Have you ever bit into a popsicle, expecting fruity deliciousness, and got blinding pain instead? If so, you might have sensitive teeth. Desensitizing toothpastes are designed to help, by blocking the pain caused by heat, cold, or pressure in a couple of different ways. But how exactly do they work? And what causes tooth sensitivity in the first place? Those are the kind of questions that you come to SciShow to get answered. 

So first, you have to understand a little tooth anatomy. The crown of a tooth is the part you can see, and it's made up of three layers: the enamel, the dentin, and the pulp. Tooth enamel is the hardest substance in your body, and it's mostly made of minerals, like the calcium-containing hydroxyapatite. Since enamel doesn't contain any living cells, your body can't replace it if it's worn away, like by grinding or lactic acid from bacteria. 

Dentin is made of some minerals and organic compounds, and has lots of microscopic pores, or tubules, that run all the way to the pulp. And the pulp has cells called odontoblasts that make the dentin, plus some connective tissue, nerve cells, and blood vessels. Without enamel covering those tubules in the dentin, stuff like air and liquids can get in and irritate your nerves, which send signals to your brain so you feel pain. 

Desensitizing toothpaste can kind of stop this from happening, with chemicals that interact with the nerves or open tubules. See, nerve cells have these proteins called ion channels, which get triggered by something, open up, and let ions move around to change the cell's electrical charge so it sends a signal. When you use toothpaste that has potassium nitrate, for example, extra potassium ions can flow through the tubules and flood your nerves, which could mess up their ability to signal. 

Basically, it works as a numbing agent. your nerves can still be exposed to the heat or cold, but your brain doesn't register it . On the other hand, a chemical like strontium chloride can block the tubules in the dentin, because strontium has a similar structure to calcium, which is one of those minerals in your teeth. With the tubules blocked, nothing can get in to irritate the nerves, so the pain is gone.

So, will brushing sensitive teeth with desensitizing toothpaste actually heal them for good? Well, no. Not at all. It's like treating hay fever with allergy medicine, just because the symptoms go away doesn't mean the problem is gone. And the real problem here is the eroded enamel, which you can't make more of.  Sometimes, achy teeth can be symptoms of something else, so you should always as a dentist to avoid bigger problems down the road. 

So, in the long run, desensitizing toothpaste probably won't toughen up your teeth. But if you just want to enjoy a popsicle pain-free it might do the trick. 

Thanks to Patreon patron Shavastak for asking, and thanks to all our patrons who keep these answers coming. If you would like to submit a question to be answered, just go to Patreon.com/SciShow, and don't forget to go to YouTube.com/SciShow and subscribe.