Dental Materials Research Center, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran.
Department of Prosthodontics, Faculty of Dentistry, Babol University of Medical Sciences, Babol, Iran.
J Esthet Restor Dent. 2017 Jul 8;29(4):264-269. doi: 10.1111/jerd.12300. Epub 2017 Apr 21.
Autopolymerized poly methyl methacrylate (PMMA) resin is commonly used for the construction of interim restorations; however, it has less than optimal mechanical properties. In this article, we evaluated the reinforcing effect of adding untreated zirconia nanoparticles on the flexural strength and surface hardness of this resin.
A total of 80 specimens were fabricated. Forty each were used for the flexural strength test and for the surface hardness test. The specimens were categorized into four groups of 10 specimens each as follows: pure PMMA, PMMA with 1%, PMMA with 2.5%, and PMMA with 5% weight of untreated zirconia nanofillers. The flexural strength of the specimens was evaluated by the three-point bending test, and the surface hardness was assessed by micro Vickers hardness test. The data obtained from these tests were statistically analyzed using one-way ANOVA and Tukey tests. In addition, the fracture surface characteristics were assessed using scanning electron microscopy.
Flexural strength testing showed a significant increase in the group with 2.5% zirconia nanofillers, but not in the groups with 1% and 5% nanofillers. Surface hardness was also significantly increased in the groups with 2.5% and 5% nanofillers, but not in the 1% group. The SEM images showed a highly brittle fracture in the pure PMMA group and noticeably less brittle fracture in the group with PMMA with 2.5% weight of zirconia nanofillers. Several cracks and void were also observed in the group with 5% weight of nanofillers.
Reinforcement of the autopolymerized acrylic resin with 2.5% weight of untreated zirconia nanofillers significantly increased its flexural strength and surface hardness.
The interim restorations play an important role in protection of hard and soft oral tissue and providing the critical function and esthetics before the final restoration replacing. Temporary restorations must have sufficient flexural strength to resist deformation during mastication force. Moreover, sufficient surface hardness is also necessary to resist abrasion. The color stability of materials is considered as an important clinical criterion, specifically in esthetics zone. Several materials have been applied to improve the flexural strength and surface hardness for representing clinical success. Zirconia nanoparticles show desirable features, such as high hardness, biocompatibility, and favorable color because of its white color. It seems that the addition of the nano zirconia to acrylic resins can be the appropriate method for improving interim restoration.
自聚甲基丙烯酸甲酯（PMMA）树脂常用于制作临时修复体，但它的机械性能并不理想。本文研究了添加未经处理的氧化锆纳米粒子对该树脂的弯曲强度和表面硬度的增强效果。
共制备 80 个样本。每组 40 个样本分别用于弯曲强度测试和表面硬度测试。将样本分为四组，每组 10 个，分别为：纯 PMMA、添加 1% PMMA、添加 2.5% PMMA 和添加 5%未经处理的氧化锆纳米填料的 PMMA。采用三点弯曲试验评估试件的弯曲强度，采用显微维氏硬度试验评估试件的表面硬度。采用单因素方差分析和 Tukey 检验对所得数据进行统计学分析。此外，还采用扫描电子显微镜评估了断裂面的特征。
弯曲强度测试显示，添加 2.5%氧化锆纳米填料的组的弯曲强度显著提高，但添加 1%和 5%纳米填料的组没有显著提高。添加 2.5%和 5%纳米填料的组的表面硬度也显著提高，但添加 1%纳米填料的组没有显著提高。扫描电镜图像显示，纯 PMMA 组呈高度脆性断裂，而添加 2.5% PMMA 组的断裂则明显不那么脆。在添加 5%纳米填料的组中还观察到了一些裂纹和空隙。
用 2.5%重量的未经处理的氧化锆纳米填料增强自聚物丙烯酸树脂可显著提高其弯曲强度和表面硬度。
临时修复体在保护口腔软硬组织和在最终修复体替换前提供关键功能和美观方面发挥着重要作用。临时修复体在咀嚼力作用下必须具有足够的弯曲强度以防止变形。此外，还需要有足够的表面硬度来抵抗磨损。材料的颜色稳定性被认为是一个重要的临床标准，特别是在美学区域。为了提高临床成功率，已经应用了几种材料来提高弯曲强度和表面硬度。氧化锆纳米粒子因其白色而具有高硬度、生物相容性和良好的颜色等理想特性。看来，将纳米氧化锆添加到丙烯酸树脂中可能是提高临时修复体的合适方法。
