Objective: The aim of this study was to investigate the relation between dentinal cracks and dentin mineral contents after irradiation with Er, Cr: YSGG laser. Settings and Design: Average power was 3.75 W, the frequency was 15 Hz, 30% water, 60% air, the energy density was 31.84 J/Cm2. Material and method: Ten teeth of single canals were biomechanically prepared and obturated then the root end was resected using carbide cross cut bur at 0° bevel. The retrograde cavity was prepared using Er, Cr: YSGG 2780 nm laser delivered through MZ6 glass tip of 660 μm diameter. Samples were prepared for SEM and examined to evaluate dentinal cracks then examined using Energy dispersive X-ray spectroscopy (EDX) which was performed to measure the mineral contents of dentin at the retrograde cavity. Results: High fluctuation of dentinal cracks´ occurrence from absence to 7 cracks. Conclusion: EDX showed no correlation between the occurrence of dentinal cracks and the weight % of Ca and P within the dentin in the retrograde cavity.