Abstract
Objective: To evaluate the vertical forces induced with Reciproc (R) and Reciproc Blue (RB) systems during canal shaping.Methods: Maxillary premolar teeth with two separate straight and constricted canals were chosen (n=26). After access cavity preparation, each tooth was fixed in a standing position on a stage connected to a force analyzing device (M5-20 Advanced Digital Force Gauge; Mark-10 Corporation, NY, USA). The glide path was prepared man-ually until K file sizes #15. Then, canals in all the groups were completely shaped with an R25/RB25 file (size 25, .08 taper). The canal shaping was done with a steady and gentle pressure on the file to give a slow "in-and-out" movement of 2 mm amplitude. The file was inserted three times until it reached the WL successfully. After each insertion, the canal was recapitulated and irrigated with a 1% sodium hypochlorite solution. The shaping time was analyzed by Student's t-test. The inward and upward peak forces were used for analysis by using the Mann -Whitney test. All statistical analyses were performed using SPSS software at a 95% confidence level.Results: Each root canal was shaped successfully with a single file inserted three times until the WL was reached. Within each group, the overall real-time force increased with the successive insertions of the file. The inward peak forces in both groups ranged from 1.71 to 8.38 N and the R group showed minimal peak forces than the RB group in the three insertions (P<0.05). The upward peak forces ranged from 1.50 to 3.26 N wherein both groups showed comparable peak forces at each insertion (P>0.05). The R and RB systems required average times of 22.01 +/- 3.08 and 23.93 +/- 4.15 s, respectively, to shape the canals completely (P>0.05). In this experiment, no file fracture took place during canal shaping. Conclusion:The blue heat treatment influenced the forces developed during canal shaping. RB file was asso-ciated with higher inward peak forces than R file.