In vitro Evaluation of an FD&C Blue No. 1-based Optical Whitening System as a as an Alternative to Peroxide-containing Agents for Teeth Whitening

Abstract Background: Tooth whitening is increasingly demanded for esthetic reasons, but peroxide-based agents may cause enamel alterations and soft-tissue irritation. Optical whitening using blue pigments offers a nonperoxide alternative that produces immediate whitening through color masking rather than oxidation. This study evaluated the whitening efficacy, enamel interaction, color stability, and biocompatibility of an FD&C Blue No. 1-based optical masking system. Materials and Methods: Thirty-two extracted human premolars were used to assess enamel microhardness, dye penetration depth, and color stability after thermocycling. The optimized formulation was evaluated using Vickers microhardness testing, stereomicroscopy, and color assessment after 833 thermocycles between 5°C and 55°C. Biocompatibility was assessed using cytotoxicity assays on human gingival fibroblasts exposed to different concentrations for 24 and 48 h. Results: The optimal formulation (0.1 g FD&C Blue No. 1 in 8 mL distilled water for 1 min) produced the best whitening effect and was selected for testing. Treated teeth showed higher microhardness than controls (376.78 ± 61.23 vs. 300.75 ± 49.60 vickers hardness number (VHN); P = 0.036). Dye penetration was minimal (6.11 ± 1.84 μm), indicating surface-level action. Whitening effect significantly decreased after thermocycling, with most samples returning to baseline shades ( P = 0.001). Cytotoxicity testing showed dose- and time-dependent reductions in fibroblast viability. Conclusion: FD&C Blue No. 1 produced rapid whitening through surface optical masking with limited enamel penetration but reduced color stability after aging and dose-dependent cytotoxicity. It may serve as a short-term adjunct to conventional bleaching methods.