The tooth sensitivity reported by patients will be assessed using a visual analog scale (VAS) and verbal rating scale (VRS). The VAS consisted of a scale 10 cm in length ranging from 0 (absence of pain) to 10 (unsupportable pain). The patient set his or her level of sensitivity by pointing on the scale corresponding to this level, while the distance from this point to the 0 border will be recorded. For VRS, the patient reported his or her level of sensitivity based on scores: 0 = none, 1 = light, 2 = moderate, 3 = considerable and 4 = severe. The tooth sensitivity will be assessed during the bleaching, immediately after bleaching agent removal and and up to 24 hours after each session. One week after each session and 30 days after the last session the tooth color will be evaluated again using the CIE L * a * b * as previously described.