The cyclic fatigue resistance of m-pro, M3pro gold, and RaCe glide path files were investigated in a double curved simulated canal. 10 files from each group were examined. The files were tested in s-shaped groove prepared in a block made of stainless steel simulating a double curved root canal. Cyclic fatigue resistance was assessed by counting the number of cycles of separation (NCS). Moreover, the lengths of the separated parts were calculated. All data were analyzed by the oneway analysis of variance. RaCe Scout files showed higher (NCS) significantly compared to m-pro and M3pro gold (P<0.00L) but when compared with each other, no significant difference (P=0.68). According to the results of this study Scout RaCe files had the highest cyclic fatigue resistance in double curved simulated canals among the three types evaluated, therefore, Scout RaCe Files could be used with more trust in preparing of S-shaped canals as the first step of clinical chemomechanical preparations.

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Purpose: our study evaluated the effect of Gallic acid irrigation as a final rinse after sodium hypochlorite (NaOCL) irrigation on the filling Quality of an expoxy resin -based sealers.Methods and Materials: Twenty single-rooted human teeth were prepared with the protaper system. The specimens were then divided into the following groups: 5.25%NaOCL irrigation (NaOCL group) and 5.25%NaOCL + 10% gallic acid (gallic acid group). The root canals were filled using single cone technique with protaper F 3 cones and Diapro -seal sealer, labeled with rhodamine B dye to allow analysis under a confocal laser scanning microscopy (CLSM). All Samples were sectioned at 3, 5 and 7 mm form the apex and prepared for CLSM analysis. The Penetration segments of the canal were calculated at the apical, middle and coronal thirds. The Mann -Whitney statistical test was used at 5 % significans level.Results: higher percentage of gaps and voids were observed at all root thirds of the NaOCL group when compared to the gallic acid group (P < 0.05). There was a significant increase in the penetration segment of gallic acid group at the coronal and middle root third when compared to the NaOCL group (P < 0.05). Conclusion:our in vitro results showed that the use of gallic acid as an antioxidant agent after NaOCL irrigation promoted a better interfacial adaptation and penetration of epoxy resin -based root canal sealers.