Development of Novel Thiol-Ene-Methacrylate Composites for Dental Restorative Mat

描述（由申请人提供）：聚合物复合牙科修复材料的性能和寿命仍然有限，主要是由于收缩引起的聚合应力并发症。其他缺点包括缺乏韧性、热膨胀不匹配、聚合后的吸湿性、固化后可提取的未反应单体以及氧抑制。收缩引起的应力主要与甲基丙烯酸酯基自由基聚合过程的链式生长性质有关，该过程导致高体积收缩和早期凝胶化。收缩应力可以通过降低反应性甲基丙烯酸酯官能团的浓度或延迟聚合过程中的凝胶化来缓解。我们提出了聚合机制的根本转变，从链式生长聚合到混合模式阶梯链式生长聚合。这种转变是通过加入硫醇组分作为反应稀释剂来实现的，它有两个明显的优点。巯基烯的聚合机制导致了较小的体积收缩和延迟凝胶化。此外，我们建议结合控制结构和大小的分子填料。适当地制造、设计和掺入分子填料将降低反应基团的浓度，并在现有水平上增加填料的负荷，同时具有相应的力学性能和收缩效益。由于反应性功能在整个分子填料中而不仅仅是在表面，因此分子填料在聚合前和聚合后将更好地整合在一起，从而防止聚集，从而提高韧性和其他机械性能。将这两种技术协同结合，形成一个复合体系，将显著降低收缩和应力，提高机械性能。这些目标是基于这样的假设：适当的材料合成和设计加上聚合机制的优化，将导致聚合物牙科复合材料在收缩应力、复合材料机械性能、聚合速度（或引发剂含量的减少）、吸湿性、可提取物的减少和生物相容性的改善方面得到增强。迄今为止的研究结果表明，该材料具有更高的双键转化率、更低的体积收缩应力、更好的机械性能，并且几乎消除了氧抑制作用。

DESCRIPTION (provided by applicant): The performance and longevity of polymer composite dental restorative materials is still limited, primarily due to complications from shrinkage induced polymerization stresses. Other drawbacks involve a lack of toughness, thermal expansion mismatch, moisture uptake following polymerization, extractable, unreacted monomer following cure, and oxygen inhibition. Shrinkage induced stresses are primarily associated with the chain growth nature of the methacrylate-based free radical polymerization process that leads to high volume shrinkage and early gelation. Shrinkage stress is alleviated either by reducing the concentration of reactive methacrylate functional groups or delaying gelation during polymerization. We propose a radical shift in the polymerization mechanism from a chain growth polymerization to a mixed mode step-chain growth polymerization. This shift is achieved by the incorporation of a thiol-ene component as the reactive diluent, which has two distinct advantages. The thiol-ene polymerization mechanism results in lower volume shrinkage and delayed gelation. Additionally, we propose the incorporation of molecular fillers of controlled architecture and size. Appropriately fabricating, designing and incorporating molecular fillers will reduce the concentration of reactive groups and increase the filler loading beyond the present levels with corresponding mechanical property and shrinkage benefits. Since the reactive functionality is incorporated throughout the molecular filler rather than only at the surface, the molecular filler will be better integrated before polymerization, which prevents aggregation, and following polymerization, which improves toughness and other mechanical properties. Synergistically combining these two developments into a composite system will result in composite systems that exhibit both dramatically reduced shrinkage and stress and improved mechanical properties. These aims are predicated on the hypothesis that appropriate materials synthesis and design coupled with optimization of the polymerization mechanism will lead to enhanced polymeric dental composites with respect to shrinkage stress, composite mechanical properties, polymerization speed (or reduction in the initiator content), moisture uptake, reduced extractables and improved biocompatibility. Results to date have already demonstrated a higher double bond conversion, lower volume shrinkage induced stress, improved mechanical properties, and near elimination of oxygen inhibition. PUBLIC HEALTH RELEVANCE: Because of the widespread use of esthetic composite dental restorative materials, significant improvements in their reliability and performance will have a very broad and positive effect on the oral health of the general public. Improvements in these materials to date have been driven by modifications in the filler phase where this application addresses the continuing deficiencies of the polymer phase through a novel chemistry approach.