Enamel Morphology

Question 1

which area of the tooth has the greatest mineralised enamel content

Answer 1

surface enamel

Question 2

which area of the tooth has the hardest enamel?

Answer 2

cups/incisal edge

Question 3

what is the basic unit of enamel?

Answer 3

enamel rod or prism

Question 4

what direction do enamel rods run?

Answer 4

from ADJ to the surface

Question 5

how many hydroxyapatite crystallites do enamel rods contain?

Answer 5

> 10^6

Question 6

what is the appearance of enamel under light microscopy due to?

Answer 6

the orientation of crystallites

Question 7

where do crystallites run in the rod regions in relation to the rods?

Answer 7

parallel

Question 8

where do crystallites run in the inter-rod regions in relation to the rods?

Answer 8

on an incline

Question 9

what region is etch more effective in?

Answer 9

inter-rod regions as it works better on the sides of crystallites compared to the tips

Question 10

what are the cross striations in the rod due to?

Answer 10

daily growth

Question 11

what are the transverse striae in the rods due to?

Answer 11

weekly growth

Question 12

what does rod structure arise from?

Answer 12

variation in crystallite orientation

Question 13

what makes up the content of enamel?

Answer 13

hydroxyapatite, water, organic matrix

Question 14

what regulates the nanomechanical properties of enamel?

Answer 14

minor protein component

Question 15

what happens if you remove the protein content from enamel?

Answer 15

you make the enamel more fragile

Question 16

what makes the enamel flexible under biting forces?

Answer 16

minor protein component

Question 17

when is crystallite orientation determined?

Answer 17

during enamel formation

Question 18

where are crystallites deposited in relation to the ameloblast membrane

Answer 18

at right angles

Question 19

describe the development of crystallites

Answer 19

ameloblasts secrete proteins which form palates which concentrate calcium and phosphate in an organised way. The calcium and phosphate can anucleate crystallites. Crystallites can only grow if they remove these proteins

Question 20

in which tooth substance are hydroxyapatite crystals the largest?

Answer 20

enamel

Question 21

what ions make up hydroxyapatite and where do they sit?

Answer 21

calcium on outskirts, hydroxyl at core, phosphate in between

Question 22

what ions are used to substitute hydroxyapatite ions?

Answer 22

magnesium for calcium, carbonate for phosphate, fluoride for hydroxyl

Question 23

what type of course do enamel rods run?

Answer 23

sinusoidal

Question 24

what type of orientation causes banding patterns?

Answer 24

periodic orientation

Question 25

where are hunter-schreger bands seen?

Answer 25

rod periodic orientation

Question 26

where are hunter-schreger bands not seen?

Answer 26

outer enamel

Question 27

what is gnarled enamel?

Answer 27

concentration of rods

Question 28

where is gnarled enamel seen?

Answer 28

in cusps

Question 29

what are the type of incremental lines?

Answer 29

brown striae of retzius and perikymata

Question 30

why does brown striae of retzius appear?

Answer 30

as a consequence of growth on enamel

Question 31

what does the brown striae of retzius share its origin with?

Answer 31

perikymata

Question 32

what are enamel tufts?

Answer 32

hypomineralised regions due to residual matrix protein at prism boundaries

Question 33

what is enamel lamella?

Answer 33

incomplete maturation of groups of prisms - fault line extending through enamel thickness

Question 34

what are enamel spindles?

Answer 34

odontoblast processes extending into enamel

Question 35

how can you tell enamel tufts and enamel spindles apart?

Answer 35

enamel spindles have a rounded end