Pan Haihua, Tao Jinhui, Yu Xinwei, Fu Lei, Zhang Jiali, Zeng Xiangxuan, Xu Guohua, Tang Ruikang
J Phys Chem B. 2008 Jun 19;112(24):7162-5. doi: 10.1021/jp802739f. Epub 2008 May 27.
It is interesting to note that the demineralization of natural enamel does not happen as readily as that of the synthesized hydroxyapatite (HAP), although they share a similar chemical composition. We suggest that the hierarchical structure of enamel is an important factor in the preservation of the natural material against dissolution. The anisotropic demineralization of HAP is revealed experimentally, and this phenomenon is understood by the different interfacial structures of HAP-water at the atomic level. It is found that HAP {001} facets can be more resistant against dissolution than {100} under acidic conditions. Although {100} is the largest surface of the typical HAP crystal, it is {001}, the smallest habit face, that is chosen by the living organisms to build the outer surface of enamel by an oriented assembly of the rodlike crystals. We reveal that such a biological construction can confer on enamel protections against erosion, since {001} is relatively dissolution-insensitive. Thus, the spontaneous dissolution of enamel surface can be retarded in biological milieu by such a smart construction. The current study demonstrates the importance of hierarchical structures in the functional biomaterials.
值得注意的是，天然牙釉质的脱矿并不像合成羟基磷灰石（HAP）那样容易发生，尽管它们具有相似的化学成分。我们认为牙釉质的层次结构是天然材料抵抗溶解的一个重要因素。实验揭示了HAP的各向异性脱矿，并且这种现象在原子水平上通过HAP-水的不同界面结构得到理解。发现在酸性条件下，HAP {001} 晶面比 {100} 晶面更耐溶解。虽然 {100} 是典型HAP晶体的最大表面，但生物体选择的是 {001} 这个最小的习性面，通过棒状晶体的定向组装来构建牙釉质的外表面。我们发现这种生物构造可以赋予牙釉质抗侵蚀的保护作用，因为 {001} 相对不敏感于溶解。因此，通过这种巧妙的构造，牙釉质表面在生物环境中的自发溶解可以得到延缓。当前的研究证明了层次结构在功能性生物材料中的重要性。
