Pictures below are the moulds for my teeth with the original sculpts pulled out- I'm going to leave the teeth in the sculpted gums until they need to be embedded into the moulds so I don't loose them or forget what order / position they're in. I then made blanks of the teeth from fast cast, with a bit of tweaking, these will go into the Kijimuna sculpt to be sculpted around and will be screwed into the inside of the fibreglass mould like the eyes.
Instead of having to integrate an additional silicone plug into the mould to stop the Platgel from filling up the mouth cavity, I decided to make the mouth cavity and the teeth into one solid unit so it is easier to build the inside core around and so I don't have to worry about the Platgel sticking to the silicone plug (which would also have to be a platinum silicone!). I fixed the teeth into a slightly open position that I was happy with and filled in the gap with filler and Milliput, It was difficult to imagine what shape to make the cavity because I am essentially sculpting a negative space, but I remembered to leave the top and bottom of the teeth blanks clear so there will be a recess in the mouth where the real teeth can glue into. I also think the teeth will be open enough to warrant making a tongue to go inside...