Authors: Weine FS, Kelly RF, Bray KE.
Title: Effect of preparation with endodontic handpieces on original canal shape.
Journal: J Endod
Date: Oct 1976
Citation: 2(10):298-303
Category: Access and Canal Instrumentation
Evidence-based Ranking: 5
Purpose/ Objectives: Two hand instrumentation techniques (reaming action and flaring with removal of flutes) and two mechanical instrumentation techniques (Giromatic and W&H handpieces) were compared by using simulated curved canals in resin blocks.

Methods and Materials: Six single and two pairs of simulated curved canals in resin blocks were prepared by each technique. Also, automated handpieces were used in an attempt to bypass ledges that were purposely made.

Results: Average time for each type of preparation technique is listed in Table 1. Of the six canals that W&H contra-angle handpiece was used, ledges occurred and couldnÂ’t be bypassed in four canals. In the canals that were intentionally ledged, neither of the automated handpieces was able to bypass the ledges.

Discussion: -In the canals prepared without instrument rotation, the increase in width between the curve and the tip of the preparation was minimal. -The mechanical handpieces and reaming action created wider apical zips at the site of exiting than did hand instrumentation with flaring and removal of flutes when preparing canals with sharp curvatures. -When canals with more gradual curves were prepared, there was little difference in the preparations.

ReviewerÂ’s Comments: Mechanical handpieces have been developed to decrease time needed for canal preparation. In this study the result was just the opposite. As mentioned in the discussion, these handpieces might be more effective in canals with less curvature.