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The purpose of this study was to determine if there are any differences between average fluorescence loss (.Q) for images collected with different QLF units. Eighty-eight 4 mm round polished enamel specimens with 43.0 (± 3) µm mean Knoop microhardness were selected. A sealant was placed on the middle of the specimen, one side being covered with nail varnish. Fifty-five specimens were demineralized with a lactic acid/Carbopol solution for up to 96 h. Images were taken with six QLF/clin systems (QLFPatient software 3.0.3.2, Inspektor Research Systems B.V., The Netherlands). Focal distance was adjusted for each camera and specimens were placed flush on the holder, using a slot on the specimen as a reference. A drop of deionized water was placed on top of the specimen, followed by drying for 20 s, and an imafe immediately captured. The same procedure was repeated on 20 specimens to measure intra-camera reproducibility. Images were analyzed using a constant computer-generated rectangle. Intra-instruments reproducibility ICC varied from 0.72 to 0.96. Three systems were able to detect significant differences (p < 0.005) in the mean .Q for each of the groups, while another three could not detect differences between the 48 and 96 h groups. The ICC for the 6 systems was 0.74, with 2 systems accounting for the greater difference. Two pairs of systems had no significant differences (p < 0.001) between the .Q, while all other combinations had significant differences. In conclusion, in general systems achieved high reproducibility and detected differences in demineralization time. If systems are to be used interchangeably within a study, the differences in .Q must be accounted for. Supported by the National Institute of Health grant #P01 DE13540. |