Institute of Advanced Ceramics, Hamburg University of Technology, Hamburg 21073, Germany.
Biomaterials. 2010 Mar;31(7):1955-63. doi: 10.1016/j.biomaterials.2009.11.045. Epub 2009 Dec 6.
The microstructure of enamel like most biological tissues has a hierarchical structure which determines their mechanical behavior. However, current studies of the mechanical behavior of enamel lack a systematic investigation of these hierarchical length scales. In this study, we performed macroscopic uni-axial compression tests and the spherical indentation with different indenter radii to probe enamel's elastic/inelastic transition over four hierarchical length scales, namely: 'bulk enamel' (mm), 'multiple-rod' (10's microm), 'intra-rod' (100's nm with multiple crystallites) and finally 'single-crystallite' (10's nm with an area of approximately one hydroxyapatite crystallite). The enamel's elastic/inelastic transitions were observed at 0.4-17 GPa depending on the length scale and were compared with the values of synthetic hydroxyapatite crystallites. The elastic limit of a material is important as it provides insights into the deformability of the material before fracture. At the smallest investigated length scale (contact radius approximately 20 nm), elastic limit is followed by plastic deformation. At the largest investigated length scale (contact size approximately 2 mm), only elastic then micro-crack induced response was observed. A map of elastic/inelastic regions of enamel from millimeter to nanometer length scale is presented. Possible underlying mechanisms are also discussed.
釉质的微观结构与大多数生物组织一样具有层次结构，这决定了它们的力学行为。然而，目前对釉质力学行为的研究缺乏对这些层次长度尺度的系统研究。在这项研究中，我们进行了宏观单轴压缩试验和不同压头半径的球形压痕试验，以研究釉质在四个层次长度尺度上的弹性/非弹性转变，即：“体釉质”（mm）、“多棒”（10μm ）、“棒内”（100nm 有多个晶粒）和最终的“单晶体”（10nm 有一个羟基磷灰石晶粒的面积）。根据长度尺度，釉质的弹性/非弹性转变在 0.4-17GPa 之间观察到，并与合成羟基磷灰石晶粒的值进行了比较。材料的弹性极限很重要，因为它可以深入了解材料在断裂前的可变形性。在所研究的最小长度尺度（接触半径约为 20nm）下，弹性极限之后是塑性变形。在所研究的最大长度尺度（接触尺寸约为 2mm）下，只观察到弹性和微裂纹诱导的响应。提出了从毫米到纳米长度尺度的釉质弹性/非弹性区域图。还讨论了可能的潜在机制。
