Vickers Microhardness Tester Research Articles

Effect of hybrid ratio and sintering temperature on hardness properties of hybrid AMCs

The present research work is aimed toward fabrication of hybrid Aluminium matrix composites (AMCs) of different hybrid ratios of Alumina (Al2O3) and Silicon Carbide (SiC) followed by investigation of their microstructure and hardness properties. Hybrid AMCs were fabricated through powder metallurgy process by adding 5 wt% and 10 wt% mixture of Al2O3 and SiC reinforcements of various hybrid ratios (0:1, 1:3, 1:2, 1:1, 3:1, 2:1 and 1:0) with the pure Aluminium powder. The mixture powder were properly mixed by ball milling arrangements for 6 h. The mixture powder were preheated at 500 °C for 2 h in a high temperature programmable tube furnace followed by immediate compaction under a closed die at 1500 psi pressure through automatic hydraulic press. The compacted specimens were then sintered at 350 °C, 500 °C and 650 °C for 2 h in the same furnace. Hardness test of the fabricated hybrid AMCs were carried out by Vickers Micro-hardness testers and hardness values were measured by the integrated software. The hardness properties of hybrid AMCs also were compared with the hardness properties of pure Aluminium specimens fabricated through the same process route and process parameters. It is interestingly observed that hardness of hybrid AMC is more when pure Aluminium powder is reinforced with only SiC of same wt.% for both the cases (5 wt% and 10 wt% reinforce AMCs) and it decreases with decrease of weight fraction of SiC and simultaneously increase of weight fraction of Al2O3 keeping total weight fraction of mixture as constant.

Influence of Graphene/h-BN and SiC/h-BN reinforcing particles on microstructural, mechanical and tribological characteristics of Al7075-based hybrid nanocomposites

Aluminium (Al) based Metal Matrix Composites (MMCs) replaced conventional alloys in numerous sectors like the automotive to aerospace industries. In this investigation, Al7075/Silicon carbide (1 wt%)/Hexagonal-boron nitride (0.5 wt%) and Al7075/Graphene (1 wt%)/Hexagonal-boron nitride (0.5 wt%) hybrid metal matrix nanocomposites (HMMNCs) prepared using an ultrasonic-assisted melt-stirring squeeze casting process. To attain the homogenous mixing of hard ceramic/nanoparticles, reduce the aggregation effect and improve wettability of the reinforcing nanoparticles in the molten slurry. Reinforcement particles mixture (Silicon carbide (1 wt%)/Hexagonal-boron nitride (0.5 wt%) and Graphene (1 wt%)/Hexagonal-boron nitride (0.5 wt%)) have been ball-milled for the duration of 1 to 6 h (hrs). To analyze the morphology of the 1–6 h ball-milled hybrid reinforcing particles mixture was analyzed via scanning electron microscope (SEM). Moreover, microstructural investigation of the Al-based HMMNCs was performed using optical microscopy (OM), field-emission scanning electron microscopy (FE-SEM) and scanning electron microscope (SEM). Also, the dispersal of hybrid reinforcing particles mixture in Al7075-based HMMNCs was examined via SEM-equipped with x-ray mapping analysis. The fabricated Al7075-based HMMNCs are tested for their tensile strength, microhardness and tribological behavior by employing universal testing machines, Vickers microhardness tester and ball-on-disc instruments. Tribological characteristics of the Al7075-based HMMNCs were observed via ball-on-disc tribometer apparatus with load (10, 15 and 20 N), time (15 min) and speed (300, 600 and 900 rpm). While investigating, it is perceived that that the wear, tensile strength, hardness and microstructure characteristics of the Al7075/Silicon carbide/Hexagonal-boron nitride and Al7075/Graphene/Hexagonal-boron nitride HMMNCs were superior over the Al7075 alloy. It is found that Vickers and Rockwell hardness of the Al7075/SiC/h-BN HMMNCs were superior by 36.87% and 16.29%, respectively, over the Al7075 specimen. Whereas, UTS of the Al7075/Graphene/h-BN HMMNCs were superior by 38.19% over the Al7075 alloy.

Investigation of mechanical properties, remineralization, antibacterial effect, and cellular toxicity of composite orthodontic adhesive combined with silver-containing nanostructured bioactive glass

BackgroundThe formation of white spots, which represent early carious lesions, is a major issue with fixed orthodontics. The addition of remineralizing agents to orthodontic adhesives may prevent the formation of white spots. The aim of this study was to produce a composite orthodontic adhesive combined with nano-bioactive glass-silver (nBG@Ag) for bracket bonding to enamel and to investigate its cytotoxicity, antimicrobial activity, remineralization capability, and bond strength.MethodsnBG@Ag was synthesized using the sol-gel method, and characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy with an attenuated total reflectance attachment (ATR-FTIR). The cytotoxicity test (MTT) and antimicrobial activity of adhesives containing 1%, 3%, and 5% (wt/wt) nBG@Ag were evaluated, and the shear bond strength of the adhesives was measured using a universal testing machine. Remineralization was assessed through microhardness testing with a Vickers microhardness tester and scanning electron microscopy (SEM). Statistical analyses were conducted using the Shapiro-Wilk test, Levene test, one-way ANOVA, Robust-Welch test, Tukey HSD method, and two-way ANOVA.ResultsThe biocompatibility of the adhesives was found to be high, as confirmed by the lack of significant differences in the cytotoxicity between the sample and control groups. Discs made from composites containing nBG@Ag exhibited a significant reduction in the growth of Streptococcus mutans (p < 0.05), and the antibacterial activity increased with higher percentages of nBG@Ag. The shear bond strength of the adhesives decreased significantly (p < 0.001) after the addition of nanoparticles, but it remained above the recommended value. The addition of nBG@Ag showed improvement in the microhardness of the teeth, although the differences in microhardness between the study groups were not statistically significant. The formation of hydroxyapatite deposits on the tooth surface was confirmed through SEM and energy-dispersive X-ray spectroscopy (EDX).ConclusionAdding nBG@Ag to orthodontic adhesives can be an effective approach to enhance antimicrobial activity and reduce enamel demineralization around the orthodontic brackets, without compromising biocompatibility and bond strength.

Influences of preheating parameters on the quality of weld by thermite rail welding

The major goal of this study is to enhance the mechanical and metallurgical characteristics of rail steel grade R260 joined by thermite welding under various preheating conditions, including preheating time and gas pressure. Mainly two conditions, referred to as the Normal Condition and Improved Condition, are carried out for experiments. Prior to welding, the Normal Condition was preheated using liquefied petroleum gas (LPG) and oxygen gas pressures of 1 bar and 4.5 bar for 3 min, and the Improved Condition was preheated using liquefied petroleum gas and oxygen gas pressures of 1.2 bar and 4.5 bar for 6 min and 30 s. To investigate the mechanical and physical properties, micro-Vickers hardness tests, tensile tests and slow bending tests were also carried out. Welded metal in Normal Condition has many defects, including gas holes and shrinkage cavities. When comparing the Normal Condition to the Improved Condition, the Improved Condition demonstrates significantly more bending load and deflection. Specifically, the thermite welded rail sample of Improved Condition demonstrated a remarkable ability to endure bending loads of 108 tonnes and a deflection of 16 mm, and this sample remained unbroken until it exceeded 50% of the standardized deflection limit (10 mm). In addition, the average hardness values for the Improved Condition of the weld metal zone and the heat-affected zone were 331 HV and 289 HV, respectively. The Normal Condition produced an unsatisfactory fracture surface after slow bending test. This was caused by weld defects at the thermite weld due to inappropriate preheating.

Experimental investigation on microstructure, hardness and corrosion resistance of an electromagnetic welded titanium-stainless steel dissimilar materials

The electromagnetic welding (EMW), often known as magnetic pulse welding, is a solid-state welding technology that is used to join two different materials using high-velocity impact. In this study an attempt was made to join the Titanium(Ti)- Stainless Steel(SS 304) materials with the help of multi turn disc coil along with the field shaper. A comparative investigation was conducted on the joint’s microstructure, as well as its mechanical and corrosion properties. Inverted optical microscopy (OM) and x-ray diffraction (XRD) were used to do the microstructural characterization of the joint. The micro-Vickers hardness test was used to analyse the material’s mechanical properties. In addition, electrochemical experiments were run on the Ti-SS 304 EMW junction as well as the component materials to establish how resistant they were to corrosion. Using an electrochemical impedance analyzer, the levels of corrosion that were caused by the structures were measured while they were submerged in a solution of nitric acid at room temperature. The microstructural pictures revealed a wave-like pattern at the material’s interface, which is evidence of strong adhesion between the components. The micro vickers hardness of the joints was within the permitted range, as was the corrosion rate.

Efficacy of peptide-based enamel coatings in the prevention of demineralization using fixed orthodontic brackets in a rat model

White spot lesions (WSLs) represent a prominent pathology encountered during orthodontic treatment, originating from enamel demineralization induced by the accumulation of bacterial biofilms. The previously developed bioinspired enamel coating form of self-assembling antimicrobial peptide D-GL13K exhibited antimicrobial activity and enhanced acid impermeability, offering a potential solution to prevent demineralization. The primary aim of this investigation is to assess the invivo anti-demineralization properties and biocompatibility of the D-GL13K coating. A rat model was developed to assess the antimicrobial enamel coating during fixed orthodontic treatment. The anti-demineralization efficacy attributed to the D-GL13K coating was evaluated by employing optical coherence tomography, Vickers microhardness testing, and scanning electron microscopy. The biocompatibility of the D-GL13K coating was investigated through histologic observations of vital organs and tissues using hematoxylin and eosin. The D-GL13K coating demonstrated significant anti-demineralization effects, evidenced by reduced demineralization depth analyzed through optical coherence tomography and enhanced Vickers hardness than in the noncoated control group, showcasing the coating's potential to protect teeth from WSLs. Scanning electron microscopy analysis further elucidated the diminished enamel damage observed in the group treated with D-GL13K. Importantly, histologic examination of vital organs and tissues using hematoxylin and eosin staining revealed no overt disparities between the D-GL13K coated group and the noncoated control group. The D-GL13K enamel coating demonstrated promising anti-demineralization and biocompatibility properties in a rat model, thereby suggesting its potential for averting WSLs after orthodontic interventions. Further research in human clinical settings is needed to evaluate the coating's long-term efficacy.

Bovine and Ovine Teeth as a Substitute for the Human Teeth: An Experimental Study.

Although various kinds of research have been conducted to compare the physical and chemical properties of dentin and enamel in animal and human samples, proving the ability of animal dentin material as a good substitute for human specimens is always a challenge for experimental studies. The aim of the present study is to investigate whether the changes in the dentin microhardness of animal samples are similar to those of human samples or not. In this in vitro study, sixty single-rooted human, bovine, and ovine teeth (n=20 in each group) were decoronated at CEJ. The remaining roots were embedded in acrylic resin and a cross-section cut was made in the middle of the samples in order to achieve dentin disks. All of the 120 samples were randomly assigned to three control (n=20 for each group) and three experimental groups (n=20 for each group). In the experimental groups, calcium hydroxide with a creamy consistency was prepared and the disks were embedded in dishes containing calcium hydroxide. Control groups were embedded in physiological saline. The samples were incubated for seven days at the 37oC and Vickers microhardness test was performed immediately. The average of three yielded values was considered as the final value of microhardness. Data were analyzed using two-way ANOVA, one-way ANOVA, and Tukey's post hoc tests. In the control group, the human samples showed the highest microhardness value, while the bovine teeth had the lowest microhardness value (p< 0.001). In the calcium hydroxide group, the human samples showed the highest microhardness value in comparison to bovine and ovine to teeth. However, no significant difference was observed between the bovine and ovine samples in microhardness value. Based on our research, substituting bovine and ovine samples with human samples in experimental studies is not recommended. Nevertheless, more studies are needed in this regard.

Assessment of the Additive Effect of Remineralizing Agents in Combination With Fluoride Releasing Adhesives in the Prevention of Enamel Decalcification in Orthodontic Patients: An In Vitro Study.

Introduction Incorporation of remineralizing agents with fluoride-releasing bracket adhesives may prevent the development of white spot lesions (WSL) or reverse the established WSL in patients undergoing fixed orthodontic treatment. We aimed to find out how effectively casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and fluoride varnish (FV) can remineralize teeth when mixed with fluoride-releasing orthodontic adhesive. Materials and methods We randomly assigned a total of 60 premolar teeth, therapeutically extracted for orthodontic purposes, into two equal groups. Group I (n = 30) utilized fluoride-releasing adhesive (FR), and Group II (n = 30) bonded with non-fluoride adhesive (NFR). Based on the applied remineralizing agent, we further divided each of the two groups into three equal subgroups of 10: Group IA (FR+FV), Group IB (FR+CPP-ACP), Group IC (control-only FR), Group IIA (NFR+FV), Group IIB (NFR+CPP-ACP), and Group IIC (control-only NFR). Following bonding procedures, all the samples underwent pH cycling for 28 days, where the enamel samples were immersed in 20 ml of demineralizing solution for three hours, followed by immersion in 30 ml of remineralizing solution for 17 hours. The samples were analyzed for shear bond strength (SBS) on a universal testing machine and hardness values (HV) by the Vickers microhardness test (VMT) using the indentation method. We also evaluated the adhesive remnant index (ARI) scores to determine the site of bracket failure. Statistical analysis The shear bond strength (SBS) and hardness value (HV) were expressed as the mean, standard deviation (SD), and median for each subgroup. We used the non-parametric Kruskal-Wallis test to analyze the SBS and HV, followed by the Dunn-Bonferroni test for intra-pair differences. The ARI score was expressed as the frequency of the percentage distribution, and the difference in the distribution of ARI scores between the groups was assessed by the Cochran chi-square test. The probability (p) value equal to or less than 0.05 was considered statistically significant. Results The results show that Group IB, bonded with a fluoride-releasing adhesive and a CPP-ACP remineralizing agent surface treatment, has the highest HV of300.23 units. Group IIC (only NFR) has the lowest hardness of153.3 units, which is statistically significant (p < 0.001). However, the ARI scores are not statistically significant between the groups tested. Conclusion The bond strength of the adhesive and the surface hardness of the enamel increased with the addition of fluoride varnish and CPP-ACP to both the fluoride-releasing and non-fluoride-releasing adhesives.

In Vitro Effect of Streptococcus mutans Biofilm Produced in Sugar-Free Coca-Cola on Enamel

ObjectiveSugary drinks such as Coca-Cola may expedite dental caries. For this reason, sugar-free drinks like Coca-Cola Zero Sugar (CZ) may be considered advantageous. This research aims to evaluate in vitro the CZ effect in the presence of Streptococcus mutans (S. mutans) biofilm on enamel demineralization. MethodsNinety-six human enamel slabs (4 × 4 mm) were used. S. mutans UA-159 72-hour biofilm was created over enamel surfaces. The specimens were soaked in CZ, HCl, or 10% sucrose in PBS solution, 3 times a day for 15 minutes over the course of 4 days. Viable counts (CFU/mL) and biofilm biomass (Crystal Violet staining) were evaluated. pH was measured after each exposure. After 4 days, Demineralization was evaluated clinically and by Vickers microhardness tests. Slabs were photographed using a stereomicroscope before and after exposure to caries-promoting conditions. ResultsSlabs that were soaked in CZ showed an increase in viable counts compared to control and almost similar counts with 10% sucrose in PBS solution exposures (1010and109CFUmL, respectivly). Biofilm biomass tests showed a 25% higher bacterial growth in the CZ group. CZ pH measures were the lowest and the only group to show a decrease in pH over time (pH ∼3). Enamel slabs that were evaluated clinically in the stereomicroscope postexposures had a chalky and matt appearance as opposed to their shiny appearance in the baseline evaluation. ConclusionsCZ creates a favourable environment for the growth of S. mutans. It may be suggested that even though CZ is sugar free it has a cariogenic effect on enamel. Clinical significanceClinicians need to educate patients that sugar-free carbonated drinks may be just as harmful as regular carbonated drinks, and hence avoided. This research emphasizes the harmful effect sugar-free carbonated drinks on teeth and sheds new light on their cariogenic potential.

Study on Microstructure and Wear Resistance of WC-based Cermet Coatings Prepared by HVAF

Abstract To mitigate the risk of vapor corrosion damage to the overflow mechanical parts, WC-based metal-ceramic coatings were applied to the surface of a 45-gauge steel substrate by supersonic air-assisted flame spraying (HVAF). The mechanical and wear-resistant qualities of the coating were identified by Vickers micro-hardness, ball-disc friction, and wear test, as well as optics, scanning electron, X-ray diffractometer, and white light interferometer systems. The findings demonstrate the layered structure of the WC-based coating, which is made up of the bonded phase and its distribution of hard phase particles that are diffusely dispersed. The coating is free of cracks, inclusions, and other defects, and its structure and organization are dense with a porosity of 0.86 ± 0.05%. The phenomenon of oxidative decarburization did not occur in the process of preparing the WC hard phase for WC-based metal-ceramic coatings. As a result, the coating’s micro-hardness of 11.83 ± 0.55 GPa is eight times that of the substrate. The results of comparing the three-dimensional abrasion patterns of the coating and the substrate reveal that the coating has superior abrasion resistance because its width and depth of abrasion are smaller than that of the substrate and a lot of furrows have formed on the substrate material’s surface. In contrast, the sprayed layer only had faint traces of abrasion. After three years of actual service, the impeller surface coating is essentially unaltered, which effectively addresses the issue of vapor corrosion damage to the slurry pump’s impeller and extends the pump’s service life to guarantee the overflow mechanical components operate safely and steadily.

Numerical and experimental study on effect of induction heating parameters on the coating of Zn layer on mild steel

The objective of the study is to determine the most effective induction heating parameters for melting pure zinc selectively over the mild steel substrate surface. The numerical simulation on effect of induction heating parameters on the mild steel substrate is studied using COMSOL Multiphysics 5.6 software. The optimised effective parameters are used for the experimental analysis for the validation. Variables such as coil configuration, stand-off distance (SOD), coil current and frequency were systematically changed, and optimal settings were chosen on the basis of time temperature contour curve and the heating rate within the material. Results of the numerical analysis portrayed that a pancake coil geometrical configuration, SOD of 2 mm, coil current of 300 A and alternating frequency of 300 kHz were found as the optimum set of parameters for the effective surface repair. An experimental investigation was carried out by depositing a thin layer of zinc on mild steel substrate using the optimized parameters. The surface integrity of the coated specimen was examined through the high-resolution optical microscopy, X-ray diffraction and electron back scattered diffraction (EBSD) techniques. The hardness property of the coated specimen was examined with a Vickers microhardness tester. The microstructure analysis and hardness measurement showed that consistent coating is achieved without affecting the base metal/substrate properties. The experimental results very much coincide with the numerical simulation.

Microhardness and Microstructure of Aluminium Alloy 5052 by High-Pressure Torsion Process and Subsequent Annealing

The grain refinement by high-pressure torsion (HPT) process and high-temperature stability have been studied in a commercial non-heat-treated aluminium alloy, 5052. The HPT process was conducted on 10 mm disks of the alloys at room temperature with an applied pressure of 6 GPa for 5 and 10 turns with a rotation speed of 1 rpm. The HPT processing leads to microstructural refinement with an average grain size of ~188 nm and ~156 nm for 5 turns and 10 turns with an increased value of dislocation density. The Vickers microhardness test was performed at 100 gf for a duration of 15 s. It was found that the hardness increased from the onset of straining and saturated at approximately 165 Hv after processing at both 5 and 10 turns. The samples were then annealed at high temperatures. The study demonstrated that annealing at 200 °C for 1 h reduced the hardness by 30% in both samples and enlarged the gain sizes to 226 nm. The results indicated that the rate of hardness decrease is faster in 10 turns compared with 5 turns thus explaining the higher kinetic annihilation phenomenon observed in higher straining in 10 turns due to the higher stored energy in the grains.

Effect of glazing and thermocycling on the fracture toughness and hardness of a New fully crystallized aluminosilicate CAD/CAM ceramic material

BackgroundThe mechanical properties of fully crystallized lithium aluminosilicate ceramics may be influenced by intraoral temperature variations and postmilling surface treatment. The purpose of this study is to explore the interplay among glazing, thermocycling, and the mechanical characteristics (namely, fracture toughness and hardness) of fully crystallized lithium aluminosilicate ceramics.MethodsBending bars (n = 40) cut from LisiCAD blocks (GC, Japan) were randomly assigned to glazed or unglazed groups (n = 20) and subjected to the single edge v-notch beam method to create notches. A glazing firing cycle was applied to the glazed group, while the unglazed group was not subjected to glazing. Half of the specimens (n = 10) from both groups underwent thermocycling before fracture toughness testing. The fracture toughness (KIC) was evaluated at 23 ± 1 °C using a universal testing machine configured for three-point bending, and the crack length was measured via light microscopy. Seven specimens per group were selected for the hardness test. Hardness was assessed using a Vickers microhardness tester with a 1 kg load for 20 s, and each specimen underwent five indentations following ISO 14705:2016. The Shapiro–Wilk and Kolmogorov-Smirnov tests were used to evaluate the normality of the data and a two-way ANOVA was utilized for statistical analysis. The significance level was set at (α = 0.05).ResultsRegardless of the thermocycling conditions, the glazed specimens exhibited significantly greater fracture toughness than did their unglazed counterparts (P < 0.001). Thermocycling had no significant impact on the fracture toughness of either the glazed or unglazed specimens. Furthermore, statistical analysis revealed no significant effects on hardness with thermocycling in either group, and glazing alone did not substantially affect hardness.ConclusionsThe impact of glazing on the fracture toughness of LiSiCAD restorations is noteworthy, but it has no significant influence on their hardness. Furthermore, within the parameters of this study, thermocycling was found to exert negligible effects on both fracture toughness and hardness.

Investigation of the Influence of Powder Fraction on Tribological and Corrosion Characteristics of 86WC-10Co-4Cr Coating Obtained by HVOF Method

Samples using powders of four different fractions, 15–20 μm, 20–30 μm, 30–40 μm and 40–45 μm, were fabricated to investigate the wear resistance, corrosion resistance and tribological properties of the 86WC-10Co-4Cr coating obtained using the HVOF method. The phase composition, microstructure and elemental distribution were analyzed using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy techniques. The hardness was measured on a Vickers microhardness tester, the friction coefficient and wear rate were investigated using a tribometer, and the corrosion resistance was evaluated on an electrochemical corrosion station. The results showed that the cross-sectional microstructure of the coating is mainly represented by multifaceted WC crystals embedded in the Co-Cr matrix and the presence of lower tungsten carbides, particularly W2C. The 15–20 μm fraction particles were subjected to superheating, contributing to the decarburization process. The 20–30 µm and 30–40 µm sized particles prevented overheating and had a more homogeneous structure. The 40–45 µm powder fractions did not reach sufficient temperature for complete melting, resulting in the formation of pores in the coating layers. The phase composition of the coatings included WC, W2C and CoO phases. According to the results of the study, it was found that the optimal powder fraction for coating the 86WC-10Co-4Cr composition with improved characteristics is the fraction of the 20–30 µm sized particles.

A Modern Multidisciplinary Method to Characterize Natural White Spot Lesions with 2D and 3D Assessments: A Preliminary Study.

In this preliminary study, a multidisciplinary method based on high-resolution analytical techniques (such as microcomputed tomography, Raman Microspectroscopy, scanning electron microscopy, and Vickers microhardness test) was exploited to evaluate the alterations that occur in human teeth at the initial stage of the carious lesion. To this purpose, six extracted molars displaying a natural white spot lesion (WSL) were investigated. Specific morphological, structural, and chemical parameters, such as the mineral density, indentation hardness, molecular and elemental composition, and surface micromorphology were obtained on the WSL, and the results were statistically compared (t-test, p < 0.05) to those of the sound enamel on the same tooth. In the WSL, with respect to the sound area, a decrease in the mineral density and crystallinity was detected together with differences in the molecular composition and surface microstructure, such as the occurrence of micropores and irregularities. Moreover, the elemental analysis highlighted in WSL showed a statistically significant decrease in Ca and P percentages. In conclusion, this multidisciplinary approach allows us to fully characterize the area of interest, providing a deeper knowledge of these enamel lesions, which could have important clinical implications.

Microhardness and elemental analysis of ion-releasing restoration/ dentin interface following enzymatic chemomechanical caries excavation

BackgroundThis study was conducted to compare chemical, elemental and surface properties of sound and carious dentin after application of two restorative materials resin-modified glassionomer claimed to be bioactive and glass hybrid restorative material after enzymatic chemomechanical caries removal (CMCR) agent.MethodsForty carious and twenty non-carious human permanent molars were used. Molars were randomly distributed into three main groups: Group 1 (negative control) - sound molars, Group 2 (positive control) - molars were left without caries removal and Group 3 (Test Group) caries excavated with enzymatic based CMCR agent. After caries excavation and restoration application, all specimens were prepared Vickers microhardness test (VHN), for elemental analysis using Energy Dispersive Xray (EDX) mapping and finally chemical analysis using Micro-Raman microscopy.ResultsVickers microhardness values of dentin with the claimed bioactive GIC specimens was statistically higher than with glass hybrid GIC specimens. EDX analysis at the junction estimated: Calcium and Phosphorus of the glass hybrid GIC showed insignificantly higher mean valued than that of the bioactive GIC. Silica and Aluminum mean values at the junction were significantly higher with bioactive GIC specimens than glass hybrid GIC specimen. Micro-raman spectroscopy revealed that bioactive GIC specimens showed higher frequencies of v 1 PO 4, which indicated high level of remineralization.ConclusionsIt was concluded that ion-releasing bioactive resin-based restorative material had increased the microhardness and remineralization rate of carries affected and sound dentin. In addition, enzymatic caries excavation with papain-based CMCR agent has no adverse effect on dentin substrate.

Effect of Postrinsing Times and Methods on Surface Roughness, Hardness, and Polymerization of 3D-Printed Photopolymer Resin.

This in vitro study investigated the effects of different postrinsing times and methods on the surface roughness, surface hardness, and degree of polymerization of materials manufactured via stereolithography (SLA). A total of 288 disk-shaped specimens were manufactured using an SLA three-dimensional (3D) printer. The specimens were randomly divided into nine groups (n = 32) based on rinsing times and methods. The groups were categorized into three rinsing methods: automated, ultrasonic, and hand washing, with rinsing times of 5, 10, and 15 minutes using a 99% isopropanol alcohol as a solvent. Linear roughness (Ra) and area roughness (Sa) were measured using a 3D confocal laser microscopy; the roughness morphology was evaluated by using scanning electron microscopy. Vickers hardness (VHN) tests were performed using a Vickers microhardness tester. Fourier-transform infrared spectrometry was used to determine the degree of conversion of treated specimens. Data were statistically analyzed using two-way analysis of variance. The post hoc Tukey tests were conducted to compare the differences between groups (p < 0.05). The choice of the rinsing time and method affected the surface properties of the SLA photopolymer resin. The 15 minutes of ultrasonic method exhibited the highest Ra scores (0.86 ± 0.1 µm), while the 15 minutes of automated method presented the highest Sa scores (1.77 ± 0.35 µm). For the VHN test, the 15 minutes of ultrasonic method displayed the highest VHN score (18.26 ± 1.03 kgf/mm2). For the degree of polymerization, the 15 minutes of automated method was initially identified as the most effective (87.22 ± 6.80). To facilitate the overall surface roughness, surface hardness, and degree of polymerization, the optimal choice of postprocessing rinsing time and method for achieving a clear photopolymer resin was determined to be the ultrasonic method with a rinsing time of 15 minutes.

Optimization of the lost PLA production process for the manufacturing of Al-alloy porous structures: Recent developments, macrostructural and microstructural analysis

The main task of this work is the optimization of the manufacturing process of Al-alloy lattice cellular structures with rhombic cell, obtained with lost-PLA technique. It is an easy, environment sustainable and economical technique (both for infrastructure and operating costs) for the manufacturing of Al porous structure based on the 3D printing of PLA and replication process alternative to that based on expensive metal 3D printers. Plaster processing, PLA burnout and AA 6082 alloy casting conditions and parameters have been suitably tuned in order to get final samples with geometry and surface finishing conditions identical to the starting ones made in PLA. A good replication process has been implemented with a high repeatability rate and accurate surface finishing, comparable with that of the PLA printed objects. Morphological analysis on PLA and Al 6082 was conducted as well microstructural analysis and Vickers microhardness tests on Al alloy samples in the as-cast conditions. Metallography reveals the presence of AlFeSi and AlFeMnSi intermetallic phases at the cell boundaries and some coarse precipitates Mg2Si in the AA 6082 alloy. Microstructures and HV measured values are aligned with literature data for this alloy in the same (as-cast) conditions.

Efficacy of different remineralization agents on microhardness and chemical composition of enamel white spot lesion.

White spot lesions (WSLs) are frequently linked with low microhardness and mineral content changes. several strategies have been employed to deal with these problems. This investigation aimed to analyze the microhardness and mineral content changes after remineralization with bioactive glass (BAG) and casein phospho-peptide-amorphous calcium phosphate with fluoride (CPP-ACPF). Twenty sound maxillary first premolars extracted were used to obtain a total of one hundred enamel samples. forty enamel slabs were split into four experimental groups (n = 10 each): Group I, BAG; Group II, BAG+CPP-ACPF; Group III, CPP-ACPF varnish; and Group IV, artificial saliva (negative control). To create artificial WSLs, all samples were preserved in a prepared demineralizing agent for 72 h before treatment with remineralizing agents. Vickers microhardness test was performed. Additionally, 60 enamel samples were selected for analysis using energy dispersive spectroscopy (EDX) and assigned to six experimental groups; the first four groups were similar to that used in the microhardness test along with Group V: WSLs, and Group VI: baseline. The statistical analyses employed in this study included Tukey's HSD (p<0.05), one-way ANOVA, and Shapiro-Wilk. Regarding surface microhardness, the BAG+CPP-ACPF group showed the most favorable recovery, which was better than the outcomes of the BAG and CPP-ACPF groups. A statistically significant change (p <0.05) was not observed between them. Similarly, for mineral content change, the BAG+CPP-ACPF group demonstrated the greatest result, The BAG group came next, and the CPP-ACPF group came last. The BAG+CPP-ACPF group might be regarded as the best course of treatment for enhancing both the surface microhardness and mineral content (Ca, P), while the control group (Artificial saliva) showed the least satisfactory results in comparison. After demineralization, mineral content and microhardness decreased in all samples. Therefore, BAG+CPP-ACPF significantly improved the surface microhardness and mineral content.

Influence of Equal Channel Angular Pressing Technique on Mechanical Properties, Corrosion Resistance, and Microstructural Behavior of Al-Alloy 5083

Introduction: During severe plastic deformation (SPD) processing, aluminum alloys exhibit moderate strength and ductility. Nevertheless, the materials' ductility, as determined by tensile testing, does not accurately represent their capacity for plastic deformation. After the tensile test, its material, aluminum alloy 5083, was observed to be super ductile. Method: The results of a more thorough plasticity analysis—applied for the first time to material following SPD processing—are presented in this paper. The aluminum alloy 5083 is examined in the patent both before and after equal channel angular pressing (ECAP). A highly effective aluminum alloy 5083 specimen preparation was suggested. Under heated temperatures, the process involves severe plastic deformation. Optical microscopy and scanning electron microscopy (SEM) were used for micro-structural research in order to look at the distribution of second-phase particles and the evolution of grain structure. Furthermore, Vickers micro-hardness testing was utilized to assess the mechanical characteristics of the alloy after processing. The outcomes showed that after ECAP processing, there was a significant decrease in grain size and an increase in micro-hardness. Result: Additionally, the production of a finer microstructure with a more uniform distribution of strengthening precipitates was clarified by electron microscopy (SEM). The micro-structural evolution and mechanical behavior of aluminum alloy 5083 under ECAP are well-explained in this patent, which may lead to improved performance in structural applications. This method can be used to forecast fractures in plastic deformation processes and estimate the final plasticity of the materials for various stress-strain states after ECAP processing, as well as the mechanical properties discussed. Conclusion: Due to its unique mechanical qualities, aluminum alloy 5083 shows great potential in a variety of structural applications. The effects of Equal Channel Angular Pressing (ECAP) on the hardness and microstructure of aluminum alloy 5083 were examined in this patent work. result: The specimen's mechanical characteristics are at their finest following a single deformation when the temperature reaches 300°C. Compared to the original specimen, the tensile strength observed enhanced after the fourth pass, and breaking elongation (28.3%) was improved. Through second-phase strengthening and fine-tuning, the recrystallized grains and second-phase particles increase the material's strength.