Developing a novel ceramic cement for endodontics based on calcium borate silicate: in vitro characteristics and biocompatibility assessment

Abstract

Conventional calcium silicate cements (CSCs) are widely applied in endodontics but often suffer from drawbacks such as long setting times, poor handling, and variable biocompatibility. A novel premixed calcium borate silicate (CBS)-based cement incorporating different radiopacifiers was developed and evaluated to address these limitations. CBS powders were synthesized via melt-quench routes, combined with Bi2O3, La2O3, or Sm2O3 at various loadings, and blended with an optimized hydrogel liquid phase. The resulting cements' physicochemical, biological, and functional properties were systematically assessed. Key tests included setting time, flow, solubility, radiopacity, and ion release measurements; bioactivity analysis via immersion in simulated body fluid; and antibacterial activity against E. faecalis. Cytocompatibility, hemocompatibility, and genotoxicity were examined using L929 fibroblasts through MTT and comet assays. Incorporation of radiopacifiers significantly modified cement performance. Bi2O3 enhanced radiopacity (>7 mm Al) and accelerated setting, while La2O3 and Sm2O3 balanced faster hardening with favorable flow characteristics. All doped formulations showed apatite formation and improved Ca/P ratios, indicating robust bioactivity. Ion release profiles confirmed controlled liberation of Ca2+, P, and Si alongside trace radiopacifier ions. Radiopacified cements achieved >75 % reduction in E. faecalis colony counts, with La2O3 demonstrating the strongest antibacterial effect. Biocompatibility studies revealed that La2O3 maintained fibroblast viability >80 % and improved hemocompatibility, whereas Bi2O3 and Sm2O3 displayed mild concentration-dependent cytotoxicity. Importantly, no formulation induced DNA damage in the comet assay, confirming non-genotoxicity. The novel CBS-based cement system demonstrated excellent radiopacity, rapid setting, strong bioactivity, antibacterial activity, and good overall biocompatibility, with La2O3 emerging as the most balanced additive. These findings support CBS-radiopacifier formulations as promising next-generation endodontic materials, warranting further in vivo and clinical evaluation.