Enamel

Question 1

enamel facts

Answer 1

hardest tissue in body, resists abrasion, brittle, covers tooth crown, translucent, transparency increases with mineralisation

Question 2

enamel regional variations

Answer 2

thicker at incisal edge, thinner at cervical edge
molars thickest cusp
surface more mineralised than deeper

Question 3

enamel rods

Answer 3

basic unit - rod, 5um-2.5mm
run from ADJ to surface, crystallites run parallel to rod, incline in inter-rod
etching = effective on crytallise side than tips
long parallel rods = cross striations, daily growth
brown transverse strai = inclin, weekly growth

Question 4

enamel content

Answer 4

hydroxyapatite - 95% weight, 90% volume
water - 4% w, 5-10 v
organic - 1% w, 1-2 v

Question 5

hydroxyapatie and caries attack

Answer 5

when high concentration of carbonate, less ressitant and more susceptible to acid attack
fluoride added, more resistant

Question 6

incremental brown lines

Answer 6

brown straie of retzius, weekly growth of enamel

Question 7

neonatal line

Answer 7

present and assocated with attrition, seperates enamel in iul and after birth

Question 8

ADJ

Answer 8

tufts - hypomineralised due to residual matrix protein
lamella - incomplete matruation of group of prisms
spindle - odontolblast region extending into enamel