This review argues that periodontitis-driven oral microbiota dysbiosis can seed the gut and, through systemic inflammation, altered neurotransmitter metabolism, and microbial metabolites (e.g., SCFAs, LPS) affecting the blood–brain barrier, influence brain function and contribute to depression and…

Relevance to Parkinson's lies in highlighted, potentially actionable pathways (oral-to-gut microbial translocation, inflammation, BBB and metabolite-mediated neural effects) that could yield novel intervention or biomarker avenues, though the paper is a broad review with limited mechanistic…

Depression has a high global prevalence and is a common mental-emotional disorder that severely jeopardizes human health. However, current treatment options remain limited, necessitating the exploration of novel pathological mechanisms and intervention targets. Recent studies indicate that periodontitis, as a prevalent chronic oral infectious disease, not only causes local microbial dysbiosis and inflammatory responses but may also influence central nervous system function through the "oral-gut-brain axis," thereby contributing to the pathogenesis and progression of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis, as well as neuropsychiatric disorders like depression. This review systematically examines the impact of periodontitis on oral microbiota and its subsequent translocation and colonization in the gut microbiota through pathways including swallowing and bloodstream circulation, ultimately leading to structural and functional dysregulation of the gut microbiota. The interaction between oral and gut microbiota can influence the brain through the "gut-brain axis," including disturbances in neurotransmitter metabolism, activation of systemic immune responses, and direct or indirect effects of bacterial metabolites (such as short-chain fatty acids, lipopolysaccharides, etc.) on the blood-brain barrier and neural function. This suggests that periodontal health management may serve as a novel strategy for the prevention and treatment of depression. This article further summarizes the potential of oral interventions for periodontitis (such as mechanical debridement and local/systemic antimicrobial therapy), microbiota modulation methods (such as probiotics, prebiotics, and fecal microbiota transplantation), and multidisciplinary collaborative comprehensive treatment strategies in improving microbial homeostasis and alleviating depressive symptoms. Finally, this paper points out the current research limitations in mechanistic details, causal relationships, and clinical translation, while envisioning the feasibility and prospects of developing personalized treatment strategies by targeting the "oral-gut-brain axis" in the future.