Microstructural characteristics and cellular responses of a potential germanium bearing titanium binary alloy for dental applications

In the present study, the as-cast Ti–5Ge (wt%) (AS-TG) alloy was used to evaluate the effect of solution heat-treatment temperatures on the microstructure, phase transformation, and biocompatibility. The AS-TG specimen was subjected to different solution heat-treatment temperatures from 700 °C to 1000 °C for 30 min, and then characterized using a field-emission scanning electron microscopy, X-ray diffractometry, transmission electron microscopy, Vickers microhardness, and contact angle goniometry. The in vitro biocompatibility levels of specimens were assessed through 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay with osteoblast-like (MG-63) and fibroblast (NIH-3T3) cell lines. Analytical results indicated that the grain size of the AS-TG specimen increased with an increasing treatment temperature. Needle-like structures were formed in the matrix when the temperature was above 900 °C. The examination of transmission electron microscopy confirmed that the AS-TG specimen was in the α phase, while α and α' phases co-existed in the specimens as temperature was above 900 °C, which also exhibited higher microhardness and lower contact angle. None of the investigated specimens showed a deleterious effect on MG-63 or NIH-3T3 cells, and were at the same level as commercial pure Ti, indicating good biocompatibility. Moreover, both MG-63 and NIH-3T3 cells presented excellent cell adhesion and proliferation abilities when temperature was 1000 °C. Thus, the AS-TG alloy heat-treated at 1000 °C possessed the greatest microhardness and wettability as well as highest cell viability, and could be considered as a potential biomaterial for dental applications.