Aztec dentists would mix iron filings, water and navel lint – then bake the mixture in a kiln to create a powerful magnetic dental bonding agent. This mixture was then inserted into cavities in order to seal them. Patients not only reported relief from cavities, but also the development of a keen sense of direction.
Please note: Some dental "facts" are not easily verifiable (like this one) and are principally provided for entertainment purposes!