Influence of porosity on osteogenesis, bone growth and osteointegration in trabecular tantalum scaffolds fabricated by additive manufacturing

Mechanical and biological properties of 3D-printed porous titanium scaffolds coated with composite growth factors

BACKGROUND

Osseointegration is considered a prerequisite for predicting implant success, and structure, biocompatibility, and properties of the implant are important parts of the factors that influence osseointegration. The focus of current research is on how to increase the strength of osseointegration on the implant and shorten the osseointegration time.

METHODS

In this research, different porous scaffolds, including uniform, radial-gradient, and axial-gradient porous, were designed and fabricated. Their mechanical properties and biocompatibility were comprehensively evaluated through mechanical tests and in vitro cellular experiments. A porous scaffold exhibiting optimal properties was identified through preliminary experiments. Subsequently, three different sets of composite scaffolds were developed, consisting of the selected scaffold modified with chitosan microspheres loaded with Bone Morphogenetic Protein-2 (BMP-2), Platelet-Derived Growth Factor-BB (PDGF-BB), or a combination of both. The biological responses to composite scaffolds were systematically examined through in vitro and in vivo experiments.

RESULTS

Finite element analysis indicated that the maximum equivalent stress of all three porous implants was lower than that of solid implants, while the maximum equivalent stress in the cortical bone of the porous group was higher than in the solid group. Compression tests confirmed that the elastic modulus of all three porous scaffold structures fall within the range of natural human bone. In vitro cell experiments showed that the radial gradient porous group scaffolds had the highest cell count and Alkaline phosphatase activity. The composite scaffolds exhibited superior wettability and water absorption properties compared to the non-coated scaffolds. Cell and animal experiments demonstrated that the titanium scaffolds co-modified with BMP-2 and PDGF-BB showed greater cell proliferation and new bone formation compared to scaffolds with single-factor coatings and uncoated scaffolds.

CONCLUSIONS

Radial-gradient porous scaffolds exhibit compatible elastic modulus, excellent cell compatibility, and osteogenic potential, making them promising candidates for bone tissue engineering applications in dentistry. Furthermore, the composite scaffolds incorporating BMP-2 and PDGF-BB-loaded chitosan microspheres demonstrated enhanced osteogenic differentiation compared to single-factor modified porous scaffolds, providing experimental evidence for the clinical application of novel implants.

Interfacing bioactive glass with silk fibroin: a soft matter approach to tunable mechanics and enhanced biocompatibility

Tissue-engineering scaffolds must balance mechanical compatibility with biological performance to support effective tissue regeneration. Bioactive glass (BG), valued for its strength and bone-bonding ability, often suffers from high stiffness, risking stress shielding. To address this limitation, we hybridized BG with silk fibroin (SF), a soft, biocompatible protein, to create (3-glycidyloxypropyl)trimethoxysilane (GPTMS)-crosslinked BG-SF scaffolds with tunable mechanics and enhanced cellular interactions. Fabricated via the sol-gel technique with varying BG-to-SF ratios, the scaffolds demonstrated increased porosity with higher SF content, positioning SF as a natural alternative to chemical porogens. Mechanical testing revealed that incorporating SF reduced BG stiffness, improved flexibility, and enhanced toughness, aligning the scaffold properties with those of native tissues. Fatigue testing confirmed greater durability in SF-enriched scaffolds, while degradation studies highlighted controllable rates conducive to tissue regeneration. Remarkably, as little as 10 wt% SF increased cell survival by 6.5-fold in biocompatibility assays. These findings underscore the synergy between BG and SF, presenting a soft matter strategy for designing scaffolds with customizable properties for tissue-engineering applications.

Effect of Ti6Al4V Alloy Surface and Porosity on Bone Osseointegration: In Vivo Pilot Study in Rabbits

Unmodified Ti6Al4V can osseointegrate, but sometimes this capacity needs to be improved. This study aimed to see how much porosity improves osseointegration in a Ti6Al4V implant. Three types of Ti6Al4V cylindrical-shaped implants (13.00 mm length × 5.00 mm diameter) were evaluated: solid sandblasted acid-etched, sintered, and porous 3D-printed (681.00 µm average pore size). Fifteen 20-week-old nullipara female parasite-free New Zealand California white rabbits were used, employing the femoral condyle defect model and undertaking µ-CT analysis and pull-out testing eight weeks later. On µ-CT densitometric analysis, the solid sandblasted rod showed the highest new bone growth around the implant. Bone growth was higher inside the implants for the porous 3D-printed (54.00 ± 5.00 mm3) than for the sintered (1.00 ± 0.05 mm3) and zero for the sandblasted implants. In the pull-out test, there were no statistically significant differences in the ANOVA analysis between the sintered (900.00 N ± 310.00 N) and porous 3D-printed (700.00 N ± 220.00 N) implants. Such differences did exist between the sandblasted material (220.00 N ± 50.00 N) and the two other materials (sintered p 0.002, porous p 0.034). The porous 3D-printed and sintered implant pull-out strength were significantly better than that of the solid rod sandblasted implant. Still, there were no statistically significant differences between the first two.

Biomechanics and Mechanobiology of Additively Manufactured Porous Load-Bearing Bone Implants

Given that they can replicate both the biomechanical and mechanobiological functions of natural bone, metal additively manufactured porous load-bearing bone implants present a significant advancement in orthopedic applications. Additive manufacturing (AM) of metals enables precise control over pore geometry, resulting in implants that provide effective mechanical support and minimize stress shielding. In addition to its mechanical benefits, the porous architecture of the implants facilitates essential mechanobiological processes, including the transmission of mechanical signals that regulate cellular processes such as adhesion, proliferation, and differentiation. Before clinical use, the implants should first be engineered to achieve a comparable elastic modulus to native bone, mitigating implant-induced bone resorption while promoting tissue regeneration. It is also noteworthy that the microstructural features of these implants support angiogenesis-a critical process for oxygen and nutrient delivery during bone healing. Despite their potential benefits, challenges remain in balancing mechanical stability for load-bearing applications with biofunctionality for effective integration and controlled degradation. This review comprehensively discusses the biomechanical and mechanobiological factors influencing the design and performance of additively manufactured porous bone implants, highlighting their potential to enhance clinical outcomes in bone repair and regeneration.

3D printed polycaprolactone scaffold incorporated with tragacanth gum/bioactive glass and cellulose nanocrystals for bone tissue engineering

Biomimetic organic-inorganic nanocomposite scaffolds hold tremendous potential to accelerate bone regeneration due to their ability to provide excellent structural and biological cues. Therefore, we employed a 3D-printed polycaprolactone host component as a mechanical support that was filled with a tragacanth gum-45S5 bioactive glass-cellulose nanocrystal guest component. The designed host-guest scaffolds were evaluated via physical, chemical, mechanical, and biological properties. Owing to the successful integration between host and guest components, the scaffolds showed enhanced physical and swelling properties (approximately 100 %) for nutrient transfer and cell proliferation. Furthermore, the host-guest scaffolds exhibited improved surface apatite formation and increased strength (3.35-16.55 MPa) within the ideal range for bone tissue engineering applications. It was verified in vitro that the host-guest scaffolds offer a highly desirable microenvironment for cell proliferation and attachment. Importantly, the host-guest scaffolds exhibited remarkable calcium deposition (4-56 %) and matrix formation. However, it was found that the proportion of cellulose nanocrystals can affect the properties of fabricated host-guest scaffolds. These results highlight the importance of optimizing the cellulose nanocrystal content in the scaffold composition to achieve the desired balance of properties for effective bone tissue engineering applications. The incorporation of cellulose nanocrystals at lower concentrations, particularly 3 wt%, represents a promising approach for developing biomimetic scaffolds that can enhance bone regeneration. Notably, the results of this study confirmed that incorporating cellulose nanocrystals at lower concentrations into the host-guest scaffolds is a viable strategy for fabricating a suitable biomaterial that enhances bone tissue engineering applications.

Mechanical and biological properties of 3D printed bone tissue engineering scaffolds

Bone defects have historically represented a significant challenge in clinical practice, with traditional surgical intervention remaining the gold standard for their management. However, due to the problem of the origin of autologous and allogeneic bone and the complex and diverse bone defects, traditional surgical methods sometimes cannot meet the treatment needs and expectations of patients. The development of bone tissue engineering and 3D printing technology provides new ideas for bone defect repair. Ideal bioscaffold materials must have good mechanical properties, biocompatibility, osteoinduction and bone conduction capabilities. Additionally, factors such as degradation rate, appropriate porosity and a sustained antibacterial effect must be taken into account. The combination of 3D printing technology and synthetic composite biomaterial scaffolds has become a well-established approach in the treatment of complex bone defects, offering innovative solutions for bone defect repair. The combined application of seed cells, signalling factors and biological scaffolds is also beneficial to improve the therapeutic effect of complex bone defects. This article will therefore examine some of the most commonly used 3D printing technologies for biological scaffolds and the most prevalent bioscaffold materials suitable for 3D printing. An analysis will be conducted on the mechanical and biological properties of these materials to elucidate their respective advantages and limitations.

Progress of porous tantalum surface-modified biomaterial coatings in bone tissue engineering

Tantalum (Ta) metal has emerged as a prominent material within the realm of bone tissue engineering, owing to its favorable biocompatibility, commendable mechanical attributes, and notable biological properties such as osteoconductivity, osteoinductivity, and angiogenic potential. However, as clinical applications have expanded, Ta implants have unveiled a spectrum of limitations. Consequently, porous tantalum (PTa) has garnered escalating interest, attributable to its unique microstructural attributes, tunable mechanical characteristics, and inherent biocompatibility. Various methodologies have been proposed to modify the surface of PTa, with the aim of accelerating and enhancing osseous integration while fostering more robust osseointegration. Strategic surface modifications have the potential to augment the inherent advantages of PTa, thereby offering diverse avenues for exploration within the realm of surface effects on PTa. This review elucidates the ongoing research endeavors concerning diverse biomaterial coatings applied to PTa surfaces in the context of bone tissue engineering.

Mechanical behaviour of additive manufactured PEEK/HA porous structure for orthopaedic implants: Materials, structures and manufacturing processes

Polyether-ether-ketone (PEEK) composites represent one of the most promising approaches to overcoming the weak osseointegration associated with the bioinertness of PEEK, making them highly suitable for clinical translation. Implants with porous structures fabricated by additive manufacturing offer the potential for long-term stability by promoting bone ingrowth. However, despite the importance of porous design, there is still no consensus on the optimal approach for PEEK-based composites. Given the significance of permeability and mechanical properties as functional indicators closely linked to osseointegration, the effects of material composition, structural design, and manufacturing processes on the permeability and mechanical properties of PEEK/hydroxyapatite (HA) scaffolds were systematically investigated in this study. In terms of permeability, the axial permeability of scaffolds with different pore sizes and representative volume elements varied within the range of 0.3-24.8 × 10-9 m2. Among scaffolds with similar relative density, the Gyroid structure exhibited the lowest permeability, while the orthogonal structure demonstrated the highest. For cylindrical scaffolds, circumferential permeability decreased with increasing penetration depth, suggesting a potential reduction in bone ingrowth speed with depth. As for mechanical properties, the experimentally determined effective elastic modulus and effective yield strength of the scaffolds ranged from 675.1 MPa to 65.2 MPa and 43.5 MPa to 4.1 MPa, respectively. The permeability and mechanical properties of PEEK/HA scaffolds with relative density ranging from 35% to 50% were aligned with the those of human cancellous bone. Heat treatment at 240 °C for 120 min increased the crystallinity of PEEK to 37.2%, resulting in a substantial improvement in both the strength and stiffness of the scaffolds. However, excessive crystallinity led to brittle fracture, which in turn reduced the strength of the scaffolds. This study employed a systematic research approach to investigate how material composition, structural design, and manufacturing processes influence the mechanical properties and permeability of PEEK composite bone scaffolds, which are crucial for bone ingrowth. The results offered insights that support the design, manufacturing, and performance evaluation of PEEK-based porous implants.

Biomechanical properties of tetrahedral microstructure for design of the porous stem in total hip arthroplasty

Different internal strut architectures affect the biomechanical performance of porous lattice structures. This study aims to investigate these properties under various conditions using different methods.The finite element simulations of tetrahedral microstructures were conducted with varying internal strut thicknesses under different loads. The effective elastic modulus from compression tests aligned with the homogenization results. However, both the number and size of unit cells can influence the modulus at identical porosity levels. Smaller unit cell sizes demonstrated superior mechanical properties while utilizing less material.

Enhancing Osteogenesis and Mechanical Properties through Scaffold Design in 3D Printed Bone Substitutes

In the context of regenerative medicine, the design of scaffolds to possess excellent osteogenesis and appropriate mechanical properties has gained significant attention in bone tissue engineering. In this review, we categorized materials into metallic, inorganic, nonmetallic, organic polymer, and composite materials. This review provides a more integrated and multidimensional analysis of scaffold design for bone tissue engineering. Unlike previous works that often focus on single aspects, such as material type or fabrication technique, our review takes a broader approach. It analyzes the interaction between scaffold materials, 3D printing techniques, scaffold structural designs, modification methods, porosities, and pore sizes, and the composition of materials (particularly composite materials). Meanwhile, it focuses on their impacts on scaffolds' osteogenic potential and mechanical performance. This review also provides suggested ranges for porosity and pore size for different materials and outlines recommended surface modification methods. This approach not only consolidates current knowledge but also highlights the interdependencies among various factors affecting scaffold efficacy, offering deeper insights into optimization strategies tailored for specific clinical conditions. Furthermore, we introduce recent advancements in innovative 3D printing techniques and novel composite materials, which are rarely addressed in previous reviews, thereby providing a forward-looking perspective that informs future research directions and clinical applications.

Precision pore structure optimization of additive manufacturing porous tantalum scaffolds for bone regeneration: A proof-of-concept study

Currently, the treatment of bone defects in arthroplasty is a challenge in clinical practice. Nonetheless, commercially available orthopaedic scaffolds have shown limited therapeutic effects for large bone defects, especially for massiveand irregular defects. Additively manufactured porous tantalum, in particular, has emerged as a promising material for such scaffolds and is widely used in orthopaedics for its exceptional biocompatibility, osteoinduction, and mechanical properties. Porous tantalum has also exhibited unique advantages in personalised rapid manufacturing, which allows for the creation of customised scaffolds with complex geometric shapes for clinical applications at a low cost and high efficiency. However, studies on the effect of the pore structure of additively manufactured porous tantalum on bone regeneration have been rare. In this study, our group designed and fabricated a batch of precision porous tantalum scaffolds via laser powder bed fusion (LPBF) with pore sizes of 250 μm (Ta 250), 450 μm (Ta 450), 650 μm (Ta 650), and 850 μm (Ta 850). We then performed a series of in vitro experiments and observed that all four groups showed good biocompatibility. In particular, Ta 450 demonstrated the best osteogenic performance. Afterwards, our team used a rat bone defect model to determine the in vivo osteogenic effects. Based on micro-computed tomography and histology, we identified that Ta 450 exhibited the best bone ingrowth performance. Subsequently, sheep femur and hip defect models were used to further confirm the osteogenic effects of Ta 450 scaffolds. Finally, we verified the aforementioned in vitro and in vivo results via clinical application (seven patients waiting for revision total hip arthroplasty) of the Ta 450 scaffold. The clinical results confirmed that Ta 450 had satisfactory clinical outcomes up to the 12-month follow-up. In summary, our findings indicate that 450 μm is the suitable pore size for porous tantalum scaffolds. This study may provide a new therapeutic strategy for the treatment of massive, irreparable, and protracted bone defects in arthroplasty.

Patient-Specific 3-Dimensional-Printed Orthopedic Implants and Surgical Devices Are Potential Alternatives to Conventional Technology But Require Additional Characterization

Background

Three-dimensional (3D) printing allows anatomical models, guides, and implants to be easily customized to individual patients. Three-dimensional-printed devices can be used for a number of purposes in the medical field, yet there is a lack of data on the implementation of 3D-printed patient-specific implants and surgical guides in orthopedics. The objective of this review of the literature was to summarize the implementation of 3D printing in orthopedic surgery and identify areas that require more investigation.

Methods

PubMed and Scopus were used to perform a literature search. Articles that described 3D-printed patient-specific orthopedic implants or intraoperative guides were reviewed. Relevant articles were compiled and summarized to determine the role of personalized 3D-printed implants in orthopedic surgery.

Results

A total of 58 papers were selected. Overall, 3D-printed implants and surgical guides were shown to be effective in the selected cases. Patients with bone tumors benefitted from custom 3D-printed implants, which allow aggressive resection while preserving the function and mechanical stability of the limb. Eighty-one percent of devices were made using titanium, and 48% of articles reported the use of 3D printing in oncology. Some reported adverse events including wound dehiscence, periprosthetic infection, dislocation, and sequelae of malignancy. Regulations surrounding the use of 3D-printed surgical devices are ambiguous.

Conclusions

Three-dimensional-printed orthopedic implants and guides present an alternative to commercial devices, as they allow for customizability that is useful in cases of anatomic complexity. A variety of materials were surveyed across multiple subspecialties. Large controlled studies are necessary to compare patient-specific implants with the standard of care and evaluate their safety profiles over time.

Advances in the application and research of biomaterials in promoting bone repair and regeneration through immune modulation

With the ongoing development of osteoimmunology, increasing evidence indicates that the local immune microenvironment plays a critical role in various stages of bone formation. Consequently, modulating the immune inflammatory response triggered by biomaterials to foster a more favorable immune microenvironment for bone regeneration has emerged as a novel strategy in bone tissue engineering. This review first examines the roles of various immune cells in bone tissue injury and repair. Then, the contributions of different biomaterials, including metals, bioceramics, and polymers, in promoting osteogenesis through immune regulation, as well as their future development directions, are discussed. Finally, various design strategies, such as modifying the physicochemical properties of biomaterials and integrating bioactive substances, to optimize material design and create an immune environment conducive to bone formation, are explored. In summary, this review comprehensively covers strategies and approaches for promoting bone tissue regeneration through immune modulation. It offers a thorough understanding of current research trends in biomaterial-based immune regulation, serving as a theoretical reference for the further development and clinical application of biomaterials in bone tissue engineering.

Biomimetic multizonal scaffolds for the reconstruction of zonal articular cartilage in chondral and osteochondral defects

Chondral and osteochondral injuries are frequently encountered in clinical practice. However, articular cartilage has limited self-healing capacity due to its sophisticated zonal structure and avascular nature, introducing significant challenges to the restoration of chondral and osteochondral tissues after injury. Improperly repaired articular cartilage can lead to irreversible joint damage and increase the risk of osteoarthritis progression. Cartilage tissue engineering using stratified scaffolds with multizonal design to match the zonal structure of articular cartilage may help to meet the complex regeneration requirements of chondral and osteochondral tissues, and address the drawbacks experienced with single-phase scaffolds. Navigating the heterogeneity in matrix organisation and cellular composition across cartilage zones is a central consideration in multizonal scaffold design. With emphasis on recent advances in scaffold design and fabrication strategies, this review captures emerging approaches on biomimetic multizonal scaffolds for the reconstruction of zonal articular cartilage, including strategies on replicating native tissue structure through variations in fibre orientation, porous structure, and cell types. Exciting progress in this dynamic field has highlighted the tremendous potential of multizonal scaffolding strategies for regenerative medicine in the recreation of functional tissues.

Evaluation of biological performance of 3D printed trabecular porous tantalum spine fusion cage in large animal models

Background

The materials for artificial bone scaffolds have long been a focal point in biomaterials research. Tantalum, with its excellent bioactivity and tissue compatibility, has gradually become a promising alternative material. 3D printing technology shows unique advantages in designing complex structures, reducing costs, and providing personalized customization in the manufacture of porous tantalum fusion cages. Here we report the pre-clinical large animal (sheep) study on the newly developed 3D printed biomimetic trabecular porous tantalum fusion cage for assessing the long-term intervertebral fusion efficacy and safety.

Methods

Porous tantalum fusion cages were fabricated using laser powder bed fusion (LPBF) and chemical vapor deposition (CVD) methods. The fusion cages were characterized using scanning electron microscopy (SEM) and mechanical compression tests. Small-Tailed Han sheep served as the animal model, and the two types of fusion cages were implanted in the C3/4 cervical segments and followed for up to 12 months. Imaging techniques, including X-ray, CT scans, and Micro CT, were used to observe the bone integration of the fusion cages. Hard tissue sections were used to assess osteogenic effects and bone integration. The range of motion (ROM) of the motion segments was evaluated using a biomechanical testing machine. Serum biochemical indicators and pathological analysis of major organs were conducted to assess biocompatibility.

Results

X-ray imaging showed that both the 3D-printed and chemical vapor deposition porous tantalum fusion cages maintained comparable average intervertebral disc heights. Due to the presence of metal artifacts, CT and Micro CT imaging could not effectively analyze bone integration. Histomorphology data indicated that both the 3D-printed and chemical vapor deposition porous tantalum fusion cages exhibited similar levels of bone contact and integration at 3, 6, and 12 months, with bone bridging observed at 12 months. Both groups of fusion cages demonstrated consistent mechanical stability across all time points. Serum biochemistry showed no abnormalities, and no significant pathological changes were observed in the heart, liver, spleen, lungs, and kidneys.

Conclusion

This study confirms that 3D-printed and chemical vapor deposition porous tantalum fusion cages exhibit comparable, excellent osteogenic effects and long-term biocompatibility. Additionally, 3D-printed porous tantalum fusion cages offer unique advantages in achieving complex structural designs, low-cost manufacturing, and personalized customization, providing robust scientific support for future clinical applications.

The translational potential of this article

The translational potential of this paper is to use 3D printed biomimetic trabecular porous tantalum spine fusion cage with bone trabecular structure and validating its feasibility in large animal models (sheep). This study provides a basis for further research into the clinical application of the 3D printed biomimetic trabecular porous tantalum spine fusion cage.

Progress in the Application of Porous Tantalum Metal in Hip Joint Surgery

Porous tantalum metal is a new orthopedic implant material made of tantalum metal that has been processed by porous treatment. This material has various advantages, including high hardness, good ductility, good biocompatibility, and strong bone integration ability. Porous tantalum metal has performed well in clinical application, demonstrating excellent medium- to long-term curative effects. The use of implant products made of porous tantalum metal, such as porous tantalum rods, porous tantalum hip prostheses, and porous tantalum augments (MAs), is gradually increasing in the clinical application of hip surgery, and these products have achieved excellent therapeutic effects in the middle and late stages of various hip diseases. In recent years, the combined application of porous tantalum metal and three-dimenional (3D) printing technology to create personalized 3D-printed porous tantalum metal has led to new development directions for the treatment of complex hip joint surgical diseases. This review presents a summary of the application of porous tantalum metal in hip surgery in recent years, including clinical treatment effects and existing problems. In addition, the prospect of progress in this field is promoted.

Fabrication and characterization of nanohydroxyapatite/chitosan/decellularized placenta scaffold for bone tissue engineering applications

Novel biomaterials are necessary to fabricate biomimetic scaffolds for bone tissue engineering. In the present experiment, we aimed to fabricate and evaluate the osteogenic properties of nanohydroxyapatite/chitosan/decellularized placenta (nHA.Cs.dPL) composite scaffolds. The human placenta was decellularized (dPL), characterized, and digested in pepsin to form the hydrogel. nHA.Cs.dPL scaffolds were fabricated using salt leaching/freeze drying and evaluated for their morphology, chemical composition, swelling, porosity, degradation, mechanical strength, and biocompatibility. Saos-2 cells were seeded on scaffolds, and their osteogenic properties were investigated by evaluating alkaline phosphatase (ALP), osteocalcin (OCN), collagen type 1 (COL I) expression, and calcium deposition under osteogenic differentiation. The dPL was prepared with minimized DNA content and a well-preserved porous structure. Scaffolds were highly porous with interconnected pores and exhibited appropriate swelling and degradation rates supporting saos-2 cell attachment and proliferation. dPL improved scaffold physicochemical features and increased cell proliferation, ALP, OCN, COL I expression, and calcium deposition under osteogenic differentiation induction. nHA.Cs.dPL composite scaffolds provide a 3D microenvironment with superior physicochemical features that support saos-2 cell adhesion, proliferation, and osteogenic differentiation.

Effect of Artificial Saliva Modification on Corrosion Resistance of Metal Oxide Coatings on Co-Cr-Mo Dental Alloy

Surface modifications not only improve the corrosion resistance of Co-Cr-Mo dental alloys (Bego Wirobond® C) but also ensure their long-term performance and reliability in dental applications. This paper describes the preparation of single-layer TiO2-ZrO2 sol-gel coatings on the Co-Cr-Mo dental alloy using the method of dip-coating. The TiO2-ZrO2 sol-gel coatings were sintered at 300 and 500 °C. SEM analysis shows that sintering at 300 °C produces a uniform, slightly dense structure without micro-cracks, while sintering at 500 °C results in a denser structure with micro-cracks due to higher stress and shrinkage. EDS confirms that sintering temperature affects the elemental composition of the coating, with higher temperatures causing the volatilization or diffusion of Ti and Zr. Roughness measurements indicate that the Ra value increases with the sintering temperature, meeting dental application requirements. Electrochemical measurements by open-circuit potential, EIS, and cyclic potentiodynamic curves demonstrate that sintering temperature and saliva composition affect corrosion resistance, with NaF and mouthwashes (Listerine Total Care Teeth Protection® and Meridol®) generally increasing charge transfer resistance and double-layer capacitance. The ceramic TiO2-ZrO2 coatings significantly reduce pitting corrosion susceptibility at physiological and acidic pH, with the 500 °C sintered coating showing better protective properties. These findings highlight the potential of TiO2-ZrO2 coatings in enhancing the performance of Co-Cr-Mo dental alloys.

Materials for 3D printing in healthcare sector: A review

Additive Manufacturing (AM) encompasses various techniques creating intricate components from digital models. The aim of incorporating 3D printing (3DP) in the healthcare sector is to transform patient care by providing personalized solutions, improving medical procedures, fostering research and development, and ultimately optimizing the efficiency and effectiveness of healthcare delivery. This review delves into the historical beginnings of AM's 9 integration into medical contexts exploring various categories of AM methodologies and their roles within the medical sector. This survey also dives into the issue of material requirements and challenges specific to AM's medical applications. Emphasis is placed on how AM processes directly enhance human well-being. The primary focus of this paper is to highlight the evolution and incentives for cross-disciplinary AM applications, particularly in the realm of healthcare by considering their principle, materials and applications. It is designed for a diverse audience, including manufacturing professionals and researchers, seeking insights into this transformative technology's medical dimensions.

Engineered nanofibrillar collagen with tunable biophysical properties for myogenic, endothelial, and osteogenic cell guidance

A goal of regenerative engineering is the rational design of materials to restore the structure-function relationships that drive reparative programs in damaged tissues. Despite the widespread use of extracellular matrices for engineering tissues, their application has been limited by a narrow range of tunable features. The primary objective of this study is to develop a versatile platform for evaluating tissue-specific cellular interactions using Type I collagen scaffolds with highly tunable biophysical properties. The kinetics of collagen fibrillogenesis were modulated through a combination of varied shear rate and pH during neutralization, to achieve a broad range of fibril anisotropy, porosity, diameter, and storage modulus. The role that each of these properties play in guiding muscle, bone, and vascular cell types was comprehensively identified, and informed the in vitro generation of three distinct musculoskeletal engineered constructs. Myogenesis was highly regulated by smaller fibrils and larger storage moduli, endothelial inflammatory phenotype was predominantly guided by fibril anisotropy, and osteogenesis was enhanced by highly porous collagen with larger fibrils. This study introduces a novel approach for dynamically modulating Type I collagen materials and provides a robust platform for investigating cell-material interactions, offering insights for the future rational design of tissue-specific regenerative biomaterials. STATEMENT OF SIGNIFICANCE: The biophysical properties of regenerative materials facilitate key cell-substrate interactions that can guide the morphology, phenotype, and biological response of cells. In this study, we describe the fabrication of an engineered collagen hydrogel that can be modified to exhibit control over a wide range of biophysical features, including fibril organization and size, nanoscale porosity, and mechanics. We identified the unique combination of collagen features that optimally promote regenerative muscle, bone, and vascular cell types while also delineating the properties that hinder these same cellular responses. This study presents a highly accessible method to control the biophysical properties of collagen hydrogels that can be adapted for a broad range of tissue engineering and regenerative applications.

Characterisation of 3D-printed acetabular hip implants

Three-dimensional printing is a rapidly growing manufacturing method for orthopaedic implants and it is currently thriving in several other engineering industries. It enables the variation of implant design and the construction of complex structures which can be exploited in orthopaedics and other medical sectors. In this review, we develop the vocabulary to characterise 3D printing in orthopaedics from terms defined by industries employing 3D printing, and by fully examining a 3D-printed off-the-shelf acetabular cup (Fig. 1). This is a commonly used 3D-printed implant in orthopaedics, and it exhibits a range of prominent features brought about by 3D printing. The key features and defects of the porous and dense regions of the implant are clarified and discussed in depth to determine reliable definitions and a common understanding of characteristics of 3D printing between engineers and medical experts in orthopaedics. Despite the extensive list of terminology derived here, it is clear significant gaps exist in the knowledge of this field. Therefore, it is necessary for continued investigations of unused implants, but perhaps more significantly, examining those in vivo and retrieved to understand their long-term impact on patients and the effects of certain features (e.g. surface-adhered particles). Analyses of this kind will establish an understanding of 3D printing in orthopaedics and additionally it will help to update the regulatory approach to this new technology.

Designing and additive manufacturing of talus implant for post-traumatic talus avascular necrosis: a case study

New technologies in additive manufacturing and patient-specific CT-based custom implant designs make it possible for previously unimaginable salvage and limb-sparing operations a practical reality. This study presents the design and fabrication of a lattice-structured implant for talus replacement surgery. Our primary case involved a young adult patient who had sustained severe damage to the talus, resulting in avascular necrosis and subsequent bone collapse. This condition caused persistent and debilitating pain, leading the medical team to consider amputation of the left foot at the ankle level as a last resort. Instead, we proposed a Ti6Al4V-based patient-specific implant with lattice structure specifically designed for pan-talar fusion. Finite element simulation is conducted to estimate its performance. To ensure its mechanical integrity, uniaxial compression experiments were conducted. The implant was produced using selective laser melting technology, which allowed for precise and accurate construction of the unique lattice structure. The patient underwent regular monitoring for a period of 24 months. At 2-years follow-up the patient successfully returned to activities without complication. The patient's functional status was improved, limb shortening was minimized.

Teicoplanin-Decorated Reduced Graphene Oxide Incorporated Silk Protein Hybrid Hydrogel for Accelerating Infectious Diabetic Wound Healing and Preventing Diabetic Foot Osteomyelitis

Developing hybrid hydrogel dressings with anti-inflammatory, antioxidant, angiogenetic, and antibiofilm activities with higher bone tissue penetrability to accelerate diabetic wound healing and prevent diabetic foot osteomyelitis (DFO) is highly desirable in managing diabetic wounds. Herein, the glycopeptide teicoplanin is used for the first time as a green reductant to chemically reduce graphene oxide (GO). The resulting teicoplanin-decorated reduced graphene oxide (rGO) is incorporated into a mixture of silk proteins (SP) and crosslinked with genipin to yield a physicochemically crosslinked rGO-SP hybrid hydrogel. This hybrid hydrogel exhibits high porosity, self-healing, shear-induced thinning, increased cell proliferation and migration, and mechanical properties suitable for tissue engineering. Moreover, the hybrid hydrogel eradicates bacterial biofilms with a high penetrability index in agar and hydroxyapatite disks covered with biofilms, mimicking bone tissue. In vivo, the hybrid hydrogel accelerates the healing of noninfected wounds in a diabetic rat and infected wounds in a diabetic mouse by upregulating anti-inflammatory cytokines and downregulating matrix metalloproteinase-9, promoting M2 macrophage polarization and angiogenesis. The implantation of hybrid hydrogel into the infected site of mouse tibia improves bone regeneration. Hence, the rGO-SP hybrid hydrogel can be a promising wound dressing for treating infectious diabetic wounds, providing a further advantage in preventing DFO.

Platelet-rich fibrin (PRF) modified nano-hydroxyapatite/chitosan/gelatin/alginate scaffolds increase adhesion and viability of human dental pulp stem cells (DPSC) and osteoblasts derived from DPSC

Bone tissue regeneration strategies have incorporated the use of natural polymers, such as hydroxyapatite (nHA), chitosan (CH), gelatin (GEL), or alginate (ALG). Additionally, platelet concentrates, such as platelet-rich fibrin (PRF) have been suggested to improve scaffold biocompatibility. This study aimed to develop scaffolds composed of nHA, GEL, and CH, with or without ALG and lyophilized PRF, to evaluate the scaffold's properties, growth factor release, and dental pulp stem cells (DPSC), and osteoblast (OB) derived from DPSC viability. Four scaffold variations were synthesized and lyophilized. Then, degradation, swelling profiles, and morphological analysis were performed. Furthermore, PDGF-BB and FGF-B growth factors release were quantified by ELISA, and cytotoxicity and cell viability were evaluated. The swelling and degradation profiles were similar in all scaffolds, with pore sizes ranging between 100 and 250 μm. FGF-B and PDGF-BB release was evidenced after 24 h of scaffold immersion in cell culture medium. DPSC and OB-DPSC viability was notably increased in PRF-supplemented scaffolds. The nHA-CH-GEL-PRF scaffold demonstrated optimal physical-biological characteristics for stimulating DPSC and OB-DPSC cell viability. These results suggest lyophilized PRF improves scaffold biocompatibility for bone tissue regeneration purposes.

Anodic Production and Characterization of Biomimetic Oxide Layers on Grade 4 Titanium for Medical Applications

Biomaterials are the basis for the development of medicine because they allow safe contact with a living organism. The aim of this work was to produce innovative oxide layers with a microporous structure on the surface of commercially pure titanium Grade 4 (CpTi G4) and to characterize their properties as drug carriers. The anodization of the CpTi G4 subjected to mechanical grinding and electrochemical polishing was carried out in a solution of 1M ethylene glycol with the addition of 40 g of ammonium fluoride at a voltage of 20 V for 2, 18, 24, and 48 h at room temperature. It was found that the longer the anodization time, the greater the number of pores formed on the CpTi G4 surface as revealed using the FE-SEM method, and the greater the surface roughness determined in profilometric tests. As the anodizing time increases, the amount of the drug in the form of gentamicin sulfate incorporated into the resulting pores decreases. The most favorable drug release kinetics profile determined via UV-VIS absorption spectroscopy was found for the CpTi G4 anodized for 2 h.

3D-printed porous tantalum artificial bone scaffolds: fabrication, properties, and applications

Porous tantalum scaffolds offer a high degree of biocompatibility and have a low friction coefficient. In addition, their biomimetic porous structure and mechanical properties, which closely resemble human bone tissue, make them a popular area of research in the field of bone defect repair. With the rapid advancement of additive manufacturing, 3D-printed porous tantalum scaffolds have increasingly emerged in recent years, offering exceptional design flexibility, as well as facilitating the fabrication of intricate geometries and complex pore structures that similar to human anatomy. This review provides a comprehensive description of the techniques, procedures, and specific parameters involved in the 3D printing of porous tantalum scaffolds. Concurrently, the review provides a summary of the mechanical properties, osteogenesis and antibacterial properties of porous tantalum scaffolds. The use of surface modification techniques and the drug carriers can enhance the characteristics of porous tantalum scaffolds. Accordingly, the review discusses the application of these porous tantalum materials in clinical settings. Multiple studies have demonstrated that 3D-printed porous tantalum scaffolds exhibit exceptional corrosion resistance, biocompatibility, and osteogenic properties. As a result, they are considered highly suitable biomaterials for repairing bone defects. Despite the rapid development of 3D-printed porous tantalum scaffolds, they still encounter challenges and issues when used as bone defect implants in clinical applications. Ultimately, a concise overview of the primary challenges faced by 3D-printed porous tantalum scaffolds is offered, and corresponding insights to promote further exploration and advancement in this domain are presented.

3D printing nacre powder/sodium alginate scaffold loaded with PRF promotes bone tissue repair and regeneration

Bone defects are a common complication of bone diseases, which often affect the quality of life and mental health of patients. The use of biomimetic bone scaffolds loaded with bioactive substances has become a focal point in the research on bone defect repair. In this study, composite scaffolds resembling bone tissue were created using nacre powder (NP) and sodium alginate (SA) through 3D printing. These scaffolds exhibit several physiological structural and mechanical characteristics of bone tissue, such as suitable porosity, an appropriate pore size, applicable degradation performance and satisfying the mechanical requirements of cancellous bone, etc. Then, platelet-rich fibrin (PRF), containing a mass of growth factors, was loaded on the NP/SA scaffolds. This was aimed to fully maximize the synergistic effect with NP, thereby accelerating bone tissue regeneration. Overall, this study marks the first instance of preparing a bionic bone structure scaffold containing NP by 3D printing technology, which is combined with PRF to further accelerate bone regeneration. These findings offer a new treatment strategy for bone tissue regeneration in clinical applications.

3D printed osteochondral scaffolds: design strategies, present applications and future perspectives

Articular osteochondral (OC) defects are a global clinical problem characterized by loss of full-thickness articular cartilage with underlying calcified cartilage through to the subchondral bone. While current surgical treatments can relieve pain, none of them can completely repair all components of the OC unit and restore its original function. With the rapid development of three-dimensional (3D) printing technology, admirable progress has been made in bone and cartilage reconstruction, providing new strategies for restoring joint function. 3D printing has the advantages of fast speed, high precision, and personalized customization to meet the requirements of irregular geometry, differentiated composition, and multi-layered boundary layer structures of joint OC scaffolds. This review captures the original published researches on the application of 3D printing technology to the repair of entire OC units and provides a comprehensive summary of the recent advances in 3D printed OC scaffolds. We first introduce the gradient structure and biological properties of articular OC tissue. The considerations for the development of 3D printed OC scaffolds are emphatically summarized, including material types, fabrication techniques, structural design and seed cells. Especially from the perspective of material composition and structural design, the classification, characteristics and latest research progress of discrete gradient scaffolds (biphasic, triphasic and multiphasic scaffolds) and continuous gradient scaffolds (gradient material and/or structure, and gradient interface) are summarized. Finally, we also describe the important progress and application prospect of 3D printing technology in OC interface regeneration. 3D printing technology for OC reconstruction should simulate the gradient structure of subchondral bone and cartilage. Therefore, we must not only strengthen the basic research on OC structure, but also continue to explore the role of 3D printing technology in OC tissue engineering. This will enable better structural and functional bionics of OC scaffolds, ultimately improving the repair of OC defects.

Additively Manufactured Zn-2Mg Alloy Porous Scaffolds with Customizable Biodegradable Performance and Enhanced Osteogenic Ability

The combination of bioactive Zn-2Mg alloy and additively manufactured porous scaffold is expected to achieve customizable biodegradable performance and enhanced bone regeneration. Herein, Zn-2Mg alloy scaffolds with different porosities, including 40% (G-40-2), 60% (G-60-2), and 80% (G-80-2), and different unit sizes, including 1.5 mm (G-60-1.5), 2 mm (G-60-2), and 2.5 mm (G-60-2.5), are manufactured by a triply periodic minimal surface design and a reliable laser powder bed fusion process. With the same unit size, compressive strength (CS) and elastic modulus (EM) of scaffolds substantially decrease with increasing porosities. With the same porosity, CS and EM just slightly decrease with increasing unit sizes. The weight loss after degradation increases with increasing porosities and decreasing unit sizes. In vivo tests indicate that Zn-2Mg alloy scaffolds exhibit satisfactory biocompatibility and osteogenic ability. The osteogenic ability of scaffolds is mainly determined by their physical and chemical characteristics. Scaffolds with lower porosities and smaller unit sizes show better osteogenesis due to their suitable pore size and larger surface area. The results indicate that the biodegradable performance of scaffolds can be accurately regulated on a large scale by structure design and the additively manufactured Zn-2Mg alloy scaffolds have improved osteogenic ability for treating bone defects.

Metallic Materials for Bone Repair

Repair of large bone defects caused by trauma or disease poses significant clinical challenges. Extensive research has focused on metallic materials for bone repair because of their favorable mechanical properties, biocompatibility, and manufacturing processes. Traditional metallic materials, such as stainless steel and titanium alloys, are widely used in clinics. Biodegradable metallic materials, such as iron, magnesium, and zinc alloys, are promising candidates for bone repair because of their ability to degrade over time. Emerging metallic materials, such as porous tantalum and bismuth alloys, have gained attention as bone implants owing to their bone affinity and multifunctionality. However, these metallic materials encounter many practical difficulties that require urgent improvement. This article systematically reviews and analyzes the metallic materials used for bone repair, providing a comprehensive overview of their morphology, mechanical properties, biocompatibility, and in vivo implantation. Furthermore, the strategies and efforts made to address the short-comings of metallic materials are summarized. Finally, the perspectives for the development of metallic materials to guide future research and advancements in clinical practice are identified.

The effect of nodal connectivity and strut density within stochastic titanium scaffolds on osteogenesis

Modern orthopaedic implants use lattice structures that act as 3D scaffolds to enhance bone growth into and around implants. Stochastic scaffolds are of particular interest as they mimic the architecture of trabecular bone and can combine isotropic properties and adjustable structure. The existing research mainly concentrates on controlling the mechanical and biological performance of periodic lattices by adjusting pore size and shape. Still, less is known on how we can control the performance of stochastic lattices through their design parameters: nodal connectivity, strut density and strut thickness. To elucidate this, four lattice structures were evaluated with varied strut densities and connectivity, hence different local geometry and mechanical properties: low apparent modulus, high apparent modulus, and two with near-identical modulus. Pre-osteoblast murine cells were seeded on scaffolds and cultured in vitro for 28 days. Cell adhesion, proliferation and differentiation were evaluated. Additionally, the expression levels of key osteogenic biomarkers were used to assess the effect of each design parameter on the quality of newly formed tissue. The main finding was that increasing connectivity increased the rate of osteoblast maturation, tissue formation and mineralisation. In detail, doubling the connectivity, over fixed strut density, increased collagen type-I by 140%, increased osteopontin by 130% and osteocalcin by 110%. This was attributed to the increased number of acute angles formed by the numerous connected struts, which facilitated the organization of cells and accelerated the cell cycle. Overall, increasing connectivity and adjusting strut density is a novel technique to design stochastic structures which combine a broad range of biomimetic properties and rapid ossification.