Application of quantitative light-induced fluorescence technology for tooth bleaching treatment and its assessment: An in vitro study

Objectives: This study aimed to determine the efficacy of a combination of photocatalysts—hydrogen peroxide at a low concentration (3.5%) and titanium dioxide (TiO ₂ )—activated at a wavelength of 405 nm using quantitative light-induced fluorescence (QLF) technology, and to quantify their tooth-bleaching efficacy using fluorescence images obtained from QLF technology. Materials and methods: Forty bovine incisors were extrinsically stained according to Stookey's method, and were randomly divided into four groups (n = 10 per group). Two bleaching solutions were prepared by mixing 3.5% H ₂ O ₂ with 0.05% of anatase and rutile TiO ₂ powders. These solutions were applied to the stained teeth using a microbrush and then irradiated for 15 min at either 306 or 405 nm to activate the bleaching agent. The color difference (ΔE ^* ) was assessed before and after every 5 min of treatment. The ΔE ^* and the changes in the fluorescence loss (ΔΔF) were obtained from white-light and fluorescence images, respectively. Results: All of the low-H ₂ O ₂ /TiO ₂ treatments caused significant tooth-bleaching efficacy after irradiation at 306 and 405 nm (p < 0.05). The results did not differ significantly between the two wavelengths (p > 0.05), but the bleaching efficacy was greater with anatase TiO ₂ at 306 nm and rutile TiO ₂ at 405 nm. Analysis of the fluorescence images revealed that the ΔF values increased significantly in all groups with the treatment time (p < 0.05). There was a statistically significant correlation between ΔE ^* and the change in ΔΔF (r = 0.822, p < 0.001). Conclusions: Combining low-H ₂ O ₂ /TiO ₂ with QLF technology at 405 nm has an efficacy of tooth-bleaching as a less harmful and biofriendly method, while the fluorescence images obtained by QLF technology could be used to assess tooth-bleaching.