title: Cytotoxic effect of a 35% hydrogen peroxide bleaching gel on odontoblast-like MDPC-23 cells.
abstract: OBJECTIVE
  This study evaluated transenamel and transdentinal cytotoxic effects of a bleaching gel on the MDPC-23 cell line.
  
  
  METHODS
  Discs obtained from bovine incisors were placed in a metallic device to simulate an in vivo pulp chamber. Groups were formed according to the enamel surface treatment: G1: 35% H(2)O(2) bleaching gel; G2: 35% H(2)O(2) bleaching gel + halogen light; G3: halogen light; and G4: control. Cell metabolism was evaluated by the methyltetrazolium assay and cell morphology by scanning electron microscopy.
  
  
  RESULTS
  Cell metabolism decreased by 31.7%, 41.6%, and 11.5% in G1, G2, and G3, respectively. Cytotoxic effects observed in G2 were significantly more severe compared with G3 and G4. In G1 and G2, a smaller number of viable cells with major morphologic alterations remained adhered to dentin.
  
  
  CONCLUSIONS
  The bleaching gel associated with light presented transenamel and transdentinal cytotoxic effects characterised by direct damage to odontoblasts and decrease of their metabolic activity.
authors.affiliation: Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry, São Paulo State University, Araraquara, Brazil.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Dias Ribeiro
authors.forename: Nancy Tomoko
authors.initials: NT
authors.lastname: Sacono
authors.forename: Fernanda Campos Rosetti
authors.initials: FC
authors.lastname: Lessa
authors.forename: Indri
authors.initials: I
authors.lastname: Nogueira
authors.forename: Cármen Regina
authors.initials: CR
authors.lastname: Coldebella
authors.forename: Josimeri
authors.initials: J
authors.lastname: Hebling
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: de Souza Costa
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004396:Coloring Agents; D003743:Dental Enamel / Q000187:drug effects; D003804:Dentin / Q000187:drug effects; D004058:Diffusion; D005782:Gels; D006861:Hydrogen Peroxide / Q000633:toxicity*; D008027:Light; D008855:Microscopy, Electron, Scanning; D009804:Odontoblasts / Q000187:drug effects*; D016877:Oxidants / Q000633:toxicity*; D011897:Random Allocation; D013778:Tetrazolium Salts; D013844:Thiazoles; D014073:Tooth Bleaching
chemical_list: D004396:Coloring Agents; D005782:Gels; D016877:Oxidants; D013778:Tetrazolium Salts; D013844:Thiazoles; D006861:Hydrogen Peroxide; C022616:thiazolyl blue