Biomechanical analysis of the osseointegration of porous tantalum implants

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.

Comprehensive Overview of Interface Strategies in Implant Osseointegration

With the improvement of implant design and the expansion of application scenarios, orthopedic implants have become a common surgical option for treating fractures and end‐stage osteoarthritis. Their common goal is rapidly forming and long‐term stable osseointegration. However, this fixation effect is limited by implant surface characteristics and peri‐implant bone tissue activity. Therefore, this review summarizes the strategies of interface engineering (osteogenic peptides, growth factors, and metal ions) and treatment methods (porous nanotubes, hydrogel embedding, and other load‐release systems) through research on its biological mechanism, paving the way to achieve the adaptation of both and coordination between different strategies. With the transition of the osseointegration stage, interface engineering strategies have demonstrated varying therapeutic effects. Especially, the activity of osteoblasts runs almost through the entire process of osseointegration, and their physiological activities play a dominant role in bone formation. Furthermore, diseases impacting bone metabolism exacerbate the difficulty of achieving osseointegration. This review aims to assist future research on osseointegration engineering strategies to improve implant‐bone fixation, promote fracture healing, and enhance post‐implantation recovery.

The effect of porous compliance bushings in a dental implant on the distribution of occlusal loads

Porous dental implants are clinically used, but the mechanism of load distribution for stepped implant shaft surrounded by compliance bushings is still not known, especially for different bone conditions. The aim of the study was to assess the impact of the design of a dental implant with compliance bushings (CBs) on the occlusal load distribution during primary and secondary stability using finite element simulation (FEA), with a distinction between low and high quality cervical support under primary stability. The FEA of the oblique occlusal load transfer (250 N; 45°) was carried out for implants under variable bone conditions. The stepped shaft in the intermediate part of the dental implant was surrounded by CBs with an increasing modulus of elasticity of 2, 10 and 50 GPa. With a smaller Young's modulus of the bushings the increase of stress in the trabecular bone indicated that more bone tissue can be protected against disuse. The beneficial effect for the trabecular bone derived from the reduction of the stiffness of the bushings in relation to the loss of the implant's load bearing ability can be assessed using the FEM method.

Bioactivity and antibacterial properties of zinc-doped Ta2O5nanorods on porous tantalum surface

This paper focuses on the preparation of Zn2+-doped Ta2O5nanorods on porous tantalum using the hydrothermal method. Porous tantalum is widely used in biomedical materials due to its excellent elastic modulus and biological activity. Porous tantalum has an elastic modulus close to that of human bone, and its large specific surface area is conducive to promoting cell adhesion. Zinc is an important component of human bone, which not only has spectral bactericidal properties, but also has no cytotoxicity. The purpose of this study is to provide a theoretical basis for the surface modification of porous tantalum and to determine the best surface modification method. The surface structure of the sample was characterized by x-ray diffractometer, x-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, and the Zn-doped Ta2O5nanorods are characterized by antibacterial test, MTT test, ICP and other methods. The sample has good antibacterial properties and no cytotoxicity. The results of this study have potential implications for the development of new and improved biomedical materials.

Strain-rate-dependent plasticity of Ta-Cu nanocomposites for therapeutic implants

Recently, Ta/Cu nanocomposites have been widely used in therapeutic medical devices due to their excellent bioactivity and biocompatibility, antimicrobial property, and outstanding corrosion and wear resistance. Since mechanical yielding and any other deformation in the patient's body during treatment are unacceptable in medicine, the characterization of the mechanical behavior of these nanomaterials is of great importance. We focus on the microstructural evolution of Ta/Cu nanocomposite samples under uniaxial tensile loading conditions at different strain rates using a series of molecular dynamics simulations and compare to the reference case of pure Ta. The results show that the increase in dislocation density at lower strain rates leads to the significant weakening of the mechanical properties. The strain rate-dependent plastic deformation mechanism of the samples can be divided into three main categories: phase transitions at the extreme strain rates, dislocation slip/twinning at lower strain rates for coarse-grained samples, and grain-boundary based activities for the finer-grained samples. Finally, we demonstrate that the load transfer from the Ta matrix to the Cu nanoparticles via the interfacial region can significantly affect the plastic deformation of the matrix in all nanocomposite samples. These results will prove useful for the design of therapeutic implants based on Ta/Cu nanocomposites.

Preparation, modification, and clinical application of porous tantalum scaffolds

Porous tantalum (Ta) implants have been developed and clinically applied as high-quality implant biomaterials in the orthopedics field because of their excellent corrosion resistance, biocompatibility, osteointegration, and bone conductivity. Porous Ta allows fine bone ingrowth and new bone formation through the inner space because of its high porosity and interconnected pore structure. It contributes to rapid bone integration and long-term stability of osseointegrated implants. Porous Ta has excellent wetting properties and high surface energy, which facilitate the adhesion, proliferation, and mineralization of osteoblasts. Moreover, porous Ta is superior to classical metallic materials in avoiding the stress shielding effect, minimizing the loss of marginal bone, and improving primary stability because of its low elastic modulus and high friction coefficient. Accordingly, the excellent biological and mechanical properties of porous Ta are primarily responsible for its rising clinical translation trend. Over the past 2 decades, advanced fabrication strategies such as emerging manufacturing technologies, surface modification techniques, and patient-oriented designs have remarkably influenced the microstructural characteristic, bioactive performance, and clinical indications of porous Ta scaffolds. The present review offers an overview of the fabrication methods, modification techniques, and orthopedic applications of porous Ta implants.

Tantalum as Trabecular Metal for Endosseous Implantable Applications

During the last 20 years, tantalum has known ever wider applications for the production of endosseous implantable devices in the orthopedic and dental fields. Its excellent performances are due to its capacity to stimulate new bone formation, thus improving implant integration and stable fixation. Tantalum's mechanical features can be mainly adjusted by controlling its porosity thanks to a number of versatile fabrication techniques, which allow obtaining an elastic modulus similar to that of bone tissue, thus limiting the stress-shielding effect. The present paper aims at reviewing the characteristics of tantalum as a solid and porous (trabecular) metal, with specific regard to biocompatibility and bioactivity. Principal fabrication methods and major applications are described. Moreover, the osteogenic features of porous tantalum are presented to testify its regenerative potential. It can be concluded that tantalum, especially as a porous metal, clearly possesses many advantageous characteristics for endosseous applications but it presently lacks the consolidated clinical experience of other metals such as titanium.

FEATURES OF BONE REMODELING AROUND SURFACE-MODIFIED TITANIUM AND TANTALUM IMPLANTS

OBJECTIVE

The aim: To study the osseointegrative properties of titanium and tantalum implants with different surface structures in animal experiments.

PATIENTS AND METHODS

Materials and methods: The histological and morphometric study was carried out on 60 male white rats after titanium implants with different surface structures made by 3D printed technology were inserted in the distal femur bone: presented by the multilayered layers of interlacing pores of 300 microns (series 1); rough (> 2 microns) (series 2); and tantalum implants with 300 microns pores and 80% porosity (series 3) as control material.

RESULTS

Results: On the 30 days we found statistically significant differences in the bone-implant contact rate between the 2nd experiment series (44.77 ± 1.86)% and 1st (59.91 ± 2.86)% (p=0.000047) and 3rd (53.89 ± 2.11)% (р=0.000065), on the 90 days between the 2nd experiment series (51.26 ± 2.7)% and 1st (66.84 ± 2.63)% (p=0.000187) and 3rd (70.35 ± 4.32)% (p=0.000349). There was a difference between the indices of the bone-implant volume at day 90 between the 1st (48.43 ± 2.2)% and 2nd (36.88 ± 2.56)% series (p=0.000919), between the 2nd and 3rd series (51.2 ± 3.06)% (p=0.000107). There were no significant differences between the studied indices in the 1st and 3rd series of the experiment.

CONCLUSION

Conclusions: Titanium implants with multilayered interlaced pore layers of 300 microns and tantalum with 300 microns pore size and 80% porosity may be promising. Rough-surface titanium also has osseointegrative qualities, but they are lower compared to other materials.

Nasal Floor Elevation—An Option of Premaxilla Augmentation: A Case Report

The atrophic edentulous maxilla is demanding for dental implant placement because of extensive resorption of the alveolar ridge after teeth loss and, consequently, the proximity of the anatomical structures, nasal cavity, and maxillary sinus. Treatment options are short implants, guided bone regeneration, onlay grafts, Le Fort I osteotomy with interpositional bone grafting, distraction osteogenesis, or nasal floor elevation. Nasal floor elevation is a method of augmentation of premaxilla by raising the base of the nose. The aim of this case report is to evaluate the success of implants placed after nasal floor elevation. A 75-year-old female patient came to the Clinical Department of Oral Surgery, University Hospital Centre Zagreb, unsatisfied with her complete removable denture. Clinical and radiological examination revealed severe maxillary alveolar ridge atrophy. Nasal floor elevation was made under local anesthesia through aperture piriformis and lateral window in the distal part. After eight months, four implants were placed and, after period of osseointegration, a bar-retained implant overdenture was made. This case report shows that nasal floor augmentation can be considered among the surgical techniques to allow implant-supported rehabilitation of the atrophic anterior maxilla.

Success Factors of Additive Manufactured Root Analogue Implants

Dental implantation is an effective method for the treatment of loose teeth, but the threaded dental implants used in the clinic cannot match with the tooth extraction socket. A root analogue implant (RAI) has the congruence shape, which reduces the damage to bone and soft tissue. Additive manufacturing (AM) technologies have the advantages of high precision, flexibility, and easy operation, becoming the main manufacturing method of RAI in basic research. The purpose of this systematic review is to summarize AM technologies used for RAI manufacturing as well as the factors affecting successful implantation. First, it introduces the AM technologies according to different operating principles and summarizes the advantages and disadvantages of each method. Then the influences of materials, structure design, surface characteristics, implant site, and positioning are discussed, providing reference for designers and dentists. Finally, it addresses the gap between basic research and clinical application for additive manufactured RAIs and discusses the current challenges and future research directions for this field.

Titanium Implants and Local Drug Delivery Systems Become Mutual Promoters in Orthopedic Clinics

Titanium implants have always been regarded as one of the gold standard treatments for orthopedic applications, but they still face challenges such as pain, bacterial infections, insufficient osseointegration, immune rejection, and difficulty in personalizing treatment in the clinic. These challenges may lead to the patients having to undergo a painful second operation, along with increased economic burden, but the use of drugs is actively solving these problems. The use of systemic drug delivery systems through oral, intravenous, and intramuscular injection of various drugs with different pharmacological properties has effectively reduced the levels of inflammation, lowered the risk of endophytic bacterial infection, and regulated the progress of bone tumor cells, processing and regulating the balance of bone metabolism around the titanium implants. However, due to the limitations of systemic drug delivery systems-such as pharmacokinetics, and the characteristics of bone tissue in the event of different forms of trauma or disease-sometimes the expected effect cannot be achieved. Meanwhile, titanium implants loaded with drugs for local administration have gradually attracted the attention of many researchers. This article reviews the latest developments in local drug delivery systems in recent years, detailing how various types of drugs cooperate with titanium implants to enhance antibacterial, antitumor, and osseointegration effects. Additionally, we summarize the improved technology of titanium implants for drug loading and the control of drug release, along with molecular mechanisms of bone regeneration and vascularization. Finally, we lay out some future prospects in this field.

Tantalum and its derivatives in orthopedic and dental implants: Osteogenesis and antibacterial properties

Implant-associated infections and aseptic loosening are some of the main reasons for implant failure. Therefore, there is an urgent need to improve the osseointegration and antibacterial capabilities of implant materials. In recent years, a large number of breakthroughs in the biological application of tantalum and its derivatives have been achieved. Owing to their corrosion resistance, biocompatibility, osseointegration ability, and antibacterial properties, they have shown considerable potential in orthopedic and dental implant applications. In this review, we provide the latest progress and achievements in the research on osseointegration and antibacterial properties of tantalum as well as its derivatives, and summarize the surface modification methods to enhance their osseointegration and antibacterial properties.

Tantalum Particles Induced Cytotoxic and Inflammatory Effects in Human Monocytes

The aim of this study is to evaluate the biological safety of tantalum (Ta) particles and to further explore the effects of Ta particles on human monocyte toxicity and inflammatory cytokine expression. Human monocyte leukemia (THP-1) cells were cultured with Ta and hydroxyapatite (HA) particles. Cell counting kit-8 method was used to evaluate the cytotoxicity of Ta and HA particles. The apoptosis effects were evaluated by flow cytometry, and the protein expression levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were evaluated by ELISA. The protein levels of inflammation-related signaling pathways including nuclear factor-kappa B (NF-κB) and extracellular regulated kinase (ERK) were detected by western blotting. The cytotoxicity test showed that the toxicity level of Ta in vitro was grade l, which is within the clinically acceptable range. Compared with the HA control, Ta had no significant effect on THP-1 cell apoptosis, IL-6, and TNF-α release. The phosphorylated levels of NF-κB and ERK at 3 h in the Ta group were lower than those in the HA and control groups (P < 0.001 both). These results reveal Ta particles behave good biosafety properties and provide some new insights for the future clinical use of Ta.

Enhancement of Bone Ingrowth into a Porous Titanium Structure to Improve Osseointegration of Dental Implants: A Pilot Study in the Canine Model

A porous titanium structure was suggested to improve implant stability in the early healing period or in poor bone quality. This study investigated the effect of a porous structure on the osseointegration of dental implants. A total of 28 implants (14 implants in each group) were placed in the posterior mandibles of four beagle dogs at 3 months after extraction. The control group included machined surface implants with an external implant–abutment connection, whereas test group implants had a porous titanium structure added to the apical portion. Resonance frequency analysis (RFA); removal torque values (RTV); and surface topographic and histometric parameters including bone-to-implant contact length and ratio, inter-thread bone area and ratio in total, and the coronal and apical parts of the implants were measured after 4 weeks of healing. RTV showed a significant difference between the groups after 4 weeks of healing (p = 0.032), whereas no difference was observed in RFA. In the test group, surface topography showed bone tissue integrated into the porous structures. In the apical part of the test group, all the histometric parameters exhibited significant increases compared to the control group. Within the limitations of this study, enhanced bone growth into the porous structure was achieved, which consequently improved osseointegration of the implant.

New Zr-Ti-Nb Alloy for Medical Application: Development, Chemical and Mechanical Properties, and Biocompatibility

The concept of mechanical biocompatibilities is considered an important factor for orthopedics and dental implants. The high Young modulus of traditional Ti-based alloys can lead to stress-shielding syndrome and late postoperative complications. The development of new Al- and V-free Ti alloys with a low elastic modulus is a critical task for implantology. Despite the relatively low Young modulus and appropriate biological response of metastable beta-Ti alloys, their production requires complex metallurgical solutions and a high final cost that limit commercial application. The current research aimed to develop a Zr-Ti-Nb system with a low Young modulus suitable for biomedical application, including orthopedics and dental implantology. Two different charges were used for new alloy production with melting in a vacuum-arc furnace VDP-1 under atmospheric control (argon + helium) with a non-consumable tungsten electrode and a water-cooled copper crystallizer. Post-treatment included a forging-rolling process to produce a bar suitable for implant production. SEM with EDX and the mechanical parameters of the new alloy were evaluated, and a cell culture experiment provided a biocompatibility assessment. The chemical composition of the new alloy can be represented as 59.57-19.02-21.41 mass% of Zr-Ti-Nb. The mechanical properties are characterized by an extremely low Young modulus—27,27 GPa for the alloy and 34.85 GPa for the bar. The different master alloys used for Zr-Ti-Nb production did not affect the chemical compound and mechanical parameters so it was possible to use affordable raw materials to decrease the final price of the new product. The cell culture experiment demonstrated a full biocompatibility, indicating that this new alloy can be used for dental and orthopedics implant production.