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).

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.

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.

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.

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.

In modern endodontics, nickel-titanium (NiTi) rotary instruments are used on a large scale for root canal shaping. Nevertheless, the separation of an instrument is a serious concern during shaping. The aim of this study is to determine and compare the torsional fracture characteristics of three types of NiTi endodontic instruments, each with different cross-section designs and movements performed during root canal shaping: Endostar E3 (Endostar, Poldent Co. Ltd., Warsaw, Poland); Reciproc R25 (VDW, Munich, Germany); and Protaper Next X2 (Dentsply Maillefer, Ballaigues, Switzerland). Fifteen instruments are used in this study, divided in three groups (n = 5): Group Endostar, Group Reciproc and Group Protaper. For testing, each instrument is used to shape five simulated root canals, following which its torsional stress to failure is measured. The fracture lengths of all three groups are roughly between 2 and 3 mm from the tip. Higher values of the moment of torsion in fracture, and smaller values of the maximum twisting angle are observed for Group Endostar, as well as closer to circular cross-sections. However, the values of the shear tension are similar for all three groups, because the disadvantage given by the fracture section shape for Groups Reciproc and Protaper is compensated either by size or by intrinsic properties of the instrument material. For the shear tension the Endostar values are insignificantly increased (Kruskal–Wallis test, p = 0.207), and in the case of the maximum twist angle the Protaper values are insignificantly increased (Kruskal–Wallis test, p = 0.287). Because of the instruments shape and conicity, the analysis had to be carried out separately with regard to the length of the fractured tip. Rules-of-thumb are extracted from the study for current practice: if a blockage of the first 2 to 3 mm part of the tip can be anticipated (by the excessive curving of the instrument), the handpiece must be adjusted to torque values that do not exceed 1.5 to 2.5 N · cm for Endostar and 1 to 2 N · cm for Reciproc and Protaper instruments.