(3) Dentine-Pulp Complex

General Dentinal Properties

  • Tubular
  • Hydrated (Dentinal Fluid; transduate of ECF from pulp)
  • Apatite Crystals
  • Collagen Matrix

Whole Story/Dentinogenesis

Pre-Secretory

1) IEE in Bell Shape

2) IEE signalling molecules

3) Signalling molecules Dental Papilla to Odontoblast

4) Odontoblast form Mantle Dentine
(Collagen fibres then mineralization)

9) IEE to Secretory Ameloblast

5) Odontoblastic process forms (Tome's Fibre)

6) Odontoblast moves towards pulp; form Circumpulpal Dentin

7) Mantle Dentin has no dentinal tubules;

Secretory

1) Initial Dentine (Mantle Dentine) stimulate Ameloblast to produce Enamel Matrix

3) Ameloblast develops Tome's Process

2) Immature Ameloblasts (without Tome's Process) dump Initial Enamel mineralized immediately (No enamel rods)

4) Final Enamel (Middle / Rod + Inter-Rod)

5) Last bit of enamel (No enamel rods)

Maturation Phase

1) Apoptosis of Ameloblasts

2) Degradation of matrix by enzymes

3) Minerals pumped out

Physical Structure

Morphological Structure

Tubules

Inter-tubular (Between tubules)

  • Quantity: Most at EDJ decreases to Pulp
  • Reason: Tubules narrower at top
  • Less calcified

Composition

Organic (20%)

  • Collagen 1
  • Collagen 3,5
  • DPP/DSP/DSPP
  • Osteonectin/Osteopontin
  • GLA Protein

Inorganic (70%)

Water (10%)

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Mantle Dentine, First Formed (No Tubules)
Weaker: No calcification
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8) unmineralized portion of cicumpulpal (pre-dentin)

Types of Dentine

Primary

  • Rate: 4um/day
  • Develops until root/enamel starts developing

Secondary

  • 0.4um/day
  • After root/enamel develops, odontoblast downregulated

Tertiary

Types of Dentine (Developement)

Odontoblast

Structure

Function

Sclerotic Dentine

  • Occluded by whitlockite crystals

Clinical Implications

Aging

Junctions between Cells:

  • Gap Junctions: Signal ions
  • Tight Junctions: Barrier pulp dentine
  • Intermediate Junctions: Integrity of odontoblastic layer

Difference between Bone & Dentine:

  • Dentine, calcification in gap junctions
  • Harder than bone

Reparative (New Odontoblast)

  • Death of original odontoblasts
  • New odontoblastic cells from mesenchymal cells

Reactionary (Upregulated Old Odontoblast)

  • Local
  • Small, slow progressing
  • Upregulation of odontoblast

DH200810_3x

Factors affecting Dentinal Strength

  • Hydration (dissipate occlusal forces)
    • Occluded dentinal tubules
    • Root canal
    • Lower BP
  • Peritubular anisotropy

Transparent dentin:

  • Sclerotic / Calcified tubules (appear transparent)

Scallop-concavity at EDJ (only for humans)

  • Increase SA for bonding
  • Reduced stress at EDJ

Root:
4) Granular Layer of Tomes: Hypomineralized
5) Hyaline Layer of Hopewell Smith

  • Facilitate adhesion of cementum to dentin
  • Produced by Hertwig's Epithelial Root Sheath (HERS - enamel organ)
  • Enamel like material

Crown:
4) Mantle: First formed dentin / Outer dentin (Adj to enamel)

  • Fibrils perpendicular to EDJ
  • No tubules
  • Mineralized by matrix vesicles
  • (alkaline phosphotase/annexin - collects PO4 & Ca respectively)
  • Higher protein content, immediate mineralizaed

General Layers
1) Predentine: immature uncalcified; fibrils perpendicular to cell processes
2) Circumpulpal: Inner dentin (Adj to pulp)
3) Interglobular: Incompletely calcified dentinal matrix

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P-C-I-M-T-H

Peritubular / Intra-tubular Dentin

  • Quantity: Most at EDJ decreases to Pulp
  • Reason: More time to calcify
  • Less dense / More permeable closer to pulp
  • More calcified
  • Responsible for anisotropy (stress)
  • Fenestrated, fluid & ions odontoblastic process (ECF)

Incremental

Von Ebner's Lines (Short period lines)

  • Odontoblasts taking rest daily
  • Like Enamel Cross Striations

Andresen Lines (Long period lines)

  • Odontoblast taking break weekly
  • Use to calculate age at death
  • Like Enamel Lines of Retzius

Histological Bands

Schreger Lines (Primary)

  • Coincidence of sigmoid peaks
  • Visible with magnification

Contour lines of owen (Secondary)

Pathogenesis

Dentine Dysplasia

  • Abnormal dentine production

Dentin

  • Tubules narrow (homogeneously)
  • Difficult to locate pulp

Pulp

  • Less volume (secondary dentin reduce size)
  • Less cellular (Fibro/Odonto/Mesen/Immun)
  • Less innervation / vascular supply
  • Fibres increase / Fibrosis
  • Pulpal calcification
  • Ondotoblast downregulated

Dentinogenesis Imperfecta

  • Impede calcification

Pulp

Structure Organization

1) Pulp Core

3) Cell Rich (Subodontoblastic layer)

4) Cell Free (Zone of Weil)

2) Plexus of Raschkow (Nerves)

5) Odontoblasts

Supporting Structures

Innervation

  • Apical foramen
  • Plexus of Raschkow
  • Fibres terminate between odontoblasts
  • Myelinated A, Unmyelinated C

Cells

  • Odontoblasts (Synthesize Dentin)
  • Fibroblasts (Synthesize ECM; Most common)
  • Dendritic cells/Macrophages/Lymphocytes
  • Undifferentiated mesenchymal cells (Differentiate into Fibroblast / Odontoblasts) eg. Reparative Dentin
  • AKA. Epithelial cell rests of Malassez

Blood Supply

  • Apical foramen
  • Branching subodontoblastic capillary plexus
  • Microcirculation / Precapillary spincters

ECM

  • Collagen
  • Elastin
  • Fibronectin
  • GAG/PG

C-N-R-F-O

Lymphatic

  • Removal of high molecular weight solutes from fludid

Function

1) Inductive

2) Formative

3) Nutritive

  • For dentin formation

4) Protective

  • Highly innervated
  • All stimulus sensed as pain

5) Defensive

  • Dentinal fluid outflow (Immunoglobulins)
  • Inflammatory response

Neurosensory

Secretes Dentine

Defense (Dentinal Fluid)