Influence of ultrasonic activation using different final irrigants on antimicrobial activity, smear layer removal and bond strength of filling material

The aim of this study was to evaluate the influence of ultrasonic activation (US) over final irrigants on antimicrobial activity, smear layer removal and bond strength. The root canals of 180 extracted human teeth were distributed into three experimental tests (n = 60). In each test, the samples were subdivided into six groups (n = 10) according to final irrigation protocols: G1:distilled water (DW); G2:DW + US; G3:17% EDTA; G4:QMix; G5:17% EDTA + US; and G6:QMix + US. The antimicrobial activity was evaluated by counting of colony-forming units (CFUs), the smear layer removal by scanning electron microscopy and the bond strength by push-out test. Statistical analysis was performed for each evaluation (alpha = 5%). Groups 4 and 6 provided higher bacterial reduction, groups 5 and 6 provided higher smear layer removal, groups 3, 4, 5 and 6 provided the higher bond strength (P < 0.05). US activation did not improve the antimicrobial activity and the bond strength, whereas it improved the smear layer removal.