title: Cytotoxicity of two autopolymerized acrylic resins used in orthodontics.
abstract: 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.
  
  
  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.
authors.affiliation: Department of Orthodontics, Pontifical Catholic University of Rio Grande do Sul, Rio Grande do Sul, Brazil. tatianasgoncalves@terra.com.br
authors.forename: Tatiana
authors.initials: T
authors.lastname: Siqueira Gonçalves
authors.forename: Virgínia
authors.initials: V
authors.lastname: Minghelli Schmitt
authors.forename: Melissa
authors.initials: M
authors.lastname: Thomas
authors.forename: Maria Antonieta
authors.initials: MA
authors.lastname: Lopes de Souza
authors.forename: Luciane
authors.initials: L
authors.lastname: Macedo de Menezes
mesh_terms: D000180:Acrylic Resins / Q000633:toxicity*; D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D003764:Dental Materials / Q000633:toxicity*; D004847:Epithelial Cells / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D008422:Materials Testing; D008768:Methylmethacrylates / Q000633:toxicity; D051379:Mice; D041681:NIH 3T3 Cells; D009967:Orthodontic Appliances; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
chemical_list: D000180:Acrylic Resins; D004396:Coloring Agents; D017077:Culture Media, Conditioned; D003764:Dental Materials; D008768:Methylmethacrylates; C463899:Orthoresin; D013778:Tetrazolium Salts; D013844:Thiazoles; C069716:Jet, dental resin; C022616:thiazolyl blue