Mitsuhashi Akira, Hanaoka Koji, Teranaka Toshio
Department of Operative Dentistry and Endodontics, Kanagawa Dental College, 82, Inaokacho, Yokosuka, Kanagawa, Japan.
Dent Mater. 2003 Dec;19(8):747-57. doi: 10.1016/s0109-5641(03)00022-8.
The objectives of the current investigation were two-fold: (1) to examine the effect of different powder/liquid (P/L) ratios on the fracture toughness of commercial resin-modified glass ionomer cement and conventional glass ionomer cement, and (2) to evaluate the effect of powder size reduction on the fracture toughness of experimental resin-modified glass ionomers in order to improve their physical properties.
The P/L ratios of the glass ionomer and resin-modified glass ionomers were varied from the manufacturer's recommended ratio to 2.0 and 1.0 by weight. The powder particle sizes for the experimental resin-modified glass ionomers tested were 2, 5, 10 and 25 micro m in diameter. Fracture toughness was determined on ring-shaped specimens with a fatigued pre-crack.
The fracture toughness of the resin-modified glass ionomers was significantly higher (p<0.005) than that of the glass ionomer and was not greatly influenced by the P/L ratio. For the experimental resin-modified glass ionomers, it was observed that fracture toughness gradually decreased as the powder particle size became finer.
The resin components in the liquid play an important role in the improvement of the physical properties of the resin-modified glass ionomer. A reduction in the powder particle size of up to 10 micro m, which resulted in a smoother surface, can maintain high fracture toughness. The high fracture toughness values of the resin-modified glass ionomer may be one of the factors contributing to a favorable clinical outcome in high stress-bearing areas.
本研究的目的有两个：（1）研究不同粉液比（P/L）对市售树脂改性玻璃离子水门汀和传统玻璃离子水门汀断裂韧性的影响；（2）评估减小粉末粒径对实验性树脂改性玻璃离子水门汀断裂韧性的影响，以改善其物理性能。
玻璃离子水门汀和树脂改性玻璃离子水门汀的P/L比从制造商推荐的比例分别改变为重量比2.0和1.0。所测试的实验性树脂改性玻璃离子水门汀的粉末粒径分别为直径2、5、10和25微米。采用带有疲劳预制裂纹的环形试样测定断裂韧性。
树脂改性玻璃离子水门汀的断裂韧性显著高于玻璃离子水门汀（p<0.005），且受P/L比的影响不大。对于实验性树脂改性玻璃离子水门汀，观察到随着粉末粒径变细，断裂韧性逐渐降低。
液体中的树脂成分在改善树脂改性玻璃离子水门汀的物理性能方面起着重要作用。将粉末粒径减小至10微米，可使表面更光滑，并能保持较高的断裂韧性。树脂改性玻璃离子水门汀的高断裂韧性值可能是其在高应力承载区域取得良好临床效果的因素之一。
