Techniques, mechanisms, and application of 3D-printed biodegradable metals for bone regeneration

Repairing severe bone defects and restoring complete bone tissue morphology are major challenges in clinical practice. Biodegradable metals (BMs) are bioactive materials with active degradation properties. The gradual improvement of threedimensional (3D) printing technology holds tremendous potential for development and has spurred on the growing utilization of 3D-printed BM materials in the clinical applications of bone regeneration. In this paper, we review the application of three BM (magnesium, iron, and zinc) materials for use in 3D-printed bone regeneration; define the principle of 3D-printed bone regeneration, including the method and selection of materials; and summarize the characteristics and uses of various printing technologies and the properties, advantages, and disadvantages of BMs. Compared to traditional nondegradable implants, 3D-printed degradable metal implants have the advantages of not leaving residue, avoiding stress shielding, promoting osteogenesis and vascularization, and exhibiting antimicrobial ability. In addition, we summarize the clinical applications of 3D-printed BMs. 3D-printed BMs can be used not only for fracture fixation and bone defect repair but also for osteoporotic fracture repair, cartilage repair, maxillofacial surgery, and other processes. In this article, we discuss the advantages and limitations of the current 3D printing degradable metallic materials and describe future development prospects.