Required to only practice dentistry in California under one’s actual name, Edgar Rudolph Randolph Parker legally changed it to his nickname Painless Parker. He was controversial mainly for his advertising and his operation as a corporate dentist (multiple offices with his name but employing other dentists to do the work). His Los Angeles office opened in 1912 and was still there under his name in 1939.
Learn more at http://www.bbc.com/news/magazine-31704287 or download this 2015 article from the American Journal of Orthodontics and Dentofacial Orthopedics: go to http://www.ajodo.org/action/showMultipleAbstracts , then search for “Painless Parker” 2015 . Apparently it can’t be linked directly.