Partially biodegradable Ti-based composites for biomedical applications subjected to intense and cyclic loading

This work presents a titanium (Ti) - magnesium (Mg) composite as a novel material that is designed for application in biomedical devices that are subjected to intense and cyclic loading (such as dental implants). This study concentrates on how the mechanical properties, fatigue endurance, in-vitro corrosion response and cytotoxicity of TiMg composites depend on the use of high-purity regular-morphology plasma atomized (PA) Ti Grade 1 powders. It also compares the desired results with those obtained for composites fabricated using hydride–dehydride (HDH) Ti Grade 4 powders. The results showed that the as-processed Ti(PA)+17 vol% Mg composite exhibited an attractive combination of an ultimate tensile strength (UTS) of 450 ± 1 MPa, 0.2% strain offset yield stress (YS0.2) of 331 ± 5 MPa, and elongation (ε) of 8.9 ± 1%), in addition to a reduced Young’s elastic modulus (E) of 88 ± 0.1 GPa. Moreover, the as-processed Ti(PA)+17 vol% Mg composite showed a reasonable fatigue life, while it reached a fatigue tensile stress of 260 MPa at 1.5·107 cycles. The advantageous mechanical properties of the Ti(PA)+17 vol% Mg composite, superior to those of Ti(HDH)+Mg counterparts, resulted from a specific ultrafine Ti grain structure. The corrosion behavior of the Ti(PA)+17 vol% Mg composite was systematically studied during immersion in a Hank’s balanced salt solution (HBSS) for up to 21 days. The elution of Mg enabled a further decrease of E down to 84.3 ± 0.3 GPa, while the tensile strengths remained unaffected, and ε and fatigue stress decreased. Nevertheless, the mechanical performance of eluted Ti(PA)+17 vol% Mg remained appropriate for a specific application of dental implants with the addition of porosity induced osseointegration. Owing to a refined Mg grain structure, in-vitro corrosion tests confirmed a reduced elution rate of the Mg component from Ti(PA)+17 vol% Mg when compared with that of Ti(HDH)+Mg counterparts. The cytotoxicity assays demonstrated that as-extruded Ti(PA)+17 vol% Mg exhibited a nontoxic response upon culturing with resistant hAD-MSC cells, which was comparable with that of the commercial purity (CP) Ti Grade 4 reference material. For a highly sensitive L929 cell line, the metabolic activity of Ti(PA)+17 vol% Mg had to be increased by surface pretreatment of a TiMg sample. All results of this study indicate that the new Ti(PA)+17 vol% Mg composite is immensely promising for use in prosthodontic surgery.