Effects of high temperature with pressure polymerization on the physical and mechanical properties and dimensional changes of 3D-printed denture teeth resin

Abstract

BACKGROUND: The optimal post-treatment methods for improving the mechanical properties and degree of conversion of three-dimensional (3D)-printed denture teeth resin remain unclear. Therefore, this study aimed to analyze the impact of high temperature with pressure polymerization on the degree of conversion, Vickers hardness, flexural strength and modulus, and dimensional changes of 3D-printed denture teeth resin. METHODS: In total, 180 specimens (Dima Print Denture Teeth A3; Kulzer) fabricated from the denture teeth resin using a digital light processing 3D printer (Cara printer 4.0; Kulzer) were randomly divided into five groups: no post-treatment (control) and post-treatment at 121 °C for 4, 30, 60, or 90 min. The air pressure applied during the treatments was set at 2 bar and was maintained throughout the post-polymerization process. Furthermore, 30 rectangular-shaped specimens (22 × 4 × 2 mm) were used for the degree of conversion test (6 specimens/group), 50 disk-shaped specimens (10 mm diameter × 2 mm thickness) were used for the Vickers hardness test (10 specimens/group), and 50 bar-shaped specimens (25 × 2 × 2 mm) each were used for the flexural strength, flexural modulus, and dimensional change tests (10 specimens/group). The degree of conversion, flexural modulus, and dimensional change of width were analyzed by one-way analysis of variance (ANOVA), followed by Tukey's honest significant difference post hoc test. The flexural strength, Vickers hardness, and dimensional change of length were analyzed by Welch's ANOVA, followed by Dunnett's T3 multiple comparisons post hoc tests. The dimensional change of thickness was analyzed with a Kruskal-Wallis analysis and a post hoc comparison using the Mann-Whitney U test (α = 0.05). RESULTS: The degree of conversion and Vickers hardness values were the lowest in the control group and the highest in the 121 °C/90 min group. The flexural properties and error rates for length, width, and thickness were also the highest in the 121 °C/90 min group. CONCLUSIONS: Post-treatment at 121 °C for 90 min increases the degree of conversion and surface hardness of 3D-printed denture teeth resin, without damaging the resin's flexural properties, and maintains dimensional changes within acceptable limits.