system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How does toothpaste protect for 12 hours?

Does it set up some sort of barrier?
gpt
the fluoride binds with the minerals in your tooth enamel and makes them protected against acids. this allows them to re-mineralize and be stronger.

you can even put fluoride toothpaste on an eggshell , then wash it off and put it in some vinegar and it won't weaken where a egg that hasn't been treated will get all gummy and elastic.