Focus On: Endodontics

L. Stephen Buchanan, DDS

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L. Stephen Buchanan, DDS, talks about the exciting impact 3-D printing will have on endodontic education and hands-on training.

Twenty-five years ago, I was chatting with a physicist, Dr. Chuck Hull, at the University of California in Santa Barbara, and asked him about his area of interest. He said, “I invented a new technology called stereolithography. It uses a laser to trace and light-cure the cross sections of a CAD model onto a plate that progressively drops further into a bath of photocatalyzed polymer after each slice has been formed, until the plate comes back out of the solution bearing the completed object.”

When I heard this, it felt like my hair was on fire! This was because my research partner Jean Pierre Hebert and I had just done the first computer reconstructions of CT scans of extracted teeth. Not surprisingly, I asked, “Could you print a tooth?” He said not for maybe 15 or 20 years, since the finest resolution of 3-D printing they were capable of at that time was a one-mm voxel (3-D pixel). His prediction turned out to be prescient because 4 years ago, the original patents expired, and competition drove the price of 3-D printers down and their resolution way, way up. Suddenly, it was possible to print replicas of extracted teeth with every nuance of natural anatomy contained inside their replicated root canal spaces, and TrueTooth Procedural Training Replicas were born.

With printed layers as small as 0.16 mm and with opaque and transparent heat-resistant polymers, it became possible, for the first time, to recreate the natural anatomy of teeth. Procedural training in dentistry will never be the same.

A frustrating part of learning to do endodontic therapy is the random walk that practicing in extracted teeth presents to students and educators alike. As root canals are microscopic in size and obscured by root structure, it is rare when a student can understand exactly what kind of anatomic challenge may be con­tained inside—or their instructors either in most cases.

The worst aspect of training in extracted teeth is the fact that there are no do-overs when students block, ledge, or rip a canal. For instance, when a canal in an extracted tooth has an apical impediment, if the student is unaware of the anatomic complexity or how to manage it successfully and ledges the canal with a file, the session is over. Finding another extracted tooth with the same anatomic form is relatively impossible, so iterative learning (the most effective method of acquiring complex skill sets) is not possible. Hence, the typical requirement is that students practice their endodontic techniques on 100 to 250 teeth (extracted or in patients’ jaws), before they are able to become unconsciously competent in treating the major anatomic forms of naturally occurring root canals.

With 3-D printed replicas, hands-on training can occur in a very predictable manner in much less time than was previously possible. For the instructor, the anatomic challenges can be chosen to match the teaching objective and, just as importantly, all the students in the class are working in the same exact root canal forms. For the students, they can see for the first time, in transparent replicas, precisely what is happening to canals as they use different instrumentation and filling methods. Even more important is the fact that they can botch the next 19 attempts in replicas (all with the same morphology) until they get it right while working in the twentieth attempt, gaining a skill that would otherwise require working in hundreds of extracted teeth.

The possibilities of replica-based hands-on training are endless. Obviously, every type of conventional root canal therapy can be taught with them; access through calcified pulp chambers; negotiating and shaping small canals with every type of canal curvature; managing large canals with small, large, and immature blunderbuss apical thirds; canals with apical bifurcations and every type of lateral and accessory canals; and conventional retreatment challenges such as file retrieval, carrier retrieval, management of apical blockage and ledges, and mineral trioxide aggregate repair of lateral and apical perforations, and so on.

Full-jaw, multi-ink replicas can be printed for post-endodontic restorative courses, and surgical endodontic retreatment courses; a wide range of implant procedures can be taught with them as well. Because each tooth in a full-jaw replica can be printed with a periodontal ligament, they can be used to teach extraction methods. Because the soft tissues can be printed in soft, rubber-like polymers, they can be incised and sutured. Even grafting techniques can be taught, as well as sinus lift procedures.

The possibilities are limited only by the creativity of the educator and the person who designs the CAD models that are printed. For me, the most difficult and intimidating aspect of implant surgical training was getting experience in the different anatomic variations that I might encounter once the soft-tissue flaps were reflected. The way I chose to cross the chasm from didactic to procedural competence in implant surgery was to engage a surgical mentor to assist me in my first 25 cases. With printed jaw replicas, dentists can do 50 or 100 implant placement exercises on scores of real-life anatomic variations without needing another dentist’s oversight, other than to review the results and offer advice for improvement.

Perhaps the most amazing possibility offered with printed replicas for procedural training is the possibility for remote hands-on training for learning new procedures in our office, with our chairside assistants, using replicas and interactive media. Not only are huge cost savings possible (no lost production, no airfare, and no hotel costs) with this new training paradigm, in some ways it is superior to training in distant simulation labs as the assisting team is involved and trained at the same time. In addition, all the instruments and materials are acquired and set up for practice before the course is even taken; thus dentists learn to use new techniques successfully in their own practice environment.

Where will this ultimately end up? Well, we have always called the practice dummies in simulation labs “phantom heads.” My fantasy life includes full-size 3-D-printed heads, not phantom heads, but real-life heads with skin, lips, muscles of mastication, articulating jaws, bone, and teeth. Kind of creepy, but so cool!

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 via the websites delendo.com or endobuchanan.com.

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