ABSTRACT
The purpose of this study was to investigate the validity and reproducibility of laser fluorescence and electrical resistance readings on root carious lesions. One hundred and three freshly extracted human teeth with various forms of natural root caries were investigated by 6 operators using the laser fluorescence device DIAGNOdent (DD) and the Electronic Caries Monitor (ECM III). As a reference, a caries-free root area of each tooth was also examined. Specimens were classified as to colour, surface texture and cavitation depth. Teeth were sectioned through the centre of the lesion and prepared for polarising light microscopy. Histological depth of the lesions was defined as the distance between the surface and zone of translucency. Depths ranged from 0.1 to 3.1 mm. Statistical analysis of the interexaminer reproducibility revealed a significant correlation (Kendall's W) for DD measurements of 0.85 and 0.76 for ECM readings. Moderate correlation between the histological depth and DD (r(s) = 0.45) or ECM scores (r(s) = -0.48) could be demonstrated. Electrical resistance readings revealed a positive correlation (r(s) = 0.43) with the thickness of the remaining dentine, whereas this was negative for laser fluorescence readings (r(s) = -0.43). However, scatter plots suggested that most lesions had very low resistance. This investigation suggests that laser fluorescence and electrical conductance measurements can be obtained reproducibly by different operators and correlate moderately with histological lesion depth and remaining thickness of the dentine bridge.