This study aims to compare the efficacy of different irrigation activation methods to remove smear layer and debris from oval-shaped root canals following retreatment. Ninety mandibular canines with oval-shaped root canals were selected. Retreatment was performed with R-Endo retreatment files. The samples were randomly divided into six groups (n=15). Groups were assigned according to agitation technique: R-Endo with classic irrigation, with self-adjustable file, with passive ultrasonic irrigation, R-Endo+Er:YAG, R-Endo+PIPS and R-Endo+Nd:YAG. Compared with the classic irrigation (R-Endo+CI) group, all other groups were more successful in reducing smear layer and debris (P<0.05). The least amount of residual smear layer and debris was detected in the Er:YAG laser group (P<0.05). Additional use of different agitation methods contributes to removal of debris and smear layer following root canal filling removal with rotary instruments; however, none of the techniques tested render root canal walls completely free of smear layer or debris.