Mechanical preparation of teeth using a conventional handpiece has been considered the gold standard in restorative dentistry, for a long time. However, it does not meet all the criteria for the ideal restorative technique. The laser technique has been introduced in dentistry, which has the advantage of a low rise of pulp temperature compared to the traditional handpiece. However, some lasers can cause damage to the pulp particularly if water cooling is not used and inappropriate parameters, such as high energy are chosen. The aim of this research was to investigate the effect of the Er:YAG laser on chemical and mechanical properties of hard tissues. The chemistry of hard tissues following the laser radiation was examined by both Fourier transform infrared spectroscopy and energy dispersive spectroscopy. Morphological changes of the hard tissues were investigated also by both two-dimensional scanning electron microscope and three-dimensional nano-CT. In restorative dentistry, the chemical and mechanical properties of the substrate play a significant role in the bonding process. Roughness of the hard tissues after laser radiation was evaluated by profilometry using both two-dimensional (2D) and three-dimensional (3D) parameters. Nano-CT readings of roughness supported the roughness measurements of the profilometer, in which a significant increase of roughness was reported following the Er: YAG laser radiation. Restorative materials (GC Fuji IXÂ® and Biodentinâ¢) were used to connect two irradiated sections of dentine. The lased GC Fuji IXÂ® showed the highest force required to detach the joined fragments. Shear bond strength testing was also done and showed a significant effect of the Er:YAG laser. The GC Fuji IXÂ® had the highest shear bond strength.