Use of AC impedance spectroscopy for monitoring sound teeth and incipient carious lesions

The objective of this study was to assess the ability of alternating current impedance spectroscopy technique (ACIST) to monitor sound tooth surfaces and incipient carious lesions.

Two hundred ninety-two teeth were examined in 30 patients. Occlusal surfaces were classified according to International Caries Detection and Assessment System (ICDAS). Two consecutive ACIST measurements at the investigation sites already visually examined were taken (t1). Examinations were repeated after 6 (t2) and 12 months (t3). Reproducibility of ACIST findings was calculated with the intra-class correlation coefficient. Values of the ACIST measurements were categorized, and kappa values were calculated. Spearman correlation coefficients (r _s) were calculated for correlations between ICDAS findings and ACIST measurements. To test whether ACIST detected changes similarly to ICDAS, Wilcoxon’s test was used (α = 0.05).

Intra-class correlation coefficient values of ACIST measurements ranged between 0.88 and 0.98. Kappa values for ACIST categories were 0.66–0.80. Rank correlation coefficient of ICDAS and ACIST readings was 0.38–0.65 at different time intervals (p < 0.01). Significant differences could be shown for ICDAS findings between t1/t2 (p = 0.001), t2/t3 (p = 0.021), and over the total duration of the study (t1/t3, p < 0.001). No significant differences between the various examination periods were found for the impedance measurements (p > 0.05).

ACIST exhibited in vivo high reproducibility but moderate correlation to visual findings at each time of examination.

ACIST can be used for monitoring sound teeth and early carious lesions although its suitability as a single detection method is limited since not all changes could be detected with respect to visual findings.