Physicochemical modification of EDTA solutions to improve the smear layer removal in dental applications

In endodontic treatment, the canal instrumentation produces debris (smear layer) that blocks the root canal and dentinal tubules reducing the adhesion with the obturation material, favouring microfiltration and bacteria growth. EDTA aqueous solution is the most used and effective de-mineralizing agent because produces a strong chelating effect on the calcium ions of the hydroxyapatite. However, its physicochemical properties (viscosity, surface tension, capillarity penetration and diffusion time) should be modified to improve its cleaning effects; this can be done by adding controlled amounts of ethanol. The diffusion time can be increased up to 244%, which renders in an increment in the residence time of the de-mineralizing agent on the root canal and tubules, providing the required time to allow the chemical reaction with the smear layer takes place. Additionally, ethanol reduces penetration (45%) making the cleaning effective near the root canal, where it is required. SEM micrographs show the tubules before and after this treatment at different ethanol concentrations.