Background and Objectives: Resin composites are widely used in restorative dentistry due to their favorable mechanical properties and aesthetics. However, their clinical performance depends on factors such as chemical composition, microhardness, and exposure to environmental challenges like acidic beverages. Materials and Methods: This study evaluated the effects of coffee, red wine, and Coca-Cola on the surface microhardness and chemical composition of two resin composites (G-ænial A’CHORD and Omnichroma). A total of 40 disk-shaped specimens (20 per composite) were fabricated and divided into four groups: control, red wine, coffee, and Coca-Cola. Specimens were immersed in their respective solutions for 10 days, after which Raman spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy and Vickers microhardness testing were conducted to assess mechanical and chemical changes. Paired t-tests were performed to compare pre- and post-immersion values, with significance set at p < 0.05. Raman and FTIR spectroscopy confirmed structural changes, including peak shifts and intensity variations, particularly in polymer–matrix interactions and filler compositions. Results: The Vickers microhardness test revealed significant reductions in hardness for both composites after immersion, with Omnichroma showing a greater susceptibility to softening than G-ænial A’CHORD (p < 0.01). Red wine and coffee immersion resulted in the most significant decreases, indicating the strong impact of polyphenolic and acidic interactions on the composite structure. Conclusions: These findings indicate that prolonged exposure to acidic and staining beverages compromises the mechanical and chemical integrity of resin composites, with Omnichroma being more affected than G-ænial A’CHORD. The findings suggest that the selection of composite materials should consider resistance to staining agents, especially in high-risk oral environments.

Background/Objectives: Composite dental restorations are continuously exposed to dietary substances, which may compromise their structural integrity. This study aimed to assess the chemical and mechanical effects of coffee, red wine, and Coca-Cola on two widely used commercial resin composites, Herculite Ultra XRV and Omnichroma. Methods: Forty disk-shaped specimens (20 per material) were immersed for 10 days in the selected beverages. Changes in chemical composition were analyzed using Fourier Transform Infrared (FTIR) and Raman spectroscopy, while Vickers microhardness testing evaluated surface hardness. Results: FTIR and Raman analyses revealed that coffee and red wine caused the most substantial chemical degradation, particularly in carbonyl (C=O), aromatic (C=C), and siloxane (Si–O–Si) groups. Herculite XRV demonstrated higher chemical stability, while Omnichroma showed more pronounced molecular degradation. In contrast, microhardness testing indicated that Omnichroma maintained better surface hardness compared to Herculite XRV after exposure. Across all solutions, Coca-Cola induced the least effect. Conclusions: The tested beverages significantly affected both the chemical and mechanical properties of the resin composites. Omnichroma exhibited superior mechanical durability, while Herculite XRV showed greater resistance to chemical degradation. These results highlight the importance of material composition in restorative dentistry and support the development and selection of composites with improved resistance to acidic and staining agents to ensure long-term clinical performance.

This article presents a study on the influence of the intensity of the welding current on the properties of the mechanical strain strength of welded joints made by using submerged arc welding technology. The influence of the welding current on the microstructure of the welded joints was also observed in different regions of the cross-section of the welding seam. Also subject to observation was the mode of influence of the welding current on the geometry and dimensions of the welding seams. The welded samples were obtained using five different welding regimes whose main variable was the intensity of the welding current, which had values between 300 A and 700 A. The criterion used as a reference for comparing the effects produced by the studied welding regimes was a standard welding regime that is used in the industry for welding railway tank wagons, with a welding current intensity of 480 A. The base material used in the experiments was a fine-grained carbon steel specially intended for the manufacture of pressure vessels identified as P355 N; the semi-finished product from which the samples were made consisted of 6 mm thick laminated sheets used in the manufacture of the covers of the vessels that make up the railway tank wagon. The aim of this study was to highlight the differences that may appear through varying the current welding parameter and identify welding regimes that can provide welded joints with superior mechanical properties compared to what is currently employed in the industry. This study focused on the most widespread technology of welding pressure vessels: the submerged electric arc welding method.

Background/Objectives: In-office bleaching commonly employs high concentrations of hydrogen peroxide (HP) or carbamide peroxide (CP), which may compromise enamel integrity. This in vitro paired-design study aimed to compare the chemical and mechanical effects of three commercial bleaching agents—Opalescence Boost (40% HP), Opalescence Quick (45% CP), and BlancOne Ultra+ (35% HP)—on human enamel. The null hypothesis assumed no significant differences between the control and treated samples. Given the ongoing debate over pH, active ingredients, and enamel impact, comparing whitening systems remains clinically important. Methods: Forty-two extracted teeth were assigned to three experimental groups (n = 14) with matched controls. Each underwent a single bleaching session per manufacturer protocol: Opalescence Boost (≤60 min), Opalescence Quick (15–30 min), and BlancOne Ultra+ (three light-activated cycles of 8–10 min). Enamel chemical changes were analyzed by Fourier transform infrared (FTIR) spectroscopy (phosphate and carbonate bands), and surface hardness by Vickers microhardness testing. Paired t-tests (α = 0.05) assessed statistical significance. Results: FTIR analysis revealed alterations in phosphate and carbonate bands for all agents, most notably for Opalescence Boost and BlancOne Ultra+. Microhardness testing showed significant reductions in enamel hardness for Opalescence Boost (control: 37.21 ± 1.74 Hv; treated: 34.63 ± 1.70 Hv; p = 0.00) and Opalescence Quick (control: 45.82 ± 1.71 Hv; treated: 39.34 ± 1.94 Hv; p < 0.0001), whereas BlancOne Ultra+ showed no significant difference (control: 51.64 ± 1.59 HV; treated: 51.60 ± 2.34 Hv; p = 0.95). Conclusions: HP-based agents, particularly at higher concentrations, caused greater enamel alterations than CP-based products. While clinically relevant, the results should be interpreted cautiously due to in vitro limitations and natural enamel variability.

Laser cladding is an essential method for strengthening and restoring component surfaces. To increase its efficacy and provide a reliable surface treatment technique, it is necessary to optimize process parameters, enhance material adhesion, and guarantee high-quality, reliable coatings. These measures help to extend the lifespan of components. In this study, the surfaces of AISI 904L stainless steel samples were cladded to prepare various Co-based composite coatings with single and multiple layers reinforced with WC–CoCr–Ni powder. The phases within the newly developed layers were investigated using X-ray Diffraction (XRD), while the microstructure was examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Further tests were performed to assess the hardness, wear resistance and corrosion performance of the deposited coatings. Analyzing and comparing the coatings, it was observed that the coating performance increased with increasing thickness and generally due to a lower amount of Fe present within the microstructure.

Fe-based coatings reinforced with TiC particles exhibit outstanding properties and are widely recognized as highly promising coatings or components with superior performance. In the present study, composite materials using a powder mixture of AISI 316 stainless steel and TiC particles were deposited by vacuum plasma spraying onto a S235 low alloyed steel substrate. The coating and the base material were characterized in terms of microstructure and surface properties. The metallographic analysis of the deposited coating revealed the uniform distribution of the TiC into the stainless steel matrix. The results show that the presence of tungsten carbide particles improved the hardness and tribological properties of the composite coating compared with the S235 base material. The wear resistance of the coating was approximately seven times higher than that of the low alloyed steel substrate. The electrochemical corrosion resistance of the coating in chloride media was much higher than that of the base material.