Abstract : The cleaning and shaping of root canals is an important step in root canal treatment. Mechanical instrumentation of root canals creates an irregular layer of debris, known as the smear layer. The aim of the study was to assess and compare the effect of different endodontics irrigant activators on the elimination of debris and smear layer from root canal dentine. Fifty single-rooted extracted mandibular premolars were instrumented with protaper Next up to size X4 and divided into five groups: the first was control group (n=10) and four experimental groups according to the activation system for irrigation, second group was activated by Endoactivator sonic system, third group by ultrasonic system Endoultra, fourth group by Xp-endo finisher and finally fifth group was activated by Finisher gentle file-brush. Teeth then sectioned longitudinally into two halves, and each half was marked into 3 parts (coronal, middle, apical) each part was examined under scanning electron microscope for evaluation of residual debris and smear layer. The data was statistically analyzed using Kruskal Wallis and Mann-Whitney U tests using IBM SPSS Statistics 21 software. The significance level was set at p < 0.05. Regarding debris and smear layer, using irrigant activators enhance debris and smear layer removal especially in middle and apical third. No activation technique was able to eliminate debris and smear layer completely from root canals. The EndoActivator did not show any improvement in smear layer removal but showed improvement in debris removal in compare with control group. XP-endo finisher showed best result in removing smear layer in coronal and middle third. Endo-ultra device showed best result in removing smear layer in apical third