Sinter-Based Additive Manufacturing for Metallic Implant Applications: Challenges and Opportunities

Patient-individualised metallic implants manufactured via additive manufacturing (AM) are gaining increasing clinical relevance, with powder bed fusion using laser or electron beam (PBF-LB/M, PBF-EB/M) currently representing the commercially established standard. While these processes enable controllable lattice structures for osseointegration, high density, and good dimensional accuracy within a high technology readiness level, sinter-based AM (SBAM) processes may offer technical or economic advantages for specific applications in the future. This review examines the current challenges and opportunities of SBAM processes for metallic, in particular titanium implant applications. Key technical hurdles include geometric accuracy due to sintering shrinkage, chemical composition control (particularly oxygen and carbon limits for titanium alloys), and mechanical properties with emphasis on fatigue performance. However, economic analysis suggests that while AM printing costs may be competitive and comparable, extensive post-processing requirements can diminish printing cost advantages. Thus, significant opportunities for SBAM, such as superior as-sintered surface quality beneficial for internal lattice structures, higher resolution enabling fine surface texturing without post-processing, and as-sintered microstructure control, exist. Furthermore, sinter-based processes enable processing of alternative materials including metastable beta-titanium alloys and biodegradable metals such as magnesium, which are challenging to process via PBF-LB/M.