Amelogenesis

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Amelogenesis
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Amelogenesis is the formation of enamel.
There are two processes involved 1) Formation
of the organic matrix 2) Mineralization of the
matrix Note There is about 30 that is
initially mineralized with no lag time. The
remainder has a lag time between laying down of
the organic matrix and mineralization.
Mineralization isnt completed until the tooth
has come into contact with the oral fluid.
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Stages of Ameloblast Life

• Morphogenic
• Organizing
• Secretory
• Maturation
• Protective

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Pre Secretory
Morphogenic -shape of crown is determined
Differentiation/Organizing -elongation of
cells -protein secretion machinery develops and
moves to apical portion of cell -basement
membrane perforates and degenerates during mantel
dentin formation -polarity changes to allow
deposition of enamel in the correct
direction -The outer dental epithelium becomes
porous to be able to give a nutrient supply
to the inner epithelial cells since the blood
supply from the CT has been cut off. This is
what causes the polarity change to take
place. -Tomes Process begin to form
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Secretory
The first layer of enamel that is laid down at
the DEJ is aprismatic -aprismatic enamel is
located in two places 1) DEJ 2) surface of
tooth as last phase of enamel
growth -aprismatic enamel initial enamel (no
lag time) The distal (or apical) is the
secretory face Presence of Tomes
Process -not stagnant comes and
goes -responsible for formation of enamel
rods/prisms -involved with the formation of the
head of the rod Elaborate and organize the
entire enamel thickness Once the ameloblast
gets tired, the Tomes process retracts permanently
Note The dark lines in the figure above are
enamel threads
Membrane Preformativa Tomes Process
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Maturation
Ameloblasts have two functions in
maturation 1) Bring mineral to be deposited 2)
Suck on water and organic material -the
above two process give the ameloblasts a ruffled
border appearance Maturation
Proper -Modulation (ruffled end/smooth end)
related to calcium transport -Secretion of
covering basal lamina enamel cuticle (may
regulate material in and out of maturing
enamel) -Mineral is being brought in and the
water and organic material is sucked out 94
becomes mineralized 4-6 becomes mineralized
when the tooth erupts due to a chemical
reaction Modulate and transport specific ions
required for the concurrent accretion of mineral
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Distal terminal bars -at the distal ends of
the ameloblasts which separate the Tomes
processes from the cell proper. -are observed
only during enamel producing stage of development
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A visual representation of the cell junction
occursterminal bars.
Tomes Processes
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Enamel Rods/Prisms
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Head Tail
The pits are where the Tome Process sits
The head is located coronally and the tail is
located cervically The rods are a sinusoidal
shape The head of the rod is generally less
susceptible to caries
It takes 4 ameloblasts to make 1 enamel rod
Each ameloblast will contribute to 4 rods