Changes In Hardness Research Articles

Effect of solution and artificial aging heat treatment on the hardness, friction and wear properties of laser cladding and roll-formed 18Ni300 materials

Abstract 18Ni300 is widely used in precision moulds, national defence, and other engineering fields due to its high strength and toughness, and because its properties can be greatly changed after heat treatment. In this research, the 18Ni300 cladding layer was fabricated on 18Ni300 substrate using the laser cladding method and a solid solution artificial aging treatment was carried out to analyse its macro morphology and metallographic organization. Comparison of hardness, friction, and wear of cladding layers manufactured by laser cladding and of materials produced by rolling was performed before and after heat treatment. The results show that the solution and artificial aging heat treatment has a significant effect on the microstructure of the cladding layer fabricated by laser cladding. There are obvious differences in the organization and morphology of different parts of the cladding layer before heat treatment; the metallographic organization and morphology of different parts of the cladding layer after heat treatment are the same. The trend of change of material hardness before and after heat treatment is the same in that the cladding layer is greater than the rolled material and the hardness of the material after heat treatment is much greater than the hardness of the material before heat treatment. The hardness and wear resistance of the material after solution and artificial aging heat treatment has been significantly improved, and the impact on the rolled production material of the melted cladding layer manufactured by laser cladding is even greater.

Effect of isometric quadriceps exercise on local microcirculation of the infrapatellar fat pad in female patients with knee osteoarthritis

ObjectiveTo elucidate the local microcirculation of the infrapatellar fat pad (IFP) in patients with knee osteoarthritis (KOA) by determining the changes in IFP hardness and hemoglobin concentration during isometric quadriceps exercise (IQE). DesignIn this observational cross-sectional study, patients diagnosed with bilateral KOA were included in the KOA group (30 knees), healthy older adults in the control group (20 knees), and younger adults in the young group (20 knees). Ultrasonography was performed at rest and during IQE to measure IFP hardness based on shear wave velocity. Near-infrared spectroscopy was performed to measure oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and total hemoglobin (cHb) in the IFP before (Baseline), during (IQE task), and after IQE (Post). IFP hardness and O2Hb, HHb, and cHb concentration were analyzed using a linear mixed model for the groups and measurement points. ResultsDuring IQE, IFP hardness changes were significantly less in the KOA group than in the other groups (KOA: 95% confidence intervals (CIs) [−0.854, 0.028]; control: 95% CI [−0.941, −0.341]; and young: 95% CI [−2.305, −1.706]). In the KOA group, O2Hb concentration exhibited no significant changes at Post compared with Baseline; however, significant changes were observed in the other groups (KOA: 95% CI [−1.176, 0.423]; control: 95% CI [−1.452, −0.276]; and young: 95% CI [−4.062, −2.102]). ConclusionsDuring IQE, changes in hardness and hemoglobin concentration in the IFP were not significant in the KOA group, suggesting impaired local microcirculation of the IFP.

Microstructure and mechanical properties of the laser welded air-hardening steel joint

The decrease in mechanical properties of high-strength steel after welding is an important issue affecting the wide application of high-strength steel. Air-hardening steel is a high-strength steel suitable for lower body structural parts such as subframes. Its application process involves welding, hot forming and other processes. The present work investigates the microstructure and mechanical properties of the air-hardening steel laser welded joint that is air-cooled after hot forming in the two-phase zone (800 °C). The microstructure was characterized by electron backscattered diffraction (EBSD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that during hot forming, the welded joint transforms from martensite to ferrite and acicular martensite, and the base metal transforms from ferrite to polygonal martensite and ferrite. The difference in martensite morphology between the welded joint and the base metal is attributed to the nucleation positions of austenite. The structural evolution of the welded joint and the base metal is accompanied with the annihilation and reproduction of dislocations, which results in significant changes in hardness. The hardness value dropped from the highest 430 HV to 271 HV in the welded joint, while increased from the lowest 184 HV to 203 HV in the base metal. After hot forming, the tensile strength of the welded sample is reduced by only 36 MPa, and the total elongation is slightly decreased by about 1.5% compared with the unwelded sample. The welded joint and the base metal have similar plastic deformation capabilities, since the acicular martensite in the welded joint displays good plastic deformation ability, and the dislocation density of the welded joint and the base metal is similar. Overall, the microstructure and dislocation density of the air-hardening steel welded joint after hot forming are similar to those of the base metal, which is responsible for the good mechanical properties of air-hardening steel welded joint.

Failure analysis and heat treatment process optimization of NOS525 rotary flat binaural hot forging die

A NOS525 steel rotary flat binaural hot forging die frequently failed too early due to collapse and wear in service. In this paper, the rotating planar binaural failure die was taken as the research object. Firstly, the sample design and sample processing of the failure die with different depths and directions were carried out. The material composition, hardness and metallographic structure of the samples were analyzed, and the tensile and impact properties were tested by direct-reading spectrometer, Rockwell hardness tester, optical microscope, scanning electron microscope, MTS testing machine and impact testing machine, etc. Meanwhile, with the help of Deform-HT software and JMatPro software, the coupling simulation of hardness, temperature and structure of the heat treatment of NOS525 steel was realized, and the hardness change of the material after heat treatment was predicted and verified by heat treatment test. The research results show that the composition of the die material is abnormal, especially the excessive P and C elements, at the same time, there is a phenomenon of quenching overheating and insufficient tempering, resulting in insufficient strength, toughness and hardness of the die material, in addition, the die surface is subjected to the cold and hot alternating load, and finally, the die surface collapses and wear too soon, resulting in its failure. Through the combination of heat treatment simulation optimization and test, the optimal heat treatment temperature of NOS525 steel was finally determined, that is, the quenching temperature of 1090℃, the first tempering temperature of 560℃, the second tempering temperature of 600℃, the third tempering temperature of 600℃, so that the mechanical properties of the material have been significantly improved.

Thermo-mechanical characteristics of spent coffee grounds reinforced bio-composites

Abstract This research examines the incorporation of spent coffee grounds (SCGs) into composite materials utilizing a three-part system composed of modified castor oil, polyester resin, and SCGs. The objective is to assess the mechanical, microstructural, and thermal characteristics of the resultant composites. The composite specimens underwent a thorough preparation and were tested through a battery of procedures comprising tensile testing, shore D hardness testing, SEM, FT-IR, and thermal conductivity measurements. Tensile testing revealed higher mechanical resilience, reinforcing the desirable properties of SCGs. The 5 % SCG-reinforced sample exhibited the highest tensile strength value, with a 41.85 % increase observed in comparison to the pure sample. The results of shore D hardness tests demonstrated that there was no significant change in material hardness up to 3 % additive content. However, a decrease in hardness was observed at higher additive rates. At a 7 % additive rate, there was a 2.82 % decrease in material hardness. Furthermore, the application of scanning electron microscopy (SEM) analysis has revealed the microstructural features of the composite matrix, which have highlighted the distribution of SCGs within it. The successful implementation of SCGs has also been verified by means of Fourier transform infrared (FT-IR) analysis. Finally, based on thermal conductivity measurements, it has been determined that SCGs are suitable for thermal insulation purposes. This study represents a significant contribution to the field of sustainable materials science, emphasising the potential benefits of SCGs in improving the effectiveness of composite materials.

Effect of Bleaching Agents on Composite Resins with and without Bis-GMA: An In Vitro Study.

The objective was to evaluate the change in color, hardness, and roughness produced by carbamide peroxide (CP) at two different concentrations on two resins. The 16% or 45% CP was applied to 66 resin discs with and without Bis-GMA. The color was measured with a spectrophotometer, and ΔEab and ΔE00 were calculated. Microhardness tester and SEM were used. In both composites, the a* and b* coordinates tended to be red and yellow, respectively, and were significant in the Bis-GMA group (p < 0.05). The ΔEab and ΔE00 were higher in the composite with Bis-GMA, regardless of the treatment received (p < 0.05). The microhardness was reduced in both composites regardless of the PC concentration compared to the control (p < 0.05). The 45% CP reduced the microhardness in the resin group with Bis-GMA compared to 16% CP (p < 0.001) but was not significant in the resin without Bis-GMA (p = 1). An increase in roughness was directly proportional to the concentration of CP, and it was more notable in the composite without Bis-GMA. The composite with Bis-GMA showed a greater tendency to darken than the one without Bis-GMA. The surface hardness of the composite was reduced in both composites and was not influenced by CP concentration in the composite without Bis-GMA. Bleaching is a common procedure nowadays. It is important to know how CP affects composites to establish a prognosis of the treatments in terms of color change, roughness, and hardness.

Enhancement of mineral density and mechanical properties in root caries treated with silver diammine fluoride and glass ionomer cement, with emphasis on silver ion distribution

ObjectivesThis study aimed to measure the distribution of silver ion (Ag+), mineral recovery, and nanohardness in carious lesions and comprehensively evaluate the degree of dentin restoration. MethodsSixty human teeth with root caries were randomly assigned to the control, silver diammine fluoride (SDF) [Safo], and SDF+Glass ionomer cement (GIC) treatment [Safo+Fuji] groups. Micro-computed tomography (micro-CT) was performed at five time points for each sample before/after treatment to evaluate mineral density within and around carious lesions. Three months following treatment, 12 samples were selected for synchrotron radiation X-ray fluorescence analysis to evaluate Ag+ distribution, while 15 samples were selected for nanoindentation. Data were analyzed using Dunnett's T3 test for micro-CT and Wilcoxon rank sum test with Bonferroni correction (p = 0.017) for nanoindentation. The correlation between hardness and mineral change was analyzed using the Spearman rank correlation coefficient. ResultsThe Safo and Safo+Fuji groups showed significantly higher mineral recovery rates than did the control group (p < 0.001). In the Safo group, Ag+ accumulated in the deeper layers rather than the superficial layer of caries. In the Safo+Fuji group, Ag+ was found evenly distributed throughout caries, with only a few Ag+ detected in the GIC layer. Hardness in the Safo+Fuji group was significantly higher compared with the Safo group at depths in the range of 10–50 µm. ConclusionIn the presence of GICs, SDF exhibited high remineralization capacity when diffusing throughout carious lesions over time. Combined treatment with SDF and GIC could strengthen root dentin even in the presence of caries. Clinical significanceWe found that combination treatment with SDF and GIC could increase mineral density in caries and improve the hardness of the tooth structure compared with fluoride-based agents alone. These findings might pave the way for future clinical trials to determine the therapeutic potential of nanotechnology-based restorative materials.

Radiographic evaluation of hard tissue changes in open flap technique versus flapless technique for implant placement

Open flap technique allows the clinician to directly visualize the alveolar bone and assess bone morphology of the ridge.However, this technique is relatively invasive and causes patient discomfort and marginal bone loss due to decreased supraperiosteal blood supply whereas the Flapless technique is one of the latest minimally invasive surgical methods of implant placement without the need to raise a mucoperiosteal flap to overcome the bone resorption process. The present study was designed to evaluate the hard tissue changes in open flap technique versus flapless ṭechnique for implant placement at the different time interval. Minimum thirty edentulous sites from Out Patient Department, Department of Periodontology (IDST) were randomly allocated to the following two groups by the flip of coin: Group I - Implant with open flap technique (fifteen sites) and Group II - Implant with flapless technique (fifteen sites). Patients were evaluated radiographically for crestal bone loss (mesial and distal) at Baseline (Immediately after implant placement), At the time of prosthetic loading and 3 months after prosthetic loading in both the groups. The result of the present study revealed that Sites where implants were placed with flapless technique showed lesser mean crestal bone loss scores as compared to sites where implants were placed with open flap technique, although the difference was insignificant. It can be concluded that flapless procedure may be considered as a better treatment option as compared to implant placed with open flap technique in terms of minimal pain, inflammation and less crestal bone loss associated with flapless technique than open flap technique.

Quality of Life (QoL) changes after orthognathic surgery: Do they correlate with the quantum of hard and soft tissue change?

Aim: To investigate the relationship between post orthognathic surgery changes in soft and hard tissue cephalometric variables in Class II and Class III patients and quality of life (QoL) measured using a condition-specific QoL questionnaire and to determine cephalometric predictors of the overall OQLQ after surgery. Methods: The sample included 50 orthodontic patients, 28 Class II and 22 Class III skeletal relationships whose treatment included orthognathic surgery. Correlations between cephalometric changes and Orthognathic Quality of Life Questionnaire (OQLQ) were tested by Pearson’s correlation. Multiple linear regression was used to determine cephalometric predictors of the overall OQLQ after surgery. Results: In Class II patients, OQLQ before surgery and changes in SNA were significant predictors for OQLQ after surgery. For Class III patients, OQLQ after surgery was significantly correlated with the change in mandibular plane angle and lower face height (r = 0.6 and r = 0.5 respectively). The decrease in facial angle was negatively correlated with OQLQ (r = -0.4). Mandibular plane angle, mandibular length, and OQLQ before surgery were significant predictors for OQLQ after surgery. Conclusion: QoL improved for Class II and III after orthognathic surgery. Changes in certain cephalometric measurements seem to predict quality of life after orthognathic surgery.

Hardness Distribution and Growth Behavior of Micro-Arc Oxide Ceramic Film with Positive and Negative Pulse Coordination.

Micro-arc oxidation (MAO) is a promising technology for enhancing the wear resistance of engine cylinders by growing a high hardness alumina ceramic film on the surface of light aluminum engine cylinders. However, the positive and negative pulse coordination, voltage characteristic signal, hardness distribution characteristics of the ceramic film, and their internal mechanism during the growth process are still unclear. This paper investigates the synergistic effect mechanism of cathodic and anodic current on the growth behaviour of alumina, dynamic voltage signal, and hardness distribution of micro-arc oxidation film. Ceramic film samples were fabricated under various conditions, including current densities of 10, 12, 14, and 16 A/dm2, and current density ratios of cathode and anode of 1.1, 1.2, and 1.3, respectively. Based on the observed characteristics of the process voltage curve and the spark signal changes, the growth of the ceramic film can be divided into five stages. The influence of positive and negative current density parameters on the segmented growth process of the ceramic film is mainly reflected in the transition time, voltage variation rate, and the voltage value of different growth stages. Enhancing the cathode pulse effect or increasing the current density level can effectively shorten the transition time and accelerate the voltage drop rate. The microhardness of the ceramic film cross-section presents a discontinuous soft-hard-soft regional distribution. Multiple thermal cycles lead to a gradient differentiation of the Al2O3 crystal phase transition ratio along the thickness direction of the layer. The layer grown on the outer surface of the initial substrate exhibits the highest hardness, with a small gradient change in hardness, forming a high hardness zone approximately 20-30 μm wide. This high hardness zone extends to both sides, with hardness decreasing rapidly.

Effect of microalloying with rare-earth lanthanum on dynamic recrystallization behavior and mechanical properties of Ti sheets

This study examines the influence of microalloying with rare earth lanthanum (La) on the dynamic recrystallization behavior and mechanical properties of Titanium (Ti) sheets. A distinctive wedge-shaped specimen was employed for experimental efficiency, enabling continuous gradient strains to be applied to the Ti-La alloy during hot-rolling, facilitating the assessment of changing microstructural, textural, and hardness features as strain increased from low to high levels. The hot-rolled plates were performed using analytical methods such as optical microscopy (OM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and hardness testing. The results show that the hardening process can be divided into four stages under continuous gradient strain (0 ∼ 0.5, 0.5 ∼ 0.7, 0.7 ∼ 1.2 and 1.2 ∼ 1.6). During these stages, grain refinement and dislocation strengthening emerge as critical contributors to changes in hardness. Furthermore, it was determined that dynamic recrystallisation (DRX) of Ti-La alloys during hot rolling occurs at the fourth stage. Analysis of the orientation distribution function (ODF) reveals that the dominant textures during this process include {1̅21̅0}, {011̅0}, and {0001} textures. When compared with commercially pure titanium (CP-Ti), the Ti-La alloy shows significantly delayed DRX under identical conditions. The DRX grain growth appears suppressed, attributable to the presence of La-rich particles on the grain boundaries. Moreover, the texture associated with rolling deformation seems subdued, providing a desirable base for future cold rolling and heat treatment.

Experimental measurement and molecular dynamics simulation analysis of thermal aging performance in composite solid propellants

As a complex mixed system, the aging mechanism of high-energy composite materials involves the aging of each component itself, interactions between components, and transformation of microstructural and thermodynamic properties. The study of a single component or performance parameter has great limitations for elaborating the cognitive complexity of aging processes, making it difficult to reveal the underlying principles of physicochemical property transformation. Thus, it can only be applied as an empirical summary. In view of this, this study comprehensively utilized numerical analysis and experimental detection to explore the evolution of micromolecular conformation and changes in macro aging performance from four aspects of composite systems, including binder aging, plasticizer migration, bond interface debonding, and mechanical property transformation. There was good consistency observed between molecular simulation and thermal aging experiments, indicating that there was basically no post curing process for HTPB propellants using TDI as the curing agent. In the early stage of aging, scission chain was the main process and, in the later stage of aging, oxidation crosslinking the main process. Oxidative crosslinking increased the mean square radius of gyration and glass transition temperature of the binder system, reduced the peak value of radial distribution function, and revealed the reason for the change of propellant hardness and CC and CO double bond content. However, chain degradation increased the number of polar groups, enhanced intermolecular polarity, reduced the solubility parameter, and increased the free volume fraction of the mixed system and the dioctyl sebacate diffusion coefficient. This resulted in an increase in the tangent value of the HTPB propellant loss angle from 0.43 to 0.44° and a decrease in the glass transition temperature from 203.3 to 202.0 K. The binding energy at the interfaces of AP/HTPB and Al/HTPB increased first and then decreased, which was consistent with SEM images of bonding interfaces. The joint effect of binding energy and mechanical properties of the binder system promoted the transformation of the stress-strain curve of aging propellant.

Toughness enhancement in TiN/Zr0.37Al0.63N1.09 multilayer films

The hardness and fracture toughness of high-temperature wear-resistant transition metal aluminum nitride multilayer films depend largely on the constituting layer's structure, compositional modulation, morphology, and interface coherency. We present a study on 1-micron thick multilayered films consisting of stacked layers of TiN and Zr0.37Al0.63N1.09, each layer being 10 nm thick. The films were grown using ion-assisted reactive magnetron sputtering on MgO(001) and Si(001) at substrate temperatures ranging from ambient to 900°C. By increasing growth temperature, we found that the ZrAlN layers transition from near amorphous to nanocrystalline wurtzite to decomposed c-ZrN and w-AlN domains. Concurrently, the TiN layers exhibit strong fiber texture, polycrystallinity, and epitaxial growth carried by the ZrN domains. Both hardness and fracture stress, evaluated by nanoindentation and micromechanical tests, increase with temperature from H=24 GPaMgO, 23 GPaSi to 36 GPaMgO, 30 GPaSi, and σFSi= 6.1-7.7 GPa, respectively. An improved fracture toughness of KIC=2.4-2.8 MPa√m is related to different toughening mechanisms for the various microstructures. The difference in hardness between the substrates is related to compressive stress due to the deposition conditions and thermal contraction. The superior fracture stress is attributed to dense multilayers, free from macroscopic defects due to ion-assisted growth. After being deposited at 200°C, the multilayers remained thermally stable when vacuum annealed for 15 hours at 900°C, with no significant change in phase composition or hardness. The improved hardness, toughness, and temperature stability of the otherwise brittle nitrides are promising for industrial applications.

Three-dimensional quantification of soft tissue changes and its relationship to skeletal changes after Le Fort III, monobloc, and facial bipartition in syndromic craniosynostosis

To determine the effect of midface surgery on soft tissue changes and their relationship to hard tissue changes in patients with syndromic craniosynostosis. A retrospective analysis of patients who had undergone Le Fort III (LFIII), monobloc (MB), or facial bipartition (FB) was conducted. A 3D soft tissue mesh was generated from the preoperative scan and registered to the postoperative scan, after which the advancement was visualised. A total of 68 patients were included: 28 had undergone LFIII, 27 MB, and 13 FB. The included diagnoses were Apert (n = 23), Crouzon (n = 34), and craniofrontonasal syndrome (n = 11). After LFIII, most soft tissue advancement was seen around subnasale and pronasale (mean 15.1 ± 5.9 mm and 14.7 ± 5.7 mm, at age 7–12 years). After MB, a greater hard tissue than soft tissue advancement was seen for most landmarks, showing a high positive correlation. In patients undergoing FB without distraction (n = 10), mean preoperative inter-canthal distance was 48.9 mm, this reduced by 6.9 mm postoperatively. This study provides a comprehensive overview of the outcomes after midface surgery using 3D quantification for a better understanding of the soft tissue changes and their relationship to hard tissue changes.

Study on temperature and hardness behaviors of Al-6060 alloy during magnetic abrasive finishing process using artificial neural networks

Magnetic Abrasive Finishing (MAF) revolutionizes surface finishing by utilizing magnetic fields to apply pressure, ensuring exceptionally high-quality surfaces. Its potential for ultra-precise finishing with fine magnetic abrasives is particularly noteworthy. This study analyzes subsurface temperature dynamics during the MAF process on Al-6060, recognizing temperature's pivotal role in shaping surface texture and mechanical-chemical properties. Unbonded magnetic abrasives containing SiC were used without lubrication or coolants in experimentation. Experimental parameters, including machining gap, abrasive weight, voltage, and rotational speed, were systematically varied using a Box-Behnken Design of Experiments. An artificial neural network facilitated comprehensive data modelling, enabling a detailed parametric study. Post-processing surface characterization provided crucial insights into the impact of surface temperature rise on surface finish and hardness. This holistic approach enhances understanding of temperature's influence on MAF efficacy and its outcomes on Al-6060 surfaces. Experimental findings demonstrate MAF's effectiveness in achieving low-temperature finishing of Al-6060, with a maximum surface temperature of 36 °C. ANOVA analysis quantitatively determined that voltage has greatest influence (55.56%), followed by abrasive weight (20.00%) and machining gap (13.89%), with rotational speed having the least impact (2.22%). Qualitatively, the developed ANN model accurately predicted changes in surface roughness (ΔRa), temperature (ΔT), and hardness (ΔH), with maximum errors of 4.107%, 5.588%, and 6.680%, respectively. XRD analysis provided quantitative evidence of SiC diffusion into the surface, resulting in a hardness increase from 2.7 HV to 5.6 HV. Additionally, chemical substrates deposition, such as silicon carbide, kaolinite, iron silicide, and cristobalite, elucidated chemical-mechanical interactions during the process at such low temperatures.

Immediate Implant Placement in the Aesthetic Area using Inverted Body-shift Design: A Prospective Clinical Pilot Study.

A prospective clinical pilot study was carried out to evaluate a novel macroimplant design with a 12° angled platform. The implant is placed at the center of the socket, optimizing all the alveolar bone. In addition, the prosthetic emergence should be ideal, as it is corrected and emerges through the cingulate area. Twelve patients were enrolled in an immediate implant placement procedure with immediate aesthetic rehabilitation to replace an anterior maxillary tooth, and were treated with inverted body-shift design with 12° angled neck. Only type I sockets according to the Elian classification were considered eligible for the study. There were no implant failures after one year of loading. Regarding the horizontal and vertical hard tissue changes, there was a statistically significant median overall horizontal change of -0.99 mm at 1 mm and of -0.61 mm at 3 mm. On the other hand, stability was observed at 5 mm, since the result obtained was not statistically significant. The median pink esthetic score (PES) at one year of follow-up was 11.5. This implant may be useful in the immediate tooth replacement treatment of maxillary anterior post-extraction sockets, nevertheless, comparative studies with conventional implants should be carried out.

Investigation of microhardness, surface roughness, and color change of preheated composite resins

Aim: Applying heat is a method currently used to enhance the depth of polymerization in composite resin. This study aimed to evaluate the effects of heat treatment on resin hardness, color change, and surface roughness. Methodology: In this study, 64 samples (8 mm2 × 2 mm2) were produced (3M Filtek Universal, G-aenial A’CHORD, Neo Spectra and Clearfil Majesty ES-2) using a Teflon mold (n = 8). Half of the samples were preheated to 50oC, while the other half were polymerized at room temperature. Initial color measurements were performed using a spectrophotometer, the surface roughness was assessed with a profilometer, and the microhardness was determined using a Vickers microhardness device. Subsequently, all samples were immersed in a coffee solution at 37oC. The color changes were documented by the seventh day. The changes in color, roughness, and hardness of the materials were examined by the thirtieth day. Results: The groups that received heat treatment exhibited higher hardness values. The unheated G-aenial A’CHORD composite resin demonstrated the most significant color change by the end of the thirtieth day, while heated and unheated Clearfil Majesty ES-2 composite samples exhibited the least color change. By the end of the thirtieth day, the surface roughness of all samples increased significantly from the baseline, with the 3M Filtek Universal samples, both heated and unheated, showing the highest surface roughness. Conclusion: According to the results of this study, heat treatment of composite resins before polymerization reduces discoloration and improves hardness. Therefore, it is recommended to heat composite resins before application. How to cite this article: Çekmez MB, Karaoğlanoğlu S, Aybala Oktay E, Aydın N, Ersöz B. Investigation of microhardness, surface roughness, and color change of preheated composite resins. Int Dent Res 2024;14(1):42-49. https://doi.org/10.5577/intdentres.523

Texture Analysis of Hard Tissue Changes after Sinus Lift Surgery with Allograft and Xenograft

In the realm of dental surgery, implants are essential for replacing missing teeth. To facilitate implant placement, techniques such as bone grafting and sinus lifts are utilized to augment the volume of atrophied alveolar bone in candidates for dental implants. Typically, patients undergo a period of recovery following bone grafts before proceeding with implant placement. This study investigates the efficacy of Cone Beam Computed Tomography (CBCT) in measuring the residual bone volume and assessing bone quality after the healing phase. A texture analysis was conducted on CBCT scans from 42 patients requiring maxillary sinus lift reconstruction. These patients were categorized into two groups based on the type of grafting material used: Xenograft or allograft. The study analyzed the distribution of various texture parameters and conducted a Mann-Whitney U test to identify significant statistical differences between the groups. Results indicated non-normal distributions for specific variables such as Area_S(1,0) and S(1,0)SumOfSqs, while others like S(1,0)Entropy displayed normal distributions. The findings revealed no significant statistical differences in the primary outcomes between the xenograft and allograft groups. However, the average values of the gray shades of pixels in the allograft group were statistically significantly higher compared to the xenograft group, suggesting differences in bone texture post-procedure.

The wash zone and habitat use among three benthic fish species in stratified lakes

AbstractMixing processes in lakes are important in determining sedimentation zones and in setting the so‐called “wash zone”, the area of lake bottom in contact with an oscillating thermocline during wind‐driven internal seiche events. The wash zone also aligns with a sharp change in sediment roughness and hardness. Taken together, these rapid changes in temperature and sediment indicate that the wash zone is a distinctive ecotone in stratified lakes. Depth stratified randomised netting was used to develop count‐based habitat use models for three common benthic fish species as a function of depth or temperature covariates. Using data from two lakes with quite different wash zone depths, we show the wash zone to describe fish habitat for two of three benthic fish species by utilising the top 50% of estimated fish abundance as an indicator of habitat use. White sucker (Catostomus commersoni) habitat use was within the boundaries of the wash zone. Lake whitefish (Coregonus clupeaformis) habitat was adjacent and within the wash zone. Longnose sucker (C. catostomus) habitat use was in the deep areas of lakes dominated by sediment focusing and did not overlap white sucker. Lake whitefish habitat use overlapped both catostomids, but peak abundance of both lake whitefish and white sucker overlapped pointing to potential interactions between these species. Smaller lakes have less vigorous mixing processes and a narrower wash zone, so with a decline in lake size the likely area of the wash zone as habitat for benthic feeding fish would become smaller.

Changes in Muscle Hardness Induced by Exercise Load and the Influence of Electroacupuncture

Changes in Muscle Hardness Induced by Exercise Load and the Influence of Electroacupuncture