In vitro comparison of the cytotoxicity of two orthodontic composite resins.

Several studies have reported that dental resin-based materials release substances with biological liability. In this work the in vitro cytotoxic potential of specimens of a self-curing and a light-curing orthodontic composite resins - prepared according to the producer instructions - was evaluated using mouse fibroblast cell line (3T3 Swiss) with the following cell-material contact systems: 1. 24 h extracts toxicity. The extracts of specimens, left for 24 h in cell culture medium, were then placed in contact with 3T3 fibroblasts for 24h; the cytotoxicity was evaluated using the thiazolyl blue tetrazolium bromide (MTT) assay. 2. Indirect method. The specimens were settled - for a period of 24 h - on a tissue culture insert placed over the cellular monolayer; the cytotoxicity of the resin components released was then tested by MTT. The results, obtained in this study, elicit a close agreement between the two procedures; from the data obtained in the reported experimental conditions, it is possible to establish that the examined chemical-cured material was more cytotoxic than the light-cured one. Further investigations about the influence of the modes of polymerization of the materials on the biological effects are warranted to verify their clinical implications.