Advancing Adhesive Strategies for Endodontically Treated Teeth-Part II: Dentin Sealing Before Irrigation Increases Long-Term Microtensile Bond Strength to Coronal Dentin.

Objective: To compare the long-term microtensile bond strength (μTBS) to coronal dentin using pre-endodontic dentin sealing (PEDS) and post-endodontic adhesion (PEA) techniques under various endodontic irrigation protocols.

Materials and methods: Ten study groups (n = 10) were established based on the timing of adhesive application (PEDS versus PEA) and irrigation protocol: distilled water (control), 3% sodium hypochlorite (NaOCl), 3% NaOCl followed by 17% ethylenediaminetetraacetic acid (EDTA), 3% NaOCl followed by 17% EDTA and 2% chlorhexidine, and a mixture of 3% NaOCl and 9% etidronic acid (HEDP). Specimens underwent μTBS testing after a six-month microspecimen aging period. Fracture patterns were analyzed, and adhesive interfaces were assessed using scanning electron microscopy (SEM). Statistical analysis employed a mixed linear regression model with a 5% significance level.

Results: PEDS consistently preserved high bond strength across all irrigation protocols (57.4-59.5 MPa), while PEA groups treated with endodontic irrigants resulted in significantly lower values (33.3-40.8 MPa; p < 0.001). No significant differences were observed within the PEDS groups (p > 0.05). SEM analysis revealed consistent hybrid layers in PEDS and PEA/Control groups, while PEA groups treated with endodontic irrigation solutions showed significant resin-dentin interface variations and interfacial gaps.

Conclusions: The PEDS technique preserved high and consistent μTBS regardless of the irrigation protocol, whereas endodontically irrigated PEA groups exhibited significantly reduced bond strength. PEDS offers a predictable approach to optimizing adhesive performance in endodontic-restorative treatments.

Clinical significance: Integrating PEDS into routine endodontic-restorative workflow is recommended to enhance long-term bond strength to coronal dentin. The PEDS technique ensures consistent adhesive performance regardless of the endodontic irrigation protocol, enhancing restorative predictability and treatment success while preserving tooth structure.