Dentin is pretty hard, but unlike enamel, it's porous.

牙本非常硬，但与牙釉不同，它是多孔的。

If your enamel is worn away, your dentin and its tubules can be exposed.

如果你的牙釉被磨掉了，你的牙本和它的小管就会暴露。

Some become odontoblasts — these cells make dentin, the tough, fibrous core of the tooth.

一些变成成牙细胞——这些细胞形成牙，坚硬的纤维牙，是牙齿的核心部分。

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

牙本层的损害继续蔓延，缺损会延伸到牙髓。

But decay is reversible until it reaches the dentin.

可是，在牙本遭到腐蚀之前，腐蚀随时都会发生。

And sometimes, the combination of sweet stuff and exposed dentin equals pain.

有时，甜味的东西和暴露的牙本的碰撞就会导致疼痛。

The demineralization of cementum and dentin can occur in a pH range of 6.2-6.8.

牙骨和牙本可以在pH6.2到6。8的范围内发生。

These growth factors cue stem cells to generate dentin, the bonelike substance that teeth are mostly made of.

这些生长因子会提示干细胞修复牙本，这是牙齿成分中的绝大部分组成物。

Odontoblasts use a more complex process, but unlike ameloblasts, they stick around, continuing to secrete dentin throughout your life.

成牙本细胞则需要更复杂的过程，但与成釉细胞不同，它们不会消失，会在我们有生之年继续分泌牙本。

They're false in that they're not made of what our teeth are made of: dentin and enamel.

“伪牙”不是由我们牙齿的材料——牙本和珐琅——构成的。

And the dentin acts as the selectively permeable barrier.

而牙本则作为选择性渗透的屏障。

This amazing structure is created by two types of cells: ameloblasts that secrete enamel and odontoblasts that secrete dentin.

分泌牙釉的成釉细胞以及分泌牙本的成牙本细胞。

That snack touching the outside of your exposed dentin has highly concentrated solutes in the form of sugar molecules.

那些接触到你暴露的牙本外部的零食含有高度集中的糖分子形式的溶。

The fluid in your dentin's microtubules rushes out of your tooth towards the sugar.

牙本的微管中的液体冲牙齿，冲向糖那里。

First, the acid eats away the very hard outer layer of yourtooth, called the enamel. Inside the enamel is the dentin.

酸性物会先腐蚀掉牙冠表层的珐琅。珐琅所包覆的便是牙本。

They are made up of an outer layer of enamel, and an inner layer of hard, dense, bony tissue called dentin.

它们的牙齿由外层的牙釉以及内层坚硬、紧密的骨组织构成，这些骨组织被称为牙。

And, like us, the inside has a pulpy part with some cells that produce dentin.

而且，像我们一样，内部有一个浆状部分，其中一些细胞会产生牙本。

Some become odontoblasts – these cells make dentin, the tough, fibrous core of the tooth.

一些变成成牙本细胞——这些细胞形成牙本，即牙齿坚韧的纤维核心。

Gradually, acid wears down a pathway for bacteria into the tooth's secondary layer called the dentin.

渐渐地，酸蚀一条通道，让细菌侵入牙齿的第二层——牙本。

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

它由三层组成：牙釉、牙本和牙髓。