Warm Vertical Obturation: A Lost Art? by Dr. Reid Pullen

In the final installment of a two-part series, a Townie endodontist explains how to perform this root canal technique

by Dr. Reid Pullen

Editor’s note: In Dr. Reid Pullen’s first article about warm vertical obturation, which ran in the November 2019 issue of Dentaltown magazine, the Townie endodontist explained why he now uses this technique to treat most cases in his endodontic office. In this month’s installment, Pullen discusses the technique that he believes gives him the best seal, set and success.

Removing the smear layer

Let’s assume that the shaping is complete and you’re ready to fill or obturate the root canal system. What’s the next step? It’s time to remove the smear layer (Fig. 1)—the debris layer made up of inorganic dentinal shavings and organic dead and live microbes that cling circumferentially to the canal wall. This crud was created by us—by our hand and NiTi shaping files.

How do we remove it? There are two excellent options:

• Use 17% EDTA for 1 minute, then flush it out with either 3–6% (I use 6%) sodium hypochlorite or saline. 17% EDTA is a weak acid and it will degrade the peritubular and intertubular dentin, so it’s important to irrigate it out after one minute.¹

• Allow QMix, an EDTA/chlorhexidine combination from Dentsply Sirona, to sit in the canals for one minute, then dry and obturate. I’ve been using QMix since 2016 and like that it removes the smear layer, has an antibacterial and substantivity effect with the chlorhexidine, is self-limiting (so theoretically it does not dissolve peritubular dentin if it sits in the canals for too long), and lastly, doesn’t require rinsing—just dry with paper points.

Fig. 1: Credit: semanticscholar.org

Fig. 2: The worst patient I’ve ever had, so I took the time to carve a smiley face into the gutta-percha with my endo explorer. (It made me happy.)

Fitting the gutta-percha cones

In my practice, I complete shaping, suck out the 6% sodium hypochlorite from the canals using an EndoVac Macrocannula from Kerr Endodontics, then flush the system with QMix to remove the smear layer. I then recapitulate with either a #10 or #15 K file to make sure each canal is patent and free of any debris.

The next step is to fit the gutta-percha cones. This is a step that needs to be taken seriously: Slow down and make sure the cones fit snugly to working length, with slight tug-back. Not every case will have tug-back, but this is the ultimate goal because it is one way to feel that the cone has slid down the shaped and tapered canal to the established working length and fits snugly at the apex. It’s a theoretical term but in a blind procedure, it does provide feedback on the state of the cone fit.

Check that the cone is actually at your established working length by taking cotton pliers and crimping the cone right at the established reference point—I use the incisal edge for all anteriors, the buccal cusp for all premolars and the MB cusp for all molars—then measuring it with a ruler (Fig. 2). If the cone is 1–2mm short, then it’s time to reassess. Is the cone the problem, or is it the shape?

I once had a dentist in my 2-Day Root Camp Boot Camp course state emphatically that the gutta-percha cones he used were defective. I told him that most likely his shaping technique was defective. There is some error rate with traditional gutta-percha —some cones may be slightly bigger or smaller than advertised—and the solution is to use micronized, machine-precision gutta-percha that matches the file system’s final nickel titanium shaping file. In my practice, I shape the majority of my cases with either the WaveOne Gold reciprocating file or ProTaper Gold, both from Dentsply Sirona. Both systems, as well as many others, have matching micronized, machine-precision gutta-percha cones that actually fit the shape you cut.

Make sure the cones fit within 0.5mm of the established working length.

• If it fits 1mm long, then trim 1–1.5mm off the tip with scissors.

• If it’s 1–2mm short, first try another cone; if it’s still short, go back and either reshape the apex with the last nickel titanium shaping file or hand-file the apical one-third to the apical size of the last shaping file, usually between sizes 25 and 35. This part is mostly glossed over by dentists, and it’s important to achieve the best possible gutta-percha fit to the established working length before cone-fit radiographs. Spending an extra two or three minutes on achieving an excellent cone fit to working length will end up saving you time.

• If the cone is 2mm short, instead of having to shape after cone-fit radiographs, refit new cones and then take new cone-fit radiographs, spend a few minutes reshaping the apical third, and then placing new QMix. Now try in the corresponding cone and usually it will slide right to working length.

When you’re happy with the cone fit, have a dental assistant take two quality straight and shift periapical radiographs. Look carefully at these two PAs, because this is your last chance to correct any gutta-percha length problems before sealing the canal system forever and ever (at least, that’s the hope). Are the cones sitting at or within 0.5mm of the established working length and near the radiographic apex? If so, well done—it’s time to obturate and seal the cleaned canal system.

If I use 17% EDTA, then I first take my cone-fit radiographs with bleach in the canals. I then irrigate the canals with 17% EDTA for one minute and then rinse out the EDTA with bleach or saline.

Drying the canals

The best way to efficiently dry the canal system is to use a small vacuum on the end of a suction. I use the EndoVac Macrocannula to suck out most of the QMix in the canals (Fig. 3), then follow this up with one or two paper points per canal (Fig. 4).

I like to use the corresponding paper point that fits the last shaping file. For example, if the shape was prepared with WaveOne Gold Primary, then I use the WaveOne Gold Primary paper points; if it was completed with ProTaper Gold F2, then I use the ProTaper Gold F2 paper points. At times, I also use either coarse or extra-coarse paper points from Benco or Henry Schein. One or two coarse paper points usually work on most shapes and dry the canal down to the apex.

If the shape is smaller than normal, I use the microcannula, followed by medium paper points. Make sure the canals are dry and a pool of fluid does not sit in the apical one-third. This could affect the apical seal and increase the chance of sealer washout in the most important area—the apical third. If the canal will not dry because of purulent exudate, I place a premixed calcium hydroxide (UltraCal XS from Ultradent) into the canal, prescribe antibiotics and complete obturation in two weeks.

On these cases, two weeks allows time for some apical “healing.” Early in my career, I would try to obturate these purulent drainage cases after only a week and would often encounter serous fluid drainage back into the canal system. I was unable to dry the apex of many of these cases, and then would place calcium hydroxide again and reschedule for a third appointment. Two weeks, in my opinion, allows for some tissue “healing.” I’m now able to dry the canal and apex on most of these cases and then complete obturation at the second appointment.

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Buttering the gutta-percha cones

In my practice, I typically use ThermaSeal Plus Ribbon sealer from Dentsply Sirona or Pulp Canal EWT from Kerr. My assistant mixes the sealer on a pad and places it on the patient’s shoulder/neck area. If it’s Pulp Canal Sealer EWT, my assistant mixes it on the thicker side. Make sure the sealer is not too thick or too thin—if it is, liquid or powder can be added and the sealer remixed.

I pick up the prefit gutta-percha cone with cotton pliers at the crimped spot on the cone (working length) and butter the apical third (Fig. 5). I want the entire apical third coated with sealer—not too much, not too little. I gently place the cone into the dried canal to within 4–5mm of working length. When I near working length, I lift the cone slightly, then slowly place it to working length (Fig. 6). This lift action just short of the apex allows the cone tip to pick up more sealer that’s either in the canal lateral or sitting on the canal walls. The theory is that this extra bit of sealer provides insurance that there’s enough sealer to provide a hermetic seal between the cone and the periradicular tissue.

How do you know that the cone has reached the established working length? The crimped spot on the cone equals the working length, so if that spots reaches the cusp reference point, then you know it’s at the correct length. If the cone stops 1–2mm short of the crimped spot, then something’s wrong—the apical end of the cone is either bent on its side or scrunched up due to some debris in the canal, preventing the cone from extending to the proper working length. If this happens, pull the cone out and check to see if it’s bent over. If it’s not, then take a #15K file and make sure the canal is still patent. Rinse out any debris with QMix or sodium hypochlorite, check that the cone fits and then dry with paper points. (Usually this all can be avoided if you have recapitulated, which removes any apical debris, during the QMix phase and the cones fit accurately to working length. Take your time on cone fit!)

Fig. 7

Fig. 8a

Fig. 8b

Fig. 9a

Fig. 9b

Fig. 10

Heat tip

Once the cone has been placed to the established working length, use a heat source to “burn” off the coronal and middle third gutta-percha. There are many heat sources on the market; my favorites are the EndoPro 270 from Brasseler and the GuttaSmart Heat Tip from Dentsply Sirona. (For years, I used the System B heat source, which also worked well, but I now prefer cordless heat and backfill devices because they’re easier to use and are more efficient because my assistants have them primed to hand to me when I’m ready.)

I use the term “heat” and “fill” to differentiate between the heat tip (Fig. 7) and the backfill device. At this point I say “heat” and my assistant hands me the heat tip device with a rubber stopper on the tip.

• With the EndoPro 270, I typically use the small 45/04 tip on regular canals, and the medium heat tip 55/08 in the bigger canals (maxillary anterior, palatal canals of maxillary molars, distal canals of mandibular canals).

• If I’m using the GuttaSmart heat device, I prefer the black tip on regular canals and the yellow tip on the larger canals.

The goal is to place the heat tip plugger to within 5–7 mm (preferably 5 mm) of the working length. Why? Heat travels from the heat tip down along the gutta-percha cone.^2,3 The goal is effectively to soften the apical third of the gutta-percha so it will mold and conform into the irregularities and shape of the apex. This should produce an excellent seal because there’s a thin layer of sealer between the compacted gutta-percha filler and the periradicular tissues, effectively sealing the foramen or portal of exit from any microbes entering or exiting the canal system.

I first place the stopper on the heat tip to within 5 mm of my working length (Figs. 8a and 8b), then turn on the heat device and remove the coronal portion of the cone. I compact the coronal gutta-percha with a large endo plugger, such as Dovgan made by Hartzell Instruments (Fig. 9a), then plunge the heat tip into the gutta-percha and try to advance the tip within 5mm of the working length. If it does, I turn the heat off for a few seconds, hold the plugger still, with gentle downward pressure, then reactivate the heat and remove the rest of the coronal/middle third gutta-percha (Fig. 9b). Gently pack the softened gutta-percha with a small-ended plugger—I prefer the white or green ends of the Dovgan pluggers—but before placing the plugger into the canal, I dip its end into a small amount of sealer and introduce it into the dry and empty canal space. There is now a 5mm apical plug of gutta-percha (Fig. 10) that theoretically should be molded into the apex, sealing the foramen with a small amount of sealer present in the coronal and middle thirds.

In some cases, it’s difficult to extend the heat tip to within 5mm of working length. Maybe the canal is curved, or the shape was minimal due to calcification or canal anatomy. In these cases, the obturation technique is not a true “warm vertical,” but more of a hybrid warm vertical/single-cone obturation technique—warm vertical in the coronal/middle two-thirds and single-cone in the middle/apical third. In other words, the heat does not transfer from the heat tip through the gutta-percha more than 4–5mm. If in a tighter or curvy canal the heat tip advances only within 7mm of the working length, then it is in effect a single-cone obturation in the apical third. This happens often, and despite this deficiency, in my opinion there is still good clinical success.

Fig. 11

Fig. 12

Fig. 13

Backfill

After the heat tip has extended to within 4–5mm of the working length, or as close to that as possible, then the canal is ready for the gutta-percha backfill. I call this the “hot glue gun portion” of obturation, and for years have used heated backfill devices such as Obtura and Calamus. My new favorite backfill system is the cordless GuttaSmart from Dentsply Sirona; the needle fits well into the canal space in a pen-grasp method, which allows accurate and efficient placement of heated gutta-percha. I have noticed few voids and an excellent, dense fill. This heat tip and backfill device has made warm vertical obturation extremely efficient, taking only two or three minutes longer to perform than when I perform the single-cone obturation technique.

Place the tip of the chosen backfill device into the canal and as close to the gutta-percha plug as possible (preferably right on top and touching the gutta-percha in the canal). Allow the backfill tip to sit for a few seconds to heat the canal and gutta-percha, then slowly extrude the hot gutta-percha. The hot gutta-percha will slowly displace the backfill device right out of the canal (Fig. 11). I usually perform the backfill in one increment, especially if I am using GuttaSmart, but an incremental backfill is also fine.

Fill the canal up to the orifice level, right at the pulpal floor junction (Fig. 12). Use a larger plugger, such as the black or blue end of the Dovgan pluggers, and gently pack the extruded gutta-percha into the canal. The root canal is now completed (Fig. 13).

If I used ThermaSeal Plus Ribbon sealer or AH–Plus, then I clean the pulp chamber with an alcohol pellet and place a composite core. If I used Pulp Canal Sealer EWT, I first use a chloroform pellet, followed by an alcohol pellet and then can place a bonded core composite.

Conclusion

Warm vertical obturation is a technique favored by many endodontists and general dentists. It is a tried-and-true technique that has had great success for many years. The disadvantage of this fill technique is that it can be considered technique-sensitive and time-consuming. But once a clinician learns the finer points, it is an excellent way to achieve a dense root canal fill and hermetic apical seal.

References
1. Calt, S and Serper, A. Time-Dependent Effects of EDTA on Dentin Structures. J Endod 2002; 28: 17-19.
2. Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1974;1: 723-44.
3. BuchananLS. The Continuous Wave of Obturation Technique: ‘Centered’ Condensation Warm Gutta-Percha in 12 seconds. Dent Today 1996;15:60 –7.