There is a controversy in the dentistry literature about how the use of associated light to activate 35% hydrogen peroxide gel during in-office tooth bleaching may increase the bleaching effectiveness. The studies that demonstrated an increased level of bleaching using light activation employed lower hydrogen peroxide gels while the ones reporting no statistical difference employed higher hydrogen peroxide gels.

The hypothesis of this study is that the effectiveness of light activation tooth bleaching in dependent on the hydrogen peroxide concentration employed.

The aim of this study is to compare the color change and tooth sensitivity of in-office bleaching using different hydrogen peroxide concentrations and with or without light activation. Sixty patients will be enrolled in this trial and divide equally into 4 groups according to the combination of the main factors hydrogen peroxide concentration (35% or 20%) or LED/laser activation (yes or no). Three 15-min applications will be performed in each clinical appointment. A LED/laser device will be used in the respective groups for three 1-min application with an interval of 2 min. The same procedure will be repeated one week later. The color change will be assessed after hte 1st and 2nd session, after 1 week and 6 months of the end of the treatment using a value-oriented shade Vita Classical and a spectrophotometer Easy Shade. The tooth sensitivity will be reported by patients using a 0 to 10 visual analog scale. The Student t test (α = .05) will be used to compare the tooth color changes and the intensity of tooth sensitivity between groups at baseline and immediately after the first and second bleaching appointments. The Fisher exact test and Student t test (α = .05), respectively, will be used to analyze the percentage of patients with tooth sensitivity and its intensity.

Inclusion Criteria:

• Participants should be at least 18 years old;
• Participants should have good general and oral health
• Participants should have six caries-free maxillary anterior teeth without restorations on the labial surfaces
• Participants should be willing to sign a consent form
• Participants should have central incisors darker than shade C2.

Exclusion Criteria:

• Participants that had undergone tooth-whitening procedures
• Participants that had labial anterior restorations, were pregnant or lactating.
• Participants with severe internal tooth discoloration (such as tetracycline stains, fluorosis, pulpless teeth).
• Participants with bruxism habits or any gross pathology in the mouth