Epidemiology is the study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems. The term study includes both surveillance, whose purpose is to monitor aspects of disease occurrence and spread that are pertinent to effective control, and epidemiologic research, whose goal is to harvest valid and precise information about the causes, preventions, and treatments for disease. The term disease refers to a broad array of health-related states and events including diseases, injuries, disabilities, and death.

Periodontitis is defined as an inflammatory disease of supporting tissues of the teeth caused by specific microorganisms or group of specific microorganisms, resulting in progressive destruction of periodontal ligament and alveolar bone with pocket formation, recession or both. Periodontitis is associated with the accumulation of plaque and calculus and has a slow to moderate rate of disease progression, but periods of more rapid destruction may be observed. Increase in the rate of disease progression may be caused by the impact of local, systemic, or environmental factors that may influence...