S. Cohen, M. D. Levin, and L. H. Berman
Endodontic practice. 2011 Volume 4 Number 2.
Thorough cleaning, shaping, and disinfection of the root canal system are the principle steps necessary for successful root canal treatment (RCT). The purpose is to remove all of the pulpal tissue and canal debris from the root canal space while also removing the inner layers of canal wall dentin. Years ago, some investigators suggested that we enlarge the canal space to at least three ISO sizes larger than the first file to bind in the apical part of the canal. This concept assumed such a preparation would remove the inner layers of the dentin walls while allowing the irrigant to reach the entire length of the root canal system. In endodontic cases where the canal configuration is relatively straight in its long axis and round in cross-section, this goal might be achieved using conventional hand and rotary-driven endodontic files.
However, the cleaning, shaping, and disinfection of canals that are flat and oval-shaped in cross-section, as well as curved canals, represent a significant clinical challenge to endodontic treatment. These canal configurations represent about 25%-50% of root canal systems. Many enhancements have resulted in better cleaning and shaping, but investigations using digital subtraction micro-CT and microbiologic assessments have shown our ineffectiveness to adapt to the true cross-sectional shape of all but the most round root canals, leaving almost half of the canal walls untouched by endodontic instruments. Until the recent introduction of “adaptive” cleaning/shaping instrument technology, the basic tenets of endodontic treatment have been unattainable.