I also think 'toothy' is more about what I can literally feel in how the edge cuts. Less about whether any 'teeth' can be seen microscopically - as previously mentioned, they'll always be there, even if not seen by the naked eye. For me, the line between 'toothy' and 'polished' is most easily defined by how it would feel if I accidentally cut myself with it. A polished edge is capable of cutting painlessly, or very nearly so, and you might not even notice until you see you're bleeding. But if you've ever dragged a truly toothy, bitey edge across a knuckle, you'll know it immediately and it'll keep reminding you for awhile after it happens, in how much it stings.
Same sort of distinctions can be felt indirectly too, in terms of what your fingers perceive in cutting paper or other materials. A really fine, thin, highly polished edge will sail through the edge of a piece of paper and you might not even be able to detect any resistance or friction in doing so. But a 'toothy' edge will always reveal itself in the zipper-like 'buzzing' you feel (or hear, if your ears are up to it) when you cut into a piece of paper. Both can be extremely aggressive in how they initiate the cut. But they each feel completely different in doing so.
