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OCB02 > Dentinogenesis > Flashcards

Dentinogenesis Flashcards

1
Q

Where are coronal and radicular dentin found?

A

Coronal = crown

Radicular = root

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2
Q

What are the two layers of coronal dentin?

A

Mantle dentin

Circumpulpal dentin

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3
Q

Where is mantle dentin found?

A

Adjacent to the EDJ

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4
Q

What are the three layers of radicular dentin?

A

Hyaline layer (Hopewell-Smith)

Granular layer of Tomes

Circumpulpal dentin

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5
Q

Where is circumpulpal dentin found?

A

Around pulp

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6
Q

Describe the process of dentinogenesis. (5)

A
  1. IEE differentiates into preameloblasts
  2. Peripheral dental papilla cells start to differentiate into preodontoblasts and odontoblasts
  3. Differentiating odontoblasts undergo elongation and polarisation and secretory organelles develop
  4. Newly formed odontoblasts develop multiple small cell processes and begin predentin secretion
  5. Odontoblast cell body moves toward pulp as matrix is deposited and process retracts over time
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7
Q

Where does cytodifferentiation (amelo/odontoblasts) start?

A

Tips of cusps/incisal edge

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8
Q

Describe odontoblasts. (5)

A

Large nucleus at base

Large Golgi complex

RER parallel to long axis of cell

Long process with many smaller ones

Cell-cell junctions (desmosomes)

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9
Q

Why do odontoblasts have desmosomes between each other?

A

Prevent leakage of predentin between cells

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10
Q

What is the function of a preodontoblast?

A

Resides in pulp tissue and responds to injury

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11
Q

What are the substances present in predentin? (7)

A

Collagen type I

Phosphoproteins

Glycoproteins/sialoproteins

Proteoglycans

Growth factors

Matrix metalloproteinases

Serum-derived proteins

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12
Q

Give three examples of phosphoproteins which are present in predentin. (3)

A

Dentin phosphoproteins

Carboxyglutamate-containing proteins (Gla-proteins)

Dentin matrix protein 1

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13
Q

What glycoproteins/sialoproteins are present in predentin? (4)

A

Osteonectin

Osteopontin

Bone sialoprotein

Dentin sialoprotein

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14
Q

What proteoglycans are present in predentin? (3)

A

Decorin (CS rich)

Biglycan (CS rich)

Lumican (KS)

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15
Q

What growth factors are present in predentin? (4)

A

TGF β-family

Insulin-like GF1/2

FGF

BMP

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16
Q

What matrix metalloproteinases are present in predentin? (5)

A

Collagenases (MMP1)

Gellatinases A/B (MMP2/9)

Stromelysin (MMP3)

Enamelysin (MMP20)

Tissue inhibitors metalloprotein

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17
Q

What serum-derived proteins are present in predentin?

A

Albumin

α2HS-glycoprotein

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18
Q

How thick is mantle dentin?

A

20-150um

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19
Q

Describe mantle predentin. (4)

A

Different composition as has contributions from pulp cells

Collagen fibres at right angles to IEE

Numerous processes lead to porous dentin

Matrix vesicles form on collagen fibres which trigger mineralisation

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20
Q

Describe circumpulpal predentin. (3)

A

Collagen fibres parallel to dentin-pulpal border

Incremental lines present

Sinusoidal path of odontoblasts (primary curvature)

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21
Q

How thick are the collagen fibres in dentin?

A

100nm

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22
Q

What two types of mineralising fronts are there (dentin)?

A

Linear

Globular

23
Q

How thick are the collagen fibres in proximal and distal predentin?

A

20nm proximally and thicken to 70nm distally (thickens through predentin)

24
Q

What is the metadentin?

A

Mineralising front

25
Q

Describe metadentin. (3)

A

2.5-5um thick

Rich in DPP, dentin sialoprotein, proteoglycans

Calcospherites are 2.5-5um thick in globules

26
Q

What is interglobular dentin?

A

Areas between unevenly fused calcospherites found in the globular layer (fast mineralisation)

Between mantle and circumpulpal dentin

27
Q

What does the diurnal variation in odontoblast secretion result in?

A

Incremental lines of von Ebner (light and dark paired bands, 2-4um apart)

28
Q

How big are the matrix vesicles in predentin mineralisation and what do they contain?

A

30-200nm

Enzymes (alkaline phosphatase) which increase phosphate concentration

29
Q

How can the matrix vesicles in predentin mineralisation be formed?

A

Cell budding or fragmentation

30
Q

How is mineralisation of predentin controlled by odontoblasts?

A

Controlling influx of Ca2+

Controlling secretion and metabolism of matrix proteins

31
Q

How is circumpulpal predentin mineralised?

A

Ca2+ nucleation at spaces present between collagen fibres under principle control of DPP

32
Q

What are the properties of dentin phosphoprotein?

A

Highly acidic so binds Ca2+

Can change shape to bind more Ca2+ to allow crystal growth

33
Q

What are the functions of dentin phosphoprotein? (4)

A

Transports Ca2+ to mineralisation front

Location of nucleation to specific areas of collagen

Stabilisation of formed crystals

Inhibits crystal formation when DPP concentration is high

34
Q

What role does osteonectin play in mineralisation in vitro?

A

Inhibits growth of hydroxyapatite

Promotes Ca2+ and phosphate binding to collagen

35
Q

What role does osteopontin play in mineralisation in vitro?

A

Promotes mineralisation

36
Q

Where is bone sialoprotein found in dentin? (3)

A

Early mineralising dentin

Predentin

Peritubular dentin

37
Q

What role do proteoglycans play in mineralisation in vitro?

A

Predentin - transport; hydroxyapatite inhibitors

Mineralising dentin - absorbed onto collagen and promotes hydroxyapatite initiation

38
Q

What are calcospherites?

A

Circular areas of mineralised dentin seen under polarised light

39
Q

What initiates the formation of root dentin?

A

Hertwig’s epithelial root sheath

40
Q

How does radicular dentin formation differ to coronal dentin?

A

Slower

Calcospherites are smaller initially with more interglobular areas

41
Q

Describe the hyaline/Hopewell-Smith layer.

A

Relatively structureless (no tubules)

Non-collagenous, fine, fibrillar matrix with enamel-like proteins

10um thick

42
Q

When is primary dentin formed?

A

During tooth development

43
Q

When is secondary dentin formed?

A

After root is fully formed

44
Q

Why does secondary dentin have a less regular tubular pattern?

A

Odontoblasts become more crowded

Slower rate of deposition

45
Q

Why is there a contour line at the edge of the secondary dentin?

A

Change in tubule direction

46
Q

How can the rate of secondary dentin formation be increased?

A

By denervation

47
Q

When is tertiary dentin laid down?

A

In response to stimulus

48
Q

Describe reactionary dentin. (3)

A

Tertiary dentin laid down in response to mild irritants

Original odontoblasts survive and upregulation of odontoblasts

More time = more regular structure

49
Q

Describe reparative dentin.

A

Tertiary dentin laid down in response to strong irritants

Odontoblasts die - progenitors recruited and differentiate

Preodontoblasts differentiate into odontoblast-like cells

50
Q

What might the appearance of tertiary dentin be like? (3)

A

Secondary dentin

Atubular

Few and irregularly arranged tubules

51
Q

What signal molecules are present in dentin matrix?

A

TGF-β 3 and 1

BMP

52
Q

What type of dentin would TGF-β3 and 1 result in?

A

Reactionary-like dentin

53
Q

What type of dentin would TGF-β3 result in?

A

Reparative-like dentin

54
Q

What type of dentin would BMP result in?

A

Bone-like dentin

OCB02 (19 decks)

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