Discussion
The present study aimed to compare the maintenance of canal anatomy, the occurrence of apical transportation, and the working time of three single-file systems having different design features and using different working motions in curved root canals. The canal anatomy conservation is extremely significant considering the fact that the root canal enlargement is able to have an additional impact on tooth weakening, and also makes the restored tooth more susceptible to be fractured in the presence of fiber posts.11e14 The results of the present study failed to demonstrate any influence of the file system used on the parameters “change of angle of curvature” and “apical transportation”. Once the preparation was finished, a considerable part of the foramens kept their same initial prepreparation position, and the shape of the prepared canals maintained the same central axes existing before the performance of preparations, although with expanded lateral dimensions, due to the uniform use aroused by the instruments employed in the canal walls.
Statistically, the standard deviation of observations may increase when curved specimens are used.10 Some studies have employed standardized artificial canals in training blocks with the aim to minimize this problem.15,16 Nevertheless, the advantage related to testing file systems in the natural dentin of extracted teeth is likely to be greater than the benefit caused by observing smaller standard deviations in simulated canals.8,10 This is a reason why natural teeth were employed in the present study. Efforts were made in the present study to safeguard the experimental groups comparability in spite of variations in the natural teeth morphology.
