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sujatabyahatti's picture
Joined: 19 Dec 2010

The main issue is that landed-blade files do not cut effectively when used with an in-and-out pecking motion, they require the blades to be set against the canal walls for cutting to occur. While this is sometimes perceived as a less effective cutting event than the bite of nonlanded blades, the time to completion of shape belies that perception. Obviously, when the GTX File finally stalls, it is retrieved, the blades are cleaned with an alcohol gauze, and then it is re-introduced for further cutting. When the same GTX File starts to stall again, it is time to drop down in size to a 20-.04 GTX File so that initial shaping in small canals can continue safely. In this case, the 20-.06 GTX File cut all the way to length in the MB1 and MB2 canals in 2 or 3 cutting cycles, but in the DB canal a 20-.04 GTX File was needed to achieve length. This is typical in maxillary molars.
One of the new technique strategies taught for GTX File use is that of visual gauging at the end of initial shaping; looking at the first 20 Series GTX File that cuts to length to determine whether there is dentin debris in the tip flutes. When the first GTX to length has debris packing the last flute space, there is a good chance that the terminus is no larger than the tip diameter of that file. When that file is devoid of chips at its tip, it is most likely that the terminal diameter of the canal is larger.
This is a time saver as it eliminates the need to introduce Ni-Ti K-files (tactile gauging) to determine if a larger apical size will be needed to create apical continuity of taper—confirmation that the taper in the preparation extends all the way to the apical terminus. Apical continuity of the taper is what gives us the greatest chance of having apical accuracy when we fill the canal, so this is a critical element of the GT and GTX technique. Visual gauging allows a quick decision to be made on the likely final shape, and in this clinical case the 20-.06 GTX File had no tip debris after reaching the terminus of the MB1 and MB2 canals, indicating that a 30-.06 GTX File should then be used. In the DB canal, the first file to length (the 20-.04 size) showed tip flutes packed with debris, indicating that a 20 Series GTX File would probably suffice to complete the shape in that canal. And in fact, when the 20-.06 file was cut to length and tactile gauging was done, this proved to be the case.
This technique shows the clinician which tip size of a .02 tapered K-file binds at length, indirectly revealing the apical diameter of the canal. Tactile gauging is done with Ni-Ti K-files to increase the accuracy of the test since the more rigid stainless steel K-files can cause misreads of apical diameters. Tactile gauging is done in the presence of 17% aqueous EDTA so that the smear layer is removed at the same time that shaping is completed (in visual gauging you will still place EDTA in the canal for a minute to remove the smear layer before re-introducing NaOCl), and it is absolutely critical that the Ni-Ti gauging files are used with a straight-in, straight-out motion—not even a wiggle can occur or the apical constricture will be cut open and further shaping will be required to recreate apical continuity of taper.
Shaping of the palatal canal (a medium-size canal) was begun with a 30-.08 GTX File and it easily cut to length, showing no chips at the tip of that file. A 40-.08 GTX File was then cut to length with visual gauging indicating that shape might then be complete—a fact that was confirmed by tactile gauging. Each canal was shaped with just two GTX Files, and the post-op radiograph (Figure 2) shows very conservative coronal shapes and excellent apical accuracy in the obturation.


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