Enamel Flashcards
composition of enamel
96% inorganic, HAP
1% organic, NON-COLLAGENOUS proteins
3% h20
where is enamel thickest
insical edge/ cusp
what are the major diseases of enamel
dental caries, genetic conditions grouped as amelogensis imperfecta
is enamel HAP pure
no, it contains impurities- carbonate
enamel HAP are hexagonal in cross-section. what are the dimensions of the HAP crystal in enamel
width= 60- 90nm
depth=25-30nm
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
what are the incremental lines of enamel
- Daily cross striations= 5um periodicity, circadian rhythm, less prominent
- Striae of Reitzus= irregular striations, superimosed on daily lines, more prominent but less frequent
what are the patterns of prisms in enamel
- circular
2. keyhole
what is inter-prismatic enamel
enamel which runs in between the enamel prisms
list all the structures found at the ADJ part of enamel
tufts
lamellae
spindles
hunter-schreger bands
what are tufts
structures that contain tuftelin protein
recur at every 100um intervals along the ADJ
why do tufts form
when residual organic enamel protein collects
what are lamella
a layer/ line running through the full thickness of enamel
why do spindles form
result of odontoblast processes (dentin forming cells) inserting themselves in between the ameloblasts during early enamel formation and disrupting it
where are hunter-schreger bands seen in enamel
inner 2/3 of enamel
what is a-prismatic enamel
‘absence of prisms’
where is aprismatic enamel found
in newly erupted teeth, the outer layer
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
what do spindles look like
dark, cigar shaped
where are spindles commonly seen
under cusps of teeth
penetrate 50um deep into enamel
what is gnarled enamel
part of enamel with abnormal, disordered prisms
why has gnarled enamel evolved
to break up lines of shear where maximum force hits the crown
why has gnarled enamel evolved
to break up lines of shear where maximum force hits the crown
what do the stria of reitzus look like
‘tree rings’ which run obliquely across prism, lateral borders of crown, under cusps
what is perkymata
caused by stria of reitzus which form a depression running around the tooth
