Engine-driven instruments make canal preparation
faster and less tedious than hand instrumentation. The
flexibility of nickel-titanium rotary instruments
facilitates shaping of curved canals and enables the
clinician to instrument canals to the desired tapered
form with a high degree of consistency.
The antimicrobial effectiveness of instrumenting
canals with rotary nickel-titanium instruments is in line
with the results seen with manual instrumentation of
root canals.
Thus, instrumentation with either
stainless steel or nickel-titanium rotary instruments in
the presence of NaOCl renders canals free of bacteria in
half to three-quarters of cases (Table 2). A recent
in vivo study that applied correlative light and electron
microscopic techniques to evaluate residual intracanal
infection after instrumentation with stainless steel hand
files in mesiobuccal canals and NiTi instruments in
mesiolingual canals of the same lower molars showed
that there was no difference in their respective ability to
eliminate infection.
That bacteria cannot be
completely eliminated after thorough instrumentation
and irrigation regardless of the technique (Fig 6) points
to the need to follow instrumentation with an anti-bacterial
dressing before obturation to better achieve
the goal of bacteria-free root canals.