clinical report _ shaping system I _Case 1: Maxillary molar treatment This case was treated as a live demonstration at the California Dental Association meeting in Anaheim in USA on 3 May 2008. Figure 1 is a radiograph showing the final negotiating files in each canal. I do not consider this a means of length determination because they are not as accurate as my J. Morita apex locator for this purpose. This image was taken to demonstrate for my audience the curvatures of the different canals in this tooth. The mesiobuccal (MB) and disto-buccal (DB) canals have obvious, significant curvatures. The palatal canal appears to be straight in this X-ray angle but could be curved in the buccal or lingual planes, a possibility that will be discovered during the shaping of the canal. This image shows the negotiating prerequisite to shaping with GTX Files: a #15 K-file (or larger) to the terminus of all canals. The shaping objective for GTX File use has been changed (streamlined) from that suggested for GT File shaping. Notably, the smallcanal shaping objective is now limited to a .06 shape and the shaping objective for medium– large canals is typically limited to a .08 shape. This is with the understanding that some medium and large canals may occasionally need a .10 or even a .12 shape, if their apical canal form is large. So, the MB and DB canals will be shaped to a .06 taper and the palatal canal to a .08 taper, with the final apical diameters to be determined by apical gauging procedures followed after the initial shape has been cut. This tooth had two MB canals that were apically confluent. GTX File shaping is achieved in the presence of 6 % NaOCl, and the shaping routine in small canals is always begun with the 20/.06 GTX File used at 300 rpm with a torque limit of around 250 gm/cm. The 20/.06 GTX File is spun up and introduced into the canal with a light but steady apical movement. This is where the biggest difference between GT File and GTX File function becomes apparent. The GT Files (with their smaller chip space) typically cut for about four to six seconds before stalling in their apical progress, owing to the cut debris filling the chip spaces; whereas the GTX Files (having twice the chip space) will cut for ten to twelve seconds before stalling. I usually let the file continue its apical progress without any interruption. However, many of my colleagues cut with the file for three to four seconds, withdraw by 0.5 mm, and then continue further apical progress until the file stalls. 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 non-landed 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 alcohol gauze, and then the file 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 two or three 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 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 dentine debris in the tip flutes. When the first GTX File 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 NiTi K-files (tactile gauging) to determine whether 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. Fig. 2 Fig. 2_Post-op radiograph showing conservative coronal shapes, apically accurate fills, and an ideally cut access cavity with the mesial and distal access walls parallel to the mesial surface of the tooth. roots 4 _ 2009 I 07