Responses of intradental nerves to chemical and osmotic stimulation of dentine in the cat.

Recordings have been made of the neural responses evoked by stimulation of dentine with solutions of NaCl, NH4Cl and dextrose. Stimulation of the outer dentine produced no response. From the inner dentine, a smaller number of impulses were recorded with solutions of NaCl than with corresponding concentrations of NH4Cl, but a much larger number than with solutions of dextrose. The discharge evoked by a solution increased in mean frequency and decreased in latency as the thickness of dentine was reduced. The responses suggest that the receptors were in the innermost dentine or the pulp and that they were excited by changes in extracellular fluid composition rather than by osmotic effects. The properties of the receptors appear to be different from those involved in pain from dentine in man.