Changes on surface morphology were more evident in specimens bleached with carbamide peroxide 22% for three sessions (G4).In figure 8 we could observe the loss of aprismatic layer, depressions, erosion, increase of the irregularities depth and pores, when compared to other groups. Such changes may be related to a significant reduction in microhardness in these specimens excessively bleached, as reported by Pinto et al.