While some periodontal disease may be as old as mankind itself, caries as a public health problem appeared with the development of flour and sugar mills, and the universal access to fermentable carbohydrates. As a consequence, during the last 500 years caries and periodontal disease have been the most common diseases afflicting the human mouth. Together, these two diseases have been responsible for untold pain and suffering, and for excessive destruction and loss of people's teeth. With improving social circumstances in most industrialised nations, increased availability and affordability of modern oral health care, and the promotion of conservative treatment concepts, the 20th century saw significant progress in eliminating pain and tooth loss. Moreover, during the last 50 years advances in the oral health sciences and in technology, have not only increased our understanding of the nature of these diseases and their causes, but also introduced and tested new approaches to their prevention.