An evaluation of studies of biologically active nanoparticles provides guidance for the synthesis of nanoparticles with the goal of developing new antibiotics/antifungals to combat microbial resistance. This review article focuses on the physicochemical properties of cerium oxide nanoparticles (CeNPs) with antimicrobial activity. Method. This systematic review followed the Guidelines for Transparent Reporting of Systematic Reviews and Meta-Analyses. Results. Studies have confirmed the antimicrobial activity of CeNPs (synthesized by different routes) using nitrate or chloride salt precursors and having sizes less than 54 nm. Conclusion. Due to the lack of standardization in studies with respect to the bacteria and CeNP concentrations assayed, comparisons between studies to determine more effective routes of synthesis are difficult. The mechanism of CeNP action likely occurs through oxidative stress of components in the cell membrane of the microorganism. During this process, a valence change occurs on the CeNP surface in which an electron is gained and Ce4+ is converted to Ce3+.

The present study aimed to evaluate the antimicrobial activity and cytotoxicity of colloidal chitosan - silver nanoparticle - fluoride nanocomposites (CChAgNpFNc), with different silver nanoparticle shapes and sizes. The syntheses of CChAgNpFNc were performed with silver nitrate added to a chitosan solution, addition of a sodium borohydride solution and solid sodium fluoride. Solution of ascorbic acid was added to synthesize larger silver nanoparticles. CChAgNpFNc obtained: S1- 100% spherical, 8.7±3.1nm; S2- 97% spherical, 15.0±7.9nm and 2.5% triangular, 22.2±9.5nm; S3- 77.3% spherical, 31.8±10.4nm, 15.9% triangular, 27.1±10.1nm and 6.8% elliptical, 33.2±7.8nm; and S4- 75.2% spherical, 43.2±14.3nm; 23.3% triangular 38.2±14.8nm, and 1.5% elliptical 38.4±11.6nm. The CChAgNpFNc showed antimicrobial activity against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans, by microdilution technique. The influence on the growth of microorganisms was evaluated using a fluorescence assay, and showed an increasing lag phase and a decreasing log phase. Cytotoxicity was investigated using Artemia salina and MTT assays. The S3 and S4 samples exhibited low cytotoxicity. The S1 and S2 samples inhibited murine macrophages and revealed lethal dose concentrations above 1000mg/mL that were classified as moderately toxic. Thus, CChAgNpFNc are potential options for the control of multiple-drug-resistant microorganisms and do not represent substantial risks to human health.

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Dental caries is a multifactor disease affecting a significant number of people throughout the world. However, in recent decades the widespread availability of fluoride and other preventive measures have resulted in a decline in the prevalence of caries among children and young adults. Currently, it is accepted that most carious dental lesions are restricted to specific anatomical sites. The aim of this chapter is to review the influence of dental anatomy on dental caries development while taking into account recent findings in cariology. Occlusal fissures in the first permanent molar are generally the first sites in the permanent dentition to develop caries. An increased risk of caries is also found in proximal contacting surfaces between two adjacent teeth. Moreover, a partially erupted tooth, which does not participate in mastication, is also at risk for caries since it may provide a more favorable environment for bacterial accumulation than a fully erupted tooth. Bacterial biofilm on the tooth is frequently a high risk caries environment. Understanding anatomical dental features is of great importance for guiding oral health hygiene and preventive measures. Finally, the development of dental disorders plays an important role in dental caries risk.

Triclosan has been used to coat sutures and reduce surgical-site infections (SSI). However, due to environmental issues search for safer antimicrobials is on the way and essential oils are promising candidates. This study aimed to investigate the antimicrobial activity of a suture containing Lippia sidoides Cham essential oil (LSEO). Staphylococcus aureus (ATCC 15656) and Escherichia coli (ATCC 25922) were cultivated in BHI (Brain Heart Infusion) medium. Broth microdilution technique for determining the Minimum Inhibitory Concentration (MIC), agar diffusion test and a monospecies biofilm experiments for testing bacteria adherence were carried out in triplicate. For diffusion agar and multispecies biofilm methods the LSEO was incorporated in a testing suture (Poliglactin 910) using chemical procedures. A suture with triclosan (Vycril® Plus) was used as a positive control. MIC values of LSEO were <15.0 μg/mL for both of strains. The halos of LSEOsuture and triclosan-sutures against S. aureus were of same magnitude (20 mm). The halo for LSEOsuture and triclosan-sutures against E.coli were 5 and 3 mm, respectively. The LSEO-suture presented the same bacterial anti-adherence effect as the triclosan-suture. This study showed that Lippia sidoides Cham oil is a promising antimicrobial material to coat sutures and reduce surgical-site infections (SSI).