Effects of changes in surface area, thickness, temperature and post-extraction time on human dentine permeability

Discs of dentine, from freshly extracted human third molars, prepared free of enamel and pulp horns, were placed in a double-chamber device. Radioactive iodide was placed on one side of the disc and iodide that permeated to the other side of the disc was continually rinsed into a fraction collector. Steady-state permeability values were calculated using the Fick equation. Doubling the surface area doubled the amount of iodide permeating dentine per unit time. The slope of the line relating these two variables depended upon how near the pulp chamber the disc was prepared. Reduction in dentine thickness from the enamel side of discs resulted in a larger increase in permeability than reductions from the pulp side. Increasing dentine temperature 10 °C almost doubled permeability to ¹²⁵I. Post-extraction time had little effect on dentine permeability measured in vitro.