The grain boundary character distribution of an equiatomic CoCrFeMnNi high-entropy alloy (HEA) was statistically determined using electron backscatter diffraction. The face-centered cubic (fcc) HEA exhibits an exceptionally high fraction of the E3 coherent twin boundary, constituting 94% of the total E3 grain boundary (GB) population, which is nearly double the levels observed in Cu (51%) and Ni (61%). This reflects an increased thermodynamic preference for the lowest-energy state, driven by suppressed GB energy anisotropy and a deeper relative energy minimum at the coherent twin configuration compared to fcc elemental metals (Au, Cu, and Ni). Beyond E3 misorientation, high-entropy effects from configurational entropy and local lattice distortion further stabilize {111} symmetrical twist configurations, leading to significant population enrichment across multiple misorientations, including E7, E13b, and E21a. Ultimately, these findings reinforce the high-entropy grain boundaries (HEGBs) framework, providing a foundation for next-generation multifunctional high-entropy materials.

Objectives: This study aimed to compare the effects of alkali-heat treatment on the surface characteristics of titanium dental implants (Ti-6Al-4V) produced by two different fabrication methods—subtractive machining and additive manufacturing using laser powder bed fusion (LPBF)—with both horizontal and vertical build orientations. Methods: Disc-shaped Ti-6Al-4V specimens were prepared using machining and LPBF techniques. All samples underwent alkali treatment with 10 M NaOH at 90°C for 24 hours, followed by heat treatment at 600 °C. Surface morphology, elemental composition, crystalline structure, roughness, and wettability were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), laser confocal scanning microscopy, and contact angle goniometry. Data were expressed as mean ± SD, with significance set at p < 0.05. Results: Alkali-heat treatment generated nanostructures—such as nanospikes and micro-crevices—on all surfaces. EDS and XRD confirmed the formation of a sodium titanate layer, evidenced by increased oxygen and sodium content and a new diffraction peak at 48.3°. LPBF specimens exhibited greater roughness than machined ones (p < 0.001), and vertically printed LPBF samples were rougher than horizontally printed ones (p < 0.05). However, the treatment did not significantly change the baseline roughness (p > 0.1). Untreated surfaces were hydrophobic (contact angle > 90°), while treated machined samples became highly hydrophilic (10.13° ± 2.78, p < 0.0001), and treated LPBF specimens achieved complete wetting (0°). Conclusions: Alkali-heat treatment successfully induced nanostructural modifications and sodium titanate layer formation on Ti-6Al-4V implants, greatly enhancing surface hydrophilicity without altering roughness. The additive manufacturing method and build orientation significantly influenced surface topography. These results suggest that combining LPBF fabrication with alkali-heat treatment could optimize implant surface bioactivity for improved osseointegration.

Background/purpose:Biodegradable magnesium (Mg)-based alloys are emerging as promising alternatives to non-resorbable titanium for bone regeneration because of their favorable mechanical properties and biodegradability. However, the interaction between Mg alloys and immunomodulatory agents in promoting osteogenesis remains poorly understood. This study aimed to evaluate the osteogenic effects of an Mg alloy on pre-osteoblasts and to investigate whether erythromycin enhances Mg-induced osteogenic differentiation through regulation of developmental endothelial locus-1 (DEL-1). Materials and methods:WE43 Mg alloy disks were immersed in culture medium to produce Mg alloy-conditioned medium at concentrations of 25%, 50%, 75%, and 100%. MC3T3-E1 cells were treated with conditioned medium alone or combined with erythromycin (20 μg/mL). Cell viability was assessed using the MTT assay. Osteogenic differentiation was evaluated by Alizarin Red S staining (ARS), quantitative PCR analysis of osteogenic markers (Runx2, Sp7, Bglap, Edil3), and Western blot analysis of DEL-1 expression. Results:WE43 Mg alloy showed no cytotoxic effects on MC3T3-E1 cells. Treatment with Mg alloy-conditioned medium significantly enhanced osteogenic differentiation and extracellular matrix mineralization. The strongest osteogenic response was observed in cells receiving combined WE43 Mg alloy and erythromycin treatment. DEL-1 expression was significantly upregulated at both mRNA and protein levels in Mg alloy-treated groups, accompanied by increased expression of osteogenic markers. These effects were further amplified by erythromycin supplementation. Conclusion:WE43 Mg alloy promotes osteogenic differentiation of MC3T3-E1 cells, and erythromycin synergistically enhances this effect, potentially via DEL-1 upregulation. These findings support the combined use of immunomodulatory agents and Mg-based biomaterials in regenerative dentistry.

BACKGROUND:3D-printed patient-specific pedicle screw guides (3DPSG) may provide accuracy comparable to intraoperative CT navigation (CTNav). Our 3DPSG workflow incorporates a virtual surgical planning (VSP) platform that uses deep-learning algorithms to automatically generate pedicle trajectories from CT data. RESEARCH DESIGN AND METHODS:This is a retrospective, single surgeon, single center comparative study of 21 patients undergoing thoracolumbar instrumentation via CTNav (11 patients, 71 screws) and 3DPSG (10 patients, 65 screws). The accuracy was assessed postoperatively using Gertzbein-Robbins and Heary classification systems. RESULTS:There were eight men and thirteen women. Gender, BMI, and diagnosis did not differ significantly between the CTNav and 3DPSG groups (p > 0.05). Accuracy was high in both cohorts. By Gertzbein-Robbins, safe placement (grades 0-1) was 97.1% (69/71) with CTNav and 100% (65/65) with 3DPSG. On the Heary system, safe placement (grades 1-2) was 98.6% (70/71) and 100% (65/65), respectively. Malpositions occurred only in the CTNav group (Gertzbein grade 2: 2/71, 2.8%; Heary grade 3: 1/71, 1.4%). Overall accuracy did not differ significantly between groups (Fisher's exact test, p > 0.05). CONCLUSIONS:3DPSG integrated with VSP platform may be a viable alternative navigation system in middle-income settings where intraoperative CTNav is unaffordable.

Laser powder-bed fusion (LPBF) presents a promising alternative to fabricate metal matrix composites (MMCs). However, the melt behavior in MMCs, particularly those reinforced with ceramics, remains poorly understood. This study introduces a high-fidelity, powder-resolved simulation framework for LPBF of titanium carbide (TiC)-reinforced Inconel 718 (IN718), combining discrete element method and finite volume method to model powder spreading and laser-material interactions at the microscale. The simulation captures key melt pool phenomena and is validated using single-track experiments. Results reveal a nonlinear response in melt pool depth with increasing TiC content, with a 17 % decrease at 1 wt% TiC followed by a 26 % increase at 5 wt%. This result is attributed to competing effects of thermal diffusivity and laser absorptivity. In addition, while cooling rates vary with reinforcement contents, the dominant columnar grain growth mode remains unaffected. Furthermore, the predicted melt pool morphology correlates closely with experimental surface roughness (Ra) measurements, showing a significant reduction of similar to 60 % in Ra from 9.3 to 3.8 mu m at 5 wt% TiC. These findings deepen the understanding of MMC behavior in LPBF and demonstrate the predictive capability of powder-scale simulation framework for LPBF process optimization.

This study investigates the mechanical and microstructural characteristics of customized Ti6Al4V dental abutments fabricated using a hybrid laser powder bed fusion (LPBF) process combined with a machined titanium preform. Customized anterior and posterior abutments were designed and produced. Internal defects were evaluated using high-resolution X-ray micro-computed tomography (micro-CT), while microstructural analysis employed scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Hardness distributions were measured across the LPBF region, heat-affected zone (HAZ), and preform substrate. Micro-CT revealed low porosity levels in both geometries, with void fractions of 0.045% in anterior and 0.019% in posterior abutments, and mean pore diameters of 23.2 mu m and 25.8 mu m, respectively. SEM confirmed a continuous metallurgical bond at the preform interface without visible cracking or delamination, while EBSD identified three distinct zones, which are fine acicular alpha ' martensite in the LPBF region, transitional HAZ, and equiaxed alpha+beta grains in the preform substrate. EPMA mapping indicated vanadium heterogeneity within the preform substrate and a more homogenized vanadium distribution in the fusion zone. Microhardness testing showed gradient values from 415 HV in the LPBF zone to 360 HV in the preform, with the HAZ averaging approximately 370 HV. The present findings reveal a strong metallurgical bond between the preform substrate and the LPBF region, demonstrating the potential use of the LPBF process for personalized implant abutments.

Mandibular reconstruction involving the temporomandibular joint (TMJ) presents clinical challenges due to the need for both structural integrity and joint function. This study developed and biomechanically evaluated patient-specific mandibular reconstruction plates integrated with TMJ prostheses, focusing on mesh-based designs as an alternative to the conventional solid plate. The samples studied in this work included the conventional plate (CON-plate) and the mesh-based variants with relative densities (RD) from 0.2 to 1.0, fabricated using metal additive manufacturing. Finite element analysis (FEA) was validated with experimental compression tests, showing strong agreement in resulting stiffness, where both results differed by <7%. Under simulated masticatory loading, mesh-based plates demonstrated more uniform stress distribution, reducing peak stresses in both plates and screws by approximately 60%. In addition, an effective stress parameter was introduced to indicate mechanical efficiency relative to mass, demonstrating that the mesh-based plates achieve an improved stress-mass trade-off than the conventional design. Additionally, tribological testing showed that post-processing of Ti-6Al-4 V pins reduced UHMWPE wear rate from 1.44 & times; 10(-4) mm(3)/Nm to 1.21 & times; 10(-4) mm(3)/Nm, highlighting the importance of surface finish. Integration of mesh-based plates also lowered von Mises stress and contact pressure in UHMWPE fossa components, indicating reduced wear potential. Overall, the mesh-based reconstruction plates present a promising strategy to enhance load transfer, minimize implant wear, and improve long-term outcomes for both mandibular reconstruction and TMJ prosthesis.

Laser power is referred to as one of the critical process parameters governing the volumetric energy density in the Laser Powder Bed Fusion (L-PBF) process. The purpose of the study is to systematically investigate the influence of laser energy density on the void morphology, microstructure, and mechanical properties of the L-PBF printed parts which were fabricated with laser power ranging from 75 to 175 W. Comprehensive analysis of void defect was conducted by employing Archimedes' method, optical microscope (OM), and X-ray microcomputed tomography (Micro-CT). Surface quality was analyzed by surface roughness measurement. Tensile testing was performed to establish the correlation between process parameters, material microstructure, and mechanical behavior in as-built samples. Under the optimal process parameters, this work achieved a minimum void fraction of 0.3%. At various laser energy densities, three distinct morphologies, namely lack of fusion (LOF), gas pores (GP), and keyhole (KH), were generated. Notably, LOF has a more detrimental effect on tensile characteristics, in comparison to GP and KH defects if laser power was less than 100 W. Interestingly, subsurface spherical pores at the hatch border demonstrate a less substantial influence on the tensile behavior of as-built samples than LOF. The correlation analysis revealed that the presence of void defects primarily influenced strength, modulus of elasticity, and strain at break. Energy density proved to play a pivotal role in defect generation, non-equilibrium microstructure, and mechanical properties of L-PBF. Based on our findings, selecting 100 W of laser power with a speed of 1200 mm/sec could be an optimal choice for achieving a satisfactory result in as-built L-PBF part.

This work explores the potential of using additively manufactured components as replacement parts in repair procedures, with particular emphasis on their integration through welding techniques. The focus is on understanding how these additively manufactured components can be effectively welded into existing structures, ensuring their durability and performance in repair applications. A 316L stainless steel plate produced by additive manufacturing using bound metal deposition was joined to a conventionally rolled plate using the fluxcored arc welding technique to create square groove weld butt joints. An analysis was conducted on the microstructure and mechanical properties of the weldment. The finding indicates that complete joint penetration was achieved in welds without significant welding defects. Microhardness measurements showed values of 132 HV in the additive manufactured base metal and up to 170 HV in the fusion zone. The transverse tensile test results showed that the tensile strength of the welded plates varied between 490 and 547 MPa with an elongation of 26 %, indicating ductile fractures in the weld metal. This demonstrates that additively manufactured parts can be successfully welded to conventionally rolled plates, highlighting their good weldability and supporting their feasibility for repair or replacement through welding.

Precise thermal control is critical for safe and effective laser-based skin treatments. Existing studies often overlook the limitations of conventional heat transfer models, particularly when applied to repetitive pulsed laser exposure. This study addresses this gap by comparing the Bioheat and Dual-Phase Lag (DPL) models for predicting thermo-mechanical responses in multi-layered human skin. A validated one-dimensional computational framework was developed, incorporating light propagation, non-Fourier heat transfer, thermal damage via the Arrhenius model, and tissue deformation analysis. The model was rigorously validated against published data, demonstrating strong agreement with measured temperature profiles. Results indicate that repetitive pulsed laser irradiation generates sharper temperature gradients and higher transient thermal stress than continuous exposure, with the Bioheat model consistently overestimating surface temperatures (60.12 °C vs. 50.53 °C) and thermal damage, exceeding DPL predictions by up to three orders of magnitude. Likewise, Bioheat-based deformation and dermal stress were ∼0.4 mm (140%) and ∼0.29 MPa (126%) higher, respectively. These findings confirm that heat transfer assumptions critically influence temperature, damage, and mechanical predictions in laser-tissue interactions. Incorporating realistic models such as DPL is essential for optimizing laser protocols, improving treatment safety, and enhancing clinical outcomes in dermatology and biomedical applications.

This study numerically investigates laser-induced photo-thermo-mechanical interactions in multilayered human skin. A two-dimensional axisymmetric finite element model was developed, coupling three light transport models comparing Beer-Lambert (BLM), Modified Beer-Lambert (MBLM), and Light Diffusion (LDM)-with a Dual-Phase-Lag (DPL) bioheat framework to evaluate responses to pulsed irradiation from 500 to 1600 nm. Simulation results demonstrate that model selection and wavelength critically influence thermal and mechanical outcomes. At 1500 nm, the absorption-only BLM predicted surface temperatures exceeding 140 degrees C, whereas the MBLM and LDM, which incorporate scattering, limited this rise to 70-80 degrees C and 60-70 degrees C, respectively. Similarly, the BLM produced von Mises stresses up to 799 kPa and surface displacements over 42 mu m, values that were reduced by 40-50 % in scattering-inclusive models. Thermal phase lag effects further reduced peak temperatures by 15-20 %, and both scattering and thermal lag notably mitigated necrotic tissue formation. These results highlight the critical importance of selecting appropriate optical models that account for scattering and finite-speed heat conduction for accurate predictive simulations in laser medicine.

This study investigates the mechanical and thermal responses of stochastic Triply Periodic Minimal Surface (TPMS) structures fabricated using the laser powder bed fusion process with Ti-6Al-4V. Stochastic Gyroid structures were generated by introducing Voronoi-based randomness, allowing for controlled variations in stochasticity. Mechanical behavior was evaluated through finite element (FE) simulations with damage modeling and compressive testing, while thermal performance was analyzed using steady-state finite element modeling with periodic boundary conditions. Experimental and FE results demonstrated that increasing stochasticity alters failure mechanisms by dispersing deformation across sub-domains, reducing macroscopic shear band formation. Among stochastic structures, greater randomness from 5 to 50 random points led to an increase in elastic modulus, initial peak stress, and energy absorption by 38 %, 27 %, and 54 %, respectively. Additionally, while uniform TPMS structures exhibited higher effective thermal conductivity, aligning with the upper limit of Maxwell-Eucken's models, stochasticity reduced effective thermal conductivity by approximately 8-16 %. Overall, although uniform Gyroid structures exhibited superior mechanical and thermal performance across all evaluated properties, these findings provide new insights into the trade-offs between mechanical resilience and thermal transport in stochastic TPMS architectures, highlighting their potential for multi-functional applications in automotive components, aerospace structures, and structural energy storage systems.

Triple periodic minimal surface lattices have been introduced to dental and medical devices. Numerous designs of these porous structures have been proposed, but the impact of the surface properties of the different topographic lattices are not fully understood. So, this study aimed to examine the cellular and inflammatory responses to different lattice designs, including strut-based and surface-based lattices. Human osteoblasts, human umbilical vein endothelial cells, and monocytes were used to evaluate cell proliferation, osteogenic differentiation, and inflammatory response on lattices after surface treatment strategies. Post-surface treatment of chemical etching, in addition to improving the surface roughness by removing some adhered metal powder, also modulated the surface energy. The lattice design had no significant impact on cell proliferation, but higher cell proliferation was found in post-surface treated lattices, regardless of topographic design. For angiogenesis, there was no difference in the release of pro-angiogenic growth factors between topographic designs or post-surface treatment groups. Moreover, lattices with the post-surface treatment were prone to have a lower inflammation phenotype when compared to an as-printed lattice, though not in a significant manner. This study implies that different topographic lattice designs may not have a major impact on bone ingrowth; nevertheless, post-surface treatment and surface properties of lattice may have an influence on a macrophage-induced inflammatory response.

There is limited information concerning the effectiveness of the combined dynamic navigation system (DNS) and dental operating microscope (DOM) technique in fiber post removal. The aim of this study was to assess the effectiveness of the DNS-DOM technique for fiber post removal compared with the freehand technique (FH)-DOM. In a phantom head-based study, 30 human mandibular teeth were utilized, with 7 mm of fiber post left in obturated canals. Under a DOM, an experienced endodontist, employing an ET18D ultrasonic tip under a rubber dam, removed the fiber posts using either FH or DNS. Pre- and post-operative CBCT scans were taken, and 3D models were reconstructed with Materialise Mimics software. Accuracy (deviation volume, distance, angle, position) and efficiency (procedure time) parameters were analyzed. Normality was assessed with the Shapiro-Wilk test, utilizing the independent samples t-test for normally distributed data and the Mann-Whitney U test for non-normally distributed data. The DNS-DOM and FH-DOM groups demonstrated comparable results in deviation volume, percent deviation volume, maximum deviation distance, deviation angle, and maximum deviation position—all accuracy-related factors. We noted higher deviation and percent deviation volumes in DNS-DOM, which were not significant, compared with FH-DOM in incisors. Conversely, in molars, FH-DOM exhibited higher values than DNS-DOM, suggesting that the free-hand technique may result in less deviation under better visibility. There was a consistent trend of a higher deviation angle for DNS-DOM compared with FH-DOM across all tooth types. DNS-DOM and FH-DOM displayed a higher deviation angle in molars than in premolars and incisors. The distance between maximum deviation points and initial drilling points was smaller in molars compared with incisors and premolars. Regarding efficiency, the DNS-DOM group demonstrated a significantly longer procedure time (8 min) compared with FH-DOM. Fiber post removal time followed a similar trend in both groups, being fastest in molars, followed by premolars and incisors. DNS-DOM showed accuracy comparable to FH-DOM in fiber post removal when performed by an experienced endodontist with appropriate ultrasonic tips. However, DNS-DOM had a longer procedure time, potentially reducing efficiency due to the additional navigation system integration, demanding increased operator operating time.

This study investigates the influence of TiC addition on defect formation, microstructural evolution, and microhardness in Inconel 718 (IN718) metal matrix composites (MMCs) manufactured using a blue-diode laser powder bed fusion (LPBF) system. Porosity and defects in the samples were analyzed using microscopes and an X-ray computed tomography system (X-ray CT). The microstructures of the baseline IN718 and MMCs were observed using microscopy and wavelength-dispersive spectrometry techniques. The microhardness measurements were conducted to confirm the effect of TiC addition and carbide precipitation. It was found that TiC addition had three main effects: (1) increased porosity from 0.02 to 0.07

The Ti6Al4V ELI alloy produced via laser powder bed fusion (L-PBF) has attracted interest for use in dental applications. However, surface finishing is an important property that can be managed by various methods. The purpose of this study was to investigate the effects of electropolishing (EP) on the surface roughness and corrosion resistance of L-PBF Ti6Al4V ELI alloy.The present study explored the influence of current density (0.3 A/cm2), voltage (15 V), and distance (2 and 4 cm) on the surface quality of L-PBF-printed Ti6Al4V ELI. The potentiodynamic polarization testing was performed to investigate the corrosion behavior of electropolished Ti6Al4V ELI alloy plates.The data variation was compared at different conditions of EP using a one-way analysis of variance and Tukey's post hoc testing at a significance level of 5%.This study showed that EP significantly reduced the surface roughness and enhanced corrosion resistance of printed Ti6Al4V ELI alloy with the best result achieved by using 15 V and 2 cm of anode-cathode distance.This study indicates that customized EP settings are crucial for optimizing the surface properties of Ti6Al4V ELI for use in dental and biomedical applications. However, the corrosion resistance can be reduced due to increased porosity resulting from the EP treatment.

Nickel based alloy was fabricated by a laser powder bed fusion using the blue laser with the wavelength of 450 nm and maximum output power of 200 W, and the effect of volumetric energy density (VED), on the porosity was evaluated for fabricated samples. A fabricated sample using the blue diode laser, recorded a porosity of 0.012% at the VED of 33 J/mm(3), indicating that it can be fabricated more efficiently than the sample fabricated using the near-infrared fiber laser. Furthermore, it was revealed that when the surface roughness of the fabricated sample reached 37.5 mu m, large voids were generated, indicating a high likelihood of void formation at a surface roughness of approximately 40 mu m or more during the layer-by-layer fabrication of nickel-based alloys using the blue diode laser in powder bed fusion.

The material properties of individual micro-struts are critical to the overall success of lattice structures. These properties can be significantly compromised by defects inherited from powder bed fusion processes. Among these defects, porous inclusions are well understood to have a detrimental effect on mechanical properties; posing a high risk to the implant under loading. While the majority of these defects can be avoided through optimisation of printing parameters, this has generally only been done for traditional bulk components with no in-designed porosity. Furthermore, a number of studies have observed changes in the frequency of such porous inclusions as feature size is reduced, indicating a size effect. This also suggests that the optimal parameters for bulk material are not necessarily translatable to the individual micro-struts which build the lattice. In this study, the relationship between parameter optimisation and feature size was investigated. Here, a higher energy density input was required for processing micro-strut lattices with an optimised relative density, than it was for bulk components. This could be attributed to faster rates of heat loss in micro-strut samples on account of their increased surface-to-volume ratio. The consequential improvement in mechanical properties was also assessed. An increase in both strength and stiffness could be largely attributed to an increase in the percentage volume of load bearing material, while improvements in failure strain were largely driven by minimisation of stress concentrations around the irregular pore morphologies. Fatigue properties did not improve beyond the effects of yielding. Rather, crack initiation was dominated by surface defects; which on account of their surface free energy, experience a much higher stress intensity factor.

This study investigates the thermal performance of topologically optimized heat sinks. The primary aims are to conduct a comprehensive parametric study, compare thermal outputs with the benchmark model, and validate numerical simulations through experimental testing. Multi-objective topology optimization is formulated based on thermal compliance and power dissipation. Selected optimized models were built and tested. The parametric study revealed promising design variables, leading to numerical convergence with interconnected flow paths. The promising variables were found under weighted thermal compliances (wh) between 0.3 and 0.9 and targeted liquid fractions (θFV) between 0.5 and 0.8. Additionally, at low operating pressures, for example, at 0.01 kPa, the temperature difference between optimized and benchmark models could be as much as 30 °C. Nonetheless, the temperature difference between both models became smaller at higher operating pressures. Furthermore, the comparison of temperature measurements, pressure drops, and thermal imaging showed reasonable agreement between experimental and numerical results. Additionally, the effect of design variables on thermal performance was confirmed through experiments. The heat sink with higher wh exhibited a lower temperature than that of the model with lower wh. In summary, this research highlights the crucial role of design variables in achieving a balance between temperature and pressure drop.