title: In-vitro study of cellular viability and nitric oxide production by J774 macrophages stimulated by interferon gamma with ceramic, polycarbonate, and polyoxymethylene brackets.
abstract: BACKGROUND
  Ceramic brackets are chemically inert in the oral cavity, whereas polycarbonate and polyoxymethylene brackets can degrade and release bisphenol-A and formaldehyde, respectively. More reliable tests are needed to assess the potential toxicity of these materials. In addition to traditional cytotoxicity tests, the study of nitric oxide (NO) cellular production stimulated by a specific material has been shown to be a reliable tool for evaluating cytotoxic potential. The purpose of this study was to assess, with esthetic brackets, cellular viability by 3,(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay (Sigma, St. Louis, Mo) in the macrophage cell line J774 stimulated with interferon gamma. Interferon gamma is a key cytokine in the activation of macrophages, plays an important role in immunologic processes, and also quantifies NO production by these macrophages.
  
  
  METHODS
  Well plates were seeded with 2 x 104 J774 cells per well, in a volume of 100 microL, resuspended in Roswell Park Memorial Institute Supplemented Medium 1640. The macrophage cell line J774 was stimulated with interferon gamma. Ceramic, polycarbonate, and polyoxymethylene brackets were added and kept in the culture for 24, 48, or 72 hours in 5% carbon dioxide at 37 degrees C; the control samples did not include brackets. At the end of each incubation period, the supernatant was collected for posterior NO quantification, and the cells were evaluated for cytotoxicity.
  
  
  RESULTS
  Cellular viability in all groups was higher at 72 hours than at 24 hours. The final means in the bracket groups did not show significant differences compared with the control group. NO production was significantly greater in all groups at the final time than at the initial time. However, the brackets with the interferon gamma stimulation did not result in greater NO production than did the cells in the control group.
authors.affiliation: Department of Orthodontics, Juiz de Fora Federal University, Juiz de Fora, Minas Gerais, Brazil.
authors.forename: Julia Cristina de Andrade
authors.initials: JC
authors.lastname: Vitral
authors.forename: Marcelo Reis
authors.initials: MR
authors.lastname: Fraga
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: de Souza
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Ferreira
authors.forename: Robert Willer Farinazzo
authors.initials: RW
authors.lastname: Vitral
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002516:Ceramics / Q000633:toxicity*; D004396:Coloring Agents; D003764:Dental Materials / Q000633:toxicity*; D007371:Interferon-gamma / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000166:cytology / Q000187:drug effects*; D008422:Materials Testing; D051379:Mice; D009569:Nitric Oxide / Q000032:analysis / Q000096:biosynthesis*; D016910:Orthodontic Brackets; D011076:Polycarboxylate Cement / Q000633:toxicity*; D012117:Resins, Synthetic / Q000633:toxicity*; D013696:Temperature; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
chemical_list: D004396:Coloring Agents; D003764:Dental Materials; D011076:Polycarboxylate Cement; D012117:Resins, Synthetic; D013778:Tetrazolium Salts; D013844:Thiazoles; C005506:polycarbonate; D009569:Nitric Oxide; D007371:Interferon-gamma; C010102:delrin; C022616:thiazolyl blue