Dentine Flashcards

1
Q

dentine is not seen unless the enamel is worn away. what are the differences between dentine and enamel

A

dentine is yellow, enamel translucent
dentine = sensitive, enamel= not sensitive
dentine is formed throughout life, enamel isn’t
dentine has a collagen protein matrix, enamel does not

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2
Q

what is dentine

A

a tissue made of small tubules arranged parallel within a collagen matrix

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3
Q

what is the diameter of the dentine tubules

A

3 um

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4
Q

what do the dentine tubules contain

A

odontoblasts- dentine forming cells

fluid

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5
Q

what is the composition of dentine

A

65% inorganic HAP

35% organic and water

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6
Q

how is HAP arranged in dentine

A

HAP is found on/in collagen fibrils of organic matrix

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7
Q

how are the collagen fibrils arranged in dentine

A

they run in PARALLEL to the pulpal surface

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8
Q

dentinal tubules run from the pulpal surface to the EDJ/CDJ. what course do they follow

A

a curved, sigmoid course = produces primary curvatures
and secondary curvatures
more branched at the EDJ, wider at the pulpal surface

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9
Q

what is the difference between the primary and secondary curvatures

A

the secondary curvatures are smaller, more frequent, wave-like tubules

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10
Q

what is peri-tubular dentine

A

over-time, the dentine that is deposited within the walls of the dentinal tubules= narrows lumen

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11
Q

what two things are distinct about the matrix of peri-tubular

A

does not have collagen fibres- rather an unidentified protein
it is hyper-mineralised

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12
Q

what are the incremental lines of dentine

A
  1. Von Ebners- daily incremental line, diurnal rhythm, 4um spacing
  2. Andresons line- superimposed on von ebner’s, 20um apart, more prominent, long-period lines
  3. Contour lines of Owen- congruence of secondary curvatures, seen due to optical effects
  4. Schreger line- congruence of primary curvatures, seen due to optical effects
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13
Q

dentine may be classified by its region. what does this include

A

mantle dentine- region beneath enamel, first formed

circumpulpal dentine

primary dentine- dentine made during initial tooth development, fast forming

secondary dentine- dentine made over life, slow forming

peritubular dentine- dentine in the walls of dentinal tubules

inter-tubular dentine- dentine found in between the dentintal tubules

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14
Q

what are the different types of dentine

A

sclerotic dentine
dead tract
irregular secondary dentine (reactionary/ reparative)

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15
Q

how is sclerotic dentine formed

A

with matruation, the dentinal tubueles become filled with peritubular dentine
the intertubular dentine and dentinal tubules both have the same refractive index= region of translucency= sclerotic dentine

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16
Q

why does sclerotic dentine form

A

normal ageing process

defensive response to stimuli (severe attrition, slow forming caries)

17
Q

why is irregular secondary dentine formed

A

when there is fast caries lesion progression, more dentine is laid down at the pulpal surface.

18
Q

secondary dentine can be divided into…

A

reactionary- dentine made by the existing odontoblasts which did recover from the insult. the dentine is ordered

reparative- dentine made by odnotoblast-like cells because odontoblasts did not recover from insult. the dentine laid down is IRregular and BONE-LIKE

19
Q

what are dead tracts

A

this defines the layer of dentinal tubules below a lesion that does not contain odontoblast processes, filled with air/debris= appear black

20
Q

what is different about the mineralisation of dentine that makes it similar to bone

A

occurs on a mineralisation front

involves calco-spherates fusing one by one with the mineralisation front

21
Q

what are calco-spherates

A

calcification spheres

22
Q

what is inter-globular dentine

A

hypo-mineralised area
caused by calco-spherates fusing with one another BEFORE fusing with the mineralisation front hence do not get mineralised properly

23
Q

which cells produce the dentine matrix

A

odontoblasts

24
Q

what is the mineralisation front

A

where the HAP is deposited.

25
Q

in which direction does the mineralisation front move across all the zones of dentine

A
mineralised dentine
un-mineralised pre-dentine 
the odontoblast layer
the cell free zone- fewer cell bodies
body of the pulp
26
Q

what is found in un-mineralised pre-dentine

A

calco-spherates
no mineral
lots of type 1 collagen fibres, and non-collagenous proteins

27
Q

describe how mineralisation occurs in dentine

A
  1. odontoblasts produce dentine matrix where dentine is deposited. the front travels in this direction
  2. at the pre-dentine, the calco-spherates each fuse with the front to become subsumed within the bulk of mineralised dentine