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

Abstract

Zirconium dioxide silver-doped nanoparticles (ZrO₂AgDNPs) impacts the adhesive material in terms of its physical characteristics, antimicrobial properties, degree of conversion (DC), and micro-tensile bond strength (μTBS) 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 μTBS testing. A light-curable orthodontic adhesive, specifically Transbond XT, was combined with ZrO₂AgDNPs at 2.5% and 5%. As a control, an adhesive with no incorporation of ZrO₂AgDNPs was also prepared. The tooth samples were divided into three groups based on the weightage of NPs: group 1: 0% ZrO₂AgDNPs (control), group 2: 2.5 wt% ZrO₂AgDNPs, and group 3: 5 wt% ZrO₂AgDNPs. EDX graph demonstrated silver (Ag), Zirconium (Zr), and Oxygen (O₂), 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 μTBS 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 μTBS values. The lowest μTBS was observed in group 1 adhesive loaded with 0% ZrO₂AgDNPs (21.25 ± 1.22 MPa). Whereas, the highest μTBS was found in group 3 (26.19 ± 1.07 MPa) adhesive loaded with 5% ZrO₂AgDNPs. ZrO₂AgDNPs in orthodontic adhesive improved μTBS and has acceptable antibacterial activity against S mutans. ZrO₂AgDNPs at 5% by weight can be used in orthodontic adhesive alternative to the conventional method of orthodontic adhesive for bracket bonding. RESEARCH HIGHLIGHTS: The highest μTBS was found in orthodontic adhesive loaded with 5% ZrO₂AgDNPs. ARI analysis indicates that the majority of the failures fell between 0 and 1 among all investigated groups. The colony-forming unit count of S. mutans was significantly less in orthodontic adhesive loaded with nanoparticles compared with control. The 0% ZrO₂AgDNPs adhesive showed the highest DC.

Keywords: EDX; FTIR; microbiology; nanoparticles; orthodontics adhesive; scanning electron microscope; μTBS.