amelogenesis Flashcards
enamel formation begins during which stage
late bell stage
function of stellate reticulum and stratum intermedium
nutrients and mechanical support
first signs of calcification in the tooth organ
late bell stage when dentin formation begins (then enamel)
how many times does amelogenesis occur in humans
twice
what mineralized first? dentin or enamel
dentin
first sign of mineralization
predentin
predentin formation signals
differentiation of ameloblasts
order of bell stage top to bottom
- stellate reticulum
- stratum intermedium
- ameloblasts
- dentin
- odontoblasts
- dental papilla
when is first sign of calcification
14 weeks of gestation (incisors)
stratum intermedium and stellate reticulum merge to form
papillary layer
secretion
30% of time
-secrete enamel
maturation
60% of time
- no growth of enamel
- organic out, calcium in (by ameloblasts)
ameloblasts eventually form
reduced enamel epithelium (shrink)
pre-ameloblasts are
cuboidal and linked by tight junctions
ameloblasts are separated from odontoblasts by
basement membrane
function of the basement membrane
- allow parallel arrangement of collagen fibers in predentin
- anchor odontoblasts
major enamel protein
amelogenin
what occurs during the secretory stage
formation of tomes’ processes
what gives ameloblasts its angular appearance and the appearance of cell processes
tomes processes
tomes process allows for the formation of
rod and interrod enamel
which forms first? rod or interrod
interrod
is the matrix on the sides of tomes processes the same
no
enamel matrix is ___ mineralized by the end of the secretory stage
30%
what is the product of secretory stage
tighly interwoven meshwork of hydroxyapetite crystals
maturation stage
change of membrane structure
pumping Ca and P ions into enamel space
ruffle-ended membrane
removal of water and organic matrix
smooth ended membrane
tight junction positions
ruffle: proximal
smooth: distal
what happens to pH when it becomes ruffled
pH drops
5 enamel matrix proteins in the SECRETORY stage
1) amelogenin*
2) ameloblastin
3) enamelin
4) enamelysin
5) kallikrein-4
which enamel proteins are proteolytic enzymes
enamelysin and kallikrein-4
proteolytic enzyme for early secretory stage
enamelysin
proteolytic enzyme for late maturation stage
kallikrein -4
in the presence of amelogenin, what type of crystals are formed
elongated HAP crystals
new basal lamina layer forms
during transition from secretory to maturation
-between ameloblast and enamel
what does the new basal layer contain
-glycoconjugates and new proteins (ODAM, AMTN, SCPP-PQ1)
during tooth eruption, the reduced enamel epi fuses with oral epi to form
junctional epithelium
