
Introduction: Evolution of dental materials has increased the indication of esthetic restorative procedures. However, composite resin materials are not suitable for posterior class II restorations because of their high wear rate and insufficient marginal adaptation. Resin composite materials undergo volumetric polymerization contraction of at least 2% which results in gap formation at cavity margins. The purpose of this study was to evaluate the effects of glass and polyethylene fiber inserts and flowable composite as a liner on the micro leakage of class II composite restorations with gingival margins on root surfaces. Methods: Class II slot preparation was on both the proximal sides of seventy five freshly extracted mandibular molars and were divided into five groups depending on the type of fiber inserts and use of flowable composite as a liner. The specimens were thermo cycled and stained with basic fuchsin dye and sectioned to evaluate the dye penetration under stereomicroscope. Statistical analysis was done using Kruskal Wallis test and Mann Whitney U test. Results and Conclusion: the study showed that the fiber inserts group showed significantly less micro leakage as compared to other groups. However no statistically significant difference was found between the groups with fiber inserts.