Biomaterials Research Group, School of Dentistry, University of Manchester, Manchester, UK. dr
Dent Mater. 2012 Feb;28(2):e15-8. doi: 10.1016/j.dental.2011.11.026. Epub 2011 Dec 27.
To compare the viscoelastic behavior (creep) of dental resin-composites under both static and cyclic loading in compression.
Ten cylindrical specimens (4 mm × 6 mm), divided into two subgroups (n = 5) were prepared from each of four commercial resin-composites, using a divisible stainless steel mold. They were thoroughly cured from all sides. Groups 1 and 2 were loaded statically and dynamically respectively after 1d of fabrication and dry storage. Group 1 was loaded with a constant static load of 35 MPa and it was applied for 2 h followed by 2 h of strain recovery to obtain the static creep (%) and permanent set (%) respectively. To Group 2 a cyclic load between 1 MPa and 50 MPa was applied at a frequency of 0.25 Hz for 30 min to obtain the "dynamic" creep strain (%). Regression and correlation analysis (α = 0.05) was performed to examine possible correlations between static and "dynamic" creep.
For the resin-composite investigated, a good correlation was found between "dynamic" creep strain (%) and maximum static creep strain (%) (r = 0.92) and a strong correlation was also found between "dynamic" creep strain (%) and permanent set (%) (r = 0.97), SIGNIFICANCE: Maximum static creep was significantly higher than "dynamic" creep. A direct numerical equivalence was not expected between static and "dynamic" creep values, as in the case of "dynamic" creep, loading was cyclic and was applied for a shorter overall period. Nevertheless a strong correlation was found between the static and dynamic creep measurement.
比较压缩状态下静态和循环载荷下牙科树脂复合材料的黏弹性行为（蠕变）。
从四种商业树脂复合材料中各制备十个圆柱形试件（4mm×6mm），使用可分割的不锈钢模具，分为两组（n=5）。从所有侧面彻底固化。在制造和干燥储存 1 天后，分别对第 1 组和第 2 组进行静态和动态加载。第 1 组在恒定静态载荷 35 MPa 下加载 2 小时，随后应变恢复 2 小时，分别获得静态蠕变（%）和永久变形（%）。第 2 组在 0.25 Hz 的频率下施加 1 MPa 和 50 MPa 之间的循环载荷 30 分钟，以获得“动态”蠕变应变（%）。进行回归和相关分析（α=0.05），以检查静态和“动态”蠕变之间可能存在的相关性。
在所研究的树脂复合材料中，“动态”蠕变应变（%）与最大静态蠕变应变（%）之间存在良好的相关性（r=0.92），“动态”蠕变应变（%）与永久变形（%）之间也存在很强的相关性（r=0.97）。
最大静态蠕变明显高于“动态”蠕变。静态和“动态”蠕变值之间预计不会存在直接的数值等效性，因为在“动态”蠕变的情况下，载荷是循环的，并且整体施加的时间较短。然而，在静态和动态蠕变测量之间发现了很强的相关性。
