Bioinspired Composites for Dental Restorations

 描述（由申请人提供）：市售树脂复合材料在前牙矫正中效果良好。然而，在后路置换中，10年后的临床失败率为25%或更高，骨折是失败的两个关键因素之一。该项目旨在通过开发一种新型牙科复合材料来改善树脂基后牙充填的临床性能，该复合材料模仿牙釉质的微观结构和机械行为。我们假设，模仿牙本质-釉质交界处（DEJ）附近的釉质可以通过增强对裂纹形成和生长以及随后的材料损失或细菌渗透和复发性腐烂的抵抗力来增加寿命。特别是，我们假设，模仿 搪瓷柱和它们之间的无序交叉杆可以增加韧性，同时相对于咬合表面提高强度。此外，我们认为，包括更硬的填充材料，如二氧化钛，可以增强向剩余牙齿的载荷传递，这将通过减少复合材料所承载的应力来减少断裂[和边缘间隙的形成]。[In此外，我们将通过“调整”填料和基质成分以更好地匹配牙齿的热膨胀系数来寻求最小化边缘间隙的形成。我们的计划是新颖的，在其方法来模仿牙釉质结构和复合材料的类型，我们建议开发。与以前试图模仿牙釉质结构，重点是控制羟基磷灰石晶体的生长口外，我们提出了一个系统，发展其结构原位。此外，与具有分散的非组织化填料颗粒的商业复合材料不同，我们提出了具有分层组织化填料颗粒的全新类别的复合材料。我们的方法将涉及在低收缩磷酸盐或硅氧烷基丙烯酸液晶单体中合成和官能化二氧化硅和二氧化钛纳米棒。这些纳米棒将被组织成模仿搪瓷棱柱的束，然后与随后在聚合过程中固化的单体中的另外的离散填料棒和颗粒一起自组装成更大的有序结构。将棒组织成束，然后组织成更大的结构将通过功能化过程和形状各向异性由热力学和界面化学控制。我们将[反复设计复合材料的微观结构和组成，并]通过系统地评估聚合收缩，在模拟口腔环境中的溶胀和机械性能，包括弯曲强度，弹性模量，储能和损耗模量和韧性，来验证复合材料作为未来修复材料的潜力。[In此外，我们将评估变形链球菌（S mutans）的相互作用，变形链球菌是引起继发性龋齿的典型细菌，以确定复合材料是否具有抗菌特性，或者细菌是否降解复合材料。由于这种方法是如此新颖，我们正在申请一项探索性资助，以开发这种新型高填充（~60体积%）复合材料所需的技术。我们的目标是从基础科学，工程和牙科的角度证明我们的方法的可行性。

 DESCRIPTION (provided by applicant): Commercial resin composites work well in anterior restorations. However, in posterior restorations the clinical failure rate is 25% or more after 10 years with fracture being one of the two key contributors to failure. This program seeks to improve the clinical performance of resin based posterior restorations by developing a new class of dental composites that mimic the microstructure and mechanical behavior of enamel. We hypothesize that mimicking enamel near the dentin-enamel junction (DEJ) can increase the lifetime by enhancing resistance to crack formation and growth as well as subsequent material loss or bacterial penetration and recurrent decay. In particular, we hypothesize that imitating the enamel columns and the disoriented crossed rods between them can increase toughness while enhancing strength relative to the biting surface. Further, we believe that including stiffer fille materials like titania can enhance load transfer to the remaining tooth which would reduce fracture [and formation of marginal gaps] by decreasing the stress carried by the composite. [In addition, we will seek to minimize marginal gap formation by 'tuning' filler and matrix composition to better match the coefficient of thermal expansion of the tooth.] Our program is novel in its approach to mimicking enamel structure and in the type of composites we propose to develop. Unlike previous attempts to mimic enamel structure that focused on the controlled growth of hydroxyapatite crystals outside the mouth, we propose a system that develops its structure in-situ. Further, unlike commercial composites that have dispersed non-organized filler particles we propose an entirely new class of composites with hierarchically organized filler particles. Our approach will involve synthesizing and functionalizing silica and titania nanorods in low shrinkage phosphate or siloxane based acrylic liquid crystal monomers. These nanorods will be organized into bundles that imitate enamel prisms and then self-assembled into larger ordered structures together with additional discrete filler rods and particles in monomers that wil be subsequently solidified during polymerization. The organization of rods into bundles and then into larger structures will be controlled by thermodynamics and interfacial chemistry through the functionalization process and shape anisotropy. We will [iteratively design the composite microstructure and composition and] validate the potential of the composites as future restoration materials, by systematically assessing the polymerization shrinkage, swelling in a simulated oral environment and mechanical properties including flexural strength, elastic modulus, storage and loss modulus, and toughness. [In addition, we will evaluate the interactions of S mutans, the bacteria typyically responsible for secondary caries to determine if the composites have anti-bacterial properties of if the bacteria degrades the composite.] Because the approach is so new, we are requesting an exploratory grant to develop the enabling techniques required for this new class of highly filled (~60 vol%) composites. Our objective is to demonstrate the feasibility of our approach from a fundamental science, engineering and dental perspective.