Technology — the revolution of evolution

Dr. Eric Herbranson reflects on technologies that have changed the practice of endodontics

Birthdays are a time for reflection. I realized at my last one I had become an official “Old Guy” in this specialty of ours. I’ve pretty much seen it all in my career. In graduate school, we were well aware of Dr. Herbert Schilder’s emphasis on 3D anatomy and his rediscovery of Dr. Walter Hess’ forgotten work on canal anatomy.

The image in Figure 1 was an epiphany for me because it showed that Hess and Schilder were right about canal anatomy and defined the challenges of endodontics. This was the time warm gutta percha with its hoped-for 3D obturation was the hot new technique, and we all made the effort to learn its secrets, so we could do it the way the guys in Boston did it.

I was 1 year out of graduate school when Dr. Schilder published his, now iconic, five mechanical objectives for shaping. For me, this time was the start of a life long journey of inquiry with adoption and replacement of ideas as research and technology advanced. It was engaging and fun. I remember how thrilled I was when the Obtura gun and System B™ were introduced because I could take my ugly Bunsen Burner off the operatory delivery system. Patients never did like the look of those!  First big technology change!

Then along came NiTi rotary file systems. The flexibility of the metal made an engine-driven file system relatively predictable and safe in curved canals. This was a true leap forward for us and lead to many permutations in design that continues to this day. The discussion all centered around the instruments and obturation methods. It was all about the process of doing endodontics, not so much about why we were doing it.

The surgical operating microscope came next, and I consider this to be the biggest technology change we’ve had. These microscopes allowed us to see. I took it on faith they would improve my clinical results and became an early adopter. I actually replaced my overhead lights with a scope in each operatory to force myself to use them. The first week I had my scopes, I did a retreatment on a symptomatic tooth I’d treated a couple of years previously. Working through a crown, I’d found the MB2 and MB3 canals but had missed the MB1. It was easily found with the scope, and I never looked back at my decision to adopt them. Most of you, I’m sure, have had similar experiences.

Computers started to help us in the mid-1990s. I became acquainted with a computer-imaging expert at Stanford Medical School who introduced me to the, then new, micro-CT technology. That ultimately led to the development of the 3D Interactive Tooth Atlas, which allowed us to see the anatomy of real teeth blown up on a computer screen while interactively manipulating the models. It became another validation for Dr. Hess and a robust example of the anatomical issues we deal with. The first computers we used to visualize these scans were $100,000 workstations. Thanks to Moore’s Law (that states that processor speeds, or overall processing power for computers, will double every 2 years), by the time the Tooth Atlas was commercialized a couple of years later, any normal PC was powerful enough to drive the program.

This growth in computer power eventually allowed for the development of the CBCT technology we have now. 3D imaging is a game changer because these scans are just good enough to see dental anatomy specific to our particular patient, and we have a much clearer picture of where the bone is around the teeth. That is a real advantage in diagnosis and treatment. But it has also raised questions and misconceptions we need to resolve. We’re still not sure of the significance of all we see on the scan, and some findings can be misinterpreted. I’ve seen people diagnose vertical root fractures when what they were looking at was scan artifact.  Some more education is in order.

Sometimes the technologies reinforce each other to allow us to make paradigm shifts. This has happened with the goal of conservation to improve tooth strength. The newest multi-taper file systems have smaller flute diameters at the D8 to D16 area of the file while still creating adequate room at the apex for irrigation and obturation. These design changes and heat treating have created files that are significantly more flexible and fatigue resistant than the older designs. CBCT imaging gives us accurate 3D modeling of the tooth, which improves our mental picture for more accurate accesses, and the scope allows us to visualize through a smaller opening that was traditionally recommended. These tools allow us to replace our legacy access designs, with their convenience form and wider occlusal opening, with ones that conserve critical peri-cervical dentin. The result is a more nuanced access preparation with safer, more root-form-appropriate shaping in the upper part of the canal system. These efforts significantly increase tooth strength and help reduce the incidence of fracture. It’s the intersection of all these technologies that allows us to gracefully do this.

I look back on all these developments with the joy of discovery because the challenges have been interesting and engaging. Most changes have been evolutionary — some disruptive, like NiTi files, the microscope, and CBCT imaging. But I look at the issues that are being discussed now and what is on the horizon, and I can’t help but feel the changes are going to accelerate and could be revolutionary in nature. People are questioning our disease model, and what radiographic findings really mean. Our traditional plantonic bacterial model is now a biofilm discussion, a much different “animal.” We see cases all the time that do not match our disease model. We see 30-year-old silver point treated molars with missed MB2s that are functional and in solid bone. There are cases that were never obturated that healed. There are cases that are open to the oral environment that healed. Our legacy research and legacy treatment protocols are coming into question more than ever before. And there are disruptive technologies like Sonendo® on the horizon. What does it all mean? I’m not sure, but it’s going to be fun to watch. I hope I am around in another 40 years to find out.