title: [Assessment of tooth bleaching efficacy with spectrophotometer].
abstract: OBJECTIVE
  To analyze the changes in CIE L*, a*, and b* at cervical, body, and incisal sites after tooth bleaching by using a spectrophotometer.
  
  
  METHODS
  Sixty-seven intact and healthy maxillary central incisors were in-vestigated. These incisors were darker than A3 according to the Vita Classical shade guide. The CIE tooth shade parameters L*, a*, and b* were simultaneously recorded at three tooth areas (cervical, body, and incisal) with a spectrophotometer before and after tooth bleaching (35%H2O2 coordinating with Beyond whitening accelerator irradiating). The shade dif-ferential (DeltaE) was calculated. ANOVA, paired t-test, and Pearson correlation analysis were used for data analysis.
  
  
  RESULTS
  The efficacy rates of tooth bleaching were satisfactory, with 86.6%, 86.6%, and 85.1% in the cervical, body, and incisal sites, respectively. The average values of DeltaE were 5.09, 4.44, and 4.40 in the cervical, body, and incisal sites. Tooth bleaching significantly increased L* and significantly decreased a* and b* in all tooth areas (P < 0.01). The decreasing range of Deltab* was more than the increasing range of DeltaL* at the cervical site; opposite results were observed at the incisal site. A positive correlation was detected between baseline b* and DeltaE.
  
  
  CONCLUSIONS
  The spectrophotometer could objectively evaluate the whitening effect of tooth bleaching at the different tooth sites. The tooth bleaching system (35%H202 coordinating with Beyond whitening accelerator irradiating) exerts powerful bleaching actions in most of the tooth areas investigated. The order of tooth bleaching effectiveness is cervicalbody>incisal. Yellow coloration is decreased mainly at the cervical site, and brightness was increased mostly at theincisal site. The effectiveness of tooth bleaching increases as the baseline b* value increases.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Zhu
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
authors.forename: Jie
authors.initials: J
authors.lastname: Pan
mesh_terms: D006801:Humans; D006861:Hydrogen Peroxide; D007180:Incisor; D008963:Molar; D013053:Spectrophotometry; D014073:Tooth Bleaching
chemical_list: D006861:Hydrogen Peroxide