dr jamal naim phd in orthodontics tissue of the teeth dentin-pulp complex

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


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

Differentiating stage

Undifferentiated cell

Basement membrane

Preameloblast


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


Basement membrane

Ameloblast

Late Bell stage/differentiating stage for 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.


• The nuclei become basally oriented.

• The cells grow in length to become

columnar (40u)

• Now the fully differentiated

odontoblasts begin their work.


Formative stage:

• Concentration of the cell organelles,

granular components and globular

elements

• Production of the dentin matrix

• The odontoblasts retreat from the

basement membrane


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.


Differentiating stage/Begin of formative stage

odontoblast


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.


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 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.


• 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


• 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.


CPD

Reparative D

CPD


• 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.


• 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.


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

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

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 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 movement stimulates intradentinal nerve receptors sensitive to pressure (BARORECEPTORS), which leads to the transmission of the stimuli .

This simulation generates pain.


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

dr jamal naim phd in orthodontics tissue of the teeth dentin-pulp complex

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