A tooth abscess can potentially cause lip numbness if the infection is big enough to compress on the mental nerve. The mental nerve does affect lip sensation and proof of that is what happens when your dentist numbs it. The result is numbness of the lower lips after they numb it.
Function of the mental nerve:
Provides chin sensation
Provides lower lip sensation
Provides sensation to the gums of the lower front teeth
The main one that we'll be focusing on is the lip numbness. In fact, after the injection your dentist will often ask you if your lip feels numb. If you say that you do, then you're most likely ready to proceed with the dental procedure.
How does a tooth abscess cause lip numbness
The only way for a dental abscess to cause lip numbness is if it happens to compress on the mental nerve, which controls the lower lip sensation. In order for this to happen the abscess has to either be close to the mental nerve and big enough to compress it.
When it gets compressed, it will pause all nerve signals and sensations. That is what gives you the numbness feeling. What is even worse is if the infection can cause permanent nerve damage. Now, we don't want that to happen do we?
Close to the mental nerve
The teeth which are the closest to the mental nerve and have the greatest potential for causing lip numbness are the lower premolars. The reason is because they are anatomically near the foramen of the nerve, which is where the nerve exits the bone.
Here is a panoramic x-ray showing the location of the two mental nerves:
As you can see, there are two mental foramens and each of them are located underneath the lower premolars on each side. Their location may vary but that is the general area of where they are. Sometimes they're a little farther forward and other times a little farther backwards. The only way to know is if you take an x-ray to see where they are.
As you can imagine, if one of the lower premolars become abscessed, the infection can grow big enough to compress on the nerve. If the mental nerve gets compressed you may get some lower lip numbness.
Therefore it is highly relevant where the mental foramen is located and which premolar is abscessed. It is most likely to occur if the tooth with the abscess is directly above where the opening of the nerve is. That would be the shortest path or distance to reaching the mental nerve.
Size matters
A lower premolar with an abscess won't always compress on the mental nerve because sometimes the nerve can be quite a distance away from the tooth. Therefore the abscess needs to grow BIG enough to reach the nerve and then compress upon it.
Most of the time, smaller abscesses are treated right away so they never get the opportunity to grow large enough to cause you lip numbness. Thank goodness for that right?
However, if you are shy or don't like going to the dentist, you may put off treatment for a long time. If you do, that can give ample time for the infection to grow big enough to compress on the nerve.
Therefore, if you feel lip numbness, it is a sign that you need to go in to see your dentist as soon as possible. You don't want that abscess causing permanent numbness. That would be a tragedy.
Takeaway
It is possible for a tooth abscess to cause lip numbness if the abscessed tooth is near the mental nerve. The mental nerve controls the lower lip sensation and the teeth with abscesses that are most likely to compress the mental nerve would be the lower premolars.
Therefore if you're having a strange numbing sensation on your lower lip, you may potentially have an abscessed lower premolar. You should go in for your dental check up if you're feeling that. Hopefully it is just that and nothing else because there are potentially more serious complications such as cancers and tumors.
The only way to know and find out is if you see your dentist.
Author: Written by Dr David Chen, a LIC dentist in NY.
