Histology Of Dentinal Tubules

Hypocalcified structures of dentin

These lines result from a coincidence of the secondary curvature between neighboring dentinal tubules.
They are caused by accentuated deficiencies in mineralization.
These are easily recognized in ground sections.
These lines are accentuated because of disturbances in the matrix and mineralization process.

Interglobular dentin is used to describe areas of unmineralized or hypo mineralized dentin where globular zones of mineralization have failed to fuse into a homogenous mass within mature dentin.
It is prevalent in persons with Vit. D deficiency or who had exposure to high levels of fluoride at the time of dentin formation.
It is mostly seen in circumpolar dentin.
The tubular pattern remains unchanged.
Dentinal tubules run uninterrupted.
No peritubular dentin exists.
Frequently seen regions area

In crown:
- Cervical and middle third followed by a cuspal and coronal third.
In root:
- Highest in the cervical third followed by the middle third.

It is first formed dentin and is not mineralized.
It lines the innermost i.e., the pulpal portion of the tooth.
It consists principally of collagen and non-collagenous components.
It is 2-6 pm wide.
It gradually mineralizes into dentin as various noncollagenous matrix proteins are incorporated at the mineralization front.
Its thickness remains constant because the amount that calcifies is balanced by the addition of a new unmineralized matrix.
It is thickest during active dentinogenesis and diminishes in thickness with age.

Dentinal tubules extend through the entire thickness of the dentin from the dentin enamel junction to the pulp.
Their configuration indicates the course taken by the odontoblasts during dentinogenesis.
They follow an S-shaped path from the outer surface of the dentin to the perimeter of the pulp.
This curvature is least pronounced beneath the incisal edges and cusps.
The tubules are longer than die dentin and are thick because diet curves through dentin.
The tubules end perpendicular to the dentin enamel and dentino cementum junction.
The curvatures result from the crowding of and path followed by odontoblasts as they move toward the center of the pulp.
In root dentin, little or no crowding results from a decrease in surface area, and tubules run in a straight course.
The tubules are farther apart in the peripheral layers and are more closely packed near the pulp.

Dentinal tubules Number:

There are more tubules per unit area in the crown than in the die root.
Near the die pulpal surface of die dentin the number per square millimeter varies between 50,000 and 90,000.

Dentinal tubules Density:

Reduction in the average density of tubules occurs in radicular dentin compared with cervical dentin.
Higher tubule density occurs on the lingual and buccal walls of the pulp than on the mesial and distal walls.

Dentinal tubules Branches:

Major branches occur more frequently in root dentin than in coronal dentin.
Branches of the dentinal tubules near the terminals are referred to as terminal branches.
The dentinal tubules have lateral branches throughout the dentin called canaliculi.
These canaliculi are ppm or less in diameter and originate more or less at right angles to the main tubule.

Dentin Structure And Histology