What is an interesting fact that you know and I don't, but shouldn't?

Here's an interesting fact that might not be widely known but is perhaps better left unshared: In the 19th century, dentures were made from the teeth of dead soldiers. After battles like Waterloo, dentists would collect teeth from the battlefield to craft dentures for the wealthy. This practice was common before the advent of modern dental materials1. While it's a fascinating piece of history, it might not be something you'd want to share at dinner parties