Biocompatibility and Cell Death Mechanisms Induced by PMMA-Based Dental Materials in Gingival Fibroblasts and OECM-1 Tumor Cells

Background/Objectives: The present study aims to test three different types of PMMA (Fotodent Guide—3D printed (M1), Aidite Temp—milled (M2), Duracryl—self-polymerized (M3) on HFIB-G and on OECM-1. Methods: The two cell types (HFIB-G and OECM-1) were kept in contact with the materials, Fotodent Guide, Aidite Temp, and Duracryl (n = 6), for 24 and 48 h, and subsequently subjected to the following tests: MTT, LDH, NO (according to ISO 10993-5:2009), and immunofluorescent detection of proteins associated with autophagy and apoptosis (mitochondria and caspases 3/7; detection of autophagosomes). Statistical interpretation was made using t-test and ANOVA (* p < 0.05; ** p < 0.01; *** p < 0.001). Results: The MTT assay revealed a reduction in cell viability for all tested materials on gingival fibroblasts compared to control cells, with the most pronounced decrease observed for the 3D-printed material (M1 viability 66.77% for 24 and 52.45% 48 h—p < 0.001), while the self-polymerizing resin (M3 viability 85.92% for 24 h and 85.63% for 48 h) showed the highest level of cellular tolerance (p < 0.001 at 24 h and p < 0.01 at 48 h). Regarding OECM-1 cells, all materials reduced cell viability, particularly M3 after 48 h of incubation (viability 61.79%—p < 0.001). LDH levels generally indicated low membrane damage for all materials. Statistically significant increases in NO levels were recorded for both cell types, suggesting a mild proinflammatory response, especially for M2 OECM-1 48 h—p < 0.05 and M3 (HFIB-G 48 h—p < 0.05, OECM-1 48 h p < 0.05). For both 24 and 48 h, fluorescence analysis demonstrated a significant increase in mitochondrial activity in gingival fibroblasts (p < 0.001), whereas tumor cells exhibited a significantly decreased mitochondrial activity (p < 0.001), particularly for the 3D-printed material M1 (p < 0.001). Caspase-3/7 expression increased in gingival fibroblasts incubated with materials for 24 and 48 h (p < 0.001), while tumor cells showed reduced caspase activity both after 24 and 48 h (p < 0.001). Autophagosome formation decreased initially in fibroblasts at 24 h (p < 0.001) but increased significantly after 48 h (p < 0.001), while tumor cells generally showed enhanced autophagic activity under most experimental conditions (p < 0.001). Conclusions: Our results suggest that all three PMMA-based materials exhibit acceptable biocompatibility profiles, of more than 70%, according to ISO 10993-5:2009, although cellular responses vary depending on the manufacturing technique and the cellular model used. In our study conditions, self-polymerized resin (M3) was the most compatible with gingival fibroblasts, while the 3D-printed and CAD/CAM milled materials (M1 and M2) had a more pronounced impact on cells’ viability and metabolic activity.