Effectiveness of NaOCl alone or in combination with EDTA on the diffusion of hydroxyl ions released by calcium hydroxide paste.

Aim: To evaluate the effect of different irrigant solutions employed during removal and replacement of calcium hydroxide paste on the diffusion of hydroxyl ions through root canal dentine in vitro.

Methodology: Thirty-five maxillary and mandibular human canines with straight and fully developed roots were used. After mechanical preparation up to 1mm short of tooth length, 30 canals were filled with calcium hydroxide paste and 5 canals were left empty; all teeth had their coronal accesses properly sealed.