Baby teeth, where your cheesy grin comes from

Written by: Captain Skellett // December 2nd, 2009 // How Things Work, Science at Home

brushing teeth

Look into the screen and smile. Ever wondered where those teeth o’ yours came from? Whence did they sprout, sharp, strong and shiny from yon glistening gums? And why did ye have baby teeth which grew and survived a good ten years before being mercilessly replaced?

I am fortunate to still have all my teeth, I blessing I attribute to my penchant for Mojitos. Being full of lime juice, they protects me from the dreaded scurvy which has taken the teeth of many a mighty pirate.

Baby teeth start forming before there is a baby, back when you are just a little itty bitty embryo, about 6 weeks after conception. Their growth is under the control of a protein called Sonic Hedgehog, one of three proteins in the Hedgehog family, the other two being Desert Hedgehog and Indian Hedgehog. The hedgehogs are involved in a lot of minor jobs when the embryo is developing, like making limbs grow in the right place.

Sonic Hedgehog was originally discovered in our favourite developmental genetics model – the Drosophila the fruit fly. Proteins in Drosophila almost always have kick-ass names, in fact an inhibitor of this pathway is called Robotnikinin, after Sonic’s nemesis Dr. Robotnik. This time we kept the cool protein name for the same protein in humans, which makes a welcome change from the usual names like APK, JAK and JEK *snore*.

The road to teeth begins with a tooth bud, a group of cells that want to be a tooth when they grow up. They organise themselves into three groups, enamel (the stuff on the outside which protects the tooth from wear and tear), dental papilla (which forms dentin, the bulk of the tooth) and dental follicle (which becomes the important stuff that attaches the tooth to your mouth). The baby teeth form first, and the adult teeth start forming around 20 weeks after conception. You’ll have 20 baby teeth and 32 adult teeth during your lifetime.

Tooth diagram

Why have baby teeth at all? Well, a baby doesn’t have a very big mouth, and 32 adult size teeth might look a tad ridiculous. The baby teeth also pave the way for adult teeth, acting as a guide for where the next lot should erupt from. Plus we can’t overlook the fact that the tooth fairy needs ammunition for her secret underground tooth-driven missile factory. The $20 or so I got over the years is enough reason for me. If only we could lose more during those years, like the Southpark gang do in The Tooth Fairy Tats, I wouldn’t have to constantly hunt for treasure.

Sharks have about three rows of teeth and as soon as they lose one (which they do constantly), another one can slip in and take it’s place while a new one grows up behind it. An endless supply of teeth! The best we do is the four wisdom teeth which kick in when we’re 20 or so, which was pretty old back in cavemen days and would have been most excellent replacements for teeth lost in battle with zombies or gnawed away on dinosaur bones. Nowadays, with both zombies and dino’s in short supply, we mostly rip out our wisdom teeth and spend a week on heavy pain medication. I remember those days through a dim fog of jelly, yogurt and Boston Legal. Aye, those were the days.

Actually that sucked. I woke up from the anaesthetic like I’d been punched in the face, and had balls of cotton in my mouth. I groggily asked the nurse if I could take out the cotton, and she tsked and took it away, but soon my mouth was full of blood and I had to ask for more cotton and she tsked even MORE! And it felt so weird, and the stitches made me feel like a poorly made doll, and I looked mostly like a chipmunk with bruised cheeks. It was not an attractive time. Not even the jelly made it worthwhile, so no more losing teeth for me. Pass me that Mojito!

Captain Skellett

I be Captain Skellett. Me blog started in April 2009 when I was working full time and didn’t get a chance to talk science. Now I have changed jobs and talk science all the time, but that doesn’t stop me blogging. More About Captain Skellett   Google

   

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