Cytotoxicity of Endodontic Filling Materials after Extended Aging

Objectives: Endodontic filling materials are in intimate, long-term contact with connective tissue and bone, yet the biological properties of newer materials remain unclear. In the current study, we tested a hypothesis that measuring the in vitro cytotoxic responses of endodontic materials over extended times would identify trends that discriminate among materials and suggest clinical consequences. Methods: Specimens (n = 6) of 6 endodontic sealers: AH-plus (AH, Dentsply), Pulp Canal Sealer (PC, KerrSybron), GuttaFlow (GF, Coltene), InnoEndo (IE, Heraus-Kulzer), Real Seal (RS, KerrSybron), Epiphany (Eph, PentronClinical Tec) and 3 core materials: Gutta-percha (GP, Obtura), Resilon (R, Sybron) Tone (Tn, Sigma-Aldrich, polycaprolactone) were tested immediately after mixing in direct contact (1.2 cm²/mL) with L929 fibroblasts (8000 cells/cm²) for 72 h. Cytotoxicity was reassessed after 1, 3, 4, and 6 weeks of ‘aging' in phosphate-buffered saline at 37°C. Cell response was estimated by mitochondrial succinate dehydrogenase (SDH) activity (MTT method), which was expressed as a percentage of Teflon® (Tf) controls. Conditions were compared with ANOVA/Tukey analysis. Results: Our results identified distinct trends in cytotoxicity among both core materials and sealers over the 6-week test. Four of the six sealers and two of the three core materials remained severely cytotoxic after 6 weeks. At week 0, all materials were severely cytotoxic (< 20% SDH) except Tn, which still significantly suppressed SDH activity (40%, p < 0.05). Over time, only Tn, GF and AH improved significantly in cytotoxicity (p < 0.05). After 6 weeks, the final SDH activity values were (%Tf(SD)): AH, 45(2); PC, 9 (1); GF, 55(5); Eph, 2(2); IE, 6(5); RS, 4(2); GP 1(0); R, 4(3); and Tn, 78(5). Conclusion: Many new endodontic materials pose a risk of adversely affecting periapical tissues over periods as long as 6 weeks. (Funding: MCG Dental Research Center)