Reinforcement potential of Bioceramic vs. Resin sealers against vertical root fracture risk in the presence of the Butterfly Effect

Vertical root fracture (VRF) is a major cause of failure in endodontically treated teeth. A distinctive dentinal configuration known as the butterfly effect, characterized by mesiodistal sclerosis, has been linked to increased fracture susceptibility. To evaluate the influence of the butterfly effect on fracture resistance of endodontically treated mandibular premolars and to compare the reinforcing potential of root canal sealers. Forty-eight freshly extracted single-rooted mandibular premolars were examined under transillumination and classified into teeth with (n = 24) and without (n = 24) the butterfly effect. Each group was further subdivided based on the sealer used for obturation (Bio-C or AH Plus; n = 12 per subgroup). All specimens were instrumented using a standardized rotary protocol and obturated with warm vertical compaction. Fracture resistance was measured under axial loading using a universal testing machine. Data were analysed using two-way analysis of variance (ANOVA) to assess the effects of sealer type and dentinal configuration, followed by independent-samples t-tests for post-hoc comparisons (α = 0.05). Both dentinal configuration and sealer type affected the fracture resistance (p < 0.001). Teeth without the butterfly effect showed higher resistance than affected teeth, and Bio-C outperformed AH Plus across all subgroups. Within the limitations of this in vitro study, the results indicate that the butterfly effect adversely affects the post-treatment fracture resistance of roots. Additionally, Bio-C provides a greater level of mechanical support than AH Plus, suggesting a potential biomechanical advantage under the conditions tested.