Dentin
Dentin – Composition, Formation, and
Structures
Dentinogenesis
Origin of the dentin
Dentin is formed by cells called odontoblasts that defferentiated
from ectomesenchymal cells of the dental papilla following an
organizing influence that emanents from the inner dental
epithelium.
Thus the dental papilla is the formative organ of dentin and
eventually becomes the pulp of the tooth.
 For dentinogenesis and amelogenesis to take
place normally, the differentiating
odontoblasts and ameloblasts will receive
signals form each other – “reciprocal
induction”.
Stages of Apposition
 1. Elongation of inner dental epithelium;
 2. Differentiation of odontoblasts;
 3. Formation of dentin;
 4. Formation of enamel.
Preparation for the formation of tooth
structures
 Continued growth of the
tooth germ leads to bell
stage, where the enamel
organ resembles a bell
with deepening of the
epithelium over the
dental papilla;
 Continuation of
histodifferentiation
(ameloblasts and
odontoblasts are defined)
and beginning of
morphodifferentiation
(tooth crown assumes its
final shape).
Start of dentinogenesis
 Begins after the final differentiation of the
odontoblats and subodontoblasts;
 Odontoblasts extended theire processes;
 Released space under the basement membrane;
 The first free space is in the growth center.
Enamel organ and
dental papilla
 The cells of inner dental
epithelium exert an
organizing influence on the
underlying mesenchymal
cells in the dental papilla,
which later differentiate
into odontoblasts;
 Outer dental epithelium cuboidal cells that have a
function to organize a
network of capillaries that
will bring nutrition to the
ameloblasts.
Dental Papilla and preodontoblasts
 Before the inner dental
preodontoblasts
Membrana
preformativa
epithelium begins to produce
enamel, the peripheral cells of
the mesenchymal dental
papilla differentiate into
odontoblasts under the
organizing influence of the
epithelium;
 First, they assume a cuboidal
shape;
 The basement membrane that
separates the enamel organ
and the dental papilla just
prior to dentin formation is
called the “membrana
preformativa”.
Odontoblasts differentiation
 It is brought about by the
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expression of signaling molecules
and growth factors in the cells of the
inner epithelium;
a.The dental papilla cells are small
and undifferentiated and exhibit a
central nucleus and few organelles;
At this time they are separated from
inner epithelium by an acellular
zone that contains some fine
collagen fibrils;
b. Committed dental
ectomessenchymal cells that are in a
state of mitosis or cell division;
c.Daughter cells that are competent
to become odontoblasts remain in
the peripheral zone;
d.Differentiated odontoblasts with a
polarized nucleus and citoplasmic
extentions;
Preodontoblast;
Undifferentiated cell;
Basement membrane;
4 and 5 - subodontoblastic cells.
Preodontoblasts
 A -preodontoblasts;
 В – preameloblasts;
 С –basement
membrane;
 With the begining of the
production of dentin it
becomes in
dentinoenamel
junction;
 Differentiation of
odontoblasts is
mediated by expression
of signaling molecules
and growth factors in
the inner dental
epithelial cells.
Acellular zone
 This zone gradually is
eliminated as the
odontoblasts
differentiate and
increase in size and
occupy this zone;
 They are characterized
by being highly
polarized, with their
nuclei positioned away
from the inner dental
epithelium
Acellular
zone
Differentiation of ectomesenchymal cells of
dental papilla to preodontoblasts
 Almost immediately after cells
of the inner dental epithelium
reverse polarity, changes also
occur in the adjacent dental
papilla;
 Ectomesenchymal cells rapidly
enlarge and elongate to become
preodontoblasts first and then
odontoblasts as their cytoplasm
increases in volume to contain
increasing amount of proteinsynthesizing organelles.
Short columnar cells bordering
the dental papilla – inner dental
epithelium will eventually
become ameloblasts ;
5. The odontoblasts as they differentiate will start elaborating
organic matrix of dentin, which will mineralize.
6. As the organic matrix of dentin is deposited, the odontoblasts
move towards the center of the dental papilla, leaving behind
cytoplasmic extensions which will soon be surrounded by dentin;
7. Therefore, a tubular structure of dentin is formed.
Differentiation of odontoblasts
 The odontoblasts appear
like protein-producing
cells;
Odontoblasts and subodontoblasts
odontoblasts
Sub
odontoblasts
Dentin formation
proceeds toward
the inside of the
tooth;
Odontoblasts
 А – nucleus;
 В - secretory end;
 С - secreted matrix.
 They are the dentin-forming
cells, differentiate from cells of
the dental papilla;
 They begin secreting an
organic matrix around the area
directly adjacent to the inner
enamel epithelium, closest to
the area of the future cusp of a
tooth;
Odontoblast process
or Tomes`fiber
 The odontoblast develops a cell
process, the odontoblast process,
which is left behind in the forming
dentin matrix;
 The organic matrix contains
collagen fibers with large
diameters (0.1–0.2 μm in
diameter);
 The odontoblasts begin to move
toward the center of the tooth,
forming an extension called the
odontoblast process;
Odontoblasts - large pear-shaped cells
 Thus, dentin formation
proceeds toward the inside of
the tooth;
 The odontoblast process
causes the secretion of
hydroxyapatite crystals and
mineralization of the matrix.
Dentinal tubules formation
 As the odontoblastic process
elongates, a dentinal tubule is
maintained in the dentin, and the
matrix is formed around this
tubule;
The beginning of dentinal deposition
Odontoblasts processes
 The plasma membrane of
odontoblasts adjacent to
inner epithelium extend
stubby processes into the
forming extracellular
matrix;
 On occasion one of these
processes may penetrate
the basal lamina and
interpose itself between
the cells of inner
epithelium to form what
later becomes an enamel
spindles;
Matrix vesicles
 As the odontoblasts form
these processes, it also
buds off a number of
small, mambrane-bound
vesicles known as matrix
vesicles, which come to
lie superficially near the
basement membrane.
 This area of
mineralization is
known as mantle
dentin and is a layer
usually about 150 μm
thick.
Odontoblast branching growths on the
periphery of the dentin
Stages of deninogenesis
 Formation of organic matrix:
 Fibrogenesis;
 Maturation of the organic matrix;
 Mineralization of the matrix.
2 steps of dentinogenesis
 Odontoblasts with
cytoplasmic
processes forming
dentinal tubules;
 1. Formation of
collagen matrix;
 2. Deposition of
calcium and
phosphate
 (hydroxyapatite)
crystals in the matrix.
Fibrogenesis;
Synthesis of collagen and its arangement in
fibrils and fibers
 The collagens in dentin
are primery type I with
trace amounts of type
V collagen and some
type I collagen trimer;
 The type I collagen is a
key structural
component of dentin
matrix.
Some of the fifteen known types of collagen
Some types (of 15) of known collagen
Type
Fibril-forming
I
Molecular
[a 1(I)]2 a 2(I)
Tissue distribution
bone, skin, tendon, ligaments
(90%) of body collagen
II
[a 1(II)]3
cartilage, intervertebral disc,
notochord, vitreous humor of eye
III
[a 1(III)]3
skin, blood vessels, internal organs
V
[a 1(V]2 a 2(V)
as type I
XI
[a 1(XI] a 2(XI) a 3(XI)
as type II
Fibril-associated IX
[a 1(IX] a 2(IX) a 3(IX)
cartilage (with type II)
[a 1(XII)]3
tendon, ligaments (with some type I)
[a 1(IV)]2 a 2(IV)
basal laminae
[a 1(VII)]3
anchoring fibrils beneath stratified
XII
Network-forming IV
VII
squmous epithelia
Korff`s fibers formation
Korff's fibers (corkscrew fibers) passing between
odontoblasts and reach predentin.
The question of the origin of these fibers is controversial.
Korff's fibers
 The first sign of dentin
formation is the appearance of
distinct, large-diameter
collagen fibrils;
 They are 0,1 to 0,2 µm in
diameter and called von Korff's
fibers;
 They originate deep among the
odontoblasts, extend toward
the inner epithelium, and fan
out in the structurless ground
substance immediately bellow
the epithelium.
Formation of the first loyer of dentin – mantle
dentin
 The next step in the
production of dentin is
formation of its organic
matrix;
 Odontoblasts
differentiate in the
preexisting ground
substance of the dental
papilla;
 The first dentin collagen
syntesized by them is
deposited in this groun
substance.
Layer of polarized
odontoblasts with Tomes'
fibers.
Von Korff`s fibers appear as convoluted, threadlike
structures that originated deep between odontoblasts
 Following differentiation
of odontoblasts, first layer
of dentin is produced,
characterized by
appearance of largediameter type III collagen
fibrils (0.1 to 0.2 μm in
dia) called von Korff’s
fibers, followed by type I
collagen fibers.
Odontoblasts and corkscrew fibers (Korff's
fibers)
Odontoblasts and nerve ends between them.
Noncollagenous proteins
 The other group of proteins is the noncollagenous
proteins;
 They are grouped into five categories;

The first and likely the most important group – two proteins,
originally classified as dentin-specific:
DPP – dentin phosphoprotein;
 DSP – dentin sialoprotein;

 After type I collagen, DPP is most abundant of
dentin matrix proteins and represent almost 50% of
the dentin ECM.
DPP
 DPP has a high affinity for type I collagen as well as
calcium and protein for initiation of dentin
mineralization and is therefore considered a key
protein for the initiation of mineralization;
 DPP may also affect the shape and size of apatite
crystals.
DSP
 DSP accounts for 5% to 8% of the dentin matrix;
 DSP played a role in cell attachment;
A second category of noncollagenous
proteins
 Osteocalcin;
 Bone sialoprotein;
 They are classified as mineralized tissue-spacific,
because they are found in all the calciffied
connective tissies.
A third group of noncollagenous proteins
 They are sinthesized by odontoblasts;
 They are:
 Osteopontin;
 Osteonectin.
 Newly secreted dentin is
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unmineralized and is called
predentin;
It is easily identified in
haematoxylin and eosin stained
section since it stains less
intensely then dentin;
It is usually 10-47 micrometers
and lines the innermost region
of the dentin;
It is unmineralized and
consists of collagen,
glycoproteins and
proteoglycans;
It is similar to osteoid in bone
and is thickest when
dentinogenesis is occurring.
Predentin
Mantle predentin
 As the odontoblasts
continue to increase in
size, they also produce
smaller collagen type I
fibrils that orient
themselves parallel to the
future dentinoenamel
junction;
 In this way a layer of
mantel predentin
appears.
The first stage is formation of mantle dentin:
 Its means the deposition of matrix which is composed of
collagen fibers in a ground substance rich in
glycosaminoglycans.
 The fibers known as Von Korff`s fibers are argyrophilic.
 Subodontoblasts may be responsible for a proportion of the
very first matrix including the von Korff`s fibers.
 Odontoblasts form the major part of mantle dentin matrix.
Prymary dentin
 Whereas mantle dentin forms from the preexisting
ground substance of the dental papilla, primary dentin
forms through a different process;
 Odontoblasts increase in size, eliminating the availability
of any extracellular resources to contribute to an organic
matrix for mineralization;
 Additionally, the larger odontoblasts cause collagen to be
secreted in smaller amounts, which results in more
tightly arranged, heterogeneous nucleation that is used
for mineralization;
 Other materials (such as lipids, phosphoproteins, and
phospholipids) are also secreted.
Mineralized dentine matrix
First loyer of mantle dentin
Cellular activity in the germ centers
Odontoblasts and subodontoblasts
Mineralization
 The mineral phase first appears within the matrix
vesicles as single crystals believed to be seeded by
phospholipids present in the vesicle membrane;
 The crystals grow rapidly and rupture from the
confines if the vesicle to spread as a cluster of
crystallites that fuse with adjacent clusters to form
a continuous layer of mineralized matrix.
Early mineralization of the dentin matrix
New free space exempted from the odontoblasts for a new
layer of dentin
Pattern of Mineralization
 Two patterns of
mineralization can be
observed, that seems to
depend on the rate of
dentin formation:
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Globular calcification;
Linear calcification.
Globular mineralization
 It involves the deposition of crystals in several
discrete areas of matrix by heterogeneous capture
in collagen;
 With continued crystal enlarge and eventually fuse
to form a single calcified mass;
 The pattern of mineralization is best seen in the
mineralization foci that grow and coalesce;
Mineralization in circumpulpal dentin
 It can progress in a globular or linear pattern;
 The size of the globules seems to depend on the rate of
dentin deposition:
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When the rate of deposition is fastest, with largest globules
occurring;
When the rate of formation progresses slowly, the mineralization
front appears none uniform and the process is said to be linear.
Vast zone
Subodontoblast
odontoblast
predentin
The two direction of dentin formation – spreads down
the cusp slope as far as cervical loop, and dentin
thickenes
A – odontoblasts; B- predntin; C – ameloblasts; D –
enamel; E – predntin.
Vascular Supply of the odontoblasts
Life cycle of odontoblasts
 There are only 3 stages
in the life cycle of
odontoblasts:
 1. Differentiating stage;
 2. Formation stage;
 3. Quiescent stage.
Differentiating stage
Formative stage:
 Concentration of the cell
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organelles, granular
components and globular
elements;
Production of the first amount
of dentin (dentin matrix);
The odontoblasts retreat from
the basement membrane;
Leaving a single process
which become enclosed in the
dentinal tubule (tomes fiber;.
With successive deposition of
dentin, tubule and process
grow in length.
Quiescent stage:
 Actively secreting odontoblasts decrease slightly in
size.
 The odontoblastic process stop to elongate;
 In this stage the odontoblasts produce only
secondary dentin.
Stages of dentin formation and
types of dentin
DENTIN IS FORMED THROUGHOUT THE LIFE
OF THE TOOTH IF THE TOOTH PULP IS
ALIVE
А – Оdontoblasts; В – Predentin; C – Dental pulp; D –
Dentin.
Primary dentin
 Primary dentin, the most prominent dentin in the tooth, lies
between the enamel and the pulp chamber;
 The outer layer closest to enamel is known as mantle dentin.
This layer is unique to the rest of primary dentin;
 Mantle dentin is formed by newly differentiated odontoblasts
and forms a layer approximately 150 micrometers wide. It is a
more mineralized dentin;
 Below it lies the circumpulpal dentin, a less mineralized dentin
which makes up most of the dentin layer and is secreted after
the mantle dentin by the odontoblasts.
Predentin, Dentin, Odontoblasts
Dentin
Predentin
Dentinal
tubules
Odontoblasts
Secondary and Tertiary Dentin
 Secondary dentin is formed after root formation is finished
and occurs at a much slower rate. It is not formed at a
uniform rate along the tooth, but instead forms faster along
sections closer to the crown of a tooth;
 This development continues throughout life and accounts
for the smaller areas of pulp found in older individuals;
 Tertiary dentin, also known as reparative dentin, forms in
reaction to stimuli, such as attrition or dental caries.
Dentinogenesis;
Primary dentin; Secondary dentin;
Secondary dentin (Regular Secondary
Dentin)
 Secondary dentin is formed after root formation is
complete, normally after the tooth has erupted and is
functional. It grows much slower than primary dentin,
but maintains its incremental aspect of growth ;
 It has a similar structure to primary dentin, although its
deposition is not always even around the pulp chamber.
It is the growth of this dentin that causes the decrease in
the size of the pulp chamber with age.
Tertiary dentin (Irregular Secondary
Dentin or Reparative Dentin)
 Tertiary dentin is dentin formed as a reaction to external
insult such as caries. It is of two types:
 reactionary, where dentin is formed from a preexisting odontoblast;
 or reparative, where newly differentiated
odontoblast-like cells are formed due to the death of
the original odontoblasts, from a pulpal progenitor
cells.
 Tertiary dentin is only formed by an odontoblast directly
affected by stimulus.
Tertiary dentin.
Composition of dentin
 Organic substance:
 30-25% from its weight;
 About 90% collagen fibers:
 About 10% ground substance:
 Inorganic substance:
 70-75% from its weight:
 Hydroxyapatite crystallites.
Properties of dentin
 Yellowish in color;
 Elastic;
 Less hard than enamel, but more than cementum;
 Less radio-opaque than enamel, but more than
cementum;
 3-10 mm thick.
 Dentin is a calcified tissue of
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the body, and along with
enamel, cementum, and pulp is
one of the four major
components of teeth.
Usually, it is covered by enamel
on the crown and cementum on
the root and surrounds the
entire pulp.
By weight, 70% of dentin
consists of the mineral
hydroxylapatite, 20% is organic
material and 10% is water;
Yellow in appearance, it greatly
affects the color of a tooth due
to the translucency of enamel;
Dentin, which is less
mineralized and less brittle
than enamel, is necessary for
the support of enamel.
Dentin
Types of Dentin
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Mantle dentin;
Interglobular dentin;
Circumpulpal dentin;
Predentin.
Mantle dentin
 The most superficial layer of dentin;
 The most highly mineralized;
 This is due to:
Predominance of Korff`s fibers;
 They are properly arranged in parallel;
 This helps in tightly arrangement of crystals;
 There are at least intercrystal spaces;
 There are at least organic matter.

Mantle dentin
 The most highly
mineralized
dentin;
 It is similar in
degree of
mineralization of
enamel;
Mantle Dentin
 It is situated
just below the
dentinoenamel
junction;
 There odontoblast processes
lose their curve.
Branches of Odontoblasts
 At DEJ odontoblasts
branch out;
 In the lower sections
of dentin, they are
united in one main
branch;
 On the surface, go out
a greater number of
processes than leave
from the pulp.
Curvature of the dentinal tubules
 A – neonatale line;
 B – Mantle dentin;
 C – circumpulpal
dentin;
 D - S-shaped primary
curvateure of the
dentinal tubules in
human crown dentin;
 E – DEJ.
S-shaped curveture of the Dentinal
Tubules
 A. S-shaped
path curveture
of the dental
tubules;
 B. DEJ;
 C. Mantle
dentin;
 D. Circumpulpal
dentin.
Dentinal Tubules
 A. Odontoblasts
in the dentinal
tubules;
 B. DEJ;
 C. Enamel;
 D. Spindles in
the enamel
Spindles in the enamel
 During
histogenesis, part
of processes were
passed the DEJ to
stimulate
ameloblasts.
Mantle dentin
Circumpulpal Dentin
 It is the thickest layer of dentin;
 It is less mineralized than mantle dentin;
 The collagen fibers of this dentin are thinner than mantle
dentin -β-fibers;
 The Korff`s fibers (α- fibers) are less;
 The crystals are arranged along the fibers;
 They are chaotically arranged and have higher
intercrystal spaces.
Circumpulpal Dentin
 Dentinal tubules
with odontoblast`s
processes;
Odontoblast processes in tubules with numerous lateral
branches.
Lateral branches of the odontoblast
processes
Longitudinal cross
section of the dentin;
Dental tubules;
Lateral branches of
the odontoblasts.
Dental tubules after
demineralization
Interglobular
Dentin
 It is the term used to describe
areas of hypomineralized
dentin where globular zones of
mineralization (calcospherites)
have failed to fuse into a
homogeneous mass within
mature dentin;
 It is seen in the circumpulpal
dentin just below the mantle
dentin;
 It is a defect of mineralization
and not of matrix formation;
 The normal architectural
pattern of the tubules remains
unchanged, and they run
uninterrupted through the
interglobular areas.
Interglobular Dentin
 D. Circumpulpal
dentin;
 Igd – interglobular
dentin;
 e – enamel.
Hypomineralized areas between the
globules, termed interglobulare spaces
Interglobulare spaces
Greater Increase
Globules of mineralization
 Globular
appearance of the
mineralization in
dentin arising
from fusion of
globules of
hydroxyapatite or
calcospherites.
Granular Layer of Tomes
 When a section of root is
studied, a granularappearing layer of dentin is
seen underlying the
cementum that covers the
root;
 This layer is known as the
granular layer of Tomes;
 This layer is prevalent when
the person has had a
deficiency in vitamin D;
 This layer is most frequently
found in the first permanent
molars.
Dentinal tubules in different layers of dentin
Dental tubules in
interglobular dentin
Dental tubules in
circumpulpal dentin
Granular Layer of Tomes
Predentin
 It is a band of newly formed, unmineralized
matrix of dentin at the pulpal border of the
dentin;
 Predentin is evidence that dentin forms in two
stages:
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First – the organic matrix is deposited;
Second – an inorganic mineral substance is added;
 During primary dentin formation, 4µm of
predentin is deposited and calcified each day;
 After occlusion and function, this activity
decreases to 1.0 to 1.5 µm per day;
Predentin
 A–
Odontoblasts in
the pulp;
 B - Predentin;
 C- Dental pulp;
 D - Dentin
В – Predentin; С –The boundary of mineralization
with a globuls of mineralization.
Predentin
Incremental lines
 All dentin is deposited incrementally, which means
that as a certain amount of matrix is deposited daily,
a hesitation in activity follows;
 This hesitation in formation results in an alteration
of the matrix known as incremental lines, or lines of
von Ebner;
 Prenatal dentin and postnatal dentin are separated
by an accentuated contour line known as the
neonatal line and reflects the disturbance in
mineralization created by the physiological trauma of
birth.
Countour lines of Owen (А)
 Another type of
incremental pattern
found in dentin is the
contour lines of
Owen;
 They are known as
caused by accentuated
deficiencies in
mineralization;
 These are recognized
in longitudinal
ground sections;
Incremental lines, or lines of von Ebner;
 This incremental lines
run at right angles to
dentinal tubules and
generally mark the
normal rhythmic,
linear pattern of dentin
deposition;
 The 5-day increment
can be seen readily in
conventional and
ground sections,
situated about 20µm
apart.
Histology of Dentin
 When the dentin is viewed microscopically, several
structural features can be identified:


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Dentinal tubules;
Peritubular dentin;
Intertubular dentin.
Longitudinal ground section of dentin
 (A) –
Intertubular
dentin
 (B) – peritubular
dentin;
 Odontoblast
processes in
canalicules, called
tubules (C).
 Each odontoblast
process is surounded
by intervined collagen
fibrils, that outline the
future dentinal tubule;
 The fibrils run
circumferentially and
perpendicular to the
process;
 Each tubule is occupied
by a process or its
ramifications;
 Peritubular dentin
(deliminated dental
tubule) is poor in
collagen and more
mineralized than the
rest of dentin.
 The dentin between
tubules is referred to as
intertubular dentin.
Dentin tubules and
odontoblasts
Cross section of dentin
Dentinal tubules(С); Intertubular dentin (В); peritubular dentin(А).
Inter- and peritubular dentin
Dentinal tubules
Dentin tubules
Collagen matrix of dentin
 Dentin tubules with
odontoblast processes
and their branches
Properties of dentin
 The inorganic component - dentin is composed of 87%
inorganic hydroxyapatite crystals, fluorapatite and
carbonatapatite in the form of small plates;
 Organic component - 13% collagen fibers with small amounts
of other proteins and water;
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Collagen is mainly typ I with small amounts of type III and V;
There are fractional inclusions of lipids and noncollagenous proteins;
The noncollagenous matrix proteins pack the space between collagen fibrils
and accumulate along the periphery of dentinal tubules;
Thay comprise the following:

Dentin phosphoprotein – phosphophoryn, dentin sialoprotein, dentin matrix
protein 1, osteonectin, osteocalcin, bone sialoprotein, osteopontin, proteoglycans
and ect.
Physiology of dentin
 Metabolism in dentin is ensured by the pulp;
 Metabolism is performed by odontoblast processes;
Odontoblasts
 They form a layer lining the periphery of the pulp
and have a process extending in the dentin;
 The number of dental tubules with odontoblasts are
of 59 000 to 76 000 per square millimeeter in a
coronal dentin;
Nerve endings around odontoblasts in the
predentin
Functions of the odontoblasts
 During dentinogenesis:
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1 Synthesising function:
 Odontoblastat synthesized
proteins, matrix
macromolecules and collagen;
2 Secreting function:
 Odontoblasts secreted Β-fibers
(collagen) and amorphous
organic and inorganic matter;
3. Both structurise and
mineralise dentinal matrix.
 During functional stage odontoblasts:
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1. Continued formative function;
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2. Ensure the exchange of the
dentin;
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3. Providing a link between enamel,
dentin and dental pulp;
5. They provide sensitivity of the
dentin;
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5. They have protective function;
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Reparative dentin;
Sclerotic dentin;
Secondary and tertiary
dentinogenesis.
Physiologic Secondary Dentinogenesis
 It represents the slower-paced deposition of dentin
matrix that continues after completion of the crown
and root of the tooth and spans a lifetime;
 While secondary dentin is deposited all around the
periphery of the tooth, its distribution is asymmetric,
with greater amounts on the floor and roof of the
pulp chamber.
Terciary Dentinogenesis
 It describes the focal
secretion of dentin in
response to external
influences (dental caries,
tooth wear, trauma, and other
tissue injury;
 Tertiary dentin encompasses
a broad spectrum of
responses:
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Regular tertiary dentin;
Displastic atubular dentin;
Reactionary dentin;
Reparative dentin.
Atubular dentin: areas without tubules
Atubular dentin: areas without tubules
Types of secondary dentin
Regular
Line of demarcation:
stain dark
Clinically:
The increase of the dentin thickness and the closure of the pulp
horns make it much less possible to expose the pulp chamber
during preparation.
Irregular
Line of demarcation:
stain dark
Clinically:
Functions as a barrier against caries.
Physiologic regular secondary dentin
The size of the pulp cavity decreases and obliteration of the pulp horns.
The course of the dentin canals is more irregular.
Osteodentin: The odontoblasts (cells) are included
in the formed dentin
Circumpulp
al dentin
Response
dentin
Reparative dentin and incorrect course
of dentinal tubules
Reactionary dentin
 Is defined as a tertiary dentin matrix secreted by
surviving postmitotic odontoblast cells in responce
to an appropriate stimuls;
 Such a responce will be made to milder stimuli and
represents up-regulation of the secretory activity of
the existing odontoblast responsible for primary
dentin secretion.
Reparative dentin
Reparative dentin
 Is defined as a tertiary dentin
matrix secreted by a new
generation of odontoblast-like
cells in response to an
appropriate stimuls after the
death of the original
postmitotic odontoblsts
responsible for primary and
fisyologic secondary dentin
secretion;
 Such a response will be made to
stronger stimuli and represents
a much more complex sequence
of biologic processes.
Reparative dentin
Репаративен дентин
Sclerotic Dentin
 Sclerotic dentin describes dentinal tubules that have
become occluded with calcified material;
 When this occurs in several tubules in the same area,
the dentin assumes a glossy appearance and becomes
translucent;
 This is deposition of mineral within the tubule
without any dentin formation and diffuse
mineralization is occurs with a viable odontoblast
process still present;
 Because sclerosis reduces the permeability of dentin,
it may help to prolong pulp vitality.
Dead tracts
 Loss a tubular contents (odontoblast processes)
results in dead tracts, wich indicate air in the
tubules;
 Below the dead tract area is sclerotic dentin, wich
protect the pulp from bacteria or bacterial products.
Dead tracts in the dentin
Vitality and sensitivity of dentin
 Vitality of dentin is its ability to react following
physiological or pathological stimuli.
 Forming secondary or tertiary dentin, feeling pain are
signs of being vital;
 Several theories have been cited to explain the mechanism
involved in dentinal sensitivity & vitality:
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The transducer theory,
the conduction theory,
the modulation theory
the Brännström's hydrodynamic theory.
The transducer theory
 The transducer theory contend that the odontoblast and its
process are capable to mediate neural impulse in the same
way as nerve cells;
 Contra:
 But investigations have proved that no pain is experienced
in exposed dentin by application of substance known to
bare nerve endings.
 The measurement of membrane potential of the
odontoblasts shows clearly that this potential is very low to
contribute in the pain excitation.
The conduction theory
 The conduction theory
(intratubular innervation
theory) contend that dentin is
richly innervated and those
nerves mediate the impulse to
the brain.
 Some new studies show that
predentin and the first layer of
circumpulpal dentin (0.2mm)
is innervated with nerve fiber
from the raschkows plexus.
 The fibers run parallel to the
tomes fiber in the dentin
tubules.
 The density of those fiber is
much higher in the coronal
dentin than cervical dentin.
Root dentin doesn’t include
such fibers.
 Some authors contend that those fibers end at the
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DEJ, but can not be seen in histological slides.
Contra:
It is uncapable to explain the higher sensitivity at the
cemento-enamel junction than that felt at other
areas.
The conduction theory
 The “hydrodynamic theory”,
developed in the 1960’s is the
widely accepted
physiopathological theory of
Dentin Sensitivity.
 Temperature, physical osmotic
changes or electrical and chemical
stimuli and dehydration are the
most pain-inducing stimuli.
 According to this theory, those
stimuli increase centrifugal fluid
flow within the dentinal tubules,
giving rise to a pressure change
throughout the entire dentine.
 The movement stimulates
intradentinal nerve
 receptors sensitive to pressure
(BARORECEPTORS),
which leads to the transmission of
the stimuli .
 This simulation generates pain.
The hydrodynamic
theory
The hydrodynamic theory
 Berman describes this
reaction as: “The coefficient
of thermal expansion of
the tubule fluid is about ten
times that of the tubule wall.
 Therefore, heat applied to
dentin will result in
expansion of the fluid and
cold will result in contraction
of the fluid, both creating an
excitation of the 'mechanoreceptor'.”
Appearance of a pain in the dentin
The fluid moves through the
tubules and excites nerves
The incentives on dentine
causes movement of fluid in
the tubules
include hot and cold,
tactile, evaporative, and
osmotic,