The effect of maintaining apical patency on periapical extrusion

Thirty-three human maxillary incisors were secured in the openings of a gla ss vial. Root canals were instrumented to the apical constriction with a st ep-back technique and a patency file was not used throughout the root canal preparation. The irrigant, 1% NaOCl, was delivered by means of a plastic s yringe with a 23-gauge needle and the overflow was suctioned with an aspira tor. The total volume of irrigant used was 10 ml. Apically extruded debris and NaOCl were measured. The apical constriction was then deliberately enla rged. With a step-back technique a new 'apical constriction' was created, c oronally to the original one. A patency file was again not used, and irriga tion was identical to the that used during the initial root canal preparati on. Extruded debris and NaOCl in each bottle were again measured. Results i ndicated that there was significant difference in the amounts of extruded m aterial before and after the enlargement of the apical constriction with gr eater extrusion when the constriction remained intact.