Air blast-induced evaporative water loss from human dentine, in vitro.

Short air blasts are commonly used to test for dentine sensitivity but their mechanism of action is poorly understood. In this study, evaporative water loss of teeth in vitro was measured under spontaneous conditions and during air blasts from three-way dental air syringes. Air blasts induced a 15-30-fold increase in evaporative water loss, which varied inversely with distance from the tooth and directly with air temperature. As water evaporation occurs readily across smear layers, which greatly impede bulk fluid movement, the use of air blasts may overestimate dentine sensitivity. Sustained air blasts may remove enough fluid from the pulp-dentine complex to cause disruption of odontoblasts and changes in pulpal blood flow.