The oral-systemic interface of micro- and nanoplastics.

Microplastics (MPs, <5 mm) and nanoplastics (NPs, <1 μm) are pervasive pollutants increasingly recognized as emerging threats to human health. While their systemic impacts on the gastrointestinal, respiratory, reproductive, and immune systems are well documented, their relevance to oral health has received limited attention. The oral cavity represents both a primary site of exposure, via ingestion, inhalation, and contact with dental and personal care products, and a sensitive biological interface where local toxicity may arise. This review synthesizes evidence on oral sources of MPs/NPs, including toothbrushes, toothpastes, orthodontic appliances, restorative composites, prostheses, implants, and impression materials. We highlight potential links to oral diseases such as gingivitis, periodontitis, peri-implantitis, denture stomatitis, oral cancer, and xerostomia. Mechanistic studies demonstrate that MPs/NPs trigger oxidative stress, inflammatory signaling, immune dysregulation, microbiome disturbances, and endocrine disruption, with implications for both local pathology and systemic dissemination. Once crossing oral and gastrointestinal barriers, these particles can accumulate in distant organs, exacerbating chronic inflammatory and metabolic disorders. We conclude by outlining key research gaps, emphasizing the need for advanced detection methods, sustainable dental materials, and translational studies to clarify clinical relevance. Collectively, this review underscores the oral cavity as a critical but underexplored interface for plastic particle exposure.