Effect of adding zinc oxide nanoparticles supported in 4A zeolite on antibacterial properties and flexural strength of self-curing acrylic resin used in removable orthodontic appliances

Background: Self-curing acrylic resins, mainly composed of Polymethyl Methacrylate (PMMA), are widely used to manufacture removable orthodontic appliances. Self-curing acrylic resins have higher porosity than heat-curing acrylic resins leading to a susceptible place for microbial plaque colonization. Due to some of these microorganisms' activities, a very unpleasant odor is emitted from orthodontic base plates, which has adverse effects on patients' cooperation. This study aimed to investigate the antimicrobial properties of cold-curing PMMA acrylic resin containing ZnO nanoparticles supported in 4A zeolite and evaluating its mechanical properties. Methods: The synthesized nanocomposite ZnO/4A zeolite was added to SR Triplex® Cold orthodontic self-curing acrylic resin powder with 2wt% and 4wt% concentrations. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), energy dispersive X-ray (EDX), MAP analysis, and Dynamic light scattering (DLS) were performed to investigate the sample's characteristics. Direct test method was used to assess the antibacterial properties of the fabricated acrylic samples against three bacterial strains Streptococcus mutans, Klebsiella Pnemoniae, and Esherichia coli. Flexural strength was evaluated by a three-point bending test, and One-way ANOVA and Tukey's post hoc test were used for statistical evaluation of data. The p-value of less than 0.05 was considered significant. Results: The addition of ZnO/4A in 2wt% and 4 wt% concentrations lead to more than 99% destruction of colonies in all three types of microorganisms. The mean flexural strength of acrylic specimens containing 2wt% and 4wt% of ZnO/4A significantly lower than the control group. Despite the considerable reduction, all mean values are greater than 50 MPa. Conclusion: The ZnO/4A zeolite nanocomposite due to its potent antibacterial properties and minimal toxicity can reduce the unfavorable odor of orthodontic base plates consequently increases patient cooperation and reaching the desired result. Method: The synthesized nanocomposite ZnO/4A zeolite was added to SR Triplex® Cold orthodontic self-curing acrylic resin powder with 2wt% and 4wt% concentrations. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy(FE-SEM), energy dispersive X-ray (EDX), MAP analysis, and Dynamic light scattering (DLS) were performed to investigate the sample's characteristics. Direct test method was used to assess the antibacterial properties of the fabricated acrylic samples against three bacterial strains Streptococcus mutans, Klebsiella Pnemoniae, and Esherichia coli. Flexural strength was evaluated by a three-point bending test, and One-way ANOVA and Tukey's post hoc test were used for statistical evaluation of data. The p-value of less than 0.05 was considered significant. Results: The addition of ZnO/4A in 2wt% and 4 wt% concentrations lead to more than 99% destruction of colonies in all three types of microorganisms. The mean flexural strength of acrylic specimens containing 2wt% and 4wt% of ZnO/4A significantly lower than the control group. Despite the considerable reduction, all mean values are greater than 50 MPa. Conclusion: The addition of ZnO/4A zeolite nanocomposite due to its potent antibacterial properties and minimal toxicity can reduce the unfavorable odor of orthodontic base plates consequently increases patient cooperation and reaching the desired result.

Gas Porosimetry by Gas Adsorption as an Efficient Tool for the Assessment of the Shaping Effect in Commercial Zeolites

A set of three commercial zeolites (13X, 5A, and 4A) of two distinct shapes have been characterized: (i) pure zeolite powders and (ii) extruded spherical beads composed of pure zeolite powders and an unknown amount of binder used during their preparation process. The coupling of gas porosimetry experiments using argon at 87 K and CO2 at 273 K allowed determining both the amount of the binder and its effect on adsorption properties. It was evidenced that the beads contain approximately 25 wt% of binder. Moreover, from CO2 adsorption experiments at 273 K, it could be inferred that the binder present in both 13X and 5A zeolites does not interact with the probe molecule. However, for the 4A zeolite, pore filling pressures were shifted and strong interaction with CO2 was observed leading to irreversible adsorption of the probe. These results have been compared to XRD, IR spectroscopy, and ICP-AES analysis. The effect of the binder in shaped zeolite bodies can thus have a crucial impact on applications in adsorption and catalysis.

Emulating Solar Spectral Reflectance of Natural Leaf with Bionic Leaf Prepared from 4A Zeolite-Derived Ultramarine Green Pigment

The emulation of the reflectance of green leaf in the solar spectral band (300–2500 nm) has garnered increasing attention from researchers. Currently, various materials have been proposed and investigated as potential bionic leaves. However, the problems such as poor weather durability, heavy metal pollution, and complex preparation technology still persist. Herein, a bionic leaf is prepared from an ultramarine green pigment as the functional material, polyvinylidene fluoride (PVDF) as the film-forming material, and LiCl as the humidizer. To prepare the ultramarine green pigment, the sulfur anion is added into the β cage of the 4A zeolite. The mechanisms and properties were discussed based on X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and spectroscopic methods. The results show that the as-fabricated bionic leaf based on the 4A zeolite-derived ultramarine green pigment was able to demonstrate a high spectral similarity coefficient of 0.91 with the green leaf. Furthermore, the spectral similarity coefficient was increased to 0.94 after being subjected to a simulated rainforest environment for 48 h, which indicated its high weather durability.