Treatments that obdurate dentin tubules have been used for reducing dentin hypersensitivity. Objective: The goal of this study was to determine the effect of a treatment with slurry of micro size calcium phosphates on the hydraulic conductance (Lp) of etched dentin discs in vitro. Methods: The treatment slurry (powder to liquid ratio = 1g/1mL) was prepared by mixing a powder mixture DCPA (< 5 μm) and Ca(OH)2 (< 5 μm), with a solution that contained mass fractions of 4% NaF and 2% carboxylmethyl cellulose. The slurry was applied on a dentin surface and then forced in by gently blowing the top of the treated side with N2 gas. After 1 min, the specimen was stored in 100 % humidity at 37 ºC for 15 min, then immersed in a saliva-like solution (SLS) [1.2-mmol/L CaCl2, 0.72-mmol/L KH2PO4, 30-mmol/L KCL and 50-mmol/L HEPES, pH=7.0] for 2 h. A modified Pashley’s flow system was used to measure Lp. The specimen was subsequently incubated in a 20 mL SLS changed daily for 8 d, and Lp measurements were taken at the same day points as the baseline Lp. Results: The mean baseline Lp was (2.07±1.45) mL cm-2 sec–1 H2O cm-1 (mean±S.D.; n=13). After one treatment and (3, 5, and 8) d of incubation in SLS, the mean relative Lps, presented as fractions of baseline Lp, were (65±16, 42±27, 36±26, and 33±27) %, respectively. The Lp values of the baseline and treatment after incubation were significantly different (p < 0.05). Scanning electron microscopic examination showed the obturation of dentin tubules in the treated dentin. X-ray diffraction indicated the product formed from the slurry was hydroxyapatite. Conclusion: Treatments appeared effective in improving the Lp of dentin discs with incubation in a SLS. Supported by NIDCR grant DE05354, ADAHF, and NIST.