This tooth-covered hat belonged to a traveling tooth-puller in the early 19th century, and you can even play with a 3D model of it. From Southward Council in London's Cuming Collection:
This cap belonged to a street "dentist" or tooth puller. It is made of brown velvet and felt, and decorated with approximately 88 decayed human teeth, once belonging to his patients. The teeth have been drilled and attached with twine. Wearing a cap like this was supposed to imply the "magician" aspect of the dentists work. As teeth pulling was painful and risky and done without anaesthetic, people needed to have some faith in the "dentist", even if it was only the evidence, worn on the cap, that he had successfully plied his trade.
You can see more images and information about this object on our website.
Here's a photo of the tooth-covered hat on Instagram. I'm chuckling at the thought of going to the dentist's office in today's time and seeing the dentist casually wearing this hat. Something about it makes me question the traveling tooth-puller's motives behind his career…
Previously: Clown themed tooth advertisement from 1887 claims dentist can remove up to 28 teeth in one minute