Types of Dentin

Types of Dentin

1. Primary dentin:

• Dentin which is formed before root completion is known as primary dentin.
• There are two types of primary dentin.
  1. Mantle dentin:
     • Mantle dentin is the first formed dentin in the crown.
     • Mantle dentin lies immediately below the dentin enamel junction.
     • Mantle dentin is formed before a tooth erupts into the oral cavity
     • Mantle dentin is the outermost, peripheral part of primary dentin.

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• Mantle dentin Thickness:
  • Mantle dentin is 20 Jim thick.
• Mantle dentin Function:
  • As Mantle dentin is soft, it provides a cushioning effect to the tooth.
• Mantle dentin Fibers:
  • Mantle dentin contains larger diameter fibers of about 0.1 – 0.2 pm in diameter.
  • Mantle dentin are argyrophilic.
  • Mantle dentin are known as von Kroff’s fibers.
  • Mantle dentin mainly contain type II collagen.
  • Mantle dentin are directed perpendicular to DEJ.
• Mantle dentin Mineralization:
  • Mantle dentin is less mineralized
  • Mantle dentin  involves globular mineralization.
  • Circumpulpal dentin:
  • Mantle dentin is the primary dentin that outlines the pulp chamber.
• Mantle dentin Fibers:
  • Smaller in diameter (0.05 Jim)
  • They are closely packed.
• Mantle dentin Mineralization:
  • Circumpupal dentin is more mineralized
  • Mantle dentin undergoes globular or linear mineralization.

Primary Secondary Tertiary Dentin

2. Secondary dentin:

• Secondary dentin is a narrow band of dentin bordering the pulp
• Secondary dentin is the dentin that is formed after root formation.
• Secondary dentin represents continued lower deposition of dentin by odontoblasts.
• Secondary dentin is not deposited evenly around the periphery of the pulp chamber.
• There is greater deposition on the roof and floor of the chamber than other parts.

Secondary dentin Tubules:

• Secondary dentin contains fewer tubules.
• They are less regular
• At the boundary between primary and secondary dentin, tubules change their direction and show a wavy course.
• These tubules sclerose more readily.
• This reduces the overall permeability of the dentin thereby protecting the pulp.

Secondary dentin Synonym:

• Regular secondary dentin – due to the regular arrangement of dentinal tubules.

Primary Secondary Tertiary Dentin

3. Tertiary dentin:

• Tertiary dentin is that dentin is produced by odontoblasts in response to irritation of the pulp caused by chemical, thermal, or microbial stimuli.
• Tertiary dentin contains very few irregular tubules.
• The quality and the quantity of tertiary dentin produced depends on the intensity and duration of the stimulus.
• Tertiary dentin is produced only by those cells directly affected by the stimulus.
• The cells forming tertiary dentin line its surface or become included in the dentin called osteopontin.
• Tertiary dentin is subclassified as
  1. Reactionary dentin:
     • It is deposited by pre-existing odontoblasts.
  2. Reparative dentin:
     • It is deposited by newly differentiated odontoblast-like cells.