Effect of maintaining apical patency on irrigant penetration into the apical third of root canals when using passive ultrasonic irrigation: an in vivo study.

INTRODUCTION The complex anatomy of the root canal system has been shown to limit the penetration of irrigating solutions into the apical third; hence, the aim of this study was to determine whether the use of a patency file is related to the presence of a radiopaque irrigating solution in the apical third of human root canals after using passive ultrasonic activation in vivo. METHODS Forty human root canals were randomly divided into two groups. Apical patency was maintained in one group (n = 21) during shaping and cleaning procedures with a no. 10 K-file 1 mm beyond the working length (WL) but not in the other group (n = 19). In both groups, the canals were shaped with the Pro Taper system (Dentsply-Maillefer, Ballaigues, Switzerland). Irrigation was performed with 1 mL of a solution prepared with a radiopaque contrast medium and sodium hypochlorite 5.25%, and then passive ultrasonic irrigation (PUI) was applied after the shaping procedure. Digital images were taken, and a calibrated reader determined the presence or absence of the irrigating solution in the apical third. RESULTS There were significantly more canals with irrigant in the apical third after PUI when apical patency was maintained with a no. 10 file 1 mm beyond the WL than when apical patency was not maintained throughout the cleaning and shaping procedures (P = .02). CONCLUSIONS Maintaining apical patency and then using PUI improves the delivery of irrigants into the apical third of human root canals.