Dentin /certified fixed orthodontic courses by Indian dental academy

DENTIN – CLINICAL
CONSIDERATION RELATED TO
OPERATIVE DENTISTRY

INDIAN DENTAL ACADEMY
Leader in Continuing Dental
Education
www.indiandentalacademy.com

INTRODUCTION
DENTINOGESNESIS
TYPES OF DENTIN
PROPERTIES OF DENTIN
INERVATION OF DENTIN
AGE AND FUNCTIONAL CHANGES
CLINICAL CONSIDERATIONS
- DENTIN SENSITIVITY
- BONDING OF DENTIN
ZONES OF DENTINAL CARIES
DEVELOPMENTAL Disturbances
CONCLUSION

INTRODUCTION
DENTIN PULP COMPLEX

Embryonically and Physiologically,
Dentin and Pulp are so intimately
related that Dentin can be
considered as the peripheral
calcified portion of the dental pulp.
Physiologically dentin protects the
pulp ; conversely dentin owes its
vitality to the pulp. It also implies
pulp would react whenever dentin is
injured in cases like caries, attrition,
abrasion, erosion or operative
procedures.

KNOWING DENTIN
►The Dentin provides the bulk and
general form of the tooth and is
characterized as a hard tissue with
tubules throughout its thickness.
since it forms slightly before the
enamel, it determines the shape of
the crown, including the cusps and
ridges and the number and size of
the roots.

Dentinogenesis...
Dentin is formed by cells of the
odontoblast that differentiates from
ectomesenchymal cells of dental papilla
following an organizing influence that
emanates from cells of the internal dental
epithelium.
Thus dental papilla is the formative organ
of dentin.
Odontoblast produce an organic matrix
that becomes mineralized to form dentin.

It begins at the cusp tips after the
odontoblasts have differentiated and begin
collagen production
As the odontoblasts differentiate they change
from an ovoid to a columnar shape and their
nuclei become basally oriented at this early
stage of development.
The length of the odontoblast then increases
to approximately 40 μm although its width
remains constant (7 μm)
Proline appears in the rough surface
endoplasmic reticulum and golgi apparatus.
One or several processes arise form the basal
lamina. www.indiandentalacademy.com

The proline then migrates into the cell
process in dense granules and is
emptied into the extra cellular
collagenous matrix of the predentin.
As the cell recedes it leaves behind a
single extension and the several initial
processes join into one which becomes
enclosed in a tubule.
As the matrix formation continues the
odontoblast process lengthens as does
the dentinal tubule.

After this time, dentin production slows
to about 1μm / day.
After root development is complete dentin
formation may decrease further.
Although, reparative dentin may form at
a rate of 4 μm/day for several months
after a tooth is restored.
As each increment of predentin is formed
along the pulp border, it remains for a day
before it is calcified and the next
increment of predentin forms.

Korff ‘s fibers have been
described as the intial dentin
deposition along the cusptips. Because
of the argyrophilic reaction (stain
black with silver) it was long believed
that bundles of collagen formed among
the odontoblasts.

Consequently all predentin is formed
in the apical end of the cell and along
the forming tubule wall.

MINERALIZATION
► The earliest crystal deposition is in the
form of very fine plates of
hydroxyapatite, on the surfaces of the
collagen fibrils and in the ground
substance. Subsequently crystals are
laid down within the fibrils themselves.
► The crystal associated with the collagen
fibrils are arranged in an orderly fashion
with their long axes paralleling the fibril
axes and in rows conforming to the
64μm (640 Aº) striation pattern.

► Within the globular islands of
mineralization , crystal deposition
appears to take place radially from
common centers in a so-called
spherulite form.
► The general calcification process is
gradual but the peritubular region
becomes highly mineralized at a very
early stage.


► Although there is obviously some
crystal growth as dentin matures the
ultimate crystal size remains very
small about 3μm (30 Aº) in thickness
and 10 μm (100 Aº) length.
► The apatite crystals of dentin
resemble those found in bone and
cementum. They are 300 times smaller
than those formed in enamel.


ODONTOBLASTIC
DIFFERENTIATION


ODONTOBLASTIC DIFFERENTIATION
The differentiation of odontoblast from
dental papilla in normal development
,requires the presence of epithelial cells
or their products.
Before the dentinogenisis begins the
cells of internal dental epithelium are
short & columnar, rapidly dividing to
accommodate growth of the tooth germ
and supported by basement membrane
that separates the epithelium from
dental papilla and inbetween those is
the formation of acellular layer.

The ectomesenchymal cells adjusting the
acellular zone rapidly enlarge to become
preodentoblast and then odontoblasts , as
their cytoplasm increases in volume to
contain increasing amount of RER & golgi
apparatus,the highly polarised nuclei
moves away form internal dental
epithelium .
The acellular zone between dental papilla
and IDE is gradually eliminated as the
odontoblast differentiates and increases in
size and occupy this zone.

During the final division of
ectomesenchymal cells, adjacent to
dental epithelium their mitotic
spindles are perpendicular to
basement membrane supporting the
IDE. therefore it is only those cells
next to the basement membrane that
differentiate into odontoblast.


As a result two layers can be
distinguished such as odontobalastic
layer and the sub odontobalastic layer.
Because they are away from the sphere
of influence of internal dental
epithelium during last cell division,
experimental evidence indicates that,
what the basal lamina provides is a
surface containing fibronectin that
permits the preodontoblast to align
themselves along the membrane and
become odontoblast.

PATTERN OF DENTIN FORMATION
CROWN DENTIN
► Dentin formation begins at the late bell
stage of development in the papillary
tissue adjacent to the tip of the folded
internal dental epithelium.
► Though actually this is not the site
where the future cusp will reside, the
cuspal development begins from here.
The dentin formation spreads down the
cuspal slopes .

►In multicusped teeth, dentin
formation begins independently at
the sites of each future cusptip
►coronal dentin deposition is approx
4μm per day.


ROOT DENTIN
► Forms slightly at a later stage of
development and requires the
proliferation of epithelial cells from
cervical loop of dental organ around
the growing dental papilla to intiate
the differentiation of root
odontoblasts.
► The tooth reaches the functional
position when about 2/3 rd of root
dentin has formed.

ROOT COMPLETION
► Deciduous teeth  18 months after
eruption
► Permanent teeth  2-3 years after
eruption


HISTOLOGY OF ODONTOBLASTS


SECRETORY ODONTOBLAST

The secretary odontoblast is seen with a
large plump cell with a open faced nucleus
situated basally and basophillic cytoplasm
containing a negative golgi image.
The apical basophillic cytoplasm is found
to contain a full complement of organelles
required for synthesis and secretion of extra
cellular material.


TRANSITIONAL ODONTOBLAST
Under electron microscope it becomes
Narrower.
nucleus is displaced from the basal
extremity.
exhibits chromatin condensation.
amount of endoplasmatic reticulum
is reduced and confirmed to the area
around the nucleus.
Autophagic vacuoles are present.

RESTING ODONTOBLASTS
Small flattened cell with a closed
nucleus,less cytoplasm and no golgi body.
In image by electron microscopy,the
nucleus is found to be situated sufficiently
apical to create a prominent infranuclear
region where a reduced amount of
cytoplastic organelle are clustered. The
supra nuclear region is devoid of
organelles except for a large lipid filled
vacuoles in cytoplasm containing tubules
& filamentous structures. secretary
granules are absent.

MICROSCOPIC STRUCTURES


MICROSCOPIC STRUCTURES
MANTLE DENTIN OR
PRIMARY DENTIN

► It is the name of the first
formed dentin in the
crown underlying the
dentinoenamel junction.

► It is 20microns thick.

► It is the area of initial
dental matrix formation.

CIRCUMPULAPAL DENTIN
► It forms the remaining
primary dentin or bulk of the
tooth.
► It is the circumpupal dentin
that represents all of the
dentin formed prior to root
completion.
► The collagen fibrils in
circumpulpal dentin is much
smaller in diameter (0.05 μm)
and are more closely packed
together.
► The Circumpulpal dentin
may contain slightly more
mineral than mantle dentin.

SECONDRY DENTIN
It is narrow band of dentin
broadening at the pulp and
representing that dentin
that is formed after root
completion.
This dentin contains fewer
tubules than primary
dentin there is usually a
bend in the tubules when
the primary and secondary
dentin interface.

REPARATIVE DENTIN
•If by extensive abrasion,
erosion, caries, poor
operative procedures the
odontoblast processes are
exposed or cut, The
odontoblasts die or if they
live deposit reparative
dentin. The majority of
odontoblast in this
situation degenerate but a
few may continue to form
dentin.

Some of the odontoblast that are killed are
replaced by the migration of undifferentiated
cells arising in deeper regions of the pulp to the
dentin interface it is believed that the origin of
the new odontoblast is from undifferentiated
neurovascular cells.
Both the damaged and the newly differentiated
odontoblasts then begin deposition of reparative
dentin. This action to seal off the zone of injury,
occurs as a healing process initiated by the pulp
resulting in resolution of the inflammatory
process and removal of dead cells.


Steps in Reparative dentin formation
► Injury to odontoblasts
► Inflammatory response to subjacent pulpal
connective tissue.
► Differentiation of new odontoblasts
a) synthesis of cytoplasmic granules
b) sulfation
► Secretion of ground substance matrix and
soluble collagen pecursors, tropocollagen .

► Formation of collagen fibrils which serve as
matrix for calcification.
► Alteration of mineral salts, calcium
phosphate is absorbed to form initial
predentin which acts as a nidus for hydroxy
apatite crystal formation.


► Sclerotic, Reactive and
Eburnated dentin.
► Sclerotic dentin results from
aging or mild irritation and
causes a change in the
composition of the primary
dentin.
► Sclerosis resulting from aging is
physiologic dentin sclerosis;
sclerosis resulting from mild
irritation is reactive dentin
sclerosis.
► Eburnated dentin refers to
outward portion of reactive
sclerotic dentin ,where slow
caries has destroyed formally
overlying tooth structure,
leaving a hard, darkened,
cleanable surface.

DEAD TRACTS
► In dried ground sections of normal dentin
the odontoblast processes disintegrate and
the empty tubules are filled with air. They
appear black in transmitted and white in
reflected light.
► loss of odontoblast processes may also
occur in teeth containing vital pulp as a
result of caries ,attrition ,abrasion, cavity
preparation or erosion.

► Their degeneration is often observed in the
area of narrow pulpal horns because of
crowding of odontoblasts.
► Again, where ever reparative dentin seals
dentinal tubules, at their pulpal ends.
dentinal tubules are filled with fluid or
gaseous substances.
► These areas demonstrated decreased
sensitivity and appear to a greater extent
in older teeth.

DEAD TRACTS


GRANULAR LAYER OF TOMES
► When dry ground sections
of the root dentin are
visualized in transmitted
light there is a zone
adjacent to the cementum
that appears granular. This
is known as (Tomes)
granular layer.
► This zone increases slightly
in amount from the
cementoenamel junction to
the root apex and is
believed to be caused by a
coalescing and looping of
the terminal portions of the
dentinal tubules.

► The cause of development of this zone is
probably similar to the branching and
beveling of the tubules at the
dentinoenamel junction.
► In any case the differentiating odontoblast
initially interacts with ameloblasts or the
root sheath cells through the basal lamina.
► In the crown, extensive branching of the
odontoblast process occurs and in the root
there is branching and coalescing of
adjacent processes.

INCREMENTAL LINES OF
VON EBNER
•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 and
correspond to the incremental
lines in enamel or bone.
•These lines reflect the daily
rhythmic recurrent deposition
of dentin matrix as well as the
daily formative process.

► The distance between lines varies form 4 to 8
μm in the crown to much less in the root .
► The daily increment decreases after a tooth
reaches functional occlusion. The course of
the lines indicates the growth pattern of the
dentin.
► Occasionally some of the incremental lines
are accentuated because of distrubacnes in
the matrix and mineralization process. Such
lines are readily demonstrated in ground
sections and are know as contour lines
(Owen).


INTERGLOBULAR DENTIN
► 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 known as
interglobular dentin.
► Interglobular dentin
formed in the crowns of
teeth is the circumpulpal
dentin that lies just below
the mantle dentin and it
follows the incremental
pattern. www.indiandentalacademy.com

► The dentinal tubules pass uninterruptedly
through interglobular dentin thus
demonstrating a defect of mineralization and
not of matrix formation.
► In dry ground sections some of the
interglobular dentin may be lost and a space
results that appears black in transmitted
light.
► However spaces in interglobular dentin are
not believed to occur naturally.


DENTINAL TUBLES
► The course of dentinal
tubules follows a gentle
curve in the crown, less so
in the root where it
resembles `S` in shape.
► Starting right angle form
pulpal surface, first
concavity of this doubly
curved course is directed
toward the apex of tooth.
► Perpendicular to DEJ and
DCJ www.indiandentalacademy.com

► Near the root tip and along the incisal edges
and cusps the tubules are almost straight.
► Over the entire lengths, the tubules exhibit
minute ,relatively regular secondary
curvatures ,that are sinusoidal in shape.


► The ratio between the outer and inner
dentin surface is about 5:1
► Accordingly, the tubules are farther apart in
the peripheral layers and more closely
packed near the pulp.
► Larger in diameter near pulp cavity (3-
4μm) and smaller at their outer ends (1μm).


► The ratio between number of tubules per
unit area on the pulpal and the outer
surface of dentin is about 4:1
► Near the pulpal surface of the dentin ,the
number per sq mm varies from 50,000 and
90,000.
► More tubules per unit area are in crown
than in roots.


PERITUBULAR DENTIN


Dentin that immediately surrounds the
tubules.
Twice thicker in outer dentin (0.75 μm) than
in inner dentin (0.4 μm) .
More highly mineralized (about 9%) than
intertubular dentin.


By its growth it constricts the
dentinal tubules to a diameter of
1μm near the DE junction. In
decalcified dentin, visualized with
a light microscope, tubule diameter
will therefore appear similar in
inner and outer dentin because of
the loss of peritubular dentin.


INTERTUBULAR DENTIN
Main body of dentin is composed of
intertubular dentin.
Located between the dentinal tubules or
more specifically between the zones of
peritubular dentin.
Although it is highly mineralized this
matrix like bone and cementum is retained
after decalcification whereas peritubular
dentin is not.

About half of its volume is organic
matrix specifically collagen fibers
which are randomly oriented around
the dentinal tubules.
Fibrils range from (0.5 to 0.2μm)
diameter and exhibit cross banding at
64nm (640 A°) interval which is typical
for collagen.
Hydroxyapatite crystals which average
0.1μm in length are formed along the
fibers with their long axes oriented
parallel to collagen fibers.

PROPERTIES OF DENTIN
PHYSIOLOGICAL PROPERTIES
Dentin is softer than enamel but harder than
bone. It becomes harder with age, due to its
mineral content.
It is some what flexible despite being hard, its
modulus elasticity being 1.67 X 10^6 PSI.
The Tenstile strength is apprx.40 Mpa.
The compressive strength of dentin is 266
Mpa.

CHEMICAL PROPERTIES
Inorganic material - 70%
Organic material - 20%
Water - 10%
Inorganic component mainly consist of
hydroxyapatite crystals.
Unit formula - 3ca3 (po4)2 , ca(OH)2
Crystals are plate shaped slightly smaller
than the hydroxyapatite crystals of
enamel.

Organic substance consists of
collagenous fibrils and a ground
substance of mucopolysaccrides
(proteoglycans &
glysosaminoglycans).
organic & inorganic substances can
be separated by decalcification or
incineration.

INERVATION OF DENTIN


Dentinal tubules contain numerous nerve
endings in the predentin and inner dentin no
farther than 100 to 150μm from the pulp.
Most of these small vesiculated endings are
located in tubules in the coronal zone
specifically in the pulp horns.
The nerves and their terminals are found in
close association with the odontoblast
process within the tubule.
The primary afferent somatosensory nerves of
the dentin and pulp project to the main
sensory nucleus of midbrain.

THEORIES OF PAIN TRANSMISSION
THROUGH DENTIN

Direct neural stimulation theory.
Fluid or Hydrodynamic theory.
Transduction theory.


DIRECT NEURAL
STIMULATION THEORY

The first is that of direct neural
stimulation meaning that stimuli in
some manner as yet unknown reach the
nerve endings in the inner dentin. There
is little scientific support of this theory.


FLUID or HYDRODYNAMIC
THEORY
The second most popular theory is the fluid or
hydrodynamic theory.Various stimuli such as
heat, cold, air blast desiccation, or mechanical
pressure affect fluid movement in the dentinal
tubules. This fluid movement either inward or
outward stimulates the pain mechanism in the
tubules by mechanical disturbance of the nerves
closely associated with the odontoblast and its
process. Thus these endings may act as
mechanoreceptors as they are affected by
mechanical displacement of the tubular fluid.

TRANSDUCTION THEORY

The Third theory is the transduction
theory, which presumes that the
odontoblast process is the primary
structure excited by the stimulus and
that the impulse is transmitted to the
nerve endings in the inner dentin.


AGE AND FUNCTIONAL
CHANGES
Since the odontoblast and its process are
an integral part of the dentin there is no
doubt that dentin is a vital tissue ,again,
if vitality is understood to be the
capacity of the tissue to react to
physiologic and pathologic stimuli dentin
must be considered a vital tissue.


► Dentin is laid down throughout life.
although, after the teeth have erupted and
have been functioning for a short time.
Dentinogenesis slows and further dentin
formation is at a much slower rate.
► Pathologic effects of dental caries, abrasion,
attrition or the cutting of dentin or operative
procedures cause changes in dentin. The
formation of reparative dentin pulpally
underlying an area of injured odontoblast
processes can be explained on the basis of
increased dentinogenic activity of the
odontoblast.

CLINICAL
CONSIDERATIONS
One should bear in mind that when 1 mm
of dentin is exposed about 30,000 living
cells are damaged.
It is advisable to seal the exposed dentin
surface with a nonirritating insulating
substance.
The rapid penetration and spread of caries
in the dentin is the result of the tubule
system in the dentin.

The dentinal tubules form a passage for
invading bacteria that may thus reach the
pulp through a thick dentinal layer.
Electron micrographs of carious dentin show
regions of massive bacterial invasion of
dentinal tubules. The tubules are enlarged by
the destructive action of the microorganisms.
Dentin sensitivity of pain unfortunately may
not be a symptom of caries until the pulp is
infected and responds by the process of
inflammation leading to toothache.

Undue trauma from operative instruments
also may damage the pulp air-driven
cutting instruments,cause dislodgement of
the odontoblast form the periphery of the
pulp and their “aspiration” within the
dentinal tubule.
The sensitivity of the dentin has been
explained by the concept that alteration
of the fluid and cellular contents of the
dentinal tubules causes stimulation of the
nerve endings in contact with these cells.

This theory explains pain throughout
dentin since fluid movement will occur
at the dentinoenamel junctions well as
near the pulp.
Because we know that reparative dentin
stimulates cavity lining materials and
that dentin forms throughout the life of a
tooth it is now possible to save teeth
that previously were lost by extraction
or treated by endodontic therapy.

Again teeth with deep penetrating carious
lesions can be treated by only partial removal
of carious dentin and insertion of a “dressing”
containing calcium hydroxide for eg , for a
period of a few weeks or months
During this period the odontoblasts form new
dentin along the pulpal surface underlying the
carious lesion and the dentist can then reopen
the cavity and remove the remaining bacteria-
laden decay without endangering the pulp.
This treatment is termed indirect pulp capping.


DENTIN PERMEABILITY

The chemical irritation of the P-D Organ
results from the diffusion of irritating
agents through the dentin.
Dentin permeability differs from one
person to another from one tooth to
another and from one area of a tooth to
another area of the same tooth.


Factors governing Dentin
Permeability
► Type of dentin from lowest to highest
permeability are Calcific barrier dentin, Sclerosed
dentin, Primary dentin, Secondary dentin, Tertiary
dentin, Globular dentin, Granular dentin &
Deadtract dentin.
► Types and nature of penetrants- Plaque acids &
highly dissociable acids penetrate quickly.
Salivary ions penetrate dentin dependent upon
their molecular cells. Calcium & Fluoride can
penetrate dentin but reaction product will
decrease dentin permeability.

The other factors governing
Dentin Permeability…
► Degree of mineralization of dentin
► Dentin exposed during tooth preparation
► Effective depth
► Induced stresses
► Hydraulic pressure
► Deficient resistance and retention form
► Microleakage
► Cracks & Microcracks in the dentin
► Type of intermediary base or restorative material
► Desiccation of dentin


REACTION OF BASES ON
DENTIN
After removing the diseased tissues and
completing the tooth preparation it is
necessary to prevent irritation of the pulp
dentin organ this is accomplished by
intermediary basing.
Zinc oxide & Eugenol, Calcium hydroxide,
Zinc phosphate cement & Polycarboxylate
cement are the bases used.


Reaction of Zinc Oxide &
Eugenol On Dentin
ZOE is the least irritating to the pulp dental organ
of all intermediary base materials. Whenever there
is any effective depth between the unmodified ZOE
and the pulp tissues the pulpal reaction will be a
healthy reparative reaction provided the pulp is
healthy. The underlying pulp dentin organ will
have odontoblastic activity stimulated, increasing
the dimensions of the peritubular dentin
peripherally (sclerosed dentin) and depositing
secondary dentin.


Reaction of Calcium
Hydroxide on Dentin
It can be an irritant to the P-D organ, if it comes
in contact with it.
Whenever there is a effective depth of
100micrometers, a healthy reparative reaction
happens. With less than 100 microns effective
depth, unhealthy reparative reaction takes place.
When calcium hydroxide comes in contact with
the pulp directly it will undergo chemical necrosis.


Reaction of Zinc Phosphate
Cement on Dentin
Zinc phosphate cement is the most irritating of
the all the intermediary base materials.
At an effective depth of 2.5mm and above zinc
phosphate cement will create a healthy
reparative reaction.
At effective depth of 1.5-2.5mm unhealthy
reparative reaction occurs.
At effective depth less than 1.5mm there will
always be a destruction in the pulpal tissue.

Reaction of
Polycarboxylate Cement on
Dentin
It is a minimally irritating base to the P-D
Organ.
With effective depth of 1mm and above
healthy reparative action occurs.
Whenever effective depth is less than 1mm
unhealthy reparative reaction takes place.
When the material comes in contact with
the pulp destruction occurs.

DENTIN HYPERSENSITIVITY
Dentin hypersensitivity is a common condition
of transient tooth pain associated with a
variety of exogenous stimuli.
There is substantial variation in the response to
such stimuli from one person to another.
Except for sensitivity associated with tooth
bleaching or other tooth pathology, the clinical
cause of dentin hypersensitivity is exposed
dentinal tubules as a result of gingival recession
and subsequent loss of cementum on root
surfaces.

The most widely accepted theory of how
the pain occurs is Brännström's
hydrodynamic theory of dentin
hypersensitivity.
Dentinal hypersensitivity must be
differentiated from other conditions that
may cause sensitive teeth prior to
treatment.


Three principal treatment strategies are used.
Dentinal tubules can be covered by gingival
grafts or dental restorations.
 The tubules can be plugged using compounds
that can precipitate together into a large
enough mass to occlude the tubules.
The third strategy is to desensitize the nerve
tissue within the tubules using POTASSIUM
NITRATE. Several over-the-counter products
are available to patients to treat this
condition.

BONDING OF DENTIN
► Dentin bonding is comparatively difficult
because of the fact that dentin is a complex
tissue and contains plenty of fluids.
► Along with chemical issue of adhesion,
biologic concern on pH, pulpal compatibility
becomes exceedingly important when dentin is
concerned.
► The successful bonding of a resin composite to
dentin includes micromechanical attachment
between resin and demineralized, primed
surface layer of intertubular dentin (Hybrid
Layer).

Chemical conditioning – (15 secs)
 37% phosphoric acid used usually
 Other acids which can be used
-Maleic acid, citric acid, nitric acid, oxalic
acid, pyruvic acid, HCl.
Objective :-
• To remove smear layer
• Simultaneously demineralizing superficial
dentin of 3 - 7µ ms to expose a microporous
collagen in which resin will penetrate.


DYNAMICS OF DENTIN
BONDING
ROLE OF PRIMER:
The dentin being a hydrophilic, the
composite a hydrophobic,intermediate between
both groups a Primer is essential. The primer
HEMA(hydroxy ethamethyl acrylate)has both
hydrobphoic and hydrofillic group to achieve
bonding.
The next is Adhesive Resin which is applied
after the application of primer.


Factors affecting the
interaction of dentinal
permeability & monomer
diffusion
Collagen Fibril Network
The resin monomers penetrate acid-
etched collagen fibrils via spaces that can
swell or shrink depending on bonding
conditions. This nearly molecular level of
enlargement of resin polymer with biologic
polymer (i.e, Collagen Molecules) may be
responsible for resin bonds collagen

Noncollagenous Proteins
They are distributed along the
collagen fibrils (constituting about 10% of
protein content of the dentinal matrix)
which are highly charged molecules that
bind large amounts of water in
dematerialized dentin. The combination of
collagen and noncollagenous proteins
with large amounts of water, may create a
matrix that is a hydrogel, these hydrogels
may serve to maintain the hydration of
wet substrate.

Primer Solubility
Some hydrophilic monomers, such
as HEMA, are extremely soluble in either
water or acetone. On the substrate side of the
applied solution, the uptake of monomer by
demineralized dentin depends on the size of
the spaces between the collagen fibrils and
on the depth that it must diffuse from the
surface. In a air-dried dentin the
permeability of that dentin to monomer
would be very low but wet demineralized
dentin exhibits high permeability.

Fluid Flow
After priming, the dental surfaces
should be uniformly shiny, but there are
regions of high permeability that are in
direct communications with pulp may
appear dull due to its high tubule density
and high water content. Such regions may
be difficult to dehydrate. With multiple
applications of primers these tubules may
become sufficiently occluded with resin
monomers to block further diffusion of
water from the pulp.

Tubular Branching
Most tubules contain multiple
lateral branches that radiate 2-6mm from
the lumen. These small branches provide
another root for monomer filtration of
hybrid layers this would be classified as a
form of inter tubular dentinal
permeability.


The Smear layer:
being an obstacle !
► When the tooth surface is
altered by rotary and
manual instrumentation
during cavity preparation,
the cut debris is smeared
over enamel and dentin
surfaces called the smear
layer, it reduces the
dentinal permeability by
86%, it is important to
remove the layer.
► Total etch or unietch is the
commonly used etchent.


Mechanism of bonding the
dentin
Acid etching of the dentin
Increase of transdentinal permeability
Mineral content removed in intertubular
dentin (aprox. 2-7 microns)
Formation of resin tags and hybrid layer.
The resin tags and hybrid layer form the
major contributors for a good dentin
bonding.

Under ideal conditions, hybrid layer
formation would be the major bonding
mechanism in superficial dentin as the
presence of dentinal tubules in this area is
less and gives a less significant credit to
resin tags but in deep dentin, the resin tags
would contribute most of the bond strength
as the tubules become larger and closer.

The diffusivity of the monomers also play a
major role in bond strength. The substrate
(dentin) with high permeability and the resin
with high diffusivity make up an ideal
combination.

DENTINAL CARIES
► One of the basic steps in restorative
operative procedure is the removal of
carious dentin.
► Carious dentin consist of two layers such
as outer & inner layer.
► Outer layer is the infected dentin which has
bacteria and it cannot be remineralized.
► Inner layer is the affected dentin which has
no bacteria and can be remineralized.

ZONES OF DENTINAL CARIES

AFFECTED DENTIN:
 Zone 1- Normal dentin
 Zone 2- Sub-transparent dentin
 Zone 3- Transparent dentin

INFECTED DENTIN:
 Zone 4- Turbid dentin
 Zone 5- Infected dentin

Zone 1-Normal dentin

►Smooth tubule with odontoblastic
process
►No crystals in lumen
►Stimulation produces sharp pain


Zone 2- Sub-Transparent
dentin

►Zone of demineralization
►Damage to odontoblastic process is
evident
►No bacteria found
►Capable of remineralization
►Stimulation produces pain


Zone 3- Transparent
dentin
► Softer then normal dentin
► Loss of mineral is more
► Many large crystals are present in the dentinal
tubules
► Stimulation produces pain
► No bacteria present
► Organic acid attack both mineral and organic
content of dentin the collagen cross linking
remain intact. This intact collagen serves as a
template for remineralization.
► This region is capable of self repair provided
pulp remain vital (kantor et al, 1989)

Zone 4- Turbid dentin

► Zone of bacterial invasion , marked by
Widening and distortion of dentinal
tubule which are filled with bacteria .
► very little mineral present .
► Collagen irreversibly denatured .
► Not capable of self repair.
► Must be removed prior to restoration.


Zone 5- Infective dentin
► This is outer most zone.
► Decomposed dentin.
► Many bacteria present.
► Absence of collagen and mineral.
► Removal is essential to sound successful
restoration procedure as well as
prevention of spreading the infection.


DEVELOPMENTAL
DISTURBANCES OF DENTIN

Dentinogenesis imperfecta (Hereditary
opalescent dentin).
Dentin dysplasia (Root less teeth).
Regional Odontodysplasia (Odontogenic
imperfecta, odontogenic dysplasia, ghost
teeth).


Dentin Hypocalcification .
Dens in dente(Dens invaginatus,
dilalated composite odontome).
Dens evaginatus (Occlusal enamel pearl
evaginated odontome) , leong’s
premolar, occlusal tuberculated
premolar.


DENTINOGENESIS IMPERFECTA
CLASSIFICATION
► TYPE 1-Dentinogenesis imperfecta(DI) that
always occurs in families with osteogenesis
imperfecta (OI) although the latter may
occur without dentinogenesis imperfecta.
► TYPE II-Dentinogenesis imperfecta that
never occurs in association with (OI) unless
by chance. This type is the one most
frequently referred to as hereditary
opalescent dentin.

► TYPE- III-Dentinogenesis imperfecta of
the “Brandywine type”. This is a racial
isolate in Maryaland with this unusual
form of DI characterized by the same
clinical appearance of the teeth as types I
and II but also by multiple pulp exposures
in deciduous teeth, a characteristic not
seen in types I or II.


DENTIN DYSPLASIA
Classification (witkop)
► Type I - Radicular dentin dysplasia
 Normal Morphologic appearance and color
(clinically).
Roots are short blunt conical or similarly
malformed.
 Pulp chamber and root canal completely
obliterated .
► Type II - coronal dentin dysplasia
 Thistle tube appearance (Radiagraphically )-
Exhibit an abnormally large pulp chamber in the
coronal portion of the tooth.

REGIONAL ODONTODYSPLASIA
► Delay or total failure in eruption
► Shape markedly altered - irregular
► X Ray- Ghost appearance
► Pulp chamber - Extensively large

Dentin hypo calcification
•This is due to failure in union of
dentinal globules leaving
interglobular areas of uncalcified
matrix

► Dens in dente
►Result of an invagination in the surface of
a tooth crown before calcification has
occurred
►Most affected - Permanent maxillary
lateral incisor
► Dens evaginatus - Appears clinically as an
accessory globule of enamel on the occlusal
surface between the buccal and lingual cusps of
premolar.
► Proliferation and evagination of an area of
inner enamel epithelium and subjacent
odontogenic mesenchyme into the dental organ
during early tooth development.

CONCLUSION
Dentin can remove 99.8% of a bacterial suspension
of streptococci that are approx. 0.5 microns, which
tend to prevent infection of the pulp even when
patients masticate on infected carious dentin. This
phenomenon is why there are no bacteria in the
tubules at the extreme front of the carious attack.
The structure and function of the dentin pulp organ
always sees that the tooth remains sound and
functional.


REFERENCES
ORAL HISTOLOGY – DEVELOPMENT &
EMBRYOLOGY(RICHARD TEN CATE)
ORBAN`S ORAL HISTOLOGY AND EMBRYOLOGY
(S.N.BHASKAR)
ART AND SCIENCE OF OPERATIVE
DENTISTRY(STURDEVANT)
RESTORATIVE DENTAL MATERIALS (ROBERT G
CRIAG &JOHN M POW ER)
TEXT BOOK OF ORAL PATHOLOGY (SHAFER)
ORAL HISTOLOGY COLOUR ATLAS (AVERY)
Hybridization of dental hard tissues (nobuo
nakabayashi)
Operative dentistry, Modern theory & practice
(M.A.Marzouk)
Dental Pulp ( Scltzer & Bender)
www.cwrv.edu/.../teeth/dentin/overview.htm

Thank You!


Dentin /certified fixed orthodontic courses by Indian dental academy

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