Use of nickel titanium instruments for cleaning and shaping root canal systems.

Rapid and significant changes in goals, techniques, instrument design, and type of metals used to manufacture endodontic instruments have been made over the last few years in an attempt to overcome canal preparation errors. Although techniques change, basic treatment objectives remain the same. Schilder has stated that "root canal systems must be cleaned and shaped: cleaned of their organic remnants and shaped to receive a three dimensional hermetic filing of the entire root canal space." The goal of root canal instrumentation is to obtain a continuously tapering funnel from the coronal access to the apex that flows with the shape of the original canal (1). The ability to prepare the canal without weakening the remaining dentin or perforating the root is essential for proper obturation and subsequent long-term success (2, 3). Procedural errors occurring during the instrumentation phase include apical zipping, instrument separation, canal transportation, ledging, and strip perforation (4-6).