This study aimed to evaluate the effects of linear elastic vs. hyper-viscoelastic periodontal ligament (PDL) models and uniform vs. nonuniform alveolar bone models on dental biomechanics. Four teeth (incisor 31, canine 43, premolar 45, and molar 36) were subjected to 1 N of force in the distal, lingual, labial, and mesial directions, respectively. The simulations indicated that when the PDL was modeled as hyper-viscoelastic, maximum stress decreased by an average of 68.93%, whereas maximum strain increased by an average of 530.02%. This study quantified the effects of different material models on dental biomechanics and provides guidance for finite element modeling.

Triply periodic minimal surface (TPMS) structures provide porous, interconnected geometries with bone-like stiffness and permeability, yet hybrid TPMS designs remain underexplored. This study develops three 3D-printed hybrid TPMS scaffolds for mandibular segmental defect reconstruction, targeting manufacturable bone analogs with optimized mechanics and pore architectures. Scaffolds were assessed for printing fidelity, mechanical behavior, fluid transport, and in vitro biocompatibility. All designs exhibited high geometric accuracy relative to their digital models. Compression tests showed elastic moduli of 3.36-3.91 GPa and yield strengths of 88.20-128.52 MPa, meeting requirements for mandibular reconstruction. Finite element simulations confirmed that the R1-type scaffold sustained complex physiological loading, with predictive accuracies of 87% for mechanical response and 53% for permeability. Flow tests further demonstrated permeabilities within the range of cancellous bone. In vitro analyses indicated that surface activation enhanced cell adhesion and proliferation, while VEGF-loaded cryogels promoted angiogenic activity. These findings highlight the potential of functionally graded-scaffold design can optimize stress distribution and nutrient transport, thereby offering a strategy for future surgical reconstruction of critical-sized bony defects.

Excessive frictional heat generated at the drill-bone interface during implant osteotomy can compromise osseointegration and lead to implant failure. This study’s objective was to use a helical milling technique for dental implant osteotomy preparation to mitigate thermal damage to the bone. This study introduces a novel helical milling technique designed to minimize thermal damage to bone during dental implant osteotomy preparations. Finite element simulations were conducted to compare the thermal distribution and cutting stress of a conventional twist drill and the newly designed helical drill. The experimental validation was performed ex vivo on animal bone using a robot-assisted osteotomy system. The finite element simulations revealed that the helical drill produced a maximum cutting stress of 128.9 MPa, higher than the 121.0 MPa generated by the twist drill, indicating improved cutting efficiency. The ex vivo study demonstrated that the helical milling technique maintained the drilling site temperature below 38.7 °C, which was significantly lower than the clinically critical threshold of 47 °C and the 61 °C recorded with the twist drill. Furthermore, the helical milling process facilitated efficient bone chip removal, reducing thermal buildup. These findings suggest that the helical milling tool and technique optimize robot-assisted osteotomy and effectively mitigate frictional heat generation at the drill–bone interface. This innovation holds promise for enhancing osseointegration success rates in dental implant procedures, offering a clinically viable solution to a long-standing challenge in implantology.

During laser cladding, welding, and other hot forming processes, dissimilar metals can form segregation bands. These bands often lead to solidification cracks that can directly affect the mechanical properties of the processed and formed materials. To study the formation mechanism and evolution of segregation bands during metallurgical bonding of dissimilar metal materials, a two-dimensional melting and solidification model for laser cladding of IN718 on 316L stainless steel was used. This model was established using the cellular automata method and Eulerian multiphase flow algorithm. The evolution of the temperature field, molten pool morphology, melt flow, and element distributions during laser cladding was comprehensively analyzed. The rationality of the model was confirmed by comparing the melt pool geometry and grain orientation. Additionally, the reliability of the model was confirmed by comparing the distribution of Fe element content in the x-and y-directions. The simulation results reveal that during the metallurgical bonding process of laser cladding IN718 alloy on the 316L stainless steel substrate, distinct segregation zones are observed, which are characterized by the enrichment of Fe and Ni elements and an unideal alternating distribution pattern. This finding is in high consistency with the experimental results. The Marangoni force drives more Fe elements from the bottom of the melt pool (substrate) to the rear end of the melt pool, increasing the temperature of the liquidus at that location. This solidification promotion at the rear end of the melt pool causes actual solidification liquidus temperature (T-a) to be biased toward substrate liquidus temperature (T-b), resulting in the formation of a region with a high concentration of Fe elements. The rear end of the melt pool takes on a "bulging" shape, increasing the melt flow rate within the pool. This increase rolls more Fe elements from the front end of the melt pool (powder) to the rear end of the pool. Consequently, the liquidus temperature at the rear end of the melt pool decreases, biasing T-a toward the liquidus temperature of the powder (T-p). This process hinders solidification at the rear end of the melt pool, resulting in the formation of a region with a reduced concentration of Fe elements. The rear end of the melt pool flattens gradually, decreasing the melt flow rate and drawing more elements from the front to the rear end. This change results in the formation of a segregation zone with an alternating distribution of high and low Fe element content, which is consistent with the experimental results. Through the analysis of the distribution of Fe elements in the melt pool, the morphology of the melt pool and the evolution of the melt flow state, it is evident that this segregation zone arises from the mismatch between fluid flow dynamics and the morphological changes of the melt pool during the solidification process. The rate at which the solid-liquid interface moves can be calculated by finding the difference in the solute concentration between the interface neighboring cells. Fluctuations in the molten pool flow cause the morphology of the rear end of the molten pool to constantly change, resulting in varying concentrations of Fe element after solidification. Therefore, increasing the homogeneity of element mixing in the molten pool can reduce the degree of segregation. During the experimental process, appropriate increase in the laser power and scanning rate reduction can improve the quality of the cladding layer.

Mechanical drilling is currently a universal standard for implant osteotomy site preparation. Without proper cooling, high frictional heat can be generated inside the bone during drilling which may be detrimental for osteocyte survival. Mechanical fracture of bone near a drill bit surface can also impede the osseointegration process. Our new concept is to use a rapid laser ablation model for dental implant osteotomy preparation to minimize adverse effects on the bone from mechanical and thermal damages. A mathematical model was developed to detail the temperature and energy distribution within bone under laser irradiation. Thermal and energy transfer in bone was predicted during laser interaction using finite element simulations. Various parameters of laser irradiation settings were analyzed. The best designed laser irradiation condition was derived from our theoretic modeling in terms of thermal and mechanical characteristics for osteotomy. We also validated our theoretical prediction with an ex vivo animal bone study. We conclude that a smooth and clean surface was successfully formed with laser power of 10 W, scanning speed of 600 mm/s, and scanning interval of 20 μm. We also achieved the highest removal rate of 0.63 mm3/s. Our finite element model demonstrated that it could effectively predict the temperature and energy distribution during an osteotomy drilling. Our validated model can potentially offer a remarkable approach for a non-contact dental implant site preparation with minimal mechanical and thermal damages to the adjacent bone tissue which likely can augment bone repair and regeneration during an osseointegration process.

Clear orthodontic appliances without metal brackets are highly favored by orthodontic patients due to their aesthetic appearance, easy to clean, and comfort. This pilot study aimed to investigate a new shape memory polyurethane (SMP) composite material for orthodontic applications. Finite element (FE) analysis was used to evaluate the mechanical performance of the composite material, which consists of polydl-lactide and hydroxyapatite (PDLLA/HA) model based on viscoelasticity and phase transition theories. Experimental characterization included determination of glass transition temperature (Tg), tensile properties, and creep behaviors. A customized UMAT subroutine was developed for Abaqus to simulate the thermodynamic process of shape memory effect based on the experimental data. Orthodontic forces generated by aligners fabricated from the composite were evaluated under simulated intraoral conditions. The results showed a progressive decline in Tg of the SMP samples following immersion in water, with Tg values decreasing to 45, 37, and 35 ℃ after 5, 10, and 15 days, respectively. When displacing teeth 0.1, 0.2, and 0.3 mm facially using this aligner, the initial orthodontic forces recorded were approximately 0.16, 0.17, and 0.35 N, respectively, achieving 85.3

Bone scaffolds for the repair of large-segment bone defects require a balance between mechanical stability and nutrient transport. This study proposes gradient Schwarz Primitive minimal surface scaffolds (P-TPMS) integrated with thin-board (B) structures, fabricated via selective laser melting (SLM). Finite element analysis (FEA) revealed that the gradient design reduced stress concentrations, achieving a layer-by-layer collapse failure mode under compression. This progressive energy absorption is critical for implant stability. Computational fluid dynamics (CFD) demonstrated that the gradient integrated scaffold (GPB70) with 70 % porosity maintained moderate permeability (6.37 × 10-9 m2) while enhancing fluid transport efficiency, mimicking the characteristics of natural trabecular bone. Surface modification with TiO2 improved hydrophilicity, reducing the contact angle from 110.8° to 31.6° for Ti6Al4V, and mitigated fabrication-induced defects. Dynamic impregnation tests revealed that the GPB70 scaffolds exhibited enhanced capillary-driven fluid transport, which is essential for efficient nutrient delivery in the early stages of implantation. In vitro studies confirmed superior adhesion and proliferation of the mouse osteoblastic cell line MC3T3-E1 within the GPB70 scaffold, attributed to the increased specific surface area. These findings suggest that the GPB70 scaffold offers a promising solution for enhanced bone tissue ingrowth by effectively balancing mechanical integrity, fluid transport, and cell ingrowth, making it a strong candidate for clinical applications in load-bearing bone defect repair.

Laser processing could drill micro holes with very high efficiency, but the micro holes suffer from recast layers, microcracks and heat-affected zones, which has limited its wide application in engineering. In this paper, the high-speed laser drilling and electrochemical post-treatment has been combined to improve the machining efficiency and surface quality. To reduce the surface sputtering and redeposit in laser drilling, avoid the stray current induced corrosion and improve the machining precision in electrochemical post-treatment, the double-side coating has been applied to the workpiece before processing. Influences of laser power ratio, frequency, duty cycle and defocus amount on the diameter and taper of the laser drilled micro holes were explored experimentally. Results showed that the micro hole diameter increased with the increase of laser power ratio, duty cycle and defocus amount and decreased with the increase of pulse frequency. The micro hole taper increased with the increase of frequency, duty cycle and defocus amount. A laser power ratio of larger than 70% was recommended to reduce the taper of the laser drilled micro holes. Additionally, orthogonal experiments were employed to study the effects of laser power ratio, frequency, duty cycle and defocus on laser drilled micro hole diameter, taper, and recast layer thickness. Results show that duty cycle has the greatest impact on aperture, and power ratio has the greatest impact on taper, and frequency has the greatest impact on the thickness of the recast layer. Micro holes with an average diameter of 0.58 mm, a taper angle of 1.77°, and an average recast layer thickness of 25 µm have been obtained by laser drilling utilizing the optimal parameters. Finally, electrochemical post-processing was adopted to improve the surface quality and mechanical properties of the laser drilled micro holes. Results had shown that micro holes without recast layer and micro cracks were obtained by electrochemical posttreatment with a processing time of 20 s. Moreover, the inner hole surface roughness has been reduced by 68.16% and the micro hardness was reduced by 63.40%. A surface roughness of Ra 0.71 μm has been achieved. The proposed laser and electrochemical machining could be applied to the fabrication of micro holes with high surface quality and high efficiency.

This study presents a novel digital interproximal enamel reduction (IER) clinical procedure, aiming to improve the effectiveness of IER processes in orthodontic treatment. A malocclusion case of skeletal-class I and angle-class I was selected for the experimental investigation. A three-dimensional (3D) model of the dentition was constructed using scanning data from a plaster model. The IER volume was measured by the overlay area of two neighboring crowns on the arranged virtual teeth. For the upper dentition, a guide plate was innovatively designed based on the original surface of the dentition and the calculated IER volume. The guide plate was fabricated using stereolithography 3D printing (SLA), and was successfully employed during the IER operation. For the lower dentition, the IER procedure was performed using the free-hand method, guided by the predesigned IER volume. Preoperative and postoperative 3D models of the dentition were compared to assess the accuracy of both IER methods. The standard deviation of upper dentition IER with guide plate was calculated as 0.13 mm, while that of lower dentition IER by freehand was 0.24 mm. Through the integration of laser scanning, 3D reconstruction, virtual arrangement, guide plate design, and 3D printing, this study not only explores a novel digital IER method, but also demonstrates its clinical applicability. The findings provide compelling evidence of the method’s superior accuracy in clinical practice, offering a new approach for high-precision IER operations in orthodontic treatment.

Laser and electrochemical hybrid machining (LECM) combines the advantages of high efficiency of laser processing and high surface quality of electrochemical machining and has been employed to process deep micro holes with high surface quality, high precision, and efficiency. However, surface pitting corrosion occurs around the entrance of the micro holes drilled by LECM, which deteriorates their surface quality and mechanical properties. This study revealed the mechanism of surface pitting corrosion formation mechanisms during LECM by characterizing surface micromorphology, chemical composition, microstructures, and surface stress. The difference between surface pitting corrosion area during LECM and the stray current corrosion during electrochemical machining was studied. Micro solid metal particles and inner microcavities were observed in micro pits. The depth of the micro pits was greater than that obtained using electrochemical machining. It has been concluded that in LECM, the surface pitting corrosion occurred owing to the enhanced stray current corrosion and the accumulation of solidified melt particles and cavitation microbubbles in the micro pits. Coaxial gasassisted LECM was also proposed to restrict the surface pitting corrosion area. Experiments and simulations were conducted to verify the feasibility of minimizing the corrosion area using coaxial gas. The surface pitting corrosion area has been decreased by 85.1 % at a coaxial gas pressure of 0.1 MPa compared with that without coaxial gas assistance. Finally, the radial cooling holes with a diameter of 1.2 mm and an aspect ratio of 125:1 in turbine blades with high surface quality were fabricated. This study provides a promising method to fabricate high-aspect-ratio micro-holes with high surface quality and high efficiency.

Laser has been adopted to improve the efficiency and localization of electrochemical machining (ECM), which is referred to as laser and electrochemical machining (LECM). Nevertheless, the electrochemical dissolution behavior under synchronous laser irradiation remains unclear. This study investigated the effects of laser irradiation on the electrochemical dissolution behavior and surface characteristics. The polarization curves and electric current efficiency were measured using synchronous laser irradiation on the electrochemical dissolution area. Furthermore, the evolution of the surface morphology, roughness, chemical content, and residual stress with varying laser power and electric current densities was characterized. Results demonstrated that laser irradiation could remove passivation film, enabling anodic dissolution at a lower potential and enhancing electric current density. Electrochemical impedance spectroscopy (EIS) results revealed that laser irradiation could decrease electrochemical impedance by three orders of magnitude. Moreover, the electric current efficiency could be increased by synchronous laser irradiation with an electric current density of smaller than 3.75 A/cm2. XPS results also indicated that laser irradiation favored the anodic reactions. Meanwhile, the surface characteristics relied on the comparison of electric current density and laser power. The enhanced electrochemical dissolution improved the surface finish with an increase in electric current density during LECM. The surface tensile stress increased with increasing laser power, which could accelerate the rate of anodic dissolution. Additionally, laser processing could improve the precision of ECM by locally removing the oxide film. This work contributes to the understanding of the material removal mechanisms of LECM, which would promote the development and utilization of LECM.

Electrochemical machining (ECM) has become more prevalent in titanium alloy processing. However, the presence of the passivation layer on the titanium alloys significantly impacts the performance of ECM. In an attempt to overcome the passivation effects, a high-temperature electrolyte or the addition of halogen ions to the electrolyte has been used. Still, it often results in compromised machining accuracy and surface roughness. This study applied laser and shaped tube electrolytic machining (Laser-STEM) for titanium alloy drilling, where the laser was guided to the machining zone via total internal reflection. The performance of Laser-STEM using different types of electrolytes was compared. Further, the effects of laser power and pulse voltage on the machining side gap, material removal rate (MRR), and surface roughness were experimentally studied while drilling small holes in titanium alloy. The results indicated that the use of passivating electrolytes improved the machining precision, while the MRR decreased with an increase in laser power during Laser-STEM. The MRR showed an increase while using aggressive electrolytes; however, at the same time, the machining precision deteriorated with the increase in laser power. Particularly, the maximum feeding rate of 6.0 mm/min for the tool electrode was achieved using NaCl solution as the electrolyte during Laser-STEM, marking a 100% increase compared to the rate without the use of a laser. Moreover, the model and equivalent circuits were also established to illustrate the material removal mechanisms of Laser-STEM in different electrolytes. Lastly, the processing of deep small holes with a diameter of 1.5 mm, a depth of 38 mm, and a surface roughness of Ra 2 µm was achieved via Laser-STEM without the presence of a recast layer and heat-affected zones. In addition, the cross-inner flow channels in the titanium alloys were effectively processed.

The laser and electrochemical hybrid machining (LECM) could realize high-efficient and quality processing of difficult-to-cut materials and has become a research topic in microfabrication. However, it was difficult to ensure the stability and efficiency of laser transmission in chemical solutions, and an external voltage and auxiliary cathode should be added. In the present study, a novel fiber laser irradiation in chemical solution (LICS) has been proposed to process microstructures. The surface microstructures and chemical composition of the surfaces processed by LICS, laser irradiation in the ultrapure water, and electrochemical machining were compared. In LICS the materials were removed by laser processing and the following high-temperature gradient induced electrochemical dissolution. The high temperature gradient induced electrochemical dissolution could enhance the MRR and improve the surface quality. LICS can be regarded as a novel LECM process. The machining efficiency of LICS had been improved by 46.2% compared with that laser irradiation in the ultrapure water, and the proportion of laser-induced electrochemical dissolution was 31.6 % in the LICS process. Further, the effects of laser power, chemical solution concentration, and optical fiber end movement control on the processing of micro grooves were explored, considering the dimension, MRR, and surface roughness. A front gap of smaller than 0.8 mm between the optical fiber end and workpiece was recommended during LICS. The repeated feeding of optical fiber was proposed to improve the depth-to-width ratio of the micro grooves fabricated by LICS. Finally, LICS was used to process microstructures with the controlled profiles on the nickel-based superalloy and titanium alloy workpieces without a recast layer, which holds great potential in surface microfabrication and texturing.

The fabrication of microstructures with high efficiency and accuracy on titanium alloys presents significant challenges due to stringent quality requirements. Hybrid laser and electrochemical machining (LECM) has emerged as a viable solution for efficient and precise processing of titanium alloys. This study investigates the material removal mechanism of titanium alloys during LECM, analyzing the machining characteristics under the combined influence of laser processing and electrochemical machining. The impacts of voltage, laser power, and feeding rate on aspects such as aspect ratio, accuracy, efficiency, and surface roughness are examined. Results reveal that synchronous laser irradiation effectively accelerates electrochemical corrosion rates, enhancing the removal capability of the passive film. Notably, LECM outperforms pure ECM, demonstrating significant improvements in parameters such as aspect ratio (394.4% increase), material removal rate (140% increase), and side gap (172.8% increase). Lower laser power is favored for high-precision LECM. An electric circuit model elucidates the titanium alloy material removal mechanism in LECM. Additionally, the study proposes the use of gradient laser power for fabricating high-aspect-ratio structures with efficiency and accuracy. The research successfully fabricates microstructures with elevated aspect ratio and flat bottoms on titanium alloys.

With the increasing improvement of living standards and the popularization of dental implant restoration, dental implantation has become the preferred treatment for patients with missing teeth. The implant sites preparation is one of the most important procedures in dental implant surgery. The thermal and mechanical damage caused to the bone tissue during this process can directly affect the formation of osseointegration. To mitigate these adverse effects, many scholars have used methods such as optimizing cutting parameters and improving the structure of surgical tools to better control heat generation and cutting forces. At the same time, many new processing technologies such as milling, ultrasonic machining, and laser machining have also been explored for shaping implant site and have made some progress. This review aims to discuss the advantages and limitations of these techniques used in osteotomy, summarizes the current research status in 97 literatures of related fields.

During the laser cladding process, complex composition distribution in the molten pool was caused from the Marangoni flow, which leading to one kind of defect termed as macrosegregation. Therefore, comprehensive understanding on the flow behaviors in the molten pool is particularly important for predicting and regulating macrosegregation. In this paper, a three-phase Eulerian model based on the volume averaging method is developed to investigate the effect of Marangoni coefficient variations on the flow and compositional distribution. The flow patterns were photographed and analyzed using a high-speed camera, and then the simulated and experimental results for chromium concentration distribution, size of the cladding layer, depth of the molten pool, and flow pattern were compared and found to be in agreement with each other; thus, the accuracy of the model was validated. Meanwhile, the effects of flow direction and intensity on the composition distribution are comprehensively studied. The results show that the flow direction extremely affects the flow path and evolution process of Cr-enriched melt in the molten pool. At the same time, the flow intensity will change the flow time of Cr-enriched melt in the molten pool and then affect the homogenization of composition distribution.

To enhance the controllability of the molten pool morphology, a directional Lorentz force is produced within the molten pool by synchronously coupling a steady electric field and magnetic field during the laser cladding process. A 2D numerical model of the molten pool considering solid-liquid phase change, heat transfer, fluid flow, deformed geometry and electromagnetic induction is established. The experimental and simulation results demonstrate that the magnetic or electrostatic field has negligible effects on the molten pool shape. The compound electromagnetic field (simply as a compound field) that generates a downward Lorentz force significantly impacts the molten pool height, and wetting angle. As revealed by the observation of the molten pool forming process, it is found that the downward Lorentz force disrupts the force balance of the molten pool, which leads to the outward expansion of the fluid due to an increased pressure difference. As a consequence, the height of the molten pool decreases. Meanwhile, the employment of a magnetic field results in a significant increase in the viscous resistance at the solidification interface. The fluid is accumulated at the bottom of the molten pool, which increases the wetting angle. Additionally, since this approach can produce a steady volume force similar to gravity, it can be used in a weightless environment, such as in a space station, thus significantly improving the process stability.

Laser and electrochemical machining (LECM) has been increasingly adopted to improve the efficiency and surface quality of micromachining. The coupling and high-efficiency transmission of laser in electrolyte are critical to the implementation of LECM, which were rarely studied in previous research. In this study, the geometric and simulation model of laser coupling and transmission within the electrolyte jet has been established for laser and shaped tube electrochemical machining (Laser-STEM). The critical coupling condition and transmission efficiency of laser beam was investigated theoretically. Influences of laser coupling errors on the laser transmission efficiency and laser power intensity distribution at the exit of hybrid tool electrode were explored. Results indicated that the angular offset had the greatest impact on laser transmission efficiency, while the longitudinal offset impact the least, which were accordance with the experimental results. The thresholds of laser power intensity and the frequency of the laser-induced electrolyte breakdown were measured. The thresholds for laser-induced breakdown in NaNO3 3 solution were higher than that in NaCl solution. The laser power intensity threshold of laser-induced electrolyte breakdown increased with the increase of focal length, and the frequency of smaller than 4.5 could be obtained with the laser power density ranging from 2.35e9 9 to 1.06e10 10 W/cm2 2 at the focal spot. The distribution trended to more uniform at the exit with the increase of hybrid tool electrode length. A laser coupling efficiency of larger than 81.2 % has been achieved by utilizing the hybrid tool electrode with NA of 0.534 and acceptance angle of 32.3 degrees. degrees . Finally, experiments with a designed raster-shaped workpiece were conducted to verify the feasibility of laser transmission in large depth in the Laser-STEM process. The high aspect-ratio small holes with a depth of 50 mm, and a diameter of 1.3 mm have been processed by using Laser- STEM.

Surgery of jawbones has a high potential risk of causing complications associated with temporomandibular joint disorder (TMD). The objective of this study was to investigate the effects of two drive modeling methods on the biomechanical behavior of the temporomandibular joint (TMJ) including articular disc during mandibular movements. A finite element (FE) model from a healthy human computed tomography was used to evaluate TMJ dynamic using two methods, namely, a conventional spatial-oriented method (displacement-driven) and a compliant muscle-initiated method (masticatory muscle-driven). The same virtual FE model was 3D printed and a custom designed experimental platform was established to validate the accuracy of experimental and theoretical results of the TMJ biomechanics during mandibular movements. The results show that stress distributed to TMJ and articular disc from mandibular movements provided better representation from the muscle-driving approach than those of the displacement-driven modeling. The simulation and experimental data exhibited significant strong correlations during opening, protrusion, and laterotrusion (with canonical correlation coefficients of 0.994, 0.993, and 0.932, respectively). The use of muscle-driven modeling holds promise for more accurate forecasting of stress analysis of TMJ and articular disc during mandibular movements. The compliant approach to analyze TMJ dynamics would potentially contribute to clinic diagnosis and prediction of TMD resulting from occlusal disease and jawbone surgery such as orthognathic surgery or tumor resection.