How to Brush Your Teeth on the International Space Station

The ISS crew just repaired their vehicle with a simple, earthly toothbrush. Here's why they had one aboard in the first place.

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NASA/Mir-23 researcher Jerry Linenger brushes his teeth in the Spektr module. Note the floating Crest. (NASA)

On the International Space Station, hygiene is generally a high-tech thing. Instead of showers, astronauts aboard the ISS take improvised sponge baths in specialized portals, washing their hair with rinseless shampoo. Bathroom needs are, similarly, highly specialized -- involving a combination of funnels, Velcro, and vacuums. Those systems exist not just to keep things pleasant for the astronauts who share the station's confined quarters. It's also a matter of health: Since bacterial life can flourish in space despite its harsh conditions, keeping clean is a matter of mission integrity as well as courtesy.

When it comes to oral hygiene, there's some tech involved, as well. There are chewable products -- toothpaste-as-gum, essentially -- that cleanse teeth without the need for traditional brushing. There's also ingestible toothpaste, which eliminates the need for eliminating used paste. NASAdent -- nicknamed "the astronaut toothpaste" due to its non-foaming and ingestible formula -- has been around since the 1960s:

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For the most part, though, oral hygiene on the Space Station remains relatively earthly. Toothbrushes, the base-and-bristles kind you or I might buy at the drug store, are still the norm. "Astronauts use the same toothpaste as on Earth," the Canadian Space Agency notes, "and can even select their preferred brand." And that's because the toothbrushing challenge isn't so much about the tools as the conditions: Space-based brushers have to keep their Crest or Colgate or what have you on their brushes, and in their mouths, in an environment where neither water nor gravity is particularly plentiful.

To overcome that challenge, astronauts usually end up resorting to creative, low-tech hacks. Many astronauts, NASA notes, keep their personal hygiene kits -- toothbrushes and toothpaste stored inside it -- anchored to a wall in their particular vehicle. And the toothpaste itself might be stored in a specialized tube, one with its top attached, thus mitigating the need to keep tiny little toothpaste caps from floating away during the toothbrushing process.

That's pretty much the only thing that keeps space-based brushing simple, though. When you're battling gravity, even the most basic task can be intricate. Former ISS denizen Leroy Chiao explains the whole brushing procedure like so:

Start by filling a drink bag with water and bring it with you to the hygiene area. Tuck it behind a rubber bungee. Remove your hygiene kit from behind its bungee and unzip it. Find your toothbrush inside of your hygiene kit, safely tucked away inside of a fabric pouch with a Velcro top. But first, take out your toothpaste tube, and stick it to the wall, using the Velcro dot on it. Secure your hygiene kit behind a rubber bungee, after partially zipping it up, so that things don't accidentally float out.

Still have your toothbrush between a couple of your fingers? Hopefully yes. Remove your drink bag, and with one thumb, flip open the straw clamp (which keeps liquid from seeping out of the bag), and gently squeeze out a bead of water onto your toothbrush, watch it get sucked into the bristles. Hold the straw of the drink bag in your teeth, and with one hand, fix the straw clamp in place, and replace the bag behind the bungee.

Almost all of the rest is fairly straightforward. Flip open the cap of the toothpaste tube, squeeze some out on your toothbrush, go to work on your teeth. Ok, you're done. Now what? Where are you going to spit? There's no sink. So -- into a tissue? Then you've got a wet tissue, and what are you going to do with that?? So, I swallowed. Filled my mouth with water and swallowed again. Drew some water onto the toothbrush and sucked the water out. Dried the toothbrush onto a towel and replaced it, and the toothpaste, into the kit.

Chiao might be a tad jaded; and it's easy to imagine that the gravity-challenged version of the familiar lather-rinse-repeat would become tiresome after awhile. Then again, though: Despite all the extra steps involved, you're still, you know, brushing your teeth in space. So there's that.