title: Use of different concentrations of carbamide peroxide for bleaching teeth: an in vitro study.
abstract: OBJECTIVE
  This in vitro study compared the shade changes in extracted teeth during 2 weeks' whitening with 5%, 10%, or 16% carbamide peroxide.
  
  
  METHODS
  After color calibration, the sole examiner selected 110 extracted unrestored, noncarious teeth, shade A3 or darker on a value-oriented guide. The teeth were randomly distributed into equal color groups. The control group (11 teeth) was treated with 0.9% saline, while the experimental groups (33 teeth each) were treated with 5%, 10%, or 16% carbamide peroxide. The solutions remained on the teeth for 8 hours. The teeth and tray were rinsed with tap water for 2 minutes, then rehydrated in 0.9% saline for 16 hours in the humidifier. The shade was assessed, and the process was repeated daily for 2 weeks.
  
  
  RESULTS
  Repeated-measures analysis of variance indicated a significant difference in overall shade values between the control and all carbamide peroxide-treated groups at days 8 and 15. A Kaplan-Meier Survival Analysis indicated a quicker two-tab color change for the 10% and 16% groups than the 5% group. However, continuation of the 5% treatment to 3 weeks resulted in shades that approached the 2-week 10% and 16% values.
  
  
  CONCLUSIONS
  Lower concentrations of carbamide peroxide take longer to whitening teeth but eventually achieve the same result as higher concentrations. Higher concentrations may cause increased sensitivity.
authors.affiliation: Department of Diagnostic Sciences/General Dentistry, University of North Carolina, School of Dentistry, Chapel Hill 27599-7450, USA.
authors.forename: R H
authors.initials: RH
authors.lastname: Leonard
authors.forename: A
authors.initials: A
authors.lastname: Sharma
authors.forename: V B
authors.initials: VB
authors.lastname: Haywood
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D000077463:Carbamide Peroxide; D003481:Cuspid; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D006801:Humans; D007180:Incisor; D010545:Peroxides / Q000008:administration & dosage*; D016019:Survival Analysis; D014073:Tooth Bleaching / Q000379:methods*; D014075:Tooth Discoloration / Q000628:therapy*; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives*
chemical_list: D004338:Drug Combinations; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea