Ti-6Al-4V ion solution inhibition of osteogenic cell phenotype as a function of differentiation timecourse in vitro

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Photoinduced properties of anodized Ti alloys for biomaterial applications

The photocatalytic properties of anodic oxides on a newly developed TiNbSn and commonly used Ti6Al4V alloys as biomaterials were investigated. The alloys were anodized in an electrolyte of sodium tartrate acid with H2O2 at a high voltage and the mechanism of the photocatalytic and antiviral activities was studied. The anodized TiNbSn and Ti6Al4V exhibited highly crystallized rutile TiO2 and poorly crystallized anatase TiO2, respectively. X-ray photoelectron spectroscopy analysis revealed the presence of oxides of the alloying elements in addition to TiO2. The anodized TiNbSn exhibited higher activities than Ti6Al4V, and electron spin resonance spectra indicated that the number of hydroxyl radicals (⋅OH) generated from the anodized TiNbSn was higher than that from the anodized Ti6Al4V. The results can be explained by two possible mechanisms: the higher crystallinity of TiO2 on TiNbSn than that on the Ti6Al4V reduces the number of charge recombination sites and generates abundant ⋅OH; charge separation in the anodic oxide on TiNbSn due to the electronic band structure between TiO2 and the oxides of alloying elements enhances photo activities. The excellent photoinduced characteristics of the anodized TiNbSn are expected to contribute to the safe and reliable implant treatment.

A review on in vitro/in vivo response of additively manufactured Ti-6Al-4V alloy

Bone replacement using porous and solid metallic implants, such as Ti-alloy implants, is regarded as one of the most practical therapeutic approaches in biomedical engineering. The bone is a complex tissue with various mechanical properties based on the site of action. Patient-specific Ti-6Al-4V constructs may address the key needs in bone treatment for having customized implants that mimic the complex structure of the natural tissue and diminish the risk of implant failure. This review focuses on the most promising methods of fabricating such patient-specific Ti-6Al-4V implants using additive manufacturing (AM) with a specific emphasis on the popular subcategory, which is powder bed fusion (PBF). Characteristics of the ideal implant to promote optimized tissue-implant interactions, as well as physical, mechanical/chemical treatments and modifications will be discussed. Accordingly, such investigations will be classified into 3B-based approaches (Biofunctionality, Bioactivity, and Biostability), which mainly govern native body response and ultimately the success in implantation.

Impact of exogenous metal ions on peri-implant bone metabolism: a review

The development of effective methods to promote the osseointegration of dental implants by surface modification is an area of intense research in dental materials science. Exogenous metal ions present in the implant and surface modifications are closely related to the bone metabolism around the implant. In the complex oral microenvironment, the release of metal ions caused by continuous corrosion of dental implants has an unfavorable impact on the surrounding tissue, and then affects osseointegration, leading to bad results such as loosening and falling off in the late stage of the implant. Besides, these ions can even be distributed in distant tissues and organs. Currently, surface modification techniques are being developed that involve different processing technologies including the introduction of exogenous metal ions with different properties onto the surface of implants to improve performance. However, most metal elements have some level of biological toxicity and can only be used within a safe concentration range to exert the optimum biological effects on recipients. In this paper, we review the adverse effects of metal ions on osseointegration and highlight the emerging applications for metal elements in improving the performance of dental implants.

Synthesis and characterization of porous bioactive SiC tissue engineering scaffold

Silicon carbide (SiC) is an inert material with excellent biocompatibility properties. A major issue that limits its use as a medical device is the difficult processing technique that requires hot pressing at a temperature (>2,000^o C) and pressure (1,000-2,000 atm). In the present study, we developed a protocol to synthesize a porous SiC scaffold by pressing the powder at 50 MPa and heating at 900^o C/2 hr. The surface of SiC was chemically modified by NaOH to facilitate sintering and induce bioactivity. Porous discs with 51.51 ± 3.17% porosity and interconnected pores in the size range from 1 to 1,000 μm were prepared using 40% PEG. The average compressive strength and Young's modulus of the scaffolds were 1.94 ± 0.70 and 169.2 ± 0.08 MPa, respectively. FTIR analysis confirmed the formation of biomimetic hydroxyapatite layer after 2 hr of immersion in simulated body fluid. The Ca/P ratio was dependent on the concentration of the silanol groups created on the material surface. Increasing the atomic % of silicon on the SiC surface from 33.27 ± 9.53% to 45.13 ± 4.74% resulted in a 76% increase in the osteocalcin expression by MC3T3-E1 cells seeded on the material after 7 days. The cells colonized the entire thickness of the template and filled the pores with mineralized extracellular matrix after 14 days. Taken all together, the porous SiC scaffolds can serve as a bone graft for tissue reconstruction and cell delivery in trauma surgery.

Materials for Orthopedic Bioimplants: Modulating Degradation and Surface Modification Using Integrated Nanomaterials

Significant research and development in the field of biomedical implants has evoked the scope to treat a broad range of orthopedic ailments that include fracture fixation, total bone replacement, joint arthrodesis, dental screws, and others. Importantly, the success of a bioimplant depends not only upon its bulk properties, but also on its surface properties that influence its interaction with the host tissue. Various approaches of surface modification such as coating of nanomaterial have been employed to enhance antibacterial activities of a bioimplant. The modified surface facilitates directed modulation of the host cellular behavior and grafting of cell-binding peptides, extracellular matrix (ECM) proteins, and growth factors to further improve host acceptance of a bioimplant. These strategies showed promising results in orthopedics, e.g., improved bone repair and regeneration. However, the choice of materials, especially considering their degradation behavior and surface properties, plays a key role in long-term reliability and performance of bioimplants. Metallic biomaterials have evolved largely in terms of their bulk and surface properties including nano-structuring with nanomaterials to meet the requirements of new generation orthopedic bioimplants. In this review, we have discussed metals and metal alloys commonly used for manufacturing different orthopedic bioimplants and the biotic as well as abiotic factors affecting the failure and degradation of those bioimplants. The review also highlights the currently available nanomaterial-based surface modification technologies to augment the function and performance of these metallic bioimplants in a clinical setting.

3D-additive deposition of an antibacterial and osteogenic silicon nitride coating on orthopaedic titanium substrate

A 3D-additive manufacturing approach produced a dense Si₃N₄ ceramic coating on a biomedical grade commercially pure titanium (cp-Ti) substrate by an automatic laser-sintering procedure. Si₃N₄ coatings could be prepared with thicknesses from the single to the tens of microns. A coating thickness, t = 15 ± 5 μm, was selected for this study, based on projections of homogeneity and scratching resistance. The Si₃N₄ coating met the 20 N threshold required for biomaterial applications, according to the standard scratch testing (ASTM C1624-05). The Si₃N₄ coating imparted both the antibacterial and osteogenic properties of bulk Si₃N₄ to the cp-Ti substrate. Both properties were comparable to those previously described for bulk Si₃N₄ biomedical implants. The newly developed Si₃N₄-coating was applied to commercially available Ti-alloy acetabular shells for total hip arthroplasty. A "glowing" test based on luciferase gene transformation was applied to visualize the colonization of gram-negative Escherichia coli on Si₃N₄-coated and uncoated Ti-alloy acetabular shells. The results showed that the coating technology conferred resistance to Staphylococcus epidermidis and Escherichia coli adhesion onto the bulk acetabular sockets.

Off-Stoichiometric Reactions at the Cell-Substrate Biomolecular Interface of Biomaterials: In Situ and Ex Situ Monitoring of Cell Proliferation, Differentiation, and Bone Tissue Formation

The availability of osteoinductive biomaterials has encouraged new therapies in bone regeneration and has potentially triggered paradigmatic shifts in the development of new implants in orthopedics and dentistry. Among several available synthetic biomaterials, bioceramics have gained attention for their ability to induce mesenchymal cell differentiation and successive bone formation when implanted in the human body. However, there is currently a lack of understanding regarding the fundamental biochemical mechanisms by which these materials can induce bone formation. Phenomenological studies of retrievals have clarified the final effect of bone formation, but have left the chemical interactions at the cell-material interface uncharted. Accordingly, the knowledge of the intrinsic material properties relevant for osteoblastogenesis and osteoinduction remains incomplete. Here, we systematically monitored in vitro the chemistry of mesenchymal cell metabolism and the ionic exchanges during osteoblastogenesis on selected substrates through conventional biological assays as well as via in situ and ex situ spectroscopic techniques. Accordingly, the chemical behavior of different bioceramic substrates during their interactions with mesenchymal cells could be unfolded and compared with that of biomedical titanium alloy. Our goal was to clarify the cascade of chemical equations behind the biological processes that govern osteoblastogenic effects on different biomaterial substrates.

Surface properties and bioactivity of TiO2 nanotube array prepared by two-step anodic oxidation for biomedical applications

A highly ordered TiO₂ nanotube array has been prepared on a commercial pure titanium substrate in a hydrofluoric (HF) electrolyte using a DC power source through two-step anodic oxidation. The morphology, composition, wettability and surface energy of the nanotube array have been characterized by using a field-emission scanning electron microscope (FE-SEM), a transmission electron microscope (JEM-2010) with energy-dispersive X-ray spectrometer EDX (INCA OXFORD), X-ray diffraction method, an atomic force microscope (AFM), an optical contact angle measuring device and the Owens method with two liquids. The electrochemical behaviours of anodic oxidation films with different structures have been investigated in Sodium Lactate Ringer's Injection at 37±1°C by potentiodynamic polarization curve and electrochemical impedance spectroscopy. The formation mechanism of the nanotube array and the advantages of two-step oxidation have been discussed according to the experimental observation and the characterized results. Meanwhile, the structural changes of nanotubes are analysed according to the results of impedance spectroscopy. Cytotoxicity testing and cell adhesion and proliferation have been studied in order to evaluate the bioactivity of the nanotube array film. The diameters of nanotubes are in the range of 120-140 nm. The nanotube surface shows better wettability and higher surface energy compared to the bare substrate. The nanotube surface exhibits a wide passivation range and good corrosion resistance. The growth of the nanotube array is the result of the combined action of the anodization and field-assisted dissolution. The nanotube array by two-step oxidation becomes more regular and orderly. Moreover, the nanotube array surface is non-toxic and favourable to cell adhesion and proliferation. Such nanotube array films are expected to have significant biomedical applications.

Does metal porosity affect metal ion release in blood and urine following total hip arthroplasty? A short term study

INTRODUCTION

The surface area of exposed metal in a trabecular-titanium acetabular component is wider compared to traditional-titanium implants. The purpose of this study is to establish if this increase in surface area can lead to a significant increase in systemic metal levels.

METHODS

19 patients with conventional acetabular component and 19 with trabecular-titanium cup were compared. Aluminum, Vanadium and Titanium in blood and urine were assessed before surgery and at intervals for 2 years. The samples were analysed using an inductively coupled plasma mass spectrometry.

RESULTS

Patients with trabecular-titanium did not have significantly higher metal ion levels compared to patients with conventional cups up to 2 years. A trend over time was statistically significant in both blood and urine for aluminum and titanium concentrations.

CONCLUSIONS

The three-dimensionality and the wide surface of the trabecular-titanium acetabular component did not affect metal ion release compared to traditional implants after 2 years.

Short term exposure to titanium, aluminum and vanadium (Ti 6Al 4V) alloy powder drastically affects behavior and antioxidant metabolites in vital organs of male albino mice

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Body weight, complete blood count and studied serum parameters remained unaffected upon Ti 6 A l 4 V alloy powder exposure.

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Short tern exposure to Ti 6Al 4V powder drastically affected neuromuscular coordination in male mice during rota rod test.

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Reduced novel object recognition ability in female mice exposed to Ti 6Al 4V alloy powder.

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Disturbed antioxidant metabolites in vital organs of mice treated with Ti 6Al 4V alloy powder.

Titanium, Aluminum and Vanadium (Ti 6Al 4V) alloy are frequently used as surgical implant but regarding their compatibility in living systems is limited. Ti 6Al 4V was prepared from high purity constituents and Ti 6Al 4V alloy powder (25 mg/ml solvent/Kg body weight) was gavaged to albino mice for 8 days. A saline treated control group was maintained in parallel. A series of behavioral (rota rod, light and dark box, open field and novel object) test performance, complete blood count, selected serum (HDL cholesterol, LDL cholesterol, creatinine, cholesterol and triglycerides) parameters, antioxidant metabolites from vital organs (superoxide dismutase, catalase and lipid peroxidation) from vital organs and body weight were determined in both treatments. It was observed that rota rod test performance in male (P = 0.05) and novel object recognition capability in female mice (P = 0.04) were significantly reduced as compared to their respective control groups. Body weight, complete blood count and studied serum parameters remained unaffected when compared between two treatments of both genders. Concentration of superoxide dismutase in liver (P = 0.008), heart (P = 0.01) and lungs (P = 0.05) was significantly elevated while catalase concentration in liver (P = 0.001) was significantly decreased in female albino mice that were exposed to 25 mg/ml solvent/kg body weight of Ti 6 A l 4 V alloy powder. In case of male albino mice, superoxide dismutase concentration in lungs was reduced (P = 0.05) in mice exposed to Ti 6 A l 4 V alloy powder.

In conclusion, our results indicated that short term exposure to 25 mg/ml solvent/Kg body weight of Ti-6Al-4V alloy powder supplementation had adversely affected selected aspects of behavior of albino mice in a gender specific manner. Analysis of antioxidant parameters in vital organs has demonstrated that the applied dose of Ti-6Al-4V alloy powder can disturb the H₂O₂ associated metabolic pathways in albino mice, especially in female mice. As this alloy is part of surgical implants, so we recommend that their effects in living systems must be extensively explored under variable dose and exposure time conditions to know more about their biocompatibility.

Effect of the Heat-Treated Ti6Al4V Alloy on the Fibroblastic Cell Response

Two heat treatments were carried out below (Ti6Al4V₈₀₀) and above (Ti6Al4V₁₀₅₀) Ti6Al4V beta-phase transformation temperature (980 °C), with the purpose of studying the effect of microstructure on the adhesion and proliferation of fibroblast cells, as well as their electrochemical behavior. These alloys were seeded with 10,000 L929 fibroblast cells and immersed for 7 days in the cell culture at 37 °C, pH 7.40, 5% CO₂ and 100% relative humidity. Cell adhesion was characterized by Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS) techniques. Polygonal and elongated cell morphology was observed independent of Ti6Al4V microstructure. Besides, C, O, P, S, Na and Cl signals were detected by Energy Dispersive X-Ray Spectroscopy (EDX), associated with the synthesis of organic compounds excreted by the cells, including protein adsorption from the medium. In certain areas on Ti6Al4V and Ti6Al4V₈₀₀ alloys, cells were agglomerated (island type), likely related to the globular microstructure; meanwhile, larger cellular coverage is shown for Ti6Al4V₁₀₅₀ alloy, forming more than one layer on the surface, where only Ca was recorded. Impedance diagrams showed a similar passive behavior for the different Ti6Al4V alloys, mainly due to TiO₂ overlaying the contribution of the organic compounds excreted by fibroblast cells.

Microrobotized blasting improves the bone-to-textured implant response. A preclinical in vivo biomechanical study

This study evaluated the effect of microrobotized blasting of titanium endosteal implants relative to their manually blasted counterparts. Two different implant systems were utilized presenting two different implant surfaces. Control surfaces (Manual) were fabricated by manually grit blasting the implant surfaces while experimental surfaces (Microblasted) were fabricated through a microrobotized system that provided a one pass grit blasting routine. Both surfaces were created with the same ~50µm average particle size alumina powder at ~310KPa. Surfaces were then etched with 37% HCl for 20min, washed, and packaged through standard industry procedures. The surfaces were characterized through scanning electron microscopy (SEM) and optical interferometry, and were then placed in a beagle dog radius model remaining in vivo for 3 and 6 weeks. The implant removal torque was recorded and statistical analysis evaluated implant system and surface type torque levels as a function of time in vivo. Histologic sections were qualitatively evaluated for tissue response. Electron microscopy depicted textured surfaces for both manual and microblasted surfaces. Optical interferometry showed significantly higher Sa, Sq, values for the microblasted surface and no significant difference for Sds and Sdr values between surfaces. In vivo results depicted that statistically significant gains in biomechanical fixation were obtained for both implant systems tested at 6 weeks in vivo, while only one system presented significant biomechanical gain at 3 weeks. Histologic sections showed qualitative higher amounts of new bone forming around microblasted implants relative to the manually blasted group. Microrobotized blasting resulted in higher biomechanical fixation of endosteal dental implants and should be considered as an alternative for impant surface manufacturing.

A Comparative Study of Stability After the Installation of 2 Different Surface Types of Implants in the Maxillae of Dogs

PURPOSE

This study was performed to investigate the histologic and histomorphometric findings of 2 different types of implant.

MATERIALS AND METHODS

Resorbable blasting media (RBM) and sandblasted with larger grit and acid etched (SLA) surfaced implants (24 fixtures in each group) were installed in posterior maxilla of dogs. The initial stability was measured using Periotest (Periotest value [PTV]). After 6 or 12 weeks, fixtures with surrounding bone were harvested.

RESULTS

The average initial stability of the SLA group (-1.71 ± 2.9) was higher than that of the RBM group (-1.25 ± 3.21), but there was no significant difference. The mean PTV of the RBM surface was higher than the SLA surface at 12 weeks. The average bone-implant contacts were 67.6% ± 16.0% at 6 weeks and 82.7% ± 8.6% at 12 weeks in the SLA group and 69.9% ± 17.6% at 6 weeks and 78.3% ± 9.2% at 12 weeks in the RBM group.

CONCLUSION

The SLA and resorbable blasting media (RBM) surface implants demonstrated good stabilities and healing processes of the surrounding bone in the posterior maxilla. Therefore, the two domestic implants could provide predictable clinical results.

Osseointegration of Ti-6Al-4V alloy implants with a titanium nitride coating produced by a PIRAC nitriding technique: a long-term time course study in the rat

This study examined bone tissue responses to Ti-6Al-4V alloy implants with a hard TiN coating applied by an original powder immersion reaction-assisted coating (PIRAC) nitriding method. Progression of implant fixation in the distal epiphysis and within the medullary cavity of the rat femur was evaluated between 3 days and 6 months postimplantation by scanning electron microscopy, oxytetracycline incorporation, and histochemistry. After 6 months, successful osseointegration was achieved in both epiphyseal and diaphyseal sites. Throughout, implant portions located within the epiphysis remained in close contact with bone trabeculae that gradually engulfed the implant forming a bone collar continuous with the trabecular network of the epiphysis. In the diaphysis, woven bone was first formed within the marrow cavity around the implant and later was replaced by a shell of compact bone around the implant. In general, higher osseointegration rates were measured for TiN-coated versus the uncoated implants, both in the epiphysis and in the diaphysis. In conclusion, our findings indicate an excellent long-term biocompatibility of TiN coatings applied by the PIRAC nitriding technique and superior osteoinductive ability in comparison with uncoated Ti-6Al-4V alloy. Such coatings can, therefore, be considered for improving the corrosion and wear resistance of titanium-based orthopedic implants.

Aluminum-free low-modulus Ti-C composites that exhibit reduced image artifacts during MRI

Feasibility studies were performed to determine the suitability of a novel synthesis technique for fabricating multifunctional composite materials for orthopedic implants. By blending paramagnetic Ti powder with diamagnetic graphite and consolidating the resulting mixtures, Ti-C composites that cannot be feasibly obtained via conventional alloying techniques or ingot metallurgy were synthesized. The synthesized composite material exhibited extremely low magnetic susceptibility (χ=67.6×10(-6)), and, as a result, exhibited fewer artifacts during magnetic resonance imaging. The strength of the composite material (σ=770MPa) was such that it could support external loads to which the human body is subjected, but its Young's modulus was low (E=81.9 GPa) such that it could mitigate the stress-shielding effect. The material was also free from toxic elements such as Al and V and, thus, can be considered less harmful.

Mechanical properties and corrosion behavior of Mg-HAP composites

Mg and Mg-HAP composites containing 5, 10 and 15 wt% of hydroxyapatite have been produced following a powder metallurgy route that consists of mixing raw powders and consolidation by extrusion. The microstructure, texture, mechanical behavior and resistance to corrosion under a PBS solution have been studied. Addition of HAP increases the microhardness of the composites, however the yield strength under compression slightly decreases. Texture analyses reveal a fiber texture for pure Mg that is weakened increasing the HAP fraction. This texture promotes twinning and softening of Mg and Mg-5HAP during the initial deformation stages. Mg-10HAP and Mg-15HAP present a strain-hardening dependence showing no softening. The volume fraction of HAP particles weakens the texture and favors the activation of secondary slip systems. Corrosion experiments in PBS solution have shown that Mg-5HAP exhibits the best resistance to corrosion. Texture and porosity appear to be the main material features controlling the corrosion rates of Mg-HAP composites under the present conditions.

Cell response to nanocrystallized metallic substrates obtained through severe plastic deformation

Cell-substrate interface is known to control the cell response and subsequent cell functions. Among the various biophysical signals, grain structure, which indicates the repeating arrangement of atoms in the material, has also proved to play a role of significant importance in mediating the cell activities. Moreover, refining the grain size through severe plastic deformation is known to provide the processed material with novel mechanical properties. The potential application of such advanced materials as biomedical implants has recently been evaluated by investigating the effect of different substrate grain sizes on a wide variety of cell activities. In this review, recent advances in biomedical applications of severe plastic deformation techniques are highlighted with special attention to the effect of the obtained nano/ultra-fine-grain size on cell-substrate interactions. Various severe plastic deformation techniques used for this purpose are discussed presenting a brief description of the mechanism for each process. The results obtained for each treatment on cell morphology, adhesion, proliferation, and differentiation, as well as the in vivo studies, are discussed. Finally, the advantages and challenges regarding the application of these techniques to produce multifunctional bio-implant materials are addressed.

Small-diameter titanium Grade IV and titanium-zirconium implants in edentulous mandibles: three-year results from a double-blind, randomized controlled trial

OBJECTIVE

The aim of this study was to compare crestal bone-level changes, soft tissue parameters and implant success and survival between small-diameter implants made of titanium/zirconium (TiZr) alloy or of Grade IV titanium (Ti) in edentulous mandibles restored with removable overdentures.

MATERIALS AND METHODS

This was a randomized, controlled, double-blind, split-mouth multicenter clinical trial. Patients with edentulous mandibles received two Straumann bone-level implants (diameter 3.3 mm), one of Ti Grade IV (control) and one of TiZr (test), in the interforaminal region. Implants were loaded after 6-8 weeks and removable Locator-retained overdentures were placed within 2 weeks of loading. Modified plaque and sulcus bleeding indices, radiographic bone level, and implant survival and success were evaluated up to 36 months.

RESULTS

Of 91 treated patients, 75 completed the three-year follow-up. Three implants were lost (two control and one test implant). The survival rates were 98.7% and 97.3%, and the mean marginal bone level change was -0.78 ± 0.75 and -0.60 ± 0.71 mm for TiZr and Ti Grade IV implants. Most patients had a plaque score of 0 or 1 (54% for test and 51.7% for control), and a sulcus bleeding score of 0 (46.1% for test and 44.9% for control). No significant differences were found between the two implant types for bone-level change, soft tissue parameters, survival and success.

CONCLUSIONS

After 36 months, similar outcomes were found between Ti Grade IV and TiZr implants. The results confirm that the results seen at 12 months continue over time.

Triethylphosphite as a network forming agent enhances in vitro biocompatibility and corrosion protection of hybrid organic–inorganic sol–gel coatings for Ti6Al4V alloys

Introduction of phosphorous into hybrid silica sol–gel coatings on Ti6Al4V gives materials demonstrating higher levels of intermolecular condensation and fibrinogen uptake as well as improved in vitro biocompatibility and corrosion protection.

Cytocompatibility of pure metals and experimental binary titanium alloys for implant materials

OBJECTIVE

This study was performed to evaluate the biocompatibility of nine types of pure metal ingots (Ag, Al, Cr, Cu, Mn, Mo, Nb, V, Zr) and 36 experimental titanium (Ti) alloys containing 5, 10, 15, and 20 wt% of each alloying element.

METHODS

The cell viabilities for each test group were compared with that of CP-Ti using the WST-1 test and agar overlay test.

RESULTS

The ranking of pure metal cytotoxicity from most potent to least potent was as follows: Cu>Al>Ag>V>Mn>Cr>Zr>Nb>Mo>CP-Ti. The mean cell viabilities for pure Cu, Al, Ag, V, and Mn were 21.6%, 25.3%, 31.7%, 31.7%, and 32.7%, respectively, which were significantly lower than that for the control group (p<0.05). The mean cell viabilities for pure Zr and Cr were 74.1% and 60.6%, respectively (p<0.05). Pure Mo and Nb demonstrated good biocompatibility with mean cell viabilities of 93.3% and 93.0%, respectively. The mean cell viabilities for all the Ti-based alloy groups were higher than 80% except for Ti-20 Nb (79.6%) and Ti-10 V (66.9%). The Ti-10 Nb alloy exhibited the highest cell viability (124.8%), which was higher than that of CP-Ti. Based on agar overlay test, pure Ag, Cr, Cu, Mn, and V were ranked as 'moderately cytotoxic', whereas the rest of the tested pure metals and all Ti alloys, except Ti-10 V (mild cytotoxicity), were ranked as 'noncytotoxic'.

SIGNIFICANCE

The results obtained in this study can serve as a guide for the development of new Ti-based alloy implant systems.

Positive Biomechanical Effects of Titanium Oxide for Sandblasting Implant Surface as an Alternative to Aluminium Oxide

The aim of this study was to evaluate the physico-chemical properties and the in vivo host response of a surface sandblasted with particles of titanium oxide (TiO2) followed by acid etching as an alternative to aluminium oxide. Thirty titanium disks manufactured in the same conditions as the implants and 24 conventional cylindrical implants were used. Half of the implants had a machined surface (Gcon) while in the other half; the surface was treated with particles of TiO2 followed by acid etching (Gexp). Surface characterization was assessed by scanning electron microscope (SEM), energy dispersive X-ray spectrometry (EDS), profilometry, and wettability. For the in vivo test, 12 implants of each group were implanted in the tibia of 6 rabbits, and were reverse torque tested after periods of 30 or 60 days after implantation. Following torque, SEM was utilized to assess residual bone-implant contact. The surface characterization by SEM showed a very homogeneous surface with uniform irregularities for Gexp and a small amount of residues of the blasting procedure, while Gcon presented a surface with minimal irregularities from the machining tools. Wettability test showed decreased contact angle for the Gcon relative to the Gexp. The Gexp removal torque at 30 and 60 days was 28.7%, and 33.2% higher relative to the Gcon, respectively. Blasting the surface with particles of TiO2 represents an adequate option for the surface treatment of dental implants, with minimal risk of contamination by the residual debris from the blasting procedure.

Cell biological responses of osteoblasts on anodized nanotubular surface of a titanium-zirconium alloy

Anodization of titanium and its alloys, under controlled conditions, generates a nanotubular architecture on the material surface. The biological consequences of such changes are poorly understood, and therefore, we have analyzed the cellular and molecular responses of osteoblasts that were plated on nanotubular anodized surface of a titanium-zirconium (TiZr) alloy. Upon comparing these results with those obtained on acid etched and polished surfaces of the same alloy, we observed a significant increase in adhesion and proliferation of cells on anodized surfaces as compared to acid etched or polished surface. The expression of genes related to cell adhesion was high only on anodized TiZr, but that of genes related to osteoblast differentiation and osteocalcin protein and extracellular matrix secretion were higher on both anodized and acid etched surfaces. Examination of surface morphology, topography, roughness, surface area and wettability using scanning electron microscopy, atomic force microscopy, and contact angle goniometry, showed that higher surface area, hydrophilicity, and nanoscale roughness of nanotubular TiZr surfaces, which were generated specifically by the anodization process, could strongly enhance the adhesion and proliferation of osteoblasts. We propose that biological properties of known bioactive titanium alloys can be further enhanced by generating nanotubular surfaces using anodization.

The improved biological performance of a novel low elastic modulus implant

BACKGROUND

The mismatch of the elastic modulus between implants and bone tissue can lead to stress shielding, bone resorption and poor osseointegration. Compared with normal bone tissue, this problem is much more serious in osteoporosis. The purpose of this study was designed to find out whether the novel Ti-24Nb-4Zr-7.9Sn (TNZS) implant with low elastic modulus and high strength was suitable for biomedical material, especially in osteoporosis.

METHODOLOGY

In vitro study, the viability and Alkaline phosphatase (ALP) activity of osteoblasts on the TNZS and Ti-6V-4V (TAV) were observed. In vivo study, 30 adult female New Zealand rabbits were selected and divided randomly into two groups: sham-operation (SHAM, n=6) and ovariectomised in combination with methylprednisolone treatment (OVX+MP, n=24). Two implants were then placed in the tibia of each OVX + MP group rabbit, one in each side (left: TAV; right: TNZS). The OVX + MP group rabbits were sacrificed at 4 and 12 weeks after the implantation. The osteoporotic bone responses to the TNZS and TAV implants were evaluated by pull-out test, Micro-CT analyses and histological observation.

PRINCIPAL FINDINGS

Compared with the TAV group, the TNZS group showed a significant increase (P<0.05) in cell viability and ALP activity, new bone formation and pull-out force.

CONCLUSIONS

The novel TNZS implants show good biological performance both in vitro and in vivo, which suggests that the alloys are suitable for biomedical applications, especially in osteoporosis.

Osseointegration and biocompatibility of different metal implants--a comparative experimental investigation in sheep

Background

In the present study, 4 different metallic implant materials, either partly coated or polished, were tested for their osseointegration and biocompatibility in a pelvic implantation model in sheep.

Methods

Materials to be evaluated were: Cobalt-Chrome (CC), Cobalt-Chrome/Titanium coating (CCTC), Cobalt-Chrome/Zirconium/Titanium coating (CCZTC), Pure Titanium Standard (PTST), Steel, TAN Standard (TANST) and TAN new finish (TANNEW). Surgery was performed on 7 sheep, with 18 implants per sheep, for a total of 63 implants. After 8 weeks, the specimens were harvested and evaluated macroscopically, radiologically, biomechanically (removal torque), histomorphometrically and histologically.

Results

Cobalt-Chrome screws showed significantly (p = 0.031) lower removal torque values than pure titanium screws and also a tendency towards lower values compared to the other materials, except for steel. Steel screws showed no significant differences, in comparison to cobalt-chrome and TANST, however also a trend towards lower torque values than the remaining materials. The results of the fluorescence sections agreed with those of the biomechanical test. Histomorphometrically, there were no significant differences of bone area between the groups. The BIC (bone-to-implant-contact), used for the assessment of the osseointegration, was significantly lower for cobalt-chrome, compared to steel (p = 0.001). Steel again showed a lower ratio (p = 0.0001) compared to the other materials.

Conclusion

This study demonstrated that cobalt-chrome and steel show less osseointegration than the other metals and metal-alloys. However, osseointegration of cobalt-chrome was improved by zirconium and/or titanium based coatings (CCTC, TANST, TAN, TANNEW) being similar as pure titanium in their osseointegrative behavior.

The influence of surface energy of titanium-zirconium alloy on osteoblast cell functions in vitro

The success of an implant used for bone regeneration and repair is determined by the events that take place at the cell-material interface. An understanding of these interactions in vitro gives insights into the formulation of ideal conditions for their effective functioning in vivo. Thus, it is not only important to understand the physico-chemical properties of the materials but, also necessary to assess the cellular responses to them to determine their long-term stability and efficacy as implants. In the present study, we have compared the physico-chemical and biological properties of titanium (Ti) and two Ti-based alloys, namely: Ti- Zirconium (TiZr) and Ti-Niobium (TiNb). The morphology, chemical analysis, surface roughness, and contact angle measurements of the alloys were assessed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), profilometer, and contact angle goniometer, respectively whereas the biological properties of the materials were evaluated by measuring the adhesion, proliferation, and differentiation of MC3T3-E1 osteoblast cells on the surfaces of these alloys. Our results indicate that the biological properties of osteoblasts were better on TiZr surface than on TiNb surface. Furthermore, the surface energy and substrate composition influenced the superior biological activity of the TiZr alloy.

Improved pre-osteoblast response and mechanical compatibility of ultrafine-grained Ti-13Nb-13Zr alloy

OBJECTIVE

Metallic implantation materials having high yield strength, low elastic modulus, and non-cytotoxic alloying elements would be advantageous for the long-term stability of implants. This study assessed the surface and mechanical properties, and also in vitro osteoconductivity of ultrafine-grained (UFG) Ti-13Nb-13Zr alloy produced by dynamic globularization without any severe deformation for future biomedical applications as an endosseous implant material.

MATERIAL AND METHODS

The surface characteristics and mechanical properties were investigated by orientation image microscopy, contact angle measurements, optical profilometry, and uniaxial tension tests. Mouse calvaria-derived pre-osteoblastic cell (MC3T3-E1) attachment, spreading, viability, alkaline phosphatase (ALP) activity, and quantitative analysis of osteoblastic gene expression on UFG Ti-13Nb-13Zr alloy were compared with coarse-grained (CG) Ti-13Nb-13Zr and CG Ti-6Al-4V alloys.

RESULTS

Dynamic globularized Ti-13Nb-13Zr alloy has an ultrafine grain size (0.3 μm) and an excellent combination of yield strength and elastic modulus compared with CG alloys, which displayed significantly lower water contact angles compared with CG alloys (P<0.05). The UFG and CG Ti-13Nb-13Zr alloys displayed significantly increased cellular attachment compared with CG Ti-6Al-4V alloy (P<0.05). The UFG Ti-13Nb-13Zr supported better cell spreading and more numerous focal adhesions. ALP activity (P<0.05) and mRNA expressions of the osteoblast transcription factor genes (osterix, Runx2) and marker gene for osteoblast differentiation (osteocalcin) were markedly increased in cells grown on the UFG substrate compared with CG substrates at early incubation timepoints.

CONCLUSION

Enhanced pre-osteoblast response to UFG Ti-13Nb-13Zr substrate is attributable to the non-cytotoxic alloying elements and the submicron scale grain size contributes to the superior surface hydrophilicity and abundant grain boundaries favorable for cell behavior. These findings indicate that dynamic globularized UFG Ti-13Nb-13Zr alloy is promising for load-bearing endosseous implant material because of excellent mechanical and biological compatibilites.

The removal of Al2O3 particles from grit-blasted titanium implant surfaces: effects on biocompatibility, osseointegration and interface strength in vivo

For the improvement of surface roughness and mechanical interlocking with bone, titanium prostheses are grit-blasted with Al(2)O(3) particles during manufacturing. Dislocated Al(2)O(3) particles are a leading cause of third-body abrasive wear in the articulation of endoprosthetic implants, resulting in inflammation, pain and ultimately aseptic loosening and implant failure. In the present study, a new treatment for the removal of residual Al(2)O(3) particles from grit-blasted, cementless titanium endoprosthetic devices was investigated in a rabbit model. The cleansing process reduces residual Al(2)O(3) particles on titanium surfaces by up to 96%. The biocompatibility of the implants secondary to treatment was examined histologically, the bone-implant contact area was quantified histomorphometrically, and interface strength was evaluated with a biomechanical push-out test. Conventional grit-blasted implants served as control. In histological and SEM analysis, the Al(2)O(3)-free implant surfaces demonstrated uncompromised biocompatibility. Histomorphometrically, Al(2)O(3)-free implants exhibited a significantly increased bone-implant contact area (p=0.016) over conventional implants between both evaluation points. In push-out testing, treated Al(2)O(3)-free implants yielded less shear resistance than conventional implants at both evaluation points (p=0.018). In conclusion, the new surface treatment effectively removes Al(2)O(3) from implant surfaces. The treated implants demonstrated uncompromised biocompatibility and bone apposition in vivo. Clinically, Al(2)O(3)-free titanium prostheses could lead to less mechanical wear of the articulating surfaces and ultimately result in less aseptic loosening and longer implant life.

In vitro evaluation of human osteoblast adhesion to a thermally oxidized gamma-TiAl intermetallic alloy of composition Ti-48Al-2Cr-2Nb (at.%)

Ti-48Al-2Cr-2Nb (at.%) (gamma-TiAl), a gamma titanium aluminide alloy originally designed for aerospace applications, appears to have excellent potential as implant material. Thermal treatment of gamma-TiAl renders this alloy extremely corrosion resistant in vitro, which could improve its biocompatibility. In this study, the surface oxides produced by thermal oxidation (at 500 degrees C, and at 800 degrees C for 1 h in air) on gamma-TiAl were characterized by X-ray photoelectron spectroscopy (XPS). hFOB 1.19 cell adhesion on thermally oxidized gamma-TiAl was examined in vitro by a hexosaminidase assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) after 1, 7 and 14 days. Ti-6Al-4V surfaces were used for comparison. Hexosaminidase assay data and CLSM analysis of focal contacts and cytoskeleton organization showed no differences in cell attachment on autoclaved and both heat-treated gamma-TiAl surfaces at the different time points. SEM images showed well organized multi-layers of differentiated cells adhered on thermally oxidized gamma-TiAl surfaces at day 14. Unexpectedly, thermally oxidized Ti-6Al-4V surfaces oxidized at 800 degrees C exhibited cytotoxic effects on hFOB 1.19 cells. Our results indicate that thermal oxidation of gamma-TiAl seems to be a promising method to generate highly corrosion resistant and biocompatible surfaces for implant applications.

Response of human bone marrow stromal cells to a novel ultra-fine-grained and dispersion-strengthened titanium-based material

A novel titanium-based material, containing no toxic or expensive alloying elements, was compared to the established biomaterials: commercially pure titanium (c.p.Ti) and Ti6Al4V. This material (Ti/1.3HMDS) featured similar hardness, yield strength and better wear resistance than Ti6Al4V, as well as better electrochemical properties at physiological pH7.4 than c.p.Ti grade 1 of our study. These excellent properties were obtained by utilizing an alternative mechanism to produce a microstructure of very fine titanium silicides and carbides (<100 nm) embedded in an ultra-fine-grained Ti matrix (365 nm). The grain refinement was achieved by high-energy ball milling of Ti powder with 1.3 wt.% of hexamethyldisilane (HMDS). The powder was consolidated by spark plasma sintering at moderate temperatures of 700 degrees C. The microstructure was investigated by optical and scanning electron microscopy (SEM) and correlated to the mechanical properties. Fluorescence microscopy revealed good adhesion of human mesenchymal stem cells on Ti/1.3HMDS comparable to that on c.p.Ti or Ti6Al4V. Biochemical analysis of lactate dehydrogenase and specific alkaline phosphatase activities of osteogenically induced hMSC exhibited equal proliferation and differentiation rates in all three cases. Thus the new material Ti/1.3HMDS represents a promising alternative to the comparatively weak c.p.Ti and toxic elements containing Ti6Al4V.

A review of the biologic effects of spine implant debris: Fact from fiction

BACKGROUND

Biologic-reactivity to implant-debris is the primary determinant of long-term clinical performance. The following reviews: 1) the physical aspects of spinal-implant debris and 2) the local and systemic biologic responses to implant debris.

METHODS

Methods included are: 1) gravimetric wear analysis; 2) SEM and LALLS; 3) metal-ion analysis; 4) ELISA, toxicity testing, patch testing; and 5) metal-lymphocyte transformation testing (metal-LTT).

RESULTS

Wear and corrosion of spine-implants produce particles and ions. Particles (0.01-1000 μm) are generally submicron ( <1 µm). Wear rates of metal-on-polymer and metal-on-metal disc arthroplasties are approximately 2-20 and 1 mm(3)/yr, respectively. Metal-on-metal total disc replacement components have significant increases in circulating metal (less than 10-fold that of controls at 4 ppb-Co and 3 ppb-Cr or ng/mL). Debris reactivity is local and systemic. Local inflammation is caused primarily by ingestion of debris by local macrophages, which produce pro-inflammatory cytokines TNFα, IL-1β, IL-6, and PGE2. Systemic responses associated with implant-debris have been limited to hypersensitivity reactions. Elevated amounts of in the liver, spleen, etc of patients with failed TJA have not been associated with remote toxicological or carcinogenic pathology to date. Implant debris are differentially bioreactive. Greater numbers are pro-inflammatory; the smaller-sized debris are more bioreactive by virtue of their greater numbers (dose) for a given amount of implant mass loss (one 100-μm-diameter particle is equivalent in mass to 1 million 1-μm-diameter particles). Elongated particles are pro-inflammatory (ie, aspect ratio of greater than 3). Metal particles are more proinflammatory than polymers, ceteris paribus.

CONCLUSION

Spinal arthroplasty designs have been in use for more than 20 years internationally; therefore, concerns about neuropathology, toxicity, and carcinogenicity are mitigated. Debris-induced inflammation still depends on the individual and the type of debris. The consequence of debris-induced inflammation is continued; vigilance by physicians is recommended monitoring of spinal implants using physical exams and testing of metal content and bioreactivity, as is planning for the likelihood of revision in younger individuals.

In-vitro and in-vivo evaluation of a new Ti-15Mo-1Bi alloy

The newly developed Ti-15Mo-1Bi alloy not only possesses all the desirable mechanical properties inherent to beta-Ti Mo alloys, but may even enjoy better clinical applicability with the addition of bismuth element, which has long been administered as antibacterial and antitumor medicines. A significantly higher viability of 3T3 cells was demonstrated when they were grown on Ti-15Mo-1Bi alloy than on Ti-15Mo and Ti-6Al-4V. Cells incubated in the medium conditioned by Bi powder at 37 degrees C for 96 h exhibited viability similar to that in the blank group and higher than that in the Ni conditioned group. In vivo experiments using 6 mm x 2 mm metal pin implanted into the epicondyle of rabbit femur revealed superior potential of new bone growth and better persistence of the deposited bony tissue with the Ti-15Mo-1Bi alloy in contrast to that with Ti-6Al-4V. The difference is evident at 12th week and become even more prominent after 26 weeks, with the new bone area measuring 249% of that around Ti-6Al-4V alloy. In summary, Ti-15Mo-1Bi alloys show no cytotoxicity in the in-vitro test and demonstrates superior ability to retain bone in the in-vivo implantation experiment as compared with Ti-6Al-4V alloys.

Biomaterials in orthopaedics

At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

Bone-like matrix formation on magnesium and magnesium alloys

Mg metal and its alloys have promise as a biocompatible, degradable biomaterials. This work evaluates the potential of in vitro cell culture work with osteoblast-like cells on Mg based materials, and investigates cell differentiation and growth on Mg alloyed with various non-toxic or low-toxicity elements. Mg based substrates support the adhesion, differentiation and growth of stromal cells towards an osteoblast-like phenotype with the subsequent production of a bone like matrix under in vitro conditions. No significant difference in the final tissue layer is observed on pure Mg, an AZ21 alloy or a 0.5 wt% Ca alloy. Only a 0.8 wt% Ca alloy which shows complete structural disintegration shows minimal cell growth. Due to association of non-soluble degradation products formed when Mg is incubated in physiological-like fluid, mass changes typically used to report Mg degradation are not viable estimates of degradation. Methods quantifying the time dependent change in the mechanical integrity of samples as a function of incubation time are required for a proper assessment of Mg degradation. We conclude that in vitro cell culture of bone cells on Mg substrates is expected to be a viable screening technique to assess the relative biological activity of Mg-based materials.