Association between staining by caries detector dye and the corresponding mineral density in dentin caries

To examine an association between coloration (red, pink) resulting from staining with Caries Detector Dye (CDD) and the corresponding mineral density in dentin caries lesions determined by transverse microradiography (TMR).

CDD coloration of the lesion sections (approx. 190 microm) prepared from extracted caries teeth was photographed, and the corresponding relative mineral densities (RMD: relative values to the sound dentin) were obtained by TMR. A parallel study was performed using artificially demineralized and then remineralized dentin lesions.

The mean RMD values in the naturally black-pigmented, red- and pink-stained portions were 46 +/- 26.7%, 64 +/- 24.5%, and 80 +/- 15.1%, respectively. There were statistical differences in the RMD values among the three portions, as well as a wider range of RMD value distributions in the red and black-pigmented portions than in the pink portion.Even among the black-pigmented and red portions, much higher RMD values more than 90% were observed in several lesions, which were close to the mineral density of the sound (unaffected) dentin tissue. On the other hand, the remineralized surface layer of artificially demineralized lesions did not show the red coloration, and there seemed a threshold value of mineral density (approx. 21%), beyond which the red coloration was not observed. Similar threshold value was noted in the remineralized lesion body. This study showed a remarkable discrepancy regarding the RMD value for the red staining behavior between the naturally occurring caries and artificial carious lesion.