Assessment of the anti-bacterial efficacy of the silver incorporated resin composites

Background and Objectives: Increased bacterial (streptococcal) biofilm aggregation on the surface of resin composite restorations in comparison with amalgam and glass ionomer restorations makes the composite restorations susceptible to secondary caries next to the restorations.  In this study, the anti-Streptococcus mutans properties of resin composites containing silver nanoparticles were investigated.   Methods: In this experimental - laboratory study, using turbidity (spectrophotometry) test, the anti-streptococcus mutans properties of resin composites containing 0, 0.02, 0.03, 0.04, 0.05% w/w of nanosilver particles, were investigated. the composites were adapted on the wall surfaces of 400µl microplates, and after curing or stiffening (by light curing apparatus), they were exposed to the bacterial suspension in broth medium. After 3, 24, and 48 hours, the optical density of the broth was read by spectrophotometer.   Results: The results of the one-way analysis of variance showed that optical density (index of bacterial proliferation) in the composites containing silver nanoparticles with concentration of 0.03% w/w significantly decreased at times of 3 h (0.080±0.0009), 24h (0.079±0.0013), and 48 h (0.079±0.008) in comparison with composites without silver nanoparticles (0.089±0.005, 0.094±0.005, and 0.101±0.009, respectively), which is indicative of significant decrease in bacterial proliferation. This antibacterial effects did not increase in composites containing 0.04 and 0.05 % w/w concentrations of silver nanoparticles.   Conclusion: The results of this study revealed that all groups of the composite containing silver nanoparticles have antibacterial effect. Furthermore, optimal antibacterial effect exists in groups containing silver nanoparticles with concentration of 0.03% w/w.