CYTOCOMPATIBILITY OF VARIOUS METAL AND DEVELOPMENT OF NEW TITANIUM-ALLOYS FOR MEDICAL IMPLANTS

The cytocompatibility of new Ti alloys not containing Al and V such as Ti-15%Zr-4%Nb-4% Ta-0.2%Pd-0.05%N-0.2%O and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd -0.2%O were investigated by comparing with those of pure Ti grade 2 an d Ti-6%Al-4%V ELI (Extra Low Interstitial) alloys. The relative growth ratio for the medium extraction of Al containing very little V ions ( less than 0.02 mass ppm) was too low as compared to that of V free Al extraction. However, mixed powder extraction such as Ti + Zr + Nb + Ta and Ti + Sn + Nb + Ta exhibited evidently no effect on the relative g rowth ratio of L929 cells. The relative growth ratios of both L929 and MC3T3-E1 cells for the new Ti alloys were almost equal to 1 and were slightly higher than pure Ti grade 2 and Ti-6%Al-4%V ELI alloys. Also, the influence of extracting with Eagle's minimum essential medium (ME M) solution for L929 cells and ultra pure water for MC3T3-E1 cells on the relative growth ratio of cells were examined. Further, wear tests were conducted with the new Ti alloys, pure Ti grade 2 and Ti-6%Al-4%V ELI alloy disks against apatite ceramics and alloy pins in Eagle's ME M solution. The relative growth ratios of L929 and MC3T3-E1 cells were estimated with these wear test solutions. The relative growth ratio o f L929 cells were almost equal to 1 for the new Ti alloys and pure Ti grade 2 against apatite ceramics pin up to 10(5) cycles. However, the relative growth ratios of L929 and MC3T3-E1 cells sharply decreased fo r Ti-6%Al-4%V ELI disk against apatite ceramics pin from 3 x 10(4) wea r cycles. It was observed that the pH of the Eagle's MEM solution grad ually increased as the number of wear cycles increased in all the case s of alloy disk against apatite ceramics pin. Also, the V ion concentr ation increased as the number of wear cycles increased. This result wa s also similar for MC3T3-E1 cells. Further, the relationship between m etallic concentration in the medium extracted with Ti, Al, V, Zr, Sn, Nb, Ta, and Pd powders and the relative growth ratios of L929 and MC3T 3-E1 cells were evaluated. A similar dependence of the concentration o f vanadium ion and the relative growth ratios of L929 and MC3T3-E1 cel ls were seen as in the case of the wear tests. (C) 1998 Elsevier Scien ce S.A. All rights reserved.