Electrical impedance. A method to evaluate subtle changes of the human oral mucosa

In a previous study, we mapped the differences in electrical impedance between various anatomical locations in the oral mucosa. We now explore the ability of the impedance technique to detect mild reactions in the buccal mucosa induced by the irritant sodium lauryl sulphate. This substance was applied for 15 min at a concentration of 2% to the mucosa of 26 healthy subjects. A contralateral site was used as a control. Responses were evaluated by measuring electrical impedance before exposure and after removal of the irritant, and also by visual inspection and histology. Magnitude and phase of impedance were determined in the frequency range 1 kHz to 1 MHz at 5 depth settings, and 4 physically distinct indices were calculated from the impedance data. The results showed the response to be at its maximum 5 min after removal of the test chamber, for all indices. These changes were statistically significant, whereas visual and histological alterations were slight or negligible. We conclude that the electrical impedance technique is capable of detecting mucosal changes in the invisible or barely visible range, and that the mucosal response to sodium lauryl sulphate is well characterised by the 4 indices.