A COMPARATIVE STUDY OF FLEXURAL RESISTANCE OF MICROWAVE-CURED ACRYLIC AND HIGH IMPACT RESINS

Introduction: Materials for complete denture bases have advanced over the last decades. The most commonly used material is poly methyl methacrylate. However, this material poses limitations as regards flexural strength and impact resistance. It has been shown that fractures at the midline of denture bases are frequent. Stronger acrylic resins, such as high impact acrylic resins, have been developed with the addition of new materials. The modifiers include co-polymers, cross-linking agents, and rubber substances in the form of butadiene styrene. Incorporation of rubber in the form of butadiene acrylate to high impact denture base resins results in greater impact resistance since it causes dispersion of the cracks. Objective: To evaluate flexural strength of Newcryl acrylic (New Stetic) applying two polymerization methods, using a universal testing device or test tubes to establish comparisons. Materials and Methods: Two experimental groups (n=20) using 3 ± 0.5 mm thick test tubes measuring 60± 0.5 mm in diameter were prepared in keeping with ISO 1567:1999 for performing tests. The samples were made using thermal curable acrylic resin polymerized by micro wave energy and high-impact acrylic resin polymerized using the conventional polymerization technique. Each sample was mounted in a universal DIGIMESS tester, with uniformly distributed load and central and perpendicular action, to measure deflection at a constant crosshead speed of 5mm/min until the specimen reached maximum flexure resistance. Results: Values corresponding to both experimental groups were compared using one way ANOVA. Statistical significance was set at a value of 0.05. Fracture resistance of micro-wave polymerized discs was 12.55+/- 2.46 MPa whereas that of high-impact acrylyc was 16.87+/- 2.16 MPa (mean +/- standard deviation); the difference between groups was statistically significant. Conclusion: The obtained results showed that flexural strength of high-impact acrylics was higher than that of micro-wave polymerized acrylics.