Chromatic Scale Values Spectrophotometer. Values (ΔE) Photoactivated Bleaching No Photoactivated Bleaching Photoactivated Bleaching No Photoactivated Bleaching Pre-bleaching Post bleaching Pre-bleaching Post-bleaching Mean 11,44 15,00 12,11 13,8 7,74 5,03 STD. Error 1,30 0,16 1,16 0,73 1,24 0,70 Difference 3,56 1,69 2,71 P Value 0,027 0,047 0,01

Table 4: Chromatic and spectrophotometric evaluation. Pre and post bleaching. (mean values, standard error, mean differences and p. Value)