牙齿的问题
A dental cavity is a hole in the tooth.牙洞是牙齿上的一个洞。
A cavity is caused by bacteria in the mouth.口腔是由口腔中的细菌引起的。
Brushing your teeth frequently and regularly can help prevent cavities.频繁的且有规律的刷牙有助于预防蛀牙。
A cracked tooth can be caused by biting down on something hard.牙齿破裂可能是咬硬东西造成的。
Dentists treat a cracked tooth by covering it with a crown.牙医用牙冠覆盖裂开的牙齿来治疗（临床）。
A dental X-ray is a picture of your teeth and gums.牙齿x光片是你牙齿和牙龈的照片。
An x-ray shows what can't be seen on the surface of the teeth and gums.x光片显示牙齿和牙龈表面看不到的东西。
Braces are used by dentists to straighten teeth over a period of years.牙套被牙医使用矫正牙齿已经很多年。
Though braces are usually for children, they can also be used for adults with crooked teeth.虽然牙套通常是给孩子用的，他们（牙套）也可以给牙齿歪的成年人使用。
To extract a tooth, means to remove it from the mouth.拔除牙齿，就是把牙齿从嘴里拔出来。
Dentists have to pull hard to extract a tooth.牙医必须使劲拔。
Dentists often inject something into the gum to block the pain during the extraction process.牙医经常在拔牙的过程中往牙龈里注射一些东西来止痛
Braces are used on people with crooked teeth or after an injury.牙套用于牙齿弯曲或受伤后的人。
