title: Transenamel and transdentinal cytotoxicity of carbamide peroxide bleaching gels on odontoblast-like MDPC-23 cells.
abstract: OBJECTIVE
  To evaluate the transenamel and transdentinal cytotoxicity of bleaching gels based on carbamide peroxide (CP) on odontoblast-like cells after different contact times of the products with enamel.
  
  
  METHODS
  Enamel/dentine discs were obtained from bovine incisors and placed in artificial pulp chambers. Bleaching gels containing 10% or 16% CP were applied for 8 h day(-1) on the enamel side of the discs during periods of 1, 7 or 14 days. Deionized water and artificial saliva served as controls. The extracts (culture medium plus bleaching gel products that diffused through the discs) were collected and applied on previously cultured MDPC-23 cells for 1 h. Cell metabolism was evaluated by the MTT assay, and the data were analysed statistically by one-way anova and Tukey's test (α=0.05). Cell morphology was analysed by SEM.
  
  
  RESULTS
  There was no significant difference (P>0.05) between the controls and the groups bleached with 10% CP gel. In the groups bleached with 16% CP gel, however, cell metabolism decreased significantly (P<0.05) by 40.32%, 30.16% and 26.61% at 1, 7 and 14 days, respectively. There was no significant difference (P>0.05) between 1, 7 or 14 applications of the gels for either of the CP concentrations.
  
  
  CONCLUSIONS
  Regardless of the number of applications on an enamel surface, the 10% CP bleaching gel did not cause transenamel and transdentinal cytotoxicity to the MDPC-23 cell cultures. However, diffusion of products from the 16% CP gel through enamel and dentine and cytopathic effects to the pulp cells occurred even after a single application of this product on enamel.
authors.affiliation: Department of Dental Materials and Prosthodontics, University of Estadual Paulista, Araraquara School of Dentistry, Araraquara, SP, Brazil.
authors.forename: D G S
authors.initials: DG
authors.lastname: Soares
authors.forename: A P D
authors.initials: AP
authors.lastname: Ribeiro
authors.forename: N T
authors.initials: NT
authors.lastname: Sacono
authors.forename: C R
authors.initials: CR
authors.lastname: Coldebella
authors.forename: J
authors.initials: J
authors.lastname: Hebling
authors.forename: C A de Souza
authors.initials: CA
authors.lastname: Costa
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000077463:Carbamide Peroxide; D002417:Cattle; D002478:Cells, Cultured; D003743:Dental Enamel / Q000187:drug effects*; D003745:Dental Enamel Permeability / Q000187:drug effects; D003804:Dentin / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005782:Gels; D009804:Odontoblasts / Q000187:drug effects*; D010545:Peroxides / Q000493:pharmacokinetics / Q000633:toxicity*; D018709:Statistics, Nonparametric; D013997:Time Factors; D058205:Tooth Bleaching Agents / Q000493:pharmacokinetics / Q000633:toxicity*; D014508:Urea / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000633:toxicity
chemical_list: D005782:Gels; D010545:Peroxides; D058205:Tooth Bleaching Agents; D000077463:Carbamide Peroxide; D014508:Urea