Influence of Filler Content on the Marginal Sealing of Light-Cured Composite Resin Restorations

本研究探讨了填料含量在光固化复合树脂涂层边缘适应性中的作用。将硅烷化的石英粉掺入Bis-GMA和TEGDMA树脂中。填料含量水平为0、22.4、39.5、50.3、63.5、69.5和71.1体积%。聚合收缩率、吸湿膨胀率和热膨胀率随着填料含量的增加而线性降低。当填料含量增加到63.5体积%时，对牛牙釉质的剪切粘结强度增加，但此后没有检测到显著差异。应力松弛速率随填料含量的增加而减小。5分钟后约为20-50%，24小时后约为45-70%。与填料含量无关，当辐照后立即抛光或/和热循环时，V类涂层的边缘密封性较差，而当仅在水中浸泡一天后抛光涂层时，边缘密封性优异。微渗漏和牙釉质裂纹增加，在低于39.5体积分数和50.3体积分数填充树脂牙釉质，分别，当牙釉质抛光和热循环后，一天的浸泡在水中。在较低的填料水平下，热循环前在水中浸泡3个月，改善了边缘密封性，与在水中浸泡1天相比，这表明辐照后最直接影响边缘密封性的因素是聚合收缩应力，抛光或热循环引起的额外应力可以破坏边缘密封性。然而，在水中浸泡一天后，收缩应力几乎被消除，影响最大的因素是树脂和牙齿结构之间的热膨胀差异。在水中浸泡三个月所引起的吸湿膨胀可以消除热膨胀的影响，即使在较低的填料水平。

This study investigated the role of the filler content in the marginal adaptation of light-cured composite resin restorations. silanized quartz powder was incorporated in Bis-GMA and TEGDMA resin. The filler content levels were 0, 22.4, 39.5, 50.3, 63.5, 69.5, and 71.1 vo1%.Polymerization shrinkage, hygroscopic expansion, and thermal expansion decreased linearly with increased filler content. The shear bond strength to the bovine enamel increased when the filler content increased up to 63.5 vo1%, but thereafter no significant differences were detected. The stress relaxation rate decreased at the filler content increased. That was about 20-50% after 5 minutes and about 45-70% after 24 houres. Independently of filler content, the marginal sealing in class V restorations was poor when the restorations were polished or/and thermal cycled immediately after irradiation, and it was excellent when the restorations were only polished after a one-day immersion in water. Microleakage and enamel cracks increased in the below 39.5 vo1% and 50.3 vo1%-filled resin restorations, respectively, when the restorations were polished and thermal cycled after a one-day immersion in water. The immersion of restorations in water for 3 months before thermal cycling improved the marginal sealing at lower filler levels as compared with one-day immersion in water.It was suggested that the factor affecting the marginal sealing the most immediately after irradiation was polymerization shrinkage stress, and that additional stresses caused by polishing or thermal cycling can destroy the marginal sealing. However, after a one-day immersion in water, shrinkage stress was almost eliminated and the factor with the greatest influence was the difference in thermal expansion between the resin and the tooth structure. Hygroscopic expansion caused by threemonths immersion in water can eliminate the influence of thermal expansion even at lower filler levels.