A Less Invasive Root Canal Option by Dr. Kevin Axx

A Townie endodontist recaps the benefits, limitations and considerations behind his preferred treatment system

by Dr. Kevin Axx

I’ve been a GentleWave user since 2017 and it’s changed the way I approach endodontics in much the same way the introduction of rotary instrumentation, operating microscopes and cone-beam CT scans did. GentleWave, at least empirically, is improving the success rates at my practice and allowing us to save teeth that previously may not have been successful.

Before we get too deep into specifics, let’s first discuss the foundation of endodontics and ask, “What is the purpose of this specialty?” The most common answers to that question cover quite a range: the elimination of bacteria and infection from the root canal space; cleaning and shaping the root canal space; curing pulpal and/or periapical pathology.

While these are all lofty goals that, arguably, may or may not be achieved through root canal therapy, they are not the purpose of the treatment we provide. According to the American Association of Endodontists, the purpose of endodontic treatment is to create an environment in which the body can heal itself. That’s a profound position statement, and one that should humble all of us who regularly perform endodontic treatment.

Our treatment isn’t actually the cure for pulpal or apical pathology. Through our procedures, it’s true that we may lower the bacterial content of the root canal spaces enough for the majority of infected teeth to heal, but it’s been shown countless times that no treatment method we currently use eliminates 100% of bacteria from teeth. I don’t think anyone would argue with that. Our goal in treatment is to reduce bacteria counts to the lowest that we possibly can and to create the right set of circumstances in the root canal system that, proven through scientific studies, will allow the body’s natural biological processes to take over and resolve pathology.

Essential equipment for endo

Now that we understand what we’re actually trying to accomplish, how can we best get there today?

Rotary instrumentation and operating microscopes were introduced to endodontics within the past 30 years and revolutionized the way endodontic treatment was performed. They’ve become the standard of care for any endodontist and should be the standard for anyone performing root canal treatment today. It’s also quickly becoming the standard to have a cone-beam scan of all teeth we intend to treat. Because we know that we can’t treat what we can’t see, having a preoperative CBCT scan that aids in the identification of all the canals, and a microscope to physically locate those canals during treatment, is essential to adequately treat complex tooth anatomy.

This doesn’t apply just to molars! Premolars and mandibular anterior teeth are some of the most difficult teeth I treat—and some of the most common for me to see in my office as re-treatment procedures. Virtually any tooth in the mouth can bifurcate or trifurcate into multiple canals or have branched apical anatomy that often is untreatable (Fig. 1). And these are the cases that will look great on postoperative radiographs because we obturated all of the main canals beautifully and completely, but come back to us with persistent pain or pathology. They’re our head-scratchers and, many times, before or after re-treatment these teeth get replaced with implants. It’s an all-too-common occurrence, and one that may be preventable with the right technology.

Expensive—but valuable

I don’t generally consider myself an early adopter of technology—not in my personal life or my professional life. I was skeptical about GentleWave when it was brought to me for an introduction, but I warmed up quickly after consulting with classmates from my endodontic residency at Temple University who had already started to use it and whom I trust very much. It involved a leap of faith for me, because moving to this system was antithetical to many of the principles of my first 11 years in practice.

To colleagues unfamiliar with Gentle­Wave, what I usually hear from them is, “I’m not paying all that money for a different irrigation system” or, “There isn’t enough research to show better results or improved efficacy, so I’m not buying in yet.” I felt the same way—until I knew better. While the latter statement is true at this time, the former couldn’t be further from the truth.

Yes, the system is very expensive—and the price has risen since I bought my two units. But to me, it’s much more than just an irrigation system. And regarding the science, it’s true that there aren’t many long-term studies to demonstrate improved efficacy and success rates, but empirically, in my own office, in the short term, we’re absolutely seeing improved success, faster healing of apical lesions and quicker regeneration of osseous tissue.

(By the way, yes, I did say “two units.” I started with one, but when I brought on an associate in late 2018, we were both using GentleWave so often that each of us needed to have our own unit to keep the schedule flowing.)

Cleaning the canals

Let’s talk about irrigation. In endodontics, we know that what we remove from the root canal space through “cleaning and shaping” is far more important to a successful result than what we put in (i.e., what we obturate with or how we obturate).

We clean the root canal system in two ways: mechanically and chemically. Mechanically, we use rotary instruments to grossly debride the canal space and canal walls, and to create spaces conducive to the introduction and action of irrigants and medications. Chemically, we augment rotary instrumentation by using one or more irrigants that work on pathology with different mechanisms of action. But no matter the choice of irrigants, the goal of chemical cleansing is to remove as much tissue, debris, toxins and bacteria as possible from the main canal lumen, from dentinal tubules and from canal ramifications not accessible to rotary instruments, such as lateral canals, anastomoses, isthmuses and complex apical bifurcations or multibranching.

Clinicians could also augment their protocols to enhance the effectiveness of chemomechanical instrumentation. For example, the EndoActivator, a tool that sonically activates sodium hypochlorite and other irrigants, can get those irrigants into lateral canals. And EDTA or QMix can debride canals of the smear layer and also gain entry into complex anatomy. But does this happen in every tooth with any degree of regularity? I’m not sure we have the answer to that.

For me, GentleWave has treated complex anatomy and all of its variations in a consistent and thorough manner. I’m seeing this happen more regularly in cases in my office (Figs. 2a–c and 3a–b). It does so through a completely different way of creating an environment in which the body can heal itself, which allows us to more thoroughly, regularly and consistently treat a larger proportion of the root canal system while keeping the tooth (and the original dimensions of the root canals) in more of a natural state. One of the ways I explain the system to my patients is to say that it’s endodontics’ answer to a minimally invasive procedure.

A different approach

A GentleWave case starts much the same way a conventional root canal treatment would start. We access the tooth, aiming to keep the access as conservative as possible. I then locate all the canals and establish working length using a Size 8 or 10 K-file. Those are the last filing instruments that need to go to working length; all other files and rotary instruments are measured 1mm short of the working length, depending on other factors specific to each case.

The goal of filing canals in a GentleWave case is no longer to shape the canals—in fact, ideally, we don’t want to alter the shape of the original canal at all. Instead, the goal becomes to simply ensure that we have a path for the GentleWave fluids to follow and flow through. So I usually finish my hand instrument sequence with a Size 15 K-file and then follow that with a Size 15/.04 and 20/.04 Vortex Blue rotary instrument (Dentsply Sirona) to the adjusted working length. That’s it for instrumentation on most canals; occasionally, I will use a Size 25/.04 Vortex Blue on larger canals. Then it’s time for the GentleWave.

Before we can start this cycle, we need to do some preparation of the tooth. The system relies on an airtight closed system—the tooth, the root canal system and the GentleWave device—created by building a flat surface (platform) on the tooth out of a light-cured resin such as SoundSeal from Sonendo or Kool-Dam from Pulpdent (Figs. 4a–c). Once I have my platform built, we then place the GentleWave procedure instrument (or PI, which is Sonendo’s term for “handpiece”) onto the platform and start the cycle (Fig. 5).

The first approximately 60 seconds is a leakage test where distilled water is cycled through the tooth and the operator inspects the tooth and platform for any fluids that are escaping or any air bubbles that are entering. If either is occurring, we can pause the leakage test, attempt to seal the leak by adding more resin, then resume the leakage test and inspect again. From here, the GentleWave moves into a timed sequence during which it will cycle through sodium hypochlorite, then rinse with distilled water and move on to EDTA, and then a final rinse with distilled water. All times are preset by the manufacturer and vary based on the diagnosis of the tooth and what type of tooth is being treated (anterior, premolar or molar). Once the final rinse is complete, the procedure instrument and the resin platform can be removed and the tooth is ready for inspection and obturation.

Any method of obturation can be used at this point, and obturation tends to be much more challenging at first. Remember, gutta-percha points are machined to fit very specific conical canal shapes and sizes, but in GentleWave cases we’re not shaping our canals to any standardized shape or size: They can be irregular, not conical in shape, and may not have any specific taper from the apex to the canal orifice. So what do you do? Because I now use bioceramic sealer (Brasseler’s EndoSequence BC Sealer HiFlow), I am less concerned with a tight or snug fit of my gutta-percha. Tugback is gone. In my cases, I typically use nonstandardized fine gutta-percha cones, and sometimes Size 20/.04 gutta-percha cones. I use Dents­ply’s Calamus Pack to apply heat and apical pressure about 1–3mm into the canal space, then I use standard pluggers to continue to apply apical pressure. The hydraulic forces in these steps allow the BC Sealer HiFlow to get into the canal ramifications. And I see this happen routinely in my GentleWave cases. It’s truly remarkable.

In the GentleWave re-treatment case in Figs. 6a–e, the mesial canals were completely calcified, as can be seen from the incomplete obturation of the first root canal treatment (Fig. 6a). I was able to achieve working length in the mesiobuccal canal, but not the mesiolingual canal. I ran the GentleWave and obturated and, on the postoperative radiograph (Figs. 6b and 6c), BC Sealer can be seen in the mesiolingual canal to the apex of the tooth. No instruments made it into the apical third of the canal—none!—but the GentleWave obviously cleaned and debrided it well enough that the BC Sealer could seal it and the tooth had healed at the one-year follow-up (Fig. 6e).

Fig. 1: In this molar, the mesial apex has four separate portals of exit as well as a lateral canal at the midroot level.

Fig. 2a: Preoperative PA radiograph.

Fig. 2b: Postoperative PA radiograph.

 
Fig. 2c: Six-month recare.

Fig. 3a: Preoperative PA radiograph.

Fig. 3b: Postoperative PA radiograph.

Fig. 4a: The template used to form the platform for GentleWave to run.

Fig. 4b: After coating the platform template with light-cured resin, it’s placed over the access preparation and cured.

Fig. 4c: The platform is modified to achieve the same shape as the original access preparation in the tooth.

 
Fig. 5

Fig. 6a: Preoperative PA demonstrating complete calcification of the mesial root canals.

Fig. 6b: Postoperative PA showing obturation of all canals to working length.

 
Fig. 6c: Red arrows indicate the mesiolingual canal, where mechanical instrumentation was unsuccessful. After running the GentleWave, the obturation was successful.

 
Fig. 6d: Six-month recare demonstrates a decrease in the size of the apical radiolucencies.

Fig. 6e: One-year recare demonstrates complete resolution of pathology.

Considerations for use

Not every tooth is a candidate for GentleWave. It can be used on about 85% of teeth and does have some limitations. It becomes particularly difficult to gain an airtight seal in heavily carious teeth, some fractured teeth and teeth with open/deficient crown margins. In these teeth, if there is an undetected leak, the system will still run through its cycle, but minimal cleansing and disinfection will happen.

Contrary to the sales and marketing strategies I’ve seen employed by Sonendo, GentleWave is not an “eight-minute root canal.” GentleWave isn’t going to find canals for you or make up for operator shortcomings. I’ve done more than 20,000 cases in my career, and the most difficult parts of the procedure are the parts leading up to the rotary instrumentation: accessing a calcified pulp chamber, locating and negotiating calcified canals, removing gutta-percha in re-treatments. All of these steps still require a skilled operator to ready a tooth for with this system.

GentleWave actually adds time to my normal root canal procedures. I’m extremely efficient with my rotary instrumentation and can complete traditional root canal procedures very quickly, but this system incorporates a timed cycle that lasts for 8–9 minutes and can’t be sped up. Considering the additional 5–10 minutes of prep time that it takes to build the platform, it adds about 15–20 minutes to each of my procedures.

Cost is also a barrier to entry. Not only do we have to consider the cost of buying each console, there are also increased procedure costs associated with each case you choose to use the system on. Each procedure instrument is encoded with a computer chip that will allow it to be used for only one cycle. For this reason, the expense of the PI is per tooth. Three root canals on the same patient? That’s three PIs. SoundSeal and EDTA are also costly supplies that each case requires, so a decision will have to be made by providers whether to pass those extra costs on to patients or to absorb them as part of your overhead. In the current insurance environment, absorbing more costs sometimes isn’t economical or even possible, and passing costs on to patients becomes necessary.

We still perform some treatments using traditional methods, but those cases are becoming fewer and fewer. I’ve been quite happy with the elevated care that this system has allowed us to provide to patients, and am eagerly awaiting independent studies that will corroborate the success and healing we’re seeing in our patients.