Microleakage of enamel preservation at gingival wall of class ii resin composite restorations (nanofilled vs bulk-fill)

Abstract

Objectives. This in vitro study tested the hypothesis that preserving a thin enamel layer at the gingival margin and using bulk-fill resin composites could minimize microleakage of class II resin composite. Materials and Methods. Thirty-six human third molars were randomly divided into three groups of 12 specimens each: Filtek Bulk Fill Posterior Restorative in Capsules (BFC), Filtek Bulk Fill Posterior Restorative in Syringes (BFS) and Filtek Z350 XT (Z350). Teeth were prepared on two sides for a class II cavity (3 mm buccolingually x 2 mm mesiodistally at occlusal and 1.5 mm at coronal x 4 mm of axial depth) with 0.5 mm under the CEJ on one side (NP) and 0.5x1 mm of thin enamel at the gingival margin was preserved on the other side (EP). The teeth were then restored, thermocycled, immersed in 0.5% methylene blue solution for 24 hours and sectioned mesiodistally through the restorations. Dye penetration was evaluated at the gingival margin by three blinded examiners using a 0-4 ordinal scale. The Kruskal-Wallis test and Dunn test were used to compare differences in microleakage scores among the three restorative materials. Mann-Whitney U test was utilized to analyze the difference between enamel preserved (EP) and non-enamel preserved sides (NP) in the same restorative material. Tests were performed with the level of significance at a = 0.05. Results. Mann-Whitney U test showed that the “NP” groups had significantly higher microleakage score than the “EP” groups. The Kruskal-Wallis test revealed significant differences in microleakage scores among the three restorative materials (P < 0.05). Compared to “Z350”, the “EP” group, “BFC” and “BFS” had significantly less microleakage score (P = 0.001) (P = 0.028). The “NE” group, “BFC” had significantly less microleakage score than “Z350” (P = 0.001). Conclusions. Preserving thin layer of enamel (“EP”) and use of two bulk-fill products (“BFC” and “BFS”) reduced microleakage of class II resin composite.