Nitrogen plasma immersion ion implantation treatment of Ti6Al7Nb alloy for bone-implant applications: Enhanced in vitro biological responses and in vivo initial bone-implant contact

Abstract

Ti6Al4V alloy has been widely applied to orthopedic and dental implants; however, V ions release may have detrimental side effects. Ti6Al7Nb alloy provides mechanical characteristics similar to those of Ti6Al4V while with fewer potentially biological side effects. In the present investigation, nitrogen plasma immersion ion implantation (N-PIII) treatment was applied to Ti6Al7Nb alloy surfaces. N-PIII surface treatment formed a thin (< 100 nm) TiN-containing film on Ti6Al7Nb surface. A higher applied N-PIII voltage resulted in a higher TiN content on Ti6Al7Nb surface. Compared to the untreated Ti6Al7Nb surface, the N-PIII treated Ti6Al7Nb surface had higher surface roughness, hydrophilicity, hardness, corrosion resistance in simulated body fluid, protein (fibronectin) adsorption, and growth of human bone marrow mesenchymal stem cells, particularly Ti6Al7Nb surface with a higher TiN content. Initial bone-implant contact was investigated in vivo by implanting Ti6Al7Nb screw-type implants (with and without N-PIII treatment) in the femur of mini-pigs for two weeks. At two weeks of post-implantation, the N-PIII treated implant surface with a higher TiN content showed a higher initial bone-implant contact than other implants. Overall, the proposed N-PIII treatment of Ti6Al7Nb alloy surface (particularly with a higher TiN content) enhanced in vitro corrosion resistance, protein adsorption, and cell response as well as in vivo initial bone-implant contact.