Modified Root Canal Sealers: A Comprehensive Review of Bioactive Enhancements, Antimicrobial Strategies, and Physicochemical Performance.

Root canal sealers are essential for achieving a three-dimensional seal of the root canal system, thereby preventing reinfection and facilitating periapical healing. Despite decades of material development, no available sealer satisfies every property expected of an ideal material. This review examines the rationale for modifying conventional sealers, focusing on recurring shortcomings including solubility, cytotoxicity, dimensional instability, and limited bioactivity. Recent work has concentrated on calcium silicate-based and bioceramic chemistries and on the incorporation of nanoparticles, bioactive glass, quaternary ammonium compounds, chitosan, and metal oxides to improve antimicrobial activity, physicochemical stability, and biological function. Experimental modifications generally enhanced antimicrobial activity, ion release, remineralization potential, or biological performance. However, their effects on flow, solubility, dimensional stability, cytocompatibility, and retreatability were formulation- and concentration-dependent, and clinical evidence remains limited. Persistent challenges, particularly retreatability and the shortage of long-term clinical validation, continue to justify further research toward optimized multifunctional endodontic sealers.