Ogawa T, Hasegawa A
The Jane and Jerry Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA, Los Angeles, CA 90095-1668, USA.
J Oral Rehabil. 2005 Mar;32(3):221-6. doi: 10.1111/j.1365-2842.2004.01406.x.
Methyl-methacrylate autopolymerizing resin is used for multiple applications. Therefore, the mechanical properties of autopolymerizing resin should be assessed comprehensively including strength, stiffness and hardness. Any methods that effectively improve these mechanical properties are desirable. The objective of this study is to examine the effects of the curing environment: air or water with/without pressure, and air or water temperature during polymerization, on the strength, stiffness and hardness of autopolymerizing resin. In addition, we examined the polymerizing behaviour associated with the mechanical properties. Autopolymerizing methyl-methacrylate resin (Unifast II) was polymerized under the following conditions: in air and water with/without pressure at 10, 23, 30, 40, 60 and 80 degrees C. The resin specimens were subjected to a transverse test (three-point flexural test) and micro-Brinell surface hardness test. Fractured surfaces of the specimens after the transverse test were examined using a scanning electron microscope (SEM). The transverse strength and transverse modulus increased with increasing curing temperature in both wet and dry conditions. Pressured wet conditions increased transverse strength and transverse modulus over non-pressured wet and dry conditions. The resin polymerized in dry conditions showed higher surface hardness than the one polymerized in wet conditions at matching temperature. The SEM images of fractured surfaces cured at lower temperature exhibited porosity within the polymer base and cracks between the base and poly-methyl-methacrylate (PMMA) particulates. Surfaces of the resin polymerized in wet conditions were characterized with PMMA particulates having rougher surfaces suggestive of water incorporation. Raising temperature and pressuring during polymerization increase strength and stiffness of autopolymerizing resin. However, wet condition reduces surface hardness of resin compared with dry condition. These altered mechanical properties are associated with polymerization behaviour of the resin.
甲基丙烯酸甲酯自聚树脂有多种用途。因此，应综合评估自聚树脂的力学性能，包括强度、刚度和硬度。任何能有效改善这些力学性能的方法都是可取的。本研究的目的是考察固化环境（空气或有/无压力的水）以及聚合过程中的空气或水温对自聚树脂强度、刚度和硬度的影响。此外，我们还研究了与力学性能相关的聚合行为。自聚甲基丙烯酸甲酯树脂（Unifast II）在以下条件下聚合：在10、23、30、40、60和80摄氏度的空气和有/无压力的水中。对树脂试样进行横向试验（三点弯曲试验）和显微布氏表面硬度试验。使用扫描电子显微镜（SEM）检查横向试验后试样的断裂表面。在潮湿和干燥条件下，横向强度和横向模量均随固化温度的升高而增加。有压力的潮湿条件下的横向强度和横向模量高于无压力的潮湿和干燥条件。在匹配温度下，在干燥条件下聚合的树脂比在潮湿条件下聚合的树脂具有更高的表面硬度。在较低温度下固化的断裂表面的SEM图像显示聚合物基体内部存在孔隙，基体与聚甲基丙烯酸甲酯（PMMA）颗粒之间存在裂纹。在潮湿条件下聚合的树脂表面的特征是PMMA颗粒表面更粗糙，表明有水掺入。聚合过程中升高温度和施加压力会增加自聚树脂的强度和刚度。然而，与干燥条件相比，潮湿条件会降低树脂的表面硬度。这些力学性能的改变与树脂的聚合行为有关。
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