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 layed down (at
the DEJ) forms the mantle layer while
subsequent dentin forms the
circumpulpal layer.
• In the crown of tooth, dentinal
tubules from S-shaped primary A, Contour line of Owen;
curves. B, Mantle layer of dentin;
C, Circumpulpal layer of dentin;
D, DEJ
3. Contour lines of Owen and Stria of
Retzius
• The contour lines of
Owen intercept the
dentino-enamel
junction and meet an
accompanying Stria of
Retzius that was
formed at the same
time.
A, Contour line of Owen;
B, Stria of Retzius
4. Lines of vonEbner
• Daily alterations in the
formation of dentin
produce imbrication lines
of von Ebner that 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 Ebner that are
perpendicular to the
dentinal tubules.
5. Dentinal tubules
• Each odontoblast has 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 odontoblasts as they get
squeezed into a smaller and
smaller space within the pulp
cavity. A, Primary curve of dentinal tubule;
• This curve is called a primary B, DEJ; C, Mantle dentin;
curve. D, Circumpulpal dentin
6. Odontoblasts in an erupted tooth
• As the dentin layer forms,
the odontoblast become
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
circumpulpal dentin
(purple with black
dentinal tubules).
• This is due to a difference
in the collagen fibers in
mantle dentin. A, Enamel;
B, Circumpulpal dentin;
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
sheres along the A, Odontoblasts; B, Predentin;
C, Calcification front;
predentin edge). 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. Interglobular dentin in globular layer -
ground section
• Between the mantle and
circumpulpal layers 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
interglobular dentin.
A, Interglobular dentin
12. Globular layer and granular layer
• In the root of the tooth, the
peripheral border of mantle
dentin adjacent to the
cementum has 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, Circumpulpal layer; 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,
intertubular dentin is layed down
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
peritubular dentin or intratubular
dentin.
A, Peritubular dentin;
• In this scanning electron micrograph, B, Intertubular dentin;
the peritubular dentin appears white. C, Dentinal tubule
14. Dentinal tubular branches in root -
transmitted and differential interface
contrast microscopy
• Dentinal tubules
generally have lateral
branches where
odontoblastic processes
can communicate with
one another.
• These branches, as seen
here, are most numerous
A, Odontoblastic process;
in the root of the tooth 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 dentity of
dentinal tubules in cross-sections of
dentin in this region.
• In this micrograph, note the
scalloped appearance of the DEJ.
A, Dentinal tubule; B, DEJ;
• The peaks of the scallops point C, Enamel; D, Enamel spindle
toward the enamel.
16. Peritubular and intertubular dentin
• In this scanning
micrograph of dentin,
the dentinal tubules
can be seen
surrounded by a
somewhat loosely
packed intertubular
dentin and a more
dense peritubular
dentin. A, Intertubular dentin;
B, Peritubular dentin;
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,
odontoblastic processes die or retract
leaving empty dentinal tubules.
• Areas with empty dentinal tubules are
called dead tracts and 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 tracts and
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 A, Dead tract;
entering the pulp cavity. B, Blind tract (containing sclerotic dentin)
23. أدعيه قبل المذاكره وبعدها...
قبل المذاكرة
اللهم أنً اسألك فهم النبٌٌن و حفظ المرسلٌن و المالئكة المقربٌن ، اللهم أجعل ألسنتنا عامرة بذكرك و قلوبنا بخشٌتك و أسرارنا
بطاعتك أنك على كل شًء قدٌر .. حسبنا هللا و نعم الوكٌل
بعد المذاكرة
اللهم أنً استودعتك ما قرأت و ما حفظت و ما تعلمت فرده عند حاجتً الٌه انك على كل شًء قدٌر ، حسبنا هللا و نعم الوكٌل
يوم اإلمتحان
اللهم أنً توكلت علٌك و سلمت امري الٌك ال ملجأ و منجا منك إال الٌك
دخول القاعة
رب أدخلنً مدخل صدق و أخرجنً مخرج صدق و أجعل لً من لدنك سلطانا نصٌرا
قبل البدء بالحل
رب أشرح لً صدري و ٌسر لً أمري و احلل عقدة من لسانً ٌفقه قولً بسم هللا الفتاح ، اللهم ال سهل أال ما جعلته سهال و انت تجعل الحزن اذا
شئت سهال ٌا ارحم الراحمٌن
أثناء األمتحان
ال إله اال انت سبحانك أنً كنت من الظالمٌن ٌا حً ٌا قٌوم برحمتك أستغٌث ، رب ان مسنً الضر أنك أرحم الراحمٌن
عند النسيان
اللهم ٌا جامع الناس فً ٌوم ال رٌب فٌه أجمعنً و ضالتً
بعد األنتهاء
الحمد هلل الذي هدانا لهذا و ما كنا لنهتدي لوال أن هدانا هللا
