Enamel

Question 1

What is enamel made up of?

Answer 1

enamel prisms

Question 2

Enamel characterisics

Answer 2

highly mineralised

strongest tissue in the body

Question 3

Chemical composition of enamel

Answer 3

97% Inorganic
1% Organic
2% Water

Question 4

Main inorganic component of enamel

Answer 4

hydroxyapatite

Question 5

Main organic component of enamel

Answer 5

protein

Question 6

How many hydroxyapatite crystallites per prism?

Answer 6

10,000

Question 7

Enamel prism diameter

Answer 7

4-7 um

Question 8

Enamel is laid down in layers which produce…

Answer 8

Incremental growth lines

Question 9

What occurs after each successive layer is produced?

Answer 9

ameloblasts retreat so there not trapped within their matrix

Question 10

What does an increase + size of prism lead to…

Answer 10

cross striations

Question 11

What changes the rate of secretion in matrix

Answer 11

daily increments

Question 12

Where does the enamel and dentin meet?

Answer 12

amelodentinal junction OR dentoenamel junction (DEJ)

Question 13

What line is a very important forensic landmark

Answer 13

Neonatal line

marks the disruption in amelogenesis at birth

Question 14

How is this virtually pure mineral substance produced?
……… mineral by weight
……….. by volume

Answer 14

98% mineral by weight

86% by volume

Question 15

Following epithelium mesenchymal tissue interactions what is laid down….

Answer 15

dentine

Question 16

What do cells differentiate to form in enamel?

Answer 16

ameloblasts

Question 17

What are the four tissue layers?

Answer 17

Internal enamel epithelium
Stratum Intermedium
Stellate Reticulum
External enamel epithelium

Question 18

What are the two types of matrix protein

Answer 18

• amelogenin
• non-amelogenins: enamelin
  (secreted by tomes process)

Question 19

What replaces matrix protein at maturation stage of amelogenesis?

Answer 19

replaced by water and mineral

very sensitive to excess fluoride at this stage

Question 20

What happens at eruption stage of amelogenesis?

Answer 20

REE (reduced enamel epithelium) fuses with oral epithelium to make junctional epithelium
Increased mineralisation and maturation of enamel in saliva

Question 21

What collapses at commencement of amelogenesis

Answer 21

stellate reticulum

Question 22

What does each ameloblast secrete? for how long?

Answer 22

matrix

around a year

Question 23

How long does matrix secretion take for a permament molar?

Answer 23

4-7 years

Question 24

What are the 3 main amelogenins

Answer 24

glutamic acid
proline
histidine

Question 25

What do thixotropic gels do?

Answer 25

help as a scaffold for mineralisation