ObjectiveThe purpose of this study was to evaluate effect of frequent bleaching regimens on the color stability of enamel.Materials and methodsThirty sound bovine incisor teeth were used representing three main groups. Group 1 (control group) was not subjected to any bleaching procedure. Group 2 was bleached with 15% carbamide peroxide (CP) gel; Opalescence PF. Group 3 was bleached with chemical-activated hydrogen peroxide bleaching gel (Opalescence Boost PF 40%). All groups were subdivided into two subgroups A and B according to the storage solution either artificial saliva or staining cycle containing three staining solutions. This was performed for 30 days, with an immersion time 6 h/day resembling a period of 24-month clinical use. All the procedures were performed twice with 2 months interval where the teeth were stored in daily renewable artificial saliva at room temperature (23 ± 1°C). Spectrophotometer was used to measure the color change of the specimens. One-way analysis of variance test and pairwise test were used, at a 95% level of significance.ResultsA statistical significant rebound was recorded after first bleaching regimen (P = 0.009 and 0.032) and after second bleaching regimen (P = 0.016 and 0.013) for groups 2 and 3, respectively. A statistical significant difference was recorded between the (ΔE) after staining for first vs second time in the tested groups (1, 2, and 3) (P = 0.000, 0.047, and 0.002), respectively. Regarding specimen preserved in saliva, no statistical significant difference between the tested groups (P = 0.074, 0.793, and 0.756), respectively.ConclusionThe hypothesis of this study was rejected as the color was proved to be unstable after frequent bleaching regimens. There was an increase in color change due to exposure to staining cycles and/or artificial saliva.