Er:YAG lazer; LED; mikrosertlik; ofis tipi beyazlatma; pürüzlülük; renk değişimi, Abstract Objective: The aim of the current study was to investigate the effect of bleaching of 40% hydrogen peroxide without any light activation, with LED light activation or with Er:YAG laser activation on colour change, surface microhardness and surface roughness. The experimental groups were the group bleaching gel was applied without any light activation (Group J), the group bleaching gel was activated with LED light source with a wavelength of 385-515 nm and power of 3200 mW/cm2 (Group LED) and the group bleaching gel was activated with Er:YAG laser in the VLP mode (1000 ps pulse time) with 50 mJ energy and 10 Hz frequency (Group Er:YAG). Statistical analysis was carried out with Oneway ANOVA test. Results: In all bleaching groups, the color change was found to be above the visual detection threshold, but there was no significant difference between the groups. (p>0.05).