把你的舌头放在牙齿后面，微笑，这样可以放松你的脸部。
Put your tongue behind your teeth and smile, which will relax your face.
非常明显，前面的牙齿先改变，后面的牙齿再改变。
这幅图片清晰显示为什么牙齿是容易替换唯一的直接的在后面的牙齿。
This photo clearly shows how the teeth are easily replaced by the ones directly behind.
这幅图片清晰显示为什么牙齿是容易替换唯一的直接的在后面的牙齿。
This photo clearly shows how the teeth are easily replaced by the ones directly behind.
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