The Effect of Adding Zirconium Oxide Nanoparticles on Fracture Strength of Heat Cured Acrylic Resin

Zirconium oxide nanoparticles have high strength and transparency to light and have been used in dentistry in dental restorations, production of high glass fillers, and improving the material's resistance to mechanical impact. The aim of this study was to investigate the effect of zirconium oxide nanoparticles on the fracture strength of heat-cured acrylic resin.Materials & Methods:This laboratory experimental study was conducted in the laboratory of the Faculty of Dentistry of Khorasan Azad University and Dr. Mousavi Research Center of Isfahan University during the spring and summer of 2018, 90 samples (22 × 10 × 2.5) were made using wooden blocks to make acrylic samples. After flasking, the samples were divided into 3 equal groups. In the first group no powder of zirconium oxide was added. In the second group, 2.5% by weight of zirconium oxide and in the third group 7.5% by weight of zirconium oxide were added to the mixture. Then, the fracture strength of the samples was evaluating using auniversal testing machine and 3-point bending test. The data were analyzed using ANOVAone-way and Tukey's test (α = 0.05).Results:There was a significant difference (p value <0.001) between the mean fracture strength of heat cured acrylic resin samples in the three studied groups (p value < 0.001). The lowest mean fracture strength was observed in the group with7.5 % weight of zirconia.Conclusion:The average strength to failure of heat-cured acrylic is reduced by adding zirconia oxide

Effect of Adding Zirconium Oxide Nanoparticles on the Growth and Adhesion of Candida Albicans in the Injection Mold Acryls

Adhesion to the surface of denture is a unique feature of oral candidiasis. Nanoparticles have antifungal and antibacterial properties that can be used in the structure of the dentures along with acrylic. The purpose of this study was to examine the inhibitory effect of zirconium oxide nanoparticles on the growth and adhesion of Candida albicansin the injection mold acryls.Materials & Methods:In this experimental laboratory study,90 acrylic blocks were prepared using the injection molding technique. The acrylic blocks were divided into three groups of 0, 2.5, and 7.5 weight percentages of zirconium oxide nanoparticles. All the plates with acrylic block were immersed and incubated in artificial saliva containing Candida. Then samples were taken from thecontrol solution and the one containing block. After analyzing the number of colonies, blocks were removed from the culture medium and their adhesion was analyzed in Sabouraud dextrose agar culture medium. One-way Analysis of Variance and post-hoc Tukey test were used to evaluate the inhibitory effect of zirconium oxide nanoparticles on Candida.Results:The growth of Candida albicanssignificantly decreased compared to that in the control group (p value < 0.001). The number of Candida albicanscolonies adhered to the block in the control group was significantly higher than that in the two groups with 2.5 and 7.5 weight percentages of zirconia However, there was no significant difference between the two groups with 2.5 and 7.5 5 weight percentages of zirconia. Nanoparticles of zirconium oxide with 2.5 and 7.5 weight percentages can significantly reduce the growth and adhesion of Candida, and due to the toxicity effect, it is better to use the lowest weight percentage of nanoparticles.Conclusion:Zirconium oxide nanoparticles of 2.5 and 7.5 weight percentages can cause a significant decrease in the growth and adhesion of Candida