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 materialsfrom the canal system is essential for optimal nonsurgical retreatment, becauseit provides effective cleaning, shaping, and re-filling of the root canal system.Objectives: This study compares the effectiveness of Reciproc Blue, HyFlexCM, Reciproc, and ProTaper Universal retreatment files (PTUR) in removingroot canal filling material (RCFM).Materials and methods: Sixty human upper central incisors were shaped withRevo-S files up to apical size 40 and were obturated using the cold lateralcompaction technique. After two weeks, the RCFMs were removed with ReciprocBlue, 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 ImageJsoftware, and the time required to remove the RCFM was recorded. Data wereanalyzed 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 remainingRCFM was significantly higher in HyFlex CM and Reciproc Blue groups thanthat of PTUR and Reciproc groups (P<0.05); however, there is no significantdifference between the HyFlex CM and Reciproc Blue groups (P>0.05).Furthermore, there is no difference between the Reciproc and PTUR filesregarding the amount of remaining RCFM (P>0.05). The Reciproc file removedthe RCFM in a shorter time than the other groups (P<0.05). However, there isno 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 andPTUR files) exhibited better performance than the files with reduced shapememory (Reciproc Blue) and controlled memory (HyFlex CM) in removingthe RCFM.