But decay is reversible until it reaches the dentin.

可是，在牙遭到腐蚀之前，腐蚀随时都会发生。

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

牙非常，但与牙釉不同，它是多孔。

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

如果你牙釉被磨掉了，你牙和它小管就会暴露出来。

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

一些变成成牙细胞——这些细胞形成牙，坚维牙，是牙齿核心部分。

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

有时，甜味东西和暴露牙碰撞就会导致疼痛。

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

那些接触到你暴露牙外部零食含有高度集中糖分子形式溶。

And the dentin acts as the selectively permeable barrier.

而牙则作为选择性渗透屏障。

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

牙层损害继续蔓延，缺损会延伸到牙髓。

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

牙骨和牙脱矿可以在pH6.2到6。8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，这是牙齿成分中绝大部分组成物。

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珐琅。珐琅所包覆便是牙。

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

分泌牙釉成釉细胞以及分泌牙成牙细胞。

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

牙微管中液体冲出牙齿，冲向糖那里。

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

“伪牙”不是由我们牙齿材料——牙和珐琅——构成。

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

成牙细胞则需要更复杂过程，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。

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 蛀牙区并不会产生疼痛，但若损害扩大 超出了牙范围持续侵入细菌。

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，里面有一些产生牙细胞。

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

他们把门上牙修好了， 我只需要明天去取。

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

它们牙齿由外层牙釉以及内层坚、紧密骨组织构成，这些骨组织被称为牙。

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

它由三层组成：牙釉、牙和牙髓。