Zr substrates (1cm 2 of anodized area) were sterilized in 2 mL 70% Ethanol for 15 min in a 6 well culture plate (Sarstedt, Germany) and washed 3 times in 2 mL PBS before 2 mL of starting bacteria inoculum were added. The plate was incubated at 37°C for 24 h.