Electrochemical and histomorphometric evaluation of the TiNiCu shape memory alloy

Abstract

By means of electrochemical and quantitative histomorphometric methods, the corrosion resistance and tissue biocompatibility of Ti₅₀Ni₅₀ and Ti₅₀Ni_50-xCu_x (x = 1, 2, 4, 6, 8) were investigated. It is discovered that the repassivation potential of Ti₅₀Ni_50-xCu_x (x = 2, 4, 6, 8) alloys is about 200 mV higher than that of Ti₅₀Ni₅₀ alloy. Namely, the addition of Cu raises the repassivation potential of TiNi shape memory alloys and improves their corrosion resistance. Pitting potentials of Ti₅₀Ni₅₀ and Ti₅₀Ni_50-xCu_x (x = 1, 2, 4, 6, 8) alloys increase with solution pH value, but the repassivation potentials keep constant. The adding of Cu has no obvious influence on pitting potential (E_pit) of TiNi alloys, meanwhile, the corrosion potential and corrosion rate of Ti₅₀Ni_50-xCu_x (x = 1, 2, 4, 6, 8) alloys are irrelevant to its Cu content and the values are almost the same as those of TiNi alloys. The connective tissue layer covering the plates is statistically significantly thicker for Ti₅₀Ni₄₂Cu₈ plates (p < 0.05) than that of Ti₅₀Ni₅₀, Ti₅₀Ni₄₈Cu₂, Ti₅₀Ni₄₄Cu₆ plates after one month. The numbers of connective tissue cells, polynucleated cells, macrophages and round cells are higher for Ti₅₀Ni₄₂Cu₈ plates than those of the other three types of plates, but no statistically significant differences are detected. There are no significant differences on tissue reaction parameters after two and three months among four alloys. After one, two and three months implantation, no corrosion is observed on the plates surfaces. A preliminary conclusion can be drawn that Ti₅₀Ni_50-xCu_x (x = 2, 6, 8) shape memory alloys have good biocompatibility.