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Dr Jamal NaimPhD in Orthodontics
Tissue of the teethDentin-Pulp
Complex
Introduction
• Dentin and pulp are related embryologically,
histologically and functionally.
• Dentin is a hard connective tissue and the
Pulp is a soft one.
• Dentin forms the bulk of the tooth.
• It is covered by cementum at the root
portion and by enamel at the crown portion.
Properties of dentin
• Bonelike 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
Compositions 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
Life cycle of odontoblasts
There are only 3 stages in the life cycle of
odontoblasts:
• Differentiating stage
• Formation stage
• Quiescent stage
Life cycle of odontoblasts
Differentiating stage:
Before Differentiation, the inner dental
epithelium is separated from the dental
papilla by the thin basement membrane.
The undifferentiated peripheral cells are
spindle and separated by great amount of
ground substance
Life cycle of odontoblasts
Differentiating stage
Undifferentiated cell
Basement membrane
Preameloblast
Life cycle of odontoblasts
Differentiating stage:
In the late bell stage, under the inductive
influence of the inner dental
epithelium, the peripheral
ectomesenchymal cells differentiate
into preodontoblasts.
In the late bell stage the UMC differentiate to preodontoblasts
Differentiating stage
preodontoblast
Undifferentiated cell
Basement membrane
Ameloblast
Late Bell stage/differentiating stage for odontoblasts
Life cycle of odontoblasts
• They assume to a columnar shape and
aligned as a single row along the
basement membrane.
• Several projections arise from the
upper part of the cells.
Life cycle of odontoblasts
• The nuclei become basally oriented.
• The cells grow in length to become
columnar (40u)
• Now the fully differentiated
odontoblasts begin their work.
Life cycle of odontoblasts
Formative stage:
• Concentration of the cell organelles,
granular components and globular
elements
• Production of the dentin matrix
• The odontoblasts retreat from the
basement membrane
Life cycle of odontoblasts
Formative stage:
• Leaving a single process which
become enclosed in the dentinal
tubule (Tomes fiber).
• With successive deposition of dentin,
tubule and process grow in length.
Life cycle of odontoblasts
Differentiating stage/Begin of formative stage
odontoblast
Undifferentiated cell
predentin
Formative stage
Formative stage
NucleusRERMitochondrion
predentin
Formative stage
Dentin
Life cycle of odontoblastsQuiescent stage:• Actively secreting odontoblasts decrease
slightly in size.• The odontoblastic process stop to elongate• In this stage the odontoblasts produce only
secondary dentin.
Life cycle of odontoblasts
Quiescent stage:
• Odontoblasts decrease in size and
function
• The dentin formation is reduced
• They produce now secondary and
tertiary dentin
Dentinogenesis
1. Matrix Formation (forming predentin)
2. Maturation(mineralization)
a. Collagen fibers
b. Ground substance
Hydroxyapatite crystallites
Dentinogenesis
Formation of predentin (dentin matrix):
1. The first indication of forming predentin is
the development of the KORFF FIBERS.• They are bundles of fibrils among the
odontoblasts.
• They are perpendicular to the basement
membrane and attached to it.
• This layer is main part of the MANTLE DENTIN
MANTLE DENTINKorffs fibers are perpendicular to the basement membrane
TOMES FIBER
Basement membrane
Dentinogenesis
2. The korffs fibers fade gradually and smaller
fibrils form a network in the dentin
subsequent to the mantle dentin, the
circumpulpal dentin.
The odontoblasts form the main components of
the dentin matrix:• the collagen fibers and • the mucopolysaccharides.
MANTLE DENTIN
CIRCUMPULPAL DENTINfibers are parallel to the DEJ
TOMES FIBER
Basement membrane
Dentinogenesis Maturation of predentin:• It occurs parallel to matrix formation• It begins at the tip of the crown• It proceeds in a rhythmic pattern to gradually
complete cervically.• The first layer of predentin begins its maturation
in a globular pattern (matrix vesicle), where
small centers of calcification spread
concentrically until they fuse together.
Dentinogenesis • If somewhere those globules do not fuse together,
areas of uncalcified dentin are known as
interglobular dentin.• The maturation goes then in linear or occasionally
globular pattern.• The mineralization begins by crystal deposition in
form of fine plates of hydroxyapatite on the surface
of the collagen fibrils.• The long axes of the crystals are paralleling to the
fibrils.
MANTLE DENTIN
CIRCUMPULPAL DENTIN
Matrix vesicle
Rupture of the MV and begin of mineralization
Mineralized MD
Maturation of dentin
Matrix vesicle
Rupture of the MV and begin of mineralization
Maturation of dentin
Begin of Crystallization
Crystal lodgment
Types of dentin
• Primary (physiological formed) dentin
• Secondary (physiological formed)
dentin
• Tertiary (reparative, irregular
secondary) dentin
Mantle dentin
Circumpulpal dentinTertiary (irregular secondary) dentin
regular secondary dentin
Enamel
Primary dentin
• All of dentin formed before root
formation has been completed is
Primary dentin.
• Physiological formed primary Dentin is
composed of:• Mantle dentin &
• Circumpulpal dentin
Histological structure of dentin
• Odontoblasts & their process
• Dentinal tubules (canals)
• Peritubular dentin
• Intertubular dentin
• Interglobular dentin
• tome's granular layer
Pulp
Circumpulpal dentin
Pulp
predentinOdontoblast
s layer
Oral Histology, 5th edition, A R Ten Cate©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl
Odontoblasts & their process
Odontoblasts & their process
• Odontoblasts are specialized in dentin forming
(primary, secondary or tertiary).• arranged in a well defined layer Adjacent to the
pulpal end of dentin.• Every cell has one process (tomes fiber) that
traverse dentin to reach the D.E.J and the C.D.J.• Adjacent to enamel and cement the
odontoblastic process ends by formation of
several terminal branches.
Odontoblasts & their process
• It is about 5000 µm long.• The process is about (4-5 µm) thick.• It becomes smaller in predentin (1-3 µm)
and more smaller in mineralized dentin
(0.5-2.0 µm).• They have several smaller branches
(terminal branches), that fuse with the
adjacent processes terminal branches.
Dentin
Predentin
odontoblasts
Dentinal Tubules
terminal branches
Odontoblastic processes
DEJ
Dentinal tubules
• They are s-shaped in the crown-dentin
and more straight in the root-dentin.• They have lateral branches (canaliculi)
enclosing the terminal branches.• The density of the tubules is higher at
the pulpal end of dentin (64000 DT/mm2)
than at the D.E.J (16000 DT/mm2).
Dentinal tubules
• The diameter of the DT at the D.E.J. is
smaller than at the pulpal end of
dentin.• The density decreases also from
coronal toward apical dentin.
S-shaped Dentinal tubules
Dentinal Tubules
Odontoblastic process (tomes fiber)
periodontoblastic space
Peritubular dentin• It is the layer of dentin surrounding
the dentin tubules• It is highly mineralized more
homogenous than intertubular dentin• It has less than 20% of its volume an
organic matrix, so it has higher x-ray opacity than intertubular dentin
• Its thickness varies according to age (thicker in old dentin) and location.
Peritubular dentin
Peritubular dentin
(Neumann sheath)
Intertubular dentin• It is the sum of dentin between the
dentin tubules• It is less mineralized and less
homogeneous than PTD• It has more than 50% of its volume an
organic matrix, so it has less x-ray opacity than peritubular dentin
• The collagen fibrils surround the tubule and form a network between them
Intertubular dentin
Odontoblastic process (tomes fiber)
Peritubular dentin
(Neumann sheath)
Mantle dentin
Circumpulpal dentin
Mantle dentin• It is the first formed layer of dentin and is about
30 µm thick.• It is less mineralized than circumpulpal dentin• The difference between it and CPD in ground
sections is the direction of the collagen (korff´s)
fibrils. They are rectangular to the dentino-
enamel or cemento-enamel junction • It hasn’t growth lines (von Ebner lines) like CPD
Mantle dentin• In ground section D.E.J. and C.D.J
appears as scalloped line. There is more irregularity in the cusp and crown area.
D.E.J. and C.D.J
Dentin
CementEnamel
Dentin
Incremental lines of von Ebner
• Like the lines of Retzius in enamel, the incremental lines of von Ebner show the growth pattern and the daily deposition of dentin.
• They are hypomineralized lines of dentin and corresponds the rest of odontoblasts.
• The distance between them varies from 3-20 µm.
• They run in rectangular direction to the dentin tubules
Contourline of Owen• If any thing (disease, fever etc.) disturbs
the dentin development, the lines of von
Ebner are wider and less mineralized. They
are called then contourlines of Owen.• The best known contour lines of Owen is
the neonatal line.• It corresponds the first weeks of a baby
life, because of the change of nutrition.
Owen contourlines
neonatal line
Interglobular dentin• The mineralization of dentin runs in
globular pattern• If the globules doesn’t fuse completely
together, the hypomineralized dentin among them is known interglobular dentin.
• Those areas follow the course of the von Ebner lines.
• The tubules in those areas hasn’t peritubular dentin
Tome's granular layer
• Black spaces in the ground section
adjacent to the CDJ, so only in the root
mantle dentin• They are also hypomineralized areas of
dentin, but smaller the interglobular
dentin• They doesn’t follow the lines of von
Ebner.
Granular layer of Tomes
Dentin (with tubules)
©Copyright 2007, Thomas G. Hollinger, Gainesville, Fl
Tome's granular layer
cementum
Granular Layer of Tomes
enamel
dentin
cementum
Interglobular dentin Tome's granular layer
Size: large
Areas of hypo-mineralized dentin
In crown and root dentin
Follows incremental lines
Size: small
Areas of hypo-mineralized dentin
Only in mantle root dentin
Doesn’t follow incremental lines
Age and functional changes
1. Physiologic regular secondary dentin2. Pathologic irregular secondary dentin3. Transparent (sclerotic) dentin
Physiologic regular secondary dentin
Secondary D
Primary D
Physiologic regular secondary dentin
• This is the type of dentin formed under Physiologic conditions after complete root formation.
• It is deposited continuously as long as the pulp is vital.
• It is formed at a lower rate and is separated by a darkly stained line from primary dentin
• It has less number of tubules.• It occurs in the entire pulpal surface.• Higher deposition at the roof and floor of the
pulp chamber.
Physiologic regular secondary dentin
CPD
Reparative D
CPD
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
Pathologic irregular secondary dentin
• It is also known as tertiary or reparative dentin
• This type of dentin is formed as a protection for the pulp against severe stimulus (pathological conditions or irritations), such as
• Attrition• Caries• Preparations
• It is formed at a localized area (e.g. pulp horn) • Some UMC in the subodontoblastic layer
differentiate to new odontoblast to form dentin.
Pathologic irregular secondary dentin
• The number of the tubules is reduced.
• Tertiary dentin has frequently twisted tubules
• Some areas doesn’t contain tubules
• Reparative dentin is separated from other types by a darkly stained line.
Pathologic irregular secondary dentin
Tertiary dentin
secondary dentin
Types of reparative dentin• Osteodentin: The odontoblasts (cells) are
included in the formed dentin
Types of reparative dentin• Atubular dentin: areas without tubules
Types of reparative dentin• Vasodentin: entrapped blood vessels
Types of secondary dentinRegular
Cause: mild stimuli (slow attrition, slowly progressing caries)
Site of formation: entire pulpal surface (thicker on pulp roof and floor)
Tubules: wavy course, decrease in number
irregularCause: severe stimuli,
severe attrition, erosion, deep caries,
Site of formation: located (eg pulp horn)
Tubules: wavy and twisted course, decrease in number or atubular
Types of secondary dentinRegular
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.
IrregularLine of demarcation:
stain dark
Clinically:Functions as a barrier
for against caries.
Transparent (Sclerotic) dentin• Sclerotic dentin can be seen as physiological
change (elderly dentin) or pathological change (caries, attrition, deep fillings, ) in primary or secondary dentin.
• Partial or complete obliteration of the dentin tubules, at first thickining of peritubular dentin, then complete obliteration of the tubules with intertubular d.
• Higher mineralized, harder and denser than normal dentin
• Appears light in transmitted light and dark in reflected light.
Transparent (Sclerotic) dentin
Young dentin
Adult dentin Sclerotic dentin
Transparent (Sclerotic) dentin
Dead tracts• Severe stimulation to dentin leads to
destruction or disintegration of the odontoblastic process and odontoblasts.
• The dentin tubules are empty and filled with air.
• Most often in areas of narrow pulp horns due to odontoblastic crowding. In ground section they appear black.
• Often surrounds with sclerotic dentin.
Dead tracts
Dead tracts
Dead tracts
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:
The transducer theory, the conduction theory, the modulation theory the Brännström's hydrodynamic 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 transducer theory
The transducer 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 ro 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.
The conduction theory
The conduction theory
Some authors contend that those fibers end at the 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 conduction theory
The hydrodynamic 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 hydrodynamic theory
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
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 'mechano-receptor'.”
Vitality and sensitivity of dentin
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