RESUMEN
Abstract Objective: To evaluate the effect of a resin coating material on the microleakage of Class V composite resin restorations with and without post-operative bleaching. Material and Methods: Eighty class V cavities (3×3×1.5 mm) were prepared and filled with Z250 XT composite resin in the buccal and lingual surfaces of 40 sound human molars. Then the samples were randomly divided into 4 groups (n=20) and treated as follows: Group A: applying a resin coating (G-Coat Plus) on the restoration, then bleaching with 40% hydrogen peroxide; Group B: Post-Operative bleaching without prior use of resin coating; Group C: applying resin coating agent, and no further bleaching; and Group D: no resin coating, no bleaching. The specimens were thermocycled and immersed in 1% methylene blue for 24 hours, then cut into sections bucco-lingually. The samples were scored regarding the amount of dye penetration under a stereomicroscope (x20). Data were analyzed with Chi-squared and Fisher exact tests (p<0.05). Results: The maximum gingival and occlusal microleakage was detected in group B, while the minimum was seen in group C. In all the groups, microleakage at gingival margins was higher than occlusal margins (p<0.001). Conclusion: Application of a resin coating is an effective method in reducing microleakage of the restorations before and after bleaching.