Oral bacterial adhesion on amorphous carbon films

It is now well established that all the different forms of amorphous carbon films are biocompatible and suitable for specific biomedical applications. On the other hand, bacterial adhesion on implant surfaces has also a strong influence on the healing and long-term outcome of biomedical devices and this has not been thoroughly studied for the carbon films. The purpose of this study was to evaluate the bacterial adhesion on graphite-like amorphous carbon (a-C) films in comparison to titanium (Ti) films and stainless steel (SS) substrates using different bacteria strains from the normal oral microbiota. Medical grade stainless steel discs of 15 mm in diameter were coated by either Ti or a-C films using magnetron sputtering. The bacterial adhesion of single species and a mixture of nine different microorganisms was tested on the three surfaces. The bacteria were anaerobically incubated on the surfaces for 24 h, then colony forming units (CFUs) were counted. The total amount of CFUs was found higher on the a-C and SS surfaces in comparison to Ti films when the nine strains were mixed together, suggesting that Ti surfaces are better than the a-C and SS to avoid bacterial adhesion. However, when single species were analyzed the individual strains showed different adhesion profiles. Some species like Aggregatibacter actinomycetemcomitans, Eikenella corrodens, Campylobacter rectus, and Fusobacterium nucleatum were found in higher counts on the a-C surfaces, while other species like Actinomyces israelii, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis were found in lower counts comparing to the Ti films. These results suggested that the determination of antibacterial properties of a surface by studying the bacterial adhesion of individual strains, as usually done, might not be representative of the in vivo response, where more than one strain are surely present.