enamel

Question 1

what is the hardest tissue in the body?

Answer 1

enamel

Question 2

why does enamel need to be so strong and hard?

Answer 2

to resist abrasion

Question 3

how is enamel strong but brittle?

Answer 3

it requires support

Question 4

what supports enamel?

Answer 4

dentine

Question 5

where is enamel located?

Answer 5

covering the crown of the tooth

Question 6

describe the thickness of enamel

Answer 6

it varies (occlusal plate of molars is thicker than that of incisors), however, is thicker towards the incisal edge due to abrasion

Question 7

how does enamel appear?

Answer 7

• translucent (increases with mineralisation)
• browner than dentine

Question 8

describe the development of enamel

Answer 8

it starts as soft tissue and becomes hard overtime doe to minerailisation

Question 9

what is the matrix development of enamel?

Answer 9

The ameloblasts start secreting large amounts of enamel matrix proteins as they move away from the dentin surface so that the nascent (new) enamel layer can thicken.

Question 10

describe enamel rods (prisms)

Answer 10

• made of crystallite
• orientation of crystallite is determined during enamel formation
• crystallites deposited at right angles to the ameloblast membrane

Question 10

describe enamel rods (prisms)

Answer 10

• basic units of enamel
• made of crystallite of hydroxyapatite
• orientation of crystallite is determined during enamel formation
• crystallites deposited at right angles to the ameloblast membrane
• rods run from amelo-dentinal junction to surface

Question 11

what part of the enamel is most mineralised?

Answer 11

surface enamel, hardness decreases from the cusp to cervical region

Question 12

what is the content of enamel?

Answer 12

• hydroxyapatite (95% weight, 90% volume)
• water (4% weight, 5-10% volume)
• organic matrix (1% weight, 1-2% volume)
• proteins- amelogenins, enamelins, peptides, amino acids

Question 13

what is hydroxyapatite crystal made up of?

Answer 13

calcium, phosphate and hydroxide in a spiral

Question 14

what is a fissure?

Answer 14

deep pits and grooves on the surfaces of the teeth

Question 15

describe the lines running through enamel

Answer 15

• one set runs at a right angle, from the enamel to the enamel-dentinal junction (appear in alternating light and dark lines)
• the other set lies almost parallel to the outer surface and are broader

Question 16

what are the brown striae of Retzius?

Answer 16

the broader parallel lines which are an indication of the incremental manner in which enamel is formed by the ameloblasts- the colouration is due to variations in crystallite orientation

Question 17

describe the surface of the EDJ (ADJ)

Answer 17

has an appearance, with the concavities pointing out towards the enamel surface. This arrangement may serve to increase the mechanical strength of the bond between enamel and dentine

Question 18

describe the surface of the EDJ (ADJ)

Answer 18

has an appearance, with the concavities pointing out towards the enamel surface. This arrangement may serve to increase the mechanical strength of the bond between enamel and dentine

Question 19

where is enamel thickest?

Answer 19

at the cusps/incisal edge

Question 20

where is enamel thinnest?

Answer 20

at the cervical region

Question 21

how much growth does each enamel rod represent?

Answer 21

7 days