The influence of mineral loss on the auto-fluorescent behaviour of in vitro demineralised dentine.

The aim of this study is to investigate the influence of demineralisation on the fluorescent properties of dentine. The fluorescence emission at 529 nm due to 515 nm excitation of in vitro demineralised lesions was determined with a micro-Raman spectroscope as a function of location. Results were compared with the mineral loss profiles of the same lesions measured by microradiography. The root surfaces of 6 in vitro demineralised human third molars (lactic acid CMC gel, pH 5; six groups: 0, 4, 7, 14, 18 and 21 days) were used in the experiment. Thin slices of +/- 130 microns were cut perpendicular to the tooth axis. The fluorescence scans corresponded to mineral loss profiles. Confocal microscope images showed increasing fluorescence with increasing mineral loss. From these results it is concluded that this mineral loss causes an increase in auto-fluorescence by a factor of at least 10, therefore the chromophore causing this green fluorescence must be organic in nature. De-quenching or modification of this fluorophore due to the demineralisation process is probably the cause for the increase of the green fluorescence.