Antimicrobial evaluation of self-cured acrylic resin used in removable orthodontic appliances following addition of encapsulated silver nanoparticles in clay cavities

Abstract

Introduction: Acrylic resin, self-hardening polymethyl methacrylate is a common material in the construction of movable orthodontic base plates. This material after polymerization and hardening due to evaporation, the remaining monomer that did not enter the polymerization process, gets a porous structure. There are various bacteria in the microbial flora of the oral cavity and they are able to colonize on different surfaces. The aim of the present study was to add silver nanoparticles to the surface of clay plates and add it with different percentages to self-hardening acrylic powder and investigate its antibacterial properties. Materials and methods: This experimental laboratory study was conducted on self-curing acrylic used in mobile orthodontic devices (triplex cold (Ivoclar vivadent AG/Liechtenstein)) following the addition of silver nanoparticles loaded in clay. First, the general synthesis containing silver nanoparticles was carried out using the acid washing method. In order to add the manufactured nanoparticles to the acrylic composition, synthesized Ag/Clay nanoparticles powder was added to self-curing acrylic polymer powder (Triplex Cold) with weight percentages of 0.2, 0.5, 1 and 1.5% and finally 4 test groups And a control group was determined to carry out the next steps. The prepared samples were prepared for cell culture and antimicrobial tests in 96 plate. XRD, FESEM, EDX and Mapping techniques were used to determine the physicochemical characteristics. To perform the cytotoxicity test (MTT assay) and to evaluate the antimicrobial properties of the acrylic samples, direct test and colony count techniques were used using Escherichia coli, Enterococcus focalis and Candida albicans bacterial strains. Results: All groups with weight percentages of 0.2, 0.5, 1 and 1.5% Ag/Clay to polymer acrylic powder had acceptable antibacterial and antifungal properties. The results of the MTT test showed that the toxicity of synthesized nanoparticles (Ag/Clay) increases with increasing concentration. So, in the groups where the percentage of silver in Clay was 5% by weight, cell survival was more than 80%. For samples with a higher percentage of silver (10% by weight of clay), cell viability showed a significant decrease with increasing percentage of clay inside the polymer and with increasing treatment time. The highest cytotoxicity was related to the negative control group (1.2 μg/ml of nanoparticles without polymer). Conclusion: Encapsulation of Ag/Clay nanoparticles inside the polymer reduces its toxicity.