hiya wa howa aswat

It’s Shark Week, and while the Discovery Channel is apparently kinda fucking it up, that shouldn’t keep us from bringing you a weird science fact about the most terrifying sea creature to probably pose you no threat whatsoever. And that fact is this: Shark teeth have built-in natural toothpaste. The outside of a shark’s tooth is made of fluoride, the same stuff that gets added to toothpaste, mouthwash, and municipal water systems to improve your dental health.
Though fluoride is a tougher material than hydroxyapatite (the stuff our teeth are made of), weirdly, shark teeth are not harder than human teeth:

“This finding is surprising, because the mineral fluoroapatite is harder than the mineral hydroxyapatite, so if a tooth were to consist of the mineral alone, a shark tooth would be harder than a human tooth,” Epple said. “It seems as if the human tooth makes up for the less hard mineral by the special arrangement of the enamel crystals and the protein matrix, and ends up being as hard as a shark tooth.”

So, you know, go ahead and bite a shark in the mouth. I will wait here for you.
Anyway, but even though they’re not harder, shark teeth are more durable because they have their own cavity-fighting ingredients. This almost seems like overkill, since sharks have multiple rows of teeth, i.e. tons of backups (and they can easily replace the ones they use). On the other hand, teeth are pretty critical to a shark’s lifestyle, and it’s hard to go to CVS when you are a fish, so it makes sense that they would have evolved teeth that contain the seeds of their own nigh-indestructability.

The question is, how do they floss?