Evaluation of the efficiency of different file systems in removing calcium hydroxide from root canal

Aim Endodontic treatment aims to clean and prepare the root canal system and to apply a three-dimensional impermeable filling. For this reason, various shaping procedures and irrigation solutions are used, but it is not possible to ensure complete disinfection due to the complex structure of the root canal system. Therefore, the use of intracanal medicaments is suggested to increase the success rate of endodontic treatment. The most prevalent preparate used as an intracanal medicament in endodontics is calcium hydroxide (Ca(OH)2). It is required to remove the entire intracanal medicament prior to the root canal filling. The Ca(OH)2 left in the root canal system blocks the dentinal tubules and prevents canal pastes' penetration. Ca(OH)2, interacting with various canal pastes chemically, also negatively affects the adhesion of pastes to root canal dentine and increases apical leakage. Therefore, many mechanical techniques, different irrigation solutions, and irrigation activation methods have been utilized to remove the Ca(OH)2 medicament from the root canals, but none of these methods could completely remove the intracanal medicament from the root canals. This study aims to compare Ca (OH)2's removal between sessions using different file systems under a stereomicroscope. Material and Method In this research, 75 extracted human mandibular premolars with a single root, single canal, and single apical foramen have been used. The crowns were removed using a diamond bur to acquire a standard root length of 15 mm. The root canals were enlarged up to the ProTaper F4 file. Ca(OH)2 paste was inserted into the root canals at working length. The coronal parts of the roots were filled with a temporary filling material. Teeth were kept in distilled water at 37oC for seven days in the incubator. Then, temporary fillings were removed. Depending on the method used for removing the Ca(OH)2 in the root canals, specimens were randomly distributed into three experimental groups (Reciproc 40, Reciproc Blue R40, WaveOne Large) and two control groups (negative, positive), a total of 5 groups (n=15). Roots were separated into two sections buccolingually, and the residual Ca(OH)2 in the canal was evaluated under a stereomicroscope at x20 magnification. Result The normal distribution of variables was examined with the Shapiro-Wilk test due to the number of units. The significance level was set at p<0.05 to interpret the results. During the examination of differences among the groups, the Kruskal-Wallis H test was used in case the variables were not normally distributed. If there were significant differences in the Kruskal-Wallis H test, Post Hoc Multiple Comparison test was conducted to determine the groups with significant differences. Although Ca(OH)2 could not be removed entirely from the root canals in any group, it was statistically determined that the removal of Ca(OH)2 was higher with Reciproc file systems than with Reciproc Blue and WaveOne Gold file systems (p<0.05). Conclusions It is determined that Reciproc file systems are more effective than Reciproc Blue and WaveOne Gold file systems in removing the Ca(OH)2 from root canals. However, none of the methods could entirely remove the Ca(OH)2 from the root canals.