Effect of Printing Orientation and Postcuring Time on the Flexural Strength of 3D‐Printed Resins

<jats:title>Abstract</jats:title><jats:sec><jats:title>Purpose</jats:title><jats:p>To evaluate the effect of printing orientation combined with different postcuring times on the flexural strength of 3D‐printed resins.</jats:p></jats:sec><jats:sec><jats:title>Materials and methods</jats:title><jats:p>A total of 480 rectangular specimens with the dimensions of 64×10×3.3 mm were designed and fabricated from two 3D‐printed acrylic resins and one heat‐polymerized resin (HP). 3D‐printed groups were divided into 3 groups according to printing orientations (0‐, 45‐, 90‐degree); each group was subdivided into 4 groups according to postcuring time (30, 60, 90, 120 min.). All specimens were subjected to thermal cycling (10,000 cycles) before testing flexural strength. Fractured surfaces were examined under a scanning electron microscope (SEM). ANOVA and Tukey's post hoc tests were used for data analysis (α = 0.05).</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>The result of this study showed that the highest flexural strength values of 3D‐printed resin (NextDent, and ASIGA) were in 0‐degree groups. Also, the flexural strength values increased when postcuring time was increased, regardless of the printing orientation; the highest flexural strength was recorded at 120 minutes postcuring time in all orientations. SEM analysis showed a rougher surface with irregular lamellae which represented a ductile fracture confirming that high energy is required for crack propagation and these features markedly increased as postcuring time increased.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>The results showed that the 0‐degree orientation groups showed higher flexural strength compared to other groups. Similarly, with increased postcuring time, the flexural strength increased.</jats:p></jats:sec>