title: Effect of incorporation of remineralizing agents into bleaching gels on the microhardness of bovine enamel in situ.
abstract: OBJECTIVE
  This study evaluated the effect of adding calcium or fluoride to 35% hydrogen peroxide (HP) bleaching gel and the effect of human saliva on the microhardness of sound and demineralized enamel, using an in situ model.
  
  
  METHODS
  Cylindrical bovine enamel specimens (3 × 2 mm) were divided into two groups (n = 30): sound enamel (SE) and demineralized enamel (DE). Each group was divided into three subgroups, according to the bleaching gel: 35% HP; 35% HP + calcium; 35% HP + fluoride. After bleaching therapy, the specimens were fixed to intraoral devices worn by 10 volunteers for 7 days. Surface enamel microhardness (SMH) was measured before and after bleaching procedures, and after 1 and 7 days of saliva exposure. Data were analyzed by Repeated Measures ANOVA (5%).
  
  
  RESULTS
  The variable time resulted in significant differences for SE and DE groups (p = 0.001). For SE, significantly lower SMH was detected for control at post-bleaching period in comparison to the baseline and after 7 days. For DE, the lowest mean values were obtained before bleaching, and the addition of calcium to the peroxide significantly increased enamel SMH. The exposure to human saliva resulted in increased SMH.
  
  
  CONCLUSIONS
  The addition of potential remineralizing agents into bleaching gels might play an important role in maintaining the microhardness of sound enamel and in inducing remineralization of artificially demineralized enamel right after bleaching, and the remineralizing action of human saliva might minimize the deleterious effects of bleaching gels on enamel. Clinical significance: The incorporation of calcium into HP bleaching gel might be beneficial for the initial phases of the bleaching procedure.
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, UNESP-Univ Estadual Paulista, Institute of Science and Technology, Säo José dos Campos, Säo Paulo, Brazil.
authors.forename: Alessandra Bühler
authors.initials: AB
authors.lastname: Borges
authors.affiliation: Graduate Student, Department of Restorative Dentistry, UNESP-Univ Estadual Paulista, Institute of Science and Technology, Säo José dos Campos, Säo Paulo, Brazil.
authors.forename: Carolina Anne
authors.initials: CA
authors.lastname: Guimaräes
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, UNESP-Univ Estadual Paulista, Institute of Science and Technology, Säo José dos Campos, Säo Paulo, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Bresciani
authors.affiliation: Adjunct Assistant Professor, Department of Social Dentistry and Pediatric Clinics, UNESP-Univ Estadual Paulista, Institute of Science and Technology Säo José dos Campos, Säo Paulo, Brazil.
authors.forename: Carolina Judica
authors.initials: CJ
authors.lastname: Ramos
authors.affiliation: Assistant Professor, Department of Dental Materials and Prosthodontics, UNESP-Univ Estadual Paulista, Institute of Science and Technology Säo José dos Campos, Säo Paulo, Brazil.
authors.forename: Alexandre Luiz Souto
authors.initials: AL
authors.lastname: Borges
authors.affiliation: Associate Professor, Department of Restorative Dentistry, UNESP-Univ Estadual Paulista, Institute of Science and Technology, Säo José dos Campos, Säo Paulo, Brazil.
authors.forename: Carlos
authors.initials: C
authors.lastname: Rocha Gomes Torres
mesh_terms: D000818:Animals; D002118:Calcium / Q000008:administration & dosage*; D002327:Cariostatic Agents / Q000008:administration & dosage*; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects*; D005459:Fluorides / Q000008:administration & dosage*; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D012463:Saliva / Q000502:physiology; D013997:Time Factors; D058205:Tooth Bleaching Agents / Q000008:administration & dosage*; D017001:Tooth Demineralization / Q000503:physiopathology; D014089:Tooth Remineralization / Q000379:methods*
chemical_list: D002327:Cariostatic Agents; D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide; D005459:Fluorides; D002118:Calcium