histology of dentin

Histology of Dentin

Professor Dr Maha Mounir

Dentin & Pulp

Odontoblastsare an integralpart of bothdentin & pulp

Composition of dentin

Inorganic componentOrganic component

Junctional Complex

Predentin

Unit of dentin= dentinal tubule

• Extend through entirethickness of dentin fromDEJ to pulp

1ry & 2ry curvatures+lateral &terminal branching

• In GS

1ry & 2ry curvatures+lateral &terminal branching

• S-shaped dentinal tubules• Lateral + terminal branchings

TS in Dentinal tubules

TS Dentinal tubules

• Sizes of DT aredifferent atdifferent locations1.ADJ2. Near pulp3. At cavity floor

Intertubular Dentin

• Dentin that is located between DT• It is primary secretory product of

odontoblast• Consists of tightlyInterwoven type I collagenfibrils where apatite crystalsare deposited

Peritubular Dentin• Dentin that immediately surrounds the

DT• It is highly mineralized & lacks collagen

fibers• Not present in DT nearpulpPeritubular D

=intratubular D(formed within the DT)

Contents of Dentinal Tubules• 1. The odontoblastic process ( that forms

the DT)• 2. Nerve terminals• 3. DT have a very thin inner organic lining

or membrane high in GAG called “LaminaLimitans”. It is important for regulation &inhibition of calcification of dntinal tubules

• 4. Within the DT there is the “peri-odontoblastic space”filled with extracellulardentinal fluid.

incremental deposition ofenamel & dentin

Incremental lines in dentin

--Incremental lines of Von Ebner--Neonatal line

Granular layer of Tomes

• kkk

Dentine mineralization

• Small mineral crystals in:1.Matrix vesicles2.nucleated in spaced within collagen fibrils

Mineralization of mantle &Circumpulpal Dentin

• Occurs by one of 2 ways• 1. Small mineral crystals appear in extra-

cellular matrix vesicles. Mineralizationspreads from these sites throughout thefirst formed dentin

• 2. Small mineral crystals are nucleated inspaces that exist within the collagen fibrils

• After the initial calcification, all crystals areassociated within or on surface of thecollagen fibrils. Crystals are oriented alongthe long axis of collagen fibrils.

Mineralization

Pattern of mineralization• 1. Globular dentin: formed from

calcospherites• 2. Interglobular dentin: hypomineralized

dentin between mantle & circumpulpaldentin ( coronal dentin only)

• 3.Tomes’Granular layer: hypomineralizedlayer in root dentin; similar to interglobularD in crown.

• 4. Sclerotic dentin: Hypermineralized,occluding intertubular dentin.

Various structures in dentin

Globular, interglobular, sclerotic &Tomes’granular layer

Changes in 1ry & 2ry Dentin

• ddd

Formation of new dentin

• 1. Regular secondary dentin• 2. Reparative tertiary dentin

Age & functional changes

• Changes in 1ry dentin1. Sclerotic or translucent dentin2. Dead tracts

Formation of new dentin

• 1. Regular or physiologic 2ry dentin• 2. Reparative 3ry dentin

Physiologic secondary dentin

Physiologic secondary dentin

Physiologic secondary dentin• mm

Physiologic secondary dentin

Dead tract & reparative dentin

• kkk

Sclerotic dentin ( Changes in 1rydentin)

Dead tract & reparative dentin

Interglobular dentin

• kkk

Knoop hardness number

Theories of dentin sensitivity

1. Direct innervations theory2. Transduction theory3. Hydro-dynamic

theory

Clinical considerations• Permeability of dentin• Response to external stimuli: 2ry & 3ry

D• Adhesion of external materials to

dentin: smear layer, etching then bonding• Endodontics: 2ry & 3ry D may complicate

endo treatment• Sensitivity of exposed D: byoccluding opened tubules

Thank You