The tooth worm

We all know oral hygiene is important, and the above picture illustrates why it's so important.  Tooth worm eggs get stuck between the teeth, where they hatch out into little worms like this and burrow into the teeth, unless they're removed by proper brushing and flossing.  This specimen, as you can see, has completely eaten away the tooth it was found in.

Remember to floss folks - you don't want one of these little sods gnawing on your molars.

Before the development of germ theory, it was commonly believed that tooth decay was caused by tiny worms, imaginatively known as "tooth worms".  The tooth worm myth has a lot of appeal for me, because it's actually a fairly good attempt at explaining tooth cavities given the science available at the time.

As early as 5000 BC people were observing the little holes made by tooth decay and hypothesizing that microscopic worms, perhaps similar to woodworm, could be the culprit.  They weren't able to test this hypothesis, since the microscope had yet to be invented, but it was still a reasonable hypothesis.  It wasn't too far away from the truth either, when you consider that bacteria are tiny little creatures.