OK, what am I doing wrong?

I've had this issue lately of the teeth I glue in my heads falling out, and it is driving me crazy!

The mouths of my heads are lined with fleece, the teeth are painted oven bake sculpey and I have been using hot glue to set them in my heads.

I've tried roughing up the bottoms before I glue them in, and both painted and unpainted bottoms where I glue them, yet they still seem to fall out easily.  Is it the sculpey, the glue?

Any advice on this would be great!

Thanks!