The emergence of microbial resistance in bacterial pathogens to common antimicrobial agents is a significant challenge in their use. The purpose of this research is to investigate the antibacterial properties of a nanocomposite consisting of calcium hydroxide and manganese oxide against the oral pathogen Enterococcus fecalis. To determine the antibacterial effect of nanocomposites on E. faecalis, a total of 9 experiments were designed using the Taguchi method. In the experimental investigations, three factors of calcium hydroxide, manganese oxide nanoparticles, and their stirring time were investigated. These agents had three different levels and finally led to the identification of the optimal ratio that showed the greatest antibacterial effect. The nanocomposites made using test conditions 6 (calcium hydroxide 150 mg/mL, manganese oxide 9 mg/mL, and stirring time 60 minutes) showed the greatest effect in growth inhibition (0.29 CFU/mL). The properties of the synthesized nanocomposite as well as its components were evaluated through material characterization techniques. The structural properties and chemical composition of this nanocomposite were found to be favorable based on its characteristics. As a result, the nanocomposite consisting of calcium hydroxide and manganese oxide has beneficial antibacterial properties that make it suitable for increasing performance in various dental fields.

This work reports on using leaf and bark extracts from the Simarouba glauca as a natural reducing agent to synthesize gold-silver bimetallic nanoparticles (Ag-Au NPs). The leaf and bark extracts contain phytochemicals such as tannins, flavonoids, and others, confirmed by Fourier transform infrared spectroscopy (FTIR), responsible for the reduction of both Au and Ag ions. The Surface Plasmon Resonance (SPR) bands obtained at 540 and 543 nm, confirmed the formation Au-Ag alloy. The average crystallite size of Au-Ag NPs synthesized using leaf and bark extracts was 29 and 35 nm. TEM images show that the Au-Ag NPs were spherical, square, pentagonal, and hexagonal morphology. The bimetallic nanoparticles were tested against Staphylococcus aureus, Streptococcus mutans, Bacillus subtilis, and gram-negative bacteria Escherichia coli, Proteus vulgaris, and Klebsiella Pneumoniae showed effective zone of inhibition against the test bacteria. Among the two extracts, the leaf extract was found to be an effective reducing agent to form different shapes of bimetallic nanoparticles. The results indicate that Au-Ag NPs have effective antibacterial activity hence, these nanoparticles can be used for the development of antibacterial agents.