Osseointegration Improvement of Co-Cr-Mo Alloy Produced by Additive Manufacturing

Bioprinted hydrogels in bone regeneration: a bibliometric analysis

Background

The application of bioprinted hydrogels in the field of bone regeneration is garnering increasing attention. The objective of this study is to provide a comprehensive overview of the current research status, hotspots and research directions in this field through bibliometric methods, and to predict the development trend of this field.

Methods

A search was conducted on 27 December 2024, for papers published on the Web of Science from 2010 to 2025. We used the bibliometrix package in the software program R to analyze the retrieved data and VOSviewer and CiteSpace to visualize hotspots and research trends in bioprinted hydrogels for bone regeneration.

Results

We identified and reviewed 684 articles published in this field between 2010 and 2025. A total of 811 institutions and 1,166 researchers from 41 countries/regions contributed to these publications. Among them, China led in terms of the number of articles published, single-country publications (SCP), and multi-country publications (MCP). Our bibliometric-based visualization analysis revealed that the mechanical properties and osteogenic differentiation capacity of biomaterials have been a focal research topic over the past decade, while emerging research has also concentrated on the in vitro fabrication of stem cells for bone regeneration and osteogenic differentiation, particularly the precise application of in situ stem cell-loaded bioprinted organoids.

Conclusion

This study provides an in-depth analysis of the research trajectory in the application of bioprinted hydrogels for bone regeneration. The number of research papers in this field is increasing annually, and the main research hotspots include bone regeneration, 3D printing, scaffolds, and hydrogels. Future research directions may focus on gelatin, additive manufacturing, and growth factors. Additionally, international collaboration is essential to enhance the effectiveness of bioprinted hydrogels in bone regeneration applications.

Biomaterials for bone tissue engineering: achievements to date and future directions

Advancement in medicine and technology has resulted into prevention of countless deaths and increased life span. However, it is important to note that, the modern lifestyle has altered the food habits, witnessed increased life-style stresses and road accidents leading to several health complications and one of the primary victims is the bone health. More often than ever, healthcare professionals encounter cases of massive bone fracture, bone loss and generation of critical sized bone defects. Surgical interventions, through the use of bone grafting techniques are necessary in such cases. Natural bone grafts (allografts, autografts and xenografts) however, have major drawbacks in terms of delayed rehabilitation, lack of appropriate donors, infection and morbidity that shifted the focus of several investigators to the direction of synthetic bone grafts. By employing biomaterials that are based on bone tissue engineering (BTE), synthetic bone grafts provide a more biologically acceptable approach to establishing the phases of bone healing. In BTE, various materials are utilized to support and enhance bone regeneration. Biodegradable polymers like poly-(lactic acid), poly-(glycolic acid), and poly-(ϵ-caprolactone) are commonly used for their customizable mechanical properties and ability to degrade over time, allowing for natural bone growth. PEG is employed in hydrogels to promote cell adhesion and growth. Ceramics, such as hydroxyapatite and beta-tricalcium phosphate (β-TCP) mimic natural bone mineral and support bone cell attachment, withβ-TCP gradually resorbing as new bone forms. Composite materials, including polymer-ceramic and polymer-glasses, combine the benefits of both polymers and ceramics/glasses to offer enhanced mechanical and biological properties. Natural biomaterials like collagen, gelatin, and chitosan provide a natural matrix for cell attachment and tissue formation, with chitosan also offering antimicrobial properties. Hybrid materials such as decellularized bone matrix retain natural bone structure and biological factors, while functionalized scaffolds incorporate growth factors or bioactive molecules to further stimulate bone healing and integration. The current review article provides the critical insights on several biomaterials that could yield to revolutionary improvements in orthopedic medical fields. The introduction section of this article focuses on the statistical information on the requirements of various bone scaffolds globally and its impact on economy. In the later section, anatomy of the human bone, defects and diseases pertaining to human bone, and limitations of natural bone scaffolds and synthetic bone scaffolds were detailed. Biopolymers, bioceramics, and biometals-based biomaterials were discussed in further depth in the sections that followed. The article then concludes with a summary addressing the current trends and the future prospects of potential bone transplants.

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.

Personalized lattice-structured prosthesis as a graftless solution for mandible reconstruction and prosthetic restoration: A finite element analysis

Oral cavity tumors are a prevalent cause of mandible reconstruction surgeries. The mandible is vital for functions like oralization, respiration, mastication, and deglutition. Current mandible reconstruction methods have low success rates due to complications like plate fracture or exposure, infections, and screw loosening. Autogenous bone grafts are commonly used but carry the risk of donor region morbidity. Despite technological advances, an ideal solution for mandible reconstruction remains elusive. Additive manufacturing in medicine offers personalized prosthetics from patient-specific medical images, allowing for the creation of porous structures with tailored mechanical properties that mimic bone properties. This study compared a commercial reconstruction plate with a lattice-structured personalized prosthesis under different biting and osseointegration conditions using Finite Element Analysis. Patient-specific images were obtained from an individual who underwent mandible reconstruction with a commercial plate and suffered from plate fracture by fatigue after 26 months. Compared to the commercial plate, the maximum von Mises equivalent stress was significantly lowered for the personalized prosthesis, hindering a possible fatigue fracture. The equivalent von Mises strains found in bone were within bone maintenance and remodeling intervals. This work introduces a design that doesn't require grafts for large bone defects and allows for dental prosthesis addition without the need for implants.

Optimization of Cobalt-Chromium (Co-Cr) Scaffolds for Bone Tissue Engineering in Endocrine, Metabolic and Immune Disorders

Approximately 50% of the adult global population is projected to suffer from some form of metabolic disease by 2050, including metabolic syndrome and diabetes mellitus. At the same time, this trend indicates a potential increase in the number of patients who will be in need of implant-supported reconstructions of specific bone regions subjected to inflammatory states. Moreover, physiological conditions associated with dysmetabolic subjects have been suggested to contribute to the severity of bone loss after bone implant insertion. However, there is a perspective evidence strengthening the hypothesis that custom-fabricated bioengineered scaffolds may produce favorable bone healing effects in case of altered endocrine or metabolic conditions. This perspective review aims to share a comprehensive knowledge of the mechanisms implicated in bone resorption and remodelling processes, which have driven researchers to develop metallic implants as the cobalt-chromium (Co-Cr) bioscaffolds, presenting optimized geometries that interact in an effective way with the osteogenetic precursor cells, especially in the cases of perturbed endocrine or metabolic conditions.

Surface modification of titanium implants with Mg-containing coatings to promote osseointegration

Titanium (Ti) and Ti alloys are commonly used in dental implants, which have good biocompatibility, mechanical strength, processability, and corrosion resistance. However, the surface inertia of Ti implants leads to delayed integration of Ti and new bone, as well as problems such as aseptic loosening and inadequate osseointegration. Magnesium (Mg) ions can promote bone regeneration, and many studies have used Mg-containing materials to modify the Ti implant surface. This systematic review summarizes the methods, effects, and clinical applications of surface modification of Ti implants with Mg-containing coatings. Database collection was completed on Janury 1, 2023, and a total of 29 relevant studies were ultimately included. Mg can be compounded with different materials and coated to the surface of Ti implants using different methods. In vitro and in vivo experiments have shown that Mg-containing coatings promote cell adhesion and osteogenic differentiation. On the one hand, the surface roughness of implants increases with the addition of Mg-containing coatings, which is thought to have an impact on the osseointegration of the implant. On the other hand, Mg ions promote cell attachment through binding interactions between the integrin family and FAK-related signaling pathways. And Mg ions could induce osseointegration by activating PI3K, Notch, ERK/c-Fos, BMP-4-related signaling pathways and TRPM7 protein channels. Overall, Mg-based coatings show great potential for the surface modification of Ti implants to promote osseointegration. STATEMENT OF SIGNIFICANCE: The inertia surface of titanium (Ti) implants leads to delayed osseointegration. Magnesium (Mg) ions, known for promoting bone regeneration, have been extensively studied to modify the surface of Ti implants. However, no consensus has been reached on the appropriate processing methods, surface roughness and effective concentration of Mg-containing coatings for osseointegration. This systematic review focus on the surface modification of Ti implants with Mg-containing compounds, highlighting the effects of Mg-containing coatings on the surface properties of Ti implants and its associated mechanisms. Besides, we also provide an outlook on future directions to promote the clinical application of Mg-modified implants.

Emerging Strategies to Improve the Design and Manufacturing of Biocompatible Therapeutic Materials

Currently, the field of medicine is drastically advancing, mainly due to the progress in emerging areas such as nanomedicine, regenerative medicine, and personalized medicine. For example, the development of novel drug delivery systems in the form of nanoparticles is improving the liberation, absorption, distribution, metabolism, and excretion (LADME) properties of the derived formulations, with a consequent enhancement in the treatment efficacy, a reduction in the secondary effects, and an increase in compliance with the dosage guidelines. Additionally, the use of biocompatible scaffolds is translating into the possibility of regenerating biological tissues. Personalized medicine is also benefiting from the advantages offered by additive manufacturing. However, all these areas have in common the need to develop novel materials or composites that fulfill the requirements of each application. Therefore, the aim of this Special Issue was to identify novel materials/composites that have been developed with specific characteristics for the designed biomedical application.

In Vivo Evaluation of Collagen and Chitosan Scaffold, Associated or Not with Stem Cells, in Bone Repair

Natural polymers are increasingly being used in tissue engineering due to their ability to mimic the extracellular matrix and to act as a scaffold for cell growth, as well as their possible combination with other osteogenic factors, such as mesenchymal stem cells (MSCs) derived from dental pulp, in an attempt to enhance bone regeneration during the healing of a bone defect. Therefore, the aim of this study was to analyze the repair of mandibular defects filled with a new collagen/chitosan scaffold, seeded or not with MSCs derived from dental pulp. Twenty-eight rats were submitted to surgery for creation of a defect in the right mandibular ramus and divided into the following groups: G1 (control group; mandibular defect with clot); G2 (defect filled with dental pulp mesenchymal stem cells-DPSCs); G3 (defect filled with collagen/chitosan scaffold); and G4 (collagen/chitosan scaffold seeded with DPSCs). The analysis of the scaffold microstructure showed a homogenous material with an adequate percentage of porosity. Macroscopic and radiological examination of the defect area after 6 weeks post-surgery revealed the absence of complete repair, as well as absence of signs of infection, which could indicate rejection of the implants. Histomorphometric analysis of the mandibular defect area showed that bone formation occurred in a centripetal fashion, starting from the borders and progressing towards the center of the defect in all groups. Lower bone formation was observed in G1 when compared to the other groups and G2 exhibited greater osteoregenerative capacity, followed by G4 and G3. In conclusion, the scaffold used showed osteoconductivity, no foreign body reaction, malleability and ease of manipulation, but did not obtain promising results for association with DPSCs.

Collagen-chitosan-hydroxyapatite composite scaffolds for bone repair in ovariectomized rats

Lesions with bone loss may require autologous grafts, which are considered the gold standard; however, natural or synthetic biomaterials are alternatives that can be used in clinical situations that require support for bone neoformation. Collagen and hydroxyapatite have been used for bone repair based on the concept of biomimetics, which can be combined with chitosan, forming a scaffold for cell adhesion and growth. However, osteoporosis caused by gonadal hormone deficiency can thus compromise the expected results of the osseointegration of scaffolds. The aim of this study was to investigate the osteoregenerative capacity of collagen (Co)/chitosan (Ch)/hydroxyapatite (Ha) scaffolds in rats with hormone deficiency caused by experimental bilateral ovariectomy. Forty-two rats were divided into non-ovariectomized (NO) and ovariectomized (O) groups, divided into three subgroups: control (empty defect) and two subgroups receiving collagen/chitosan/hydroxyapatite scaffolds prepared using different methods of hydroxyapatite incorporation, in situ (CoChHa1) and ex situ (CoChHa2). The defect areas were submitted to macroscopic, radiological, and histomorphometric analysis. No inflammatory processes were found in the tibial defect area that would indicate immune rejection of the scaffolds, thus confirming the biocompatibility of the biomaterials. Bone formation starting from the margins of the bone defect were observed in all rats, with a greater volume in the NO groups, particularly the group receiving CoChHa2. Less bone formation was found in the O subgroups when compared to the NO. In conclusion, collagen/chitosan/hydroxyapatite scaffolds stimulate bone growth in vivo but abnormal conditions of bone fragility caused by gonadal hormone deficiency may have delayed the bone repair process.

Zinc-Based Biodegradable Materials for Orthopaedic Internal Fixation

Traditional inert materials used in internal fixation have caused many complications and generally require removal with secondary surgeries. Biodegradable materials, such as magnesium (Mg)-, iron (Fe)- and zinc (Zn)-based alloys, open up a new pathway to address those issues. During the last decades, Mg-based alloys have attracted much attention by researchers. However, the issues with an over-fast degradation rate and release of hydrogen still need to be overcome. Zn alloys have comparable mechanical properties with traditional metal materials, e.g., titanium (Ti), and have a moderate degradation rate, potentially serving as a good candidate for internal fixation materials, especially at load-bearing sites of the skeleton. Emerging Zn-based alloys and composites have been developed in recent years and in vitro and in vivo studies have been performed to explore their biodegradability, mechanical property, and biocompatibility in order to move towards the ultimate goal of clinical application in fracture fixation. This article seeks to offer a review of related research progress on Zn-based biodegradable materials, which may provide a useful reference for future studies on Zn-based biodegradable materials targeting applications in orthopedic internal fixation.

The Antibacterial Activity Comparison between Novel Carbon-Based Nanofilm Coated Titanium Alloy and Co-Cr-Mo Alloy

Objective. The purpose of this study was to reveal the antibacterial activity of carbon-based nanofilm titanium alloy. Methods. The experiments were performed both in vitro and in vivo of animals using two circular-piece test specimens of the same specification, which were made from carbon-based nanofilm coated titanium alloy and commonly used in artificial joints Co-Cr-Mo alloy, respectively. In the in vitro experiments, the two test specimens were cocultured with standard strains of Staphylococcus aureus and Escherichia coli, and the antibacterial properties of the two test specimens were evaluated via inhibition zone size, scanning electron microscopy, fluorescence staining, colony forming unit count, and others; the cytotoxicities of the two test specimens were evaluated by coculturing and them with rabbit bone marrow mesenchymal stem cells (BMSCs). In the in vivo experiments, the two test specimens were implanted in the muscle tissue of experimental rabbits to evaluate their histocompatibilities. Results. Both in vitro cocultures of the carbon-based nanofilm titanium alloy and the Co-Cr-Mo alloy with Staphylococcus aureus and Escherichia coli failed to form inhibition zone. However, some biofilms were observed on the surface of the Co-Cr-Mo alloy. Fewer bacteria adhered to the carbon-based nanofilm titanium alloy can be observed via scanning electron microscopy and fluorescence staining techniques. Meanwhile, the colony forming counts showed that, compared with the Co-Cr-Mo alloy, the carbon-based nanofilm titanium alloy had fewer bacteria adhered ( $P<0.05$ ). After coculture of the two test specimens with rabbit BMSCs, there was no significant difference in cell count, and both cell counts showed no cytotoxicity. In the in vivo experiment of animals, there are relatively fewer giant cells and better histocompatibility in tissues near the carbon-based nanofilm titanium alloy. Conclusion. Compared with Co-Cr-Mo alloy, the novel carbon-based nanofilm titanium alloy enjoys stronger in vitro antibacterial activity and better in vivo histocompatibility.