Four-Year Clinical Evaluation of Different Bulk-Fill Restorative Resins After Amalgam Replacement.

OBJECTIVE: The aim of this study was to assess the clinical performance of three bulk-fill systems and a conventional composite after amalgam replacement in posterior teeth after 6, 24 and 48 months. METHODS: Forty-seven patients received at least four restorations placed with a conventional resin composite (Z350XT - ZXT) or bulk-fill systems (Filtek BulkFill - FBF; SonicFill - SF and Opus BulkFill - OBF). Each resin composite was used with its respective adhesive system according to the manufacturers' instructions. A total of 188 Class I and/or II restorations were blindly evaluated at baseline, 6, 24 and 48 months using the FDI criteria. The Pearson chi-square test was used to compare restoration groups and timepoints (α=0.05). RESULTS: The recall rates were 100%, 91.5% and 72.3% at 6, 24 and 48 months, respectively. Retention remained high for all groups, with no significant differences. ZXT presented major marginal discrepancies compared to baseline. At 24M, ZXT and FBF showed worse marginal adaptation than SF and OBF (p=0.003), and marginal discoloration increased in ZXT (p<0.001), FBF (p=0.016) and SF (p=0.027). After 48M, ZXT showed higher marginal discoloration than the other groups (p=0.020), whereas OBF showed no significant variation over time (p=0.102). No secondary caries were detected in any group. CONCLUSION: All materials demonstrated acceptable clinical performance, although differences in marginal adaptation and marginal discoloration were observed over time. CLINICAL SIGNIFICANCE: Bulk-fill restorations showed satisfactory long-term clinical performance after amalgam replacement.