Cytotoxicity, calcium release, and pH changes generated by novel calcium phosphate cement formulations

Few published studies describe the biological properties of calcium phosphate cements (CPCs) for dental applications. We measured several biologically relevant properties of 3 CPCs over an extended (8 wk) interval. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light-activated modified polyalkenoic acid, or 35% w/w polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs, respectively. Set cements were placed in direct contact with L929 fibroblasts for up to 8 weeks. Media Ca⁺² and pH were determined by atomic absorption spectroscopy and pH electrode respectively. Cell mitochondrial function was measured by MTT assay. Type I cements suppressed mitochondrial activity > 90% (vs. Teflon controls), but significantly (p < 0.05) improved to control levels over 8 weeks. Type II cements suppressed mitochondrial activity > 90% at all times. Type III cements elevated mitochondrial activity significantly after 7 wks. The pH profiles approached neutrality by 24 h, and all cements released calcium into the storage medium at all periods (24 h - 8 wk). We concluded that several types of cements had long-term biological profiles that show promise for dental applications.