Ang Siang Fung, Scholz Torben, Klocke Arndt, Schneider Gerold A
Institute of Advanced Ceramics, Hamburg University of Technology, Denickestr. 15, Hamburg 21073, Germany.
Dent Mater. 2009 Nov;25(11):1403-10. doi: 10.1016/j.dental.2009.06.014. Epub 2009 Aug 3.
OBJECTIVES/METHODS: From a materials scientist's perspective, dental materials used for tooth repair should exhibit compatible mechanical properties. Fulfillment of this criterion is complicated by the fact that teeth have a hierarchical structure with changing mechanical behavior at different length scales. In this study, nanoindentation with an 8 microm spherical indenter was used to determine the elastic/plastic transition under contact loading for enamel.
The indentation elastic/plastic transition of enamel at the length scale of several hundreds of hydroxyapatite crystallites, which are within one enamel rod, is revealed for the first time. The corresponding penetration depth at the determined indentation yield point of 1.6GPa and 0.6% strain is only 7 nm. As a consequence of the small depth it is decisive for the experiment to calibrate the indenter tip radius in this loading regime. The elastic modulus of 123GPa was evaluated directly by the Hertzian penetration and not by the unloading part of the indentation curve.
We believe these data are also a valuable contribution to understand the mechanical behavior of enamel and to develop nanoscale biomimetic materials.
目标/方法：从材料科学家的角度来看，用于牙齿修复的牙科材料应具有相容的机械性能。由于牙齿具有层次结构，在不同长度尺度下机械行为会发生变化，因此满足这一标准变得复杂。在本研究中，使用直径为8微米的球形压头进行纳米压痕试验，以确定釉质在接触载荷下的弹性/塑性转变。
首次揭示了在一根釉柱内数百个羟基磷灰石微晶长度尺度下釉质的压痕弹性/塑性转变。在确定的1.6GPa压痕屈服点和0.6%应变下，相应的穿透深度仅为7纳米。由于深度较小，在这种加载条件下校准压头尖端半径对实验至关重要。弹性模量123GPa是通过赫兹穿透直接评估的，而不是通过压痕曲线的卸载部分。
我们认为这些数据对于理解釉质的机械行为以及开发纳米级仿生材料也有重要贡献。
