Hard Dental Tissue Demineralization Followed With SOPROLife™ And Raman Microscopy

A fluorescence based method for dental caries detection was recently developed. Objectives: The aim of this study was to investigate correlations between variation of dental hard tissues fluorescence and structural changes during dentin demineralization. Methods: Tooth longitudinal slices with a thickness up to 0.5mm were prepared from freshly extracted sound teeth. The samples were grinded to 0.25 mm, polished and cleaned up in an ultrasound bath for 5 min. Four samples were demineralized in 2.5% aqueous nitric acid solution (pH 1) and another four-in 4% aqueous solution of lactic acid in carboxymethylcellulose sodium salt (pH 3.5) for seven days. Demineralization solutions were changed every two days. The samples were rehydrated in ultrapure water (Milli-Q®18.2 MOhm.cm) for five days. Two samples from each group were incubated into a PBS solution of Methylglyoxal 1,1-dimethyl acetal 10 mmol/L at 37 C° for four weeks. For each stage we recorded pictures of the samples with intraoral fluorescent camera SOPROLife™ in daylight mode, diagnostic mode and treatment mode. Raman spectra of each type of sample were registered with confocal Raman microscope (Lab RAM ARAMIS IR2 / HORIBA JOBIN YVON) at 633nm. Results: The nitric acid treated samples lost completely their green fluorescence, which reappeared partially after rehydration. An incomplete lactic acid demineralization decreased the email translucency, but the dentin fluorescence did not disappear. Raman spectra of several samples revealed a decrease of the phosphate and collagen matrix (Amide I, II, III) bands. Conclusion: The fluorescence of dental tissue was correlated with the degree of mineral component in dentine and with the modification of collagen matrix structure.