ZrO₂ Ceramic without and with Fullerene C₆₀ Films: In Vitro Direct-Contact Model Using E. coli and S. aureus Bacteria

Zirconia is known as a strong and bioinert load-bearing material for dental implants. It typically exhibits no antibacterial activity. Inflammation is a crucial problem for dental implant surgery: about 3-5% of all dental implants experience inflammation. This study demonstrates that either fullerene C₆₀ films or a tribomechanical loading of zirconia without the fullerene C₆₀ coating can cause an improvement in antibacterial activity against Gram-positive Staphylococcus aureus. This moderate antibacterial activity is especially important, because a strong antibacterial effect could disturb the sensitive and beneficial oral bacterial biota. In the present study, different fullerene C₆₀ films were examined. In addition to fullerene C₆₀ film in an "as deposited" condition, treatment with nitrogen plasma as well as tribomechanical produced surface patterns with and without plasma post-treatment were tested. An 85.8% (log reduction 0.85) reduction in Gram-positive Staphylococcus aureus bacterial formation was observed on the zirconia with fullerene C₆₀ film. Plasma treatment of the C₆₀ film increases the antibacterial impact to 72.2% (log reduction 0.56) in comparison to zirconia without fullerene C₆₀ film. Also, tribomechanical loaded fullerene C₆₀ films suppress the growth of Gram-positive Staphylococcus aureus. The tribomechanical loading seems to compensate for the effect of the plasma treatment. ZrO₂ samples with fullerene C₆₀ film and tribomechanical loading achieve an increase in antibacterial impact of 83.36% (log reduction 0.78). Furthermore, surprisingly yttria-stabilized zirconia bioceramic without fullerene C₆₀ film also shows an improved antibacterial efficacy after a tribomechanical patterning procedure. The addition of surface patterning on the ZrO₂ by scratching microgroove arrangements with a diamond tip, increased the antibacterial effect against Gram-positive Staphylococcus aureus by 70.46% (log reduction 0.53).