Further Investigations of Age-Related Changes in Dentine Using ac-Impedance Spectroscopy

Ac impedance spectroscopy has been used to identify caries. However, in-vitro impedance measurements were affected by a number of external factors, such as size of the electrode area and change of temperature. There have been no impedance spectroscopy investigations reported on the effect of dentine age on impedance.

Objective: to investigate the effect of age on impedance measurements of human dentine using ac-impedance spectroscopy on samples of known ages.

Method: dentine samples were prepared from freshly extracted sound third molars. Five samples were prepared for each age group (20, 25, 30, 40 and 50 years old). The dentine sample was inserted into a special holder filled with physiological saline which allowed for constant electrodes contact. Electrical impedance measurements were performed over a frequency range of 100mHz to 10MHz. The impedance data were analyzed and modeled by Z-view software, which include a complex non-linear least-square fitting. After impedance measurements, dentine samples were characterized using scanning electron microscopy.

Results: impedance measurements showed differences in impedance between young and older dentine. One-way ANOVA of the means of resistance and capacitance for all age groups (20, 25, 30, 40 and 50 years old dentine) revealed a significant difference (ANOVA, p<0.0001) as a function of age. Applying Tukey's post hoc test, to the same data showed that this difference was due to the 50years old dentine for resistance and was due to the 40 and 50 years old dentine for capacitance which were statistically different to all other groups.

Conclusion: the study has shown that impedance spectroscopy technique can be used to detect structural changes in human dentine due to age. This finding and further investigation finding may have potential implications in designing commercial instrumentation for forensic or anthropological applications, such as age-assessment of dentine samples of isolated teeth or even partial tooth fragments.