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Composite Materials for Oral and Craniofacial Repair or Regeneration
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Teresa Russo, Roberto De Santis, Antonio Gloria
Different scenarios may be foreseen in relation to the development of advanced cranioplasty including, but not limited to polymer based composite design, additive manufacturing techniques and the tissue regeneration approach. The emerging additive manufacturing approach is invading all the engineering fields, including biomaterials, showing a very high potential especially as customization, complexity and low weight design are concerned. It is not surprising that this approach has recently been applied to cranioplasty. 3D printing of biomaterials, without the use of a mould, represents the cutting edge technology in bone cranioplasty. This integrated approach combines reverse engineering and additive manufacturing. Recent advances in additive manufacturing technologies for direct production of implants avoids limitations related to the constraints in shape, size and internal structure. On the other hand, from a material point of view, medical-grade PEEK filaments represent the future trends in cranioplasty, and carbon fibre reinforced PEEK filaments provide further mechanical enhancement.
Quality assurance
Published in Peter R Hoskins, Kevin Martin, Abigail Thrush, Diagnostic Ultrasound, 2019
Nick Dudley, Tony Evans, Peter R Hoskins
In this device, the moving string simulates moving blood. The components of the string phantom are illustrated in Figure 15.13. Choice of the string is important as the scattering characteristics of blood need to be matched. Filaments, such as cotton and silk, are spiral wound, with a repeat pattern at distances that are comparable with the wavelength of ultrasound. This repeat pattern gives rise to high-amplitude scattering along certain directions, which distorts the Doppler spectrum, making this type of filament unsuitable (Cathignol et al. 1994). The use of commercial systems based on the use of spiral-wound filaments is not advised. A suitable filament is O-ring rubber, as this scatters ultrasound in all directions in a similar manner to blood (Hoskins 1994). The most important feature of the string phantom is that the velocity can be accurately measured. The true string velocity may be calculated from the speed of rotation of the drive wheel. The device is especially suited to the checking of velocity estimates made using Doppler.
Histology and Cytology of the Aortic Valve*
Published in Mano Thubrikar, The Aortic Valve, 2018
The cytoskeletal and secretory features of these cells and similar cells in the leaflet attachment region are so striking that they invite functional conjectures. These regions of the valve undergo the greatest degrees of flexion and thus could be expected to require continual replacement of tissue components.51 Perhaps the role of the filaments is to resist excess stretching of the cell processes attached to collagenous fibers, and in doing so to transmit information to the cells about the strain in the surrounding tissues. Strain in excess of what the tissue customarily bears might then induce the cell to secrete more of the matrix elements.
3D printing – an alternative strategy for pediatric medicines
Published in Expert Review of Clinical Pharmacology, 2023
Alice P McCloskey, Louise Bracken, Nicola Vasey, Touraj Ehtezazi
Inkjet printing involves the organized placing of liquid droplets in a Drop-on-Powder or Drop-on-Drop approach [3,6]. In the Drop-on-Powder method, the droplets are a binder or other liquid. Products manufactured using this method are highly porous and friable with associated and tailorable dissolution profiles. In Drop-on-Drop deposition, the droplets are the actual building material. This is a trickier process to control, but end products have a higher resolution. Extrusion printing on the other hand involves the ejection of semi-solid material through a nozzle and the building up of successive layers. Fused deposition modeling is a common extrusion method used to generate SODFs that uses thermoplastic solid filaments as starting materials. These either have the drug incorporated already or are modified to include the drug using hot melt extrusion. The filaments are molten, extruded, and then solidified on deposition. Pressure-assisted microsyringes are an alternative extrusion method, where the semi-solid product is extruded by a pressurized air piston and is then dried. This is a less favorable extrusion approach as solvents are often involved raising toxicity concerns and product resolution is low (Figure 1).
Development of filaments for fused deposition modeling 3D printing with medical grade poly(lactic-co-glycolic acid) copolymers
Published in Pharmaceutical Development and Technology, 2019
Tim Feuerbach, Sara Callau-Mendoza, Markus Thommes
In order for 3D printing to be viable for implant manufacturing or drug dosage preparation, it is necessary to utilize medical- and pharmaceutical-grade materials to make regulatory approval of the 3D printed product possible (FDA 2017). In FDM 3D printing, the materials deployed in the printing process must be in filament form. These filaments can be produced by hot-melt extrusion (Kleinebudde et al. 2017). The filaments need to have a specific and uniform diameter in order to be processable in the 3D printer (Valknaers et al. 2013) and to ensure a constant volumetric flow rate of material during the printing process. In addition to these geometric constraints, the extruded filaments must have sufficient mechanical strength, in order to be conveyable in the 3D printer without filament deformation or failure. While the manufacturing of filaments with different pharmaceutical grade polymers such as poly(ethylene oxide), methacrylic acid copolymer, poly(vinyl alcohol), poly(vinyl alcohol)–poly(ethylene glycol) graft copolymer, ethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl methyl cellulose acetate succinate, and poly(vinyl caprolactam)–poly(vinyl acetate)–poly(ethylene glycol) graft copolymer by hot-melt extrusion has already been published (Melocchi et al. 2016), medical grade poly(lactic-co-glycolic acid) (PLGA) copolymers have not been subject to filament production yet. Furthermore, no study investigating the influence of the material properties on a material’s suitability for use as filament material has been conducted.
The involvement of liquid crystals in multichannel implanted neurostimulators, hearing and ENT infections, and cancer
Published in Acta Oto-Laryngologica, 2019
Chouard Claude-Henri, Christiane Binot, Jean-François Sadoc
It forms a highly organized 2-dimensional lattice of 8-nm-thick filaments at 30–80 nm intervals, oriented circumferentially, reinforced by 2–4 nm filaments along the longitudinal axis. It comprises three filament networks: actin filaments, involved in cytoplasm elasticity and maintenance; intermediate filaments; and microtubules located along microfibrils, playing a support role. Actin and myosin are grouped in contractile fibrils in a geometry, comparable to that of the A and C nematic and smectic bodies (mesophases), with the helical variant and the same symmetry groups [49]. It has been shown [50] that cytoskeletal actomyosin plays a pivotal role in the organization of the OHC tip in the transition between round and non-convex forms. The actin cytoskeleton, bound to the microtubules, plays a determining role in the dynamics of assembly and disassembly of intercellular junctions.