Surface conditioning of additively manufactured titanium implants and its influence on materials properties and in vitro biocompatibility
Customized osteosynthesis materials of titanium alloy can be generated by additive manufacturing replacing the complex adaptation to the patient individual anatomy, especially to the lower jaw bone which shows a highly individual surface area. After printing further conditioning is necessary to adjust surface roughness. The aim of the present study was to analyse the effect of different grinding and polishing procedures on sample surface and composition and in vitro biocompatibility. Ti-6Al-4V ELI samples printed by laser powder bed fusion (LPBF) were post-treated by multi-level procedures to adjust surface roughness using the surface conditioning technologies sandblasting, vibratory finishing, electro polishing or plasma polishing. Topography and chemical composition of the surfaces was analysed. Furthermore, the release of metal ions in contact to cell culture medium was quantified. Human osteoblasts as well as primary human gingiva cells (fibroblasts and epithelial cells) were cultivated in extracts or directly on the surfaces to analyse cytotoxicity, cell adhesion and cell proliferation. Surface roughness of the different materials after final polishing was in between 0.2 and 0.5 mm, which is in the same range as usually found for conventional titanium materials used in maxillofacial surgery. Furthermore, the wettability was comparable for all post-processing techniques. The chemical compositions of the finished surfaces showed a remarkable impact by the applied finishing technique. Extracts of the samples showed low cytotoxicity with exception of the plasma polished samples, which were shown to release significantly higher amounts of vanadium ions. Accordingly, cells showed good adhesion and proliferation on all samples except plasma polished specimens. Customized devices for midline osseodistraction were exemplarily printed with LPBF starting with patient's 3D data. Those devices can be considered for clinical use, since the printed and finished material meets the requirements of ISO 10993-5 for medical devices.