Toothworms don't exist. But from ancient times up through sometime in the Middle Ages, in many different areas of the world, toothworms were thought to be the cause of toothaches.

It was thought that an imbalance in the spiritual forces in your body could give rise to a demon inhabiting any organ or body part, including a tooth. Or it could have been inflicted upon you as a punishment or a curse. In any case, toothworms were thought to wiggle around in a tooth and cause pain, or might eat the tooth from within like a bad apple. It is thought that this myth of toothworms may have arisen from the fact that the pulp inside teeth looks a bit like worms.

There were many ways to get rid of toothworms. Some of them worked more often than others. In Ancient Rome, it was thought that the worms disliked the smell of mint leaves, so chewing on them could kill or disable the worm or even keep them from ever inhabiting your teeth. (Obviously, mint is still used in toothpaste and other dental products for a similar reason.) You could boil spiders alive in a pot of oil with other rank substances and then swish with the concoction for two minutes. Or you could build a metal coat around the tooth, bore a hole in it, and pour a strong acid in. If these things worked, it was only because the disturbing processes killed the nerves in the tooth.

Another common way people tried to rid themselves of toothworms was to exorcise the demons. Most often this was attempted by casting the toothworm demon out into a tree. There were several ways to do this, some of which were quite nasty; such as jamming a nail into the tooth or gum until blood was on its tip, then driving the nail into a tree while chanting a prescribed rhyme, hoping that the toothworm would be moved into the tree.

This was once the up-to-date, cutting-edge medical advice you would receive from your "dentist."