title: Trans-enamel and trans-dentinal cytotoxic effects of a 35% H2O2 bleaching gel on cultured odontoblast cell lines after consecutive applications.
abstract: OBJECTIVE
  To evaluate the trans-enamel and trans-dentinal cytotoxic effects of a 35% H(2)O(2) bleaching gel on an odontoblast-like cell lines (MDPC-23) after consecutive applications.
  
  
  METHODS
  Fifteen enamel/dentine discs were obtained from bovine central incisor teeth and placed individually in artificial pulp chambers. Three groups (n = 5 discs) were formed according to the following enamel treatments: G1: 35% H(2)O(2) bleaching gel (15 min); G2: 35% H(2)O(2) bleaching gel (15 min) + halogen light (20 s); G3: control (no treatment). After repeating the treatments three consecutive times, the extracts (culture medium + gel components that had diffused through enamel/dentine discs) in contact with the dentine were collected and applied to previously cultured MDPC-23 cells (50 000 cells cm(-2)) for 24 h. Cell metabolism was evaluated by the MTT assay and data were analysed statistically (alpha = 5%; Kruskal-Wallis and Mann-Whitney U-test). Cell morphology was analysed by scanning electron microscopy.
  
  
  RESULTS
  Cell metabolism decreased by 92.03% and 82.47% in G1 and G2 respectively. G1 and G2 differed significantly (P < 0.05) from G3. Regardless of halogen light activation, the application of the bleaching gel on the cultured odontoblast-like cells caused significantly more severe cytotoxic effects than those observed in the nontreated control group. In addition, significant morphological cell alterations were observed in G1 and G2.
  
  
  CONCLUSIONS
  After three consecutive applications of a 35% H(2)O(2) bleaching agent, the diffusion of the gel components through enamel and dentine caused severe toxic effects to cultured pulp cells.
authors.affiliation: Departments of Dental Materials and Prosthodontics, Araraquara School of Dentistry, São Paulo State University, Araraquara, SP, Brazil.
authors.forename: F Z
authors.initials: FZ
authors.lastname: Trindade
authors.forename: A P D
authors.initials: AP
authors.lastname: Ribeiro
authors.forename: N T
authors.initials: NT
authors.lastname: Sacono
authors.forename: C F
authors.initials: CF
authors.lastname: Oliveira
authors.forename: F C R
authors.initials: FC
authors.lastname: Lessa
authors.forename: J
authors.initials: J
authors.lastname: Hebling
authors.forename: C A S
authors.initials: CA
authors.lastname: Costa
mesh_terms: D000287:Administration, Topical; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D003743:Dental Enamel / Q000187:drug effects; D003745:Dental Enamel Permeability / Q000187:drug effects*; D003804:Dentin / Q000187:drug effects; D003806:Dentin Permeability / Q000187:drug effects*; D004334:Drug Administration Schedule; D006861:Hydrogen Peroxide / Q000008:administration & dosage / Q000633:toxicity*; D008027:Light; D009804:Odontoblasts / Q000187:drug effects* / Q000528:radiation effects; D016877:Oxidants / Q000008:administration & dosage / Q000633:toxicity; D018709:Statistics, Nonparametric; D014073:Tooth Bleaching / Q000009:adverse effects* / Q000379:methods
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide