Collagen type I acts as a scaffold tht accommodates a large proportion(app. 56%) of the mineral in the holes and pores of fibrils.Noncollagenous matrix proteins pack the space between collagen fbrils and accumulate along the periphery of dentinal tubules.Thy regulate mineral deposition and can act as inhibitor, promoter, and/or stabilizer; their distribution is suggestive of their role. These proteins are DPP, DSP, DGP, dentin matrix protein-1(DMP-1), bone sialoprotein (BSP) osteopontin, osteonecin.DPP DSP DGP are expressed at gene level as a single molecule called dentin sialophosphoprotein (DSPP) that is then processed into individual components with distinct physiochemical properties.
Thus d DP is the formative organ of dentin and eventually becomes the pulp of the tooth.
The DP cells are small and undifferentiated , and they exhibit a central nucleus and few organelles.At this tym they r seperated from IEE by an acellular zone that contian some fine collagen fibrils.The ectomesenchymal cells adjoining the acellular zone rapidly enlarge and elongate to become preodontoblast first and thnodontoblast as their cytoplas increases in vol to contain inceasingamt of protein-synthesizing organells.The acellular zone b/w BP and IEE gradually is eliminated as the odontoblast differentiate and increase in size and occupy this zone.These newly differentiated cells are charecterized by being highly polarized , with theirnuclei positioned away from the IEE.
korff’sfiber have been described as the initial dentin deposition along the cusp tip.These fiber consist of collagen typ III associated , with fibronectin. The odontoblast process or Tomes’ fiber, left behind in the forming dentin matrix as the odontoblast moves away toward the pulp
Globular calcification involves the deposition of crystals in several discrete areas of matrix by heterogenous capture in collagen. with continued crystal growth , globular masses are formed that continue to enlarge and eventually fuse to form a single calcified mass. This pattern of mineralization is best scene in mantle dentin region, where matrix vesicles give rise to mineralization foci that grow and coalesce.In circumpulpal dentin minerlization front can progress in a globular or lenear pattern .Size of globule seems to depends on the rate of dentin deposition, with the largest globules occuring where dentin deposition is fastest.When the rate of formation progresses slowly , the mineralization front appears more uniform and the process is said to be linear.Occurs by globular/calcospheric calcification deposition of crystals in several discrete areas at a time.Continued crystal growth forms globular masses which coalesce to form a single calcified mass.Seen in circumpulpal dentin.When these globular masses do not completely fuse, small areas of uncalcified matrix are left – Interglobular dentin
From that point , dentin formation spreads down the cusp slope as far as the cervical loop of enamel organ, and the dentin thickens until all the coronal dentin is formed.The onset of root formation proceeds the onset of tooth eruption.By the tym tooth reaches to its functional position, about 2/3rd of root dentin will hav been formed.Completion of root dentin formation does not occur in deciduoud tooth untillabt 18 mnts after it erupts and in permanent tooth untill 2-3 yrs after it eruptDentin formation continuous through out the life of the tooth, and its formation results in gradual but progressive reduction in size of pulp cavity.
Dentin is harder in permanent teeth than in deciduous teeth. Dentin becomes harder with age, primarily due to increase in mineral content
Hydroxyapatite crystals, which average 0.1µm in length, are formed along the fibers with their long axis oriented parallel to the collagen fiber.
It is seen most frequently incircumpulpal dentinIt is defect in mineralization pattern , not in matrix pattern ,normal architechtural pattern of the tubule remain unchanged , and they run unitturuped through the interglobular areas.
A progressive increase in granularity from CEJ to the apex of tooth.It found only in root dentin , and seen only because of light reflection in thick ground section.More recent interpretation relates this layer to a special arrangement of collagen and non-collagenous matrix proteins at the interface between dentin and cementum.C. These lines are not incremental lines of von Ebner, but rather contour lines of Owen. They reflect a major interruption in the deposition of dentin due to a metabolic distruption during odontogenesis
They run at right angles to the dentinal tubules.These lines reflect the daily rhythmicdeposition of dentin matrix as well as a hesitation in the daily formative process. The distance between them varies from 4 to 8µm in the crown to much less in the root. spherical configurationThese are the incremental lines of von Ebner. This is a ground section, but these lines can also be seen in demineralized sections. The lines of von Ebner represent cyclic activity of the odontoblasts during dentin formation. These incremental lines illustrate the daily pattern of dentin deposition that progresses at about 6 µm per day in the crown and about 3.5 µm per day in the root.
The rounded projections of enamel fit into the shallow depressions of dentin. This interdigitation seems to contribute to a firm attachment between dentin and enamel.
1.The attachment of cementum to dentin in either case is quite firm although the nature of this attachment is not fully understood. 2.Predentin-pulp junction is made up of dense collageneousfibers and is present between the uncalcified dentin (predentin) and pulp. 3.Dentin-Predentin junction is the interface between the calcified and uncalcified newly formed dentin called predentin.
Pulp recession can be readily detected on radiographs and is important in determining the form of cavity preparation for restorative procedures
These dead tracts appear dark in ground section in transmitted light and white in reflected light.Blind tracts appear white in transmitted light.the dentin in blind trcs is called sclerotic dentin.The adaptive advantageof blind tracts is the sealing off of dentinal tubules to prevent bacteria from entering the pulp cavity.Their disintegation is often observed in the area of narrow pulpal horn, bcoz of crowding of odontoblast.Again where repairative dentin seals dentinal tubbules at their pulpal ends, dentinal tubules fill with fluid or gaseous substance.
This structural appearance of the dentinal tubule in the primary tooth dentin may be one of the factors contributing to the faster progression of caries
While it’s a gud protective barrier, it has relatively weak attachment to the dentin and is subject to dissolution by acids.Its removal during canal prepration increases the quality of seal between endodontic filling materials and root dentinIt may also increses the bond strength of resin posts.
Is done for the purpose of removal of smear layer and demineralization of dentin by which microporosities are exposed on dentinal surface.
1st yr PG
• Primary dentin Vs
• Infected dentin Vs affected
• Smear layer
• Dentin bonding system
• Composition of dentin
• Physical properties of dentin
• Histology of dentin
• Types of dentin
• Innnervation of dentin
• Age and functional changes
• Dentin is a
mineralized, elastic, yellowish-
white, avascular tissue enclosing the
central pulp chamber.
• Dentin is characterized by multiple
closely packed dentinal tubules that
traverse its entire thickness and
contain the cytoplasmic extensions
of odontoblasts that once formed
the dentin and then maintain it.
• Inorganic material 70%
– Consist of hydroxyapatite in form of small plates
• Organic material 20%
– It is about 90% collagen (mainly type I with small amount of
type III and type V)
– noncollagenous matrix proteins and lipids
• Water 10%
Composition of dentin
• It is a two phase sequence
– collagen matrix formation
• Outlines are
– Differentiation of odontoblast
– Formation of mantle predentin
• Differentiation of odontoblast is brought about by
the expression of signaling molecule and growth
factors in cells of IEE
• The first sign of dentin formation is the
appearance of distinct, large-diameter collagen
fibrils (0.1-0.2 mm in dia) called von Korff’s fibres.
• As odontoblast continue to increases in size, they
also produce smaller collagen type I fibrils that
orient themselves parallel to future DEJ.
• In this way a layer of mantle predentin appears.
Fromation of mentle predentin
• Throughout dentinogenesis, mineralization is
achieved by continuous deposition of mineral,
initially in the matrix vesicle and then at the
• Factors :‽
• Proteins are :
– Dentin phosphoprotien (DPP)- key protein
– Osteonectin-inhibitory effect
– Osteopontin- promoter
– Gla protein- seeder / nucleaator
– Chondrointin sulphate-
• Two pattern:
1) Globular mineralization
Deposiotion of crystals in
several discrete areas of matrix
by heterogenous capture in
2) Linear mineralization
When the rate of formation
progresses slow, the
mineralization front appears
Pattern of mineralization
Scanning electron micrograph of
• Dentin formation begins at the
bell stage of tooth development in
tissue adjacent to concave tip of
the folded inner enamel
epithilium.(it is the site where
cuspal development begins.
• Root dentin forms at a slightly
later stage of development.
• requires the proliferation of
epitilial cells ( hertwig’s epithelial
root sheath) from the cervical loop
of enamel organ around growing
pulp to initiate the differentiation
of root odontoblast.
Pattern of dentin formation
• Many genes are implicated in dentinogenesis, the
newer ones being
– MAP1B for odontoblast differentiation, and
– PHEX for dentin mineralization
Genetic regulation of dentinogenesis
Kaneko T, Arayatrakoollikit U, Yamanaka Y, Ito T, Okiji T. Immunohistochemical and gene
expression analysis of stem-cell-associated markers in rat dental pulp. Cell and tissue research.
2013 ; 351 (3): 425-432.
• Color :
Pale yellow in deciduous teeth ,Yellow in permanent
Light passes through thin, highly mineralized
enamel and is reflected by underlying dentin.
Thicker or hypomineralized enamel does not permit
light to pass through readily.
• Thickness of dentin:
Ratio of thickness in primary and permanent teeth is
Physical properties of
Dentin is softer than enamel but more hard than
bone or cementum.
Hardness of dentin is one fifth (1/5th ) that of
enamel; near the DEJ it is three times greater than
near the pulp.
• The compressive strength of dentin is 217-300
MPa which is much higher than enamel.
• Modulus of elasticity of dentin is 1.67x 10⁶ PSI.
• Tensile strength of dentin is approx. 40MPa
, which is less than cortical bone and approx one half
(1/2) that of enamel.
• Extend through entire thickness
of dentin from DEJ to pulp.
• ‘S’-shaped path from the outer
surface of the dentin to the
perimeter of the pulp in coronal
• Less pronounced in root dentin
in the cervical third and in
incisal edges and cusps .
• Straight in deciduous teeth.
Histology of dentin
• Diameter of dentinal tubules :
– Larger in diameter near pulp - 3 to 4µm, and
smaller at the DEJ- 1µm.
• Number of Dentinal tubules :
– At the pulpal surface of dentin the number /sq mm
varies between 50,000 & 90,000.
– At DEJ : 8000- 15,000
• More tubules per unit area in the crown than in the
• The dentin that immediately surrounds the dentinal
tubules is termed peritubular dentin.
• This dentin forms the walls of the tubules.
• It is highly mineralized (about 9% more) than
– The formation of
intratubular dentin is a
slow continuing process
causing reduction in size
Peritubular dentin/ intratubular dentin:
• The main body of dentin is
composed of intertubular
• It is located between the
dental tubules more
specifically, between the
zones of peritubular
• About one half of its
volume is organic
collagen fibers which are
randomly oriented around
the dentinal tubules.
• It is term used to describe areas
of unmineralized or hypo
mineralized dentin where
globular zones of mineralization
(calcospherites) have failed to
fuse into a homogenous mass
within mature dentin.
• These areas are prevelent
especially in person which has
had a deficiency in vit D or
exposure to high level of fluoride
at the time of dentin formation.
Inter globular dentin:
• When root dentin is viewed under
transmitted light in ground
section , a granular- appearing
area, the granular layer of Tomes,
can be seen just below the surface
of the dentin where the root is
covered by cementum.
• Caused by a coalescing and
looping of the terminal branches
of the dentinal tubules. These
areas remain unmineralized.
Granular layer of TOMES:
• Incremental lines of von Ebner appear as fine lines or
• A that reflect rhythmic dentin deposition are more
distinctly visualized in this demineralized section.
• B is devoid of such lines. This is a characteristic of
• C that reflects the spherule-
like mineralization pattern of
Incremental/Imbrication Lines of von
• Unique bond between two very
• It is scalloped or pitted or wavy
in outline, with the crest of the
waves penetrating towards the
• Function- prevention of
Shimizu D, Macho A. functional significance of microstructral detail of the primate dentino-
enamel junction: A possible example of exaptation. J Hum Evol. 2007;52 :103-111.
• There is a smooth line junction
between the dentin and
cementum in permanent teeth.
• The cemento-dentinal junction
in deciduous teeth is
• In human teeth three types of dentin can be
– Primary dentin
– Secondary dentin
– Tertiary dentin
Types of dentin
• Formed prior to the eruption of the teeth and root
• Major bulk of dentin.
• It is composed of Mantle dentin and Circumpulpal
• Completed 2-3 years after tooth eruption for
permanent teeth and 18 months for deciduous teeth.
• The first-formed dentin in the crown underlying the
• Large collagen fibrils perpendicular to DEJ (0.1-
0.2µm in diameter) : argyrophilic or silver-stained
and called von Korffs fibers.
• 4% less mineralized than circumpulpal dentin.
• Forms bulk of the tooth.
• Formed prior to root completion.
• Smaller collagen fibrils (0.05µm in diameter); more
closely packed together.
• Formed after completion of root formation.
• Continuing, but much slower deposition of dentin.
• Narrow band of dentin bordering the pulp.
• Contains fewer tubules than primary dentin.
• Greater deposition of secondary dentin on the roof
and floor of the pulp chamber leads to an asymmetric
reduction in size and shape of the chamber and the
• The tubules of secondary dentin undergo sclerosis
more readily than primary dentin.
• This process tends to reduce the overall permeability
of the dentin and thereby to protect the pulp.
• Tertiary dentin is also known as Reactive,
Reparative or Irregular secondary dentin.
• It is the dentin that is formed in response to
abnormal stimuli such as attrition, abrasion,
erosion, trauma, moderate dentinal caries and
• Usually appears as a localized dentin deposit on the
wall of the pulp cavity immediately subjacent to the
area on the tooth that has received the injury (dentin
deposits underneath the affected tubules).
• Types of tertiary dentin:
• When the original odontoblasts that made secondary
dentin are responsible for focal tertiary dentin
• Rate of formation of dentin is increased.
• Tubules remain continuous with the secondary
• If the provoking stimulus causes destruction of the
original odontoblasts, the newly differentiated
odontoblast -like cells secrete less tubular, more
irregular dentin called Reparative dentin.
• Here, tubules are usually not continuous with those
of secondary dentin.
• Nerve fibers were shown to accompany 30-70%
odontoblastic process, and these are reffered to as
• Nerve and their terminal are found in close
association with odontoblast process withih
• It is believed that most of these are terminal
processes of mylinated nere fibers of dental pulp.
Innervation of dentin:
• 3 basic theories of pain conduction through
• Direct neural stimulation: by which the nerve in
dentin get stimulated.
• Transduction theory: which presumes that the
odontoblast process is primary structure excited
by the stimulus and that impulse is transmittes to
the nerve endings in inner dentin.
Theories of pain transmission
• Hydrodynamic theory: various
stimuli affect fluid movement in
• This fluid movement , either
inward/ outward stimulates pain
mechanism in tubules by
mechanical distribution of nerves
closely associated with the
odontoblast and its process.
• Thus these endings may act as
mechanoreceptors as they are
affeced by mechanical
displacement of tubular fluid.
• Dead tracts and blind tract:
• When dentin is damaged,
odontoblastic processes die or
retract leaving empty dentinal
tubules. These areas with empty
dentinal tubules are called dead
• With time these tracts can
become completely filled with
mineral. This region is called
Age and functional changes:
• Longitudinal ground section of
permanent teeth dentin showed
DT following an ‚S‛-shaped
curve, where as in primary DT
follow a straight curve.
• Density of innervation is less in
primary teeth as compare to the
Primary dentin and permanent
Chowdhary N ,Subba Reddy VV. Dentin comparison in primary and permanent molars under transmitted
and polarised light microscopy: An in vitro study. J Indian Soc Pedod Prev Dent. 2010; vol 28(3) : 167-172
• Primary tooth showing incremental lines at an
angle to the dentinal tubules, whereas permanent
tooth showing incremental lines at right angles to
the dentinal tubules
• Infected dentin: Superficial layer which is
soft and leathery in consistency and dark
brown in color.
– It has a high concentration of bacteria and
collagen is irreversibly denatured .
– It is not remineralizable and must be removed
• Affected dentin: Deeper layer which is
hard in consistency and light brown in
– It does not contain bacteria and is reversibly
denatured. Therefore this layer preserved
Infected dentin & affected dentin
• Whenever dentin has been cut or abraded, a thin
altered layer is created on the surface.
• Composed of denatured collagen, hydroxyapatite
and other cutting debris.
• Serves as a bandage over the cut dentinal surface
because it occludes many of dentinal tubules with
debris called smear plugs.
• Clinical significance :
• The fundamental principle of adhesion to tooth
substrate is based upon an exchange process by
which inorganic tooth material is exchanged for
• This process involves 2 phases
1. Etching of tooth surface,
2. Hybridization phase
• Clinical relevance of etching time on dentin
Dentin bonding system
Perdigấo J, Lopes M. The effect of etching time on dentin demineralization.
Quintessence int.2001 ; 32:19-26.
• Dentin is a living tissue. It is covered by enamel in
crown portion and by cementum in root portion.
• It will become sensitive if covering of either
enamel or cementum will lost due to any reason.
• So, all efforts should be made during restorative
procedures to preserve as much healthy dentinal
tissue as possible.
• Chowdhary N ,Subba Reddy VV. Dentin comparison in primary
and permanent molars under transmitted and polarised light
microscopy: An in vitro study. J Indian Soc Pedod Prev Dent. 2010;
vol 28(3) : 167-172
• Kaneko T, Arayatrakoollikit U, Yamanaka Y, Ito T, Okiji T.
Immunohistochemical and gene expression analysis of stem-cell-
associated markers in rat dental pulp. Cell and tissue research.
2013 ; 351 (3): 425-432.
• Shimizu D, Macho A. functional significance of microstructral
detail of the primate dentino-enamel junction: A possible example
of exaptation. J Hum Evol. 2007;52 :103-111.
• Gallagher R, Balooch M, Balooch G, Wilson R, Marshall S,
Marshall G. Coupled nanomechanical and Raman
microspectroscopic investigation od human third molar
dentinoenamel junction. J Dent Biomech. 2010;1:1-4.
• Perdigấo J, Lopes M. The effect of etching time on dentin
demineralization. Quintessence int.2001 ; 32:19-26.
• Nanci A. Tencate’s Oral histology. 8th ed. 2013
• Kumar GS. Orban’s oral histology and embryology. 12th ed. India: