title: The effect of tooth bleaching on the enamel surface and the tensile force to debond orthodontic brackets.
abstract: OBJECTIVE
  The aim of this study was to evaluate the influence of successive tooth bleaching on the tensile force to debond orthodontic brackets and dental enamel.
  
  
  METHODS
  In vitro study.
  
  
  METHODS
  Department of Orthodontics, Faculty of Dentistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
  
  
  METHODS
  Seventy-two human premolars were divided into three groups: Group 1 was not submitted to bleaching, Group 2 was subjected to one tooth bleaching (35% hydrogen peroxide enabled by LEDs) and Group 3 was subjected to two tooth bleachings interspersed by aging. Twenty teeth from each group were subjected to tensile test, failure pattern after debonding and evaluation of resin/enamel interface. Four teeth from each group were not submitted to tensile bond testing and had their external surfaces and internal structure analyzed by SEM and polarized light microscopy.
  
  
  RESULTS
  The strength of the brackets decreased in Groups 2 and 3, but was not significant (P=0.635). In general, the failure pattern appeared at the resin/bracket interface or within the resin. The experimental groups showed an increase in slots and erosions on the surface of the enamel and were more pronounced in Group 3. There were no changes to the internal structure of the enamel.
  
  
  CONCLUSIONS
  The use of a 35% hydrogen peroxide in-office bleaching system, in vitro, seven days before bonding, does not significantly reduce the tensile force to debond orthodontic brackets, even after a second bleaching procedure. In most cases, debonding occurred at the adhesive/bracket interface or within the adhesive. Bleaching alters the enamel surface and the resin/enamel interface, but it does not influence bond strength.
authors.affiliation: Associate professor, Department of Orthodontics, Faculty of Dentistry, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Fernanda D
authors.initials: FD
authors.lastname: Mishima
authors.forename: Raquel Gomes A
authors.initials: RG
authors.lastname: Valentim
authors.forename: Monica Tirre S
authors.initials: MT
authors.lastname: Araújo
authors.forename: Antonio Carlos O
authors.initials: AC
authors.lastname: Ruellas
authors.forename: Eduardo F
authors.initials: EF
authors.lastname: Sant'Anna
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D001641:Bicuspid / Q000187:drug effects / Q000648:ultrastructure; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D017005:Dental Debonding; D003743:Dental Enamel / Q000187:drug effects* / Q000648:ultrastructure; D006801:Humans; D006813:Humidity; D006861:Hydrogen Peroxide / Q000627:therapeutic use*; D008027:Light; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets; D016877:Oxidants / Q000627:therapeutic use*; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012464:Saliva, Artificial / Q000737:chemistry; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D014466:Ultraviolet Rays
chemical_list: D003722:Dental Alloys; D016877:Oxidants; D010756:Phosphoric Acids; D019279:Resin Cements; D012464:Saliva, Artificial; C477790:Transbond XT; D013193:Stainless Steel; D006861:Hydrogen Peroxide; C030242:phosphoric acid