Enamel

Question 1

Enamel is composed of

Answer 1

interlocking rods

Question 2

Enamels rods are formed by?

How fast?

Answer 2

Ameloblasts

Rods deposited at 4 microns/day

Question 3

Both dentin and enamel are made of

Answer 3

HAP

Question 4

Enamel crystal size vs dentin

Answer 4

enamel crystals 30x larger –> harder

Question 5

Enamel living? inert?

Answer 5

Not living, but not inert (constant ion flux)

Question 6

Once formed, how much more enamel can be deposited

Answer 6

none

Question 7

% mineralized enamel

Answer 7

96%

Question 8

Enamel is very hard therefore

Answer 8

it is very brittle

Question 9

range of thickness from O to cervical

Answer 9

2.5mm on O to knife like

Question 10

Color of enamel

Answer 10

greyish white/translucent

Question 11

Enamel rods run where to where

Answer 11

DEJ to outer surface

Question 12

Each rod is formed by how many ameloblast

Answer 12

4

Question 13

Each ameloblast forms how many heads, necks, and tails

Answer 13

1 head, a part of 2 forms neck, 1 forms tail

Question 14

in cervical area rods are orientated how? Significance?

Answer 14

perpendicular

less strong –> more prone to cavities

Question 15

At the cusps the rods are orientated how

Answer 15

gnarled and intertwined which allow for bonding and strength

Question 16

sheath has more or less organic matter?

Answer 16

more

Question 17

Light and dark bands of rods show up why

Answer 17

light is not transmitted along adj rods, only along the long axis of one group

Question 18

How much of the thickness do light and dark bands run in ename

Answer 18

1/2 to 2/3 thickness of enamel

Question 19

Incremental lines of enamel form how

Answer 19

result of rythmic recurrent deposition

Question 20

one line in enamel layer at interface forms, what is it? Why?

Answer 20

neonatal line, environment changes enamel quality before orafter birth

Question 21

neonatal enamel is less or more irregular

Answer 21

less

Question 22

Enamel lamelllae are waht

Answer 22

crack in surface visible to naked eye

Question 23

Enamel lamellae run where to where

Answer 23

Surface towards DEJ

Question 24

Risk of enamel lamella

Answer 24

caries risk here

Question 25

Enamel tufts

Answer 25

hypo-mineralized enamel rods, arise at DEJ, defect filled with organic matter

Question 26

Enamel tufts orientation

Answer 26

right angles to DEJ

Question 27

Enamel tufts length

Answer 27

1/10th to 1/5th from DEJ to surface

Question 28

Enamel tufts significance

Answer 28

alt path for lateral spread of caries

Question 29

Perikymata aka

Answer 29

imbrication lines

Question 30

Peikymata are a result of

Answer 30

termination of line of retzius at surface

Question 31

Enamel crystals

made of, shape, bundles

Answer 31

Organized HAP, long and parallel, in bundles called prisms

Question 32

Prismless enamel is ___ thick at DEJ

Answer 32

5 microns

Question 33

Prismless enamel is ___ thick at outer surface of crown

Answer 33

20-40microns

Question 34

Clinical importance of permeability

Answer 34

fluid, bacteria and products can pass into

Question 35

can fluid pass thru unbroken enamel

Answer 35

yes; lamellae, cracks, tufts, and spindles

Question 36

Permeability with age

Answer 36

decreases, thank Fluoride

Question 37

Enamel remin?

Answer 37

yes

Question 38

etching purpose

Answer 38

create a surface which can be bonded to, alters the surface of enamel by demin sheath areas

Question 39

how etching makes surface better for bonding

Answer 39

demins sheath

Question 40

sheath or core more resistant to demin

Answer 40

sheath

Question 41

resin tags

Answer 41

micro-mechanical bonds created by etching so material can penetrate better

Question 42

hardest bio tissue in body

Answer 42

enamel

Question 43

enamel functions (2ish)

Answer 43

Shape and contour and covers and protects

Question 44

why is enamel density varibale

Answer 44

just based on where crystals did not form before rods