Scanning electrochemical microscopy (SECM) is used in the constant height imaging mode to characterize fluid flow through a porous dentine slice, subjected to pressures similar to pulpal pressures measured in vivo, and to assess the effectiveness of calcium oxalate as a blocking agent of dentinal tubules. Local fluid flow rates and the topography of the dentine surface are mapped by monitoring the transport-limited current for the oxidation of ferrocyanide mediator at a tip ultramicroelectrode, scanned in close proximity to a target area of the surface, with and without an applied pressure across the slice. Following the application of the blocking agent, calcium oxalate, to the surface, subsequent scans in the same area reveal that all of the dentinal tubules are occluded and solution flow is inhibited. By converting diffusion-limited current images measured in the absence of pressure, before and after the application of the blocking agent, to corresponding topographical maps, it is demonstrated that the thickness of the precipitated calcium oxalate layer covering the surface can be estimated.