Background: The goal of this research was to see how effective various irrigation methods were at eliminating smear layer and debris. Study design: Sixty extracted single rooted human mandibular premolar teeth were used in this study. The root canals were shaped with a WaveOne large (040.08) rotary file after decoronating all the teeth to a uniform 16 mm root length. Root canals were rinsed with 6 ml of 2.5 percent sodium hypochlorite solution during instrumentation. After instrumentation, teeth were arbitrarily classified into four categories, each containing 15 specimens according to the technique of activation of final irrigant. Smear Clear solution (6 ml) was employed in all the categories as irrigating solution. In Group1- Rotary canal brush, Group 2 – EndoActivator, Group 3 – Passive ultrasonic irrigation (PUI), Group 4 – Continuous ultrasonic irrigation was employed. After sectioning the roots longitudinally, the apical, middle and coronal thirds of the canals were inspected with the help of scanning electron microscopy. Results: Group 4 was most effective in eliminating debris and smear layer at the coronal, middle, and apical thirds. But Group 4 was not significantly different to Group 3 at the middle third in eliminating debris and at middle third and apical third in elimination of smear layer. Conclusion: Continuous ultrasonic irrigation eliminated debris and smear layer most effectively, followed by PUI, EndoActivator, and Rotary canal brush. Keywords: Smear layer, Passive Ultrasonic Irrigation, Continuous ultrasonic irrigation, EndoActivator, Rotary canal brush