Doctor:Sit in the chair please .Lean your head back against the chair now .患者:我牙痛得厉害。医生:哪个牙痛呢?患者:我不知道是哪个牙。患者:对,晚上痛得不能入睡。患者:是的,喝冷的饮料就特别痛。Doctor:Please open your mouth and let me examine your teeth .One of your back teeth has a big cavity .医生:请张开口我给你检查一下。你后 ......