Tam L E, Pilliar R M
Centre for Biomaterials, Faculty of Dentistry, University of Toronto, Ontario, Canada.
J Dent Res. 1993 May;72(5):953-9. doi: 10.1177/00220345930720051801.
The reliability and validity of tensile and shear bond strength determinations of dentin-bonded interfaces have been questioned. The fracture toughness value (KIC) reflects the ability of a material to resist crack initiation and unstable propagation. When applied to an adhesive interface, it should account for both interfacial bond strength and inherent defects at or near the interface, and should therefore be more appropriate for characterization of interface fracture resistance. This study introduced a fracture toughness test for the assessment of dentin/resin-composite bonded interfaces. The miniature short-rod specimen geometry was used for fracture toughness testing. Each specimen contained a tooth slice, sectioned from a bovine incisor, to form the bonded interface. The fracture toughness of an enamel-bonded interface was assessed in addition to the dentin-bonded interfaces. Tensile bond strength specimens were also prepared from the dentin surfaces of the cut bovine incisors. A minimum of ten specimens was fabricated for each group of materials tested. After the specimens were aged for 24 h in distilled water at 37 degrees C, the specimens were loaded to failure in an Instron universal testing machine. There were significant differences (p < 0.05) between the dental adhesives tested. Generally, both the fracture toughness and tensile bond strength measurements were highest for AllBond 2, intermediate for 3M MultiPurpose, and lowest for Scotchbond 2. Scanning electron microscopy of the fractured specimen halves confirmed that crack propagation occurred along the bond interface during the fracture toughness test. It was therefore concluded that the mini-short-rod fracture toughness test provided a valid method for characterization of the fracture resistance of the dentin-resin composite interface.
牙本质粘结界面拉伸和剪切粘结强度测定的可靠性和有效性一直受到质疑。断裂韧性值（KIC）反映了材料抵抗裂纹萌生和不稳定扩展的能力。当应用于粘结界面时，它应同时考虑界面粘结强度和界面处或其附近的固有缺陷，因此更适合用于表征界面抗断裂性能。本研究引入了一种断裂韧性测试方法来评估牙本质/树脂复合材料粘结界面。采用微型短棒试样几何形状进行断裂韧性测试。每个试样包含一片从牛切牙切下的牙片，以形成粘结界面。除了牙本质粘结界面外，还评估了釉质粘结界面的断裂韧性。还从切割后的牛切牙的牙本质表面制备了拉伸粘结强度试样。对每组测试材料至少制备十个试样。将试样在37℃的蒸馏水中老化24小时后，在Instron万能试验机上加载直至破坏。所测试的牙科粘结剂之间存在显著差异（p < 0.05）。一般来说，AllBond 2的断裂韧性和拉伸粘结强度测量值最高，3M多功能粘结剂居中，Scotchbond 2最低。对断裂试样的两半进行扫描电子显微镜观察证实，在断裂韧性测试过程中裂纹沿粘结界面扩展。因此得出结论，微型短棒断裂韧性测试为表征牙本质-树脂复合材料界面的抗断裂性能提供了一种有效的方法。
