Fatigue Crack Propagation in Composite Resins

1. Paris law （da/dN=C（DELTAK）^m） could be applied to the fatigue crack growth rate of the materials used in this study。常数m在复合树脂24.3-32.2的范围内，19.7-21.0的范围内。DELTA K_<th>was in the range of 0.43-0.82 MPa·m^&lt;1/2&gt; for composite resins and 0.20- 0.21 MPa·m^&lt;1/2&gt; for unfilled resins。牙科复合物的体积比金属（m=2-7）要大得多，但它们之间并没有很大的差别。fatigue crack growth rate of dental composites depended on DELTA K_<th>rather than constant m. 2.通过SEM研究，在非有机填充物和基质之间传播的脂肪裂纹表面的微结构实验，以及一些有机填充物被脂肪裂纹渗透的复合物.3.脂肪裂纹增长率是更敏感的，通过在水中老化而不是反向强度.4.The脂肪裂纹的复合物的特性的抵抗力测量为DELTA K_decreased <th>by衰老在水中。SEM观察显示，在三个月的水中老化后，脂肪裂纹在两者之间传播，并在水中老化3个月。这些结果表明，由非有机填充物增加了复合物的脂肪抵抗力，以及老化中的脂肪抵抗力造成的退化是由沉积矩阵的退化引起的。从目前的研究中，它显示了肥胖裂纹传播试验是一种有效的方法来调查牙科复合物的咀嚼和降解。

1.The Paris law (da/dN=C(DELTA K)^m) could be applied to the fatigue crack growth rate of the materials used in this study. Constant m was in the range of 24.3-32.2 for composite resins and 19.7-21.0 for unfilled resins. The DELTA K_<th> was in the range of 0.43-0.82 MPa・m^<1/2> for composite resins and 0.20-0.21MPa・m^<1/2> for unfilled resins. Constant m of dental composites was extremely higher than that of metal(m=2-7), but did not differ very much from each other. The fatigue crack growth rate of dental composites depended on DELTA K_<th> rather than constant m. 2.Microstructural examination of fatigue fracture surfaces by SEM indicated that the fatigue crack of dental composites propagated along the interface between inorganic filler and matrix, and that some organic fillers were penetrated with fatigue cracks.3.Fatigue crack growth rate was more sensitive to degradation of composites by aging in water than transverse strength.4.The fatigue resistance of composites measured as DELTA K_<th> decreased by aging in water. SEM observation showed that fatigue crack propagated in both matrix and filler-matrix interface after aging in water for three months.These results indicated that that crack deflection and crack bridging by inorganic filler increased the fatigue resistance of composites, and that decrease of fatigue resistance by aging in water was caused by the degradation of resin matrix. From the present study, it was shown that the fatigue crack propagation test was an effective method to investigate toughening and degradation of dental composites.