This is the first of two articles providing an overall view of oral diseases and conditions, taking the oral cavity and its organs and tissues as integrated parts of the human body. This article provides an overview of three oral diseases and conditions that are associated directly with loss of tooth structure or loss of teeth and reviews their risk factors and preventive and treatment interventions. Two of these conditions, dental caries and periodontal diseases (or their sequelae), remain the main cause of tooth loss in the U.S. Prevention, treatment, and control of these diseases require many hours of training during dental education and many hours of treatment in dental practice. The profession has fragmented into specialties based on diseases; as a result, many dentists fail to see them as integral elements of the human experience. As primary care specialists, dentists must be reminded that they need to make prevention the first choice, provide the best treatment possible based on available scientific evidence, and keep informed of new advances in research while always remembering that the oral cavity is an integral part of the human body. The changes and trends observed in the epidemiology of oral diseases will demand new skills in our dental graduates. Future dental graduates may achieve a solid understanding of oral diseases at both the biological and population level by using oral tissues and saliva to diagnose systemic diseases, relying on medical facilities to order laboratory tests, and diagnosing and treating patients in close collaboration with their medical colleagues.