AbstractBackground and ObjectivesThe intrinsic fluorescence of carious human teeth, of different stages of teeth demineralization, and the correspondence of such fluorescence to the mineral and organic distribution within the lesions were investigated.Study Design/Materials and MethodsFluorescence spectra of teeth excited with 337 nm nitrogen laser were recorded. Spectra were obtained from healthy enamel, dentine, demineralized areas, and different carious stages of the teeth investigated.ResultsSpectra obtained from sound enamel consisted of one intensive peak at 480–500 nm and one secondary peak at 430–450 nm. In dentine, this secondary component had much higher intensity. Fluorescence spectra of normal teeth were similar to those of enamel layer. A significant decrease of the intensity of the fluorescence signal was observed in both cases—in demineralized teeth and in carious lesion. The appearance of a fluorescence peak in the red spectral region was observed in the spectra of the initial carious lesions. In the teeth demineralization process, we observed an increase of the relative fluorescence peak intensity at 430–450 nm related to thinned out of enamel.ConclusionsA differentiation between initial tooth demineralization and early stages of caries could be made by the laser‐induced fluorescence spectroscopy method. Lasers Surg. Med. 34:249–253, 2004. © 2004 Wiley‐Liss, Inc.