Mental Model of Dental Hygiene

Story time

I’ve never been all that diligent about dental care. I got cavities constantly as a kid.

I don’t know how, but I must’ve been much tougher back then, since I would get multiple teeth drilled without anesthetic since I was (and am) terrified of needles.

I tried that recently and in less than 5 seconds had resigned myself to the awful taste of Novocaine and the worse feeling of a needle in my mouth.

I think that’s what scared me straight enough to read about proper dental care.

The Point

Turns out my mental model was wrong. I imagined that the brush scrubbed away bacteria and floss was to get food out of your teeth.

It’s more like: brushing is to clean bacteria but also spread fluoride, amount doesn’t matter but frequency does, and xylitol is magic.

What causes cavities

Sugar and acid.

Sugar is eaten by bacteria and they produce acid, which damages your teeth (duh). Avoiding sugar totally is pretty damned hard, even for the paleo type.

Soda will damage your teeth even more since it has acid of its own, and lots of sugar besides.1

You don’t want to brush when your enamel is soft or you’ll scrape it off, and it doesn’t grow back.

It’s about frequency, not amount

If you chug down a Coke in 10 seconds, that’s better for your teeth than sipping it over 2 hours. If you took a funnel and poured it down like you’re a goose bred for foie gras, that’s the best of all2

Every sip bathes your mouth in acid, each one lasting for about 20 minutes.

Same thing for sugar. Eating candy isn’t that bad for your teeth, provided you do it infrequently, even if you eat a bunch of it each time.

But if you eat it every few hours, it’ll have lots of time to damage your teeth.

That’s why you don’t want to brush after meals. Food often has some acid in it, so you want to wait 20 minutes after to brush. Rinsing is fine since it doesn’t involve actively rubbing the enamel with abrasives.


Brushing is a bit of a misnomer. If you have an electric toothbrush (and you really should), you shouldn’t be brushing, but wiggling. This video shows how to do it correctly.3

Most of the bacteria live around the gums, so you need to focus there. Other effort is almost wasted by comparison.

Hardening Enamel

Your enamel is supposed to be hard. Fluoride makes it harder by remineralizing it. Half the point of a toothbrush is to evenly coat your teeth in fluoride, which is what stuff like Blizzident fails at.

Saliva also remineralizes, which is why dry mouth is bad. Chewing (sugar free) gum is good because it encourages saliva production. Chewing tobacco and drinking are bad because they dry your mouth.

This is why brushing before you sleep is more important. Your mouth is dryer when you sleep, plus bacteria have 8 hours to damage your mouth if you leave sugar in there.

Most mouthwashes contain alcohol, which makes them worse than useless. You do want fluoride. Mouthwash without fluoride is a defective product.

Only buy alcohol-free, high fluoride mouthwash.


Gums don’t grow back. Brushing too hard will damage them and expose the soft dentin4. Don’t do that. Watch the video on brushing. Describing it in text won’t get the idea across.

Use soft bristles5. Hard bristles are worthless.


Floss isn’t for getting food out, but for scrubbing the gaps between teeth. You essentially scrub the gap with it, and need to go under the gum too.


Most bad breath is from junk on your tongue. Use a tongue scraper, or just scrub your tongue with the brush. No chance of damaging gums there, so scrub as hard as you like.


Xylitol is an artificial sweetener. Unlike others, it’s poisonous to bacteria that try to eat it. Think of it as revenge on them for making you brush.

Xylitol gum is great for you, as long as xylitol is the only sweetener in it. No sugar or aspartame or whatever. It both poisons bacteria and produces saliva.

  1. Those who know me will find that sentence hilarious coming from me. 

  2. For your teeth. Not for the rest of you. 

  3. TLDR, 45 degree angle, focus on gums, don’t scrub hard. 

  4. Soft pulp inside teeth. 

  5. And replace the heads every 3 months. 

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