What’s Happening in That Tooth? A Middle Mesial Canal Tooth Story

When a patient comes to you with tooth pain, it can be easy to forget just how many possibilities there are for what’s actually going on. You see a tooth that’s failing, and your first instinct is to say that it’s cracked. But to come to an accurate diagnosis, you need to do some investigating and take a look inside, because what you find may not match your first instinct—especially as those endodontic instincts are still developing! Today, I’m sharing a tooth story that demonstrates just how important it is to put on your endodontic detective hat and do some digging. The villain of the story? The middle mesial canal!

Background: A Previously Treated Tooth With Tenderness to Percussion

Our tooth story begins with a patient who was previously treated. They came into my office with tenderness to percussion, so the initial diagnosis was: previously treated and symptomatic apical periodontitis.

Looking at the radiographs alone, it’s impossible to tell just exactly what’s going on. As you can see, the obturations are a few millimeters short, which is an immediate red flag for bacteria. Questionable patency in this case, for sure!

Now let’s look a bit closer. Do you see that “J-shaped” radiolucency around the mesial root? Studies have shown that the mesial root of the mandibular first molar is one of the most common roots to fracture.

Based on the evidence we have so far, the cause of this patient’s pain could be reinfection or a tooth fracture. But which one is it?

To get our answer, we have to go inside!

Uncovering the Culprit: A Middle Mesial Canal

With two possibilities to explore, I continued my investigation by removing the gutta percha. As I started working, I did something I do in every mandibular molar: I troughed in between the MB and the ML canals.

And it’s a good thing I did, because what I found was this:

A middle mesial canal!

No wonder there was a lesion around the mesial root. Just as I had suspected, there was still original bacteria in that canal, which is why we saw a radiolucency around that root on the radiographs.

After retreating the tooth, I sealed it back up and sent the patient home until their follow-up. In a situation like this, you just have to play the waiting game to see how the tooth responds to treatment.

Takeaway: Check Those Mandibular Molars

Now at this point, you may be wondering just how common it is to have a middle mesial canal. As it turns out, the percentage of middle mesial canals can be anywhere from 2 to 18%, which is pretty high.

So, what does this mean for you?

Well, for one thing, it means you should add the middle mesial canal to the list of possibilities you consider when diagnosing tooth pain.

For another, it means it’s a good idea to look for it in EVERY SINGLE mandibular molar as part of your treatment process, because there’s a good chance it could be the culprit you’re looking for!
Perfect your diagnosis skills with my Pulpal and Periapical Diagnosis Checklist, totally free! Click here to download it.

– Sonia