Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 5 3 2008 09 15 126 130 F. Sharafeddin Associate Professor, Department of Operative Dentistry, School of Dentistry, Shiraz University of Me H. Moradian Post Graduate Student, Department of Pediatric Dentistry, School of Dentistry, Shiraz University of 2015 10 03 Objective: The purpose of the present study was to assess the microleakage of composite restorations with and without a cervical amalgam base and to compare the results of dif-ferent composites and bonding agents. Materials and Methods: One hundred and twenty mesio-occlusal (MO) and disto-occlusal (DO) Class II cavities were prepared on sixty extracted permanent premolar teeth. The teeth were randomly divided into four groups of 30 and restored as follows: In group A, the mesio-occlusal cavity (MO), Scotchbond multi purpose plus + Z250 and in the disto-occlusal (DO) cavity, Prompt-L-Pop + Z250 were applied. As for group B, in the MO and DO cavities, Clearfil SE Bond + Clearfil APX, and varnish + amalgam (In box) + Clearfil SE Bond + Clearfil APX were used respectivelywhile in group C; the teeth were restored with amalgam and varnish mesio-occlusally and with amalgam only disto-occlusally. As for group D, varnish + amalgam (in box) + Scotchbond multi purpose plus + Z250 were applied mesio-occlusally and Varnish + Amalgam (in box) + Prompt–L–Pop + Z250 disto-occlusally. Marginal leakage was assessed by the degree of dye penetration into various sections of the restored teeth. Chi-square and Fisher's exact tests were used for data analysis. Results: Microleakage in gingival margin was more than that in occlusal margin (P<0.05) and microleakage of combined amalgam-composite restorations was significantly lower than that of conventional composite and amalgam restorations. Conclusion: Marginal microleakage decreased by using amalgam at the base of the box in Class II composite restorations. https://fid.tums.ac.ir/index.php/fid/article/view/160 https://fid.tums.ac.ir/index.php/fid/article/download/160/160