Studies on the testing methods for interfacial fracture toughness for evaluating the interfacial property of dental prostheses.

通过改变试件的厚度、宽度、长度和初始裂纹长度，研究了不透明瓷/金属界面和粘接树脂/金属界面的界面断裂韧性（Ⅰ型和Ⅱ型）的测试方法。试样为夹层结构，具有初始裂纹。在模式I测试中，通过使用两个正方形横截面块来加载测试样本，所述正方形横截面块在测试样本端部上具有用于加载的孔。用显微镜测量裂纹长度，并结合边缘载荷和裂纹张开位移的测量。通过3点弯曲试验完成模式II试验。从他们的测量结果，界面断裂韧性的两个值得到。获得的结果如下。对于不透明瓷/金属试件，其厚度为0.3-0.5mm，宽度为3- 5 mm，长度在30- 40 mm范围内足够。初始裂纹长度在8- 10 mm范围内较为合理。测试速度以0.05mm/min为宜。作为参考数据，该试样的界面断裂韧性约为15 j/m^2。其次，在粘合树脂/金属试样中，其厚度在1.5-2.0mm范围内是合理的，因为断裂韧性值显示为400- 500 j/m^2。从粘接过程来看，宽度为5 mm比10 mm的粘接效果好。长度仅为50 mm。顺便说一下，粘合树脂层的厚度为约70 μ m。初始裂纹长度取15- 20 mm较好，因为裂纹扩展长度比较容易测量。因此，为了评价界面性能，人们认识到这种断裂韧性的测试方法是更有效的。

Testing method for interfacial fracture toughness (modes I and II) between two different materials in a dental prosthesis, such as opaque porcelain/metal and adhesive resin/metal interfaces, was investigated by changing thickness, width, length and intial crack length of test specimen. Test specimen is of sandwich construction with an intial crack. In mode I testing, the test speciman was loaded by using two square cross-sectional block with a hole for loading bonded on test specimen end. And the crack length was measured by using a traveling microscope in conjunction with the measurement of the marginal load and crack opening displacement. Mode II testing was done by 3-point bending test. From their results of measurement, both values of interfacial fracture toughness was obtained. Results obtained are as follows. In case of the opaque porcelain/metal test specimen, its thickness of 0.3-0.5mm and its width of 3-5mm were appliciated, and its length was enough in region of 30-40mm. Initial crack length in region of 8-10mm was reasonable. Testing speed of 0.05mm/min was appreciated. As reference data, interfacial fracture toughness of this test specimen was about 15j/m^2. Next, in adhesive resin/metal test specimen, its thickness in region of 1.5-2.0mm was reasonable because the values of fracture toughness were shown for 400-500j/m^2. Width of 5mm was good than that of 10mm considering the procedure of adhesion. Length was 50mm only. By the way, thickness of adhesive resin layr was about 70mum. Initial crack length of 15-20mm was good because th crack length propagated was comparatively easy to measure. Therefore, in order to evaluate the interfacial property, it was recognized that such the testing methods for fracture toughness were more effective.