BONE RESPONSE TO SURFACE-MODIFIED TITANIUM IMPLANTS - STUDIES ON THE EARLY TISSUE-RESPONSE TO MACHINED AND ELECTROPOLISHED IMPLANTS WITH DIFFERENT OXIDE THICKNESSES

The bone formation around titanium implants with varied surface proper ties is investigated. Machined and electropolished samples with and wi thout thick, anodically formed surface oxides were prepared, surface c haracterized and inserted in the cortical bone of rabbits (1, 3 and 6 weeks). Scanning electron microscopy, scanning Auger electron spectros copy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differ ences in surface chemical composition, between the different groups of implants. Light microscopic morphology and morphometry showed that al l implants were in contact with bone and had a large proportion of bon e within the threads at 6 weeks. The smooth, electropolished implants, irrespective of anodic oxidation, were surrounded by less bone than t he machined implants after 1 week. After 6 weeks the bone volume as we ll as the bone-implant contact were lower for the merely electropolish ed implants than for the other three groups. Our study shows that a hi gh degree of bone contact and bone formation are achieved with titaniu m implants which are modified with respect to oxide thickness and surf ace topography. However, the result with the smooth (electropolished) implants indicates that a reduction of surface roughness, in the initi al phase, decreases the rate of bone formation in rabbit cortical bone .