Beavers don’t brush their teeth, and they don’t drink fluoridated water, but a new Northwestern University study reports beavers do have protection against tooth decay built into the chemical structure of their teeth: iron. This pigmented enamel, the researchers found, is both harder and more resistant to acid than regular enamel, including that treated with fluoride. This discovery is among others that could lead to a better understanding of human tooth decay, earlier detection of the disease and improving on current fluoride treatments.