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Changes in the hydration state of the enamel, sound or deficient, has proved to cause changes in its fluorescence, thus creating a potential problem especially for in vitro caries assessment with the light-induced fluorescence method (QLF). The aim of this study was to test the possibility of stabilizing the hydration state of the enamel when measuring the enamel fluorescence in vitro. The rate of fluorescence change in 8 incipient artificial enamel lesions was measured while gradually dehydrating the tooth blocks. Enamel fluorescence in the lesions was measured immediately after removal of the tooth blocks from the liquid environment, followed by measurements every minute for 10 min, thereafter once every 5 min until 30 min. In order to rehydrate the enamel blocks they were then kept in a wet environment for 24 h under +4°C. Subsequently, a thin film of olive oil was applied on the enamel blocks. The enamel fluorescence was then remeasured at the same frequency as the first day. All the enamel blocks showed a drop in their fluorescence after a few min. However, after oil treatment the drop in fluorescence was less and slower than without oil treatment. Before oil treatment, the half-life time (mean B SD) elapsed until the lesions reached a steady fluorescence level was 6.0B1.1 min, and after oil treatment it was 13.9B4.6 min. Thus, oil treatment significantly retarded the time of in vitro dehydration of the enamel. From this in vitro study it was concluded that oil treatment could be used as a means to obtain more stable and thereby more reliable QLF measurements on a longitudinal basis. Further investigations, however, are needed to study other effects of oil on the enamel fluorescence. |