Background: Multiple sclerosis and periodontal disease are chronic inflammatory conditions that may share immune-mediated mechanisms, including cytokine activation, oral dysbiosis, oxidative stress, and systemic inflammatory burden. This systematic review aimed to synthesize recent evidence on common inflammatory pathways linking periodontal disease and multiple sclerosis. Methods: The review was conducted according to PRISMA 2020 guidelines. PubMed/MEDLINE, Cochrane Library, and Scopus were searched for English-language studies published between June 2020 and June 2026. Eligible studies addressed multiple sclerosis, periodontal disease, oral microbiome alterations, systemic inflammation, or neuroinflammatory outcomes. Study selection and data extraction were performed independently by three reviewers. Risk of bias was assessed using AMSTAR 2, the Newcastle-Ottawa Scale, and the Joanna Briggs Institute checklist, according to study design. Results: Seventeen studies were included in the qualitative synthesis. The main shared mechanisms were cytokine-mediated inflammation involving TNF-α, IL-1β, IL-6, and IL-17; NF-κB signaling; Th17/Treg imbalance; blood-brain barrier disruption; oxidative stress; matrix metalloproteinase activity; complement activation; and oral-gut-brain axis dysregulation. The evidence suggests that periodontal inflammation may contribute to systemic immune activation and may amplify neuroinflammatory processes in multiple sclerosis. Conclusions: Current evidence supports a biologically possible association between periodontal disease and multiple sclerosis through shared inflammatory and microbial pathways. However, causality remains unproven, and further longitudinal and interventional studies are needed.
