i think it all depends how u smile lor. if the way u smile seemed fake, cfm ppl would say u suck in smiling.

so i think, just practice how to smile. i rmbed ppl say a standard smile is letting people to see your 8 teeth altogether.
and one more thing is your teeth and gums, i guess. if a person has "cow" teeth, u wan him/her to smile?

IMO, those ppl who smile and can still see the upper portion of the gums, i think damn suck la. lol
*anyways, this is just my point of view la. if anyone fits in all these, please dont come and flame me.

*