(1836–1915) Greene Vardiman Black is considered to be one of the founders of modern dentistry. He began studying medicine at the age of 17 and in 1857 met Dr. J. C. Speer, who taught him the practice of dentistry. He researched many aspects of dentistry, including the composition of dental amalgam and the cause of dental fluorosis. He established the basic principles of tooth preparation including the idea of ‘extension for prevention’, which has only recently been superseded, largely due to the advent of adhesive restoratives. He devised a caries classification system which is still in use today (see Black's classification of cavities). He was appointed professor of pathology in the Chicago College of Dental Surgery. He was awarded a DDS by Missouri Dental School in 1877 and later an MD from Chicago Medical School. In 1897 he became the first dean of Northwestern University Dental School.