3D-printed Ti6Al4V Research Articles

The Microstructural and Phase Evolution of the 3D Printed Ti–6Al–4V Alloy during Mechanical Loading

The Microstructural and Phase Evolution of the 3D Printed Ti–6Al–4V Alloy during Mechanical Loading

The Microstructural and Phase Evolution of the 3D Printed Ti–6Al–4V Alloy during Mechanical Loading

This paper presents the results of an in situ study on the evolution of the microstructure and phase composition of 3D-printed Ti–6Al–4V samples under tension in the transmission electron microscope col-umn. The microstructure of Ti–6Al–4V specimens manufactured by wire-feed electron beam additive tech-nology is shown to consist of columnar primary β-grains inside of which are α/α'-Ti laths separated by layers of the residual β-phase and gathered into packets. A characteristic feature of 3D-printed Ti–6Al–4V samples is the concentration nonuniformity of the alloying elements due to the partial decomposition of the marten-sitic α'-phase. The reorientation of the α/α'-Ti lattice near interfaces takes place during uniaxial tension. Deformation-induced α'→α" transformations can develop in the reoriented regions of the α/α'-Ti lattice, in places enriched in vanadium.

A preclinical study comparing single- and double-root 3D-printed Ti–6Al–4V implants

Recently, double-root implants have been investigated using 3D-printed technology. Here, we investigated damping capacity, microcomputed tomographic (micro-CT) and histological analyses of double-root 3D-printed implants compared with single-root 3D printed implants. Single- and double-root 3D-printed implants were fabricated and placed at both sides of mandibular third and fourth premolars in four beagle dogs. The damping capacity was measured, and periapical X-rays were taken every 2 weeks for 12 weeks. The bone volume/tissue volume (BV/TV) and bone mineral density (BMD) around the implants were measured with micro-CT. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were measured in histological samples. The implant stability values between the groups were not significantly different, except at 4 and 12 weeks. The marginal bone changes were similar at the mesial and distal areas between the groups. The BV/TV and BMD values of the double-root 3D-printed implants showed no statistical difference through micro-CT analysis, but the double-root 3D-printed implants showed lower BIC and BAFO values through histomorphometric analysis compared to the single-root 3D-printed implants. Compared to single-root implants, 3D-printed double-root implants demonstrated comparable stability and bone remodeling around the fixtures, but the statistically significant bone loss in the furcation area remains problematic.

A pH-neutral bioactive glass coated 3D-printed porous Ti6Al4V scaffold with enhanced osseointegration.

Osseointegration is vital for the success of non-degradable implants like those made of titanium alloys. In order to promote osseointegration, implants are made porous, providing space for bone ingrowth. Despite extensive optimization of the pore geometry and porosity, bone ingrowth into implants is still marginal; further modification to promote bone ingrowth as well as osseointegration becomes paramount. In this study, a pH neutral bioactive glass with the composition of 10.8% P2O5-54.2% SiO2-35% CaO (mol%; hereinafter referred to as PSC) was successfully coated on 3D-printed porous Ti6Al4V scaffolds using an in situ sol-gel method. This PSC coating is strongly bonded to the substrate and quickly induces the formation of hydroxyapatite on the scaffold surface upon contact with body fluid. In vitro, the PSC-coated Ti6Al4V scaffolds showed superior biocompatibility, cell proliferation promotion, cell adhesion, osteogenic differentiation and mineralization compared to their bare counterparts, implying better osseointegration. In vivo experiments confirmed this expectation; after being implanted, the coated scaffolds had more bone ingrowth and osseointegration, and consequently, higher push-out strength was achieved, proving the validity of the proposed concept in this study. In conclusion, PSC coating on 3D-printed porous Ti6Al4V scaffolds can improve osteogenesis, bone ingrowth, and osseointegration. Together with the versatility of this in situ sol-gel coating method, titanium alloy implants with better biological performances may be developed for immediate clinical applications.

Additive manufacturing of bionanomaterials for biomedical applications based on TI6AL4V and PLA: a systematic review

Additive manufacturing (AM) is the owner of a huge potential as a manufacturing technology in fabricating functional implants, and scaffolds for biomedical applications. AM, which includes 3D printing (3DP) and 3D bioprinting, can be the solution to produce several needs such as scaffolds/implants, tissue or organs, or medical devices by combining different biomaterials with nanomaterials. Titanium and its alloys and Polylactic acid (PLA) are commonly used in bone tissue repair with their superior bio-functionality. The rapid advancement of three-dimensional (3D) printing technology has enabled the fabrication of porous titanium and polymer composite scaffolds with controllable microstructures, which is regarded as an effective method for promoting rapid bone repair. An electronic literature search was conducted in PubMed, Web of Science, Scopus, Elsevier, Embase, and other numerous databases up to December 2021 which are accessed by Karabuk university. To evaluate the possibility of bias and methodological quality, the SYRCLE tool and the last version of the CAMARADES list were used, respectively, a meta-analysis could not be performed. This systematic review is aimed to evaluate the common biomedical potential of 3D-printed porous Ti6Al4V (Ti64) and PLA matrix scaffold for repairing bone defects to investigate the influential factors that might affect its osteogenic availability. The most ideal parameters for designing the Ti64 scaffold were found to be a pore size of around 300-400 m and porosity of 60-70%, while PLA scaffolds show 350-400 m and nearly the same percentage in porosity as Ti64.

Cell response and bone ingrowth to 3D printed Ti6Al4V scaffolds with Mg-incorporating sol–gel Ta2O5 coating

A Mg-incorporating Ta coating was deposited on a 3D-printed Ti6Al4V scaffold using a sol–gel method. The coating enhanced osteogenic differentiation of BMSCs and bone ingrowth in vivo.

Characterization of biomaterials with reference to biocompatibility dedicated for patient-specific finger implants

Purpose The research was focused on determining basic mechanical properties, surface and phase structure taking into consideration basic cytotoxicity analysis towards human cells. Methods Biological tests were performed on human C-12302 fibroblasts cells using 3D-printed Ti6Al4V alloy (Ti64), produced by laser-based powder bed fusion (LB-PBF) and Alumina Toughened Zirconia 20 (ATZ20), produced by lithography-based ceramic manufacturing (LCM). Surface modifications included electropolishing, and hydroxyapatite or hydroxyapatite/zinc coating. Structure analysis was carried out using a variety of techniques such as X-Ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM), followed by mechanical properties evaluation using nanoindentation testing. Results Samples subjected to surface modifications showed diversity among surface and phase structure and mechanical properties. However, the cytotoxicity towards tested cells was not significantly higher than the control. Though, a trend was noted among the materials analysed, indicating that HAp/Zn coating on Ti64 and ATZ20 resulted in the best biological performance Conclusions Hydroxyapatite coating on Ti64 and ATZ20 resulted in the best biological properties. Tested materials are suitable for in vivo toxicity testing.

Whole Blood Titanium Concentration after Limb Salvage Surgery with Three-Dimensional-Printed Ti6Al4V Implants.

Three-dimensional (3D)-printed customized implants can be fabricated and utilized for all bones with massive bone defects. The main safety issues with 3D-printed implants made of Ti6Al4V alloy are related to the release of metal debris and residual powder. In this study, we investigated the perioperative titanium concentrations in whole blood and peri-implant fluid samples of patients who underwent limb salvage surgery with a 3D-printed Ti6Al4V implant. Nineteen patients who underwent limb salvage surgery with 3D-printed Ti6Al4V implants were divided into two groups: the serial samples group and the follow-up group. To observe metal distribution and clearance in the body, serial samples of blood and peri-implant fluid from the surgical drain were prospectively collected for five patients in the serial samples group. For the remaining 14 patients who were followed up for more than a year, blood samples were collected only once. In the serial samples group, the mean baseline titanium concentration was 0.78 µg/L (range, 0.1-2.2 µg/L): 3 patients showed peak concentration before the third postoperative month, while 2 patients still showed an increasing pattern at this point. Total titanium mass in the surgical drain showed a wash-out phenomenon in a week, with a significant uniform decrease (p = 0.04). In 14 patients in the follow-up group, the mean titanium concentration in the whole blood was 10.8 µg/L (range, 0.3-36.6 µg/L). For the 14 patients with a long-term follow-up, the aluminum and vanadium concentrations were all negligible. Whole blood titanium concentrations were higher after surgery using 3D-printed implants than after that using conventional orthopedic implants, but markedly lower than in patients with implant failure. None of the patients developed serious clinical adverse effects during follow-up.

Investigation on fluid jet polishing of AISI H13 die steel using a single nozzle tool

The fluid jet polishing (FJP) is an ultra-precision and non-contact type polishing process for generating high-quality surface finish in automotive dies manufactured from ductile materials like AISI H13 die steel. This paper presents a study on FJP polishing of AISI H13 die steel material using a custom-designed 3D-printed Ti6Al4V (Ti64) nozzle and silicon carbide (SiC) abrasive slurry. The study presents an effect of pressure, stand-off distance and polishing time on the surface finish while using water-based abrasive slurry mixed with water-soluble cutting oil. The Central Composite Design (CCD) method was used to develop the experimental plan. ANOVA analysis was performed to develop a regression model and find the contribution of each parameter on the percentage change in surface roughness. The regression model developed for the FJP process was validated by polishing the plate specimen of AISI H13 having [Formula: see text] average initial surface roughness with the optimized parameters; pressure of [Formula: see text], stand-off distance of [Formula: see text] and polishing time of [Formula: see text]. The optimized FJP parameters were able to generate the surface roughness of [Formula: see text] in one of the confirmation tests. The results of percentage change in surface roughness obtained from the confirmation experiments were found to be very close to the predicted results which validated the regression model developed for polishing of AISI H13 using FJP process. In addition, the optimal feed rate of 20 mm/min was used to polish [Formula: see text]plate made of AISI H13, the surface roughness was reduced from 500 nm to 130 nm in 99.2 min showing the reduction in peaks and valleys with surface improvement of 74% which results in enhanced polishing efficiency.

Increasing the Fatigue Durability of an 3D-Printed Ti–6Al–4V Alloy Electron-Beam Welded Joint by Ultrasonic Electropulsing Shock Treatment

Increasing the Fatigue Durability of an 3D-Printed Ti–6Al–4V Alloy Electron-Beam Welded Joint by Ultrasonic Electropulsing Shock Treatment

Combined Effects of Polydopamine-Assisted Copper Immobilization on 3D-Printed Porous Ti6Al4V Scaffold for Angiogenic and Osteogenic Bone Regeneration

Numerous studies have demonstrated that biological compounds and trace elements such as dopamine (DA) and copper ions (Cu) could be modified onto the surfaces of scaffolds using a one-step immersion process which is simple, inexpensive and, most importantly, non-cytotoxic. The development and emergence of 3D printing technologies such as selective laser melting (SLM) have also made it possible for us to fabricate bone scaffolds with precise structural designs using metallic compounds. In this study, we fabricated porous titanium scaffolds (Ti) using SLM and modified the surface of Ti with polydopamine (PDA) and Cu. There are currently no other reported studies with such a combination for osteogenic and angiogenic-related applications. Results showed that such modifications did not affect general appearances and microstructural characteristics of the porous Ti scaffolds. This one-step immersion modification allowed us to modify the surfaces of Ti with different concentrations of Cu ions, thus allowing us to fabricate individualized scaffolds for different clinical scenarios. The modification improved the hydrophilicity and surface roughness of the scaffolds, which in turn led to promote cell behaviors of Wharton’s jelly mesenchymal stem cells. Ti itself has high mechanical strength, therefore making it suitable for surgical handling and clinical applications. Furthermore, the scaffolds were able to release ions in a sustained manner which led to an upregulation of osteogenic-related proteins (bone alkaline phosphatase, bone sialoprotein and osteocalcin) and angiogenic-related proteins (vascular endothelial growth factor and angiopoietin-1). By combining additive manufacturing, Ti6Al4V scaffolds, surface modification and Cu ions, the novel hybrid 3D-printed porous scaffold could be fabricated with ease and specifically benefited future bone regeneration in the clinic.

The Effect of Electropulsing-Assisted Ultrasonic Impact Treatment on the Microstructure, Phase Composition, and Microhardness of Electron-Beam-Welded 3D Printed Ti–6Al–4V Alloy

The Effect of Electropulsing-Assisted Ultrasonic Impact Treatment on the Microstructure, Phase Composition, and Microhardness of Electron-Beam-Welded 3D Printed Ti–6Al–4V Alloy

Development and evaluation of hydroxytite-based anti-microbial surface coatings on polydopamine-treated porous 3D-printed Ti6Al4V alloys for overall biofunctionality

The current investigation aims to develop hydroxyapatite-based biofunctional composite coatings on polydopamine-treated porous 3D-printed Ti6Al4V alloy implant specimens for orthopedic uses. The porous 3D-printed implants based on Ashby Gibson’s mathematical model for cellular materials are fabricated at a 65% level of porosity, so as to attain the mechanical strength of human bones. Further, the addition of strontium and silver in hydroxyapatite for improved biocompatibility of the 3D-printed implant to enhance its biofunctionality and its validation is performed. The resulting coated substrates are subjected to a series of morphological, elemental, phase, mechanical, and biological tests. When subjected to the uniaxial compression, the values for modulus of elasticity and yield strength of 3D-printed substrates are compared to the targeted value of elastic modulus and yield strength for the human bones (10–30 GPa and 148–240 MPa, respectively). The effect of polydopamine-treated 3D-printed Ti6Al4V substrates on the coating compositions of calcium and phosphorus has been compared to the untreated samples. The coating thickness and adhesion strength have been calculated and compared for different coating groups. All the samples, except untreated pure hydroxyapatite samples, displayed antimicrobial activity for both the gram-positive and gram-negative bacteria in the zone inhibition test. Hence, the current experiment provides a novel option to fabricate porous Ti6Al4V scaffolds, with a low-temperature surface coating to attain improved biofunctionality for orthopedic applications.

In vivo study of dual functionalized mussel-derived bioactive peptides promoting 3D-printed porous Ti6Al4V scaffolds for repair of rabbit femoral defects.

The 3D printed porous titanium alloy scaffolds are beneficial to enhance angiogenesis, osteoblast adhesion, and promote osseointegration. However, titanium alloys are biologically inert, which makes the bond between the implant and bone tissue weak and prone to loosening. Inspired by the natural biological marine mussels, we designed four-claw-shaped mussel-derived bioactive peptides for the decoration of porous titanium alloy scaffolds: adhesion peptide-DOPA, anchoring peptide-RGD and osteogenic-inducing peptide-BMP-2. And the bifunctionalization of 3D-printed porous titanium alloy scaffolds was evaluated in vivo in a rabbit model of bone defect with excellent promotion of osseointegration and mechanical stability. Our results show that the in vivo osseointegration ability of the modified 3D printed porous titanium alloy test piece is significantly improved, and the bifunctional polypeptide coating group E has the strongest osseointegration ability. In conclusion, our experimental design partially solves the problems of stress shielding effect and biological inertness, and provides a convenient and feasible method for the clinical application of titanium alloy implants in biomedical implant materials.

Construction of a Hierarchical Micro-/Submicro-/Nanostructured 3D-Printed Ti6Al4V Surface Feature to Promote Osteogenesis: Involvement of Sema7A through the ITGB1/FAK/ERK Signaling Pathway.

Constructing hierarchical hybrid structures is considered a facile method to improve the osseointegration of implants. Herein, a hierarchical micro-/submicro-/nanostructured surface feature of Ti6Al4V implants (3DAT group) was successfully constructed by combining the inherently formed three-dimensional (3D)-printed microscale topography, acid-etched sub-micropits, and anodized nanotubes. Compared with the classical SLA surface, the microscale topography and sub-micropits increased the three-dimensional space for the cell growth and mechanical stability of implants, while the modification of nanotubes dramatically improved the surface hydrophilicity, protein adsorption, and biomineralization. Most importantly, the 3DAT surface feature possessed excellent osteogenic performance in vitro and in vivo, with the involvement of semaphorin 7A (Sema7A) as revealed by RNA-seq through the ITGB1/FAK/ERK signaling pathway. The present study suggested that the hierarchically structured surface design strategy could accelerate the osseointegration rate of 3D-printed Ti6Al4V implants, promising personalized reconstruction of bone defects.

Quercetin-Coating Promotes Osteogenic Differentiation, Osseointegration and Anti-Inflammatory Properties of Nano-Topographic Modificated 3D-Printed Ti6Al4V Implant.

The capabilities of osseointegration and anti-inflammatory properties are of equal significance to the bio-inert titanium implant surface. Quercetin has proved its capacities of activating anti-inflammation through macrophage modulation and promoting osteogenic differentiation. Herein, we fabricated quercetin-coating on nano-topographic modificated 3D-printed Ti6Al4V implant surface. Subsequently the biological cells responses in vitro, anti-inflammatory and osseointegration performance in vivo were evaluated. In vitro studies indicated that quercetin-coating can enhance the adhesion and osteogenic differentiation of rBMSCs, while modulating the polarization of macrophages from M1 to M2 phase and improving the anti-inflammatory and vascular gene expression. Moreover, quercetin-loaded implants reduced the level of peri-implant inflammation and ameliorated new bone formation and rapid osseoinegration in vivo. Quercetin-coating might provide a feasible and favorable scheme for endowing 3D-printed titanium alloy implant surface with enhanced the rapid osseointegration and anti-inflammatory properties.

Biomimetic design strategy of complex porous structure based on 3D printing Ti-6Al-4V scaffolds for enhanced osseointegration

Ti6Al4V is extensively utilized as orthopedic implants owing to its outstanding biocompatibility and mechanical qualities. However, because Ti6Al4V has a high strength, it is substantially stiffer than natural bone, resulting in stress shielding. To resolve this issue, an effective way is to construct porous titanium alloy scaffolds with adjustable pore size and porosity, and 3D printing technology may be utilized to build complex bespoke forms that fit our specifications. In this work, 3D-printed porous Ti6Al4V scaffolds with imitation of trabecular structure (ITS) and the corresponding regular structure scaffolds (RS), which have three different average pore size (300/400/500 μm), were prepared by selective laser melting technology. A series of in vitro and in vivo experiments were used to assess the scaffolds' physiochemical characteristics, as well as their osseointegration capabilities. The findings revealed that the ITS scaffolds were conducive to cell proliferation and osteogenic differentiation. And the in vivo performance was examined through rabbit tibia bone defect model, the results demonstrated that the ITS scaffolds with average pore size of 400 μm showed the ideal osseointegration potential. Therefore 3D-printed titanium scaffolds with imitation of trabecular structure provides a viable bio-inspired structural and functional design method of titanium alloy orthopedic implants.

Mesh Ti6Al4V Material Manufactured by Selective Laser Melting (SLM) as a Promising Intervertebral Fusion Cage.

Intervertebral cages made of Ti6Al4V alloy show excellent osteoconductivity, but also higher stiffness, compared to commonly used polyether-ether-ketone (PEEK) materials, that may lead to a stress-shielding effect and implant subsidence. In this study, a metallic intervertebral fusion cage, with improved mechanical behavior, was manufactured by the introduction of a three-dimensional (3D) mesh structure to Ti6Al4V material, using an additive manufacturing method. Then, the mechanical and biological properties of the following were compared: (1) PEEK, with a solid structure, (2) 3D-printed Ti6Al4V, with a solid structure, and (3) 3D-printed Ti6Al4V, with a mesh structure. A load-induced subsidence test demonstrated that the 3D-printed mesh Ti6Al4V cage had significantly lower tendency (by 15%) to subside compared to the PEEK implant. Biological assessment of the samples proved that all tested materials were biocompatible. However, both titanium samples (solid and mesh) were characterized by significantly higher bioactivity, osteoconductivity, and mineralization ability, compared to PEEK. Moreover, osteoblasts revealed stronger adhesion to the surface of the Ti6Al4V samples compared to PEEK material. Thus, it was clearly shown that the 3D-printed mesh Ti6Al4V cage possesses all the features for optimal spinal implant, since it carries low risk of implant subsidence and provides good osseointegration at the bone-implant interface.

Practically applicable water oxidation electrodes from 3D-printed Ti6Al4V scaffolds with surface nanostructuration and iridium catalyst coating

This study establishes the applicability of 3D printing (additive manufacturing) towards the generation of titanium alloy scaffolds for water oxidation electrodes. The scaffolds can be subsequently nanostructured by electrochemical anodization to enhance their surface area and coated with iridium as the electrocatalyst. We focus on the characterization of the functional electrodes in process-relevant conditions (1 M H2SO4, 60 ∘C, stirring) in terms of their performance and stability in a holistic manner. Various preparative conditions yield various patterns of performance and stability, as quantified by overpotentials η10 in steady-state electrolyses, maximum current densities jmax in dynamic voltammetry, surface roughness rf, and by overpotential increase, iridium loss, and jmax decrease after 100 h of operation, on the other hand. In other words, the system is highly flexible and can be adapted to specific constraints depending on the application chosen.

Facile Fabrication of 3D-Printed Porous Ti6Al4V Scaffolds with a Sr-CaP Coating for Bone Regeneration.

To improve osseointegration caused by the stress-shielding effect and the inert nature of titanium-based alloys, in this work, we successfully constructed a strontium calcium phosphate (Sr-CaP) coating on three-dimensional (3D)-printed Ti6Al4V scaffolds to address this issue. The energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) results indicated that the coatings with and without Sr doping mainly consisted of CaHPO4. The bonding strength of Sr doping coating met the required ISO 13 779-4-2018 standard (≥15 MPa). The in vitro results suggested that the Sr-CaP-modified Ti6Al4V scaffolds were found to effectively promote mice bone-marrow stem cell (mBMSC) adhesion, spreading, and osteogenesis. The in vivo experiments also showed that the Sr-CaP-modified Ti6Al4V scaffolds could significantly improve bone regeneration and osseointegration. More importantly, Sr-doped CaP-coated Ti6Al4V scaffolds were found to accelerate bone healing in comparison to CaP-coated Ti6Al4V scaffolds. The Sr-CaP-modified Ti6Al4V scaffolds are considered a promising strategy to develop bioactive surfaces for enhancing the osseointegration between the implant and bone tissue.