Kotche Miiri, Drummond James L, Sun Kang, Vural Murat, DeCarlo Francesco
Department of Bioengineering, University of Illinois, Chicago, Illinois, USA.
J Biomed Mater Res B Appl Biomater. 2009 Feb;88(2):412-8. doi: 10.1002/jbm.b.31111.
Dental composites are subjected to extreme chemical and mechanical conditions in the oral environment, contributing to the degradation and ultimate failure of the material in vivo. The objective of this study is to validate an alternative method of mechanically loading dental composite materials. Confined compression testing more closely represents the complex loading that dental restorations experience in the oral cavity. Dental composites, a nanofilled and a hybrid microfilled, were prepared as cylindrical specimens, light-cured in ring molds of 6061 aluminum, with the ends polished to ensure parallel surfaces. The samples were subjected to confined compression loading to 3, 6, 9, 12, and 15% axial strain. Upon loading, the ring constrains radial expansion of the specimen, generating confinement stresses. A strain gage placed on the outer wall of the aluminum confining ring records hoop strain. Assuming plane stress conditions, the confining stress (sigma(c)) can be calculated at the sample/ring interface. Following mechanical loading, tomographic data was generated using a high-resolution microtomography system developed at beamline 2-BM of the Advanced Photon Source at Argonne National Laboratory. Extraction of the crack and void surfaces present in the material bulk is numerically represented as crack edge/volume (CE/V), and calculated as a fraction of total specimen volume. Initial results indicate that as the strain level increases the CE/V increases. Analysis of the composite specimens under different mechanical loads suggests that microtomography is a useful tool for three-dimensional evaluation of dental composite fracture surfaces.
牙科复合材料在口腔环境中会受到极端的化学和机械条件影响，这会导致材料在体内降解并最终失效。本研究的目的是验证一种对牙科复合材料进行机械加载的替代方法。受限压缩测试更能准确模拟口腔修复体在口腔中所经历的复杂载荷。制备了纳米填充和混合微填充两种牙科复合材料的圆柱形试样，在6061铝制环形模具中光固化，两端打磨以确保表面平行。对样品施加受限压缩载荷，使其产生3%、6%、9%、12%和15%的轴向应变。加载时，环形模具会限制试样的径向膨胀，从而产生约束应力。放置在铝制约束环外壁上的应变片会记录环向应变。假设为平面应力条件，可在样品/环界面处计算出约束应力（σ(c)）。机械加载后，使用阿贡国家实验室先进光子源2-BM光束线开发的高分辨率显微断层扫描系统生成断层扫描数据。材料内部存在的裂纹和孔隙表面的提取在数值上表示为裂纹边缘/体积（CE/V），并计算为试样总体积的一部分。初步结果表明，随着应变水平的增加，CE/V也会增加。对不同机械载荷下的复合材料试样进行分析表明，显微断层扫描是评估牙科复合材料断裂表面三维结构的有用工具。
