Dentin

1. Dentin

2. Contour lines of Owen
•During development of dentin,
variations in the metabolism of the
organism cause variations in the
amount of organic material deposited
in the dentin, just as occurs in the
enamel.
•Changes in the coloration of the
dentin are called contour lines of
Owen.
•The first dentin that is layeddown (at
the DEJ) forms the mantle layerwhile
subsequent dentin forms the
circumpulpallayer.
•In the crown of tooth, dentinal
tubules from S-shaped primary
curves.
A, Contour line of Owen;
B, Mantle layer of dentin;
C, Circumpulpallayer of dentin;
D, DEJ

3. Contour lines of Owen and Striaof
Retzius
•The contour lines of
Owen intercept the
dentino-enamel
junction and meet an
accompanying Striaof
Retziusthat was
formed at the same
time.
A, Contour line of Owen;
B, Striaof Retzius

4. Lines of vonEbner
•Daily alterations in the
formation of dentin
produce imbricationlines
of von Ebnerthat are
approximately 5 µm in
length, are seen as banding
along the dentinal tubules
and are comparable to the
cross-striations in enamel.
•Arrow indicates the
direction of the lines of
von Ebnerthat are
perpendicular to the
dentinal tubules.

5. Dentinal tubules
•Each odontoblasthas a long
process that projects through the
dentin to the DEJ.
•The hole or tube in the dentin
through which this process
projects is called the dentinal
tubule.
•The course of the dentinal
tubules in the crown of the tooth
is S-shaped due to the crowding
of the odontoblastsas they get
squeezed into a smaller and
smaller space within the pulp
cavity.
•This curve is called a primary
curve.
A, Primary curve of dentinal tubule;
B, DEJ; C, Mantle dentin;
D, Circumpulpaldentin

6. Odontoblastsin an erupted tooth
•As the dentin layer forms,
the odontoblastbecome
increasingly crowded as they
are squeezed into a smaller
area.
•The single layer of
odontoblasts(as occurs in
early development) has now
changed to stacks of
odontoblasts.
A, Odontoblasts; B, Predentin;
C, Pulp cavity;
D, Dentinal tubules

7. Secondary curves
•During the deposition of
dentin, the odontoblast
makes slight undulations
that creates wavy dentinal
tubules.
•This waviness of the
dentinal tubules is called
secondary curves.
A, Secondary curve of dentinal tubule

8. Mantle dentin
•When viewed in polarized
light, mantle dentin (red
band), which is about 10
µm wide, can be
differentiated from
circumpulpaldentin
(purple with black
dentinal tubules).
•This is due to a difference
in the collagen fibers in
mantle dentin.
A, Enamel;
B, Circumpulpaldentin;
C, Mantle dentin

9. Globular calcification of dentin
•Dentin is calcified after it
is formed.
•The calcification begins in
small spherical areas.
•These become larger and
fuse with one another to
form a calcification front
(row of calcification
sheresalong the
predentinedge).
A, Odontoblasts; B, Predentin;
C, Calcification front;
D, Calcified dentin

10. Calcification pattern of dentin -
decalcified section
•In mature dentin,
globules of well-
calcified dentin are
apparent (arrow)
along with areas of
less calcified dentin
(white areas).
A, Globule of well-calcified dentin

11. Interglobulardentin in globular layer -
ground section
•Between the mantle and
circumpulpallayers is a
layer of dentin in which
the calcified globules do
not fuse evenly.
•This is called the globular
layer.
•In a ground section of
dentin, the less-calcified
areas of dentin appear as
irregularly shaped
crescents called
interglobulardentin.
A, Interglobulardentin

12. Globular layer and granular layer
•In the root of the tooth, the
peripheral border of mantle
dentin adjacent to the
cementumhas a granular
appearance and is called the
granular layer of Tomes.
•The granular layer is a less
calcified layer like that of the
globular layer.
•Generally, interglobular
dentin is seen only in the
crown, but in this specimen it
extends into the root. A, Circumpulpallayer; B, Globular layer;
C, Mantle layer; D, Granular layer; E, CEJ;
F, Enamel; G, Cementum

13. Dentinal tubules
•Dentinal tubules are the hollow tubes
that run through the dentin in which
are located the odontoblastic
processes.
•During formation of dentin,
intertubulardentin is layeddown
between the odontoblastic
processes.
•Then a second layer of more
mineralized dentin is added to "coat"
the inside of the tubules.
•This layer of dentin is called
peritubulardentinor intratubular
dentin.
•In this scanning electron micrograph,
the peritubulardentin appears white.
A, Peritubulardentin;
B, Intertubulardentin;
C, Dentinal tubule

14. Dentinal tubular branches in root -
transmitted and differential interface
contrast microscopy
•Dentinal tubules
generally have lateral
brancheswhere
odontoblasticprocesses
can communicate with
one another.
•These branches, as seen
here, are most numerous
in the root of the tooth
A, Odontoblasticprocess;
B, Lateral branches of dentinal tubules

15. Terminal branching of dentinal
tubules
•Dentinal tubules are closely spaced
but have a large diameter close to
the pulp cavity.
•Dentinal tubules become more
widely spaced in the dentin but
have a narrower diameter as they
approach the DEJ.
•At the DEJ, dentinal tubules branch.
•This causes an increased dentityof
dentinal tubules in cross-sections of
dentin in this region.
•In this micrograph, note the
scalloped appearance of the DEJ.
•The peaks of the scallops point
toward the enamel.
A, Dentinal tubule; B, DEJ;
C, Enamel; D, Enamel spindle

16. Peritubularand intertubulardentin
•In this scanning
micrograph of dentin,
the dentinal tubules
can be seen
surrounded by a
somewhat loosely
packed intertubular
dentinand a more
dense peritubular
dentin.
A, Intertubulardentin;
B, Peritubulardentin;
C, Dentinal tubule

17. Forms of dentin
•Primary dentin, with straight tubules, is
laid down before completion of the apical
foramen.
•Regular secondary dentin is characterized
by a slower rate of deposition and an
abrupt change in the direction of the
dentinal tubules.
•Tertiary or irregular secondary (also
called irritation, reparative or reactive)
dentin is laid down in response to an
irritation or damage to the overlying
dentin and/or enamel.
•This dentin has irregularly arranged and
few dentinal tubules. With aging or severe
damage, tertiary dentin can totally
obliterate the pulp cavity.
A, Primary dentin;
B, Secondary (regular) dentin;
C, Reactive dentin

18. Dead tracts and blind tracts
•When dentin is damaged,
odontoblasticprocesses die or retract
leaving empty dentinal tubules.
•Areas with empty dentinal tubules are
called dead tractsand appear as dark
areas in ground sections of tooth.
•With time, these dead tracts can
become completely filled in mineral.
•This region is called blind tractsand
appears white in sections of ground
tooth.
•The dentin in blind tracts is called
sclerotic dentin.
•The adaptive advantage of blind tracts
is the sealing off of the dentinal
tubules to prevent bacteria from
entering the pulp cavity.
A, Dead tract;
B, Blind tract (containing sclerotic dentin)

20. This slide from:
Sharifa Abdulla Alhaj

21. This slide from:
Dalia.

22. Good
Luck
All
Done by: Bedour Al-Arfaj.

23. أاهدعبو هركاذملا لبق هيعد...
ةركاذملا لبق
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ناحتملإا موي
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