Enamel structure

Question 1

enamel is composed of what percent mineral?

Answer 1

96%

Question 2

enamel is composed of what percent matrix?

Answer 2

1-2%

Question 3

enamel is composed of what percent water?

Answer 3

2%

Question 4

enamel can be cut using what?

Answer 4

high speed with either diamond or tungsten carbide bur

Question 5

enamel is what kind of product?

Answer 5

mineralised epithelial product

Question 6

what is the main inorganic (mineral) component of enamel?

Answer 6

hydroxyapatite

Question 7

what is the structure of hydroxyapatite?

Answer 7

OH- ion surrounded by
3 Ca2+ ions surrounded by
3 PO4 3- ions surrounded by
6 Ca2+ ions

Question 8

enamel is not always pure hydroxyapatite the OH- can be replaced by fluoride ion -> fluorapatite
compare the critical pH of fluroapatite and hydroxyapatite

Answer 8

hydroxyapatite critical pH 5.5
flurapatite critical pH 4.5

Question 9

what is the basic unit of enamel?

Answer 9

enamel prisms

Question 10

enamel prisms are composed of what two parts?

Answer 10

prism core
prism sheath

Question 11

name this part

Answer 11

prism core

Question 12

name this part

Answer 12

prism sheath

Question 13

describe the structure of prism cores

Answer 13

tightly packed hydroxyapatite crystals of same orientation

Question 14

describe the structure of prims sheaths

Answer 14

hydroxyapatite crystals of different orientations so less tightly packed and more space for organic components

Question 15

how is enamel formed?

Answer 15

by ameloblasts through amelogenesis

Question 16

what is this wiggly enamel called and why is it there?

Answer 16

gnarled enamel
provides strength

Question 17

what does acid etching do?

Answer 17

dissolves the hydroxyapatite crystals, since the prism sheaths have more space for acid etch to enter this usually gets dissolved

Question 18

where are there aprismatic regions of enamel?

Answer 18

• Innermost enamel where first formed
• Surface enamel where last formed

Question 19

what is this called?

Answer 19

stria of retzius

Question 20

what are stria of retzius?

Answer 20

incremental lines that represent growth

Question 21

accentuated stria of retzius represent what? example?

Answer 21

systemic disturbance e.g. birth -> neonatal line

Question 22

name this structure

Answer 22

perikymata

Question 23

name this structure

Answer 23

imbrication lines of pickerill

Question 24

what are perikymata?

Answer 24

shallow troughs where stria of retzius meet the surface

Question 25

what are imbrication lines of pickerill

Answer 25

ridges (bumps) between perikymata

Question 26

what are enamel spindles?

Answer 26

dentin tubules that run into the enamel

Question 27

what are enamel tufts?

Answer 27

Hypomineralised areas at the ADJ where enamel has not quite formed yet

Question 28

what are lamella?

Answer 28

• developmental - region of enamel that has not formed properly and has more protein
• acquired (fracture line) or cracks formed during preparation of tooth by dentist -> artefact

Question 29

how do you distinguish between lamella and enamel tufts?

Answer 29

lamella go through from the ADJ to enamel surface

Question 30

how do you distinguish between enamel tufts and enamel spindles?

Answer 30

enamel tufts branch off