A filling may come out for various reasons. Often, tooth decay has been present under or around the filling. It comes out or breaks because its not sitting on solid tooth surface anymore. Other times a portion of a filling or a part of the tooth itself breaks off.

Whatever the reason, if something comes loose that shouldn't, there is probably an underlying reason for it happening. Make the time to have it checked out as early as you can. Even if there is no pain, there's undoubtedly a problem that can only get worse.