evaluation of different dentin bonding agents accompanied with composite coronal barrier

introduction: the purpose of this study was to evaluate the sealing ability of dentin bonding agents in root canals obturated with gutta-percha and mta. methods: forty-five single rooted human premolar teeth were decoronated so that remaining root portions were 12 mm in length. the samples were divided randomly into three experimental (n=13) and two control groups (n=3). all teeth were instrumented up to #40 k-file using step-back technique. the roots were obturated with gutta-percha/ah26 and mta for 5 and 3 mm, respectively. excite, clearfil se bond, and ibond were applied for experimental groups and then 2mm was filled with composite filtek z250. the roots in the controls were merely instrumented and obturated. two coats of nail varnish were applied on the surface of the teeth in the experimental and positive groups, except 2 mm around the apical foramen and coronal surfaces. in the negative control, the surfaces were completely covered by two layers of nail varnish. after thermocycling, the roots mounted in plastic caps of tubes containing bhi medium and inoculated coronally with enterococcus faecalis. the data were statistically analyzed using fisher's exact and kaplan-meier survival analysis. results: there were no statistically significant differences between three experimental groups regarding the leakage rate (p=0.738). conclusion: within the limitations of this study, it was observed that the adhesive systems in alliance with gutta-percha and mta obturation could not entirely