Surface Hardness Measurements Research Articles

Impacts of WWII bomb explosions on weathering damage of architectural heritage: Bath, England

The effects of bomb impacts, including the explosive force and combustion associated with these impacts, are preserved in only a few cities across the UK. In particular, World War Two (WWII) has left scars across a wide range of structures as a result of air raids. On immovable heritage, such as architectural structures, these impacts commonly take the form of craters, fractures and fire damage to stonework. This instantaneous damage is subsequently exposed to environmental stresses, such as moisture cycling, thermal stress and the movement of soluble elements and can thus lead to further deterioration of the stone. In this study, Rock Surface Hardness (RSH) measurements, permeametry measurements and microscopic observations were selected to capture stone deterioration data from 80-year-old bomb impacts on two walls of the Labour Exchange in Bath (UK) for spatial distribution analysis (Kriging) in Geographic Information Systems (GIS). The results show that the weathering forms that were found on the two walls can be attributed to nine different types. They can provide quantitative assessment of damage caused by bomb explosions and combustion in the war. The increase in permeability of walls and craters is shown to be primarily caused by the bomb explosion and combustion, whereas the decrease of hardness is associated with subsequent stone deterioration processes. This indicates that the interplay of initial damage likely accelerates subsequent response to environmental stress, extending the initial damage patterns from the impact crater to larger areas of stonework.

Comparison of fatigue test results of high-strength steel DED-Arc specimens with milled and unmilled surfaces

The surface characteristics of direct energy deposition (DED)-Arc specimens have been previously explored, revealing the dual effect of the surface topography on fatigue strength. This effect includes a reduction in the nominal load-bearing cross-section due to the waviness of the surface and the initiation of fatigue cracks at combined geometric and metallurgical notches from the surface. To complement these findings, this study focuses on the fatigue life and crack initiation of milled DED-Arc samples, e.g., after removal of the geometric notches. Fatigue tests on DED-Arc specimens validate the impact of surface topography on fatigue strength, emphasizing the significance of surface characteristics in determining structural integrity. The additional tests conducted on milled surfaces provide insights into the failure mechanisms specific to these samples. Fracture surface analysis, microstructure characterization, and hardness measurements are performed. For both surface conditions, cracks originate in the interlayer zone, where local hardness is reduced. In unmilled specimens, this is due to the stress concentration effect, and in milled samples, this is due to softened interlayer zones. The fatigue life of milled specimens is comparatively high, demonstrating the importance of optimizing surface characteristics for improved fatigue resistance.Highlights1. Both, unmilled and milled specimens, show crack origins in the interlayer areas. For unmilled specimens, this is because of the local stress concentration in the notch; for milled specimens, it was shown that soft zones between the layers act as the weakest link.2. The fatigue strength of unmilled test coupons is significantly lower than those of milled specimens.3. Unmilled samples exhibit multiple crack origins.

Heavy aggregate and different admixtures effect on pavings: pyrite, corundum and water-retaining polymer

Concrete pavings are widely used in the construction industry as flooring for decorative and structural purposes in the gardens, parks, and roads of America, and Europe. In the present study, the effects of pyrite, corundum, and water-retaining polymer additives on the surface wear resistance of concrete pavings were investigated. Concrete pavings were poured in 2 stages and all of the bottom layers of samples were the same, but upper layers of pavings were produced by adding pyrite in the ratio of 0.10, 0.20, 0.30, 0.40 according to the mass of the aggregate, 5 kg /m2 corundum-based surface hardener to the paving surface area, and a high amount of water-absorbing polymer at a ratio of 0.05 and 0.10 to the water content of the mixture. Vertical abrasion, splitting tensile strength, water absorption, freeze-thaw resistance, pendulum footed friction, and surface hardness measurements with Schmidt test hammer experiments were made to TS 2824 EN 1338 standard. Also, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were carried out to characterize the produced materials. Results of the study indicate that the use of pyrite, corundum, and water-retaining polymers provided improvements in the surface wear resistance of concrete pavings.Concrete pavings are widely used in the construction industry as flooring for decorative and structural purposes in the gardens, parks, and roads of America, and Europe. In the present study, the effects of pyrite, corundum, and water-retaining polymer additives on the surface wear resistance of concrete pavings were investigated. Concrete pavings were poured in 2 stages and all of the bottom layers of samples were the same, but upper layers of pavings were produced by adding pyrite in the ratio of 0.10, 0.20, 0.30, 0.40 according to the mass of the aggregate, 5 kg /m2 corundum-based surface hardener to the paving surface area, and a high amount of water-absorbing polymer at a ratio of 0.05 and 0.10 to the water content of the mixture. Vertical abrasion, splitting tensile strength, water absorption, freeze-thaw resistance, pendulum footed friction, and surface hardness measurements with Schmidt test hammer experiments were made to TS 2824 EN 1338 standard. Also, X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were carried out to characterize the produced materials. Results of the study indicate that the use of pyrite, corundum, and water-retaining polymers provided improvements in the surface wear resistance of concrete pavings.

Analysis Of the Effect of Vegetal and Coking Coals on the Surface Hardness of Carburized AISI 8620 Steel

In this investigation, the comparative study of the superficial hardness of AISI 8620 steel thermally treated by carburizing, using vegetable and coking coals, was developed. The objective was to propose an alternative to the element used to generate the carburizing atmosphere. The previous stages have been described, such as the preparation of the material and its verification, as well as the dimensions and characteristics, defined by the ASTM E-18 standard. By considering four variables, each one with two levels, an orthogonal array matrix of 16 experiments was generated. The surface hardness measurements were processed through an analysis of variance (ANOVA), where the significance of each variable considered as a factor was obtained. Coking coal can be used as an element for the generation of carburizing atmosphere since a maximum relative error of 3.86 % was obtained between the experimental values and the values in the literature. In contrast, the vegetable coal did not improve the mechanical properties of the steel, reaching an average hardness of 25.95 HRC after heat treatments.

Change in surface properties of two different dental resin composites after using various beverages and brushing

BackgroundThe study aimed to evaluate the influence of various beverages; with and without brushing; on the surface mechanical properties of two resin composites.MethodsA total of 160 disc-shaped specimens were prepared for each of the following dental composites; nanohybrid ormocer (Admira fusion, VOCO GmbH, Cuxhaven, Germany) and nanohybrid resin composite (Grandio, VOCO GmbH, Cuxhaven, Germany). The baseline surface hardness and roughness measurements were carried out after 24 h. The composite samples were randomly distributed into one of the two groups; brushing and non-brushing, which were further divided into one of the four subgroups (n = 10); artificial saliva as control, coffee, red wine, and soft drink. In the non-brushing group, the specimens were immersed in the different beverages for five minutes three times daily for 30 days. The same procedure was done for the brushing group, in addition to brushing the specimens for five seconds. The surface hardness and roughness measurements were repeated after 30 days. One-way ANOVA and independent t-tests were used for statistical analysis.ResultsThe soft drink had the most deteriorating effect and artificial saliva had the least. The change in surface properties was higher in the brushing subgroups. Grandio exhibited a higher change in surface microhardness while Admira fusion exhibited a higher change in surface roughness.ConclusionsThe surface properties of both dental resin composites were negatively affected by using beverages and brushing.

Wire-EDM cutting strategies of WC-Co hardmetals: Effect of number of EDM pass on surface integrity

In this study, the effect of the number of wire-EDM passes on the surface integrity of WC-Co hardmetals was investigated. As-received doughnut-shaped WC-25 wt%Co samples were wire EDM’ed with one, two, three and five passes. The resulting surface conditions were investigated in terms of macroscopic and microscopic examinations. Surface roughness and hardness measurements were carried out. Detailed SEM investigations were coupled with EDS analyses. Based on the experimental findings, a detailed cutting strategy was offered for WC-Co hardmetals depending on the expectations of surface conditions, production route, cost and productivity. If there is at least one subsequent process including material removal, wire-EDM with one pass is suggested to decrease cost and increase productivity. However, heat-affected zone (HAZ), recast layer and lower surface hardness region should be removed at subsequent production steps. If there are no production steps to remove HAZ, recast layer and lower surface hardness region, the number of wire-EDM passes should be maximised.

Enhancing compatibility and properties of polylactic acid/polystyrene (PLA/PS) bioblend for sustainable food packaging: Experimental and quantum computational insights

This study investigated the impact of incorporating maleic anhydride grafted styrene-ethylene-butylene-styrene (SEBS-g-MAH) at varying concentrations (2.5, 5.0, 7.5, and 10.0 wt%) into binary blends of polylactic acid (PLA) and polystyrene (PS) with a weight ratio of 75/25. The blends were prepared using melt mixing in an internal Brabender mixer, followed by compression molding. Various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyses (TGA), differential scanning calorimetry (DSC), tensile testing, surface hardness measurements, and scanning electron microscopy (SEM) were employed to evaluate the structural, thermo-mechanical, surface, and morphological properties of the blends. FTIR results indicated the presence of n-π interaction between PLA and PS polymers. However, the introduction of SEBS-g-MAH to the blends resulted in specific interactions. TGA investigations demonstrated that compatibilized blends exhibited more excellent stability at high temperatures than their non-compatible counterparts. The DSC data align with the mechanical tests, revealing that the addition of SEBS-g-MAH reduced the crystallinity of the blends. Tensile strength, Young's modulus, and surface hardness diminished with the addition of SEBS-g-MAH, although the elongation at break improved. SEM analysis of the PLA/PS blends illustrated that incorporating SEBS-g-MAH enhanced the PS phase's distribution throughout the PLA matrix. Furthermore, molecular dynamic simulations revealed a significant enhancement in binding interaction energies upon adding SEBS-g-MAH, increasing from 2037.972 kcal/mol to 2826.946 kcal/mol for the PLA-PS and PLA-PS (5) systems, respectively. Density of state (DOS) analysis indicated that SEBS-g-MAH played an intermediary role, promoting compatibility between PLA and PS. These findings suggest that SEBS-g-MAH can effectively be a compatibilizer for PLA-PS blends.

Failure of surface modification 3D printed polymer materials by UV/ozone irradiation

In today's technology, AM processes are widely adopted in the aerospace, energy, automotive, medicine, and agriculture industries. Fused Deposition Modeling (FDM) is one of the most remarkable methods in the AM family because of its superiorities. Besides the advantages provided, the mechanical strength of the printed parts is still not at a satisfactory level. Here, there are various secondary processes applied to polymer materials to improve both the mechanical properties and functionality of the printed part. Among these processes, the UV/O3 surface treatment method stands out as the most suitable one in terms of ease of application. In this study, two different infill orientation angles were applied to two standard test models. The fabrication process was initiated using suitable process parameters for filaments made of Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) materials. The purpose of this investigation was to examine the mechanical strength of 3D printed polymer structures. For the same purpose, the UV/O3 (UV/Ozone) process was applied to the manufactured samples. The samples are then subjected to tensile and compression tests, Shore surface hardness measurements and Scanning Electron Microscopy (SEM) analyze for both the evaluation of mechanical properties and the examination of fracture surface structures. Consequently, significant increases of 28.33%, 25.21%, 27.90%, and 32.92% were observed in material surface hardness levels. This study is important in terms of presenting that the mechanical properties of 3D printed parts can be significantly improved with UV/O3 application, which is an effective and a practical process.

Effects of multiple post cure cycles on properties of composite carbon fibre and epoxy materials

Post-curing cycles have an effective impact on the thermal and mechanical properties of thermoset composite materials. Typically, post-cure cycles use heat to expose cured resin parts to high temperatures in an attempt to maximize their final properties. In most cases, these processes allow composite parts to achieve the highest possible strength and become stable. In industrial practice, however, it has been found that there are potential consequences of performing localized repairs on composite parts in an autoclave where the localized repair undergoes a normal curing process while the parent part undergoes an additional curing process. Thus, for the parent part, prolonged exposure to high temperatures can trigger a process of decomposition of the resin matrix, as could be the aging phenomena of composites in service. In such a scenario, two practical questions are worth asking: (1) to what extent can a resin matrix be post cured without risking degrading its thermal properties? (2) what are the residual mechanical and physical properties resulting from prolonged exposure of composite parts to elevated temperatures? In this work, an analysis was carried out to estimate the potential adverse effects on thermoset composite parts made of carbon fibre and epoxy resin materials commonly used in aerospace, in terms of thermal, physical and mechanical properties after a long exposure to high temperatures caused by multiple post cure cycles. Two types of prepreg laminates were used to make monolithic test panels using twill and plain weave architectures for the M21 and 8552 test panels respectively. Thermal tests were conducted to evaluate the evolution of the degree of cure, the glass transition temperature and the inter-laminar shear strength of post-cured panels, which were subjected to a different number of post cure cycles. The study found that multiple post cure cycles alter thermal properties, which in turn have adverse effects on physical and mechanical properties. The results demonstrated that the two types of composite materials respond differently to changes in properties. Twill weave panels quickly reach full cure after three stages while plain weave panels have undergone gradual curing. This difference in the curing process of the resin matrix clearly influenced the changes in the measurements of shear, surface hardness and compressive strengths.

Abrasion resistance and hardness evaluation of FCAW-S hard-facing following elevated temperature exposure

Proprietary compositional blends were welded for hardfacing applications. The blends were subsequently heat treated at progressively increasing temperatures followed by testing using industry key performance indicators. Each blend was developed to be used as a self-shielded FCAW wire for high-amperage, high-productivity deposition. Heat treatment of each consumable was completed in three conditions: as-welded, 400 °C (750 °F), and 700 °C (1290 °F). Microstructural analysis complimented mechanical testing and included field-emission scanning electron microscopy, surface hardness (HV10kg), ASTM G65 Method A abrasion mass loss, carbide volume fraction analysis, and rotary impact testing. The results of hardness testing showed that there was a differentiated decrease in average surface hardness between the blends as the heat treatment temperature was increased. All surface hardness measurements met the stringent industry performance indicator of 600 HV10 minimum. ASTM G65 Method A abrasion testing was performed following each heat treatment. All blends had acceptable abrasion mass loss as-welded, after a 400 °C heat treatment, and after a second heat treatment at 700 °C. Rotary impact testing of the consumables was completed after high temperature exposure in accordance with the Alberta Oil Sands procedure. Microstructural comparisons of the blends showed performance-indicating variation to support the mechanical testing results.

Use of eggshell waste: A green and effective method for the synthesis of pure calcium hydroxide suspensions

This paper presents a rapid method to obtain pure suspensions of Ca(OH)2 dispersed in 2-propanol. To this aim eggshell wastes (CaCO3) were decarbonated to calcium oxide (CaO) followed by sonication-assisted hydrolysis in water/2-propanol to form calcium hydroxide (Ca(OH)2). An important advantage of the method is that it does not require chemical reagents due to the high purity of eggshell in CaCO3. Moreover, CaO is fully converted into Ca(OH)2 which means that purification steps are not needed, as occurs in conventional routes of synthesis. To assess the reliability of the synthetic procedure, the purity and amount of Ca(OH)2 were studied by X-ray diffraction (XRD), infrared spectroscopy (FTIR) and thermal analysis (TG). In addition, the morphology and crystallite size were examined by transmission electron microscopy (TEM) and X-ray diffraction (XRD) using Rietveld refinement method. It was found that sonicated Ca(OH)2 suspensions (5 g/L) were composed of particles that ranged in size from several nanometers to few micrometers. Finally, the suitability of Ca(OH)2 from eggshell to reinforce architectural stone was also studied by microscopy examination, colour change tests, surface hardness and surface erosion measurements. All tests confirmed the consolidation effectiveness was comparable to conventional nanolime treatments and surface erosion was visibly reduced.

Assessing the efficacy of several impact-based mechanical techniques on fatigue behavior of additive manufactured AlSi10Mg

Post-processing methods to reduce issues associated with the presence of internal and external anomalies are often necessary for obtaining adequate structural performance for additively manufactured products. However, the choice of the proper post-treatment and the corresponding parameters is still a challenge requiring adaption to the material type, geometry, size and undeniably costs. In this study, four different pure impact-based mechanical operations involving ultrasonic nanocrystal surface modification (UNSM), ultrasonic shot peening (USSP), severe shot peening (SSP), and severe vibratory peening (SVP) to investigate their efficacy on the fatigue behavior of hourglass AlSi10Mg specimens manufactured via laser powder bed fusion (LPBF) were considered. Experimental characterizations involving microstructural approach, porosity level and surface texture, hardness and residual stresses measurements, as well as tensile and fatigue testing, were conducted. The results exhibited considerable improvement in mechanical/physical performances leading to substantially enhanced fatigue performance of the mechanically treated specimens. Based on a cost-performance analysis, it was found that UNSM, while having reasonable cost, presented considerable improvement on fatigue behavior.

Micromagnetic and Robust Evaluation of Surface Hardness in Cr12MoV Steel Considering Repeatability of the Instrument.

The combination of multifunctional micromagnetic testing and neural network-based prediction models is a promising way of nondestructive and quantitative measurement of steel surface hardness. Current studies mainly focused on improving the prediction accuracy of intelligent models, but the unavoidable and random uncertainties related to instruments were seldom explored. The robustness of the prediction model considering the repeatability of instruments was seldom discussed. In this work, a self-developed multifunctional micromagnetic instrument was employed to perform the repeatability test with Cr12MoV steel. The repeatability of the instrument in measuring multiple magnetic features under both static and dynamic conditions was evaluated. The magnetic features for establishing the prediction model were selected based on the consideration of both the repeatability of the instrument and the ability of magnetic features in surface hardness evaluation. To improve the robustness of the model in surface hardness prediction, a modelling strategy considering the repeatability of the instrument was proposed. Through removing partial magnetic features with higher mean impact values from input nodes, robust evaluation of surface hardness in Cr12MoV steel was realized with the multifunctional micromagnetic instrument.

Antifrictional Effects of Group IVB Elements Deposited as Nanolayers on Anodic Coatings

The utilization of anodized aluminum (Al) components would contribute greatly to combat against dry friction if good tribological properties could be attained. Despite its hardness, the wear rate of anodic coatings presents a major problem in many applications, including automotive, aerospace and high-tech industries. Recently, nanolayers of Ti demonstrated high tribological effectiveness and unusually low dry friction on anodic coatings. However, few researchers focus on the tribological characterization of nanolayers of other elements. In this study, nanolayers of Ti, Zr, Hf, Cu, Cr, Nb and Sn were deposited on anodized 1050 and 6082 alloys by magnetron sputtering and Atomic Layer Deposition. Major attention was devoted to surface roughness and hardness measurements, because of their importance for static friction. The results showed that structural, chemical and other intrinsic properties of nanolayers of Group IVB elements in many cases led to significant friction reduction, when compared to those of Cu, Cr and Hf. Nanolayers of 15 nm to 75 nm thicknesses appeared most effective tribologically, while 180 nm or thicker layers progressively lost their ability to sustain low dynamic friction. Deposition of nanoscale structures could provide advantages for the anodized Al industry in protection against incidental friction and wear.

Influence of filler types on wear and surface hardness of composite resin restorations.

Wear and surface hardness of resin composites are of relevance from the clinical standpoint. With the incorporation of novel filler system, more studies need to be performed to investigate newly marketed resin composites. The objective of this study was to investigate the abrasive wear and surface hardness of dental restorative with different filler types. Nanohybrid filled Harmonize (HM) and Tetric N-Ceram (TNC), microhybrid filled Filtek Z250 (Z250), nanofilled Filtek Z350 (Z350) were included in the study. Twelve cylindrical resin composites specimens with 10 mm in diameter and 6 mm in thickness were prepared for abrasive wear test. Eight hundred cycles under 17 kg load were conducted for final wear by CW3-1 wear machine. The specimen was cleaned with an ultrasonic unit for 3 min followed with drying procedure. After measurement of weight loss and the density of specimens, the specimens were kept for measurement of surface hardness. Surface hardness was measured using a micro-hardness tester with a Vickers diamond indenter after polishing. Three specimens of each material were observed by scanning electron microscopy (SEM) after the abrasion to evaluate the morphology of the surface. Data were analyzed using one-way analysis of variance (ANOVA), followed by Tukey HSD test (α = .05). Z250 performed the least volume wear loss (41.1 ± 2.1 mm3), as well as the hardest value (102.7 ± 2.9 HV). There was no significant difference with the volume wear loss (p = 1.000) and surface hardness (p = 0.874) of HM and TNC. SEM images of nanohybrid filled HM and TNC represented smoother surface compared with other types of resin composites. Microhybrid Z250 showed the highest wear resistance and surface hardness, nanofilled and nanohybrid resin composites may still face the insufficient of wear and surface hardness quality.

Experimental Investigation of a New Design of Insulation Gypsum Plaster Blocks

Green building materials are an alternative to ordinary materialsoffering multiple environmental benefits. This study consists of an experimental investigation of a new design of gypsum plaster blocks. First, a mix design of gypsum plaster and water mixture was prepared. The optimal mix composition was determined according to the mechanical and physical properties, such as the water absorption, the temperature of hydration, the density, and the compressive strength of different gypsum plaster and water mixtures made by varying the water dosage. The second part of this investigation aims to study a new design of green blocks prepared from the optimal water and gypsum plaster mixture. The new blocks are perforated to lighten them and to reduce their thermal conductivity in order to make them moreinsulate. Experimental tests were conducted on the block prototype, such as the measurement of dimensional tolerances, compressive strength, density, flatness, water absorption, residual moisture, surface hardness, and thermal conductivity. Experimental test results show that the new blocks have very low density, and their compressive strength is sufficient for wall construction. In addition, the manufacturing process of the new blocks is very easy and very fast. Finally, the obtained physical and mechanical properties of the new gypsum plaster blocks give it the opportunity to be used for interior walls for building constructions.

The Influence of Tool Pin Geometry and Speed on the Mechanical Properties of the Bobbin Tool Friction Stir Processed AA1050.

AA1050 plates of 8 mm thickness were processed via bobbin-tool friction stir processing technique at a constant rotation speed of 600 rpm and different travel speeds ranging from 50 to 300 mm/min using three-pin geometries of triangle, square, and cylindrical. The temperatures of the processed zone, the advancing side, and the retreating side were measured; the machine torque during processing was also recorded. The processed materials were evaluated in terms of surface roughness, macrostructure, tensile properties, and hardness measurements. The fracture surfaces of the tensile fractured specimens were investigated using SEM. The results indicated that the pin geometry and processing speed significantly affect the generated heat input and the morphology of the processed zone. The peak temperature in the center of the processed zone decreases with increasing the travel speed from 50 to 300 mm/min at all applied pin geometries. The maximum temperature of ~400 °C was reached using the cylindrical pin geometry. The machine torque increases with increasing the travel speed at all applied pin geometries, and the highest torque value of 73 N.m is recorded using the square pin geometry at 300 mm/min travel speed. The top surface roughness of the processed area using the cylindrical pin is lower than that given by the other pin geometries. Under all applied conditions, the hardness of the processed area increases with increasing travel speed, and the cylindrical pin shows a higher hardness than the other pin geometries with 19% enhancement over the BM. The AA1050 processed using a cylindrical pin at 200 mm/min travel speed and a rotation speed of 600 rpm produces a sound processing zone with the highest ultimate tensile strength of 79 MPa.

Innovative Calcium Carbonate-Based Products to Repair Cracked Cement Mortars.

The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone consolidants, was evaluated in terms of crack filling or sealing and consolidation. Realistic cracks were induced in quasibrittle cement mortar prisms using a custom-designed test rig. The effectiveness and the performance of the considered treatments, investigated on specimens, were evaluated by optical and scanning electron microscopy, colourimetry, water absorption rate, ultrasonic pulse velocity, and surface hardness measurements. Results revealed that, in the examined conditions, the products were more suitable as surface consolidants than as crack fillers.

Influence of Propolis Extract (Caffeic Acid Phenethyl Ester) Addition on the Candida albicans Adhesion and Surface Properties of Autopolymerized Acrylic Resin.

Background Denture stomatitis has been linked to the adhesion and proliferation of Candida albicans (C. albicans) on denture bases, which is a common and recurrent problem in denture wearers. The current study aimed to evaluate the effect of incorporating caffeic acid phenethyl ester (CAPE) into autopolymerized polymethyl methacrylate (PMMA) acrylic resin on C. albicans adhesion, surface roughness, and hardness as well as the correlation between tested properties. Methods Autopolymerized acrylic resin discs (N = 100, 50/C. albicans adhesion; 50/C. albicans surface roughness and hardness test) were fabricated in dimensions 15 × 2.5 mm, samples were categorized into 5 groups (n = 10) based on CAPE concentrations; unmodified (control), 2.5, 5, 10 and 15% wt of acrylic powder. Specimens were stored in distilled water for 48 h at 37°C. C. albicans adhesion was evaluated via direct culture method. Profilometer and Vickers hardness tester were used for surface roughness and hardness measurement. Post hoc Tukey's HSD with ANOVA test was performed to compare the difference of means amongst groups. P values were statistically significant at ≤0.05. Results The addition of 2.5% of CAPE to PMMA has significantly reduced C. albicans counts in comparison to higher CAPE concentrations (p < 0.001). As for surface roughness, it was noticed that it increased with increased CAPE concentrations (p < 0.0001). While surface hardness decreased as CAPE concentrations increased (p < 0.0001). All tested properties showed a significant difference amongst groups for C. albicans colony count and surface parameters. Conclusion The addition of 2.5% of CAPE to PMMA acrylic resin significantly decreased C. albicans count compared to higher CAPE concentrations. CAPE can be used as an adjunct in the prevention of DS by incorporating in the PMMA acrylic resin.

Comparison of Surface Roughness and Microhardness of Reinforced Glass Ionomer Cements and Microhybrid Composite

Objectives: The purpose of this study was to compare high viscosity glass ionomer cement (HVGIC), giomer and microhybrid composite using the atomic force microscopy (AFM) and Vickers microhardness. Methods: Three different restorative materials Equia Forte (HVGIC), Beautifil II (giomer) and Solare X (microhybrid composite)were used in this study. A total of 30 samples were prepared, 10 of each of the restorative materials used in our study. Samples were prepared using standard cylindrical Teflon molds with a diameter of 8 mm and a height of 2 mm. The measurements of surface roughness and hardness were performed by using AFM and Vickers microhardness, respectively. The surface roughness was analyzed using the Kruskal Wallis test. One-way variance analysis (ANOVA) and LSD test was used for the surface hardness (α = 0.05). Results: There was no significant difference between the groups according to surface roughness values (p&gt; 0.05). A statistically significant difference was found between all groups in terms of surface hardness. Conclusion: Reinforced glass ionomer cements had similar and surface properties than composite resin.