Objectives: the objective of the current study was to determine the effect of different methods of vital tooth bleaching (power in-office, at-home and over the counter) on the resistance of enamel to erosion. Material and methods: Square enamel sections (4 mm × 4 mm × 3 mm) were obtained from the middle third of the crown of bovine teeth and then embedded in self-curing acrylic resin blocks measuring (2 cm wide and 3 cm high). The samples were divided randomly into 4 groups according to the method of bleaching used. Group 1(control group): where all specimens of the group were placed in artificial saliva at 37 0 C during the study period. Group 2 (power in-office bleaching): The gel was applied directly on the enamel surface of the specimens where the thickness of the gel was about 1-2 mm, then the LED bleaching device was used. The lamp was located close to enamel surface, then it was turned on for 15 minutes for total application time 45 minutes. Group 3 (Crest 3D White Luxe Supreme FlexFit White strips (over the counter) : the strips were applied to the enamel surface for 30 min twice daily for 14 days according to manufacturer instructions. Group 4 (At-home bleaching): bleaching gel was applied to the enamel surface. Teeth were placed for 6 hours at 37 0 C daily for 8 days. Then, all the samples were subjected to erosive challenge where the bleached samples and the samples of control group were immersed in 1% citric acid solution. Mineral analysis via EDS was carried out before bleaching (base line), then of bleached enamel and finally after erosive cycle. Two representative samples of each group after each step were examined by scanning electron microscope. Results: There was a significant difference regarding the percentage weight of (Ca%), (P%) and (Ca/P%) among the four tested groups. The difference was not significant between group 1 and group 4 after erosion. Conclusions: 1-At-home beaching is considered the least harmful to enamel compared to power in-office and over the counter bleaching materials, and it is more resistant to erosive challenges. 2-Bleaching agents containing calcium decrease the adverse effects of the bleaching procedure. 3-Bleached enamel is less resistant to erosion especially when power in -office or over the counter protocol is used.