What Causes Periodontitis?

Periodontitis is a chronic inflammatory disease that affects the supporting structures of the teeth—including the gingiva, periodontal ligament, and alveolar bone. It typically arises from the progressive accumulation of dental plaque, a biofilm composed of diverse bacterial species that adheres to tooth surfaces and subgingival areas.

The primary etiological factor is dysbiosis within the oral microbiome: an imbalance in the microbial community where pathogenic bacteria—such as Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola—overgrow and trigger a sustained host immune-inflammatory response. This leads to gingival inflammation (gingivitis), which, if left untreated, can advance to periodontitis with irreversible loss of connective tissue attachment and bone resorption.

While microbial biofilm is necessary for disease initiation, several modifiable and non-modifiable risk factors influence susceptibility and progression. These include smoking, uncontrolled diabetes mellitus, genetic predisposition, hormonal fluctuations, certain medications (e.g., those causing xerostomia or gingival hyperplasia), and systemic conditions associated with immunosuppression or chronic inflammation.

Importantly, periodontitis is not merely a localized oral condition—it is increasingly recognized as a bidirectional contributor to systemic health. Epidemiological and mechanistic evidence links severe periodontitis with elevated risks of cardiovascular disease, adverse pregnancy outcomes, rheumatoid arthritis, and poor glycemic control in diabetic patients.