I couldn't find a printable skull on Thingiverse that had a removable mandible with the teeth included so I created one.
Originally this was a Sketchup model that I imported and sliced and diced to print as large as I could on my Thing-O-Matic.
Print all the pieces and glue together and enjoy.
My apologies I forgot to upload the bottom part of the mandible. It is now uploaded.
NEW: uploaded new top part of the mandible with a thing that stretches across so you can hook a rubber band though to make the jaw movable. Just screw a hook in the bottom of the nasal cavity and then you should be able to loop a rubber band and make the attach so you can move it.