chapter 8 dentin copyright © 2014 by mosby, an imprint of elsevier inc

Chapter 8

Dentin

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Dentin: Learning Objectives

After reading this chapter, the student will be able to: Describe the various types of dentin and the

structures they contain. Describe the dental process that lies in the dental

tubules. Discuss the relationship of the enamel to the

dentin at their junction.

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 2

Dentin

Physical properties Dentin classification Predentin Tubular and intertubular relations Incremental lines Granular layer Odontoblastic cell processes Dentinoenamel junction Permeability Repair process


Dentin


Dentin: Physical Properties

Forms bulk of tooth Yellowish in color Composed of 70% inorganic hydroxyapatite

crystals, 20% organic fibers, with small amounts of other proteins and 10% water

Softer than enamel Harder than bone or cementum Resilient


Dentin Classification

Primary dentin forms the body of the tooth. Mantle Circumpulpal dentin

Secondary dentin forms only after tooth eruption. Narrow band that borders the pulp

Tertiary or reparative dentin forms only in response to trauma to the pulp.


Dentin Classification: Primary Dentin

Mantle dentin is deposited first at the dentinoenamel junction (DEJ).

Normal circumpulpal dentin underlies mantle and globular dentin.


Dentin Classification: Structural Differences

Mantle dentin is composed of large collagen fibers.

Circumpulpal dentin fibers are tenfold smaller than those in mantle dentin.

Mantle dentin is slightly less mineralized and contains fewer defects than circumpulpal dentin.


Dentin Classification: Structural Differences


Dentin Classification: Secondary Dentin

Forms internally to primary dentin

Develops after crown is in clinical occlusal function and roots near completion

Deposited slowly, perhaps to prevent pulp obliteration


Dentin Classification: Tertiary Dentin

Results from pulpal stimulation Attrition Abrasion Caries Restorative

procedures Forms only at site

of odontoblastic activation


Dentin Classification: Tertiary Dentin


Predentin

A band of newly formed, unmineralized matrix of dentin at the pulpal border


Tubular and Intertubular Relations: Primary and Secondary Tubules


Intratubular or Peritubular Dentin

A hypermineralized collar or dental matrix that immediately surrounds the tubules

Present in tubules throughout dentin, except near the pulp

Missing from dentinal tubules in interglobular dentin


Sclerotic Dentin

This is the term for dentin with tubules that are completely obliterated.

Increases in amount with age

Believed to be mechanism to protect pulp

Pulp permeability eliminated in areas of sclerotic dentin


Intertubular Dentin

The body of dentin that comprises the crown and root

Consists of organic matric fibers and inorganic crystals of hydroxyapatite

Less highly calcified than intratubular dentin Changes little throughout life


Incremental Lines, Imbrication Lines, or Lines of von Ebner

Lines indicating a hesitation in deposit of matrix activity


Neonatal Line

This line reflects the abrupt change in environment that occurs at or near birth.


Granular Layer of Tomes


Odontoblastic Cell Processes

Cytoplasmic extensions of the cell body positioned at the pulp-dentin border


Dentinoenamel Junction


Permeability


Repair Process

Changes in dentin are caused by: Odontoblastic degeneration Formation of dead tracts Calcification of tubules, leading to sclerosis Tertiary or reparative dentin formation

After death and degeneration of odontoblast, dead tracts appear, sclerosis may occur, and further reparative dentin secreted by replacement odontoblast in the pulp forms.


Repair Process


Questions and Considerations

Which type of dentin comprises the greater part of the crown and root?

What factors affect permeability of the dentin?

Why are newly restored teeth sensitive for a period of time?

What is sclerotic dentin?


chapter 8 dentin copyright © 2014 by mosby, an imprint of elsevier inc

Documents

primary dentin mantle

peritubular dentin

globular dentin

tertiary dentin copyright

reparative dentin forms

circumpulpal dentin

imprint of elsevier

normal circumpulpal