Trial design: This study will be a randomized-controlled, single-blind clinical trial with a parallel design. The patients included will be submitted to two in-office bleaching sessions with a 7-day interval receiving 35% hydrogen peroxide (control) or 37% carbamide peroxide in a single application of 45 minutes; while the same treatments will be allocated for each session. The study will be conducted at the clinic of the School of Dentistry of the local university from May 2016 to December 2016.