Baran G, Sadeghipour K, Jayaraman S, Silage D, Paul D, Boberick K
School of Dentistry, Temple University, Philadelphia, Pennsylvania 19140, USA.
J Dent Res. 1998 Nov;77(11):1864-73. doi: 10.1177/00220345980770110201.
Posterior composite restorative materials undergo accelerated wear in the occlusal contact area, primarily through a fatigue mechanism. To facilitate the timely development of new and improved materials, a predictive wear model is desirable. The objective of this study was to develop a finite element model enabling investigators to predict crack propagation directions in resins used as the matrix material in composites, and to verify these predictions by observing cracks formed during the pin-on-disc wear of a 60:40 BISGMA:TEGDMA resin and an EBPADMA resin. Laser confocal scanning microscopy was used to measure crack locations. Finite element studies were done by means of ABAQUS software, modeling a cylinder sliding on a material with pre-existing surface-breaking cracks. Variables included modulus, cylinder/material friction coefficient, crack face friction, and yield behavior. Experimental results were surprising, since most crack directions were opposite previously published observations. The majority of surface cracks, though initially orthogonal to the surface, changed direction to run 20 to 30 degrees from the horizontal in the direction of indenter movement. Finite element modeling established the importance of subsurface shear stresses, since calculations provided evidence that cracks propagate in the direction of maximum K(II)(theta), in the same direction as the motion of the indenter, and at an angle of approximately 20 degrees. These findings provide the foundation for a predictive model of sliding wear in unfilled glassy resins.
后牙复合修复材料在咬合接触区域会加速磨损，主要是通过疲劳机制。为了促进新型改良材料的及时研发，需要一个预测磨损模型。本研究的目的是建立一个有限元模型，使研究人员能够预测用作复合材料基体材料的树脂中的裂纹扩展方向，并通过观察在60:40双酚A缩水甘油醚:三乙二醇二甲基丙烯酸酯树脂和EBPADMA树脂的销盘磨损过程中形成的裂纹来验证这些预测。使用激光共聚焦扫描显微镜测量裂纹位置。通过ABAQUS软件进行有限元研究，对在具有预先存在的表面裂纹的材料上滑动的圆柱体进行建模。变量包括模量、圆柱体/材料摩擦系数、裂纹面摩擦和屈服行为。实验结果令人惊讶，因为大多数裂纹方向与先前发表的观察结果相反。大多数表面裂纹虽然最初与表面垂直，但会改变方向，在压头运动方向上与水平方向成20至30度角。有限元建模确定了亚表面剪应力的重要性，因为计算结果表明裂纹沿最大K(II)(θ)方向扩展，与压头运动方向相同，且角度约为20度。这些发现为未填充玻璃态树脂滑动磨损的预测模型奠定了基础。
