underbreath

例句：

1. 1. She had a small underbite that made her smile look crooked.
   她有一颗小下颚，让她的笑容看起来不自然。
2. 2.The dentist fixed her underbite with a metal plate.
   牙医用金属板矫正了她的下颚。
3. 3. When she smiled, you could see the difference in her underbite.
   当她微笑时，你可以看到她下颚的不同。