and selective matrix withdrawal

18
Q

what is the maturation stage of life as an ameloblast?

A

Cycling of ruffled and smooth ameloblasts, final degradation and withdrawal of matrix, crystal growth and final third mineralised

19
Q

what is the postmaturation stage of life as an ameloblast?

A

enamel organ degenerates, enamel coverings established, eruption, exposure to oral cavity

20
Q

what is pre-dentine?

A

Is the organic matrix that makes up Dentine before it is calcified.

21
Q

what is in the organic matrix?

A

colognes I,III, V,VI
proteoglycans
glycoproteins

22
Q

what is dentine?

A

mineralised pre-dentine

23
Q

how does predentine go to dentine?

A

1) The first layers of dentine matrix are unmineralised but when reach a certain
thickness mineralisation takes place at same rate as matrix formation.
2) Mineral deposited comes from odontoblasts or present in extracellular fluid.
3) Odotoblasts control everything in this process- from calcium ion
concentration to where matrix proteins are laid down.
4) This is primary dentine

24
Q

what is in enamel ?

A

-different proteins from dentine
2 groups:
-The Amelogenins which are multiple splice variants making up 90-95%
-Enamelins (or non amelogenins) making up 5-10%

25
Q

what do these groups in enamel do?

A

Some have signalling properties and some initialise mineralisation, others control crystallite growth and determination of prismatic pattern

26
Q

what stage does tooth shape determination occur?

A

late cap stage and early bell stage

rapid growth - cell division throughout IEE

27
Q

what is tooth shape determined by?

A

◦ Differential rates of cell division/maturation
◦ NOT by forces within the papilla, however…..
◦ Signal for tooth shape from dental papilla
◦ Evidence from recombination studies…..

28
Q

what drives tooth shape?

A

mesenchyme but initiated by epithelium?

29
Q

what happens in tooth shape determination?

A
  • IEE cell division

- IEE cell maturation

30
Q

Describe the determination of shape.

A

Dentition is formed at specific places in response to the switching on of various transcription factors.
MSX-1, MSX2, Dlx1/2, Barx-1 and Alx-3 determine what sort of tooth is found where

31
Q

why is it only specific areas that a tooth forms?

A
  • Down to transcription factors
  • The first transcription factor is PitX2 this is very important in tooth development as once oral cavity is formed then it is only expressed in Dental epithelium.
32
Q

what do transcription factors control?

A

gene expression -Shh gene is also over-expressed which is a major determinant in where tooth develop

33
Q

how does Shh affect tooth development?

A

Shh is restricted to the dental epithelium. As Shh increases cell proliferation, restriction of expression is important and this seems to be done by interactions with Wnt signalling molecules.
Wnt boundaries between tooth forming and non tooth forming regions. Wnt/7b signalling seen by inhibiting activity –leads to arrest of tooth morphogenesis.
Wnt signalling is stimulated (beta catenin) in the oral epithelium- results in dozens of extra teeth

34
Q

what forms when enamel formation is complete?

A

reduced enamel epithelium

35
Q

what is reduced enamel epithelium derived from?

A
  • reduced ameloblasts
  • other remnants of enamel organ
  • OEE,SR,SI
36
Q

what is reduced enamel epithelium role?

A
  1. protection of enamel surface from :
    -resorption
    -prevention of cementum formation
  2. provide an epithelial lined pathway for eruption
  3. forms initial junctional epithelium
    (reduced enamel epithelium -> fusion of basal lamina ->cell death ->junctional epithelium
37
Q

what is anodontia?

A

absence of primary or permanent teeth

38
Q

what is supernumerary tooth or teeth?

A

development of extra teeth - extra tooth germs

39
Q

what is microdontia or macrodontia?

A

Either abnormally small or large teeth can be partial or complete

40
Q

what is dens in dente?

A

Enamel organ invaginates into the dental papillae commonly affects the permanent maxillary lateral incisor. Deep ligual pit forms that may need endodontic treatment

41
Q

what is fusion?

A

Union of two adjacent tooth germs resulting in one large tooth

42
Q

what is germination?

A

Tooth germs tries to divide-large single rooted tooth with one pulp cavity and two teeth.

Oral biology (29 decks)

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