Department of Chemical and Biological Engineering, Engineering Center, CB 424, University of Colorado, Boulder, CO 80309, USA.
Dent Mater. 2012 Aug;28(8):888-93. doi: 10.1016/j.dental.2012.04.016. Epub 2012 May 18.
To reduce polymerization-induced shrinkage stress while maintaining mechanical properties, reversible addition-fragmentation chain transfer (RAFT)-capable functional groups were incorporated into a photopolymerizable dimethacrylate-based dental composite. We hypothesize that the incorporation of trithiocarbonate-based RAFT functional groups into conventional dimethacrylate dental resins will reduce polymerization stress.
A trithiocarbonate dimethacrylate (TTCDMA) monomer, capable of undergoing radical-mediated RAFT, is mixed with 70 wt% BisGMA (bisphenylglycidyl dimethacrylate) and compared to a conventional dental resin comprised of TEGDMA (triethylene glycol dimethacrylate) and 70 wt% BisGMA. The shrinkage stress and methacrylate conversion were simultaneously measured during polymerization. The fracture toughness and elastic modulus were measured to evaluate the effect of the TTCDMA monomer on the mechanical properties. All the materials used herein were evaluated as a composite, including 75 wt% silica fillers. ANOVA (CI 95%) was conducted to assess the differences between the means.
The TTCDMA composite exhibited a 65% stress reduction compared with TEGDMA-BisGMA though the reaction rate was slower than the conventional dental composite, owing to the additional RAFT reaction. The fracture toughness and elastic modulus of the TTCDMA-based composite were not significantly different than in the TEGDMA-based composite, while the T(g) was decreased by 30 °C to 155 ± 2 °C.
Despite only replacing the reactive-diluent, significant and dramatic stress reduction was observed while maintaining the elastic modulus and fracture toughness. This new RAFT-capable monomer shows great promise to replace the reactive diluent in BisGMA-based dental materials. Formulation optimization and further exploration of other RAFT-capable functional groups will provide further stress reduction in dental materials.
在保持机械性能的同时，减少聚合诱导的收缩应力，将可进行可逆加成-断裂链转移（RAFT）的官能团引入光聚合性二甲基丙烯酸酯基牙科复合材料中。我们假设，将基于三硫代碳酸酯的 RAFT 官能团掺入传统的二甲基丙烯酸酯牙科树脂中，将降低聚合应力。
将一种可进行自由基介导的 RAFT 的三硫代碳酸酯二甲基丙烯酸酯（TTCDMA）单体与 70wt%BisGMA（双酚缩水甘油二甲基丙烯酸酯）混合，并与由 TEGDMA（三乙二醇二甲基丙烯酸酯）和 70wt%BisGMA 组成的传统牙科树脂进行比较。聚合过程中同时测量收缩应力和甲基丙烯酸酯转化率。评估 TTCDMA 单体对机械性能的影响，测量断裂韧性和弹性模量。本文中使用的所有材料均作为复合材料进行评估，包括 75wt%的二氧化硅填料。采用方差分析（置信区间 95%）评估平均值之间的差异。
与 TEGDMA-BisGMA 相比，TTCDMA 复合材料的应力降低了 65%，尽管由于额外的 RAFT 反应，反应速率较慢。基于 TTCDMA 的复合材料的断裂韧性和弹性模量与基于 TEGDMA 的复合材料没有显著差异，而 T(g) 降低了 30°C，至 155±2°C。
尽管仅替换了反应性稀释剂，但在保持弹性模量和断裂韧性的同时，观察到了显著且显著的应力降低。这种新的 RAFT 官能团单体有望取代基于 BisGMA 的牙科材料中的反应性稀释剂。配方优化和进一步探索其他可进行 RAFT 的官能团将在牙科材料中进一步降低应力。
