Bioinspired Composites for Dental Restorations

 说明(申请人提供)：商用树脂复合体在前牙修复中效果良好。然而，在后路修复体中，10年后临床失败率为25%或更高，骨折是导致失败的两个关键因素之一。该项目旨在通过开发一种新型的牙科复合材料来模拟牙釉质的微观结构和力学行为，以提高树脂基后部修复的临床性能。我们假设，在牙本质-牙釉质交界处(DEJ)附近模拟牙釉质可以通过增强对裂纹形成和生长以及随后的材料丢失或细菌渗透和反复腐烂的抵抗力来延长寿命。具体地说，我们假设模仿 釉质柱和它们之间无定向的交叉棒可以增加韧性，同时增强相对于咬合面的强度。此外，我们认为，加入更坚硬的牙槽材料，如二氧化钛，可以通过减少复合材料所承受的应力来增强向剩余牙齿的载荷转移，从而减少折裂[和边缘间隙的形成]。[此外，我们将通过调整填充剂和基质成分以更好地匹配牙齿的热膨胀系数来尽量减少边缘间隙的形成。]我们的程序在模仿牙釉质结构和我们计划开发的复合材料类型方面是新颖的。与以前模仿釉质结构的尝试不同，我们提出了一种原位开发其结构的系统，该系统专注于口腔外羟基磷灰石晶体的受控生长。此外，与分散无组织填充颗粒的商业复合材料不同，我们提出了一种全新的具有分级组织填充颗粒的复合材料类别。我们的方法将包括在低收缩磷酸盐或硅氧烷基丙烯酸液晶单体中合成二氧化硅和二氧化钛纳米棒并使其功能化。这些纳米棒将被组织成模仿珐琅棱柱的束状，然后自组装成更大的有序结构，以及额外的离散填充棒和单体中的颗粒，随后将在聚合过程中固化。通过官能化过程和形状各向异性，棒材的组织成束，然后形成更大的结构，将受到热力学和界面化学的控制。我们将[迭代设计复合材料的微观结构和成分]，通过系统地评估聚合收缩、在模拟口腔环境中的膨胀以及包括弯曲强度、弹性模数、储存和损失模数以及韧性在内的力学性能，验证复合材料作为未来修复材料的潜力。[此外，我们将评估S变形杆菌的相互作用，以确定复合材料是否具有抗菌性能，以确定细菌是否会降解复合材料。变形杆菌通常是导致继发性龋齿的细菌。]由于这种方法是如此之新，我们正在申请探索性拨款，以开发这种新型高填充(~60VOL%)复合材料所需的使能技术。我们的目标是从基础科学、工程学和牙科的角度证明我们方法的可行性。

 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.