I used a sharpie and marked where I thought the teeth would fit, then cut the fiberglass underskull accordingly. The clay I am using is Super Sculpey.
After I had a basic set of teeth that I was ok with (and I mean ok.. because I will likely replace these teeth with a more anatomically correct version later) I hardened the sculpey with a hot air gun and prepared it for molding.
The mold below is Smooth-On OoMoo.
Resin curing in the mold, with the sculpey master on top.
My airbrush was having major issues. I think the paint was just too old to use, so I used a brush instead. I drilled holes and mounted the teeth with small hex bolts with self locking nuts.
Next: Lip Mechanism!