Lecture Notes on Dentin Sensitivity

Definition of Dentin Sensitivity

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

Conditions for Dentin Sensitivity

• Occurs when dentin is exposed to the outside environment.
• In healthy teeth:
  • Dentin in the crown is covered by enamel.
  • Dentin in the root is covered by cementum.
• Exposure occurs due to:
  • Cavitation by caries.
  • Periodontal disease leading to exposure of root dentin.

Characteristics of Dental Tissues

• Enamel: Non-vital, no sensation.
• Cementum: Lacks neural tissue, no sensation.
• Dental Pulp: Vital, full of nerves, can elicit pulpal pain.
• Dentin: Only dental tissue linked with tooth sensitivity.

Structure of Dentin

• Completely mineralized.
• Odontoblasts: Present in pulp, their processes run through dentin in dentinal tubules.
• Dentinal Fluid: Fills peri-odontoblastic space, continuous with pulpal tissue fluid.
• Pulpal Nerves: From Plexus of Raschkow, extend between odontoblasts, may enter dentinal tubules.

Theories Explaining Dentin Sensitivity

Direct Neural Stimulation Theory

• Pulpal nerves enter dentinal tubules, extend full length to dentino-enamel junction.
• Mechanical stimulation of these nerves causes pain.
• Drawback: Pulpal nerves do not extend the full length of dentinal tubules.

Transduction Theory

• Nerves in dentinal tubules are limited to inner part.
• Exposed dentin excites odontoblastic process like nerve impulse.
• Impulse transmitted to nerve endings, causing pain.
• Basis: Odontoblasts from neural crest cells thought to have neural properties.
• Drawback: Odontoblasts cannot be excited or produce neural impulses; lack neurotransmitter vesicles for synaptic junctions.

Hydrodynamic Theory

• Also known as Fluid Theory; most accepted explanation.
• Dentinal fluid within dentinal tubules connects to outer environment when exposed.
• Movement of fluid in response to stimuli (physical, thermal, chemical) causes sensitivity.
• Examples:
  • Cold stimulus contracts fluid.
  • Heat expands fluid.
  • Air blast or sweet food dehydrates fluid.
• Fluid movement stimulates nerves, causing dentinal sensitivity.