Molecular structural analysis of carious lesions using micro-Raman spectroscopy.

In clinical situations carious dentine tissues can be discriminated by most caries fluorescence detection tools, including a new fluorescence intra-oral camera. The objectives of this study were: (i) to analyze the Raman spectra of sound, carious, and demineralized dentine, (ii) to compare this spectral analysis with the fluorescence variation observed when using a fluorescence camera, and (iii) to evaluate the involvement of the Maillard reaction in the fluorescence variations. The first positive hypothesis tested was that the fluorescence of carious dentine obtained using a fluorescence camera and the Raman spectra variation were closely related. The second was that the variation of fluorescence could be linked with the Maillard reaction. Sound dentine, sound dentine demineralized in aqueous nitric acid solution, carious soft dentine, sound dentine demineralized in lactic acid solution, sound dentine demineralized in aqueous nitric acid solution and immersed in methylglycoxal solution, and sound dentine demineralized in aqueous nitric acid solution and immersed in methylglycoxal and glucose solutions, were studied using micro-Raman spectroscopy. Modifications in the band ratio of amide, phosphate, and carbonate were observed in the decayed and demineralized groups compared with the sound dentine group. The results indicate that a close relationship exists between the Maillard reaction and fluorescence variation.