Molecular and omics-related biomarkers associated with bruxism in adults: a systematic review with functional...

Bruxism is a heterogeneous jaw-muscle activity with multifactorial neurobiological underpinnings, and adult evidence on molecular and omics-related biomarkers remains fragmented. This systematic review with functional meta-synthesis and exploratory meta-analysis aimed to identify, critically appraise, and synthesize molecular and omics-related biomarkers associated with bruxism in adults. PubMed/MEDLINE, Scopus, and Embase were searched from inception to March 2026, without language restrictions. Eligible studies included adult human participants with bruxism and extractable biomarker comparisons. Data extraction and risk-of-bias assessment were performed independently by two reviewers using design-specific tools and complementary criteria for genetic, omics, and genomic causal-inference studies. Narrative synthesis and functional meta-synthesis were the primary analytic approaches; random-effects meta-analysis was performed for comparable salivary cortisol studies. Ten studies were included. Four biological domains were identified: neuroendocrine stress-related signaling, genetic susceptibility or genomic liability, inflammation and peripheral physiological dysregulation, and multi-omics oral-brain communication. Stress-related biomarkers, particularly salivary cortisol, showed the most recurrent signal, although findings were inconsistent. Genetic and genomic studies suggested possible inherited susceptibility, but the evidence was heterogeneous. Exploratory meta-analysis of three salivary cortisol studies suggested higher cortisol levels in adults with bruxism (standardized mean difference = 0.91; 95% Confidence Interval: 0.21 to 1.60), with substantial heterogeneity (I² = 76.4%). Overall, current evidence suggests possible convergence around stress-related endocrine markers, particularly cortisol, in adults with bruxism; however, the evidence remains heterogeneous, methodologically limited, and insufficient to define a reproducible biomarker signature.