Gut–Brain–Jaw Axis: The Emerging Role of Gut Microbiota in Temporomandibular Disorders and Orofacial Pain—A Narrative Review

BACKGROUND: Temporomandibular disorders (TMDs) and chronic orofacial pain are multifactorial conditions influenced by complex neurobiological and systemic mechanisms. Recent findings emphasise the gut-brain axis as a central modulator of pain, neuroinflammation, and immune signalling. Nevertheless, the role of the gut microbiota in TMD pathogenesis and oral rehabilitation remains insufficiently characterised. METHODS: A structured literature search was conducted in PubMed/MEDLINE, Scopus, and Web of Science up to December 2024 using combinations of keywords including "gut microbiota," "temporomandibular disorder," and "orofacial pain." Eligible publications included clinical studies, systematic and narrative reviews, meta-analyses, and theoretical works addressing microbiota-pain relationships. RESULTS: Recent Mendelian randomization studies reveal causal associations between specific bacterial genera and TMD risk. Experimental models demonstrate that gut dysbiosis exacerbates temporomandibular joint inflammation and neuroinflammatory responses, while restoring microbial balance through probiotics or faecal microbiota transplantation alleviates pain hypersensitivity. Mechanistic studies suggest that microbial metabolites such as short-chain fatty acids, GABA, and serotonin modulate trigeminal pain pathways via vagal and immune signalling. CONCLUSION: Current evidence supports a bidirectional gut-brain-jaw communication system influencing both peripheral and central pain mechanisms. Incorporating microbiome-targeted approaches-such as dietary modulation, probiotics, and microbial therapy-may enhance TMD management and promote a more holistic, personalised model of oral rehabilitation.