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Tooth loss impairs mastication, deglutition and esthetics and affects systemic health through nutritional deficiency, weight loss, muscle weakness, delayed wound healing, and bone fragility. Approximately 90% of tooth loss is due to dental caries and periodontal disease. Accordingly, early treatment of dental caries is essential to maintaining quality of life. To date, the clinical diagnosis of dental caries has been based on each dentist's subjective assessment, but this visual method lacks objectivity. To improve diagnostic ability, highly sensitive quantitative methods have been developed for the diagnosis and prevention of dental caries and are gradually becoming a mandatory item in modern dentistry. High-resolution Raman spectroscopy is a suitable tool for recognizing the subtle structural changes that occur in dental enamel in already developed or, more importantly, incipient dental caries. Raman analysis could soon emerge as a breakthrough in dentistry because of its high diagnostic sensitivity. In this study, we build upon our previous findings in a new analysis of dental caries using Raman spectroscopy imaging and discuss the possibility of using Raman photonic imaging in support of objective diagnostics in dentistry. Our findings support the Raman method of caries detection in comparison with other conventional or new approaches.

Polyvinyl-siloxane (PVS) is a modified condensation silicon that has found applications in the field of dental impression materials thanks to its high biocompatibility and the ability to be modeled on solid surfaces with a micrometric resolution. Major concerns have been raised on the possibility to sterilize PVS without distorting its geometrical shape, as immersion in antibacterial solutions often results in swelling. As a possible alternative, both radiofrequency glow discharge and UV sterilization have been successfully applied. In this paper, we focus on the possible use of a cheap, bio-compatible ceramic reinforcement powder (BaTiO3) to obtain a higher resistance to colonization and contribute to the prevention of bacterial infections, not only for temporary applications but also long-term. We also use a vacuum treatment to transform the composite polymer into soft scaffolds with relative densities between 35 and 65%) with similar biological properties. Testing with fractions of ceramic reinforcement up to 25% has clearly shown a beneficial effect in terms of bacteria viability against Staphylococcus epidermidis, with potential for future applications as soft biomedical scaffolds, medical clothing, sanitary materials, and filters for the sterilization of air and water. [ABSTRACT FROM AUTHOR]

The present work investigated the effect of Polylactic acid (PLA) fibers produced by centrifugal spinning with incorporated BaTiO3 particles to improve their bacteriostatic behavior. The PLA matrix and three composites, presenting three different amounts of fillers, were subjected to UV/O3 treatment monitoring the possible modifications that occurred over time. The morphological and physical properties of the surfaces were characterized by different microscopic techniques, contact angle, and surface potential measurements. Subsequently, the samples were tested in vitro with human dermal fibroblasts (HDF) to verify the cytotoxicity of the substrates. No significant differences between the PLA matrix and composites emerged; the high hydrophobicity of the fibers, derived by the polymer structure, represented an obstacle limiting the fibroblast attachment. Samples underwent bacterial exposure (Staphylococcus epidermidis) for 12 and 24 h. Increasing the concentration of BT, the number of living bacteria and their distribution decreased in comparison with the PLA matrix suggesting an effect of the inorganic filler, which generates a neutralization effect leading to reactive oxygen species (ROS) generation and subsequently to bacterial damages. These results suggest that the barium titanate (BT) fillers clearly improve the antibacterial properties of PLA fibers after aging tests made before bacterial exposure, representing a potential candidate in the creation of composites for medical applications. [ABSTRACT FROM AUTHOR]

Previous studies using gram-positive and -negative bacteria demonstrated that hydrolysis of silicon nitride (Si 3 N 4 ) in aqueous suspensions elutes nitrogen and produces gaseous ammonia while buffering pH. According to immunochemistry assays, fluorescence imaging, and in situ Raman spectroscopy, we demonstrate here that the antipathogenic surface chemistry of Si 3 N 4 can be extended to polymethylmethacrylate (PMMA) by compounding it with a minor fraction (~8 vol.%) of Si 3 N 4 particles without any tangible loss in bulk properties. The hydrolytic products, which were eluted from partly exposed Si 3 N 4 particles at the composite surface, exhibited fungicidal action against Candida albicans. Using a specific nitrative stress sensing dye and highly resolved fluorescence micrographs, we observed in situ congestion of peroxynitrite (ONOO - ) radicals in the mitochondria of the Candida cells exposed to the PMMA/Si 3 N 4 composite, while these radicals were absent in the mitochondria of identical cells exposed to monolithic PMMA. These in situ observations suggest that the surface chemistry of Si 3 N 4 mimics the antifungal activity of macrophages, which concurrently produce NO radicals and superoxide anions (O 2 • - ) resulting in the formation of candidacidal ONOO - . The fungicidal properties of PMMA/Si 3 N 4 composites could be used in dental appliances to inhibit the uncontrolled growth of Candida albicans and ensuing candidiasis while being synergic with chemoprophylaxis. STATEMENT OF SIGNIFICANCE: In a follow-up of previous studies of gram-positive and gram-negative bacteria, we demonstrate here that the antipathogenic surface chemistry of Si 3 N 4 could be extended to polymethylmethacrylate (PMMA) containing a minor fraction (~8 vol.%) of Si 3 N 4 particles without tangible loss in bulk properties. Hydrolytic products eluted from Si 3 N 4 particles at the composite surface exhibited fungicidal action against Candida albicans. Highly resolved fluorescence microscopy revealed congestion of peroxynitrite (ONOO - ) radicals in the mitochondria of the Candida cells exposed to the PMMA/Si 3 N 4 composite, while radicals were absent in the mitochondria of identical cells exposed to monolithic PMMA. The fungicidal properties of PMMA/Si 3 N 4 composites could be used in dental appliances to inhibit uncontrolled growth of Candida albicans and ensuing candidiasis in synergy with chemoprophylaxis., Competing Interests: Declaration of Competing Interest B. Sonny Bal and Bryan J. McEntire are employees of Sintx Technologies Corporation, an industrial producer of medical grade silicon nitride. Other authors have no interest to disclose., (Copyright © 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)