Arola Dwayne D, Rouland Joseph A
Department of Mechanical Engineering, University of Maryland, Baltimore, Maryland 21250, USA.
J Biomed Mater Res A. 2003 Oct 1;67(1):78-86. doi: 10.1002/jbm.a.10089.
The fracture of restored teeth is a significant obstacle to lifelong oral health. Recent studies suggest that fatigue cracks originate at flaws introduced during cavity preparation and that fatigue crack growth is a principle cause of restored tooth fractures. In this study, the rate of fatigue crack growth in bovine dentin was estimated under mode I cyclic loading. Double cantilever beam (DCB) specimens were obtained from bovine molars and subjected to high cycle fatigue loading (10(5) < N < 10(6)). The fatigue crack growth rates were measured and used to estimate the crack growth exponent and coefficient according to the Paris Law. The average fatigue crack growth exponent was 4.7 +/- 0.6 for crack growth parallel to the dentin tubules, which was significantly larger than 4.3 +/- 0.5 for crack growth perpendicular to the tubules (t-test, CI > 80%). Although the crack growth rates varied considerably, there was no significant dependence on tubule orientation or tubule density. However, specific features of the fracture surfaces and tendencies for crack curving away from the tubules suggested preferential fatigue crack growth perpendicular to the dentin tubules. Results from this study are being used to guide an experimental investigation of fatigue crack growth in human dentin.
修复牙体的折断是终身口腔健康的一个重大障碍。最近的研究表明，疲劳裂纹起源于窝洞制备过程中引入的缺陷，并且疲劳裂纹扩展是修复牙体折断的主要原因。在本研究中，在I型循环加载下估算了牛牙本质中疲劳裂纹的扩展速率。从牛磨牙获取双悬臂梁（DCB）试样，并对其进行高周疲劳加载（10⁵ < N < 10⁶）。测量疲劳裂纹扩展速率，并根据Paris定律估算裂纹扩展指数和系数。对于平行于牙本质小管的裂纹扩展，平均疲劳裂纹扩展指数为4.7±0.6，显著大于垂直于小管的裂纹扩展的4.3±0.5（t检验，置信区间> 80%）。尽管裂纹扩展速率变化很大，但对小管方向或小管密度没有显著依赖性。然而，断口表面的特定特征以及裂纹偏离小管的弯曲趋势表明，疲劳裂纹优先垂直于牙本质小管扩展。本研究结果正用于指导对人牙本质中疲劳裂纹扩展的实验研究。
