Surface Modification of Porous Titanium and Titanium Alloy Implants Manufactured by Selective Laser Melting: A Review

Titanium (Ti) and its alloy implants with porous structures manufactured by selective laser melting (SLM) can match the elastic modulus of human bone to reduce the stress‐shielding effect and satisfy the personalized requirement in orthopedic surgery. Compared with conventional casting and forging Ti and its alloy implants, SLM implants possess unique microstructural features and excellent comprehensive mechanical properties. However, the unmelted powder particles inevitably adhere to the surfaces of SLM implants, which may result in excessive surface roughness and potential health risks. Moreover, there are significant issues encountered, such as bioactivity, toxicity, antibacterial activity, corrosion, and wear resistance. Consequently, surface modification methods are essential to remove the unmelted powder particles and improve biological and mechanical properties of SLM implants. Herein, the research efforts focus exclusively on chemical (acid treatment, alkali treatment, sol–gel, chemical vapor deposition, and atomic layer deposition) and electrochemical methods (anodization and microarc oxidation) for SLM Ti and its alloy implants, especially for porous structures. Particularly, the characteristics of these methods are summarized, and their commonly used pre‐ and post‐treatment methods are introduced. In addition, the development trends and challenges in surface modification of SLM Ti and its alloy implants are discussed.