RESUMEN
Abstract Objective: To compare the marginal degradation (susceptibility to marginal adaptation and marginal discoloration) of composite restorations placed in class II and V cavities using conventional and bulk-fill resin composites. Material and Methods: This study was approved by PROSPERO database (#42020201596). PubMed, Scopus, Embase, Web of Science, Lilacs, Cochrane, Open Grey, Clinical Trials, and Rebec databases were searched by three independent investigators using MeSH terms, supplementary concepts, synonyms, and free keywords, based on the PICOS strategy (P, population: restoration in permanent teeth; I, intervention: bulk-fill resin composite; C, comparison: conventional resin composite; O, outcome: marginal discoloration and adaptation; and S, study design: randomized and non-randomized clinical trials). The risk of bias was evaluated according to the Cochrane Collaboration's tool, the meta-analyses by RevMan software, the certainty of evidence by the Grading of Recommendations Assessment, Development, and Evaluation, and the leave-one-out sensitivity test. The prevalence of successful events and the total number of restorations were used to calculate the risk difference at a confidence interval of 95%, according to a fixed-effect model. The heterogeneity was evaluated using the I2 index. Results: 16 from 10,780 studies were selected and included for qualitative and quantitative analysis. Two studies were considered as high risk of bias, one showing some concerns, and 13 as low risk of bias. Four meta-analyses evaluated the marginal adaptation and marginal discoloration in class II and V cavities, with a nonsignificant heterogeneity (I2 = 0%, p>0.05). The certainty of evidence was considered high, except for two subgroups of each outcome. Conclusion: There is evidence that composite restorations using conventional and bulk-fill resin composites present similar clinical performance related to marginal degradation (AU).