The GCO group will receive the application of an experimental gel based on copaiba oil resin for post tooth bleaching sensitivity

The GN group will receive the application of a potassium and sodium nitrate gel for post tooth bleaching sensitivity

The GC group will receive the application of a placebo gel for post tooth bleaching sensitivity

Prior to bleaching treatment with 35% hydrogen peroxide, the dental elements of the GCO will receive the application of the experimental desensitizing gel on the buccal surfaces of the central incisors, lateral incisors, canines and upper and lower premolars, with a rubber cup in an active way, for 10 minutes.

For the assessment of postoperative sensitivity, patients were instructed to fill out a form to record tooth sensitivity daily, during the 21 days of treatment, based on individual pain perception. This form was delivered at each bleaching session, being returned to the researcher in the following session, that is, always one week after each bleaching session. The evaluation form consisted of the visual analogue scale (VAS). This scale consists of a 10 cm horizontal line, with scores of 0 and 10 at its ends, where 0 means no sensitivity and 10 means severe tooth sensitivity. The patient was instructed to draw a vertical line along the horizontal line of the scale, recording the intensity of tooth sensitivity per day. So that the distance in millimeters from the zero end could be later measured with the aid of amillimeter ruler, thus obtaining the patient's level of pain intensity.

The VITA Easyshade spectrophotometer (VITA Zahnfabrik, Bad Säckingen, Germany) was used to measure the color, where the area of dental correspondence to be evaluated was the middle third of the buccal surface of the upper canines. To standardize the color readings, silicone trays were made, where the impression was extended from canine to canine. A window was created on the buccal surface of each canine of the silicone guide using a metal device with a 6 mm radius, corresponding to the diameter of the spectrophotometer tip. Thus, the tip of the device was inserted into the silicone guide to obtain the color parameters. Subsequently, the color difference between baseline (T i) and one week after the 3rd bleaching session (T f ) was calculated using the CIEDE2000 formulas (ΔE00).