title: Can intracoronally bleached teeth be bonded safely?
abstract: BACKGROUND
  Our objective was to determine the effects of intracoronal bleaching on the shear bond strength and failure side location of metallic brackets at 2 times (bleaching immediately before bonding and 30 days before bonding).
  
  
  METHODS
  Sixty freshly extracted mandibular incisors were randomly divided into 3 groups; each group contained 20 teeth. After finishing canal preparation and root canal filling, the root fillings were removed to a level 2 mm apical to the cementoenamel junction. Glass ionomer base (Vitrabond, 3 M Dental Products, St Paul, Minn) was placed approximately 2-mm thick. Bleaching agent (Whiteness Perfect, FGM Dental Products, Joinville, Brazil) was placed into the rest of the cavity for 4 days at 2 times. Shear bond strength of these brackets was measured in megapascals. The adhesive remnant index (ARI) scores were determined after the brackets failed. Data were analyzed with analysis of variance (ANOVA), Tukey, and chi-square tests.
  
  
  RESULTS
  The bond strengths of the group with no bleaching (mean, 20.25 +/- 7.06 MPa) were significantly higher (P >0.001) than those of the group that had bleaching immediately before bonding (mean, 4.85 +/- 3.22 MPa) and the group that had bleaching 30 days before bonding (mean, 8.70 +/- 4.93 MPa). The results of the chi-square comparisons indicated significant differences among the 3 groups. In the group with no bleaching, there was a higher frequency of ARI scores of 2 to 4, indicating cohesive failures in the resin. In the other 2 groups, the failures were mostly adhesive at the resin-enamel interface (ARI scores of 4 and 5).
  
  
  CONCLUSIONS
  Intracoronal bleaching with carbamide peroxide adversely affected the shear bond strength and changed the site of failure during debonding when bonding was done immediately or 30 days after bleaching.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey. tancanuysal@yahoo.com
authors.forename: Tancan
authors.initials: T
authors.lastname: Uysal
authors.forename: Ozgur
authors.initials: O
authors.lastname: Er
authors.forename: Burak
authors.initials: B
authors.lastname: Sagsen
authors.forename: Ayca
authors.initials: A
authors.lastname: Ustdal
authors.forename: Gulsen
authors.initials: G
authors.lastname: Akdogan
mesh_terms: D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D001840:Dental Bonding; D017005:Dental Debonding; D003743:Dental Enamel / Q000187:drug effects; D003786:Dental Pulp Cavity / Q000187:drug effects; D003799:Dental Stress Analysis; D003804:Dentin / Q000187:drug effects; D004338:Drug Combinations; D006801:Humans; D007180:Incisor; D008334:Mandible; D016910:Orthodontic Brackets; D016877:Oxidants / Q000494:pharmacology; D010545:Peroxides / Q000494:pharmacology; D033081:Shear Strength; D018709:Statistics, Nonparametric; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D019553:Tooth, Nonvital; D014508:Urea / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea