Discoloration, radiopacity, and push-out bond strength of bismuth-based radiopacifiers in endodontic sealers

Aim This study aimed to evaluate the efficacy of nanostructured bismuth oxychloride (nano-BiOCl) in endodontic sealers with respect to radiopacity, color stability, and push- out bond strength under thermocycling conditions. Materials and Methods In this in vitro study, the disk-shaped Elastomeric Polyurethane Sealers (EPS) without radiopacifiers sealer served as the control group, whereas EPS with 20% bismuth oxide (Bi₂O₃), with 20% bismuth oxychloride (BiOCl), with 20% nano-BiOCl, and AH26 were designated as the test groups. The specimens were thermocycled to evaluate both short and long-term changes. Discoloration of all photographs was analyzed using ImageJ software. The ΔE values for discoloration were analyzed using one-way ANOVA, followed by Tukey's post-hoc test. Results: The discoloration levels of sealers containing nano-BiOCl and BiOCl showed significantly lower compared to Bi₂O₃ and AH26 samples (P < 0.05). However, the discoloration of the BiOCl samples was greater than that of the nano-BiOCl samples. Sealers containing nano-BiOCl exhibited significantly higher radiopacity than the other sealers (P < 0.05). The PBS for nano-BiOCl and BiOCl were significantly higher than those of Bi₂O₃ and AH26, despite no significant difference between the Bi₂O₃ and AH26. EPS without radiopacifier exhibited significantly lower radiopacity compared to all test groups, while its push-out bond strength (PBS) was comparable to sealers containing BiOCl and nano-BiOCl. Its discoloration after 100 cycles was higher than nano-BiOCl but not significantly different from BiOCl, Bi₂O₃, or AH26. Conclusion Nano-BiOCl can be an appropriate alternative choice for Bi₂O₃ in endodontic sealers, as it demonstrated lower discoloration, higher radiopacity, and greater PBS.