Sharp and/or constant tooth pain is a known dental emergency, and if you've started experiencing this, you need to call an emergency dentist immediately. The same goes for constantly bleeding gums, signs of infection, and so on. But there are times when pain is not severe and constant, and it doesn't prevent you from going about your day, but it does get your attention. At what point is that pain an emergency? Any unknown tooth pain needs to be checked out by a dentist, of course, but there is pain that you call the next business day about, and pain that you call a dentist right then about. 

Occurs in Response to Temperature and Sweetness Changes

If the pain is sudden, short-lived, and appears only when you drink something hot or cold, or when you have something sweet, you're likely dealing with tooth sensitivity. Tooth sensitivity and cavities can have similar pain, so don't assume it's sensitivity until the dentist confirms this. But this is something you'd likely wait until a business day to call about as long as there was no bleeding or inflammation (or other signs of infection). In the meantime, you can start using toothpaste made for sensitive teeth. If the tooth pain dies down after you start using that, sensitivity is the likely culprit – but don't cancel that dentist appointment. Go, and get confirmation.

Occurs in Several Teeth at Once

When the pain occurs in several teeth at once, that can point to something going on around the roots. It doesn't mean the problem itself is throughout that part of your jaw, but the pain could be radiating out. That's something you want to call the emergency dentist about because you don't mess with the roots of your teeth. You could have an infection forming somewhere, and you need to stop the infection quickly.

Occurs Throughout Lower Jaw Occasionally

This is a tough one as the pain could be due to an infection – something you'd consider a dental emergency – or due to you unconsciously clenching your teeth as you concentrate on something. If you know you're not clenching your teeth tightly, call the emergency dentist. If you think you might be, monitor yourself for a few hours to see if the pain does not occur when you consciously keep your jaws apart. If no pain occurs and you do think you were clenching your jaw right before you noticed the pain, call the dentist the next business day morning, first thing.

Occurs Near the Joint When You Move Your Jaw

If the pain feels like it's at the back and appears related to the movement of your jaw, you might have something related to temporomandibular joint syndrome, or TMJ. If the pain prevents you from opening your mouth all the way, call an emergency dentist. If it's mild, occasional, and is not accompanied by signs of infection or bleeding, then you could potentially call on the next business day if it's say, Sunday night. (If this starts happening earlier, though, it's better to call and let the dental office decide.) Do monitor the pain, though, and call the emergency dentist if it gets worse. There's a difference between something that's merely sore and something that's new and increasing.