Microplastics released from dental materials induce oral inflammatory bone resorption and apoptosis via mitochondrial dysfunction

Microplastics (MPs) are emerging pollutants that are associated with many diseases including atherosclerosis, inflammatory bowel disease (IBD), and Alzheimer's. The oral cavity is the primary point for the uptake of MPs by human, where MPs could pose risks to oral and even system health. Various polymer-based materials have been used as dental materials in oral treatment, however, the assessment of MPs in dental treatments remains limited and the processes and mechanisms by which MPs affect human health through the oral route are elusive. Here, we report the assessment of the risks and sources of MPs in dental clinics, the establishment of the relationship between MPs and oral inflammatory disorders, and also the elucidation of underlying mechanisms. Our results showed that commonly used therapeutic dental materials could generate MPs in dental clinics with proportions significantly higher than those in office areas and outdoors. As a representative, polymethyl methacrylate (PMMA) MPs showed significant toxicity to human oral keratinocytes (HOK), human periodontal ligament stem cells (hPDLCs), and THP-1-derived macrophages. Mechanistic investigations of apoptosis and inflammation processes revealed that MPs could lead to mitochondrial stress and autophagy and trigger the Notch signaling pathway and the JAK-STAT signaling pathway. Mice experiments showed that prolonged high-dose MPs exposure induced periodontal inflammatory reactions and even led to inflammatory bone resorption. This study provides a scientific basis for the oral health risks by MPs in dental practice and addresses the need for the development of dental materials with higher biocompatibility and environmentally sustainability.