1760-1819

American dentist who, in 1790, invented the first dental drill. Greenwood was George Washington's dentist, an irony since Washington is famous for having had wooden dentures. Greenwood's invention of the dental drill helped dentistry to become a preventative practice because dentists could treat dental cavities by removing the diseased tooth, replacing it with silver, gold, or some other material. Previously, all that could be done was to pull the tooth when it became too painful or too rotten for the patient to tolerate.