When a Patient Has Tooth Pain in an Old Root Canal
December 18, 2022
How to Remove Gutta Percha Like a Boss
January 24, 2023
Key Takeaways:
- A failed root canal can happen to anyone, but there are things you can do to help prevent them. Following the two cardinal rules of root canals is the very best way to ensure a successful root canal, so it’s important you take them seriously.
- What are the cardinal rules of root canals? The first cardinal rule is to find every single canal, as a missed canal can cause infection. The second is to get to the end of every single canal—including the entire surface area within the canal. This ensures you’ve cleared out as much of the bacteria as possible.
- Another way you can prevent failed root canals is by using endodontic technology. Modern technology can do things that even the best provider can’t! For example, while traditional x-rays are pretty good at helping you visualize a tooth’s anatomy, they aren’t 100% reliable. It’s well worth it to upgrade to cone beam computed tomography (CBCT), which lets you see the tooth in 3-D. That way, you never miss a canal.
A failed root canal infection can really give root canals a bad name.
As an endodontist and educator, one of my primary responsibilities is to continue to dispel the harmful myths that have emerged and persisted around root canals. For decades, the dental community has had to contend with literature and even full-length documentaries that drive fear around root canals and what they do to our bodies. Most of these false claims are grounded in the idea that root canals never truly heal—they will always be home to harmful bacteria that will only cause further pain and infection.
If that were true, I would understand why so many patients assume they’ll need to have their teeth extracted! Fortunately, though, all those fears about root canals are totally unfounded. As every trained endodontist knows, a properly performed root canal is a perfectly safe, regenerative procedure, and it has the added benefit of balancing out a patient’s microbiome while saving their natural teeth.
However, as with any medical procedure, it is true that a failed root canal can cause infection and other complications later on. That’s why it’s imperative for any dentist to stick to the two cardinal rules of root canals:
- Find every single canal
- Get to the end of every single canal
Actually, I want to add a little nuance to #2. It’s not just about getting to the end of the root canal; it’s about getting to all of the surface area (including instrumenting grooves!) within the canal.
When we follow these two rules to the letter, our patients’ root canals will heal just fine, and they’ll all become believers in the power of endo… but when we miss these rules, that’s when the problems start. And that’s exactly what happened in the tooth story I want to share with you today.
The Story of a Missed Root During a Root Canal
The patient in this tooth story was a 28-year-old woman. About a year and a half prior to seeing me, her general dentist had performed a root canal on her upper premolar. Although the root canal had seemed like a success (foreshadowing for our discussion on failed root canals), the patient was now experiencing a painful bump around the previously treated tooth.
When I looked at the patient’s periapical x-ray (Image 1), everything appeared to be in order. But upon clinical evaluation (don’t forget your pulpal and periapical diagnosis!), I found the tooth to have pain to percussion and biting. I knew it was time to take a second look with my cone beam.
When I reviewed the CBCT scans (Images 2 and 3), I quickly found the source of the patient’s discomfort: There was a missed root during the root canal. Somehow over the course of the original procedure, this patient’s dentist had failed to identify—or to treat—a DB root.
I want to be clear: This tooth story isn’t about shaming this patient’s general dentist. Instead, it’s yet another example of how much it pays off to invest in endodontic technology. That missed root during the root canal was almost impossible to see using traditional x-rays, but it was clear and defined in the 3-dimensional cone beam scan. Having a cone beam on hand could have prevented this failed root canal infection, and patient’s prolonged suffering.
With the help of my CBCT, I was able to diagnose the patient with a previously treated tooth with symptomatic apical periodontitis.
Retreating the Missed Canal
With a newly-minted diagnosis on this failed root canal infection, I got started on retreating the patient’s tooth. If you take a look at the coronal view of the cone beam scan (Image 4), you’ll see I really had my work cut out for me!
That image shows the bone resorption around the root that resulted from the tooth infection. It also shows how the tooth infection thickened the maxillary sinus membrane. (Both of those symptoms normally resolve themselves after retreatment.)
I opened the patient’s tooth back up and removed the restorative filling material. Then I got to work with my file. Image 5 shows that working file in the untreated DB root, identifying its correct length and location.
As with any endodontic retreatment, I made sure to clean and fill all of the canals, even the previously treated ones. The last thing I wanted was for this tooth to get another infection! You can see all the cleaned and refilled canals in the cone fit x-ray (Image 6). Lastly, here’s an image of the final filling and obturation of the retreated root canal.
How to Avoid Failed Root Canals and Infections
I am thrilled to report that this patient’s second root canal was entirely successful—her bone regenerated, and that annoying bump went away!
But even though this tooth story had a happy ending, it still makes me a little sad. That poor patient never should have had to step into my office, and I hate to think that her initial experience of the failed root canal and infection may have contributed to some of the harmful myths around their efficacy.
So, in the spirit of endodontic education, let’s do a recap of the key takeaways from this tooth story.
- Always follow the two cardinal rules of root canals: Find every canal, and get to the end of every canal! If you don’t do that, the patient’s risk of contracting some new infection drastically increases.
- Invest in endodontic technology. This patient’s general dentist wasn’t bad at his job—it was impossible for anyone (including me!) to see that third canal without a cone beam. Traditional x-rays are great, but relying on them can lead to a missed root during a root canal.
- Refer your patients to specialists when applicable. This relates back to the previous takeaway—general dentistry offices may simply not have access to the advanced endodontic technology available at a specialist’s office. Additionally, endodontists have years of experience identifying and treating tricky-to-find canals.
All that being said, a missed root during a root canal can happen to the best of us. When it does, it’s even more imperative to retreat the tooth quickly and effectively!
If you’re ready for endodontic confidence like never before, I encourage you to enroll in E-School, my award-winning online curriculum for dentists. We cover all of these topics and much more inside.
Frequently Asked Questions
1. Are root canals safe?
Absolutely! Despite persistent myths and misinformation claiming that root canals are toxic, they are a safe and effective procedure to save teeth when done correctly. That said, a failed root canal can certainly cause infection and other complications, so it’s extremely important to follow the cardinal rules of root canals: 1) find every canal, and 2) get to the end of each one.
2. Is it my fault if a root canal fails?
A failed root canal can happen to anyone, including the most experienced specialists. Even when you do everything by the book, there are factors out of your control that can cause it to fail, like missing a canal due to not having advanced endodontic technology in your practice. The important thing is to always do your best and to not be afraid to refer a case out to a specialist when you don’t feel comfortable taking it on. That way, you avoid dealing with a failed root canal and ensure the best possible care for your patient!
3. How can I avoid failed root canals?
There are three main ways you can avoid failed root canals: 1) Always follow the two cardinal rules of root canals, 2) Invest in endodontic technology that can help you locate all the canals, and 3) refer patients to a specialist when you don’t feel confident in treating a tooth. And of course, invest in your endodontic training!
– Sonia
24 Comments
Which material is used for closing the crown opening…
Thank you so much ma for sharing. The use of contemporary imaging is key too, as it could help in locating occult canals.
Thanks so much for reading Dr!
-Sonia
very helpfull ma’am and thanks for sharing.
Thanks for reading!
-Sonia
Abdul, I use composite.
-Sonia
i have a missed canal, funny i had the impression that i had but when i pointed to the spot the dentist saud it was just tooth decay there. but i also got tbe bump now and the choice between root tip resection and pulling. as a revision toot canal isnt covered by dental insurance.
Hi there. If the option is there to redo the root canal, I am a firm believer that is always the best option. Of course, I do not have all the data to give you an accurate diagnosis, so I would trust your provider. Unfortunately, dental insurance does not cover much and I always urge patients not to rely on your dental benefits since they do not work like medical benefits.
-Sonia
It should be the dentist’s responsibility to refund the cost of the failed RCT and insurance cost so the patient is able to use their insurance benefits to have a chance to save the tooth, e.g. , retreat and re-crown the tooth. As mentioned, insurance won’t pay for same procedure on the same tooth for up to 5 years. This is really unfair to patients, especially when they are not advised that they have the option of having root canals done by an Endodontist. It is not fair to have to lose a tooth, bone loss, thousands of dollars and insurance benefits due to dentist’s error…not to mention the pain and suffering because the dentist missed cleaning a canal and “sealed in” the infection, allowing it to spread. It is really the patient who loses out in so many ways when this happens. By the time a complaint can even be reviewed, it is too late for the tooth.
Hannah,
You have a really good point. This is why I encourage all patients to be advocates of their oral health and to understand their options. Everyone has the option to have their treatment done by a specialist, but first we need to create the awareness that specialists exist. On the flip side, there are many patients who refuse to see the specialist. The risks and benefits need to be understood by everyone. You as the patient have a right to make your own choice.
-Sonia
Hello Dr Sonia, I have a question is long term prognosis of a successfully done RCT. I have told from multiple endodontists say, every rootcanal will eventually fail at some point. How are your though on this? what is your time line of how long a RCT last or if that even true or is it just a myth.
Levi,
I don’t know any endodontists that would say that. My goal is for that patient to take that tooth to their grave with them when they go :).
-Sonia
Hi Dr Chopra! It’s been a while since we last chatted , This was possibly on one of your lectures. Anyway how are you? I’ve been following your postings and try to read them all!
I’ve learnt so much from you.
I’ve had a few retreats sent to me for other general dentists . The last one being a left mandible second molar. The patient presented with the usual symptoms: pain, buccal sinus .
I removed all the GP points from the previously treated RCT and located an untreated MB CANAL. The hardest part was removing the old GP points . I used a hybrid rotary file and has some eucalyptus oil over each orifice . This did the job and I’m happy to report the patient is now symptom free.
How do you remove your old GP points for your retreatments?
Do you obturate in that sitting or do you medicate the canals for 6 weeks ?
Let me know .
Could you please do a blog explaining proper protocol for retreatment.
Dear Dr. Chopra,
An excellent article.
Having a CBCT for endodontics is getting closer to the accepted standard of care, certainly in the specialist’s offices.
For those of us in small clinics or solo practitioners, the costs of a CBCT are challenges for competing technologies.
I would suggest the surgical operating microscope should be the priority.
Do you have any suggestions on how offices without CBCTs can obtain those services in a time-sensitive manner?
Thank you,
Douglas
Patient came to me for root canal tooth #5. Took cone beam and identified two canals. Cleaned and filled both, placed post and crown. Patient returned in six months with symptoms. Took another cone beam and the buccal canal split into two about 1/3 of the way down. I failed on my initial exam and review of the cone beam to view the entire tooth closely all the way to the apex. Ugh! Patient lost faith in me and went elsewhere. I now look at all angles, all the way to the apex in all views!!
Tim,
I sure will get that in queue, but I believe I have written one in the past. I would check the blog page on the website a bit more closely and even check out my videos on youtube.
-Sonia
The CBCT will save us every time! Thanks for sharing.
-Sonia
Douglas,
Perhaps you can work with your specialists or a scan center. I don’t really know the answer to this, however, there is always a return on your investment. It’s all in how you look at these things. Thank you for your comment.
Micheal,
I take my GP out with a rotary on high RPMs after I have dissolved it a bit. And if I am retreating my own case, then I definitely do it over at least one month.
-Sonia
I have a question I had a root canal done and in two days it failed.I asked the dentist what happened why did it fail he said it didn’t fail the root canal was successful and I signed a waiver that complications may arise and that he tried his Best.Not a Good Enough answer for me I know what I signed and I know he may have tried his best no fault of his own but I felt he should have taken the time to explain and educate me on the reason it failed and it did fail cause they had to extract the tooth especially when I had to pay $ 4000 out of pocket I deserve a explanation I’m left in the dark without knowing what happened what led to this failure.And why did he not give me other options before pulling the tooth like retreatment etc.He never discuss my options with me he never discuss anything with me come to find out later from family and friends that there were other options before making the decision to pull my tooth his communication skills not good at all actually horrible in this area.Im not Blaming him for anything but I thought I had the Right to an explanation as to why the root canal wasn’t successful and he didn’t give me that Right.whats your take on this matter
Hi Suzanne, without knowing the particulars of your case, I won’t be able to give you any insight, and I’m unable to give feedback on how other dentists run their practice. However if you have a clinical question about your case and are looking for some insight, I am happy to help! You can book a consultation with me here: https://soniachopradds.thrivecart.com/patient-dental-consult/
Hi I had a redo of an old root canal by an Endodontist bc I had a bump on my gum – I was not experiencing pain – after the procedure I still had no pain but the bump never went away – a year and a half later the bump is still there with no pain but pus is present – not sure what to do at this point- the Endodontist said likely failed but cannot another year- appreciate any insight!
Hi Mary, thanks for reaching out to me about your case. I really care about patients, and I want to make sure you get the best care you can. I’m not able to give any clinical advice without seeing your tooth or scans. The easiest option for me to assist you is for you to make an appointment to come see me at my practice in Charlotte, NC. Or you can book a consultation with me here: https://soniachopradds.thrivecart.com/patient-dental-consult/ – and I can give you more insight on your case then! I’d be happy to help.