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Oral biology > OB D9: Pulpo-dentinal complex : Dentine > Flashcards

OB D9: Pulpo-dentinal complex : Dentine Flashcards

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1
Q

what is the composition of dentine?

A

mineral - 70%
Matrix- 20%
water - 10%

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2
Q

Name some features of dentine.

A
  • Specialised connective tissue -Hard (KHN 75)
  • Strong and resilient
  • ~70% mineral - hydroxyapatite
  • ~20% organic - collagen
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3
Q

what is the direction of collagen fibres in dentine?

A
  • mainly parallel to ADJ

- Gives dentine strength

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4
Q

In what dentine are the collagen fibres not parallel to the ADJ?

A

mantle

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5
Q

what structures make up dentine?

A

dentinal tubules

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6
Q

what are the tubules continuous with?

A

pulp

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7
Q

how many tubules are there?

A

15 000-65 000 tubules per mm2

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8
Q

what do tubules contain?

A
  • cell processes
  • nerves
  • fluid - flows out
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9
Q

Is dentine vital?

A

yes

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10
Q

what is the difference in number of tubules per mm2 in amelodentinal junction and predentine?

A

ADJ - 15 000 - 20 000
Pre dentine - 45 000 - 65 000
(more tubules in pre dentine )

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11
Q

what is the difference in tubule diameter in ADJ and pre dentine?

A

ADJ - 0.5-1.0 microns

Predentine - 2.0-3.0 microns

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12
Q

what is the difference in tubule distance apart (microns) in ADJ and pre dentine?

A

ADJ - 15 microns

Predentine - 6 microns

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13
Q

what is the difference in % of surface occupied by tubules in ADJ and pre dentine?

A

ADJ - 4%

Predentine - 28%

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14
Q

Deep dentine is more …..?

A
  • more porous

- wetter

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15
Q

What are the curvatures in dentine?

A
  • primary curvatures - sigmoid

- secondary curvatures - wiggle lines

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16
Q

where are the curvatures more sigmoid?

A
  • in the crown

- less nearer the root

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17
Q

Give 3 examples of what could be found in a cross section of a tubule.

A
  • no cell process just dentinal fluid
  • odontoblast process
  • odontoblast process and nerves
18
Q

How much does the odontoblast process extend in dentine?

A

LIKELY extends approximately 1/3 the way through dentine

19
Q

what are the percentages of tubules containing nerves in pre-dentine?

A

pulp horn - 27%-85%
cervical margin - 7%
root- 7%

20
Q

what are the percentages of tubules containing nerves in the inner 1/3?

A

pulp horn - 10%
cervical margin- 2%
root- 0%

21
Q

what are the percentages of tubules containing nerves in the outer 2/3?

A

pulp horn - 0%
cervical margin - 0%
root - 0%

22
Q

Give a summary of nerves in dentine.

A
  • Dentine is sparsely innervated
  • Most nerves in pre-dentine/inner dentine in pulp horns
  • Few at cervical margin – clinically a sensitive area
23
Q

what are the 3 ways to classify dentine?

A
  1. mantle or circumpulpal
  2. Primary , secondary or tertiary (used clinically)
  3. Intertubular or peri- (or intra-) tubular dentine
24
Q

what is mantle and circumpulpal dentine?

A
  • mantle - first formed dentine

- circumpulpal dentine - everywhere else

25
Q

what is primary, secondary and tertiary dentine?

A
  • Primary - formed during tooth development (up to root completion)
  • Secondary - formed after root completion , forms slowly throughout life of the tooth
  • Tertiary - response to pulp insult
26
Q

what happens to the pulp volume with age and what problems can arise with this?

A
  • decreases

- endodontic access problems

27
Q

what is the stimulus for tertiary dentine production?

A

-caries

28
Q

what is tertiary dentine under stimulus?

A

localised

29
Q

what is the reactionary reaction to produce tertiary dentine?

A
  • uses existing odontoblasts

- slow formation

30
Q

what is the reparative reaction to produce tertiary dentine?

A
  • existing odontoblasts destroyed
  • recruit newly differentiated “odontoblasts”
  • rapid formation
  • poor structure
31
Q

what is the function of tertiary dentine?

A

remove pulp from stimulus

32
Q

what is peri-tubular (intra -tubular dentine?

A
  • around tubule

- highly mineralised (40% more)

33
Q

what is inter-tubular ?

A

between tubules

34
Q

what do the incremental lines of von ebner show?

A

the position of the odontoblasts at different times during development

35
Q

what is the coincidence of secondary curvatures?

A

Contour line of Owen

36
Q

what is interlobular dentine?

A

failure of calcospherite fusion

37
Q

what is the appearance of the granular layer of tomes?

A

surface of dots, looks black, gritty

38
Q

what are the possible reason for the granular layer of tomes?

A
  • spaces

- looped/expamded tubules?

39
Q

what are the age changes of secondary dentine?

A

Translucent sclerotic dentine:
– Tubules occluded with calcified material
– Progresses cervically from apex
– Forensics – age teeth
– Clinical:
• More peritubular dentine
• Root less flexible – fracture risk for extraction

40
Q

what are the dentine changes in response to insult (tertiary)?

A 
Sclerosis:
– Tubules blocked off
– Appears transparent
– Nature of material in tubule?
• ? peritubular dentine
• ? Not formed by odontoblast
• ? Mineralisation of odontoblast process? 
• ? Precipitate of calcium phosphate
41
Q

what are dead tracts? (dentine changes in response to insult)

A
  • odontoblasts die
  • empty tubules sealed with reparative tertiary dentine
  • appear dark
  • can occur under normal cusp tips- odontoblast overcrowding
42
Q

what is the result of dentinogenesis imperfecta?

A
  • Primary and permanent dentitions
  • Bulbous crowns
  • Short roots
  • Teeth translucent - grey –> brown/blue colour
  • Pulp space rapidly obliterated
  • Enamel poorly supported by dentine

Oral biology (29 decks)

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