To compare the in vitro effects of three desensitizing agents on hydraulic conductance of human dentin: Protect (n = 10), Gluma Desensitizer (n = 10), MS Coat (n = 10) (Pain-Free in the USA).Dentin discs were prepared from 40 freshly extracted normal human third molars. The pulpal side of the dentin discs was etched with 37% phosphoric acid for 15 s and then rinsed under tap water. The coronal side was sequentially ground and the dentin discs were sonicated for 30 min. The hydraulic conductance was measured filtering 20% serum in phosphate buffered saline under a pressure of 15 cm H2O. The hydraulic conductance of each dentin specimen was measured before using the desensitizing agent and this value was designated as 100%. Thirty dentin discs were treated, the hydraulic conductance was remeasured and expressed as a percentage of the hydraulic conductance of that specimen before treatment. The teeth were stored for 1 month at 37 degrees C in deionized water and the hydraulic conductance of the 40 dentin discs was recorded again. Ten dentin discs were left untreated to serve as a control.No statistical difference was found between the immediate hydraulic conductance of the three groups after treatment. After 1-month storage, the control group showed a statistically higher hydraulic conductance than the three treated groups. There was no statistical difference between the three dentin desensitizing agents evaluated.