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Kathryn Ryan talks to retired dentist Harvey Brown, about his biography of the dental pioneer Sir John Walsh. As Dean of the Faculty of Dentistry at Otago for 25 years until 1971, Sir John changed the education and practice of dentists, and was a leader in the development of the modern high-speed dental drill. He was also an advocate of adding fluoride to drinking water and introducing a sugar tax way back in the 1950s.