The definition of dentin hypersensitivity highlights a
number of stimuli which can evoke a response. Evaporative
stimuli such as a triple syringe air jet or cold windy weather
results in desiccation of the dentin surface and is thought to
increase in the outward flow of fluid in the tubules, as does a
cold thermal stimulus and osmotic stimuli such as sugar or
acidic fluid [36]. A thermal hot stimulus appears to result in
contraction of the fluid in the tubules from in vitro research
[37]. Physical stimulation is more difficult to understand,
but in theory, compression of the surface such as a “stiletto
heel effect” is thought to compress the surface tissue and on
release cause expansion and hence increased outward fluid
flow [37]. Of all the stimuli, cold is reported as most
problematic and is used routinely in clinical trials as a
positive stimulus [38]. Alternative interpretations of the
hydrodynamic theory have been proposed including the idea
that fluid movement may cause an electrical streaming
potential [39, 40]. Whether this can reach proportions to
electrically stimulate nerves is not known, but possible.