['To evaluate the cytotoxicity of new root canal filling material-composite oyster shell paste.', 'According to the evaluated criteria of medical materials, biology and animal trials recommended in ISO 10993,the extracts of powder part and the mixture of the new material were prepared separately and selected as the experimental. The RPMI1640 subject was used as the negative control and the V79 cell as the experimental cell. The cells were cultured in extract of different thickness compound for 2,4,7 days respectively and the changes of the cells were observed under microscope.The proliferation of the cells were examined and the optical density(OD)was obtained using MTT assay. SPSS12.0 software was used for statistical analyses.', 'During all culture periods, the V79 cells showed normal morphology and proliferation increased with culture time. The OD of the experimental groups were not significantly different from that of the negative groups(P>0.05)and the OD increased as time goes on.'] Do [ Cytotoxicity study of composite oyster shell paste as a root canal filling material ]?