Effect of conditioners on dentin permeability using an impedance method

The aim of our in vitro study was to contribute to an elaboration of a protocol to evaluate the permeability of dentin and the effect of different acid conditioners by means of the electrochemical impedance technique.

Twenty-four 1.1mm thick dentin disks were embedded in a hollow polyurethane resin cylinder. The system used was a 'like' permeation cell: two electrodes immersed in a 10(-1) KCl solution were attached to a potentiostat. It was connected to a microcomputer controlled frequency response analyzer and a 10 mV sinusoidal voltage signal over a frequency range of 1 Hz to 65 kHz was applied between the electrodes. The current passing through the dentin was measured to enable a calculation of impedance expressed in a complex number. To establish an evaluation of permeability variation, the resistance was noted for all specimens before and after the application of dentin conditioners.

The highest resistance decrease was obtained with 32% phosphoric acid and 10-3 solution which improved the permeability, respectively, 9.0 and 6.9% with no significant difference. The acidic monomer can be considered as intermediate (4.3%) between 10-3 solution and the polyacrylic acid (2.8%) with no significant difference.

By measuring electrical resistance of dentin disks with the impedance method, we can evaluate the ionic conduction through the sample and achieve quantitative values about permeability. The action of dentin conditioners can be significantly evaluated regarding their action in terms of resistance of the etched zone (REZ) and increasing dentin permeability.