Cytotoxicity of composite resins polymerized with different curing methods

Aim To compare the relative cytotoxicity of resin-based composite materials polymerized with three different curing methods on L 929 cells over a period of 1 week. Methodology Ten discs of each material (Flowline(R), P 60(R) and Z 250(R)) were cured from one side with either standard cure (Optilux 401(R)), soft-start cure (Elipar Free Light(R)) or fast cure (Hilux Ultra Plus(R)). Then the samples were aged for 1, 2, 3, 5 and 7 days in Dulbecco's Modified Eagle Medium/Ham's F12 (DMEM/F12). After each ageing interval, cytotoxicity of the extracts to cultured fibroblasts (L 929) was measured by MTT assay. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells with a pure culture medium. Statistical significance was determined by one-way analysis of variance (ANOVA), followed by the Student's Newman-Keuls test. Results Exposure of L 929 cells to the test materials resulted in a high survival fraction at 1 and 7 days. Flowline(R) specimens, either cured with Optilux 401(R) or Elipar Free Light(R), had no toxic effect on the cells, whereas the other groups were moderately toxic on the 2-day interval. All experimental groups presented lower cell viability than the control at the 3- and 5-day intervals. Conclusions The composite resins used in this study were cytotoxic after 48 h pre-incubation, but this toxicity disappeared after pre-incubation in a biological medium for 7 days. Curing did not have a significant effect on the cytotoxicity of the composite materials tested.