Development of Bioactivity and Pull-out Torque Control Technology on Ti Implant Surface and its Application for Cold Thread Rolled Bone Screw

The influence of cold thread rolling conditions and a production method of titania (TiO2) films on surface bioactivity and pull-out torque of a titanium bone screw was investigated. The bone screw with micro surface roughness distribution was formed by cold thread rolling with a pair of parallel dies. The die shape and surface roughness distribution were changed to the 3 grades. The TiO2 films were coated on the surface of the bone screw using anodizing in aqueous solutions (hydro-coating). We introduced the rolled bone screws into tibia of rats for two weeks and examined the effects of the combinations of the surface morphology and the TiO2 film on osteoconductivity in an in-vivo experiment. As the results, it is found that we could control the bioactivity and pull-out torque by controlling the surface roughness at the bottom of the screw root.