OB D9: Pulpo-dentinal complex : Dentine

Question 1

what is the composition of dentine?

Answer 1

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

Question 2

Name some features of dentine.

Answer 2

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

Question 3

what is the direction of collagen fibres in dentine?

Answer 3

• mainly parallel to ADJ

- Gives dentine strength

Question 4

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

Answer 4

mantle

Question 5

what structures make up dentine?

Answer 5

dentinal tubules

Question 6

what are the tubules continuous with?

Answer 6

pulp

Question 7

how many tubules are there?

Answer 7

15 000-65 000 tubules per mm2

Question 8

what do tubules contain?

Answer 8

• cell processes
• nerves
• fluid - flows out

Question 9

Is dentine vital?

Answer 9

yes

Question 10

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

Answer 10

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

Question 11

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

Answer 11

ADJ - 0.5-1.0 microns

Predentine - 2.0-3.0 microns

Question 12

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

Answer 12

ADJ - 15 microns

Predentine - 6 microns

Question 13

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

Answer 13

ADJ - 4%

Predentine - 28%

Question 14

Deep dentine is more …..?

Answer 14

• more porous

- wetter

Question 15

What are the curvatures in dentine?

Answer 15

• primary curvatures - sigmoid

- secondary curvatures - wiggle lines

Question 16

where are the curvatures more sigmoid?

Answer 16

• in the crown

- less nearer the root

Question 17

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

Answer 17

• no cell process just dentinal fluid
• odontoblast process
• odontoblast process and nerves

Question 18

How much does the odontoblast process extend in dentine?

Answer 18

LIKELY extends approximately 1/3 the way through dentine

Question 19

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

Answer 19

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

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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

Question 22

Give a summary of nerves in dentine.

Answer 22

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

Question 23

what are the 3 ways to classify dentine?

Answer 23

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

Question 24

what is mantle and circumpulpal dentine?

Answer 24

• mantle - first formed dentine

- circumpulpal dentine - everywhere else

Question 25

what is primary, secondary and tertiary dentine?

Answer 25

- 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

Question 26

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

Answer 26

- decreases | - endodontic access problems

Question 27

what is the stimulus for tertiary dentine production?

Answer 27

-caries

Question 28

what is tertiary dentine under stimulus?

Answer 28

localised

Question 29

what is the reactionary reaction to produce tertiary dentine?

Answer 29

- uses existing odontoblasts | - slow formation

Question 30

what is the reparative reaction to produce tertiary dentine?

Answer 30

- existing odontoblasts destroyed - recruit newly differentiated "odontoblasts" - rapid formation - poor structure

Question 31

what is the function of tertiary dentine?

Answer 31

remove pulp from stimulus

Question 32

what is peri-tubular (intra -tubular dentine?

Answer 32

- around tubule | - highly mineralised (40% more)

Question 33

what is inter-tubular ?

Answer 33

between tubules

Question 34

what do the incremental lines of von ebner show?

Answer 34

the position of the odontoblasts at different times during development

Question 35

what is the coincidence of secondary curvatures?

Answer 35

Contour line of Owen

Question 36

what is interlobular dentine?

Answer 36

failure of calcospherite fusion

Question 37

what is the appearance of the granular layer of tomes?

Answer 37

surface of dots, looks black, gritty

Question 38

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

Answer 38

- spaces | - looped/expamded tubules?

Question 39

what are the age changes of secondary dentine?

Answer 39

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

Question 40

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

Answer 40

``` 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 ```

Question 41

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

Answer 41

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

Question 42

what is the result of dentinogenesis imperfecta?

Answer 42

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