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Objectives: Quantitative Light-induced Fluorescence (QLF) measures the percentage loss in fluorescence of carious tooth tissue with respect to surrounding sound tissue, and relates it to the amount of mineral lost during demineralization. However, the hydration state of caries lesion affects its fluorescence; therefore to ensure the reproducibility of QLF analysis in a longitudinal assessment of a lesion, it is essential that the same hydration state be maintained on each measurement occasion. The aim of the present study was to determine a method of achieving a reproducible hydration state in the use of QLF for caries assessment. Methods: Incipient caries lesions were created on the buccal surface of 15 human premolar teeth by 3-day demineralization in acidic buffer solution. Three experiments (A, B, C) were devised. In A, the problem was demonstrated by measurement of the fluorescence change (DQ) in each lesion at 10-second intervals up to 5 minutes while the lesion dehydrates on the bench. In B, each lesion was mopped with a cottonwool roll for 3 seconds on withdrawal from saliva, then DQ measurement taken and the tooth replaced in saliva. The procedure of withdrawal from saliva, mopping and measurement was repeated 10 times for each lesion. In C, each lesion was mopped with a cottonwool roll for 3 seconds on withdrawal from saliva, then coated with thin a film of ethyl acetate varnish and DQ measurement taken at 10-second intervals for up to 3 minutes. Results: In A, mean (n=15) values of DQ (%.mm2) increased significantly (ANOVA, p<0.001) with increasing dehydration time. In B, no significant difference in DQ between the 10 measurements taken. In C, no significant difference in DQ between the measurement intervals. Conclusions: Application of a cottonwool roll and/or an anti-dehydration varnish offered a reproducible hydration state in a caries lesion. |