Boron Nitride Nanosheets to Enhance Dental Composite Performance

项目摘要/摘要 为了提高现有牙科修复体的性能和耐久性，我们将开发一种 新型氮化硼纳米片(BNNS)基填充体系。类似于石墨烯，剥离的六方硼 氮化物产生单层或几层BNNSS，具有有用的优点。像石墨烯一样，BNNSS的尺寸很小 已经观察到分布自组装成胶体液晶，这种胶体液晶非常强并且 轻质、耐磨、化学稳定性好。牙科复合材料中BNNSS作为填料的层状组织 会降低复合材料的粘度，增加整体填充量，使复合材料剪切变稀，以及 增强操控性能和复合材料放置。BNNSS还具有非常低的摩擦系数， 会降低复合磨损率。它们可以充当光学管道(取决于方向)来引导和 在固化过程中分配光子能量，并潜在地增加固化深度。它们是疏水性的，可以 赋予复合材料疏水性并保护其不被降解。它们可以形成片状层， 可以起到水屏障的作用。最后，与石墨烯不同的是，BNNSS(也称为“白色石墨烯”)比石墨烯更便宜 制造，透明和无色，因此它们在美学复合材料中有希望作为填充物。这个 这些特征的意义在于，它们应该会显著增加综合寿命。 我们已经开发出新的方法来剥离、浓缩和表面处理BNNSS，用于 纳米复合材料。这些BNNSS用环氧乙烷官能化，并与环氧乙烷/丙烯酸酯结合 互穿网络树脂系统(OASYS)复合材料(根据单独的NIH U01授权开发)。 即使在0.5wt%的很低浓度下，用未经优化的剥离方法制备的BNNSS， 显著提高复合材料的弹性系数，降低粘度，增加疏水性的相容性 在复合材料中加入含氟单体，提高了复合材料的透光率。因此，我们将进一步优化 BNNS剥离方法，并探索BNNSS可以赋予更常见的 传统的牙科复合系统在更高的负荷下。 提出了四个具体目标：1)确定BNNS的剥离、加载和定向的影响 复合材料的总填充量、固化、物理和光学性能。2)测定其生物相容性。 遵循ISO7405和ISO 10993系列的BNNS载药复合材料的临床前生物兼容性 医疗器械的评估。来自Aim 1的具有临床可接受性能的复合材料将在 遵循目标。3)确定了BNNS浓度和取向对复合材料静力学和力学性能的影响 随时间变化的力学性能，包括断裂韧性和三体磨损。4)确定 BNNS浓度对生物膜形成的影响。

PROJECT SUMMARY/ABSTRACT In order to improve the performance and durability of current dental restorative composites, we will develop a novel boron nitride nanosheet (BNNS)-based filler system. Similar to graphene, exfoliated hexagonal boron nitride yields single- or few-layer BNNSs with useful advantages. Like graphene, BNNSs with narrow size distributions have been observed to self-assemble into colloidal liquid crystals that are extremely strong and light, wear resistant, and chemically stable. The lamellar organization of BNNSs as a filler in dental composites would reduce composite viscosity, increase overall filler loading, make the composite shear-thinning, and enhance handling properties and composite placement. BNNSs also have very low coefficient of friction that would reduce composite wear rate. They can act as an optical conduit (depending on orientation) to guide and distribute photon energy during cure and potentially increase depth of cure. They are hydrophobic and can impart hydrophobicity to the composite and protect it from degradation. They can form lamellar layers that could act as water barriers. Finally, unlike graphene, BNNSs (aka “white graphene”) are less expensive to manufacture and are transparent and colorless, so they have promise as fillers in esthetic composites. The significance of these features is that they should result in substantially increased composite longevity. We have developed novel methods for exfoliating, concentrating, and surface treating BNNSs for use in nanocomposites. These BNNSs were functionalized with oxiranes and incorporated into Oxirane/Acrylate interpenetrating network resin System (OASys) composites (developed under a separate NIH U01 grant). Even at the very low concentration of 0.5 wt%, BNNSs made with an unoptimized exfoliation method, significantly enhanced composite modulus, reduced viscosity, increased compatibility of the hydrophobic fluorinated monomer in the composite, and increased composite translucency. As such, we will further optimize the BNNS exfoliation method and explore the properties that BNNSs could impart on a more common conventional dental composite system at much higher loadings. Four specific aims are proposed: 1) To determine the effects of BNNS exfoliation, loading and orientation on composite total filler loading, curing, physical and optical properties. 2) To determine the biocompatibility of BNNS-loaded composites following the ISO 7405 and ISO 10993 series for pre-clinical biocompatibility evaluation of medical devices. Composites from Aim 1 with clinically acceptable properties will be tested in the following aims. 3) To determine the effects of BNNS concentration and orientation on composite static and time-dependent mechanical properties, including fracture toughness and three-body wear. 4) To determine the effect of BNNS concentration on biofilm formation.