Background: The human oral cavity harbours over 700 microbial species constituting one of the most complex and diverse microbiomes in the body. Disruption of this community, termed oral dysbiosis, is central to the pathogenesis of periodontal disease. Accumulating evidence demonstrates that periodontitis is not merely a localised infection but a systemic inflammatory condition with wide-ranging implications for chronic non-communicable diseases.

Objectives: This review critically appraises the mechanistic and epidemiological evidence linking oral microbiota dysbiosis and periodontal disease to cardiovascular disease, type 2 diabetes mellitus, rheumatoid arthritis, adverse pregnancy outcomes, Alzheimer’s disease, and colorectal cancer, while evaluating pharmacological and non-pharmacological management strategies.

Methods: A structured narrative review of peer-reviewed literature published from 2020 to 2025 was conducted using PubMed, Scopus, and Web of Science databases.

Results: The keystone periodontal pathogen Porphyromonas gingivalis orchestrates immune subversion via complement manipulation and gingipain activity, enabling bacteraemia and systemic dissemination of pro-inflammatory mediators including IL-1β, TNF-α, and CRP. Bidirectional relationships exist between periodontitis and T2DM, while molecular mimicry underpins the oral-RA axis. Emerging data implicates P. gingivalis gingipains in neuroinflammation relevant to Alzheimer’s disease.

 Conclusion: Periodontal treatment, including scaling and root planning, demonstrably reduces systemic inflammatory markers and improves glycaemic control, supporting the incorporation of oral health management into multidisciplinary chronic disease care. Future research should prioritise mechanistic causal studies and multicentre randomised controlled trials.