Robert Neumann: a pioneer in periodontal flap surgery.

The contributions of Robert Neumann to the development of periodontal flap surgery are acknowledged. Neumann, born in 1882 was the leader of the Berlin group of dentists who advocated "the radical surgical treatment of pyorrhea". This approach was widely reported in European journals and sometimes referred to as the "Neumann operation". A biographical sketch and detailed descriptions of his operative procedures are included. Some of the historical background surrounding the priority question in the development of flap surgery is outlined.