The effect of multiple usages of nickel-titanium rotary endodontic files on cutting efficiency.

摘要

Nickel-titanium rotary (NTR) files have been used in endodontic therapy to efficiently clean and shape root canals since the early 1990's. These files are the single most expensive disposable clinical supply used in non-surgical endodontics. When NTR files are new, they are being used in their sharpest state, with the least probability of breaking and their highest cutting efficiency (CE). As they are used in successive cases in order to contain clinical expenses, an increased risk of file separation occurs, possibly along with a decreased CE.;The purpose of this study was to determine the measurable changes in CE of NTR files as they are used in five simulated clinical situations. Three brands of NTR files were chosen for their distinct design features. The Brasseler EndoSequence is a non-landed, negative rake angle file. The Sybron Endo K3 is a non-landed, positive rake angle file. And the Dentsply ProFile is a landed, negative rake angle file. Ten files of each brand were tested, one of which was used as the negative control. Clinical use was simulated by instrumenting two canals of extracted human teeth. CE was determined using acrylic endodontic training blocks, measuring depth of penetration of the file and the mass change of the block from the material removed.;The results of this study support that the relative degree of CE between brands of NTR files could be predicted by their cross-sectional design. The Brasseler file (negative rake angle, non-landed) had an overall greater CE than either the K3 (positive rake angle, landed) or ProFile (negative rake angle, landed).;Also supported is the notion that the sharper the file's cutting edges, the quicker it will dull. This was evident by the CE change between Trials 1 and 2 of the Brasseler file. But once this change in CE had occurred, the CE for the Brasseler and the other two file brands did not change significantly over the five clinical trials.;Therefore, multiple usages of these NTR files did not show a significant decrease in CE over the course of five simulated clinical trials.