动态载荷下树脂-牙本质粘接界面的力学降解机制及疲劳寿命研究

The resin-dentin bonding interface, which is consisted of a series of components with different physico-chemical properties, is crucial to the bonding performance of dental restorations. The lack of durability of the resin-dentin interface greatly contributes to the clinical failures in dental restorative practice. As the biochemical mechanism has been proved to be insufficient in interpreting the degradation of the interface, the effect of mechanical loading on the premature failure of it should not be overlooked. We hypothesized that the interaction between stress fatigue and biochemical degradation pathway plays an important role in the premature failure of the interface, by which the spatial configuration and entropy of the interfacial components is modified under mechanical loading, putting effects on the degradation rate of it by the biochemical pathway; while the latter changes the mechanical properties of the components as well as influences the stress distribution whthin the whole interface and fatigue life of it.Therefore, the aim of this project is to study the effect of the interaction between stress fatigue and biochemical pathway on the degradation of the main components of the resin-dentin bonding interface (such as the resinous adhesive, hybrid layer, exposed collagen fibrils and partially demineralized dentin), to explore the compound mechanisms of the degradation of it.Meanwhile, the fatigue life is also to be studied, to identify the crucial component in determining the overall durability of the interface, which will be greatly helpful in developing novel dental adhesive materials and modifying the strategy of dentin bonding in the future research, which aimed to enhance the stability and durability of the resin-dentin interface, as well as to improve the clinical performance of dental restorations in clinical practice.

树脂-牙本质粘接界面是由理化性质迥异的多种成分共同构成的复合界面，是决定牙科修复体长期粘接效果的关键结构。粘接界面耐久性不足是粘接失败最主要的原因。证据表明，应力载荷与生物-化学降解机制一道参与了粘接界面的降解过程。根据前期研究和文献，我们认为树脂-牙本质界面的降解是一个功能状态下的动态过程。在此过程中，应力载荷通过空间构象改变和熵变等机制不同程度影响界面各结构成分的生物-化学的降解速率，反之，生物-化学降解引起的各结构成分不同程度的力学性质改变又影响其疲劳寿命和界面应力分布。为此，我们拟在循环载荷下，研究应力疲劳和生物-化学降解在树脂-牙本质界面主要结构成分(粘接剂、混合层、胶原纤维和脱矿牙本质)在动态降解过程中的相互作用，探索动态载荷下粘接界面的联合降解机制，明确影响界面疲劳寿命的关键结构成分，为针对性地开发新型粘接材料和改进粘接策略奠定基础，以改善树脂-牙本质粘接界面的稳定性。

树脂-牙本质粘结界面的稳定性是决定口腔粘结修复效果的关键。粘结界面中暴露胶原纤维成分的水解和树脂材料的降解是导致界面稳定性的重要原因，但多个证据表明单一的生物-化学降解机制并不足以解释树脂-牙本质粘接界面在功能状态下的动态降解过程。本项目探索应力载荷对树脂-牙本质粘结界面功能状态下降解进程的影响，从而为寻找粘结界面降解过程中的薄弱环节，进一步改进粘结策略探索新的方向。本研究制备全酸蚀与自酸蚀粘结试件，并分别构建了全酸蚀和自酸蚀粘结界面的三维有限元显微模型，通过实验研究和有限元力学分析静态载荷下两种粘结策略下应力分布模式的差异，证实自酸蚀粘结界面各组分中的应力分布更为均匀，有助于提升粘结界面的稳定性；比较不同粘结前脱矿处理方法对粘结界面中胶原成分稳定性的影响，证实与EDTA处理相比，37%磷酸脱矿更为高效，并有助于保存胶原纤维的酶解稳定性；探索了人工老化中全酸蚀和自酸蚀粘接界面降解的微观形貌和粘接强度变化，探索了以太赫兹光谱技术无创连续监测粘结界面破坏的可行性，为将来无创性在体研究树脂-牙本质粘结界面的连续变化进程提供了可能；结合前期研究，构建了纤维树脂桩核修复的动态载荷模型，比较动态载荷下压缩界面与拉伸界面的粘结界面降解进程，证实拉伸应力显著加速粘结界面破坏，界面破坏以胶原纤维组分的降解为主要表现；构建动态载荷下全酸蚀和自酸蚀粘结界面的三维有限元显微模型，通过不同老化进程中应力分析与应力集中因子计算，证实动态应力载荷下，粘结界面破坏并非总发生于裸露胶原纤维层，而是取决于界面中疲劳寿命最短的结构成分，并绘制了两种粘结策略下粘结界面的疲劳寿命预测曲线。本研究对应力载荷下粘结界面的降解进程进行了系统的深入研究，证实应力疲劳也是树脂-牙本质粘结界面的重要破坏机制。研究结果有助于为具有适宜力学性能的树脂粘结材料研发和粘结策略改进提供新的研究方向，具有较好的临床意义和应用前景。