Staining of non-carious human coronal dentin by caries dyes

This study tested the hypothesis that commercially available caries dyes stain non-carious human coronal dentin in freshly extracted teeth. Multiple sections were cut from 10 non-carious and two control carious teeth using a water-cooled saw. Each section was stained with one of five caries dyes. The location of staining, if any, was noted and the staining intensity was scored on a four-point scale. One of the sections from each tooth was subsequently decalcified and processed for observation under a light microscope using four histologic staining techniques to evaluate morphology, collagen distribution and bacterial content. The association between the stain intensity scores on the undecalcified sections and the five dyes was evaluated using the Kruskal-Wallis One-Way ANOVA by Ranks test. Outer carious dentin in the control specimens stained intensely with each of the five dyes. In the undecalcified, non-carious sections, all had at least one area of staining. However, this staining could be differentiated from the intensity of dye staining in the carious controls, except in two instances. The association between stain intensity scores and the five dyes was not statistically significant. In the histologic sections, numerous bacteria were seen within the dentinal tubules of carious lesions of the two control specimens; however, no bacteria were found in any of the sections from non-carious specimens. Histologically, no differences were observed in the morphology or staining pattern within mantle or circumpulpal dentin in areas stained with caries dye, and in only one unique instance within the main body of the dentin. These results suggest that the five dyes evaluated in this study can stain non-carious dentin, however, this stain can be differentiated from the staining of outer carious dentin in vitro.