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Michael Penkowski, Bart Truyen, K. Lewandowska, Peter Bottenberg, Magdalena Lewandowska, Lucia Henin, Jerzy Wtorek, Jan Cornelis
 

Caries Research

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Abstract 

Electrical Impedance Spectroscopy (EIS) has been demonstrated experimentally to be a remarkably sensitive tool for revealing the presence and extent of caries decay in whole tooth samples. This study sought to reassess previously reported results [Huysmans et al.: J Dent Res 199675:1871–1878, Longbottom et al.: Nature Medicine 19962:235–237] using an optimized experimental procedure and more accurate measurement equipment. Results are included for 5 unrestored extracted posterior teeth stored in KCl solution. For each tooth, one proximal measurement site without clinical signs of caries was selected. To exclude lateral surface conduction pathways between measurement and counter electrode, an insulating acrylic resin collar was cast around each tooth, allowing its distal part to hermetically engage in the sample holder. The measurement electrode consisted of a dental explorer tip. Unlike previous studies, a calibrated electrode pressure (0.5N) was ensured throughout the experiment. Measurements were acquired over a frequency range between 100kHz and 10Hz using a Solartron 1260 Impedance Analyzer (Solartron Analytical, Farnborough, UK). A surprising consistency was found among the measurements. Rdc values calculated from fitting an equivalent circuit to the spectral impedance data were in the range of 13.1MO±1%. Without removing the tooth from its sample holder, each measurement was replicated using a Solartron 1294A high-impedance interface, yielding Rdc values of 1.6·1011O±4%. This is almost 3 magnitudes higher than reported earlier, and is to be contrasted with the open circuit Rdc of 13.2MO±1%, respectively 3.1·1011O±5%, as measured with and without Solartron 1294A. The deviating outcomes of this study raise serious concerns regarding the application of EIS to the diagnosis of incipient caries, and may to some extent explain the inability of existing methods to discriminate between lesion depth in enamel.

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