Spanky the Dolphin: According to Newtype 100% Collection (page 101), EVA-01's mouth is actually bolted shut with a horizontal peg at the front teeth, and the pieces flying out is the destroyed bolt.
Sharp-kun: It's actually that way for all the Evas. Watch EVA-03 when she goes crazy in episode #18.
Reichu: If they bother bolting the Evas' mouths shut, why don't they just go the safer route and not give them a separate jaw piece to begin with?
felineki: See that odd little “exo-tooth” EVA-01 has in the blue portion of the upper jaw? I think this is the only time it's depicted.
