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24 I I case report _ endodontic zone As a confirmation of our definitive pulp testing results, however, the elimination of her symptoms after anaesthesia was good to see. After anaesthesia had been confirmed by heat testing and percussion, tooth #14 was isolated with a rubber dam and an access cavity into the pulp chamber was cut. As was expected from the tooth’s sensitivity to heat stimulus, the pulp was partially necrotic—the MB and distobuccal (DB) canals having fully degenerated tissue and the palatal canal pulp virtually intact (Fig. 7). ThevolumetricimagesgatheredwithmyAccuit- omo (J. Morita) revealed that the MB root held two canals that diverged from a single orifice and then joinedagainintheapicalthird,whereitappearedto have a severe palatal curve (Figs. 3–6). As I had learned from my friend and colleague Dr John Khademi, I cut a shallow MB2 groove in the mesial access wall to facilitate treatment of the only canal intheuppermolarsthatdoesnothaveanaccessline angle dropping into it (Fig. 8). All canals were negotiated with rotary NiTi instruments—first with a Vortex (DENTSPLY Tulsa) 15/.06 file to mid-root, followed by a Vortex 15/.04 to length in each canal except the MB1 and MB2, which required the more flexible PathFiles (DENTSPLY Tulsa) to reach the terminus owing to their abrupt apical curves. Rotary negotiation (in most cases without using hand files beforehand) has been a gratifying procedural upgrade in my practice. While I have not found the PathFiles to be dependable as first instruments in tight canals, Vortexfilesaccomplishthisinawaythatiscounter- intuitive to my previous paradigm (using # 8, 10 and then 15 K-files to length in the presence of a lubricant). By a fluke I found that in all but the most severelycurvedcanals(ofcoursethosewithimped- iments as well) these small Vortex instruments usually cut to length in less than a half-minute. I am not exactly certain why Vortex files work so well for handpiece-driven negotiation, but my best guess is that their triangular cross-sectional geometry has enough space between the three cutting flutes to auger, rather than compact, vital pulp tissue from the apical thirds of small canals. I have yet to block a canal with these instruments, althoughIamverycarefultostopusingthematthe slightesthintofapicalresistance.Ifthe15/.06meets resistance, I use the 15/.04. If the 15/.04 becomes stuck, I bring in hand files in sizes 08 and 10 C-files tolength,andthenIusethe#1,2and3rotaryPath- Files to length (all 0.02 tapered with tip diameters of 0.13, 0.16 and 0.19mm). IusedtheRootZXII(J.Morita)withallinitialfiles taken to length, thereby knowing at all times when Ihadreachedthetermini,andobviatingtheneedfor a length determination X-ray. As usual, I used the straight apex locator probe instead of the test clip version. Even with hand files, I dislike the spring clip file probe, as it interferes with my tactile sense and it gets in the way of the rubber dam field. With rotary negotiation, the straight probe with its v-cut tip makes it very easy to pick up as estimated length is approached with the rotary negotiating file, and its tip notch rides smoothly on the rotating file. The final reason I prefer this probe set is because it is thinner and fits more easily between the stop and handle and it is very effective at positioning the stop exactly at the reference point once length has been indicated. An additional advantage of doing theinitialnegotiationprocedurewithVortex15/.06 and 15/.04 files is that with these tapers being greater than the typical 0.02 tapered hand files, there is less change in curved canal lengths during the shaping procedures to follow. Fig. 7_Dental pulp extirpated from the palatal canal. A bent #25 broach was rotated as it was carefully inserted into the canal, after which it was gently and slowly removed with the intact pulp wrapped around it. Bending a #25 broach causes its mid-portion to sweep around the periphery of the canal wall of medium and large canals regardless of their size and taper, obviating the need for other sizes. Fig. 8_Access cavity in tooth #14, showing the preparation limited to the mesial half of the occlusal surface. Note the Khademi Groove cut into the mesial wall for easier treatment of the MB2 canal— the only canal in the upper molars without an access line angle to guide instruments and materials. The small amount of time needed to cut this groove pays dividends throughout the procedure, especially during negotiation when lubricant is filling the access cavity. roots2_2011 Fig. 7 Fig. 8