With that much distortion coupled with his extremely powerful fingers all he needed to do was push on the strings firmly and the note would be played nearly the same as if he were to have plucked it.
I cant be positive about this. Perhaps his teeth did strike the strings but I doubt it. Anyway you just cant tell from any of the footage available.
Here are some of my favourites that I've seen in person:
Robert Pollard, of Guided By Voices
Black Lips
King Khan
Nobunny
David Yow, of The Jesus Lizard
Emily Haynes, of Metric
CPC Gangbangs (RIP)
Jon Spencer, of Jon Spencer Blues Explosion
Tim Harrington, of Les Savy Fav
And yes, I've seen Angus too, and he was pretty good. 🙂