A re-evaluation of electrical resistance measurements for the diagnosis of occlusal caries.

Clinical and radiographic diagnosis of occlusal caries is difficult. Resistance measurements in pits and fissures have shown better sensitivity compared with the more conventional methods of diagnosis. Two machines have been manufactured for this purpose: the Vanguard and the Caries Meter L. The aims of this study were to calibrate the readouts of these machines against a variable standard resistance box and use the Vanguard to compare readings taken in vivo and in vitro after extraction of the teeth. The diagnostic accuracy of clinical, radiographic, Vanguard and Caries Meter L diagnoses were also assessed. One hundred occlusal sites in 40 teeth of 20 patients were investigated in vivo with the Vanguard, noting clinical and radiographic appearances. The teeth were then extracted and the Vanguard readings repeated in vitro, together with Caries Meter L readings. The in vivo/in vitro comparison between Vanguard readings showed excellent reproducibility (Cohen's Kappa = 0.80). The sensitivity and specificity for the different examination techniques at the enamel level of diagnosis were 27% and 89% for visual, 6% and 100% for radiographic, 81% and 78% for the Vanguard and 74% and 74% for the Caries Meter L. In conclusion, this study supports the renewed interest in resistance measurements as a diagnostic technique and indicates that the in vitro model used gives results comparable to those in vivo.