The throbbing sensation in the dentin layer exposed due to gum recession or enamel erosion is explained by Brännström’s “Hydrodynamic Theory.” Dentin tissue consists of millions of microscopic tubes (dentin tubules) containing fluid. When the tooth is exposed to cold, hot, sweet, or air currents, the microscopic fluid molecules within these tubules move very rapidly inward or outward (displace). This sudden fluid movement mechanically deforms the nerve endings (A-delta fibers) waiting at the bottom of the tubules, at the pulp boundary, sending a sudden, lightning-like pain signal to the brain. In clinical management, it is necessary to close the openings of the tubules to stop this fluid movement. For this purpose, the tubule openings are artificially sealed and fluid movement is blocked using laser enamel dissolution, fluoride varnishes, or pastes containing potassium nitrate/calcium sulfate.
