Effect of violet LED light on in-office bleaching protocols: a randomized controlled clinical trial

J Appl Oral Sci. 2020;28:e20190720. doi: 10.1590/1678-7757-2019-0720. Epub 2020 May 18.


Objective This study evaluated the clinical effect of violet LED light on in-office bleaching used alone or combined with 37% carbamide peroxide (CP) or 35% hydrogen peroxide (HP). Methodology A total of 100 patients were divided into five groups (n=20): LED, LED/CP, CP, LED/HP and HP. Colorimetric evaluation was performed using a spectrophotometer (ΔE, ΔL, Δa, Δb) and a visual shade guide (ΔSGU). Calcium (Ca)/phosphorous (P) ratio was quantified in the enamel microbiopsies. Measurements were performed at baseline (T 0 ), after bleaching (T B ) and in the 14-day follow-up (T 14 ). At each bleaching session, a visual scale determined the absolute risk (AR) and intensity of tooth sensitivity (TS). Data were evaluated by one-way (ΔE, Δa, ΔL, Δb), two-way repeated measures ANOVA (Ca/P ratio), and Tukey post-hoc tests. ΔSGU and TS were evaluated by Kruskal-Wallis and Mann-Whitney, and AR by Chi-Squared tests (a=5%). Results LED produced the lowest ΔE (p<0.05), but LED/HP promoted greater ΔE, ΔSGU and Δb (T 14 ) than HP (p<0.05). No differences were observed in ΔE and ΔSGU for LED/CP and HP groups (p>0.05). ΔL and Δa were not influenced by LED activation. After bleaching, LED/CP exhibited greater Δb than CP (p>0.05), but no differences were found between these groups at T 14 (p>0.05). LED treatment promoted the lowest risk of TS (16%), while HP promoted the highest (94.4%) (p<0.05). No statistical differences of risk of TS were found for CP (44%), LED/CP (61%) and LED/HP (88%) groups (p>0.05). No differences were found in enamel Ca/P ratio among treatments, regardless of evaluation times. Conclusions Violet LED alone produced the lowest bleaching effect, but enhanced HP bleaching results. Patients treated with LED/CP reached the same efficacy of HP, with reduced risk and intensity of tooth sensitivity and none of the bleaching protocols adversely affected enamel mineral content.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Adult
  • Analysis of Variance
  • Carbamide Peroxide / administration & dosage*
  • Colorimetry
  • Combined Modality Therapy
  • Dental Enamel / drug effects
  • Dental Enamel / radiation effects
  • Dentin Sensitivity / chemically induced
  • Female
  • Humans
  • Hydrogen Peroxide / administration & dosage*
  • Light*
  • Male
  • Phototherapy / methods*
  • Reference Values
  • Risk Factors
  • Spectrophotometry
  • Statistics, Nonparametric
  • Surface Properties / drug effects
  • Surface Properties / radiation effects
  • Tooth Bleaching / methods*
  • Tooth Bleaching Agents / administration & dosage*
  • Treatment Outcome
  • Young Adult


  • Tooth Bleaching Agents
  • Carbamide Peroxide
  • Hydrogen Peroxide