Replacement resorption is followed by the delayed replantation of an avulsed tooth. Currently no effective treatment is substantiated for replacement resorption. The purpose of this study was to investigate the effect of stannous fluoride, bisphosphonate (etidronate disodium) and gallium nitrate, which have been shown to reduce dentin resorption, on human dentin. Osteoclasts were collected from tibeas of chick embryo. The cells were well agitated to prevent adhesion and seeded onto the sliced human dentin wafers which had been soaked in either culture media (control), or several different concentrations of stannous fluoride, etidronate disodium (l-hydroxyethylidene -1,1-bisphosphonate disodium), and gallium nitrate. Resorption was measured by counting the number of resorptive pit produced by the cells. Results are as follows. Stannous fluoride and etidronate disodium showed statistically significant reduction of dentin resorption(p<0.05) but the effect of stannous fluoride seemed to be its high cytotoxicity. Etidronate disodium did not show cytotoxicities in all experimented concentrations. Gallium nitrate did not show differences in resorption either between different concentrations or from the control group.