Flexural strength, accuracy, and translucency of 3D printed denture base resins: Effect of post-polymerization time and thermal stress

Statement of problem: The performance of 3-dimensionally (3D) printed dentures is influenced by postpolymerization conditions and intraoral thermal variations. Studies investigating the postpolymerization duration that could improve long-term denture strength without causing dimensional or color changes are still scarce. Purpose: This study aimed to investigate the effect of postpolymerization time (PPT) and thermal cycling (TC) on the flexural strength (FS), accuracy, and translucency (TR) of 3D printed denture base resins. Material and methods: Two resins (NextDent and ASIGA) were used to fabricate 180 specimens, including 120 bars (64×10×3.3 mm) for FS and accuracy testing and 60 disks (Ø15×2.5 mm) for TR evaluation. Each resin was divided into 3 groups according to PPT (15, 60, and 90 min), and specimens (n=10 per condition) were tested before and after 5000 thermal cycles (5 to 55°C). FS was measured using a universal testing machine, accuracy by dimensional error rate (%), and TR with a spectrophotometer. The data were analyzed with 1-way ANOVA and the Tukey post hoc test (α=.05). Results: FS significantly increased with longer PPT for both materials (P<.001), with highest values at 90 minutes for ASIGA 90.6 (4.1) MPa and NextDent 89.2 (1.9) MPa. TC significantly reduced FS except for NextDent-15 minutes (P=.070). PPT showed no significant effect on accuracy (length, width, or thickness) for ASIGA (P>.05) or NextDent (P>.05). TR remained stable for ASIGA (P=.649) but decreased for NextDent after TC (P=.007). Conclusions: The performance of 3D printed dentures could be improved by increasing the PPT, leading to increased flexural strength without significant change in accuracy or translucency. Thermal cycling reduced the flexural strength of both tested resins and reduced the translucency of NextDent.