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  1. Article ; Online: Effect of the saliva biomolecules on the interface zirconia/Ti6Al4V triboactivity

    H. Teixeira / A.P Serro / C. G. Figueiredo-Pina

    Annals of Medicine, Vol 53, Iss sup1, Pp S53-S

    2021  Volume 54

    Abstract: AbstractIntroduction In some dental implants zirconia artificial dental crowns are fixed through a custom-built abutment made of a titanium alloy (Ti6Al4V) that, in turn, is tightly screwed to the implant. The rotational misfit at the implant-abutment ... ...

    Abstract AbstractIntroduction In some dental implants zirconia artificial dental crowns are fixed through a custom-built abutment made of a titanium alloy (Ti6Al4V) that, in turn, is tightly screwed to the implant. The rotational misfit at the implant-abutment hexagonal interface can lead to relative motion between the parts, resulting in interfacial wear. Usually, the wear tests are performed using artificial saliva (AS) without the addition of proteins. However, it is well documented that proteins can adsorb onto the biomaterials surface and may change the tribological response of the systems [1]. The objective of the present work was to evaluate the effect of theb main proteins of natural saliva on the tribological behaviour of the pair zirconia/Ti6Al4V.Materials and methods Reciprocating pin on plate wear tests were performed using 6 mm balls of Ti6Al4V and plates of zirconia inside of a corrosion cell. The ball (working electrode) was connected to a potentiostat (GAMRY 600), through a wire and a calomel electrode was used as reference electrode. The wear tests were carried out in AS (composition described in [1]) without and with the addition of proteins (lysozyme 0.042 g/L + mucin 0.83 g/L + albumin 0.1 g/L) at 35 °C, during 2 h, with an applied load of 1 N, a sliding distance per cycle of 3 mm and a frequency of 1 Hz. The tests were performed after open circuit potential (OCP) stabilisation (Figure 1). OCP was recorded before, during and after wear testing.[Figure: see text]Results The results showed that the presence of proteins leads to a reduction of the total wear and of the corrosion activity at the interface zirconia/Ti6Al4V during sliding, at the initial stage of the wear test. In fact, the wear rate decreases form ∼15 × 10−5 to ∼7 × 10−5 mm3/Nm. In addition, the OCP obtained during sliding for AS + proteins is much higher than the one observed for AS during the first 15 min and it equals the AS OCP just after 113 min of wear testing.Discussion and conclusions The results suggest that the proteins adsorb at ...
    Keywords Medicine ; R
    Subject code 670
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher Taylor & Francis Group
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Development of Composites of PLA Filled with Different Amounts of Rice Husk Fibers for Fused Deposition Modeling

    Daniel F. Pereira / A.C. Branco / Ricardo Cláudio / Ana C. Marques / C. G. Figueiredo-Pina

    Journal of Natural Fibers, Vol 20, Iss

    2023  Volume 1

    Abstract: Polylactic acid (PLA) has been used as a matrix material to produce composites with natural fibers, which present several advantages, being one of them the addition of value to agricultural waste. Thus, this study aims to develop a PLA 3D filament with ... ...

    Abstract Polylactic acid (PLA) has been used as a matrix material to produce composites with natural fibers, which present several advantages, being one of them the addition of value to agricultural waste. Thus, this study aims to develop a PLA 3D filament with the incorporation of a waste agriculture product (rice husk (RH)). For that, RH fibers were prepared, and PLA was loaded up to 20% RH. The filaments were obtained by extrusion. Finally, samples were produced by fused deposition modeling (FDM). The fibers and filaments’ density and thermal stability (TGA) were determined, and their chemical structure changes due to alkali treatment were accessed by Fourier Transform Infrared Spectroscopy (FTIR). Printability tests were performed, and printed samples were characterized in terms of density, water absorption, and mechanical behavior (compression, tensile, and flexural tests). The results showed that the alkali treatment changed the chemical structure of RH fibers and TGA showed that the filaments did not degrade significantly until 250ºC. The best printability was achieved with 5% of HR content and was the one that showed the lowest mechanical properties reduction. Overall, the present work showed that RH fibers can be successfully used as a filler in PLA filaments for FDM.
    Keywords rice husk ; natural fiber-filled polymer ; additive manufacturing ; pla ; mechanical properties ; composites ; Science ; Q ; Textile bleaching ; dyeing ; printing ; etc ; TP890-933
    Subject code 660
    Language English
    Publishing date 2023-04-01T00:00:00Z
    Publisher Taylor & Francis Group
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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    Inter-library loan at ZB MED

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  3. Article ; Online: Effect of pH of H2O2 solutions on the morphology and wear resistance of human dental enamel

    A. C. Branco / M. Polido / R. Colaço / C. G. Figueiredo-Pina / A. P. Serro

    Annals of Medicine, Vol 53, Iss sup1, Pp S52-S

    an AFM study

    2021  Volume 52

    Abstract: AbstractIntroduction Teeth whitening is a highly demanded aesthetic dental procedure to remove teeth stains and get a whiter and perfect smile. This type of treatment is usually performed by the application on the teeth surface of hydrogen or carbamide ... ...

    Abstract AbstractIntroduction Teeth whitening is a highly demanded aesthetic dental procedure to remove teeth stains and get a whiter and perfect smile. This type of treatment is usually performed by the application on the teeth surface of hydrogen or carbamide peroxides which diffuse through the external layer of the teeth, enamel [1]. Although whitening treatments improve teeth appearance, they can impair teeth health, due to the eventual degradation of the teeth tissues. This may lead to abnormal wear and weaken the tooth structure. The aim of this work is to study the effect of the pH of 30% H2O2 solutions on the surface of human enamel.Materials and methods Human molars were collected for the study with informed consents of the patients. Teeth were bleached in 30% H2O2 solution with different pH values (2, 4 and 6). All samples were submitted to 11 bleaching sessions of 10 min each with alternate periods (2 min) of exposition to blue light. Microhardness, surface roughness and topography/morphology were characterised by microindentation tests, atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively, before and after the whitening treatments. AFM scratching tests (10 × 10 µm2) were performed, using a diamond probe. After the nanowear tests, topographical images of larger areas (20 × 20 µm2) which include the scratched squares were obtained with a silicon probe. The wear mechanisms were evaluated by SEM. Acceptance of the study protocol was obtained from a local ethics committee.Results The most significant changes on enamel surface were obtained for pH = 2: the microhardness decreases, and the surface roughness significantly increases as confirmed by the SEM image analysis. A higher wear rate was observed for pH = 2 in the AFM scratching tests. SEM observation of the wear zone showed differences in the wear mechanisms, which depend on the pH.Discussion and Conclusions Enamel microhardness, surface roughness and wear resistance are affected by the pH of the bleaching solution: pH = 2 led to ...
    Keywords Medicine ; R
    Subject code 620
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher Taylor & Francis Group
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  4. Article ; Online: 3D-Printing of zirconia dental prostheses

    I. Rodrigues / S. Olhero / M. Guedes / A. P. Serro / C. G. Figueiredo-Pina

    Annals of Medicine, Vol 53, Iss sup1, Pp S89-S

    2021  Volume 90

    Abstract: AbstractIntroduction Yittria-stabilised-zirconia is a biomaterial widely employed in the production of dental prostheses through several traditional manufacturing and shaping processes (such as machining and surface grinding of a green or sintered block, ...

    Abstract AbstractIntroduction Yittria-stabilised-zirconia is a biomaterial widely employed in the production of dental prostheses through several traditional manufacturing and shaping processes (such as machining and surface grinding of a green or sintered block, gel-casting and injection moulding) which carry relatively high labour, tooling, moulding and waste material costs. Additive manufacturing 3D-printing processes, such as robocasting, enable the quick production of customised and intricate parts without the need for costly milling tools and moulds [1,2]. In this work, the robocasting process was employed in the production of zirconia parts using a layer-by-layer deposition strategy of a dispersed ceramic powder slurry through a numerically controlled extruder and nozzle. The highest possible solid content allowing for proper extrusion through a fine nozzle was determined for a plain, inexpensive water-based slurry of zirconia powders and dispersing agent.Materials and methods A commercial open-source 3D printer was modified to use a standard micrometric syringe and needle as an extruder Figure 1. An initial batch of 80 wt.% solid zirconia powder slurry was produced using a predetermined optimal CE64 dispersant ratio and equal portions were subsequently condensed through air-drying at 50 °C until an 82, 84, 86, 88 or 90 wt.% solid content ratio was reached. Each slurry was then used for the robocasting of zirconia cuboid samples, which were air-dried for 48 h at 50 °C and sintered at 1500 °C for 2 h. Sintered sample densities were measured using the Archimedes method and the polished base sample surfaces were characterised through microscopy analysis, hardness and toughness tests. The slurry yielding the best results was, thus selected for the production of a sintered tooth prototype using the same sample extrusion speeds, nozzle travel speeds and diameter (0.45 mm).[Figure: see text]Results The best sample print quality was attained using 88 wt.% solid content slurries, which resulted in minimal microscopic ...
    Keywords Medicine ; R
    Subject code 670
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher Taylor & Francis Group
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

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