How did eliezer lose his gold tooth

In a concentration camp, just about anything can become a highly-prized item. The only law is the law of the jungle. Everyone has to do whatever they can to survive, and if someone has anything of value, then they must be prepared to protect it at all costs. In such an unmitigated hellhole, where human life is cheap, a gold tooth such as Eliezer's is almost priceless. Indeed, a dentist at the camp ends up being hanged for dealing in gold teeth, so it's just a matter of time before Eliezer's tooth attracts attention.
And so it does. Franek, the brutal prison foreman, notices Eliezer's gold tooth and immediately demands it. Eliezer refuses, so Franek beats up Eliezer's father until he finally relents. Franek then gets a dentist to pry it out with a rusty spoon. A gold tooth may be priceless in a concentration camp, but Eliezer knows that the life of his father is so much more valuable.