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Written by L. Stephen Buchanan, DDS Monday, 01 September 2008 00:00
Endodontic treatment is just a space maintainer for implants.” This joke, often told by implant surgeons and implant salespeople, dramatically illustrates the current and very serious challenge to endodontic therapy remaining as a respected method of saving our patients’ teeth. Ironically, while many endodontists think of this as an us-versus-them conflict, I would argue otherwise and point out that much of this threat has grown out of the seeds of our success. The pendulum of change swings, but it always swings too far before it returns closer to a state of equilibrium.
So, how have we come to this state of affairs? Well, back in the dark ages of dentistry, the focal infection era, teeth with endodontic pathoses were blamed for the medical profession’s failures. That is, until the courageous fathers of modern endodontics said, “Enough! We can save our patients’ teeth by eliminating the disease within them rather than by ripping them out.” And people learned that they no longer had to expect to be wearing dentures by the time they were 40-years-old. I often have laughed aloud when I consider that we convinced physicians it was all right to save teeth by doing aerobic culturing of root canals (a nearly useless method) to prove that we had sterilized them during our preparation procedures. Nevertheless, they fell for it, and we then saved millions and millions of teeth. And in this case, the end really did justify the means.
However, as we treated a greater number of cases, we found that our success rates were not predictable. It was really Dr. Herbert Schilder—defining the objective of root canal therapy (RCT) as consistency of long-term outcomes or “predictability”—who began the next chapter of endodontic therapy. He stated and taught that our success wholly depended on our ability to treat root canal systems to their full apical and lateral extents. Granted, that was not easy at the time, but technological developments have since made those definitive outcomes accessible to any dentist who understands the precursors to that result and is willing to do the work necessary to achieve success at that level.
So, what are the issues that threaten the credibility of endodontic therapy as the first choice when pulpal pathosis or persistent infection occurs in a root canal system? There are actually a fair number of them, some very obvious and some a bit more obscure. In Part 1 of this 2-part article, I will cover 3 factors that I have seen in my own practice, as well as those that I have become aware of in my educational pursuits, both domestically and internationally.
NEEDLESSLY WEAKENED TEETH
This first topic of discussion may be a surprise to many endodontists in terms of its priority on the list. However, I am starting here because this is one that we totally control and for which we are definitely accountable.
With all of the fantastic conceptual and procedural advances that came from Dr. Schilder’s paradigm shifts in root canal therapy, a negative that haunts us still today is that of over-enlargement of the spaces we work through. At that time, without magnification or the hyperflexible nickel-titanium shaping files that we have today, we needed larger access cavities to find and treat canals better. We also needed larger coronal shapes to allow for ideal management of the tortuous apical regions of canals. And, for the tools we had at our disposal in that era, these convenience forms were necessary. This was because the larger view of the edict to conserve tooth structure meant that, if we were to save the whole tooth, then we needed to sacrifice some of that tooth’s structure to enable a predictable endodontic treatment result. Unfortunately, the pendulum always swings too far…
Sadly, despite advances that allowed us to be more conservative in our preparations and yet achieve consistent outcomes, many endodontists and general dentists are still working for that full-bodied “look” at the end of the case because it became associated with better treatment results. However, one of the primary concerns that prosthodontists and enlightened endodontists have about the long-term prognosis of endodontically treated abutments is their propensity to come apart under chewing forces—to fracture vertically. Indeed, the primary reason I have for considering a tooth unworthy of retreatment is when it’s structural integrity is gone.
|Figure 1. Endodontically treated maxillary molar with a vertical root fracture in the mesiobuccal root. While the endodontic therapy was quite good in the apical regions (note the apical accuracy of filling and the significant lateral canal filled in the mesiobuccal root), unnecessary over-enlargement of the canals’ coronal regions resulted in a loss of structural integrity and splitting of the mesiobuccal root within 5 years of treatment.||Figure 2. Maxillary premolar with narrow root structure and proportionately narrow coronal preparation, enhancing its long-term prognosis. Note the subtle curvatures that were maintained due to the landed blades and the maximum flute diameter limitation of the single 20 .06 GTX File (DENTSPLY?Tulsa Dental Specialties) used to cut the shape.|
|Figure 3. Mandibular molar with overextended fill in the distal canal and underextended treatment in the mesiolingual canal. The patient had significant pain referred over the upper and lower teeth on that side of his face for more than 18 months. The most common treatment plan for this case would be apicoectomy of the distal root.||Figure 4. This postoperative radiograph shows the mesiolingual canal after conventional retreatment (of only that canal) revealed a previously untreated 3-mm-long accessory canal in addition to the apical segment of the primary canal. All of the patient’s referred pain was resolved in spite of the distal canal, which was left in its original state.|
|Figure 5. This photo shows a maxillary molar after treatment by a general dentist. When this case failed, the patient was referred to an implant surgeon, who recommended extraction with implant placement. Only because the patient sought a second opinion (from a different general dentist) was the tooth saved.||Figure 6. Postoperative radiograph after retreatment in a single 2-hour visit using only 1 to 3 GTX?Files per canal. Note the conservative coronal shapes.|
I can fix most problems present in a root canal, but I cannot reestablish strength in the crown or root structure. So when I see that teeth have been needlessly weakened by previous treatment, I feel sickened at the missed opportunity by the previous practitioner to do no harm in this respect (Figure 1).
Dentists who do endodontic procedures should consider my definition of success—seeing a patient’s name in the obituary before he or she needs a retreat or implant—and cut tooth structure with that in mind. After coronal leakage, the most common reason for long-term failure of endodontically treated teeth is vertical root fracture. As an aside, any tooth with a vertically directed coronal fracture that extends even a millimeter into the soft-tissue attachment must be extracted.
Really the only rational but misguided reason to overshape root canals, now that we have nickel-titanium shaping files and flexible gutta-percha condensers, is to create enough coronal space in a root canal to do cold lateral condensation. Dr. Schilder used to joke, saying that, “cold lateral condensation of gutta-percha was like filling a room with telephone poles.” While that is a funny overstatement, I care less about the quality of the resulting fill than I do about the over-enlargement needed to wedge 3 to 5 master cones next to a cold lateral cone. Why not keep the coronal shape smaller and instead use a narrow posterior heat spreader powered by a Touch ‘n Heat or System B Heat Source (SybronEndo). A single, warm lateral condensation stroke followed by a single, Autofit (SybronEndo) backfill cone will actually create a small hydraulic wave through the softened master cone. This will accomplish some lateral extension of filling with the smaller coronal shape that is needed in order to maintain the structural integrity of the root. That’s better, right?
The fact is that there are many ways to obturate root canal systems that do not require over-enlarging the canal space. The most effective are the centered-condensation warm gutta-percha methods such as the Continuous Wave of Condensation Technique or carrier-based filling using a Thermafil or GT or GTX Obturators (DENTSPLY Tulsa). Regardless of which of these filling techniques one chooses, long-term prognoses will be enhanced when we quit weakening root structure, and perhaps then the restorative dentists will come to have greater confidence in endodontically treated teeth as crown and bridge abutments (Figure 2).
ABANDONMENT OF SURGICAL RETREATMENT ALTERNATIVES
Another milestone in our endodontic capabilities came with the introduction by Dr. Gary Carr of operating microscopes and ultrasonic instrumentation into our procedures. Initially, these devices were used to better our surgical outcomes, but then morphed into tools that provide greater possibilities for conventional retreatment. With better vision and tiny ultrasonic tips, we found that we could remove posts and broken files, as well as find previously undiscoverable canals. Great, huh? Yes of course, however, the pendulum always swings too far…
The new dogma of retreatment became that nonsurgical approaches were always done first, even when the coronal seal was intact. For the most part, this was very good, because in cases that failed due to coronal leakage, our retreatment success increased significantly. However, the law of unintended consequences is real, and after this change in treatment planning, post-graduate students in many residencies left school without enough surgical training to feel confident with that retreatment approach for failed endodontic treatment in posterior teeth. Remarkably, I have heard of incoming residents at some programs being informed that they will probably do fewer than 10 surgical cases during their term in graduate school. This is something to consider for dentists applying to postgraduate endodontic programs. In addition, when undertrained in this respect, endodontists are limited to nonsurgical retreatment options, occasionally resulting in the destruction of well-done restorative work during the disassembly procedures required for nonsurgical retreatment. This means spending many difficult hours retreating these teeth with new post/cores and crowns that are subsequently needed. It is a general truism that dentists are more likely to treatment plan procedures that they are capable of providing and that limited training will inevitably limit the treatment alternatives being discussed with the patient.
We know that a great number of endodontic failures occur because the coronal seal has been lost and conventional retreatment is, of course, necessary in those cases. But surgery, in my opinion, has been poorly described as a “nonconservative” treatment approach. I believe it was Dr. Donald Arens, one of the great surgical endodontists of the previous generation, who wrote that taking a surgical approach to resolve endodontic failures often could be more conservative than a nonsurgical ap-proach. To the endodontists who have good surgical skills, consider, as I do, that sometimes surgery can be the quickest, least expensive way to save a failing endodontic case, all things considered.
While most endodontists will in-form their patients that a nonsurgical treatment plan should be pursued first, and that surgery may be necessary if success is not achieved, I am suggesting that in certain cases it should be the opposite. When a surgical retrograde procedure is simpler, it should be done first; with the caveat that if it is unsuccessful, the more expensive and time-consuming coronally directed treatment will follow. It is unarguable in my mind that the surgical approach, in many situations, is more definitive. Consider these facts: a retrograde approach will never be hampered by a broken file that cannot be removed or an apical blockage or ledge that cannot be bypassed; and the terminal point of an elusive fourth canal in a mesiobuccal root of an upper molar is always found when you take a retrograde approach.
In fact, the increasing loss of surgical skills in the specialty is greatly threatening our claim to be specialists, if not due to the unpredictable conventional retreatment results that implant surgeons see so often, then because it begs the question of what separates an endodontist from a skilled and well-trained general dentist who does a wide range of nonsurgical endodontic procedures? To the endodontists who were undertrained in this procedure, do not despair. Surgical techniques have also advanced. Surgical retreatment is now a very straightforward procedure, if one knows how to microsurgically raise and suture flaps, achieve perfect hemostasis in every case, and how to find and retrofill apices in just a few minutes regardless of the tooth position.
In specialty group practices, where at least one of the partners is a competent surgeon, and in regions where oral surgeons have been trained to actually treat root canal systems—from a surgical approach instead of extraction with an implant—it is not necessary for individual endodontists to do surgical retreatment. However, in practices or areas without these alternatives, it will become increasingly important for endodontists to attain and/or refine these skills. Fortunately, many excellent training centers exist through-out the United States where this can be accomplished.
INADEQUATE TREATMENT RESULTS
It is embarrassing to say this, but there are still many undergraduate as well as graduate programs teaching endodontic techniques that are inefficient and ineffective. Believe it or not, some educators still inculcate their students with a phobia about going to and through the ends of root canals during treatment without one shred of scientific evidence that any lessening of prognosis results. In fact, the greatest number of failures (aside from missed canals and coronal leakage situations) occur because treatment was short of the full apical and lateral extents of root canals. That is where the bugs are; that is where the se-verely inflamed tissue, close to a rich blood supply, will remain alive and angry (Figures 3 and 4).
When and if we ever figure out how to predictably sterilize these internal spaces, we won’t even need to fill the primary canals. Instead, we’ll just provide a perfect coronal seal to the CEJ level and be done with it. Until then, we must shape and clean to the apical and lateral termini of root canal systems, where the inside of the root becomes the outside of the root, where a limited im-munologic response changes to a hemispheric capability. This means full treatment of all primary canals, irrigating with sodium hypochlorite solution as effectively as possible, and then filling 3-dimensionally to the fullest apical and lateral extents of these systems so that we can entomb any bacteria we didn’t kill during our cleaning procedures.
Now that I do implant surgery, I am even more amazed at the paranoia that some of my colleagues in the specialty have about taking a K-file that is 0.1 mm wide just a millimeter through the end of primary canals to clear their apical regions. When we do implant surgery, we take a drill that is 5 mm wide and 13 mm long and use it to core through the center of our patient’s jaw and place a like-sized foreign body into that space. And that is okay! Actually, it’s more than okay. It’s great! However, to “peek” through the end of a root canal with a tiny root canal file and leave a small button of biocompatible sealer there? Horrors!
My advice for any of you who still feel nervous or guilty about treating the whole root canal is this: either get some psychotherapy or quit doing root canal therapy if you are unwilling to do what you are paid for. To date, I have never had a patient tell me to intentionally leave parts of a root canal untreated. Ironically, the other threat to endodontics are the wing-nut health paranoids who are informing our patients that root canals are very complex and that persistent infections can reside in these spaces. I hate it when I agree with these guys, but isn’t it a better thing to explain to these concerned patients that we agree and that is why we are so committed to thorough treatment?
There are also CE educators who recommend substandard procedures, such as single-cone filling methods, because it helps them sell rotary files in an era when 3-D filling results can be accomplished in less than a minute. If you ever hear of a CE course advertised claiming that you can do any molar in 30 minutes, run away! This is the lowest form of ethics in education and does nothing but truly promote endodontic therapy as a space maintainer for an implant. I would rather have a nice tooth replaced with a well-done implant than pay good money, put up with the hassle and discomfort of a useless procedure, and then have my tooth extracted anyway.
Most embarrassing for the specialty are endodontists who have “sold out.” I can more readily forgive the failures of clinicians who were inadequately trained than I can endodontists who know better but have entered the specialty to retire early. Any diligent endodontist who cares about providing state-of-the-art treatment results, with today’s technology, will do very well by retirement age. Any endodontist who thinks that the meaning of a specialty practice is to do 15 one-shot molars a day is victimizing his or her patients, is destroying the hard-won confidence in endodontics as a predictable procedure, and really is destroying confidence in him- or herself, since expedient treatment can never be more than a short-term strategy for success. The thing that really irritates me is when an endodontist does a poor job. When the tooth fails, uninformed dentists will assume that since a specialist treated it, root canal treatment just couldn’t save that tooth. Then we all get a black eye.
Restorative dentists who have access to well-trained, conscientious endodontists know from long experience that endodontic therapy is consistently a very successful procedure. They know that it is the least costly, least time-consuming approach to resolving endodontic pathosis. They also know that a diseased tooth successfully treated and retreated is the most consistently aesthetic abutment to restore.
It is a bit different when a general dentist does a case that fails. The perception about the relative success of en-dodontic therapy in these cases will de-pend on whom the dentist refers that pa-tient to after the failure becomes apparent. Here lies the sticky wicket for endodontists. If the general dentist refers the patient to an endodontic specialist, and that specialist even hints that the previous treatment was substandard, then the referring dentist will be asked to refund his or her fee, at a minimum. Worse yet, the referring dentist will likely lose the patient with all associated friends and relatives in that practice. Conversely, if the dentist refers the patient to an implant surgeon, then the implant surgeon doesn’t have to say, “Your dentist botched the case.” The surgeon can say that root canal treatment really isn’t very predictable (Figures 5 and 6). This is just something to think about if you are an endodontist. Ratting out general dentists will not convince them to quit doing root canals; rather it will just convince them to cut out the endodontist as an option when the case fails. When the pendulum swings….
These were just 3 of the factors that I feel threaten the credibility of endodontic therapy as the first choice when pulpal pathosis or persistent infection occurs in a root canal system. In Part 2 of this article, I will cover 3 more issues that must be considered when faced with failing endodontically treated teeth.
Dr. Buchanan is a Diplomate of the American Board of Endodontics and a Fellow of both the International College of Dentists and American College of Dentists. Dentists interested in his videotape series, The Art of Endodontics, and his hands-on laboratory workshops in Santa Barbara, Calif, can call (800) 528-1590. For more information related to this article, visit endobuchanan.com for GTX updates and answers to frequently asked questions indexed by topic. A free online CE course on the GTX System is available, as well as other topics. Questions concerning challenging cases can be directed to (800) 528-1590.
Disclosure: Dr. Buchanan consults for and holds patents to the GT and GTX System of instruments manufactured and sold by DENTSPLY. He also holds patents with the System B Heat Source and is the inventor of the Continuous Wave of Condensation technique.
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