Department of Prosthodontics and Periodontology, Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
J Prosthodont. 2011 Dec;20(8):606-12. doi: 10.1111/j.1532-849X.2011.00770.x. Epub 2011 Oct 7.
This study evaluated the cumulative effects of different microwave power levels on the physical properties of two poly(methylmethacrylate) (PMMA) denture base resins.
Eight sets of four PMMA specimens each (two polymerized in a water bath and two using microwave energy) were immersed in beakers containing 200 ml of distilled water. Each beaker was subjected to microwave irradiation for 3 minutes at a power level of 450,630, or 900 W. The surface roughness, surface hardness, linear stability, flexural strength, elastic modulus, impact strength, and fractographic properties were evaluated after either 6 or 36 simulated disinfection cycles. The data were statistically analyzed using ANOVA and the Tukey post hoc test (α= 0.05).
The polymerization method did not influence any property (p > 0.05) except linear stability. The surface roughness (p < 0.001) and hardness (p= 0.011) increased after 36 irradiation cycles at 630 or 900 W. The resin polymerized using microwave energy exhibited greater linear distortion (p= 0.012), and there was a cumulative effect on linear stability for both resins (p < 0.001). No significant change (p > 0.05) was observed in flexural strength; however, the elastic modulus decreased (p= 0.008) after 36 disinfection cycles. The impact strength and crack propagation angles displayed no significant differences (p > 0.05).
Within the limitations of this study, it can be concluded that microwave disinfection at 450 W to 630 W for 3 minutes is safe for PMMA.
本研究评估了不同微波功率水平对两种聚甲基丙烯酸甲酯（PMMA）义齿基托树脂物理性能的累积影响。
将八组（每组四个）PMMA 样本分别（两组在水浴中聚合，两组使用微波能聚合）浸入盛有 200ml 蒸馏水的烧杯中。每个烧杯用 450、630 或 900W 的微波辐射 3 分钟。经过 6 或 36 次模拟消毒循环后，评估表面粗糙度、表面硬度、线性稳定性、弯曲强度、弹性模量、冲击强度和断口特性。使用方差分析和 Tukey 事后检验（α=0.05）对数据进行统计学分析。
聚合方法不影响任何性能（p>0.05），除了线性稳定性。在 630 或 900W 下经过 36 次照射循环后，表面粗糙度（p<0.001）和硬度（p=0.011）增加。用微波能聚合的树脂表现出更大的线性变形（p=0.012），两种树脂的线性稳定性都有累积效应（p<0.001）。弯曲强度没有明显变化（p>0.05）；然而，经过 36 次消毒循环后，弹性模量降低（p=0.008）。冲击强度和裂纹扩展角没有显著差异（p>0.05）。
在本研究的限制范围内，可以得出结论，微波消毒功率为 450W 至 630W 持续 3 分钟对 PMMA 是安全的。
