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Why Is There A Sore On The Corner Of My Mouth After Dental Work?

Updated: Sep 26, 2023

Sores on the corner of your mouth may appear as a result of dental work or it could be purely coincidental and non-dental related. What often happens is that most people walk out of the dental appointment feeling fine but may notice a sore shortly after.

canker sore

This article will explain what could've possibly caused it and what you can do about it.

Table of Contents:

Dental related causes for sore on corner of mouth after dental work

That sore on the corner of the mouth could indeed have been an unintended consequence of dental work. It was most likely unintentional and your dentist may not have even realized it during the procedure at all.

Here are some common scenarios which may have caused the sore.

Wisdom tooth cavity filling or extraction

Chances are if it was the very last tooth in your mouth needing treatment such as the wisdom tooth, the sore could've been a result of that. The reason is because when the teeth are that far back, it is difficult for the dentist to get access to it. A person's mouth can only open so wide and if you happen to have a small mouth, it only makes it more difficult. Your dentist may have needed to stretch your lips out to be able to get back there with the drill.

As you can imagine, this situation would apply to any cavity filling on a back tooth and also to taking out a wisdom tooth as well. It is also possible if you needed a deep teeth cleaning on a wisdom tooth as well. The stress from stretching your lips can cause a sore on the corner of your mouth the next day.

Post operative stress

Believe it or not, according to this study: canker sores can break out as a result of stress. As you are well aware, anything but a dental cleaning can be a very stressful visit at the dentist.

Most patients have dentophobia and dental anxiety from simply being in the dental chair. If you add on needing a cavity filling or a wisdom tooth removal, the stress levels would be extremely elevated. This stressful hour at the dentist may induce the sore at the corner of your mouth. Let's not forget that the most feared dental procedure of all time, the root canal.

Burn from dental drill

It is also possible that you got burned from the dentist's drill during the procedure. You were probably very numb and couldn't feel that it was hot so you never said anything. Yes, the drill gets very hot and that is the reason why it sprays a lot of water during the entire procedure.

It sprays the water to cool your tooth down and also to keep the drill from over heating. There are times when there is not enough water spraying so it can get hot. This can result in a burn on the corner of your mouth or even leave you with a burnt tongue as well.

Eating while you're still numb

The dental appointment took about an hour and then it takes another 2-3 hours for the numbing to wear off. You might've been hungry and tried to eat while you were still numb and accidentally chewed up your lips. That could very well be the reason for the injury to your mouth.

Non-dental related causes for sore on corner of mouth

Sometimes it is not your dentist's fault and whatever happened to your mouth could've been a pure coincidence. It just happened to have occurred right after receiving dental treatment. Here are a couple of reasons as to why there is a sore.

Coincidental cold sore outbreak

If you are someone who gets frequent canker sores, it may have just decided to appear after your dental visit. Canker sores can often be induced by stress or it could be from a vitamin deficiency.

Studies have shown that patients with recurrent aphthous stomatitis typically have a reduced dietary intake of vitamin B12. If this sounds like you, you may want to ask your primary care physician to check your vitamin levels at your next annual check up.

Coincidental herpes outbreak

Perhaps it was just a herpes outbreak that coincided with dental work. Of course, a lot of herpes outbreaks are also stress induced. Were you stressed out during the dental procedure? The good news is that there are antiviral treatments for herpes outbreaks. You may take one of these antivirals.

  • Acyclovir

  • Famciclovir

  • Valacyclovir

To get the prescription for these, you must visit your primary care doctor.

Fungal infection

It is also possible that you caught a fungal infection after receiving dental work. Despite what you think, it is a fairly common occurrence for the mouth to get a fungal infection. Patients who wear dentures are typically more prone to it. The condition is called oral candidiasis and that can be treated with anti-fungals.

  • Fluconazaole

  • Clotrimazole

  • Miconazole

  • Nystatin

What should you do about it?

If you happen to get a sore on the corner of your mouth after dental work, there are precautions and treatments that you can do at home.

  • Minimize mouth opening. Don't open your mouth all the way because stretching it will make it worse.

  • Lubricate mouth. Apply some vaseline to the corner to keep it moist so it doesn't crack.

  • Stay hydrated. Drrink enough water to prevent the lips from chapping.

  • Numbing gel. If it is painful you can apply some anbesol to it.

  • Painkillers. You can also take over the counter pain medication like ibuprofen or acetaminophen.

  • Rest and nutrition. Your body only heals if it has the nutrients it needs. It also repairs itself while you are sleeping so get some rest.

If it happens to be one of the non-dental related sores, you can take the medications as described above.

How long do the sores on the corner take to heal?

The sores on the corner of your mouth may take 1-2 weeks for it to fully heal and go away. Some people may take longer if they do not follow any of the precautions or at home treatments listed above. Make sure you get plenty of rest and nutrients so that your body has all of the materials necessary for healing.


Sores on the corner of the mouth that appear shortly after a visit to the dentist may have been treatment related or it could've been non-dental related but coincidentally appeared at the same time. Nonetheless, there are steps that you can take to help the healing process and not delay it. When in doubt, always consult your dentist by making a dental check up appointment.



David Chen 200 x 200.jpg

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!

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