Tooth Story: The Tooth that Wouldn’t Heal and Root Canal Anatomy

Root canal anatomy is tricky. When a tooth doesn’t heal from a root canal, most people just assume that the tooth is cracked and that it can’t be saved—basically a one-way ticket to extraction. 

This is probably my biggest pet peeve that is all too common in dentistry. The term “cracked tooth” gets thrown around way too loosely. In fact, there aren’t nearly as many cracked teeth as you may think in dentistry, and often it’s just a flat out misdiagnosis.

This tooth story—or should I say tooth SAGA!—will illustrate why getting to the root of a failed root canal isn’t as simple as it’s made out to be. Spanning three treatments and seven years, this totally illuminating case blew my mind, and I think it’s going to blow yours, too.

Hopefully once you make it to the end (buckle your seatbelt—it’s gonna be a long ride!), you’ll walk away thinking about how you might approach failing root canal cases differently.

The Saga Begins: A Lesson in Root Canal Anatomy:

I first met this patient way back in 2013. (Oh gosh, was it really more than 10 years ago?) Her preoperative radiograph, which I’ve included below, showed that she had a nice ol’ lesion on the MB root. You could even say it looked exactly like that “J shaped radiolucency” that defines a cracked root. 

What’s more, the tooth had no response to cold, no pain to percussion or palpation, and all of her probing depths were within normal limits.

Here is an off-angle radiograph to give you another view:

And the bitewing, for good measure:

Applying a clinical eye to the anatomy of the root canal, you can see all the microleakage and the way that bacteria managed to sneak into this tooth. It’s pretty clear these are childhood amalgams that have never been replaced and now allow bacteria to make their way to the pulp. 

Leaving restorations to sit for decades is not the move, folks! When you start to see these spider webs emanating from the restoration, you know they’re leaking, and the teeth are developing cracks. BUT, these cracks are coronal and they don’t probe, so keep that in mind.

Also be aware that there is a HUMONGUS difference between a crack in the tooth and a vertical root fracture! Nomenclature is really important here and when it comes to a case like this, you can’t be too careful with your words.
Adding an additional tricky layer to the root canal anatomy, this patient had no pain because there was a sinus tract. But since there was a sinus tract, we traced it and… sure enough, it led to a lesion. Thought it was sneaky, didn’t it!

The final diagnosis for this tooth was Necrotic Pulp and Chronic Apical Periodontitis #3. Keep in mind, I performed this case when I was a baby endodontist. It was one of my earlier root canals, so at that time, I only found 3 canals in this maxillary first molar.

What I Learned Along the Way: Look for MB2s!

This is the case that made me realize that MB2s are always there, and that if you don’t find one, you should probably use a CBCT to get a closer look at the root canal anatomy. Better yet, just start making preoperative CBCTs a habit so you get a more complete picture before you even start. Doing so can help you do proper risk assessment and lead to greater success down the line.

Listen, MB2s don’t always have to stare you in the face. They’re often a bit deeper and more apical than the orifice of the MB1, and you have to selectively trough the area in order to find them.

But, hindsight being 20/20, one thing I wish I would’ve noticed is just how offset that single MB canal is within the MB root. That is a dead giveaway that there is a second canal hanging out waiting to be found in the root. In the radiograph below you can very clearly see the offset that I’m talking about.

The Saga Continues: One Year Later

The patient ended up returning to my office in 2014, and the sinus tract was still there. She had never healed. Great. 😥

At the time, I wasn’t in the practice of taking a CBCT on every patient, but I ended up taking one when this one returned—and thank goodness I did. The axial slice showed me this bad boy:

I can see from this radiograph that there is a very broad MB root and that means there’s room for an MB2. Now, I can’t see the actual canal on the CBCT, but that doesn’t mean that the MB2 is not there—it’s probably just super skinny. So now I have to put on my detective hat and FIND IT.

And I did. There was honestly so much more to this tooth’s root canal anatomy than I realized. In the radiograph below you can catch a glimpse of that teeny tiny MB2.

And here is the final result:

And the off angle radiograph …

But GET THIS— the story doesn’t end here.

The Never-Ending Saga: Fast Forward 7 Years

Jump ahead to 2021 (SEVEN YEARS LATER, y’all) and the lesion is still there. ARE. YOU. KIDDING?! 😵😱

Okay, okay. Let’s slow down.

What could this mean? Is this tooth cracked? I mean we saw all of those cracks coming from that amalgam, so perhaps one of them propagated over time. There is clearly a vertical root fracture, right? Well, I’m not so sure. We’ll need to take another look at the anatomy of the root canal to find out.

Check out the radiograph below. Can you see the tiny sealer track coming from the MB2? Could that be an MB3? And if it is… how am I supposed to get to that?!

I had a long, honest talk with the patient about her treatment options. I told her that since her last retreatment was done, there have been some advances in technology like the GentleWave Procedure. So we could choose to retreat the tooth one more time with it, or we could take the surgical approach and do an apico. The patient opted for the surgical approach.

My partner (who was my associate at the time), Dr. Tanya Reiter, did the surgery—and dang, did she knock it out of the park! 

She did the root resection and used an ultrasonic to really clean out the isthmus that existed between the MB1 and the MB2.

She followed that up with the retrofill:

This is what the root end looked like. There was way more to the root canal anatomy than was expected: an apical MB3, one heck of an isthmus, and not one crack to be found!

And when you take the postoperative off-angle radiograph, it looks like this. Holy smokes, right?!

But we can’t close out this huge saga without a killer finale—and that’s exactly what we got. Check out these images from a year after the patient’s apicoectomy. All healed up!

Lessons Learned From This Epic Tooth Story

I know the patient must be frustrated that it took her three treatments (and seven years!) to get this far. The reality is that part of this stems from my inexperience when she first came to me as a patient. But it also has to do with the lack of endodontic technology back then and the root canal anatomy of the tooth.

I point this out because I think it’s important not to beat yourself up when a treatment doesn’t go exactly how you want. You don’t deserve that. Instead, learn from it!

This case was a HUGE learning opportunity for me. It made me start taking CBCTs when I don’t find an MB2 because I know they should be there almost every single time. It also taught me that troughing can help you find the MB2 and get a handle on the oh-so-variable anatomy of a root canal. So don’t forget it!

Let MY mistake be YOUR lesson.

Many people would’ve extracted this tooth, but my goal is for this tooth story to make you think about the other possibilities and help you inform your patients so you can make the best decisions together.

What comes up for you when you check out this tooth story? Let me know in the comments!

If you enjoyed this exciting saga and want to be the first to know about future tooth stories, endodontic resources, and updates, make sure you join my email list at https://soniachopradds.com/subscribe/.

–  Sonia