A tooth sensitive to heat is usually a sign that the nerve inside the tooth is dying. Unfortunately this process cannot be stopped or reversed once it has started. At some point in the very near future, you will probably need to get the tooth taken out, or get a root canal treatment if you want to keep the tooth.
But let's back up a little bit first, and look at the main reasons WHY you might have a tooth sensitive to heat.
The microscopic bacteria can then get into the nerve of the tooth and the nerve becomes inflamed. Read more about this at TOOTH NERVE PAIN.
Those are the most common four reasons for having a tooth sensitive to heat.
How can you tell if it will settle down? Or if the tooth will need treatment?
The main clues are; WHEN the tooth is sensitive to heat, HOW LONG it is sensitive to heat, and whether it also reacts to COLD. Let's take these clues one by one.
This difference is quite important, and it's probably the OPPOSITE of what you're thinking. If the tooth reacts immediately on taking a hot drink, then the nerve is in a better state of health than if the ache starts 30 seconds AFTER you have swallowed the hot coffee. The chances of it settling down are better.
So, in the BEST CASE situation, you might have had a deep cavity in a tooth, which a dentist cleaned and filled for you. And now you have a tooth sensitive to heat BUT ALSO to cold, which reacts immediately when you have a hot drink or a cold drink, but the pain subsides within 10 seconds or so. Most likely, the tooth will settle down on it's own. BUT if the tooth is also sensitive to bite on, then the new filling could be a little too high when you bite.
The general rule of thumb here is that, if the tooth has not settled down in about a week, you probably need to go back to the dentist to get the filling adjusted slightly.
At the other extreme, if you just have a cavity in a tooth, which is trapping food, which reacts to a hot drink AFTER you have already swallowed the drink, and COLD either makes no difference or makes the pain LESS, then the nerve is likely damaged beyond healing. Unfortunately you are then faced with one of just two options; getting the tooth extracted or getting a root canal to save the tooth. You can read more about these two options at GETTING A TOOTH PULLED and ROOT CANAL PROCEDURE.
So, if you have a tooth sensitive to heat, I recommend getting along to a dentist as soon as you can to get it checked and treated; thinly exception is if you've had a recent filling, and the tooth is sensitive to both hot AND cold, and subsides relatively quickly.
If you CANNOT get to see a dentist anytime soon, I recommend you take a look at my ebook Toothache Survival Guide. This tells you EVERYTHING you need to know, including some home remedies to help you out!