BONE BONDING BEHAVIOR OF TITANIUM AND ITS ALLOYS WHEN COATED WITH TITANIUM-OXIDE (TIO2) AND TITANIUM SILICATE (TI5SI3)

It has been proposed that the essential requirement for artificial mat erials to bond to living bone is the formation of bone-like apatite on their surfaces in the body. Recent studies have shown that titanium h ydrogel and silica gel induce apatite formation on their surface in a simulated body fluid. In this study, the influence of titanium oxide a nd titanium silicate on the bonding of titanium alloys to bone was stu died. Rectangular implants (15 x 10 x 2.2 mm) of titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with T i5Si3 were implanted into the tibial metaphyses of mature rabbits. At 8 and 24 weeks after implantation, the tibiae containing the implants were dissected out and subjected to a detaching testing. The failure l oad for titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated With TiO2 , and Ti-6Al-4V coated with Ti5Si3 were, respectively, 0.68 +/- 0.48, 0.22 +/- 0.46, 0.67 +/- 0.59, 2.18 +/- 0.71 and 2.03 +/- 0.41 kgf at 8 weeks, and 2.7 +/- 0.91, 2.58 +/- 1.29, 2.38 +/- 0.41, 3.79 +/- 1.7, and 2.79 +/- 0.87 kgf at 24 weeks after implantation. Histological exa mination by Giemsa surface staining, CMR, and SEM-EPMA revealed the co ated titanium alloy implants directly bonded to bone tissue during ear ly implantation. A Ca-P layer was observed at the interface of the coa ted implants and the bone. The results of this study indicated that Ti O2 and Ti5Si3 can enhance the early bonding of titanium alloys to bone by inducing a Ca-P layer (chemical apatite) on the surface of titaniu m alloys. It also is suggested that the direct bone contact occurs in relation to the calcium and phosphorus adsorption onto the surface of the titanium passive layer formed during long-term implantation. (C) 1 996 John Wiley & Sons, Inc.