Everyone knows the story of George Washington's wooden teeth. Except they weren't wooden. They were made from something considerably more exotic: hippopotamus ivory.

By the time Washington became America's first president in 1789, he had only one natural tooth left. He was 57 years old and had been struggling with tooth decay and painful dental problems since his twenties.

His dentist, John Greenwood, fashioned a set of dentures using hippopotamus ivory, human teeth, gold springs and brass screws. He even left a space for Washington's sole surviving tooth, believing that a natural tooth should be preserved whenever possible.

Over the years, Washington wore several sets of dentures made from an assortment of materials, including walrus ivory, cow and horse teeth, human teeth and various metals.

The human teeth have a darker history. In 1784, Washington's financial records document a payment for nine teeth obtained from enslaved people at Mount Vernon. The teeth went to a visiting dentist, Jean Pierre Le Mayeur. Whether they were used in Washington's dentures remains unknown.

Washington's dentures required frequent repairs and adjustments. The ivory could become stained and develop fine cracks, giving it an appearance resembling wood. Historians believe this may explain how the famous wooden-teeth myth began.

Washington's only surviving complete set of dentures is preserved at Mount Vernon, where visitors can see just how inventive, and uncomfortable, eighteenth-century dentistry could be.