Search

The nature of the electronic ground state of the Ti2C MXene is unambiguously determined by making use of density functional theory-based calculations including hybrid functionals together with a stringent computational setup providing numerically converged results up to 1 meV. All the explored density functionals (i.e., PBE, PBE0, and HSE06) consistently predict that the Ti2C MXene has a magnetic ground state corresponding to antiferromagnetic (AFM)-coupled ferromagnetic (FM) layers. A spin model, with one unpaired electron per Ti center, consistent with the nature of the chemical bond emerging from the calculations, is presented in which the relevant magnetic coupling constants are extracted from total energy differences of the involved magnetic solutions using an appropriate mapping approach. The use of different density functionals enables us to define a realistic range for the magnitude of each of the magnetic coupling constants. The intralayer FM interaction is the dominant term, but the other two AFM interlayer couplings are noticeable and cannot be neglected. Thus, the spin model cannot be reduced to include nearest-neighbor interactions only. The Néel temperature is roughly estimated to be in the 220 ± 30 K, suggesting that this material can be used in practical applications in spintronics and related fields.

The synthesis, properties, and reactivity of monocyclopentadienyltitanium(III) complexes stabilized by hydridoborato (BH3R)(-) ligands are reported. The reactions of the titanium(IV) trichlorides [Ti(eta(5)-C5H5-nMen)Cl-3] with excess LiBH3R (R = H, Me) afford dimeric [{Ti(eta(5)-C5H5-nMen)(BH4)(mu-BH4)}(2)] (n = 5 (1), 4 (2), 0 (3)) or monomeric [Ti(eta(5)-C5Me5)(BH3Me)(2)] (4) titanium(III) derivatives. Compound 3 is a thermally unstable oil and decomposes at room temperature forming a mixedvalence Ti-II/Ti-III tetrametallic species [{Ti(eta(5)-C5H5)(BH4)}(2){(mu(3)-B2H6)Ti(eta(5)-C5H5)}(2)] (5) with dianionic diborane(6) ligands in a rare mu(3)-kappa(2):kappa(2):kappa(2)-B2H6 coordination mode. Density functional theory (DFT) calculations for 5 agree with a triplet ground state with two inner titanium(II) atoms bonded by a single bond and two outer titanium(III) centers. In contrast to 3, the monomeric tetrahydrofuran adduct derivative [Ti(eta(5)-C5H5)(BH4)(2)(thf)] (6) is a stable solid. Dimeric 1-3 react with 2,6-lutidinium salts (LutH)X (X = BPh4, OSO2CF3) to afford ion pairs, [Ti(eta(5)-C5H5-nMen)(BH4)L-2](BPh4) (L = thf, n = 5 (7), 4 (8), 0 (9); L = py, n = 5 (10)), or molecular aggregates, [{Ti(eta(5)-C5Me5)(BH4)(mu-O2SOCF3)}(2)] (11) and [{Ti(eta 5C5H5-nMen)(mu-O2SOCF3)(2)} x] (n = 5, x = 3 (12); n = 4, x = 4 (13)), via formation of H-2 and (Lut)BH3. Diamagnetic titanium(II) derivatives [{Ti(eta(5)-C5Me5)(mu-H)}(2){(mu-H)(2)Al(BH3R)(thf)}(2)] (R = H (14), Me (15)) were isolated in reactions of complexes 1 and 4 with LiAlH4 in tetrahydrofuran., Spanish Structures of Excellence María de Maeztu, Ministerio de Ciencia, Innovación y Universidades, Universidad de Alcalá

Titanium mini-implants are used as anchorage for orthodontic tooth movements. However, these implants present problems due to the infection of surrounding tissues. The aim of this work was to obtain a polyethylene glycol (PEG) layer by plasma in order to achieve a bacteriostatic surface. Titanium surfaces were activated by argon plasma and, after, by PEG plasma with different powers (100, 150 and 200 W) for 30 and 60 min. The roughness was determined by white light interferometer microscopy and the wettability was determined by the contact angle technique. Surface chemical compositions were characterized by X-ray photoelectron spectroscopy (XPS) and cytocompatibility and cell adhesion studies were performed with fibroblast (hFFs) and osteoblast (SAOS-2) cells. Bacterial cultures with Spectrococcus Sanguinis and Lactobacillus Salivarius were performed, and bacterial colonization was determined. The results showed that plasma treatments do not affect the roughness. Plasma makes the surfaces more hydrophilic by decreasing the contact angles from 64.2° for titanium to 5.2° for argon-activated titanium, with values ranging from 12° to 25° for the different PEG treatments. The plasma has two effects: the cleaning of the surface and the formation of the PEG layer. The biocompatibility results were, for all cases, higher than 80%. The polymerization treatment with PEG reduced the adhesion of hFFs from 7000 to 6000 and, for SAOS-2, from 14,000 to 6500, for pure titanium and those treated with PEG, respectively. Bacterial adhesion was also reduced from 600 to 300 CFU/mm2 for Spetrococcuns Sanguinis and from 10,000 to 900 CFU/mm2 for Lactobacillus Salivarius. The best bacteriostatic treatment corresponded to PEG at 100 W and 30 s. As a consequence, the PEG coating would significantly prevent the formation of bacterial biofilm on the surface of titanium mini-implants. info:eu-repo/semantics/publishedVersion

Reaction of [TiCp*Cl-3] (Cp*=eta(5)-C5Me5) with one equivalent of magnesium in tetrahydrofuran at room temperature affords the paramagnetic trinuclear complex [{TiCp*(mu-Cl)}(3)(mu(3)-Cl)], which reacts with dinitrogen under ambient conditions to give the diamagnetic derivative [{TiCp*(mu-Cl)}(3)(mu(3)-eta(1) : eta(2) : eta(2)-N-2)] and the titanium(III) dimer [{TiCp*Cl(mu-Cl)}(2)]. The structure of the trinuclear mixed-valence complexes has been studied by experimental and theoretical methods and the latter compound represents the first well-defined example of the mu(3)-eta(1) : eta(2) : eta(2) coordination mode of the dinitrogen molecule. The reaction of [{TiCp*(mu-Cl)}(3)(mu(3)-eta(1) : eta(2) : eta(2)-N-2)] with excess HCl in tetrahydrofuran results in clean NH4Cl formation with regeneration of the starting material [TiCp*Cl-3]. Therefore, a cyclic ammonia synthesis under ambient conditions can be envisioned by alternating N-2/HCl atmospheres in a [TiCp*Cl-3]/Mg(excess) reaction mixture in tetrahydrofuran., Ministerio de Ciencia, Innovación y Universidades, Universidad de Alcalá, Spanish Structures of Excellence María de Maeztu

The influence of the surface topography of dental implants has been studied to optimize titanium surfaces in order to improve osseointegration. Different techniques can be used to obtain rough titanium, however, their effect on wettability, surface energy, as well as bacterial and cell adhesion and differentiation has not been studied deeply. Two-hundred disks made of grade 4 titanium were subjected to different treatments: machined titanium (MACH), acid-attacked titanium (AE), titanium sprayed with abrasive alumina particles under pressure (GBLAST), and titanium that has been treated with GBLAST and then subjected to AE (GBLAST + AE). The roughness of the different treatments was determined by confocal microscopy, and the wettability was determined by the sessile drop technique; then, the surface energy of each treatment was calculated. Osteoblast-like cells (SaOs-2) were cultured, and alkaline phosphatase was determined using a colorimetric test. Likewise, bacterial strains S. gordonii, S. oralis, A. viscosus, and E. faecalis were cultured, and proliferation on the different surfaces was determined. It could be observed that the roughness of the GBLAST and GBLAS + AE was higher, at 1.99 and 2.13 μm of Ra, with respect to the AE and MACH samples, which were 0.35 and 0.20 μm, respectively. The abrasive treated surfaces showed lower hydrophilicity but lower surface energy. Significant differences could be seen at 21 days between SaOS-2 osteoblastic cell adhesion for the blasted ones and higher osteocalcin levels. However, no significant differences in terms of bacterial proliferation were observed between the four surfaces studied, demonstrating the insensitivity of bacteria to topography. These results may help in the search for the best topographies for osteoblast behavior and for the inhibition of bacterial colonization. info:eu-repo/semantics/publishedVersion

Background: The objective of this study was to evaluate the accumulation of ions in blood and organs caused by Ti metal particles in a mandibular defect in rats, together with a description of the local reaction of oral tissues to these titanium alloy debris. Methods: Twenty Sprague-Dawley rats were randomly distributed into three groups: an experimental group with a mandibular bone defect filled with metallic debris obtained by implantoplasty; a positive control group; and a negative control group. Thirty days after surgery, the rats were euthanized and perilesional tissue surrounding the mandibular defect was removed, together with the lungs, spleen, liver and brain. Two blood samples were collected: immediately before surgery and before euthanasia. The perilesional tissue was histologically analyzed using hematoxylin-eosin staining, and titanium, aluminum and vanadium ion concentrations in blood and organs were measured by TQ-ICP-MS. Descriptive and bivariate analyses of the data were performed. Results: All rats with implanted metal debris showed metal particles and a bone fracture callus on the osseous defect. The metal particles were surrounded by a foreign body reaction characterized by the presence of histiocytes and multinucleated giant cells. The experimental group had a significant higher concentration of Ti ions in all studied organs except lung tissue (p < 0.05). In addition, there were more V ions in the brain in the experimental group (p = 0.008). Conclusions: Although further studies are required to confirm the clinical relevance of these results, Ti metal particles in the jaw might increase the concentration of metal ions in vital organs and induce a foreign body reaction. This article is protected by copyright. All rights reserved. Keywords: Ion release; Ti6Al4V; implantoplasty; metal particles; peri-implantitis; titanium.

The augmentation of the alveolar crest after the loss of one or several teeth can be carried out using different bone augmentation techniques. These techniques include bone distraction, ridge expansion, bone block grafts, etc. Guided bone regeneration is an alternative to increase the volume of the hard tissues for the subsequent placement of the implants in the optimal three-dimensional position. The objective of this paper is to show a case report of the use of customized titanium mesh for posterior vertical bone regeneration. Case report and Results: A 59-year-old woman comes to rehabilitate edentulous spaces with implants. After taking the anamnesis and the intra and extraoral exploration, a vertical and horizontal bone defect is observed in the third quadrant. After the radiological study with CBCT, a bone height of 6.04 mm to the inferior alveolar nerve and a width of the bone crest of 3.95 mm was observed. It was decided to carry out a regeneration with a preformed titanium mesh (Avinent®, Santpedor, Spain) and four microscrews (Avinent®, Santpedor, Spain). The flap was closed without tension. Regular check-ups were performed without complications. At 7 months, the mesh was removed and two osteoingrated implants (Avinent®, Santpedor, Spain) were placed with a torque greater than 45 N/cm and an ISQ of 82 and 57 N/cm, respectively. The bone gain obtained was 1.84 and 1.92 mm in width and 4.2 and 3.78 mm in height for positions 3.5 and 3.6. The newly formed bone, obtained by trephine, was well-structured and histologically indistinguishable from the previous bone. Conclusion: The use of a customized pre-formed titanium mesh together with the mixture of autologous bone and xenograft is a feasible and predictable technique for vertical bone regeneration.

[eng] This thesis consists in the development of a new methodology of α-alkylation of carbonyl compounds and its application to the synthesis of small molecules with therapeutic interest. In this context, the alkylation of carbonyl compounds is usually achieved by alkylation of nucleophilic metal enolates with alkyl halides through a SN2 substitution mechanism. This approach entails a limited scope in terms of alkylating agent since the alkyl halide should be activated enough to undergo such substitution. In this thesis, a radical alternative which uses titanium(IV) enolates is presented. In fact, titanium enolates are found in equilibrium between a nucleophilic species, the titanium(IV) enolate, and a biradical species, the titanium(III). This equilibrium is the result of a valence tautomerism that lies in an electron transfer from the ligand (the enolate) to the metal center (titanium), which is reduced to titanium(III). As a consequence of this redox process, the enolate becomes an open shell species with three electrons in the acyl moiety instead of four, which grants the enolate with radical reactivity. In chapter one, this reactivity is exploited to achieve the radical alkylation of titanium(IV) enolates from chiral N-acyl oxazolidinones with diacyl peroxides. When mixed with the enolate, these species break homolytically to give an acyloxy radical, which upon decarboxylation, generates an alkyl radical that recombines with the titanium enolate to give a single diastereomer of the alkylated product. The high reactivity of alkyl radicals permits us to perform the alkylation with deactivated primary and secondary alkyl groups, a transformation that is difficult to achieve by other established methodologies. A broad scope of primary and secondary diacyl peroxides including different functional groups such as unsaturations, phenyl or esters is described. In addition, the alkylation can be performed on a vast range of titanium enolates, which can also include such functionalities as well as an oxygen, nitrogen or chlorine in the α position. This methodology is finally applied to the straightforward synthesis of arundic acid. In chapter two, the total synthesis of umuravumbolide, a substituted pyrone extracted from a medicinal plant, is described. The synthesis includes the abovementioned alkylation of a titanium enolate derived from glycolic acid to furnish the stereocenter in the side chain. Other key steps are the formation of a Z double bond and an asymmetric allylation of a sensitive aldehyde intermediate. Chapter three describes an analogous alkylation procedure to that one investigated in the first chapter, only this time, tert-butyl peresters are used instead of diacyl peroxides. This change allows the alkylation of titanium enolates derived from chiral N-acyl oxazolidinones with secondary and even tertiary alkyl groups, a transformation that is rarely reported in the literature. A broad scope of secondary and tertiary peresters is described for this transformation. And similarly to chapter one, different titanium enolates including functional groups such as esters, unsaturations or heteroatoms can be used for such alkylation procedure. Finally, in chapter four other alkylating agents that are able to render an alkyl radical are investigated. However, the alkylation product is not obtained in any of the examples tested against titanium enolates. Therefore, the substitution of titanium for another metal that can render biradical enolates but at the same time can be used in catalytic amounts is attempted. For that, a screening of different metals in various oxidation states is performed. In this case, TEMPO is used to trap a putative biradical enolate., [cat] Aquesta tesi es basa en el desenvolupament d’una metodologia d’α-alquilació de compostos carbonílics i l’aplicació d’aquesta a la síntesis de petites molècules orgàniques d’interès terapèutic. La característica més rellevant d’aquesta nova metodologia és el seu mecanisme radicalari, que es manifesta gràcies a l’ús d’enolats de titani(IV). De fet, aquests enolats es troben en equilibri a través d’un procés de tautomeria de valència entre una espècie de caràcter nucleòfil, l’enolat de titani(IV), i una espècie biradicalaria, l’enolat de titani(III). En el primer capítol, s’estudia l’alquilació d’enolats de titani derivats de N-acil oxazolidinones quirals amb peròxids de diacil. L’escissió d’aquests últims dona lloc a un radical aciloxi que, després d’un procés de descarboxilació, forma un radical alquil que reacciona amb l’enolat de titani per donar lloc al producte d’alquilació com a únic diastereòmer. Aquest procediment permet l’alquilació amb un ampli ventall de peròxids de diacil que contenen grups d’alquil primaris i secundaris amb diversos grups funcionals, tals com dobles i triples enllaços, fenils o esters. A més a més, també permet alquilar diversos enolats amb funcionalitats semblants, fins i tot, amb oxigen, nitrogen i clor en posició alfa. Aquesta metodologia s’aplica a la síntesis directa de l’àcid arúndic. En el segon capítol, es duu a terme la síntesis total de la umuravumbolida, una pirona substituïda que s’extreu d’una planta medicinal. En aquesta síntesi es fa servir l’alquilació anteriorment descrita per formar l’estereocentre de la cadena lateral de la umuravumbolida. En el tercer capítol es desenvolupa una alquilació d’enolats de titani anàloga a la del primer capítol, aquest cop, però, emprant perèsters de tert-butil. Aquest canvi permet l’alquilació amb grups secundaris i terciaris, una transformació que normalment és difícil d’aconseguir. Com en el primer capítol, l’alquilació també permet l’ús de diferents enolats de titani amb funcionalitats diverses. Finalment, en el quart capítol es busquen altres agents alquilants que formin radicals alquil. No obstant, no s’aconsegueix l’alquilació de l’enolat de titani en cap dels casos. Per tant, es fa un canvi d’objectiu i es busca trobar un metall substitut del titani que també pugui formar enolats amb activitat radicalària però de manera catalítica.

Treballs Finals de Grau d'Enginyeria Biomèdica. Facultat de Medicina i Ciències de la Salut. Universitat de Barcelona. Curs: 2021-2022. Director: Javier Fernández González. Tutora: Raisha Lorena García Cadme., Increased life expectancy leads to the increasing use of metallic prostheses. Titanium and its alloys are the most widely used materials for metallic prostheses thanks to their biocompatibility, but further work still necessary to improve bioactivity and reduce osseointegration problems. Developing nanostructured titanium dioxide (TiO2) coatings increases the biocompatibility of titanium prostheses. Using the electrolytic anodizing process, nanostructures can be achieved easily and economically. This project aims to optimize the voltage and anodizing time conditions to obtain titanium dioxide nanotubes on the surface of Ti-6Al-7Nb alloy, as well as to propose ideas for industrial implementation of the project. To this purpose, a market study, a project implementation plan and a technical and economic feasibility analysis were carried out. An electron microscope image processing method and a rigorous statistical analysis have been studied to obtain an average pore diameter quantify the effect of the studied variables. Potentials of 15, 30 and 60 volts and anodizing times of 15 and 30 minutes were studied. The effect of the concentration of fluoride ions and the type of cathode used in anodizing has also been studied. The optimum conditions for the smallest pore size we have found are anodizing at 15V and 15 minutes, with a grid cathode. With these conditions, an average pore diameter of 0,48 ± 0,05 μm was obtained.

Low-valent titanium species were prepared by reaction of [TiCp*X3] (Cp* = eta5-C5Me5; X = Cl, Br, Me) with LiEH4 (E = Al, B) or BH3(thf), and their structures elucidated by experimental and theoretical methods. The treatment of trihalides [TiCp*X3] with LiAlH4 in ethereal solvents (L) leads to the hydride-bridged heterometallic complexes [{TiCp*(mu-H)}2{(mu-H)2AlX(L)}2] (L = thf, X = Cl, Br; L = OEt2, X = Cl). Density functional theory (DFT) calculations for those compounds reveal an open-shell singlet ground state with a Ti-Ti bond and can be described as titanium(II) species. The theoretical analyses also show strong interactions between the Ti-Ti bond and the empty s orbitals of the Al atom of the AlH2XL fragments, which behave as sigma-accepting (Z-type) ligands. Analogous reactions of [TiCp*X3] with LiBH4 (2 and 3 equiv) in tetrahydrofuran at room temperature and at 85 ºC lead to the titanium(III) compounds [{TiCp*(BH4)(mu-X)}2] (X = Cl, Br) and [{TiCp*(BH4)(mu-BH4)}2], respectively. The treatment of [TiCp*Me3] with 4 and 5 equiv of BH3(thf) produces the diamagnetic [{TiCp*(BH3Me)}2(mu-B2H6)] and paramagnetic [{TiCp*(mu-B2H6)}2] complexes, respectively., Ministerio de Ciencia, Innovación y Universidades, Universidad de Alcalá

The lack of bioactivity of titanium (Ti) is one of the main drawbacks for its application in biomedical implants since it can considerable reduce its osseointegration capacities. One strategy to overcome this limitation is the coating of Ti with hydroxyapatite (HA), which presents similar chemical composition than bone. Nonetheless, most of the strategies currently used generate a non-stable coating and may produce the formation of amorphous phases when high temperatures are used. Herein, we proposed to generate a Ti-HA composite coating on Ti surface to improve the stability of the bioactive coating. The coating was produced by cold gas spraying, which uses relatively low temperatures, and compared to a Ti coating. The coating was thoroughly characterized in terms of morphology, roughness, porosity and phase composition. In addition, the coating was mechanically characterized using a tensile loading machine. Finally, biological response was evaluated after seeding SaOS-2 osteoblasts and measuring cell adhesion, proliferation and differentiation. The novel Ti-HA coating presented high porosity and high adhesion and bond strengths. No change in HA phases was observed after coating formation. Moreover, osteoblast-like cells adhered, proliferated and differentiated on Ti-HA coated surfaces suggesting that the novel coating might be a good candidate for biomedical applications. info:eu-repo/semantics/acceptedVersion

International audience; This paper is an experimental research about the mechanical effects on Ti-6Al-4V surfaces treated with an ultrasonic vibration-assisted ball burnishing process. Its aim is to define the process parameters to achieve the best surface integrity on the target workpiece, as well as identifying the effects caused by the introduction of vibrations as a means of assistance. A Taguchi orthogonal array including five factors (preload, number of passes, feed velocity, strategy and original surface texture) was applied to perform the process on ball-end milled surfaces. A comprehensive analysis of the effects was performed, by considering in depth three different facets of surface integrity, namely, topology, residual stress and hardness. Hence the extensive result datasets presented in this paper, which deliver an exhaustive description of the process effects by combining a triple approach in the results analysis section. The effect of vibrations is proved positive to enhance the texture as long as the original surface is not characterized by Sq >2 μm. Furthermore, only the preload and number of passes influence the results. In terms of residual stress, all parameters are influential in the results, especially the burnishing strategy, through which a specific direction can be reinforced. Finally, the burnishing operation proves to modify the hardness of deep layers down to 0.5 mm, applying the vibration-assisted process. The main conclusion derived from these works is a technical recommendation to treat the Ti-6Al-4 V surface through the process, aiming to find a balanced comprehensive surface integrity enhancement.

Featured Application In this paper, a fast, one-step method to prepare acrylate-based coatings on titanium through the atmospheric pressure plasma polymerization of HEMA is described. The coating shows lower surface bacterial adhesion and enhanced cell adhesion when compared with pristine titanium. Dental implants can fail due to various factors, in which bad tissue integration is believed to have a significant role. Specific properties of the implant surface, such as its chemistry and roughness, are of paramount importance to address specific cell responses, such as the adsorption of proteins, as well as the adhesion and differentiation of cells, which are suitable for biomaterial and tissue engineering. In this study, an acrylate-containing coating was produced on titanium surfaces through the atmospheric pressure plasma treatment of a liquid precursor, 2-hydroxyethyl methacrylate. A hydrophilic coating was obtained, showing retention of the monomer chemistry as assessed by FTIR analysis and XPS. Enhanced fibroblast adhesion and decreased Staphylococcus aureus and Escherichia coli adhesion were recorded, showing that this is a suitable method to produce biocompatible coatings with a reduced bacterial adhesion.

The use of individualized titanium meshes has been referred to in scientific literature since 2011. There are many advantages to its use, however, the main complications are related to early or late exposures. As some aspects such as its surface properties have been pointed out to influence the soft tissue response, this study was designed to compare the surface characteristics of three commercially available individualized titanium meshes between them and according to the manufacturer&rsquo, s specifications. The results from the scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and the contact profilometry measurements were analyzed and cross-checked. It was discovered that, the BoneEasy&rsquo, s post-processing superficial treatment was more refined, as it delivers the mesh with the lowest Ra value, 0.61 &plusmn, 0.14 &micro, m, due to the applied electropolishing. On the other hand, the Yxoss CBR&reg, mesh from ReOss&reg, was sandblasted, presenting an extremely rough surface with a Ra of 6.59 &plusmn, 0.76 &micro, m.

The purpose of this study is to assess the use of grade V titanium mini transitional implants (MTIs) immediately loaded by a temporary overdenture. For this, a histomorphometric analysis of the bone area fraction occupancy (BAFO) was performed by backscattered scanning electron microscopy (BS-SEM). Four female patients were submitted to surgery in which two MTIs were installed and immediately loaded with a temporary acrylic prosthesis. During the same surgery, two regular diameter implants were placed inside the bone and maintained without mechanical load. After 8 months, the MTIs were extracted using a trephine and processed for ultrastructural bone analysis by BS-SEM, and the regular-diameter implants were loaded with an overdenture device. A total of 243 BAFOs of MTIs were analyzed, of which 94 were mainly filled with cortical bone, while 149 were mainly filled with trabecular bone. Bone tissue analysis considering the total BAFOs with calcified tissues showed 72.13% lamellar bone, 26.04% woven bone, and 1.82% chondroid bone without significant differences between the samples. This study revealed that grade V titanium used in immediately loaded MTI was successfully osseointegrated by a mature and vascularized bone tissue as assessed from the BAFO.

Two-pieces dental implants must provide stability of the implant-abutment-interface. The connection type and platform diameter could influence the biomechanical resistance and stress distribution. This study aims to evaluate the fatigue for different types of connections, external and internal, and different platform diameters. Three implant designs with the same length were used: (a) external hexagon/narrow platform, (b) internal double hexagon/narrow platform, (c) internal octagon/regular platform. A fatigue test was developed to establish the number of cycles needed before fracture. A 30&ordm, oblique load with a sinusoidal function of fatigue at a frequency of 15 Hz and 10% stress variation was applied to each system. The fatigue load limit (FLL) for design (a) was 190N, being the nominal-curvature-moment (NCM) = 1.045, FLL = 150 N, with a NCM = 0.825 for (b), and FLL = 325 N, with a NCM = 1.788 for (c). The platform diameter affects the FLL, obtaining lower FLL on a narrow platform. The connection type interferes with the implant walls&rsquo, width, especially in narrow implants, making internal connections more unstable at this level. Long-term clinical studies to assess the restoration&rsquo, s success rate and survival are mandatory.

Passivation of titanium alloy dental meshes cleans their surface and forms a thin layer of protective oxide (TiO2) on the surface of the material to improve resistance to corrosion and prevent release of ions to the physiological environment. The most common chemical agent for the passivation process of titanium meshes is hydrochloric acid (HCl). In this work, we introduce the use of Piranha solution (H2SO4 and H2O2) as a passivating and bactericidal agent for metallic dental meshes. Meshes of grade 5 titanium alloy (Ti6Al4V) were tested after different treatments: as-received control (Ctr), passivated by HCl, and passivated by Piranha solution. Physical-chemical characterization of all treated surfaces was carried out by scanning electron microscopy (SEM), confocal microscopy and sessile drop goniometry to assess meshes’ topography, elemental composition, roughness, wettability and surface free energy, that is, relevant properties with potential effects for the biological response of the material. Moreover, open circuit potential and potentiodynamic tests were carried out to evaluate the corrosion behavior of the differently-treated meshes under physiological conditions. Ion release tests were conducted using Inductively Coupled Plasma mass spectrometry (ICP-MS). The antibacterial activity by prevention of bacterial adhesion tests on the meshes was performed for two different bacterial strains, Pseudomonas aeruginosa (Gram-) and Streptococcus sanguinis (Gram+). Additionally, a bacterial viability study was performed with the LIVE/DEAD test. We complemented the antibacterial study by counting cells attached to the surface of the meshes visualized by SEM. Our results showed that the passivation of titanium meshes with Piranha solution improved their hydrophilicity and conferred a notably higher bactericidal activity in comparison with the meshes passivated with HCl. This unique response can be attributed to differences in the obtained nanotextures of the TiO2 layer. However, Piranha solution treatment decreased electrochemical stability and increased ion release as a result of the porous coating formed on the treated surfaces, which can compromise their corrosion resistance. Framed by the limitations of this work, we conclude that using Piranha solution is a viable alternative method for passivating titanium dental meshes with beneficial antibacterial properties that merits further validation for its translation as a treatment applied to clinically-used meshes. info:eu-repo/semantics/publishedVersion

Commercially pure grade 2 titanium in sheet form was processed by equal channel angular sheet extrusion (ECASE) up to two passes at room temperature. The ECASE process generated a heterogeneous state of deformation, mainly affecting the sheet metal edges´ vicinity. The deformation heterogeneity gave rise to notable microstructural changes throughout the sheet thickness with high densities of twins located around 600 μm from the sheet edges. At the same time, the middle zone was kept free of twins. The highest twin density generated with the ECASE process corresponds mostly to tension twins of type 10 1 ¯ 2 10 1 ¯ 1 oriented towards the extrusion direction. The heterogeneous structure produced a material strength increase of 200 MPa, maintaining a uniform deformation zone of 10%. The good strength-ductility combination was related to a heterogeneous distribution of geometrically necessary dislocations (GNDs) between the hardest and softest areas. The edge areas presented greater GNDs of type ⟨a⟩ on the twins' exterior than in their interior while in the middle zone, the highest GND densities grouped around triple points and grain boundaries. It was found that the grains with the most significant capacity to nucleate twins and store GNDs were those with the c-axis of the crystals parallel to the normal direction (ND). According to the Hall-Petch relationship, the strength improvement of the heterogeneous material comes from the grain size reduction mainly due to twins induced by deformation around the edge areas.

One of the major problems faced by metallic implants is the high probability of bacterial infections, with significant consequences for the patient. In this work, a thermochemical treatment is proposed to obtain silver-doped calcium titanate coatings on the Ti surface to improve the bioactivity of porous 3D-printed Ti structures and simultaneously provide them with antibacterial properties. A complete characterization of the new coating, the study of the ion release and the analysis of its cytotoxicity were carried out together with evaluation of the natural apatite forming in simulated body fluid (SBF). Moreover, the antibacterial properties of the coatings were assessed against Pseudomona aeruginosa and Escherichia coli as gram-negative and Staphylococcus aureus and Staphylococcus epidermidis as gram-positive bacterial strains. Ag ions were integrated into the Ca titanate layer and Ag nanoparticles were formed within the entire 3D Ti surface. Ca and Ag ions were released from both porous and solid samples into the Hanks' solution for 48 h. The treated surfaces showed no cytotoxicity and an apatite layer precipitated on the entire porous surface when the samples were immersed in SBF. The release of Ag from the surface had a strong antibacterial effect and prevented bacterial adhesion and proliferation on the surface. Moreover, the nanostructured topography of the coating resulted also in a reduction of bacterial adhesion and proliferation, even in absence of Ag. In conclusion, the cost-effective approach here reported provided protection against the most predominant bacterial colonizers to the Ti porous implants, while maintaining their bioactivity.

Background:The topographical features on the surface of dental implants have been considered as a critical parameter for enhancing the osseointegration of implants. In this work, we proposed a surface obtained by a combination of shot blasting and double acid etching. The double acid etching was hypothesized to increase the submicron topography and hence further stimulate the biological properties of the titanium implant.Methods:The topographical features (surface roughness and real surface area), wettability and surface chemical composition were analyzed.Results:The results showed that the proposed method produced a dual roughness, mainly composed of randomly distributed peaks and valleys with a superimposed nanoroughness, and hence with an increased specific surface area. Despite the fact that the proposed method does not introduce significant chemical changes, this treatment combination slightly increased the amount of titanium available on the surface, reducing potential surface contaminants. Furthermore, the surface showed increased contact angle values demonstrating an enhanced hydrophobicity on the surface. The biological behavior of the implants was then assessed by culturing osteoblast-like cells on the surface, showing enhanced osteoblast adhesion, proliferation and differentiation on the novel surface.Conclusions:Based on these results, the described surface with dual roughness obtained by double acid etching may be a novel route to obtain key features on the surface to enhance the osseointegration of the implant. Our approach is a simple method to obtain a dual roughness that mimics the bone structure modified by osteoclasts and increases surface area, which enhances osseointegration of dental implants.

Simple treatment of chiral titanium(IV) enolates with diacyl peroxides produces highly diastereoselective decarboxylative alkylations to efficiently deliver the corresponding adducts, most of which are not accessible through any of the current alkylating procedures. Such an unprecedented alkylation proceeds through an SET process that triggers the decomposition of the peroxide into a carbon-centered radical that finally combines with the resulting Cα radical. The procedure has been applied to the enantioselective synthesis of arundic acid.

Methane is an extremely stable molecule, a major component of natural gas, and also one of the most potent greenhouse gases contributing to global warming. Consequently, the capture and activation of methane is a challenging and intensively studied topic. A major research goal is to find systems that can activate methane even at low temperature. Here, combining ultrahigh vacuum catalytic experiments followed by X-ray photoemission spectra and accurate density functional theory (DFT) based calculations, we show that small Ni clusters dispersed on the (001) surface of TiC are able to capture and dissociate methane at room temperature. Our DFT calculations reveal that two-dimensional Ni clusters are responsible of this chemical transformation, evidencing that the lability of the supported clusters appears to be a critical aspect in the strong adsorption of methane. A small energy barrier of 0.18 eV is predicted for CH4 dissociation into adsorbed methyl and hydrogen atom species. In addition, the calculated reaction free energy profile at 300 K and 1 atm of CH4 shows no effective energy barriers in the system. Comparing with other reported systems which activate methane at room temperature, including oxide and zeolite-based materials, indicates that a different chemistry takes place on our metal/carbide system. The discovery of a carbide-based surface able to activate methane at low temperatures paves the road for the design of new types of catalysts towards an efficient conversion of this hydrocarbon into other added-value chemicals, with implications in climate change mitigation.

El primer mineral de titanio, una arena negra de Cornualles (Gran Bretaña), fue identificado en 1791 por William Gregor, un clérigo inglés y geólogo aficionado, del que extrajo un óxido de un metal desconocido. En 1795, el químico alemán Martin Heinrich Klaproth investigando una turmalina roja de Hungría detectó el óxido de un nuevo elemento, que resultó ser el descrito por Gregor, al que llamó titanio, en alusión los Titanes, los hijos de la diosa Tierra en la mitología griega.

Evaluate the quality of finishing and degree of contamination before and after handling and surface treatment of titanium (Ti) orthodontic mini-implants (OMIs). A scanning electron microscope (SEM) study on ninety-six titanium OMIs was done. Energy-Dispersive X-ray Analysis (EDX) identified the present particles on manufactured OMIs surfaces. Then, OMIs were manipulated with gauze (dry sterile, soaked in chlorhexidine) and gloves (latex, nitrile) to evaluate the contamination of these handling materials. Finally, OMIs underwent surface treatments and were placed in bone to observe the contaminants they released. Roughness (Ra) and wettability with contact angle parameter (CA) were measured on these treated OMIs. Machined OMIs presented surface irregularities and were contaminated with manufacturing-process particles (carbon, plastic Polyvinyl Chloride PVC, aluminum). Hand-manipulated OMIs were also contaminated by the handling materials. OMIs surface characteristics were as follows: acid-etched (Ra 1.3 m, CA 66 ), machined (Ra 0.3 m, CA 68 ), SB (Ra 3.3 m, CA 78 ), and SBAO (Ra 3.1 m, CA 92 ). Bone was contaminated by OMIs surface defects and extra particles. Manufactured OMIs have surface contaminants that increase with clinical handling. Surface treatments (SBAO, a combination of sandblasting and anodic oxidation) increase the roughness and contact angle, which play an important role in osseointegration. Surface-treated OMIs leave titanium particles in the bone during their insertion-removal. The use of a gauze soaked in chlorhexidine is recommended when handling OMIs. Further investigations would be interesting to study more variables and confirm the present results. Spanish Government and and European Union FEDER Generalitat de Cataluña

Atmospheric plasma spraying is used here to obtain titanium sub-oxide coatings on the following electrode substrates: a 316 stainless steel sheet, an aluminium alloy 2024 sheet, a carbon–polymer composite and nickel foam. It is necessary to increase the roughness of the substrate to aid the adhesion of the coating to the smooth electrodes; this is especially critical for the fragile carbon–polymer composite. High-energy conditions increase the strain caused by the mismatch between coefficients of thermal expansion when coating the thin steel and aluminium sheets, and degraded the carbon–polymer composite and nickel foam. Therefore, it is necessary to adjust the spraying parameters to lower-energy conditions in order to achieve well-bonded and homogeneous coatings on all four substrates and avoid the presence of cracks in their cross-section area. The suitability of the coated materials as battery electrodes was studied.

A highly rough titanium coating obtained by Cold Gas Spray (CGS) has been characterized by means of high-resolution 3D microtomography (micro-CT) with the aim to evaluate its open and close porosity for possible use in orthopaedic implants to promote osseointegration. Micro-CT allowed a qualitative and quantitative description of the main features, morphology of the pores and surface roughness of the coating. Several numerical values were obtained to describe size, form and distribution of the closed/inner and open/outer pores. Additionally, surface roughness and open porosity were image-analyzed to find the effective surface for osseointegration.

Three different surface treatments on a Ti6Al4V alloy have been in vitro tested for possible application in cementless joint prosthesis; all of them involve the novelty of using the Cold Spray technology for their deposition: (i) an as-sprayed highly rough titanium and, followed by the deposition of a thin hydroxyapatite layer with (ii) microcrystalline or (iii) nanocrystalline structure. Primary human osteoblasts extracted from knee were seeded onto surfaces and cell viability using MTS and LIFE/DEAD assays, osteoblasts differentiation by alkaline phosphatase (ALP) quantification as well as cell morphology were tested at 1, 7 and 14 days of cell culture. Different cell morphologies between titanium and hydroxyapatite surfaces were exhibited; at 1 day of cell culture, cells on the titanium coating were spread and flattened, expanding the filopodia actin filaments in all directions, while cells on the hydroxyapatite coatings showed round like-shape morphology due to a slower attachment. Higher cell viability was detected at all times of cell culture on titanium coating due to a better attachment at 1 day. However, from 7 days of cell culture, cells on hydroxyapatite showed good attachment onto surfaces and highly increased their proliferation, mostly on nanocrystalline, achieving similar cell viability levels than titanium coatings. ALP levels were significantly higher in titanium, in part, because of greatest cell number. Overall, the best cell functional results were obtained on titanium coatings whereas microcrystalline hydroxyapatite presented the worst cellular parameters. However, results indicate that nanocrystalline hydroxyapatite coatings may achieve promising results for the faster cell proliferation once cells are attached on the surface.

In this study, highly-interconnected porous titanium implants were produced by powder sintering with different porous diameters and open interconnectivity. The actual foams were produced using high cost technologies: Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), and spark plasma sintering, and the porosity and/or interconnection was not optimized. The aim was to generate a bioactive surface on foams using two different strategies, based on inorganic thermo-chemical treatment and organic coating by peptide adsorption, to enhance osseointegration. Porosity was produced using NaCl as a space holder and polyethyleneglicol as a binder phase. Static and fatigue tests were performed in order to determine mechanical behaviors. Surface bioactivation was performed using a thermo-chemical treatment or by chemical adsorption with peptides. Osteoblast-like cells were cultured and cytotoxicity was measured. Bioactivated scaffolds and a control were implanted in the tibiae of rabbits. Histomorphometric evaluation was performed at 4 weeks after implantation. Interconnected porosity was 53% with an average diameter of 210 &micro, m and an elastic modulus of around 1 GPa with good mechanical properties. The samples presented cell survival values close to 100% of viability. Newly formed bone was observed inside macropores, through interconnected porosity, and on the implant surface. Successful bone colonization of inner structure (40%) suggested good osteoconductive capability of the implant. Bioactivated foams showed better results than non-treated ones, suggesting both bioactivation strategies induce osteointegration capability.

[eng] In the present Thesis we continued a previous study of the nucleophilic character of titanium(IV) enolates. Particularly,we focused our attention on the analysis of substrate-controlled Michael additions to enones and other acceptors.Thus, the Michael addition of (S)-2-benzyloxy-3-pentanoneto enones was thoroughly evaluatedin Chapter 1. In the case of vinyl ketones, the best reaction conditions involved the use of two TiCl4 equivalents and afforded the 2,4-antiadducts as single diastereomers in excellent yields. In addition, the developed methodology was also evaluated with β- substituted enones, whose optimised conditions using TiCl4 and SnCl4 afforded the 2,4- anti-4,5-antiadducts with diastereoselectivities above 90:10 in all cases with good yields. Furthermore, the Michael addition of (S)-2-benzyloxy-3-pentanoneto α,β- unsaturated nitroalkenes was alsoanalysed inChapter 1. The use of two equivalents of TiCl4and aromatic nitroalkenes led to the 2,4-anti-4,5-syn adducts with excellent yields and diastereoselectivities. In turn, aliphatic nitroalkenes needed optimised conditions using TiCl4 and SnCl4 to afford the 2,4-anti-4,5-syn adducts in good diastereoselectivities and yields. Finally, the nitro group was converted into other useful functional groups. Another objective of the first part of this thesis wasto re-evaluate the synthesis of the tetrahydropyran ring from the C1-C9 fragment of herboxidiene/GEX1A. Thus, in Chapter 2 we analysed the initial retrosynthesis of the C1-C9 fragment and studied the oxa-Michael cyclization. Finally, we designed two parallel sequences to improve the first synthetic approach.The stereoselective synthesis of the tetrahydropyran ring was successfully accomplished following two different approaches. In approach 1, the number of steps was increased, but the sequence pursued a fully stereoselective pathway taking advantage of the great selectivity offered by a dimethylpyrrole amide under acidic conditions attaining a 54% yield (46% for the original approach). In approach 2, the original sequence of reactions was followed, but the suppression of unnecessary purification operations and a final isomerisation step increased notably the yield up to 58% (39% for the original approach). Keepingin mind the biradical character of certain titanium enolates, the second objective of this Thesis was to examine the uncommon radical reactivity of titanium enolates derived from chiral N-acyl oxazolidinones when exposed to radical reagents. In Chapter 3, the aminoxylation of chiral N-acyl oxazolidinones was improved using a chiral tert-butyl oxazolidinethionederived from tert-leucine. This chiral auxiliary provided the aminoxylated products as single diastereomers in all cases with excellent yields. Finally, the resulting adducts were transformed into synthetical useful intermediates. Furthermore, in Chapter 3 we also reported a highly stereoselective oxidation of titanium enolates from chiral N-acyl oxazolidinones with molecular oxygen. The direct hydroxylation of biradical titanium(IV) enolates derived from chiral oxazolidinones with O2 proved to be feasible. Thus, we described a novel approach for the synthesis of enantiomerically pure α-hydroxy carboxylic derivatives. We describe in Chapter 4 a comprehensive search of compounds capable of participating in radical reactions, which involved a brief exploration of photoredox catalysis. Finally, such research led to the discovery of a new and highly stereoselective alkylation with aliphatic diacyl peroxides. Decarboxylation of the diacyl peroxides from aliphatic acids promoted by the titanium enolates produced primary and secondary radicals and triggered the formation of the alkylated adducts as single diastereomers with excellent yields., [spa] En la presente Tesis continuamos un estudio previo sobre el carácter nucleófilo de los enolatos de titanio(IV) en adiciones de Michael con control por sustrato. Así, la adición de Michael de (S)-2-benciloxi-3-pentanona a enonas y nitroalquenos se evaluó a fondo en el Capítulo 1. En el caso de las vinil cetonas, las mejores condiciones de reacción implicaban el uso de dos equivalentes de TiCl4 o un equivalente de TiCl4 y otro de SnCl4 y proporcionaban los aductos 2,4-anti-4,5-anti con rendimientos excelentes y diastereoselectividades superiores a 90:10. Además, la metodología desarrollada también se empleó con nitroalquenos α,β-insaturados, conduciendo a proporcionar los aductos de 2,4-anti-4,5-syn con buenas diastereoselectividades y rendimientos. En el Capítulo 2 se reevaluó la retrosíntesis inicial del anillo tetrahidropiránico del fragmento C1-C9 del herboxidieno/GEX1A. La síntesis estereoselectiva del anillo de tetrahidropirano se logró con éxito siguiendo dos enfoques diferentes. En el primer enfoque, se aumentó el número de pasos, pero la secuencia siguió una ruta completamente estereoselectiva aprovechando la gran selectividad ofrecida por una dimetilpirrolamida en condiciones ácidas. En el segundo enfoque, se siguió la secuencia original, pero la supresión de operaciones de purificación innecesarias y la inclusión de una etapa de isomerización final aumentaron notablemente el rendimiento. El segundo objetivo de esta Tesis fue examinar la reactividad radical poco común de enolatos de titanio derivados de N-acil oxazolidinonas quirales cuando se exponen a reactivos radicalarios. Así, en el Capítulo 3, la aminoxilación de N-acil oxazolidinonas quirales se mejoró usando una tiazolidintiona de tert-butilo quiral derivada de tert-leucina que proporcionó los productos aminoxilados como únicos diastereómeros con rendimientos excelentes. Además, en el Capítulo 3 también llevamos a cabo una hidroxilación directa altamente estereoselectiva de enolatos de titanio a partir de N-acil oxazolidinonas quirales con oxígeno para la síntesis de derivados α-hidroxicarboxílicos enantioméricamente puros. En el Capítulo 4 describimos una búsqueda exhaustiva de compuestos capaces de participar en reacciones radicales, lo que implicó una breve exploración de la catálisis fotoredox. Finalmente, tal investigación llevó al descubrimiento de una nueva alquilación altamente estereoselectiva con peróxidos de diacilo alifáticos que conducía a la formación de los aductos alquilados como diastereómeros únicos con rendimientos excelentes.

Quantum chemical calculations have unveiled the unexpected biradical character of titanium(IV) enolates from N-acyl oxazolidinones and thiazolidinethiones. The electronic structure of these species therefore involves a valence tautomerism consisting of an equilibrium between a closed shell (formally Ti(IV) enolates) and an open shell, biradical, singlet (formally Ti(III) enolates) electronic states, whose origin is to be basically found in changes of the Ti−O distance. Spectroscopic studies of the intermediate species lend support to such a model, which also turns out to be crucial for a better understanding of the overall reactivity of titanium(IV) enolates. In this context, a thorough computational analysis of the radical addition of titanium(IV) enolates from N-acyl oxazolidinones to TEMPO has permitted us to suggest an entire mechanism, which accounts for the experimental details and the diastereoselectivity of the process. All together, this evidence highlights the relevance of biradical intermediates from titanium(IV) enolates and may be a useful contribution to the foundations of a more insightful comprehension of the structure and reactivity of titanium(IV) enolates.

Hierarchical structures were obtained applying two different nanotexturing surface treatments onto highly rough commercial pure titanium coatings by cold spray: (i) anodic oxidation and (ii) alkaline treatments. An extended surface characterization in terms of topography, composition, and wettability has been performed to understand how those parameters affect to cell response. Primary human osteoblasts extracted from knee were seeded onto the as-sprayed titanium surface before and after the nanotexturing treatments. Cell viability was tested by using MTS and LIVE/DEAD assays, as well as osteoblasts differentiation by alkaline phosphatase (ALP) quantification at 3 and 10 days of cell culture. The combination of micro-/nano-roughness results in a significantly increase of cell proliferation, as well as cell differentiation after 10 days of cell culture in comparison with the non-treated coatings.

Lewis acid-mediated substrate-controlled reactions of the titanium(IV) enolates of chiral a-benzyloxy ketones with conjugated nitroalkenes give the 2,4-anti-4,5-syn Michael adducts in good yields and diastereomeric ratios. The supplementary Lewis acid plays a key role in the outcome of these transformations, probably as a consequence of the formation of bimetallic enolates that increase the reactivity of the enolate and direct the approach of the nitroalkene. Importantly, the most appropriate Lewis acid depends on the electrophilic partner: TiCl4 is the most suitable Lewis acid for b-aryl nitroalkenes while the best results for b-alkyl nitroalkenes are obtained with SnCl4. Finally, the nitro group of the resultant compounds can be converted into the corresponding amino, oxime, and nitrile groups under mild conditions, which permits the synthesis of a variety of enantiomerically pure derivatives with excellent yields.

Treball Final de Grau d'Odontologia, Facultat de Medicina i Ciències de la Salut, Universitat de Barcelona, Curs: 2016-2017, Director: Gemma Sanmartí Garcia, Introducció: Estudi experimental preliminar, sobre el despreniment de partícules de titani (Ti) durant la col·locació i explantació d’implants dentals, sobre mostres cadavèriques d’origen humà. Objectius: L’objectiu principal de la investigació, és la determinació, mitjançant microscòpia òptica i electrònica, i l’anàlisi química microscòpica, de la presència o absència de partícules de Ti, exfoliades durant els processos d’inserció i/o explantació, d’implants dentals. Disseny de l’estudi: Es van col·locar 13 implants, sobre 4 mostres cadavèriques d’origen humà. Del total d’implants emprats, 5 van ser explantats posteriorment, per l’anàlisi microscòpica de les superfícies dels alvèols post-explantació; els 8 implants restants, van romandre a l’os, pel posterior estudi microscòpic de l’os periimplantari i l’os alveolar. Així mateix, la primera mostra cadavèrica estudiada, presentava 7 implants col·locats ante mortem. Resultats: L’anàlisi mitjançant el microscopi electrònic de rastreig Quanta X200, va permetre la detecció de partícules de Ti en 2 de les 5 mostres dels alvèols d’explantació estudiats, i de traces de Ti en 3 de les superfícies d’explantació analitzades, corresponents a les mostres 1, 4 i 11. Es va descartar una possible contaminació de les mostres dels alvèols post-explantació, a partir d’una anàlisi microscòpica i química del disc diamantat emprat en les seccions. Les mostres d’implantació van experimentar una contaminació de partícules de Ti, originada per les seccions efectuades amb serra de precisió i baixa velocitat. Tanmateix, no es van detectar partícules de Ti compatibles amb l’exfoliació de partícules de Ti durant la inserció dels implants, segons la forma i mida de les partícules localitzades en els alvèols d’explantació. L’observació de les mostres mitjançant microscòpia òptica no va proporcionar informació rellevant. Conclusions: S’han detectat partícules de Ti despreses en 2 de les 5 mostres d’explantació analitzades, però una major densitat òssia o una força elevada d’inserció dels implants, no han estat factors determinants en l’aparició de partícules de Ti. La detecció d’aquestes no comporta conseqüències significants a nivell clínic. Es requereixen nous estudis per a determinar l’origen de les partícules de Ti observades.

Producción Científica, The main clinical problems for dental implants are (1) formation of biofilm around the implant—a condition known as peri-implantitis and (2) inadequate bone formation around the implant—lack of osseointegration. Therefore, developing an implant to overcome these problems is of significant interest to the dental community. Chitosan has been reported to have good biocompatibility and anti-bacterial activity. An osseo-inductive recombinant elastin-like biopolymer (P-HAP), that contains a peptide derived from the protein statherin, has been reported to induce biomineralization and osteoblast differentiation. In this study, chitosan/P-HAP bi-layers were built on a titanium surface using a layer-by-layer (LbL) assembly technique. The difference in the water contact angle between consecutive layers, the representative peaks in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), and the changes in the topography between surfaces with a different number of bi-layers observed using atomic force microscopy (AFM), all indicated the successful establishment of chitosan/P-HAP LbL assembly on the titanium surface. The LbL-modified surfaces showed increased biomineralization, an appropriate mouse pre-osteoblastic cell response, and significant anti-bacterial activity against Streptococcus gordonii, a primary colonizer of tissues in the oral environment, Ministerio de Economía, Industria y Competitividad (Project MAT2013-42473-R and MAT2015-68901R), Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA244U13, VA313U14 and VA015U16)

[eng] The Cold Spray (CS) is a novelty technique for the production of coatings within the field of Thermal Spray. The use of low work temperatures (under the melting point of the material) is what makes it different from the other conventional spraying techniques. CS is an ideal technique to spray materials that are sensitive to temperature, such as nanostructured and amorphous materials, or sensitive to the oxygen, as could be titanium. These characteristics may be specially promising within the field of biomedical coatings. Compared to the conventional processes, it would allow to produce coatings in a more cost-effect and environmental friendly way. The research is mostly focused on the obtaining of highly rough Commercial Pure Titanium (CP-Ti) and Calcium Phosphate (CP) coatings by CS for joint prosthesis application. An exhaustive development of coating parameter optimization has been developed and the different deposition mechanisms for each feedstock powder were analyzed as well. The mechanical and biological properties of the optimal coatings were evaluated consequently. The mechanical testing (e.g. Tensile and shear strength test and Taber test), was performed on the optimized CP-Ti coating overcoming the ASTM standard specifications for joint, shoulder and knee prosthesis; CP-Ti coating showed good bonding between particles as well with the substrate. The used of coarse titanium particles provided high roughness (Ra=40±12 µm and Rz=235±44 µm) that shows an increase in cell viability, proliferation and differentiation as well as mineralization, in comparison with a low-roughness titanium surface obtained by Sand Blasted (SB).Afterwards, additional surface modification procedures were investigated to obtain nanotextured surfaces on the as-sprayed CS titanium coatings to evaluate their in-vitro response for comparison. The anodic oxidation treatment leads to a TiO2 Nanotube (NT) layer with a pore diameter between 50-100 nm and a roughness of Ra=36.8±4.6 nm, whereas the alkaline treatment leads to a nanosurface of Ra=1.2±0.2nm, composed by very fine porosity PS). To sum up, CS has shown to be suitable to produce metallic and ceramic coatings for joint applications, especially those dealing with materials that are sensitive to the temperature and oxygen. The non-microstructural changes from the feedstock powder to the coatings leads to a big advantage in CS to obtain customized coatings., [spa] La Proyección Fría o también conocida por el nombre de Cold Spray (CS), es una técnica muy novedosa para la obtención de recubrimientos en el ámbito de la proyección térmica. El uso de bajas temperaturas de trabajo (siempre por debajo del punto de fusión del material) es lo que la hace diferente respecto al resto de técnicas convencionales, ya que la hace ideal para depositar materiales sensibles a la temperatura (ej. Materiales nanoestructurados y amorfos) o reactivos al oxígeno (ej. Titanio). Además tiene un gran potencial a nivel económico y ambiental por ser un proceso eficiente y respetuoso con el medio ambiente. La investigación se basa principalmente en la obtención de recubrimientos de titanio rugoso y fosfato cálcico mediante proyección fría, donde se han estudiado los diferentes mecanismos de deposición de las materias primas y se ha elaborado un estudio a nivel mecánico y biológico. Además, se han realizado tratamientos adicionales sobre los recubrimientos de titanio para obtener superficies nanotexturizadas y poderlas comparar in vitro. El uso de partículas gruesas de titanio facilita la obtención de grandes rugosidades superficiales en los recubrimientos de titanio, mejorando así la viabilidad y proliferación celular, al igual que la diferenciación y mineralización celular, en comparación a superficies con bajas rugosidades (como las superficies de titanio granalladas). Aun así, los tratamientos de nanotexturización, tales como el anodizado (donde se obtuvieron nanotubos de TiO2 con un diámetro entre 50-100nm) y el tratamiento alcalino (en el cual se obtuvieron porosidades

Au atoms in contact with TiC(001) undergo significant charge polarization. Strong metal–support interactions make Au/TiC(001) an excellent catalyst for the low-temperature water–gas shift (WGS), with turnover frequencies orders of magnitude larger than those observed for conventional metal/oxide catalysts. DFT calculations indicate that the WGS reaction follows an associative mechanism with HOCO as a key intermediate.

Bacterial infection represents a major cause of implant failure in dentistry. A common approach to overcoming this issue and treating pen-implant infection consists in the use of antibiotics. However, the rise of multidrug-resistant bacteria poses serious concerns to this strategy. A promising alternative is the use of antimicrobial peptides due to their broad-spectrum activity against bacteria and reduced bacterial resistance responses. The aim of the present study was to determine the in vitro antibacterial activity of the human lactoferrin-derived peptide hLf1-11 anchored to titanium surfaces. To this end, titanium samples were functionalized with the hLf1-11 peptide either by silanization methods or physical adsorption. X-ray photoelectron spectroscopy analyses confirmed the successful covalent attachment of the hLf1-11 peptide onto titanium surfaces. Lactate dehydrogenase assay determined that hLf1-11 peptide did not affect fibroblast viability. An outstanding reduction in the adhesion and early stages of biofilm formation of Streptococcus sanguinis and Lactobacillus salivarius was observed on the biofunctionalized surfaces compared to control non-treated samples. Furthermore, samples coated with the hLf1-11 peptide inhibited the early stages of bacterial growth. Thus, this strategy holds great potential to develop antimicrobial biomaterials for dental applications. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Objectives: The aim of this study was to determine the antibacterial properties of silver-doped titanium surfaces prepared with a novel electrochemical anodizing process. Material and methods: Titanium samples were anodized with a pulsed process in a solution of silver nitrate and sodium thiosulphate at room temperature with stirring. Samples were processed with different electrolyte concentrations and treatment cycles to improve silver deposition. Physicochemical properties were determined by X-ray photoelectron spectroscopy, contact angle measurements, white-light interferometry, and scanning electron microscopy. Cellular cytotoxicity in human fibroblasts was studied with lactate dehydrogenase assays. The in vitro effect of treated surfaces on two oral bacteria strains (Streptococcus sanguinis and Lactobacillus salivarius) was studied with viable bacterial adhesion measurements and growth curve assays. Nonparametric statistical Kruskal-Wallis and Mann-Whitney U-tests were used for multiple and paired comparisons, respectively. Post hoc Spearman's correlation tests were calculated to check the dependence between bacteria adhesion and surface properties. Results: X-ray photoelectron spectroscopy results confirmed the presence of silver on treated samples and showed that treatments with higher silver nitrate concentration and more cycles increased the silver deposition on titanium surface. No negative effects in fibroblast cell viability were detected and a significant reduction on bacterial adhesion in vitro was achieved in silver-treated samples compared with control titanium. Conclusions: Silver deposition on titanium with a novel electrochemical anodizing process produced surfaces with significant antibacterial properties in vitro without negative effects on cell viability. info:eu-repo/semantics/acceptedVersion

Synergizing integrin and cell-membrane heparan sulfate proteoglycan signaling on biomaterials through peptidic sequences is known to have beneficial effects in the attachment and behavior of osteoblasts, however, controlling the exact amount and ratio of peptides tethered on a surface is challenging. Here, we present a dual molecular-based biointerface combining integrin (RGD) and heparin (KRSR)-binding peptides in a chemically controlled fashion. To this end, a tailor-made synthetic platform (PLATF) was designed and synthesized by solid-phase methodologies. The PLATF and the control linear peptides (RGD or KRSR) were covalently bound to titanium via silanization. Physicochemical characterization by means of contact angle, Raman spectroscopy and XPS proved the successful and stable grafting of the molecules. The biological potential of the biointerfaces was measured with osteoblastic (Saos-2) cells both at short and long incubation periods. Biomolecule grafting (either the PLATF, RGD or KRSR) statistically improved (p &lt, 0.05) cell attachment, spreading, proliferation and mineralization, compared to control titanium. Moreover, the molecular PLATF biointerface synergistically enhanced mineralization (p &lt, 0.05) of Saos-2 cells compared to RGD or KRSR alone. These results indicate that dual-function coatings may serve to improve the bioactivity of medical implants by mimicking synergistic receptor binding.

Intervertebral implants should be designed with low load requirements, high friction coefficient and low elastic modulus in order to avoid the stress shielding effect on bone. Furthermore, the presence of a highly interconnected porous structure allows stimulating bone in-growth and enhancing implant-bone fixation. The aim of this study was to obtain bioactive porous titanium implants with highly interconnected pores with a total porosity of approximately 57¿%. Porous Titanium implants were produced by powder sintering route using the space holder technique with a binder phase and were then evaluated in an in vivo study. The size of the interconnection diameter between the macropores was about 210¿µm in order to guarantee bone in-growth through osteblastic cell penetration. Surface roughness and mechanical properties were analyzed. Stiffness was reduced as a result of the powder sintering technique which allowed the formation of a porous network. Compression and fatigue tests exhibited suitable properties in order to guarantee a proper compromise between mechanical properties and pore interconnectivity. Bioactivity treatment effect in novel sintered porous titanium materials was studied by thermo-chemical treatments and were compared with the same material that had undergone different bioactive treatments. Bioactive thermo-chemical treatment was confirmed by the presence of sodium titanates on the surface of the implants as well as inside the porous network. Raman spectroscopy results suggested that the identified titanate structures would enhance in vivo apatite formation by promoting ion exchange for the apatite formation process. In vivo results demonstrated that the bioactive titanium achieved over 75¿% tissue colonization compared to the 40¿% value for the untreated titanium.

The aim of this work is to describe and compare mechanical properties of eight widely used nickel–titanium orthodontic wires under uniform testing conditions and to determine the influence of the heat treatments on the loss of the superelasticity. Ten archwires from two batches from eight different manufacturers were evaluated. A three-point bending test was performed, in accordance with ISO 15841:2006, on 80 round nickel–titanium archwire segments of 0.016 inch. To obtain a load-deflection curve, the centre of each segment was deflected to 3.1 mm and then unloaded until force became zero. On the unloading curve, deflection at the end of the plateau and forces delivered at that point, and at 3, 2, 1 and 0.5 mm of deflection, were recorded. Plateau slopes were calculated from 3 and from 2 mm of deflection. Data obtained were statistically analysed to determine inter-brand, intra-brand and inter-batch differences (P

Novel researches are focused on the prevention and management of post-operative infections. To avoid this common complication of implant surgery, it is preferable to use new biomaterials with antibacterial properties. Therefore, the aim of this work is to develop a method of combining the antibacterial properties of antibiotic-loaded poly(3-hydroxybutyrate) (PHB) nano- and micro-spheres and poly(ethylene glycol) (PEG) as an antifouling agent, with titanium (Ti), as the base material for implants, in order to obtain surfaces with antibacterial activity. The Ti surfaces were linked to both PHB particles and PEG by a covalent bond. This attachment was carried out by firstly activating the surfaces with either Oxygen plasma or Sodium hydroxide. Further functionalization of the activated surfaces with different alkoxysilanes allows the reaction with PHB particles and PEG. The study confirms that the Ti surfaces achieved the antibacterial properties by combining the antibiotic-loaded PHB spheres, and PEG as an antifouling agent.

Objetivo: el objetivo de este estudio fue evaluar la eficacia y la rapidez de la lima rotatoria ProGlider (Dentsply Maillefer, Ballaigues, Suiza) para crear una vía de deslizamiento en el conducto radicular versus PathFile (Dentsply Maillefer, Ballaigues, Suiza) y Race ISO 10 (FKG Dentaire, Le Chaux-deFonds, Suiza) mediante el uso del CBCT. Material y método: se seleccionaron sesenta conductos mesiales de molares mandibulares humanos extraídos con ángulos de curvatura entre 25-60º. Éstos fueron distribuidos aleatoriamente en tres grupos (n = 20) de acuerdo con el sistema de instrumentación del conducto: PathFile 13/02; 16/02; 19/02 (grupo PF); RaCe ISO 10 10/02; 10/04; 10/06 (grupo RI), y ProGlider 16/02 (grupo PG). Se utilizó CBCT antes y después de la instrumentación y el software AutoCAD para determinar el transporte apical y los cambios en el ángulo de curvatura. También se midió el tiempo de trabajo de cada sistema. Resultados: no se encontraron diferencias significativas en los cambios en el ángulo de curvatura (p = 0,076) ni en el transporte apical (p = 0,42) entre los tres grupos. ProGlider requirió significativamente menos tiempo de trabajo. Conclusiones: ProGlider creó la vía de deslizamiento y el mantenimiento de la anatomía del conducto original en menos tiempo en comparación con PathFile y RaCe ISO 10. Los tres sistemas fueron igualmente efectivos en el mantenimiento de la anatomía del conducto radicular.

Treballs Finals de Grau d'Enginyeria Química, Facultat de Química, Universitat de Barcelona, Curs: 2015-2016, Tutores: Irene Garcia Cano i Núria Cinca Luis, Commercial titanium alloys, which are used in automotive and aerospace applications, are characterized by a low specific weight, high strength and an excellent corrosion resistance at relatively low temperatures. In some applications, they are exposed to a combination of high temperatures and mechanical loading as well as wear damage. However, the oxidation and abrasive resistance of titanium at high temperatures are rather poor; alloys such as Ti6Al4V have applications which are limited to temperatures below 500ºC; therefore it is of interest to increase their application temperatures. Several methods have been employed to increase the oxidation resistance to 900ºC. Among them, the use of titanium aluminide coatings has been considered of interest, especially the titanium trialuminide, which possesses enough aluminium content to form protective alumina layers. Some approaches to this strategy have included the use of conventional thermal spray technologies. In the present work, we proposed the use of the Cold Gas Spray (CGS) process to first try to form γ-TiAl coatings on Ti6Al4V substrates. Due to some handicaps given by the low deformability of such powder alloy, γ-TiAl+Al composite coatings were produced and annealed afterwards to form the TiAl3. These coatings have been characterized from the microstructural point of view as well as their wear resistance and oxidation performance

It is known that surface roughness and chemical composition of the titanium surface influence the osseointegration of titanium implants. Most commercial dental implants offer a shot-blasted rough surface. It is also known that apatite layers coating the surface of titanium implants improve bone response, but the adhesion of the layer to the substrate poses some problems. In this study the roughness and adhesion strength to a titanium dental implant surface of an apatite layer deposited via wet chemistry after a thermochemical treatment were compared with those of plasma-sprayed apatite layers and machined titanium surfaces. Different surface conditions have been studied: (a) as-received machined dental implant surface; (b) grit-blasted titanium surface; (c) grit-blasted and thermochemicallytreated titanium surface; (d) titanium surfaces coated with plasma-sprayed apatite. The morphology and roughness of the samples were measured and compared. The adhesion of the apatite layers to the titanium was compared by means of a scratch test. Measured roughness showed that the deposition of an apatite layer did not affect roughness but plasmasprayed apatite produced a decrease on roughness values when compared to control samples. Both roughness and adhesion strength of the deposited apatite layer to the titanium substrate were higher than those of the plasma-sprayed apatite.

Porous titanium specimens have been produced by means of the space holder method. Titanium grade 3 (TiCP3) has been used as material and ammonium bicarbonate as spacer. Process parameters (compaction pressure, metal grain size range and spacer volume) influence on porosity morphology and distribution and bending strength has been analysed. The results denote an important loss of strength when comparing samples sintered without and with spacer. On the other hand, a higher bending strength was observed in the porous samples with a smaller size of ammonium bicarbonate particles. Finally, the evolution of bending strength with the compaction pressure depends on the spacer volume, having a direct dependency for reduced amounts and inverse for higher contents.

In this work, we analysed 56 clinically failed and retrieved implants by means of scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and histological studies. The surface contamination was compared to that of unused control implants and with that of the same implants after cleaning in a basic medium. The surfaces of the unused implants presented considerable contamination. In particular, high levels of carbon were detected. The nature of this C was elucidated by XPS analysis of the lubricant used in the machining process. The same contamination was observed in the retrieved implants. Histological studies were carried out by means of light microscopy. Fibrosis and granulomatous lesions were detected in the tissues. XPS analysis indicated the presence of traces of other elements (Na, Ca, Zn, S, F, etc.) that were not related to impurities in cpTi. We examined a cleaning process in a basic medium that eliminates the organic components of the implant surfaces. The cleaned implants were implanted in the patients and the results were excellent. None of the implants failed in following 7 months.

The use of tantalum as biomaterial for orthopedic applications is gaining considerable attention in the clinical practice because it presents an excellent chemical stability, body fluid resistance, biocompatibility, and it is more osteoconductive than titanium or cobalt-chromium alloys. Nonetheless, metallic biomaterials are commonly bioinert and may not provide fast and long-lasting interactions with surrounding tissues. The use of short cell adhesive peptides derived from the extracellular matrix has shown to improve cell adhesion and accelerate the implant’s biointegration in vivo. However, this strategy has been rarely applied to tantalum materials. In this work, we have studied two immobilization strategies (physical adsorption and covalent binding via silanization) to functionalize tantalum surfaces with a cell adhesive RGD peptide. Surfaces were used untreated or activated with either HNO3 or UV/ozone treatments. The process of biofunctionalization was characterized by means of physicochemical and biological methods. Physisorption of the RGD peptide on control and HNO3-treated tantalum surfaces significantly enhanced the attachment and spreading of osteoblast-like cells; however, no effect on cell adhesion was observed in ozone-treated samples. This effect was attributed to the inefficient binding of the peptide on these highly hydrophilic surfaces, as evidenced by contact angle measurements and X-ray photoelectron spectroscopy. In contrast, activation of tantalum with UV/ozone proved to be the most efficient method to support silanization and subsequent peptide attachment, displaying the highest values of cell adhesion. This study demonstrates that both physical adsorption and silanization are feasible methods to immobilize peptides onto tantalum-based materials, providing them with superior bioactivity. info:eu-repo/semantics/publishedVersion