Dentin

Physical Physical

propertiesproperties

Chemical CompositionChemical CompositionInorganic phase

Organic phase

Development (genesis):Development (genesis):Forming cells: (life history)

Matrix formation (protein

synthesis)

Calcification (mineralization)

Ultra-structure: Ultra-structure: Structural unit-Regional variation

Incremental linesIncremental linesAge changes ‹Clinical

consideration

Histological Study of Hard Dental Tissues:

Methods of StudyingMethods of Studying ” ”hard tissueshard tissues””

GROUND SECTIONGROUND SECTION DECALCIFIED SECTIONDECALCIFIED SECTION

Inorganic part Organic part

DentinDentin::

☻☻ Forms Dentin-Pulp ComplexForms Dentin-Pulp Complex

Specialized calcified C.T. forms the main bulk of the tooth☻☻In crown it In crown it

is covered is covered by enamelby enamel

☻☻In root it is In root it is covered by covered by cementumcementum

COLOR : YELLOWISH

HARDNESS: less than enamel, but more than cementum and boneELASTICITY:highly elastic

PERMEABILITY: Semi permeable in both directions(to & from the pulp)

Physical Properties of Dentin:

Organic:• 20% organic

• 10% water

CHEMICAL COMPOSITION OF DENTIN:

70% 30%By weight:

Inorganic: “Hydroxyapatite

crystals” Ca 10(PO4)6 (OH)2

Collagen – 90%Phos.pr. – 8%Pospho-lip.Ground.sub – 2%

Histological Structure Of Histological Structure Of DentinDentin

Odontoblasts

Predentin

Dentin

Dentinal tubules

Histological Histological StructureStructure dentina

l tubulespulp spac

eS- shaped curvature

Dentinal

tubules

Inter-tubular

dentin Peritubula

r dentin

Closely packed dentinal Closely packed dentinal tubulestubulesenclosed within &

surrounded by

Inter-tubular dentinInter-tubular dentinInterwoven network of collagen type I

fibrils in which apatite crystals are deposited

Surrounded byHypermineralized rings

Dentinal Dentinal TubulesTubulesCoursCours

eePrimary curvatur

e

S- shaped

curvature

Secondary

curvature

Dentinal Dentinal TubulesTubules

NumbeNumberrNo. / unit area

75,000Pulpal side : peripheral

layer 4 : 1

DiametDiameterer D.T. taper from pulpal surface outwardsClosely packed near the pulp than

in the peripheral layer

BranchBrancheses lateral

branchesterminalal branches

ContentContent

Near peripheral

surface

Amorphous non cellular material

Intermediate dentin

Odontoblastic

process,orempty with tissue fluid

Inner denti

n

Odontoblastic process &

Sensory nerve terminals

Dentinal TubulesDentinal Tubules

Ground Section of D.Ts.Ground Section of D.Ts.

At the cusp tip or (incisal edge)

At cervical area

Mid portion of root and apically

Straight

S shape

Straight

Secondary curvatures

Odontoblasts

Predentin

Dentin

Sec

. cu

rvat

ure

s

Terminal branches

Decalcified Section of D.Ts.Decalcified Section of D.Ts.

T.S. In Dentinal TubulesT.S. In Dentinal Tubules

Ground section

Neumann’s sheath

Odontoblastic process (Tomes’ fiber)

Periodontoblastic space

Scanning microscope

Decalcified section

Size: Size: 7u 7u in diameter in diameter

40u40u in length. in length.

They are They are columnarcolumnar in the in the crown , then becomecrown , then become cuboidal cuboidal rootwise, may be rootwise, may be almost almost flattened. flattened. at the root at the root apex. apex.

OdontoblasOdontoblaststs: :

They form a layer lining the They form a layer lining the periphery of the pulp.periphery of the pulp.

Each has a single process Each has a single process extending into a dentinal extending into a dentinal tubule.tubule.

Odontoblastic layerOdontoblastic layer

OdontoblasOdontoblasts ts

Active synthetic

state

Restingstate Criteria for Protein Criteria for Protein

Synthesizing and Synthesizing and Secreting Cells:Secreting Cells:

Large open-faced nucleusLarge open-faced nucleus Abundant cytoplasmAbundant cytoplasm no. of mitochondriano. of mitochondria rough endoplasmic rough endoplasmic

reticulum RERreticulum RER in size of Golgi apparatusin size of Golgi apparatus Presence of secretory Presence of secretory

granulesgranules Microtubules and microfilamentsMicrotubules and microfilaments Smaller cell size Smaller cell size

Decreased Decreased organellesorganelles

Little cytoplasmLittle cytoplasm

Regional Regional Variation: Variation:

Types of DentinTypes of Dentin Mantle Dntin

Circumpulpal dentin

Interglobular dentin

Intertubular dentin

Peritubular dentin

Primary

dentin

Mantle Dntin

Circumpulpal dentin

(outermost layer)

(around the pulp)

Circumpulpal Dentin

Mantle

Dentin

20um wide

Mantle dentinMantle dentinCircumpulpal Circumpulpal dentindentin

First dentin formed First dentin formed aginst DEJaginst DEJ

Dentin formed after Dentin formed after mantle dentin, around mantle dentin, around

the pulpthe pulp

Large collagen fibersLarge collagen fibers

Perpendicular to DEJPerpendicular to DEJFine collagen fibres Fine collagen fibres

parallel to dentin surfaceparallel to dentin surface

Ground substance from Ground substance from dental papilla and dental papilla and

odontoblastsodontoblasts

Ground substance from Ground substance from odontoblasts onlyodontoblasts only

Linear calcificationLinear calcificationGlobular and linear Globular and linear calcificationcalcification

Mantle dentin & Circumpulpal Mantle dentin & Circumpulpal dentindentin

Peritubular dentin & Intertubular Peritubular dentin & Intertubular dentindentin

• Dentinal tubules surrounded by hypermineralized dentin.• its formation is continuous.

•Located between the tubules•Formed of interwoven collagen fibers •apatite crystals are deposited within & in-between them.

Interglobular Interglobular dentindentin

Tomes’ Granular Tomes’ Granular layerlayer

Interglobular Interglobular dentindentin

Tomes’ granular Tomes’ granular layerlayer

may bemay be present in the present in the crown or root related to crown or root related to

disturbance in disturbance in mineralizationmineralization

A constant feature of A constant feature of the root surface the root surface dentindentin

Follow the Follow the incremental patternincremental pattern

Present at the dentin Present at the dentin –cementun interface–cementun interface

Arc-likeArc-like areas due to areas due to incomplete fusion of incomplete fusion of calcospherites related calcospherites related to disturbance in to disturbance in mineralizationmineralization

Spotty granular Spotty granular appearance due to appearance due to hypomineralizationhypomineralization or or looping looping of the of the terminal branches of terminal branches of odontoblastic odontoblastic processesprocesses

Detinal tubules pass Detinal tubules pass through these areas through these areas uninterrupted, but uninterrupted, but peritubular dentin is peritubular dentin is absentabsent

No dentinal tubules No dentinal tubules pass through this pass through this layerlayer

von Ebner

Contour lines

of Owen

Neonatal line

Incremental Lines Of Incremental Lines Of DentinDentin

Incremental Lines Of Incremental Lines Of DentinDentin

Incr

emen

tal l

ines

o

f vo

n E

bn

er

Neonatal line

Contour line of Owen

Incremental Incremental LinesLines

von Ebnervon Ebner

Contour linesContour lines of Owenof Owen

Neonatal lineNeonatal line von Ebnervon Ebner

Blood Supply of DentinBlood Supply of Dentin

11 Matrix formationMatrix formation

(Predentin)(Predentin)

Collagen GroundCollagen Ground

fibers substance fibers substance

22 MaturationMaturation (mineralization(mineralization))

Hydroxyapatite Hydroxyapatite

crystalscrystals

depositiondeposition

DentinogenesisDentinogenesis

11 - -Matrix FormationMatrix Formation Differentiation of Differentiation of

odontoblastsodontoblasts..

Differentiate from the peripheral dental papilla cells (UMC)

At first become short columnar cell with many

stubby processes

I D E

Basement membrane

The cells grow in length (40u) and closely packed together

Ameloblasts

Odontoblast becomes Odontoblast becomes a protein forming and a protein forming and

secreting cell.secreting cell. R E R , Mitochondria and Golgi bodiesR E R , Mitochondria and Golgi bodies Ribonucleic acid and alkaline phosphataseRibonucleic acid and alkaline phosphatase

Inner dental epith side

Large open faced N

R E R

Mitochondria

Golgi bodies

Predentin

Early dentin Early dentin formationformation

Odontoblast Odontoblast differentiationdifferentiation

predentinpredentin

dentindentin

odontoblastsodontoblasts

Odontoblastic process formationOdontoblastic process formation

At first more than one process

As more D is laid down, the cells receed and leave single process ( Tomes’ fiber)

22--MineralizatioMineralizatio

nnBudding of

matrix vesicles

Rupture of matrix vesicles

Mineralization of the mantle dentin

Has membrane rich in alkaline phosphatase

Calcium and phosphate ions undergo crystallization

Matrix vesicle

Pattern Of Pattern Of MineralizationMineralization

M V in matrix

Crystallization

Lodgment of crystals

Rupture

1- Linear at the mantle dentin area

2- Globular in circumpulpal

dentin just below mantle dentin

3- Combination in the remaining circumpulpal dentin of the crown and root

Innervation of Innervation of DentineDentine

Subodontoplastic Subodontoplastic plexus of plexus of Raschkow.Raschkow.

Nerves bundles:Nerves bundles:

- Myelinate- Myelinate

- Unmyelinated- Unmyelinated Free nerve Free nerve endingsendings

Intratubular Intratubular nerve fibrilsnerve fibrils

Innervations Of DentinInnervations Of Dentin

Plexus of Raschkow (suodontoblastic layer)

The nerve will loose its schwann caoting then pass between the odontoblasts bodies and enter the dentinal tubules ( In crown and fewer in the root )

High at D E J

High near the pulpal surface

Less sensitive area

Sensitivity of DentineSensitivity of Dentine::

1.1. Direct innervation Direct innervation theorytheory

2.2. Trasduction Trasduction theorytheory

3.3. Hydrodynamic Hydrodynamic theory.theory.

Transparent or Transparent or Sclerotic dentine.Sclerotic dentine.

Dead tracts.Dead tracts.

↓↓ permeability & permeability & sensitivitysensitivity

Age and Functional Age and Functional Changes in DentineChanges in Dentine

►►Primary dentine changes:Primary dentine changes:

Transparent (Sclerotic Transparent (Sclerotic Dentin)Dentin)

Mild stimulus leads to changes for the dentin already present.

1- Odontoblast and its process undergo fatty degeneration.

2- calcification occurs intratubular. Tubules first become narrow ,then become blocked

The affected area has occluded dentinal tubules, so the dentin will have uniform refractive index. This area of dentin appears translucent by transmitted light.

Transparent D

Dead TractsDead Tracts Severe stimulation to Severe stimulation to dentin leads to dentin leads to destruction of the destruction of the odontoblastic process odontoblastic process and odontoblasts. This and odontoblasts. This leads to embty and leads to embty and wide dentinal tubules.wide dentinal tubules.

These areas apear These areas apear black with transmitted black with transmitted light.light.

Under the dead tracts Under the dead tracts from the pulpal surface from the pulpal surface , reparative dentine , reparative dentine will be formed. will be formed.

The dead tract The dead tract serounded by sclerotic serounded by sclerotic dentin.dentin.

Occurs on the entire pulpal surface.

In multirooted teeth it is thicker on the roof and floor of pulp chamber.

The size of the pulp cavity decreases and obliteration of the pulp horns occurs

The dentinal tubules change their direction to a more wavy course

The no. of dentinal tubules is fewer

Line of demarcation (dark).

►► Secondary dentinSecondary dentinRegular Secondary Regular Secondary DentinDentin

Irregular Secondary Dentin Irregular Secondary Dentin (Reparative or tertiary (Reparative or tertiary

dentin)dentin)

Severe stimulusSevere stimulus The dentin is formed The dentin is formed

at a localized area.at a localized area. The dentinal tubules The dentinal tubules

are less in number are less in number and irregular in and irregular in arrangement.arrangement.

UMC from the UMC from the subodontoblastic subodontoblastic layer will differentiate layer will differentiate and replace the and replace the degenerated degenerated odontoblasts to form odontoblasts to form reparative dentin reparative dentin

Irregular D T

Types Of Types Of Reparative DentinReparative Dentin

Atubular dentin ( area without dentinal tubules)

Osteodentin (entrapped cells).

Vasodentin (entrapped b.v.)