Dentine permeability and its role in the pathobiology of dentine sensitivity.

The classical hydrodynamic theory implicated fluid movement as a transducing mechanism in the production of dental sensitivity. This theory assumes that sensitive dentine must be permeable. Various measurements of dentine permeability are discussed, including: (1) factors that influence diffusive permeation across dentine; (2) factors that influence convective fluid movement across dentine; (3) osmotic activities of solutions; (4) comparison of evaporative and convective fluid movement; (5) the interaction between outward convective fluid flux on the inward diffusive flux of molecules; and (6) the importance of pulpal blood flow in the clearance of noxious substances from dentine and pulp, a balance concept. The variables involved in achieving good penetration of desensitizing agents in the presence of outward movement of dentinal fluid are also discussed, along with the presentation of a new hypothesis which emphasizes the importance of dentine as a dynamic physiological barrier that works in harmony with neurovascular elements in the pulp in an attempt to maintain the health of the pulp-dentine complex.