Anti-bacterial Effects of Polymethylmethacrylate with In situ Generated Silver Nanoparticles on Primary Colonizers of Human Dental Plaque and Cariogenic Bacteria

Abstract

Aims: Polymethylmethacrylates (PMMAs) remain the most popular material for use in orthodontics, particularly in developing countries, because of their low cost and ease of use. Biofilm formation of cariogenic bacteria on these surfaces may contribute to tooth decay, gingivitis, and periodontitis. Nanoparticle-sized silver (NanoAg) inhibits the growth of microorganisms, but anticariogenic effects of NanoAg in situ in PMMA (NanoAg-IS-PMMA) in orthodontics have not been explored. Therefore, the primary purpose of the current study was to evaluate the antimicrobial activity of NanoAg-IS-PMMA against primary colonizers of human dental plaque and cariogenic bacteria in planktonic and biofilm cultures, grown as mono-species biofilms and mixed-species biofilms. Study Design: In vitro. Place and Duration of Study: Department of Medical Microbiology, Department of Orthodontics, Pediatrics Infectious Disease Research Center; Tehran, Iran. August, 2012–May, 2013. Methodology: Chemical-cure orthodontic resin was used to synthesize NanoAg-IS-PMMA using silver benzoate. Antibacterial effects of NanoAg-IS-PMMA were assessed against Streptococcus sobrinus, S. sanguinis, S. mitis, and Actinomyces naeslundii as well as cocultures of the four species by inhibition of bacterial adherence and growth inhibition of planktonic and biofilm bacterial cells on NanoAg-IS-PMMA. Results: NanoAg-IS-PMMA reduced bacterial adhesion by 36.2%–88.1%, depending on the bacterial type. Planktonic cultures of the microorganisms exposed to NanoAg-IS-PMMA showed a significant decrease (99.99%) in a time-dependent manner, over 28 days. Exposure to NanoAg-IS-PMMA inhibited biofilm formation of all test bacteria and their cocultures by 77.6%–99.96%, compared to PMMA. In addition, NanoAg-IS-PMMA retained some inhibitory effects for the third generation of biofilm formation. Conclusion: Our data supports the finding that NanoAg-IS-PMMA effectively inhibited adherence of primary colonizers of human dental plaque and cariogenic bacteria to NanoAg-IS-PMMA surfaces, in addition to rendering strong anticariogenic effects in the planktonic and subsequent mono-species biofilms and mixed-species biofilms formation. This demonstrated that NanoAg-IS-PMMA has the potential to minimize colonization of cariogenic bacteria and biofilm formation on orthodontic appliances.