amelogenesis(author v.mazuru)
DESCRIPTION
amelogenesisTRANSCRIPT
![Page 1: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/1.jpg)
SMPhU “Nicolae Testemitanu”
Department of Histology, Cytology and Embryology
Amelogenesis,
Structure of Enamelum,
Assistant professor
PhD:
Mazuru Vitalie
![Page 2: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/2.jpg)
Amelogenesis
process of Enamel formation provided by Ameloblasts
During Amelogenesis ameloblasts become columnar, polarized,
secreting cell
at the moment of Eruption Ameloblasts cease their function,
decrease in volume and undergo gradually involution
![Page 3: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/3.jpg)
Ameloblasts life cycle
1. Morphogenetic
2. Differentiation
3. Secretory
4. Maturation
5. Protective
![Page 4: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/4.jpg)
Morphogenetic
During this stage, the cells
assume columnar shape
Develops RER
GA
Mitochondria
![Page 5: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/5.jpg)
Differentiation
Coincide with the moment
of the beginning of enamel
secretion.
Cells elongate (columnar)
Changes the polarity
![Page 6: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/6.jpg)
Differentiation
RER and GA are above
the nucleus => secretory
AP and non-secretory BP.
Arangement of actin
filaments forms two
terminal bars – basal and
apical.
Organizing of the
epithelium (desmosomes,
tight and gap junctions)
![Page 7: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/7.jpg)
Secretory
Most of the enamel
formation period
↑↑↑ RER, GA, Mtch
Above the apical terminal
bar appears one elongation
– Tomes’ process
![Page 8: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/8.jpg)
Secretory
Tomes’ process responsible
for prisms formation
![Page 9: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/9.jpg)
Advanced secretory ameloblasts
Cells are highly polarized
Tomes’ process gives an
ruffled aspect to the enamel
surface
![Page 10: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/10.jpg)
Maturation
Entire thickness of
Enamel has been
formed.
E is 30% mineralised
E crystals increase in
width and thickness
Water and proteins are
removed
![Page 11: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/11.jpg)
Maturation
Tomes’ process is lost
Organelles reduced in number
Appear two types AB
Ruffle-ended (A)
Smooth-ended (B)
Alternates 6-7 times
A B
![Page 12: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/12.jpg)
Protective (Post-maturation) stage
Enamel maturation is complete
Cells become flattened
Secrete primary E cuticle a type of
basement membrane between apical
surface and Enamelum
Are formed many hemidesmosomes
![Page 13: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/13.jpg)
![Page 14: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/14.jpg)
Protective (Post-maturation) stage
Other layers of
enamel organ merge
Forming Reduced
Epithelium
![Page 15: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/15.jpg)
Enamel formation
1. Organic matrix
formation
2. Mineralisation
![Page 16: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/16.jpg)
Dissociation of BM – TF
Mutual induction
![Page 17: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/17.jpg)
Formation of enamel matrix
Enamel matrix produced in
RER
Enpacked in GA
Transported to the TP
Merocrine secretion
![Page 18: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/18.jpg)
Sequential secretion (4µ/day)
Moving outward (4µ/day)
Appear incremental lines
![Page 19: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/19.jpg)
Mineralisation
Two stages
1. Instant partial (30%)
2. Complete (4 s/stages)
Sources of Ca2+
1. Ca2+ from dentine
2. Ruffle-ended AB
3. Tuftelinum
4. AlcPh-ase of IntEE
![Page 20: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/20.jpg)
Physical properties of the Enamel- Covers the crown
- It is the thickest over the cusps (1.3 - 2.5 mm thick), and the thinnest at cervical margins
- Is the hardest biological tissue
- Has high abrasion resistance, but low tensile strength
- Can undergo neither repair nor replacement (final structure)
- Surface enamel is harder, denser and less porous than subsurface enamel
- The translucency of enamel increases with age
![Page 21: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/21.jpg)
Demineralised section:
Organic components remain, while
calcified are lost.
Ground section of the tooth:
Organic components are lost, while
mineral components remain.
![Page 22: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/22.jpg)
Chemical properties
Non-organic SBST
96-98%
Calcium hydroxyapatite (88-90%)
Ca10(PO4)6(OH)2 – crystallites
Fluoride
Chloride
Sodium
Strontium
Aluminium
Magnesium
Water
![Page 23: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/23.jpg)
Organic SBST
2-4%Proteins:
Amelogenins
Enamelins (non-Amelogenins)
Carbohydrates
Lipids
![Page 24: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/24.jpg)
Enamel prisms (rods)
Enamel prisms cut longitudinally and running towards the surface
of the enamel.
Oblique lines – enamel stria
![Page 25: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/25.jpg)
All 3 patterns are present in humansPattern I
![Page 26: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/26.jpg)
Pattern IIIthe most common in humans
This pattern shows clearly “head” and “tail” regions. The
tail is placed between the heads of 2 neighbors prisms
![Page 27: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/27.jpg)
The prisms meet the enamel surface at different angles
depending on the shape of EDJ and the thickness of enamel.
Have sinusoidal arrangement
Are organized in groups of 10-13 layers of prisms, that follow
the same direction, are blocked above and below by another
group of prisms that are oriented in different direction.
These periodic changes in prisms direction give rise to a banding
pattern – Hunter-Schreger bands.
![Page 28: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/28.jpg)
-Size of the bands ~ 50µm.
- are visible as different bands
of prisms that reflect the light
in different directions.
- the bands of prisms cut
longitudinally – parazones
(pale)
- the bands of prisms cut
transversally – diazones (dark)
The sinusoidal direction of the
enamel prisms in alternating
sheets results in alternately
reflecting bands on the cut
surface.
![Page 29: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/29.jpg)
Hunter-Schreger bands
A. DiazoneB. Parazone
![Page 30: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/30.jpg)
Hunter-Schreger bands
![Page 31: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/31.jpg)
Hunter-Schreger bands
“Gnarled” enamelum
![Page 32: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/32.jpg)
The outer 20-100µm of enamel is prismless (aprismatic).
![Page 33: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/33.jpg)
Incremental lines
Enamel is formed incrementally, periods of activity alternating
with periods of quiescence.
This results in structural appearances known as incremental lines.
Short period IL (cross-striation)
Long period IL (enamel striae)
Neonatal IL
![Page 34: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/34.jpg)
Cross-striation
Are seen as lines transversing
the enamel prisms at right
angles to their long axes.
![Page 35: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/35.jpg)
Enamel striae (Retzius lines)
Represent weekly enamel deposition
![Page 36: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/36.jpg)
Neonatal line
Is the largest Retzius line
Specific only for deciduous teeth
Is formed at birth
Reflects the metabolic changes at
birth
The most less mineralised enamel
![Page 37: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/37.jpg)
Surface enamel
Perikymata grooves
Perikymata ridges
Enamel caps
Enamel holes
![Page 38: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/38.jpg)
On the lateral surface of
enamel, enamel striae
reaches the surface in a
series of fine grooves that
running circumpferentially
around the crown –
perikymata grooves.
Between them – P ridges
![Page 39: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/39.jpg)
Enamel caps
Surface elevations 10-15 µm across
Are thought to be enamel deposition on
top of non-mineralisable debris late in
development.
![Page 40: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/40.jpg)
Enamel holes
Surface depressions that results
from loss of caps and underlying
material.
![Page 41: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/41.jpg)
Enamel-Dentine Junction (EDJ)
A. Enamel tufts
B. Enamel spindles
C. Enamel lamellae
![Page 42: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/42.jpg)
Enamel spindles
Narrow, elongated tubules that extend
up to 25 nm into the enamel.
Represent hypomineralised areas
Are thought to be:
Distal edges of OB processes
Dentine collagen fibers
Remnants of dead OB
![Page 43: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/43.jpg)
Enamel tufts
Represent hypomineralised
enamel areas.
Have the same direction and
undulate the same like prisms.
Appears at 100µm intervals
along the junctions.
![Page 44: Amelogenesis(Author v.mazuru)](https://reader034.vdocuments.mx/reader034/viewer/2022042610/5695d1281a28ab9b0295629e/html5/thumbnails/44.jpg)
Enamel lamellae
Hypomineralised enamel areas
that results from incomplete
maturation of groups of prisms.
Thereby, in these areas amount
of enamel proteins is much
higher. Are the most common
for the cervical area of the
tooth
Run through the entire
thickness of enamel.