Nanosilica's Impact on Resin-Based Pulp Capping Material Incorporating Tricalcium Silicate From White Portland Cement

Pulp capping is vital for maintaining pulp health in restorative dentistry, traditionally using Mineral Trioxide Aggregate (MTA) due to its high bioactivity and biocompatibility. Recently, tricalcium silicate from white Portland cement (TSWPC) has gained attention as a cost-effective alternative. This study investigates how the addition of nanosilica (NS) affects the bioactivity and mechanical properties of a resin-based TSWPC-ZrO₂ formulation for pulp capping. Two formulations, TSWPC-ZrO₂ and TSWPC-SiO₂-ZrO₂, were prepared and tested for compressive strength, flexural strength, and elastic modulus in accordance with ISO 9971-1 and ISO 4049. Hydration-driven bioactivity (pH, Ca²⁺/OH^- release), NIH/3 T3 viability, and cell attachment were monitored for 28 days. NS increased 24 h compressive strength from 105 ± 6 MPa to 116 ± 4 MPa and elastic modulus from 7.19 ± 0.27 GPa to 7.55 ± 0.32 GPa, but reduced flexural strength from 83 ± 5 MPa to 61 ± 7 MPa. Both cements generated alkaline conditions (pH 8.0-9.5) and sustained Ca²⁺ release (≤ 31 mg L^-1), with no significant differences between groups. The NS formulation showed higher cell viability after 72 h (244% ± 22%) and enhanced fibroblast attachment. The results indicate that nanosilica accelerates hydration and improves compressive stiffness without compromising bioactivity, offering a mechanically robust, cost-effective alternative to Mineral Trioxide Aggregate for vital-pulp therapy.