Lecture Notes: Dentin Structure and Composition

Overview

• Dentin: Calcified tissue forming the bulk of the tooth, with pulp at its center.
• Surroundings:
  • Crown: Surrounded by enamel.
  • Root: Surrounded by cementum.
• Formation: Created by odontoblasts located in the pulp.
  • Odontoblastic processes extend throughout the dentin.

Morphology of Dentin

• Dentinal Tubules:
  • Contain odontoblastic processes.
  • Parts:
    • Peritubular Dentin: Walls of tubules.
    • Intertubular Dentin: Bulk between tubules.

Dentinal Tubules

• Structure:

  • Hollow, run from pulp to dentinoenamel or cementodentinal junction.
  • Shape: S-shaped, sigmoid curves due to odontoblast pathways.
    • Primary Curvatures: Two opposing curvatures.
    • Secondary Curvatures: Minute curvatures visible at high magnification.
  • Contour Lines of Owen: Formed by coinciding secondary curvatures.

• Dimensions:

  • Length varies with dentin thickness; longer due to curvatures.
  • Diameter: Wider at pulp (4 microns) than external end (1 micron).

• Branches:

  • Lateral Branches: Along course.
  • Terminal Branches: At outer end.

Contents of Dentinal Tubules

• Odontoblast Processes:

  • Extend from odontoblasts into tubules.
  • Lack major organelles, contain tubules and filaments.
  • May extend into enamel (enamel spindles).

• Dentinal Fluid:

  • Found in peri-odontoblastic space between processes and tubule walls.
  • Derived from plasma transudate; linked to dentin sensitivity.

• Lamina Limitans:

  • Organic layer rich in glycosaminoglycans, lining the tubules.

Peritubular Dentin

• Location: Peripheral to dentinal tubules.
• Composition:
  • Low in collagen, high in non-collagenous proteins.
  • More mineralized than intertubular dentin.
• Changes with Age:
  • Increases in thickness from pulp outward.
  • Leads to sclerotic dentin (occluded tubules), especially in apical third.
  • Results in transparent/translucent dentin.

Intertubular Dentin

• Location: Main body between dentinal tubules.
• Composition:
  • Rich in type I collagen fibers aligned perpendicularly to tubules.
  • Less mineralized than peritubular dentin.