Authors: Miserendino LJ, Moser JB, Heuer MA, Osetek EM.
Title: Cutting efficiency of endodontic instruments. Part 1: a quantitative comparison of the tip and fluted regions.
Journal: J Endod
Date: Oct 1985
Citation: 11(10):435-41
Category: Access and Canal Instrumentation
Evidence-based Ranking: 5
Purpose/Objective: (1) To compare the cutting characteristics of several types of endodontic instruments used for biomechanical preparation (2) to attempt to relate specific design characteristics of the tip of these instruments to the overall cutting efficiency of the instruments and (3) to provide a model system for comparing the relative cutting efficiency of various types of root canal files, reamers and other instruments.

Materials and methods: 7 designs of #50 endodontic instruments were examined to determine variation in the tip and fluted portions of the instruments. The tip angles were measured, presence or absence of cutting edges was noted, shapes of the tip cross-section determined, and whether tips were rounded or pointed were all recorded. The instruments were mounted in a quarter-turn endodontic contraangle handpiece. The instruments were tested into bovine femur with 0.33 and 0.40mm diameter pilot holes. Cutting efficiency was evaluated in terms of volume of bone removed per unit of energy expended during enlargement.

Results: Comparing the cutting efficiency of the tips, it appeared that in the larger diameter holes, K-files outperformed the other instruments. In smaller diameter holes, the reamers outperformed the files and the instruments of K-type geometry. Comparing the fluted portion of the instruments, files ware superior when used in larger diameter holes. In smaller diameter holes, the K-Flex ranked first although not significantly better than the Kerr file, Union Broach reamer or Kerr reamer.

AuthorÂ’s conclusions: Separation of the cutting effects of the tip of the instrument from the fluted portion indicated that the design of the tip of an endodontic instrument significantly affects its ability to enlarge pilot holes of greater or lesser diameter. Instruments that performed better in the larger diameter holes were not found to be the most efficient when tested in the more constricted holes. For most instruments tested, the tip is a significantly more efficient cutting surface than the fluted portion of the same instrument.

ReviewerÂ’s comments: The conclusions drawn from this article can only be directly applied to instruments using quarter-turn endodontic contra angle handpieces (Giromatic by Micromega).