In vivo performance of a rare earth free Mg-Zn-Ca alloy manufactured using twin roll casting for potential applications in the cranial and maxillofacial fixation devices

A magnesium alloy containing essential,non-toxic,biodegradable elements such as Ca and Zn has been fabricated using a novel twin-roll casting process(TRC).Microstructure,mechanical properties,in vivo corrosion and biocompatibility have been assessed and compared to the properties of the rare earth(RE)element containing WE43 alloy.TRC Mg-0.5 wt% Zn-0.5 wt% Ca exhibited fine grains with an average grain size ranging from 70 to 150μm.Mechanical properties of a TRC Mg-0.5Zn-0.5Ca alloy showed an ultimate tensile strength of 220 MPa and ductility of 9.3%.The TRC Mg-0.5Zn-0.5Ca alloy showed a degradation rate of 0.51±0.07 mm/y similar to that of the WE43 alloy(0.47±0.09 mm/y)in the rat model after 1 week of implantation.By week 4 the biodegradation rates of both alloys studied were lowered and stabilized with fewer gas pockets around the implant.The histological analysis shows that both WE43 and TRC Mg-0.5Zn-0.5Ca alloy triggered comparable tissue healing responses at respective times of implantation.The presence of more organized scarring tissue around the TRC Mg-0.5Zn-0.5Ca alloys suggests that the biodegradation of the RE-free alloy may be more conducive to the tissue proliferation and remodelling process.