Nano-particle coated or impregnated acrylic resins in dental applications: A systematic review of in Vivo Evidence on mechanical properties, biocompatibility and clinical performance.

Background: Acrylic resins are extensively used in prosthodontics, orthodontics and maxillofacial prosthetics due to their ease of fabrication and cost-effectiveness. However, conventional acrylic materials are susceptible to microbial colonization, mechanical deterioration and esthetic compromise. To overcome these limitations, recent research has explored the incorporation of nanoparticles into polymethyl methacrylate (PMMA)-based resins to enhance their antimicrobial efficacy, mechanical strength, biocompatibility, and long-term durability. Methods: This systematic review was conducted according to PRISMA guidelines. An extensive literature search was performed across PubMed/MEDLINE, Scopus, Web of Science, Cochrane Library and Embase for studies published up to January 18, 2025. Only in vivo studies conducted on humans or animals evaluating nanoparticle-coated or nanoparticle-impregnated acrylic resins were included. Standalone in vitro studies were excluded. Risk of bias was assessed using Cochrane's RoB 2.0 tool for randomized controlled trials (RCTs), ROBINS-I for non-randomized studies and the SYRCLE tool for animal studies. Results: Out of 3154 records initially identified, six studies met the eligibility criteria. The nanoparticles incorporated included silver, titanium dioxide, nanocopper, nanogold and quaternary ammonium polyethyleneimine (QPEI). All included studies reported antimicrobial activity with nanogold, nanocopper and QPEI showing sustained microbial inhibition. Mechanical outcomes varied: silver and titanium dioxide nanoparticles were associated with reduced material strength, whereas nanocopper maintained mechanical performance. Esthetic outcomes indicated that silver-based modifications caused discoloration, while nanocopper and QPEI preserved color stability. Conclusion: Nanoparticle-modified acrylic resins exhibit enhanced antimicrobial and biocompatibility profiles with certain formulations particularly those incorporating nanocopper, nanogold and QPEI showing greater clinical potential. However, mechanical durability and esthetic alterations remain challenges especially with silver and titanium-based additives. Further well-designed, long-term randomized controlled trials are warranted to validate the clinical applicability of these nano-enhanced acrylic materials.