Assessment of antimicrobial and mechanical properties of nanoparticle-modified orthodontic elastomeric ligatures: A systematic review of in-vitro studies

OBJECTIVE: This systematic review aimed to assess the impact of incorporating nanoparticles (NPs) into elastomeric orthodontic ligatures, focusing on the antimicrobial efficacy and the evaluation of mechanical properties. SEARCH METHODS: A systematic literature search was conducted in 10 electronic databases - PubMed, Scopus, Web of Science, ScienceDirect, ProQuest, Ovid, Livivo, Virtual Health Library, Cochrane Library and Google Scholar. Eligible studies were in-vitro investigations comparing nanoparticle-modified ligatures to unmodified ones that served as controls, reporting outcomes, such as antimicrobial effect and mechanical changes. The systematic review was prepared and reported according to the PRISMA standards. The risk of bias was assessed with the QUIN tool. RESULTS: A total of 9113 articles were identified through electronic search. After removing duplicates and screening, 9 studies met the inclusion criteria. A wide range of different NP modifications was found, including silver, bismuth, silica, nanocellulose, graphene-curcumin, and plant-extract-based. Most studies demonstrated enhanced antibacterial activity, especially against Streptococcus mutans, while a reduced biofilm formation was observed. Antimicrobial duration varied among studies, while some findings highlighted the need for further biocompatibility testing. Several NPs affected elastomeric ligature surface properties or colour, however, their mechanical integrity was generally preserved or even improved. Most of the studies included in this review were assessed as having medium risk of bias according to the QUIN tool, with three of them assessed as having low risk. CONCLUSIONS: The integration of nanoparticles into elastomeric orthodontic ligatures has revealed promising results in preventing biofilm formation and exerting antimicrobial effects, without compromising their mechanical properties. Further in-vitro and clinical studies with further testing of combined antibacterial/mechanical properties focusing on long-term safety and biocompatibility, should be conducted before clinical application.