The in vitro reduction of the bacterial population in
the root canal by the mechanical action of instrumentation
and irrigation was evaluated. Root canals
inoculated with a Enterococcus faecalis suspension
were instrumented using hand Nitiflex
files, Greater Taper (GT) files, and Profile 0.06 taper
Series 29 rotary instruments. Irrigation was performed
using sterile saline solution. Root canals
were sampled before and after instrumentation. In
the group of the Nitiflex files, samples were also
taken after each file size. After serial dilution, samples
were plated onto Mitis-Salivarius agar, and the
colony forming units grown were counted. All techniques
and instruments tested were able to reduce
significantly the number of bacterial cells in the
root canal. Instrumentation to a Nitiflex #30 was
significantly more effective than GT files. There
were no significant differences when comparing
the effects of the Profile instrument #5 with either
the GT files or the Nitiflex #30. Enlargement to a
Nitiflex #40 was significantly more effective in eliminating
bacteria when compared with the other
techniques and instruments tested (p < 0.05). The
results of this study showed that the instrumentation
and irrigation can mechanically remove more
than 90% of bacterial cells from the root canal.
Because