Orthodontic adhesive loaded with different proportions of ZrO₂ silver-doped nanoparticles: An in vitro TBS, SEM, EDX, FTIR, and antimicrobial analysis

Zirconium dioxide silver-doped nanoparticles (ZrO2 AgDNPs) impacts the adhesive material in terms of its physical characteristics, antimicrobial properties, degree of conversion (DC), and micro-tensile bond strength (mu TBS) of orthodontic brackets to the enamel surface. A comprehensive methodological analysis utilizing a range of analytical techniques, including scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, DC analysis, and mu TBS testing. A light-curable orthodontic adhesive, specifically Transbond XT, was combined with ZrO2 AgDNPs at 2.5% and 5%. As a control, an adhesive with no incorporation of ZrO2 AgDNPs was also prepared. The tooth samples were divided into three groups based on the weightage of NPs: group 1: 0% ZrO2 AgDNPs (control), group 2: 2.5 wt% ZrO2 AgDNPs, and group 3: 5 wt% ZrO2 AgDNPs. EDX graph demonstrated silver (Ag), Zirconium (Zr), and Oxygen (O-2 ), The antibacterial efficacy of adhesives with different concentrations of NPs (0%, 2.5%, and 5%) was assessed using the pour plate method. The FTIR spectra were analyzed to identify peaks at 1607 cm(-1) corresponding to aromatic C=C bonds and the peaks at 1638 cm(-1) indicating the presence of aliphatic C=C bonds. The mu TBS was assessed using universal testing machine (UTM) and bond failure of orthodontic brackets was seen using adhesive remanent index (ARI) analysis. Kruskal-Wallis test assessed the disparities in survival rates of Streptococcus mutans. Analysis of variance (ANOVA) and post hoc Tukey multiple comparisons test calculated mu TBS values. The lowest mu TBS was observed in group 1 adhesive loaded with 0% ZrO2 AgDNPs (21.25 +/- 1.22 MPa). Whereas, the highest mu TBS was found in group 3 (26.19 +/- 1.07 MPa) adhesive loaded with 5% ZrO2 AgDNPs. ZrO2 AgDNPs in orthodontic adhesive improved mu TBS and has acceptable antibacterial activity against S mutans. ZrO2 AgDNPs at 5% by weight can be used in orthodontic adhesive alternative to the conventional method of orthodontic adhesive for bracket bonding.