Cytotoxicity of composite resins before and after expiration date. Preliminary report.

The aim of this study was to compare the cytotoxic effects of expired and non-expired resin-based composite materials at two, five and seven days on L929 cells. Disc-shaped test samples of expired and non-expired composite materials were prepared according to manufacturers' instructions. The samples were transferred into a culture medium for 24 hours. Eluates were obtained and pipetted onto L-929 mouse fibroblast cultures and incubated for evaluation after two, five and seven days. After each of the incubation periods, measurements were performed by MTT assay. The degree of cytotoxicity of each sample was determined according to the reference value represented by the cells with a control. Statistical significance was determined by two-way analysis of variance, followed by Duncan's test. Among all composite materials, expired composites presented lower cell viability than the non-expired composites over the three-day time period; the difference in survival rates between the expired and non-expired groups was statistically significant (P < 0.05). Non-expired Quadrant Universal LC demonstrated high survival rates, followed by Filtek Z250 and Alpha-dent at two and five days. It can be concluded that expiration dates have a significant effect on the cytotoxicity of the composite materials.