Correction: Compressive strength evaluation of thin occlusal veneers from different CAD/CAM materials,before and after acidic saliva exposure

In the present study are depicted valuable observations for practitioners, obtained from an in vitro study which aims to evaluate the compressive strength of occlusal veneers fabricated from 3 type of restorative materials, before and after 1 month of acidic artificial saliva exposure (pH = 2.939). In this context, 90 extracted human molars were prepared to receive computer-aided design/computer-aided manufacturing (CAD/CAM) occlusal veneers. The restorative materials considered in this study were: Cerasmart; Straumann Nice and Tetric CAD. The occlusal veneers were designed, milled and cemented with an adhesive dual-cure resin cement. From all the extracted human molars, only sixty specimens were immersed in acidic artificial saliva, for 1 month, at 37 °C ± 1 °C and part of this specimens were also thermo-cycled, between 5 and 55 °C ± 2 °C, before compressive strength test. The results showed a lower compressive strength for both the samples exposed to acidic artificial saliva as well as for the samples exposed to acidic artificial saliva and thermo-cycled. Scanning electron microscopy (SEM) showed that after compressive strength, all the specimens non-exposed to acidic artificial saliva, present extensive cracks formation at the surface of the restorations, and after exposure to acidic artificial saliva for 1 month, the surface damage was characterized by longitudinal and profound fractures of the restoration, as well as the fracture of the tooth structure. Between CAD/CAM materials tested, nanoceramic resin shows more favorable fracture patterns, both before and after acidic artificial saliva exposure.

     

Green Synthesis of Silver Nanoparticles Using Populi gemmae Extract: Preparation,Physicochemical Characterization,Antimicrobial Potential and In Vitro Antiproliferative Assessment

Green route is an economic, facile and eco-friendly method, employed for the synthesis of various types of nanoparticles, having it as a starting point biological entity, especially as a plant extract. The present study aims to obtain silver nanoparticles (AgNPs) starting from an ethanolic extract of Populi gemmae (Pg), by adjusting the reaction parameters. The morphological and structural characterization exhibited that both the reaction temperature and the concentration of metal salt, contributes to the obtaining of Pg-AgNPs with adjustable size and shape. The newly synthesized nanoparticles exhibited a good antibacterial activity on Gram-positive bacteria as well as antifungal activity. The in vitro antiproliferative activity of Pg-AgNPs was assessed on two different cancer cell lines (breast cancer cells—MCF7 and lung carcinoma epithelial cells—A549). Results have shown that the green-synthetized Pg-AgNPs_S2 (obtained at 60 °C, using AgNO₃ of 5 M) induced a substantial decrease in tumor cell viability in a dose-dependent manner with an IC₅₀ ranging from 5.03 to 5.07 µg/mL on A549 cell line and 3.24 to 4.93 µg/mL on MCF7 cell line.     

Scaffold-Type Structure Dental Ceramics with Different Compositions Evaluated through Physicochemical Characteristics and Biosecurity Profiles

The design and development of ceramic structures based on 3D scaffolding as dental bone substitutes has become a topic of great interest in the regenerative dentistry research area. In this regard, the present study focuses on the development of two scaffold-type structures obtained from different commercial dental ceramics by employing the foam replication method. At the same time, the study underlines the physicochemical features and the biological profiles of the newly developed scaffolds, compared to two traditional Cerabone^® materials used for bone augmentation, by employing both the in vitro Alamar blue proliferation test at 24, 48 and 96 h poststimulation and the in ovo chick chorioallantoic membrane (CAM) assay. The data reveal that the newly developed scaffolds express comparable results with the traditional Cerabone^® augmentation masses. In terms of network porosity, the scaffolds show higher pore interconnectivity compared to Cerabone^® granules, whereas regarding the biosafety profile, all ceramic samples manifest good biocompatibility on primary human gingival fibroblasts (HGFs); however only the Cerabone^® samples induced proliferation of HGF cells following exposure to concentrations of 5 and 10 µg/mL. Additionally, none of the test samples induce irritative activity on the vascular developing plexus. Thus, based on the current results, the preliminary biosecurity profile of ceramic scaffolds supports the usefulness for further testing of high relevance for their possible clinical dental applications.     

Comparative Toxicological In Vitro and In Ovo Screening of Different Orthodontic Implants Currently Used in Dentistry

Selecting the most biocompatible orthodontic implant available on the market may be a major challenge, given the wide array of orthodontic devices currently available on the market. The latest scientific data have suggested that in vitro evaluations using oral cell lines provide reliable data regarding the toxicity of residual particles released by different types of orthodontic devices. In this regard, the in vitro biocompatibility of three different commercially available implants (stainless steel and titanium-based implants) was assessed. Methods: As an in vitro model, human gingival fibroblasts (HGFs) were employed to evaluate the cellular morphology, cell viability, and cytotoxicity by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays at 24 h and 72 h post-exposure to test implants. Results: The results correlate the composition and topography of the implant surface with biological experimental evaluations related to directly affected cells (gingival fibroblasts) and toxicological results on blood vessels (hen’s egg test-chorioallantoic membrane (HET-CAM) assay). The stainless steel implant exhibits a relative cytotoxicity against HGF cells, while the other two samples induced no significant alterations of HGF cells. Conclusion: Among the three test orthodontic implants, the stainless steel implant induced slight cytotoxic effects, thus increased vigilance is required in their clinical use, especially in patients with high sensitivity to nickel.     

Development and Characterization of Fe3O4@Carbon Nanoparticles and Their Biological Screening Related to Oral Administration

The current study presents the effect of naked Fe₃O₄@Carbon nanoparticles obtained by the combustion method on primary human gingival fibroblasts (HGFs) and primary gingival keratinocytes (PGKs)—relevant cell lines of buccal oral mucosa. In this regard, the objectives of this study were as follows: (i) development via combustion method and characterization of nanosized magnetite particles with carbon on their surface, (ii) biocompatibility assessment of the obtained magnetic nanoparticles on HGF and PGK cell lines and (iii) evaluation of possible irritative reaction of Fe₃O₄@Carbon nanoparticles on the highly vascularized chorioallantoic membrane of a chick embryo. Physicochemical properties of Fe₃O₄@Carbon nanoparticles were characterized in terms of phase composition, chemical structure, and polymorphic and molecular interactions of the chemical bonds within the nanomaterial, magnetic measurements, ultrastructure, morphology, and elemental composition. The X-ray diffraction analysis revealed the formation of magnetite as phase pure without any other secondary phases, and Raman spectroscopy exhibit that the pre-formed magnetic nanoparticles were covered with carbon film, resulting from the synthesis method employed. Scanning electron microscopy shown that nanoparticles obtained were uniformly distributed, with a nearly spherical shape with sizes at the nanometric level; iron, oxygen, and carbon were the only elements detected. While biological screening of Fe₃O₄@Carbon nanoparticles revealed no significant cytotoxic potential on the HGF and PGK cell lines, a slight sign of irritation was observed on a limited area on the chorioallantoic membrane of the chick embryo.