Questions and Answers
What is the diameter of dentinal tubules near the pulp?
What is the term for the hypermineralised ring of dentin found within the dentinal tubule?
What are the lines that represent the rhythmic recurrent deposition of matrix?
What is the function of odontoblasts and their processes?
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What is the term for the area of hypomineralised/unmineralised dentin found in the crown of teeth?
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What is the zone of unmineralised dentin located adjacent to pulp tissue?
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What is the term for the process by which the tubules are blocked, reducing the permeability of dentin and prolonging pulp vitality?
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What is the theory that suggests stimuli affect fluid movement in the dentinal tubules, causing mechanical disturbance of the nerves closely associated with odontoblasts and their processes?
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What is the primary function of alkaline phosphatase activity in dentinogenesis?
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What is the term for the area of dentin that is formed before birth?
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What type of dentin is characterized by a slower rate of formation and is composed of globular and linear patterns?
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What is the term for the layers of dentin that are formed in a rhythmic, incremental manner?
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Which of the following is a characteristic of radicular dentin?
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What is the primary component of the organic matrix in dentin?
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What is the function of Tomes granular layer in radicular dentin?
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What is the term for the doubly curved course of dentinal tubules?
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What is the term for the process by which odontoblasts produce dentin in response to stimuli?
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What is the composition of the inorganic content of dentin?
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What is the term for the process by which dentin forms in layers, resulting in incremental growth lines?
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What is the function of matrix vesicles in dentinogenesis?
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What is the primary function of dentin in the tooth structure?
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What is the term for the process by which dentin is formed?
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What type of collagen fibrils are found in mantle dentin?
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What is the term for the short, stubby processes of the odontoblast that penetrate the basal lamina?
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What is the function of matrix vesicles in dentinogenesis?
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What is the term for the layer of unmineralized matrix between the odontoblast and the mineralizing front?
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What type of dentin is formed in response to tooth wear or injury?
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What is the characteristic of collagen fibrils in circumpulpal dentin?
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What is the term for the dentin formed during the initial development of the tooth?
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What is the term for the tubules in dentin that contain the odontoblastic process?
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Study Notes
Dentin Structure and Development
- Dentin is a hard tissue portion of the tooth that protects the pulp and supports enamel.
Dentinal Tubules
- Course of dentinal tubules: S-shaped curve (primary curvature) that becomes doubly curved, starting at right angles to the pulpal surface and ending perpendicular to the DEJ and CDJ.
- The first convexity is directed towards the apex of the tooth.
Types of Dentin
- Coronal dentin and radicular dentin
- Primary dentin, secondary dentin, and tertiary dentin
- Primary dentin: mantle dentin and circumpulpal dentin
- Tertiary dentin: reactionary dentin, reparative dentin, and osteodentin
Dentinogenesis
- Primary dentin forms two types: mantle dentin and circumpulpal dentin
- Mantle dentin formation: • Odontoblasts differentiate from ectomesenchymal cells • Secrete organic matrix collagen (type III) into preexisting ground substance of dental papilla • Collagen fibrils intermingle with aperiodic fibrils (type VII collagen) and are aligned at right angles to the basal lamina • Odontoblasts give out short stubby processes, with one penetrating the basal lamina (enamel spindles) • Odontoblasts bud off matrix vesicles containing calcium and phosphate ions, alkaline phosphatase enzyme, and calcium-binding lipids • Matrix vesicles permit the formation of hydroxyapatite crystals • Crystals grow and more crystals form around them, fusing to form islands of calcifications • Collagen fibrils are obscured, and deposition of mineral lags behind organic matrix formation
Circumpulpal Dentin Formation
- Intercellular space between odontoblasts is obliterated, with no contribution from the subodontoblastic layer
- Collagen fibrils are smaller, type I, closely packed, and interwoven with each other, aligned at right angles to the odontoblastic process
- No matrix vesicles are present in circumpulpal dentin formation
Dentin Properties
- Color: light yellowish, becoming darker with age
- Hardness: harder than bone and cementum, softer than enamel
- Strength: organic matrix and tubular architecture provide compressive, tensile, and flexural strength
- Permeability: depends on size and patency of tubules, declining with age
- Chemical composition: 70% hydroxyapatite crystals, 20% collagen type I, III, and V, and 10% water
Non-Collagenous Proteins
- Includes amelogenins, dentin phosphoprotein/phosphoryn (DPP), dentin sialoprotein (DSP), and dentin glycoprotein (DGP)
Mantle Dentin
- First formed, mineralized dentin
- Outermost part of primary dentin
- Seen in the crown between DEJ and interglobular dentin, and in the root underlying the Tomes granular layer
- About 20 μm thick, with fibrils perpendicular to DEJ and larger in size than those in circumpulpal dentin
Circumpulpal Dentin
- Forms the bulk of the tooth and the dentin formed before root formation is complete
- Collagen fibrils are smaller, closely packed, and more mineralized than mantle dentin (4%)
- Fewer defects than mantle dentin
Secondary Dentin
- Represents dentin formed after root formation is complete
- A narrow band of dentin bordering the pulp
- Has fewer tubules than primary dentin
- There is a bend between primary dentin and secondary dentin
Tertiary Dentin
- Reactive, reparative, or irregular secondary dentin
- Localized formation of dentin on the pulp-dentin border in response to various stimuli (attrition, caries, restorative procedures)
- Tubules may be regular, irregular, or sparse in number, or absent altogether
- Osteodentin: odontoblasts entrapped in dentin, mimicking osteocytes in bone
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Description
This quiz covers the structure and development of dentin, including dentinal tubules, types of dentin, and more.
