This study focused on the so far unsolved problem for transgingival dental implant surfaces, i.e., the contest between bacterial and tissue cell colonization to that same surface after implantation.

Titanium nano-pillars were fabricated by nanosphere lithography and reactive ion etching, which allows for the parallel fabrication of randomly distributed nano-pillar structures. Different etching parameters were tested on wafers sputter coated by titanium to produce homogeneously distributed pillars with six different parameter combinations. 

Human Gingival Fibroblasts (HGF) were used as gingival soft tissue cells. Gram positive Streptococcus gordonii and gram negative Prevotella intermedia were tested separately and in co-culture on these surfaces. Adherence and spreading was investigated by fluorescent live/dead and crystal violet staining of cells and bacteria, proliferation rate for HGF by CCK8 photometric assay. For attachment strength, focal contacts of fibroblasts were visualized by a coupled immunoassay.

Fibroblasts grow healthy on 50 nm high (100 nm width) pillars that are distributed close to each other, but grow slower on higher pillars. They also aligned best to each other on the closely spaced 50 nm structures, but no difference could be seen on the quantity of focal contacts built.

Strepto­­coccus gordonii grew strongest on 50 nm high (200 nm width) pillars. For Prevotella intermedia no consistent results could be shown yet.

After 15h co-culture conditions (adding bacteria and HGF at the same time) the HGF cells did not survive for long, but the bacteria population stayed healthy.

Thus, these currently-tested surface modifications under the applied experimental conditions do not simultaneously promote cellular health and decrease bacterial colonization. The growth behaviour of both cells and bacteria however could be influenced by the surface modifications.

Supported by a grant from the ITI Foundation, Switzerland