Departamento de Física, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, 780-0024 Ñuñoa, Santiago, Chile.
J Mech Behav Biomed Mater. 2011 Oct;4(7):1011-20. doi: 10.1016/j.jmbbm.2011.03.001. Epub 2011 Mar 9.
Hydroxyapatite (HAP) and fluorapatite (FAP) are essential components of dental enamel and bone. In this paper, we report a computational study of the elastic properties of HAP and FAP using ab initio and force field techniques. We have obtained the HAP and FAP elastic stiffness constants in hexagonal symmetry by fitting the Hooke law for both the energy-strain and stress-strain relations. Our ab initio HAP stiffness constants differ from the results of previous calculations, but follow similar trends. The HAP and FAP stiffness constants calculated with the ab initio method are very similar, although FAP is slightly stiffer than HAP in the hexagonal plane, and more compliant along the hexagonal axis. The pseudo-single-crystal HAP experimental stiffness constants in current use are critically reviewed. Combining the data from the ab initio simulations with the experimental FAP stiffness constants, several alternative sets of HAP stiffness constants are proposed. The mismatch in properties between HAP and FAP is evidently too small to assume it to be directly responsible for dental enamel mechanical degradation with fluorosis disease.
羟基磷灰石（HAP）和氟磷灰石（FAP）是牙釉质和骨骼的重要组成部分。在本文中，我们使用从头算和力场技术对 HAP 和 FAP 的弹性性质进行了计算研究。我们通过拟合能量-应变和应力-应变关系的胡克定律，得到了六方对称性下的 HAP 和 FAP 弹性刚度常数。我们的从头算 HAP 刚度常数与以前的计算结果不同，但趋势相似。用从头算方法计算的 HAP 和 FAP 刚度常数非常相似，尽管 FAP 在六方平面内比 HAP 稍硬，而沿六方轴方向更具弹性。目前使用的拟单晶 HAP 实验刚度常数受到了严格的审查。将从头算模拟数据与 FAP 刚度常数结合起来，提出了几组替代的 HAP 刚度常数。HAP 和 FAP 之间的性能不匹配显然太小，不能认为它是氟斑牙疾病导致牙釉质机械退化的直接原因。
