The aim of this study was to evaluate the dentinal tubule sealing and acid resistance of dentin specimens following the application of calcium phosphate glass powder prior to irradiation with a CO 2 (carbon dioxide) laser. Dentin models simulating open dentinal tubules were divided into two groups: experimental (calcium phosphate glass slurry applied to the dentin surface) and control (no slurry applied to the surface). All specimens in the experimental group and five specimens in the control group were irradiated with a CO 2 laser. The defocused laser beams (0.5 and 1 W) were applied (spot size, 5 mm in diameter) from a distance of 20 mm for 10 s. The surfaces and cross-sectional areas of the specimens were examined using an SEM (scanning electron microscope). In addition, the resistance to acid was evaluated in these specimens. The open dentinal tubules in the control groups were sealed following irradiation with the CO 2 laser at 0.5 W and 1.0 W. Likewise, sealing of open dentinal tubules was observed in the experimental group after CO 2 laser irradiation. The acid resistance of the dentin surface was improved after CO 2 laser irradiation; specimens in the experimental group presented with significantly lower amounts of Ca ion release compared to those in the control group. These findings indicate that CO 2 laser irradiation alone or after the application of calcium phosphate glass powder can effectively seal the dentinal tubules and alleviate dentin hypersensitivity.