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

牙本质非常硬，但与牙釉质不同，它是多孔的。

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

如果你的牙釉质被磨掉了，你的牙本质和它的管就会暴露出来。

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

一些变成成牙质细胞——这些细胞形成牙质，坚硬的纤维牙质，是牙齿的核心部分。

But decay is reversible until it reaches the dentin.

可是，在牙本质遭到腐蚀之前，腐蚀随都会发生。

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

有，甜味的东西和暴露的牙本质的碰撞就会导致疼。

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。

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质，这是牙齿成分中的绝大部分组成物质。

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

牙骨质和牙本质脱矿可以在pH6.2到6。8的范围内发生。

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质的成牙本质细胞。

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——牙本质和珐琅质——构成的。

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

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

And the dentin acts as the selectively permeable barrier.

而牙本质则作为选择性渗透的屏障。

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质外部的零食含有高度集中的糖分子形式的溶质。

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

牙本质的微管中的液体冲出牙齿，冲向糖那里。

But if the damage extends beyond the dentin, the bacterial invasion progresses causing excruciating pain as the nerves become exposed.

在此阶段，逐渐扩大的 蛀牙区并不会产生疼，但若损害扩大 超出了牙本质的范围持续侵入的细菌。

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

酸性物质会先腐蚀掉牙冠表层的珐琅质。珐琅质所包覆的便是牙本质。

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质以及内层坚硬、紧密的骨组织构成，这些骨组织被称为牙质。

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

而且，和我们一样，里面有一个浆状部分，里面有一些产生牙本质的细胞。

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。

And they fixed the dentin the door, I just need to go and pick it up tomorrow.

他们把门上的牙本质修好了， 我只需要明天去取。