The effects of waterjet peening on a random-topography metallic implant surface

Surface roughening is often applied to various devices, such as orthopedic and dental implants, in order to promote bone-implant attachment (osseointegration). In this study, we investigate the influence of pure waterjet peening on a generated random metallic surface. The deformation of the substrate, the height distributions, material ratio curves of deformed surfaces, and 12 area roughness parameters were analyzed for different impact velocities, ranging from 100 m/s to 700 m/s, and different initial arithmetic mean heights (Sa), ranging from 0.62 μm to 1.88 μm. As the impact velocity increases, the height distribution becomes wider. The dispersion parameters Sa and Sq, extreme parameter Sz, and asymmetry parameter Ssk all reach their higher values at a higher impact velocity. The root mean square height Sq relates to surface energy where both cell adhesion and protein adsorption can be enhanced by a higher surface energy. The negative skewness Ssk surface obtained from the waterjet peening process corresponds to improved load bearing surface since most peaks can be worn away quickly, thereby providing a good contact condition for the implant and surrounding tissues. The material ratio curves obtained at different impact velocities demonstrate that higher impact velocity results in higher values of valley depth (Svk), which indicates a larger available surface area for cell adhesion, proliferation/differentiation. It is recommended that when describing the roughness in the context of cell adhesion research, the roughness parameters Sq, Ssk, Svk be reported as a minimum set.