Fashion and beauty are not constant one. They vary on each individual’s vision; a fashion liked by one might not be liked by others. So, here I put my thought,
I actually find models (and people in general) with imperfect teeth, but they really look sexy. It gives them personality and character. I can think of a few models like Lara Stone, Lauren, Hutton, Romina lanaro, Adriana Lima, Louise P and many more. And I think they did not make any measures to make it perfect. They deserves for what they worked. It gives unique identity for them.
And in Japan it is called yaeba. Women are paying dentist to craft their teeth crooked. They take it as a fashion trend. There are few famous fashion models with crooked teeth in Japan.
I personally believe crooked teeth might look very sexy if they are in harmony with the face. And it seems, teeth might not be a worrying thing for a anyone to think about modeling career.