title: Cytotoxicity of monomers, plasticizer and degradation by-products released from dental hard chairside reline resins.
abstract: OBJECTIVE
  The aim of this study was to evaluate the cytotoxic effect of the monomers isobutyl methacrylate (IBMA) and 1,6-hexanediol dimethacrylate (1,6-HDMA), the plasticizer di-n-butyl phthalate (DBP), and the degradation by-products methacrylic acid (MA) and benzoic acid (BA) on L929 cells. Based on previous investigations on the release of these compounds from hard chairside reline resins, a range of concentrations (micromol/L) were selected for the cytotoxicity tests (IBMA, 5.49-1406.57; 1,6-HDMA, 1.22-39.32; DBP, 1.12-143.8; MA, 9.07-581; BA, 3.19-409).
  
  
  METHODS
  Cytotoxic effects were assessed using MTT and (3)H-thymidine assays after the cells had been exposed to the test compounds at the given concentrations for 24 h. Cytotoxicity was rated based on cell viability relative to controls (cells exposed to medium without test substances).
  
  
  RESULTS
  DNA synthesis activity was inhibited by all compounds. Mitochondrial dehydrogenase activity decreased in cells treated with monomers, plasticizer and MA by-product, whereas no cytotoxic effect was observed on contact with BA at the majority of concentrations tested. The ranges of suppression for (3)H-thymidine assay were: IBMA, 25-95%; 1,6-HDMA, 95-98%; DBP, 40-98%; MA, 97-99%; BA, 54-71%. For MTT assay, the ranges of suppression were: IBMA, 0-96%; 1,6-HDMA, 26-89%; DBP, 17-80%; MA, 52-66%; BA, 0-27%. The (3)H-thymidine assay was more sensitive than the MTT assay.
  
  
  CONCLUSIONS
  This study evaluated the cytotoxicity of a wide range of concentrations of monomers (IBMA and 1,6-HDMA), plasticizer (DBP) and degradation by-products (MA and BA), including those expected to be released from hard chairside reline resins. The differences observed in the cytotoxicity of these compounds, along with other properties, may assist the dental practitioners in the selection of reline materials with improved service life performance and low risk of adverse reactions in patients who wear relined dentures.
authors.affiliation: UNESP - Univ Estadual Paulista, Araraquara Dental School, Department of Dental Materials and Prosthodontics, Rua Humaitá, 1680, Araraquara, CEP 14801-903, São Paulo, Brazil.
authors.forename: Carolina de Andrade Lima
authors.initials: CA
authors.lastname: Chaves
authors.forename: Ana Lucia
authors.initials: AL
authors.lastname: Machado
authors.forename: Iracilda Zeppone
authors.initials: IZ
authors.lastname: Carlos
authors.forename: Eunice Teresinha
authors.initials: ET
authors.lastname: Giampaolo
authors.forename: Ana Cláudia
authors.initials: AC
authors.lastname: Pavarina
authors.forename: Carlos Eduardo
authors.initials: CE
authors.lastname: Vergani
mesh_terms: D000818:Animals; D019817:Benzoic Acid / Q000633:toxicity*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D004249:DNA Damage; D003822:Denture Liners / Q000009:adverse effects*; D003823:Denture Rebasing / Q000009:adverse effects; D003993:Dibutyl Phthalate / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects; D007739:L Cells; D008689:Methacrylates / Q000633:toxicity*; D051379:Mice; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D010968:Plasticizers / Q000633:toxicity*; D013778:Tetrazolium Salts / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism
chemical_list: D008689:Methacrylates; D033681:Mitochondrial Membrane Transport Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D010968:Plasticizers; D013778:Tetrazolium Salts; C008384:methacrylic acid; D003993:Dibutyl Phthalate; D019817:Benzoic Acid; D013936:Thymidine