Instrumenting Grooves: A Modern Root Canal Technique

Since becoming an endodontist in 2008, I’ve learned A LOT over the years. In fact, it’s only because I continue to practice that I’m able to further enhance my skills, learn modern root canal techniques, and appreciate the things that make root canals so gosh darn fascinating.

Today, I want to share with you two tooth stories that may just blow your mind—and that’s saying something because I’ve seen a lot of interesting cases! But even beyond that, these stories demonstrate a little-talked about truth that can help you improve your outcomes: When it comes to root canals, you shouldn’t just instrument canals—sometimes you’ve gotta get into the grooves too!

What exactly does that mean? Well, take a trip with me down Tooth Story Lane…

Tooth Story #1: A J-Shaped Radiolucency in an Abutment Tooth

Our first story begins with a patient who came in with a previously treated tooth #2 that was draining through the sulcus. Although they had no pain to cold or percussion, their initial radiographs showed a J-shaped radiolucency around the MB root. 
To complicate matters, the tooth was also an abutment (i.e., support) to the bridge you see in the x-ray. That alone makes this tooth extra important—lose the one, and we essentially lose three!

Was the tooth fractured from all that pressure to support the bridge? That’s a common thought when we look at the 2D radiograph. But let’s get a deeper look with our 3D imaging to get a better understanding of what’s going on.

Well, that image just looks scarier, doesn’t it?!? You can really see that J-shaped radiolucency now. But, don’t assume the worst just yet! We haven’t looked at the tooth in all its 3D slices.

The coronal slice allows us to appreciate just how broad that mesial buccal root is. But it’s the axial view that made me realize that I should really give this tooth a chance. After all, with so many modern root canal techniques at my disposal, there are few teeth that can’t be saved!

As you can see, there’s a groove connecting the MB canal with the palatal canal. Bingo! We’ve found the source of the problem.

Confused? Let me explain.

You see, back in the day, I used to only instrument canals, or the “dots” on the image. I mean that’s what they teach us in school, right? They’re called root CANALS for a reason! But with time and experience, I learned that even with all of the modern root canal techniques and technology available to us, when we only consider the canals, we can sometimes miss out on important pieces of the puzzle—like the tooth’s grooves.

Grooves are depressions and fissures on the surface of a tooth that resemble riverbeds and valleys on a terrain. They’re a natural part of the tooth’s anatomy—NOT cracks! But they do need to be cleaned out in order to get rid of the infection. 

That was the case in this particular tooth story. Thanks to 3D imaging, I was able to see that it was the groove connecting the MB and palatal canals that was the true culprit. Without that information, I could have overlooked it altogether, treated the canals, and went on my merry way. 

But instead, I managed to identify the problem and make an accurate diagnosis (Previously Treated and Chronic Apical Abscess #2) that would allow me to properly treat—and hopefully save—the patient’s tooth. 

Making That Groove Squeaky Clean

To treat the tooth, I removed the gutta percha and started attacking the groove with a rotary file, slowly but surely making my way to the apex. Trying to use a hand file in a case like this won’t work, because you need some motion behind the file in order to get it into the groove. 

After using the rotary file, I hit the tooth with my trusty GentleWave system (one of my favorite of all the modern root canal techniques and technologies!) to make sure it got a serious power wash before moving on to the obturation.

My backfill radiograph showed me more than I expected. I could really start to see those connections filled by my obturation material.

My final radiograph looked a bit sloppy, but that was just the tooth’s anatomy talking. There was simply WAY more surface area that needed to be treated.

A little concerned, I took a postoperative CBCT to make sure that everything was okay inside that tooth, and this is what I saw, first in the sagittal view:

Then in the coronal view:

The axial view (more coronal):

And the axial view (more apical):

Isn’t that incredible? When you think there’s no more room for improvement for a tooth, think again, because sometimes it’s just not as obvious as you’d expect! I can’t wait for the follow-up on this case. 

Tooth Story #2: A Frequent Flyer With Asymptomatic Apical Periodontitis

Now let’s take a look at the second tooth story, which might just be an even better example of why instrumenting grooves is such a vital modern root canal technique. The patient was a “frequent flyer” in my office, having already come to me for 3 or 4 root canals in the past. (I love that he trusts me enough to come back time and time again!) 

In the case of this particular tooth, he had some pain the week prior, but then his symptoms seemed to resolve on their own. Nevertheless, he came to my practice to get things checked out, and this is what I saw on the radiographs:

No symptoms, but that is most certainly a lesion! So, I diagnosed tooth #19 as Previously Treated with Asymptomatic Apical Periodontitis (and yes, we discussed the periodontal bone loss on this tooth as well).  

What I think is most interesting here is that the lesion is mainly only on the mesial root. And maybe if I had stopped there, I would have thought I could get away with treating only part of the tooth. But after looking at the CBCT, it became clear that I was going to have to re-treat the whole tooth, because there was an untreated canal in the distal root.

The CBCT never lies, so off I went to re-treat the entire tooth, using my GentleWave and other modern root canal techniques and technologies to make sure those canals looked spick and span. 

A Surprising Discovery

Once the tooth was squeaky clean, I started to obturate the tooth. Here’s the conefit at different angles:

And the backfill:

And the final radiographs:

When I saw this very last image, I had a nagging suspicion that something wasn’t quite right. So, I got a postoperative CBCT, and that’s when I made a surprising discovery: There was a little line that connected the mesial root obturations!

It was the axial and coronal views that really blew my mind:

Look at just how connected those mesial canals are! 

Let this be a lesson that when you see a failing root canal of a mandibular molar, and the mesial root has a bigger lesion than the distal, you should start thinking about what else besides a crack could be causing the root canal to fail. In most cases (just like this one), it’s some middle mesial anatomy that’s getting in the way, and more advanced irrigation is needed.

Instrumenting Grooves as a Modern Root Canal Technique

These two tooth stories are great examples of why it’s important to pay attention to grooves—not just because they can be home to bacteria, but because they can be an alternative and very treatable diagnosis to a crack.

With modern root canal techniques and technology like the GentleWave and dental laser at your disposal, there’s no reason teeth like these can’t be saved. So throw that crack diagnosis out the window and start giving more teeth a chance!

Great Outcomes Start With Accurate Diagnoses

I could have never treated these patients’ teeth without making a proper diagnosis, and an important part of the process is conducting cold and percussion tests. With my free Pulpal and Periapical Diagnosis Checklist, you’ll be able to enhance your skills, improve your diagnoses and treatment plans, and achieve better outcomes for your patients.

– Sonia