Root canal irrigants and their role in the adhesion of pre-endodontic restorations.

Objectives To evaluate the influence of root canal irrigating protocols on the micro-shear bond strength (µSBS) and endogenous enzymatic activity (MMPs) of pre-endodontic resin composite restorations at baseline and after artificial aging. Materials and methods Deep dentin surfaces from human molars (n = 16) were exposed and embedded in acrylic resin. A universal adhesive (iBond Universal, Kulzer) and resin composite (Venus Pearl, Kulzer) simulated pre-endodontic restorations. The following groups were formed according to the endodontic irrigating protocol (n = 20/group): C (no treatment); SH (5.25% NaOCl + water rinse); CHX (SH + 2% chlorhexidine rinse); EDTA (SH + EDTA rinse). Additional teeth (n = 3) were used for in situ zymography. µSBS and MMPs activity were assessed after 24 h or 10,000 thermocycles (5–55 °C, 30s). Data were statistically analyzed (p < 0.05). Results Irrigation, aging, and their interaction significantly influenced µSBS (p < 0.001). At baseline, EDTA showed the highest µSBS (p < 0.05), while C, SH, and CHX were statistically similar (p > 0.05). Thermocycling reduced µSBS in all groups, with no post-aging differences among irrigating protocols (p > 0.05). Enzymatic activity was affected by irrigation and aging. SH showed the highest MMPs activity while CHX the lowest (p < 0.05). No differences were observed between EDTA and C (p > 0.05). Conclusions Irrigating solutions do not affect the adhesive bond strength of pre-endodontic resin composite restorations after aging. However, enzymatic activity increases after NaOCl, but is reduced when NaOCl is combined with EDTA or CHX. Clinical relevance Clinically, this supports preserving interproximal pre-endodontic resin composite walls for final restorations.