Effects of Build Orientation and Post-polymerization Method on the Mechanical Properties of a 3D-printed Permanent Resin Material

Aim. The purpose of this study was to investigate how different build orientations and post-polymerization protocols influence the microhardness and biaxial flexural strength (BFS) of 3D-printed permanent resin material.Materials and Methods. Ninety disc-shaped specimens were manufactured using a digital light processing (DLP) 3D printer at three build orientations (0°, 45°, 90°). Specimens were post-processed using either a desktop curing unit (FC) or a handheld polywave light emitting diode (LED) light-curing unit (LCU). Microhardness (VHN) was measured using a Vickers microhardness tester, and BFS was evaluated using a piston-on-three-ball test. Two-way ANOVA and Tukey HSD tests were used for statistical analysis (α = .05).Results. The post-polymerization method significantly affected BFS (p < .001), with the LCU group exhibiting higher strength (336.8 ± 81.6 MPa) than the FC group (255.2 ± 83.3 MPa). Build orientation also had a significant influence on BFS (p < .001); the 0° groups showed higher values than the 45° and 90° groups. Microhardness was significantly influenced by the post-polymerization method (p = .04), whereas build orientation had no significant effect on VHN values (p = .63).Conclusion. Both build orientation and post-polymerization method influenced the mechanical behavior of the 3D-printed resin, particularly its BFS. The handheld polywave LCU provided superior flexural performance compared with the desktop curing unit, suggesting that it may serve as a reliable alternative for post-polymerization of 3D-printed dental materials. Optimizing printing and post-polymerization parameters is essential to enhance the mechanical reliability of additively manufactured restorations.