Do Root Canals Hurt? And What About The "Hot Tooth"?

Sometimes a patient will ask me the question "Do root canals hurt?" when we are talking about possible root canal treatment for a hot tooth.

A hot tooth is what dentists call a tooth with a very inflamed nerve. It aches constantly, and it reacts painfully to hot drinks.

There seems to be a general feeling out there that getting a root canal treatment is one of the worst things that can happen at a dentists' office!

One patient even asked me "why do root canals hurt so much?"


What I write on this page is very likely to make me unpopular with many dentists. But I believe what I am writing is true, based on what I have seen, heard and read over the past 30 years.

Here goes!

I believe that there is no good reason why having a root canal treatment should hurt any more than any other dental work. In fact, it shouldn't hurt at all!

Dentists are trained how to get teeth numb. It's an essential part of being a dentist. But sometimes they don't get it exactly right.

There are two main reasons why a tooth may not be as numb as you'd wish.

  • I believe that the main reason is time. The dentist may not take enough time to give the local anesthetic shot properly. He needs to make sure he gets the local anesthetic in exactly the right spot.

    Syringe with anaesthetic

    And then he needs to wait long enough for the shot to work.

    If you tend to clench your teeth when asleep at night, it frequently takes longer for the numbing effect to work. This is because your jaw muscles are more active, and therefore have more lactic acid in them. This can slow down the numbing effect.

  • I think the second main reason is that some dentists really don't know enough about exactly how anesthetics work, and how to give a great shot every time.

    Sure, modern local anesthetics are very good, and they will work if they are given half a chance. So if the dentist gets it more than half right, there's still a good chance that the tooth will be numb enough.

But not always!

If you have a hot tooth and need a root canal, the dentist needs to use ALL the dental anesthetic tricks to get it numb.

There are several reasons why a tooth may be slower or more resistant to numbing.

  • A hot tooth with a very inflamed nerve will need MORE anesthetic, and MORE time before the dentist starts to work.

  • Patient "resistance" to local anesthetics. This is actually quite rare, but if you clench your teeth at night the anesthetic will take longer to work.

  • An anesthetic solution that is out of date.

  • An anesthetic solution that has lost effectiveness due to storing it somewhere too warm.
Your dentist simply may not allow enough time for the anaesthetic to work

These are all reasons for a tooth not to be numb enough - but I don't believe that they are VALID reasons! A dentist should be able to deal with these issues.

If you are worried about a root canal hurting, ask your dentist. If he can't give you complete reassurance, I'd suggest that you ask around your friends and workmates for a recommendation with regard to a dentist who always gets his tooth numb!

Listen out for the comment "Oh, I never feel a thing when I go to Dr. Smith's office". These are the words that tell you that Dr. Smith will get your tooth numb.

Quite a bit of research has been done into how to get a tooth properly numb. The American Association of Endodontists has published excellent guidelines, which every dentist should read.

You can read all about dental anesthetics here.

So when a patient asks me "do root canals hurt?", I always tell them "Not in this office!"