Antibacterial activity of silver ions implanted in SiO2 filler on oral streptococci

Objective. To evaluate the role of silver ions in composite resin dental materials, an in vitro investigation was conducted into the antibacterial effect of SiO2 filler implanted with silver ions on oral streptococci. Methods. SiO2 filler samples (0.1g) were implanted with silver ions. The effect of the filler with silver ions (Ag+ filler) was tested on oral streptococci bacteria. These bacterial strains had been isolated predominantly from composite resin surfaces. The organisms tested were anaerobically cultured in 5 mL Trypticase Soy Broth containing 0.5 per cent yeast extract at 37°C for 10–12 h. Each bacterial strain was adjusted to a concentration of 1 × 106 cells per mL with reduced transport fluid (RTF). Ag+ filler was immersed in 1 mL of RTF and anaerobically incubated 2, 6 and 12 h to study the antibacterial effect. The survival of bacteria was then estimated by culturing on TSBY agar plates. A plate with approximately 100 discrete colonies was chosen from the serial agar cultures, and the number of colonies was counted at each sampling time. Results. The Ag+ filler showed significantly more antibacterial activity than the control filler without silver ions. Significance: These results indicate that the antibacterial effect found in this study was due to the silver ions released by the Ag+ filler and that it may be useful to add this filler to composite resin dental materials for secondary caries protection.