The electrical resistance of enamel—dentine cylinders. Influence of NaCl content in storage solutions

Objectives: To investigate the influence of different electrolyte concentrations on the electrical resistance of sound human enamel-dentine cylinders in vitro. Methods: Forty cylinders of 3-mm diameter and 2-mm length were drilled from 40 extracted caries-free third molar teeth. For ease of handling the samples were fixed in Perspex discs by means of a cyanoacrylate-adhesive. An a.c. source (frequency 500 Hz, amplitude 1 μA) with a high internal resistance was applied. Only Ohmʹs resistance was measured. The resistance measurements on the samples were made after storage in distilled water, 0.16 mM NaCl, 1.6 mM NaCl, 16 mM NaCl and 160 mM NaCl for 24 h. Results: The mean resistance values were 2026 ± 152, 1835 ± 178, 1605 ± 364, 483 ± 265 and 60 ± 33 kΩ, respectively. All values were statistically significantly different (Wilcoxon test; P < 0.0001). Conclusion: It is concluded that the choice of electrolyte solution influences the resistance values of the enamel-dentine samples. This effect should be taken into account when measuring electrical resistances in vivo and in vitro.