Prior to bleaching procedure, the teeth will be cleaned using rubber cups associated to pumice and water. The shades of six upper anterior teeth will be assessed on a baseline using the bleach guide scale and for CIE L*a*b* measurement, ΔE will be calculated by the following equation: ∆E= [(∆L)2 + (∆a)2 + (∆b)2]1/2, while ∆L = L1 - L0; ∆a = a1 - a0; e ∆b = b1 - b0.