Comparison of microleakage of low-shrinkage and conventional composite resins

Polymerization shrinkage and the resultant microleakage are still the problems with composite resin restorations. To overcome these problems, new low-shrinkage composite resins have been introduced by different manufacturers. The aim of this study was to compare microleakage in two low-shrinkage composite resin, Filtek-Silorane and GC-Kalore with two conventional composite resins, Filtek-Z250 and GC-Gradia.
In this experimental study, round cavities 5 mm in diameter and 1 mm in depth, were prepared on the middle of the buccal surfaces of 40 human third molars and divided into 4 groups (n=10). In group 1, the cavities were filled with Filtek-silorane composite resin and the relevant adhesive. In groups 2, 3 and 4, the cavities were filled with Filtek-Z250, GC-Kalore and GC-Gradia composite resins, using Adper Single Bond Plus bonding agent. After thermocycling and immersion in AgNO3, the samples were sectioned to evaluate dye penetration under a stereomicroscope (×10) at enamel margins and at cervical dentin contacting cementum. Data were statistically analysed with Kruskal-Wallis, Wilcoxon and Mann-Whitney tests (α = 0.05).
There were not significant differences at enamel margins between the 4 groups. However, at cervical margins, microleakage in Filtek-Silorane composite resin was significantly lower than Z250 and Gradia composite resins (p value = 0.05). Microleakage with Kalore was significantly less than that with Gradia composite resin. In all the 4 groups, microleakage at cervical margins was significantly higher than that at occlusal margins.
There were no significant differences in microleakage at occlusal margins between all the composite resins. The highest and lowest microleakage at dentin margins was related to GC-Gradia and Filtek-Silorane silorane, respectively.