Bone Ingrowth Evaluation on Ti-13Nb-13Zr Implants Fabricated Via Powder Metallurgy

According to the literature, there are mainly two classes of porous materials: solid substrate with a porous surface and integral porous body that permits the ingrowths of new-bone tissues into the implantable device. Objectives: present the processing, physical characterization, and “in vivo” bone ingrowth evaluation into a Ti-13Nb-13Zr (wt.%) alloy obtained with different porosity degrees via powder metallurgy (P/M). Methods: Cylindrical samples were fabricated by mixing metallic powders hydrides TiH₂ NbH, ZrH₂) followed by controlled pressing and sintering parameters: G1- 1000°C/5h, G2- 1300°C/3h, and G3- 1500°C/2h and subsequently characterized by density measurements, crystalline phases (XRD), and microstructure (SEM-EDS). After an 8-week healing period in rabbit tibias, the implants were retrieved and evaluated by backscattered electron images (BSEI-SEM) and Energy Dispersive Spectroscopy (EDS) for new-bone formation inside the pores. Results: Based on SEM micrographs, it was possible to observe the presence of α and β-phases with the Widmanstätten microstructure formation. The (α+β) Ti-13Nb-13Zr alloy formation was confirmed by XRD. The highest porosity levels, approximately 30% was noted for samples sintered at 1000°C, which present an open and interconnected structure with pores measuring 50-100µm, even though sites with non-reacted Nb particles were identified. On the other hand, samples sintered at 1300°C and 1500°C resulted in low porosity degrees (10%) and a better alloy homogenization. According to BSEI-EDS analyses, bone ingrowth occurrence was evidenced only inside G1 samples. It was also noted that newly-formed bone was able to adapt into pore geometry. Mineralized tissue was observed inside pores of diameter as low as 30 µm (Figure). Conclusions: P/M technology demonstrated to be an alternative tool to obtain porous materials for biomedical applications.