Cytotoxicity assessment of Tera Harz TC-85DAC direct-printed clear aligners and effects of post curing time

To evaluate the cytotoxicity of direct 3D-printed aligners fabricated from Tera Harz TC-85DAC resin (TC) compared with conventional thermoformed aligners, and to investigate the effect of different post curing durations on TC cytotoxicity.

Human gingival fibroblasts (HGFs) were exposed to eluates from TC and three thermoformed aligners (Essix ACE, Duran, Invisalign). TC aligners were postcured for 14, 20, and 40 minutes (TC80, TC100, TC200). Cell viability was assessed using the CCK-8 assay at 1, 3, 5, and 7 days, and cell migration was evaluated using a scratch wound healing assay at 24 and 48 hours. Statistical analysis was performed using ANOVA with Tukey's post hoc test.

Cell viability was significantly reduced in the TC group compared with thermoformed aligners at days 3, 5, and 7. Cell migration was also significantly impaired in the TC group at 48 hours. Among TC subgroups, day-7 viability was significantly lower in TC80 compared with TC100 and TC200, whereas no significant differences in migration were observed among curing times.

TC aligners significantly reduced cell viability over the 7-day incubation period compared to control and conventional thermoformed aligners. The cell migration was also significantly reduced in the TC group at 48 hours. Under-curing significantly decreased cell viability, whereas extending the post curing time beyond the manufacturer's recommendation did not result in additional improvement. Furthermore, the amount of cell migration across varying post curing durations was not different at both 24 and 48 hours.