Essential Oil-Containing Mouthrinses for Plaque and Gingivitis Control: Formulation Chemistry, Human Salivary Biomarkers, Mechanistic Evidence, and Research Priorities

Selected essential oil (EO)-containing mouthrinses improve plaque and gingivitis control when used alongside mechanical oral hygiene, but their molecular effects in human saliva remain poorly defined. This narrative review integrates formulation chemistry, oral exposure, human salivary evidence, and mechanistic studies. Three studies identified in this review evaluated salivary immunoglobulin A, immunoglobulin G, or interleukin-1β. Differences in populations, co-interventions, sampling, and analytical methods limit comparison and do not establish reproducible modulation of a single biomarker. Other human studies assessed salivary flow, pH, proteomic responses, microbial counts, nitrate reduction, and oral biofilms. Mechanistic evidence largely derives from isolated constituents in cellular, animal, or computational models. A study of a complete zinc-containing formulation in human oral cells provides formulation-level evidence, but neither this study nor the constituent literature establishes target engagement after mouthrinsing in humans. Future trials should connect chemically characterized formulations and measured oral exposure with target-specific assays, validated salivary endpoints, microbial function, clinical outcomes, and safety. Current evidence supports selected formulations for plaque and gingivitis control; it does not establish an EO class effect or a validated salivary mechanism of clinical benefit.