Background: Different side effects of tooth bleaching have been recognized and reviewed by many authors .Limited evidence exists regarding the effect of amorphous calcium phosphate (ACP) on the treatment of these side effects. Purpose: Literature surveys revealed sparse data on the effect of Relief ACP as post bleaching agent. Consequently, the goal of the current study was to compare the effect of this novel post bleaching agent with that of conventional fluoride on the enamel surface of human extracted teeth using scanning electron microscope (SEM)(qualitative) and energy dispersive X-ray analysis (EDAX)(quantitative). Methodology: Sixty extracted human premolars teeth were prepared and each crown was divided into four quarters. These quarters were distributed over four groups. Three quarters of each tooth received the dental bleaching treatment on the buccal surfaces while the fourth quarter of each tooth was used as control. The experimental groups were dividing into three groups: one acted as Positive control group, another one was subjected to post bleaching (Floro-Opal) while the last one was subjected to post bleaching ( Relief ACP) for one hour. After preparation, each group was evaluated by SEM and EDAX. Results: Bleaching procedure significantly altered the enamel superficial surface structure causing: dissolution of the enamel, surface erosion, depressions, craters and porosity as well as noticeable decrease of the calcium and phosphorous levels of teeth as compared to the control ones. However Relief ACP was better than Floro-Opal in restoring, rebuilding and repairing enamel surface changes after bleaching alteration. The qualitative analysis was confirmed by the quantitative analysis which in its turn showed significant increase in calcium and phosphorous levels that helped in teeth remineralization. Conclusion: The exposure to light activated 35% hydrogen peroxide significantly altered enamel surface morphology and affected the calcium and phosphorous levels of teeth. When tooth bleaching was followed by post bleaching agents application, a significant increase in calcium and phosphorous levels was recorded. Relief ACP post bleaching agent gave better results than conventional (Floro-Opal) concerning surface morphological alterations recovery as well as calcium and phosphorous levels.