Because the surfaces of the oral cavity are contiguous with those of the trachea and lower airway, pathogenic bacteria that colonize the oral cavity can be aspirated into the lower airway to cause infection.
There are four possible mechanisms of the presence of oral bacteria in the pathogenesis of respiratory infections:
- The oral cavity might be a reservoir for micro-organisms that contaminate saliva and is then aspirated into the lungs.
- Periodontal disease-associated enzymes in saliva may facilitate the adherence of respiratory pathogens in the mucosal surfaces.
- Periodontal disease-associated enzymes may destroy protective salivary pellicles, resulting in fewer nonspecific host defense mechanisms in high-risk patients.
- Cytokines and other molecules originating from untreated periodontal tissues are continuously released in saliva. Aspiration of these may alter respiratory epithelium and promote respiratory pathogen colonization.