After doing enough endo there’s a chance you’ve run into the elusive C-shaped canal … and didn’t even know it.

Wait, that can’t be right, can it? YEP. I’m here to tell you that while you were accessing a tooth, you may have totally missed it.

But we’re here to fix that. Today, I want to talk about C-shaped canal anatomy inside teeth, so you can navigate these canals with ease. 

The What, Where, and Why of C-Shaped Canal Anatomy

First identified by Cooke and Cox in 1979, the C-shaped canal anatomy is significant because it’s notoriously challenging to diagnose, clean, shape, and most of all, obturate. These canals are most commonly seen as narrow, ribbon-like shapes with interconnecting isthmuses. Because of this, getting your file deep enough to clean the whole canal can be pretty difficult.

So what do you do about this problem?

C-shaped canals usually are hiding in mandibular second molars, but they can be seen in the maxillary second molars, too. A teeny-tiny endo tip: if you do find one, definitely check the contralateral side of the tooth, because there’s a good chance that it appeared there, too.

Even if you’ve never seen them before, these canals really aren’t that uncommon. Believe it or not, they occur in about 2-8% of teeth. 

What I’m saying is that if you look for them, you will start to notice them. This is especially true in Asian and Lebanese populations, which I think is an interesting and very specific ethnic predilection. Just don’t take this to mean certain people can’t get C-shaped canals. Everyone can have them.

The real kicker is that you can’t fully trust your preoperative radiograph to tell the whole story (a thing I’ve talked about before), because C-shaped canal anatomy can be hard to spot. It’s only when you access or use your CBCT that you can really see something deeper is happening. Anatomy can be tricky like that.

Coming Across a C-Shaped Canal: a Tooth Story

Take this tooth, for example. The patient was relatively asymptomatic, demonstrating intermittent cold sensitivity and zero pain to percussion. The official diagnosis was Asymptomatic Irreversible Pulpitis and Normal Apical Periodontium #18.

(Note that this tooth has a conical shape. That’s a pretty typical finding with a C-shaped canal.)

c-shaped canal

C-Shaped Canal

Look more closely at the inside of the tooth. In the axial view, you can really appreciate how ribbon-like those canals can be, and just how connected they are. It’s honestly very pretty!

C-shaped Canal

As I’m sure you can imagine, cleaning a tooth like this is no simple feat. Penetrating that isthmus with a rotary file can feel kind of impossible.

Where does that leave us? It’s time to get creative! You won’t be able to lean on the comforts of your typical mechanical debridement, so to disinfect those roots, you’ll have to leverage the strengths of your chemical disinfection with your irrigants.

Deep Disinfection for That Hard-to-Reach Endo

Believe it or not, I haven’t always had access to the best tech on the market. Like many, my practice had more humble beginnings, and advanced irrigation was NOT on the table.

I would take two steps—start with calcium hydroxide into the isthmuses to break down deep tissue, then send in sodium hypochlorite for round two, providing a deeper, more purifying disinfection.

Admittedly, I don’t really do this anymore because I don’t need to. With access to the GentleWave Procedure, I can wrap up a full disinfection in one go. But not all practices can justify investing in GentleWave right now, so it’s helpful to have a backup plan.

A piece of technology you can invest in sooner than GentleWave is the Endo Activator! It can also perform deep irrigation. You could also invest in the Fotona Laser, although it is not as accessible, price-wise, as the Endo Activator.

You owe it to yourself to stay on top of what technology is currently available and successful in yielding good outcomes. Whatever you do, I do recommend bringing something into your practice that can activate your irrigant and push it into those hard-to-reach places.

Avoid the Voids in Obturation

As for obturation, that’s a WHOLE different animal!

This is where warm vertical condensation really shines. In endo, the clinician who does a single cone obturation is probably going to run into some frustration here because their final radiograph is covered in blank spots. Those voids can be aggravating to look at, let me tell you. Especially when they’re totally avoidable.

It comes down to the gutta percha. In a case like this, it will need some heat activation in order to densely fill the isthmus and provide the hermetic seal we need. No matter the size or shape of the canal (C-shaped, tiny, wide, curvy,…just about anything), warm vertical condensation is a versatile life-saver. This is something I teach in my in-person, live-patient program, E-School LIVE, so that dentists can walk away from the 4-day experience feeling super confident!

Not All C-Shaped Canals Look the Same

Let’s look at C-shaped canal anatomy again, because I want to bring attention to how variable they can be in all of the different shapes they can take. Here’s an example:

C-shaped Canal

Coronally, this is what the tooth looked like in the axial view.

C-shaped Canal

And then the canal morphology changed as I marched my way down the canal towards the apex. Now the mesial and distal canals merge all the way across.

C-shaped Canal

Finally, this is what the apex looks like. Look at that lateral canal!

C-shaped Canal

Understanding endodontic anatomy is, well, kind of limitless. Every single tooth that has ever existed or will ever exist is entirely unique.

Plus, research is ever-evolving, and we’re always learning new things about teeth and the people who have them. 

To be honest, it is such an exciting time to be doing endo!

C-shaped canal anatomy is just another example of an area where our care can evolve as we learn more. Once you internalize what we’ve discussed in this blog, I hope you will be able to manage your time a bit better, improve your outcomes, and engage with tricky anatomy. You might be more comfortable with C-shaped canals now, or you might not. Maybe you see another way to use your CBCT for risk assessment. But either way, you’re feeling more knowledgeable and empowered, and that’s what I’m after!

There’s so much to learn in endo. If you want to become more confident in your diagnosis, access, instrumentation, obturation, and more, I promise you don’t need to go far. Check out my award-winning, game-changing E-School course right here, and see for yourself.

– Sonia