Materials and Methods: In this in vitro study, class V cavities with occlusal margins in enamel and cervical margins in dentin/cementum were prepared on the buccal and lingual surfaces of 54 extracted premolars. The prepared teeth were randomly assigned to three groups (3 group’s × 18 teeth each), with each group being restored with microhybrid (Point 4) nanohybrid (Herculite XRV Ultra), and packable (Packable Premise) resin composite. Following finishing and polishing procedures, each group was randomly subdivided in to three subgroups (n = 12). The margins of two groups were both etched and re-bonded with surface sealant (Optiguard) or dentin adhesive (Opti Bond Solo Plus) and control group received no treatment. Specimens were thermocycled 1500 cycles, immersed in a methylene blue, sectioned, evaluated for microleakage using a stereomicroscope at a x 20 and scored on a scale of 0-3. Data were analyzed with Kruskal — Wallis, Mann — Whitney, and Wilcoxon tests (á = 0.05).

Results: There were no significant differences among the three resin composites tested, and also no significant differences among subgroups with the same surface treatment. Only the microhybrid and packable composite restorations sealed with Optiguard had significantly lower microleakage compared to the control subgroups at the occlusal margin. There were no significant differences between occlusal and cervical margins regarding the microleakage scores when compared to the control subgroups of microhybrid and packable composite restorations. 

  Conclusion: The re-bonding technique could be considered as an advisable procedure in order to minimize microleakage and its effect might be material-dependent.