These orifices containing the files were filled with epoxy resin. After 24 hours of resin curing, the resin cylinders were removed from the device and sectioned by using a diamond disk (Arotec, São Paulo, Brazil) mounted in an Isomet cutting machine (Buehler, Lake Bluff, IL) under constant irrigation with alcohol. The cut positions were selected in such a way to correspond

to the D14, D6, and D3 of the files. Consequently, flat surfaces containing the whole cross section of each file were obtained (Fig. 1). The metallic this website surface was then polished by using sandpapers of different granulations: 220, 400, 600, and 1200 (3M, São Paulo, Brazil). After polishing, the surface of each fragment was abraded with a steel fine tip by using ultrasonic vibration. This method was adopted to promote the mechanical removal of any protector layer resultant from the previous surface polishing. http://www.selleckchem.com/products/sotrastaurin-aeb071.html Consequently, 3 types of file fragments

were created, generating 3 experimental groups: group D14, group D6, and group D3 composed of fragments with exposed cross section correspondent to the D14, D6, and D3, respectively. Current register tests were used to evaluate the dissolution process of the embedded fragments. An electrochemical cell was used that contained a saturated calomel electrode as reference, platinum as counter-electrode, and a platinum wire with diameter equal to 0.1 mm as the working electrode. The working electrode was used in contact with the file fragment. A polymeric tube with internal diameter equal to 0.15 mm was used to support the platinum wire. Cyanoacrylate ester was used to attach the platinum wire to the polymeric tube. Another polymeric tube with internal diameter equal to 0.40 mm was used as an overlay of the first tube to increase the mechanical

resistance of the described setup. The attachment aminophylline between the tubes containing the working electrode was made by using the same cyanoacrylate ester. The electrodes were immersed in a [NaF 5 g/L + NaCl 1 g/L] solution with pH 5.0 and connected to a digital potentiostat (Metrohm Autolab, Herisau, Switzerland). The fragment of file was immersed in the same solution in such position that the center of the file cross-section surface could be in contact with the working electrode. An anodic potential equal to 700 mVsce was applied to the fragment during 50 minutes, and the potentiostat registered the anodic current generated. The total electrical charge of each test was obtained by integrating the current value over the time by using the program of data analysis Origin 6.0 (Microcal Software Inc, Northampton, MA). Three fragments of each group were tested in these conditions. Analysis of variance (ANOVA) (P < .05) was used to compare the total electrical charge among the fragments of the 3 groups.