Background/Objectives: The integration of silver nanoparticles (AgNPs) into plastic materials has emerged as a promising strategy to provide biomedical and dental devices with an active antimicrobial barrier. In this review, we aimed to synthesize the scientific evidence published between 2013 and 2024 regarding the therapeutic efficacy, biocompatibility, and safety of AgNP-functionalized plastics by following the 2020 PRISMA guidelines. Methods: Searches were conducted in PubMed, Scopus, Web of Science, SciELO, and ScienceDirect. A total of 634 records were identified, of which 21 studies met the inclusion criteria after full-text evaluation. Results: Plastics containing AgNPs show a significant reduction in microbial load (Escherichia coli, Stafilococcus aureus, and Candida albicans) and exhibit controlled release of Ag⁺ ions, with generally low cytotoxicity levels. The most frequent applications included catheters, dental prostheses, dressings, and orthodontic resins. However, methodological heterogeneity and the scarcity of clinical trials limit the extrapolation of findings. Conclusions: AgNPs confer relevant therapeutic advantages to polymers, but long-term clinical studies are needed to confirm their safety and effectiveness.