title: Two-year clinical evaluation of tooth whitening using an at-home bleaching system.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the 2-year effectiveness of a carbamide peroxide at-home bleaching gel used to provide tooth lightening treatment.
  
  
  METHODS
  Twenty-nine patients participated in the original study, during which they treated their maxillary teeth with a 10% carbamide peroxide gel nightly for 2 weeks. Shades were determined before and after treatment by comparison with a Vita shade guide. Twenty-four patients (a recall rate of 83%) were recalled for evaluation 2 years after the initial bleaching treatment. The shade of the maxillary incisors was evaluated and compared with shades before, immediately after, and at 6 months and 2 years after initial treatment. Data were analyzed using a repeated-measures analysis of variance.
  
  
  RESULTS
  At 2 years after bleaching with a 10% carbamide peroxide gel, the median shade was D2, a six-increment difference from the baseline median of D3. Twenty of 24 patients (83.3%) had a shade change of two or more units, which is the threshold value for bleaching efficacy using American Dental Association guidelines. The lightening result remained statistically significant (p < .0001) at 2 years.
  
  
  CONCLUSIONS
  Although some reversal of the lightening effect occurs over time following the original bleaching treatment, loss of the lighter color appears to be gradual for most patients. Although the longevity of the lightening effect remains to be determined, this clinical trial indicates that the majority of patients have a satisfactory result 2 years after treatment.
authors.affiliation: Department of Operative Dentistry, School of Dentistry, University of North Carolina at Chapel Hill, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Swift
authors.forename: K N
authors.initials: KN
authors.lastname: May
authors.forename: A D
authors.initials: AD
authors.lastname: Wilder
authors.forename: H O
authors.initials: HO
authors.lastname: Heymann
authors.forename: S C
authors.initials: SC
authors.lastname: Bayne
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000077463:Carbamide Peroxide; D003116:Color; D004338:Drug Combinations; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010545:Peroxides / Q000627:therapeutic use*; D011795:Surveys and Questionnaires; D014073:Tooth Bleaching / Q000379:methods*; D014075:Tooth Discoloration / Q000628:therapy*; D014508:Urea / Q000031:analogs & derivatives* / Q000627:therapeutic use
chemical_list: D004338:Drug Combinations; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea