Effect of Printing Orientation and Post-Curing Time on the Mechanical Properties of 3D-Printed Denture Base Resin

Additive manufacturing is increasingly integrated into dental technology, yet the mechanical performance of 3D-printed denture base resins remains strongly influenced by printing orientation and post-curing duration. This study evaluated the combined effect of three printing orientations (0°, 45°, 90°) and three post-curing times (30, 45, 60 min) on the flexural strength and surface microhardness of a denture base resin. Specimens designed in Blender and fabricated using NextDent Denture 3D+ resin were subjected to three-point bending tests (n = 5 per group) and Vickers microhardness measurements (n = 10 per group). One-way ANOVA assessed main and interaction effects. Printing orientation had a significant influence on flexural strength, with horizontally printed specimens exhibiting the highest values, whereas vertically printed specimens were consistently weaker. Post-curing time did not significantly affect flexural strength within any orientation. In contrast, microhardness increased progressively with longer post-curing durations, regardless of orientation, indicating continued surface polymerisation. Because flexural strength and hardness responded differently to curing duration, no single post-curing time was universally optimal; however, 0° printing consistently produced the strongest specimens for this resin–printer system. This trade-off is clinically relevant, because dentures require high flexural strength to resist fracture and sufficient hardness to minimise wear.