Bajaj Devendra, Sundaram Naryana, Nazari Ahmad, Arola D
Department of Mechanical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA.
Biomaterials. 2006 Apr;27(11):2507-17. doi: 10.1016/j.biomaterials.2005.11.035. Epub 2005 Dec 9.
A preliminary study of the effects from age and dehydration on fatigue crack growth in human dentin was conducted. Compact tension (CT) fatigue specimens of coronal dentin were prepared from extracted molars and subjected to high cycle fatigue (10(5)<N<10(6)) under Mode I loading. Young hydrated dentin (mean age=25+/-7 years), old hydrated dentin (mean age=55+/-14 years) and young dehydrated dentin (mean age=20+/-2 years) were examined. Fatigue crack growth rates were quantified according to the Paris Law in terms of the crack growth exponent (m) and coefficient (C). The average fatigue crack growth exponent for the young hydrated dentin (m=13.3+/-1.1) was significantly less than that for the hydrated old (m=21.6+/-5.2; p<0.003) and dehydrated young dentin (m=18.8+/-2.8; p<0.01). Fatigue cracks in the old dentin underwent initiation at a lower stress intensity range than in young dentin and propagated at as significantly faster rate (over 100x). Differences in the microscopic features of the fracture surfaces from the old and young dentin suggested that particular mechanisms contributing to energy dissipation and crack growth resistance in the young hydrated dentin were not present in the old dentin. Based on results of this study, the fatigue crack growth resistance of human dentin decreases with both age of the tissue and dehydration.
开展了一项关于年龄和脱水对人牙本质疲劳裂纹扩展影响的初步研究。从拔除的磨牙制备冠部牙本质的紧凑拉伸（CT）疲劳试样，并在I型加载下进行高周疲劳试验（10⁵ < N < 10⁶）。研究了年轻含水牙本质（平均年龄 = 25 ± 7岁）、年老含水牙本质（平均年龄 = 55 ± 14岁）和年轻脱水牙本质（平均年龄 = 20 ± 2岁）。根据巴黎定律，依据裂纹扩展指数（m）和系数（C）对疲劳裂纹扩展速率进行了量化。年轻含水牙本质的平均疲劳裂纹扩展指数（m = 13.3 ± 1.1）显著低于年老含水牙本质（m = 21.6 ± 5.2；p < 0.003）和年轻脱水牙本质（m = 18.8 ± 2.8；p < 0.01）。与年轻牙本质相比，年老牙本质中的疲劳裂纹在较低的应力强度范围内萌生，且扩展速率显著更快（超过100倍）。年老和年轻牙本质断裂表面微观特征的差异表明，年轻含水牙本质中有助于能量耗散和裂纹扩展阻力的特定机制在年老牙本质中不存在。基于本研究结果，人牙本质的疲劳裂纹扩展阻力随组织年龄和脱水而降低。
