[tunap]

American here, I have always found it disingenuous and a little creepy when people smile while baring all of their teeth. There is a difference from showing some when extremely happy and the practiced facade people selling something have learned to do unconsciously, notably when lower lip curls down for more dental exposure.

[_puk]

Brings to mind the smiling with upper and lower teeth sketch from Silicon Valley

https://www.youtube.com/watch?v=KGSJ8b9raJs&t=16