Fretting fatigue properties of Ti-6Al-4V alloy in pseudo-body fluid and evaluation of biocompatibility by cell culture method

Abstract

Plain and fretting fatigue tests of an annealed Ti-6Al-4V alloy are carried out in ca. 150 mL of a pseudo-body fluid. A phosphate-buffered saline without calcium and magnesium salts (PBS(-)) is used as a pseudo-body fluid, and nitrogen gas is bubbled into the saline during the tests in order to reduce the concentration of dissolved oxygen in the saline. The fretting fatigue strength in PBS(-) is lower than those in the air at higher and lower stress amplitudes ranges, while the fatigue strengths in both environments are almost equivalent to each other. Released metallic ions and debris in PBS(-) recovered after fretting fatigue tests under two different conditions are quantitatively analyzed by graphite furnace atomic absorption spectrophotometry. Results of biocompatibility investigation suggest that metallic substances in small concentrations as 10 ppb have cytotoxicity, and that not merely the amount but also the state of metallic elements affect the extent of cytotoxicity of the fluids.