The aim of this study was to evaluate the efficiencies of the self-adjusting file (SAF) system, passive ultrasonic irrigation (PUT), and conventional irrigation (CI) in removing calcium hydroxide (CH) from root canals. Fifty-one mandibular premolars were used. After root canals were instrumented and filled with a CH paste, 45 teeth were randomly assigned to three experimental groups according to CH removal technique: SAF system, PUI, or CI. The remaining 6 teeth served as positive and negative controls. All samples were evaluated by scanning electron microscopy (SEM) and scored. None of the techniques removed CH completely. However, results at coronal, middle and apical thirds showed that PUT technique was significantly more effective than SAF and CI in removing CH dressing residues from root canal walls.