Enamel, Dentine and Bonding

Question 1

describe enamel

Answer 1

epithelial product 
96% organic material = hydroxyapatite
2 mm thick
very hard and brittle
translucent
non vital

Question 2

what is the chemical formula for hydroxyapatite?

Answer 2

Ca10(PO4)6(OH)2

Question 3

how long are hydroxyapatite crystals?

Answer 3

very long

Question 4

describe the structure of a hydroxyapatite crystal

Answer 4

OH^- ion surrounded by 3 Ca^2+ ions, which are then surrounded by 3 PO4^3- ions, all encapsulated by 6 Ca^2+ ions

Question 5

what is the basic unit of enamel that is formed by tightly packed hydroxyapatite crystals?

Answer 5

enamel prisms/rods

Question 6

what are the 2 parts of the structure of enamel prisms

Answer 6

prism core

prism sheath

Question 7

describe the prism core

Answer 7

tightly packed hydroxyapatite crystals

Question 8

describe the prism sheath

Answer 8

• hydroxyapatite crystals LESS tightly packed
• more space for organic components
• boundary of clearly different crystal orientation

Question 9

give the term for:

prisms appear twisted around each other at the cusps

Answer 9

gnarled enamel

Question 10

what does gnarled enamel provide?

Answer 10

strength at the cusps where there is the most force

Question 11

what are Striae of Retzius?

Answer 11

brown incremental growth lines of enamel

Question 12

what 2 things are known to accentuate (darken) Striae of Retzius?

Answer 12

systemis illness

birth

Question 13

what is the accentuated Stria of Retzius due to birth called?

Answer 13

neonatal line

Question 14

give the term for:

shallow furrows where Striae of Retzius reach the surface

Answer 14

perikymata

Question 15

what are the ridges between perikymata termed?

Answer 15

Imbrication lines of Pickerill

Question 16

describe dentine

Answer 16

porous biological composite of hydroxyapatite crystals in a collagen matrix

Question 17

what direction do collagen fibres mainly run?

Answer 17

parallel to ADJ

Question 18

what property to collagen fibres give dentine?

Answer 18

strength

Question 19

describe primary and secondary dentine tubules

Answer 19

wiggly lines within wiggly tunnels that fan out from the pulp to the ADJ

Question 20

are there more or less tubules per mm2 in Pre-dentine compared to ADJ?

Answer 20

MORE tubules in pre-dentine than at the ADJ

Question 21

What does dentine become deeper towards the pulp?

Answer 21

becomes more porous and wetter

Question 22

where are more nerves found in dentine?

Answer 22

in pre-dentine

Question 23

where is the clinically sensitive area in dentine?

Answer 23

cervical margin

Question 24

give the 3 ways to classify dentine

Answer 24

developmental
primary, secondary, tertiary
tubule

Question 25

what are the 2 types of dentine, classified developmentally

Answer 25

mantle dentine | circumpulpal dentine

Question 26

describe mantle dentine

Answer 26

- 1st formed - adjacent to enamel - thin-ish layer - LARGE COLLAGEN FIBRILS

Question 27

describe circumpulpal dentine

Answer 27

- the rest of dentine - closely packed and interwoven collagen fibrils - small collagen fibrils next to ADJ

Question 28

describe primary dentine

Answer 28

formed during tooth development up to root completion

Question 29

describe secondary dentine

Answer 29

formed after root completion and forms slowly throughout life

Question 30

describe tertiary dentine

Answer 30

localised under the pulpal insult stimulus | 2 types of tertiary dentine

Question 31

give the 2 types of tertiary dentine

Answer 31

``` reactionary = slow formation and uses existing odontoblasts reparative = existing odontoblasts are destroyed and new differentiated 'odontoblasts' are recruited. new dentine is rapidly formed but the structure is poor ```

Question 32

what is the function of tertiary dentine?

Answer 32

to remove pulp from the stimulus (pulp running away from caries/fracture etc)

Question 33

give the term for the dentine around the tubule

Answer 33

peri-/intra- tubular dentine

Question 34

give the term for the dentine between the tubules

Answer 34

inter-tubular dentine

Question 35

contents of dentine tubules?

Answer 35

odontoblast process and nerves

Question 36

give the 2 ways in which dentine can change in response to insult

Answer 36

- tertiary dentine | - sclerosis

Question 37

describe sclerosis of dentine

Answer 37

tubules are blocked off and appear transparent

Question 38

give the 2 ways that dentine changes with age

Answer 38

- secondary dentine | - translucent sclerotic dentine

Question 39

give the 8 changes in dentine that LOWER BOND STRENGTH

Answer 39

1. Caries affected dentine 2. Cervical abfraction lesion 3. Aged dentine 4. Tooth depth 5. Smear layer 6. Dentine permeability 7. Pulpal pressure 8. Desensitising treatments

Question 40

Give the name for the growth lines in dentine

Answer 40

incremental lines of von ebner

Question 41

Give the name for the lines that run antiparallel to and are a coincidence of secondary curvatures

Answer 41

contour lines of owen

Question 42

what forms in dentine as a result of failure of calcospherites to fuse?

Answer 42

interglobular dentine

Question 43

what occurs once the enamel lesion has been cavitated?

Answer 43

bacterial invasion

Question 44

what is always occurring (at the intact surface and the cavitated surface) of a lesion?

Answer 44

demineralisation