INTRODUCTION
If instrumentation were 100% effective in removing all bacteria and debris from the canal, irrigation would be an insignificant adjunct to mechanical debridement. We would irrigate only to lubricate and facilitate canal instrumentation. Unfortunately, this is not the case. There are many studies that show the limited ability of instrumentation alone to debride and clean the canal.1-5 Wu and Wesselink6 reported uninstrumented areas in 65% of instrumented oval canals. Rödig et al7 studied nickel-titanium (Ni-Ti) rotary instrumentation of buccal and lingual extensions of oval canals and found inadequate controlled debridement.
The complete shaping and debridement of root canals is often very difficult because of the morphology of the canals. Many canals are oval in shape with outpocketing, evaginations and undercuts containing tissue. Peters et al,studying the effect of 5 Ni-Ti rotary instrumentation systems, found that all techniques left 35% or more of the canal unchanged. Using ProTaper, GT rotary, Light Speed, and Profile, approximately 35% to 40% of the root canal surface was not prepared, and no significant differences between the systems were noted when studied and reported by Vaudt et al. Sherman and Sultan compared smear layer removal after instrumentation and irrigation using SafeSiders reciprocal system, ProTaper, Mtwo, and HeroShaper rotary Ni-Ti instrumentation systems. All systems removed the smear layer in the coronal third. SafeSiders, a reciprocal system, demonstrated far better smear layer removal in the middle and apical thirds than did any of the 3 other rotary systems.
It seems from the literature that most rotary instrumentation systems do an adequate job in shaping the canal but a poor job when it comes to debridement and cleaning of the canal. No instrumentation technique comes close to sterilization of the canal.
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