Boron Nitride Nanosheets to Enhance Dental Composite Performance

项目概要/摘要 为了提高目前牙科修复复合材料的性能和耐久性，我们将开发一种 新型氮化硼纳米片（BNNS）基填料体系。与石墨烯类似，剥离的六方硼 氮化物产生具有有用优点的单层或少层BNNSs。与石墨烯一样，具有窄尺寸的BNNSs 已经观察到这种分布自组装成胶体液晶，这种胶体液晶非常强， 轻、耐磨、化学稳定。BNNSs作为牙科复合材料填料的层状组织 会降低复合材料的粘度，增加总的填料含量，使复合材料剪切变稀， 增强处理性能和复合材料放置。BNN还具有非常低的摩擦系数， 会降低复合材料的磨损率。它们可以充当光学导管（取决于方向）来引导和 在固化期间分布光子能量并潜在地增加固化深度。它们是疏水性的， 赋予复合材料疏水性并保护其免于降解。它们可以形成层状层， 可以作为水的屏障。最后，与石墨烯不同，BNNSs（又名“白色石墨烯”）的成本较低， 它们是透明无色的，因此它们有希望作为美学复合材料的填料。的 这些特征的重要性在于它们应导致复合材料寿命的显著增加。 我们已经开发了用于剥离、浓缩和表面处理BNNSs的新方法， 纳米复合材料将这些BNNSs用环氧乙烷官能化并掺入环氧乙烷/丙烯酸酯中， 互穿网络树脂系统（OASys）复合材料（在单独的NIH U 01资助下开发）。 即使在0.5wt%的非常低的浓度下，用未优化的剥离方法制备的BNNS， 显著增强的复合材料模量、降低的粘度、增加的疏水材料的相容性， 复合材料中的氟化单体，以及增加的复合材料透明度。因此，我们将进一步优化 BNNS剥离方法，并探索BNNS可以赋予更常见的 传统的牙科复合材料系统在高得多的负载。 提出了四个具体目标：1）确定BNNS剥离，负载和取向对 复合材料的总填料量、固化、物理和光学性能。2)确定生物相容性 符合ISO 7405和ISO 10993系列的BNNS负载复合材料的临床前生物相容性 医疗器械的评价。目标1中具有临床可接受性能的复合材料将在 的目标。3)为了确定BNNS浓度和取向对复合材料静态和动态性能的影响， 随时间变化的机械性能，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.