Cu alloying enabling dual biocorrosion suppression and fatigue crack mitigation in SLM-processed titanium implants with retained osteogenic activity

Abstract

Titanium (Ti) alloys are extensively utilized in dental and orthopedic implants due to superior mechanical strength, biocompatibility, and corrosion resistance. Their vulnerability to concurrent microbiologically influenced corrosion (MIC) under oral biofilm colonization and cyclic fatigue critically compromises long-term reliability. While antibacterial functionality integration with MIC resistance remains underexplored in Ti alloys, the synergistic effect of copper (Cu) alloying on corrosion-fatigue performance in physiological environments represents a significant knowledge gap. This study systematically investigates MIC and corrosion-fatigue degradation mechanisms of selective laser melting (SLM)-processed Ti versus Ti-5Cu alloys exposed to Streptococcus mutans (S. mutans). Multimodal characterization integrating electrochemical analysis, in-situ fatigue monitoring, and surface/microstructural diagnostics reveal synergistic enhancements in biofilm-inhibiting capability and fatigue durability through Cu incorporation. After 14-day incubation with S. mutans, Ti-5Cu exhibits 48% lower corrosion current density than pure Ti, attributed to Cu-mediated biofilm suppression. Following 90 days of dual microbial/cyclic stress exposure, Ti-5Cu demonstrates 47.5% reduced ultimate tensile strength loss (42.5 vs. 81 MPa) and 57.3% lower fatigue life degradation (15.1 vs. 35.4 MPa). Crucially, 70% shallower maximum pitting depth (3.3 vs. 10.9 μm) and inhibited crack propagation directly correlate with Cu’s antimicrobial efficacy. SLM-driven microstructural refinement further amplifies damage tolerance. Cytocompatibility assays confirm uncompromised cell viability and osteoblast adhesion on alloyed surfaces. These findings establish a dual-functional implant design paradigm combining antimicrobial surface chemistry with fatigue-resistant microstructural engineering to extend biomedical device service lifetimes.