Poly(methyl methacrylate) (PMMA) is one of the most widely used polymeric biomaterials in prosthodontics and digital dentistry because of their clinical reliability and compatibility with computer-aided design/computer-aided manufacturing (CAD/CAM). Its widespread use raises questions regarding material consumption, manufacturing waste, recyclability, and circularity. A critical narrative review supported by a structured literature search was conducted. PubMed, Scilit, OpenAlex, and ScienceDirect were searched for English-language literature published from January 2000 to June 2026. Targeted Google Scholar searches, cross-referencing, standards, and official technical sources supplemented the search. Evidence was organized according to its directness to dental PMMA and synthesized thematically. Prepolymerized CAD/CAM PMMA provides consistent material quality and generally improved mechanical performance compared with conventionally processed PMMA; however, subtractive manufacturing generates disc remnants, milling particles, and polishing residues. Mechanical recycling and depolymerization demonstrate technical recovery potential, although evidence specific to heterogeneous dental waste streams, environmental performance, and clinical-grade reuse remains limited. Technical recyclability should not be automatically equated with a viable circular economy or a net environmental benefit. Future research should quantify dental PMMA waste, establish effective collection and recovery pathways, and integrate life-cycle assessments with clinical performance and safety standards.