Hammaspeikko

Hammaspeikko, Finnish for "tooth troll", is a metaphorical device for explaining tooth decay (caries) to children, akin to the Tooth Fairy. Eating candy lures tooth trolls, which drill holes into teeth and look scary. Brushing the teeth scares them away. It is not clear whether the tooth troll is a single entity, or if there are many.

Similar spirits were believed to cause toothache in the old Finnish religion.