[Intracanal aspiration technique for root canal irrigation: evaluation of smear layer removal]

A new irrigation technique (intracanal aspiration technique, IAT) was developed to minimize the extrusion of root canal irrigant. Fifteen instrumented canals of extracted canines were divided into one control and four experimental groups of 3 teeth each. Each root was fixed in a case and surrounded with colored saline agar to measure the meter value of the Root ZX and to evaluate the extrusion of the irrigant. In control teeth, no irrigation was performed. In Groups 1 and 2, the root canal was irrigated using IAT with an aspiration needle placed 2 or 3 mm short of the apex. In Groups 3 and 4, the root canal was irrigated in a conventional manner with a washing needle placed 2 or 3 mm short of the apex. The file folder of a Root ZX was attached to the aspiration needle in Groups 1 and 2, and to a washing needle in Groups 3 and 4. Each canal was irrigated with 9 ml of 14% EDTA solution and 6 ml of 6% NaClO in experimental groups, and the meter value of the Root ZX during irrigation was recorded. After the irrigation, cleanliness of the canal was evaluated using a SEM and extrusion of NaClO by discoloration of the agar. Irrigation using IAT was more effective for removing smear layer compared to the conventional method and extrusion of the irrigant was minimized. In addition, the Root ZX measurement during IAT could monitor the extent of the irrigant in the apical canal.