12 Opening the mouth
The best way to sculpt an open mouth is to slice the head at the jaw. I mask off the lower jaw, then go to the Subtool menu and select Split Unmasked Points. This gives me a separated jaw. I then go to Geometry>Modify Topology>Fill Holes, to fill in the open spaces where the cutting took place. I can now part the lips using the SnakeHook brush. If I wanted to I could now change the insides of her mouth.