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This question was originally published on Quora. Answer by Irene Grijalvo Tarres.

Let's start with the misconceptions: Your mouth is not equipped to take care of itself, and animals don't really pull it off.

First of all, people have been brushing their teeth in rudimentary ways since 3.000 BCE. Not using a store-bought toothbrush and toothpaste doesn't mean you're not brushing them. At its most rudimentary, chewsticks ( Teeth cleaning twig ) have been used in Africa since then. Something else you're missing is that we live A LOT longer today than people used to. So now you have an extra 40 years for your teeth to decay. As many people have pointed out, if you stopped brushing your teeth and kept eating normally, you'd end up losing your teeth within 5-10 years.

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As for what animals do, it depends. Their lifespan is much shorter to start with. As other commenters have pointed out, meat eaters have serious problems with teeth hygiene. Domestic animals such as cats and dogs are a good example of that. That's why they sell these Greenies Teenie Dental Dog Treats to treat plaque build-up in dog's teeth.

Some dogs can live up to 15 years. Do the math if you plan on living until you're 90.

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Other animals, like some marsupials and rodents, get around it differently. Hamsters and wombats, for example, have ever-growing teeth. They use them to chew hard things so they keep wearing them down. Koalas, on the other hand, don't, and when their teeth wear down, they starve to death.

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