Microplastics (MPs) as a systemic hazard: Unveiling the potential link to oral inflammation through shared inflammatory pathways and the oral-intestinal axis.

The physicochemical properties of MPs, including particle size, shape, and surface charge, determine their ability to penetrate biological barriers and induce toxic effects by triggering oxidative stress and inflammatory responses. The pollutants adsorbed on their surfaces can also produce synergistic toxic effects. Through exposure routes such as ingestion and inhalation, MPs can enter the systemic circulation, causing cellular oxidative stress, mitochondrial dysfunction, and apoptosis, leading to multi-organ inflammatory responses, barrier function impairment, and dysbiosis, and increasing the risk of cancer. Although there is no direct evidence that MPs cause oral diseases, the inflammatory pathways activated in systemic organs (such as NF-κB, NLRP3, etc.) are highly consistent with the mechanisms of chronic oral diseases such as periodontal disease and oral ulcers, suggesting that MPs may affect oral health through similar pathways. In addition, MPs can also exacerbate the bidirectional transmission of inflammation through local physical damage and regulation of the oral-intestinal axis, thereby amplifying the potential threat to overall and oral health. This provides a theoretical basis for the prevention and control of microplastic risks in oral medicine. This review systematically constructs a theoretical framework linking MPs' physicochemical properties to potential oral health risks, providing critical directions for future research and risk assessment.