Microbial dysbiosis: The root cause of periodontal disease.

Graphical abstract: A eubiotic oral microbial community resembles a house of cards in its highly regulated and precise assembly, structural complexity, and co-operativity between the resident members and the oral immuno-inflammatory apparatus. Change in one or more of these organizing principles can result in expansion of selected resident species (pathobiont bloom), loss of key species that regulate nutrient flow in the system (keystone species), or a general increase in diversity because of random changes in species abundances. These events, either in isolation or in combination, cause this house of cards to collapse into a state of dysbiosis.