The quest for technological advances and improvement on existing techniques is actively sought after in dentistry. Who does not want to do things better, faster, and more effectively? For decades, we have sought to improve obturation concepts, instruments and procedures to dramatically make them simpler and better.
Dr. Herbert Schilder in 19671 gave birth to a predictable means of obturating the canals in 3-dimension using thermosoftened gutta-percha and sealer. He showed how his technique could generate hydraulic forces that could fill lateral canals, fins, cul-de-sacs, and many of the complex anatomical irregularities within a root canal system. However, the Schilder Technique has proven to be a difficult procedure to master and time consuming. His original technique involved the use of a heat carrier that was flamed over a torch until it burned cherry red. This instrument was then quickly stabbed into the fitted gutta-percha cone and withdrawn to leave thermosoftened material that is condensed apically with a plugger. This sequence is repeated several times with various fitted pluggers until the gutta-percha is down packed to within 5-7mm of the radiographic terminus. The canal is then back filled using several pieces of gutta-percha and again in cycles of heating and condensing until the canal is obturated.
Over the years, technological improvements have been made which significantly improve the clinician’s ability to perform warm vertical condensation. In 1982, the Touch’n Heat electric heat carrier (Fig. 1) was introduced which eliminated the need for a flaming torch. Patients also preferred this innovation since it decreased the incidence of burnt lips since the heat carrier on the Touch’n Heat is only activated prior to the tip entering into the canal instead of being transferred to the area when it is flaming red. With this technology, the canals could be obturated efficiently and quickly.
In 1987, Dr. Stephen Buchanan developed the Continuous Wave of obturation Technique2 that further improved on the Schilder Technique of obturation. It eliminated the need to fit multiple pluggers and allows for condensation of the gutta-percha in one downward compaction movement. This technique allows a single tapered plugger to capture a wave of condensation at the orifice of a canal and “ride it”, without release to the apical extent of down packing a single continuous movement. This builds a continuous wave of hydraulic forces that can push warm gutta-percha and sealer into anatomical irregularities and lateral canals. In the Schilder technique, this wave is interrupted several time, thus the pressure wave, and heat is lost each time condensation stops and the gutta-percha cools. This technique use a modification of the Touch’n heat machine called the System B (Fig. 2).
The System B heat source can monitor the temperature at the tip of its heat carrier device, delivering a precise amount of heat for a long period of time. The heat carriers or Buchanan pluggers (Fig. 3) were designed with geometries that closely approximate the shapes of tapered root canal preparations. These pluggers come in four sizes: fine, fine-medium, medium and medium-large which resemble the taper of non-standardize master cones. In addition, these dead-soft stainless steel heat pluggers are fairly flexible, allowing for deeper condensation especially in narrow, curved canals. These heat carriers are designed to soften the gutta-perch and at the same time condense it. The System B has temperature settings of up to 600C. Hand et al.3, have shown that quick burst of heat to temperatures as high as 360C will cause short and mild inflammation of the periodontal tissues that is not visible after 12 hours. Therefore, high temperatures of up to 350C for short periods of time will not cause irreversible periradicular damage.
Recently, a new obturation technique has been developed that utilizes the System-B device. This technique has been named the Thermo-Hydraulic-Condensation (THC) Technique. THC takes advantage of the System-B while modifying Dr. Buchanan’s original obturating procedure resulting in improved hydraulics during the downpack. The improved thermal-hydraulics from the THC technique result in obturation of more lateral canals (Figs. 4).
It is believed the process works by increasing the time for the gutta-percha to flow along with pressures obtained during the procedure. Traditional System B techniques use high temperatures which result in the tip melting the gutta-percha quickly like a hot knife through butter. This in turns, the authors feel, does not provide enough time for the ‘cementopercha’ to flow properly.
In order to obturate the root canal system with the THC technique, certain objectives must be met: 1) maintain the apical constriction as small as practical, 2) the pre fitted gutta-percha cone must have a snug fit to within 0.5 mm of radiographic terminus used, 3) have a gradual taper, 4) allow a Dovgan 04 tapered Niti Plugger (Thompson, Moyco, #35/45, #60/80) (Fig. 5), and a preselected system B plugger to fit within 3-5mm from the working length.
MATERIALS
Non-standardized gutta-percha cones (FM, M, ML) and standardized cones.
Kerr Pulp Canal Sealer
System B with Buchanan pluggers (F, FM, M, ML)
Dovgan Plugger(s) as needed
Obtura II with 23 gauge tip
TECHNIQUE
A non-standardized (FM, M, ML) gutta-percha cone is fitted to within 1mm of the working length (Fig. 6).
A Buchanan Plugger is chosen according to the gutta-percha size. If a size medium cone was fit, a medium plugger should be used. The tips of all the pluggers are 0.5mm in diameter and should fit to within 4-7mm from the apical terminus. Prefit the plugger to verify that its’ binding point in the canal is between 4-7mm (Figs. 7a & b). Place a silicone stopper to mark the plugger.
Dry the canal and cement the cone in place.
Set the Obtura II at 200C (Fig. 8a). Place the heated tip at the orifice and sear off the coronal portion of the cone while injecting the thermoplasticized gutta-percha into the canal (Fig. 8b). Inject approximately 2-3 mm of the material. Condense the gutta-percha with a Schilder plugger (choose a plugger sized slightly smaller than the orifice). This will create an orifice plug that will maximize the hydraulic pressure during the downpack.
Turn the system B heat source on to the “use” and place it in the “touch” mode. Set the heat at 100C and the power on maximum. This low temperature setting will allow the gutta-percha to thermoplasticise without burning. Hold the button on, drive the preheated plugger smoothly through the gutta-percha until you reach within 3-4mm of the binding point. You will feel an increase in resistance to your downward push or the tip may even stop (Fig. 9). This will take approximately 2 seconds.
At this point, have your assistant immediately turn up the temperature to 300C. Apply apical pressure to push the plugger to the binding point, then quickly withdraw the plugger. This “separation burst” will take about 1.5 sec (Fig. 10). The heat is turned up to 300C to plastize the gutta-percha in the most apical portion of the canal.
Using a Dovgan plugger that fits within 3 – 5 mm of working length, apply pressure while tapping (up-down packing motion) and condense the gutta-percha for a few seconds. As the material cools, stop condensing and apply apical pressure for about 10 sec. This will prevent the material from shrinking (Fig. 11).
The canal is now ready for the backfill. The authors recommend backfilling using the Obtura II thermoplasticized gutta-percha injection system. This can be accomplished by injecting small aliquots of gutta-percha (2-3mm) into the canal and vertically compacting with a plugger (Fig. 12). This is repeated until the whole canal is obturated. If Obtura II is not available, any other technique can be used.
ADVANTAGES OF THE THC TECHNIQUE
Excellent apical control
Thorough condensation of the main and lateral canals
Less technique sensitive than the classic Schilder technique
Downpack in one motion
Fast, easy and predictable
DISADVANTAGES OF THE THC TECHNIQUE
Must have good shape and apical resistance form.
Initial purchase of System-B unit, Dovgan pluggers and Obtura II.
In summary, the THC introduces a third generation warm gutta percha technique utilizing the System B and Obtura II with Dovgan Niti pluggers. Maximize your endodontic obturation by generating the improved hydraulic pressures needed over slightly longer period of time with lower overall temperature. This will result in 3 dimensional “cementopercha” flow demonstrating the complexity of the case (Figs. 13 & 14).
Yosef Nahmias DDS, MS, currently maintains a private practice specializing in endodontics in Oakville, ON, Canada. He is also a clinical instructor at the University of Toronto, department of endodontics.
Terence Mah DDS, MS, maintains private practices specializing in periodontics and implant dentistry in Toronto and Chicago, IL. He is currently a graduate student at the University of Toronto, specializing in endodontics.
Joseph S. Dovgan DDS, MS is a Diplomate, American Board of Endodontics with a full time private practice limited to endodontics in Paradise Valley, AZ. He is the inventor of over 15 endodontic instruments/disposables.
Oral Health welcomes this original article.
REFERENCES
1.Schilder H. Filling root canals in three dimension. Dent Clin North Amer 1967; 723-44.
2.Buchanan LS. The continuous wave of condensation technique: a convergence of conceptual and procedural advances in obturation. Dentistry Today 1994; 13(10): 80, 82, 84-5.
3.Hand RE. Effects of a warm gutta-percha technique on the lateral periodontium. Oral Surg 1976; 42(3): 395-401.
