Efficacy of Endodontic Files with Different Metallurgical Characterization in Removing Root Canal Filling Material

Statement of problem: Safe and efficient removal of all root filling materials from the canal system is essential for optimal nonsurgical retreatment, because it provides effective cleaning, shaping, and re-filling of the root canal system. Objectives: This study compares the effectiveness of Reciproc Blue, HyFlex CM, Reciproc, and ProTaper Universal retreatment files (PTUR) in removing root canal filling material (RCFM). Materials and methods: Sixty human upper central incisors were shaped with Revo-S files up to apical size 40 and were obturated using the cold lateral compaction technique. After two weeks, the RCFMs were removed with Reciproc Blue, HyFlex CM, Reciproc, or PTUR (ProTaper Universal Retreatment) files. Teeth were cleaved longitudinally, and digital images were then captured. The amounts of RCFMs in the obtained images were analyzed using ImageJ software, and the time required to remove the RCFM was recorded. Data were analyzed using a one-way of variance (ANOVA) test. Results: There was no significant difference among the files in the coronal third (P>0.05). In contrast, in the middle and apical thirds, the amount of remaining RCFM was significantly higher in HyFlex CM and Reciproc Blue groups than that of PTUR and Reciproc groups (P<0.05); however, there is no significant difference between the HyFlex CM and Reciproc Blue groups (P>0.05). Furthermore, there is no difference between the Reciproc and PTUR files regarding the amount of remaining RCFM (P>0.05). The Reciproc file removed the RCFM in a shorter time than the other groups (P<0.05). However, there is no difference among the other three groups (P>0.05). Conclusions: None of the tested files could completely remove the RCFM. Under the limitation of this study, the files with shape memory (Reciproc and PTUR files) exhibited better performance than the files with reduced shape memory (Reciproc Blue) and controlled memory (HyFlex CM) in removing the RCFM.