Removable Partial Denture Prosthodontics, Department of Masticatory Function Rehabilitation, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
J Mech Behav Biomed Mater. 2013 Apr;20:98-104. doi: 10.1016/j.jmbbm.2012.12.011. Epub 2013 Jan 8.
The aim of this study was to assess the effect of high-pressure polymerization on mechanical properties of denture base resin. A heat-curing denture base resin and an experimental PMMA were polymerized under 500MPa of pressure by means of an isostatic pressurization machine at 70°C for 24h to make rectangular specimens whose dimensions were 30mm×2mm×2mm. Each specimen was deflected on a three-point flexural test until either fracture occurred or the sample was loaded up to 8mm in deflection. The molecular weight of the PMMA without filler was analyzed using the high-speed liquid chromatography system. Increased ductility without fracture was shown in the specimens subjected to high pressure, while most of the control specimens (ambient pressure) fractured. The mean toughness of the PMMA specimens polymerized under the high pressure was significantly higher than the same material polymerized under ambient pressure (p<0.01). The high pressure groups of the denture resin and the PMMA revealed a significantly lower mean 0.2% yield stress, flexural strength, and elastic modulus than control groups (p<0.01). There were certain amounts of higher molecular weight polymers in the high pressure specimens than were present in the controls. The increased toughness shown in the PMMA polymerized under the high pressure was presumably attributed to the higher molecular weight produced by the pressure. The result suggests a potential application of the high-pressure polymerization to the development of PMMA-based denture resin with improved fracture resistance.
本研究旨在评估高压聚合对义齿基托树脂力学性能的影响。采用等静压机，在 70°C 下对热固性义齿基托树脂和实验性 PMMA 分别在 500MPa 的压力下聚合 24 小时，制成尺寸为 30mm×2mm×2mm 的矩形试件。每个试件在三点弯曲试验中弯曲，直到断裂或样品的挠度达到 8mm 为止。使用高速液相色谱系统分析未填充 PMMA 的分子量。结果表明，高压处理的试件表现出较高的延展性，而大多数对照试件（常压）则发生断裂。在高压下聚合的 PMMA 试件的平均韧性明显高于在常压下聚合的相同材料（p<0.01）。在义齿树脂和 PMMA 的高压组中，0.2%屈服应力、弯曲强度和弹性模量的平均值明显低于对照组（p<0.01）。与对照组相比，高压组的 PMMA 中存在一定数量的高分子量聚合物。在高压下聚合的 PMMA 中显示出的韧性增加，可能归因于压力产生的高分子量。结果表明，高压聚合在开发具有更高抗断裂性的基于 PMMA 的义齿树脂方面具有潜在的应用前景。
