Application of Photocatalytic Thin Titanium Dioxide Films for Antibacterial and Stain-proof Dental Materials

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The purpose of the present study was to investigate the antibacterial activity of thin silver-ion-containing titanium dioxide films coated on light-activated resin composite against Streptococcus mutans and Candida albicans. The resin composite was composed of powder (silanized SiO2 filler) and liquid (49.5 wt% triethylene glycol dimethacrylate (TEGDMA), 49.5 wt% urethane dimethacrylate (UDMA), 0.5 wt% camphorquinone, and 0.5 wt% 2-(dimethylamino) ethyl methacrylate). The powder and liquid were mixed at a 3/1 ratio by weight and the specimen disks were polymerized on each side in a photo-curing unit for 90 s. Coating treatment was performed in a colloidal solution dispersing 1.5 wt% fine particles (average 5 nm) of silver-ion-containing titanium dioxide. Some specimens were dipped in 20wt% colloidal solution at 0.4 MPa, 80℃ for 30 min. For controls, noncoated TEGDMA-UDMA-based resin composite was used. The specimens were immersed in water at 37℃ for 1 day or 3 months. The surface properties, antibacterial activities, and release of titanium and silver ions were examined. A coating film with an approximately 0.1 μm thickness was confirmed on the resin composite surface by atomic force microscopy. The coated specimens inhibited the growth of S.mutans and C.albicans after immersion in water for 1 day and 3 months, whereas the noncoated specimens did not. There was no release of titanium ions from the coated specimens after immersion in water during either experimental period. Only small amounts of silver ions (15.6±1.4 ng/cm^2) were detected in the water from the coated specimens stored for 3 months. These results suggest that the activity of light-activated resin composite coated silver-ion-containing titanium dioxide films can be attributed to both silver ions released and the catalytic action of silver at the surface. Thus, this coating treatment appears to be suitable for clinical use.