Increased bone formation to unstable nano rough titanium implants.

Early bone response to cylindrical smooth titanium implants (S(a)=0.1 microm) inserted into the rabbit tibia was compared in a stable and nonstable regime. Surface roughness parameters were calculated from measurements obtained with optical interferometry and atomic force microscopy. Contrary to our hypothesis, the nonstable implant showed higher bone to metal contact and increased bone area in the endosteal region compared with the stable implant after 4 weeks of healing. Bone area measurements in the cortical region revealed similar values. Primitive woven bone was found in close contact with both implants, but significantly more with the nonstable implant. Finding more bone-to-implant contact (BIC) need not necessarily indicate that unstable implants were more strongly integrated. Primitive bone stage development observed indicates less strong implant anchorage than could be expected from BIC percentage alone. Stable implant design used in this study is a reliable model to evaluate submicron and nanostructures in vivo, as implant stability was achieved in the absence of microirregularaties.