Loose tooth!

My 8 year old chihuahua, Lilly, jumped up onto the bed yesterday, and when she landed she hit her chin really hard on my knuckle. It hurt us both.
Today I noticed one of her tiny front bottom teeth is gone, and the top tooth directly above it is loose!
The missing bottom tooth is long gone in the carpet somewhere I'm sure, and her teeth there were cramped anyway, so I feel like that one is not so big of a deal.
Is there anything I can do to help her keep that top one from falling out?
I recognize that I should take her to the vet, and I will. In the meantime, any advice?

p.s. her teeth and gums are otherwise healthy.. I don't think this resulted from gum disease.

Not much you can do at this point. The incisors are a single root tooth and are easily lost with trauma. There is a possibility that the tooth will re-stabilize, but if not, it would easily be extracted if it causes discomfort. Dogs do not use these teeth often, just for shredding, which most domestic dogs no longer do. For a while, avoid giving your dog anything to chew on such as toys, bones, etc. to give the tooth a chance. Good luck.

I think taking her to a vet is the best option. Don't take any risk and visit a vet first.