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Questions and Answers
What is the primary function of dentin in the tooth structure?
What is the primary function of dentin in the tooth structure?
What type of dentin occupies the peripheral area where the basement membrane was previously present?
What type of dentin occupies the peripheral area where the basement membrane was previously present?
What is the primary type of collagen found in the organic matrix of mantle dentin?
What is the primary type of collagen found in the organic matrix of mantle dentin?
What is the term used for the layer of unmineralized matrix between the odontoblast and the mineralizing front?
What is the term used for the layer of unmineralized matrix between the odontoblast and the mineralizing front?
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What type of dentin is formed as a response to stimuli and is characterized by its reactive nature?
What type of dentin is formed as a response to stimuli and is characterized by its reactive nature?
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What type of odontoblast process may penetrate the basal lamina to form enamel spindles?
What type of odontoblast process may penetrate the basal lamina to form enamel spindles?
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In circumpulpal dentin formation, what is the nature of the collagen fibrils?
In circumpulpal dentin formation, what is the nature of the collagen fibrils?
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What type of dentin is known for its calcification islands that form during its development?
What type of dentin is known for its calcification islands that form during its development?
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Which of the following is not a type of dentin mentioned?
Which of the following is not a type of dentin mentioned?
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What cellular origin do odontoblasts differentiate from?
What cellular origin do odontoblasts differentiate from?
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What type of mineralization is characterized by a slow rate of dentin formation?
What type of mineralization is characterized by a slow rate of dentin formation?
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Which component forms the bulk of the tooth before root formation is complete?
Which component forms the bulk of the tooth before root formation is complete?
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What is the primary characteristic of radicular dentin compared to coronal dentin?
What is the primary characteristic of radicular dentin compared to coronal dentin?
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Which type of dentin is formed after root formation is complete?
Which type of dentin is formed after root formation is complete?
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What contributes to the hardness of dentin compared to enamel?
What contributes to the hardness of dentin compared to enamel?
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What initiates the differentiation of odontoblasts during root dentin formation?
What initiates the differentiation of odontoblasts during root dentin formation?
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Which type of dentin is associated with localized formation in response to stimuli?
Which type of dentin is associated with localized formation in response to stimuli?
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Which mineral is primarily responsible for the inorganic content of dentin?
Which mineral is primarily responsible for the inorganic content of dentin?
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What is the primary curvature of dentinal tubules characterized by?
What is the primary curvature of dentinal tubules characterized by?
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What explains the increase in the permeability of dentin with age?
What explains the increase in the permeability of dentin with age?
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What is the diameter of dentinal tubules near the pulp?
What is the diameter of dentinal tubules near the pulp?
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Which type of dentin is primarily located between the dentinal tubules?
Which type of dentin is primarily located between the dentinal tubules?
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What is the significance of the neonatal line in dentin?
What is the significance of the neonatal line in dentin?
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What causes the Tomes granular layer to increase in amount?
What causes the Tomes granular layer to increase in amount?
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Which structure represents a hypermineralised ring of dentin found within the dentinal tubule?
Which structure represents a hypermineralised ring of dentin found within the dentinal tubule?
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What does the fluid/hydrodynamic theory explain about dentin sensitivity?
What does the fluid/hydrodynamic theory explain about dentin sensitivity?
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How do density and distribution of tubules change from the pulp to the periphery?
How do density and distribution of tubules change from the pulp to the periphery?
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What is the primary reason for the formation of reparative dentin?
What is the primary reason for the formation of reparative dentin?
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What occurs to the odontoblastic process in cases of caries?
What occurs to the odontoblastic process in cases of caries?
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Which lines represent disturbances in the mineralisation matrix?
Which lines represent disturbances in the mineralisation matrix?
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What is typically seen in areas of interglobular dentin?
What is typically seen in areas of interglobular dentin?
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What is the role of the odontoblastic process?
What is the role of the odontoblastic process?
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Which type of dentin is recognized as having similar refractive indices and is often referred to as transparent dentin?
Which type of dentin is recognized as having similar refractive indices and is often referred to as transparent dentin?
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Study Notes
Dentin Overview
- Dentin is the hard tissue forming the bulk of a tooth.
- It protects the tooth's pulp.
- It supports the tooth's enamel.
Dentin-Pulp Complex
- Dentin and pulp are embryologically, histologically, and functionally related.
Types of Dentin
- Coronal dentin
- Radicular dentin
- Primary dentin
- Secondary dentin
- Tertiary dentin
Primary Dentin
- Consists of mantle dentin and circumpulpal dentin.
Tertiary Dentin
- Also known as reparative dentin or reactive dentin.
- Formed in response to damage or stimulation.
- Produced by cells that are directly affected.
Sclerotic Dentin
- Similar refractive indexes
- Response to stimuli such as caries, attrition, abrasion, cavity preparation or erosion.
- Appears white in transmitted light and black in reflected light.
- Collagen fibres and apatite crystals appear in the dentinal tubules.
Intratubular Dentin
- A hypermineralised ring of dentin.
- Found within the dentinal tubule. -It is (40%) more mineralised compared to intertubular dentin.
Intertubular Dentin
- Major body of dentin.
- Located between dentinal tubules.
Interglobular Dentin
- Areas of hypomineralised/unmineralised dentin.
- Found in tooth crowns.
- Mineralisation pattern is mainly globular.
Dentinogenesis
- Primary dentin can be of two types.
- Mantle dentin occupies the peripheral area where the basement membrane was earlier present.
- Circumpulpal dentin is the remaining larger segment of dentin.
Odontoblast Differentiation
- Important for understanding the formation of normal and reparative dentin.
Mantle Dentin Formation
- Odontoblasts differentiate from ectomesenchymal cells.
- Secrete collagen (type III) into existing ground substance of dental papilla.
- Collagen fibrils are large (0.1-0.2µm) and called von Korff's fibres.
- These fibres intermingle with aperiodic fibrils (type VII collagen).
- They sit at right angles to the basal lamina.
Matrix Vesicles and Crystal Formation
- Odontoblasts release matrix vesicles containing calcium, phosphate, alkaline phosphatase, and calcium-binding lipids, enabling hydroxyapatite crystal formation within the vesicles.
Dentin Tubule Course, Extent, and Diameter
- Dentinal tubule course is generally S-shaped curve, called primary curvature.
- They make a double curve, starting perpendicular to the pulpal surface and ending perpendicular to the DEJ and CDJ
- Extent: crown - DEJ to pulp and root - CDJ to pulp
- Tubules are longer than the thickness of dentin.
- Diameter: 2.5μm near the pulp, and 1.2μm in the mid portion, and 900μm near the DEJ.
Dentin Tubule Density and Branching
- Tubules are farther apart in the periphery and closer near the pulp.
- Tubules per unit area in the pulpal surface are 50,000-90,000.
- Major and more frequent branching is in the root compared to the crown.
Secondary Dentin
- Formed after root formation is complete.
- A narrow band bordering the pulp.
- Fewer tubules than primary dentin.
- Different from primary dentin and has a boundary between it and primary dentin.
Reparative Dentin
- Reaction to various stimuli including abrasion, erosion, and caries.
- Odontoblasts are killed and replaced by migrated undifferentiated cells.
- This forms the reparative dentin.
Dead Tracts
- Odontoblastic processes are lost and the empty tubules are filled with air
- Can be caused through various procedures.
Contour Lines of Owen
- Disturbed matrix and mineralisation process results in hypocalcified areas.
- Accentuated incremental lines that are a result of coincidence of neighbouring dentinal tubules
Neonatal Line
- Found in deciduous and permanent first molars.
- Shows an abrupt change in environment, occurring at birth.
Tomes Granular Layer
- In dry ground sections, a granular zone adjacent to cementum in transmitted light.
- Increase in amount occurs from the CEJ to the root apex.
- Produced by coalescing and looping of terminal portions of dentinal tubules.
Predentin
- Located adjacent to pulp tissue. -~2-6µm wide
- Unmineralised dentin.
Chemical Composition
- 70% inorganic content is hydroxyapatite crystals that are smaller than enamel.
- Other inorganic components are phosphates, carbonates, sulfates, and fluoride.
- 20% organic content consists of collagen types I, III, V. and other non-collagenous proteins and lipids.
- Water makes up approximately 10%.
Non-Collagenous Proteins
- Amelogenins
- Dentin Phosphoprotein (DPP)/ Phosphoryn.
- Dentin Sialoprotein (DSP).
- Dentin Glycoprotein (DGP).
Dentin Sensitivity
- There are 3 theories related to pain transmission through dentin.
- Direct Neural Stimulation
- Fluid/Hydrodynamic Theory
- Transduction Theory
Contents of Dentinal Tubules
- Odontoblastic process
- Dentinal fluid (dental lymph)
- Lamina limitans
- Peritubular dentin
- Nerve endings (predentin and inner dentin)
Clinical Considerations
- 1mm² of exposed dentin contains 30,000 cells that could be damaged.
- It's important to seal exposed dentin with non-irritating insulators against bacteria, drugs, undue operative trauma, thermal changes, and irritating restorative materials.
Spread of Caries
- The tubular system undermines the enamel at the DEJ.
- It enables invasion of microorganisms.
- Dentin sensitivity is not a symptom of caries unless the pulp is affected.
Trauma from Operative Instruments
- Trauma may result in odontoblast aspiration.
- Reparative dentin formation occurs in the subodontoblastic layer.
Age Changes
- Dentin vitality, reparative dentin, dead tracts, and sclerotic dentin undergo modifications.
Age and Dentin Vitality
- Odontoblasts are an integral part of dentin.
- Dentin reacts to physiologic and pathologic stimuli.
- Dentin is laid down throughout life.
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Description
Explore the essential aspects of dentin, the hard tissue that forms the majority of a tooth. This quiz covers the dentin-pulp complex, types of dentin, and their unique properties. Enhance your understanding of how dentin supports enamel and responds to various stimuli.
