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J Orthod Sci. 2017 Jan-Mar;6(1):16-21. doi: 10.4103/2278-0203.197394.

Efficacy of quercetin flavonoid in recovering the postbleaching bond strength of orthodontic brackets: A preliminary study.

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Department of Orthodontics, University of Medical Sciences, Babol, Iran.
Department of Pharmacology, University of Medical Sciences, Babol, Iran.
Department of Restorative Dentistry, University of Medical Sciences, Babol, Iran.
Social Determinants of Health Research Center, University of Medical Sciences, Babol, Iran.
Department of Pediatric Dentistry, Dental Branch, Islamic Azad University, Tehran, Iran.



To evaluate comparatively the effect of quercetin on postbleaching shear bond strength (SBS) and adhesive remnant index (ARI).


Intact maxillary premolars were divided randomly into 12 groups of 10 each: (1) bonding the bracket immediately after bleaching, (2) bonding 1 week after bleaching, (3-8) application of three experimental concentrations of quercetin (0.1%, 0.5%, and 1%) at two time durations (5 and 10 min), (9-10) application of the solvent of quercetin at two time periods (5 and 10 min), (11) application of 10% sodium ascorbate for 10 min, and (12) bonding the brackets on nonbleached teeth. Bleaching was performed using 15% carbamide peroxide gel for 5 days (6 h daily). After incubation and thermocycling, the SBS of brackets was measured. The ARI too was recorded at ×20. The data were analyzed statistically (α =0.05).


Bleaching reduced the SBS below 10 Megapascal (MPa) level (P < 0.05) while all the postbleaching treatments (except the application of the solvent of quercetin) recovered the SBS back to values greater than 10 MPa (P < 0.05) and also back to nonbleached SBS levels (P > 0.01). All eight postbleaching treatments had rather similar efficacies (P = 0.1396). The concentration of quercetin (beta = 0.259, P = 0.042) but not its duration (beta = 0.213, P = 0.093) significantly improved its efficacy.


Bleaching can weaken the bond strength of orthodontic brackets below acceptable levels. The application of quercetin or Vitamin C or delaying the bracket bonding improved the postbleaching SBS.


Antioxidants; ascorbic acid; delayed bonding; orthodontic brackets; quercetin; shear bond strength; tooth bleaching

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