Improper Curing of 3D Printed Restorations and Intraoral Degradation: Microplastic Release Health Risks and the Role of Oxygen-Free Polymerisation

Three-dimensional (3D) printing technology has significantly revolutionised the field of restorative dentistry by facilitating the remarkably swift and highly accurate production of customised dental restorations tailored to meet individual patient needs and specifications. Nevertheless, a growing body of evidence increasingly underscores the presence of substantial health risks that are associated with the intraoral degradation of resin-based materials that have not been appropriately cured during the manufacturing process. The phenomenon of incomplete polymerisation—often a consequence of factors such as oxygen inhibition, insufficient exposure to light, or the implementation of suboptimal curing protocols—results in the release of residual monomers and microplastics into the oral cavity, thereby raising serious concerns. These released substances are progressively being recognised as biologically active contaminants that possess the potential to induce a variety of adverse effects, including cytotoxicity, oxidative stress, endocrine disruption, and inflammatory responses that can impact both local tissues within the oral cavity and systemic tissues throughout the body. This comprehensive review aims to synthesise the most current research regarding the chemical and mechanical consequences that arise from inadequate curing processes, the biological pathways that are affected by the ingestion of microplastics and the leaching of monomers, and the broader implications this has for the long-term safety and well-being of patients undergoing such dental procedures. Various strategies that have been proposed—including oxygen-free polymerisation techniques, the use of optimised curing wavelengths (for example, at 385 nm), and the development of modified resin formulations—are discussed as potential means to effectively mitigate these significant health risks associated with dental materials. The findings presented in this review emphasise the pressing necessity for the establishment of standardised protocols and the pursuit of further research endeavours aimed at addressing the concealed health burden that is posed by the degradation of 3D printed dental restorations in the context of clinical dentistry. Ultimately, addressing these challenges will require a collaborative effort among researchers, clinicians, and manufacturers to enhance the safety and efficacy of dental materials in restorative practices.