Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Gustav Mahlerlaan 3004, 1081LA Amsterdam, the Netherlands; Center of Dental Medicine, Policlinic of Operative Dentistry and Periodontology, University of Cologne, Kerpener Str. 32, D-50931 Köln, Germany.
Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, Gustav Mahlerlaan 3004, 1081LA Amsterdam, the Netherlands.
Dent Mater. 2024 Oct;40(10):1697-1701. doi: 10.1016/j.dental.2024.08.001. Epub 2024 Aug 3.
Polymerization shrinkage of bonded resin composite restorations will result in the development of curing contraction stresses during setting and can cause debonding of the restoration or failure of the surrounding tooth structure. However, the hygroscopic expansion that occurs after exposure of the restorative to the wet oral environment can compensate for this shrinkage.
The purpose of this study was to determine the hygroscopic expansion of six commercial resin composites and relate it to their composition, mechanical properties, shrinkage, and contraction stress development.
Short-term volumetric shrinkage and contraction stress of the different composites were measured by mercury dilatometry and a universal testing machine. The long-term contraction stress was measured by the deflection of a bilayer strip of metal and a resin composite, which were stored dry as well as wet to determine the effect of hygroscopic expansion. The curvature of the strip was measured by profilometry over a period of 3 months.
The curvature of the strip correlated well (r =0.74) with the initial contraction stress, showing that the contraction stress is an important factor in initial deformation. The water sorption in all specimens showed that the initial deformation, within 2-4 weeks after curing, was completely counteracted. A high correlation (r =0.90) between deflection and relative water sorption was found, where the relative water sorption is defined as the absolute water sorption corrected for the inorganic filler volume of the composite.
Within a period of 2-4 weeks after curing most of the curing contraction stresses of resin composite restoratives will be released by hygroscopic expansion.
黏结树脂复合材料修复体的聚合收缩会在固化过程中产生固化收缩应力，并可能导致修复体脱黏或周围牙体结构失效。然而，修复体暴露于湿口腔环境后发生的吸湿膨胀可以补偿这种收缩。
本研究的目的是确定六种商业树脂复合材料的吸湿膨胀，并将其与它们的组成、机械性能、收缩和收缩应力的发展联系起来。
通过汞膨胀计和万能试验机测量不同复合材料的短期体积收缩和收缩应力。通过双层金属和树脂复合材料的挠度测量长期收缩应力，将其储存在干燥和湿润条件下，以确定吸湿膨胀的影响。通过轮廓仪在 3 个月的时间内测量带材的曲率。
带材的曲率与初始收缩应力很好地相关（r=0.74），表明收缩应力是初始变形的一个重要因素。所有试件的吸水率表明，在固化后 2-4 周内，初始变形完全被抵消。发现挠度和相对吸水率之间存在高度相关性（r=0.90），其中相对吸水率是指用复合材料的无机填料体积校正后的绝对吸水率。
在固化后 2-4 周的时间内，树脂复合材料修复体的大部分固化收缩应力将通过吸湿膨胀释放。
