Effect of different peracetic acid chemical formulations on dentin residues persistence, bond strength and dentinal penetration of autoconditioned cement used for fiber post cementation

Abstract

To evaluate the residues persistence and effect on the adhesion of a self-etching resinous cement used to fiber posts cementation in dentin, after the root canal irrigation with several chemical formulations of 1% peracetic acid. Sixty root human canines freshly extracted will be standardized in length and 17.0 mm and root canals instrumented at F5 instrument (ProTaper) and irrigated with 2.5% sodium hypochlorite. As final irrigation will be used 17% EDTA and 2.5% sodium hypochlorite. The root canals will be filled with F5 gutta-percha and an epoxy-based sealer (AH Plus), by single cone technique. After 7 days, the root canals will be prepared using a #2 bur (FGM, Joinville, SC BR), in the extension of 11.0mm. Upon completion of the preparation, the roots will be distributed randomly into 4 groups (n = 15, each group) according to the final irrigation protocol: G1- distilled water (negative control); G2- 2.5% Sodium hypochlorite (positive control); G3- 1% Peracetic acid solution with a high peroxide concentration (Peresal; Prophylactic Curitiba, Brazil) and G4- 1% Peracetic acid solution with low concentration of peroxide (Sigma Chemical Co., St. Louis, MO, USA). In all groups, irrigation will be performed with 5 ml of the solution and maintained within the canal for 3 min. After the final irrigation protocol, the root canals will be aspirated and dried with F5 absorbent paper tip. At this time, the surfaces of the fiber posts (White Post DC; FGM, Joinville, SC, Brazil) will be cleaned with 70% alcohol solution. The self-etching cement (RelyX U200; 3M ESPE - St. Paul - USA) added with Rhodamine B in a proportion of 0.01% (by weight) will be inserted in the root canal and fiber post positioned in root canal prepared space and photoactivated for 40 seconds. Forty-eight hours later, the roots will be cross-sectioned, with sections were taken 2.0 mm thickness from 1.0 mm (cervical), 5.0 mm (medium), and 8.0 mm (apex) of the root cervical face. Immediately after, the specimens will be submitted to the push-out test using a load cell 5 KN, in the electromechanical testing machine at a speed of 0.5 mm/min. After the push-out test, the penetration of the cement into the dentine will be evaluated using Confocal laser microscopy, an increase of 100 X. The images obtained will be analyzed with the software Image J, after a proper calibration program and penetration perimeter will be obtained. In sequence, the specimens will be examined in scanning electron microscopy (500X) to evaluate the fracture pattern that occurred and is classified in adhesive, cohesive, or mixed. The results obtained in the push-out test will be transformed into MPa and analyzed by ANOVA (p = 0.05), in each of the root thirds evaluated. To evaluate the penetration will be used the Kruskal-Wallis test (p = 0.05). In n sequence, forty freshly human extracted canines will be submitted to similar root canal procedures and final irrigation protocols before glass fiber cementation. After to specific final irrigation, the root wib be split in the longitudinal axis and prepared to SEM. The image obtained in root canal medium third (in 500X and 1000X, respectively) will be analyzed and assigned scores to dentin residues persistence (debris and smear layer, respectively). The data will be submitted to the Kruskal Wallis test (p=0,05). (AU)