The bone tissue compatibility of a new Ti–Nb–Sn alloy with a low Young’s modulus

Abstract

A Ti–Nb–Sn alloy was developed as a new β-type titanium alloy which had a low Young’s modulus and high strength. The Young’s modulus of the Ti–Nb–Sn alloy was reduced to about 45 GPa by cold rolling, much closer to human cortical bone (10–30 GPa) than that of Ti–6Al–4V alloy (110 GPa) and other β-type titanium alloys developed for biomedical applications. The tensile strength of the Ti–Nb–Sn alloy was increased to a level greater than that of Ti–6Al–4V alloy by heat treatment after severe cold rolling. In this study the cytotoxicity of Ti–25Nb–11Sn alloy was evaluated in direct contact cell culture tests using metal disks and the bone tissue compatibility – examined using metal rods inserted into the medullary canal of rabbit femurs. The remarkable findings were that: (1) there were no significant differences in the relative growth ratio and relative absorbance ratio between cells grown with the Ti–Nb–Sn alloy, Ti–6Al–4V alloy and CP-Ti in direct contact cell culture tests; (2) there were no significant differences in the load at failure between the Ti–Nb–Sn alloy and Ti–6Al–4V alloy in pull-out metal rods tests; (3) there were no significant differences in new bone formation around metal rods between the Ti–Nb–Sn alloy and Ti–6Al–4V alloy in histological evaluations. The new Ti–Nb–Sn alloy with an elasticity closer to that of human bone is thus considered to be bioinert while also having a high degree of bone compatibility similar to that of Ti–6Al–4V alloy.