Lewis Steven H, Fugolin Ana Paula P, Bartolome Anissa, Pfeifer Carmem S
Division of Biomaterial and Biomedical Sciences, Oregon Health & Science University, Portland, OR.
JADA Found Sci. 2024;3. doi: 10.1016/j.jfscie.2024.100033. Epub 2024 Apr 5.
Low-stress resin-based composites (RBCs) are available to the clinician, some using stress relaxation mechanisms on the basis of network reconfiguration, modulated photopolymerization, or chain transfer reactions. This study investigated those materials in terms of their overall stress relaxation and their relationship with polymerization kinetics and compared them with an experimental low-stress thiourethane (TU) material.
Experimental composites (bisphenol-A-diglycidyl dimethacrylate, urethane dimethacrylate, and triethylene glycol dimethacrylate [50:30:20 mass ratio]; 70% barium aluminosilicate filler; camphoroquinone, ethyl-4-dimethylaminobenzoate, and 2,6-di-tert-butyl-4-methylphenol [0.2:0.8:0.2% by mass]) with or without TU oligomer (synthesized in-house) and commercial composites (SureFil SDR Flow+ Posterior Bulk Fill Flowable Base [SDR Flow+] [Dentsply Sirona], Filtek Bulk Fill Posterior Restorative [3M ESPE], and Filtek Supreme Ultra Universal Restorative [3M ESPE]) were tested. Polymerization kinetics (near-infrared) and polymerization stress (Bioman) were evaluated during light-emitting diode photoactivation at 100 mW/cm for 20 seconds. Stress relaxation was assessed using dynamic mechanical analysis. Data were analyzed with a 1-way analysis of variance and Tukey test (α = 0.05).
The kinetic profiles of all materials differed substantially, including more than a 2-fold difference in the rate of polymerization between TU-modified composites and SDR Flow+. TU-modified RBCs also showed more than a 2-fold higher conversion at the onset of deceleration vs the experimental control and commercial materials. RBCs that used stress reduction mechanisms showed at least a 34% reduction in polymerization stress compared with the controls and significantly reduced the amount of early-onset stress buildup. SDR Flow+ and the TU-modified RBCs showed the greatest amount of viscoelastic stress relaxation postpolymerization.
The novel TU-modified materials showed similar or improved performance compared with commercial low-stress RBCs, showing that chain transfer may be a promising strategy for stress reduction, both during polymerization and after polymerization.
临床医生可使用低应力树脂基复合材料（RBCs），其中一些基于网络重构、调制光聚合或链转移反应采用应力松弛机制。本研究从整体应力松弛及其与聚合动力学的关系方面对这些材料进行了研究，并将它们与一种实验性低应力硫脲烷（TU）材料进行了比较。
测试了含或不含TU低聚物（内部合成）的实验性复合材料（双酚A - 二缩水甘油二甲基丙烯酸酯、聚氨酯二甲基丙烯酸酯和三乙二醇二甲基丙烯酸酯[质量比50:30:20]；70%铝硅酸钡填料；樟脑醌、4 - 二甲基氨基苯甲酸乙酯和2,6 - 二叔丁基 - 4 - 甲基苯酚[质量分数0.2:0.8:0.2%]）以及商业复合材料（SureFil SDR Flow+后牙大块充填可流动垫底材料[SDR Flow+][登士柏西诺德]、Filtek大块充填后牙修复材料[3M ESPE]和Filtek Supreme Ultra通用修复材料[3M ESPE]）。在100 mW/cm的发光二极管光活化20秒期间评估聚合动力学（近红外）和聚合应力（Bioman）。使用动态力学分析评估应力松弛。数据采用单因素方差分析和Tukey检验进行分析（α = 0.05）。
所有材料的动力学曲线有很大差异，包括TU改性复合材料和SDR Flow+之间的聚合速率有2倍以上的差异。与实验对照材料和商业材料相比，TU改性的RBCs在减速开始时的转化率也高出2倍以上。采用应力降低机制的RBCs与对照材料相比，聚合应力至少降低了34%，并显著减少了早期应力积累量。SDR Flow+和TU改性的RBCs在聚合后表现出最大量的粘弹性应力松弛。
新型TU改性材料与商业低应力RBCs相比表现出相似或更好的性能，表明链转移可能是在聚合过程中和聚合后降低应力的一种有前景的策略。
