system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does chewing aluminum foil cause a shocking sensation where dental fillings are present?
gpt
You're creating a rudimentary battery inside your mouth.

The fillings are one metal, the foil is another type of metal, and your saliva acts as an electrolyte. Ions move from one metal electrode to the next and this is an electric current.