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，甜的东西和暴露的牙本的碰撞就会导致疼痛。

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

那些接触到你暴露的牙本外的零食含有高度集中的糖分子形式的溶。

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，坚硬的纤维牙，是牙齿的分。

And the dentin acts as the selectively permeable barrier.

而牙本则作为择性渗透的屏障。

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。

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分组成物。

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出牙齿，冲向糖那里。

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

牙骨和牙本脱矿可以在pH6.2到6。8的范围内发生。

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。

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。

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。

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痛，但若损害扩大 超出了牙本的范围持续侵入的细菌。

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

而且，和我们一样，里面有一个浆状分，里面有一些产生牙本的细胞。

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

他们把门上的牙本修好了， 我只需要明天去取。

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 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。

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