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Year 2 CSA > Histology of dentine > Flashcards

Histology of dentine Flashcards

1
Q

how can dentine be studied

A

in both ground sections and demineralised sections

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2
Q

what are ground sections

A

where the mineral is retained and the section is unstained

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3
Q

what are demineralised sections

A

where the mineral is removed and the section is stained

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4
Q

how can pulp be studied

A

only in demineralised sections

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5
Q

what is a characteristic feature of dentine

A

the dentinal tubules which run from the pulp to the outer dentinal surfaces

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6
Q

what are dentinal tubules

A

channels running from the pulp to the outer dentine surface

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7
Q

what do the tubules contain

A

fluid and odontoblasts

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8
Q

what shape do the dentinal tubules follow

A

they follow an S shape called the primary curvature

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9
Q

what is on top of the primary curvature

A

the secondary curvature is superimposed on the top of the primary curvature

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10
Q

what does the secondary curvature look like

A

more frequent and small wave like deviations

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11
Q

what might happen to the tubules

A

the tubules might be branched

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12
Q

where is branching more evident

A

evident at the ADJ especially under the enamel in the tooth crown

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13
Q

why does interglobular dentine form

A

arises due to incomplete fusion of calcospherites

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14
Q

what is the mineral front as

A

dentine is laid down and mineralised

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15
Q

what does the fusion trap do

A

it traps areas of poorly mineralised dentine in the form of arches which reflect the spherical nature of the calcospherites

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16
Q

where can calcospherites be seen visibly

A

at the mineralisation front of forming dentine

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17
Q

what can dentine be divided into

A

primary or secondary dentine

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18
Q

what dentine is found in circumpulpal dentine

A

primary dentine
secondary dentine

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19
Q

which is the first dentine laid down adjacent to the ADJ

A

mantle dentine

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20
Q

how are the collagen fibres arranged in the mantle dentine

A

they are located perpendicular to the ADJ

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21
Q

where do the collagen fibres in the mantle dentine arise from

A

some people think it arises from sub odontoblastic mesenchyme origin and not odontoblasts

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22
Q

where is the evidence that the collagen fibres come from sub odontoblastic mesenchyme

A

from von korff fibres which are evident when to developing tooth is stained with silver

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23
Q

how do we see the von korff fibres

A

when the developing tooth is stained with silver

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24
Q

what lays down the basic shape of the dentine

A

primary dentine

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25
Q

what happens once the tooth erupts

A

a slower rate of dentine production at the pulpal surface happens and the root is completed

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26
Q

what is the dentine called that is produced slowly after the tooth erupts

A

regular secondary dentine

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27
Q

what is the junction between the two types of dentine shown by

A

by a change in the direction of dentinal tubules

28
Q

how do dentinal tubules pass through from the ADJ to the pulpal surface

A

by following a shape called the primary curvature

29
Q

what might happen in the ground section

A

path of some of the tubules is more obvious because they appear black

30
Q

why might tubules be black

A

they are empty (fluid filled and have no cell process or mineral deposit)and fill with debris during the grinding process

31
Q

what might the tubules look like in a carious area

A

In an area of dentine where a number of odontoblasts have been affected by caries, for instance, there may be a large and prominent group of tubules which appear black - this area is termed a ‘dead tract

32
Q

what is the pulp dentine interference

A

described as a series of layers

33
Q

the pulp dentine interface is composed of from exterior to interior

A

mineralised dentine
pre-dentine (unmineralised except for the presence of calcospherites)
odontoblasts
cell free zone (of Weil)
cell rich zone
body of the pulp (a loose, vascular and well innervated connective tissue)

34
Q

what is predentine

A

the initial collagenous matrix of dentine before it is mineralised.

35
Q

what lies between the mineralised layer and odontoblast layer

A

homologous to osteoid on the surface of forming bone

36
Q

what is the cell responsible for forming dentine

A

odontoblast

37
Q

how is dentine formed

A

odontoblasts initially secrete a collagenous matrix (the predentine) which is then subsequently mineralised (partly by the fusion of calcospherites).

38
Q

what projects into the dentinal tubule

A

A process from the distal end of the odontoblast projects into a dentinal tubule

39
Q

what happens to pulp size as dentine mineralises

A

As dentine production progresses and the pulp becomes reduced in size the odontoblast layer becomes pseudostratified

40
Q

what happens to the cell count as dentine production continues

A

decreases as the cell moves from the rapid production of primary dentine to the slower, long term, production of regular secondary dentine.

41
Q

what does the odontoblast layer contain

A

unmyelinated nerve fibres and numerous capillary loops, both of which arise from a sub-odontoblastic plexus.

42
Q

where do capillary loops and unmyelinated nerve fibres orginate from

A

a sub-odontoblastic plexus.

43
Q

what are calcospherites

A

small isolated globular areas of mineralisation within predentine which eventually fuse with the mineralisation front (and each other)

44
Q

where does the cell free zone lie

A

beneath the odontoblast layer

45
Q

what does the cell free zone contain

A
  • numerous cell processes
  • many small capillaries loops run through it as they pass from the sub-odontoblastic capillary plexus into the odontoblast layer. It is less obvious in radicular pulp.
46
Q

is the cell free zone real

A

arising from shrinkage of the pulp tissue away from the odontoblast layer (which is attached firmly to the dentine) during processing.

47
Q

what does the cell rich zone contain

A

the cell rich zone (unlike the cell free zone) appears to contains a high concentration of cell nuclei

48
Q

what does the body of the pulp contain

A

loose connective tissue which occupies the space in the remainder of the pulp chamber.

49
Q

what is the predominant cell type

A

fibroblast although macrophages may be present (if pulp inflamed)

50
Q

what is also located in sub odontoblastic layers

A

Undifferentiated mesenchyme to replace odontoblasts which may be damaged

51
Q

the pulp also has

A

the nerves and capillaries which supply the odontoblast layer (as well as the pulp itself)

52
Q

where do nerves and capillaries enter the pulp from

A
  • these enter the pulp through the apical foramen
53
Q

where do the nerves have endings

A

between odontoblasts or within dentinal tubules

54
Q

what might happen to the capillaries

A

the capillaries form numerous loops within the odontoblast layer and may be fenestrated.

54
Q

what might happen to the capillaries

A

the capillaries form numerous loops within the odontoblast layer and may be fenestrated.

55
Q

why does the lesion in the dentine spread wider than the enamel

A

because of the arrangement of enamel prisms around the fissure
and because of some lateral spread at the ADJ.

56
Q

how does sclerotic dentine arise

A

because the dentinal tubules have been completely occluded by the laying down of additional peritubular dentine within the tubules by the odontoblasts.

57
Q

why does sclerotic dentine arise

A

-occurs either as a general aging process)
-as a defensive mechanism in response to some overlying trauma (the caries lesion in enamel).

58
Q

when only can the sclerotic dentine arise

A

process only occurs if the progress of the lesion is slow enough to allow the cells to fill-in the tubules in good order.

59
Q

what is a dead tract

A

when odontoblasts not able to produce defence response (by producing loads of sclerotic dentine) and withdrew their cell processes, leaving behind empty tubules (which during the grinding process fill with air and debris and appear black).

60
Q

what will happen if the odontoblast cell is still alive

A

The odontoblast will (if still extant) attempt to seal the pulpal end of the tubule with reparative (or irregular secondary) dentine.

61
Q

what happens if the odontoblast cells are dead

A

If the odontoblasts are killed then this process is completed by sub-odontoblastic cells which produce a bone-like material.

62
Q

what is reparative dentine

A

produced by odontoblasts in an attempt to seal the dentinal tubules to prevent direct access through the dentine to the pulp

63
Q

what else is reparative dentine called

A

irregular secondary dentine

64
Q

what happens if odontoblasts have been killed by rapid progression of lesion

A

then the function of sealing the tubules will be taken over by sub-odontoblastic cells which produce a non-tubular bone-like material

65
Q

what is reactionary dentine

A

reparative dentine produced by extant odontoblasts

66
Q

what should reparative dentine be reserved for

A

reserved for situations where the original odontoblasts have died and have been replaced by subodontoblastic cells.

Year 2 CSA (6 decks)

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