Influence of irrigating needle-tip designs in removing bacteria inoculated into instrumented root canals measured using single-tube luminometer.

This study tested the mechanical efficacy of various irrigating needle tip designs on bacteria inoculated into instrumented root canals. Root canals of 30 extracted permanent canines were prepared to size 60 at working length (WL) using ProFile 0.04 taper rotary nickel-titanium files. Root canals were autoclaved and inoculated with a 20-microl suspension (1.4 x 10(7) cells) of genetically engineered Escherichia coli pYUB556. Bioluminescence was measured before inoculation (baseline), after inoculation and after irrigation with 6 ml of saline using luminometer. Safety-ended needles with single (group 1) and double (group 2) side-port and hypodermic needles (group 3) were used upto 1 mm short of WL. The percentage of bacteria remaining after irrigation was 67.9 +/- 9.5, 75.3 +/- 12.9 and 77.7 +/- 11.8 respectively (p < 0.05; Kruskal-Wallis) with no difference between group II and group III (p > 0.05; Mann-Whitney). Irrigation using safety needles with single side port was significantly effective.