Between your lips and teeth.

你的唇齿之间。

youdao

The supportive relationship between lips and teeth; (FIG) to be in a close, interdependent relationship.

唇齿相依是对我们关系的最好形容。

youdao

Parts sales and automobile maintenance are the relationship of dependence on each other as lips and teeth, mutual promotion, mutual reliance, which makes parts industry suffered badly shock.

零部件销售与汽车维修是唇齿相依、互相促进、互为依托的关系，使得零部件行业也受到重挫。

youdao

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

Lifting your eyebrows makes the device open its grip, clenching your teeth shuts it and moving your lips to the left and right twists the claw, while other motions are currently handled by using a PlayStation 2 controller.

ENGADGET

The back of my throat went on tightening, and other muscles lower down my neck joined in, tugging at my lips, trying to stretch them over my teeth.

NEWYORKER: Hand on the Shoulder