Let’s start out with defining this technology. Steve, what is dynamic guidance and how does it apply to root canal therapy?
Dr. Buchanan: Dynamic guidance (DG) has recently been introduced as an alternative to the printed or milled (static) drill guides that implant surgeons have used for more than a decade. While static drill guides must be planned and fabricated some time before the surgical appointment, DG works in real time during the procedure. The X-NAV (X-NAV Technologies) system (Figure 1) has an overhead 3-D camera system that watches fiducials attached to the clinician’s handpiece and the patient’s jaw during the procedure, then its computer calculates the x, y, and z positions of the handpiece drill relative to the patient’s jaw, displaying to the clinician a target-like graphic of the drilling path and the drill overlaid on the CBCT volume.
X-NAV was developed for implant surgery; however, Dr. Maupin and I immediately recognized this system as a perfect solution for guided endodontics (Figures 2 and 3) without the numerous difficulties encountered when using static drill guides for endodontic access.
Do all of you use this in your practices?
Dr. Khademi: Steve and Charles have been on the hunt for guided endodontics for many years, and they began using the X-NAV system shortly after it was released at the 2015 Academy of Osseointegration meeting. I’m the new guy to DG, and my first experience with it was last August when the 3 of us did a research study to determine the accuracy of seasoned and novice users. I was the novice in this research.
|Figure 1. (a) An X-NAV (X-NAV Technologies) optical tracking system and (b) a computer displayed avatar of a drill, jaw, and a programmed drill path.|
How did that go for you, John?
Dr. Khademi: Having known both of these guys and their skills for many years, I was really nervous about doing it for the first time in front of them—really nervous! Of course, I didn’t know the planning software, so Steve and Charles planned my first case (Figure 4). When I sat down to cut the access, I was astonished at how easy it was to follow the computer monitor that displayed the planned drill path overlaid on an avatar of the patient’s tooth. It sounds difficult to do a procedure without looking directly at the patient’s tooth, but it turns out that anyone who has played his or her fair share of computer video games has all the heads-up skills that are needed. I think that any endodontist who works using the microscope will readily pick up the needed skills within the first few cases.
Charles, how does this help dentists doing endodontic procedures? It requires a bit of preoperative setup, so there must be a compelling reason, right?
Dr. Maupin: The most obvious application is for the most difficult cases referred to endodontists: calcified pulp chambers and canals. The majority of endodontists have CBCT machines, making it a simple matter to treatment plan drill paths and to use guidance immediately. DG allows us, in a single visit, to confidently and precisely drill 8.0 to 12.0 mm through solid dentin roots, finding canals in the apical third (Figures 5 and 6), and done through minimally invasive openings 1.0-mm wide or smaller. In teeth without severe calcification, DG can be used to reduce structural weakening through minimally invasive endodontic (MIE) procedures.
John, I know that you and Dr. David Clark have written about MIE objectives for our readers in Dentistry Today. How helpful is DG in achieving MIE outcomes?
Dr. Khademi: The dentin preservation shift really started with Steve and his GT files, designed to have maximum flute diameter limitations to control coronal canal enlargement. David and I extended this basic idea of dentin preservation to the coronal portions of the tooth with endodontic access cavities. Before we had dynamically guided access (DGA), cutting dentin-preserving access cavities required a lot of skill, experience, and luck. While restorative dentists universally loved these ideas, these access cavities were difficult and error-prone in the best of hands. DGA makes performing these “conventional” and “traditional” kinds of dentin-preserving accesses both safe and predictable.
|Figure 2. (a) A preoperative radiograph shows a maxillary molar with total calcific occlusion of its pulp chamber. (b) A radiograph showing that root canal therapy (RCT) was done through separate access openings that were cut using dynamic guidance (DG), (c) one exactly to each canal orifice. Images (d) and (e) show the completed case.|
Dr. Buchanan: With DG, specialists can cut perfect MIE accesses right off the bat and, beyond that, DG is so precise that it allows us to think about planning and cutting unconventional access paths. If you can plan it, you can drill it!
Dr. Khademi: Steve showed me some wildly unconventional access designs several years ago that he was cutting in his TrueTooth replicas that had my head spinning (Figure 7). Up to this point, all existing access designs and thought have been limited by the technology that we have had available for access; instrumentation and obturation; and, probably most importantly, for vision. The sea change that Steve brings up involves a combination of the incredible precision of DGA and today’s very small, flexible heat-treated NiTi instruments. We will need an entire new body of research to help us figure out where to cut access when you don’t actually need to see what you’re doing but instead know what you’re doing by working off of a computer screen.
|Figure 3. (a) The pre-op radiograph shows the access openings cut using DG. (b) A radiograph shows a completed RCT. This case is conceivably as structurally intact as before RCT.|
|Figure 4. Dr. Khademi’s first X-NAV DG outcome. Guided by the X-NAV system, he drilled a minimally invasive endodontic (MIE) access opening through a TrueJaw tooth replica modeled without a pulp chamber, intersecting the canal exactly at the CEJ.|
So, Steve, what makes DG for endo procedures superior to static traditional drill guidance?
Dr. Buchanan: The most profound advantage is the just-in-time nature of the DG treatment planning, allowing access to be cut in a difficult emergency case within 10 minutes of the CBCT capture. Even with static guides fabricated just in time with 3-D printers or milling machines, the 4-hour step of actually making the guide is obviated with DGA. In the same vein, the immediacy of this guidance method allows changes to be made in programmed drill paths literally during the procedure—for example, altering a drill path when faced with unexpected clinical difficulties. Also, DGA is done with the same lengths of access burs that would normally be used, unlike static drill guides that require drills 10 mm longer than usual, which makes static guidance an impossibility in posterior teeth. Finally, guide rings cannot be overlapped in static drill guides, requiring a separate guide for each canal, making it cost prohibitive.
|Figure 5. (a) A pre-op radiograph shows a maxillary lateral incisor (b) broken at the gumline with no canal seen on conventional or CT imaging until 4.0 mm from the foramen. (c) A working radiograph shows the drill as guided to mid-root. (d) Working radiographs and (e) a postoperative image show the completed RCT with post space.|
Charles, how did you get the idea to apply dynamic navigation to endodontics?
Dr. Maupin: Implant surgery primarily deals in millimeters, while endodontics deals in fractions of a millimeter. Steve and I have done implant surgery in our practices for many years, and our endless drive for microscopic precision naturally led us to using guidance. As we moved into implant surgery, we wanted the same accuracy in our implant cases as we accomplished in our endodontic procedures. After performing several dynamic navigation implant cases with precision, the wheels started to turn on bringing this technology into endodontics. When the right case presented, I went for it and the rest is history. Implant dentistry has changed all fields of dentistry, so it’s not surprising to see this technology crossover being led by endodontists who place implants. For endodontists and GPs who perform both procedures, DG is a slam dunk.
John, you’re the imaging and probability expert in this crew; what can you tell us about the relative accuracies with DG?
Dr. Khademi: Damon, your reaction (“I am blown away!”) to the pictures that we first showed you probably captures it the best: We need one of those mind-blown emojis! Typical molar endodontic access cavities have 4.0- to 6.0-mm-width dimensions. When we started our pilot project, we went with 2.0-mm-diameter access plans. However, we quickly found out that even these were far too large, so we reduced them down to 0.5 mm. Our initial look at the data tells us that we can achieve accuracy within 0.5 to 0.25 mm of the planned target at full planned depth. All this comes from the exact 1:1 representation of our patient’s anatomy with CBCT.
Steve, as a really experienced endodontist, do you think DGA is an innovation that you even need, considering the thousands of root canal procedures you’ve done?
Dr. Buchanan: Despite performing root canal treatment (RCT) procedures since 1977, cutting perfect access cavities remains the most challenging thing I do. In teeth with pulp chambers still extant, I want to cut the least amount of dentin as possible yet still create an ideal file path into each canal. That is difficult, but not nearly as difficult as getting this outcome in teeth with totally calcified pulp chambers—the bane of every endodontist’s existence. Losing my fear of calcified teeth is the greatest gift I’ve experienced from using DG. I actually look forward to these cases now.
|Figure 6. (a) A pre-op radiograph and (b) a radiograph showing RCT completed. (c) and (d) Working radiographs show that (e) the access opening was as minimally invasive as it gets.|
Charles, are there other endodontists who use X-NAV for access procedures, and are you planning to teach this to colleagues?
Dr. Maupin: You know that all 3 of us love to teach, so of course we will be sharing our knowledge with our peers. Steve and I have already spoken about DGA at a few meetings, and a handful of endodontists have purchased X-NAV systems, and many others have expressed an interest. The team at X-NAV Technologies is still working to provide the specific features that we have asked for since their machine was not originally designed for endodontics. We are hoping that functionality should be coded and delivered as an update by mid-2018.
|Figure 7. TrueTooth with access paths cut to 4 canals from below the occlusal surface.|
In a way, DG is more important for endo than it is for implant surgery, as static guides are an established alternative for implant surgery, but not for endo access. The endodontic application of DG may end up being used more for endo than implant procedures, both in the number of clinicians using it and in the number of procedures performed. Implant surgeons have other guidance methods they have learned to use successfully. Endodontists have no guidance but dynamic guidance.
Regarding our teaching efforts, Steve and I are doing a live demonstration of DG on a TrueJaw surgical training replica at the American Association of Endodontists Annual Meeting this month (April 25 to April 28) in Denver. It will be informative and fun, so maybe some of your interested readers will want to attend!
In closing, my dear colleagues, what you have introduced here is nothing short of incredible! From what you’ve told me, the digital revolution is supercharging endodontics just as it has re-energized prosthodontics and implant surgery. It looks like a brave new world for the field!
I want to take this opportunity to thank all of you for sharing this important, cutting-edge information on dynamic guidance with all of our Dentistry Today readers and me!
Dr. Buchanan owns a private practice limited to endodontics and implant surgery in Santa Barbara, Calif. He is the founder of Dental Education Laboratories, a hands-on training center serving general dentists and endodontists by upgrading their skills with new endodontic and implant technologies. Dr. Buchanan is a Diplomate of the American Board of Endodontics (ABE) and an assistant clinical professor at the postgraduate endodontic programs at the University of Southern California (USC) and the University of California, Los Angeles (UCLA). He can be reached via the website delendo.com or via email at firstname.lastname@example.org.
Dr. Khademi received his DDS from the University of California, San Francisco (UCSF), while his certificate in endodontics and his MS in digital imaging are from at the University of Iowa. He has a full-time private practice in Durango, Colo. Dr. Khademi was an associate clinical professor in the department of maxillofacial imaging at USC and is an adjunct assistant professor at St. Louis University. As a Radiological Society of North America member for more than 20 years, his background in medical radiology allows him a perspective shared by few dental professionals. He can be reached via email at email@example.com.
Dr. Maupin owns a private practice called Maupin Endodontics in Lubbock, Texas. He received his DDS degree from the Baylor College of Dentistry. Following graduation, Dr. Maupin attended UCLA, where he served as chief resident and received his certificate in endodontics. He is a Diplomate of the ABE, making him the only board-certified endodontist in Lubbock. He is an active member of the American Association of Endodontists, the ADA, the Texas Dental Association, and the South Plains District Dental Society. He is a founding member of the International Academy of Endodontics and is excited to be at the forefront of revolutionizing endodontics. He can be reached at (806) 589-3390.
Disclosure: Drs. Buchanan, Maupin, and Khademi report no disclosures.