AUTOFLUORESCENCE OF BULK SOUND AND IN-VITRO DEMINERALIZED HUMAN ROOT DENTIN

The aim of this paper is to report on the demineralization-induced cha nges in dentin autofluorescence. Confocal laser scanning microscopy (C LSM) images and fluorescence excitation and emission spectra of in vit ro demineralized root surfaces and sound controls on the same tooth ro ots were compared. When observed in CLSM images, demineralized dentin, excited at 488 nm, gave an increased emission at 529 nm compared to s ound dentin. The difference in fluorescence decreased deeper into the root, as the sound dentin underneath the lesion was reached. In contra st, when using fluorescence spectrophotometry, excitation around 460 a nd 488 nm yielded a lower emission around 520 nm for demineralized den tin than for sound dentin, but in a more pronounced peak. From excitat ion spectra for emission around 520 nm, it could be seen that in demin eralized dentin the contribution of excitation between 480 and 520 nm was more important than in sound dentin. The recorded fluorescence in CLSM images was not affected by demineralization-caused changes in sca ttering and absorption properties, due to the small measurement volume . Thus, the increased fluorescence for demineralized dentin implies an increased quantum yield. In fluorescence spectrophotometry, where the measurement volume is large, changes in scattering and absorption do have an influence on the fluorescence signal. Then, increased absorpti on by non-fluorescing chromophores and increased re-absorption around the emission wavelength may compensate for the increase in quantum yie ld and absorption around the excitation wavelength by fluorophores.