Long-term Cytotoxicity of Calcium Phosphate Cements

Objectives: New calcium phosphate cements (CPCs) have been developed with physical properties that are promising for dental applications such as pulp capping, endodontic sealing, and restorative applications (bases/liners). However, information about the biological properties of these new materials is scarce, particularly in long-term contexts. In the current study, we measured the biologic properties of 3 types of CPCs in an extended (8 wk) in vitro cytotoxicity test. Methods: Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with one of three aqueous solutions: 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 (n = 6) were placed into cell-culture in direct contact (1.2 mm² surface area/mL medium) with L929 mouse fibroblasts (8000 cells/cm²) for 72 h, after which cellular function was assessed using the MTT assay. Specimens were then aged in sterile phosphate buffered saline for 96 h and tested in culture again. This sequence was repeated for 8 weeks. MTT activity was expressed as a percentage of Teflon negative controls, and cytotoxic responses were compared with ANOVA and Tukey post-hoc analyses. Results: The Type I cements were severely (> 90% suppression) cytotoxic initially, but significantly (p < 0.05) improved over the 8 week evaluation and were statistically equivalent to Teflon after 4 weeks. Type II cements were severely cytotoxic over the entire 8 week evaluation. Type III cements were equivalent (p > 0.05) to Teflon the entire time. Conclusions: CPCs have different long- term biological properties depending on the nature of the polymeric acid used to initiate the reaction. Several types of cements had long- term cytotoxicity profiles that show promise for dental applications. (Funding: Egyptian Government and MCG Dental Research Center)