Pires-de-Souza Fernanda de Carvalho Panzeri, Drubi Filho Brahim, Casemiro Luciana Assirati, Garcia Lucas da Fonseca Roberti, Consani Simonides
Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, SP, Brazil.
Braz Dent J. 2009;20(4):319-24. doi: 10.1590/s0103-64402009000400010.
The purpose of this study was to compare the polymerization shrinkage stress of composite resins (microfilled, microhybrid and hybrid) photoactivated by quartz-tungsten halogen light (QTH) and light-emitting diode (LED). Glass rods (5.0 mm x 5.0 cm) were fabricated and had one of the surfaces air-abraded with aluminum oxide and coated with a layer of an adhesive system, which was photoactivated with the QTH unit. The glass rods were vertically assembled, in pairs, to a universal testing machine and the composites were applied to the lower rod. The upper rod was placed closer, at 2 mm, and an extensometer was attached to the rods. The 20 composites were polymerized by either QTH (n=10) or LED (n=10) curing units. Polymerization was carried out using 2 devices positioned in opposite sides, which were simultaneously activated for 40 s. Shrinkage stress was analyzed twice: shortly after polymerization (t40s) and 10 min later (t10min). Data were analyzed statistically by 2-way ANOVA and Tukey's test (alpha=5%). The shrinkage stress for all composites was higher at t10min than at t40s, regardless of the activation source. Microfilled composite resins showed lower shrinkage stress values compared to the other composite resins. For the hybrid and microhybrid composite resins, the light source had no influence on the shrinkage stress, except for microfilled composite at t10min. It may be concluded that the composition of composite resins is the factor with the strongest influence on shrinkage stress.
本研究的目的是比较经石英钨卤素灯（QTH）和发光二极管（LED）光活化的复合树脂（微填料、微混合填料和混合填料）的聚合收缩应力。制作了玻璃棒（5.0毫米×5.0厘米），其中一个表面用氧化铝进行空气磨蚀，然后涂覆一层粘结系统，并用QTH装置进行光活化。将玻璃棒成对垂直组装到万能试验机上，将复合材料施加到下棒上。将上棒放置在较近位置，距离为2毫米，并在棒上连接一个引伸计。20种复合材料分别通过QTH（n = 10）或LED（n = 10）固化装置进行聚合。使用位于相对两侧的2个装置进行聚合，同时激活40秒。对收缩应力进行两次分析：聚合后不久（t40s）和10分钟后（t10min）。数据通过双向方差分析和Tukey检验进行统计学分析（α = 5%）。无论激活源如何，所有复合材料在t10min时的收缩应力均高于t40s时。与其他复合树脂相比，微填料复合树脂的收缩应力值较低。对于混合填料和微混合填料复合树脂，光源对收缩应力没有影响，但在t10min时微填料复合材料除外。可以得出结论，复合树脂的组成是对收缩应力影响最大的因素。
