The effect of maintaining apical patency on periapical extrusion.

Thirty-three human maxillary incisors were secured in the openings of a glass vial. Root canals were instrumented to the apical constriction with a step-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 syringe with a 23-gauge needle and the overflow was suctioned with an aspirator. The total volume of irrigant used was 10 ml. Apically extruded debris and NaOCl were measured. The apical constriction was then deliberately enlarged. With a step-back technique a new 'apical constriction' was created, coronally to the original one. A patency file was again not used, and irrigation was identical to the that used during the initial root canal preparation. Extruded debris and NaOCl in each bottle were again measured. Results indicated that there was significant difference in the amounts of extruded material before and after the enlargement of the apical constriction with greater extrusion when the constriction remained intact.