Carmen Opriș

The interaction between restorative materials and microbial biofilms plays an important role in restoration longevity and the development of secondary caries. This study aimed to perform a multidimensional characterization of four commercially available flowable resin-based dental composites by evaluating their surface roughness, Vickers microhardness, surface morphology, and microbial biofilm formation under standardized in vitro conditions. Filtek™ Bulk Fill Flowable Restorative (3M), Tetric EvoFlow (Ivoclar Vivadent), BRILLIANT Flow (Coltene), and G-ænial™ Universal Injectable (GC) were investigated. Surface roughness was determined by contact profilometry, microhardness was assessed using the Vickers method, and microstructural characteristics were analyzed by scanning electron microscopy (SEM). Microbial biofilm biomass formed by Gram-positive bacteria, Gram-negative bacteria, and Candida albicans, including both reference strains and clinical isolates, was quantified using a crystal violet assay to compare material-dependent microbial colonization. G-ænial™ Universal Injectable exhibited the lowest roughness values, whereas BRILLIANT Flow showed the highest microhardness. SEM analysis revealed a more homogeneous surface morphology for Filtek™ Bulk Fill Flowable Restorative and G-ænial™ Universal Injectable, while Tetric EvoFlow and BRILLIANT Flow displayed increased topographical heterogeneity. Although modest differences in biofilm biomass accumulation were observed among the investigated composites (4.37–12.21% relative biomass reduction compared with the control), no material demonstrated a distinct advantage under the experimental conditions. The integrated evaluation of surface roughness, microhardness, surface morphology, and microbial biofilm formation provides a comparative characterization of commercially available flowable resin-based composites and contributes to a better understanding of material–biofilm interactions. These findings may support the future development of multifunctional restorative biomaterials with improved biofilm-modulating properties.

Cobalt–chromium (CoCr) alloys have gained significant importance in the field of medical implants due to their outstanding combination of mechanical strength and excellent wear and corrosion resistance. Compared with other state-of-the-art materials, such as stainless steel or titanium, CoCr alloys typically exhibit superior fatigue strength, which is particularly advantageous for implants and components exposed to long-term repetitive loading. The present study investigates the feasibility of using commercially available CoCr alloy powders in the Laser Powder Bed Fusion (PBF-LB/M) process for the fabrication of biomedical implants. Microstructural characterization of the PBF-LB/M-manufactured CoCr samples revealed a dense, refined cellular–dendritic microstructure with a high degree of densification, characteristic of the rapid solidification associated with the PBF-LB/M process. The evaluation of mechanical performance, wear behavior, and corrosion resistance provides valuable insights into the suitability of these alloys for biomedical applications, especially in the design of complex implants requiring enhanced durability and long-term reliability. Furthermore, compression testing highlighted the influence of layer orientation on mechanical properties, emphasizing the importance of strategic prototyping and building orientation selection in the PBF-LB/M process. Tribological behavior assessed under dry sliding conditions demonstrated a significantly reduced coefficient of friction and lower wear rate compared to a conventional 316L stainless steel, which is frequently used in similar applications. Corrosion resistance was evaluated by potentiodynamic polarization measurements in Ringer electrolyte, showing that the PBF-LB/M-fabricated CoCr samples exhibit good corrosion resistance in environments resembling physiological fluids. Overall, the PBF-LB/M technique represents a promising manufacturing route for next-generation CoCr biomedical implants, particularly for orthopedic and dental applications. Beyond the biomedical field, the findings of this study also support the potential extension of PBF-LB/M-processed CoCr alloys to industrial sectors requiring high wear and corrosion resistance, including aerospace and automotive applications.

This editorial aims to highlight current trends in conventional and advanced materials-joining methods, as well as the current challenges in this field

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.

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.

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.

Abrasive water jet machining has become an indispensable process for cutting Kevlar fiber-reinforced polymers used in applications such as ballistics protection, race cars, and protective gloves. The complex and diffuse action of a large number of input parameters leads to the need to evaluate the quality characteristics of the technological transformation as a result of the deployment of experimental studies adapted to the specific processing conditions. Thus, the paper focuses on identifying the influence of different factors and modeling their action on the characteristics that define the quality of the cut parts, such as the kerf taper angle and the Ra roughness parameter, by applying statistical methods of design and analysis of experiments.

The objective of this study was to evaluate the influence of hydrofluoric acid (HF) and conditioning time on the micro-shear bond strength (µSBS) between dual-cure resin cement and glass-ceramic materials, such as lithium disilicate ceramic (IPS e.max CAD, Ivoclar Vivadent) (EX) and leucite-reinforced ceramic (IPS Empress CAD, Ivoclar Vivadent) (EP), and also a hybrid ceramic (Vita Enamic, Vita Zahnfabrik) (VE). Eighteen sections with 1 mm thickness were cut from each CAD/CAM material and randomly divided into three groups, according to the surface etching time (30 s, 60 s, 90 s). The surface treatment was performed using 9.5% HF acid gel, then resin cement was applied on the prepared ceramic plates and light cured. µSBS values between resin cement and the ceramic material were measured with a universal testing machine at a crosshead speed of 0.5 mm/min until the failure occurred. The fractured surfaces of specimens were microscopically evaluated, and failure modes were classified as: adhesive between resin cement and ceramic, cohesive within ceramic or cement and mixed failure. Surface roughness of etched samples was examined using a scanning electron microscope. Obtained data were statistically analysed using one-way analysis of variance (ANOVA) and Bonferroni post hoc test with a level of significance α = 0.05. The results of the statistical methods applied indicate that µSBS mean difference for leucite-reinforced ceramic (EP) was statistically significant (p < 0.05). However, µSBS values for hybrid ceramic (VE) and lithium disilicate ceramic (EX) were not affected, from a statistical point of view, by the conditioning time (p > 0.05).

As water is essential to life and is an indispensable resource for ecosystems and their services and for nearly all human activities, the goal of this research was to evaluate the surface water quality of the Danube as it passes through the Romania–Serbia border in the nature reservations Djerdap and Iron Gate. The study aimed to assess the oxygen regime, nutrients and heavy metals contamination of the surface waters of the Danube on a length of about 240 km, between Bazias and Iron Gate II. Reference sampling and analytical methods (UV-VIS and AAS) were deployed to reach this goal. In addition, sediments were analyzed through back scattered SEM-EDAX for the elemental analysis of the sediment surface. Results obtained show a low environmental impact of heavy metals, while the Danube’s oxygen regime is under stress due to nutrients’ (nitrites and orthophosphates) significant concentration in the Danube surface water in the analyzed sector. Our approach can be applied to other water bodies in the area, to increase available scientific data together with societal awareness of the Danube’s environmental risks.