Two blind reviewers record the color of the right maxillary central incisor patients through the scale VITA Classical (Vita Zahnfabrik, Bad Sackingen, Germany). At the following times : initial, 1st week, 2nd week, 3rd week (active phase bleaching) and post- bleaching periods : 1 week, 1 month, 2 and 3 months. Evaluators always record the color independently in the same room with the same lighting. If there is a discrepancy in the color registration, a new evaluation will be conducted together until a consenso. The area chosen for color measurement is the middle third of the labial surface of the central incisor, according to the ADA specifications . The color change will be evaluated by means of varying scale Vita units ( ΔUEV ) organized by value.