Department of Conservative Dentistry and Dental Research Institute, Seoul National University, Yeongeon-Dong, Jongro-Gu, South Korea.
Dent Mater. 2010 May;26(5):463-70. doi: 10.1016/j.dental.2010.01.004. Epub 2010 Feb 18.
The aim of this study was to measure the initial dynamic viscoelastic modulus change of dental composites during light curing using a custom made oscillation rheometer.
Six commercial universal hybrid resin composites: Z100 (Z1), Z250 (Z2), Z350 (Z3), DenFil (DF), Tetric Ceram (TC), and Clearfil AP-X (CF) were examined. A custom designed oscillation rheometer was made, which consisted of three parts: (1) an oscillatory shear strain induction unit, (2) a measuring unit of parallel plates made of glass rods, and (3) a stress measurement unit. For the measurement of the initial viscoelastic modulus change of composites during light curing as a function of time, a dynamic oscillatory shear test was undertaken at a frequency of 6Hz and strain amplitude of 0.00579rad for 10s. From the strain-stress curves, the complex shear modulus (G*), storage shear modulus (G'), loss shear modulus (G'') and loss tangent (tandelta), and the time to reach a G* of 10MPa were determined. The data were analyzed with one-way ANOVA and Tukey's post hoc test (alpha=0.05).
There were great differences in the development of viscoelasticity among materials. At 10s, the complex modulus G* of Z1 was the highest (563.7MPa), followed by CF, Z2, Z3, TC, and finally DF being the lowest (150.3MPa). The time to reach the G* of 10MPa ranged from 2.55s (Z1) to 4.06s (DF). The tandelta of the composites decreased with time as the polymerization reaction proceeded.
The initial modulus development of composites during curing plays a very important role in determining the polymerization shrinkage stress. The custom made oscillation rheometer was able to measure the very initial dynamic viscoelasticity change of several commercial composites during light curing; therefore, the instrument can be used to study the initial curing kinetics of newly developed composites.
本研究旨在使用定制的振荡流变仪测量光固化过程中牙科复合材料的初始动态粘弹性模量变化。
研究了六种商业通用混合树脂复合材料：Z100（Z1）、Z250（Z2）、Z350（Z3）、DenFil（DF）、Tetric Ceram（TC）和 Clearfil AP-X（CF）。制作了一个定制设计的振荡流变仪，它由三个部分组成：（1）振荡剪切应变感应单元，（2）由玻璃棒制成的测量单元，和（3）应力测量单元。为了测量光固化过程中复合材料的初始粘弹性模量随时间的变化，在 6Hz 的频率和 0.00579rad 的应变振幅下进行了动态振荡剪切试验 10s。从应变-应力曲线中，确定了复剪切模量（G*）、储能剪切模量（G'）、损耗剪切模量（G"）和损耗正切（tandelta），以及达到 10MPa 的 G*的时间。使用单向方差分析和 Tukey 的事后检验（alpha=0.05）对数据进行分析。
材料的粘弹性发展存在很大差异。在 10s 时，Z1 的复合模量 G最高（563.7MPa），其次是 CF、Z2、Z3、TC，而 DF 最低（150.3MPa）。达到 10MPa 的 G的时间范围为 2.55s（Z1）至 4.06s（DF）。随着聚合反应的进行，复合材料的 tandelta随时间降低。
复合材料在固化过程中的初始模量发展对于确定聚合收缩应力起着非常重要的作用。定制的振荡流变仪能够测量光固化过程中几种商业复合材料的非常初始动态粘弹性变化；因此，该仪器可用于研究新开发复合材料的初始固化动力学。
