Abstract A series of experiments have been conducted to examine the manner in which the removal of dentinal fluid can give rise to pain. Histologic examination and theoretical calculations indicate that at the same time there is a rapid outward flow in the dentinal tubules as a result of capillary forces. It was suggested that the sensitivity of the tooth to temperature may also be explained on the basis of hydrodynamic transmission to the pulp. Extremely small displacements can have a great effect because of the large number of tubules involved simultaneously.