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