Evaluation of photopolymer resins for dental prosthetics fabricated via the stereolithography process at different polymerization temperatures—Part I: Conversion rate and mechanical properties

Statement of problem: Improvement in the mechanical properties of 3-dimensional (3D) printed dental prostheses is necessary to prevent wear caused by an antagonist or fracture. However, how different printing temperatures affect their mechanical properties is unclear. Purpose: The purpose of this in vitro study was to evaluate the mechanical properties of 3D printed parts fabricated at different printing temperatures. Material and methods: Photopolymer specimens were fabricated at 3 different temperatures (room temperature, 50 °C, and 70 °C) using a stereolithography 3D printer. After rinsing to remove the residual monomer, the specimens were divided into 2 groups: with or without postprocessing. The viscosity of the photopolymerization resin was measured while the temperature was increased. Furthermore, the double-bond conversion (DBC) of the printed part was evaluated (n=3). Mechanical properties were investigated via dynamic mechanical analysis (n=1) and tensile testing (n=5). Statistical comparisons were performed via 1-way analysis of variance, followed by the Tukey honestly significant difference test (α=.05). Results: The DBC rates of the green condition group increased from 66.67% to 86.33% with increasing temperature. In addition, these specimens exhibited improved mechanical properties and reduced residual monomer levels. Conclusions: Specimens fabricated at a temperature of 70 °C exhibited mechanical properties suitable for clinical application.