Evaluation of Transverse Strength of Heat-Cure Denture Bases Repaired with Different Joint Surface Contours: An In Vitro Study

Background: Patients frequently prefer repair of their fractured dentures rather than fabrication of new prostheses, provided that esthetics, occlusion, and vertical dimension remain satisfactory. Heat-cured polymethyl methacrylate (PMMA) denture bases, although widely used, are prone to fracture, and the success of repair is influenced by multiple factors, including joint surface design. Objective: This in vitro study aimed to evaluate and compare the effect of two joint surface contours—45° bevel and round joint—on the transverse strength of repaired heat-cured acrylic denture base resin, in comparison with intact unrepaired specimens. Methodology: Ninety heat-cured acrylic resin specimens (64 × 10 × 3 mm) were fabricated and divided into three groups (n = 30): Group A (control, unrepaired), Group B (45° bevel joint), and Group C (round joint). Specimens in Groups B and C were sectioned at the midpoint and repaired using auto-polymerizing acrylic resin. Transverse strength was assessed using a three-point bending test on a universal testing machine at a crosshead speed of 5 mm/min and a span length of 50 mm. Transverse strength values were calculated in megapascals (MPa). Statistical analysis was performed using one-way ANOVA followed by post hoc tests. Results: The highest mean transverse strength was observed in Group A (88.67 ± 8.75 MPa), followed by Group B (47.80 ± 9.62 MPa) and Group C (40.56 ± 10.44 MPa). One-way ANOVA demonstrated a statistically significant difference among groups (p < 0.001). Post hoc analysis revealed that both repaired groups exhibited significantly lower transverse strength compared with the control, and the 45° bevel joint demonstrated significantly higher strength than the round joint. Conclusion: Within the limitations of this in vitro study, joint surface contour significantly influenced the transverse strength of repaired heat-cured acrylic denture base resin. The 45° bevel joint exhibited superior transverse strength compared with the round joint; however, neither repair technique restored strength comparable to intact specimens. Keywords: Auto-Polymerizing Repair Material, Denture Repair, Heat-Cure Denture Base, Joint Surface Design, Transverse Strength.