A blinded clinician put in the patient bleaching trays the UltraEZ desensitizing gel, patients had to wear it 30 minutes before the session of in-office bleaching

A blinded clinician put in the patient bleaching trays the placebo desensitizing gel, patients had to wear it 30 minutes before the session of in-office bleaching

General Examination with bite-wings, dental prophylaxis, alginate impressions of both arches, creation of individualized bleaching trays and position finder trays. Application of the UltraEZ in the bleaching trays for 30 minutes. Isolation of the gingival tissues. Two applications of the bleaching agent of 20 minutes

General tooth sensitivity was assessed using a 5-point Numeric Rating Scale (NRS), where 0 = no sensitivity; 1 = mild discomfort; 2 = moderate discomfort that does not interfere with daily activities; 3 = considerable discomfort leading to avoidance of certain foods and beverages; and 4 = severe sensitivity requiring interruption of the bleaching treatment. Participants selected the numeric value that best represented their perceived level of tooth sensitivity.

Pain intensity was recorded at the following time points:

• Perioperative
• 1 hour postoperatively
• 24 hours postoperatively
• 48 hours postoperatively

Tooth color will be measured using a dental spectrophotometer, recording the following parameters: L (lightness, representing the shade from black to white on a scale of 0 to 100), a (color variation along the red-green axis, with positive values toward red/purple and negative values toward green/blue), b (color variation along the yellow-blue axis, with positive values toward yellow and negative values toward blue/purple), C (chroma, describing the intensity or saturation of a color, expressed on a scale from 0 to 40, where 0 indicates no saturation and 40 the maximum saturation), and hº (hue, representing the dominant wavelength of a color on a continuous circular scale from 0° to 360°).

Color changes between visits will be calculated using the CIELab, CIEDE2000, and White Index for Dentistry (WID) formulas.

Color measurements will be recorded at the following time points:

• Baseline (Bleaching Day 1)
• One week after baseline (Before Bleaching Day 2)
• Follow-up (One week after)