by the skin of one's teeth 肯定不是“靠牙齿的皮肤”的意思，它是一个习惯用语，可以意为“侥幸，勉强，幸免于难”。

【例句】
I made the 5 o'clock train by the skin of my teeth.
我勉强赶上了5点的火车。

He went to college by the skin of his teeth.
他侥幸考上了大学。