The first thing you should do if a dental crown falls off is to bring it to the dentist. They may be able to clean it up and re-insert it into your mouth. If it’s not possible right now, contact your dentist and ask if there are any special instructions you need to follow until your appointment. The dentist may suggest you clean the crown with toothpaste before reinstalling it. As a temporary cement, you might use a dental adhesive available in pharmacies. It would be beneficial to be cautious when eating and avoid chewing on the crown until your new one arrives. Stick to soft foods and beverages until you can replace them.