Titanium Alloy Implants Research Articles

Preparation and surface modification of 3D printed Ti–6Al–4V porous implant

Three-dimensional (3D) printed titanium alloy implants hold enormous potential in orthopedic applications to avoid stress shielding. However, titanium alloy is bioinert, limiting its application and making surface modification a necessity. In this paper, porous implants were treated by acid etching and anodizing to improve the bioactivity, which was evaluated by simulated body fluid (SBF) immersion test. The results showed that, after surface modification, micro–nanocomposite structures were obtained on the titanium surface, and after immersing in SBF for 2 weeks, the implants showed a drastically enhanced apatite forming ability, confirming improved bioactivity. However, the surface structures were different at different positions and it is believed that this phenomenon is closely related to the different current densities of the surfaces during anodic oxidation. Our research evaluates the effect of anodic oxidation at different voltages on the surface modification and provides a reference for improving the bioactivity of the medical porous implant surface prepared by 3D printing.

Diffusion tensor magnetic resonance imaging of the postoperative spine with metallic implants.

There has been a growing need to understand the mechanism of development of acute spinal cord injury (SCI) and to optimize treatment. The paramagnetic nature of metallic implants has hampered the application of diffusion tensor imaging (DTI) in postsurgical SCI monitoring. We describe here a successful implementation of spinal DTI in postsurgical SCI patients. Data were acquired using a single-shot turbo-spin-echo sequence, where an extra gradient is applied before the refocusing pulse train to eliminate contributions from the non-Carr-Purcell-Meiboom-Gill components following a diffusion preparation block where a single-spin echo scheme is deployed. The DTI images were acquired in axial orientation with a 2 x 2 x 4 mm3 resolution and a total of 18 slices. Diffusion gradients were applied in six directions with b values of 0 and 600 seconds/mm2 . The whole scan took ~10 minutes. The sequence was compared with SENSE-DW-EPI and ZOOM-DW-EPI on a phantom, eight patients with either anterior or posterior titanium alloy implants, and a pork loin with a similar implant. The protocol resulted in dramatically reduced geometric distortions compared with routine imaging sequences, however, the SNR efficiency was compromised. The spinal cord signal displacement was 0.68±1.00 mm (mean±SD, n = 8) for the proposed protocol, and 5.14±3.07 and 2.82±1.60 mm for the SENSE-DW-EPI and ZOOM-DW-EPI sequences, respectively. Fiber tracking was achieved in the presence of implants, which in one case was accompanied by central spinal cord caviation. Mathematical analysis concluded that the proposed protocol would be generally applicable in the spinal cord when the titanium alloy implant is ~15 mm away (<0.5 kHz B0 field drift). The protocol described is capable of DTI in postsurgery SCI patients with metallic implants at sufficient resolution and SNR.

In Vitro Bioactivity and Biocompatibility of Bio-Inspired Ti-6Al-4V Alloy Surfaces Modified by Combined Laser Micro/Nano Structuring.

The bioactivity and biocompatibility play key roles in the success of dental and orthopaedic implants. Although most commercial implant systems use various surface microstructures, the ideal multi-scale topographies capable of controlling osteointegration have not yielded conclusive results. Inspired by both the isotropic adhesion of the skin structures in tree frog toe pads and the anisotropic adhesion of the corrugated ridges on the scales of Morpho butterfly wings, composite micro/nano-structures, including the array of micro-hexagons and oriented nano-ripples on titanium alloy implants, were respectively fabricated by microsecond laser direct writing and femtosecond laser-induced periodic surface structures, to improve cell adherence, alignment and proliferation on implants. The main differences in both the bioactivity in simulated body fluid and the biocompatibility in osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti-6Al-4V samples with smooth surface, micro-hexagons and composite micro/nano-structures, respectively. Of note, bioinspired micro/nano-structures displayed the best bioactivity and biocompatibility after in vitro experiments, and meanwhile, the nano-ripples were able to induce cellular alignment within the micro-hexagons. The reasons for these differences were found in the topographical cues. An innovative functionalization strategy of controlling the osteointegration on titanium alloy implants is proposed using the composite micro/nano-structures, which is meaningful in various regenerative medicine applications and implant fields.

Cone beam computed tomography artefacts around dental implants with different materials influencing the detection of peri-implant bone defects.

To investigate the diagnostic accuracy of cone beam computed tomography (CBCT) for the diagnosis of peri-implant bone defects of titanium (Ti), zirconium dioxide (ZrO2 ) or titanium-zirconium (Ti-Zr) alloy implants. Ti, Ti-Zr or ZrO2 implants with two diameters (3.3mm, 4.1mm) and one length (10mm) were inserted in the angle of the mandible of six fresh defrosted pig jaws. Out of the 12 implants inserted, 6 served in the test group with standardized buccal peri-implant bone defects, whereas 6 served as control without bone defects. CBCTs were performed with three acquisition protocols (standard, high and low dose) using two devices. Four observers analysed CBCTs as follows: (a) presence of a peri-implant defect; (b) presence of peri-implant artefacts and impact on defect diagnosis; and (c) linear measurements of buccal peri-implant defect including height and width (in mm). CBCT device, CBCT settings, implant material, implant diameter and observer background did not significantly influence diagnostic accuracy. The sensitivity and specificity values were high for defect detection. ZrO2 led to a lower than average diagnostic accuracy (0.781). The linear measurements of peri-implant defect were underestimated by <1mm on average. The subjective impact of artefacts on defect diagnosis was significantly affected by implant material and observer background. CBCT showed high diagnostic accuracy for peri-implant bone defect detection regardless of the device, imaging setting or implant material used. If CBCT is indicated to assess peri-implant bone disease, low dose protocols could be a promising imaging modality.

Immunomodulation‐Based Strategy for Improving Soft Tissue and Metal Implant Integration and Its Implications in the Development of Metal Soft Tissue Materials

AbstractThe difficulties associated with metal implants and soft tissue integration have significantly affected the applications of metal implants in soft‐tissue‐related areas. Prompted by the close association between soft tissue integration and the immune response, an immunomodulation‐based strategy is proposed to manipulate the immune microenvironment and improve metal implant–soft tissue integration. Considering their vital roles in soft tissue responses to metal implants, macrophages are used and the cytokines fingerprints of M1 and M2 macrophage immune microenvironments are evaluated for their potential modulatory effects on metal implant–soft tissue integration. The modulatory effects of different immune microenvironments on model soft tissue cells (human gingival epithelium cells) cultured on model metal implants (titanium alloy disks) are then described, with the underlying possible mechanism FAK‐AKT‐mTOR signaling unveiled. As further proof of concept, IL‐4/PDA (polydopamine)‐coated titanium alloy implants, aiming at modulating M2 macrophage polarization, are prepared and found to improve the in vivo metal implant‐soft tissue integration. It is the authors' ambition that this immunomodulation‐based strategy will change the negative perception and encourage the active development of metal materials with favorable soft tissue integration properties, thus improving the success rates of perforating metal implants and broadening their application in soft‐tissue‐related areas.

Bioinspired surface hierarchical microstructures of Ti6Al4V alloy with a positive effect on osteoconduction

Osteoconduction is critical for the success of dental and orthopaedic implants. Inspired by the remarkable adhesion of the skin structures in tree frog toe pads, biomimetic hierarchical surface structures on titanium alloy implants are fabricated by laser surface texturing and chemistry surface treatment in this work, to improve osteoconduction on implants. The main differences in the wettability, bioactivity in simulated body fluid and osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti6Al4V samples with smooth surface, micro-hexagons and hierarchical structures, respectively. Noteworthy, bioinspired hierarchical structures displayed the lowest contact angle in hydrophilicity, best bioactivity and excellent cell proliferation. The reasons for these differences were found and discussed in the topographical cues and bioactive surface layer. An innovative functionalization strategy of improving the osteoconduction on titanium alloy implants was proposed using the hierarchical structures, which is meaningful in various tissue engineering applications and implant fields.

Reducing MRI susceptibility artefacts in implants using additively manufactured porous Ti-6Al-4V structures

Magnetic Resonance Imaging (MRI) is critical in diagnosing post-operative complications following implant surgery and imaging anatomy adjacent to implants. Increasing field strengths and use of gradient-echo sequences have highlighted difficulties from susceptibility artefacts in scan data. Artefacts manifest around metal implants, including those made from titanium alloys, making detection of complications (e.g. bleeding, infection) difficult and hindering imaging of surrounding structures such as the brain or inner ear.Existing research focusses on post-processing and unorthodox scan sequences to better capture data around these devices. This study proposes a complementary up-stream design approach using lightweight structures produced via additive manufacturing (AM). Strategic implant mass reduction presents a potential tool in managing artefacts.Uniform specimens of Ti-6Al-4V structures, including lattices, were produced using the AM process, selective laser melting, with various unit cell designs and relative densities (3.1%–96.7%). Samples, submerged in water, were imaged in a 3T MRI system using clinically relevant sequences. Artefacts were quantified by image analysis revealing a strong linear relationship (RR2 = 0.99) between severity and relative sample density. Likewise, distortion due to slice selection errors showed a squared relationship (RR2 = 0.92) with sample density. Unique artefact features were identified surrounding honeycomb samples suggesting a complex relationship exists for larger unit cells.To demonstrate clinical utility, a honeycomb design was applied to a representative cranioplasty. Analysis revealed 10% artefact reduction compared to traditional solid material illustrating the feasibility of this approach.This study provides a basis to strategically design implants to reduce MRI artefacts and improve post-operative diagnosis capability. Statement of SignificanceMRI susceptibility artefacts surrounding metal implants present a clinical challenge for the diagnosis of post-operative complications relating to the implant itself or underlying anatomy. In this study for the first time we demonstrate that additive manufacturing may be exploited to create lattice structures that predictably reduce MRI image artefact severity surrounding titanium alloy implants. Specifically, a direct correlation of artefact severity, both total signal loss and distortion, with the relative material density of these functionalised materials has been demonstrated within clinically relevant MRI sequences. This approach opens the door for strategic implant design, utilising this structurally functionalised material, that may improve post-operative patient outcomes and compliments existing efforts in this area which focus on data acquisition and post-processing methods.

Benefits of additive manufacturing and micro and nano surface texture modifications on mechanical strength and infection resistance of skin-implant interfaces in rats.

Patients find existing exo-prostheses utilizing traditional socket connections uncomfortable and irritating, as they do not provide the dexterity and proprioception which is often expected by active patients. Transcutaneous osseointegrated implants are a potential solution, but carry risk of infection at the skin–implant interface. Histological and observational studies previously demonstrated that textured implants have both improved epidermal ingrowth and decreased skin retraction. This study aimed to determine effects on mechanical integration, barrier to bacterial colonization, and infection of the skin–implant interface using additive manufacturing and post-manufactured surface modifications. In this study, titanium alloy implants were made by either computer numerical control machining (CNC) or electron beam melting (EBM). Implants in each group were left either unaltered (CNC-control and EBM-control), acid etched (CNC-micro and EBM-micro), or oxidatively treated (CNC-nano and EBM-nano) creating six distinct surface textures. This study was divided into two phases, each utilizing 10 rats. Six implants—one of each texture—randomized for position were placed in each rat. Phase 1 animals healed for three weeks and skin-implant mechanical pull-off strength was measured. Phase 2 animals were challenged by S. aureus inoculation during the three-week healing process and serial dilutions of the sonicated implants were performed to quantify bacterial colonization. The three EBM implant groups had 830% greater force at pull-off compared to the three CNC groups. Additionally, the pull-off force of EBM-micro implants was 101% and 83% stronger, respectively, than EBM-nano and EBM-control implants. There was negligible mechanical attachment of skin to any CNC implant. Bacterial colonization counts were collectively 63% ( P &lt; 0.05) lower for EBM implants relative to CNC implants. CNC-control implants exhibited 90% ( P &lt; 0.01) greater bacterial colonization than EBM-controls. No significant differences in bacterial colonization were noted between the other implant groups. Both manufacturing technique and post-manufacturing surface texture modification affected the skin-implant interface’s mechanical integration and effectiveness as a barrier to infection. EBM manufacturing produced markedly superior transcutaneous implants compared to machining.

Модификация поверхности ортопедических имплантатов на основе титановых сплавов

This review is devoted to modern technologies for various modifications of a surface of orthopedic implants made from titanium alloys. This approach will allow improving such characteristics of the implants as a corrosion resistance, biocompatibility and osteointegration. Modifications of titanium alloys with hydroxyapatite and calcium phosphate, multifunctional polymer or antibacterial coatings are considered. Analysis of the studies shows that the implant material can only provide a certain degree of biocompatibility and corrosion resistance, and that the nature and design of its surface have a strong influence on the body's response. Surface modification of implants is a good approach to overcome and solve various problems associated with the disadvantages of titanium alloys for orthopedic implants. titanium alloys, orthopedic implant, functional coating, ceramic coating, polymer coating, antibacterial coating The reported study was funded by RFBR, project No 19-18-50015.

Assessing osseointegration of metallic implants with boronized surface treatment.

Background Modification of endosteal implants through surface treatments have been investigated to improve osseointegration. Boronization has demonstrated favorable mechanical properties, but limited studies have assessed translational, in vivo outcomes. This study investigated the effect of implant surface boronization on bone healing. Material and Methods Two implant surface roughness profiles (acid etched, machined) in CP titanium (type II) alloy implants were boronized by solid-state diffusion until 10-15µm boron coating was achieved. The surface-treated implants were placed bilaterally into 5 adult sheep ilia for three and six weeks. Four implant groups were tested: boronized machined (BM), boronized acid-etched (BAA), control machined (CM), and control acid-etched (CAA). Osseointegration was quantified by calculating bone to implant contact (BIC) and bone area fraction occupancy (BAFO). Results Both implant types treated with boronization had BIC values not statistically different from machined control implants at t=3 weeks, and significantly less than acid-etched control (p<0.02). BAFO values were not statistically different for all 3-week groups except machined control (significantly less at p<0.02). BAFO had a significant downward trend from 3 to 6 weeks in both boronized implant types (p<0.03) while both control implant types had significant increases in BIC and BAFO from 3 to 6 weeks. Conclusions Non-decalcified histology depicted intramembranous-like healing/remodeling in bone for controls, but an absence of this dynamic process in bone for boronized implants. These findings are inconsistent with in vitro work describing bone regenerative properties of elemental Boron and suggests that effects of boron on in vivo bone healing warrant further investigation. Key words:Boronization, acid-etched, machined, implants, osseointegration, in vivo, solid-state diffusion.

Picosecond laser texturing on titanium alloy for biomedical implants in cell proliferation and vascularization.

Introducing specific textures to titanium alloy implant surface is helpful to modify the surface properties of materials. In this article, biomedical TC4 (Ti-6Al-4V) alloy was textured by a 10-ps infrared laser. Laser parameters that directly affected the detailed dimension of textures and its characteristics were optimized within laser power, defocusing amount, and scanning parameters via response surface methodology. These textures consisted of groove array about 30-90 μm in depth and 100 μm in width were prepared and their surface property (including surface morphology, element composition, wetting behavior, and biocompatibility) was analyzed. Surface characteristic analysis indicated that picosecond laser texturing improved surface properties and biocompatibility mainly by altering the microstructure and morphology of materials. In addition, laser textured groove array promoted contact area and hydrophobicity of material surface. Cell culture experiments and animal studies showed that titanium alloy implants with 30- and 60-μm-deep groove arrays on the surface-enhanced cell proliferation and adhesion. Meanwhile, compared to the polished samples, these groove arrays promoted the growth of new blood vessels and enhanced the combination of blood vessel and implants in vivo. That is, the deeper groove array was, and the better vascularizing effect the blood vessel exhibited.

Carbides formation in weld metal produced by recycling of titanium machining swarf

Application of titanium alloys for orthodontic implants have increase in last years and it has generated a great amount of titanium chips which are disposed as metal scrap. Titanium carbide has high hardness and can be applied as coating reinforcement against wear. Chips of titanium alloys were processed and used in the fabrication of experimental hardfacing consumables for improving the resistance of wear of mechanical components. Coatings were produced in cast steel specimens using the gas tungsten arc welding process. Microstructure was investigated by means of scanning electron microscopy. Microhardness of the coatings was analyzed by a dynamic ultra-micro hardness tester. The microstructure of the welding metal was composed of circular particles of titanium carbide surrounded by a ferritic matrix. The measures made by electron dispersive spectroscopy showed a variation in titanium amount trough the weld, where larger contents of titanium were found, and the matrix. The crystallographic analyses reinforced the formation of titanium carbides embedded in a ferrite matrix into welding metal.

New Dental Implant with 3D Shock Absorbers and Tooth-Like Mobility-Prototype Development, Finite Element Analysis (FEA), and Mechanical Testing.

Background: Once inserted and osseointegrated, dental implants become ankylosed, which makes them immobile with respect to the alveolar bone. The present paper describes the development of a new and original implant design which replicates the 3D physiological mobility of natural teeth. The first phase of the test followed the resistance of the implant to mechanical stress as well as the behavior of the surrounding bone. Modifications to the design were made after the first set of results. In the second stage, mechanical tests in conjunction with finite element analysis were performed to test the improved implant design. Methods: In order to test the new concept, 6 titanium alloy (Ti6Al4V) implants were produced (milling). The implants were fitted into the dynamic testing device. The initial mobility was measured for each implant as well as their mobility after several test cycles. In the second stage, 10 implants with the modified design were produced. The testing protocol included mechanical testing and finite element analysis. Results: The initial testing protocol was applied almost entirely successfully. Premature fracturing of some implants and fitting blocks occurred and the testing protocol was readjusted. The issues in the initial test helped design the final testing protocol and the new implants with improved mechanical performance. Conclusion: The new prototype proved the efficiency of the concept. The initial tests pointed out the need for design improvement and the following tests validated the concept.

Titanium Alloy Intramedullary Nails and Plates Affect Serum Metal Ion Levels within the Fracture Healing Period.

Titanium alloy implants are the most used materials for the fixation of lower extremity fractures. Although these implants were thought to be inert materials in vitro, several studies have shown increased serum and remote tissue metal ion levels due to wear of implants and friction of the bone-implant interface in vivo. The aim of this study was to investigate the alteration of serum metal ion levels that are released from intramedullary nails and plates used for the fixation of lower extremity fractures, within the fracture healing period. The study included 20 adult patients, who were treated with intramedullary nail or plate osteosynthesis due to closed lower extremity fractures. Alterations of serum titanium, aluminum, molybdenum, and vanadium levels were evaluated at 6, 12, 18, and 24 weeks postoperatively. A statistically significant increase was determined in serum titanium, aluminum, molybdenum, and vanadium ion levels in the intramedullary nail and plate groups at the end of the follow-up period. Pairwise comparisons of metal ion levels between implant groups revealed no significant difference during a 24-week follow-up period. Compared to the control group, statistically significant increased levels of serum titanium, aluminum, vanadium, and molybdenum ions were determined in the implant groups used for the fixation of lower extremity fractures at the end of 24 weeks. In the current literature, the potential toxic effects of prolonged exposure to low levels of these metal ions are still unknown. It can be predicted that long-term metal ion exposure could result in vivo pathological processes in the future.

Enhanced Osseointegration of Titanium Alloy Implants with Laser Microgrooved Surfaces and Graphene Oxide Coating.

Rapid and effective osseointegration, as a critical factor in affecting the success rate of titanium (Ti) implants in orthopedic applications, is significantly affected by their surface microstructure and chemical composition. In this work, surface microgrooved Ti-6Al-4V alloys with graphene oxide coating (Ti-G-GO) were fabricated by a combination of laser processing and chemical assembly techniques. The osteogenic capability in vitro and new bone formation in vivo of the implants were systematically investigated, and biomechanical pull-out tests of the screws were also performed. First, in vitro studies indicated that the optimal microgroove width of the titanium alloy surface was 45 μm (Ti-G), and the optimum GO concentration was 1 mg/mL. Furthermore, the effects of the surface microstructure and GO coating on the in vitro bioactivity were investigated through culturing bone marrow mesenchymal stem cells (BMSCs) on the surface of titanium alloy plates. The results showed that the BMSCs cultured on the Ti-G-GO group exhibited the best adhesion, proliferation, and differentiation, compared with that on the Ti-G and Ti groups. Micro-computed tomography evaluation, histological analysis, and pull-out testing demonstrated that both Ti-G and Ti-G-GO implants had the higher osseointegration than the untreated Ti implant. Moreover, the osteogenic capability of the Ti-G-GO group appeared to be superior to that of the Ti-G group, which could be attributed to the improvement of surface wettability and apatite formation by the GO coatings. These results suggest that the combination of the microgroove structure and GO coatings exhibits considerable potential for enhancing the surface bioactivation of materials, and the combination modification is expected to be used on engineered titanium alloy surfaces to enhance osseointegration for orthopedic applications.

Assessment of signal-to-noise ratio and contrast-to-noise ratio in 3 T magnetic resonance imaging in the presence of zirconium, titanium, and titanium-zirconium alloy implants.

We quantitatively compared the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in T1 weighted imaging (WI) and T2 WI sequences in 3 Tesla (T) magnetic resonance imaging (MRI) using zirconium, titanium (grades 4 and 5), and titanium-zirconium alloy implants to evaluate the effect of implant type and imaging sequence. MRI was acquired using a 3 T magnet with a 16-channel head coil. Implants of each type were mounted in gel and scanned in axial, coronal, and sagittal planes using fast spin echo sequences in T1 WI (TR = 600, TE = 12 milliseconds) and T2 WI (TR = 3000, TE = 80 milliseconds) sequences. Data were transferred to Synapse 3-D software, and images were measured twice by an oral and maxillofacial radiologist blinded to the type of implants. Zirconium implants resulted in the lowest SNR and CNR values (P < .05). No significant differences were identified between titanium (grades 4 and 5) and titanium-zirconium implants. The T2 WI sequence had a significantly higher SNR and CNR than T1 WI. There was no difference in intraobserver agreement between T1 WI and T2 WI. CNR and SNR at 3 T MRI are dependent on implant type and imaging sequence. Titanium (grades 4 and 5) and titanium-zirconium implants and the T2 WI sequence produced higher SNR and CNR values.

Self-organized TiO2 nanotube layer on Ti–Nb–Zr alloys: growth, characterization, and effect on corrosion behavior

Ti alloys are widely applied in implanted biomedical devices due to their unique mechanical and biological performances. A strategy employed to improve bone integration on orthopedic and dental implants is to grow a self-organized TiO2 nanotube layer on the surface of titanium alloy implants. This paper describes the formation of self-organized TiO2 nanotubes on Ti–35Nb–2Zr and Ti–35Nb–4Zr alloys by the anodization process, as well as the effects of Zr content on TiO2 phase stability. The morphological and chemical characteristics of the nanotubes were analyzed by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron microscopy. In addition, a comparison was made of the electrochemical stabilities of TiO2 nanotube-coated surfaces and surfaces without nanotubes, which revealed higher corrosion resistance for the nanotube-modified surface. The electrochemical impedance spectroscopy results were fitted with two-time constant equivalent circuit representing the barrier layer (nanotube bottom) and the porous layer (nanotube wall). The addition of Zr suppressed ω-phase formation, preserving the alloy’s low elastic modulus (64 GPa). This Zr addition also delayed the anatase-to-rutile transformation and slightly increased the nanotubes’ length to 1.14 µm. These features make the Ti–35Nb–4Zr alloy a very good candidate for use in the biomedical field, especially for applications that require low elastic modulus with enhanced corrosion resistance.

Research of dental cements properties in experiment on remote teeth reinforced by individual transdental implants

The paper presents the results of experimental studies of the adhesion strength at a static load on the gap of dental cement joints of an individual milled transdental implant with solid tissues of the tooth root. The samples consisted of a composition composed of a conical-shaped structure (similar to a transdental implant made of titanium alloy and zirconium dioxide) inserted into the canal of a natural tooth stump and fixed in it with cement gluing. The experiments were performed on previously removed teeth with a resected root tip in the amount of 78 units. As a result of the study, cements were identified that ensure the highest adhesive strength of the joint “individual transdental implant–dental cement–stump of an extracted tooth” in the specimen. For the root fixation of titanium alloy implants, composite Multilink-N cement is recommended, and for zirconium dioxide implants, Fuji-1 glass ionomer cement is recommended. At the second stage, the effect of artificial surface roughness of the implant on the adhesion properties of the cement joint implant–tooth was investigated. To this end, before conducting experiments on the extrusion of the pins, the samples surfaces were sandblasted with aluminum oxide granules of 50, 150, 250 microns in size. Cements were used for fixation, which showed the highest adhesive characteristics at the previous stage. It turned out that an increase in the roughness size in the range of 50–250 μm improves the adhesion parameters of the cement joint implant – tooth for all tested cements. The presence of implant roughness allows one to withstand a significantly greater load compared to a smooth implant, and an increase in the implant surface roughness value from 50 to 250 μm also significantly (almost 2.5 times) increases the load.

Fabrication and Analysis of a Ti6Al4V Implant for Cranial Restoration

A custom made implant is critical in cranioplasty to cushion and restore intracranial anatomy, as well as to recover the appearance and attain cognitive stability in the patient. The utilization of customized titanium alloy implants using three-dimensional (3D) reconstruction technique and fabricated using Electron Beam Melting (EBM) has gained significant recognition in recent years, owing to their convenience and effectiveness. Besides, the conventional technique or the extant practice of transforming the standard plates is unreliable, arduous and tedious. As a result, this work aims to produce a customized cranial implant using 3D reconstruction that is reliable in terms of fitting accuracy, appearance, mechanical strength, and consistent material composition. A well-defined methodology initiating from EBM fabrication to final validation has been outlined in this work. The custom design of the implant was carried out by mirror reconstruction of the skull’s defective region, acquired through computer tomography. The design of the customized implant was then analyzed for mechanical stresses by applying finite element analysis. Consequently, the 3D model of the implant was fabricated from Ti6Al4V ELI powder with a thickness of ≃1.76–2 mm. Different tests were employed to evaluate the bio-mechanical stability and strength of the fabricated customized implant design. A 3D comparison study was performed to ensure there was anatomical accuracy, as well as to maintain gratifying aesthetics. The bio-mechanical analysis results revealed that the maximum Von Mises stress (2.5 MPa), strain distribution (1.49 × 10−4) and deformation (3.26 × 10−6 mm) were significantly low in magnitude, thus proving the implant load resistance ability. The average yield and tensile strengths for the fabricated Ti6Al4V ELI EBM specimen were found to be 825 MPa and 880 MPa, respectively, which were well over the prescribed strength for Ti6Al4V ELI implant material. The hardness study also resulted in an acceptable outcome within the acceptable range of 30–35 HRC. Certainly, the chemical composition of the fabricated EBM specimen was intact as established in EDX analysis. The weight of the cranial implant (128 grams) was also in agreement with substituted defected bone portion, ruling out any stress shielding effect. With the proposed approach, the anatomy of the cranium deformities can be retrieved effectively and efficiently. The implementation of 3D reconstruction techniques can conveniently reduce tedious alterations in the implant design and subsequent errors. It can be a valuable and reliable approach to enhance implant fitting, stability, and strength.

Mechanical and biological properties of graded porous tantalum coatings deposited on titanium alloy implants by vacuum plasma spraying

Tantalum (Ta) has excellent mechanical properties, biocompatibility and chemical stability, and is more osteoconductive than titanium or cobalt-chromium alloys. However, it has a relatively high cost and is not easily fabricated. Accordingly, in the present study, a vacuum plasma spraying technique was used to deposit Ta powder in three successive layers on Ti6Al4V substrates. In the deposition process, the melting rate of the Ta powder was controlled by regulating the spray power and powder particle size in such a way as to form a coating with a porosity which increased from the inner layer to the outer layer. The Ta-coatings were processed by alkali treatment (AT), AT and heat treatment (AHT), and AHT with ultrasonic cleaning (AHT-UC), respectively. The average bond strength of the as-sprayed coating was approximately 54.5 ± 2.3 MPa. Moreover, the average porosity and roughness Ra of the coating surface were around 13% and 22.2 μm, respectively. The average porosity of the coating (with a thickness of 350–380 μm) increased from 0.6% in the inner layer to 7.6% in the outer layer. The corresponding hardness and elastic modulus (E) values decreased from 240 ± 20 to 167 ± 62 HV0.1 and 148 ± 5 to 123 ± 4 GPa, respectively. Bone-like apatite inducement tests performed in simulated body fluid (SBF) showed a particularly rapid growth of apatite on the AHT-UC Ta-coating due to the formation of amorphous sodium tantalate during AT. Furthermore, the results obtained from initial in vitro biocompatibility tests showed that osteoblast-like osteosarcoma MG-63 cells had a significantly better attachment and spreading on the Ta-coating and AHT-UC coating following culturing for 3 h than on the untreated Ti6Al4V sample. In other words, both coatings provided a better initial biocompatibility than the native Ti6Al4V substrate.