Dental biofilms in health and disease

Abstract

The mouth is colonised by a diverse range of microorganisms (the oral microbiota) that exist as biofilms on dental and mucosal surfaces. This microbiota is natural, enjoys a synergistic relationship with their host and confers benefits that are important to the well-being of that individual. On occasions, however, this synergistic relationship breaks down, and disease can occur (dysbiosis). In people who regularly consume fermentable carbohydrates, their dental biofilms spend longer periods at a low pH, and this selects for bacteria with a phenotype that is adapted for growth under these conditions, such as mutans streptococci, bifidobacteria and lactobacilli. Numerous clinical studies of people of various ages and in different countries have found increased proportions of these acidogenic and acidtolerating bacteria in biofilms overlaying caries lesions compared to sound enamel. However, this relationship is not absolute, and other bacteria can be implicated. An ‘Ecological Plaque Hypothesis’ has been proposed to explain the relationship between the microbiota and the host in health and disease. A key feature of this hypothesis is that caries can be prevented not just by targeting the causative bacteria but also by interfering with the factors that cause the dysbiosis.