In-Vitro Evaluation of Microleakage of Class II Cavities Restored with Bulk-Fill Flowable Composite

Background and Aim: Composite placement poses many challenges, especially in the gingival floor with dentinal margins. Microleakage is one of the factors affecting the longevity of dental restorations. We aimed to compare the microleakage of cavities filled with bulk-fill composite at enamel and dentinal margins. Materials and Methods: In this experimental study, a total of 102 sound human premolars were randomly divided into six groups. In groups 1, 3, and 5, Class II cavities were prepared with their gingival margins above the cementoenamel junction (CEJ). In groups 2, 4, and 6, standard Class II cavities were prepared with their gingival margins below the CEJ. In groups 1 and 2, cavities were incrementally filled with Filtek Z250. In groups 3 and 4, the gingival 2 mm of the cavity was filled with Filtek bulk-fill, and the rest of the cavity was restored with Filtek Z250. In groups 5 and 6, the gingival 4 mm of the cavity was restored with Filtek bulk-fill, and the remaining part was restored with Filtek Z250. The teeth were immersed in 2% basic fuchsine for 24 hours, sectioned mesiodistally, and evaluated under a stereomicroscope at ×40 magnification. Data were analyzed using Kruskal-Wallis test. Wilcoxon signed-rank test was used for intergroup comparisons (α=0.05). Results: No significant difference was noted in the microleakage scores of the gingival margins of the six groups (P=0.168). No microleakage was noted at enamel margins. Conclusion: Neither Filtek bulk-fill nor Filtek Z250 could completely eliminate gingival microleakage. It seems that Filtek bulk-fill flowable composite can be safely and reliably used in 4-mm-thick increments.