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.