Evaluation of the mechanical properties of 3D printed interim resins polymerized with different postpolymerization units

Statement of problem The effect of different postpolymerization units on the mechanical reliability and degree of conversion (DC) of 3-dimensional (3D) printed interim resins remains unclear, particularly when third-party units are used instead of manufacturer-recommended devices. Purpose The purpose of this in vitro study was to evaluate the effects of 5 different postpolymerization units on the mechanical properties and DC of 5 commercially available 3D printed interim resins. Material and methods Five commercially available 3D printed dental resins were printed and postpolymerized using 5 different postpolymerization units (LC-3D Print Box, Tera Harz Cure, OneJet Cure+, ODS Cure Box, and ARUM UV Curing Machine). A total of 500 specimens were fabricated, including 250 bar-shaped specimens for flexural testing and 250 disk-shaped specimens for DC analysis. Statistical analysis included Kruskal–Wallis tests with Mann-Whitney U post hoc comparisons (Bonferroni correction) (α=.05). Reliability of mechanical performance was evaluated using Weibull analysis to calculate the Weibull modulus ( m ) and characteristic strength/modulus (σ₀) with 95% confidence intervals (CI). Results All resins exceeded the International Organization for Standardization (ISO) 10477 standard minimum flexural strength requirement (≥50 MPa). Flexural strength and modulus differed significantly depending on the resin–postpolymerization unit combination. The ODS Cure Box and Tera Harz Cure generally yielded higher flexural performance, whereas OneJet Cure+ produced the lowest values across materials. DC varied widely across polymerization conditions and showed no significant association with flexural strength or flexural modulus ( P >.05). Conclusions Mechanical properties varied across resin–postpolymerization unit combinations, with certain third-party units showing flexural performance comparable with that of manufacturer-recommended systems. Although the DC differed among polymerization conditions, the surface DC measured in this study did not show a significant association with flexural strength or modulus.