Vijayaraghavan T V, Hsiao J
Department of Dental Materials Science and Pediatric Dentistry, New York University, Kriser Dental Center, USA.
Dent Mater. 1994 Nov;10(6):347-52. doi: 10.1016/0109-5641(94)90058-2.
The purpose of this study was to investigate the effect of temperature of the flexural behavior for four visible light-cured hybrid composite materials.
Light-cured samples were post-cured for 24 h at 37 degrees C in 100% relative humidity prior to testing. Flexural tests were performed at the following water immersion temperatures: 5, 15, 25, 37, 45 and 55 degrees C, as well as in the dry condition which served as control. The following flexural property parameters were obtained as a function of test temperature: flexural strength, sigma fs, flexural modulus, Efs, flexural stress at 0.06% total offset strain, 0.06% (yield stress), and the total displacement at fracture, delta fs. Statistically significant differences (p < 0.01) in flexural parameters were noted for all the materials as a function of test temperature.
The yield stress, sigma 0.06% was found to be most sensitive to thermomechanical changes. The results of this study indicate significant softening due to temperature under wet immersion test conditions for all materials. The temperature range at which two of the materials show significant reduction in yield stress compare well with "Wet Tg" values obtained by dynamic thermal mechanical analysis (Culbertson et al., 1990; 1991).
The effect of damage accumulation on surface or subsurface microstructure due to transient thermomechanical loads needs to be taken into account in the correlation of in vitro and in vivo wear or creep behavior.
本研究旨在探究四种可见光固化复合树脂材料的温度对其弯曲性能的影响。
在测试前，将光固化样品在37摄氏度、相对湿度100%的环境中后固化24小时。弯曲测试在以下水浸温度下进行：5、15、25、37、45和55摄氏度，以及作为对照的干燥条件下。以下弯曲性能参数是作为测试温度的函数获得的：弯曲强度，σfs，弯曲模量，Efs，0.06%总偏移应变时的弯曲应力，0.06%（屈服应力），以及断裂时的总位移，δfs。所有材料的弯曲参数随测试温度的变化均存在统计学显著差异（p < 0.01）。
发现屈服应力σ0.06%对热机械变化最为敏感。本研究结果表明，在湿浸测试条件下，所有材料的温度都会导致显著软化。其中两种材料屈服应力显著降低的温度范围与动态热机械分析获得的“湿Tg”值（Culbertson等人，1990年；1991年）相当。
在体外和体内磨损或蠕变行为的相关性研究中，需要考虑瞬态热机械载荷对表面或亚表面微观结构损伤积累的影响。
