Effect of surface roughness on adhesion of Streptococcus oralis to titanium surfaces

Surfaces designed to promote osseo-integration of dental titanium implants often have an average surface roughness (Sa) close to 1.5 µm. However, such a degree of surface roughness may enhance adhesion of bacteria and hinder their removal, thus increasing the risk of chronic infections at implant sites. Objective: To determine how surface roughness affects the adhesion of different clinical strains of S. oralis (isolated from peri-implant infections) to titanium surfaces used in dental implants.Methods: Mid-exponential growth phase cultures (OD600 = 0.5) of three fresh isolates of S. oralis (LA11, 89C and 192B) were passed over titanium plates with Sa = 0.1 µm (turned) or 1.4 µm (blasted) in a flow-cell system for 2 hours. Numbers and viability of adhered bacteria were assessed using confocal microscopy after staining with the Live/Dead Baclight viability kit. Results: The bacteria showed a high degree of viability (>95%) and overall adhesion of all three strains was 2 to 5 times greater to blasted surfaces than that to turned ones, even after correction for the greater surface area (Sdr value of 58%) of the blasted surfaces. Strain 192B displayed the lowest number of adherent cells whereas binding of strain 89C was 5 times greater on both surfaces.Conclusions: These data suggest that different strains of S. oralis strains have different capacities to bind to titanium surfaces. In addition, we show that surface roughness is an important factor in determining adhesion and early biofilm formation by streptococci on oral implant surfaces