Effectiveness of Four Different Final Irrigation Activation Techniques on Smear Layer Removal in Curved Root Canals : A Scanning Electron Microscopy Study

Objective: The aim of this study was to assess the efficacy of apical negative pressure (ANP), manual dynamic agitation (MDA), passive ultrasonic irrigation (PUI) and needle irrigation (NI) as final irrigation activation techniques for smear layer removal in curved root canals. Materials and Methods: Mesiobuccal root canals of 80 freshly extracted maxillary first molars with cur vatures ranging b etween 25 0 and 350 were used. A glide path with #08-15 K files was established before cleaning and shaping with Mtwo rota- ry instruments (VDW, Munich, Germany) up to size 35/0.04 taper. During instrumen- tation, 1 ml of 2.5% NaOCl was used at each change of file. Samples were divided in- to 4 equal groups (n=20) according to the final irrigation activation technique: group 1, apical negative pressure (ANP) (EndoVac); group 2, manual dynamic agitation (MDA); group 3, passive ultrasonic irrigation (PUI); and group 4, needle irrigation (NI). Root canals were split longitudinally and subjected to scanning electron micros- copy. The presence of smear layer at coronal, middle and apical levels was evaluated by superimposing 300-µm square grid over the obtained photomicrographs using a four-score scale with X1,000 magnification. Results: Amongst all the groups tested, ANP showed the overall best smear layer re- moval efficacy (p < 0.05). Removal of smear layer was least effective with the NI technique. Conclusion: ANP (EndoVac system) can be used as the final irrigation activation technique for effective smear layer removal in curved root canals