it's got to be the pogo-stick villain - because it just makes sense that he should be able to drill into tooth enamel : maybe think of him as having a sharp point but a lower body like a spring? Not like this guy, but you get the gist:http://magicroundabout.com/Characters/Time-For-Bed-Said-Zebedee.jpg
I think so too. Just like the idea of number 8. (:
Just an idea but Heidi perhaps he could resemble a food that is hard to swallow or to get out of your teeth. For example when people eat crisps sometimes it will get stuck in between our teeth and gums. So ragged edges would help sustain the belief that this character has been here for a long duration.