title: Comparison of the effect of hydrogel and solution forms of sodium ascorbate on orthodontic bracket-enamel shear bond strength immediately after bleaching: an in vitro study.
abstract: OBJECTIVE
  This study compared the effects of hydrogel and solution forms of sodium ascorbate (SA) with two different application times on bracket bond strength subsequent to bleaching.
  
  
  METHODS
  A total of 72 sound premolars were randomly divided into six groups (n = 12): An unbleached control group (group one) and five experimental groups of carbamide peroxide. Specimens in group two were bonded immediately after bleaching; specimens in groups three and four were bleached, then treated with SA solution for ten minutes and three hours, respectively, and then bonded. In groups five and six, SA hydrogel was used and the specimens were prepared similar to groups three and four, respectively. Following debonding, bond strengths were recorded in MPa. To evaluate the amount of resin left on the enamel surfaces, adhesive remnant index (ARI) scores were used.
  
  
  METHODS
  The bond strength data were analyzed with ANOVA and pairwise comparisons were made by Tukey test. The ARI data were subjected to Kruskal-Wallis test and two-by-two comparisons were made by the Mann-Whitney U test.
  
  
  RESULTS
  There were significant differences in bond strengths between the groups ( P < 0.0005). However, the differences between groups three, four, five and six were not significant. Furthermore, there were no significant differences between group one and groups four and six, whereas the differences between the other groups were significant ( P < 0.05). Regarding ARI, there were significant differences among the groups ( P = 0.004).
  
  
  CONCLUSIONS
  Bleaching significantly decreased the bracket bond strength. Compromised bonding was reversed with a three-hour application of both forms of SA.
authors.affiliation: Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Soodabeh
authors.initials: S
authors.lastname: Kimyai
authors.forename: Siavash Savadi
authors.initials: SS
authors.lastname: Oskoee
authors.forename: Ali
authors.initials: A
authors.lastname: Rafighi
authors.forename: Hadi
authors.initials: H
authors.lastname: Valizadeh
authors.forename: Amir Ahmad
authors.initials: AA
authors.lastname: Ajami
authors.forename: Zahra Norooz Zadeh
authors.initials: ZN
authors.lastname: Helali
mesh_terms: D000704:Analysis of Variance; D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry*; D000077463:Carbamide Peroxide; D001840:Dental Bonding; D003743:Dental Enamel; D006801:Humans; D020100:Hydrogels; D016910:Orthodontic Brackets; D016877:Oxidants; D010545:Peroxides; D012996:Solutions; D018709:Statistics, Nonparametric; D014073:Tooth Bleaching / Q000379:methods; D014508:Urea / Q000031:analogs & derivatives
chemical_list: D000975:Antioxidants; D020100:Hydrogels; D016877:Oxidants; D010545:Peroxides; D012996:Solutions; D000077463:Carbamide Peroxide; D014508:Urea; D001205:Ascorbic Acid