title: Hydrogen peroxide diffusion with and without light activation.
abstract: OBJECTIVE
  The aim of this study was to assess the dental bleaching efficacy of 37.5% hydrogen peroxide (HP), with and without light activation, in HP-exposed and unexposed areas.
  
  
  METHODS
  28 bovine teeth were selected and divided into two groups (n = 14). Crowns were detached and stained with tea. The gingival half was covered with a gingival barrier. In the incisal half, 37.5% HP (Pola Office+, SDI) was applied three times, with a 1-week interval between applications. In HP-A group, the bleaching agent was activated for 3 min with a LED lamp. No light activation was applied in HP-N group. Dental color variation was determined through a spectrophotometer in both halves. Statistical analysis between groups was performed with an ANOVA test, and intragroup differences were evaluated, with an ANOVA test for paired data, with a significance level of P < 0.05.
  
  
  RESULTS
  An increase in lightness and a decrease in chroma were found in both groups and halves. No significant differences in ΔE between groups (P > 0.5) were detected in the incisal half. After treatment, a significantly higher ΔE was found in the gingival half for HP-A group (P < 0.05). For the same group, a significantly higher bleaching effect was found in the gingival half, compared with the incisal half (P < 0.05).
  
  
  CONCLUSIONS
  LED activation did not have a significant effect in terms of bleaching in the incisal half, but increased clearance in the gingival half.
  
  
  CONCLUSIONS
  HP light activation does not significantly increase the whitening effect, but it can improve the bleaching diffusion to areas where it has not been directly applied.
authors.forename: Carmen
authors.initials: C
authors.lastname: Llena
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Forner
authors.forename: María
authors.initials: M
authors.lastname: Vazquez
mesh_terms: D000818:Animals; D002417:Cattle; D003116:Color; D004058:Diffusion; D006861:Hydrogen Peroxide / Q000493:pharmacokinetics* / Q000528:radiation effects; D008297:Male; D008422:Materials Testing; D010778:Photochemotherapy / Q000379:methods*; D013053:Spectrophotometry / Q000295:instrumentation; D013997:Time Factors; D014070:Tooth / Q000187:drug effects / Q000378:metabolism; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000493:pharmacokinetics* / Q000528:radiation effects; D014075:Tooth Discoloration / Q000188:drug therapy
chemical_list: D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide