With all of the advertising today about teeth whiteners, surely this is a relatively new miracle of modern science. So just how new? Try the Middle Ages. The problem with having the treatment in those unenlightened years was that your neighborhood barber-surgeon would file down your teeth and then soak them in a concentrated solution of nitric acid. The procedure would turn them pearly white, all right, but it also destroyed the tooth enamel and led to massive tooth decay.