Dentin Sensitivity

Definition

• Characterized by short, sharp pain from exposed dentin.
• Occurs due to stimuli: thermal, evaporative, tactile, osmotic, or chemical.
• Pain cannot be attributed to other dental defects or diseases.

Dentin Exposure

• In healthy teeth, dentin is covered by enamel (crown) or cementum (root).
• Exposure occurs through:
  • Cavitation by caries.
  • Periodontal disease exposing root dentin.
• Exposed dentin reacts to various stimuli.

Sensation in Dental Tissues

• Enamel: Non-vital tissue, no sensation or pain.
• Cementum: Lacks neural tissue, no sensation or pain.
• Dental Pulp: Vital tissue with nerves, causes pulpal pain.
• Dentin: Only dental tissue associated with sensitivity.

Dentin Structure

• Odontoblasts in pulp; their extensions (odontoblastic processes) run through dentin in dentinal tubules.
• Peri-odontoblastic space filled with dentinal fluid, continuous with pulpal fluid.
• Pulpal nerves (Plexus of Raschkow) extend between Odontoblasts, may enter dentinal tubules.

Theories of Dentin Sensitivity

Direct Neural Stimulation Theory

• Pulpal nerves enter dentinal tubules and may cause mechanical stimulation.
• Drawback: Nerves do not extend the full length of dentinal tubules.

Transduction Theory

• Nerve-like excitation of odontoblastic process upon exposure.
• Basis: Odontoblasts from neural crest cells.
• Drawback: Odontoblasts cannot produce neural impulses or form synaptic junctions.

Hydrodynamic Theory (Fluid Theory)

• Most accepted theory.
• Dentinal tubules contain odontoblastic process and dentinal fluid.
• Mechanism:
  • Exposure connects dentinal fluid to the environment.
  • Stimuli cause fluid movement, which stimulates nerves in deeper layers.
  • Cold contracts fluid, heat expands it; air and sweets dehydrate, causing fluid movement.
• Fluid dynamics responsible for sensitivity.