title: Clinical Evaluation of Genotoxicity of In-office Bleaching.
abstract: OBJECTIVE
  The aim of this study was to evaluate the genotoxicity of in-office bleaching with 35% hydrogen peroxide in epithelial cells from the gingival and lip tissues.
  
  
  METHODS
  Thirty volunteers with central incisors shade A1 or darker were selected for this study. The gingival tissue of the teeth to be bleached was isolated with a light-polymerized resin dam, and the 35% hydrogen peroxide gel was administered during three 15-minute applications over the course of the 45-minute application period. Two bleaching sessions with a one-week interval in between were performed. Exfoliated oral mucosa gingival epithelial cells and upper lip lining were collected at baseline and one month after the in-office dental bleaching. The scraped cells were placed on clean glass slides and smears were prepared. After staining with Giemsa solution, two blinded examiners performed cell and micronuclei counts under a 100× optical microscope. Tooth sensitivity was evaluated using the Visual Analogue Scale (VAS). Shade evaluation was recorded before and one month after the bleaching treatment with the value-oriented shade guide Vita Bleachedguide 3D-MASTER and the spectrophotometer Vita Easyshade. Data from the shade guide units and the micronuclei (MN) frequency were subjected to a Mann-Whitney test (α=0.05). The overall difference between before and one month after the bleaching treatment (ΔE and ΔSGU), absolute risk, and intensity of tooth sensitivity (TS) were calculated, as was the 95% confidence interval (CI).
  
  
  RESULTS
  The frequency of MN was not increased after bleaching with 35% hydrogen peroxide in both study groups (p>0.05). The absolute risk of TS of the participants was 93% (95% CI, 79%-98%), with a mean VAS intensity of 5.7 ± 2.9 (95% CI, 4.6-6.8). Meaningful whitening was observed after bleaching. The change in shade guide units in the Bleachedguide 3D-MASTER was 2.3 ± 1.4. In terms of ΔE, the change in color was 7.7 ± 3.5.
  
  
  CONCLUSIONS
  The in-office bleaching did not induce DNA damage to the gingival and lip tissue during the bleaching period. Although effective whitening was observed, most of the participants experienced TS.
authors.forename: M
authors.initials: M
authors.lastname: Rezende
authors.forename: J L
authors.initials: JL
authors.lastname: De Geus
authors.forename: A D
authors.initials: AD
authors.lastname: Loguercio
authors.forename: A
authors.initials: A
authors.lastname: Reis
authors.forename: D
authors.initials: D
authors.lastname: Kossatz
mesh_terms: D003116:Color; D003807:Dentin Sensitivity; D005881:Gingiva / Q000166:cytology; D006801:Humans; D006861:Hydrogen Peroxide; D015162:Micronucleus Tests; D014070:Tooth; D014073:Tooth Bleaching; D058205:Tooth Bleaching Agents / Q000633:toxicity*; D014075:Tooth Discoloration; D014508:Urea
chemical_list: D058205:Tooth Bleaching Agents; D014508:Urea; D006861:Hydrogen Peroxide