the purpose of the present study was to compare sodium hypochlorite irrigation with endovac to needle irrigation regarding the apical extrusion and antimicrobial efficacy. one hundred and four upper incisors were used in this study. teeth were divided into two experimental groups and two control groups according to method of irrigation. group i (experimental): teeth irrigated with 6% naocl using endovac system (n=40). group ii (experimental): teeth irrigated with 6% naocl using conventional needle (n=40). group iii (control): teeth irrigated with saline using endovac system (n=12). group iv (control): teeth irrigated with saline using conventional needle (n=12). each group was further subdivided into two subgroups (a) and (b) according to evaluation method: subgroup (a): teeth used for evaluation of apical extrusion of irrigation solution. experimental group (n=20), negative control group (n=6). subgroup (b): teeth used for evaluation of antimicrobial efficacy of irrigation solution. experimental group (n=20), positive control group (n=6). for evaluation of apical extrusion, teeth were decapitated, embedded in 0.2% agarose gel containing 1ml 0.1% m-cresol purple, mechanically prepared using protaper universal rotary instruments. in each subgroup half of the roots were apically prepared to #30 and the rest of the roots were apically prepared to #50. color change of the gel from summary and conclusions 60