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The aim of this clinical study was to present potential sources of errors influencing the analysis of fluorescence images by using quantitative light-induced fluorescence (QLF). Fluorescence images of 1,835 lingual/buccal surfaces and 517 occlusal fissures of 34 15-yearold adolescents were captured after professional tooth-cleaning four times during a longitudinal study. Images were taken with a CCD camera with the mirror version in a dental office without any ambient light under standardised conditions. The computer program (Inspektor QLF 2.00) was used to display, store and analyse the images. QLF images were analysed by two trained examiners. Average fluorescence loss (¢F) of the lesion, the area (A) of the lesion (mm2) and ¢Q (¢FW A) were determined. Based on a large number of analysed fluorescence images the following confounding factors were identified: (1) Despite professional tooth-cleaning performed before QLF recordings red fluorescing areas caused by residual plaque or calculus may limit longitudinal measurements. (2) Different brightness of fluorescence images observed in sequential clinical examinations can mimic remineralisation of lesions. (3) The analytical stage of the QLF method is limited if lesions extend to the gingival margin or to more than one surface. (4) Surfaces attacked by hypoplasia and developmental disorders have to be differentiated clinically from caries lesions before QLF assessment. (5) Angular errors during image capturing cannot be adjusted or eliminated completely by the time-consuming analytical process. An efficient control of all confounding factors is an important prerequisite in longitudinal studies. The new Video Repositioning System may be able to eliminate some sources of errors in future studies. |