The Composition and Structure of Dentin
Provides the bulk and general form of tooth.
Determines the shape of the crown.
Physically & chemically the dentin closely
resembles the bone.
The main morphologic
difference between bone
& dentin
is that some of the osteoblasts that
form bone marrow enclosed within its matrix
substance as osteocytes, whereas the dentin
contains only the processes of the cells that form
it.
Both are considered vital tissue because they
contain because they contain
living protoplasm
.
1
2
•
It is light
yellowish
in color, becoming darker
with age.
•
It is
elastic
and subject to slight deformation.
•
Harder than bone but softer than enamel.
•
Lower
content of
mineral
salts in dentin
renders it
more radiolucent
than enamel.
3
Consists of 35% organic matter and water & 65%
inorganic material.
The organic substance consists of collagenous
fibrils and a ground substance of
mucopolysaccharides (proteoglycans and glycos
aminoglycans).
The inorganic component consists of
hydroxyapetite as in bone, cementum & enamel
.
Organic constituents can be removed from the
mineral by
incineration or organic chelation
.
4
•
The
bodies of the odontoblasts are arranged in a
layer on the pulpal surface of the dentin,
and only
their cytoplasmic processes are included in the
tubules in the mineralized matrix.
•
Each cell gives rise to one process
, which traverses
the predentin & calcified dentin within one tubule.
•
Terminates in a branching network at the junction
with enamel or cementum.
•
Tubules
are found throughout normal dentin & are
therefore characteristic of it.
5
•
The course follows a gentle curve in the crown,
less so in the root, where it resembles
S in shape
.
•
Starting at right angles from the pulpal surface,
the first convexity of this doubly curved course is
directed toward the apex of the tooth.
•
These tubules end perpendicular to the
dentinoenamel and dentinocementum junctions.
•
Near the root tip & along the incisal edges and
cusps the tubules are almost straight.
6
7
8
•
The ratio between the
outer and inner surfaces of
dentin
is about
5:1.
•
The ratio between the
numbers of tubules per unit
area
on the pulpal and outer surfaces of dentin is
about 4:1.
•
There are more tubules per unit area in the crown
than in the root.
•
The dentinal tubules have lateral branches
throughout dentin, which are termed
canaliculi
or
microtubules.
•
A
few dentinal tubules extend through the
dentinoenamel junction into the enamel. These are
termed enamel spindles.
9
10
The dentin that
immediately surrounds the
dentinal tubules.
It is more highly mineralized than intertubular
dentin.
It is twice as thick in outer dentin (approx.
0.75um) than in inner dentin (0.4um).
11
12
13
•
Forms the
main body of dentin.
•
It is located between the dentinal tubules or, more
specifically, between the zones of peritubular dentin.
•
Its organic matrix is retained after decalcification.
•
About
one-half of its volume is organic matrix
,
specifically collagen fibers. The fibrils range from 0.5
to 0.2um in diameter and exhibit
crossbanding at
64um intervals, which is typical for collagen.
14
Is located adjacent to the pulp tissue
.
Is
2 to 6 um wide
, depending on the activity of
the odontoblast.
It is the
first formed dentin and is not
mineralized.
As the collagen fibers undergo mineralization
at the predentin- dentin front, the predentin
then becomes dentin and a new layer of
predentin forms circumpulpally.
15
16
They are the
cytoplasmic extensions of the
odontoblasts.
The odontoblasts reside in the peripheral pulp
at the pulp- predentin border and their
processes extend into the dentinal tubules
.
The processes are largest in diameter near the
pulp and taper further into dentin.
The odontoblast cell bodies are approximately
7um in diameter and 40um in length.
17
18
RELATIONSHIP
BETWEEN
ODONTOBLASTIC
PROCESS AND
DENTINAL TUBULE
•
Mantle dentin
is the first formed dentin in the crown
underlying the dentinoenamel junction.
•
It is the
outer or most peripheral part
of the primary
dentin & is about 20um thick.
•
The fibrils found in this zone are perpendicular to the
dentinoenamel junction.
•
Circumpulpal dentin
forms the remaining primary
dentin or bulk of the tooth.
•
Represents all of the
dentin formed prior to root
completion
.
•
The fibrils are much smaller in diameter & are more
closely packed together.
•
Slightly more mineral content than mantle dentin.
19
20
A narrow band of dentin bordering the pulp
and representing the
dentin formed after root
completion.
Contains
fewer tubules
than primary dentin.
There is usually a bend in the tubules where
primary and secondary dentin interface.
21
22
23
The
incremental lines (von ebner), or imbrication
lines
, appear as fine lines or striations in dentin.
They run at right angles to the dentinal tubules.
These lines reflect the
daily rhythmic, recurrent
deposition
of dentin matrix as well as hesitation
in the daily formative process.
The course of the lines indicates the growth
pattern of the dentin.
Some of the incremental lines are accentuated
because of
disturbances in the matrix and
mineralization process.
Such lines are known as
contour lines of owen.
24
25
26
These lines represent hypocalcified bands.
In the deciduous teeth and in the first permanent
molars, the prenatal and postnatal dentin is
separated by an accentuated contour line. This is
termed
the neonatal line.
This line reflects the
abrupt change in
environment
that occurs at birth.
The dentin matrix formed prior to birth is usually
of better quality than that formed after birth.
27
28
•
Sometimes mineralization of dentin begins in small
globular areas that fail to fuse into a homogenous
mass. This results in zones of
hypomineralization
between the globules.
These zones are called
interglobular dentin.
•
Forms in crowns of teeth in the
circumpulpal dentin
just below the mantle dentin.
•
Follows an incremental pattern.
•
The dentinal tubules pass uninterruptedly, thus
demonstrating a
defect of mineralization
& not of
matrix formation.
29
30
31
There is a zone
adjacent to the cementum
that
appears granular. This is known as
Tomes’
granular layer.
Caused by
coalescing and looping of the terminal
portions of the dentinal tubules.
32
Dentin
Cementum
Granular layer
of Tomes
Hyaline layer
34
•
Direct conduction theory
in which stimuli directly
effect the nerve endings in the tubules.
•
Transduction theory
in which the membrane of the
odontoblast process conducts an impulse to the
nerve endings in the predentin, odontoblast zone,
and pulp.
•
Fluid or hydrodynamic theory
in which stimuli
cause an inward or outward movement of fluid in
the tubule, which in turn produces movement of
the odontoblast and its processes.
35
36
•
The odontoblast processes disintegrate, & the
empty
tubules are filled with air.
•
Appear black in transmitted light & white in reflected
light.
•
Often observed in the area of
narrow pulpal horns
because of crowding of odontoblasts.
•
Demonstrate decreased sensitivity.
•
Appear to a greater extent in older teeth.
•
Probably the initial step in the formation of sclerotic
dentin.
37
Primary
physiological
dentin
Secondary
physiological
dentin
Tertiary
dentin
Dead tracts
Collagen fibers and apatite crystals begin
appearing in the dentinal tubules.
Apatite crystals are initially only sporadic in a
dentinal tubule but gradually fill it with a fine
meshwork of crystals.
Gradually, the
tubule lumen is obliterated with
mineral,
which appears very much like the
peritubular dentin.
The
refractive indices
of dentin in which the
tubules are occluded
are equalized
, and such
areas become transparent.
Found specially in
roots.
Transparent or
light in transmitted
and
dark in
reflected light.
39
Deantal caries
Sclerotic dentin
41
Dentinal tubules
Predentin
Odontoblast layer
Dentin is a vital tissue in teeth that provides bulk and shape, resembling bone but with distinct differences. It is yellowish, slightly elastic, and consists of inorganic hydroxyapatite and organic materials. Tubules within dentin contain odontoblast processes and follow a curved course throughout the tooth. Dentin plays a crucial role in tooth function and structure.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
You are allowed to download the files provided on this website for personal or commercial use, subject to the condition that they are used lawfully. All files are the property of their respective owners.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author.
E N D
Presentation Transcript
Provides the bulk and general form of tooth. Determines the shape of the crown. Physically resembles the bone. The main morphologic difference & & dentin form bone marrow enclosed within its matrix substance as osteocytes, whereas the dentin contains only the processes of the cells that form it. Both are considered vital tissue because they contain because they contain living & chemically the dentin closely difference between between bone bone dentin is that some of the osteoblasts that living protoplasm protoplasm. 1
It is light yellowish with age. yellowish in color, becoming darker It is elastic elastic and subject to slight deformation. Harder than bone but softer than enamel. Lower renders it more Lower content of mineral more radiolucent mineral salts in dentin radiolucent than enamel. 3
Consists inorganic The fibrils mucopolysaccharides aminoglycans) The hydroxyapetite Consists of inorganic material The organic fibrils mucopolysaccharides (proteoglycans aminoglycans). . The hydroxyapetite as of 35 material. . organic substance and 35% % organic organic matter matter and and water water & & 65 65% % substance consists and consists of ground (proteoglycans and of collagenous substance and glycos collagenous substance a a ground of of glycos inorganic inorganic component as in component in bone, consists consists of of bone, cementum cementum & & enamel enamel. Organic constituents can be removed from the mineral by incineration incineration or or organic organic chelation chelation. 4
The bodies layer their cytoplasmic processes are included in the tubules in the mineralized matrix. bodies of layer on the odontoblasts the pulpal of the pulpal surface odontoblasts are surface of are arranged of the arranged in dentin, and only in a a on the the dentin, Each the predentin & calcified dentin within one tubule. Each cell cell gives gives rise rise to to one one process process, which traverses Terminates in a branching network at the junction with enamel or cementum. Tubules therefore characteristic of it. Tubules are found throughout normal dentin & are 5
The course follows a gentle curve in the crown, less so in the root, where it resembles S S in in shape shape. Starting at right angles from the pulpal surface, the first convexity of this doubly curved course is directed toward the apex of the tooth. These dentinoenamel and dentinocementum junctions. tubules end perpendicular to the Near the root tip & along the incisal edges and cusps the tubules are almost straight. 6
The ratio between the outer dentin outer and and inner inner surfaces surfaces of of dentin is about 5 5: :1 1. . The ratio between the numbers area about 4:1. numbers of of tubules tubules per per unit unit area on the pulpal and outer surfaces of dentin is There are more tubules per unit area in the crown than in the root. The dentinal tubules have lateral branches throughout dentin, which are termed canaliculi microtubules. canaliculi or A few dentinoenamel termed few dentinal dentinoenamel junction termed enamel dentinal tubules junction into enamel spindles tubules extend into the spindles. . extend through the enamel through the enamel. . These the are These are 9
The dentin that immediately dentinal It is more highly mineralized than intertubular dentin. It is twice as thick in outer dentin (approx. 0.75um) than in inner dentin (0.4um). immediately surrounds surrounds the the dentinal tubules tubules. . 11
Forms the main body of dentin. main body of dentin. It is located between the dentinal tubules or, more specifically, between the zones of peritubular dentin. Its organic matrix is retained after decalcification. About one specifically collagen fibers. The fibrils range from 0.5 to 0.2um in diameter and exhibit crossbanding 64 one- -half half of of its its volume volume is is organic organic matrix matrix, crossbanding at for collagen at 64um um intervals, intervals, which which is is typical typical for collagen. . 14
Is located adjacent to the pulp tissue Is located adjacent to the pulp tissue. Is 2 2 to the odontoblast. to 6 6 um um wide wide, depending on the activity of It is the first formed dentin and is not mineralized. first formed dentin and is not mineralized. As the collagen fibers undergo mineralization at the predentin- dentin front, the predentin then becomes dentin and a new layer of predentin forms circumpulpally. 15
They are the cytoplasmic odontoblasts cytoplasmic extensions extensions of of the the odontoblasts. . The at processes The odontoblasts at the processes extend odontoblasts reside the pulp extend into reside in predentin border into the the peripheral border and the dentinal in the peripheral pulp and their dentinal tubules pulp their pulp- - predentin tubules. The processes are largest in diameter near the pulp and taper further into dentin. The odontoblast cell bodies are approximately 7 7um um in in diameter diameter and and 40 40um um in in length length. . 17
RELATIONSHIP BETWEEN ODONTOBLASTIC PROCESS AND DENTINAL TUBULE 18
Mantle underlying the dentinoenamel junction. It is the outer dentin & is about 20um thick. The fibrils found in this zone are perpendicular to the dentinoenamel junction. Mantle dentin dentin is the first formed dentin in the crown outer or or most most peripheral peripheral part part of the primary Circumpulpal dentin or bulk of the tooth. Represents all of the dentin completion The fibrils are much smaller in diameter & are more closely packed together. Slightly more mineral content than mantle dentin. Circumpulpal dentin dentin forms the remaining primary dentin formed formed prior prior to to root root completion. 19
A narrow band of dentin bordering the pulp and representing the dentin completion dentin formed formed after after root root completion. . Contains fewer tubules fewer tubules than primary dentin. There is usually a bend in the tubules where primary and secondary dentin interface. 21
The incremental lines They run at right angles to the dentinal tubules. These lines reflect the daily deposition in the daily formative process. The course of the lines indicates the growth pattern of the dentin. incremental lines lines, appear as fine lines or striations in dentin. lines (von (von ebner), ebner), or or imbrication imbrication daily rhythmic, rhythmic, recurrent recurrent deposition of dentin matrix as well as hesitation Some of the incremental lines are accentuated because of disturbances mineralization contour disturbances in process. . Such lines are known as lines of in the the matrix matrix and and mineralization process contour lines of owen owen. . 24
These These lines lines represent represent hypocalcified hypocalcified bands bands. . In the deciduous teeth and in the first permanent molars, the prenatal and postnatal dentin is separated by an accentuated contour line. This is termed the the neonatal neonatal line line. . This environment line reflects the abrupt abrupt change change in in environment that occurs at birth. The dentin matrix formed prior to birth is usually of better quality than that formed after birth. 27
Sometimes mineralization of dentin begins in small globular areas that fail to fuse into a homogenous mass. This results in zones of hypomineralization between interglobular dentin. hypomineralization between the the globules globules. . These zones are called Forms in crowns of teeth in the circumpulpal just circumpulpal dentin dentin just below below the the mantle mantle dentin dentin. . Follows an incremental pattern. The dentinal tubules pass uninterruptedly, thus demonstrating a defect matrix formation. defect of of mineralization mineralization & not of 29
There is a zone adjacent appears granular. This is known as Tomes granular adjacent to to the the cementum cementum that Tomes granular layer layer. . Caused by coalescing portions coalescing and of the and looping tubules. . looping of of the the terminal terminal portions of the dentinal dentinal tubules 32
Dentin Cementum Granular layer of Tomes Hyaline layer
Direct effect the nerve endings in the tubules. Direct conduction conduction theory theory in which stimuli directly Transduction odontoblast process conducts an impulse to the nerve endings in the predentin, odontoblast zone, and pulp. Transduction theory theory in which the membrane of the Fluid cause an inward or outward movement of fluid in the tubule, which in turn produces movement of the odontoblast and its processes. Fluid or or hydrodynamic hydrodynamic theory theory in which stimuli 35
The odontoblast processes disintegrate, & the empty tubules empty tubules are are filled filled with with air air. . Appear black in transmitted light & white in reflected light. Often observed in the area of narrow because of crowding of odontoblasts. narrow pulpal pulpal horns horns Demonstrate decreased sensitivity. Appear to a greater extent in older teeth. Probably the initial step in the formation of sclerotic dentin. 37
Dead tracts Tertiary dentin Secondary physiological dentin Primary physiological dentin
Collagen fibers and apatite crystals begin appearing in the dentinal tubules. Apatite crystals are initially only sporadic in a dentinal tubule but gradually fill it with a fine meshwork of crystals. Gradually, the tubule mineral, peritubular dentin. The refractive tubules are occluded are areas become transparent. Found specially in roots. Transparent or light reflected tubule lumen lumen is is obliterated obliterated with with mineral, which appears very much like the refractive indices indices of dentin in which the are equalized equalized, and such roots. light in in transmitted transmitted and dark dark in in reflected light light. . 39
Deantal caries Sclerotic dentin
Odontoblast layer Predentin Dentinal tubules
