What if they have no teeth?
For me, I suspect (although I'd not care to stake my life on it) that what I notice first depends one heckuva lot on circumstances. A few examples:
--People headed my way on the sidewalk as I'm strolling through gang territory. Here I'm looking first for numbers, body language, weapons, and how they're positioned strategically.
--Pretty girl going away from me, then I'm checking out the hip action. It's how I got married 7 times. Pretty tail, who cares about the rest, don't date her, just marry her.
--If eye contact is possible and appropriate, then yes, that for sure. Today in Wal-Mart, a tall girl and I passed each other (going opposite directions) and there was a flash in her eyes that said she knew I'd been admiring the view. Had, too: Nice form, well clad, great confident stride, hot boots.
--If in the men's john, then I notice whether the other guy is paying attention to his business and not mine.