title: Evaluation of an experimental rat model for comparative studies of bleaching agents.
abstract: Dental materials, in general, are tested in different animal models prior to their clinical use in humans, except for bleaching agents.
  
  
  OBJECTIVE
  To evaluate an experimental rat model for comparative studies of bleaching agents by investigating the influence of different concentrations and application times of H2O2 gel in the pulp tissue during in-office bleaching of rats' vital teeth.
  
  
  METHODS
  The right and left maxillary molars of 50 Wistar rats were bleached with 20% and 35% H2O2 gels, respectively, for 5, 10, 15, 30, or 45 min (n=10 rats/group). Ten animals (control) were untreated. The rats were killed after 2 or 30 days, and the maxillae were examined by light microscopy. Inflammation was evaluated by histomorphometric analysis with inflammatory cell counting in the coronal and radicular thirds of the pulp. The counting of fibroblasts was also performed. Scores were attributed to the odontoblastic layer and to vascular changes. The tertiary dentin area and the pulp chamber central area were histomorphometrically measured. Data were compared by the analysis of variance and the Kruskal-Wallis test (p<0.05).
  
  
  RESULTS
  After 2 days, the amount of inflammatory cells increased in the occlusal third of the coronal pulp until the time of 15 min for both concentrations of bleaching gels. In 30 and 45 min groups of each concentration, the number of inflammatory cells decreased along with the appearance of necrotic areas. After 30 days, a reduction in the pulp chamber central area and an enlargement of tertiary dentin area were observed without the detection of inflammation areas.
  
  
  CONCLUSIONS
  The rat model of extra coronal bleaching showed to be adequate for bleaching protocols studies, as it was possible to observe alterations in the pulp tissues and in the tooth structure caused by different concentrations and periods of application of bleaching agents.
authors.affiliation: Departamento de Endodontia, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: Luciano Tavares Angelo
authors.initials: LT
authors.lastname: Cintra
authors.affiliation: Departamento de Endodontia, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: Francine
authors.initials: F
authors.lastname: Benetti
authors.affiliation: Departamento de Endodontia, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: Luciana Lousada
authors.initials: LL
authors.lastname: Ferreira
authors.affiliation: Departamento de Odontologia Restauradora, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Rahal
authors.affiliation: Departamento de Ciências Básicas, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: Edilson
authors.initials: E
authors.lastname: Ervolino
authors.affiliation: Departamento de Endodontia, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: Rogério de Castilho
authors.initials: Rde C
authors.lastname: Jacinto
authors.affiliation: Departamento de Endodontia, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: João Eduardo
authors.initials: JE
authors.lastname: Gomes Filho
authors.affiliation: Departamento de Odontologia Restauradora, Faculdade de Odontologia de Araçatuba, Univ. Estadual Paulista, Araçatuba, SP, Brasil.
authors.forename: André Luiz Fraga
authors.initials: AL
authors.lastname: Briso
mesh_terms: D000818:Animals; D002452:Cell Count; D003782:Dental Pulp / Q000187:drug effects* / Q000473:pathology; D003786:Dental Pulp Cavity; D005347:Fibroblasts / Q000187:drug effects; D005782:Gels; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D008297:Male; D023421:Models, Animal; D009804:Odontoblasts / Q000187:drug effects; D017208:Rats, Wistar; D015203:Reproducibility of Results; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000008:administration & dosage*
chemical_list: D005782:Gels; D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide