Written by Samuel I. Kratchman, DMD Thursday, 01 May 2003 00:00
There have been numerous articles written on instrumentation techniques utilizing the different rotary nickel-titanium files on the market. I have found that practitioners develop a system that works best in their own hands. Often this is a hybrid of several techniques discussed in various articles. After creating a clean, tapered canal, one must adequately obturate this root canal system. The purpose of this article is to describe the author’s technique for obturation.
Several years ago, I made the transition from hand stainless steel files to nickel-titanium rotary files. I was still obturating with cold lateral condensation of gutta-percha and found that the obturation process took twice as long because of the taper created in the canals. That is when I made the transition to warm gutta-percha. Not only did the radiographic appearance improve, but I found it to be more time efficient.
INSTRUMENTATION AND TECHNIQUE
|Figure 1. System B unit from Sybron Endodontics.||Figure 2. New set of 3 S Kondensers from Obtura Corporation.|
|Figure 3. The Obtura II unit comes complete with instructional video and plastic practice blocks.||Figure 4. The medium System B tip compares closely to a medium gutta-percha cone, and the medium fine System B tip resembles a medium fine gutta-percha cone.|
The technique described in this article uses the following instrumentation: the System B heat transfer system (Sybron Endodontics, Figure 1); the new S Kondensers (Obtura Corp, Figure 2); and the Obtura II (Obtura Corp, Figure 3). I finish canals with a 0.06 taper rotary file. This is not relevant for this article, other than when choosing the proper tip for the System B unit (Figure 4), the 0.06 taper most closely resembles the medium tip on the System B. If you finish with 0.04 taper rotary files instead, then the medium fine System B tip would be indicated.
As I am instrumenting, I want a size 40 to 45 rotary to go within 4 mm of the working length of each canal, so that the medium System B tip will then be able to fit approximately 4 to 5 mm from the working length. This allows for the proper removal of the bulk of gutta-percha from the canal while transferring heat to the 4- to 5-mm apical plug. This is accomplished by activating the System B coil with your finger while advancing the now hot tip (set the unit at 220°C) down the canal to within 4 to 5 mm of the working length. Now remove your finger from the coil and allow the System B tip to cool down. Because the System B tips are hollow, they heat up almost instantaneously to the set temperature. Let the tip cool for 10 seconds while still in the canal, then engage the coil for a split second while pushing apically, then withdraw the tip from the canal with the now severed gutta-percha wrapped around the tip.
|Figure 5. Gutta gauge, used to customize the gutta-percha cone.|
There will be a short learning curve when you will pull out the entire gutta-percha cone from the canal instead of leaving behind that apical plug. This means you did not have adequate tug back of your master cone and will need to refit a new cone. I use nonstandardized medium gutta-percha cones and a gutta gauge to customize those master cones (Figure 5). I find that the medium gutta-percha cones most closely resemble the 0.06 taper created in the canals, but you can now buy 0.04 and 0.06 taper standardized gutta-percha.
|Figure 6. Apical plug of gutta-percha remains in canal and can now be packed down.||Figure 7. Notches at 5-mm intervals on the nickel-titanium end of the S Kondensers.|
|Figure 8. Indentation in handle of S Kondenser for finger rest during condensation.|
There is now a softened apical plug of gutta-percha in the canal, thanks to the heat transfer process of the System B. Next step is to condense that plug of gutta-percha, achieving a better seal apically (Figure 6). This is where the new S Kondensers from Obtura Corp. come in handy. The S Kondensers have improved on several problems that existed with other condensers. They are ISO standard colors, so that the black is size 40 nickel-titanium on one end and size 80 stainless steel on the other end. The yellow S Kondenser is 50 nickel-titanium and 100 stainless steel, and the blue S Kondenser is 60 nickel-titanium and 120 stainless steel. The nickel-titanium end is marked at 5-mm intervals (Figure 7) to better gauge when you have reached the desired apical distance and has a 0.02 taper that gives you excellent compressive strength without compromising flexibility. The handles are made of an anodized aluminum, which is easy to clean and maintains its color throughout autoclaving. The handles are notched to provide a finger rest, positioned so that you can grip the S Kondenser comfortably and apply firm pressure during condensation (Figure 8).
|Figure 9. Obtura II unit ready to go.|
After down-packing the apical plug of gutta-percha, you are ready for the Obtura II to back fill each canal (Figure 9). The Obtura has helped to improve the density of my fills as well as increase efficiency. The obturation phase of treatment, for me, has now become the easy, relaxing part of root canal treatment. The Obtura unit is nicely packaged with an instructional video and a plastic practice block. The tips come in 23 gauge and a thinner 25 gauge. If you choose to use the 25-gauge tip, you must use the gutta-percha pellets designed for this tip, which soften at a lower temperature.
|Figure 10. Installation of needle.||Figure 11. Tip bending instrument.|
|Figure 12. Void in gutta-percha filling.|
There is a little trick to installing the Obtura tip that will allow you to obturate either maxillary or mandibular teeth without changing the tip. First, you screw the tip into place with the wrench and use the bending tool to place between a 45° to 60° curve on the tip (Figures 10 and 11). Now place the wrench back over the tip and quarter-turn counterclockwise, loosening the tip slightly. This will allow you to rotate the tip, whether you are obturating a mandibular tooth or a maxillary tooth, without it loosening so much that gutta-percha would extrude out the sides. You must place the Obtura tip in the canal and come in contact with the apical plug of gutta-percha before back-filling. Once the tip is in contact with the now-cooled apical gutta-percha plug, let it remain there for 3 seconds, reheating that apical plug. This will prevent voids from occurring between the apical gutta-percha and the remainder of the filling (Figure 12). If you hear a crackling noise while injecting the gutta-percha, it is an air pocket and will not affect the fill as long as you continue to press the trigger, filling the canal. I back-fill in one motion, not segmentally, and after completing the back-filling of each canal, I back-pack with the stainless steel end of the S Kondenser. The root canal is now complete.
|Figure 13. Gutta-percha extruding through apex.|
Most so-called problems with obturation are actually problems with one’s instrumentation. The obturation is in essence an “impression” of what the canal looks like after it has been instrumented. If you are not happy with the appearance of the final radiograph, you are actually criticizing the instrumentation/flaring of the canals. If the master gutta-percha cone does not seat all the way to the desired working length, you must go back with a file to make sure there is no debris in the canal and that the flaring is adequate. If the master cone goes beyond the apex (Figure 13), you must attempt to achieve an apical stop with further instrumentation at a shorter working length.
|Figure 14a. Retreatment of maxillary first molar (courtesy of Dr. Kevin Edwards); preoperative radiograph.||Figure 14b. Postoperative radiograph.|
Although we obturate every case with warm vertical condensation, in the method just described, there are some cases where this technique makes an impossible case approachable. As an example, examine the pre-operative radiograph of a maxillary molar with previous root canal therapy, shown in Figure 14a. Note that the periapical lesion associated with the palatal root is not only at the radiographic apex, but also towards the side of the apex. This maxillary molar had an apical bifurcation of its palatal canal, and instead of burning out the gutta-percha with the System B to within 4 to 5 mm of the working length, this time it was burned to within 2 mm of the working length, making room to place the second master cone to the desired length. That second master cone was then burned out to within 4 to 5 mm, and the entire canal was back-filled in one motion with the Obtura (Figure 14b). This case could not have been obturated using a cold lateral gutta-percha technique because of an inability to properly seat 2 master cones side by side in the palatal canal.
|Figure 15a. Mandibular bicuspid with trifurcation of canals (courtesy of Dr. Kevin Edwards); preoperative radiograph.||Figure 15b. Mid-obturation radiograph.|
Another case where I believe the warm vertical technique to be necessary is the mandibular bicuspid with a trifurcation of its canal, shown in Figure 15a. Three separate master cones were used, with each cone being burned out apically to the trifurcation, allowing room for the next master cone to be seated. After the 3 master cones had been placed and the System B utilized to leave 3 apical plugs of gutta-percha, the whole system was back-filled with the Obtura (Figure 15b).
|Figure 16. Four-canal maxillary molar.||Figure 17. Maxillary molar with long-but-gentle curvature of MB root.|
|Figure 18. Mandibular molar with lateral canal filled in apical third of distal root.|
In other case examples depicting the results obtainable with the described obturation technique, note a maxillary molar with 4 canals (Figure 16), and another maxillary molar with a long gentle curve (Figure 17). Figure 18 shows a mandibular molar that has small lateral canal in the apical third. With the warm vertical technique using a thermoplasticized (semi-solid) form of gutta-percha, you will see a higher incidence of filling such lateral canals.
An old expression states there are many ways to skin a cat. Similarly, in endodontics, there are several ways to instrument and to obturate root canals. Practitioners often develop their own “hybrid” technique, utilizing ideas from several colleagues. The purpose of this article was to share the author’s personal technique of obturation, with the hope that others may incorporate some of its aspects into their own style.
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