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Photograph of the additive manufacturing machine used to fabricate the studied parts. Selective Laser Melting (SLM) process, model 125 HL , commercialized by SLM Solutions GmbH.
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![Fig. 1. Photograph of the studied dental implant [10].](publication/320998726/figure/fig1/AS:559354946752513@1510372019222/Photograph-of-the-studied-dental-implant-10_Q320.jpg)
Several cylindrical specimens and dental implants, presenting diagonal lattice structures with different cell sizes (600, 900 and 1200 μm) were additively manufactured by selective laser melting process. Then they were implanted for two months in a sheep. After removal, they were studied by Archimedes’ method as well as X-ray computed tomography in...
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Citations
... Obaton et al. used XCT to confirm that additively manufactured parts were geometrically consistent with theoretical specifications. The authors concluded that lattice implants made by selective laser melting improve bone integration [9]. ...
With the rapid growth of the manufacturing industry, laser-based metal additive manufacturing, such as laser powder bed fusion, has the potential to usher in a revolution. However, its widespread adoption is contingent on the resolution of several challenges. A significant challenge is the uncertainty associated with part consistency when standardized materials are used in additive manufacturing processes. To ensure the quality and reproducibility of AM parts, consistency is essential. This study delves into an assessment of part-to-part consistency, leveraging a Pyramid learning-based technique that utilizes X-ray computed tomography (XCT) images for four nominally identical parts. Employing machine learning, this approach adopts a hierarchical feature system to enhance model performance. Pyramid Learning not only improves the accuracy of part-to-part consistency scanning but also reduces noise, bolstering overall robustness. The findings showcased the efficacy of pyramid learning in enhancing performance metrics when sufficient detail is present. It also provides guidance on locating defects and deformations for the AM parts.
... Authors noted that these porous structures not only promote osseointegration, but they are also a good alternative for the infiltration of enzymes and drugs in the damaged area. In 2017, Obaton et al. (2017) implanted different AM dental and cylindrical implants in a sheep during two months and analysed the bone penetration after two months. They employed dental implant with external DNA-type lattices and cylindrical specimens with diagonal-type cells at the upper zones and diamond cells at the bottom. ...
Additive Manufacturing (AM) enables the generation of complex geometries and controlled internal cavities that are so interesting for the biomedical industry due to the benefits they provide in terms of osseointegration and bone growth. These technologies enable the manufacturing of the so-called lattice structures that are cells with different geometries and internal pores joint together for the formation of scaffold-type structures. In this context, the present paper analyses the feasibility of using diamond-type lattice structures and topology optimisation for the redesign of a dental implant. Concretely, a new ultra-short implant design is proposed in this work. For the manufacturing of the implant, digital light processing additive manufacturing technique technology is considered. The implant was made out of Nano-zirconia and Nano-Calcium Silicate as an alternative material to the more common Ti6Al4V. This material combination was selected due to the properties of the calcium-silicate that enhance bone ingrowth. The influence of different material combination ratios and lattice pore sizes were analysed by means of FEM simulation. For those simulations, a bio-material bone-nanozirconia model was considered that represents the final status after the bone is integrated in the implant. Results shows that the mechanical properties of the biocompatible composite employed were suitable for dental implant applications in dentistry. Based on the obtained results it was seen that those designs with 400 μm and 500 μm pore sizes showed best performance and led to the required factor of safety.
... The benefit of this internal bone growth is the improved mechanical interlocking of bone to the implant, which improves the secondary stability of the implant [16,17]. The pore size range for promoting osteogenesis is 400-1000 µm, in which numerous additively manufactured lattices have been demonstrated with in vivo and in vitro studies [18][19][20][21][22][23][24][25][26][27][28][29]. ...
... Two different strut geometries (cubic and body-centered cubic) and four different pore sizes (400, 500, 600, and 900 µm, representing 40-90% porosity in a 10 mm cube) were utilized. The porosities chosen for these lattices have been shown to promote internal bone growth for orthopedic implants [20][21][22][23][24][25][26][27][28][29]. In addition, structural characterization was performed using scanning electron microscopy (SEM). ...
In an effort to contribute to the ongoing development of ASTM standards for additively manufactured metal lattice specimens, particularly within the field of medicine, the compressive and tensile mechanical properties of biomimetic lattice structures produced by laser powder bed fusion (L-PBF) using Ti-6Al-4V feedstock powder were investigated in this research. The geometries and porosities of the lattice structures were designed to facilitate internal bone growth and prevent stress shielding. A thin strut thickness of 200 µm is utilized for these lattices to mimic human cancellous bone. In addition to a thin strut size, two different strut geometries were utilized (cubic and body-centered cubic), along with four different pore sizes (400, 500, 600, and 900 µm, representing 40–90% porosity in a 10 mm cube). A 10 mm3 cube was used for compression testing and an experimental pin-loaded design was implemented for tensile testing. The failure mode for each specimen was examined using scanning electron microscopy (SEM). Lattice structures were compared to the mechanical properties of human cancellous bone. It was found that the elastic modulus of human cancellous bone (10–900 MPa) could be matched for both the tensile (92.7–129.6 MPa) and compressive (185.2–996.1 MPa) elastic modulus of cubic and body-centered cubic lattices. Body-centered cubic lattices exhibited higher compressive properties over cubic, whereas cubic lattices exhibited superior tensile properties. The experimental tensile specimen showed reacquiring failures close to the grips, indicating that a different tensile design may be required for consistent data acquisition in the future.
... The part of the sample starting 3 mm below nominal bone level and therefore all implant features below the embedding plane are not considered in these tests. Since the purpose of porous dental implants is primarily to increase osseointegration, many designs reported in the literature (Obaton et al., 2017;Yang et al., 2017;Hong et al., 2020) incorporate pores located in this "blind spot". As such, alternative methods have been employed to test these designs, either experimentally (e.g., three point bending, uniaxial compression) (Chakraborty et al., 2020;Huang et al., 2020;Xiong et al., 2020), or numerically (e.g., simulating the implant's behavior in bone) (Liu et al., 2017;Zhang et al., 2020). ...
Although 3D-printed porous dental implants may possess improved osseointegration potential, they must exhibit appropriate fatigue strength. Finite element analysis (FEA) has the potential to predict the fatigue life of implants and accelerate their development. This work aimed at developing and validating an FEA-based tool to predict the fatigue behavior of porous dental implants.
Test samples mimicking dental implants were designed as 4.5 mm-diameter cylinders with a fully porous section around bone level. Three porosity levels (50%, 60% and 70%) and two unit cell types (Schwarz Primitive (SP) and Schwarz W (SW)) were combined to generate six designs that were split between calibration (60SP, 70SP, 60SW, 70SW) and validation (50SP, 50SW) sets.
Twenty-eight samples per design were additively manufactured from titanium powder (Ti6Al4V). The samples were tested under bending compression loading (ISO 14801) monotonically (N=4/design) to determine ultimate load (F ult ) (Instron 5866) and cyclically at six load levels between 50% and 10% of F ult (N=4/design/load level) (DYNA5dent). Failure force results were fitted to F/F ult = a(N f ) b (Eq1) with N f being the number of cycles to failure, to identify parameters a and b . The endurance limit (F e ) was evaluated at N f = 5M cycles. Finite element models were built to predict the yield load (F yield ) of each design. Combining a linear correlation between FEA-based F yield and experimental F ult with equation Eq1 enabled FEA-based prediction of F e .
For all designs, F e was comprised between 10% (all four samples surviving) and 15% (at least one failure) of F ult . The FEA-based tool predicted F e values of 11.7% and 12.0% of F ult for the validation sets of 50SP and 50SW, respectively. Thus, the developed FEA-based workflow could accurately predict endurance limit for different implant designs and therefore could be used in future to aid the development of novel porous implants.
Acknowledgements: This study was funded by EU's Horizon 2020 grant No. 953128 (I-SMarD). We gratefully acknowledge the expert advice of Prof. Philippe Zysset.
... The part of the sample starting 3 mm below nominal bone level and therefore all implant features below the embedding plane are not considered in these tests. Since the purpose of porous dental implants is primarily to increase osseointegration, many designs reported in the literature (Obaton et al., 2017;Yang et al., 2017;Hong et al., 2020) incorporate pores located in this "blind spot". As such, alternative methods have been employed to test these designs, either experimentally (e.g., three point bending, uniaxial compression) (Chakraborty et al., 2020;Huang et al., 2020;Xiong et al., 2020), or numerically (e.g., simulating the implant's behavior in bone) (Liu et al., 2017;Zhang et al., 2020). ...
Introduction: Porous dental implants represent a promising strategy to reduce failure rate by favoring osseointegration or delivering drugs locally. Incorporating porous features weakens the mechanical capacity of an implant, but sufficient fatigue strength must be ensured as regulated in the ISO 14801 standard. Experimental fatigue testing is a costly and time-intensive part of the implant development process that could be accelerated with validated computer simulations. This study aimed at developing, calibrating, and validating a numerical workflow to predict fatigue strength on six porous configurations of a simplified implant geometry.
Methods: Mechanical testing was performed on 3D-printed titanium samples to establish a direct link between endurance limit (i.e., infinite fatigue life) and monotonic load to failure, and a finite element model was developed and calibrated to predict the latter. The tool was then validated by predicting the fatigue life of a given porous configuration.
Results: The normalized endurance limit (10% of the ultimate load) was the same for all six porous designs, indicating that monotonic testing was a good surrogate for endurance limit. The geometry input of the simulations influenced greatly their accuracy. Utilizing the as-designed model resulted in the highest prediction error (23%) and low correlation between the estimated and experimental loads to failure (R² = 0.65). The prediction error was smaller when utilizing specimen geometry based on micro computed tomography scans (14%) or design models adjusted to match the printed porosity (8%).
Discussion: The validated numerical workflow presented in this study could therefore be used to quantitatively predict the fatigue life of a porous implant, provided that the effect of manufacturing on implant geometry is accounted for.
... Indeed, better and faster osseointegration of the implant into the human body allows the patient to recover faster. In a previous article [6], we already demonstrated "in vivo" that the lattice promotes osseointegration by implementing the titanium alloy Ti6Al4V grade 23 containing aluminum (Al) and vanadium (V), already widely used for dental and hip implants. This study concerned mainly the conformity of the implants to their computer-aided design (CAD) and the powder particle adhesion to the lattices, and investigated the osseointegration as a function of the shape and size of the lattice cells. ...
... According to the surgeon's experience, this can be attributed to the material's properties of the new proposed titanium alloy, Ti-19Nb-14Zr, containing Nb and Zr instead of Al and V, and more precisely to the Nb. Indeed, the surgeon who performed the operation did not observe such an overlap with conventional and AM titanium alloys [6]. ...
The osseointegration in/around additively manufactured (AM) lattice structures of a new titanium alloy, Ti–19Nb–14Zr, was evaluated. Different lattices with increasingly high sidewalls gradually closing them were manufactured and implanted in sheep. After removal, the bone–interface implant (BII) and bone–implant contact (BIC) were studied from 3D X-ray computed tomography images. Measured BII of less than 10 µm and BIC of 95% are evidence of excellent osseointegration. Since AM naturally leads to a high-roughness surface finish, the wettability of the implant is increased. The new alloy possesses an increased affinity to the bone. The lattice provides crevices in which the biological tissue can jump in and cling. The combination of these factors is pushing ossification beyond its natural limits. Therefore, the quality and speed of the ossification and osseointegration in/around these Ti–19Nb–14Zr laterally closed lattice implants open the possibility of bone spline key of prostheses. This enables the stabilization of the implant into the bone while keeping the possibility of punctual hooks allowing the implant to be removed more easily if required. Thus, this new titanium alloy and such laterally closed lattice structures are appropriate candidates to be implemented in a new generation of implants.
... Indeed, a better and faster osseointegration of the implant into the human body allow the patient to recover faster. In a previous article [1], we have already demonstrated that the lattice promotes osseointegration implementing the titanium alloy Ti6Al4V grade 23, containing aluminum (Al) and vanadium (V), already widely used for dental and hip implants. This study concerned mainly the conformity of the implants to their computer-aided design (CAD) and powder particle adhesion to the lattices. ...
... According to the surgeon's experience, this can be attributed to the material's properties of the new proposed titanium alloy, Ti-19Nb-14Zr, containing Nb and Zr instead of Al and V, and more precisely to the Nb. Indeed, the surgeon who performed the operation did not observe such an overlap with conventional and AM titanium alloys [1]. ...
The osseointegration process in and around additively manufactured (AM) lattice structures of a new titanium alloy, Ti–19Nb–14Zr, was evaluated. Three different implants, including lattices with increasing high sidewalls gradually closing them, were designed, manufactured and implanted in the tibia and metatarsal bone of two sheep for twelve weeks. After removal, they were characterized with X-ray computed tomography (XCT). The 3D XCT images were segmented using machine learning. The bone-interface implant (BII) and bone-implant contact (BIC) were studied. The results show that, since AM naturally leads to high roughness surface finish, the wettability of the implant is increased. The new alloy possesses an increased affinity to the bone enhancing the quality of osseointegration. The lattice provides crevices, in which the biological tissue can jump in and cling. The combination of these factors is pushing ossification beyond its natural limits. Therefore, the quality and speed of the ossification and osseointegration in and around these Ti–19Nb–14Zr AM laterally closed lattice implants open the possibility of bone spline key of prostheses. This enables the stabilization of the implant into the bone while keeping the possibility of punctual hooks allowing the implant to be removed more easily if required.
... Applications of XCT with AM in a medical context are extensive, particularly in dentistry, where there is great demand for personalised products [207,[252][253][254][255]. Primary applications of XCT with AM in medicine include: the production of anatomical models, surgical guides, endoprosthetics and orthotics, stand-alone implants and scaffold implants [256]. ...
Image-Based Simulation (IBSim) is the process by which a digital representation of a real geometry is generated from image data for the purpose of performing a simulation with greater accuracy than with idealised Computer Aided Design (CAD) based simulations. Whilst IBSim originates in the biomedical field, the wider adoption of imaging for non-destructive testing and evaluation (NDT/NDE) within the High-Value Manufacturing (HVM) sector has allowed wider use of IBSim in recent years. IBSim is invaluable in scenarios where there exists a non-negligible variation between the ‘as designed’ and ‘as manufactured’ state of parts. It has also been used for characterisation of geometries too complex to accurately draw with CAD. IBSim simulations are unique to the geometry being imaged, therefore it is possible to perform part-specific virtual testing within batches of manufactured parts. This novel review presents the applications of IBSim within HVM, whereby HVM is the value provided by a manufactured part (or conversely the potential cost should the part fail) rather than the actual cost of manufacturing the part itself. Examples include fibre and aggregate composite materials, additive manufacturing, foams, and interface bonding such as welding. This review is divided into the following sections: Material Characterisation; Characterisation of Manufacturing Techniques; Impact of Deviations from Idealised Design Geometry on Product Design and Performance; Customisation and Personalisation of Products; IBSim in Biomimicry. Finally, conclusions are drawn, and observations made on future trends based on the current state of the literature.
... 3D printing is a form of additive manufacturing that is revolutionising the manufacturing industry by providing an efficient method for producing complex, customised, and lightweight structures such as lattices [1,2] which cannot be manufactured by common manufacturing methods. A lattice is a cellular structure which has been widely used in aerospace [3][4][5] and medical industries [6][7][8][9] with great properties, such as high specific stiffness and strength [3,10,11], heat insulation [12], and energy damping attenuation [13]. One of the most common filament arrangements in lattice structures is body-centred cube (BCC) which has been extensively used for energy absorption applications [14]. ...
This paper studies theoretical, numerical, and experimental studies on static compression behaviour of polyamide 12 body-centred cube (BCC) lattices manufactured using the selective laser sintering (SLS) method. In the analytical formulation, the influence of imperfections that happened during 3D printing such as material overlapping in the vicinity of filament joints is considered to provide predictions of mechanical properties of a macro lattice structure. Finite element (FE) models of the BCC lattices are performed to predict the compressive behaviour and deformation localisation of filaments. In order to determine a material model and input parameters for FE simulation of the lattice cubes, an individual 3D-printed filament is subjected to transverse compressive loading utilising a custom-made filament compression rig. Then, true experimental stress and strain data are generated that are imported into an inverse calibration technique using MCalibration software to determine the material parameters for the FE simulation. A series of BCC lattice cubes were printed using the SLS method. Compression experiments were conducted utilising digital image correlation (DIC) techniques in order to determine localisation of deformations and strains and validate the material properties obtained by the analytical modelling and numerical simulations. Good agreements are observed among the analytical, numerical, and experimental results. The results show that effect of filament defects should be taken into account to find the accurate responses in analytical model and FE simulation.
... Cat.pool SLAMW, % 19 (13)(14)(15)(16)(17)(18)(19)(20) 18 (16)(17)(18)(19)(20)(21) 16 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) 18 (15)(16)(17)(18)(19)(20) 16 (13)(14)(15)(16)(17)(18)(19) 16 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) 14 (13)(14)(15)(16)(17) Note: * -significant differences with preoperative indices in р < 0,05. ...
... Cat.pool SLAMW, % 19 (13)(14)(15)(16)(17)(18)(19)(20) 18 (16)(17)(18)(19)(20)(21) 16 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) 18 (15)(16)(17)(18)(19)(20) 16 (13)(14)(15)(16)(17)(18)(19) 16 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) 14 (13)(14)(15)(16)(17) Note: * -significant differences with preoperative indices in р < 0,05. ...
... Cat.pool SLAMW, % 19 (13)(14)(15)(16)(17)(18)(19)(20) 18 (16)(17)(18)(19)(20)(21) 16 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) 18 (15)(16)(17)(18)(19)(20) 16 (13)(14)(15)(16)(17)(18)(19) 16 (10)(11)(12)(13)(14)(15)(16)(17)(18)(19) 14 (13)(14)(15)(16)(17) Note: * -significant differences with preoperative indices in р < 0,05. ...
Relevance Application of 3D printing using the method of selective laser fusion for production of intervertebral cages is a topical trend of the spinal
surgery. Purpose Assessment of the efficiency and safety of original interbody fusion implant application made of titanium alloy according to 3D printing
technology with selective laser fusion. Materials and methods The original flattened bean-shaped cages, with an integral side part and an internal
configuration in the shape of three-dimensional 1.5 × 1.8 mm porous lattice were tested . The products were made of Ti6Al4V powder using 3D printing
technology with selective laser fusion. Post-processing of the products surface included abrasive blast cleaning using the SLA method and sterilization
with ethylene oxide. Experiments on modeling interbody fusion with replacement of intervertebral discs with cages at levels L4 – L5 and L5 – L6 were
performed in 8 mongrels. Additional primary stabilization of the lumbar spine was produced with an external fixator within 30 days after implantation.
The total follow-up period lasted 180 days. Radiography, scanning electron microscopy, roentgenospectral and biochemical analysis methods were
applied. Results X-ray examination demonstrated the contact between the frontal surfaces of the cages and the bone tissue of the vertebral bodies
and the development of fusion in all experimental animals. Biochemical analysis did not reveal the signs of intoxication, indicating the danger of the
products application. The microrelief of the implants was characterized by microroughness ranged from 1to 50 μm. In the surface layer of products, in
addition to the elements of titanium, aluminum and vanadium, the carbon, oxygen, silicon, trace amounts of other organic and inorganic elements were
found. Newly formed bone trabeculae were macroscopically and submicroscopically visualized in the sawcuts of bone blocks in the porous lattice of the
internal part of the implants. Conclusions Experimental testing of porous implants made of titanium alloy using selective laser fusion has shown their
effectiveness in obtaining interbody fusion and acceptable safety.
