Vickers Microhardness Tester Research Articles

The effect of thermal aging on microhardness and SEM/EDS for characterisation bioactive filling materials

BackgroundThe aim of this study is to evaluate the surface microhardness, surface chemical composition of bioactive restorative materials pre- and post- thermal aging.MethodA total of 200 disc-shaped samples were prepared by using the materials: Cention N, ACTIVA BioActive Restorative, Equia Forte HT Fil, Glass Fill glass carbomer cement (GCP), and Fuji II LC. Vickers microhardness test were used to measure surface hardness. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM/EDS) was used to determine the characterization of the microstructures and elemental analysis of the materials. These measurements were repeated after thermal aging. One-Way ANOVA test, Bonferroni test and the Games-Howell test was used for data analysis. The significance level was accepted as 0.05.ResultsCention N had the highest vickers microhardness value before thermal cycle. The highest fluoride ion ratio among the materials before thermal aging was detected in the Equia Forte HT Fil and Fuji II LC groups. While a decrease in fluorideF ion was detected in all groups except the Cention N group after thermal aging. It is observed that ACTIVA BioActive Restorative has a more microporous and rougher surface in the scanning electron microscopy image after the thermal cycle than in the image before the thermal cycle.ConclusionsThe chemical properties of the materials and the properties of the filler particles may be related to the differences in the mechanical properties, surface characterizations and ion releases of the materials Thermal aging affected the microhardness, surface characteristics and elemental mass ratios of the studied materials. Alkasite bioactive materials are more similar to composite restorative materials and show better mechanical properties than other materials, but do not have the same effect on fluoride release.Clinical relevanceMost of the bioactive materials showed a decrease in the fluoride ion ratio after thermal aging, while no difference was found in the ion exchange of alkasite materials. Material selection should be made more carefully in caries-active individuals whose fluoride release is clinically important.

Effect of heat input on ultrahard Fe-Cr-B-C-W-Mo-Nb hardfacing

Multicomponent alloys (Cr, Mo, W, Nb, C, B) nanostructured iron base with complex carboborides have been developed to provide great protection against abrasive wear to elements of agricultural and mining machines. These overlays are subject to severe material losses due to impact and abrasion of hard particles and therefore optimizing their wear resistance is critical when it comes to their lifespan, increasing it as a result. The objective of this work was to study the influence of heat input on the wear resistance through of the analysis of the solidification rate. In this sense, the increase of welding speed was produced a decrease of heat input and refined of microstructure. In order to explain these effects, an analysis was made of of the influence of welding speed on the geometry of the deposited metal, dilution with the base metal, microstructural evolution and hardness of iron-based nanostructured deposits with complex carbides. For this, four samples were welded with different speeds; these being 1, 2.5, 5 and 12 mm/s. A semi-automatic welding process was used with a 1.6 mm wire rope used to provide gas protection. The chemical composition was analyzed on a dilution free welded sample. For the each welded sample the dilution percentage was determined, the dimensional survey of the beads was carried out and the microstructure was characterized by X-ray diffraction and optical and scanning electron microscopy. In addition, Vickers microhardness tests were measured in the central area of the beads and the microhardness of phases were measured. The dilution of the deposited metals ranged from 17% to a maximum of 28%. A microstructure formed by a matrix with complex metal carbides and carboborides was observed. The hardness of the beads varied between 960 and 1350 HV2. The highest wear resistance was found in the sample with highest speed welding.

Re-evaluation of Microhardness of Mineral Trioxide Aggregate and Biodentine After Removal From Root Using Different Types of Solvents: An In Vitro Study.

Objective This study aimed to evaluate the effects of different solvents on the microhardness of mineral trioxide aggregate (MTA) and Biodentine, which are used in endodontic therapy for their biocompatibility and ability to create a hermetic seal. Methods A total of 150 extracted human single-rooted teeth were selected and sectioned into 4 mm slices. The samples were divided into two groups according to the material used: MTA and Biodentine. Then the samples were incubated at 37°C and 100% humidity for 28 days. After that, 15 MTA and Biodentinesampleseach were sent for microhardness test and the remaining samples were subdivided into four subgroups according to the solvent used, i.e., treated with normal saline, 5.25% sodium hypochlorite, 10% citric acid, or 40% hydrofluoric acid. The microhardness of the upper and lower surfaces of the samples was measured using a Vickers microhardness tester. Results The average microhardness values for Biodentine and MTA were found to be 74.4 HV and 69.9 HV, respectively. Treatment with sodium hypochlorite, citric acid, and hydrofluoric acid significantly reduced the microhardness of both materials. Hydrofluoric acid had the most pronounced effect, followed by citric acid and sodium hypochlorite. Statistical analysis using one-way analysis of variance (ANOVA) 'F' test showed highly significant differencesbetween the groups. Discussion The study demonstrated that solvents such as hydrofluoric acid, citric acid, and sodium hypochlorite effectively reduced the microhardness of MTA and Biodentine, facilitating their removal during retreatment. This reduction in microhardness is attributed to the chemical interactions of the solvents with the materials, leading to disintegration and reduced structural integrity. Conclusion Biodentine had greater microhardness compared to MTA, and hydroflouric acid reduced the microhardness to a greater extentcompared to other solvents.

Investigation on growth, structural, mechanical, linear and nonlinear optical properties of DiLithium Fumarate TetraHydrate single crystal

In this work reports on the growth and characterization of semiorganic NLO single crystal of DiLithium Fumarate TetraHydrate (DLFTH) using a slow evaporation technique. The crystal structure was an orthorhombic crystal system with the centrosymmetric space group Pbcn, as demonstrated by single crystal X-ray diffraction (SCXRD) investigations. The UV–Vis-NIR spectrum is used to derive optical parameters, such as the lower cut off wavelength (277 nm) and optical energy band gap Eg = 4.98 eV. DLFTH crystals belongs to hard material category using Vickers microhardness test. From NLO studies, the nonlinear optical parameters were studied, such as the nonlinear refractive index (n2), absorption coefficient (β) and third order NLO susceptibility (χ3). The crystal has the properties of saturable absorption and self-defocusing nature. Third order NLO susceptibility (χ3) were found to be 4.14384 × 10-10esu. The higher χ3 number is due to the presence of hydrogen bonds between C-H-O and O-H-O atoms. Therefore, we confirm that it’s applicability for optical device applications.

Study of phase composition, microstructure and hardness of multicomponent zirconia-based ceramics

The manufacture of products from refractory ceramics requires high temperatures due to the high activation energies of the sintering process of refractory oxides. Processing temperatures for ceramics made of ZrO2, Al2O3, MgO can be reduced if a flux or glass-forming component is selected. Furthermore, in multicomponent ceramics it is possible to create more favorable thermoresistive properties. This study examines the synthesis, structural, phase and mechanical properties of multicomponent porous ZrO2-WO3-Al2O3-MgO ceramics with varying weight concentrations of components. Experimental samples were obtained by standard solid state reaction method. The analysis of fabricated samples was carried out using X-ray phase analysis, scanning electron microscopy and the Vickers microhardness test. In this work, a new approach to increasing the microhardness of porous refractory ceramics is presented, in which WO3-based flux forms a matrix composed of glass-like formations that “attach” particles of ZrO2 and MgAl2O4 phases. The obtained ceramics demonstrates high microhardness values HV0.05 for porous materials ranging from 500 to 600. Studies have shown that the selected composition of multicomponent ceramics (x = 0.10–0.25) can be used as a refractory material up to temperatures of ∼1300 °C. The fabricated refractory ceramics potentially possess chemical stability and optimal microhardness properties, which makes these materials promising as a heat insulating lining in the metals, ceramics and glass manufacturing, as well as for components in the chemical industry.

Role of the novel aloe vera-based titanium dioxide bleaching gel on the strength and mineral content of the human tooth enamel with respect to age.

There has been an increased demand for dental bleaching globally irrespective of age and gender. Main drawbacks associated with conventional tooth bleaching agents have been compromised strength and mineral-content of tooth enamel which results in sensitivity, discomfort, roughness, and structure loss of human teeth. Currently, nanoparticles synthesized by green synthesis have gained popularity especially in medical and dental applications because of their versatile and beneficial nano-scaled features. Titanium dioxide nanoparticles (TiO2Nps) in this study were prepared from green ecofriendly source using the aloe vera plant extract and were then characterized via dynamic light scattering (DLS), scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), and energy dispersive X-ray (EDX), for size, shape, composition and true-phase. These TiO2 Nps were incorporated in commercial bleaching gel containing hydrogen peroxide to form a novel TiO2-bleaching gel which was used to bleach extracted anterior teeth belonging to four different age groups: 20-29 years, 30-39 years, 40-49 years and ≥50 years. These teeth were investigated for micro-hardness (Vickers microhardness tester) and mineral-content (EDX spectroscopy) including sodium, magnesium, phosphorus, calcium in an in-vitro environment both before and after bleaching. Results revealed that TiO2 Nps prepared by aloe vera plant were nanos-sized of about 37.91-49 nm, spherical shape, true anatase phase with pure titanium and oxygen in their composition. The values of Vickers micro-hardness and mineral-content (Na, Mg, P, Ca) of enamel specimens belonging to different age groups enhanced in a linear pattern before bleaching with the increase in age (p value < 0.05). There was negligible reduction observed in Vickers micro-hardness and mineral-content elements (Na, Mg, P, Ca) of all enamel specimens belonging to different ages after the bleaching (p value > 0.05). The novel TiO2-bleaching gel prepared was effective enough in preventing the declination in Vickers micro-hardness strength and mineral-content of all the enamel specimens belonging to different age groups even after the bleaching procedure which makes it a promising biomaterial.

Comprehensive analysis of ferroelectric, piezoelectric, mechanical, and nonlinear optical properties of imidazolium d-camphorsulfonate single crystals

Single crystals of imidazolium d-camphorsulfonate (D-ImCS) are synthesized through the slow evaporation solution method. Powder X-ray diffraction reveals that the grown crystals have crystallized in the monoclinic phase with non-centrosymmetric space group P21. UV–visible spectroscopy measurements showed that D-ImCS crystals only absorb in the UV region. Photoluminescence studies indicated emissions in the blue and violet regions. The functional groups present in the crystal were identified through FTIR analysis. The soft nature of the crystal was identified using Vicker's microhardness testing. Dielectric analysis reveals the transition temperature Tc= 365.7 K. The piezoelectric charge constant (d22) is determined to be ±8 pC N−1. The polarization hysteresis loop demonstrates the ferroelectric nature. The presence of NLO property is demonstrated through SHG. Density Functional Theory (DFT) utilizing Gaussian 16 W software provided the optimized structure, UV–visible absorbance, FTIR spectra, frontier molecular orbitals, density of states, molecular electrostatic potential, atomic charge distribution, natural population analysis and non-linear optical properties (NLO). This computational approach complements and validates experimental findings, resulting in a thorough knowledge of D-ImCS behavior and properties.

Development of new β Ti-10-Mo-Mn alloys for biomedical applications

Metallic biomaterials play a crucial role in various biomedical applications, particularly in developing implants and prostheses. Hence, this study aimed to produce and analyze the structure, microstructure, hardness, and preliminary cytotoxicity of Ti-10Mo-xMn system alloys (with x ranging from 0 to 8 wt%) intended for biomedical applications as biomaterials. The alloys underwent thorough characterization, including chemical composition analysis through EDS measurements, mapping, and density assessments. Structural and microstructural analyses were conducted using x-ray diffraction (XRD), Rietveld refinement, optical (OM), and scanning electron microscopy (SEM), while Vickers microhardness testing provided insights into mechanical properties. Rapid cytotoxicity tests via MTT were also performed to assess biocompatibility. Results indicated that the produced alloys exhibited good quality and homogeneity regarding chemical composition. Adding Mn to the Ti-10Mo alloy facilitated the formation of the β phase, transforming it from a biphasic (α" + β) to a single-phase alloy.Moreover, Mn-induced reductions in lattice parameters and average crystallite size of the β phase were observed due to the smaller atomic radius of substituting Mn than Ti. Despite a decrease in hardness attributed to β phase formation, all alloys demonstrated non-cytotoxic behavior in cell adhesion and viability assays, with values exceeding 70 %. Overall, these findings highlight the potential of Ti-10Mo-xMn alloys as viable biomaterials, warranting further exploration and development in biomedical engineering.

Assessment of surface microhardness of enamel surface treated with Nano- HAP serum before and after bleaching

Background: Although bleaching is typically considered a safe procedure, various investigations have found minor negative effects and changes in mineral composition. The aim was to Evaluate and compare the efficacy of using Nanohydroxyapatite serum on surface microhardness of enamel surface before and after bleaching with chemically cured Boost bleaching. Material and methods: ten sound human permanent upper and lower premolar teeth were used and their roots were removed 2 mm apically to the cementoenamel junction, the crowns were sectioned mesiodistally into two halves buccal and lingual/palatal, the buccal surface was further subdivided into two halves. The samples were embeded in an acrylic resin, resulting in 30 specimens divided into 3 groups: Control group: using Boost bleaching and stored in artificial saliva for 14 days, prevention group: nanohydroxyaptite (n-HAP) serum applied 2-3 min once daily for 10 days followed by bleaching then stored for 14 days in artificial saliva and treatment group: in which bleaching used before nanohydroxyapatite serum and stored in artificial saliva for 14 days. The samples were subjected to a Vickers microhardness test measured at 4 times: base line, after nanohydroxyapatitem, after one day of bleaching and after storage in artificial saliva for 14 days in all groups. The data were analyzed statistically using repeated analysis of variance (ANOVA) test followed by Tukey's test. Results: there was a significant increase in microhardness in the prevention group (p&lt;0.05) while there was no significant difference in microhardness readings in control and treatment groups (p&gt; 0.05). Conclusion: n-HAP may enhance the microhardness of a bleached enamel surface when used as a preventive &amp; treatment measure. Suggested that a higher increase in enamel microhardness occurs when n-HAP is used for 2-3 min once daily for 10 days before bleaching and maintaining this increase even after storage for 14 days in artificial saliva.

Mechanical study reinforced magnesium-yttrium alloys by eggshell powder using resistance casting

Magnesium-based alloys are relatively new materials for orthopedic implants. One common component that makes magnesium-based alloys biocompatible and chemically stable is the addition of minor compositions of rare earth metals like yttrium to anchor other chemically active components. From an orthopedic perspective, two goals are of primary concern. One is sufficient mechanical support to stabilize the fracture and reduce inflammation. Another is assistance for the transition of osteogenesis and intramembranous ossification for bone production and remodeling. To attain both goals and further improve the current magnesium-yttrium alloys, adding extra ingredients to improve osseointegration is a common and effective approach. By the nature of bone chemistry, calcium is the top choice as calcium is the key element in maintaining bone integrity and biochemical metabolism. In this study, the mechanical behaviors of a calcium-added magnesium-based alloy (Mg-Y3.5 wt%) are investigated by experiments. This inventive idea for the natural source of calcium is obtained from chicken eggs due to their (1) cost-effective and abundant availability, and (2) naturally synthesized calcium carbonate along with a minor content of organic materials. The fabrication processes involved are the ball-milling of eggshells as an additive at 1, 3, and 5 wt%. into magnesium-yttrium alloys and resistance casting to form composites. Material characterization includes microstructural analysis by X-ray diffraction, morphological/elemental analysis via optical microscopy, field emission scanning electron microscopes, energy-dispersive X-ray spectroscopy, mechanical properties by uniaxial compression and Vickers microhardness tests. Experimental results supplemented by statistical and finite element analysis indicate that the new composite exhibits enhanced ductility; and the 3 wt% eggshell-added alloys show better reinforcement of mechanical properties among all samples with an ultimate compression strength of 161.19 MPa, maximum elongation of 17.53 %, and hardness of 457.48 (N/mm2). Note that the comparable mechanical strength of the composite to that of human bones could reduce the stress shielding on bones and further help the process of bone remodeling.

Multi-objective, multi-constraint high-throughput design, synthesis, and characterization of tungsten-containing refractory multi-principal element alloys

Refractory multi-principal element alloys (RMPEAs) have gained interest recently due to their superior properties at elevated temperatures, including outstanding yield and ultimate strengths, high thermal conductivity, and resistance to creep. RMPEAs can be designed to exhibit a wide range of properties by tailoring their composition. However, the vast chemical design space makes brute-force experimental screening inefficient and costly. In this work, we follow a closed-loop, iterative computational/experimental screening approach that combines computational alloy design methodologies with high-throughput synthesis and characterization tools to explore the vast RMPEAs space and design new RMPEAs that satisfy multiple objectives and constraints. In particular, we targeted compositions with yield strengths higher than 50 MPa at 2000 °C, W content of more than 30 at.% for high-temperature strength and operability up to 2000 °C, narrow solidification range for additive manufacturability, competitive ductility metrics, among other property constraints. We evaluated the mechanical properties and microstructure of 58 alloys designed in 5 batches, in both as-cast and homogenized conditions, synthesized using vacuum arc melting, utilizing scanning electron microscopy, X-ray diffraction, Vickers microhardness, nanoindentation, and high-temperature compression testing. Based on the microhardness screening experiments in each batch, the best-performing alloys were selected for scale-up. High-temperature compression at 1800 °C was performed in these alloys, demonstrating that the designed alloys exhibit up to five times higher yield strength than a pure tungsten benchmark. We conclude that W-containing RMPEAs designed in this study merit further consideration for next-generation structural materials for ultra-high temperature applications.

Friction stir welding of AA2024-T3 and SS304 alloys: microstructural analysis, microhardness evaluation, and tensile performance

This study examines the feasibility of friction stir welding (FSW) for dissimilar butt joints formed between 3 mm thick 2024-T3 aluminum alloy and AISI 304 stainless steel. It explores the impact of operational parameters, particularly traverse speeds of 20 and 40 mm min−1, a fixed tool rotation speed of 450 rpm, a tool pin offset of 1.5 mm, and a tool shoulder diameter of 18 mm, on microstructure, microhardness, and tensile strength. A traverse speed of 40 mm min−1 resulted in a lower peak temperature of 257.75 °C, while optimal conditions at a speed of 20 mm min−1 led to peak temperatures of 356.5 °C. This higher temperature facilitated material deformation, improved flow, enhanced mixing, and contributed to grain refinement, with an average grain size of 4.2 μm. Vickers microhardness tests revealed a maximum hardness of 339 Hv at a traverse speed of 40 mm min−1 and 413 Hv at 20 mm min−1. The ultimate tensile strength (UTS) reached 338 MPa, resulting in a joint efficiency (JE %) of 76.81% for the weld performed at optimal conditions.

Comparing the remineralization potential of undemineralized dentin powder versus chicken eggshell powder on artificially induced initial enamel carious lesions: an in-vitro investigation

BackgroundWhite spot lesions are a widespread undesirable effect, especially prevalent during fixed orthodontic treatments. The study compared the in vitro enamel remineralization potential of undemineralized dentin matrix (UDD) versus chicken eggshell powder (CESP) for artificially induced enamel lesions.Methods100 caries-free and sound maxillary premolars were randomly divided into four groups each contain 25 teeth: Group I (Baseline): No treatment was done to the enamel surface. Group II (Negative control ): The enamel surface of the teeth underwent demineralization using demineralizing solution to create artificial carious lesions then kept in artificial saliva. Group III (CESP treated): After demineralizing the tooth surface, the teeth have been suspended in the CESP remineralizing solution. Group IV (UDD treated): After enamel demineralization, the teeth were suspended in UDD remineralizing solution. The remineralization potential was assessed by Vickers microhardness testing, scanning electron microscopic examination (SEM), and energy dispersive X-ray (EDX).ResultsThe current study demonstrated an increase in the mean microhardness of CESP and UDD-treated groups; however, It was nearer to the baseline level in the UDD group. SEM imaging revealed greater enamel remineralization in the UDD group compared to the remaining groups. The UDD group disclosed complete coverage for the prismatic enamel compared to the CESP group, which revealed a partially remineralized enamel surface. Interestingly, the Ca/P ratio increased significantly in the CESP group compared to the negative control group. In contrast, a higher significant increase in the mean Ca/P ratios was recorded in the UDD group compared to the test groups.Conclusionbiomimetic UDD and CESP powder should be utilized to treat enamel early carious lesions. However, UDD demonstrated the most significant remineralization potential.

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

Background 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). Methods 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&lt;0.05), one-way ANOVA, and Shapiro-Wilk. Result 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 &lt;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. Conclusion 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.

THE EFFECT OF CALCIUM HYDROXIDE PARTICLE SIZE ON DENTIN TUBULI HARDNESS

Background: Calcium hydroxide (Ca(OH)2) is an effective root canal treatment, with calcium and hydroxyl ions effectively released on day 7. However, prolonged use can diminish dentinal tubule hardness and dissolve the hydroxyapatite crystals within them. Nanoparticle Ca(OH)2 demonstrated superior antimicrobial activity compared to conventional Ca(OH)2 because of its deeper penetration into the dentinal tubules.. Purpose: This study aimed to evaluate the effect of particle size on dentinal tubule hardness. Methods: True experiment with fifteen premolars with one root canal, no caries, and apical closure were divided into three treatment groups: conventional Ca(OH)2 (group 1, n=5), Ca(OH)2 nanoparticles (group 2, n=5), and untreated (control group), n=5. All samples were incubated for 7 days, and hardness was measured using a micro-Vickers hardness tester at 1/3 of the root canal. Kruskal-Wallis test followed by Mann-whitney post hoc analysis was used to compare the mean microvickers hardness values among different groups. The level of significance was set at p&lt;0.05. Results: The results showed that there was significant difference between conventional Ca(OH)2 (73.00 ± 2.71) and Ca(OH)2 nanoparticles (67.40 ± 0.62) p=0.01 and the control group (70.68 ± 1.70; p&gt;0.05) and Ca(OH)2 nanoparticles p=0.03. Conclusions: The use of Ca(OH)2 nanoparticles as an intracanal medicament for 7 days reduced dentin microhardness, whereas conventional Ca(OH)2 did not result in any change in microhardness. Particle size affects the hardness of dentinal tubules.

Impact of CC and PCTIG Welding on SMO 254 Joints Using Alloy 625 Filler

Objectives: This investigation analyzes the microstructure, mechanical and corrosion characteristics of SMO 254 joints welded using constant current TIG (CCTIG) and pulse current TIG (PCTIG) with alloy 625 (ERNiCrMo-3) filler metal. Method: Optical microscopy and SEM with EDAX were employed for microstructural characterization and phase analysis. Mechanical properties were assessed through Vickers microhardness, tensile, and Charpy impact tests, followed by fracture analysis. Findings: EDAX point analysis indicates reduced Mo segregation and the absence of Nb segregation in PCTIG weldments. The overall corrosion resistance remains acceptable despite a slightly higher corrosion rate in PCTIG weldments. The study highlights the superior mechanical properties and microstructural control achieved with PCTIG welding, making it a preferable technique for SMO 254 joints. Novelty: Notably, the research establishes PCTIG as a superior method for welding SMO 254, demonstrating that it not only refines the grain structure but also significantly enhances mechanical properties, particularly toughness, by 50% compared to CCTIG. Keywords: SMO 254, SASS, Microstructural characterization, Mechanical properties, CCTIG, PCTIG

Comparison of the Effect of Bioglass, Chitosan, and SDF Compounds on Remineralization of Primary Caries Lesions in Primary Teeth: An in vitro Study.

Dental caries are among the most common oral and dental diseases affecting adults and children. To prevent caries, either the factors that cause caries should be reduced or the host resistance should be increased. Several compounds, such as bioglass, chitosan, and silver diamine fluoride (SDF), can enhance enamel remineralization. This study was conducted to investigate the effects of chitosan, bioglass, chitosan-bioglass, and SDF compounds on remineralizing primary enamel lesions. In this in vitro study, seventy-two primary canine teeth were collected. The teeth were exposed to a demineralization solution for 72 hours to create primary caries lesions. The primary Vickers microhardness test (VMT) was conducted to measure the initial values. The samples were randomly divided into six groups (n=12): Group 1: bioglass-chitosan solution; Group 2: chitosan; Group 3: bioglass solution; Group 4: SDF; Group 5: remineralization solution; Group 6: distilled water. The solutions of Groups 1, 2, and 3 were applied to the samples for 7 days, while the SDF solution was applied only once. The samples were immersed in an artificial saliva solution, which was refreshed daily. After the treatment, the final Vickers microhardness test (VMT) values were recorded. The data were analyzed statistically using a two-way ANOVA and Tukey's test (p< 0.05). The results indicated a statistically significant effect of remineralizing compounds on both pre-treatment and post-treatment microhardness (p< 0.0001). However, no significant difference in microhardness was observed between the groups studied (p= 0.225). All the compounds utilized in this study demonstrated a significant remineralizing effect on enamel lesions caused by primary caries in primary teeth. The chitosan-bioglass and bioglass groups exhibited the highest levels of remineralization, respectively. However, the comparison between the groups yielded insignificant results due to the dispersion of the samples. Therefore, further studies with larger sample sizes are recommended.

A Comparative Evaluation of the Effect of Different Endodontic Irrigating Solutions on Microhardness of Root Canal Dentin: An in vitro Study.

During endodontic therapy, irrigation solutions applied in the root canal may affect the physicochemical properties of the dentinal wall, thereby changing its microhardness. This may adversely affect the sealing ability and adhesion of dental materials. Therefore, many studies have focused on the search for an ideal root canal irrigant that has a minimal effect on dentinal microhardness. This in vitro study was conducted to determine the changes in dentin microhardness after root canal irrigation with different endodontic irrigants. Ninety-five freshly extracted maxillary central incisor teeth with straight single canals were selected. These teeth were sectioned transversely at the level of the cementoenamel junction. The working length of each tooth was determined, and canal space was prepared by the HyFlex CM rotary file system. During instrumentation, normal saline was used for irrigation. Then, teeth were split longitudinally into two segments. According to the irrigating solution employed, samples were divided into five groups (n=19): normal saline (Group A), 3% sodium hypochlorite (Group B), 2% chlorhexidine (Group C), 5% calcium hypochlorite (Group D), and 0.2% nanochitosan (Group E).3 mL of the corresponding irrigating solution was administered for total15 minutes in each prepared sample. The Vickers micro-hardness tester was then used to assess micro-hardness. The data was analyzed using one-way analysis of variance (ANOVA). All tested irrigating solutions decreased the dentinal microhardness. Samples irrigated with 5% calcium hypochlorite demonstrated dentinal microhardness of 42.43±1.62, which is the lowest among all the tested groups, followed by nano chitosan, sodium hypochlorite, and chlorhexidine. Samples treated with control group (saline) demonstrated the maximum microhardness of dentin in the present study. Within the limitations of this research, it can be concluded that the tested novel irrigating solutions, 5% calcium hypochlorite and 0.2% nanochitosan, were more detrimental to radicular dentin microhardness when compared with conventional endodontic irrigants.

Pulsed electroplating of ZrO2-reinforced Ni-Cr alloy coatings from the duplex complexing agents-containing bath for engineering applications: Importance of operating conditions

The progress in tribocorrosion performance of the engineering parts is in dire need of improving their surface properties. In the present contribution, Ni-Cr-ZrO2 layers were electrodeposited on St37 steel. The stress was put on optimizing the process factors, including the parameters involved in pulsed current electrodeposition and level of the ZrO2 reinforcing nanoparticles (0–20 g/L) in the bath. The surface characteristics of the electrodeposits were evaluated using FESEM, EDS, AFM, and XRD. The tribomechanical characteristics of the films were determined using a Vickers microhardness tester and pin-on-disk apparatus. The electrochemical behavior of the samples was studied using OCP, EIS, PDP, and immersion techniques. The results demonstrated that the included ZrO2 nanoparticles led to more homogenous, rougher, and defect-free surfaces, while they did not change the phase composition of the alloy electrodeposits. The polarization resistance of the Ni-Cr alloy coating increases by 6.7 times when 10 g/L of the reinforcing nanoparticles is added to the electrolyte. A decrease of ≈42 % in the mean COF value was obtained by the incorporation of 10 g/L ZrO2 nanoparticles into the plating bath. The coating system developed holds the promise to address both technical requirements and health concerns.

Comprehensive analysis of organic dye doped metal-coordinated single crystals: A study of structural, optical, thermal, dielectric, piezoelectric and mechanical characteristics

Organic dye can induce positive changes in optical, mechanical and electrical properties of semi-organic single crystals. Single crystals of pure and 0.01 mol% SSY dye doped ZTS are grown from a slow evaporation solution technique. The structural properties of pure and SSY-dyed ZTS crystals are characterized using SCXRD and PXRD, confirming the maintenance of crystallinity and incorporation of dye molecules within the host lattice of ZTS crystal. Both ZTS crystals belong to orthorhombic crystal system with space group Pca21. The refined lattice parameters and cell volume of present pure ZTS crystal are a = 11.1723 Å, b = 7.7989 Å, c = 15.5357 Å, α = β = γ = 90°, V = 1353.6762 Å3. The intensity of all Raman peaks in ZTS is enhanced by the incorporation of dye. Optical spectroscopic UV–visible and photoluminescence techniques highlight the comparative studies of light absorption, energy bandgap, optical constants and fluorescence emission. An increment of 0.05 eV in optical bandgap is observed in dyed ZTS. The dielectric properties with variation in frequency range (23 Hz–10 MHz) at different temperature range (30–100 °C) are evaluated through impedance spectroscopy, showing an increase in dielectric constant around 15 % and reduction in dielectric loss, indicating potential for improved performance in electronic applications. A significant enhancement is observed in the piezoelectric coefficient (d33) in dyed ZTS single crystals. The d33 value of ZTS is increased from 2.75 to 2.95 pC/N by the doping of organic dye. Vickers micro-hardness tester is used to know the mechanical strength through micro-indentation, which illustrated an increase in the hardness nature of dyed ZTS single crystals. These findings provide a foundation for the future development of ZTS-based materials for technological applications, offering a promising route for the advancement of functional materials in the domain of piezoelectric and optoelectronic technologies.