3. Life History Of Odontoblasts
.Differentiation of odontoblasts -1
Ameloblasts
Preameloblasts
Basement
membrane
Differentiate from At first become
the peripheral short columnar cell The cells grow in length
dental papilla cells with many stubby (40u) and closely packed
(UMC) together
processes
6. Formation of the predentin -2
Odontoblast become a protein forming and secreting
cell.
• R E R , Mitochondria and Golgi bodies
• Ribonucleic acid and alkaline phosphatase
Large open
faced N
Inner dental
RER
epith side
Mitochondria
Golgi Predentin
bodies
7. Odontoblastic process formation -3
As more D is laid down, the
At first more than one cells receed and leave single
process process ( Tomes’ fiber)
8. Quiescent state of odontoblasts -4
The odontoblasts decrease in size and form
dentin in a slowly diminishing rate until
stimulated to form reparative dentin.
11. Matrix formation -1
• A- Mantle dentin Fibers are perpendicular
to D E J
• The first formed dentin
layer in crown
• And root
Fibers are parallel to
basement membrane
12. B) Circumpulpal dentin
Mantle dentin
Circumpulpal
dentin. The fibers
are parallel to DEJ
( right or oblique
angle to DT)
Crowding of the
cells and
appearance of
junctional
complex
13.
14. Mantle dentin Crown Root Circumpulpal dentin
• Thickness: 10-20 um • Thickness: bulk of the tooth
• Diameter of collagen • Diameter of collagen fibers:
fibers: large (0.1-0.2 um) small (0.05um)
• Direction of collagen • Direction of collagen fibers :
fibers : have right angle have right or oblique angle to
to DEJ and parallel to dentinal tubules (parallel to
basement membrane in dentin surface)
root • Ground substance: from
• Ground substance: from odontoblasts
odontoblasts and the • Mineralization: Globular
cell free zone below mantle dentin then
• Mineralization: linear become mixed in the
form (contains matrix remaining circumpulpal
vesicles). dentin (no M V ).
15. Mineralization -2
Budding of
matrix Rupture of matrix Mineralization of the
vesicles vesicles mantle dentin
Has
membrane
rich in
alkaline
Matrix phosphatas
vesicle e
Calcium and
phosphate
ions undergo
crystallization
16. Pattern Of Mineralization
1- Linear at the
mantle dentin area
2- Globular in
M V in Crystal
matrix
circumpulpal
lization
dentin just below
mantle dentin
3- Combination in
the remaining
Lodgment circumpulpal
Rupture
of crystals dentin of the
crown and root
17.
18. Age Changes Of Dentin
1-Regular secondary
dentin (Mild stimulus)
• Occurs on the entire pulpal
surface. In multirooted
teeth it is thicker on the
roof and floor of pulp
chamber.
• The size of the pulp cavity
decrease and obliteration
of the pulp horns
• The dentinal tubules
change their direction to a
more wavy course
• The number of dentinal
tubules are fewer
• Line of demarcation (dark).
19. Irregular Secondary Dentin (Reparative-2
(or tertiary dentin
• Severe stimulus
• The dentin is formed at
a localized area.
• The dentinal tubules are
less in number and
irregular in Irregular D T
arrangement.
• UMC from the
subodontoblastic layer
will differentiate and
replace the degenerated
odontoblasts to form
reparative dentin
20. Types Of Reparative Dentin
Osteodentin (entrapped cells).
Atubular dentin ( area
without dentinal
tubules)
Vasodentin
(entrapped b.v.)
21. Thus Secondary Dentin may be:
• Regular • Irregular
• Cause:
Mild stimuli (slow attrition and Severe stimulus (abrasion,
slowly progressing caries) erosion, severe attrition and
Site of formation: deep caries)
Occurs on the entire pulpal
surface of the tooth ( thicker Formed at the area
on the roof and floor of the corresponding to the pulpal
pulp chamber in multirooted end of the exposed dentin.
teeth).
Dentinal tubules: - Have irregular or twisted
- Change their direction and course
have more wavy course
- They decrease in number per -
unit area. They decrease in number and
some areas may have no
tubules
Line of demarcation (a tubular dentin).
Present and stained dark.
May or may not present
22. • Clinically:
• The decrease of the • The localized area of
pulp chamber height dentin formation
and obliteration of increase the time
the pulp horns make taken by caries to
the liability of pulp reach the pulp
exposure during (barrier)
cavity preparation
much less likely to
occur
23. (Transparent (Sclerotic Dentin -3
Mild stimulus leads to changes
in the dentin already present.
1- Odontoblast
and its process
undergo fatty
degeneration.
2- Then there will be
calcification of
dentinal tubules. First
become narrow by
widening of the 3- Then the DT
peritubular dentin. become obliterated.
The affected area have occluded dentinal tubules, so
the dentin have uniform refractive index. So this area
of dentin appear translucent by transmitted light.
25. 4-Dead Tracts
• Severe stimulation to
dentin leads to
destruction of the
odontoblastic process
and odontoblasts. This
leads to embty and wide
dentinal tubules.
• These areas apear black
with transmitted light.
• Under the dead tracts
from the pulpal surface ,
reparative dentine will be
formed.
• The dead tract
serounded by sclerotic
dentin.
26. Discuss theories of pain transmission through dentin.
Compare between interglobular dentin and Tomes’ granular layer.
Compare between mantle and circumpulpal dentin.
Mention different types of secondary dentin and compare between them.
27. Mention different types of dentin and
their histological features.
•Predentin
•Primary dentin (mantle, circumpulpal, peritubular, intertubular and interglobular
dentin)
Regular Atubular dentin
•Secondary dentin
Irregular Vasodentin
Osteodentin
•Sclerotic dentin
