ABSTRACT
This study investigated reduction of the bandgap of silica by applying nano-silver doping technique and possible application of such silica as a filler in dental resin. Due to reduce band gap, newly fabricated nano-silver doped silica was able to release ROS in accordance with exposure of visible light. Nano-silver doped silica was composed of below 20 nm size crystal silver nanoparticle and 100~500 nm size amorphous silica. These two components were chemically attached to each other (Si-O-Ag). The reduced bandgap was 2.10 eV, which the value could be interpreted as occurrence of surface plasmon resonance generating ROS in visible light exposure conditions. When such nano-silver doped silica was used as a filler in dental resin, increased antibacterial property of nano-silver ion was observed which was related to releasing of ROS when exposed in visible light. The antibacterial properties were statistically significant following exposure to visible light when 0.7 to 1.5 wt% of nano-silver doped silica were incorporated into resin. When the contents of nano-silver doped silica were below 0.7 wt%, minimal ROS release resulted in no significant increase in antibacterial properties as there would be less exposed nano-silver doped silica on the resin surface by visible light. Meanwhile, more than 1.5 wt% of nano-silver doped silica also resulted no significant increase in antibacterial properties following exposure to visible light as the antibacterial effects from nano-silver ion itself were greater than effects from released ROS. Hence, it was concluded that dental resin containing 0.7 to 1.5 wt% of nano-silver doped silica would provide antibacterial properties when exposed to visible light, significantly greater than in dark conditions.