I was flossing as usual & one pair of teeth felt unusually tight. when i pulled up the floss, the filling flew out! no pain. is it an emergency?

Not emergency: No. But in the morning you should contact your dentist.

See dentist: It is important to see your dentist as soon as you can to have the filling replaced. You may have some sensitivity in your tooth and gums and this area is open to food, bacteria, and decay can progress until it is fixed.

Yes: the tooth need to be examined to determine if it salvageable. prolonged time of no treatmrnt may lead to tooth loss.

Not an emergency,: However, it can be painful because the exposed tooth tissue is often sensitive to temperature, pressure or air. If you've lost the filling you can put dental cement (OTC) directly on the tooth surface. This will help to protect and seal the area until you're able to see your dentist. Good luck.