Objective: This study evaluated the effectiveness of the XP-endo Finisher file (XP) in cleaning root canals compared to passive ultrasonic irrigation (PUI). It also compared multiple activation techniques to a single form of activation. Furthermore, it analysed the sequence of using them in regard to cleaning efficiency. Materials and methods: The root canals of 60 extracted single human mandibular premolars were prepared using the NiTi iRaCe rotary system and then were randomly divided into five groups (n = 12) according to the final activation of irrigation technique as follows: CI (negative control), using conventional irrigation by an irrigating syringe; PUI, activation by PUI; XP, activation by XP; XP-PUI, activation by XP then PUI; PUI-XP, activation by PUI then XP. Specimens were scanned using a scanning electron microscope with a magnification of 2000×. Results: In all groups, the coronal and middle third demonstrated a significantly higher percentage of patent dentinal tubules compared to the apical third (P 0.05). The XP showed a higher percentage of patent dentinal tubules than PUI in the apical area with a statistically insignificant difference (P > 0.05). The percentage of patent dentinal tubules was higher in multiple activation techniques as in XP-PUI and PUI-XP than with a single form of activation as with XP file alone or PUI alone (P 0.05). There was no statistically significant difference between XP-PUI and PUI-XP (P > 0.05). Conclusions: Within the limitations of this study it can be concluded that no activation technique completely eliminated the smear layer. The XP was more effective in cleaning the apical area than PUI. Combining two methods of activation improved the cleanliness of the canals. Using either XP or PUI first had no effect on smear layer removal. Keywords: passive ultrasonic irrigation, scanning electron microscope, XP-endo Finisher file