he identification of dental caries and periodontal disease as infectious diseases by the 1960s heralded the first revolution in dental research. We are now in the midst of a second revolution where oral health research is taking its place in an ever-changing scientific world driven by the need to understand health and disease through the intricate interactions of human behavior, environment, and biology.

What is emerging is a biology of complexity as we approach the 21st century. Infectious diseases that took the young lives of our ancestors have been replaced with chronic and degenerative diseases that victimize us in our old age. These changing patterns of disease and demographics now challenge science to shift its focus from its success in extending life to the challenge of improving the quality of life from before birth until death. To reach this goal, science cannot look at a single molecule, or cell, or system in isolation, but rather at how these act in concert with behavioral, environmental, and genetic influences to heighten or minimize one's risk of disease.

Once the grist of science fiction, today a human genetic book is in process that will eventually decode each of the 100,000 genes that comprise the human genome. We now know that virtually all human diseases have a genetic component, including inherited, infectious, neoplastic, and chronic disabling craniofacial-oral-dental diseases and disorders. We are learning about inherited susceptibility genes that predispose to disorders such as diabetes and severe periodontitis, and we are finding that some chronic diseases may share major genetic determinants and, perhaps, diagnostic and therapeutic approaches as well.

The oral and systemic health connection, then, lies in the many factors they hold in common. Fully integrated into the realm of biomedical research, oral health science is not only expanding our understanding of craniofacial-oral-dental diseases and disorders, but also is broadening the critical knowledge base of fundamental disease processes.