Line, Line, Dot: CBCT & Endodontic Diagnosis

I recently teamed up with Dr. Bruno Azevedo, the Cone Beam Guy, to give you an amazing training all about how you can use your imaging to help you with endodontic diagnosis and cracking the cracked tooth code. If you want to sign up for future free CE trainings, click here. Since his hands-on course has been a game changer for me, I wanted to share the love with you.

Cone beam computed tomography can make a huge difference in your endodontic diagnosis and treatment planning. Like many of you, I am self-taught when it comes to CBCT. I bought my own cone beam, had it installed, spent one day with my rep, and then was left to my own devices. So if you, like me, think that a machine that comes with this much complexity deserves a little bit more education, then keep reading—because I want to share a tooth story that will be useful for your toolbox.

Cracking the Code of Endodontic Diagnosis

Sometimes figuring out if a tooth is cracked can be a real challenge. Dr. Bruno always teaches that, for successful endodontic diagnosis, you should be on the lookout for patterns that appear again and again. Here is a perfect example of how to tell the difference from a lateral canal and a crack on the cone beam.

This patient was initially referred to an oral surgeon for the extraction of tooth #18. The patient had been told that the tooth was cracked. But the surgeon couldn’t figure out where the crack was, so he referred the patient to me. Upon clinical evaluation, I discovered that the probings were all within normal limits. And that although there was some slight tenderness to percussion, there was no response to cold. I diagnosed tooth #18 with a Necrotic Pulp and Symptomatic Apical Periodontitis.

I was a bit baffled at why the dentist had thought there was a crack in the tooth. But I was willing to give the doc the benefit of the doubt. After all, anything is possible on a second molar. Plus, I didn’t see a true pathway to the pulp (the buildup was deep, but not deep enough).

How CBCT helped in giving correct Endodontic Diagnosis?

So, when I took the CBCT, I saw something that could possibly be mistaken for a crack. When I looked at the sagittal slice in the mid root area, I saw a LINE extending laterally from the distal canal. There was also a lateral root lesion in the bone adjacent to this line. And also one developing at the apex, confirming the necrotic pulp.

If you take a look at the axial slice, you can see the LINE extending from the distal canal—a line that looks a lot like a crack. You can also appreciate in this view that there are 3 canals: two mesial canals and one distal canal.

However, it’s the coronal section that really shows us what’s going on. In this view, the line no longer is a line—it’s a DOT. That translates to the opening of the tube of the lateral canal.

Pay Attention to Patterns

Since the distal area of the second molar is also a location prone to cracks and fractures. So, this endodontic diagnosis can be confusing. But, as Dr. Bruno says, the key is to look for patterns. And this one specifically has the LINE, LINE, DOT pattern.

There is a line in the sagittal view and a line in the axial view. And also a dot in the coronal view in this particular case. Note that this could change based on the direction of the lateral canal. For example, if the lateral canal were extending buccally. Then you would see the dot in the sagittal view instead of the coronal view. Usually in the axial view, you will see the line.

Back to the tooth story: Knowing that this was a lateral canal, I decided to treat the case and start the root canal. I wasn’t able to find one of the mesial canals. And I definitely could not instrument the lateral canal.So, I knew that much of my instrumentation was going to have to be based on my irrigation. I knew that this was a perfect case for my GentleWave, where I could let the fluid dynamics do their thing.

Here is my conefit—it shows only two gutta percha points because I could not find that other mesial off-shoot of a canal.

You can see that once I obturated, the sealer flows into that other mesial canal and the lateral canal.

Here is another beautiful angle that shows you just how well the anatomy was sealed, even though an actual rotary file was not taken into those hard-to-reach spaces.

CBCT, Endodontic Diagnosis, and Treatment Planning 

This tooth story is just one of the many examples of an incorrect endodontic diagnosis nearly causing a tooth to be unnecessarily extracted. If it weren’t for this patient’s surgeon referring them to me (and for my trusty cone beam), they would have lost a tooth that could have been saved. 

I hope that, after reading this tooth story—even if you are not the one doing the root canal—you can see just how important it is to be able to provide the correct endodontic diagnosis and treatment planning. I think that Dr. Bruno would agree with my favorite catchphrase: Give teeth a chance!