BONE-BONDING BEHAVIOR OF TITANIUM-ALLOY EVALUATED MECHANICALLY WITH DETACHING FAILURE LOAD

Although titanium (Ti) and Ti alloy are generally classified as bioine rt materials in terms of their bonding to bone tissue, it is still unc lear whether they bond chemically to bone. In this study, we examined the bone-bonding ability of Ti alloy (Ti-6Al-4V) using smooth-surfaced plates under non-load-bearing conditions. The bone-bonding behavior w as evaluated mechanically by means of the detaching test reflecting te nsile force. After implantation of the plates into the tibiae of rabbi ts for 4, 8, 16, and 25 weeks, detaching tests were performed. The fai lure load of the Ti alloy plates was close to 0 kg at 4 and 8 weeks, b ut gradually increased with time, reaching 0.334 kg at 16 weeks and 2. 852 kg at 25 weeks on average. Histologic examination by Giemsa surfac e staining and SEM showed no differences between specimens at 8, 16, a nd 25 weeks, when Ti alloy plate made direct content with bone without any fibrous tissue. By SEM-EPMA, no clear calcium-phosphorus (Ca-P)-r ich layer at the interface between the Ti alloy and bone tissue was ev ident, although a thin bone tissue was observed on the detached Ti all oy plate. The present results indicate that from both mechanical and h istologic viewpoints, Ti alloy bonds directly to bone under static con ditions after some time, probably more than 8 weeks. The possibility o f chemical bone-bonding of Ti alloy was suggested. (C) 1995 John Wiley and Sons, Inc.