Denture care and maintenance are necessary for both denture longevity and underlying tissue health. However, the effects of disinfectants on the strength of 3D-printed denture base resins are unclear. Herein, distilled water (DW), effervescent tablet, and sodium hypochlorite (NaOCl) immersion solutions were used to investigate the flexural properties and hardness of two 3D-printed resins (NextDent and FormLabs) compared with a heat-polymerized resin. The flexural strength and elastic modulus were investigated using the three-point bending test and Vickers hardness test before (baseline) immersion and 180 days after immersion. The data were analyzed using ANOVA and Tukey’s post hoc test (α = 0.05), and further verified by using electron microscopy and infrared spectroscopy. The flexural strength of all the materials decreased after solution immersion (p < 0.001). The effervescent tablet and NaOCl immersion reduced the flexural strength (p < 0.001), with the lowest values recorded with the NaOCl immersion. The elastic modulus did not significantly differ between the baseline and after the DW immersion (p > 0.05), but significantly decreased after the effervescent tablet and NaOCl immersion (p < 0.001). The hardness significantly decreased after immersion in all the solutions (p < 0.001). The immersion of the heat-polymerized and 3D-printed resins in the DW and disinfectant solutions decreased the flexural properties and hardness.

Objectives: This in vitro study assessed the accuracy (trueness and precision) of different 3D-printed resin denture bases with 0°, 45°, and 90° printing orientations. Methods: Denture base was designed and fabricated using three 3D-printed denture base resins (DentaBASE, Denture 3D+, and FormLabs). Each resin was printed with its own printer and fabricated with different printing orientations, resulting in a total of 72 specimens (n = 8). Trueness and precision were evaluated before and after thermal aging using the superimposition method with best-fit alignment. The data were collected and analyzed using two-way ANOVA followed by post hoc Tukey’s test (α = 0.05). Results: The printing orientation significantly affected the trueness of 3D-printed resins (p < 0.001). The highest trueness was observed for NextDent at 0° printing orientation, while the lowest value was observed for ASIGA at 0° and 45° printing orientations. The precision of the denture base was significantly affected by different printing orientations for ASIGA (p = 0.006) and NextDent (p < 0.001) before thermal cycling, while the precision of FormLabs was significantly affected (p = 0.017) after thermal cycling. The highest precision was recorded for FormLabs at 45° printing orientation, while the lowest precision was observed for NextDent at 45° and 90° printing orientations. Moreover, the effect of thermal cycling on trueness was only significant for ASIGA at 0° printing orientation; however, the effect of thermal cycling on precision was significant for NextDent at 0° and 90° printing orientations. A 45° printing orientation provided the most accurate clinical fit. Conclusions: ASIGA showed the lowest trueness, while FormLabs exhibited the lowest precision, revealing performance differences between printers.