Thermal Diffusion Potentials In Dentine: A Contributor to Dentine Hypersensitivity?

Objectives: The purpose of this investigation was to determine the magnitude and duration of thermal diffusion potentials (TDPs) in three selected in vitro dentine models: 1) silica micro capillary array as a homogeneous model of dentine tubules (Icom Inc USA); 2) mid-coronal human dentine disks and 3) a human maxillary premolar tooth. This investigation was conducted to determine whether these TDPs could be of sufficient magnitude for nerve excitation and hence possibly be a contributory factor in dentine hypersensitivity (DH) related pain, and to better understand the contribution of thermally-derived electrical effects.
Methods: A temperature gradient was applied to each model individually by means of two water baths set at 37°C and 3°C to mimic the oral environment and a cold stimulus respectively. The dentine model was equilibrated in the 37°C electrolyte solution before being transferred to the 3°C electrolyte solution and the electrical potential difference recorded in real time. A comparison between the use of platinum and Ag/AgCl electrodes was made to evaluate the most suitable experimental setup.
Results: Measured TDPs from +23 and +40mV were recorded when moving the models from 37°C to 3°C. This was the case with both the platinum and Ag/AgCl electrodes. However, when moving the selected models from 3°C to 37°C, a larger potential difference of -40mV was observed with platinum electrode whereas the Ag/AgCl electrode measured between -8 and -15mV.
Conclusions: These results demonstrated that TDPs were observed when a temperature gradient, mimicking a cold stimulus, was applied to the in vitro models. These observations support the hypothesis that a stimulus may be translated via electrical activity due to thermally induced processes (leading to a TDP). These TDPs are of sufficient magnitude to excite sensory nerves. Further work is therefore needed to determine to what extent, if any, this process contributes to DH.