Study on Human Tooth Tissue by Polarization Microfluorometry in Nanosecond Region

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Human teeth fluoresce as a result of illumination by UV-light. The fluorescence characteristics of human teeth were investigated with respect to aging and presence of caries. To measure nanosecond decay features of a tooth's fluorescence, a time-resolved fluorescence microspectrometer equipped with an air discharge lamp and polarization optics was devised. The lamp emits very short duration light with high repetition frequency ; duration-0.9 ns fwhm and repetition-7 kHz. Using this fluorometer, we found that the fluorescence intensity and fluorescence decay cuirve were age dependent in dentin tissue ; the fluorescence intensity increased and the fluorescence decay time decreased with increasing human age. This may result from a gradual maturation of fluorescent cross-linked collagen, such as pyridinoline, which increases markedly with age. The fluorescence intensity, anisotropy and fluorescence decay curves of caries enamel were more similar to that of hydroxyapatite than to the sound enamel. The data suggest that both quantitative and qualitative changes in the organic matrix of enamel may affect the fluorescence. of caries tissue.