please check this clip out and help settle something.
The poster in the youtube page says that you can see the actors teeth inside the Rex mask. I say the teeth inside the mask is part of the mask. In other words, Rex has 2 mouths, one inside the main mouth with the K9 teeth. Just pause it at 6:42 - 6:44.
It looks to weird to be real teeth.
What do you think?
http://www.youtube.com/watch?v=JBYESa9kL5w