Contribution of a* to Dental Bleaching After Combined Dental Bleaching

Contribution of the a* Parameter to Dental Bleaching After Combined Bleaching: A Prospective Non-randomized Single-arm Interventional Clinical Study

A prospective, non-randomized, single-arm interventional clinical study with a before-after design will be conducted to assess changes in CIELab color parameters and the Whiteness Index for Dentistry (WID) following a standardized combined dental bleaching protocol. The study aims to evaluate the contribution of the a* parameter (green-red axis) to overall dental whiteness.

Tooth whitening is one of the most commonly requested aesthetic dental treatments, requiring objective and reproducible methods to quantify color changes. The CIELab color system (L*, a*, b*) and the Whiteness Index for Dentistry (WID) are widely used for this purpose.

While increases in L* and decreases in b* are recognized as the main contributors to dental whitening, the role of the a* parameter remains unclear. Variations in a*, including the presence of negative values or changes in sign during treatment, have been insufficiently studied.

A prospective, non-randomized, single-arm interventional clinical study with a before-after design will be conducted to evaluate changes in L*, a*, b*, and WID following a combined dental bleaching protocol consisting of an in-office phase with hydrogen peroxide and an at-home phase with carbamide peroxide.

Spectrophotometric measurements will be performed at baseline, after the in-office phase, and after completion of the at-home phase. The study will also analyze the relationship between changes in CIELab parameters and WID.

The study will be conducted in accordance with ethical standards and will be approved by the corresponding institutional review board. All participants will provide written informed consent prior to inclusion.

Inclusion Criteria

• Age 18 to 65 years
• Good oral health
• Presence of natural anterior teeth (incisors, canines, premolars)
• Anterior teeth without restorations
• Indication for tooth bleaching treatment
• Ability to comply with study procedures and visits

Exclusion Criteria

• Smoking
• Previous tooth bleaching treatment
• Pregnancy
• Breastfeeding
• Restorations in anterior teeth
• Presence of diseases affecting tooth color
• Conditions that may interfere with study outcomes