The Role of Proinflammatory Cytokines in Temporomandibular Disorders: A Systematic Review.

Temporomandibular disorders (TMDs) are the prevalent causes of orofacial pain and dysfunction of the temporomandibular joint (TMJ) and masticatory muscles. Previous studies have revealed that proinflammatory cytokines play a key role in promoting inflammation, pain, and degeneration within the TMJ. In this context, the present systematic review synthesizes current evidence on various cytokines involved in the pathophysiology of TMDs and evaluates their associations with clinical signs and structural TMJ damage. A PRISMA-guided search (PROSPERO: CRD420251163290) was conducted in PubMed/MEDLINE, Embase, Scopus, and the Cochrane Library to identify human-based, in vivo, and in vitro studies (January 2014 to September 2025) that assessed the roles of proinflammatory cytokines in TMDs. The following data were extracted from the identified studies: cytokine profiles, sampling methods, clinical outcomes, and TMJ structural changes. Study quality and risk of bias were systematically evaluated. A total of 15 studies (clinical, animal, and mechanistic) were included in the review. Tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-17 (IL-17) consistently emerged as the major contributors to synovitis, cartilage degradation, nociceptive sensitization, and bone resorption. Human studies showed that high levels of TNF-α, IL-1β, and IL-6 and chemokines such as C-C motif chemokine ligand 2 (CCL2) and regulated on activation, normal T-cell expressed and secreted (RANTES) were associated with TMJ pain, restricted mandibular motion, crepitus, malocclusion, and erosive changes on imaging. An increased ratio of TNF to soluble TNF receptor in synovial fluid correlated with both pain and condylar damage, suggesting that loss of cytokine control contributes to progressive joint destruction. TMDs, particularly inflammatory and degenerative subtypes, are cytokine-driven pathologies rather than purely mechanical disorders. TNF-α, IL-1β, and IL-6 are the promising candidate biomarkers of local inflammation and structural joint pathology. Standardized longitudinal studies are required to validate cytokine-based diagnostics and develop anti-cytokine therapeutics.