Endodontic Hybridization Access and Answers

During the past decade there has been a proliferation and advancement of endodontic techniques. The vast array of courses, instrumentation, and obturation systems can at times be dizzying at best. It seems everyone is searching for the perfect armamentarium to simplify endodontic therapy. Unfortunately, no one technological advancement has been able to distill root canal therapy into a succinct cookbook recipe. However, all is not lost, because in this maze, multiple overlooked critical enhancements can turn every moderately difficult case into routine endodontics. I like to refer to these enhancements as endodontic hybridization.

ENDODONTIC HYBRIDIZATION

Basically, hybridization involves borrowing the best methodology and instrumentation systems from leading researchers and manufacturers and incorporating them into sound practice that makes clinical sense time and time again. Endodontic hybridization rests on sound, evidence-based techniques, not on flashy advertisements or unproven newest wave endodontic therapy. It does not ignore previous older instrumentation methods or products that can still deliver superior results in an efficient, cost-effective manner.

Endodontic hybridization is a journey that may lead some clinicians to utilize techniques in one manner, while other dentists may choose a slightly different course. If we begin this journey with the premise that the end result will not be one technique but a blending of multiple methods, then it will allow an easy transition to successful endodontic therapy. The goal here is to encourage all highly motivated general clinicians to perform the vast majority of these cases with confidence and ease.

It has been a sound principle in endodontics that complete instrumentation and obturation of the apical one third is the goal of root canal therapy. Although this premise is accurate, only recently has it become possible to gain control of this critical apical one-third zone by understanding how to manage the coronal zone properly.

Access is the key. It is the one fundamental that can never be lost no matter what technique is utilized. Access management does not begin once all canals are visualized through loupes or a microscope. Access control starts with a thorough analysis of radiographs, canal recession, calcifications, and angulations of canal morphology. Access management determines if previous restorations or crowns will hinder entrance into the root portion of that tooth. It is imperative to incorporate patient management into the equation so there is agreement, when necessary, to sacrifice old restorations in order not to jeopardize an ideal endodontic result. As a practicing endodontist, I can think of no better suggestion than this to prevent future mediocrity in clinical skills.

Once you have thoroughly diagnosed access concerns, it is time to start treatment. Several manufacturers have produced burs with much improved characteristics. To reduce vibrations and gain rapid access through metallic restorations I utilize various burs. One such bur is the Amalgam Bur by Lexicon. Other diamond access burs with rounded safe tips are terrific in creating smooth entrances into the chamber. It is imperative to remember that endodontic access does not start at the pulp chamber and end at the orifice of the canals. Viewing access as extending 3 to 5 mm into the coronal aspect of the canal creates a more complete picture of what is actually occurring. It is unique in endodontics that access leads to an indirect end product, since the apex is never fully visualized. Therefore, extreme effort must be taken at this juncture to ensure straight line access to the canal system. If skewed access angulation is called for in order to achieve straight line access, then an immediate adjustment is necessary and coronal restorations need to be sacrificed if at all possible.

Figure 1a. Preoperative: large restoration recurrent decay. Figure 1b. Preoperative radiograph shows severe curvature of mesial canals.
Figure 1c. Incomplete access binding against coronal walls with initial hand instruments. Figure 1d. Note severe angulation of mesial file prior to completing access.
Figure 1e. Ideal access completed elimination of binding. Figure 1f. Postoperative radiograph obturation of mesial canal verifies ideal access management.

A telltale sign of incomplete coronal access occurs when initial hand instruments still contact or bind against tooth or restoration walls during their passage into the root end portion of the canal system (Figures 1a through 1f). This issue becomes paramount in order to alleviate NiTi file separation during eventual instrumentation.

As in all areas of dentistry, preparation is the key to success. It should by now be crystal clear that eventual endodontic success rests on ideal access preparation initially. The changing perspectives in endodontics, especially the proliferation of 1-visit treatment, has actually created a dichotomy in successful care. On one hand, 1-visit root canal treatment (RCT) can be efficient, less traumatic for the patient, and more cost effective for the dentist. On the other hand, the pressure to complete certain cases in a predetermined time frame can lead to less-than-ideal results. It is my contention that what appears to be time-consuming preparatory access management will actually lead to timesaving instrumentation techniques down the line. This will allow greater control for general practitioners to manage more cases in 1 visit without sacrificing clinical superiority. It is my suggestion that 1-visit root canal therapy should be thought of as a procedure reserved for pre-scheduled treatment. Procedural exposures, either carious or mechanical, often times should be thought of as emergency care, with RCT then scheduled for a separate, 1-visit procedure. This slight change in mindset can definitely improve a future endodontic result.

Figure 2. Top: LA Axxess bur; bottom: Sx File. Figure 3. Top: peeso reamer; bottom: Gates Glidden.

Emergency care, which often consists of a pulpotomy, can be modified into a straight line access pulpotomy, or as I refer to it, an "enhanced pulpotomy." This deeper pulpotomy incorporates the enhancements mentioned earlier so that ideal access can be attained into the coronal one third of the canal system. Once coronal binding and interferences are eliminated, gaining entrance into the coronal one third becomes truly routine. Although all manufacturers recommend specific shaping NiTi files (eg, Sxfile, DENTSPLY, Figure 2), which can be superior in many cases, most straight or slightly curved orifices can be initially shaped with peeso reamers or Gates Glidden files (Figure 3) without gouging the side walls of the canal system. These traditional rotary files are stainless steel based and have the advantage of quick tooth structure removal without significant separation issues. Older endodontic techniques that did not eliminate all coronal binding issues were not able to utilize these stainless steel rotary instruments properly. Another addition in this arena, which is excellent in initial shaping at the orifice, are the LA Axxess burs (SybronEndo, Figure 2). They are hybrid rotary files that are stainless steel based but sized and shaped to leave the coronal one third almost completely shaped.

The disadvantage of Gates Glidden and peeso reamers lies in the nature of their flutes, which can at times preferentially push organic debris apically rather than allowing for coronal movement of this material. The apical movement of dentinal shavings and debris can block canal entrances and eliminate a canal pathway. Every dentist has been frustrated with finding all the canals in a particular tooth only to spend the next 45 minutes trying to renegotiate the same canal system clogged by a peeso or Gates Glidden. This issue will rarely occur if 2 protocols are utilized. One, of course, is ideal coronal access. The other is a soft, brush-like stroke in the use of Gates Glidden and peeso reamers and never pushing on the head of the handpiece. Minimizing all apical pressure on these stainless steel files creates a smoother coronal one-third zone and will prevent gouging into side walls.

Although crown-down instrumentation is a standard to be used with NiTi files, I have found that routine use of smaller to larger diameter peeso reamers adds to easier penetration into the canal system, with confidence that side effects will be minimized. Once the coronal one third is flared and shaped, you have actually created a deep pulpotomy and spent the time necessary either to continue and fully instrument or to stop and reappoint the patient for what I consider a 1-visit RCT. Remember, this coronal flaring takes less than 2 to 3 minutes if proper coronal access is achieved.

At this juncture, complete instrumentation in most routine cases can be accomplished easily with a hybrid of NiTi rotary and stainless steel files. I utilize ProTaper files (DENTSPLY Tulsa Dental). They are more aggressive but quickly shape canals with a beautiful, smooth, flared finish. They are end-cutting instruments and are best suited for practitioners with more advanced skills in the NiTi arena. It should be noted that the learning curve is rapid in the utilization of these files, and most general practitioners will be able to benefit from their design. If just beginning the NiTi experience, then 2 file systems that can give super results are GT files (DENTSPLY Tulsa Dental) and the K3 file system (SybronEndo). Both of these file systems are less aggressive, with radial lands to help maintain the files in the center of the canal and noncutting tips for extra safety.

Didactic-based endodontic instruction is just that. It is not possible to explain fully how to instrument a canal without actually utilizing the techniques firsthand. Endodontics involves a common sense approach. However, not all things are what they appear. Manufacturers of NiTi products are constantly trying to reduce the number of instruments in their series of files to instrument a case completely. This trend to minimize instruments makes it appear that it is easier to treat each canal with just a few rotary files. The problem is that fewer does not mean faster. This counterintuitive statement is because many practitioners don't utilize NiTi files properly. On one hand, the files preferentially remove organic debris coronally. However, no system is perfect, and there is always an apical movement of some debris after use of each rotary file. The easy fix occurs when stainless steel files are blended into the instrumentation sequence. This hybrid use of old and new will maintain apical patency and continually give tactile feel back to the dentist, which is missing from the rotary instruments. Utilizing stainless steel files of smaller diameter than a corresponding NiTi file will prevent clogging near apical curvatures and produce more enjoyable results for the clinician.

Figure 4a. Preoperative: massive distal decay. Figure 4b. Ideal access utilizing peeso reamers (1 and 2) followed by Sx shaping file.
Figure 4c. Master cone radiograph verifies ideal straight line access. Figure 4d. Completed obturation shows truer taper after recapitulation with NiTi files done twice.

Another overlooked aid in NiTi instrumentation involves recapitulation with the same series of rotary files just used. This "redundancy of filing, especially with coronal and mid-root files, allows for easier penetration into the apical one third and a truer taper, which of course allows for predictable obturation. Remember, it is much easier to use 4 NiTi files twice than to search for a way down a blocked canal (Figures 4a through 4d).

CONCLUSION

Endodontics as we know it is a series of multiple steps. Often, we can take each step in a cookbook manner. However, statistically speaking, any misstep that prevents a high level of success will deny the practitioner an ideal result. Most missteps occur long before we reach for the gutta-percha, and therefore, it is my hope that several of these endodontic enhancements through improved access management will allow a smoother, more successful endodontic journey.



Dr. Roth is a fellow of the American College of Dentists, an assistant clinical professor of endodontics at Columbia University, and an attending at the Manhattan VA Medical Center in New York. He maintains a full-time practice limited to endodontics in Manhattan. He can be reached at (212) 838-2011.

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