Some mechanical properties of a highly cross-linked, microwave-polymerized, injection-molded denture base polymer

Purpose: The impact strength and the flexural properties of denture base ma terials are of importance in predicting their clinical performance upon sud den loading. This study compares the impact and transverse strengths and th e flexural modulus of three denture base polymers. Materials and Methods: T he investigation included a relatively new microwave-polymerized polyuretha ne-based denture material processed by an injection-molding technique, a co nventional microwave-polymerized denture material, and a heat-polymerized c ompression-molded poly(methyl methacrylate) (PMMA) denture material. Impact strength was determined using a Charpy-type impact tester. The transverse strength and the flexural modulus were assessed with a three-point bending test. The results were subjected to statistical analysis using a one-way an alysis of variance and the Scheffe test for comparison. Results: The impact strength of the microwave-polymerized injection-molded polymer was 6.3 kJ/ m(2), while its flexural strength was 66.2 MPa. These values were lower tha n those shown by the two compression-molded PMMA-based polymers. The differ ences were statistically significant. The flexural modulus of the new dentu re material was 2,832 MPa, which was higher than the conventional heat-poly merized polymer but was comparable to the other microwave-polymerized PMMA- based polymer. The difference in the flexural modulus was statistically sig nificant. Conclusion: In terms of the impact and flexural strengths, the ne w microwave-polymerized, injection-molded, polyurethane-based polymer offer ed no advantage over the existing heat- and microwave-polymerized PMMA-base d denture base polymers. However, it has a rigidity comparable to that of t he m microwave-polymerized PMMA polymer.