Mesoporous Bioactive Glass Nanoparticle-Reinforced Calcium Silicate Sealer for Reduced Microleakage and Enhanced Antibacterial Performance

Long-term success of root canal therapy depends not only on effective disinfection but also on durable sealing of the obturated canal system. However, currently available sealers still face persistent challenges in balancing handling, interfacial stability, bioactivity, and antibacterial performance. Here, we developed an injectable calcium silicate-based root canal sealer reinforced with mesoporous bioactive glass nanoparticles (MBGN) to improve sealing-related performance. The formulation integrated a hydration-active calcium silicate matrix with a mesoporous bioactive component while maintaining practical handling characteristics. MBGN incorporation enhanced dentin-associated mineralization, promoted intratubular crystal deposition, reduced apical microleakage, and decreased internal porosity after obturation. The 5% MBG formulation showed the most favorable sealing profile, reducing the dye penetration depth from 2.68 ± 0.41 mm in the 0% MBG group to 1.87 ± 0.32 mm, together with decreased open and closed pore parameters in the apical region. In parallel, the MBGN-reinforced sealer preserved acceptable cytocompatibility and exhibited stronger antibacterial activity against Streptococcus mutans than the reference formulations. The improved performance may be associated with effective initial adaptation and bioactive interfacial densification. Together, these findings suggest that MBGN incorporation may be a promising route for engineering more bioactive calcium silicate sealers with improved sealing stability and antibacterial function for endodontic applications.