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3 Oral Biology > Dentine structure > Flashcards

Dentine structure Flashcards

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1
Q

what is the percentage composition of mineral in dentine by weight?

A

70%

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2
Q

what is the percentage composition of matrix by weight?

A

20%

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3
Q

what is the percentage composition of water by weight?

A

10%

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4
Q

what is the mineral of dentine made up of?

A

hydroxyapatite

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5
Q

what is the matrix of dentine made up of?

A

collagen

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6
Q

what are the directions of the collagen fibres in the dentine? why?

A

parallel to ADJ to give strength

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7
Q

the tubules in dentine are wiggly, why?

A

Dentine grows inward, this pressure causes tubules to be wiggly

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8
Q

what forms dentine?

A

odontoblasts

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9
Q

the contents of dentine tubules can be what 3 things?

A

no cell processes just dentinal fluid

odontoblast process

odontoblast process and nerves

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10
Q

how far through dentine does odontoblast process extend?

A

roughly 1/3 the way through dentine so outer 2/3rds unlikely to expose process or nerve innervations

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11
Q

where is dentine more innervated?

A

closer to the pulp

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12
Q

why wont acid etching diffuse into the pulp?

A

due to pulpal pressure and hydrostatic pressure of dentinal fluid moving outwards of exposed tubules

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13
Q

name 3 ways dentine is classified

A

developmental
primary, secondary, tertiary
tubule

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14
Q

what are the types of developmental dentine classification?

A

mantle dentine
circumpulpal dentine

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15
Q

what developmental classification of dentine is this?

A

mantle

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16
Q

what developmental classification of dentine is this?

A

circumpulpal

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17
Q

what is mantle dentine?

A

First formed dentine adjacent to enamel.

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18
Q

describe the collagen fibrils in mantle dentine

A

Large collagen fibrils at 90 degrees to ADJ - disadvantageous as angle where demineralisation is more likely

19
Q

what is circumpulpal dentine?

A

the rest of the dentine that surrounds the pulp and makes up most of the dentine

20
Q

describe the collagen fibrils in circumpulpal dentine

A

Small collagen fibrils parallel to ADJ

21
Q

which is more mineralised, mantle dentine or circumpulpal dentine?

A

circumpulpal dentine

22
Q

what is primary dentine?

A

Formed during tooth development, stops when root is complete (2/3yrs after eruption)

23
Q

what is secondary dentine?

A

forms after the root is fully developed throughout life.

24
Q

why are endodontic procedures harder in older teeth?

A

vital pulp enables continuous formation of secondary dentine which shrinks the pulp chamber

25
Q

what is tertiary dentine?

A

dentine forms in response to insult

26
Q

what is reactionary dentine?

A

in response to mild stimulus
uses existing odontoblasts to make secondary dentine

27
Q

what is reparative dentine?

A

in response to strong stimulus

no existing odontoblast so recruit newly differentiated odontoblasts hard tissue wall forms to slow down carious pathway to protect pulp

28
Q

what tubule classification of dentine is this?

A

inter-tubular dentine

29
Q

what tubule classification of dentine is this?

A

peri-tubular/intra-tubular

30
Q

what is Peri-tubular or intra-tubular dentine?

A

Around tubules

31
Q

what is inter-tubular dentine?

A

Between tubules

32
Q

which is more mineralised, peri/intra-tubular or inter-tubular dentine?

A

peri/intra-tubular dentine

33
Q

what are these lines?

A

incremental lines of von ebner

34
Q

what do the incremental lines of von ebner represent?

A

the position of the odontoblasts at different times during development

35
Q

what is this line?

A

contour line of owen

36
Q

what is the contour line of owen?

A

coincidence of secondary curvatures

37
Q

what is globular dentine?

A

failure of calcospherites to fuse

38
Q

what is the granular layer of tomes?

A

hypomineralized area of radicular dentin

39
Q

name three ways dentine responds to insult

A

tertiary dentine
sclerosis
dead tracts

40
Q

what is sclerosis?

A

highly mineralised - precipitation of calcium and phosphate which block off tubules so appear transparent

41
Q

what are dead tracts?

A

odontoblasts die, empty tubules sealed with reparative tertiary dentine so appear darker

42
Q

dead tracts are caused by what two things?

A

Could be due to insult or overcrowding of odontoblasts

43
Q

how does dentine change as we get older?

A

more secondary dentine -> smaller pulp chamber
more sclerosis -> more transparent and easily fracture when extracted due to being less flexible as more mineralised

44
Q
A

3 Oral Biology (14 decks)

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