Search Results (667)

Bone loss represents a significant clinical burden that has driven the development of improved orthopedic graft substitutes. Although current grafting options, including autografts, allografts, and xenografts, have demonstrated considerable therapeutic potential, their widespread application is constrained by limitations such as donor scarcity, limited availability, and associated clinical risks. Consequently, biologically derived materials, including avian eggshells and marine bivalve shells, have emerged as promising alternative sources to produce bone precursor materials and next-generation bone graft substitutes. This review summarizes recent advances in avian eggshell- and marine shell-derived calcium carbonate (CaCO₃) materials for bone regeneration and examines their preclinical evaluation in diverse animal models, including critical-size defects in calvarial, femoral, radial and mandibular bone. Relevant studies published over the past ten years were systematically analyzed, focusing on natural calcium carbonate systems derived from avian eggshell and marine shells, including oyster, mussel, clam, scallop, cockle, and sea urchins. A structured literature search was conducted using PubMed, Scopus, and Google Scholar to identify studies published between 2015 and 2025 investigating eggshell- and aquatic-derived biomaterials for bone repair and regeneration. Eligible studies were screened, and data were comparatively analyzed with respect to biomaterial source, scaffold fabrication, physicochemical characteristics, mechanical performance, biocompatibility, osteogenic potential, and the use of preclinical animal studies. Eggshell-derived biomaterials currently show the strongest translational evidence, while aquatic shell-derived biomaterials remain promising but underexplored for bone regeneration. Furthermore, this review critically examines the scientific, manufacturing, and regulatory challenges that must be addressed before clinical implementation. Full article

Guided bone regeneration (GBR) is a widely used clinical approach for managing bone defects associated with periodontal disease in dogs, employing barrier membranes to selectively direct tissue regeneration. The performance of these membranes is influenced by composition, structural design, and degradation behavior, which together determine biological responses and clinical outcomes. Biodegradable GBR membranes, fabricated from natural polymers, synthetic polymers, or composite materials, offer advantages over non-biodegradable membranes, including controlled resorption, elimination of secondary surgery, and the potential for delivery of bioactive agents. Preclinical studies in dogs have demonstrated that GBR membranes can promote periodontal regeneration, including bone and cementum formation and space maintenance; however, optimization of degradation behavior remains critical to align membrane resorption with tissue healing in some cases. Clinical studies in dogs with naturally occurring periodontal disease remain scarce, and only two biodegradable membranes (Ossiflex^® and Doxirobe^®) are commercially approved for veterinary use, while all others are applied off-label. These limitations highlight the need for more adaptable and cost-effective regenerative strategies, including membranes that can be customized to different defect sizes and multifunctional membranes incorporating bioactive agents that will offer an advanced regenerative potential and improved predictability in veterinary periodontal therapy. Full article

Critical-sized bone defects remain a significant clinical challenge, and dipyridamole (DIPY)-coated 3D-tricalcium phosphate (β-TCP) scaffolds have shown promising osteogenic efficacy in preclinical models. However, the literature on the systematic physicochemical characterization of this scaffold system, including optimization of DIPY loading parameters, release kinetics, and surface properties, is lacking. This study addresses these gaps by characterizing DIPY-loaded 3D-printed β-TCP scaffolds across solid and porous architectures, three coating concentrations (10, 100, and 1000 µM), and three coating volumes (250, 500, and 1000 µL). Under static PBS conditions, drug release over 21 days was quantifiable only at 1000 µM, and release-kinetics modeling (zero-order, Higuchi, and Korsmeyer–Peppas) was therefore restricted to this highest concentration. At 1000 µM, both scaffold types showed biphasic release profiles, with standard empirical models reasonably approximating the overall kinetics, while not fully capturing the biphasic behavior over the entire duration. Porous scaffolds showed significant volume-dependent release (p = 0.002, η² = 0.88), attributable to drug penetration into the interconnected macropore network, whereas solid scaffolds displayed volume-independent release confined to external surfaces. Scanning electron microscopy revealed concentration-dependent needle-shaped DIPY crystal deposition while contact angle measurements indicated no significant changes in surface hydrophilicity. MTT assay demonstrated biocompatibility at all concentrations, with viability influenced by coating volume rather than drug concentration. These findings establish a foundational physicochemical framework for DIPY-loaded β-TCP scaffolds, providing the baseline data necessary to guide subsequent biological evaluation and translational efforts toward critical-sized craniofacial and orthopedic bone defect repair. Full article

Background and Clinical Significance: Implant rehabilitation of patients with acquired maxillofacial defects remains challenging, particularly following high-energy war-related trauma. Gunshot and mine blast injuries frequently result in extensive hard and soft tissue loss, often requiring complex reconstructive procedures. Although cortically anchored implants have been successfully used in patients with severe maxillary atrophy and selected traumatic defects, evidence supporting their use for the immediate rehabilitation of critical-size war-related maxillary defects remains limited. Cortically anchored single-piece implants used in conjunction with an immediate loading protocol may provide an alternative rehabilitation strategy for selected patients who decline, or are unsuitable for, conventional implants and bone-grafting procedures. Case Presentation: Two patients with critical-size maxillary defects (approximately 3 cm) resulting from gunshot and mine blast injuries are presented. Treatment consisted of extraction of non-restorable teeth, placement of cortically anchored single-piece implants, including tubero-pterygoid implants, followed by immediate loading with fixed hybrid metal–acrylic hybrid prostheses. Clinical and radiological evaluation was performed using panoramic radiography and cone-beam computed tomography. Conclusions: Successful implant-supported prosthetic rehabilitation was achieved in both patients. Cortically anchored implants engaging the basal bone of the maxilla provided stable support for immediately loaded fixed prostheses despite substantial hard and soft tissue loss. Functional and aesthetic outcomes were satisfactory. Immediate prosthetic rehabilitation was successfully completed in both patients. A 12-month clinical and radiographic follow-up was available for one patient and demonstrated stable implant function without biological or prosthetic complications. Long-term follow-up of the second patient was not available because of active military service. Cortically anchored implant-supported hybrid prostheses may represent a viable treatment option for selected patients with critical-size maxillary defects resulting from gunshot or mine blast injuries, enabling rapid restoration of oral function and facial aesthetics while avoiding extensive bone-grafting procedures. Full article

Hard and brittle material components with complex curved surfaces are widely used in critical foundational parts within aerospace, optoelectronics, and other fields. Their machining quality directly determines the performance and reliability of high-end equipment. However, the inherent properties of hard and brittle materials make them prone to surface/subsurface damage during traditional polishing processes, and maintaining the form accuracy of complex curved surfaces is challenging. Although abrasive waterjet polishing enables non-contact flexible processing, its energy efficiency is low. Additionally, although ultrasonic-assisted polishing can improve material removal, its spatial localization is insufficient, limiting energy utilization efficiency. To address these issues, this paper proposes a novel method of focused, ultrasonic, vibration-assisted abrasive waterjet polishing. The influence of the radiation force and cavitation force of the focused ultrasonic field on abrasive particle motion is analyzed, and analytical equations for abrasive particle velocity are established. Subsequently, single-factor and response surface methodologies are employed to systematically evaluate the influence of process parameters on machining quality and efficiency. The material removal process during FUAP involves both plastic shearing/chip formation and localized brittle fracture. Focused ultrasonic assistance promotes micro-cutting and plastic shearing, while localized crushing pits indicate that brittle fracture remains non-negligible. The focused ultrasound superimposes alternating stress onto the impact action, mitigating microscale crushing pit defects during the brittle removal process of monocrystalline silicon. Furthermore, appropriately increasing ultrasonic power, enlarging abrasive particle size, and raising abrasive concentration all contribute to enhanced material removal from monocrystalline silicon. Adjusting the nozzle height to the effective region of the focused ultrasonic energy field promotes material removal via chip formation while avoiding pit defects caused by excessive fracture. These results suggest that focused ultrasonic energy can be effectively integrated into abrasive waterjet polishing to enhance material removal while suppressing brittle surface defects, thereby offering a promising strategy for the ultra-precision finishing of hard and brittle components with complex curved surfaces. Full article

Two design solutions such as modular and mono-block Ti6Al4V porous implants for femoral defect repair were implemented and compared. Static stress analysis on each model was performed via finite element analysis to investigate potential critical elements that might cause system failure under physiological loads. Prior to calculations, a mesh convergence study was realized by varying the minimum element sizes. The entire bone–prosthetic system was modeled, and design optimization was performed. For mono-block implants, a less stressed configuration was found by changing the plate design. Comparison of the maximum Von Mises stress ${\sigma }_{max}$ and equivalent strain ${\epsilon }_{eq}$ between the models allowed for an understanding of the distribution of the loads and identify areas with critical stress concentration. The modular implant appeared to be highly solicited with stress shielding on epiphyses due to enhanced rigidity at the metal/bone interface. Finally, a study of the deformation on cancellous and cortical bone suggested that a more elastic junction with balanced strain delivery to the bone might improve tissue regeneration when using a mono-block implant. Full article

Critical-size segmental bone defects remain a major challenge in orthopedic surgery, often requiring complex reconstruction strategies associated with significant morbidity. This study evaluated the regenerative potential of a self-crosslinking bone substitute (SCBS) composed of biphasic calcium phosphate (BCP) granules suspended in a silanized hydroxypropyl methylcellulose (Si-HPMC) hydrogel, with or without recombinant human bone morphogenetic protein-2 (rhBMP-2), in a canine load-bearing defect model. Bilateral 2-cm segmental defects were created in the ulnae of five adult beagle dogs. Defects were filled with SCBS alone or SCBS loaded with rhBMP-2. Bone regeneration and biomaterial remodeling were assessed after 20 weeks using micro-computed tomography (micro-CT), scanning electron microscopy (SEM), histomorphometry, elemental analysis, and histology. SCBS loaded with rhBMP-2 resulted in complete defect bridging, with 35% newly formed bone and only 5% residual BCP granules. In contrast, SCBS alone induced limited bone formation (10%), primarily at host interfaces, with substantial persistence of BCP (33%). Newly formed bone in the rhBMP-2 group exhibited a dense lamellar structure with Haversian organization and direct contact with residual biomaterial. Elemental analysis revealed a lower Ca/P ratio compared with control, suggesting ongoing remodeling. These findings demonstrate that controlled delivery of rhBMP-2 from a self-crosslinking CaP/hydrogel composite enhances both bone formation and biomaterial resorption, supporting a coupled regeneration process. This approach represents a promising strategy for the treatment of segmental bone defects and non-unions in orthopedic applications. Full article

The nano-hydroxyapatite/β-tricalcium phosphate composite (nano-HA/β-TCP) is widely used in various medical and dental procedures. The absence of in vivo toxicity of nano-HA/β-TCP has been extensively studied, and it is considered one of the most effective synthetic biomaterials for promoting cell differentiation in bone regeneration. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are the primary cell type involved in the osteoinductive process of guided bone regeneration following injury. In the present study, rat BM-MSCs were cultured with nano-HA/β-TCP (80/20%) composite spheroids, and the interaction between the cells and the composite was analyzed using transmission electron microscopy (TEM). Ultrathin sections examined by TEM showed extensive interaction between nano-HA/β-TCP and BM-MSCs. Semi-thin sections stained with toluidine blue revealed the incorporation of the biomaterial into the cell cytoplasm. For the immunohistochemistry analysis, eight adult male Wistar rats weighing approximately 300 g were used in each group. Two bilateral, non-critical-sized 3 mm defects were created in the parietal bones of the calvaria: Control, Bio-Oss^®, and Blue Bone^® (n = 24) during a 12-week experimental period. Bone formation was evaluated through osteonectin and osteopontin expression. At the ultrastructural level, internalization of the biomaterial and close association with the endoplasmic reticulum (ER) and mitochondria were observed. TEM analysis also revealed no harmful effects on the cells, such as apoptotic or necrotic bodies or cell lysis. These findings indicate that the nano-HA/β-TCP composite demonstrates in vitro biocompatibility and interacts appropriately with BM-MSCs, including incorporation into the cell cytoplasm. In vivo, the Blue Bone^® group exhibited superior bone formation when compared with the other groups. Full article

Lamb waves propagation analysis is among the leading-edge approaches for the Non-Destructive Testing of composite thin-walled structures. The underlying diagnostic principle relies on the dependence of elastic waves wavelength on the plate thickness through which they propagate. Therefore, critical defects in composite panels, such as delaminations, can be detected by a non-contact, automated and high-resolution method such as Laser Doppler Vibrometry. The general approach applied in signal processing is referred to as Local Wavenumber Estimation. It consists of creating an image of the average wavelength over the acquisition frequency band in which the pixel element corresponds to a point of the vibrometer scan grid. The standard signal processing approach is typically implemented via the Short Space Fourier Transform. While effective at creating an average wavelength image over the acquisition frequency band, a major drawback of the Short Space Fourier Transform is its heavy reliance on the a priori selection of a spatial window size; a suboptimal choice can severely degrade detection robustness and spatial resolution. To overcome this limitation, we propose a novel method based on the 2D Continuous Wavelet Transform for the detection of defects in composite structures based on the isotropic Morlet wavelet. Thereafter, the proposed method is experimentally validated exploiting a glass fiber reinforced plate with an induced delamination. The proposed method proves superior on average by eliminating parameter dependency while preserving the original image resolution, resulting in a 66% Intersection over Union metric, comparable with the values of the standard method, but with a lower computational time. Full article

Bone regeneration remains a significant clinical challenge, particularly for large or critical-sized defects caused by trauma, disease, or congenital abnormalities. Mesenchymal stem cells (MSCs) have emerged as a promising cell source for bone tissue engineering, with their osteogenic differentiation playing a crucial role in bone repair. Biomaterials serve as scaffolds that facilitate MSC-mediated bone regeneration by providing structural support and mimicking the extracellular matrix (ECM). This review explores recent advancements in biomaterials designed to promote MSC osteogenesis through two primary approaches: biochemical and physicomechanical stimuli. Therapeutic agent-loaded scaffolds, incorporating growth factors, small molecules, gene materials, peptides, proteins, and extracellular vesicles (EVs), have been extensively studied for their ability to enhance osteogenic differentiation. However, concerns regarding toxicity, off-target effects, and regulatory limitations have led to increasing interest in biomaterials that utilize physicomechanical cues such as stiffness, viscoelasticity, topography, porosity, and dynamic forces (shear stress, compression, vibration) as alternative or complementary strategies. Furthermore, the synergistic effects of multiple physicomechanical cues are being explored to regulate MSC behavior for promoting bone regeneration. This review discusses current challenges, emerging trends, and future directions in the development of next-generation biomaterials that integrate biochemical and physicomechanical approaches for clinical applications in bone repair and regeneration. Full article

Perovskite solar cells (PSCs) have reached certified efficiencies exceeding 26%, yet the gap to the Shockley–Queisser limit and insufficient operational stability remain key obstacles to commercialization. Quantum dots (QDs) offer a versatile platform to address both challenges through their size-tunable bandgaps, high photoluminescence yields, and solution processability. This review systematically examines four QD integration strategies in PSCs: transport layer modification, active layer doping, UV conversion layers, and tandem sub-cells. The underlying mechanisms—including defect passivation, energy-level engineering, crystallization control, and ion migration suppression—are critically compared across these approaches. Despite significant advances, challenges persist, including the ligand–charge transport trade-off, the environmental toxicity of Pb/Cd-containing QDs, poor reproducibility, and the absence of standardized stability testing protocols. By providing a mechanism-oriented assessment across all device components, this review offers a clear framework for selecting appropriate QD strategies and identifies priority research directions. The perspective of QD strategies in this review provides a useful and significant reference for approaching the theoretical PCE limits of single-junction PSCs by reducing non-radiative recombination and improving light utilization, while QD-based tandem architectures offer a viable route toward surpassing the single-junction Shockley–Queisser limit. Full article

To address the weak interfacial transition zone and insufficient mechanical properties of recycled aggregate pervious concrete, this study proposes a dual modification strategy using basalt fibers and ultra-fine mineral powder. The macroscopic mechanical and hydraulic properties of the material were analyzed through orthogonal experiments. Techniques including X-ray diffraction, scanning electron microscopy, and micro-computed tomography were employed to systematically reveal the microstructural evolution and internal pore network topology of the modified system. Based on range analysis of mechanical stiffness and drainage efficiency, the optimal mix proportions were determined as 5–10 mm aggregate, a water–cement ratio of 0.31, and a fiber content of 0.50%. Microscopic tests confirm that the pozzolanic reaction of ultra-fine mineral powder increases matrix density and enhances the shear bond strength between fibers and the cement paste, enabling the physical bridging effect of basalt fibers. The dual modification exhibits a synergistic effect on load-bearing capacity and crack resistance. CT scan results show that the internal pore cross-sectional area follows a unimodal skewed distribution, with the characteristic distribution peak located at 3.5 mm². This homogeneous microporous network limits the critical defect size, optimizing the stress transfer path while ensuring fluid transport. Full article

As mineral resource extraction progressively extends to greater depths, the complex deep underground environment poses severe corrosion-induced deterioration risks to anchoring structures such as rock bolts. Anchorage failure has thus become a critical safety concern constraining the stability of deep roadways. To address the failure mechanisms of anchoring systems under multi-physical field coupling effects, this study conducts numerical simulations of multi-field corrosion processes and ultrasonic nondestructive testing (NDT) based on a numerical modeling platform. The influence of temperature on corrosion rate and current density is systematically analyzed, and interface response characteristics are extracted and interpreted for defects of varying dimensions. A spatial complementary mechanism under different corrosion defect configurations is revealed, and a health diagnosis system incorporating multiple critical indicators is established. The results indicate that elevated temperature significantly accelerates bolt corrosion: the rise in temperature shifts the equilibrium potential negatively and exponentially increases the reaction rate constant, both of which synergistically promote anodic dissolution. In ultrasonic testing, monitoring points along the main axis are positioned within the transmission-focused zone, where defects induce acoustic wave diffraction and superposition such that even minor defects cause a multiplication of the dominant frequency. Lateral monitoring points lie in the reflection–interference zone, where small defects preferentially attenuate energy, while larger defects manifest as amplitude reduction and first-arrival wave lag; all characteristic indices increase monotonically with defect size. Based on the numerical simulation outcomes, a four-level grading diagnosis standard and a “bottom–lateral” detection scheme are proposed as simulation-based reference indicators. The model effectively reproduces both corrosion deterioration and acoustic wave propagation characteristics, thereby providing a quantitative basis for the assessment of anchoring structures in high-temperature deep underground environments. Full article

With increasing rail traffic intensity, reliable detection of shallow subsurface rail damage is essential for operational safety. This critical narrative review evaluates non-destructive testing technologies relevant to defects whose active crack front or principal scattering zone lies within the upper approximately 0.5–10 mm of the rail, while treating the 10–15 mm range as a transition to deeper-defect verification. Magnetic flux leakage, magnetic particle inspection, visual inspection, eddy current testing, and conventional ultrasonic testing are first examined as screening or confirmatory comparators. The review then focuses on four ultrasonic surface-wave excitation routes—contact piezoelectric, active air-coupled, electromagnetic acoustic, and laser ultrasonic—and distinguishes source-specific laboratory capability from demonstrated field evidence. Because the cited studies use different defect geometries, rail conditions, sensor configurations, speeds, and decision criteria, their numerical values are reported as source-conditioned evidence rather than as a normalized ranking. An engineering decision matrix links defect depth and size, inspection speed, surface condition, and noise environment to a recommended screening–confirmation workflow. The synthesis identifies contact piezoelectric UT/PAUT as the most mature quantitative confirmation route, while EMAT, air-coupled UT, and laser UT retain method-specific advantages but require stronger natural-defect and in-service validation. Full article

Anti-friction bearings are fundamental components in rotating machinery. Any bearing fault appearing during operation could lead to catastrophic damages and failures without proper maintenance. Numerous methods have been developed for bearing fault detection to reduce maintenance costs and avoid unscheduled downtime. However, once a bearing fault is detected, assessing defect severity may be of more critical concern to industries, as it determines the urgency of interventions such as replacement scheduling and maintenance strategies. This paper presents an efficient estimation method for bearing fault severity using vibration-based input parameters and machine learning. Based on modal characteristics, key input parameters, the vibration amplitudes at the bearing fault frequencies and their harmonics, are extracted from acceleration envelope spectra for their close correlations with physical defect conditions. The nonlinearity between these spectral parameters and bearing fault severity is revealed with experimental observations and is represented using artificial neural networks. The model is validated on experimental vibration data measured from a bearing rig, covering various defect scenarios of different sizes and shapes. The classification criteria of bearing fault severity levels, ranging from healthy to severe, are formulated based on physical defect sizes with maintenance recommendations. Robust and accurate fault severity estimation is achieved across three bearing datasets collected under different operating conditions. The proposed method addresses both fault detection and degradation assessment for anti-friction bearings using simple vibration-based parameters based on rotor and bearing dynamics, providing a practical framework for predictive maintenance in industrial applications. Full article