The fatigue and fracture behavior of hard tissues are topics of considerable interest today. This special group of organic materials comprises the highly mineralized and load-bearing tissues of the human body, and includes bone, cementum, dentin and enamel. An understanding of their fatigue behavior and the influence of loading conditions and physiological factors (e.g. aging and disease) on the mechanisms of degradation are essential for achieving lifelong health. But there is much more to this topic than the immediate medical issues. There are many challenges to characterizing the fatigue behavior of hard tissues, much of which is attributed to size constraints and the complexity of their microstructure. The relative importance of the constituents on the type and distribution of defects, rate of coalescence, and their contributions to the initiation and growth of cracks, are formidable topics that have not reached maturity. Hard tissues also provide a medium for learning and a source of inspiration in the design of new microstructures for engineering materials. This article briefly reviews fatigue of hard tissues with shared emphasis on current understanding, the challenges and the unanswered questions.

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生物材料的疲劳：硬组织

硬组织的疲劳和断裂行为是当今相当感兴趣的话题。这组特殊的有机材料包括人体高度矿化和承重的组织，包括骨骼、牙骨质、牙本质和牙釉质。了解他们的疲劳行为以及负荷条件和生理因素（例如老化和疾病）对退化机制的影响对于实现终身健康至关重要。但是，该主题远不止眼前的医疗问题。表征硬组织的疲劳行为存在许多挑战，其中大部分归因于尺寸限制和其微观结构的复杂性。成分对缺陷类型和分布、聚结率、以及它们对裂纹萌生和发展的贡献，是尚未成熟的艰巨课题。硬组织还提供了学习的媒介和工程材料新微结构设计的灵感来源。本文简要回顾了硬组织的疲劳，共同强调了当前的理解、挑战和未解决的问题。