Thats the million dollar question on the lair. Grusderk has a method, and there's a video flaoting around on youtube for the working mandibles using some kind of hair clip and wires.
Well bud, those are the methods that we know of. Lair members make necessary sacrifices to achieve what they want, so unless you discover a groundbreaking new method, good luck.
ok so heres my dental rig i made up...the thin flat pieces are from tha straps in hard hat harness.then some coat hanger wire and rc truc drive shafts for the arms and actuating arms with ball joints from a rc helicopter gyro..wen u open your mouth it pushes the chin strap piece down and the push rods ...well..push out the two side mandibles...but its kinda floppy and not rigid enough to work properly.
heres my mandible mechanix.made from hard hat plastic straps,coat hanger wire,rc chopper gyro push rods,and rc truc drive shaft parts.it kinda worx but because of the thin plastic it kinda bends and doesnt function 100%.