Endontics: Obturation of the Root Canal System

by Samuel I. Kratchman, DMD

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, we now need to adequately obturate this root canal system. The purpose of this article is to describe the author’s technique of obturation, utilizing warm gutta percha, with the System B heat transfer system (Sybron Endodontics) (Fig. 1), the new S Kondensers (Obtura Corp) (Fig. 2), and the Obtura II (Obtura Corp) (Fig. 3).

Several years ago, I made the transition in my own practice 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, due to the taper I had created in the canals. That is when I made the transition to warm gutta percha, and not only did the radiographic appearance improve, but I found it to be more time efficient as well.

Personally, I finish my canals with a .06 taper rotary file. This is not relevant for this article, other than when choosing the proper tip for the System B unit (Fig. 4). The .06 taper most closely resembles the Medium tip on the System B, and if you finish with .04 taper rotary files instead, then the Medium Fine System B tip would be indicated. Also, in the back of my mind while instrumenting, I want a size 40-45 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 4-5mm from the working length. This allows for the proper removal of the bulk of gutta percha from the canal, while transferring heat to the 4-5mm. apical plug. This is accomplished by activating the system B coil with your finger, while advancing the now hot tip (I set the unit at 220 degrees Celsius) down the canal to within 4-5 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. I let the tip cool for 10 seconds while still in the canal, and then engage the coil for a split second while pushing apically and then withdraw the tip from the canal with the now severed gutta percha wrapped around the tip. 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 re-fit a new cone. I use non-standardized Medium gutta percha cones and a gutta gauge to customize those master cones (Fig. 5). I find that the Medium gutta percha cones most closely resemble that .06 taper I have created in the canals, but you can now buy .04 and .06 taper standardized gutta percha.

We now have a softened apical plug of gutta percha in the canal; thanks to the heat transfer process of the System B. Next we want to condense that plug of gutta percha, achieving a better seal apically (Fig. 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 (Fig. 7), to better gauge when you have reached the desired apical distance, and has a .02 taper which 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 (Fig. 8).

After down packing the apical plug of gutta percha we are ready for the Obtura II to back fill each canal (Fig. 9). The Obtura II has helped to improve the density of my fills as well as increasing efficiency. The obturation phase of treatment, for me, has now become the easy, relaxing part of a root canal. The Obtura II unit is nicely packaged with an instructional video and a plastic block to practice with. 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. There is a little trick to installing the Obtura II 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 45-60 degree curve on the tip (Figs. 10 & 11). Now place the wrench back over the tip and quarter turn counter-clockwise, loosening the tip slightly. This will allow you to rotate the tip, whether you are obturating a lower tooth or an upper tooth, without it loosening too much that gutta percha would extrude out the sides. You must place the Obtura II 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 three seconds, re-heating that apical plug. This will prevent voids from occurring between the apical gutta percha and the remainder of the filling (Fig. 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.

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 one is not happy with the appearance of the final x-ray, 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 (Fig. 13), you must attempt to achieve an apical stop with further instrumentation at a shorter working length.

Although I obturate every case with warm vertical condensation, in the method I have just described, there are some cases where this technique makes an impossible case approachable. Examine the pre-operative x-ray of a maxillary molar with previous root canal therapy (Fig. 14). Note 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 4-5 mm of the working length, this time we went down to within 2mm of the working length, making room to place the second master cone to the desired length. That second master cone is then burned out to within 4-5 mm, and the entire canal is back filled in one motion with the Obtura II. This case could not have been obturated using a cold lateral gutta percha technique, due to an inability to properly seat two master cones side by side in the palatal canal.

Another case where I believe the warm vertical technique to be necessary is this mandibular bicuspid with a trifurcation of its canal (Fig. 15). 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 three master cones have been placed and the System B utilized to leave three apical plug
s of gutta percha, the whole system is back filled with the Obtura II.

A few more cases such as this maxillary molar with four canals (Fig. 16) and another maxillary molar with a long gentle curve (Fig. 17), depict the results obtainable with the above described obturation technique. These two mandibular molars (Fig. 18) have small lateral canals in the apical third, and 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.

The 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 my personal technique of obturation, with the hope that others may incorporate some aspects into their own style.

Dr. Sam Kratchman currently serves as an Associate Professor of Endodontics and the Assistant Director of Graduate Endodontics, in charge of the microsurgical portion of the program, University of Pennsylvania. He lectures throughout the US, Europe, Scandinavia, and Asia. He also maintains a private practice, limited to endodontics, in Exton, PA.

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