Oral bacterial interactions in periodontal health and disease

Periodontal disease and dental caries are infectious diseases resulting from the interactions of oral bacteria residing dental plaque and the host. The indigenous bacteria residing dental plaque are thought to be a relatively stable community of high species diversity, which may vary from site to site throughout the mouth. When this stability is disturbed, due to many host-specific and environmental factors, in addition to oral hygiene and dietary habits which the subjects can regulate, other less benign bacteria may colonize the oral cavity and the bacteria that are normally present in very low number may increase to cause oral diseases. The aim of this review paper is to highlight the oral microbial ecosystems in oral health and disease and to investigate the ecological changes that shift the indigenous bacteria residing dental plaque to be increased in number and cause oral diseases. The paper reviews the different oral ecosystems involving a variety of microbes and the balance between the growth of those microbes and the host health. In addition, the paper discusses the development of periodontal disease and dental caries according to plaque hypotheses