Halo Around The Root In Xray After Root Canal

Updated: Aug 24

When you had the root canal done, your dentist showed you a dark halo around the root of the tooth on the x-ray and said that it was a nerve infection. Since it was infected, you needed to have the entire nerve of the tooth removed, which is essentially what a root canal treatment is.


However, at your next check up appointment or maybe even years later, your dentist points out the same situation again. There is another halo around the tooth root once again! Does that mean the tooth needs treatment again?


This article will explain everything that you need to know about this condition. What it could be and whether or not you need to do anything about it.



What a halo around a root in the xray could mean after a root canal:



The halo around the root could mean that the tooth is still healing

Immediately after finishing the root canal, your dentist will take an x-ray of the tooth to verify completion of the procedure. If the tooth had a dark halo around the root prior to beginning treatment, it will still have it afterwards. This is completely normal because the tooth is still healing and it takes time for the dark circle to go away on the x-ray.


Here is an x-ray of what the halo looks like before the root canal. It is basically a dark circle around the tip of the root. We call that dark halo a radiolucent lesion. This is an x-ray of what a tooth that needs root canal looks like.


halo on tooth root before root canal

Here is an x-ray of what the tooth is supposed to look like with a successful root canal immediately after completing the treatment. The halo should still be present around the tip of the root. The difference on this x-ray is that the root filling material is present, which is the white line going through the entire root.


xray of tooth after root canal


Why is the halo still present on the x-ray?

The halo on the x-ray is basically devoid of bone because the abscess destroyed all of it. The healing process is initiated after the completion of the root canal but it takes time for your body to heal. It will take at least 1-2 years for your body to fill back in all of the destroyed bone.


If you go in for your dental check ups every 6 months, you should see that halo get smaller with each subsequent x-ray. That is an indication that the tooth is healing.


The reason for the extended healing time is because bone tends to heal slowly. It is similar to if you broke your arm, you're in a cast for at least weeks if not months. It takes time for the bone to repair.



What you need to do

There isn't much that you need to do about this condition aside from keeping good oral hygiene practices. You simply need to give your body time to heal the tooth and the surrounding bone.


We would like to stress that you should maintain good oral habits so that nothing bad happens to the tooth such as tooth decay or an infection.

  • Brush for at least two minutes, once in the morning and once before bed.

  • Try your best to floss all of your teeth before bedtime.

  • Minimize the sugar intake so that you decrease the chances of getting a cavity.




The halo on the x-ray is just scar tissue

If the halo around the root of a root canal treated tooth is still present many years later, it could potentially just be scar tissue. The tooth did heal but in a non-traditional way, which left a lot of scar tissue behind instead of filling it back in with bone.


The scar tissue around the root tip would be analogous to if you had an injury or laceration, which resulted in a permanent scar afterwards. Even though the wound healed, it left a scar. Your tooth is no different, sometimes it can leave a scar from healing and that is what the halo could be.


Criteria for it to be scar tissue

Just to be clear, that dark halo is only scar tissue if it meets these requirements:

  • Root canal looks good. The root canal has to look clinically acceptable or near perfect on the x-ray. This gives your dentist confidence that the treatment was a success.

  • No gum boil. Usually a pimple on the gums forming near a root canal treated tooth would be an indication of an abscess returning. If you see a gum boil, that halo is NOT scar tissue.

  • No pain. You must be asymptomatic because if you are feeling pain, that is not normal. Pain is an indication that something is wrong with your tooth so as long as you are pain free, it could potentially mean that its just scar tissue.


Here is a clinical photo of what a gum boil looks like. It basically looks like a small pimple on the gums besides the affected tooth. It is red to white in color and may ooze out pus if you try to pop it.


pimple on the gums

What you need to do

Since it is just scar tissue and not an infection, you don't have to worry about it. There isn't anything that you need to do for it except monitor it by taking an x-ray every 6 months to make sure that it doesn't become an infection.


You can tell that its becoming an infection if you notice the halo start getting BIGGER on the x-rays. That is trending towards something bad. However, if the size of the radiolucency on the x-ray remains the same then it is most likely stable and just scar tissue.




The root canal got reinfected

Unfortunately, one of the possibilities of what the halo could be is a recurrent infection, meaning that the tooth somehow got infected once again. After all, any dark halos or radiolucencies on the x-ray indicates that it is not solid and devoid of bone. Only infections and abscesses can eat through bone.


Therefore, that dark circle could very well mean that an infection has somehow returned. Here are some possible causes:

  • Infection never went away. Sometimes, you infection may not have been cleaned out completely because it could've hidden away in a spot that avoided detection.

  • Tooth had extra nerves. If your tooth had more nerves than usual, the remaining nerve will eventually develop a new abscess.

  • New infection. The treatment could've went perfectly but the tooth is not immune to future infections. This could just have been new bacteria that got into the tooth years after the root canal was completed.


This is an x-ray showing how many nerves a normal molar tooth has. Both of these molars had root canals done on them and you can tell because they have the white filling material inside of the canals. Both of these teeth have three nerves each, which is normal for molars.


two molars with three nerves each

Here is an x-ray showing a lower molar that has two extra nerves, making it a total of five. This is very rare and not very likely. If your tooth has extra nerves, it could be the reason whys the halo did not go away.



What you need to do

Since this halo is not healing nor is it scar tissue, it will require further treatment. This infection will need to be retreated with a second root canal along with antibiotics to ensure that all of the bacteria have been eliminated.

  • Root canal retreatment. Basically your dentist will redo the entire root canal all over again. They will disinfect the tooth much more aggressively compared to the previous time you had it done.

  • Antibiotics. Your dentist will most likely place antibiotics within the tooth. This is different from taking oral antibiotics. This medication is placed inside the canal of the tooth and it makes the environment hostile for the bacteria.


After completing the retreatment along with the round of antibiotics, the tooth should slowly start healing. All you need to do is to take another x-ray every 6 months to make sure that the halo is decreasing in size.




Root canal completely failed and tooth is fractured

The absolute worse case scenario for a halo around the root of the tooth is a tooth fracture. That halo signifies that there is a crack somewhere along the root.


This is what a tooth fracture can look like on an x-ray. It certainly has a deep dark halo around the entire root of the tooth. It is very distinct from the adjacent tooth.


halo on x-ray signifying root fracture


Here is a 3D scan (CBCT) of what the fractured tooth looks like. You can see a halo around it on various different views: sagittal, distal root, mesial root, and axial view. The 3D scan is usually used as confirmation of a definitive diagnosis of a root fracture.


3D scan of root fracture with halo on root


What you should do

Unfortunately if the halo around the root means that the tooth is fractured, it will require an extraction. That is the only available treatment option for a cracked tooth. You cannot repair or uncrack a tooth once it happens.


You should expect to have the tooth removed and then after it heals, an implant can be placed. The implant is a medical grade titanium screw that goes into the jaw bone. Once it fully integrates with your jaw, you can get an implant crown on top. The whole process may take up to a year to complete.




Takeaway

A halo around the root of a tooth that already had a root canal can mean many things, it could be good and it could also be bad news. If you're fortunate, it may just mean that the tooth is still healing and requires more time or it could just potentially be scar tissue. Although if you're unfortunate, the halo may be a recurrent infection or even worse, a fractured tooth.


You won't know until you get a consultation with your dentist. They're the only ones who can diagnose and make a distinction between whether the dark circle is good news or bad news. This is why it is very important to go in for your regular dental check ups every six months so that you can catch these things early.

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About the author: Dr David Chen, DDS

Hello, I'm Dr Chen and I'm an actively practicing dentist in Long Island City, NY. I graduated from Columbia University College of Dental Medicine in 2016 but prior to going to dental school I was already working in the dental field. It's been more than a decade since I first got to know dentistry and let me tell you, time flies by quickly. Since then I've developed a fondness for writing, which is how this all got started!

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Medical Disclaimer:

This blog is purely meant for information purposes and should not be used as medical advice. Each situation in your mouth is unique and complex. It is not possible to give advice nor diagnose any oral conditions based on text nor virtual consultations. The best thing to do is to go in person to see your dentist for an examination and consultation so that you can receive the best care possible.

The purpose of all of this oral health information is to encourage you to see your dentist and to inform you of what you may expect during your visit. Due to the unfortunate nature of dentistry, there isn't really any true home remedies that will get rid of dental problems. Roughly 99.99% of them require in-person intervention by a healthcare professional.

Hint: That is the reason why you can't eliminate seeing dentists in your life!