Mechanical properties of Ti6Al4V fabricated by laser powder bed fusion: a review focused on the processing and microstructural parameters influence on the final properties

Ti6Al4V alloy is an ideal lightweight structural metal for a huge variety of engineering applications due to its distinguishing combination of high specific mechanical properties, excellent corrosion resistance and biocompatibility. In this review, the mechanical properties of selective laser-melted Ti6Al4V parts are addressed in detail, as well as the main processing and microstructural parameters that influence the final properties. Fundamental knowledge is provided by linking the microstructural features and the final mechanical properties of Ti6Al4V parts, including tensile strength, tensile strain, fatigue resistance, hardness and wear performance. A comparison between Laser Powder Bed Fusion and conventional processing routes is also addressed. The presence of defects in as-built Ti6Al4V parts and their influences on the mechanical performance are also critically discussed. The results available in the literature show that typical Laser Powder Bed–Fused Ti6Al4V tensile properties (>900 MPa yield strength and >1000 MPa tensile strength) are adequate when considering the minimum values of the standards for implants and for aerospace applications (e.g., ASTM F136–13; ASTM F1108–14; AMS4930; AMS6932).This work was supported by FCT national funds, under national support to an R&D units grant, through the reference projects UIDB/04436/2020 and UIDP/04436/2020 and also through the projects ADD2MECBIO (PTDC/EME-EME/1442/2020) and Additive_Manufacturing to Portuguese Industry_POCI-01-0247-FEDER-024533

Hydrothermal ageing behavior of bioinspired material with piezoelectric functions for implant applications

Implant-bone fixation loss can occur 10-15 years after surgery. This is related to bone resorption and consecutive biofilm formation in the generated gap, which could lead to tissues inflammation and implant loss [1]. Current solutions are focused on primary osseointegration for implant early survival rate. In long term, they lose effectiveness due to implant foreign body reaction once bone metabolism is challenged by a non-part of the body. Bone is composed of piezoelectric materials with production of biological electricity due to collagen deformation and displacement of the local electric field [2]. Barium titanate is a lead-free piezoelectric bioceramic without toxicological risk and absence of foreign body reactions that can mimic natural bone piezoelectricity and inhibit bacterial adhesion [3]. The focus of this work is design, produce, and characterize a smart, bio-inspired, and multi-functional composite material to improve implant long-term bone regeneration and antibacterial effect. In this sense, a composite with BaTiO3 particles and bioinert ZrO2 was produced. 5%BaTiO3-ZrO2 composites were mixed in isopropanol alcohol and ultrasonicated for total dispersion, followed by press (200MPa) and sintering technic (1300-1500ºC). The different samples were characterized with SEM (Fig1.(a)), that present two distinct phases, XRD analysis, and subjected to hydrothermal ageing (Fig1.(b)), to evaluate the stability of the tetragonal zirconia phase. After 5h of accelerated ageing (≈10 years), monoclinic phase is more evident with the sintering temperature increment, but always lower than 25%, staying in according with ISO 13356:200, promising to be promising a potential replacement material for implant applications.This work was supported by FCT national funds under the national support to R&D units grant, through the reference project UIDB/04436/2020, UIDP/04436/2020, FunImp POCI-01-0145-FEDER-030498 and through the grant 2021.09001.BD

Customized root-analogue implants: a review on outcomes from clinical trials and case reports

(1) It is estimated that 10% of the world’s population will need a dental implant in their lifetime. Despite all the advances in the comprehension of dental implant designs, materials and techniques, traditional implants still have many limitations. Customized root-analogue implants are, therefore, gaining increased interest in dental rehabilitation and are expected to not only preserve more hard and soft tissues but also avoid a second surgery and improve patient overall satisfaction. In this sense, the aim of this review was to collect and analyse the clinical trials and case reports on customized root-analogue implants available in the literature; (2) This review was carried out according to the PRISMA Statement. An electronic database search was performed using five databases: PubMed, Google Scholar, Medline, Science Direct, and Scopus. The following keywords were used for gathering data: custom-made, dental implants, root-analogue, anatomical, customized and tooth-like; (3) 15 articles meeting the inclusion criteria—articles reporting clinical trials, case reports or animal studies and articles with root-analogue implants and articles with totally customized implant geometries—were selected for the qualitative synthesis. The design and manufacturing techniques, implant material and surface treatments were assessed and discussed; (4) The performance of some root-analogue implants with specific features (i.e., macro-retentions) was successful, with no signs of infection, periodontitis nor bleeding during the follow-up periods.This work was supported by FCT-Portugal through the grant PD/BD/140202/2018, and the projects POCI-01-0145-FEDER-030498-FunImp and UID/EEA/04436/2019

How does the Alzheimer’s disease brain respond to optomechanical stimuli?: a narrative review

This abstract will be presented as a poster at the 4th International Brain Stimulation Conference, in December 2021, in Charleston, USA.Alzheimer's disease (AD) is a neurodegenerative condition with enormous social and economic impact at a global scale. Given the inefficacy of the pharmacological treatments developed so far in decelerating/blocking AD pathology, the study and development of so-called alternative (i.e., non-pharmacological) and non-invasive therapies has become one of the major focuses of biomedical research on AD in recent years. Indeed, several researchers have demonstrated the therapeutic potential of optical and mechanical (i.e., optomechanical) stimuli in brain lesions. Among them, photobiomodulation (PBM, the application of modulated red/NIR light for therapeutic purposes) and tailored ultrasonic waves applied to the brain through transcranial ultrasound stimulation (TUSS) are at the forefront of clinical interventions with the potential to improve associated neuropathology and symptomatology of AD (e.g., reduction of protein aggregates deposition in the brain, increased functional connectivity and synchronization of neuronal activity, cognitive improvements), both at the preclinical and clinical levels. However, the biologic mechanisms differentially activated/stimulated during optomechanical stimulation are far from being understood. There are no proven data about the bioavailability of the stimulus energy and their bioeffects on signaling pathways, inflammation and clearance mechanisms, as well as on how these alterations relate with the behavioral improvement observed. Thus, this review compiles and describes possible biological mechanisms and alterations through which optomechanical stimuli can be effective in mitigating AD neuropathology and clinical symptoms. The topics reviewed here will be crucial for further development in the field of alternative, noninvasive brain stimulation approaches against AD, also contributing to all therapeutic interventions by transcranial stimulation in the future, enabling the development of customized therapies

Devices used for photobiomodulation of the brain-a comprehensive and systematic review

A systematic review was conducted to determine the trends in devices and parameters used for brain photobiomodulation (PBM). The revised studies included clinical and cadaveric approaches, in which light stimuli were applied to the head and/or neck. PubMed, Scopus, Web of Science and Google Scholar databases were used for the systematic search. A total of 2133 records were screened, from which 97 were included in this review. The parameters that were extracted and analysed in each article were the device design, actuation area, actuation site, wavelength, mode of operation, power density, energy density, power output, energy per session and treatment time. To organize device information, 11 categories of devices were defined, according to their characteristics. The most used category of devices was laser handpieces, which relate to 21% of all devices, while 28% of the devices were not described. Studies for cognitive function and physiological characterisation are the most well defined ones and with more tangible results. There is a lack of consistency when reporting PBM studies, with several articles under defining the stimulation protocol, and a wide variety of parameters used for the same health conditions (e.g., Alzheimer's or Parkinson's disease) resulting in positive outcomes. Standardization for the report of these studies is warranted, as well as sham-controlled comparative studies to determine which parameters have the greatest effect on PBM treatments for different neurological conditions.This work was supported by the project PTDC/EME-EME/1681/2021—Brain-StimMap, with DOI: https://doi.org/10.54499/PTDC/EME-EME/1681/2021, and by the FCT (Fundação para a Ciência e Tecnologia), under the reference projects UIDB/04436/2020 and UIDP/04436/2020. Sofa Oliveira and Francisca Monteiro thank FCT for their grant UI/BD/150951/2021 and UI/BD/09735/2020, respectively. Susana Catarino thanks FCT for her contract funding provided through 2020.00215.CEECIND, with DOI: https://doi.org/10.54499/2020.00215.CEECIND/CP1600/CT000

Improving the interface between orthopaedic implants and bone - a comparison between different surface treatments

Apresentação efetuada em "Junior Euromat 2022", em Coimbra, 2022Orthopedic implants for load-bearing applications are usually composed of titanium-based materials. However, insufficient bioactivity of metallic materials impairs the bonding with bone, compromising osseointegration at an early stage. The implant-bone interface may be improved by regulating some surface properties of the biomaterials, including surface chemical composition, surface energy, roughness and topography, which influence the behavior of bone cells. In the present study, commercially pure titanium and Ti6Al4V alloy were used to investigate the effect of three surface treatments, after performing two different chemical pre-treatments, on the characteristics of the obtained oxide films. Regarding the pre-treatments, no major differences were observed between performing alcohol cleaning or acidic pre-treatment, considering the surface crystallinity, roughness and wettability. However, the TiO2 layer formed upon anodic oxidation, hydrothermal treatment and anodic oxidation followed by hydrothermal treatment presented different characteristics regarding its crystallinity, roughness, thickness and wettability. This study compared specific surface treatments and the hydrothermal treatment is proposed as a simple treatment capable of improving the characteristics of the implant surface, thereby promoting osteoconductivity. In fact, the culture of human Mesenchymal Stem Cells on Ti-based materials subjected to hydrothermal treatment and consequent induction of osteogenic differentiation confirm the improved surface characteristics.This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/141056/2018 and the projects PTDC/EME-EME/1442/2020, POCI-01-0145-FEDER-030498, UIDB/04436/2019 and UIDP/04436/2020. In addition, this work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC)

Enhancement of Gingival Tissue Adherence of Zirconia Implant Posts: In Vitro Study

Prevention of bacterial inflammation around dental implants (peri-implantitis) is one of the keys to success of the implantation and can be achieved by securing the gingival tissue-abutment interface preventing penetration of bacteria. Modern dental practice has adopted zirconia abutments in place of titanium, but the adhesion of gingival tissue to zirconia is inferior to titanium. The aim of this study was to assess and improve the adhesion of mucosal tissues to zirconia posts using sol-gel derived TiO2 coating following dynamic mechanical testing. The posts were cultivated with porcine bone-gingival tissue specimens in vitro for 7 and 14 days and then subjected to dynamic mechanical analysis simulating physiological loading at 1 Hz up to 50 mu m amplitude. In parallel in silico analysis of stresses and strains have been made simulating "the worst case" when the fixture fails in osseointegration while the abutment still holds. Results show treatment of zirconia can lead to double interface stiffness (static shear stiffness values from 5-10 to 17-23 kPa and dynamic from 20-50 to 60-125 kPa), invariant viscostiffness (from 5-35 to 45-90 kPa center dot s(alpha)) and material memory values (increased from 0.06-0.10 to 0.17-0.25), which is beneficial in preventing bacterial contamination in dental implants. This suggests TiO2-coated zirconia abutments may have a significant clinical benefit for prevention of the bacterial contamination

3D Multi-Material Laser Powder Bed Fusion of 420 stainless steel-Cu parts for Plastic Injection Mold Inserts

Plastic injection molding is one of the fastest-growing industries in the world. However, although it presents numerous advantages, the costs associated with the mold and machine are high and, therefore, this process is only profitable for mass production. Moreover, the reduction in the cycle time, more specifically the cooling time, has been a never-ending challenge since it has a direct influence on production costs. This study is focused on the production of 420 stainless steel-copper solutions by 3D multi-material laser powder bed fusion. This novel material’s design concept allows combining the high mechanical resistance of the steel alloy and the high thermal conductivity of the copper. The processing parameters and strategies as well as the transition zone between these materials are of the most challenging and important aspects both from a mechanical and metallurgical point of view. The obtained results show that this approach is effective to produce inserts of copper in a 420 stainless steel capable of improving the in-service conditions of a plastic injection mold, enhancing its performance and life

Zirconia implants with improved attachment to the gingival tissue

BackgroundGingival tissue attachment is known to be important for long term prognosis of implants. This in vitro study evaluated the gingival attachment to zirconia implants and zirconia implants modified with sol‐gel derived TiO2 coatings.Materials and methodsZirconia endodontic posts (n = 23) were used to function as implants that were inserted into the center of full thickness porcine gingival explants (n = 31). The tissue/implant specimens were then individually placed at an air/liquid interface on a stainless‐steel grid in cell culture wells containing a nutrient solution. The tissue cultures were incubated at 37°C in a 5% CO2 environment and at days 7 and 14, the specimens were harvested and analyzed by dynamic mechanical analysis (DMA) measurements under dynamic loading conditions mimicking natural mastication. Specimens were also analyzed by immunohistochemical staining identifying the laminin (Ln) γ2 chain specific for Ln‐332, which is known to be a crucial molecule for the proper attachment of epithelium to tooth/implant surface.ResultsTissue attachment to TiO2 coated zirconia demonstrated higher dynamic modulus of elasticity and higher creep modulus, meaning that the attachment is stronger and more resistant to damage during function over time. Laminin γ2 was identified in the attachment of epithelium to TiO2 coated zirconia.ConclusionBoth DMA and histological analysis support each other, that the gingival tissue is more strongly attached to sol‐gel derived TiO2 coated zirconia than uncoated zirconia. Immunohistochemical staining showed that TiO2 coating may enhance the synthesis and deposition of Ln‐332 in the epithelial attachment to the implant surface.</div

Buildings contain chemicals that are toxic, sensitizing and promote colonisation by microbes of health concern

Antimikrobisia biosideja ja muita bioreaktiivisia kemikaaleja sisältyy rakennus tuotteisiin ja käytetään rakennusten ylläpidossa, huollossa, siivouksessa ja (home)saneerauksessa. Käytetyt aineet ovat pääosin pitkävaikutteisia biosideja, jotka sisätiloissa käytettyinä kertyvät muodostaen tilojen käyttäjille pysyvän kemiallisen rasitteen, koska mekanismit (luonnonvalo, sade, tuuli, biohajottavat mikrobit, jotka niitä hävittäisivät, puuttuvat. Selvitimme kokeellisesti ja kirjallisuudesta näiden kemikaalien: 1) antimikrobista tehoa terveyshaitallisiksi tunnettuihin, toksiineja tuottaviin mikrobilajeihin; 2) herkistävyyttä ja muita vaikutuksia ihmisen ja muiden lämminveristen soluihin; 3) tekijöitä, jotka vaikuttavat mikrobien haitta-aine päästöihin ja läpäisevyyteen rakennuksessa