Biofunctional micro/nanostructured "volcano-like" layer-coated 3D porous Ti-10Ta-2Nb-2Zr scaffolds improve osteogenesis and osseointegration for dental implants in vitro and in vivo

Ti-10Ta-2Nb-2Zr (TTNZ) alloy has been previously suggested to be a promising alternate biomaterial for implant applications. However, its mismatch in elastic modulus with human bone and its lack of sufficient bioactivity are two concerns that need to be addressed further. In this study, for the first time, we attempted to use macroporous structures on TTNZ alloy scaffolds manufactured by selective laser melting (SLM) to reduce their modulus of elasticity and strengthen bone interlocking. Then, we modified scaffold surfaces with hydroxyapatite (HA) coating by microarc oxidation (MAO) to promote osseointegration. The microstructure, surface morphology, chemical composition, mechanical properties, biological activities and osteogenesis performance of this scaffold were systematically investigated in vitro and in vivo. The results revealed that scaffolds with this novel porous alloy possess a lower elastic modulus than solid structures. A micro/nanostructured layer with HA was successfully formed, which was verified by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). At the same time, this surface has increased hydrophilicity and roughness compared to unmodified surfaces and commercial pure titanium (CP-Ti). Furthermore, in vitro studies found that compared with MAOTTNZ samples with lower porosity, bare TTNZ samples, and CP-Ti samples, MAOTTNZ with adequate porosity could improve protein adsorption, cell proliferation, adhesion, alkaline phosphatase (ALP) activity and osteogenesis-related gene expression. In vivo studies, including those in which microcomputerized tomography, histological examination and biomechanical testing of macroporous MAOTTNZ scaffolds were performed, demonstrated that the formation of new bones was significantly boosted in rabbits after implantation. Consequently, this research presents an option for conventional titanium alloys with improved osteogenesis and osseointegration that could be used in further dental implant applications.