Gallery of open-mouthed animals, great for teeth models? - http://www.animalyawns.com
Mirror site of the above - http://www.gapingmaws.com

From: Spiked Punch, replying to a list member:

Well, I at least know that teeth for snouts of costumes have been made
from at least ceramic or dental acrylic, but that's about all I know there…

Sculpy, foam, rubber, plastic, felt, and using those “teeth necklaces” from a costume store are a few sources for making teeth.

From: John D. Autore

Well, I at least know that teeth for snouts of costumes have been made
from at least ceramic or dental acrylic, but that's about all I know there…

… so would anyone be able to describe the method of creating teeth for
the snouts of costumes and wouldn't mind having the answer placed on the
FAQ? Materials, location of materials, preparation method?

With things that are available these days there really is no need to make teeth, unless you want custom ones like vampire fangs that my dental lab friend (Fangmasters, Phoenix, AZ) makes to fit in one's real human mouth.

I get my teeth, jaws, tongues, and eyeballs from Jonas Supply Company, a taxidermy supply place. Call them. They have a great free 200 page catalog of these items for all sizes to make your own real stuffed animal (That's my problem…no free time to make any new costumes with what I have already bought from them.) They also have foam bodies for the animal hides. I bought a standing raccoon and a standing ferret body so I could create own fantasy/sit on your shoulder animal in some exotic color and fur, but no time again. So call for a catalog, and you may also find a snarly mouth & wavy red tongue in your mailbox like I did.

You can also mold your teeth and gums from latex…