Purpose: Dentin hypersensitivity is a potential threat to oral health. Laser irradiation may provide reliable and reproducible treatment but remains controversial. The present study aimed to evaluate the effects of $CO_2$ or erbium-doped yttrium aluminium garnet (Er:YAG) laser therapy, and to assess mineral content. Methods: Eighteen human single-rooted teeth affected with advanced periodontitis were obtained. Buccal and lingual surfaces were planed to form 36 specimens. Ethylenediaminetetraacetic acid gel (24%) was applied to remove the smear layer and simulate hypersensitive teeth. The experimental groups were: group 1, control (no irradiation); group 2, $CO_2$ laser (repetitive pulsed mode, 2 W, $2.7J/cm^2$); and group 3, Er:YAG laser (slight contact mode, 40 mJ/pulse and 10 Hz). To evaluate dentinal tubule occlusion, six specimens per group (2-mm thickness) were prepared and observed using scanning electron microscopy (SEM) for calculation of the occlusion percentage. To evaluate the mineral content, six specimens per group (0.6-mm thickness) were used, and then the levels of Ca, K, Mg, Na, and P were measured by inductively coupled plasma-atomic emission spectrometry. In addition, the surface temperature of the specimens during laser irradiation was analyzed by a thermograph. Results: The SEM photomicrographs indicated melted areas around exposed dentinal tubules and a significantly greater percentage of tubular occlusion in the $CO_2$ and Er:YAG laser groups than the control, and in the Er:YAG group than the $CO_2$ laser group. In addition, no significant differences were noted among the experimental groups for the mineral elements analyzed. The $CO_2$ laser group showed an evident thermal effect compared to the Er:YAG group. Conclusions: $CO_2$ and Er:YAG laser are effective in treating dentin hypersensitivity and reducing its symptoms. However, the Er:YAG laser has a more significant effect; thus, it may constitute a useful conditioning item. Furthermore, neither $CO_2$ nor Er:YAG lasers affected the compositional structure of the mineral content.