Effect of final irrigation protocols on the bond strength and dentinal tubule penetration of root canal sealers: an ex vivo laboratory study

Effective disinfection and sealing of the root canal system are essential for the long-term success of endodontic treatment. Final irrigation solutions can influence the interactivity between dentin and sealers. This study aimed to evaluate the effect of different final irrigation protocols on the bond strength and dentinal tubule penetration of an epoxy resin-based and a bioceramic-based root canal sealers. One hundred and twenty extracted single-rooted human teeth were prepared and randomly assigned to five final irrigation regimens: distilled water (DW), NaOCl + DW + EDTA, NaOCl + DW + EDTA + DW + OCT, NaOCl + DW + EDTA + DW + CHX, and NaOCl + DW + EDTA + DW + NaOCl. Teeth were obturated using a single-cone technique with either an epoxy resin-based or a bioceramic-based sealer. Push-out bond strength was measured using a universal testing machine, and dentinal tubule penetration was analyzed by confocal laser scanning microscopy. Data were analyzed with two-way analysis of variance and Tukey post hoc tests (p = 0.05). Both the type of sealer and the irrigation protocol significantly influenced bond strength, whereas only the sealer type affected dentinal tubule penetration. The epoxy resin-based sealer exhibited higher bond strength across all groups, while the bioceramic sealer demonstrated greater dentinal tubule penetration regardless of the irrigation protocol. Among the irrigation protocols NaOCl + EDTA and NaOCl + EDTA + CHX resulted in higher bond strength compared with distilled water. The inclusion of octenidine did not enhance adhesion or penetration. The epoxy resin based sealer showed superior adhesion, whereas the bioceramic sealer achieved deeper dentinal tubule penetration. Final irrigation protocols influenced bond strength but did not affect tubular penetration. Octenidine showed no additional benefit under the tested conditions.