Chapter 31 Thyroid and Antithyroid Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Chapter 8 Dentin Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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Transcript of 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
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Dentin
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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
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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.
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Dentin Classification: Primary Dentin
Mantle dentin is deposited first at the dentinoenamel junction (DEJ).
Normal circumpulpal dentin underlies mantle and globular dentin.
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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.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 8
Dentin Classification: Structural Differences
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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
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Dentin Classification: Tertiary Dentin
Results from pulpal stimulation Attrition Abrasion Caries Restorative
procedures Forms only at site
of odontoblastic activation
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Dentin Classification: Tertiary Dentin
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Predentin
A band of newly formed, unmineralized matrix of dentin at the pulpal border
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Tubular and Intertubular Relations: Primary and Secondary Tubules
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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
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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
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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
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Incremental Lines, Imbrication Lines, or Lines of von Ebner
Lines indicating a hesitation in deposit of matrix activity
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Neonatal Line
This line reflects the abrupt change in environment that occurs at or near birth.
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Granular Layer of Tomes
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Odontoblastic Cell Processes
Cytoplasmic extensions of the cell body positioned at the pulp-dentin border
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Odontoblastic Cell Processes
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Odontoblastic Cell Processes
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Odontoblastic Cell Processes
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Dentinoenamel Junction
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Permeability
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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.
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Repair Process
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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?
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