Clinical Relevance Treating defective restorations with sealants, repair or refurbishing is an effective way to preserve and treat existing restorations. SUMMARY This investigation assessed the effectiveness of alternative treatments for the replacement of amalgam and resin-based composite restorations. Sixty-six patients (age 18 to 80 years, mean=26.6) with 271 (amalgam [n=193] and resin-based composite [n=78]) defective restorations were randomly assigned to one of five different treatment groups: A) Repair (n=27); B) Sealing of margins (n=48); C) Refurbishing (n=73); D) Replacement (n=42) and E) Untreated (n=81). USPHS/Ryge criteria were used to determine the quality of the restorations. Two calibrated examiners (Cohen's Kappa 0.74) assessed the restorations independently at the beginning of the study (baseline) and at two years after treatment using seven parameters from the USPHS/Ryge criteria (Marginal Adaptation, Anatomic Form, Roughness, Marginal Stain, Occlusal Contact, Secondary Caries and Luster). Results: Two-hundred and fifty-six restorations (178 amalgam and 78 resin-based composite) were examined at the two-year recall exam. The sealing of marginal defects showed significant improvements in marginal adaptation ( p <0.05). Refurbishing of the defective restorations significantly improved anatomic form ( p <0.0001), luster ( p <0.016), marginal adaptation ( p <0.003) and roughness ( p <0.0001). The repair significantly improved anatomic form ( p <0.002) and marginal stain ( p <0.002). Replacement showed significant improvements for all parameters ( p <0.05). The Untreated group showed significant deterioration on marginal adaptation ( p <0.013). Conclusions: The two-year recall examination showed that sealant, repair and refurbishing treatments improved the clinical properties of defective amalgam and resin-based composite restorations by increasing the longevity of the restorations with minimal intervention.