Received: 2 December 2023 Accepted: 17 April 2024 DOI: 10.1111/jopr.13866 ORIGINAL ARTICLE Influence of different printing orientations and post-polymerization time on the translucency of three-dimensional (3D) printed denture base resins Mohammed M. Gad BDS, MSc 1 Shaimaa M. Fouda BDS, MSc, PhD 1 Hend Alshammary BDS 2 Raand Altayyar BDS 2 Ahmed Elakel BDS, MSc, PhD 3 Essam A. Nassar BDS, MSc, PhD 3 Soban Q. Khan BSc, MSc, PhD 4 Ahmed M. Rahoma BDS, MSc, PhD 5 Ahmed Fathey Elhagali BDS, MSc, PhD 6 Mutlu Özcan PhD, FADM, FICD, FDS RCPS (Glasgow) 7 Fahad A. Al-Harbi BDS, MSD, DScD, FACP 1 1 Department of Substitutive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia 2 College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia 3 Department of Preventive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia 4 Department of Dental Education, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia 5 Department of Restorative Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia 6 Department of Removable Prosthodontics, Faculty of Dental Medicine, Al-Azhar University, Assiut, Egypt 7 Clinic of Masticatory Disorders and Dental Biomaterials, Center of Dental Medicine, University of Zurich, Zurich, Switzerland Correspondence Mohammed M. Gad BDS, MSc, Department of Substitutive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia. Email: mmjad@iau.edu.sa Abstract Purpose: To evaluate the effect of different printing orientations and post- polymerization time with thermal cycling on the translucency of 3D-printed denture base resins. Methods: Heat-polymerized (HP) acrylic resin specimens were fabricated and 3D- printed denture base materials (NextDent, ASIGA, FormLabs) were printed with different printing orientations (0, 45, 90 degrees) and subjected to different post- polymerization times (15-, 30-, 60-, and 90-min). All specimens were polished and immersed in distilled water for 1 day at 37 ◦ C. CIEDE2000 was used to measure the translucency parameters (TP 00 ) before and after thermal cycling (5000 cycles) record- ing the color parameters (L*, a*, b*) against a black and white background using a spectrophotometer. k-factors ANOVA followed by post hoc Tukey’s test (α = .05) was performed for statistical analysis. Results: The k-factors ANOVA test showed a significant effect of resin material, post-polymerization time, and printing orientation on translucency (p < 0.001). In comparison to HP, all 3D-printed resins showed lower translucency with all post- polymerization times and printing orientation (p < 0.001) except FormLabs resin (p > 0.05). For all 3D-printed resins, the translucency increased, with increasing the post-polymerization time (p < 0.001) and 60- and 90-min showed the highest translucency. For printing orientation, 90 and 45 degrees significantly showed high translucency in comparison to 0 degrees (p < 0.001). FormLabs showed significantly higher translucency when compared with NextDent and ASIGA per respective print- ing orientation and post-polymerization time. The translucency significantly decreased after thermal cycling for all tested resins (p < 0.001). Conclusion: The findings of this study demonstrated that the translucency of 3D- printed resins is influenced by the printing orientation, post-polymerization time, and resin type. As a result, choosing a resin type, and printing orientation, with a longer post-polymerization time should be considered since it may improve the esthetic appearance of the 3D-printed resins. KEYWORDS 3D printing, complete denture, dental materials, polymerization, printing parameters, translucency J. Prosthodont. 2024;1–12. © 2024 by the American College of Prosthodontists. 1 wileyonlinelibrary.com/journal/jopr