Antimicrobial and osteoconductive properties of copper-bearing implant materials.

Objectives: Dental implants are susceptible to failure due to a variety of causes with bacterial infection being of particular concern. The aim of this study was to investigate the antimicrobial and osteoconductive properties of copper-bearing implant materials; titanium, cobalt/chromium and stainless steel alloys together with Cu-doped nanohydroxyapatite (nHA) coated onto titanium substrates.
Methods: Metal alloys (Institute of Metal Research, Shenyang) and nano-coated titanium substrates (Johnson Matthey and Promethean) were subjected to antimicrobial and bioactivity testing. Anti-biofilm assays were conducted against Escherichia coli and Staphylococcus aureus as indicator species. Alamar blue assays, alkaline phosphatase production and lactate dehydrogenase release were conducted with osteoblasts (MG-63 osteosarcoma cells) to investigate cell proliferation, differentiation and cytotoxicity, respectively.
Results: CoCrCu (2.8% Cu), 316L-Cu SS (Stainless Steel; 4.5% Cu), Ti-6Al-4V-5Cu (5.0% Cu) and Ti-5Cu (5.0% Cu) alloys reduced E. coli populations by 28%, 79%, 90% and 93%, and S. aureus populations by 25%, 48%, 76% and 79% respectively, as compared to control titanium substrate. Whereas, Cu-doped nHA (2 - 31% Cu) coated substrate demonstrated biofilm reductions of 31- 98% and 45 – 90% for E. coli and S. aureus respectively. Osteoblast proliferation and differentiation was not significantly different between test materials and control substrate. However, significant cytotoxic effects were observed with nano-coatings containing higher copper concentrations.
Conclusions: The addition of appropriate amounts of copper into metal alloys and coatings for dental implant materials offers excellent antimicrobial and biocompatibility properties. Further studies are required to examine copper ion release and mechanism of antimicrobial activity.