Enamel and dentine basic histo Flashcards
Most mineralised tissue in the body
enamel
mineral percentage of enamel and dentin
96 and 70%
where does enamel come from
produced by ameloblasts
why doesnt enamel have no capacity for repair?
ameloblasts are lost during development
why is enamel difficult to study?
tissue is so hard
what feature does ground section lack compared to a decalcified section of the tooth?
no pulp in ground sections
what are the enamel crystals called and where do they reside?
hydroxyapatite, arranged into rods and interrods
enamel rods are —– to DEJ.
perpendicular
how thick are the enamel rods?
4 microns
what is interrod?
enamel material between rods
what direction are the crystals in the rod?
obliquely
what is rod sheath and its feature?
where rod and interrod meet and its highly organic material
what does each ameloblast produce specifically?
one rod and adjacent interrod
what is tomes process?
a cytoplasmic projection is a conical structure that points towards the forming enamel matrix; produces rod enamel and interrod enamel.
ameloblasts secrete enamel matrix through the ….
tomes process
amelogenesis begins at — of tooth development and intiated on —- sides of tooth through a — process.
bell stage, reciprocal induction
what causes the formation of incremental lines?
rhythmic production of enamel
what causes dark and light bands in the enamel
diurnal rhythm of ameloblats which varies amount of matrix and mineral
in ground sections of the enamel the rods appear —- and the interrod appear —.
rods light , interrod dark.
why can we distinguish rods and interrods in ground sections?
crystallites of calcium and hydroxyapatite are oriented parallel in the rods but obliquely in the interrod- so light can pass the rods more than the interrod hence light rod dark interrod.
how are enamel spindles formed?
when odontoblast processes extend across DEJ
lamellae extend from — towards—.
enamel surface towards DEJ.
tufts extend from —- to —
DEJ towards enamel
what are hunter schreger bands?
fully mineralised rods following a twisted path through enamel layer that causes these visible bundles in ground sections.
what are gnarled enamel?
in regions of high curvature rods follow curved path and twists.
which one forms first enamel or dentin?
enamel
2nd hardest tissue in the body?
dentin
what produces dentin?
odontoblasts
is dentin fixable/able to regrow?
yes, odontoblasts stick around unlike ameloblasts
odontoblasts reside at —-
periphery of the pulp
what is dentin before mineralisation?
pre dentin
where are odontoblasts organised?
they remain the pulp, however their processes extend into dentinal tubules which extends towards DEJ.
