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Sugar is supposed to be one of the best things in life. But you might have bitten into something really sweet only to have it betray you.

糖应该是生活中最美好的事物之一。但是你可能刚刚咬到非常甜的东西，突然发现它却背叛了你。

Instead of sugary deliciousness, you got immediate, sharp, eye-watering pain. And sure, eating lots of sugary food can cause cavities that don't feel great, but that wasn't some sort of insta-cavity.

你得到的并不是糖的美味，而是即刻的、尖锐的、催泪的疼痛。当然了，吃大量的含糖食物会导致龋齿，这种感觉并不好，但我在讨论的并非是龋齿的情况。

What you experienced was a consequence of dentin hypersensitivity — or having sensitive teeth as it's known in the toothpaste aisle. Pain due to this condition is more commonly caused by consuming hot or cold things, but it can also be caused by eating really sweet stuff.

这是牙本质过敏所带来结果——或者可以说是牙膏货架上所说的牙齿敏感。这种情况引起的疼痛更常见于食用热的或冷的东西的时候，但也可能是由于吃了非常甜的东西引起的。

But what makes sugar so special? To understand this, it helps to know a little about tooth anatomy in general.

但是是什么导致了糖是如此特别的呢？为了理解这一点，了解一些关于牙齿解剖学的基础知识是很有帮助的。

Your teeth have three main layers. There's an outer layer of hard enamel, an inner layer of pulp, which contains blood vessels and nerves, and a layer of dentinin between.

你的牙齿主要有三层。外层是坚硬的牙釉质，内层是含有血管和神经的牙髓，中间还有一层牙本质。

Dentin is pretty hard, but unlike enamel, it's porous. It contains microscopic, fluid-filled tubules that run from the pulp to the underside of the enamel.

牙本质非常硬，但与牙釉质不同，它是多孔的。它包含微小的、充满液体的小管，从牙髓一直到牙釉质下层。

Even though tooth enamel is the hardest substance in your body, it can still be damaged, like if you grind your teeth, have cavities, or drink lots of acidic sodas. If your enamel is worn away, your dentin and its tubules can be exposed.

尽管牙釉质是你身体中最坚硬的物质，但它仍然可以被损坏，比如磨牙、有蛀牙，或喝大量酸性汽水。如果你的牙釉质被磨掉了，你的牙本质和它的小管就会暴露出来。

And sometimes, the combination of sweet stuff and exposed dentin equals pain. And it's all because of your old friend from science class: osmosis.

有时，甜味的东西和暴露的牙本质的碰撞就会导致疼痛。而这一切都是因为你在科学课上的老朋友：渗透作用。

Osmosis is the movement of something like water across a selectively permeable barrier. It goes from the side where there's less stuff dissolved to the side with more stuff.

渗透是指像水这样的东西跨越选择性渗透的屏障的运动。它从含量低的一侧进入到含量高的一侧。

Or, in official terms, from the side with a lower concentration of solutes to one with a higher concentration. Osmosis likes things to be equal.

或者，用更正式一点的话说，从溶质浓度较低的一侧到浓度较高的一侧。渗透作用喜欢一切都是等量的。

Now, say you bite into something very sweet, like a piece of leftover candy corn. That snack touching the outside of your exposed dentin has highly concentrated solutes in the form of sugar molecules.

假设你在吃非常甜的东西，比如一块吃剩的玉米糖。那些接触到你暴露的牙本质外部的零食含有高度集中的糖分子形式的溶质。 =xqy=

And the dentin acts as the selectively permeable barrier. The fluid in your dentin's microtubules rushes out of your tooth towards the sugar.

而牙本质则作为选择性渗透的屏障。牙本质的微管中的液体冲出牙齿，冲向糖那里。 [eusoft]

And that flow stimulates the nerves in the pulp of your tooth, causing shooting pain. Other solutes, like salts or even sugar substitutes, are often better dissolved than sugar, and are in lower concentrations in food and drink, so they don't cause as much fluid to rush through the dentin.

而这种流动刺激了你的牙髓中的神经，导致射痛。其他溶质，如盐甚至糖的替代品，通常比糖的溶解性更好，而且在食物和饮料中的浓度较低，所以它们不会导致那么多液体冲过牙本质。

Which means they cause less nerve stimulation and less pain. Really, though, you're much more likely to experience pain in response to cold or hot things which contract or expand the fluid in those tubules than you are in response to sugar.

这意味着它们对神经的刺激更少，因而导致疼痛也就更少。不过，和对糖的反应相比，你更有可能在对冷或热的东西作出反应时体验到疼痛，这些东西会导致这些小管中的液体收缩或膨胀。

When we talked to Dr. Kenneth Markowitz of the Rutgers School of Dental Medicine, he said sweet foods are actually a relatively weak stimulus for tooth pain. Usually, they only trigger pain when the tooth's inner pulp and its nerves are already inflamed.

当我们与罗格斯大学牙医学院的肯尼思·马科维茨博士交谈时，他说甜食实际上是对牙齿疼痛的一种相对较弱的刺激。通常情况下，它们只在牙齿的内部牙髓及其神经已经发炎的情况下才引发疼痛。

That means your tooth was already in trouble before you bit into that candy corn — maybe because of a cavity or defective filling. So if your sweet tooth is causing you agony, you should probably go see a dentist.

这意味着在你咬玉米糖之前，你的牙齿就有问题了——也许是因为有蛀牙或有缺陷的填充物。因此，如果你的甜食让你感到痛苦的话，你可能应该去看牙医了。

Thanks for asking, and special thanks to Dr Kenneth Markowitz for his insight. If you want new episodes like this every day, just hit that little subscribe button and ring the notification bell!

感谢提问，特别感谢肯尼思·马科维茨博士在这方面提供的洞见。如果你想每天都看到新的科学秀的话，点击订阅按钮并打开通知即可！