Inherent variation in surface roughness of Selective Laser Melting (SLM) printed titanium caused by build angle changes the mechanomicrobiocidal effectiveness of nanostructures.

Additively manufactured titanium implant materials are rapidly advancing prosthetics and orthopaedic devices by making them more cost-effective and customisable. However, the surface finish of materials printed via Selective Laser Melting (SLM) currently limits their integration into the medical device field. Printing parameters, such as build angle inclination, can cause variations in the surface roughness of a part, often exceeding what is suitable for implant materials. Excessive roughness can promote microbial attachment and proliferation, potentially leading to implant rejection. Nanostructuring titanium has previously demonstrated success in mitigating bacteria and fungi via a mechanomicrobiocial mechanism on traditionally flat titanium and complex SLM-made parts but its effectiveness on the inherent roughness of three-dimensional (3D) printed titanium remains unexplored. This study examines the surface roughness of 3D-Ti at three build angles (0, 40 and 90 degrees), before and after nanostructuring. Surfaces were assessed against methicillin-resistant Staphylococcus aureus (MRSA) and Candida albicans, representative antimicrobial resistant pathogens. Results showed the nanostructures were more effective against MRSA, but microbial attachment increase with steeper angles, regardless of the presence of nanostructures. This study investigates how surface roughness of 3D printed titanium substrates impacts bacterial and fungal adhesion and the resulting nanomorphology of the surface post-hydrothermal modification.