当摄像机在执行它的神奇的职责时，你就要保持露齿笑，这实在是太让人难以想象了，于是，一种坚定而茫然的凝视成了常态。

The thought of holding a fixed grin as the camera performed its magical duties was too much to contemplate, and so a non-committal blank stare became the norm.

youdao

年轻女性们，求你们了，微笑、傻笑、假笑或露齿而笑，怒视或瞪视，或者如果你愿意，漫无目的地闲逛都行，看在上帝的份上，别摆那张鸭子脸了。

Please, young women, smile or simper or smirk or grin, glower or glare, or just mope about if you like, but for the love of God, please put away the duck face.

youdao

她看起来是客客气气的，一旦脾气发作起来，就张牙露齿不那么客气了。

She had always seemed friendly until suddenly she began to show her teeth.

《新英汉大辞典》

Professor Paul Bloom: I don't know if that's--The question is, "Is there a difference between smiling with your teeth versus just your lips closed?"

我不知道是否，问题是，微笑露齿与不露齿有不同吗“

耶鲁公开课 - 心理学导论课程节选

This characteristic thing we do with our lips exposing our teeth and so forth.

这种特有的,咧嘴露齿的动作

耶鲁公开课 - 死亡课程节选