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.