The sample calculation will be based on the primary continuous outcome for superiority control. Power of the test will be set at 80%, considering a type I error of 0.05; for a minimum detectable difference between treatments 25%, based on a prior study using similar bleaching agent, while a coefficient of variation of 30% of control treatment will be expected. The calculation resulted in fifty patients, through the formula used n = f(α/2, β) × [p1 × (100 − p1) + p2 × (100 − p2)] / (p2 − p1)2. The calculation resulted in fifty patients.