PREMOLARS

　　前臼齿

　　Adults have eight premolar teeth, two next to each canine tooth in the upper and lower jaw. Their job is to chew and grind up food.

　　成人长有八颗前臼齿，分别位于上下颚犬齿后端，他们主要负责咀嚼与研磨食物的工作。

　　PROBLEMS: Premolars are more vulnerable to gum abrasions, caused by brushing teeth too harshly. This can lead to inflammation and, in the long term, gum -disease (causing teeth to fall out).

　　问题：错误的刷牙方式常常会致使前臼齿的牙龈“受伤”，久而久之，则会引起牙龈疾病（从而发生脱落的现象）。
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