He's got a front tooth missing.

他有一颗门牙掉了。

《牛津词典》

Another has a single front tooth.

另外一位门牙只有一颗。

youdao

To have one upper front tooth pulled out?

被拔掉一个上颚前门牙？

youdao

For example, how much would you have to be paid to have one upper front tooth pulled out?

比如，给你多少钱,你才愿意拔掉自己的一颗门牙？

耶鲁公开课 - 公正课程节选

Usually patients have less serious mutations: a single front tooth or a slightly deformed face.

FORBES: The Curious Case of The One-Eyed Sheep

Another has a single front tooth.

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His hair is short in length and is grey on the sides, while his front-left tooth has a chip in it.

BBC: Owain Roberts