"Is the enamel on our bathtub the same stuff that's on my teeth?"

One night as she was splashing around in her bright pink bath water The Four-Year-Old asked me what the tub was made of. As it turns out, the bathtub she uses is one of those old timey clawfoot jobs made of cast iron with a porcelain enamel coating. When I told her this, she immediately perked up and asked, "Is the enamel on our bathtub the same stuff that's on my teeth?"

Considering that the enamel that's used on our bathtub is made of powdered glass, I was happy to report that the answer to her question is no. The stuff on her tub merely shares a name with the stuff on her teeth.

Of course, as my husband helpfully pointed out, to be certain that two things aren't the same, you really have to know what both are made of.  I had merely assumed that the two enamels couldn't be the same based on a conjecture that our teeth weren't made of powdered glass fused onto metal at a high temperature. Without knowing for certain what tooth enamel was made of, I couldn't state that the enamel on our bathtub was not in fact the same as the enamel on our teeth. Or so he claimed.

Hearing this, The Four-Year-Old perked up again. (After all, her bathtub is really cool. "It has paws and everything, Mommyo.")

So I asked my husband, "What is tooth enamel made of?"

My husband, the Harvard-trained ICU physician, just shrugged. "I don't know. We only spent one day on teeth in medical school, and I only have so much room in my brain. Why don't you Ask the iPhone?"

(Well, I suppose to remember all those things about how to run life support something had to go.)

As it turns out, tooth enamel is mostly calcium. Wikipedia goes into great detail on the precise composition of those calcium crystals, but since the entry also includes lots of photos of teeth (and as I have since learned, looking at closeups of teeth makes my gums itch), I'll let you read the entry on tooth enamel for yourself.

Although Caterpickles appears only once a week on the Patch, you can find a new post every day of the week at caterpickles.com. C'mon over. So far this week, we've answered timeless mysteries, such as "what is cream of tartar?", "how do they make cooking oil?" and played the animal, vegetable, or mineral game with sand dollars.

Or if books are more your thing, check out my new blog, BostonWriters. It's all about books and the process of writing them. This week on BostonWriters, we look at The Lady in Red, a non-fiction account of a scandal that rocked Regency England, and Read Me Another Story, a collection of children's stories targeted for The Four-Year-Old.