Doesn't it get stuck more easily into the armor?
Assuming the teeth don't bend or snap against it, maybe.
In the case of a torso strike, the teeth don't look long enough to actually reach the person. Gothic Maximillian/Italian White armor had really cavernous breastplates.
Beyond that, underneath the armor they'd likely be wearing riveted chainmail over a gambison.
EDIT: On another note, while you've mildly inconvenienced the other person, you've basically lost your weapon.
And on another another note, the cavernous breastplates really make any sort of reasoning for boob plates completely idiotic.