In vitro biocompatibility evaluation of surface-modified titanium alloys

Biomechanical study of 3D-printed titanium alloy pad for repairing glenoid bone defect

Background: The purpose of this study was to investigate the effect of 3D-printed technology to repair glenoid bone defect on shoulder joint stability. Methods: The shoulder joints of 25 male cadavers were tested. The 3D-printed glenoid pad was designed and fabricated. The specimens were divided into 5 groups. Group A: no bone defect and the structure of the glenoid labrum and joint capsule was intact; Group B: Anterior inferior bone defect of the shoulder glenoid; Group C: a pad with a width of 2 mm was installed; Group D: a pad with a width of 4 mm was installed; Group E: a pad with a width of 6 mm was installed. This study measured the distance the humeral head moved forward at the time of glenohumeral dislocation and the maximum load required to dislocate the shoulder. Results: The shoulder joint stability and humerus displacement was significantly lower in groups B and C compared with group A (p < .05). Compared with group A, the stability of the shoulder joint of group D was significantly improved (p < .05). However, there was no significant difference in humerus displacement between groups D and A (p > .05). In addition, compared with group A, shoulder joint stability was significantly increased and humerus displacement was significantly decreased in group E (p < .05). Conclusion: The 3D-printed technology can be used to make the shoulder glenoid pad to perfectly restore the geometric shape of the shoulder glenoid articular surface. Moreover, the 3D-printed pad is 2 mm larger than the normal glenoid width to restore the initial stability of the shoulder joint.

Powder metallurgical Ti-Mg metal-metal composites facilitate osteoconduction and osseointegration for orthopedic application

In this work, Ti—Mg metal-metal composites (MMCs) were successfully fabricated by spark plasma sintering (SPS). In vitro, the proliferation and differentiation of SaOS-2 cells in response to Ti—Mg metal-metal composites (MMCs) were investigated. In vivo, a rat model with femur condyle defect was employed, and Ti—Mg MMCs implants were embedded into the femur condyles. Results showed that Ti—Mg MMCs exhibited enhanced cytocompatibility to SaOS-2 cells than pure Ti. The micro-computed tomography (Micro-CT) results showed that the volume of bone trabecula was significantly more abundant around Ti—Mg implants than around Ti implants, indicating that more active new-bone formed around Ti—Mg MMCs implants. Hematoxylin-eosin (H&E) staining analysis revealed significantly greater osteointegration around Ti—Mg implants than that around Ti implants.

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Bioactive Ti—Mg metal-metal composites (MMCs) were successfully fabricated by spark plasma sintering.

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The proliferation and ALP activity of SaOS-2 cells were promoted by Ti—Mg MMCs extraction medium.

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In vivo results showed that Ti—Mg MMCs exhibited enhanced osseointegration compared to pure Ti.

Transcriptomic profiling of tantalum metal implant osseointegration in osteopenic patients

OBJECTIVES

The long-term success of dental implants is established by literature. Although clinically well defined, the complex genetic pathways underlying osseointegration have not yet been fully elucidated. Furthermore, patients with osteopenia/osteoporosis are considered to present as higher risk for implant failure. Porous tantalum trabecular metal (PTTM), an open-cell porous biomaterial, is suggested to present enhanced biocompatibility and osteoconductivity. The goal of this study was to evaluate the expression patterns of a panel of genes closely associated with osteogenesis and wound healing in osteopenic patients receiving either traditional titanium (Ti) or PTTM cylinders to assess the pathway of genes activation in the early phases of osseointegration.

MATERIAL AND METHODS

Implant cylinders made of Ti and PTTM were placed in osteopenic volunteers. At 2- and 4 weeks of healing, one Ti and one PTTM cylinder were removed from each subject for RT-PCR analysis using osteogenesis PCR array.

RESULTS

Compared to Ti, PTTM-associated bone displayed upregulation of bone matrix proteins, BMP/TGF tisuperfamily, soluble ligand and integrin receptors, growth factors, and collagen genes at one or both time points. Histologically, PTTM implants displayed more robust osteogenesis deposition and maturity when compared to Ti implants from the same patient.

CONCLUSIONS

Our results indicate that PTTM properties could induce an earlier activation of genes associated with osteogenesis in osteopenic patients suggesting that PTTM implants may attenuate the relative risk of placing dental implants in this population.

An in vivo study on the effect of coating stability on osteointegration performance of collagen/hyaluronic acid multilayer modified titanium implants

Aseptic loosening of implant is one of the main causes of Ti-based implant failure. In our previous work, a novel stable collagen/hyaluronic acid (Col/HA) multilayer modified titanium coatings (TCs) was developed by layer-by-layer (LBL) covalent immobilization technique, which showed enhanced biological properties compared with TCs that were physically absorbed with Col/HA multilayer in vitro. In this study, a rabbit model with femur condyle defect was employed to compare the osteointegration performance of them. Results indicated that Col/HA multilayer with favourable stability could better facilitate osteogenesis around implants and bone-implant contact. The Col/HA multilayer covalent-immobilized TC may reduce aseptic loosening of implant.

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Stability of Col/HA multilayer could promote the growth of trabecular bone around implants.

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New bone was induced to grow into the hole of Col/HA multilayer covalently immobilized TC implants.

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New bone contacted with Col/HA multilayer covalently immobilized TC implants closely.

Early osseointegration of implants with cortex-like TiO2 coatings formed by micro-arc oxidation: A histomorphometric study in rabbits

In our previous studies, a novel cortex-like TiO₂ coating was prepared on Ti surface through micro-arc oxidation (MAO) by using sodium tetraborate as electrolyte, and the effects of the coating on cell attachment were testified. This study aimed to investigate the effects of this cortex-like MAO coating on osseointegration. A sand-blasting and acid-etching (SLA) coating that has been widely used in clinical practice served as control. Topographical and chemical characterizations were conducted by scanning electron microscopy, energy dispersive X-ray spectrometer, X-ray diffraction, contact angle meter, and step profiler. Results showed that the cortex-like coating had microslots and nanopores and it was superhydrophilic, whereas the SLA surface was hydrophobic. The roughness of MAO was similar to that of SLA. The MAO and SLA implants were implanted into the femoral condyles of New Zealand rabbits to evaluate their in-vivo performance through micro-CT, histological analysis, and fluorescent labeling at the bone-implant interface four weeks after surgery. The micro-CT showed that the bone volume ratio and mean trabecular thickness were similar between MAO and SLA groups four weeks after implantation. Histological analysis and fluorescent labeling showed no significant differences in the bone-implant contact between the MAO and SLA surfaces. It was suggested that with micro/nanostructure and superhydrophilicity, the cortex-like MAO coating causes excellent osseointegration, holding a promise of an application to implant modification.

Covalently immobilised type I collagen facilitates osteoconduction and osseointegration of titanium coated implants

Background/Objective

Plasma-sprayed titanium coating (TC) with rough surfaces has been successfully applied in hip or knee prostheses. This study aimed to investigate the osteoconduction and osseointegration of Type I collagen covalently immobilised on TC (TC-AAC) compared with those of TC.

Methods

In vitro, the migration of human mesenchymal stem cells (hMSCs) on TC and TC-AAC was observed by scanning electron microscopy and visualised fluorescent live/dead assay. In vivo, a rabbit model with femur condyle defect was employed, and implants of TC and TC-AAC were embedded into the femur condyles.

Results

Collagen immobilised on TC could promote hMSCs' migration into the porous structure of the TC. Micro computed tomography images showed that bone trabeculae were significantly more abundant around TC-AAC implants than around TC implants. Fluorescence micrographs indicated more active new-bone formation around implants in the TC-AAC group than in the TC group. The measurement of bone–implant contact on histological sections indicated significantly greater osteointegration around TC-AAC implants than around TC ones.

Conclusion

Immobilised Type I collagen could improve the osteoconduction and osseointegration of TC implants.

Nanosized Hydroxyapatite Coating on PEEK Implants Enhances Early Bone Formation: A Histological and Three-Dimensional Investigation in Rabbit Bone

Polyether ether ketone (PEEK) has been frequently used in spinal surgery with good clinical results. The material has a low elastic modulus and is radiolucent. However, in oral implantology PEEK has displayed inferior ability to osseointegrate compared to titanium materials. One idea to reinforce PEEK would be to coat it with hydroxyapatite (HA), a ceramic material of good biocompatibility. In the present study we analyzed HA-coated PEEK tibial implants via histology and radiography when following up at 3 and 12 weeks. Of the 48 implants, 24 were HA-coated PEEK screws (test) and another 24 implants served as uncoated PEEK controls. HA-coated PEEK implants were always osseointegrated. The total bone area (BA) was higher for test compared to control implants at 3 (p < 0.05) and 12 weeks (p < 0.05). Mean bone implant contact (BIC) percentage was significantly higher (p = 0.024) for the test compared to control implants at 3 weeks and higher without statistical significance at 12 weeks. The effect of HA-coating was concluded to be significant with respect to early bone formation, and HA-coated PEEK implants may represent a good material to serve as bone anchored clinical devices.

In situ electrochemical study of the interaction of cells with thermally treated titanium

Micromotion and fretting wear between bone and Ti-based alloys in stem and dental implants breaks the passive film and exposes the metal to the action of the complex surrounding medium, generating substantial amounts of debris and continuous Ti ion release. In this work, oxidation treatments at low temperatures (277 °C, 5 h) have been used to promote the formation of wear-corrosion resistant titanium oxide on the Ti surface. The objective of this paper has been the study of the influence of live cells on the protectiveness of the oxide formed at these low temperatures. The interaction of cells with the modified surface has been studied by scanning electron microscopy, electrochemical impedance spectroscopy, polarization curves, and x-ray photoelectron spectroscopy (XPS). The chemical composition of the thermally treated Ti surface is mainly TiO2 as anatase-rich titanium dioxide with a low concentration of hydroxyl groups and a low mean nanoroughness that could promote good cell adhesion. The electrochemical results indicate that the cells alter the overall resistance of the thermally treated Ti surfaces by decreasing the oxide resistance with time. At the same time, the anodic current increases, which is associated with cathodic control, and is probably due to the difficulty of access of oxygen to the Ti substrate. XPS reveals the presence of proteins on the surface of the treated specimens in contact with the cells and a decrease in the Ti signal associated with the extracellular matrix on the surface and the reduction of the oxide thickness.

Interaction of human osteoblast-like Saos-2 and MG-63 cells with thermally oxidized surfaces of a titanium-niobium alloy

An investigation was made of the adhesion, growth and differentiation of osteoblast-like MG-63 and Saos-2 cells on titanium (Ti) and niobium (Nb) supports and on TiNb alloy with surfaces oxidized at 165°C under hydrothermal conditions and at 600°C in a stream of air. The oxidation mode and the chemical composition of the samples tuned the morphology, topography and distribution of the charge on their surfaces, which enabled us to evaluate the importance of these material characteristics in the interaction of the cells with the sample surface. Numbers of adhered MG-63 and Saos-2 cells correlated with the number of positively-charged (related with the Nb₂O₅ phase) and negatively-charged sites (related with the TiO₂ phase) on the alloy surface. Proliferation of these cells is correlated with the presence of positively-charged (i.e. basic) sites of the Nb₂O₅ alloy phase, while cell differentiation is correlated with negatively-charged (acidic) sites of the TiO₂ alloy phase. The number of charged sites and adhered cells was substantially higher on the alloy sample oxidized at 600°C than on the hydrothermally treated sample at 165°C. The expression values of osteoblast differentiation markers (collagen type I and osteocalcin) were higher for cells grown on the Ti samples than for those grown on the TiNb samples. This was more particularly apparent in the samples treated at 165°C. No considerable immune activation of murine macrophage-like RAW 264.7 cells on the tested samples was found. The secretion of TNF-α by these cells into the cell culture media was much lower than for either cells grown in the presence of bacterial lipopolysaccharide, or untreated control samples. Thus, oxidized Ti and TiNb are both promising materials for bone implantation; TiNb for applications where bone cell proliferation is desirable, and Ti for induction of osteogenic cell differentiation.

Magnesium ion implantation on a micro/nanostructured titanium surface promotes its bioactivity and osteogenic differentiation function

As one of the important ions associated with bone osseointegration, magnesium was incorporated into a micro/nanostructured titanium surface using a magnesium plasma immersion ion-implantation method. Hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 30 minutes (Mg30) and hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 60 minutes (Mg60) were used as test groups. The surface morphology, chemical properties, and amount of magnesium ions released were evaluated by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, field-emission transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used to evaluate cell responses, including proliferation, spreading, and osteogenic differentiation on the surface of the material or in their medium extraction. Greater increases in the spreading and proliferation ability of rBMMSCs were observed on the surfaces of magnesium-implanted micro/nanostructures compared with the control plates. Furthermore, the osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) genes were upregulated on both surfaces and in their medium extractions. The enhanced cell responses were correlated with increasing concentrations of magnesium ions, indicating that the osteoblastic differentiation of rBMMSCs was stimulated through the magnesium ion function. The magnesium ion-implanted micro/nanostructured titanium surfaces could enhance the proliferation, spreading, and osteogenic differentiation activity of rBMMSCs, suggesting they have potential application in improving bone-titanium integration.