Evaluation of microleakage in posterior nanocomposite restorations with three types of different liners

Microleakage is one of the most important reasons for the failure of composite resin restorations. Use of liners releases the stresses of polymerization shrinkage. The aim of this study was to evaluate microleakage of posterior nanocomposite restorations with three types of liners. In this in vitro study forty-eight sound human premolars were randomly assigned to four groups. Classic class II cavities were prepared with gingival margins 1 mm coronal to the CEJ. Cavities were lined in group I with Filtek Z350 flowabl composite resin، in group II with F2 dual-cured composite resin and in group III with Fiji II LC resin-modified glass-ionomer; no liner was placed in cavities in group IV. All the teeth were restored with a posterior nanocomposite (Filtek Z350) to a thickness of 2 mm using horizontal technique except the teeth in group IV in which first a 1-mm layer was placed، followed by a 2-mm second layer; each layer was light-cured for 40 seconds. The teeth were immersed in 2% fuchsin dye، sectioned mesiodistally and observed under a stereomicroscope for dye penetration. Data was analyzed with non-parametric Kruskal-Wallis and Mann-Whitney tests (α=0. 05). Statistically significant differences were observed between the groups (p value = 0. 048). Group I (lined with flowable composite) exhibited maximum leakage; group III (lined with resin-modified glass-ionomer) exhibited the minimum microleakage، which was significantly different only from Group I (p value = 0. 006). The results of this study indicated that none of the liners under study could thoroughly eliminate microleakage of posterior nanocomposites. No differences were observed in microleakage between the groups with liner application.