Key Engineering Materials Vol. 638

Abstract: In this paper the author’s main goal was to determine if the roughness of the substrate (a Ti6Al4V alloy) shows any influence on the hydroxyapatite (HA) crystal morphology and distribution. Disks of Ti6Al4V, 24mm in diameter and 1mm thickness are sandblasted with Al₂O₃ particles with different mean size: 29, 45 and 110μm. The disks are analyzed prior coating by atomic force microscopy (AFM) to determine the surface roughness. The samples are then cleaned and coated with HA by immersion in a solution derived from [Ca (NO₃)₂.4H₂O] and P₂O₅ dissolved in ethylene glycol – the process was repeated 3 times. The coated samples are analyzed by scanning electron microscopy (SEM) to observe HA crystal shape, size and distribution.

Abstract: This work aims to investigate the influence of surface conditioning of porous Ti for enhancing its biological activity, as assessed by in vitro stem cell testing. Porous Ti samples with an average porosity of 32% were processed by Powder Metallurgy with dextrin as a space holder. The samples were subjected to H₂O₂ treatment to form an enhanced TiO₂ film, followed by a heat treatment at 400°C and 600°C aiming to the crystallization of the as-formed amorphous titanium oxide. Samples characterization was performed by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray Diffraction (XRD). The treated surfaces revealed to be made of both anatase and rutile TiO₂, with groove–shaped structure and cracks on the surface of the TiO₂ film. The intrinsic biocompatibility of the chemically modified porous Ti surfaces was assessed in vitro. In our cell culture tests, stem cells were found to attach and proliferate better on the chemically treated Ti surfaces compared to the control untreated Ti surfaces.

Abstract: Sutures and cyanoacrylate high strength tissue adhesives are commonly used for wound closure in several surgical applications. Although effective for closing simple and small incisions, cyanoacrylate adhesives were limited by compromising adhesion and stiffness, i.e. cyanoacrylates with short alkyl chain length showed higher adhesion but lower flexibility than the ones with long alkyl chain length. In this paper, a new concept of flexible and high strength tissue cyanoacrylate based adhesive - Adhflex^®- is presented. The balance between adhesion and flexibility in Adhflex® was achieved by adding an inert (i.e. non-reactive) chemical to a short alkyl chain length cyanoacrylate able to partially inhibit its polymerization in presence of moisture. Adhesion properties of Adhflex^® were superior as compared to other commercial cyanoacrylate tissue adhesives (i.e. higher traction and shear strength). Furthermore, Adhflex^® has been successfully used in a clinical trial for inguinal hernia repair (case study) as the surgery time with respect to suturing was reduced substantially, the comfort of the patient was improved (i.e. reduced tension after surgery, reduced allergic reaction) and the scare was minimal.

Abstract: Stainless steels, titanium and titanium alloys are the most widely used artificial surgical biomaterials for a long time. These alloys with non-degradability properties present long-term adverse effects or stress shielding and require a second surgery for a complete healing. The ongoing scientific research to avoid this problem found a new kind of biocompatible alloys for implants made of biodegradable materials witch should be used as alternative. Among the various biodegradable materials, magnesium alloys have unique biodegradability properties in the physiological environment, have stimulatory effects on new bone formation and have an elastic modulus similar to that of human bone. Roentgen structural analysis was used to detail the global chemical composition analysis, especially the analysis to determine the phase-pick sites characteristic diffraction and crystallographic orientation parameters Miller constituent phases. On studied alloys Mg and Mg₂Ca type compounds with different crystallographic orientations were identified. The results obtained on the Mg-Ca and Mg-Ca-Si systems will be correlated with results from previous tests and analyses, to finally obtain an alloy with biodegradability that may be controlled.

Abstract: Functionalized multiwalled carbon nanotubes (MWCNTs) by various groups (carboxyl or amino) can improve the properties of anti-tumoral drugs (cisplatin, docetaxel, zometa). Functionalization was evidenced by infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Platinum ions released in simulated body fluid (SBF) were measured by inductively coupled plasma ion spectrometry (ICP-MS).

Abstract: Optimization of fractured or destroyed removable partial dentures realized from CoCrMo alloys are possible due to modern welding equipments. The aim of study was to offer the processing and welding optimal parameters for some long lasting prosthetic pieces made of a new alloy from the system CoCrMoTi. Laser welding equipments was a Mini Laser XXS (Orotig Italia) and the tested samples were welded in butt joint, without filler material. There are presented in comparison results concerning macro and micro structural analysis made on stereomicroscope and microscope type OLYMPUS. Finally a correlation between different welding parameter values and structural features was made for the new dental cobalt alloy.

Abstract: Surface morphological characteristics of a copolyimide film prepared from a fluorine-based dianhydride combined with an aliphatic siloxane-based diamine and an aromatic containing ether linkages one, were studied before and after oxigen plasma treatment using atomic force microscopy (AFM). The three-dimensional texture parameters calculated from the AFM data have highlighted a more pronounced surface morphology (higher average roughness and developed interfacial area ratio), improved bearing properties and no predominant orientation, as the plasma exposure time was increased from 6 to 10 minutes, using the same power (40 W). The reactive groups generated on the binding surface have facilitated the interaction with a biocidal agent, such as silver nitrate. This creates silver-containing nanoparticles, of about 120-150 nm, uniformly distributed on the copolymer surface, with a density of 10±2 particles/μm². The functionalization with the biocidal agent of the flourinated copolyimide surface was conducted for testing its antimicrobial properties, namely the inhibition/destruction of Escherichia coli bacterium.

Abstract: The effect of calcium addition in modifying the microstructural aspects and corrosion behavior was investigated on two different biodegradable magnesium alloys type Mg-xCa binary alloys (x = 0.8, 1.8 wt. (%)). Systematic microstructure investigations was made using optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray. Following these experimental investigations, in the microstructure of the investigated Mg-Ca alloys a notable refinement was observed occurred with increasing the calcium content. The evaluation of corrosion resistance was performed both using electrochemical measurements and hydrogen release in simulated body fluid (SBF), as proposed by Kokubo and his colleagues, maintaining the temperature at 37°C. The results showed a lower corrosion resistance when the calcium content was increased, due to the increased Mg₂Ca intermetallic phase in grain boundaries. Consequently, our preliminary results showed that MgCa0.8 alloy having a minimal amount of Mg₂Ca appear to be a promising alloy to be used as a biomaterial for orthopedic implants.

Abstract: The aim of the study is to highlight the influence of the cooling conditions on cortical bovine bones derived hydroxyapatite. Bone samples with thicknes of 50 mm were cut from the central part of the bovine femur with a jigsaw. Then, they were processed in order to remove all the proteins and collagen traces by boiling for 4 hours and heating and holding them at 450°C for 2 hours. They were heat treated at temperatures ranging from 1000° to 1300°C, being held for 3 hours and then rapidly cooled in air atmosphere or ice-water. A natural fracture of the samples appeared after the applied heat treatments, which allowed us to analyse the fragments without a further preparation. The morphological changes that occurred during the sample processing were highlighted using the scanning electron microscopy (SEM) techniques. The morphological changes occurred not only between the heat treated samples at different temperature, but also in samples cooled in different environments. Also, it was noticed that crystals sizes proportionaly increased with temperature, while the porosity considerably decreased and also a condensation of the porous matrix/structure appeared.

Abstract: In this study, nano-silicon (Si) thin films were deposited on biodegradable Fe–1.5Mn–1Si substrate by pulsed laser deposition (PLD) method. Biodegradable metallic materials represent a good solution in implantology field based on the elimination of the second surgical operation required for the extraction of the material. Also, using biodegradable materials medical complications between the metallic implant and the human body that might appear during the recovery period are excluded. In this sense we propose a metallic material based on iron with a longer degradation period compared to Mg-Ca based materials. Scanning electron microscopy (SEM) and X-ray dispersive energy analyze (EDAX) were use to analyze the implant material surface before and after Si thin film deposition and before and after implantation.