Root Canal Treatment: Back to His Roots by Dr. Reid Pullen

In the first installment of a two-part series, a Townie endodontist explains why he prefers warm vertical obturation over single-cone techniques.

by Dr. Reid Pullen

I want to tell you a story: a story based on 13 years of endodontic private practice experience and noticeable patterns; what appears to “work” and what doesn’t. The story of how I came back to my obturation “roots.”

The goal of obturation is to three-dimensionally seal a cleaned root canal system, entomb any existing microbes and provide a hermetic seal to keep the bad bugs out.¹ In a perfect world free of bacteria, we wouldn’t even need to fill the canals, but life is messy, dentistry is difficult and what comes out of the canal must be replaced with a filling so that bacteria, fungus and viruses (microbes) can’t repopulate and thrive in the root canal system.

Bioceramic sealers and single-cone techniques

With the advent of bioceramic sealer, single-cone has become a popular mode of obturation² because it’s extremely easy and efficient to perform: Inject sealer into the canal and gently place the gutta-percha cone with firm downward pressure until it reaches working length. Sear off the coronal piece of the cone at the orifice, gently pack down with a plugger, and done. Quick and simple. This obturation method is often referred to as “single-cone hydraulic condensation” and it is meant to be used with bioceramic sealers such as BC Sealer, Total Fill BC Sealer, iRoot SP, BioRoot RCS and Endoseal–MTA.

The phrase “single-cone hydraulic condensation” describes the gutta-percha cone hydraulically “pushing” the sealer into all the nooks and crannies of the root canal system—the isthmuses, apical deltas and anastamosies, lateral and secondary canals— and forming a hermetic seal between the gutta-percha cone inside the canal from the outside world of the periradicular tissue.

Single-cone obturation is intended to be performed with bioceramic sealers because these sealers serve not just as traditional sealers but also as fillers, like gutta-percha. Theoretically, if a clinician were able to place sealer easily and predictably to the apex and then fill up the entire canal, a gutta-percha cone would not be needed. Which then raises the question: How do you re-treat it? This is precisely why we still use gutta-percha cones as the main filler inside the root canal system: It allows any future clinician to re-treat the case if it fails, and allows for a more predictable obturation, which appears dense and to length.

Using the wrong products leads to bad results

Unfortunately, in my experience, a high number of dentists are performing single-cone obturation with just about any sealer they can find in their office. I’ve spent the past six years lecturing all over the country and have surveyed almost every audience on their obturation practices and technique of choice. The majority use single-cone with either a wide array of sealers or carrier-based obturation like Thermafil or GuttaCore.

Dentists who are using nonbioceramic sealers and performing single-cone obturation are asking the sealer to not only hermetically seal the apex and all portals of exit but also act as a filler where the gutta-percha cone does not reach. Many of these single-cone obturation cases are successful by virtue of cleaning and shaping—removing the diseased pulp tissue and microbes and sealing the cleaned system.

The problem with this approach is that it’s a gamble: It may seal, it may not. Take, for instance, a case where the gutta-percha cone slips down the canal and stops 2mm short of working length. The last 2mm of the canal is devoid of any filler except the nonbioceramic sealer. The sealer is now “asked” to not just seal the apical foramen from the periapical tissues but also act as a 2mm space filler. Nonbioceramic sealer is not meant for this type of obturation; it was designed only to form a thin layer between the gutta-percha cone and the canal foramen, not as a 2mm space filler.

Solubility and sealants

That being said regarding nonbioceramic sealers, some bioceramic sealers may have an internal problem: solubility. Solubility refers to the loss of material mass when a sealer is immersed in water over a certain amount of time, usually evaluated at 1 day, 1 week, 2 weeks and 3–4 weeks.³ Endodontic specifications state that root canal sealers should present solubility of less than 3%.^4,5 Studies show that some bioceramic sealers can have a solubility index of upward of 10%, while traditional resin sealers such as AH–Plus from Dentsply DeTrey have a solubility index of only 0.03%.^6,7 What does this mean? Some bioceramic sealers are more soluble and possibly could degrade in the presence of tissue or periradicular fluid or wetness.

Interestingly, it is recommended to maintain some moisture in the canals to provide a vehicle for bioceramic sealers to set. The question I often hear is, “How much moisture?” An article by Nagas et al. shows that iRootSP, which is comparable to BC Sealer, showed the highest bond strength when compared with AH–Plus, MTA Fillapex and Epiphany in canals dry with paper points and ethanol, paper-point dry, moist and completely wet. Also, iRoot SP showed similar push-out bond strengths in very dry, paper-point dry and moist canals.⁸ The author stated, “The experimental levels of moisture from dry to wet had differential effects on the tested sealers, suggesting that it may be advantageous to leave the canals slightly moist before filling procedures.”⁸ Another study states that bioceramic sealer sets when it comes into contact with moisture inside the root canal system.⁹

Testing out a new technique

As an endodontist in private practice for the past 13 years, I’ve treated well over 10,000 cases. Initially, I used Kerr’s Pulp Canal Sealer EWT (extended working time) because that’s what we decided in residency to use after reviewing the past and current literature on sealers. (To be fair, BC Sealer and BioRoot were not yet in the mainstream.) From 2004 to 2012, I used only that product and the warm vertical obturation technique. During that period, I was becoming a better endodontist, learning from my mistakes and my successes.

In 2012, I started experimenting with single-cone obturation, mainly because if you could achieve predictable success with this technique, it would save hours and hours of obturation time. After incorporating laser disinfection in my office using the photon-induced photo acoustic streaming technique, or PIPS, using a Fotona laser, I tried the single-cone technique using a hydrophilic resin sealer. I saw a pattern of increased postoperative “checks”—continued discomfort three months and longer after root canal treatment—and failure, and ended up needing to re-treat 200-plus cases, all documented.

When I re-treated these cases, I discovered that I was able to pull the single cone right out—the sealer I had used did not always set inside the canal. This product does not set in the presence of oxygen; because of this, the clinician must use a specific file conditioner so as not to introduce oxygen into the canal system. But that raises the question: How do you know if the canal is oxygen-free? If a little bit of oxygen is present in the canal system, will the sealer still set? These are good questions to ask before incorporating this type of sealer into your practice.

Running the numbers

I then decided to try a bioceramic sealer, still sticking with the single-cone technique. I was much more careful this time and reviewed the product’s studies, which showed it to have a similar success rate to traditional sealer using warm vertical obturation. A 2018 retrospective cohort study examined 307 cases (initial and re-treatment) obturated with a bioceramic sealer in a single cone technique, with a minimum one-year recall and an average of 30.1 months. The outcome produced a 90.9% success rate, where “success” was defined as apical lesions healed and healing.¹⁰

I used a bioceramic sealer from 2012 to 2017 on the majority of my cases and anecdotally, I had fairly good success. But around early 2017, I noticed a pattern that seemed to recur frequently: More “check” patients were coming back to my office because they either still had postoperative discomfort after a few months or developed discomfort a year later. Not just the normal “It’s sore when I push on the side of the tooth or when the electric toothbrush hits it” but “It’s sore when I bite, or push down on top of the tooth.” Anytime you perform root canal treatment and the tooth is sore to chewing months later, it’s not a good sign that the tooth is healing. (This assumes that there is no clear and evident parafunctional habits like bruxism.)

There are a variety of reasons why postoperative discomfort can occur—missed canals, poorly cleaned canals, improper seal, etc. Taking out the anomaly cases and seeing from the CBCT that there were not missed canals or poorly filled canals, I noticed a pattern with the single-cone cases with this type of sealer: It appeared that in some cases, just like the ones with the hydrophilic resin sealer, these sealers did not fully set. When I re-treated a number of these cases, I was able to easily remove the single cone and what appeared to be some unset sealer. I also often noted a “chalky”-type sealer set on some cases and I theorized that maybe the sealer never fully set. I may be incorrect on this, but when I treated some cases surgically, I noticed that the bioceramic sealers appeared unset at the apical foramen. (Keep in mind that this may not be a reliable indicator of sealer set, but is more of a clinical observation.)

Another interesting fact is that I could easily re-treat all of these cases and obtain patency. Isn’t the main concern with these sealers re-treatment? The biggest objection I heard is, “How do you re-treat these MTA like bioceramic sealers?” They’re supposed to set up as hard as stone, so re-treatment should have been very difficult, but re-treatment was actually quite easy; it appeared that these sealers just didn’t always fully set, and that they may be more soluble than Specification #57 of ANSI/ADA allows (<3% within 24 hours).

After conducting a literature review of 71 articles, Jafari concluded that, “Through screening of results of articles on the solubility of MTA-based sealers, it can be concluded that most of the sealers of this type show high solubility and dimensional and structural change after immersion in water when comparing with the standard resin based sealers.”⁶

• One 2019 article showed that two calcium silicate sealers had a high solubility rate after 24 hours—between 9.4% and 13.1%. (AH–Plus had a 0% solubility rate at 24 hours.) After 4 weeks the solubility rate of the calcium silicate sealers had increased to between 14.2% and 19.3%.⁷ (The 4-week solubility rate of AH–Plus is 0.1%.
• Borges et al. showed the solubility of one bioceramic sealer to reach 20.64%, whereas AH–Plus was only 0.28%.¹¹
• A recent 2019 article showed that one bioceramic sealer had a solubility rate of 10.6%, whereas AH–Plus was at 0.2%.¹²
• Another study showed the EndoSequence BC Sealer was at 2.9% solubility and within the ANSI/ADA standards.¹³

It’s important to note that because bioceramic sealers absorb water, the solubility rates may be higher than traditional sealers, but the volumetric change seems to stay below 2% for at least one sealer.⁷ The higher solubility is also a direct result of the bioactivity of these bioceramic sealers.⁷

Back to tradition

Because of these concerns associated with using bioceramic sealers in a single-cone obturation, in early 2017 I moved back to the traditional warm vertical obturation using either ThermaSeal Plus Ribbon Sealer (Dentsply Sirona) or Pulp Canal Sealer EWT (Kerr). I believed that while I was taking a step back in terms of biocompatibility, it was a step forward in the right direction of setting and solubility. The solubility of these two sealers is extremely low—0.1%, far below the 3% standard set by the AAE.⁷

These sealers and obturation technique give me the best opportunity for a set, seal and success and are considered the gold standard of root canal sealers.^14–16 I want a sealer that you can throw against the wall and it will set—one that sets all of the time, not just some of the time.

Since I’ve gone back to warm vertical obturation and these sealers, fewer patients present with problems of long-term postoperative discomfort. There were still a few, of course, mostly bruxers, but if you perform root canal treatment, that’s part of the game. The majority of my cases looked “better” sealed with a well-condensed fill, and I stopped seeing the lateral voids that came along with the single-cone technique, and I started seeing success results like those I’d seen from 2004 to 2012: Apical lesions were healing and filling in with new bone consistently.

I understand that this is anecdotal, but clinical experience and clinical patterns of success and failure are important in our journey for success. I wanted to share the patterns that I as one endodontist have observed after completing 10,000 cases using various sealers and obturation techniques. This is a story based on patterns of success and failure where shaping, cleaning and disinfection all stayed nearly the same—what changed was the sealer and the obturation technique. This is a story of postoperative discomfort, failure to heal consistently, and poor obturation outcomes with apical and lateral voids. This is my single-cone obturation story, and I wanted to share my opinions in hopes of helping dentists increase their endodontic success rate.

Like all clinicians, I hate failure and I loathe re-treating my own work three to six months after the initial root canal. It’s embarrassing, it costs revenue and, most importantly, the poor patients have to sit in the dental chair for another one or two hours. In my hands, warm vertical obturation using traditional, tried, true and tested sealers gives me the best success with the fewest postoperative problems. This makes me happy, and I hope it makes you happy too.

References
1. Branstetter, J. and von Fraunhofer, J.A. The physical properties and sealing action of endodontic sealer cements: a review of the literature. J Endod. 1982; 8: 312–316.
2. Wang, Z. Bioceramic materials in endodontics. Endod Topics. 2015; 32: 3–30
3. Versiani MA, Abi Rached-Junior FJ, Kishen A, et al. Zinc oxide nanoparticles enhance physicochemical characteristics of Grossman sealer. J Endod 2016;42:1804–10.
4. American National Standards/American Dental Association. Specification no. 57 for endodontic sealing materials. Chicago, IL: American National Standards/American Dental Association; 2000. p. 1–12.
5. International Organization for Standardization. ISO 6876: dental root canal sealing materials. Geneva, Switzerland: International Organization for Standardization; 2012. p. 3–4.
6. Jafari F, Jafari S. Composition and physicochemical properties of calcium silicate based sealers: A review article. J Clin Exp Dent. 2017 Oct; 9(10): e1249-e1255. Published online 2017 Oct 1
7. Elyassi Y., Moinzadeh, A., Kleverlaan C. Characterization of Leachates from 6 Root Canal Sealers. J Endod 2019; 45: 623-27.
8. Nagas E., Uyanik M., Eymirli A., et al. Dentin Moisture Conditions Affect the Adhesion of Root Canal Sealers. J Endod. 2012; 38: 240-44.
9. Xu, H.H., Carey, L.E., Simon, C.G. Jr. et al. Premixed calcium phosphate cements: synthesis, physical properties, and cell cytotoxicity. Dent Mater. 2007; 23: 433–441
10. Chyboswski E.,, Glickman G.,, et al. Clinical Outcome of Non-Surgical Root Canal Treatment Using a Single-cone Technique with Endosequence Bioceramic Sealer: A Retrospective Analysis. J Endod. 2018; 44: 941-45.
11. Borges, R.P., Sousa-Neto, M.D., Versiani, M.A. et al. Changes in the surface of four calcium silicate- containing endodontic materials and an epoxy resin-based sealer after a solubility test. Int Endod J. 2012; 45: 419–428.
12. Zordan-Bronzel C, Torres F. Et al. Evaluation of Physicochemical Properties of a New Calcium Silicate–based Sealer, Bio-C Sealer. J Endod 2019; Vol. In Press: 1-5.
13. Zhou H.,Shen Y., Zheng W., et al. Physical Properties of 5 Root Canal Sealers. J Endod 2013; 39: 1281-86.
14. Bouillaguet, S., Shaw, L., Barthelemy, J. et al. Long-term sealing ability of Pulp Canal Sealer, AH-Plus, GuttaFlow and Epiphany. Int Endod J. 2008; 41: 219–226.
15. Versiani, M.A., Carvalho-Junior, J.R., Padilha, M.I. et al. A comparative study of physicochemical properties of AH Plus and Epiphany root canal sealants. Int Endod J. 2006; 39: 464–471.
16. Versiani MA, Abi Rached-Junior FJ, Kishen A, et al. Zinc oxide nanoparticles enhance physicochemical characteristics of Grossman sealer. J Endod 2016;42:1804–10.