EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Background: Additive manufacturing (AM) have become increasingly important in personalized medicine. To finally introduce AM to the clinic, preclinical investigations are necessary to guarantee patients’ safety. 3D-printed parts must be free of pathogens and contaminants, but reliably maintain their mechanical properties. PMMA (Polymethylmethacrylate) has already been used for years for medical applications and shows optimal characteristics in its milled form.
Material and Methods: Standard PMMA samples with dimensions of 80x10x4 mm were manufactured by FFF or APF. Samples underwent standard clinical washing and formaldehyde sterilization procedures for low-temperature polymers according to ISO 14937. Internal porosity was assessed with µCT image data. Finally, they were tested for their mechanical properties by 3-point bending and charpy impact tests (ISO 178 & 179). To investigate potential negative effects of sterilization procedures on biocompatibility, cubes with dimensions of 10x10x10 mm were manufactured. Cleaned or untreated samples were soaked into culture medium, eluates obtained from this procedure were tested for their influence on cell viability.
Results: In 3-point bending tests, there was no significant differences in the flexural stress – flexural strain curves of the treatment groups (untreated, washed & formaldehyde-sterilized). FFF specimens neither showed a maximum nor failure before reaching the conventional deflection, while APF specimens fractured before reaching the deflection limit. Charpy tests also did not show differences in impact strength neither for FFF nor for APF samples. Eluates obtained from incubation of FFF specimens resulted in lower cell viability compared to those from APF specimens. This difference correlated well with the higher porosity in FFF specimens detected by µCT analyses
Conclusion: Clinical washing and sterilization procedures do not seem to have an effect on mechanical characteristics of AM PMMA samples. FFF specimens seem to release formaldehyde over a longer period compared to APF specimens due to a lower sample density.