Differences in the intensity of light-induced fluorescence emitted by resin composites

• Different fluorescence intensities were emitted from resin composites under QLF-D.
• The fluorescence of the restored composite was brighter or darker than the tooth.
• QLF-D provides superior detection of restored composites than the naked eye.

BackgroundThe aims of this study were to compare the intensities of fluorescence emitted by different resin composites as detected using quantitative light-induced fluorescence (QLF) technology, and to compare the fluorescence intensity contrast with the color contrast between a restored composite and the adjacent region of the tooth.MethodsSix brands of light-cured resin composites (shade A2) were investigated. The composites were used to prepare composite discs, and fill holes that had been prepared in extracted human teeth. White-light and fluorescence images of all specimens were obtained using a fluorescence camera based on QLF technology (QLF-D) and converted into 8-bit grayscale images. The fluorescence intensity of the discs as well as the fluorescence intensity contrast and the color contrast between the composite restoration and adjacent tooth region were calculated as grayscale levels.ResultsThe grayscale levels for the composite discs differed significantly with the brand (p < 0.001): DenFil (10.84 ± 0.35, mean ± SD), Filtek Z350 (58.28 ± 1.37), Premisa (156.94 ± 1.58), Grandio (177.20 ± 0.81), Charisma (207.05 ± 0.77), and Gradia direct posterior (211.52 ± 1.66). The difference in grayscale levels between a resin restoration and the adjacent tooth was significantly greater in fluorescence images for each brand than in white-light images, except for the Filtek Z350 (p < 0.05). However, the Filtek Z350 restoration was distinguishable from the adjacent tooth in a fluorescence image.ConclusionsThe intensities of fluorescence detected from the resin composites varied. The differences between the composite and adjacent tooth were greater for the fluorescence intensity contrast than for the colors observed in the white-light images.