The influence of dentine on the in vitro cytotoxicity testing of dental restorative materials

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Abstract
Few in vitro systems for testing dental restorative materials have taken into account the protection afforded by the residual dentine in vivo. In turn opinions differ as to whether an increase in residual dentine thickness increases this protection. In this study an increase in the depth of dentine powder beneath zinc oxide eugenol (ZOE) reduced its toxicity, while this was not the case with the glass ionomer cement. Compaction of the powder had no effect, suggesting that protection was due to binding of the toxicant to the dentine rather than it acting as a physical barrier. Protein was shown to be very important in moderating the cytotoxicity of ZOE. These results suggest that in vivo the irritancy of some materials may be related to the depth of residual dentine but not others. The effect of exposure period and volume of these materials on their cytotoxicity was also investigated. Increasing the volume of ZOE while retaining the same surface area increased the toxicity of ZOE, while with the glass ionomer it had no effect.