Endodontics: A Key Opinion Leader Colloquy

Diwakar Kinra, DDS, MS; L. Stephen Buchanan, DDS; and Lisa Germain, DDS, MScD

An interview with Dr. Damon Adams, editor-in-chief of Dentistry Today, and 3 key opinion leaders in endodontics: L. Stephen Buchanan, DDS; Lisa Germain, DDS, MScD; and Diwakar Kinra , DDS, MS; on the present and future state of the specialty.

What is the greatest challenge facing endodontics today?
Dr. Buchanan: The biggest challenge is doing root canal therapy (RCT) in an implant-based dental world. We now live in a world where economic pressures are weighing on dentists to buy screws and parts instead of saving teeth, and I have to mention the elephant in the room: Are we not in this profession with the primary goal being to save our patients’ natural dentition?

Don’t get me wrong, I’m a big fan of implants…they are truly miraculous and that’s why I took training to be able to place them; however, as healthcare professionals, we are currently a bit too quick on the trigger. Nudging us away from our Hippocratic Oath is a worldwide phenomena in which an implant fee is always much higher than that paid for well-done RCT.

Dr. Germain: There is a ubiquitous misconception that RCT, particularly retreatment and surgery, is an inferior treatment option to dental implants. Nothing could be further from the truth. Well-done RCT, including retreatment, is just as successful as well-done implant surgery.

So it’s not about endo versus implants; it’s about what is in the patient’s best interest. I frequently replace hopeless teeth with implants when the tooth is unrestorable, or is likely to destroy the bone. While I am happy to offer my patients that alternative, I do not assume that a tooth with an inadequate root canal needs to be extracted. I still believe it is my responsibility, as a well-trained endodontist, to save a patient’s tooth if possible.

Dr. Buchanan: Exactly! Retreatment, by definition, means that the original endodontic therapy failed, but, in most cases, the etiology is easily discernable, and the most complicated endodontic retreatment plan can usually be completed within 2 to 5 hours. But we can do better. In keeping with that, some of the best dentists and dental thinkers, as well as some of the best companies in dentistry, are working to make endodontic therapy easier to do, cheaper to provide, and more reliable for the long term.
Dr. Germain: As professionals, we must carefully weigh the advantages, costs, and expected predictability of outcome for endodontic retreatment versus implant replacement. Our fundamental imperative, indeed, our only imperative must be: What is best for our patient?

Dr. Buchanan, I’ll address the next series of questions to you. What is happening in the endodontic file business these days?
Dr. Buchanan: It’s been an amazing 20 years of Ni-Ti rotary file innovation, but the original Ni-Ti file patents have expired or will soon, so the rotary file market is looking like the Wild West these days. This will be good for dentists—although a bit confusing with all the players and all the marketing claims—as prices for Ni-Ti rotary files will trend down as the market matures.

Where do you see rotary file technology heading in the near future?
Dr. Buchanan: On the design side, there haven’t been any transformative leaps in efficacy. It seems like recently introduced files have been designed by marketing experts, not by clinicians. Reciprocation is a great example. Reciprocating files cut slower than rotary files, and they pump debris out the ends of root canals if not carefully used. They also require a new electric endodontic handpiece. Personally, I never did understand the allure.

So what could interest me in terms of a new file design? It would have to provide a big leap in efficacy, as I now negotiate and shape small molar canals with only one to 3 rotary files. The most unique new shaping instrument design in the last 5 years was the self-adjusting file (SAF). Laser-cut out of nickel titanium tubing, they were the first hollow endodontic shaping instruments and resembled a cardiac stent.
Despite their transformative promise—a hollow center for irrigants to flow through and the ability to adjust to asymmetric canal shapes—SAF instruments failed in the market for a variety of reasons. Conceptually, the SAF was a great design and an amazing science project. Don’t be surprised if we see a better-cutting sequel to the SAF one of these days.

The last time we spoke, I asked you if there were any transformative new instrument designs on the horizon and you said, “Transformative is a tall order these days, considering the remarkable efficacy of so-called hybrid techniques.”
Dr. Buchanan: Hybrid shaping strategies gained popularity after most endodontists figured out that sharp, nonlanded rotary files with small tip diameters are safe in curved canals because of the inherent flexibility of small file diameters. Not so in larger diameters, so final apical preparations are typically cut with a different type of rotary file—a rotary file with radial lands.

Figure 1a. TrueTooth Procedural Training Replica of a maxillary central incisor with a complex MB root canal system. (Courtesy of Dental Education Laboratories.)	Figure 1b. Close-up of TrueTooth Replica showing a bent No. 10 K-file advancing into an apical accessory canal. (Courtesy of Dental Education Laboratories.)
Figure 2. Left: Pre-op radiograph of maxillary second premolar with failing root canal therapy. Middle: Post-op radiograph shows retreatment of the primary canal which bifurcates 1.5 mm from its terminal points. Note the 2 to 3 lateral canals filled off the distal side of the primary canal. Right: Recall radiograph at one-year post-op showing near-total healing. (Courtesy of Dr. Germain.)	Figure 3a. Post-op radiograph of a mandibular second molar, its mesial canals significantly curved—mid-root—to the distal, then re-bent with a mesial kick approaching the terminus; the distal canal is a mirror image of the mesial canal curvatures; the distal root less curved than the mesial root, but with a canal that changes direction and exhibits more severe, apically accelerating curvature as the terminus is met. Also note the conservative access cavity, cut in 1992. (Courtesy of Dr. Germain.)

Figure 3b. Recall radiograph at a 12-year recall, showing each of the 3 canals and all their multiplanar curvatures, as well as ideal periradicular bone pattern and a thin periodontal ligament from crest to crest. (Courtesy of Dr. Germain.)

What’s the first file you put into a small and curved canal?
Dr. Buchanan: Vortex Blue (VB) 15-.06 Rotary File (DENTSPLY Tulsa Dental Specialties). It has flute angles like the GTX Files (DENTSPLY Tulsa Dental Specialties), is open at the shank end for cutting efficiency, and is tighter toward the tip to strengthen it and to reduce torsional stresses on the tip-half of the file during rotation; and its triangular cross section is wicked sharp. Used in small sizes, like 15-.06 and 15-.04, VB Rotary Files do not transport curved canals. This is because they are heat-treated to remove some of the shape memory. In addition, they are extremely resistant to the accumulation of cyclic fatigue during rotation around curved canals.

Once the 15-.06 VB File is cut to length, a .06 shape has been imparted to most of the canal, setting the clinician up to gauge the terminal diameter of the canal. One can choose the ideal finishing file for that specific root canal geometry and cut it to length, finishing the shaping portion of the RCT procedure for that canal. Small canals are typically finished with a 20-.06 or a 30-.06 GTX Rotary File. Two to 3 files—total—in 75% of small canals.

Medium and large canals seldom require initial shaping files. I simply cut a 30-.08 GTX File to length, gauge the apical diameter, and, in the cases where it measures larger than 0.3 mm, I finish with a 40-.08 GTX File. One to 2 files—total—in 97% of medium and large canals.

Wow, I need to take your course in Santa Barbara again. It sounds like there have been some fairly big strides in the last 3 to 5 years. What’s coming in the near future?
Dr. Buchanan: In the next couple of years, I think optimal file design will move in the direction that we have seen begun with the ProTaper Next (DENTSPLY Tulsa Dental Specialties) File with its core spiraling eccentrically to provide a bigger chip space. I think we will see, within the next 3 years, tapered, pigtail spiral files taking the prize for cutting the safest, fastest, and cheapest.

Dr. Kinra, could you fill us in on the latest improvements irrigation technology?
Dr. Kinra: In the months and years to come, we will see many changes with respect to endodontic irrigation. While mechanical instruments shape the canal, irrigants are paramount for disinfecting the canal and facilitating the removal of pulpal tissue. Traditionally, in order to properly perform endodontic irrigation, we need to first have an effective endodontic irrigant, and then we need to have an effective way of delivering it.

Researchers and clinicians have always preferred the use of sodium hypochlorite (NaOCl) as the irrigating solution of choice during endodontic treatment. It has the unique ability to dissolve vital and nonvital tissue and is effective as a bactericide as well as for removing biofilms. However, the most efficacious concentration, volume, temperature, and time needed to perform complete disinfection continue to be debated in academia.

Figure 4. Immediate post-op radiograph of an endodontically treated mandibular second premolar with a classic apical bifurcation of the primary canal and 2 barely visible lateral canals (just coronal to the root apex). Note the symmetry of the radiolucency about the canal’s portals of exit into the periapical tissues. (Courtesy of Dr. Kinra.)	Figure 5a. Preoperative radiograph of a necrotic maxillary central incisor; a mid-root lateral canal is seen branching off the mesial side of the primary canal. (Courtesy of Dr. Kinra.)
Figure 5b. Post-op radiograph showing a mid-root lateral canal filled into the buccal plane, and 2 to 3 lateral canals exiting everywhere but at the root apex—a common anatomic occurrence. (Courtesy of Dr. Kinra.)	Figure 6. Post-op radiograph showing a minimally invasive, yet very 3-dimensional root canal treatment of a mandibular molar with a healthy retained deciduous tooth root. The canals were shaped with GTX Rotary Files (DENTSPLY Tulsa Dental Specialties) and filled with GuttaCore Obturators. Note the 2 separate distal canals, both having apical delta systems, and the swooping 90° curvature of the MB canal before it reverses direction in the apical one mm. With current technology, there is no need for large access or canal shapes. (Courtesy of Dr. Kinra.)
Figure 7. Maxillary first molar—all canals were initially negotiated with a single 15-.06 Vortex Blue Rotary File (DENTSPLY Tulsa Dental Specialties) and finished with GTX Rotary Files; size 30-.06 for the MB1 and MB2 canals, 20-.06 for the DB canal, and 30-.08 for the palatal canal. Canals were filled with The Continuous Wave of Condensation Obturation Technique using the new elementsfree cordless oburation system (Axis|SybronEndo). Note the conservative access cavity preparation. (Courtesy of Dr. Buchanan.)	Figure 8. Four-canal maxillary molar with significant curvatures in each canal. Note the minimally invasive access preparation. This case was done as a live demonstration for a Molars Only workshop in Santa Barbara, Calif. (Courtesy of Dr. Buchanan.)

Although highly effective in removing organic components, supplemental irrigation, using acids such as 17% aqueous ethylenediaminetetraacetic acid (EDTA), is necessary for the removal of the debris produced by mechanical instrumentation. This organic/inorganic coating on the canal wall is known as the smear layer. Other disinfecting solutions have also been introduced; however, all of them have required the additional use of NaOCl for the most effective disinfection and tissue dissolution. Unfortunately, NaOCl can be toxic to periapical and intraoral tissues if expressed beyond of the terminus of the canal.

Recently, several devices have been introduced which help facilitate the effectiveness of the irrigation solutions used during RCT. Manufacturers have developed various methods of passive and negative pressure irrigation, subsonic, sonic, and ultrasonic agitation, as well as the use of lasers for disinfection and tissue removal. While these products have had some mixed success in providing better canal cleaning, endodontic treatment still relies on NaOCl and a chelating agent for optimal success.

Even with our improved Ni-Ti rotary instruments and various irrigation solutions and adjuncts, endodontics is still challenged in effectively removing infection and debris within the canal ramifications. Since this is the key component of endodontic treatment, the future for canal cleaning will emphasize more effective methods of delivery and activation of NaOCl and aqueous EDTA to remove unwanted soft- and hard-tissue remnants from lateral canal spaces, as well as for killing all the intracanal microflora and fauna.

As the rate of new dental technology introduction increases, it becomes exceedingly difficult to keep current in training. How do you see the future of continuing dental education, in light of this challenge?
Dr. Germain: Our profession needs to provide an increase in quality training opportunities for current and future dentists. First, new concepts need to be explained. These concepts then need to be put together so that proper clinical decisions can be made. However, just because you understand how it works does not mean you know how to do the procedure. Hands-on courses taught by skilled and experienced clinicians are the most important part of dental continuing education (CE).

To give you a sneak peak at what is on the horizon, imagine taking a procedural online training course that would allow you to get clinical instruction and experience without traveling. It currently costs between $5,000 to $15,000 to take a hands-on course, if you consider lost production (the biggest part), tuition, airfare, hotel, and dining.

By using clear and opaque 3-D replicas of teeth as procedural training models, we can eliminate the variability of extracted teeth and provide exceptional and consistent hands-on procedural training remotely; in your own office, with your own assistant, working together, led by interactive content on the Internet. This is a huge development, since most webinars are currently restricted to didactic courses.

Amazing! It looks like it’s a brave new world in dental CE. Dr. Kinra, does the rapid spread of corporate dentistry affect the outlook of endodontics in the future?
Dr. Kinra: Historically, dentists worked as solo practitioners for most of their careers. Recently, corporate dentistry has become a new practice model throughout the United States. Often, corporate dentistry will hire new graduates right out of dental school. This can be a positive opportunity for a new dentist facing mounting debt and the need for a stable and consistent income.

The hiring of new graduates also creates certain challenges when it comes to endodontics. Unfortunately, there is a wide discrepancy among graduates and their level of endodontic experience and training. Many have not treated even slightly complex cases, but are now faced with such cases due to the volume of patients seen in these types of practices. Due to human nature, when confronted with more complex treatment plans or procedures, an inexperienced recent graduate may naturally opt for an easier alternative, such as extraction.

Many may look at this as a challenge, but in reality, it should be addressed as an opportunity. Corporate dental offices often have vast resources to provide their incoming dentists with thorough, continuing hands-on education. They may also have the assets for a new dentist to try the latest instruments and materials that may not be available in a smaller setting. This, along with the assignment of a senior dentist to mentor recent graduates, can really help guide new dentists to improve their skill set and provide the best care possible for their patients.

For our final topic, do you think a rotary instrument can be developed that does not break?
Dr. Germain: Instruments break because of cyclic fatigue and/or when they meet excessive torque loads. While this nightmare can be minimized by good technique and timely disposal, it is currently an inevitability in endodontics.

What precautions can a clinician take to minimize breakage?
Dr. Germain: I could give an all-day lecture on this topic alone! However, there are some basic rules of thumb. Use a torque-limiting endodontic handpiece, set it at the correct torque and speed for each type and size of instrument, and make sure you enter the canal while the file is rotating. Creating a glide path prior to entry is imperative, as is proper lubrication. An instrument should never be forced or pushed. Ni-Ti rotaries require a very light touch. Be aware that dentin debris in the canal and in the flutes of the instrument will increase the forces placed on it. Hence, copious irrigation and wiping the flutes of the instrument are good preventative measures. And, be wary of difficult canal anatomy, particularly canals that divide and have sharp curves.

Most companies recommend single usage. What does that mean exactly?
Dr. Germain: This is a very confusing issue. My interpretation of the “single-use” recommendation is that we should not be sterilizing Ni-Ti files for re-use on another patient. But, it is often misinterpreted to mean that you should be able to get through an entire case with that instrument. A 4-canal molar will put a lot more stress on an instrument than a central incisor. I invariably use more than one set of instruments on a complicated case.

Since the key is to dispose of the instrument right before it breaks, is there a way to tell if it is overstressed?
Dr. Germain: Since excessive torque creates enormous stress on an instrument, I will toss it if my motor goes into auto-reverse mode. Another tip is to inspect the blades of each file every time it is removed from the tooth. If it has begun to unravel or is distorted in any way, it should be discarded. If you do enough endodontics, you can almost sense when it is time. It is important to trust your gut. When in doubt, throw it out.

Once an instrument breaks, what is the best current technique to remove it?
Dr. Germain: A recent breakthrough is the development of a kit by Dr. Yoshi Terauchi from Japan. It is designed to make removal of the separated segment manageable and predictible. Currently we use modified ultasonic tips to loosen the segment, but the challenge to actually remove the broken piece remains daunting, especially around curves. What I like about this new system is that it has 2 unique design elements specific for the task at hand. The ultrasonic tips used to loosen the segment are shaped like a thin “spoon,” which allows minimal tooth structure removal while trephinating around the instrument. But the most innovative part is the “loop device,” which is used to lasso the recalcitrant file segment and make actual removal of the fragment a fairly straightforward procedure.

Dr. Adams: I want to thank all of you for taking the time to share your clinical expertise as well as your candid opinions and insights on some important issues related to endodontics. All of you have painted a remarkable picture for the near future of your specialty! This discussion will definitely help our readers in their quest to know more about the current state of the art in endodontics.

Dr. Buchanan is a Diplomate of the American Board of Endodontics, a Fellow of the National and International Colleges of Dentists, and part-time faculty at University of California, Los Angeles’ and University of Southern California’s graduate endodontic programs. He is the founder of Dental Education Laboratories, a hands-on teaching center in Santa Barbara, where he also maintains a practice limited to conventional/microsurgical endodontic therapy and implant surgery. He can be reached at delendo.com or at endobuchanan.com.

Disclosure: Dr. Buchanan designed the GT Series X Files and receives royalties. He also has a commmerical interest in TrueTooth Procedural Training Replicas and the file removal kit designed by Dr. Terauchi.

Dr. Germain graduated from Boston University School of Graduate Dentistry with a specialty degree and master’s in endodontics in 1981. She is a Diplomate of the American Board of Endodontics, on the faculty of the American Academy of Facial Esthetics, and a Fellow of the International Congress of Oral Implantologists. Dr. Germain has maintained a private practice in New Orleans, La, since 1984, where she specializes in endodontic and implant procedures. She can be reached via e-mail at roots@bellsouth.net.

Disclosure: Dr. Germain reports no disclosures.

Dr. Kinra received his DDS degree from the University of Michigan School of Dentistry in 1999. In 2002, he obtained his master’s degree in endodontics at the University of Detroit-Mercy School of Dentistry. In 2004, he began his solo private practice limited to endodontics in Flint, Mich. Dr. Kinra is an adjunct professor of graduate endodontics at the University of Detroit-Mercy School of Dentistry and at the University of Southern California Dental School. Dr. Kinra has taught clinical endodontics and practice management at more than 35 universities and hands-on courses in more than 50 international locations. He can be reached at (810) 235-0100, dkinra@gmail.com, or via the Web site located at kinraendo.com.

Disclosure: Dr. Kinra reports no disclosures.