Dentine structure

Question 1

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

Answer 1

70%

Question 2

what is the percentage composition of matrix by weight?

Answer 2

20%

Question 3

what is the percentage composition of water by weight?

Answer 3

10%

Question 4

what is the mineral of dentine made up of?

Answer 4

hydroxyapatite

Question 5

what is the matrix of dentine made up of?

Answer 5

collagen

Question 6

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

Answer 6

parallel to ADJ to give strength

Question 7

the tubules in dentine are wiggly, why?

Answer 7

Dentine grows inward, this pressure causes tubules to be wiggly

Question 8

what forms dentine?

Answer 8

odontoblasts

Question 9

the contents of dentine tubules can be what 3 things?

Answer 9

no cell processes just dentinal fluid

odontoblast process

odontoblast process and nerves

Question 10

how far through dentine does odontoblast process extend?

Answer 10

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

Question 11

where is dentine more innervated?

Answer 11

closer to the pulp

Question 12

why wont acid etching diffuse into the pulp?

Answer 12

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

Question 13

name 3 ways dentine is classified

Answer 13

developmental
primary, secondary, tertiary
tubule

Question 14

what are the types of developmental dentine classification?

Answer 14

mantle dentine
circumpulpal dentine

Question 15

what developmental classification of dentine is this?

Answer 15

mantle

Question 16

what developmental classification of dentine is this?

Answer 16

circumpulpal

Question 17

what is mantle dentine?

Answer 17

First formed dentine adjacent to enamel.

Question 18

describe the collagen fibrils in mantle dentine

Answer 18

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

Question 19

what is circumpulpal dentine?

Answer 19

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

Question 20

describe the collagen fibrils in circumpulpal dentine

Answer 20

Small collagen fibrils parallel to ADJ

Question 21

which is more mineralised, mantle dentine or circumpulpal dentine?

Answer 21

circumpulpal dentine

Question 22

what is primary dentine?

Answer 22

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

Question 23

what is secondary dentine?

Answer 23

forms after the root is fully developed throughout life.

Question 24

why are endodontic procedures harder in older teeth?

Answer 24

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

Question 25

what is tertiary dentine?

Answer 25

dentine forms in response to insult

Question 26

what is reactionary dentine?

Answer 26

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

Question 27

what is reparative dentine?

Answer 27

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

Question 28

what tubule classification of dentine is this?

Answer 28

inter-tubular dentine

Question 29

what tubule classification of dentine is this?

Answer 29

peri-tubular/intra-tubular

Question 30

what is Peri-tubular or intra-tubular dentine?

Answer 30

Around tubules

Question 31

what is inter-tubular dentine?

Answer 31

Between tubules

Question 32

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

Answer 32

peri/intra-tubular dentine

Question 33

what are these lines?

Answer 33

incremental lines of von ebner

Question 34

what do the incremental lines of von ebner represent?

Answer 34

the position of the odontoblasts at different times during development

Question 35

what is this line?

Answer 35

contour line of owen

Question 36

what is the contour line of owen?

Answer 36

coincidence of secondary curvatures

Question 37

what is globular dentine?

Answer 37

failure of calcospherites to fuse

Question 38

what is the granular layer of tomes?

Answer 38

hypomineralized area of radicular dentin

Question 39

name three ways dentine responds to insult

Answer 39

tertiary dentine sclerosis dead tracts

Question 40

what is sclerosis?

Answer 40

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

Question 41

what are dead tracts?

Answer 41

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

Question 42

dead tracts are caused by what two things?

Answer 42

Could be due to insult or overcrowding of odontoblasts

Question 43

how does dentine change as we get older?

Answer 43

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