Dentinal Tubules Structure and Formation

Study Notes

Dentinal Tubules

The number ratio of dentinal tubules per unit area on the pulpal and outer surfaces is 4:1.
Dentinal tubules are closely packed together at the pulpal surface than the outer surface.
The diameter of dentinal tubules is narrower at the outer surface (1 micron) than the pulpal surface (2-3 microns).
The course of dentinal tubules from the pulp surface to the outer surface takes an S shape, called primary curvature.
In the root portion and under the tip of the cusp or incisal edge, the dentinal tubules take a straight course.

Odontoblastic Process and Periodontoblastic Space

The odontoblastic process is also known as Tomes' fiber.
Periodontoblastic space is the space between the odontoblastic process and the wall of dentinal tubules.
This space results from the looping of the terminal portions of dentinal tubules, which is a result of different orientation of odontoblastic process.

Interglobular Dentine

Interglobular dentine appears in the crown just below mantle dentine, and sometimes in the root dentine.
It results from the incomplete fusion of calcified globules.
Dentinal tubules cross the interglobular dentine without hindrance.

Mechanism of Attachment between Enamel and Dentine

The dentino-enamel junction (D.E.J.) is scalloped in shape, providing a mechanical junction.
The firm union between enamel and dentine is due to the collagen fiber bundles of mantle dentine projecting beyond the D.E.J. and becoming continuous with the organic substance of dentino-cemental junction.

Innervations of Dentine

Dentine is sensitive, and the most sensitive area is at the D.E.J.
The response to any stimuli is pain.
Pulpal nerves (free nerve endings) pass between the odontoblasts and enter the dentinal tubules.

Theories of Dentine Sensitivity

Direct neural stimulation theory: explains that dentine contains nerve endings that respond when dentine is stimulated.
Odontoblastic transduction theory: explains that odontoblasts serve as receptors and are coupled to the nerve in the pulp.
Fluid or hydrodynamic theory: explains that the tubular nature of dentine permits fluid movement to occur within the tubules when stimulus is applied.

Dentine Development

Odontoblasts differentiate from the peripheral short columnar dental papilla cells with many stubby processes.
The cells grow in length (40u) and are closely packed together.
Dentine formation has two stages: matrix formation and maturation (mineralization).

Types of Dentine

Mantle dentine: the first formed dentine layer in the crown and root.
Circumpulpal dentine: the remaining primary dentine after mantle dentine is formed.

Reparative Dentine

Osteodentine: a type of reparative dentine with entrapped cells.
Atubular dentine: a type of reparative dentine without dentinal tubules.
Vasodentine: a type of reparative dentine with entrapped blood vessels.

Secondary Dentine

Regular secondary dentine: formed in response to mild stimuli, such as slow attrition and caries.
Irregular secondary dentine: formed in response to severe stimuli, such as abrasion and erosion.
Clinically, regular secondary dentine increases the time taken by caries to reach the pulp, making the liability of pulp exposure during cavity preparation much less likely to occur.

Description

Learn about the structure and formation of dentinal tubules, including their ratio on pulpal and outer surfaces, odontoblastic processes, and more. Test your knowledge of dental anatomy and histology.