system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does it hurt to chew tin foil?

This has been biting me since I first was a stupid child who decided it was a good idea to bite down on a big ball a tin foil only to have what felt like Zeus' thunder and wrath run through my enamel. I assume it has something to do with the aluminum oxide coating. Why does it react to your teeth when chewed?
gpt
When you have fillings, the saliva connects the two dissimilar metals, creating a minute current, that hurts so badly because it touches those sensitive nerves.

Similar to the 9-volt to your tongue thing.