OBJECTIVE: To test in vitro the null hypothesis that the toxic effect of different acrylic resins used in orthodontics cannot be reduced when a prior elution is performed. MATERIALS AND METHODS: Three established cell lines were used (HeLa, NIH3T3, and Hep2) and cultured under standard conditions. Resin segments were immersed in a culture medium and left to elute for 24 and 48 hours. Cells were exposed to medium containing eluates for 24 or 48 hours. The 3-(4,5 dimethyl-2-thiazolyl)-2.5-diphenyl-2H-tetrazolium bromide (MTT) assay was used as the cytotoxicity test. Control cells contained standard medium with no eluate. Analysis of variance and Tukey test were used for statistical analysis. RESULTS: Fibroblastic viability was not affected when the elution time was 24 hours, but treatments showed higher cell viability than controls when the elution time was 48 hours. When left to elute for 24 hours, both resins had a cytotoxic effect on epithelial cells, but this effect was not observed when the elution time was 48 hours. CONCLUSIONS: The hypothesis was rejected as both tested materials showed lower cytotoxic effect when treated with 48-hour elutes compared with 24-hour elutes, which indicates that a longer elution time reduces resin toxicity.
OBJECTIVE: To test in vitro the null hypothesis that the toxic effect of different acrylic resins used in orthodontics cannot be reduced when a prior elution is performed. MATERIALS AND METHODS: Three established cell lines were used (HeLa, NIH3T3, and Hep2) and cultured under standard conditions. Resin segments were immersed in a culture medium and left to elute for 24 and 48 hours. Cells were exposed to medium containing eluates for 24 or 48 hours. The 3-(4,5 dimethyl-2-thiazolyl)-2.5-diphenyl-2H-tetrazolium bromide (MTT) assay was used as the cytotoxicity test. Control cells contained standard medium with no eluate. Analysis of variance and Tukey test were used for statistical analysis. RESULTS: Fibroblastic viability was not affected when the elution time was 24 hours, but treatments showed higher cell viability than controls when the elution time was 48 hours. When left to elute for 24 hours, both resins had a cytotoxic effect on epithelial cells, but this effect was not observed when the elution time was 48 hours. CONCLUSIONS: The hypothesis was rejected as both tested materials showed lower cytotoxic effect when treated with 48-hour elutes compared with 24-hour elutes, which indicates that a longer elution time reduces resin toxicity.