The complete removal of obturation material can be a challenge in nonsurgical root canal retreatment. The insufficient removal of obturation material is a reason for root canal retreatment failure. The purpose of this study was to assess the efficacy of different final root canal irrigation activation methods in removing debris and smear layers in the apical and middle portions of root canals during retreatment. Sixty-six distal roots of freshly extracted molars were randomly divided into six groups: (1) primary root canal treatment with no obturation (negative control); (2) retreatment with only conventional instrumentation and irrigation (positive control); (3) retreatment with additional ultrasonic irrigation using the Piezon Master 700; (4) ultrasonic irrigation with the ENDOSONIC Blue; (5) sonic irrigation with the EDDY; and (6) multisonic irrigation with the GentleWave system. Roots were split and prepared for scanning electron microscopic (SEM) evaluation. Acquired images were assessed to quantify the amount of debris and smear remaining. Among the treatment groups, Group 6 had a significantly lower debris score than Group 2 (positive control) in both the middle and apical regions (p = 0.004, p = 0.012). All treatment groups showed significantly lower smear scores than Group 2 in the middle and apical regions (p < 0.05). The GentleWave multisonic System showed a more optimal cleaning efficacy of the root canal debris but did not differ significantly with the tested passive ultrasonic or sonic irrigation method.
Keywords: irrigation; multisonic; retreatment; scanning electron microscopic (SEM); sonic; ultrasonic.