In-vitro observations on fluid flow through human dentine caused by pain-producing stimuli

Fluid movement through human dentine produced by solutions of CaCl2, NH4Cl, NaCl, urea and Golden Syrup and by thermal stimuli and drying was estimated from records of pressure changes in the pulp chambers of recently extracted teeth. The fluid movement caused by solutions of different substances could not always be predicted on the basis of their osmotic pressures alone, and some, such as urea, caused flow from the dentine towards the pulp. In general, those stimuli which were close to the threshold for pain in man caused similar rates of fluid movement, although the flow rate produced by a rise in temperature of 8 °C was similar to that caused by water. It is concluded that fluid flow through dentine may cause pain but that some stimuli may cause pain by other mechanisms.