Prior to bleaching procedure, the teeth will be cleaned using rubber cups associated to pumice and water. The shades of canine upper teeth will be assessed on a baseline with a spectrophotometer Vita EasyShade (Vita-Zahnfabrik, Bad Säckinge, Germany) using the CIE L * a * b *. 3 measurements on each tooth will be conducted, with the end result the average of 3 values (L *, a * and b *).