IADR Abstract Archives
Tuning the Photo-activities of TiO2 Nanoparticles Using Dental Resins
Objectives: The unique photo-active properties of TiO2 nanoparticles made them attractive in many potential dental applications. The objective of this study is to optimize the benefits of the photo-activities of TiO2 nanoparticles embedded in dental resins.
Methods: The photo-activities of TiO2 nanoparticles were evaluated using electron paramagnetic resonance (EPR) and UV-vis spectroscopy, respectively, to determine the amount of the radicals generated and the energy required for their production. The beneficial effects of the radicals were assessed through the improvement of degree of vinyl conversion (DC; quantified by Fourier Transform Infrared spectroscopy) and the modification of hydrophilicity of dental resins (expressed by measuring the water contact angle (CA)). One-way ANOVA with a 95% confidence interval was used to indicate a significant differences (n=5). Light-cure (initiators: camphorquinone/amine) resins were formulated from ethoxylated-bisphenol-A-dimethacrylate (EBPADMA), BisGMA, TEGDMA, pyromellitic-glycerol-dimethacrylate and/or hydroxyethyl-methacrylate monomers. The viscosity and the number of hydroxyl groups of the experimental resins were correlated with the photo-activities of TiO2 nanoparticles (up to 0.5wt%).
Results: EPR and UV-vis results clearly showed that the TiO2 nanoparticles indeed generate radicals under visible light irradiation. The presence of the hydroxyl functionality played an important role in DC enhancement. In case of EBPADMA resin, the increase in DC was up to 22 % by adding only 0.1wt% TiO2 nanoparticles. On the other hand, viscosity of the resins had minimal or no role in DC improvement. In resins with abundant hydroxyl groups, radicals were more effective in making the resin more hydrophilic: CA dropped up to 25-degree by adding 0.5wt% of TiO2 nanoparticles.
Conclusions: Dramatic improvement in DC and a significant change in resin hydrophilicity can be achieved through modifying resin composition. Knowledge learned from this study will help formulating nanocomposites with optimized use of TiO2 photo-activities as initiators for photo-polymerization, additives for making super-hydrophilic materials and/or antibacterial agents.
Methods: The photo-activities of TiO2 nanoparticles were evaluated using electron paramagnetic resonance (EPR) and UV-vis spectroscopy, respectively, to determine the amount of the radicals generated and the energy required for their production. The beneficial effects of the radicals were assessed through the improvement of degree of vinyl conversion (DC; quantified by Fourier Transform Infrared spectroscopy) and the modification of hydrophilicity of dental resins (expressed by measuring the water contact angle (CA)). One-way ANOVA with a 95% confidence interval was used to indicate a significant differences (n=5). Light-cure (initiators: camphorquinone/amine) resins were formulated from ethoxylated-bisphenol-A-dimethacrylate (EBPADMA), BisGMA, TEGDMA, pyromellitic-glycerol-dimethacrylate and/or hydroxyethyl-methacrylate monomers. The viscosity and the number of hydroxyl groups of the experimental resins were correlated with the photo-activities of TiO2 nanoparticles (up to 0.5wt%).
Results: EPR and UV-vis results clearly showed that the TiO2 nanoparticles indeed generate radicals under visible light irradiation. The presence of the hydroxyl functionality played an important role in DC enhancement. In case of EBPADMA resin, the increase in DC was up to 22 % by adding only 0.1wt% TiO2 nanoparticles. On the other hand, viscosity of the resins had minimal or no role in DC improvement. In resins with abundant hydroxyl groups, radicals were more effective in making the resin more hydrophilic: CA dropped up to 25-degree by adding 0.5wt% of TiO2 nanoparticles.
Conclusions: Dramatic improvement in DC and a significant change in resin hydrophilicity can be achieved through modifying resin composition. Knowledge learned from this study will help formulating nanocomposites with optimized use of TiO2 photo-activities as initiators for photo-polymerization, additives for making super-hydrophilic materials and/or antibacterial agents.