I clinical report _ shaping system Fig. 3 Fig. 4 Fig. 3_Mandibular molar with failing endodontic therapy due to apically inadequate treatment in all canals. Fig. 4_Negotiation files in mesial canals after removal of filling material and advancement through apical blockage; note the severe curvatures. Fig. 5_Post-op radiograph showing apical confluence of mesial canal shapes and the second apical portal of exit branching off the point of confluence; note the apical ledge at the curvature in the distal canal, bypassed with bent stainless-steel K-files and finished with a pre-bent GTX Rotary File. 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 File 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 achieved, 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 achieved with NiTi K-files to increase the accuracy of the test because the more rigid stainless-steel K-files can cause misreadings of apical diameters. Tactile gauging is achieved 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 dentists will still place EDTA in the canal for a minute to remove the smear layer before reintroducing NaOCl), and it is absolutely critical that the NiTi 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 the 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 postoperative radiograph shows very conservative coronal shapes and excellent apical accuracy in the obturation (Fig. 2). _Case 2: Mandibular molar re-treatment Figure 3 shows a previously treated tooth that was sensitive to percussion and biting pressure. It had an overt apical lesion on the mesial root apex due to the inadequacy of apical treatment. After removal of the gutta-percha, lubricant and small K-files were used to bypass the apical blockage in the mesial canals (Fig. 4) and the ledge in the distal canal. The mesial canals had separate apical openings that were each negotiated. However, they were also confluent Fig. 5 08 I roots 4_ 2009