Abstract: Objective: To endow the resin bonding agents with antibacterial characteristic by applying the in situ synthesized silver nanoparticles, and to evaluate the antibacterial properties of resin bonding agents. Methods: The sliver 2-ethylhexanoate was dissolved into 2-(tert-butylamino) ethyl methacrylate to form a silver amine solution with a mass fraction of 8%. Then the silver amine solution was added to the adhesive part of Clearfil SE Bond, obtained three resin adhesives having 0wt%, 0.10wt%, and 0.20wt% of 2-ethylhexnoate respectively. All groups were irradiated by 1 000 mW/cm² for 20s to form specimens with diameter of 6mm and thickness of 1 mm. The size and distribution of silver nanoparticles were observed and measured by transmission electron microscope. Specimens were separately immersed in the sterile artificial saliva for 1 day or 1 week. After the saliva immersion, the resistance to streptococcus mutans of each group was calculated by colony counting method, and the antibacterial effect on the bacterial membrane was observed using a live/dead bacterial staining method under laser confocal microscopy. Results: The mean particle sizes of the group of 0.10wt% and 0.20wt% under transmission electron microscopy were respectively 3.12±0.82 nm and 3.64±0.65 nm, and the dispersion of the silver nanoparticles were evenly. The antimicrobial activity was significant after immersing in saliva for 1 day. After 1 week of immersion, the antibacterial activity of the 0wt% group was decreased, and the antimicrobial activity of 0.10wt% and 0.20wt% were increased, and significantly higher than that of 0wt% group (P<0.05). Conclusion: The application of in situ synthesized silver nanoparticles is feasible in the antibacterial modification of resin bonding agent.

Key words: Silver nanoparticles, Self-etching adhesive, Antibacterial activity, Streptococcus mutans