Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle simultaneously for estate on an implant surface, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2 OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium(Ti), titanium-zirconium(Ti Zr) alloys and zirconia surfaces. Monoculture studies with either U2 OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2 OS osteoblasts were favourable on all materials. Adhering U2 OS osteoblasts cells, however,were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from Ti Zr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity. Sub-gingival anaerobic pathogens can colonize an implant surface to compromise osseointegration of dental implants once the soft tissue seal around the neck of an implant is broken. In vitro evaluations of implant materials are usually done in monoculture studies involving either tissue integration or bacterial colonization. Co-culture models, in which tissue cells and bacteria battle for for on on implant surfaces, have been demonstrated to provide a better in vitro mimic of the clinical situation. Here we aim to compare the surface coverage by U2 OS osteoblasts cells prior to and after challenge by two anaerobic sub-gingival pathogens in a co-culture model on differently modified titanium (Ti), titanium-zirconium (Ti Zr) alloys and zirconia surfaces. Monoculture studies with either U2 OS osteoblasts or bacteria were also carried out and indicated significant differences in biofilm formation between the implant materials, but interactions with U2 OS osteoblasts were fav ourable on all materials. Adhering U2 OS osteoblasts cells, however, were significantly more displaced from differently modified Ti surfaces by challenging sub-gingival pathogens than from Ti Zr alloys and zirconia variants. Combined with previous work employing a co-culture model consisting of human gingival fibroblasts and supra-gingival oral bacteria, results point to a different material selection to stimulate the formation of a soft tissue seal as compared to preservation of osseointegration under the unsterile conditions of the oral cavity.