Critical analysis of an experimental set-up generally used for the permeability evaluation of dental lining material.

The diffusion constants of iodide through dentine membranes were determined. The DI-values were within the range generally obtained by other investigators. When the estimation of the diffusion coefficient through a well defined polycarbonate membrane was calculated the value was strongly affected by the diffusion through the unstirred diffusion layer. By using such an experimental approach it seems necessary to develop a new cell equipped with a double stirring system (one in each compartment) in order to reduce strongly the thickness of the unstirred diffusion layer.