Lateral canals — they are so easy to forget about as a potential culprit for root canal failure. When teeth don’t act right, we need to think outside of the box. It’s easy to blame a crack or even a missed canal, but what about a lateral canal?  I forget about this little guy all the time, and it often stumps me in my diagnosis.

Let me walk you through this case so that I can show you exactly what I am talking about.  Here are the preoperative radiographs…


Investigating the Case

When I first examined the radiographs, I felt as if tooth #3 should have been the problem. I really liked the way #2 looked on the radiograph, but I was too quick to judge because this patient had pain to percussion on tooth #2.  That said, I diagnosed her with Previously Treated Tooth and Symptomatic Apical Periodontitis #2.  I think we all know by now that in a case like this, I will take a CBCT.  So, here we go…

Even after the CBCT, I still felt like the culprit tooth should have been tooth #3.  This axial slice shows me that all the canals appear to have been found and obturated in tooth #2, but there was a potential for a missed MB2 in tooth #3.  I was really surprised when I saw that it was #2 that was bothering her, and she was very localized to the percussion test on tooth #2.  So I looked deeper into the CBCT, and here’s what I found…

I found this furcation breakdown and I didn’t know what it meant.  Was it a sign of a crack? Was the root canal just recontaminated?  Or was there a separate periodontal issue superimposed onto this root canal?  I was stumped!  Luckily, the patient was highly motivated to save her tooth.  She BEGGED me to re-treat the tooth, and since we just don’t know sometimes until we try, that’s what we did.

Sneaky Lateral Canals

My root canal doesn’t look much different from the pre-op except for one minor difference — one of the lateral canals is radiating from the MB root that leads right into that furcal breakdown.

Now, I need to give a little disclaimer here.  I re-treated this tooth with the GentleWave, and I don’t think that I would have been able to pick up that anatomy any other way.  I wish I could fast forward a few months to see this thing heal.  If it does, that will blow my mind — and it should blow yours, too, because it’s crazy that something so small could have such an effect!  I promise to post the recall in another future post.

The moral of the story? We can’t forget that even one of these tiny little lateral canals going into the furcation can also make a tooth appear “cracked”.

Another Example

Let me show you another case. This patient had no pain, but clearly had a problem.

You can see that the tooth has been previously treated, but there is some furcation breakdown. Once again, the root canal looks fabulous!!

You can see from the bitewing that the tooth was not in occlusion, so the idea of a crack was just not in my differential diagnosis.  Now I had to think outside the box.  What else could be wrong?  When I took the CBCT, all I could see was this….

Do you see it? It’s a periapical lesion that went into the furcation.  This can be a very typical endodontic lesion, but I know that this would scare most dentists.  This appearance of a PARL is normal to me, but I always want to know “why?” (and I absolutely hate it when it is not obvious).  I let the patient know that I could try to retreat it, but that I couldn’t promise anything.  Luckily, I once again had a motivated patient who wanted to try to save his tooth no matter what, so we re-treated the case.


Again, this root canal does not look any different than the pre-op besides that little lateral canal.  But could this canal be the cause for failure? Probably!

My point with this blog is that we need to think outside the box with our diagnosis and consider that these tiny little lateral canals could be the cause of a failing tooth.  So don’t be so quick to extract!  Instead, re-treat to try to see if you can save a natural tooth.

Again, I can’t wait to fast forward a few months to see how this puppy heals.

A Handy Tool for Accessing Lateral Canals (and more)

Due to what I learned in the previous case, I also re-treated this case with the GentleWave.  Not all dentists have embraced this technology, and it took me time to get used to it, for sure.  However, the difference it has made is not the “slap in your face” evidence, but rather these little things that I am finding as I obturate. (You can read more on my GentleWave recommendations here.) But I do know one thing — it’s irrigating better than my syringe, that’s for sure! I don’t think that I could have made access into this lateral canal with the conventional root canal methods.  Time will tell! (And I’ll make sure to show you the recall.)

Remember: Not all “bad” teeth are cracked!


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