Objective This study aims to investigate the effect of three different bleaching applications on structural integrity, mineral volume (MV) and density of the enamel by using micro-computed tomography (Micro-CT) and evaluate the colour effectiveness using CIEDE2000. Materials and methods Twenty-four maxillary premolar teeth were divided into three groups (n = 8) (group 1: 40% HP gel with erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser activation; group 2: 40% HP gel with diode laser activation; group 3: 16% CP gel). Bleaching protocols were applied and colour alteration was obtained. Data were calculated with CIEDE2000 before and after bleaching. A Micro-CT was used to scan the specimens before and after the bleaching application. Statistical analysis was performed by ANOVA. Results No significant difference was observed between the groups for colour changes (p > .05). Micro-CT analysis showed significant differences in structural thickness, structural separation, mineral density and MV for the different ROIs before and after bleaching for all groups (p<.05). Conclusions All of the bleaching methods represented similar efficiency. However, bleaching with Er,Cr:YSGG laser was less harmful to enamel in comparison with other bleaching methods. The present results may be useful for establishing a numerical standard for the change in bleaching with laser systems in dental hard tissues.