Then, the teeth were randomly divided into 13 groups of four teeth

each according to the time and substances used. The substances used were 17% EDTA (Biodinâmica, Ibiporã, PR, Brazil), 10% citric acid (Formulativa, Rio de Janeiro, RJ, Brazil), 37% phosphoric acid solution see more (COPPE, Rio de Janeiro, RJ, Brazil), and 37% phosphoric acid gel (Condac, Joinville, SC, Brazil). The irrigation protocols and experimental time periods used in this study are described in Table 1, and 1 mL of substance was used without replacement. After the removal of the smear layer, all teeth were irrigated again with 5 mL distilled water and dried with medium-sized paper points (Endopoints, Paraiba do Sul, RJ, Brazil). Finally, two longitudinal grooves were prepared on both buccal and lingual surfaces by using a diamond disc without penetrating the canal. The roots were then split into two halves with a hammer

and chisel. For each root, the half containing the most visible part of the apex was used for study. The Gefitinib samples were coated with gold and analyzed with a scanning electron microscope (JSM 6460 LV; JEOL, Tokyo, Japan). All samples were numbered, and the images were performed without knowledge of the group tested. First, a scan of all samples was made at 30× magnification for each group. Then, the most representative area of each third of each tooth was selected and magnified at 100×. Each 100× image was scanned, and the three most representative areas were magnified at 2,000×. For example, if the image of 100× showed 70% of the surface covered with smear layer, two images with smear layer and one without were selected. Therefore, three

images of each third were obtained Phospholipase D1 for each tooth, providing nine images per tooth and 36 images per group (n = 4). In the end, each group had 12 images for the three thirds. To evaluate the degree of smear layer removal, the scoring system described by Takeda et al (16) was used but with modifications. Briefly, score 1 = no smear layer, with all tubules cleaned and opened; score 2 = few areas covered by smear layer, with most tubules cleaned and opened; score 3 = smear layer covering almost all the surface, with few tubules opened; and score 4 = smear layer covering all the surfaces. It was a blinded evaluation performed by three independent observers. Intraexaminer and interexaminer reliability for the SEM evaluation was verified by Kappa test. Data were analyzed using Kruskal-Wallis and Mann-Whitney U tests (p < 0.05). The Kappa test showed good agreement between observers, with values of 0.9 or above. Figure 1 shows representative images of the scores. The results of the smear layer scores for each group are listed in Table 2. At 30 seconds, citric acid solution, phosphoric acid solution, and phosphoric acid gel were more effective than EDTA and control group for the apical and middle thirds.