Effects of auxiliary device use on smear layer removal

This study evaluated the effects of different auxiliary irrigation devices on smear layer removal with a chelating solution (QMix). Fifty single-rooted permanent human teeth were shaped with a sequence of nickel-titanium instruments. A 2% chlorhexidine gel was used as a chemical auxiliary substance during preparation. Samples were assigned to five groups (n = 10 each) according to final irrigation protocol, namely, distilled water (control group), QMix 1 min, QMix + passive ultrasonic irrigation (PUI), QMix + plastic endodontic finishing file (EC), and QMix 3 min. Teeth were prepared and evaluated by scanning electron microscopy, and three photomicrographs (magnification, 1,000×) were obtained for each root third. Two blinded and precalibrated evaluators analyzed and scored the images, and the data were statistically analyzed by the Kruskal-Wallis and Dunn tests (P < 0.05). Groups were ranked according to the extent of smear layer removal. The total area of the root canal walls and apical root thirds was calculated, and the groups ranked PUI > EC = QMix 3 min > QMix 1 min > control. QMix 1 min was effective for smear layer removal only when used with auxiliary devices, and QMix + passive ultrasonic irrigation yielded the best results, particularly for the apical third.(J Oral Sci 58, 561-567, 2016).