Effects of different surface treatments and artificial aging on the dentin bond strength and failure modes of 3D printed and milled resins.

The principles of green chemistry have progressively expanded into green analytical chemistry (GAC) and green sample preparation (GSP), fostering the development of quantitative tools such as AGREE and AGREEprep to assess the environmental sustainability of analytical workflows. Although these tools are increasingly adopted, their application is often limited to numerical scoring, with scarce discussion of the underlying assumptions and decision-making processes. This study critically evaluates the applicability and effectiveness of AGREE and AGREEprep in the context of Microwave-induced Plasma Atomic Emission Spectroscopy (MP-AES) analyses, using a real analytical workflow adopted within the Italian PRIN2022 project SECURE-COATS focused on developing functionalized and sustainable coatings for the conservation of stone materials in cultural heritage. The case study involves the determination of Ag, Zn, Ca and P in aqueous solutions obtained from immersion tests in bacterial growth media and from artificial ageing tests, aimed at assessing, respectively, the release of potentially antibacterial metals and the durability of the new coatings. A systematic and transparent data collection was performed to populate both AGREE tools, and the rationale behind each input parameter is explicitly discussed. This approach allows a critical assessment of how methodological choices, instrumental features and sample preparation steps influence the final greenness scores. This work demonstrates their value as decision-support instruments for improving analytical processes also in the field of chemistry for cultural heritage, by reducing both environmental impact and operational costs. The provided data and proposed methodology could serve as a useful reference framework for future green assessments.

This article aims to evaluate and compare the fracture resistance of three CAD/CAM veneer materials-a polymer-infiltrated ceramic network (VE; Vita Enamic), a lithium disilicate glass-ceramic (LD; IPS e.max CAD), and a zirconia-reinforced lithium silicate ceramic (ZLS; Vita Suprinity)-before and after artificial accelerated aging. Sixty standardized epoxy resin replicas of a prepared maxillary central incisor were fabricated using a stereolithographic 3D printing technique and randomly allocated into three groups (n = 20): Vita Enamic (VE), IPS e.max CAD (LD), and Vita Suprinity (ZLS). Laminate veneers were designed digitally and milled using a five-axis CAD/CAM milling unit. After appropriate surface treatment, veneers were adhesively luted using light-cured resin cement. Each material group was subdivided into two subgroups (n = 10): no aging or artificial aging via thermocycling (10,000 cycles between 5 and 55°C). Fracture resistance was measured using a universal testing machine with loading at 135 degrees to the long axis at a crosshead speed of 1 mm/min. Data were analyzed using one-way ANOVA, independent t-tests, and two-way ANOVA (α = 0.05). Significant differences were observed among materials before and after aging (p < 0.05). Before aging: ZLS 191.89 ± 6.24 N, LD 182.69 ± 6.00 N, VE 159.12 ± 9.16 N. After aging: ZLS 149.64 ± 5.98 N, LD 136.09 ± 5.69 N, VE 132.44 ± 5.30 N. Two-way ANOVA demonstrated significant effects of material type, aging condition, and their interaction (p < 0.05). Artificial aging significantly reduced the fracture resistance of all tested materials. ZLS demonstrated the highest fracture resistance both before and after aging under the conditions tested. Although VE initially showed lower fracture resistance than LD, fracture resistance after aging was not significantly different between LD and VE under the single load-to-fracture conditions tested in this in vitro study (p > 0.05). ZLS remained significantly superior to both LD and VE after aging (p < 0.05).

In this work the ultrasound propagation speed on the three spatial planes (Vx,Vy,Vz) and the weight loss/gain of three ornamental granites (Ávila, Spain) were determined before, during, and after being subjected to 90 cycles of three types of accelerated ageing processes (typical of cold regions): a) freezing/thawing and cooling/heating, b) salt crystallisation, and c) freezing/thawing and cooling/heating + salt crystallisation. A three-way mixed multivariate analysis of variance (MANOVA) was used for data analysis. Significant variations in the ultrasonic propagation speed and weight loss/gain of the different granites were observed for the three types of accelerated artificial ageing processes compared to the data obtained from the quarry samples, with the Airón Biotitic Granite (G) variety being the most altered granite and the combined freezing/thawing and cooling/heating + salt crystallisation accelerated artificial ageing test being the most damaging. To determine the durability of the different varieties of granite against the accelerated artificial ageing tests studied, the estimated data of compressive strengh, obtained from the ultrasound propagation speed data, were determined, with the Ávila Grey Granite (C) being the most resistant to the ageing tests studied.

To investigate the effect of print orientation (0°, 45°, and 90°) and artificial aging on flexural strength and fatigue resistance of 3D-printed denture bases compared to CAD/CAM milled controls, we fabricated 320 maxillary complete dentures, divided into 8 groups based on the fabrication method: horizontal, oblique, and vertical printing, alongside milled controls. Half of the specimens in each group were pre-conditioned via thermocycling and 240,000 cycles of chewing simulation. All specimens underwent static flexural strength testing and cyclic fatigue testing, followed by SEM fractography. The CAD/CAM milled bases demonstrated the highest mechanical durability, with non-aged specimens peaking at 149.43 ± 5.35 MPa. The horizontally 3D-printed non-aged specimens yielded the highest flexural strength (101.14 ± 4.80 MPa), while vertically printed aged specimens recorded the lowest (70.35 ± 8.18 MPa). Artificial aging degraded flexural strength uniformly across all orientations. Conversely, cyclic loading disproportionately devastated the older people's vertical group, resulting in a 70% fracture rate. Fractography corroborated these findings, revealing severe interlaminar delamination in vertical builds, contrasting with cohesive, trans-layer fractures in horizontal prints. In conclusion, Horizontal orientation provided improved structural durability; however, CAD/CAM milled dentures remain superior and are recommended for long-term clinical applications.

Introduction: The goal of this study was to evaluate the influence of combined artificial aging protocols on the surface roughness and Vickers microhardness of bulk-fill resin composites, compared with a nanofilled composite used as a reference. Materials and Methods: A total of 120 cylindrical specimens were prepared from three bulk-fill composites (Tetric EvoCeram Bulk Fill, Filtek One Bulk Fill, Venus Bulk Fill) and one nanofilled composite (Filtek Supreme Ultra). Specimens were allocated into three aging conditions: mechanical wear (A), mechanical wear combined with pH-cycling (B), and mechanical wear combined with thermocycling (C). Surface roughness (Ra) and Vickers microhardness (VHN) were evaluated at two time points (T1: 120,000 cycles; T2: 240,000 cycles). Non-parametric statistical tests were applied (α = 0.05). Results: Aging protocols significantly influenced both Ra and VHN (p < 0.05). Overall, higher surface roughness and lower Vickers microhardness values were observed after cumulative aging, with material-dependent variations between T1 and T2. The greatest post-aging differences were observed under combined mechanical wear and pH-cycling (subgroup B), whereas mechanical wear alone showed the lowest changes. Filtek One Bulk Fill and Filtek Supreme Ultra showed more favorable post-aging Ra and VHN values, whereas Venus Bulk Fill showed less favorable post-aging surface properties. No significant correlation was found between Ra and VHN (rho = -0.009; p = 0.958). Conclusions: Combined aging conditions significantly affected the surface roughness and Vickers microhardness of resin composites, with the greatest post-aging differences observed under acidic challenges. Bulk-fill materials exhibit variable resistance depending on composition, emphasizing the importance of material selection for long-term clinical performance. Clinical relevance: Composite restorations exposed to combined mechanical and acidic challenges may show altered surface roughness and microhardness, highlighting the need for materials with enhanced resistance in high-risk oral environments.

In recent years, the Japanese architectural industry has seen a growing trend toward timber construction, driven by increasing environmental awareness. However, despite the use of timber in structural elements, aluminium sash frames remain prevalent in many buildings. This study aims to develop a durable, all-timber sash system by focusing on the Structural Silicone Glazing (SSG) method. The method allows timber components to be used without direct exposure to outdoor conditions, thereby enhancing durability. This research investigates the adhesion performance of SSG sealant on timber. Initially, adhesion tests were conducted on various timber specifications to identify optimal candidates. Subsequently, residual adhesion performances were investigated on selected specimens pre-treated by several artificial aging methods. Experimental validation was performed using a full-scale specimen. A timber SSG unit (GW2940×GH805) was installed in a wind pressure chamber. The unit was subjected to 2.2 million cycles +1 kPa wind pressure, followed by a single application of ±4.5 kPa. After testing, the specimens were extracted from the unit for adhesion tests to assess residual performance. Additionally, full-scale mock-ups of arches and a circular shape were fabricated. CNC machining enabled the precise shaping of timber to match the edge curve of glass, which confirmed the feasibility of producing timber SSG units with complex geometries[A1.1][A1.2]. These results demonstrate the feasibility of applying SSG to timber sash systems with appropriate material selection.

Atomic-scale TEM characterization of dislocation-precipitate interaction mechanisms in a cold-worked Al-Cu-Mg-Si alloy.

The clinical use of universal resin composites for direct restorations has increased significantly in recent years due to their versatility and simplified shade-matching approach. However, limited long-term data exist on their stability under aging conditions. This study evaluated the optical and mechanical properties of six universal resin composites (Omnichroma, Charisma Topaz One, Vittra APS Unique, OptiShade, G-aenial A'Chord, and Neo Spectra ST) after six months of artificial saliva aging, while examining the influence of spectrophotometer type and inorganic filler composition on their performance. Color differences [CIEDE2000 (ΔE00)], translucency (TP00), gloss (GU), surface roughness (Ra, μm), and flexural strength (MPa) were measured before and after six months of artificial saliva aging. Statistical analysis was performed using non-parametric tests, including Kruskal Wallis, Mann Whitney U, and Wilcoxon signed-rank tests, with a significance level set at α < 0.05. Statistically significant differences were observed in color differences (ΔE00), translucency (TP00), gloss (GU) and flexural strength among the tested resin composites following aging (p < 0.05). Vittra APS Unique exhibited the highest translucency (TP00 = 55.35) and flexural strength (initial = 140.0 MPa, aged = 99.7 MPa), while G-aenial A'Chord demonstrated the lowest surface roughness (Ra = 0.124 μm) and highest gloss (56 GU). The type of spectrophotometer used significantly impacted the color differences (p < 0.05). Optical and mechanical properties of universal resin composites varied significantly after six months of artificial saliva aging. Moreover, this study showed that the type of spectrophotometer utilized had a significant effect on color differences.

The influence of simulated gastric acid aging on the Martens indentation parameters of subtractive and additive manufactured resins.

Surface treatment of Y-TZP with glass beads: Effects on flexural strength and bonding to resin cement.

This study aimed to evaluate the impact of artificial aging on the surface integrity, mechanical properties, and thermal stability of three commercially available denture base materials: conventional heat-polymerized polymethyl methacrylate (PMMA), CAD/CAM-milled PMMA, and 3D-printed photopolymerizable resin. Cylindrical samples (6mm diameter × 3mm height) were fabricated for each material. All samples were finished, and measurements were performed on the finished flat surface. A total of 20 samples were prepared for each material; half were tested at baseline and half after artificial aging, yielding a final sample size of n = 10 per group. Artificial aging was performed using 5000 thermocycles between 5°C and 55°C with a 10-second dwell time. Surface roughness (mean Ra, µm) was measured using non-contact optical profilometry, while surface microhardness (mean Vickers hardness, HV) was assessed using the Vickers hardness test. Thermal stability was evaluated using thermogravimetric analysis (TGA; mass loss, %) and differential scanning calorimetry (DSC; heat flow, mW/mg). Surface morphology was examined through scanning electron microscopy (SEM). Results indicated a significant increase in surface roughness for all materials post-aging (p < 0.05), with 3D-printed resin showing the greatest change (0.04 → 0.07μm) and milled PMMA the least (0.04→0.06μm). Milled PMMA had the highest baseline hardness (20.01 HV) and exhibited the least reduction after aging, while 3D-printed resin experienced the most pronounced decline (16.96→16.21 HV). TGA showed mass gain in conventional PMMA (+ 0.23%) and 3D-printed resin (+ 0.13%), whereas milled PMMA lost mass (-0.16%). Overall, CAD/CAM-milled PMMA demonstrated superior thermal aging resistance, maintaining hardness and surface quality, followed by conventional PMMA. In contrast, 3D-printed resin was most vulnerable to surface deterioration and softening under artificial aging. CAD/CAM-milled PMMA can be a recommended choice for the denture base.

The aim of this study was to evaluate the influence of artificial saliva ageing and cyclic hydrothermal loading on the mechanical properties of dental composite materials. Two commercial composites (Filtek Z550 and Filtek Ultimate Flow) and two experimental materials representing flow-type and hybrid composites were investigated. SENB specimens were prepared in accordance with ASTM E399, together with flat specimens intended for impact strength testing using the Dynstat method. All samples were aged in artificial saliva for approximately one month at 37 ± 1 °C, and subsequently, half of the specimens were subjected to thermocycling in the temperature range of 10-65 °C for 10,000 cycles. Static mechanical tests, including three-point bending (TFS), biaxial flexural strength (BFS), and compression strength (CS), were performed before and after thermocycling. In addition, impact strength and fracture toughness expressed by the stress intensity factor KIC were determined. The results were analyzed in terms of the residual work of fracture (WOF), while the durability of the materials was evaluated using Weibull distribution parameters. The experimental analysis was complemented by SEM observations of the microstructure. The obtained results demonstrated a pronounced deterioration of mechanical properties after hydrothermal loading. The average impact strength after artificial saliva ageing reached 11.69 J/mm2 for Filtek Z550, 11.57 J/mm2 for Ex-hyb(P), 16.39 J/mm2 for Filtek Ultimate Flow, and 10.27 J/mm2 for Ex-flow(P), whereas after thermocycling, these values decreased to 5.38 J/mm2, 8.86 J/mm2, 4.55 J/mm2, and 4.39 J/mm2, respectively. A similar trend was observed for the fracture toughness parameter KIC, which decreased considerably after thermocycling for all investigated materials. The analysis of the residual work of fracture revealed the influence of thermocycling on the energy-related parameters of the composites. In the case of TFS, the average WOF decreased, among others, from 13.65·10-3 J to 1.90·10-3 J for Filtek Ultimate Flow and from 4.76·10-3 J to 2.37·10-3 J for Filtek Z550. For BFS, a noticeable decrease in WOF was also observed, particularly for Ex-flow(P) and Filtek Ultimate Flow. In the compression tests (CS), the changes were less unambiguous, and some materials exhibited an increase in WOF after thermocycling. Furthermore, changes in the scale and shape parameters of the Weibull distribution were identified, indicating degradation of composite durability under hydrothermal loading. The results confirmed that cyclic hydrothermal loading exerts a greater influence on impact strength and fracture toughness than on static flexural strength. While all investigated materials exhibited degradation, the extent of changes was material-dependent, and compression behaviour showed non-uniform responses. Weibull analysis confirmed reduced reliability and increased heterogeneity of the composites after ageing, indicating that hydrothermal fatigue is a dominant factor governing long-term mechanical deterioration of dental resin-based composites.

Retinal age gap (RAG), defined as the difference between artificial intelligence-predicted retinal age and chronological age derived from fundus photographs, has been proposed as a potential biomarker of biological aging; however, the influence of ocular factors on RAG remains unclear. This retrospective observational study investigated clinical determinants of RAG in 283 eyes of adults who underwent 45-degree color fundus photography at the University of Yamanashi Hospital between February 2010 and April 2025. Retinal age was estimated using a deep learning-based algorithm developed from the Japan Ocular Imaging Registry. Associations between RAG and ocular and clinical variables were evaluated using linear mixed-effects models to account for within-subject correlations. The mean chronological age was 65.5 ± 11.7years, the mean predicted retinal age was 59.9 ± 17.0years, and the mean RAG was - 5.7 ± 19.1years. Lens status was strongly associated with RAG, with phakic eyes showing greater RAG values than pseudophakic eyes. Worse visual acuity and more hyperopic refractive error were also associated with greater RAG values. Overall glaucoma severity was not significantly associated with RAG, and mean deviation was not associated with RAG when analyzed as a continuous variable. In phakic eyes, glaucoma eyes showed greater RAG values than control eyes. These findings indicate that fundus-based retinal age estimation is influenced by ocular structural and optical factors, particularly lens status, and should be interpreted with consideration of ocular conditions.

Artificial reef age reshapes benthic microbial communities and modulates the genetic potential for nitrogen and sulfur cycling.

The durability of bonded CAD/CAM restorations depends largely on effective adhesion to dentin. Immediate dentin sealing (IDS) has been proposed to enhance bonding effectiveness compared with conventional delayed dentin sealing (DDS). Additionally, while resin cements remain the gold standard for luting, flowable composites have emerged as potential alternative. This study aimed to evaluate the effect of different dentin sealing techniques and luting materials on the microtensile bond strength (µTBS) of CAD/CAM composite disc to dentin after immediate and long-term aging. Twenty flat dentin specimens were obtained from extracted human molars and randomly assigned to two main groups according to the dentin sealing techniques into (group 1: No-IDS and group 2: IDS with a universal adhesive). The two groups were provisionally restored with temporary materials for two weeks. Afterwards the temporary materials were removed, and surface was reactivated with air borne abrasion. Each group was subdivided according to the luting material used for CAD/CAM composite discs into (subgroup 1: dual-cure self-adhesive resin cement and subgroup 2: submicron hybrid flowable composite). The specimens were sectioned into micro-bars and tested for µTBS either after 48h (immediate) or 6 months (long-term aging) in water storage. Data were analyzed using three-way ANOVA and post-hoc comparisons (α = 0.05). Failure modes were analyzed. Immediate µTBS values displayed no significant differences among the tested groups. Following long-term aging, IDS combined with a flowable composite yielded significantly higher µTBS compared to groups without IDS. Furthermore, the flowable composite demonstrated significantly higher bond strength than the self-adhesive resin cement, regardless of the dentin sealing protocol used. The microtensile bond strength of CAD/CAM composite to dentin is dependent on both the dentin sealing technique and the luting material. Immediate dentin sealing combined with a submicron hybrid flowable composite demonstrated the highest bond strength after long-term aging, compared to the tested self-adhesive resin cement. The effect of artificial aging was highly material-dependent; therefore, long-term aging is necessary to accurately evaluate the bond durability.

Role of hydrogen embrittlement on resistance to crack extension of 2024 aluminium alloy for different artificial aging conditions under short corrosion exposure times

Innovative coatings for corrosion protection of historical aluminium alloys in aerospace heritage

To evaluate the impact of preheating on the physical properties of bulk-fill resin composites, with a particular focus on microhardness and surface roughness. In this study, seven bulk-fill resin composites (SonicFill 3, Opus Bulk-Fill Flow, Opus Bulk-Fill, Metafil Bulk-Fill, Tetric PowerFlow, Tetric N-Ceram, and Estelite Bulk-Fill Flow) and one conventional resin composite (Filtek Z250) were tested. Specimens were divided into two main groups: Group 1 (preheated 68°C for 10 minutes) and Group 2 (stored at room temperature). For each group, five disc-shaped resin composites (4 mm thickness x 5 mm diameter) were prepared. Each bulk-fill resin composite was applied in a single increment, whereas Filtek Z250 was placed in the molds in 2 mm layers. To complete the polymerization, the samples were kept in distilled water at 37°C for 24 hours. Then, the surfaces of the samples were polished with Twist Dia (Clearfil) polishing discs to imitate the finishing and polishing processes. Baseline microhardness and surface roughness values were measured. Subsequently, specimens underwent artificial aging simulating 2 years of clinical use (10,000 brushing cycles + 1,200 thermal cycles). Post-aging measurements were repeated, and statistical analyses were conducted. Significant differences in microhardness values were observed among the experimental groups for all restorative materials, except for Estelite Bulk-Fill Flow (P> 0.05). The highest bottom-to-top hardness ratio was found in both preheated and non-preheated Opus Bulk-Fill Flow, while the lowest was observed in preheated Tetric PowerFlow. Microhardness generally decreased with depth, and the impact of preheating varied among materials. Post-aging surface roughness increased in all groups. Preheated Metafil Bulk-Fill exhibited the highest surface roughness, whereas Estelite Bulk-Fill Flow (both preheated and non-preheated) showed the lowest. Preheating reduced viscosity and enhanced microhardness in certain resin composites but also increased surface roughness over time. The effects of preheating are material-dependent due to compositional differences. Preheating may improve handling and selected properties of resin composites; however, its long-term effects should be considered when selecting materials for clinical use.

This in vitro study evaluated the effect of collagen crosslinking agents (grape seed extract, riboflavin, and chitosan nanoparticles with UVA light) on hybrid layer thickness, resin tag length, and shear bond strength (SBS) of a fifth-generation adhesive resin to caries-affected dentin of primary molars. Seventy-five carious human primary molars were selected, exhibiting lesions that reached the middle third of the dentin, according to the International Caries Detection and Assessment System (ICDAS) criteria 5. Infected dentin was removed. The crowns were shortened in height up to CAD, and etching was performed, followed by division of the samples into five groups (n = 15 each). Group 1: No collagen crosslinking (CCL) agent; Group 2:6.5% Grape Seed Extract (GSE); Group 3:0.1% riboflavin (RF)-UVA; Group 4:0.2% chitosan nanoparticles (CHNPs)-UVA; and Group 5: chlorhexidine (CHX). Composite restorations were built using a fifth-generation etch-and-rinse (ER) adhesive, followed by artificial aging. Scanning electron microscopy (SEM) was used to determine the resin tag length (RTL) and hybrid layer (HL) thickness. The SBS and failure modes were assessed using a universal testing machine and a stereomicroscope. One-way ANOVA and post-hoc Tukey tests were used to evaluate the means across all tested groups (p < 0.05). Group 4-CHNPs-UVA demonstrated the highest RTL (20.03 ± 3.54μm) and thickest HL (5.65 ± 0.42μm). Group 1 (No CCL agent) displayed the shortest RTL (7.11 ± 1.05μm) and thinnest HL (1.23 ± 0.11μm). The CHNPs-UVA pretreated samples showed maximum bond strength (10.31 ± 0.23MPa). Group 1 (No CCL agent) tested samples presented minimum bond integrity (6.18 ± 0.33MPa). Within the limitations of this in vitro study, CHNPs-UVA appears promising as a biomodification strategy for CAD in primary molars and warrants further long-term in vivo investigations before clinical recommendations can be made.