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

Purpose: Due to its vulnerable structure in the danger zone, the selection of an endodontic instrument becomes very important to avoid excessive root canal preparation in this area. It was aimed to compare the effect of different retreatment file systems and solvents on the amount of removed dentin thickness in the danger zone of mandibular molar teeth using cone beam computed tomography (CBCT).
Methods: A total of 120 mesiobuccal root canals were prepared and obturated with BioRoot RCS root canal sealer using the single cone technique. Specimens were divided randomly into three 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 two subgroups according to whether a solvent was 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 the 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 were used without solvent (p = 0.004). The removed dentin thickness in RB was lower than in 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 with solvent.