Here are the pictures used in the study that were shown to the participants. The guys are on the bottom, for those who can't tell anymore. Bottom left is the smiling, happy guy. I wouldn't go so far as to say that's an unattractive smile (although the participants did). But there's something unnerving and unsettling about it. He either looks like a dork, or that he's liable to knife you as soon as your back is turned.
I agree there are attractive smiles and unattractive smiles. PUA theory always pushes the "smirk" instead, but smirkers make me want to punch them.
The female's Pride shot makes her look too butch.