Mineral Density at Dentin Caries and Staining by Dyeing Solution

Objectives: This study aimed to examine an association between color appearance (red, pink) of dentin caries stained by Caries Detector Dye (CDD) and the corresponding mineral density. Methods: Extracted teeth including dentin caries were stained by CDD, and the cut surfaces were photographed. The cut teeth were sectioned for transverse microradiography analysis to obtain relative mineral density (RMD: relative value to sound dentin, 100%). For comparative study with natural caries, artificially de-/remineralized dentin lesions were stained, and similarly the photos and RMD were obtained. Results: RMD values for the naturally black-pigmented, red- and pink-stained portions were 54±20.2%, 62±24.0% and 81±13.9%, respectively. The pink-stained portions showed significantly higher RMD value than those of other two portions (ANOVA, p<0.01). However in some cases of the black-pigmented and red-stained portions, quite higher RMD values close to that of sound dentin were observed. While it was found the intact and denatured collagen matrix, artificially demineralized by neutral EDTA or by acetate solutions (pH4.0, 5.0), were equally stainable by CDD. Furthermore, remineralized surface layer didn't show the red staining in all the cases. Moreover the red staining was observed only in the inner lesion body with the RMD value being approximately less than 21%. These findings suggested that limited mineral deposition on the collagen fibers would result in loss of staining property of the fibers. But in the natural caries the red portions with a wider range of RMD value (18-100%) were stainable. The discrepancy regarding the staining might imply other factor(s) than remineralization process. Conclusions: The authors concluded that the pink-stained portion should be conserved for the higher RMD in different grade, as has been claimed. While concerning the removal of the red-stained portion, further studies are needed due to the frequent occurrence of those higher RMD values.