The purpose of this study is to examine the effect of occlusion of dentinal tubules bydipotassium oxalate in vitro with scanning electron microscopy and electron probe.Four pairs of sec-tions were taken from the roots of extracted teeth and divided into two groups randomly.One group ofthe sections was treated with 30% dipotassium oxlate and the other as the control.The SEM observa-tion of the treated dentin showed no orifices of dentinal tubules and there were many oxalate crystalson the surface.On frozen fractured surfaces,most dentinal tubules were occluded in the oxalate-treat-ed samples and empty in the control.The concentration of calcium on the surfaces was significantlyhigher in the oxalate group than that in the control.These results suggesed that 30% dipotassium ox-alate can occlude the dentinal tubules and may be recommended as an effective agent for dentinal hy-persensitivity. The purpose of this study is to examine the effect of occlusion of dentinal tubules bydipotassium oxalate in vitro with scanning electron microscopy and electron probe. Fur pairs of sec-tions were taken from the roots of extracted teeth and divided into two groups randomly. One Group of the sections was treated with 30% dipotassium oxlate and the other as the control. SEM observations-the treated dentin showed no orifices of dentinal tubules and there were many oxalate crystals on the surface. Frozen fractured surfaces, most dentinal tubules were occluded in the oxalate-treat-ed samples and empty in the control. concentration of calcium on the surfaces was significantlyhigher in the oxalate group than that in the control .sese results suggesed that 30% dipotassium ox-alate can occlude the dentinal tubules and may be recommended as an effective agent for dentinal hy-persensitivity.