Sarikaya Rizacan, Song Linyong, Ye Qiang, Misra Anil, Tamerler Candan, Spencer Paulette
Institute for Bioengineering Research, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
Department of Mechanical Engineering, University of Kansas, 1530 W. 15th Street, Lawrence, KS 66045-7609, USA.
Polymers (Basel). 2020 Sep 12;12(9):2076. doi: 10.3390/polym12092076.
The inherent degradation property of most dental resins in the mouth leads to the long-term release of degradation by-products at the adhesive/tooth interface. The by-products increase the virulence of cariogenic bacteria, provoking a degradative positive-feedback loop that leads to physicochemical and mechanical failure. Photoinduced free-radical polymerization and sol‒gel reactions have been coupled to produce a novel autonomous-strengthening adhesive with enhanced hydrolytic stability. This paper investigates the effect of network structure on time-dependent mechanical properties in adhesives with and without autonomous strengthening. Stress relaxation was conducted under 0.2% strain for 8 h followed by 40 h recovery in water. The stress‒time relationship is analyzed by nonlinear least-squares data-fitting. The fitted Prony series predicts the sample's history under monotonic loading. Results showed that the control failed after the first loading‒unloading‒recovery cycle with permanent deformation. While for the experimental sample, the displacement was almost completely recovered and the Young's modulus increased significantly after the first test cycle. The experimental polymer exhibited higher degree of conversion, lower leachate, and time-dependent stiffening characteristics. The autonomous-strengthening reaction persists in the aqueous environment leading to a network with enhanced resistance to deformation. The results illustrate a rational approach for tuning the viscoelasticity of durable dental adhesives.
大多数牙科树脂在口腔中的固有降解特性会导致在粘合剂/牙齿界面长期释放降解副产物。这些副产物会增加致龋菌的毒力，引发一个导致物理化学和机械失效的降解正反馈循环。光引发自由基聚合和溶胶-凝胶反应已被结合起来，以生产一种具有增强水解稳定性的新型自增强粘合剂。本文研究了网络结构对有或无自增强粘合剂随时间变化的力学性能的影响。在0.2%应变下进行8小时的应力松弛，然后在水中恢复40小时。通过非线性最小二乘法数据拟合分析应力-时间关系。拟合的Prony级数预测了样品在单调加载下的历史。结果表明，对照样品在第一次加载-卸载-恢复循环后因永久变形而失效。而对于实验样品，位移几乎完全恢复，并且在第一次测试循环后杨氏模量显著增加。实验聚合物表现出更高的转化率、更低的浸出液以及随时间变化的硬化特性。自增强反应在水性环境中持续存在，导致形成具有增强抗变形能力的网络。结果说明了一种调节耐用牙科粘合剂粘弹性的合理方法。
