Antibacterial activity and bond strength of silver nanoparticles modified orthodontic bracket adhesive: A systematic review and meta-analysis of in-vitro and in-vivo studies

Abstract The formation of white spot lesions (WSLs) around orthodontic brackets as a result of biofilm accumulation is a common complication of fixed orthodontic therapy. A systematic review and meta-analysis were conducted to assess the antibacterial efficacy and bond strength of silver nanoparticles (AgNPs) incorporated orthodontic bracket adhesive to prevent WSLs. An electronic search of English literature was performed using Dissertations and Theses Global, Web of Science, LILACS, Cochrane, Scopus, and MEDLINE/PubMed using predetermined inclusion criteria. Specific terms were utilized in searching from the inception of the respective database up to April 2021. After the search strategy was applied by a reviewer, the data was extracted and results were analyzed. The focused question was: “whether AgNPs containing orthodontic bracket adhesives are superior to non-modified orthodontic bracket adhesives in terms of antibacterial activity and shear bond strength for the prevention of WSLs around brackets.” Ten articles were included and a meta-analysis was performed. The bacterial growth inhibition was assessed in 7/10 included studies. Out of them, 2 studies showed no bacterial growth inhibition zone adjacent to orthodontic bracket adhesives supplementing AgNPs, while 5 articles exhibited a significant microbial growth inhibition zone diameter against varying bacteria. Streptococcus mutans was the main bacteria considered by the included studies (n = 10). In the included studies, the mean SBS scores of control group adhesives ranged between 5.48 ± 1.98 MPa and 24.53 ± 4.1 MPa, while the mean SBS scores of experimental group adhesives ranged between 5.22 ± 1.16 MPa and 17.63 ± 3.2 MPa. Low risk of bias of the included articles was observed in the meta-analysis. Although, studies have confirmed that the incorporation of AgNPs into orthodontic adhesive enhances its antibacterial activity, however, a degree of heterogeneity was observed throughout the studies due to the deficit in the in vitro models standardized protocols.