In my line of work, I’m often asked about periapical lesion classifications. How do I know if it is scar tissue or an active lesion, especially when the lesion is small and/or, more importantly, asymptomatic?

To which I say, “IT’S COMPLICATED.” My answer is usually multidimensional, and I can’t know for sure until I have an understanding of the whole tooth story. Many professionals leave these types of cases alone, while others treat them no matter what. There’s definitely a debate around this topic, but I’d like to throw in my two cents, so you know where I stand on the subject.

Let me walk you through two cases dealing with periapical lesion classifications. Both patients were asymptomatic, but the treatment plans were different.

The First Tooth Story

Case #1 had a previous root canal on tooth #8. You know me, I went straight into diagnosis! There were normal probings, no pain to palpation or percussion…the tooth was so asymptomatic that the patient was questioning why he was even in my office.

You know what kind of patient I am talking about, right? 

Well, there was definitely a reason he was there! My diagnosis for this tooth was Previously Treated and Asymptomatic Apical Periodontitis #8.  

The CBCT shows the periapical lesion a bit more clearly.

And you can see from the coronal view and the axial view that there’s a bit more surface area to the canal than what was obturated.

When I see something like this, it makes me question the disinfection protocol from the original root canal. Are there still original bugs in that canal that could potentially flare up on the patient in the future? Especially on a Friday afternoon or the weekend when nobody is available? In this case, I think that’s a possibility, and that is bad news for the poor patient.

HECK NO, I’m not leaving this one alone! I would treat it.

And if you’re worried about the patient refusing treatment, don’t. They’ll unfortunately be in pain before long, and they’ll be back, swearing you’re some kind of tooth prophet.

Patient education is the best medicine here, and I would show them the imaging so it’s crystal clear why the patient is in my chair and why I’m giving them the treatment plan that I am. 

It’s all about setting their expectations properly! They need to understand what can happen if they don’t treat the tooth. 

These types of cases take me more time during the consultation because I know the patient needs to have a deep understanding of what is going on in their body in order to make an educated decision.  And that education has to come from me (or you 😊). 

The Second Tooth Story: The Diagnosis

This patient had a strange sensation in the upper left area and was nervous that “it was this tooth again.” He couldn’t say 100% that this sensation was coming from tooth #14, but proceeded to tell me about how he has had two root canals previously performed on this tooth. Not gonna lie, that’s pretty rough. The first time, “they missed the fourth canal” he said. He remembers there being a really big dark area around that tooth on the x-ray, and it was painful, and he was also swollen at the time.  

He had a lot going on, and had previous oral surgery in the area too. Here is the PAN.

So, I did my diagnostic tests like usual, and they were pretty inconclusive. I couldn’t reproduce any symptoms for this guy. His probings were normal and there was no pain to palpation or percussion. All the other teeth in the quadrant tested normal.

So, next we went to imaging and I took a CBCT. The sagittal view did show a small lesion on the MB root. My diagnosis for tooth #14 was Previously Treated and Asymptomatic Apical Periodontitis.  

I then looked at each root individually in the CBCT. Here is the palatal root.

Here is the disto-buccal root.

And the MB root.

The Second Tooth Story: The Decision

The palatal root and the disto-buccal root look pristine, so we’re good there. The bone is healthy and the PDL is intact. It’s the MB root that has a little something funky going on, but as I listened to my patient and learned he had a big infection, one that even he could remember was big, and there was a missed canal (usually the MB2 right?), I concluded this area was most likely one that was healing. This periapical lesion probably started very large and is now much smaller.  

I also like the quality of this root canal, and feel like it was done well. So for this one, I would like to leave it alone until I see the symptoms worsen. This area could very well be scar tissue from something that was really big at one time. 

Truthfully, I don’t really believe in scar tissue, but if there is such a thing, it would be represented in this case. Remember, only some histology would give us the real answer.  

On a side note, I thought perhaps something could be going on with the hardware from his previous surgery, so if the problem persists or gets worse, then perhaps a follow-up with the surgeon wouldn’t be a bad idea. I also made him aware that, if the tooth is the problem, it would most likely start to get really sore when chewing or biting and, if that happens, he should return to me for further evaluation. Again, it’s all about setting expectations!

The Takeaway about Periapical Lesion Classifications

You can’t just make a guess as to what’s going on with your patient and assume everything will be okay. That might work sometimes, but it definitely wouldn’t have worked in Case #1!

So in a nutshell, use your critical thinking hat and really evaluate the endo along with your patient’s symptoms. Periapical lesion classifications can’t just be guesswork.

1. Listen to your patient and ask questions until you know the entire tooth story.  
2. Is there any sign of missed root canal anatomy or more surface area to the canal that could be the etiology for root canal failure?
3. Is it a quality obturation?
4. Is there any coronal leakage that might create a lesion or a new infection?
5. Is there any immediate, necessary restorative care that would prompt you to treat now versus later?
6. Are you going to watch it? What is a reasonable length of time to watch it? And do you know WHY you’re watching it and what changes you’re looking for?
7. If your patient totally refuses treatment, make sure you document the discussion.

I think there will be many different opinions on this topic and how to approach it, so it will be interesting to hear what you have to say in the comments. I hope you can see the difference in these two cases and how my rationale works in both.  

You never know from a glance or quick assumptions. Sometimes you catch someone on a good day when they aren’t having much pain. You don’t want to brush it off and put them in a situation where the pain can sneak up on them later, when you aren’t available to help.

Use your best discretion. And, as always, empower yourself to save those teeth!

– Sonia