Periodontitis and respiratory infections – exploring the oral–systemic link

Periodontitis is a chronic inflammatory disorder that has been recognized as a significant public health concern worldwide. An imbalance between the protective oral microbiota and numerous oral pathogens has been implicated in its pathogenesis. Periodontitis not only impacts an individual's oral health but also has systemic implications. The pathogenesis of periodontitis and these respiratory infections has been shown to be intricately linked. Numerous clinical research and animal studies have highlighted that the oral health of a population is closely related to their systemic health. It has been suggested that the periodontal pockets can act as a reservoir for oral pathogens, which can later migrate into the respiratory tract through aspiration or systemic circulation. This is a narrative review conducted after a wide literature search on databases such as PubMed, Cochrane, and Google Scholar with keywords including "Periodontitis," "Respiratory," "Infections," "Tuberculosis," 'COVID-19', "Pneumonia," "Asthma," and "COPD" published in the last 15 years. The cornerstone of this comprehensive review lies in deciphering the pathogenesis and epidemiology of periodontitis and how these periodontal bacteria contribute to respiratory infections through numerous biological mechanisms, inflammatory pathways, and the potential pathways of infection transmission. We also explore the empirical evidence through research studies supporting the periodontitis-respiratory infections link and also studies with conflicting or inconclusive results. By connecting the dots between this crucial oral-systemic link, we hope to uncover the gaps in the current research and find new avenues for developing cost-effective, targeted, transformative preventive and therapeutic strategies that will not only improve oral health but will also support respiratory health and help reduce the global burden of respiratory infections. Strengthening oral hygiene programs could reduce the burden of respiratory diseases, particularly in elderly and high-risk populations.