Dental pain evoked by hydrostatic pressures applied to exposed dentin in man: a test of the hydrodynamic theory of dentin sensitivity.

The hydrodynamic theory of dentin sensitivity holds that pain is evoked by stimuli producing minute shifts in tubule fluid. In human volunteers hydrostatic pressures were applied to prepared dentinal cavities. The subjects reported the magnitude and quality of their sensations of pain by means of an intermodal matching technique in combination with verbal descriptors. No pain could be elicited when the smear layer was present. After removal of this layer, pressure stimuli of either direction evoked sharp pain. Rapid changes in pressure induced higher pain intensities than slow changes, indicating that the dental A-delta system is dynamic and gradient dependent. These results provide support for the hydrodynamic theory of dentin sensitivity and also lend credence to the notion that the movement of fluid across dentin induces a selective activation of the A-delta nerves in healthy pulps which is highly correlated with a sensation of sharp and/or shooting pain.