Objective

Water sorption, high volumetric shrinkage, polymerization stress, and potential estrogenic effects triggered by leached compounds are some of the major concerns related to BisGMA-TEGDMA co-monomer systems used in dental composites. These deficiencies call for the development of alternative organic matrices in order to maximize the clinical lifespan of resin composite dental restorations. This study proposes BisGMA-free systems based on the combination of UDMA and a newly synthesized diurethane dimethacrylate, and evaluates key mechanical and physical properties of the resulting materials.

Methods

2EMATE-BDI (2-hydroxy-1-ethyl methacrylate) was synthesized by the reaction between 2-hydroxy-1-ethyl methacrylate with a difunctional isocyanate (1.3-bis (1- isocyanato-1-methylethylbenzene) – BDI). The compound was copolymerized with UDMA (urethane dimethacrylate) at 40 and 60 wt%. UDMA copolymerizations with 40 and 60 wt% TEGDMA (triethylene glycol dimethacrylate) were tested as controls, as well as a formulation based in BisGMA (bisphenol A-glycidyl methacrylate)-TEGDMA 60:40% (BT). The organic matrices were made polymerizable by the addition of DMPA (2.2-dimethoxyphenoxy acetophenone) and DPI-PF6 (diphenyliodonium hexafluorophosphate) at 0.2 and 0.4 wt%, respectively. Formulations were tested as composite with the addition of 70 wt% inorganic content consisting of barium borosilicate glass (0.7 μm) and fumed silica mixed in 95 and 5 wt%, respectively. All photocuring procedures were carried out by a mercury arc lamp filtered to 320–500 nm at 800 mW/cm². The experimental resin composites were tested for kinetics of polymerization and polymerization stress in real time. Flexural strength, elastic modulus, water sorption, and solubility were assessed according to ISO 4049. Biofilm formation was analyzed after 24 h by luciferase assay. Data were statistically analyzed by one-way ANOVA and Tukey's test (α ≤ 0.05).

Results

In general, the addition of 2EMATE-BDI into the formulations decreased the maximum rate of polymerization (RP_MAX), the degree of conversion at RP_MAX (DC at RP_MAX), and the final degree of conversion (final DC). However, these reductions did not compromise mechanical properties, which were comparable to the BT controls, especially after 7-day water incubation. The incorporation of 60 wt% 2EMATE-BDI reduced water sorption of the composite. 2EMATE-BDI containing formulations showed reduction in polymerization stress of 30% and 50% in comparison to BT control and TEGDMA copolymerizations, respectively. Biofilm formation was similar among the tested groups.

Significance

The use of the newly synthesized diurethane dimethacrylate as co-monomer in dental resin composite formulations seems to be a promising option to develop polymers with low-shrinkage and potentially decreased water degradation.

中文翻译：

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不含 BisGMA 的树脂复合材料配方的替代单体。

客观的

吸水、高体积收缩、聚合应力和浸出化合物引发的潜在雌激素效应是与牙科复合材料中使用的 BisGMA-TEGDMA 共聚单体系统相关的一些主要问题。这些缺陷要求开发替代有机基质，以最大限度地延长树脂复合牙科修复体的临床寿命。本研究提出了基于 UDMA 和新合成的二氨基甲酸酯二甲基丙烯酸酯组合的不含 BisGMA 的系统，并评估了所得材料的关键机械和物理性能。

方法

2EMATE-BDI (2-hydroxy-1-ethyl methacrylate) 是通过 2-hydroxy-1-ethyl methacrylate 与双官能异氰酸酯 (1.3-bis (1-isocyanato-1-methylethylbenzene) – BDI) 之间的反应合成的。该化合物与 40 和 60 重量％的 UDMA（氨基甲酸酯二甲基丙烯酸酯）共聚。UDMA 与 40 和 60 wt% TEGDMA（二甲基丙烯酸三乙二醇酯）的共聚被测试为对照，以及基于 BisGMA（双酚 A-甲基丙烯酸缩水甘油酯）-TEGDMA 60:40% (BT) 的配方。通过分别添加 0.2 和 0.4 wt% 的 DMPA（2.2-二甲氧基苯氧基苯乙酮）和 DPI-PF6（六氟磷酸二苯基碘鎓），使有机基质可聚合。配方作为复合材料进行了测试，添加了 70 wt% 的无机成分，由硼硅酸钡玻璃 (0.7 μm) 和气相二氧化硅组成，以 95 和 5 wt% 的比例混合，分别。所有光固化程序均通过在 800 mW/cm 下过滤至 320–500 nm 的汞弧灯进行² . 实时测试实验树脂复合材料的聚合动力学和聚合应力。根据ISO 4049评估弯曲强度、弹性模量、吸水性和溶解度。24 小时后通过荧光素酶测定分析生物膜形成。数据通过单因素方差分析和 Tukey 检验 ( α  ≤ 0.05) 进行统计分析。

结果

通常，将 2EMATE-BDI 添加到配方中会降低最大聚合速率 (RP _MAX )、RP MAX 下的转化率（RP _MAX下的DC ）和最终转化率（最终 DC）。然而，这些减少并没有损害机械性能，这与 BT 控制相当，尤其是在 7 天的水孵化之后。60 wt% 2EMATE-BDI 的加入降低了复合材料的吸水率。与 BT 对照和 TEGDMA 共聚相比，含有 2EMATE-BDI 的配方显示聚合应力分别降低了 30% 和 50%。测试组之间的生物膜形成相似。

意义

在牙科树脂复合配方中使用新合成的二氨基甲酸酯二甲基丙烯酸酯作为共聚单体似乎是开发低收缩和可能减少水降解的聚合物的一个有前途的选择。