Karius and Baktus

The main characters are Karius (black haired) and Bactus (red haired). Their names are puns on Caries and Bacteria, and they are two small “tooth trolls” that live inside cavities in the teeth of a boy named Jens. They have a very good life, especially when Jens eats white bread with syrup and fails to brush his teeth afterwards.
Eventually their homes are destroyed by the work of a dentist and they are rinsed out of Jens’ mouth through proper dental care.