Significant Differences In Hardness Research Articles

Lemongrass (Cymbopogon citratus) oil nanoparticle synthesis, characteristic, and evaluation of antibacterial and antifungal effects and the influence on hardness of acrylic resin

Context: Acrylic resin is used in dentistry as a removable denture base. It can cause various pathologies when not properly cleaned. One of the pathologies is denture stomatitis caused by Candida albicans and Streptococcus mutans accumulation on the acrylic resin surface. Therefore, microbial agents such as denture cleansers are needed. Aims: To evaluate the characteristics of lemongrass (Cymbopogon citratus) nanoparticles as a better antibacterial and antifungal herbal ingredient and their relationship with acrylic hardness. Methods: C. citratus oil nanoparticles (LON) were synthesized and analyzed by transmission electron microscopy (TEM). Electrospray ionization tandem mass spectrometry (ESI-MS) analysis was used to analyze the characteristics of LON bioactive components. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) against C. albicans and S. mutans and mechanical hardness test of acrylic were performed. Results: The LON concentration of MIC and MBC against C. albicans and S. mutans was 25 and 100%, respectively. One-way ANOVA showed no significant difference between groups of LON with different concentrations (p=0.687). A paired t-test showed significant differences in acrylic resin hardness before and after treatment of LON with 100% (p=0.022) and 50% (p=0.021) concentration. There was no significant difference in hardness before and after treatment of other concentrations of LON and chlorhexidine as positive control. Conclusions: LON treatment on acrylic resin decreased the growth of C. albicans and S. mutans without altering the mechanical properties (hardness).

Hardness Analysis of Foods in a Diet Based on the Mediterranean Diet and Adapted to Chilean Gastronomy.

The human diet is a factor for disease prevention and the extension of life expectancy. Loss of teeth can adversely affect chewing capacity, which can lead patients to modify their diet and subsequently result in a poor dietary intake. This work is conducted within the framework of an ongoing research project in the Dentistry School of Universidad de la Frontera aimed at designing a diet for patients with complete removable dental prostheses (CRDP). This study aimed to evaluate the hardness of foods in a diet designed for patients using CRDP, using texture profile analysis (TPA). TPA was used to measure the hardness of 43 foods, categorized into seven groups, dairy, animal protein, fruits, vegetables, cereals and grains, high-lipid foods, and vegetable protein, to understand their impact on masticatory performance in CRDP wearers. TPA consists of two compression cycles where the food sample is compressed until it reaches a pre-established deformation. The first force peak achieved in the first cycle is used as a measure of sample hardness. Significant differences in hardness were identified within each food group, indicating a wide spectrum of textural properties that could influence chewing behavior. These findings suggest that assessing food hardness can help tailor dietary recommendations to improve masticatory efficiency in patients with dental prostheses.

Effect of artificial aging on fracture toughness and hardness of 3D-printed and milled 3Y-TZP zirconia.

This study aimed to evaluate the impact of artificial aging on the fracture toughness and hardness of three-dimensional (3D)-printed and computer-aided design and computer-aided manufacturing (CAD-CAM) milled 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP). Forty bar-shaped specimens (45 × 4 × 3mm) were prepared using two manufacturing technologies: 3D printing (LithaCon 3Y 210, Lithoz GmbH, Vienna, Austria; n = 20) and milling (Initial Zirconia ST, GC, Japan; n = 20) of 3Y-TZP. The chevron-notch beam method was used to assess the fracture toughness according to ISO 24370. Specimens from each 3Y-TZP group were divided into two subgroups (n = 10) based on the artificial aging process (autoclaving): nonaged and aged. Nonaged specimens were stored at room temperature, while aged specimens underwent autoclave aging at 134°C under 2bar-pressure for 5 h. Subsequently, the specimens were immersed in absolute 99% ethanol using an ultrasonic cleaner for 5 min. Each specimen was preloaded by subjecting it to a 4-point loading test, with a force of up to 200 N applied for three cycles. Further 4-point loading was conducted at a rate of 0.5mm/min under controlled temperature and humidity conditions until fracture occurred. The maximum force (Fmax) was recorded and the chevron notch was examined at 30 × magnification under an optical microscope for measurements before the fracture toughness (KIc) was calculated. Microhardness testing was also performed to measure the Vickers hardness number (VHN). A scanning electron microscope (SEM) coupled with an energy dispersive X-ray unit (EDX) was used to examine surface topography and chemical composition. X-ray diffraction (XRD) was conducted to identify crystalline structure. Data were statistically analyzed using two-way ANOVA and Student's t-test with a significance level of 0.05. The nonaged 3D-printed 3Y-TZP group exhibited a significantly higher fracture toughness value (6.07MPam1/2) than the milled 3Y-TZP groups (p < 0.001). After autoclave aging, the 3D-printed 3Y-TZP group maintained significantly higher fracture toughness (p < 0.001) compared to the milled 3Y-TZP group. However, no significant differences in hardness values (p = 0.096) were observed between the aged and nonaged groups within each manufacturing process (3D-printed and milled) independently. The findings revealed that the new 3D-printed 3Y-TZP produced by the lithography-based ceramic manufacturing (LCM) technology exhibited superior fracture toughness after autoclave aging compared to the milled 3Y-TZP. While no significant differences in hardness were observed between the aged groups, the 3D-printed material demonstrated greater resistance to fracture, indicating enhanced mechanical stability.

Effect of carbide refinement on high temperature erosive wear behavior of high chromium white cast iron with different titanium and carbon additions

It is known that better erosion wear resistance of high chromium (27 wt% Cr) white cast iron (HWCI) with titanium (Ti) addition can be achieved by controlling the size of M7C3 carbides. Nevertheless, it might not be directly applicable to high temperature conditions due to the more complex factors involved, especially the hot oxidation behavior. Therefore, the effect of 0–2 wt% Ti and 3–4 wt% carbon (C) addition on the high temperature erosion wear behavior of HWCI has been investigated in this research. The results show that there are TiC and M7C3 carbides precipitated in the material matrix. The size of M7C3 carbides decreases drastically as the amount of Ti increases. On the contrary, it is effectively enlarged with the addition of higher C. In addition, there is no significant difference in hardness among all specimens due to the relatively similar carbide volume fraction (CVF). The wear resistance of HWCI is improved by increasing the amount of Ti although it has a lower value as the C content increases. It means that hardness is not an important factor in evaluating the wear characteristics of HWCI at high temperatures. The worn surfaces and cross-sections show that the smaller M7C3 carbides are more likely to undergo plastic deformation rather than being directly peeled out. In addition, the effect of hot oxidation behavior was negligible because there is only a very thin oxidation layer on the worn surface. Therefore, it can be concluded that the erosive wear behavior of the material is greatly influenced by the size of M7C3, which the material with better erosive wear resistance contains finer carbides.

Quantitative Analysis of the Impact of Different Delivery Modes on Cervical Elasticity Based on Real-time Shear Wave Imaging Technology and Artificial Intelligence.

Real-time shear wave elastography (SWE) has emerged as a useful imaging modality for detecting the lesion location of various diseases, including cervical diseases. In this paper, the SWE was used to quantitatively determine the tissue hardness of the internal and external orifice of the cervix (IOC & EOC) and to relatively objectively analyze the impact of different production methods on the hardness of the cervical tissue. A total of 48 patients were selected, and they were divided into three groups according to different production methods: control group (16 cases), cesarean section group (16 cases), and spontaneous delivery group (16 cases). Artificial intelligence has also been incorporated into this work. A deep flexible neural tree model and a new set of FNT models were proposed to assist in classifying cervical physical data in different states. The physical data was extracted as the features, and the different states were considered as category labels. There was no statistically significant difference in the elasticity of the IOC and the EOC between the groups. However, the difference in the elasticity of the IOC and the EOC within each group was statistically significant. The classification results corresponded with the results of the statistical analysis. The hardness of the EOC is generally lower than that of the IOC, and there was no significant difference in hardness between the IOC and the EOC in the three groups. There is no significant difference in the cervical elasticity hardness between different delivery modes.

Formation of structure and physical and mechanical properties of reinforcing steels during high-temperature thermomechanical treatment

The effect of high-temperature thermomechanical treatment (HTMT) modes on the formation of the structure and physical and mechanical properties of reinforcing St5 steel is considered. It is shown that with HTMT in the mode of intensive (interrupted) cooling, there is a significant difference in hardness (47 HRC on the surface versus 31 HRC in the core) and a significant change in mechanical properties (σв, σ0,2, δ5). It is established that under conditions of maximum intensive cooling, the reinforcing bar does not have time to completely calcinate. The use of continuous cooling mode allows for a more uniform distribution of mechanical properties. The production of high-strength reinforcement of А800, А1000, Аt1200 strength classes after the HTMT is ensured by the formation of a dispersed martensitic-troostite structure in steel.

Magnetic property regulation and mechanism analysis of FeSiBC soft magnetic composites by mixing with FeSiCr or carbonyl iron powder

FeSiBC, FeSiCr, and CIP (carbonyl iron powder) are the main raw materials for the preparation of molding choke. In this study, water atomized FeSiCr powder with three particle size groups and CIP with a fixed particle size were used as raw materials to explore the influence of fine powder size and type on soft magnetic properties of FeSiBC SMPCs (soft magnetic powder cores). The results show that by adding a certain proportion of FeSiCr fine powder, the pores between large-size FeSiBC amorphous powder could be effectively filled, so that the density and permeability of SMPCs increased monotonically with the increase of FeSiCr content, while the porosity and DC bias performance decreased monotonically. In addition, the smaller the particle size of the FeSiCr, the more beneficial it was to reduce the eddy current loss of SMPCs. In the mixed FeSiCr scheme, adding 10 wt% FeSiCr with an average particle size of 6 μm was the best. In this case, the permeability of SMPCs was 18.01 and the core loss was 239.15 mW·cm−3 (100 kHz, 50 mT). Compared with hard FeSiCr, the deformation of CIP was greater during the pressing process due to its extremely low hardness, which could effectively fill the pores of SMPCs, thus greatly improving the comprehensive performance. The FeSiBC/30 %CIP SMPCs prepared in this study had excellent soft magnetic properties (permeability of 26.26, DC bias performance of 94.58 % at 100 Oe and core loss of 192.10 mW·cm−3 at 100 kHz and 50 mT), highest strength (6.54 ± 0.08 MPa) and lowest cost (13.7 $∙kg−1), and the comprehensive performance was significantly better than that of FeSiBC/FeSiCr SMPCs with different particle sizes. It can be seen that mixing FeSiBC amorphous powder with a small amount of powder that has a significant difference in hardness and particle size and complementary soft magnetic properties is an effective way to improve the magnetic properties of SMPCs.

Effects of chia seed gum on the physicochemical properties of frozen dough and the quality of dumplings

This study was designed to investigate the properties of chia seed gum (CSG) and its use in frozen dough. The CSG prepared by vacuum freeze-drying had the lowest water separation (4.22 ± 0.11 %) after three freeze–thaw cycles and the best color among the samples. The addition of 0.4 % to 1.0 % CSG significantly increased the peak, trough and final viscosity and decreased the breakdown and setback of the flour. The water absorption and cooking stability of the dough increased with increasing CSG content. The addition of 0.8 %–1.0 % CSG significantly increased the content of strongly bound water in dough during frozen storage. The CSG improved the texture of dough, and there were no significant differences in hardness, springiness, cohesiveness or chewiness of dough with 0.8 %–1.0 % CSG during frozen storage for 30 days. The cooking loss rate and the cracking rate of the dumpling wrappers with 0.8 % CSG were reduced by 2.31 % and 21.34 %, respectively. In conclusion, CSG can be used to improve the quality of wheat dough and its products and has promising applications in flour products.

Welding on C67 steel grade sheet: Influence of the parameters and post welding heat treatment

&lt;abstract&gt; &lt;p&gt;In batch operation, most industries require engineers to maintain low hardness on the welded parts, particularly for low carbon steel. This article focuses on tungsten inert gas (TIG) welding performed on 0.90 mm of a C67 grade sheet by varying different welding parameters such as current, velocity, and temperature. Samples were collected from the tool side, mid-wall, and operator side for metallographic and micro-hardness examinations considering various parameters. Without post welding heat treatment (PWHT), the welded parts were quenched at room temperature, while with PWHT the welded parts were kept at 710 ℃ for 99 s after welding, and subsequently, the samples were cooled slowly by air at ambient temperature. An increase in hardness was registered in either the fusion zone or melted zone, with decrements in the heat affected zone (HAZ) for both procedures. When the the welding was performed without PWHT, a martensitic and bainitic microstructure was noticed in the melting zone (MZ) and HAZ, respectively. In contrast, a bainitic microstructure was observed in either the melting or heat affected zone in the welding with PWHT. Metallographic images revealed crack propagation when welding was performed without PWHT. A larger HAZ was noted in the welding sample with PWHT, and hardness was also relatively lower compared the samples without PWHT. There was no significant difference in hardness among the samples taken from tool side, mid-wall, and operator side for both procedures. Finally, the lowest microhardness (265 HV) was found in the MZ when the welding was carried out with PWHT employing a 90 A current and 10 mm/s velocity.&lt;/p&gt; &lt;/abstract&gt;

SENSORY QUALITY OF STIFF PORRIDGE (UGALI) PREPARED FROM PUMPKIN AND SOY BEAN SEEDS FORTIFIED MAIZE FLOUR

Maize is a major food staple in most of the sub- Saharan African countries. Maize flour is mostly rich in carbohydrates, which provide energy to the human body. Nutritionally, maize flour is deficient in the other major diet requirements of proteins, vitamins and essential minerals. In this study, maize flour was enriched using pumpkin and soybean seed flours and the sensory qualities of the resulting composite flours were evaluated. Four formulations of maize, soy bean and pumpkin seeds flours were prepared by compositing various proportions of each ingredient. The flours were produced by grinding the seeds using a hammer mill to a particle size fine enough to go through a 1 mm sieve size. The composite flours were using to prepare stiff porridges (ugali), which is the popular format of preparation for this meal. Sensory quality of the flours and stiff porridges were evaluated. Sensory attributes evaluated for the composite flour ugali were aroma, color, texture, general appearance, smell, flavour, hardness, springiness, oiliness, taste and general acceptability. There was no significant difference in smell, appearance, texture, flavour, hardness, springiness across the formulations among the panelists. A significant difference was observed on color, oiliness, taste, appearance. The mean score was above 5 for all parameters, which is in the middle of the 9- point hedonic scale. These findings indicate that generally all the formulations were accepted. The instrumentally evaluated results using a texture analyzer indicated a significant difference in hardness, cohesiveness and springiness in the stiff porridge samples. But all samples were accepted regardless of the differences, indicating that the differences were not big enough to influence the human sensory organs.

Orientation controlled microstructure and mechanical properties of TiN-Cu nanocomposite films

Adding soft metal phases into transition metal nitrides to generate nanocomposite structures can considerably tune the mechanical properties of films. We prepared TiN-Cu nanocomposite films with different orientations on MgO (100) and (110) substrates; the hardness of the film with 〈110〉 orientation was 40.4 GPa, while the 〈111〉-oriented film hardness was 28.1 GPa. This significant difference in hardness was attributed to orientation affecting Cu segregation at grain boundaries (GBs) to form different thicknesses of amorphous layers. This study opens a new avenue for tuning the mechanical properties of ceramic thin films.

Hydrothermal treatment of bamboo and its effect on nano-mechanic and anti-mildew property

Bamboo has shown great potential in many fields, including construction, furniture, and decoration due its fast growth rate, excellent mechanical properties, and short rotation cycle. Vascular bundles of bamboo culm walls are less studied owing to their complexity and uneven distribution. In this study, the changes in the mechanics of bamboo cell walls from the bamboo inner (BI) layer to the bamboo outer (BO) layer after hydrothermal modification of the bamboo sample were analyzed. These changes were investigated using a scanning electron microscope, nano-indentation, X-ray photoelectron spectroscopy, atomic force microscope, wet chemistry method, and Fourier transform infrared spectroscopy. The use of high-temperature water and high-pressure treatment deformed and distorted the structure of thermal-modified bamboo. In addition, the hemicellulose and cellulose contents of the bamboo cell wall decreased. Thermal-modified bamboo exhibited a higher lignin content (27.2%) than the control (22.4%). Statistical analysis showed no significant difference in hardness from the BI layer to the BO layer. However, the elasticity modulus of the bamboo middle layer was lower than that of BI and BO. Moreover, the creep ratio of the sample decreased after hydrothermal modification at 170 °C. Furthermore, the changes in macro-physical, mechanical, and anti-mildew properties and surface hydrophobicity were investigated. This study revealed and analyzed the change tendency in mechanical properties of bamboo cell walls from the BI layer to the BO layer. Furthermore, compared with untreated bamboo sample, hydrothermally modified bamboo samples exhibited excellent anti-mildew property in 30 days.

Vickers Hardness Variation on the Part and Welding Cord Subjected to Plastic Deformation

By performing Vickers identifications in the area of the weld bead and the areas adjacent to it, the degree of plastic deformation can be assessed, highlighting the different hardness in the case of welding and the base material. During this work, welded specimens were made in the central area with a double V-shaped cord. One of the specimens was loading until breaking, noting that the rupture occurred in an area further away from the welding area. Another 13 specimens were required at varying degrees of deformation. Stresses above the elastic limit create differences in the plastic deformation of the areas of the weld bead and those in its vicinity. Due to the fact that the base material and the material of the weld bead have different elastic characteristics, much more pronounced plastic deformations occur in the base material compared to the weld bead. It was found that the base material suffered significantly greater plastic deformation than the weld bead. Significant differences in hardness occur in the area of the weld bead relative to the area of the base material.

Effect of Cooling Rate on Mechanical Properties, Translucency, Opalescence, and Light Transmission Properties of Monolithic 4Y-TZP during Glazing.

A standard cooling rate has not been established for glazing; therefore, the effects of the cooling rate on the properties of zirconia need to be evaluated to predict outcomes in clinical practice. 4Y-TZP glazed at three different cooling rates was analyzed to estimate the effect of cooling rate during glazing on the mechanical and optical properties. Hardness tests, field-emission scanning electron microscopy analysis, X-ray diffraction analysis, flexural strength measurement, and optical property evaluations were performed. When 4Y-TZP was glazed at a higher cooling rate (Cooling-1) than the normal cooling rate (Cooling-2), there was no significant difference in grain size, flexural strength, average transmittance, and translucency parameters. The hardness was slightly reduced. The opalescence parameter was reduced for the 2.03 mm thick specimens. When 4Y-TZP was glazed at a lower cooling rate (Cooling-3) than the normal cooling rate, there was no significant difference in hardness, grain size, flexural strength, and translucency parameters. In addition, the average transmittance and opalescence parameters were slightly reduced for the 0.52 and 2.03 mm specimens, respectively. The effects of the cooling rate during glazing on the mechanical and optical properties of 4Y-TZP appear to be minimal and clinically insignificant. Therefore, even if the cooling rate cannot be strictly controlled during glazing, the clinical outcomes will not be significantly affected.

Effect of Composite or Ceramic Thickness on the Polymerization Hardness of 5 Different Dual-cured Resin Luting Cements

Objective: The aim of the present study was to evaluate the influence of ceramic and composite thickness on polymerization hardness of five different dual-cure resin cements. Materials and Methods: A total of 100 disc-shaped spacer, 10-mm in diameter and five varying thicknesses (1.0mm, 2.0mm, 3.0mm, 4.0mm, 5.0mm) were fabricated from ceramic and composite materials. Dual-cure resin cement specimens with 8-mm diameter were prepared using metal brass mold and activated by light beneath the composite and ceramic disc shaped spacers. A total of 100 specimens of five different dual-cure resins (RelyX, Variolink, NX3, Calibra, Panavia F2.0) were prepared. Knoop hardness of each dual-cure resin cement was measured at five different point using a microhardness device with a 500 gm load, after 1 hr, 1 day, and 1 week polymerization. All data were statistically evaluated using one-way ANOVA. Results: Multivariate analysis of variance revealed significant differences in hardness of specimens dual-cured under composite resin or ceramic spacers and different time intervals (P&amp;lt;.001). Specimens cured through composite resin spacers showed less hardness values than ceramic spacers, with increasing thickness of the spacer. Also increasing the thickness of the composite or ceramic spacers produced a statistically significant decrease in microhardness of the dual-cure cements (P&amp;lt;.05). Conclusions: Hardness values significantly reduced when composite spacers were thicker than 2 mm and ceramic spacers thicker than 3 mm. Dual-cured resin cements are needed to be improved to achieve sufficient degree of hardening under composite and ceramic restorations. Different commercially available brands have different polymerization properties.

Differences in physicochemical properties of high-moisture extrudates prepared from soy and pea protein isolates

This study aimed to compare the physicochemical properties of high-moisture extrudates prepared from soy protein isolate (SPI) and pea protein isolate (PPI) at different barrel temperatures (BTs) of 120 °C, 140 °C, and 160 °C. Increasing BT promoted more anisotropic structures and darker extrudates. PPI extrudates produced more fibrous structures than SPI extrudates under the same BT. Textural and rheological properties of SPI extrudates elevated significantly with increasing BT. Compared to SPI extrudates at the same BT, PPI extrudates displayed apparently weaker shear thinning (gel-like) behavior and showed less textural properties of hardness, chewiness, and tensile strength. PPI extrudates showed no significant differences in hardness and chewiness to the cooked chicken breast. Heat-treatment during low-field nuclear magnetic resonance (LF-NMR) measurements promoted the release of intra-space water of the fibrous structure for both SPI and PPI extrudates. Water in PPI extrudates was more prone to migrate compared to SPI extrudates. Hydrogen bonds and hydrophobic interactions played marginally more essential roles than the disulfide bonds to stabilize protein structure for both SPI and PPI extrudates. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that most protein subunits were still present after extrusion, except two bands over 100 kDa in SPI extrudates extracted by phosphates buffer. This study provided valuable information for improving the quality of high-moisture extrudates based on SPI and PPI.

Effect of Treated Zirconium Oxide (ZrO2) Nanoparticles on the Color and Surface Properties of Interim Fixed Prostheses.

ABSTRACTObjective:Zirconium oxide (ZrO2) nanoparticles addition to interim fixed prostheses (IFPs) was suggested to improve the mechanical properties. However, the effect of ZrO2 on the color and surface properties of IFP was neglected. Therefore, this study aimed to investigate the effect of ZrO2 on the color, hardness, and surface roughness of IFP.Materials and Methods:Customized split-press metal molds were used for the fabrication of forty disk-shaped acrylics (10 mm × 1.5 mm). The salinized ZrO2 particles were weighed using an electronic balance and added in concentrations of 1wt %, 2.5wt %, and 5wt % of auto-polymerized acrylic polymer powder. Based on ZrO2 concentrations, specimens were divided into one control group without ZrO2 and three ZrO2 study groups 1 ZrO2, 2.5 ZrO2, and 5 ZrO2, respectively. A double beam ultraviolet-visible reflection spectrophotometer was the instrument used for recording the color measurements (CIEDE2000). The Microhardness and surface roughness (Ra, μm) of all samples were tested. ANOVA test was used for data analysis (α = 0.05)Results:Notable changes were seen between the group containing 1% and the other two groups in Δa*, ΔΕab, and ΔΕ00 parameters. Statistically significant differences were observed among the three groups for the ΔL* parameter. No notable changes were seen between the group containing 1% and the group containing 5% for the Δb* parameter. The 1% group showed a statistically significant difference in hardness in comparison to the 5% group. For surface roughness, the 2.5% group presented statistically significant higher surface roughness as opposed to the 0% control group.Conclusions:The addition of ZrO2 in high concentrations resulted in a noticeable color change in IFP. However, the surface properties did not change hardness and roughness with ZrO2 addition except roughness increased with 2.5% ZrO2. Low ZrO2 addition did not result in a change in color and surface properties of IFP.

In vitro assessment of polyetheretherketone for an attachment component for an implant-retained overdenture

Statement of problemFrequent maintenance because of the limited lifetime of overdenture attachments with O-rings has led to the development of materials that might improve their functionality and longevity. However, testing of newly developed attachment materials is lacking. PurposeThe purpose of this in vitro study was to evaluate a newly developed attachment made of polyetheretherketone (PEEK) for an implant-retained overdenture. Material and methodsSpecimens of PEEK, polyacetal, and Teflon O-ring materials were prepared for analysis of roughness, surface hardness, and compressive strength. For the fatigue resistance test, new specimens based on acrylic resin were subjected to 2880 insertion and removal cycles. Compression and roughness data were compared with the Kruskal-Wallis and Dunn post hoc test; hardness data with ANOVA and t test; and fatigue and stereomicroscopy with ANOVA with repeated measures, t test, and Bonferroni adjustment (α=.05). ResultsPolyacetal had the lowest surface roughness (P=.038). There was a significant difference in hardness among the materials (P<.05). PEEK presented the highest compressive strength among the materials (P<.001). For the fatigue resistance, only polyacetal showed a difference between the initial time-point (P<.05) and subsequent time-points. Polyacetal had a higher fatigue resistance than Teflon (P<.001) and PEEK (P<.05). Regarding the internal deformation of the attachments, a significant difference was observed among the materials (P<.05). ConclusionsPEEK showed promising results regarding the physicomechanical properties necessary for use as an overdenture attachment when compared with other evaluated materials. In addition, the PEEK attachment showed results comparable to those in the control group (O-rings) in terms of retention.

Palm oil substitution in hazelnut spread

AbstractOne of the most important components in spreads is the fat phase. The characteristics of the used fat determine most of the quality factors of the products such as viscosity, texture, colour, shelf life, etc. In these kinds of products, the commonly used fat is palm fat, however, in recent years it has had a bad press due to its negative environmental impact and health concerns. Therefore, the aim of our research was to develop a palm oil free hazelnut spread. We investigated the effect of replacing the fat in the fat phase with milk fat or coconut fat to the apparent viscosity, colour and texture properties of the product. According to our results the palm fat had the highest and coconut fat had the lowest viscosity. In texture analyses palm fat and milk fat showed no significant difference in hardness and in work of penetration. Coconut fat was significantly different in every texture attributes from the other samples. In the case of colour measurement all samples were significantly different. Despite the observed differences in some parameters the suitability of milk fat for hazelnut spread production should be further investigated (sensory analyses, shelf-life).

The Impact of Free Radical Stabilization Techniques on in vivo Mechanical Changes in Highly Cross-Linked Polyethylene Acetabular Liners

IntroductionNumerous thermal free radical stabilization techniques are used in the production of highly cross-linked polyethylene (HXLPE) to improve oxidative stability. Little knowledge exists on the effects of in vivo time on the mechanical properties of HXLPE. The purpose of this study was to determine if free radical stabilization of HXLPE impacts mechanical properties as well as oxidative stability of acetabular liner rims after extended in vivo time.MethodsRetrieved and control remelted, single annealed and sequentially annealed HXLPE liner rims were tested for mechanical properties. Oxidation was measured with FTIR spectroscopy and crystalline phase composition measured with Raman spectroscopy.ResultsNo correlation was found between in vivo, ex vivo time and hardness for annealed groups. A statistically significant difference in hardness was identified between free radical stabilization groups. No correlation between maximum rim oxidation and in vivo time was found. Detectable levels of rim oxidation were present in 100% of single annealed, 75% of sequentially annealed, and 25% of remelted retrieved liners. Single and sequentially annealed liners demonstrated oxidation and increased crystallinity. Rim mechanical properties change in vivo for implant types. With in vivo time, retrieved remelted HXLPE demonstrated decreased mechanical properties, whereas retrieved single and sequentially annealed HXLPE properties remained stable. All liner cohorts demonstrated evidence of rim oxidation. Subsequent changes in crystallinity were only observed in oxidized annealed liners.ConclusionHXLPE acetabular liner rims show evidence of in vivo mechanical property degradation, notably in remelted HXLPE, which may be a risk factor in rim fracture and catastrophic implant failure.