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Does Tooth Decay Smell?

Updated: Feb 6

Tooth decay can cause a bad odor in your mouth if it is left untreated and allowed to develop a hole in your tooth. A physical hole in your tooth becomes a food trap that allows food to be fermented by bacteria. An analogy would be making cheese in your mouth, where food is being fermented.


The smell from tooth decay is a result of a combination of fermented food and volatile sulphur compounds produced by bacteria.

  • Fermented food. Food which is exposed to bacteria will begin the fermentation process, where bacteria break down the food into alcohol and acids. Some common fermented foods include cheese, vinegar, and kimchee and a common trait among all of them is a particular odor. The fermentation is made possible because there are a LOT of bacteria in our mouths and a hole in your tooth provides trapped food for the bacteria to break down.

  • Volatile sulphur compounds. When bacteria break down carbohydrates and sugars in your mouth, some common by-products are volatile sulphur compounds (VSC). VSC are commonly associated with halitosis, which is bad breath. Another associated condition would be morning breath and they're all caused by the volatile sulphur compounds.

Therefore, if you're getting a bad odor that is coming from your mouth that doesn't seem to go away with brushing or flossing, you may potentially have a cavity. It may even be a fairly large one at that because the small ones aren't serious enough to cause a cavitation. Only the big ones are decayed enough to form a hole and trap food.

Alternatively, decay underneath a filling can also cause a rancid smell.

What does tooth decay smell like?

Since the smell from tooth decay is a result of bacterial activity and food fermentation, it would basically smell like something is rotting. Depending on what your diet is composed of, the decay would smell like the rotting version of your breakfast, lunch, and dinner.

If you wanted to know for certain what it smells like exactly, here is an experiment that you can try:

  1. Take your lunch and leave it on the table.

  2. Allow the lunch to sit out there for 2 weeks.

  3. Smell the lunch.

Whatever that rotten lunch smells like would probably be pretty close to what a rotten tooth would smell like. Since you are what you eat, you are also what it would smell like. Whatever left over food that you did not remove is what would be fermenting inside of your mouth.

In case you wanted to know what a cavity looks like, here are all the stages of tooth decay.

How to get rid the decayed tooth smell

The only way to get rid of the rotten tooth smell is doing a cavity filling procedure with your dentist. The procedure involves removing the decayed part of your tooth and then filling it back in with a tooth filling material.

Here are the steps for a cavity filling procedure so you know what to expect at the dentist:

  1. Numb the tooth with local anesthesia.

  2. Drilled out the tooth decay.

  3. Condition, prime, and bond the tooth.

  4. Place tooth filling material.

  5. Cure and harden the dental filling.

  6. Adjust the filling so that the bite is even.

  7. Polish and you're done!

Now that wasn't so scary was it? You should be very confident when you go in for your next dental filling appointment since you already know all of the steps.

Will home remedies get rid of the rotten tooth smell?

Unfortunately home remedies cannot fix the rotten tooth smell because they're unable to remove tooth decay. The only way to get rid of decay in a tooth is by drilling it out and only a dentist can do that.

However, home remedies may help you temporarily mask the smell such as making your breath smell fresher. It still wouldn't fix the problem permanently though because the source of the smell comes from the rotting tooth.

Nonetheless, here are some home remedies you may try to make your breath smell better:

  • Listerine - rinse for 30 seconds and then spit out; You can use any type of mouth wash

  • Oil pulling - most commonly uses coconut oil; Swish and gargle for 15-20 minutes and then spit out.

Just to reiterate, you can try home remedies but if you want a permanent solution you will have to go in and see your dentist. You can't do your own cavity fillings at home because it is impossible. You don't have the tools nor the expertise to do so.


Tooth decay can cause a smell but only if the cavity is big enough to cause a hole in your tooth. The smell is a result of food being fermented in the hole as well as bacteria producing volatile sulphur compounds as a byproduct.

If you're getting a malodor from your mouth, you should go get a dental check up and cleaning because it could very well be a cavity in one or more of your teeth. You don't want them growing bigger either so take care of them as soon as possible.

If you leave them untreated they will grow and then the treatment becomes more complex. They will also get more expensive as well so if you want to save yourself some money, address the dental problems while they're small and not large.

Author: Written by Dr David Chen, a LIC dentist in NY.



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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