2 days only. These is temporary remedy until you can see your dentist to have permanent cement placed. The better solution is just to leave it off for a few days preventing complications like gum problem, bite problem and crown aspiration into the lungs. Call your dentist and inform that you have lost a crown. Most offices will see you the same day. If not see "emergency dentist". Take care.
1day-1week. Denture adhesive is a great way to keep a temporary crown in place if there is no access to a dentist. It will still dislodge, though, with eating any food that is hard or sticky. There is danger of swallowing or dislodging at night. And it won't prevent decay from developing if the temporary crown is on too long. Best bet while traveling is to see a local dentist to recement the temporary crown.
Loose crown. I generally advise patients not to use Fixodent or any other temporary cement that they can purchase at a local pharmacy. More often than not, they cannot properly place the crown back, which will then break, loosen or cause more problems than it solves. It should only be used as a temporary last resort. If you can't see your own dentist the same day, see someone else on an emergency basis. .