The Oral Microbiome: Composition, Dysbiosis, and Its Role in Systemic Health and Disease

This chapter presents a comprehensive account of the oral microbiome in health and disease, drawing on advances in next-generation sequencing and multi-omic approaches to characterise the complex polymicrobial communities inhabiting distinct oral niches. It reviews the mechanisms by which oral dysbiosis contributes to the aetiopathogenesis of dental caries, periodontitis, and oral mucosal diseases, and examines the growing body of evidence linking the oral microbiome to systemic conditions including cardiovascular disease, diabetes mellitus, rheumatoid arthritis, adverse pregnancy outcomes, and Alzheimer’s disease. The chapter critically assesses microbiome-targeted therapeutic strategies and the potential of microbiome modulation — including probiotics, prebiotics, and precision antimicrobials — in oral health promotion.