Magnesium Silicate-Based Cement with Moderated Alkalinity: Physicochemical Characterization and Human Dental Pulp Cell Responses

To establish a lower-alkalinity alternative to calcium silicate-based endodontic materials, this study developed a self-setting magnesium silicate-based cement (MSC) that hardens through magnesium silicate hydrate (M-S-H) formation. MSC was formulated from magnesium oxide, reactive silica, and zirconium oxide. Hydration and phase evolution were characterized by X-ray diffraction, thermogravimetric analysis, thermodynamic modeling, and scanning electron microscopy. pH, early penetration resistance, and compressive strength were compared with ProRoot mineral trioxide aggregate (MTA), and cement extracts were evaluated for human dental pulp cell viability, alkaline phosphatase activity, intracellular calcium mobilization, and YAP localization. MSC hydration involved progressive Mg(OH)2 consumption and formation of an M-S-H-rich matrix. Its pH decreased from approximately 9.7 to 8.9, whereas MTA remained near pH 12. The lower-water formulation containing additives exceeded 40 MPa in compressive strength at 28 days and showed greater early penetration resistance. MSC-0.3 extracts showed higher 7-day cell viability than ProRoot MTA at 1:4 and 1:8 dilutions, increased alkaline phosphatase activity, were accompanied by increased intracellular calcium fluorescence that was not observed following NPS 2143 pretreatment, and increased nuclear YAP localization. These findings identify MSC as a functional cement platform combining moderated alkalinity, progressive strength development, and favorable early pulp-cell responses.