Plaque formation on surface modified dental implants - An in vitro study

Bacterial adhesion on titanium implant surfaces has a strong influence on h ealing and long-term outcome of dental implants. Parameters like surface ro ughness and chemical composition of the implant surface were found to have a significant impact on plaque formation. The purpose of this study was to evaluate the influence of two physical hard coatings on bacterial adhesion in comparison with control surfaces of equivalent roughness. Two members of the oral microflora, Streptococcus mutans and Streptococcus sanguis were u sed. Commercially pure titanium discs were modified using four different su rface treatments: physical vapour deposition (PVD) with either titanium nit ride (TIN) or zirconium nitride (ZrN), thermal oxidation and structuring wi th laser radiation. Polished titanium surfaces were used as controls. Surfa ce topography was examined by SEM and estimation of surface roughness was d one using a contact stylus profilometer. Contact angle measurements were ca rried out to calculate surface energy. Titanium discs were incubated in the respective bacterial cell suspension for one hour and single colonies form ed by adhering bacteria were counted by fluorescence microscopy. Contact an gle measurements showed no significant differences between the surface modi fications. The surface roughness (R-a) of all surfaces examined was between 0.14 and 1.00 mum. A significant reduction of the number of adherent bacte ria was observed on inherently stable titanium hard materials such as TIN a nd ZrN and thermically oxidated titanium surfaces compared to polished tita nium. In conclusion, physical modification of titanium implant surfaces suc h as coating with TiN or ZrN may reduce bacterial adherence and hence impro ve clinical results.