Is there a number one doctor-recommended quick fix for lose dental bridge-crown?

Fixodent, toothpaste: Fixodent denture adhesive if you can get some, or just Fluoride toothpaste if you can't.

See Dentist ASAP: Having a loose bridge can cause other issues that can cost you thousands of dollars. Breaking an abutment, the porcelain, etc. Once it becomes loose, it can act like a class-i fulcrum and the cantilever action can damage other teeth. Best thing, is to see your dentist asap, it may be a simple fix if seen early.

Determine the cause.: If you can't get to your dentist you may recement it with temporary cement from your local drugstore or place small amount of wax in to the crown to reposition it. If this is loose and not removeable, go to your dentist before you swallow or worse, aspirate the crown or bridge into your lungs requiring an emergency room visit. You probably require a new crown or bridge if decay is the reason.

Go to a dentist: Do not spend more time figuring that, go to your dentist and get it fixed asap, you may develop caries or gum desease on that tooth...

Denture adhesive: Any quick fix is only temporary, so see your dentist as soon as you can.

Re-cement: There are several over the counter remedies that you can use. Speak to your pharmacist. If you can remove the bridge and dry it you should be able to re-cement it with a product called temp bond. However quick fixes for dental bridges will last less than a week. The bridge needs to be professionally evaluated and the reason it came loose determined. Only then will it not happen again.

White tooth paste: White not gel tooth paste is a quick and easy fix to hold your fixed bridge securely until you can get to your dentist which should be done asap.

Re-Cement: I will recommend you to have a dentist putting back for you. It there is some cement left over the tooth or the crown, anything you put to glue it back will make your bite higher. This will be very uncomfortable. Also, there is a possibility it came loose because it had some saliva leaking. If this is the case, you could have some decay that needs to be taken care of before. Call your dentist.

Toothpaste: If it is a crown or fixed bridge and it has come out of the mouth, put toothpaste into crown or bridge and place back over the teeth. If you talking about a removable partial, use dental adhesive either a paste or cream never use sea bond as it damages your gum ridges. But if the problem persists see your dentist as you may need a reline or a new set of dentures.