LONDON, UNITED KINGDOM - circa 1920: A new invention enabling to X- ray the inside of a patient's mouth has caused a stir at the Medical Exhibition, circa 1920 in London, United Kingdom. (Photo by Gamma-Keystone via Getty Images)
LONDON, UNITED KINGDOM - circa 1920: A new invention enabling to X- ray the inside of a patient's mouth has caused a stir at the Medical Exhibition, circa 1920 in London, United Kingdom. (Photo by Gamma-Keystone via Getty Images)