A well made crown or bridge can be a long lasting and reliable solution to lengthen the life of a damaged tooth. There will come a time though, when the crown will need replacing and if the seal of the cement which holds it in place fails unexpectedly, the crown will eventually fall out. This will leave you with a crown which, when you look inside it will be empty apart from possibly some traces of the cement layer. If the inside of the crown is full then unfortunately it is not the crown that has come loose but a fracture of the tooth has occurred. This will almost certainly mean that the crown cannot be cemented back on. A new crown however can probably still be constructed after rebuilding the core.
Under normal circumstances the crown will come loose completely when the cement fails and you must therefore be careful not to swallow your crown as retrieving it after that becomes a little harder! If there is some movement in the crown but it has not dislodged completely there may be a root filling with a screw post underneath and the cement fixing the post has failed. This can sometimes be fixed by simple re-cementation, dependant on the fit of the crown /post combination into the root. Do attend the surgery as soon as you feel movement in a crown or bridge as it will need recementing as soon as possible. In the situation where the crown is moving around but has not come off, with every movement, bacteria will be dragged into the inside of the tooth as the vertical movement of the crown starts to work like a pump, sucking in food and plaque. This will soon lead to tooth decay in the centre of the tooth and will reduce the chances of a simple recementation drastically. One dental problem with similar symptoms as mentioned above is where it is not the crown that is moving around but the whole tooth. This is normally caused by gum disease having compromised the bone attachment of the tooth. The difference between the the loose crown and the loose tooth is quite easy to diagnose in the surgery but hard or even impossible to distinguish by you as a patient.