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The aim of this paper was to study the different patterns for sound, demineralized and remineralized enamel observed when measuring fluorescence as function of dehydration time. 48 bovine enamel specimens were used. The enamel surfaces were varnished leaving a small window exposed. Specimens were demineralized for 1, 2, 3 or 4 weeks using a lactic-acid covered MC gel at either pH 4.6 or 4.9 after which the varnish was removed and specimens were remineralized for 2 weeks at pH 7.0 in the presence of 1 ppm fluoride. The remineralization solution was refreshed weekly. Fluorescence time series were collected with quantitative light-induced fluorescence (QLF) after demineralization and 1 and 2 weeks of remineralization. Dehydration was induced by continuous airflow over the specimen surfaces. The ratio of dehydration half-time of demineralized and sound enamel Ùd/Ùs was derived from the time series. After each series of dehydration measurements 2 specimens per group were sectioned for analysis of mineral profiles with TMR. No difference was found between the different demineralization times or pH groups. Directly after demineralization none of the sectioned specimens had a surface layer and Ùd/Ùs = 0.1 (SD 0.04). After 2 weeks remineralization Ùd/Ùs = 0.5 (SD 0.4), with values c1 for the lesions with mineral losses of less than 500 Vol% Ìm. The values of Ùd/Ùs increased significantly between demineralization and 1 week remineralization and again between 1 and 2 weeks remineralization (one-way Anova, pd0.05). A correlation of r = 0.6 was found for Ùd/Ùs versus mineral uptake in the lesion. We conclude that QLF can be used to determine changes in caries activity of incipient caries lesions by controlled dehydration when lesions are followed longitudinally in time. |