Heterogeneity of auto-fluorescence of human tooth tissue progressed by aging

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Age changes of auto-fluorescence intensities of six regions of buccolingual and longitudinal directions in human dentin were studied using a time-resolved fluorescence microphotometer. Static measurement mode showed that fluorescence intensity increased with aging in the all regions. Wavelength of the maximum fluorescence and full width of half maximum of fluorescence spectrum, however, did not change ; the values of the former and the latter were around 440nm and about 100nm, respectively, in the all regions of all teeth studied. The dynamic mode suggested that the auto-fluorescence of 440nm wavelength had at least three fluorescent components with different fluorescence decay times, fast, intermediate and slow. Fluorescence intensities of these components increased with aging in the six regions ; the intensity of the fast component showed an increase in proportion to aging after 18 years old, while in the other two components, the increasing rate of fluorescence intensities decreased at old aged teeth. Age changes of ratios of intensities of the three components to the static fluorescent intensities were distinguishable among the regions of longitudinal direction ; the ratio of the fast component increased with aging in the coronal dentin, while in the root apex dentin, the ratio of the slow one decreased. A tendency intermediate between the former two regions was seen in the cervical dentin. The above results showed that patterns of age changes were different in the longitudinal direction, from which it was inferred that factors affecting age changes were different between the coronal and root apex dentins.