Clinical Roles of Nanoparticles in Orthodontic Bonding Materials

Orthodontic treatment with fixed appliances increases the risk of enamel demineralization and biofilm accumulation around brackets and other devices. Conventional orthodontic bonding materials provide adequate mechanical retention but limited bioactive protection. This narrative review summarizes current in vitro, in vivo, and clinical evidence on nanoparticles (NPs) incorporated into orthodontic adhesives and cements, focusing on antimicrobial and remineralizing effects, mechanical performance, potential clinical relevance, and safety. Electronic searches of PubMed, Science Direct and Google Scholar identified laboratory, animal, and human studies evaluating NP-modified orthodontic bonding systems. Most available data derive from in vitro experiments, which consistently show that silver, zinc oxide, titanium dioxide, calcium phosphate-based particles, and related nanoparticles can inhibit cariogenic biofilms, reduce enamel demineralization surrogates, and, in many formulations, maintain clinically acceptable shear bond strength while enabling fluoride or calcium/phosphate ion release. A smaller number of in vivo and short-term clinical studies suggest reduced plaque accumulation and fewer or less severe white-spot lesions when nanoparticle-containing materials are used, although study designs and outcome measures are heterogeneous. Overall, NP-enhanced orthodontic bonding materials appear promising for combining mechanical durability with biological protection. However, the current level of evidence is limited by the predominance of in vitro data, small sample sizes, and short follow-up in clinical studies. Well-designed, long-term clinical trials with standardized outcomes are required before routine clinical adoption can be recommended.