This study investigates the impact of printing layer orientation on the mechanical properties of 3D-printed temporary prosthetic materials. Traditionally, temporary prostheses are fabricated using acrylic resin (polymethyl methacrylate), but advancements have introduced bis-acrylic resins, CAD/CAM-based acrylic resin (milled), and 3D printing technologies. In 3D printing, material is manufactured in overlapping layers, which can be oriented in different directions, directly affecting the material’s resistance. Specimens were designed as bars (2 mm × 2 mm × 25 mm) and grouped according to their printing orientation: BP0 (0 degrees), BP45 (45 degrees), and BP90 (90 degrees). The models were created using Fusion 360 software (version 2.0.12600) and printed on a 3D DLP printer with DLP Slicer software (Chitu DLP Slicer, CBD Tech, version v1.9.0). The bars were then subjected to 3-point bending tests using an Instron Universal Testing Machine to measure Flexural Strength (FS) and Flexural Modulus (FM). Results demonstrated that the BP90 group exhibited the highest Flexural Strength (114.71 ± 7.61 MPa), followed by BP45 (90.10 ± 8.45 MPa) and BP0 (80.90 ± 4.01 MPa). Flexural Modulus was also highest in the BP90 group (3.74 ± 3.64 GPa), followed by BP45 (2.85 ± 2.70 GPa) and BP0 (2.52 ± 2.44 GPa). Significant statistical differences (p < 0.05) were observed, indicating changes in the mechanical properties of the 3D-printed material. The study concludes that printing orientation significantly influences the mechanical properties of temporary prosthetic materials, making the selection of an optimal orientation essential to enhance material performance for its intended application.

Introduction: 3D printing resins have gained popularity in dentistry due to their practicality and reproducibility. However, differences in chemical composition have a direct influence on the mechanical properties of these materials and the various evaluation methods have generated different results which make it difficult to compare their properties. Objective: The aim of this study was to evaluate the influence of the orientation of the impression layers on the mechanical properties (flexural strength and flexural modulus) of biocompatible printed resins. Methods: 100 specimens (n=20) were made from bars measuring 2 x 2 x 25 mm, divided according to the angulation relative to the printing platform (V0, V22.5, V45, V67.5, V90). The bars were designed using Autodesk Meshmixer CAD software and printed on a 3D LCD printer. For the control group, composite resin specimens were made following the same patterns as the printed resins. These bars were subjected to 3-point bending tests on a universal testing machine and flexural strength (FS) and flexural modulus (MF) were evaluated. Results: The mean values of flexural strength and flexural modulus showed no statistically significant differences between the groups. The composite resin control group showed significantly higher mean values in both factors analyzed. Conclusion: It can be concluded that the groups showed minimal differences in the angles studied in both flexural strength and flexural modulus, showing the anisotropic behavior of the restorative material manufactured by 3D printing, suggesting that the choice of any printing angle can determine the applicability according to the characteristics and function of the object to be printed.