الفهرس 
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Abstract
Objectives: To evaluate microleakage and marginal adaptation of class II resin composite placed in freshly cut cavities of premolars versus replacement of amalgam following 12-months water storage. Materials and Methods: Forty sound maxillary human premolars were mounted in autopolymerizing acrylic resin. Standardized occluso-mesial cavities preparations were prepared on all teeth. Each cavity was restored with high- copper amalgam restoration. After one year storage in distilled water at 37°C, amalgam restorations were carefully removed. Then, another cavity with the same dimensions was prepared on the occluso-distal side of the teeth. A tofflemire matrix band was placed and both cavities were restored with resin composite material (Filtek Z350 XT, 3M ESPE, ST Paul, MN, USA) bonded with universal adhesive system (Single Bond Universal, 3M ESPE, ST Paul, MN, USA). Teeth were randomly divided into 2 groups (n=20). For microleakage test, twenty teeth were subjected to dye penetration using 2% basic fuchsin dye. The specimens were analyzed with a stereomicroscope at a magnification of 20X; two readings were taken for each restoration at the occlusal and proximal margins. For marginal adaptation test, twenty teeth were photographed with scanning electron microscope (JEOL, JSM-6510, USA) at X500 and X1000 magnification. The results were analyzed by Mann–Whitney test. The level of significance was set at p<0.05. Results: Results demonstrated that there was no statistically significant differences in microleakage and marginal adaptation of class II resin composite placed in freshly cut cavities of premolars versus replacement of amalgam. Conclusion: Within the limitation of this study, we can conclude that microleakage and marginal adaptation of class II resin composite restoration placed following to existing amalgam restoration seems to be not adversely affected.