In vitro cytotoxicity of resin-containing restorative materials after aging in artificial saliva

Studies have reported that dental resin-based materials release substances which have biological liabilities. However, some current methods for detecting these substances may not be adequate to detect biologically relevant concentrations. In the current study, we hypothesized that resin-based materials exhibit cytotoxic effects and alter cellular function in vitro when high-pressure liquid chromatography (HPLC-UV detection) cannot detect any release of substances. We further hypothesized that this release continues even after aging the samples in artificial saliva. Five types of composite or compomer materials (Z-100, Tetric Ceram, Dyract AP, Solitaire, and Clearfil AP-X) and one organically modified ceramic material (Definite) were tested after aging in artificial saliva for 0, 7, or 14 days. Cytotoxicity was assessed using direct contact with fibroblasts and measurement of succinic dehydrogenase activity after 48 h of exposure post aging. Release of substances from the materials was assessed using HPLC with UV detection. Altered cellular function was estimated by measuring proliferation of MCF-7 cells with sulforhodamine staining. HPLC showed that whereas initial release of substances was higher without aging, this release dropped significantly after 7 or 14 days of aging, and was equivalent to the Teflon controls after 14 days for four of the materials (Tetric Ceram, Definite, Solitaire, and Clearfil AP-X). Without aging in saliva, all materials had cytotoxicities > 50% of the Teflon negative controls. After 14 days of aging, all materials except the Definite continued to show severe cytotoxicity. Only the Definite could be tested for its ability to alter cellular function because of the continuing toxicity of the other materials. This modified ceramic material caused a significant proliferative effect on the MCF-7 cells indicating that sufficient substances were released to alter cellular function. We concluded that all of these commercially available resin-based dental materials continue to release sufficient components to cause lethal effects or alter cellular function in vitro even after 2 weeks of aging in artificial saliva.