Efficiency of Final Irrigation Using Manual Dynamic Agitation in Smear Layer Removal

Objectives: To compare the efficiency of conventional techniques and manual dynamic agitation (MDA) in smear layer removal from mechanically-prepared root canal walls after root canal irrigation

Methods: The root canals of 120 extracted single-rooted premolar teeth were prepared using Mtwo® rotary instruments up to size 40/0.04 with 20 mL of 2.5% NaOCl. The roots were randomly divided into six groups (n=20) according to different irrigation protocols.
Group 1) control group; irrigated with normal saline solution, Group 2) irrigated with 17% EDTA followed by 2.5% NaOCl, Group 3) irrigated with 17% EDTA followed 2.5% NaOCl with MDA, Group 4) irrigated with 17% followed by 2.5% NaOCl (both with MDA), Group 5) irrigated with EDTA containing 0.25% cetrimide followed by 2.5% NaOCl (both with MDA), and Group 6) irrigated with Smear Clear™ EDTA followed by 2.5% NaOCl (both with MDA). The volume of solution and irrigating time were uniform in all groups. Subsequently, the specimens were split longitudinally and evaluated under scanning electron microscopy. The amount of smear layer in each specimen, 3 mm from the root apex, was scored using the scoring system of Guttman et al, and statistically analyzed using the Kruskal-Wallis and Mann-Whitney U tests.


Results: The group using EDTA containing 0.25% cetrimide with MDA (Group 5) had the smallest amount of smear layer on the root canal surface (P<0.05). When MDA was applied with both irrigants (Groups 4, 5 and 6), the amount of smear layer was significantly reduced compared to that in the group using MDA with NaOCl alone (Group 3) (P<0.05). The amount of smear layer was significantly less in all groups which used MDA.
Conclusions: The supplement of MDA in the final root canal irrigation step significantly promoted a cleaner surface of the mechanically-prepared root canal wall at the apical level. The use of EDTA containing 0.25% cetrimide significantly improved smear layer removal.