This study aims to investigate bacterial adhesion on different titanium and ceramic implant surfaces, to correlate these findings with surface roughness and surface hydrophobicity, and to define the predominant factor for bacterial adhesion for each material.

Zirconia and titanium specimens with different surface textures and wettability (5.0 mm in diameter, 1.0 mm in height) were prepared. Surface roughness was measured by perthometer (R _a ) and atomic force microscopy, and hydrophobicity according to contact angles by computerized image analysis. Bacterial suspensions of Streptococcus sanguinis and Staphylococcus epidermidis were incubated for 2 h at 37 °C with ten test specimens for each material group and quantified with fluorescence dye CytoX-Violet and an automated multi-detection reader.

Variations in surface roughness (R _a ) did not lead to any differences in adhering S. epidermidis, but higher R _a resulted in increased S. sanguinis adhesion. In contrast, higher bacterial adhesion was observed on hydrophobic surfaces than on hydrophilic surfaces for S. epidermidis but not for S. sanguinis. The potential to adhere S. sanguinis was significantly higher on ceramic surfaces than on titanium surfaces; no such preference could be found for S. epidermidis.

Both surface roughness and wettability may influence the adhesion properties of bacteria on biomaterials; in this context, the predominant factor is dependent on the bacterial species. Wettability was the predominant factor for S. epidermidis and surface texture for S. sanguinis. Zirconia did not show any lower bacterial colonization potential than titanium. Arithmetical mean roughness values R _a (measured by stylus profilometer) are inadequate for describing surface roughness with regard to its potential influence on microbial adhesion.