microleakage of class ii combined amalgam-composite restorations using different composites and bonding agents

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.