Currently, broken dentures composed of high-impact acrylic polymers are difficult to treat. Therefore, the purpose of this study was to evaluate the fracture force, toughness, and deflection of three different types of thermoplastic denture base resins made of repaired injection-molded polymethyl methacrylate. The sample size for this in-vitro study was calculated using the G*power 3.0.10 program with an alpha error of 5% and a power of 80% in each group (groups A, B, and C) of 20 samples. Therefore, 60 high-impact injection-molded acrylic resin samples with dimensions of 39 × 4 × 8 mm were prepared, and a diamond disc was used to create a pre-crack along the designated centerline to a depth of 3.0 ± 0.2 mm. Probase cold, Triplex SR cold, and Lukafix light cure resin were used to repair the broken sections. The repaired site was tested using a three-point bending test, and the results were statistically examined using Tukey's post hoc test (α < 0.05) and one-way ANOVA. Significant variations in flexural force, deflection, and fracture toughness between groups were shown by the statistical analysis. Group A showed an increase in fracture toughness of 245.06 N, a flexural strength of 24.0 Mpa, and a deflection of 0.14 cm. It was found that samples repaired using auto-polymerizing PMMA resin had substantial fracture force, deflection, and toughness. Therefore, the study concludes that compared with other resins, the auto-polymerizing resin can be utilized more effectively for auto-polymerizing PMMA resin repair.
