An in vitro evaluation of the removed dentin thickness of different retreatment systems using with and without solvent in the danger zone of mandibular molar teeth

Objectives: Due to its vulnerable structure of danger zone, the selection of an endodontic instrument may become very important to avoid excessive root canal preparation at this area. It was aimed to compare the effect of different retreatment file systems and solvent on the amount of removed dentin thickness in the danger zone of mandibular molar teeth using cone beam computed tomography (CBCT). Material and methods: A total of 120 mesiobuccal root canals were prepared and obturated with BioRoot RCS root canal sealer using single cone technique. Specimens were divided randomly into 3 groups according to the retreatment system used (n=40). ProTaper Universal Retreatment (PTUR), Reciproc Blue (RB) and XP-Endo Retreatment (XPR). Thereafter, each group was divided into 2 subgroups according to solvent used or not (n=20).CBCT images were obtained from specimens before and after removing root canal filling materials. The removed dentin thickness was calculated in axial sections obtained from 4 mm below furcation area. Data were statistically analyzed using two-way ANOVA and Bonferroni tests (p=0.05). Results: In terms of removed dentin thickness no significant difference was found between retreatment systems when used with solvent (p=0.964),whereas a significant difference was found when they used without solvent (p=0.004). The removed dentin thickness in RB was lower than XPR (p=0.008) and PTUR (p=0.018). Conclusion: Solvent did not affect the amount of removed dentin thickness of XPR and PTUR files. Removed dentin thickness of RB was less when used without solvent than used with solvent.