A novel root canal irrigant enabling rapid formation of a tannic acid–silver nanocoating for sustained antibacterial therapy in root canal infections

Abstract

Continuous intracanal disinfection facilitates the complete elimination of residual pathogenic microorganisms and prevents the recurrence of root canal infections. Current prolonged disinfection strategies rely on calcium hydroxide or antibiotic pastes; however, these agents require thorough subsequent removal, which extends the treatment cycle and increases procedural complexity. Herein, we report a two-component irrigation system based on tannic acid (TA) solution and silver nitrate (AgNO₃) solution that rapidly forms a long-lasting antibacterial coating (≤3 min) without the need for subsequent removal. Delivered via a dual-chamber syringe, this system generates a TA–Ag nanocoating in situ on the root canal wall through phenolic hydroxyl–Ag⁺ coordination and subsequent reduction, enabling long-term disinfection through sustained Ag⁺ release. Antibacterial assays demonstrated that the TA–Ag irrigation system achieved over 99% eradication of Enterococcus faecalis biofilms after a 3-min treatment and maintained inhibition of bacterial colonization on dentin for up to 2 weeks. In addition, TA molecules can chelate calcium ions from body fluid via phenolic hydroxyl groups, inducing calcium crystallization and promoting root canal wall remineralization. In vivo mouse wound infection models confirmed that the TA–Ag irrigant efficiently eliminates bacteria, attenuates inflammation, and accelerates tissue healing. Dental pulp stem cell experiments and oral mucosal contact tests verified its biocompatibility and safety. Collectively, this study presents a safe and effective root canal irrigation system capable of sustained intracanal disinfection and remineralization, showing great promise in root canal therapy and also other biomedical applications.