Dental Dentine Characteristics and Functions

Functions of Dentine

• Dentine is 70% mineralized, making it rigid.
• Composed of 20% collagen, giving it elasticity to absorb some shock.
• Dentine supports enamel.
• It protects the pulp.
• Dentine communicates with the pulp through the odontoblastic process.
• Dentine repair mechanisms can be triggered.
• Healthy dentine is more yellow and absorbs more light than enamel due to being less mineralized.
• Color changes to brown in diseased dentine, giving the crown a grey shadowing appearance.

Clinical Significance

• Caries can be detected via tooth surface loss and/or pulpal involvement.
• Yellowing of teeth with age and new adult teeth is reassuring.

Permeability

• Dentine's permeability comes from its tubules and organic content; permeability varies with structure.
• Tubules at the enamel-dentine junction (EDJ) are the least permeable due to their narrow diameter.
• Tubules near the pulp are more permeable because of their wider diameter.
• Caries progress quicker and more extensively through dentine than enamel.
• Dentine innervation and porous tubules facilitate pulp communication.

Communication

• Dentine tubules and the odontoblastic process allow communication with the pulp, triggering sensation.
• Clinical implications include dentine hypersensitivity, which can complicate restorative procedures and require anesthetics.

Fluid Content in Dentine

• Dentine hypersensitivity occurs when exposed, and fluid movement triggers sensitivity or pain.
• Restorative procedures and plastic materials are used for etching and bonding to dentine

potassium nitrate

• Potassium nitrate like in Sensodyne can block tubules.

Structural Features of Dentine

• Interglobular dentine refers to unmineralized or hypomineralized areas that failed to fuse during dentinogenesis.
• Interglobular dentine often appears in circumpulpal dentine, just below the mantle dentine.
• Interglobular dentine isn't present in all teeth, but appears if a vitamin D deficiency or high fluoride exposure occurs during maturation.
• Sclerotic dentine describes dentine tubules that have calcified as part of mineral deposition.
• Sclerotic dentine is common in the apical third of the root and midway in the crown between the DEJ and the pulp.
• Sclerotic dentine increases with age, reducing dentine permeability.
• This can impact root canal treatments/extractions, reduce sensitivity to stimuli, and improve ability to repair.
• Dead tracts refer to empty dentine tubules where the odontoblastic process has retracted or died.
• Dead tracts are thought of as the first stage of sclerotic dentine formation, increasing with age from pathological or physiological processes.
• Microscopic incremental lines present within dentine.
• Lines of Von Ebner: Reflect the pattern/process of dentinogenesis
• Contour lines of Owen: Distinct incremental lines found at the interface of primary and secondary dentine
• Granular layer of Tomes: Narrow layer of dentine with granular appearance
• The granular layer of tomes can only be found in root dentine beneath the cemento-dentinal junction
• It is more numerous towards the apex
• The granular layer of tomes is visible in ground sections only
• The granular layer of tomes results from interference with dentine mineralization by the inner layer of the dental sac.

Tertiary Dentine

• Tertiary dentine is reactionary or reparative dentine formed in response to stimuli.
• Tertiary dentine is localized to where the stimulus occurred.
• The structure of tertiary dentine depends on the intensity and duration of the stimulus.
• It may have tubules continuous with the secondary dentine or may have tubules that appear irregular in structure/arrangement.
• Caries, attrition, and abrasion are examples of stimuli.
• Reactionary dentine is deposited by pre-existing odontoblasts.
• Reparative dentine is deposited by newly differentiated odontoblast-like cells from the ectomesenchyme of the pulp; cells may form osteodentine and become trapped.
• Reparative dentine formation is a slower process than reactionary dentine formation.

Functions of Dentine

• Partially absorbing shock because it is slightly elastic.
• Rigidity adds structure and supports enamel.
• Providing protection for the pulp and serves as a physical and restorative barrier.
• Communicating with the pulp via the odontoblastic process, triggering repair.

Types of Dentine

• Dentine has varying types and a heterogeneous structure.
• There are three key types of dentine.
• Mantle Dentine: The initial formed dentine that outlines the periphery of the dentine adjacent to the enamel and cementum.
• Circumpulpal Dentine: The bulk of dentine and contains the dentine tubules, and lies in-between the mantle and pre-dentine.
• Pre-dentine (dentine matrix): Surrounds the pulp chamber enabling dentinogenesis to continue throughout life.
• Primary Dentine: This is the bulk of dentine in the tooth crown formed, prior to root formation and is made of both mantle and circumpulpal dentine.
• Secondary Dentine: Begins after root formation and forms slowly throughout life, mainly concentrated at the roof and floor of the pulp, reducing the size of the pulp chamber and causing pulp recession. While similar to primary dentine, it is less organized

Clinical Significance-Secondary Dentine

• Aging results in more secondary dentine deposition, causing the pulp to shrink with increased pulpal exposure for carious lesions and sensitivity in younger teeth

Histology of Dentine

• Dentine consists of 70% inorganic minerals (calcium hydroxyapatite), 20% organic material (collagen and non-collagenous matrix & lipids), and 10% water.

Structure of Dentine

• Dentine tubules are the main structural units.
• Dentine Tubules: Minute tubules that permeate the dentine from DEJ to pulp border.
• Dentine tubules traverse in an S shape.
• Dentine tubules are more widely spread near the DEJ compared to near the pulp, but straighter and underneath cusps.
• This pattern reflects odontoblasts' path during dentinogenesis.
• The wall of the tubules is called peritubular/intratubular dentine which minimal collagen, it is highly calcified.
• The dentine between tubules is less calcified and more collagenous, known as intertubular dentine, and makes up the bulk of dentine.
• Each tubule contains an odontoblastic process (cytoplasmic extension of odontoblast).
• Periodontoblastic space filled with fluid surrounds the odontoblastic process and allows communication between dentine and pulp.
• The odontoblasts' body sits in the pulp-dentine border within the pulp.
• Dentine has no blood supply; the pulp has nutrients.

Explore the characteristics, functions, and clinical significance of dentine. Understand dentine's role in shock absorption and its response to stimuli like caries and abrasion. Learn about dentine hypersensitivity and how it's treated, along with the differences between reactionary and reparative dentine.