The human oral cavity contains a number of different habitats, including teeth, tongue, cheeks, hard and soft palates, which are colonized by bacteria. The oral microbiome is comprised of more than 600 identified species, and probably many more remain still unnamed.
Some taking up residence on the mouth lining (red) within days after birth. Harmful species form biofilms, like the plaque that encourages tooth decay, or colonize the crevices between teeth and gums, causing periodontal disease. Oral probiotics designed to boost the population of species that outcompete pathogenic ones could help prevent or reverse dental disease.