【作者】 葛俊；

【导师】 崔福斋；

【作者基本信息】 清华大学 ， 材料科学与工程， 2005， 博士

【摘要】 本论文以成熟的人类牙釉质和野生型斑马鱼脊椎骨为模型,对两类典型的经不同矿化过程形成的磷酸钙基硬组织生物材料的分级结构、纳米力学性能和组织脱矿过程进行了研究,从而对磷酸钙基生物矿化材料的分级结构特点,分级结构存在的规律性,以及纳米力学性能等功能的分级对应性进行了深入论述。人类牙釉质的性能与其主要成分羟基磷灰石晶体的分级组装结构密切相关。基于从纳米尺度到微米尺度对釉质的微结构的研究结果,我们首次提出了人类牙釉质7级分级结构的新模型。羟基磷灰石纳米纤维是釉质的分级结构基础,进而经过多级组装形成了微纤维以及纤维束等高级组装结构。纤维的取向和致密度变化构成了釉柱和釉质鞘。釉柱在釉质层的不同区域有不同的排列方式。此外,我们首次报道了釉柱与釉质鞘的纳米硬度和弹性模量存在显著差异,从而证明了釉质的纳米力学性能存在与其微结构一一对应的分级特性。沿斑马鱼脊椎骨骨壁径向对胶原纤维的矿化程度、分级组装结构和纳米力学性能的对比为研究骨分级结构的形成和重塑提供了有效途径。靠近外骨膜的新生骨组织中主要包含的是未进行高级组装的矿化胶原纤维。骨壁中央区域的骨组织发育成熟,矿化胶原纤维排列有序,并组装形成胶原纤维束以及更高级的板层结构。而在内骨膜附近,胶原纤维束虽然发育更成熟,但因为溶解和重塑作用,组织不存在板层结构。由组装程度不同的矿化胶原纤维形成的骨分级结构导致脊椎骨骨壁的纳米硬度和弹性模量从外到内逐渐增加。通过对釉质酸蚀软化模型的微结构和力学性能的分析,我们系统报道了软化表面的构造,结构与力学性能对应性以及软化表面的各分层内釉质分级结构的变化。基于对酸腐蚀软化的研究结果,我们设计了氟化物与唾液中的钙磷离子在釉质表面原位矿化的方法对软化层进行修复,并证明了这种方法在一定程度上能够从成分、结构和力学性能等方面修复受损釉质。更多还原

【Abstract】 The hierarchical structure, nanomechanical properties and their response during demineralization of mature human dental enamel and wild type zebrafish (Danio rerio) skeletal bone, two representative systems of the apatite-based hard tissues formed under different mineralization mechanisms, were studied in this work. Then from the point of hierarchical assembly, the microstructural characteristics of the apatite-based mineralized biomaterials, as well as their fine-tuning to the nanomechanical properties were discussed in detail.Human dental enamel is mostly built up of hydroxyapatite crystals in well controlled assembly manners. Based on the investigations to its microstructure from nano-scale to micron-scale, we for the first time proposed a novel model of 7 levels hierarchical structure of enamel and described its organization with a scheme representing a complete spectrum that covers a wide scale from nanometer to millimeter. Hydroxyapatite nano-fibrils are the fundamental hierarchical structure level, which then assemble into fibrils and fibers level by level. With the different orientations and densities of the crystal nano-fibrils, the prism/interprism/sheath continuums are imposed that are differently arranged across the whole enamel layer. More than that, we for the first time reported the significant alternations of the nanohardness and elastic modulus between prisms and sheaths, which can strongly support the close relationship between the microstructure and nanomechanical properties of enamel in terms of hierarchy.The zebrafish skeleton is another model with hierarchical structure. Explorations to the mineralization of the collagen fibrils, the hierarchical assembly structure and the nanomechanical properties across the whole thickness of the bone wall provide an efficient way to understand the formation and remodeling of the hierarchical structure of bone. The new formed bone near the periosteum mainly contains the mineralized更多还原