Temporary crown fell out
A temporary crown or bridge covers and protects the involved teeth and serves as an anchor that keeps adjacent teeth from moving. Temporary crowns or bridges are generally cemented in place with temporary cement. This cement allows your dentist to easily remove the temporary crown or bridge once the permanent bridge is ready to be placed. Unlike most of the permanent cements your dentist uses, temporary cements may eventually be dissolved by your saliva. If this happens, your temporary bridge or crown (which is precisely fitted) may come loose.
If a temporary comes off, it's very important that it be replaced immediately to prevent shifting of the teeth next to the crown or bridge and the opposing teeth that chew against it. This shifting, which can happen in only a few hours, can permanently change your bite and make it impossible to place the permanent crown or bridge. If your temporary crown or bridge comes off, be sure to save it, and call your dentist immediately to have it re-cemented. Warning: don't try to replace it yourself. Your bridge or crown may come off and cause more problems, particularly when you are asleep. Never use any glue, especially Super Glue, in your mouth.
Permanent crown fell out
Some kinds of permanent dental cements over time may be dissolved by the water in your saliva and allow your crown or bridge to come off. Sticky foods such as gum, caramels or suckers may also pull crowns off of your teeth, even though they were properly cemented with permanent dental cements.
When a crown or bridge comes off, take great care to save it! In many cases it can be cleaned up and re-cemented. It's very important that a crown, bridge or inlay that has come off be replaced immediately. Taking immediate action will prevent shifting of the teeth next to the affected area and those that they chew against.
This shifting, which can happen in only a few hours, can permanently change your bite and make it impossible for your permanent restoration to be re-cemented. If your crown, bridge or underlying teeth have been damaged, a new restoration may have to be fabricated.