title: Shear Bond Strength of Orthodontic Brackets to Tooth Enamel After Treatment With Different Tooth Bleaching Methods.
abstract: BACKGROUND
  Bleaching treatments decrease shear bond strength between orthodontic brackets and teeth; although definite results have not been reported in this regard.
  
  
  OBJECTIVE
  This study determined the effects of different bleaching protocols on the shear bond strength of orthodontic brackets to teeth.
  
  
  METHODS
  This experimental study was performed in Iran. Forty-eight extracted human premolars were randomly assigned into four groups. In the control group, no bleaching treatment was performed. In groups 2 - 4, the bleaching procedures were performed using carbamide peroxide 45%, carbamide peroxide 20% and diode laser, respectively. Two weeks later, brackets were bonded to teeth and thermocycled. The shear bond strengths of the brackets to the teeth were measured. Data was analyzed by one-way ANOVA and Dunnett post-hoc test.
  
  
  RESULTS
  Shear bond strength of the brackets to the teeth were 10.54 ± 1.51, 6.37 ± 0.92, 7.67 ± 1.01 and 7.49 ± 1.19 MPa, in groups 1 - 4, respectively. Significant differences were found between control group and all other groups (P < 0.001); and also between groups 2 and 3 (P < 0.05). No significant differences were found between the other groups.
  
  
  CONCLUSIONS
  The bleaching procedures using 20% carbamide peroxide and 45% carbamide peroxide and diode laser significantly decreased shear bond strength of brackets to the teeth. 45% carbamide peroxide had a more significant effect on bond strength compared to 20% carbamide peroxide. The difference in bond strength was not significant between laser group and either carbamide peroxide groups.
authors.affiliation: Department of Orthodontics, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Elahe
authors.initials: E
authors.lastname: Vahid Dastjerdi
authors.affiliation: Department of Operative Dentistry, Dental School, International Branch of Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Negar
authors.initials: N
authors.lastname: Khaloo
authors.affiliation: Department of Laser and Surgery, Dental School, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Seyed Masoud
authors.initials: SM
authors.lastname: Mojahedi
authors.affiliation: Department of Operative Dentistry, Dental School, International Branch of Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Mohadese
authors.initials: M
authors.lastname: Azarsina
keywords: Carbamide Peroxide; Hydrogen Peroxide; Shear Strength; Tooth Bleaching