Evaluation of flexural strength of additively manufactured resin materials compared to auto-polymerized provisional resin with and without hydrothermal aging

Purpose Additive manufacturing (AM) technologies are used to fabricate 3D-printed provisional dental restorations. The purpose of this study was to investigate the flexural strength of 3D-printed resins and compare their mechanical performance with those of conventional resins indicated for provisional restorations. Materials and methods This study included six different 3D-printed resin materials, namely (Nextdent (ND); Temp PRINT (TP); Optiprint temp (OT); 3Delta Etemp (DE); Saremco print | CROWNTEC (SA); MED690 (ST)), and one conventional (Protemp (PT)) (Control) provisional resin material. Specimens (N = 168) were prepared (25x2x2 mm³) following ISO 10477:2018 guidelines for temporary materials using a printer (Asiga MAX 3D). Post-processing was accomplished following each manufacturer's recommendation. While half of the specimens were tested after 24 H without aging, the other half was subjected to thermomechanical aging in a custom-made chewing simulator (1.200.000 cycles, 5 °C and 55 °C). Flexural strength of the specimens was determined using a Universal Testing Machine. Data were analyzed using two-way ANOVA followed by Tukey's post-hoc test (α = 0.05). Weibull modulus for each group was calculated based on parametric distribution analysis of censored data for maximum fracture load. Results No significant difference was observed in mean flexural strength (MPa) when non-aged and aged conditions were compared in the OT and PT groups (p>0.05). Groups ND, SA, TP, DE, and ST presented significant differences ranging between 12.67 and 57.39 MPa (p<0.05). All groups presented lower shape and scale values in aged groups compared to their non-aged counterparts. While OT and PT maintained their flexural strength after aging, ND exhibited the highest decrease (30%), followed by DE (23.8%), SA (16.2%), TP (12%), and ST (8.6%) in descending order. Weibull modulus decreased as a function of aging except in group ST. Conclusion Significant effect of themomechanical aging especially on ND and DE materials should be considered with caution when such materials are indicated as interim or long-term interim provisional restorations. SA and TP exceeded the expectations from a provisional material compared to that of the conventional control material PT.