Recent endodontic studies have dis­ cussed various methods of root canal preparation. Some of these studies have raised questions about the effec­ tiveness of hand instrumentation. Gutierrez and Garcia1 showed that endodontic instrumentation leaves areas of the root canal unprepared. Haga² showed that instrumentation to a size 0.35 file did not smooth the canal walls. Davis and others 3 and Laws4 considered the elimination of morphologic aberrations an important criterion for satisfactory root canal preparation.