Efficiency of Invisalign First® to promote expansion movement in mixed dentition: a retrospective study and systematic review.

Aim: The present study aimed: i) to retrospectively evaluate the expansion movement predicted by the Clincheck® software and the achieved expansion using Invisalign First® in children needing maxillary expansion to correct malocclusions; and ii) to critically compare these clinical results with the outcomes obtained for maxillary expansion using conventional removable and cemented expanders. Material and Methods: The 3D digital models of the dental arches of 24 children undergoing orthodontic treatment exclusively with Invisalign First® aligners between 2018 and 2021 were sequentially selected for this study. Three digital models were analysed: pre-treatment (P0), the Clincheck®-predicted tooth positions (P1), and post-treatment (P2) models. The maxillary dental arch width and expansion efficiency were measured andcalculated. An in-depth review of the available literature on maxillary expansion was performed following PRISMA guidelines. Results: Invisalign First® was able to achieve a total effectiveness of maxillary expansion of 62.6%, compared to the predicted movement. Similarly, the total effectiveness of mandibular expansion was 61.6%. Conclusions: Our data shows that Invisalign First® system can increase the arch width with maxillary expansion effectiveness, providing similar results to those achieved with conventional removable appliances. However, neither Invisalign First® aligners nor conventional removable expanders are as much efficient as cemented-retained appliances.

Effects and mechanotransduction pathways of therapeutic ultrasound on healthy and osteoarthritic chondrocytes: a systematic review of in vitro studies.

OBJECTIVE: To investigate the effects and mechanotransduction pathways of therapeutic ultrasound on chondrocytes. METHOD: PubMed, EMBASE and Web of Science databases were searched up to 19th September 2021 to identify in vitro studies exploring ultrasound to stimulate chondrocytes for osteoarthritis (OA) treatment. Study characteristics, ultrasound parameters, in vitro setup, and mechanotransduction pathways were collected. Risk of bias was judged using the Risk of Bias Assessment for Non-randomized Studies (RoBANS) tool. RESULTS: Thirty-one studies were included comprising healthy and OA chondrocytes and explants. Most studies had high risk of performance, detection and pseudoreplication bias due to lack of temperature control, setup calibration, inadequate semi-quantitatively analyzes and independent experiments. Ultrasound was applied to the culture plate via acoustic gel, water bath or culture media. Regardless of the setup used, ultrasound stimulated the cartilage production and suppressed its degradation, although the effect size was nonsignificant. Ultrasound inhibited p38, c-Jun N-terminal kinases (JNK) and factor nuclear kappa B (NFκB) pathways in OA chondrocytes to reduce apoptosis, inflammation and matrix degradation, while triggered phosphoinositide-3-kinase/akt (PI3K/Akt), extracellular signal-regulated kinase (ERK), p38 and JNK pathways in healthy chondrocytes to promote matrix synthesis. CONCLUSION: The included studies suggest that ultrasound application induces therapeutic effects on chondrocytes. However, these results should be interpreted with caution because high risk of performance, detection and pseudoreplication bias were identified. Future studies should explore the application of ultrasound on human OA chondrocytes cultures to potentiate the applicability of ultrasound towards cartilage regeneration of knee with OA.

Multi-functional Ti6Al4V-CoCrMo implants fabricated by multi-material laser powder bed fusion technology: A disruptive material's design and manufacturing philosophy.

A home-made 3D Multi-Material Laser Powder Bed Fusion (3DMMLPBF) technology was exploited to manufacture novel multi-material Ti6Al4V-CoCrMo parts. This multi-material concept aims to bring to life a new and disruptive material's design concept for the acetabular cup. Only using a layer-by-layer approach it is possible to manufacture an acetabular cup capable to combine CoCrMo alloy wear resistance and Ti6Al4V alloy bone-friendly nature, in a single component, fabricated at once. This system works with multiple powder deposition functions and vacuum cleaning procedures allowing to use two different powders (Ti6Al4V and CoCrMo) in each layer and thus, allowing to construct 3D Multi-Material transition between distinct materials, point-by-point and layer-by-layer. In this sense, the manufacturing strategies and the functional transition between Ti6Al4V and CoCrMo with a mechanical interlocking were analyzed and discussed both from mechanical and metallurgical point of view. A small diffusion area and no evidence of defects or cracks can be found in the transition's regions between the distinct materials which are strong evidences of a solid metallurgical bonding at the interfacial regions of Ti6Al4V and CoCrMo materials. A functional transition is also obtained through a design capable to provide a 3D mechanical interlocking with potential of assuring, simultaneously, tensile and compressive strength. This proof of concept might be a step-ahead in Laser Powder Bed Fusion in which the most desired intrinsic of individual materials can be combined in a single component targeting biomedical disruptive solutions.

Development of a novel hybrid Ti6Al4V-ZrO2 surface with high wear resistance by laser and hot pressing techniques for dental implants.

The development of implant metal-free surfaces has gained attention since non-benefic results have been reported related to the metallic ions released from metal implants to the human body. Ceramic coatings have been proposed as a possible solution however, the detachment of these coatings, during implantation or even in function, can compromise its function. In order to overcome this problem, this work proposes a novel hybrid Ti6Al4V-ZrO2 surface, starting with laser texturing of the Ti6Al4V substrate by Laser Nd:YV04, followed by the allocation of the zirconia (ZrO2) powder and its subsequent sintering by hot pressing process. Results revealed that zirconia strongly adheres to titanium textured surfaces since no detachment was found under tribological and adhesion scratch tests. Moreover, the tribological results showed that the incorporation of zirconia into textured titanium surface reduces significantly the wear rate of titanium (≈93%), which is a good indicator of low metallic particles/ions released to the body. These results suggest that this novel surface with good aesthetic properties and improved wear resistance (given by zirconia) and mechanical resistance (from titanium) can be a promising solution for dental implants, especially for implant/abutment or abutment/ceramic contact zones, and thus have a huge impact on the long-term performance of implants.

Multi-Material Additive Manufacturing for Advanced High-Tech Components.

Multi-Material Additive Manufacturing for Advanced High-Tech Components is a new open Special Issue of Materials, which aims to publish original and review papers regarding new scientific and applied research and make great contributions to finding, exploring and understanding novel multi-material components via additive manufacturing [...].

Multi-material cellular structured orthopedic implants design: In vitro and bio-tribological performance.

In this study, Selective Laser Melting (SLM) was used to produce mono-material Ti64Al4V- and NiTi-cubic cellular structures with an open-cell size and wall thickness of 500 µm and 100 µm, respectively. Bioactive beta-tricalcium phosphate (ßTCP) and polymer poly-ether-ether ketone (PEEK) were used to fill the produced structures open-cells, thus creating multi-material components. These structures were characterized in vitro in terms of cell viability, adhesion, differentiation and mineralization. Also, bio-tribological experiments were performed against bovine plate to mimic the moment of implant insertion. Results revealed that metabolic activity and mineralization were improved on SLM mono-material groups, when compared to the control group. All cell metrics were improved with the addition of PEEK, conversely to ßTCP where no significant differences were found. These results suggest that the proposed solutions can be used to improve implants performance.

RHCE variant alleles and risk of alloimmunization in Brazilians.

Variant RHCE alleles are found mainly in Afro-descendant individuals, as well as in patients with sickle cell disease (SCD). The most common variants are related to the RHCE*ce allele, which can generate partial e and c antigens. Although RHCE variant alleles have been extensively studied, defining their clinical significance is a difficult task. We evaluated the risk of RhCE alloimmunization as a consequence of partial antigens in patients with a positive phenotype transfused with red blood cell (RBC) units with the corresponding antigen. A retrospective study was performed with Brazilian patients, evaluating the number of antigen-positive transfused RBC units (incompatible due to partial antigen) in 27 patients with SCD carrying RHCE variant alleles who did not develop antibodies as well as evaluating the variants present in 12 patients with partial phenotype and correlated antibody (one patient with SCD and 11 patients with other pathologies). Two patients showed variant alleles with molecular changes that had not yet been described. Variant RHCE alleles were identified in a previous study using molecular methods. RHCE*ceVS.01 was the most frequent allele found among the patients without antibodies. Six patients with partial c antigen had a mean of 3.8 c+ RBC units transfused, and 10 patients with partial e antigen were exposed for a mean of 7.2 e+ RBC units. Among the variant alleles found in alloimmunized patients, the most frequent was RHCE*ceAR, which was found in five patients; the antibodies developed were anti-hrS and/or anti-c. Our results showed that RHCE*ceVS.01 is indeed the most frequent variant allele in our cohort of patients with SCD, but the partial antigens that were identified have low risk of alloimmunization. RHCE*ceAR is the most impactful variant in the Brazilian population with high risk of alloimmunization and clinically significant anti-hrS formation.

Selective Laser Melting of Ti6Al4V sub-millimetric cellular structures: Prediction of dimensional deviations and mechanical performance.

Ti6Al4V sub-millimetric cellular structures arise as promising solutions concerning the progress of conventional orthopedic implants due to its ability to address a combination of mechanical, physical and topological properties. Such ability can improve the interaction between implant materials and surrounding bone leading to long-term successful orthopedic implants. Selective Laser Melting (SLM) capability to produce high quality Ti6Al4V porous implants is in great demand towards orthopedic biomaterials. In this study, Ti6Al4V cellular structures were designed, modeled, SLM produced and characterized targeting orthopedic implants. For that purpose, a set of tools is proposed to overcome SLM limited accuracy to produce porous biomaterials with desired dimensions and mechanical properties. Morphological analyses were performed to evaluate the dimensional deviations noticed between the model CAD and the SLM produced structures. Tensile tests were carried out to estimate the elastic modulus of the Ti6Al4V cellular structures. The present work proposes a design methodology showing the linear correlations found for the dimensions, the porosity and the elastic modulus when comparing the model CAD designs with Ti6Al4V structures by SLM.

Laser-assisted production of HAp-coated zirconia structured surfaces for biomedical applications.

OBJECTIVES: The aim of this study was to develop a novel design for implants surface functionalization through the production of HAp-coated zirconia structured surfaces by means of hybrid laser technique. The HAp-rich structured surfaces were designed to avoid hydroxyapatite (HAp) coating detachment from the zirconia surface during implant insertion, thus guaranteeing an effective osseointegration. MATERIALS AND METHODS: The functionalization process of zirconia surface started by creating micro-textures using a Nd:YAG laser and subsequent deposition of a HAp coating on the designated locations by dip-coating process. Afterwards, a CO2 laser was used to sinter the HAp coating. The potential of the HAp-coated zirconia structured surfaces was inspected concerning HAp bioactivity preservation, surface wettability, HAp coating adhesion to the textured surfaces and mechanical resistance of zirconia, as assessed by different approaches. RESULTS: The functionalized surfaces exhibited a superhydrophilic behavior (2.30 ± 0.81°) and the remaining results showed that through the hybrid strategy, it is possible to maintain the HAp bioactivity as well as promote a strong adhesion of HAp coating to the textured surfaces even after high energy ultrasonic cavitation tests and friction tests against bovine bone. It was also verified that the flexural strength of zirconia (503 ± 24 MPa) fulfills the strict requirements of the ISO 13356:2008 standard and as such is expectable to be enough for biomedical applications. SIGNIFICANCE: The promising results of this study indicate that the proposed surface design can open the window for manufacturing zirconia-based implants with improved bioactivity required for an effective osseointegration as it avoids the coating detachment problem during the implant insertion.

Engineering the elastic modulus of NiTi cellular structures fabricated by selective laser melting.

Nickel-titanium (NiTi) cellular structures are a very promising solution to some issues related to orthopaedic implant failure. These structures can be designed and fabricated to simultaneously address a combination of mechanical and physical properties, such as elastic modulus, porosity, wear and corrosion resistance, biocompatibility and appropriate biological environment. This ability can enhance the modest interaction currently existing between metallic dense implants and surrounding bone tissue, allowing long-term successful orthopaedic implants. For that purpose, NiTi cellular structures with different levels of porosity intended to reduce the elastic modulus were designed, modelled, selective laser melting (SLM) fabricated and characterized. Significant differences were found between the CAD design and the SLM-produced NiTi structures by performing systematic image analysis. This work proposes designing guidelines to anticipate and correct the systematic differences between CAD and produced structures. Compressive tests were carried out to estimate the elastic modulus of the produced structures and finite element analyses were performed, for comparison purposes. Linear correlations were found for the dimensions, porosity, and elastic modulus when comparing the CAD design with the SLM structures. The produced NiTi structures exhibit elastic moduli that match that of bone tissue, which is a good indication of the potential of these structures in orthopaedic implants.

Reengineering Bone-Implant Interfaces for Improved Mechanotransduction and Clinical Outcomes.

The number of patients undergoing joint replacement surgery has progressively increased worldwide due to world population ageing. In the Unites States, for example, the prevalence of hip and knee replacements has increased more than 6 and 10 times, respectively, since 1980. Despite advances in orthopaedic implant research, including the development of novel implantable biomaterials, failures are still observed due to inadequate biomechanical compliance at the bone-implant interface. This comprises static and dynamic mechanical mismatch between the bone and the implant surface. The importance and robustness of biomechanical cues for controlling osteogenic differentiation of mesenchymal stem cells (MSC) have been highlighted in recent studies. However, in the context of bone regenerative medicine, it remains elusive how mechanobiological signals controlling MSC osteogenic differentiation dynamics are modulated in their interaction with the bone and with implants. In this review, we highlight recent technological advances aiming to improve host bone-implant interactions based on the osteogenic and mechanoresponsive potential of MSC, in the context of joint replacement surgery. First, we discuss the extracellular and intracellular mechanical forces underlying proper receptivity and stimulation of physiological MSC differentiation and linked osteogenic activity. Second, we provide a critical overview on how this knowledge can be integrated towards the development of biomaterials for improved bone-implant interfaces. Third, we discuss cross-disciplinarily which contributes to the next generation design of novel pro-active orthopaedic implants and their implantation success. Graphical Abstract.

Physicochemical properties and cytocompatibility assessment of non-degradable scaffolds for bone tissue engineering applications.

Bone is a dynamic tissue with an amazing but yet limited capacity of self-healing. Bone is the second most transplanted tissue in the world and there is a huge need for bone grafts and substitutes which lead to a decrease in bone banks donors. In this study, we developed three-dimensional scaffolds based on Ti6Al4V, ZrO2 and PEEK targeting bone tissue engineering applications. Experimental mechanical compressive tests and finite element analyses were carried out to study the mechanical performance of the scaffolds. Overall, the scaffolds presented different hydrophilicity properties and a reduced elastic modulus when compared with the corresponding solid materials which can in some extension minimize the phenomenon of stress shielding. The ability as a scaffold material for bone tissue regeneration applications was evaluated in vitro by seeding human osteosarcoma (SaOS-2) cells onto the scaffolds. Then, the successful culture of SaOS-2 cells on developed scaffolds was monitored by assessment of cell's viability, proliferation and alkaline phosphatase (ALP) activity up to 14 days of culturing. The in vitro results revealed that Ti6Al4V, ZrO2 and PEEK scaffolds were cytocompatible allowing the successful culture of an osteoblastic cell line, suggesting their potential application in bone tissue engineering. Statement of Significance. The work presented is timely and relevant since it gathers both the mechanical and cellular study of non-degradable cellular structures with the potential to be used as bone scaffolds. This work allow to investigate three possible bone scaffolds solutions which exhibit a significantly reduced elastic modulus when compared with conventional solid materials. While it is generally accepted that the Ti6Al4V, ZrO2 and PEEK are candidates for such applications a further study of their features and their comparison is extremely important for a better understanding of their potential.

Management of Challenging Cardiopulmonary Bypass Separation.

SEPARATION from cardiopulmonary bypass (CPB) after cardiac surgery is a progressive transition from full mechanical circulatory and respiratory support to spontaneous mechanical activity of the lungs and heart. During the separation phase, measurements of cardiac performance with transesophageal echocardiography (TEE) provide the rationale behind the diagnostic and therapeutic decision-making process. In many cases, it is possible to predict a complex separation from CPB, such as when there is known preoperative left or right ventricular dysfunction, bleeding, hypovolemia, vasoplegia, pulmonary hypertension, or owing to technical complications related to the surgery. Prompt diagnosis and therapeutic decisions regarding mechanical or pharmacologic support have to be made within a few minutes. In fact, a complex separation from CPB if not adequately treated leads to a poor outcome in the vast majority of cases. Unfortunately, no specific criteria defining complex separation from CPB and no management guidelines for these patients currently exist. Taking into account the above considerations, the aim of the present review is to describe the most common scenarios associated with a complex CPB separation and to suggest strategies, pharmacologic agents, and para-corporeal mechanical devices that can be adopted to manage patients with complex separation from CPB. The routine management strategies of complex CPB separation of 17 large cardiac centers from 14 countries in 5 continents will also be described.

Cell adhesion evaluation of laser-sintered HAp and 45S5 bioactive glass coatings on micro-textured zirconia surfaces using MC3T3-E1 osteoblast-like cells.

Laser texturing is a technique that has been increasingly explored for the surface modification of several materials on different applications. Laser texturing can be combined with conventional coating techniques to functionalize surfaces with bioactive properties, stimulating cell differentiation and adhesion. This study focuses on the cell adhesion of laser-sintered coatings of hydroxyapatite (HAp) and 45S5 bioactive glass (45S5 BG) on zirconia textured surfaces using MC3T3-E1 cells. For this purpose, zirconia surfaces were micro-textured via laser and then coated with HAp and 45S5 BG glass via dip coating. Afterwards, the bioactive coatings were laser sintered, and a reference group of samples was conventionally sintering. The cell adhesion characterisation was achieved by cell viability performing live/dead analysis using fluorescence stains and by SEM observations for a qualitative analysis of cell adhesion. The in vitro results showed that a squared textured pattern with 100µm width grooves functionalized with a bioactive coating presented an increase of 90% of cell viability compared to flat surfaces after 48h of incubation. The functionalized laser sintered coatings do not present significant differences in cell viability when compared to conventionally sintered coatings. Therefore, the results reveal that laser sintering of HAp and 45S5 BG coatings is a fast and attractive coating technique.

In silico evaluation of the stress fields on the cortical bone surrounding dental implants: Comparing root-analogue and screwed implants.

Tooth loss is a problem that affects both old and young people. It may be caused by several conditions, such as poor oral hygiene, lifestyle choices or even diseases like periodontal disease, tooth grinding or diabetes. Nowadays, replacing a missing tooth by an implant is a very common process. However, many limitations regarding the actual strategies can be enumerated. Conventional screwed implants tend to induce high levels of stress in the peri-implant bone area, leading to bone loss, bacterial bio-film formation, and subsequent implant failure. In this sense, root-analogue dental implants are becoming promising solutions for immediate implantation due to their minimally invasive nature, improved bone stress distribution and because they do not require bone drilling, sinus lift, bone augmentation nor other traumatic procedures. The aim of this study was to analyse and compare, by means of FEA, the stress fields of peri-implant bone around root-analogue and screwed conventional zirconia implants. For that purpose, one root-analogue implant, one root-analogue implant with flaps, two conventional implants (with different threads) and a replica of a natural tooth were modelled. COMSOL was used to perform the analysis and implants were subjected to two simultaneous loads: 100 N axially and 100 N oblique (45°). RESULTS: revealed that root-analogue implants, namely with flaps, should be considered as promising alternatives for dental implant solutions since they promote a better stress distribution in the cortical bone when compared with conventional implants.

Novel laser textured surface designs for improved zirconia implants performance.

The development of new surface designs to enhance the integration process between surgically placed implants and biological tissues remains a challenge for the scientific community. In this way and trying to overcome this issue, in this work, laser technology was explored to produce novel textures on the surface of green zirconia compacts produced by cold pressing technique. Two strategies regarding line design (8 and 16 lines design) and different laser parameters (laser power and number of laser passages) were explored to assess their influence on geometry and depth of created textures. The produced textures were evaluated with Scanning Electron Microscopy (SEM) and it was observed that well-defined textured surfaces with regular geometric features (cavities or pillars) were obtained by laser combining different strategies lines design and parameters. The potential of proposed textures was also evaluated regarding surface wettability, friction performance (static and dynamic coefficient of friction evolution) against bone, aging resistance and flexural strength. Results demonstrated that all the produced textures display a super hydrophilic or hydrophilic behavior. Regarding the friction behavior, it was experimentally observed a high initial static coefficient of friction (COF) for all produced textures. Concerning the aging resistance, all the textured surfaces revealed a low monoclinic content, less than 25% after 5 h of hydrothermal aging. The flexural strength results showed that the mechanical resistance of zirconia was not significantly compromised with the laser action. Based on the obtained results, it is possible to prove that the processing route used for manufacturing the new and different surface designs (cold pressing technique followed by laser texturing) showed to be particularly effective for the production of zirconia implants with customized surface designs according to the properties required in a specific application. These new surface designs besides to enhance the surface wettability and also to improve the fixation at the initial moment of the implantation, do not significantly compromise the resistance to aging and the mechanical performance of zirconia. Hence, a positive impact on the long-term performance of the zirconia implants may be expected with the proposed novel laser textured surface designs.

Micro-CT based finite element modelling and experimental characterization of the compressive mechanical properties of 3-D zirconia scaffolds for bone tissue engineering.

The present study aims at developing a computational framework with experimental validation to determine the mechanical properties of zirconia foams for bone tissue engineering. A micro-CT based finite element model that allows characterizing the mechanical property of such cellular structures is developed. Micro-CT images are filtered to vanish noises and smooth boundaries before constructing 3D zirconia foams using an adaptive Body-Centered Cubic background lattice. In addition to micro-CT images, the local material property at the scaffold struts is measured using a micro-indentation test, which shows a considerable difference with that of common zirconia owing to the manufacturing process. The computational model also takes the plastic deformation of material into account employing the Voce law, a nonlinear isotropic hardening law, as well as Von-mises yield criterion. Zirconia foams with different pore sizes are manufactured using the replica method and their mechanical properties determined experimentally. Such experimental outcomes are to validate and demonstrate the capability of the developed model, which can be used for pre-operational evaluations and preclinical tests of zirconia scaffolds. The stress magnitude and distribution within the scaffold as well as plastic strains and flow stress of the zirconia scaffold are computed and analysed. Using the proposed approach, a deep insight into the association of macroscopic behaviour of the scaffold to microscopic features, e.g. strut waviness, Plateau border, thickness variation of cells, irregularity, microstructural variability, imperfections and strut's material property associated with to the manufacturing procedure, can be gained.

A low cost alternative, using mycorrhiza and organic fertilizer, to optimize the production of foliar bioactive compounds in pomegranates.

AIM: To select the best combination of arbuscular mycorrhizal fungi and efficient vermicompost dose in maximizing the production of leaf metabolites in Punica granatum seedlings. METHODS AND RESULTS: The experimental design was in a 3 × 3 factorial arrangement: three inoculation treatments (inoculated with Gigaspora albida, inoculated with Acaulospora longula and control not inoculated) × 3 doses of vermicompost (0, 5 and 7·5%). After 120 days of inoculation, biomolecules, plant growth parameters and mycorrhizal colonization were evaluated. The combination of 7·5% of vermicompost and A. longula was favourable to the accumulation of leaf phenols, with an increase of 116·11% in relation to the non-inoculated control. The total tannins was optimized/enhanced when G. albida and 7·5% of fertilizer were used, registering an increase of 276·71%. CONCLUSIONS: The application of 7·5% of vermicompost associated with A. longula and G. albida is a low cost alternative to increase the levels of bioactive compounds in pomegranate leaves. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first published report of optimization of bioactive compound production in P. granatum by the combined use of mycorrhiza and vermicompost doses.

Additive manufactured porous biomaterials targeting orthopedic implants: A suitable combination of mechanical, physical and topological properties.

Orthopedic implants are under incessant advancement to improve their interactions with surrounding bone tissue aiming to ensure successful outcomes for patients. A successful biological interaction between implant and surrounding bone depends on the combination of mechanical, physical and topological properties. Hence, Ti6Al4V cellular structures appear as very promising solutions towards the improvement of conventional orthopedic implants. This work addresses a set of fundamental tools that allow improving the design of Ti6Al4V cellular structures produced by Selective Laser Melting (SLM). Three-point bending tests were carried out to estimate the elastic modulus of the produced structures. Morphological analysis allowed to evaluate the dimensional differences that were noticed between the model CAD and the SLM structures. Finite element models (adjusted CAD) were constructed with the experimentally obtained dimensions to replicate the mechanical response of the SLM structures. Linear correlations were systematically found for the dimensions of the SLM structures as a function of the designed model CAD dimensions. This has also been observed for the measured porosities as a function of the designed CAD models. This data can be used in further FE analyses as design guidelines to help engineers fabricating near-net-shape SLM Ti6Al4V cellular structures. Besides, polished and sandblasted surface treatments performed on the Ti6Al4V cellular structures allowed to obtain suitable properties regarding roughness and wettability when compared to as-produced surfaces. The capillarity tests showed that all the analyzed Ti6Al4V structures are able to transport fluid along its structure. The cell viability tests demonstrate Ti6Al4V cellular structures SLM produced did not release toxic substances to the medium, indicating that these structures can assure a suitable environment for cells to proliferate and attach. This study proposes a design methodology for Ti6Al4V cellular structures, that owe suitable mechanical properties but also provide a proper combination of porosity, roughness, wettability, capillarity and cell viability, all of them relevant for orthopedic applications. A Ti6Al4V cellular structured hip implant prototype gathering the suitable features addressed in this study was successfully SLM-produced.

Predicting the output dimensions, porosity and elastic modulus of additive manufactured biomaterial structures targeting orthopedic implants.

SLM accuracy for fabricating porous materials is a noteworthy hindrance when aiming to obtain biomaterial cellular structures owing precise geometry, porosity, open-cells dimension and mechanical properties as outcomes. This study provides a comprehensive characterization of seventeen biomaterial Ti6Al4V-based structures in which experimental and numerical investigations (compression stress-strain tests) were carried out. Mono-material Ti6Al4V cellular structures and multi-material Ti6Al4V-PEEK cellular structures were designed, produced by SLM and characterized targeting orthopedic implants. In this work, the differences between the CAD design and the as-produced Ti6Al4V-based structures were obtained from image analysis and were used to develop predictive models. The results showed that dimensional deviations inherent to SLM fabrication are systematically found for different dimensional ranges. The present study proposes several mathematical models, having high coefficients of determination, that estimate the real dimensions, porosity and elastic modulus of Ti6Al4V-based cellular structures as function of the CAD model. Moreover, numerical analysis was performed to estimate the octahedral shear strain for correlating with bone mechanostat theory limits. The developed models can help engineers to design and obtain near-net shape SLM biomaterials matching the desired geometry, open-cells dimensions, porosity and elastic modulus. The obtained results show that by using these AM structures design it is possible to fabricate components exhibiting a strain and elastic modulus that complies with that of bone, thus being suitable for orthopedic implants.