Tension bending deformability of Mg-Ca and Mg-Zn alloy wires by coiling and evaluation of degradability in vitro

Magnesium is a metal material with both bioabsorbability and biocompatibility, and the fine wire is expected to be applied to bioabsorbable implants. It is desirable that the alloy composition is composed only of bioessential elements such as calcium and zinc, and the composition does not form the second phase precipitate of unknown biological toxicity. However, there are few studies on magnesium fine wires, and their degradability. In the case of surgical clips, staples, sutures, etc., it is necessary to consider bending deformation during ligation. In this study, fine wires of Mg-0.3 mol%Ca and Mg-0.3 mol%Zn were fabricated, and the coil was formed by the winding tester to evaluate the bending deformation. As a result, it was confirmed that Mg-0.3 mol%Zn was hard to crack, while Mg-0.3 mol%Ca was easy to crack after the deformation. In addition, an in vitro test was conducted using the prepared coil to investigate the effect of alloying elements on the degradability. After the tension bending deformation, surface appearance was inspected to know the effect of the trace alloying on the deformability. Continious observation revealed that the alloying element affect the degradability, since the shape of coil using Mg-0.3 mol%Ca and Mg-0.3 mol%Zn remained for 21 days and 35 days, respectively.