Dentine Composition

Dentine Composition and Structure

• Dentine is a hard, calcified tissue found in the tooth
• It is located beneath the enamel and surrounds the pulp
• Dentine is composed of approximately 70% inorganic minerals, primarily calcium hydroxyapatite, which is smaller than enamel's hydroxyapatite crystals
• Dentine also contains 20% organic material:
  • Majority is a collagenous rich matrix (18%)
  • Minority is non-collagenous matrix proteins and lipids (2%)

Dentin: Composition and Structure

• Dentine is a hard, calcified tissue that forms the bulk of a tooth, located beneath the enamel.
• About 70% of dentine is composed of inorganic minerals, primarily calcium hydroxyapatite, but the crystals are smaller than those in enamel.
• Roughly 20% of dentine's composition is organic material, including collagenous rich matrix (about 18%) and non-collagenous matrix proteins and lipids.
• The mineral composition and structure of dentine contribute to its hardness and ability to resist wear and tear.
• Dentin is vital for the tooth's structural integrity and supports the enamel.
• It also plays a crucial role in the tooth's response to stimuli like temperature changes and pressure, contributing to tooth sensitivity.
• Knowledge about dentine's composition and structure is essential for understanding dental pathologies, restorative procedures, and management of oral health conditions.

Tertiary Dentine

• Tertiary dentine forms in response to various stimuli such as caries or abrasion.
• Tertiary dentine can be reactionary or reparative, depending on the severity of the stimulus.
• Reactionary dentine is produced by pre-existing odontoblasts.
• Reparative dentine is formed by newly differentiated odontoblast-like cells.
• Reparative dentine can sometimes create osteodentine.

Colour of Dentine

• Healthy dentine is typically yellow due to lower mineralization compared to enamel.
• Diseased dentine can turn brown or darker affecting the tooth's appearance.

Dentine Permability

• Dentine is somewhat permeable due to tubules, with permeability levels varying by location.
• Tubule permeability affects caries progression and can impact sensation transmission to the pulp.
• Fluid content in dentine can trigger sensitivity or pain.

Radiographic Appearance of Dentine

• Dentine appears as a radio-opaque structure on radiographs.
• Caries lesions in dentine show as radiolucent areas.
• Dead tracts are empty dentine tubules where the odontoblastic process has died or retracted.

Incremental Lines of Von Ebner

• Thin, closely spaced lines in dentine formed during incremental dentinogenesis.

Contour Lines of Owen

• More pronounced incremental lines found at the interface between primary and secondary dentine.

Granular Layer

• A narrow layer with a granular appearance located in root dentine beneath the cemento-dentinal junction.

Types of Dentine

• Mantle dentine: Initial dentine formed, adjacent to enamel and cementum.
• Circumpulpal dentine: Forms the bulk of dentine, containing dental tubules.
• Pre-dentine: Surrounds the pulp chamber, allowing dentinogenesis to continue.

Primary Dentine

• Forms before root development completion, including both mantle and circumpulpal dentine.

Secondary Dentine

• Formed after root completion, slowly throughout life, leading to gradual pulp recession.

Clinical Significance of Secondary Dentine

• Secondary dentine accumulation shrinks the pulp space, reducing sensitivity in older teeth.

Clinical Significance of Tertiary Dentine

• Tertiary dentine protects the pulp by creating a barrier against further damage.
• Tertiary dentine is formed due to caries, attrition, or abrasive brushing.

Dentine Composition

• Inorganic (70%): Calcium hydroxyapatite.
• Organic (20%): Majority collagenous matrix and some non-collagenous proteins and lipids.
• Water (10%).

Dental Tubules

• The main structural feature of dentine, extending from the DEJ to the pulp chamber.
• Contribute to dentine's role in sensation and permeability.

Tubule Structure

• Tubules follow an S-shaped curve.
• Tubules are more widely spaced near the DEJ, creating a tapered structure closer to the pulp.

Tubule Composition

• Tubule walls are composed of peritubular (or intratubular) dentine which is highly calcified with minimal collagen content.
• Intertubular dentine, found between tubules, is less calcified and more collagenous.

Odontoblastic Process

• Each tubule contains an odontoblastic process.
• The periodontoblastic space around this process contains fluid, crucial for understanding dentine hypersensitivity.

Interglobular Dentine

• Areas of unmineralized dentine, often found near the circumpulpal dentine.

Sclerotic Dentine

• Tubules that have become calcified due to mineral deposits.
• Sclerotic dentine increases with age and reduces dentine permeability.