A study to evaluate the transverse strength of repaired acrylic denture resins with conventional heat-cured, autopolymerizing and microwave-cured resins: An in vitro study

Statement of Problem: Acrylic resin dentures are susceptible to fracture after clinical use; it is an unresolved problem in prosthodontics. The repair procedure should be simple, strong and should not affect dimensional accuracy. Purpose: This study evaluated the transverse strength of a conventional heat-polymerized (DPI-Heat Cure, Group I) acrylic resin and a microwave-polymerized (Acron MC, Group III) acrylic resin that were repaired with the same resins and with an autopolymerized acrylic resin (DPI-Repair Resin, Group II). Materials and Methods: Sixty rectangular specimens of Groups I and III and 15 of Group II were manufactured and stored in distilled water at room temperature for 7 days. Forty-five specimens of Groups I and III were selected randomly. Fifteen specimens of each material remained intact (control), 15 from each group were sectioned in the middle to create a 10-mm gap and repaired with the materials of Groups I, II and III. After 7 days of storage at room temperature, transverse strength of the repaired and intact specimens was measured using a 3-point bending test. The nature of failure was noted as adhesive, cohesive or mixed. Student′s unpaired t -test was performed. Results: The intact microwave-cured resin (Group III) showed the highest transverse strength value (90.25 MPa), which was significantly stronger (P < 0.05) than other materials tested. No statistically significant difference was noted amongst the repaired groups. Repaired specimens exhibited three types of failure: adhesive (15.56%), cohesive (15.56%) and mixed being the maximum (68.89%). Conclusion: Microwave-polymerized resin showed the highest intact transverse strength, and autopolymerized resin exhibited repair strength similar to those found for the conventional heat- and microwave-polymerized acrylic resins.