A comparison between a smooth wire and a K-file in removing artificially placed dentine debris from root canals in resin blocks during ultrasonic irrigation

To compare the efficacy of a smooth wire with a conventional K-file, in removing dentine debris from grooves in root canals made in resin blocks, during ultrasonic irrigation.

Each resin block containing a standard simulated canal was split longitudinally through the canal, forming two halves. In one canal wall, a standard groove 4 mm in length, 0.2 mm in width and 0.5 mm in depth was cut 2-6 mm from the apical end of the canal, to simulate uninstrumented canal extensions. Each groove was filled with fresh dentine debris mixed with 2% NaOCl to simulate a situation when dentine debris accumulates in uninstrumented canal extensions. Each canal was reassembled by joining the two halves of the resin block by means of wires and sticky wax. In each canal ultrasonic irrigation was performed for 3 min using 2% NaOCl as irrigant. In one group (n = 20) a conventional K-file size 15 was used. In the other group (n = 20) a smooth wire was used which had the same length and diameter as the size 15 K-file. Before and after irrigation, images of each half of the canal with a groove were taken, using a microscope and a digital camera, after which they were scanned into a PC as TIFF images. The quantity of dentine debris in the groove was evaluated using a scoring system: the higher the score, the larger the amount of debris remaining. The score data were analysed by means of the Mann-Whitney U-test.

After ultrasonic irrigation, the debris was completely removed from the groove in 35 canals (87.5%), and there was no significant difference between the groups (P = 0.429).

Using a smooth wire during ultrasonic irrigation is as effective as a size 15 K-file in removal of artificially placed dentine debris in grooves in simulated root canals in resin blocks.