Microhardness Evaluation Research Articles

Comparative Evaluation of Microhardness between Monolithic and Multilayered Zirconia: An in-vitro Study

This study aimed to evaluate and compare the microhardness of monolithic zirconia and multilayered zirconia to investigate the influence of material composition and structural design on their mechanical properties. ‏Cylindrical specimens were designed using AutoCAD software and fabricated from monolithic zirconia (Group A) and multilayered zirconia (Group B blocks via CAD/CAM milling systems. The specimens were sectioned into discs with a diameter of 10 mm and a thickness of 1.5 mm. Microhardness testing was performed on these discs using a standardized protocol. Statistical analysis was conducted using a student’s t-test (P < 0.05) with a sample size of 10 specimens per group to ensure 80% power and 95% confidence. ‏Results revealed significant differences in microhardness between monolithic and multilayered zirconia. Monolithic zirconia exhibited superior hardness, attributable to its single-layered structure, which enhances its mechanical strength and wear resistance. In contrast, multilayered zirconia, while exhibiting lower microhardness, demonstrated esthetic advantages due to its gradient layering and maintained sufficient durability for clinical use. ‏The findings underscore the impact of zirconia composition and structural design on mechanical properties, providing clinicians with valuable insights for material selection. While monolithic zirconia is ideal for high-load posterior restorations, multilayered zirconia offers an esthetic solution with adequate mechanical performance, making it suitable for anterior applications.

Bone quality analysis of the mandible in alcoholic liver cirrhosis: Anatomical, microstructural, and microhardness evaluation.

Alcoholic bone disease has been recognized in contemporary literature as a systemic effect of chronic ethanol consumption. However, evidence about the specific influence of alcoholic liver cirrhosis (ALC) on mandible bone quality is scarce. The aim of this study was to explore microstructural, compositional, cellular, and mechanical properties of the mandible in ALC individuals compared with a healthy control group. Mandible bone cores of mаle individuаls with ALC (n = 6; age: 70.8 ± 2.5 yeаrs) and age-matched healthy controls (n = 11; age: 71.5 ± 3.8 yeаrs) were obtаined postmortem during аutopsy from the edentulous аlveolаr bone in the mandibular first molаr region аnd the mаndibulаr аngulus region of each individual. Micro-computed tomogrаphy wаs used to аssess bone microstructure. Analyses based on quаntitаtive bаckscаttered electron microscopy included the characterization of osteon morphology, osteocyte lаcunаr properties, and bone mаtrix minerаlizаtion. Composition of bone minerаl аnd collаgen phаses was assessed by Rаmаn spectroscopy. Histomorphometry wаs used to determine cellulаr аnd tissue chаrаcteristics of bone specimens. Vickers microhardness test was used to evaluate cortical bone mechanical properties. The ALC group showed higher closed cortical porosity (volume of pores thаt do not communicаte with the sаmple surfаce) (p = 0.003) and smaller lacunar area in the trabecular bone of the molar region (p = 0.002) compared with the Control group. The trabecular bone of the angulus region showed lower osteoclast number (p = 0.032) in the ALC group. There were higher carbonate content in the buccal cortex of the molar region (p = 0.008) and lower calcium content in the trabecular bone of the angulus region (p = 0.042) in the ALC group. The cortical bone showed inferior mechanical properties in the ALC cortical bony sites (p < 0.001), except for the buccal cortex of the molar region (p = 0.063). There was no significant difference in cortical thickness between the groups. Bone quality is differentially altered in ALC in two bony sites and compartments of the mandible, which leads to impaired mechanical properties. Altered mandible bone tissue characteristics in patients with ALC should be considered by dental medicine professionals prior to oral interventions in these patients. Knowledge about mandible bone quality alterations in ALC is valuable for determining diagnosis, treatment plan, indications for oral rehabilitation procedures, and follow-up procedures for this group of patients.

Evaluation of Flexural Strength and Vickers Micro Hardness of Three Different Denture Base Resin Materials

ABSTRACT Objectives: To evaluate the Vickers hardness and flexural strength of computer-aided design/computer-aided manufacture (CAD/CAM) milled, 3D-printed, and traditional heat-polymerized denture base resins used in computer-aided design and manufacture. Materials and Methods: A total of 60 samples were fabricated from CAD/CAM milled resin (PMMA dental material-Ruthinium disc, Badia Polesine (Rovigo) Italy), CAD/CAM 3D-printed resin (NextDent Denture 3D+, Soesterberg, The Netherlands) and conventional heat-polymerized (HP) denture base resin (DBR) (Triplex hot Ivoclar-Vivadent, Liechtenstein). Based on the three different denture base resin materials (n = 10/material) (30/flexural strength and 30/microhardness), the samples were split into six groups. The 3-point bending test was used to assess flexural strength, while Vickers microhardness test was used to assess surface hardness. The acquired data was statistically assessed. Results: CAD/CAM milled resins showed appreciably greater values for both the flexural strength and surface hardness, followed by conventional HP denture base resin and CAD/CAM 3D-printed resin. Pairwise comparison for Flexural Strength and Vickers microhardness revealed significant differences between groups. Conclusion: CAD/CAM milled resins had the highest surface hardness and flexural strength compared to Conventional HP denture base resin and CAD/CAM 3D-printed resin.

Synergetic effect of in-situ TiB2 reinforcement and nano precipitation on wear behavior of ZE41 magnesium matrix composite

The rise in carbon dioxide pollution and energy consumption has increased the demand for lightweight materials such as magnesium in automotive and aerospace industries. However, magnesium alloys face challenges like poor wear resistance and mechanical strength. To overcome these limitations, a promising approach involves developing heterogeneous hybrid microstructures through reinforcement addition and microstructural engineering. This study focuses on the tribological performance of a newly developed in-situ sub-micron sized TiB2/ZE41 composite under various microstructural conditions, comparing it to the unreinforced ZE41 Mg alloy. Wear experiments were conducted using a pin-on-disc tribometer under normal loads of 10, 20, 40, and 60 N at a sliding velocity of 1 m/s. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) was used to analyze the worn surfaces in order to identify damage types and surface distortions. By correlating worn surface microstructures with test parameters, predominant wear mechanisms for each material condition under specific loads were determined. Results consistently showed that the presence of in-situ TiB2 reinforcements, β-phase, and rare-earth precipitates enhanced wear resistance regardless of the load conditions. Additionally, the study established a scientific understanding of the wear behavior of ZE41 Mg alloy, with and without in-situ TiB2 particles and precipitates, through analysis of dominant wear mechanisms, wear-induced subsurface deformation mechanisms, kernel average misorientation, grain orientation spread, and microhardness evaluation.

Evaluation of Micro Hardness of Magnesium Alloy Coated with ZnO and Al2O3

Magnesium and its alloys have wide range of application in automobile and aircraft industries because of their excellent mechanical properties i.e. high strength to weight ratio, availability and good castability etc. However, some challenges occur in using magnesium in aquas service applications, due to its highly reactive nature and low tribological properties such as low wear and corrosion resistance. In this work an experimental study has been done on uncoated and ceramic coated AZ91 alloy to compare hardness and wear properties of both. The coating was applied on varying weight percentage of ZnO and Al2O3ceramic particles. The effect of presence of ceramic particles on the surface of substrate was studied using scanning electron microscope. Micro Vickers hardness test and wear tests were conducted on the samples, and it was found that coating of ceramic particles made the surface harder and wear resistant as compared to the uncoated Mg alloy. Contribution of Al2O3 particles plays an importantrole in increasing the hardness and wear resistance of coated surface. A decrease of 84% in coefficient of friction, increase in wear resistance by 99% and increase in micro hardness by 92% was reported for Al2O3 coated sample as compared to the uncoated surface.

Comparative evaluation of compressive strength and microhardness of two commercially available luting cements stored in artificial saliva: An in vitro study

Comparative evaluation of compressive strength and microhardness of two commercially available luting cements stored in artificial saliva: An in vitro study

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.

Evaluation of Surface Microhardness of Artificial White Spot Lesion Treated with Three Different Treatment Approaches. An in-vitro study

Evaluation of Surface Microhardness of Artificial White Spot Lesion Treated with Three Different Treatment Approaches. An in-vitro study

Evaluation of Surface Microhardness of Artificial White Spot Lesion Treated with Three Different Treatment Approaches. An in-vitro study

Evaluation of Surface Microhardness of Artificial White Spot Lesion Treated with Three Different Treatment Approaches. An in-vitro study

Comparative Evaluation of Tooth Enamel Surface Microhardness Exposed to Novel Modified Casein Phosphopeptide Amorphous Calcium Phosphate, APF Gel and GC Tooth Mousse

Comparative Evaluation of Tooth Enamel Surface Microhardness Exposed to Novel Modified Casein Phosphopeptide Amorphous Calcium Phosphate, APF Gel and GC Tooth Mousse

Potential remineralizing effect of cuttlefish bone and eggshell Powder's on demineralized human enamel (an invitro study)

Dental treatment has been shifted towards more conservative approaches that focus on caries identification at early stage, remineralization of dental surfaces, and preservation of tooth structure. So that, newly safe alternative methods for teeth remineralization have to be created. There is minimal evidence to support the use of eggshell powder (ESP) for remineralizing enamel and Cuttlefish bone powder (CBP) as an alternative calcium source in bone replacement.The aim of this study is to evaluate the capacity of eggshell powder (ESP) and cuttlefish bone powder (CBP) solutions to remineralize early initiated demineralized lesions of enamel in permanent teeth. 40 extracted premolars were divided into four groups: Group1 (which received no treatment), Group2 (which was subjected todemineralizing solution), Group3 (which was subjected todemineralizing solution and then treated with CBP solution), and Group4 (which was subjected todemineralizing solution and then treated with ESPsolution). All groups were prepared forscanning electron microscope (SEM), X-ray microanalysis (EDAX), and microhardness evaluation. The demineralization process significantly changed the surface structure of the enamel, resulting in erosive lesions. CBP and ESP solutions both had a reparative effect, enhanced surface morphology, and increased Ca and P content and microhardness.

Comparative Evaluation of Surface Microhardness of Artificially Demineralised Human Enamel with Organic Extracts as Remineralising Agents: An in Vitro Study

Comparative Evaluation of Surface Microhardness of Artificially Demineralised Human Enamel with Organic Extracts as Remineralising Agents: An in Vitro Study

Evaluation of microhardness, degree of conversion, and abrasion resistance of nanoglass and multiwalled carbon nanotubes reinforced three-dimensionally printed denture base resins.

To assess the effect of nanoglass (NG) particles and multiwalled carbon nanotubes' (MWCNTs) addition on Vickers hardness (VH), degree of conversion (DC), and abrasion resistance of 3D-printed denture base resin. 3D-printed denture base resin was reinforced using silanized NG and MWCNTs to obtain four groups: Control, 0.25 wt% NG reinforced resin, 0.25 wt% MWCNTs reinforced resin, and a combination group of 0.25 wt% of both fillers. All specimens (N = 176) were tested before and after thermal aging (600 cycles) for VH (n = 22), DC, and abrasion resistance (n = 22). Abrasion resistance specimens were subjected to 60,000 brushing strokes, and then assessed for surface roughness (Ra) and weight loss. Specimens were then scanned with a benchtop scanner before and after abrasion to produce a color map of topographical changes from superimposed images. Data were analyzed using ANOVA tests followed by Tukey post hoc test. Kruskal-Wallis test was used to compare percent change among groups, followed by Dunn post hoc test (α = 0.05). The interaction between nanofiller content and thermal cycling displayed a significant effect on VH and DC. The 0.25% NG expressed the highest VH before aging but revealed the highest percent decrease after aging. Nanofiller content, thermal aging, and brushing displayed a significant interaction impact on the Ra values. The addition of nanofillers resulted in an overall improvement in resin microhardness and abrasion resistance. The 0.25% MWCNTs group revealed the lowest Ra with the least percent change in VH and DC, while the combination one displayed the least change in weight.

Combining Ultrafast Laser Texturing and Laser Hardening to Enhance Surface Durability by Improving Hardness and Wear Performance

Aluminum alloy 7075 is utilized widely across marine, aerospace, and automotive sectors. However, its surface wear resistance has hindered its application in certain tribological environments. Addressing this challenge, the current study examines a hybrid laser method to increase surface wear resistance by combining two techniques: ultrafast laser texturing and laser‐based surface hardening. Ultrafast laser processing is conducted using 3 W laser power, 100 kHz pulse repetition rate, 4 mm s−1 scanning speed, and three different scan patterns. After the texturing operation, laser‐based surface hardening is then performed on these textures using a continuous wave laser. The laser heat treatment is conducted using laser powers of 400 and 500 W with three different scan speeds of 1, 2, and 3 mm s−1. Microhardness evaluations show a notable increase in hardness, with the hardest sample exhibiting a 17.8% increase compared to the pristine sample. The laser‐textured and laser heat‐treated samples exhibit a significant reduction in the average coefficient of friction and wear volumes compared to samples that were laser‐textured but not laser heat‐treated. The investigated laser processing strategy offers a promising approach for surface modification, enhancing both mechanical properties and wear resistance of aluminum alloy 7075 surfaces.

Microstructural Analysis and Microhardness Evaluation of Stainless Steel SS304 Joints Utilizing Microwave Hybrid Heating (MHH) and Cold/Heat Processing: A Fuzzy Logic Approach

Stainless steel SS304 is extensively used in dental applications for its high strength, hardness, and corrosion resistance. However, Conventional dental joining techniques such as soldering and fusion welding, reliant on elevated temperatures and toxic fluxes, present substantial oral health risks, leading to potential health deterioration due to toxic emissions. The study proposes the utilization of a microwave hybrid heating process (MHH) for joining stainless steel SS304 (15mm × 7.9mm × 0.2mm) and pure zinc metal powder (44 µm, 99% purity), citing its enhanced efficiency, speed, precision, and diminished environmental footprint as key characteristics without fume. It explores heat processing between 30°C to 60°C and cold temperature processing from 0°C to 10°C to analyze alterations in hardness properties and microstructures. The study identified a direct correlation between temperature and microhardness, observing an increase in microhardness with rising temperatures. Optimal microhardness of 208.6 HV was achieved at 60°C during a 3 min heat treatment. Cold temperatures induced slight deformation and grain transformation, while heat treatment enhanced grain density and hardness, particularly in the strongly bonded boundary layer, with experimental and predicted values using Fuzzy logic showing promising outcomes and errors below 10%. In conclusion, the study demonstrates that achieving a specific hardness value in stainless steel joints is highly desirable for dental applications, alongside the observation of favorable microstructures. These findings underscore the potential of MHH to propel dental technology forward and promote sustainable practices while addressing environmental concerns.

Evaluation of Surface Roughness and Microhardness of Bulk-fill and Nanohybrid Composite after Exposure to Different Beverages at Various Time Intervals - An In vitro Study.

The aim of the study was to compare the surface roughness and microhardness of bulk-fill composite and nanohybrid composite resin after exposure to three different beverages at different time intervals. In this study, 60 composite discs each for bulk fill and nanohybrid, of dimensions 10 mm × 2 mm were made. Both composites were randomly divided into four subgroups, i.e., 15 samples each for artificial saliva, tea, coffee, and soft drinks which were further subdivided into five samples for three time intervals. Composite resin discs were immersed in beverages for 4 min in 24 h for 7, 15, and 30 days. All samples were evaluated for surface roughness and microhardness before and after immersion. Both the composites showed a significant increase in surface roughness in all the beverages with maximum change in surface roughness observed in nanohybrid composite resin immersed in soft drinks. Furthermore, the microhardness of both the composites was decreased significantly in all beverages with maximum change in microhardness observed in nanohybrid composite resin immersed in soft drinks. Bulk-fill composite resin has better resistance to surface roughness and higher microhardness as compared to nanohybrid. Furthermore, acidic beverages highly affect the physical properties of both composite resins for longer periods.

Evaluation of flexural strength and microhardness in Vaccinium macrocarpon (cranberry)-added self-cure polymethyl methacrylate dental resin: An in vitro study.

Occurrence of denture stomatitis and prosthesis breakage are common problems faced by elderly people wearing removable dentures. To overcome this, several attempts are made to improve the denture material by addition of antimicrobials without compromising original properties. The aim of the study was to evaluate flexural strength and microhardness of self-cured polymethyl methacrylate (PMMA) denture base resin after addition of Vaccinium macrocarpon (commonly called as cranberry), extract as antimicrobial, at varying proportions. Experimental in vitro study. Frozen cranberry fruits were subjected to extraction process in the presence of aqueous solvents. Lyophilized extract was added in proportions of 0, 0.5, 1.0, 1.5, and 2.0 dry wt/wt % into polymer of self-cure PMMA denture base resin. Based on cranberry inclusion, the study comprised one control (0%) and four test groups (0.5%-2%) with total of 100 samples. A three-point bending test for flexural strength was done for fifty study samples (n = 10). Surface of fractured samples was analyzed using a scanning electron microscope (SEM). Microhardness was determined using Vickers hardness test. One-way statistical ANOVA test was done to find the difference between groups, followed by Tukey's post hoc test for multiple pairwise comparison. Flexural strength ranged from 66.80 to 69.28 MPa, and a statistically insignificant difference was observed between groups (P > 0.05). SEM evaluation showed uniformly dispersed strands of cranberry extract in PMMA matrix. With higher concentration, less voids were seen. Vickers microhardness value significantly decreased from 15.96 in the control group to 14.57 with 2% cranberry addition (P < 0.05). Incorporation of cranberry extract into self-cure PMMA denture base resin, up to 2 dry wt %, did not decline the flexural strength. However, there was a significant decrease in Vickers microhardness values when compared against the control group (0% cranberry inclusion).

Comparative Evaluation of Microhardness and Polymerization Shrinkage in Residual Zirconia Reinforced Provisional Restorations: An In Vitro Study.

Aim The aim of this study is to evaluate and compare the microhardness and polymerization shrinkage of polymethyl methacrylate reinforced with residual zirconia. Materials and methods A total of 360 resin samples were fabricated, with dimensions of 12 mm × 12 mm × 3 mm and 12 mm × 8 mm × 6 mm. Zirconia dust (40% by weight) was added to 180 of these samples. The study included four groups: Group A (autopolymerizing acrylic resin), Group H (heat-polymerizing acrylic resin), Group ZA (autopolymerizing acrylic resin with zirconia dust), and Group ZH (heat-polymerizing acrylic resin with zirconia dust). Each group consisted of 90 samples, with 45 samples used for evaluating microhardness and 45 samples for assessing polymerization shrinkage. Results Group ZH exhibited the highest microhardness at 6.06 ± 0.31 GPa. It also recorded the lowest shrinkage values, measuring 52.11 ± 3.21 mm³. Tukey's honestly significant difference test revealed that microhardness was significantly higher in Group ZA (4.53 ± 0.29 GPa) compared to Group A (3.51 ± 0.25 GPa). However, Group H (5.42 ± 0.26 GPa) demonstrated greater hardness than Group ZA. Regarding shrinkage, the addition of zirconia dust resulted in reduced values, with Group ZA (73.93 ± 3.55 mm³) showing less shrinkage compared to Group A (91.9 ± 6.38 mm³). Similarly, Group ZH (52.11 ± 3.21 mm³) had lower shrinkage than Group H (66.71 ± 5.97 mm³). Group A exhibited the highest shrinkage among all the groups. Conclusion Within the limitations of this study, it can be concluded that there is an increase in hardness and a decrease in shrinkage values of the resin with the addition of zirconia dust in heat and autopolymerizing acrylic resin used for the fabrication of provisional restorations. Zirconia-incorporated heat-activated resin showed superior microhardness and decreased shrinkage values. Although the addition of residual zirconia to autopolymerized samples demonstrated better hardness, it was observed that pure heat-polymerized samples showed greater hardness. Reusing computer-aided design and computer-aided manufacturing powder waste can cut down on economic losses and aid in environmental sustainability.

Effect of continuous vs sequential chelation on the mechanical properties of root dentin: An ex vivo study

ObjectivesTo evaluate the mechanical properties of root canal dentin treated with sodium hypochlorite (NaOCl) in combination with hydroxyethylidene diphosphonic acid (HEDP) or ethylenediaminetetraacetic acid (EDTA). MethodsFor testing fracture resistance, 45 single-rooted teeth were instrumented and irrigated with NaOCl/HEDP, NaOCl/EDTA, or distilled water. Fifteen untreated teeth served as control. After obturation, specimens from the experimental groups were thermocycled, dynamically-loaded, and then statically-loaded in a universal testing machine until failure. For flexural strength analysis, 15 teeth were instrumented and irrigated with NaOCl/HEDP or NaOCl/EDTA. Root segments were sectioned into dentin bars and tested for flexural strength using a universal testing machine. For microhardness evaluation, 20 teeth were instrumented and irrigated with NaOCl/HEDP or NaOCl/EDTA. Dentin disks from the coronal-third of each root segment were prepared, one before and one after irrigation, for microhardness testing with a Knoop hardness tester. ResultsThe highest fracture resistance was recorded in the untreated group, and the lowest in the EDTA group. Although the HEDP group had higher fracture resistance than the EDTA group, the distilled water group demonstrated even greater fracture resistance than the HEDP group. Specimens treated with HEDP had significantly higher flexural strength and microhardness values when compared with those treated with EDTA. ConclusionThe fracture resistance, flexural strength, and microhardness of root canal dentin were higher when root canals were irrigated with NaOCl/HEDP, when compared with NaOCl/EDTA. Clinical significanceIrrigating root canals with NaOCl combined with HEDP significantly improves the mechanical integrity of root canal dentin compared to the use of NaOCl with EDTA.

On the synthesis and sintering behavior of a novel Mg-Ca alloy, Part II: Spark plasma sintering

With the growing interest in lightweight materials, magnesium and its alloys have received substantial attention for replacing existing alloys. After investigating the mechanical alloying process of Mg-Ca alloys and determining the optimum parameters for milling in part I of this study, the current research aims to examine the second step: the sintering process. This study proposes the powder metallurgy method to process Mg-Ca alloy through the spark plasma sintering technique at 420 °C under an applied pressure of 38 MPa. Samples with different additives (starch or paraffin) were sintered for various dwell times (7 and 10 min) to determine the optimal mechanical and physical properties. To study the microstructure and phase composition of the sintered alloys, X-ray diffractometer (XRD), field scanning electron microscopy (FESEM), and X-ray energy dispersive spectroscopy (EDS) were utilized. Density measurement, compression test, and micro-hardness evaluation were also conducted for the physical and mechanical feathers analysis. The results indicated that samples with a dwell time of 10 min exhibited superior mechanical properties. Additionally, the starch-containing sample outperformed the paraffin-containing sample in both physical and mechanical properties.