Enamel 1

Question 1

properties of mature enamel

Answer 1

acellular, non vital. non vascular
ectodermal origin
hardest (most mineralized) in body
brittle
dynamic (deminerlaized and remineralized)

Question 2

enamel composition

Answer 2

1-2% organic component
NO COLLAGEN
major enamel proteins are amelogenins, ameloblastins, enamelin, tuftelin
2-3% water
HA

Question 3

Enamel Crystals

Answer 3

HA
lots are actually carbonatoapatite- substitute for PO4 3- and OH-
also incorporates magnesium- more vulnerable to acid attacks
Carbon and Mg in inner enamel
flouride in outer enamel

Question 4

Enamel Crystal shape

Answer 4

hexagonal
60-70 nm wide 25-30 nm thick
hexagonal symmetry increases as crystals mature, fully mature lose their shape a bit

Question 5

Enamel Rods

Answer 5

cylindrical accumulations of enamel crystals.
perpendicular to DEJ
not completely strait and curve towards surface
meshwork of fibers (kinda like hair)

Question 6

rod sheath

Answer 6

protein rich area of enamel that surrounds the rods
runs 3/4 the way around each rod, seperating rod and interrod enamel-in the gaps the crystals are continuous with interrod enamel
bend towards the outside
ameloblastins and amelogenins are the proteins

Question 7

interrod enamel

Answer 7

simply a different crystal orientation

fills gaps between rods

Question 8

formation of enamel

Answer 8

initial deposit only about 30% mineralized
ameloblast maturations (3 stages)
1- pre-secretory: preameloblast to ameloblast
2- secretory: deposits enamel
3- maturation: reduce the organic matrix and increase minerlaization

Question 9

deposition of enamel

Answer 9

via secretory vesicles apically
enamel is laid down directly in apposition to predentin (mantle dentin)
Tomes process forms and projects into the developing enamel
ameloblasts bound together by junctional complexes
interrod enamel first then forms a groove for the enamel rod (tomes process)

Question 10

maturation of enamel

Answer 10

once enamel is laid down ameloblast goes back to being a squat cell
loss of stellate reticulum and fusion of oee and iee result in single layer of reduced enamel epithelium
prior to eruption enamel hardens
relatively slow- some up to 5 years 2/3 of amelogenesis is maturation
produces a unique basal lamina at external enamel surface (not collagen 4) disruption leads to enamel hypoplasia

Question 11

ruffled cells

Answer 11

pumps ca 2+ in

lower pH favors minerlaization

Question 12

smooth cells

Answer 12

allow diffusion of protein fragments out of enamel

Question 13

fate of Enamel Organ

Answer 13

becomes REE
fuses with oral epithelium to cover the tooth
epithelial layer becomes dentogingivl junction
membrane on tooth that comes off during eruption/ right after

Question 14

primary enamel cuticle

Answer 14

mineralized coating

last secretory product of ameloblasts (perhaps basal lamina)

Question 15

secondary enamel cuticle

Answer 15

or dental cuticle
remains of ree merged with oral epthilium
removed fairly quickly by mechanical stresses