The first-principles calculations based on density functional theory with generalized gradient approximation were carried out to investigate the fundamental features of hydroxyapatite, the primary constituent of human bone and tooth, for use in light-curable dental composites. Moreover, the influence of strontium incorporation into hydroxyapatite on structural, electronic and optical properties of hydroxyapatite was comprehensively studied while we believe this substitution can promote radiopacity and remineralization ability of apatite. After geometry optimization, the computed structural parameters are found to yield a satisfactory agreement with the reported experimental results indicating the accuracy of the calculations. The elastic characteristics demonstrate that both hexagonal apatites possess higher Young’s modulus and Poisson’s ratio compared silica glass which is known as traditional filler used in dental composites. The analysis of the electronic density of states reveals that some variation in macroscopic mechanical properties can arise from difference between d state energy of calcium and strontium elements. Moreover, the origins of optical features affecting the curing depth of composite have been discussed in terms of the dielectric function and refractive index. The weak energy loss in the range of 3–3.5 eV demonstrates that these biocompatible fillers can provide an increased curing depth when are used in a UV-LED cured restorative dental materials.

中文翻译：

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Sr掺杂羟基磷灰石作为光固化牙科复合材料生物相容性填料的第一性原理研究

进行了基于密度泛函理论和广义梯度近似的第一性原理计算，以研究用于光固化牙科复合材料的人骨和牙齿的主要成分羟基磷灰石的基本特征。此外，已全面研究了锶掺入羟基磷灰石中对羟基磷灰石的结构，电子和光学性质的影响，而我们认为这种替代可以促进磷灰石的不透射线性和再矿化能力。经过几何优化后，发现计算出的结构参数与报告的实验结果显示出令人满意的一致性，表明计算的准确性。弹性特性表明，与被称为牙科复合材料的传统填充剂的石英玻璃相比，六方磷灰石都具有更高的杨氏模量和泊松比。对状态的电子密度的分析表明，宏观机械性能的某些变化可能是由于d态能量的钙和锶元素。此外，已经从介电功能和折射率方面讨论了影响复合材料固化深度的光学特征的起源。在3-3.5 eV范围内的微弱能量损失表明，当用于UV-LED固化的修复性牙科材料中时，这些生物相容性填充剂可以提供更大的固化深度。