What Does a Tooth, Cake, and an Ogre Have in Common?

I know you remember the scene where Shrek is explaining to Donkey that ogres are more than the frightening fairy tale lore they are known for.  “They have layers.  Onions have layers” explains Shrek huffily.  Donkey thinks for a minute and replies, “Not everybody likes onions.  CAKE!  Cake’s got layers.  Everybody likes cake.” Teeth, like cake, have layers. 

The white outer layer is called enamel.  Enamel is the second hardest compound in the world, preceded only by one of my other favorite things, diamonds!  Enamel protects the inner tooth layers from extreme temperature changes and normal wear and tear from chewing food.  Enamel is densely mineralized and is constantly responding to changes in its environment.

The middle layer is called dentin.  It is less mineralized than enamel and has a yellow hue.  Dentin is amazing because it can sense if a cavity is forming, and it will lay down more dentin to wall off the cavity and protect the nerve and blood supply inside the tooth.

The innermost layer is called the dental pulp which contains the nerve and blood supply to the tooth.  This is why a tooth can feel cold, heat, and pain.  If a cavity comes close to or reaches the pulp, it can allow a pathway for bacteria to proliferate and cause an infection.   

Each layer has its unique purpose.  It is amazing how a tooth can fight a cavity without a single action from us.  Whether it be a cake, an ogre, or a tooth, I am a fan of layers, and you should be too.  Now, please pass the cake!