Effects of Post-Curing on Mechanical Strength and Cytotoxicity of Stereolithographic Methacrylate Resins

This study investigated the influence of curing temperature and time on both the mechanical properties and cytotoxicity of stereolithographic polymethyl methacrylate (PMMA) resin. After printing using stereolithographic equipment, the resin was cured at 45 °C, 60 °C, and 75 °C for up to 120 min. Our results reveal that the mechanical properties achieved a peak after approximately 30 min of curing at the two highest temperatures, followed by a subsequent decrease, while curing at 45 °C resulted in a constant increase in mechanical properties up to 120 min. Testing with S. epidermidis and E. coli exhibited a bland antibacterial effect, with the number of living bacteria increasing with both the time and temperature of curing. To assess potential cytotoxicity, the materials were also tested with human fibroblasts, and the trends observed were similar to what was previously seen for both bacteria strains. Interestingly, an association was observed between the intensity ratio of two Raman bands (around 2920 and 2945 cm^-1), indicative of long-PMMA-chain formation and cytotoxicity. This finding suggests that Raman spectroscopy has the potential to serve as a viable method for estimating the cytotoxicity of 3D printed PMMA objects.