牙科复合树脂的仿生梯度设计及力学改性研究

In recent years, light-cured resin composites have been widely used as restorative materials to restore the function, integrity, and morphology of missing tooth structure. However, the service quality and life span of current dental restorations remain to be improved by enhancing the mechanical properties of the resin composites and reducing the shrinkage stress caused by constrained polymerization shrinkage. The shrinkage stress usually increases with the increase of the elastic modulus (one of the most important mechanical properties) of the composite and this positive correlation induces a conflict between improving mechanical properties and reducing shrinkage stress of dental composites. To overcome this conflict, we attempt to design and fabricate bio-inspired gradient resin composites (GRCs) in this study, aiming at simultaneously tuning and optimizing the mechanical properties and shrinkage stress of the resin composites by controlling the spatial distributions of the composite fillers. The concept of GRCs is inspired by the gradient structure and resultant superior mechanical properties of human tooth. To this end, we will first develop a home-built setup to fabricate GRCs with different gradient design and uniform composites as the control. The mechanical properties and shrinkage stresses of the GRCs will be studied in comparison with the uniform counterparts and the reinforcing mechanisms of the former will be explored based on the combination of experiments and finite element modeling. The gradient design and fabrication procedure for the GRCs applied to different types of dental cavity will then be optimized in order to synergistically improve the mechanical properties whilst reduce the polymerization shrinkage stress. The presented study may open a new, biomimetic route for the development of next generation dental composites with improved service quality and life time.

光固化树脂复合材料（简称复合树脂）作为牙体修复通用材料，其临床服役质量和寿命还远不理想，提高复合树脂力学性能和减小聚合收缩应力是解决这一问题的关键。然而，提高弹性模量（重要力学性能之一）通常会引起收缩应力的同时增大，致使力学性能和收缩应力的协同改性存在矛盾。应对此矛盾，本研究拟借鉴天然牙齿的梯度结构，设计和制备“仿生梯度复合树脂”，通过调节复合体系内填料的空间分布，调控复合树脂的力学性能和聚合收缩应力，实现对二者的协同改性。为此，我们将搭建实验平台，制备不同梯度设计的复合树脂和与之对照的均匀复合树脂，采用实验测试与数值仿真相结合的方法，研究并对比梯度和均匀复合树脂的各力学性能与聚合收缩应力，揭示填料的梯度分布对上述特性的影响机制，进而对不同牙体修复工况的复合树脂的梯度设计进行优化。研究成果将为提高牙科复合树脂的服役质量和寿命提供新的思路和途径，对新型牙体修复材料的开发具有指导意义。

光固化复合树脂作为当前牙体修复通用材料，其临床服役质量和寿命还远不理性，提高复合树脂力学性能和减小聚合收缩应力是解决这一问题的关键。然而，提高材料刚度通常会引起收缩应力的同时增大，致使力学性能和收缩应力的协同改性存在矛盾。在本项目的支持下，我们首先实验表征了天然牙齿牙釉质—牙本质的力学梯度结构，提出了基于纳米压痕测试技术的高精度力学成像方法，揭示了牙齿在不同功能位置处的力学梯度构造与其生物力学功能间的关系，为牙齿修复材料的仿生梯度设计提供了原型；其次，基于天然牙齿的梯度构造原理，我们发展了一套利用磁场激励的可控功能梯度纳米复合材料的制备方法，结合实验测试和数值计算，探讨了纳米增强颗粒对牙科树脂力学增强的机理，为复合树脂的梯度设计和制备奠定了理论基础；然后，利用梯度纳米复合材料的磁场调控技术，通过调节硬质颗粒在柔性树脂基体内的空间分布，研制出多种刚柔渐进梯度复合材料，结合实验测试和有限元模拟，验证了梯度设计对于改性牙科复合树脂多种力学性能的可行性；最后，我们将梯度纳米复合材料的制备技术扩展到了其它仿生表界面：梯度界面，梯度涂层，和梯度纤维，实验测试表明梯度设计能够在保持各种表界面强度要求的同时，大大提高其承受循环荷载的耐久性能。本项目的研究成果不仅为牙科复合树脂的梯度设计和力学改性提供了坚实的理论基础和切实可行的实验技术，也为各种梯度材料的设计与先进制造提供了参照。