An in vitro comparison of ultrasonic and conventional methods of irrigant replacement.

The effectiveness of irrigant replacement in fine canals was compared using three sizes of irrigating needle and an ultrasonic method. The results showed that irrigant replacement became progressively less effective towards the apex regardless of the method of irrigation or needle size. With conventional methods, irrigation performance varied with the size of needle and volume of irrigant. With the ultrasonic method results depended on irrigation time, but was independent of irrigant flow rate through the handpiece, the size of the canal or the file size.