치과용 Ti-Ag 합금의 특성

Abstract

The purpose of this study is to develop Ti-Ag alloys with high corrosion resistance, low ion release rate and biocompatibility and to evaluate the electrochemical properties of Ti-Ag alloys in an artificial saliva. Ti-Ag alloys were designed to increase Ag content from zero to 4.5 at% by 0.5 at%. The alloys were arc-melted, homogenized at 950 ℃ for 1 hour and quenched into water bath. Chemical compositions, phase identification, hardness, electrochemical properties and cytotoxicity of the alloys were investigated.

The purity of Ti-Ag alloys was maintained above 99.9%. It was considered because the impurities were little introduced into the alloys through the making process. In Ti-Ag alloys, α phase was stable up to 1.5 at% Ag, and α+β phase were coexisted above 2.0 at% Ag. This means that Ag was β phase stabilizing element in Ti-Ag alloys. In the range of 2.0~3.5 at% Ag addition, acicular α grains were observed in β grain. Hardness values increased with Ag content, and the increments were about 100% in the range of 2.0~3.0 at% Ag addition. It was thought that high increases of hardness values above 2.0 Ag content were due to the effects of solid solution strengthening and α to β phase transition. Ti-Ag alloys had higher corrosion resistance than Ti. These results mean that Ag addition to Ti can improve their corrosion resistance. Passive current densities in the anodic polarization curves were dependent on the chemical compositions of Ti-Ag alloys, however, they did not showed the linear relationship according to Ag contents. Ti-Ag alloys did not show pitting corrosion in artificial saliva. It was considered that Ag addition to Ti strengthened the passive film due to Ti dissolution induced by the difference of the electromotive force between Ti and Ag. In the agar overlay test, the cytotoxicity of Ti-Ag alloys and Ti was none or mild.

Conclusively, Ti-Ag alloys had higher mechanical properties and corrosion resistance than Ti, and demonstrated the similar toxicity to Ti. Therefore, it is thought that Ti-Ag alloys can be applied gradually to biomedical and dental fields.