Methods to characterize the surface roughness of metallic implants

Abstract

The surface roughness of surgical implants has a significant influence on the tissue reaction at the interface. The purpese of the present study is to describa methods which allow a detailed characterization of the surface roughness. Pure titanium plates with different surface treatments and electropolished stainless steel plates, were analysed. For the surface roughness measurement, a profilometer with a 4 μm tip was used to determine the following roughness parameters: R a = arithmetic mean of the roughness height, S m = arithmetic mean of the groove distance, R tm = average of the roughness height. Furthermore the surface was observed under a scanning electron microscope (SEM) at a magnification of 1000x and 2000x so that even small pores which cannot be measured using the profilometer are detectable. Standard reflected light microscopy and interference contrast microscopy was used to optically measure the height of depressions and elevations, and to study in particular the surface colour, which is related to the thickness of the oxide film of anodized implants. It is concluded that, for the characterization of the surface roughness of metallic implants, the measurements using the profilometer and SEM are recommended. For anodized surface treatments, interference contrast microscopy seems to be a valuable aid to judgement of the homogeneity and, via colour, the thickness of the oxide layer.