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The summer sun is blazing and you get an ice cream cone when, ouch! That intense shooting cold pain in the teeth just hits differently than, say, making a snowball with your bare hands.

So what makes cold teeth feel so much more painful than cold skin? Recently, scientists uncovered a receptor that you can blame. Skin can normally sense cold thanks to a receptor called TRPM8, which tells nerves to fire when they get cold.

But studies have shown that TRPM8 isn’t the primary receptor involved in teeth cold sensitivity. So scientists started to hypothesize how the teeth can sense cold. In 2011, researchers found another cold-sensitive receptor called TRPC5 in the tissues outside the brain and spinal cord.

When you’re cold, a pore in cell membranes containing a TRPC5 opens and lets ions through, setting off a “brr, that’s cold” signal to the brain. But scientists were puzzled to find that TRPC5 doesn’t come into play in the skin, so they engineered mice to lack the receptor, and they still sensed cold. Where the heck TRPC5 was sensing cold remained a mystery for a decade.

Until one day, over lunch, the team was using their teeth to eat when, eureka! Scientists realized there was part of the body that had been overlooked: teeth. And in 2021, researchers published a study on a previously unrecognized pain sensor in teeth.

Researchers discovered this by connecting the brains of mouse cadavers to electrodes and measuring signals sent through the intact system of jawbone, teeth, and tooth nerves. When they applied an ice-cold solution to the teeth, mice with TRPC5 sent signals to the brain that they sensed cold. And engineered mice without TRPC5, or with that receptor blocked, sent weak signals or no signals at all in the presence of icy temperatures.

Not only did they find TRPC5 in healthy teeth, but they also found that it’s more prevalent in areas with cavities. Which explains why people with tooth decay have it way worse in the eating cold things department. Researchers uncovered that TRPC5 is mainly found in dentin-producing cells called odontoblasts that hang out between the protective tissue right under the tooth enamel known as dentin and the inner tooth pulp.

The findings suggest that cavities make cold teeth more painful because they’re basically holes in the enamel and dentin that expose those cells to what’s in your mouth. So if you have a cavity and have something really cold then, well, brace yourself. Researchers also looked at extracted human teeth and found that expression of TRPC5 is higher in teeth with pulp inflammation, which is the immune response to decay.

That’s one way that teeth are, well, not like skin. Teeth become hypersensitive to cold when inflamed, while muscle and skin tend to become heat-sensitive when they’re inflamed. Scientists think there could be other factors contributing to this sensation, so more research is warranted.

But it does explain enough that the next time you feel the pain of biting into a popsicle you can be like, “Dangit TRPC5! You win this round.” Thanks for watching this episode of SciShow! We’ve made thousands of educational videos over the years, and we’ve been able to offer them for free because of our patrons on Patreon.

So, to all our patrons, thank you for what you do to make SciShow happen. If you’re not a patron but you want to learn more about what that means, you can go to Patreon.com/SciShow. [♪ OUTRO].