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Enamel, Dentine and Pulp > Enamel > Flashcards

Flashcards in Enamel Deck (25)
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1

composition of enamel

96% inorganic, HAP
1% organic, NON-COLLAGENOUS proteins
3% h20

2

where is enamel thickest

insical edge/ cusp

3

what are the major diseases of enamel

dental caries, genetic conditions grouped as amelogensis imperfecta

4

is enamel HAP pure

no, it contains impurities- carbonate

5

enamel HAP are hexagonal in cross-section. what are the dimensions of the HAP crystal in enamel

width= 60- 90nm
depth=25-30nm

6

how is HAP arranged in enamel

each HAP crystal is bigger than bone and dentine. millions of HAP crystals packed into a prism.
each prism runs from the EDJ to the tooth surface in a sinosodial path therefore meet at varying lengths.
each prism is perpendicular to the EDJ

7

what are the incremental lines of enamel

1. Daily cross striations= 5um periodicity, circadian rhythm, less prominent
2. Striae of Reitzus= irregular striations, superimosed on daily lines, more prominent but less frequent

8

what are the patterns of prisms in enamel

1. circular
2. keyhole

9

what is inter-prismatic enamel

enamel which runs in between the enamel prisms

10

list all the structures found at the ADJ part of enamel

tufts
lamellae
spindles
hunter-schreger bands

11

what are tufts

structures that contain tuftelin protein
recur at every 100um intervals along the ADJ

12

why do tufts form

when residual organic enamel protein collects

13

what are lamella

a layer/ line running through the full thickness of enamel

14

why do spindles form

result of odontoblast processes (dentin forming cells) inserting themselves in between the ameloblasts during early enamel formation and disrupting it

15

where are hunter-schreger bands seen in enamel

inner 2/3 of enamel

16

what is a-prismatic enamel

'absence of prisms'

17

where is aprismatic enamel found

in newly erupted teeth, the outer layer

18

why does aprismatic enamel occur

there is an outer layer region in newly erupted teeth where all the prisms are aligned at right angles to the tooth surface, are parallel to one another

19

what do spindles look like

dark, cigar shaped

20

where are spindles commonly seen

under cusps of teeth
penetrate 50um deep into enamel

21

what is gnarled enamel

part of enamel with abnormal, disordered prisms

22

why has gnarled enamel evolved

to break up lines of shear where maximum force hits the crown

23

why has gnarled enamel evolved

to break up lines of shear where maximum force hits the crown

24

what do the stria of reitzus look like

'tree rings' which run obliquely across prism, lateral borders of crown, under cusps

25

what is perkymata

caused by stria of reitzus which form a depression running around the tooth