The Effect of Microwave Disinfection on Dimensional Stability and Flexural Strength of Acrylic Resins

اثر ضد عفوني كردن با ميكروويو بر ثبات ابعادي و استحكام خمشي رزين‌هاي آكريلي

Abstract Background and Aim: Several studies have evaluated the effect of microwave radiation on physical properties of acrylic resins. However, due to the recent introduction of heat-cure and cold-cure acrylic resins into the dental market and rapid popularity of cold-cure resins with less distortion in denture base, the present study sought to assess the effect of microwave disinfection on dimensional stability and flexural strength of two recently introduced heat-cure (Ivoclar) and cold-cure (FuturaGen) acrylic resins. Materials and Methods: In this laboratory study, acrylic models were fabricated of an edentulous maxillary model using Ivoclar and FuturaGen acrylic resins. Three ref-erence points were marked on the model: two in the back and one in the front of the edentulous arch. These reference points were used for the measurement of dimen-sional stability in the anteroposterior and cross-arch dimensions. Ten specimens of each acrylic resin were not disinfected. Ten samples were subjected to two 3 min cycles of microwave disinfection with 600 watt power. Distances between the refer-ence points were measured by a Profile Projector. To evaluate flexural strength, a metal mould measuring 64x10x3.3 mm was used for the fabrication of resin speci-mens. Similar to what was done for dimensional stability testing, 10 specimens of each acrylic resin were not disinfected and 10 other samples were subjected to 3-point bending test after disinfection. Data were compared and statistically analyzed using Mann-Whitney U test. Results: The mean difference in anteroposterior and cross-arch dimensions revealed that two cycles of microwave disinfection of Ivoclar and FuturaGen acrylic resins did not have a significant effect on their dimensional stability (P > 0.017). The mean and standard deviation of the flexural strength of FuturaGen acrylic resin before and after disinfection was 76.86±16.80 and 70.18±8.48, respectively. These values for Ivoclar acrylic resin were 85.92±12.23 and 81.91±6.59, respectively. Two cycles of disinfection with microwave did not cause a significant effect on flexural strength of the two understudy acrylic resins (P > 0.05). Conclusion: Two cycles of microwave disinfection had no negative effect on dimensional stability or flexural strength of FuturaGen and Ivoclar acrylic resins. Key Words: Acrylic resin , disinfection , microwave