Fracture resistance of retreated teeth obturated with novel root canal sealers: An In Vitro and finite element analysis study

SUMMARY Objective: The purpose of this study was to compare the effects of different root canal sealers on the fracture resistance of retreated teeth and to assess the biomechanical implications of the findings using finite element analysis (FEA). Materials and Methods: A total of 124 extracted single-rooted mandibular premolars were used. Following canal preparation, all specimens were obturated with AH Plus sealer. Twelve teeth were randomly assigned to the positive control group. After removal of the root fillings in the remaining specimens, twelve teeth were designated as the negative control group, and the others were randomly divided into five experimental groups (n=20): Group 1 (AH Plus/lateral compaction), Group 2 (GuttaFlow Bioseal/single cone), Group 3 (TotalFill BC/single cone), Group 4 (BioRoot RCS/lateral compaction), and Group 5 (NeoSealer Flo/single cone). No retreatment filling was performed in the negative control group, whereas the canals in the experimental groups were filled with the respective sealers. After thermocycling, fracture resistance tests were carried out under oblique loading at a 45° angle to the long axis of the teeth. In addition, three-dimensional FEA models were constructed for each sealer group, and stress distribution within dentin, sealer, and surrounding tissues was evaluated under both lesion and non-lesion conditions. Results: The Kruskal–Wallis test revealed significant differences in fracture resistance among the groups (p<0.001). The negative control group, in which no refilling was performed, showed the lowest fracture resistance, whereas the positive control group exhibited the highest values (p<0.05). No statistically significant differences were found among the experimental groups (p>0.05). According to FEA results, bioceramic sealers with higher elastic modulus values (NeoSealer Flo and TotalFill BC Sealer) absorbed stresses within their structure and reduced stress accumulation in dentin. Conversely, GuttaFlow Bioseal, with a lower elastic modulus, generated more pronounced stress concentrations in dentin and exhibited limited stress-distribution capacity. Conclusion: Bioceramic-based sealers demonstrated comparable fracture resistance. However, FEA findings indicated that sealers with higher elastic modulus values provided a more protective biomechanical effect on dentin. These results highlight the importance of considering biomechanical compatibility in the selection of materials following endodontic treatment. Keywords: Endodontic retreatment, root canal sealer, bioceramic, fracture resistance, finite element analysis