And this part of your tooth is super sensitive.

牙髓部分非常敏。

And that flow stimulates the nerves in the pulp of your tooth, causing shooting pain.

流动刺激了你的牙髓中的神经，导致射痛。

If destruction continues into the dentin layer, then the caries lesion enlarges towards the pulp.

牙本质层的损害继续蔓延，缺损会延伸到牙髓。

It contains microscopic, fluid-filled tubules that run from the pulp to the underside of the enamel.

它包含微小的、充满液体的小管，从牙髓一直到牙釉质下层。

Eventually, the bacteria penetrate into the pulp, causing irritation and damage to the nerves.

最终细菌侵犯牙髓，对神经产生刺激损害。

From there, they enter the soft center of the tooth, called the pulp, where they provide nutrition and sensation.

自此进入牙齿柔软的中心：牙髓，它可以提供营养，产生觉。

Usually, they only trigger pain when the tooth's inner pulp and its nerves are already inflamed.

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。

These kinds of toothaches are often infections in the pulp of the tooth.

些类型的牙痛通常是牙髓。

So in order to protect the delicate pulp inside of your teeth, you have take really good care of the outside.

所以，为了保护牙齿内部脆弱的牙髓，你必须好好保护牙齿外层。

We call this pulpitis, although there are different strains of this.

我们称之为牙髓炎， 尽管它有不同的类。

And it’s made up of three layers: the enamel, the dentin, and the pulp.

它由三层组成：牙釉质、牙本质和牙髓。

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.

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。

But the cavity doesn't really start to hurt until it gets through the dentin to the soft pulp. That'swhen you get a toothache.

但是，要等到酸性物质通过牙本质，开始腐蚀牙髓了才会对牙齿造成本质的伤害。个时候牙齿也就开始疼起来了。

These tubules are important for sensory nerves as well, which use them to travel through the dentin from the pulp to the dentin-enamel junction.

牙本质中的小管对觉神经也很重要，因为觉神经可以通过它们从牙髓到达本釉质交界处。

The outer wall of the pulp, contains odontoblasts which are cells that secrete a bonelike substance called dentin, which is filled with protein and minerals.

牙髓外层有成牙质细胞，它们可以分泌一叫牙本质的骨样组织，其中充满了蛋白质和矿物质。

And the pulp of your teeth can replenish proteins in the dentin, though not the enamel—so it's unclear whether these effects would cause permanent damage in real, living teeth.

牙髓可以补充牙本质中的蛋白质，但不能补充牙釉质——因此尚不清楚些作用是否会对真正的活牙造成永久性损伤。

Just below that tough outer layer, there's another layer called dentin that's not as hard. And below that, there's the inner layer of the tooth, called the pulp, which has blood vessels and nerves inside it.

在层坚硬的外层下，还有另一层物质叫做牙本质，它没有牙釉质坚硬。牙本质下面是牙齿的内层，叫做牙髓，里面有血管和神经。