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    Recent progress in inorganic and composite coatings with bactericidal capability for orthopaedic applications [electronic resource]

    , Article Nanomedicine-nanotechnology Biology and Medicine - NaoMed- NanoTechnol- Biol Med ; 2011, Vol. 7, No. 1, PP. 22-39 Simchi, A. (Abdolreza) ; Tamjid, E ; Pishbin, F ; Boccaccini, A. R ; Sharif University of Technology
    Abstract
    This review covers the most recent developments of inorganic and organic-inorganic composite coatings for orthopedic implants, providing the interface with living tissue and with potential for drug delivery to combat infections. Conventional systemic delivery of drugs is an inefficient procedure that may cause toxicity and may require a patient's hospitalization for monitoring. Local delivery of antibiotics and other bioactive molecules maximizes their effect where they are required, reduces potential systemic toxicity and increases timeliness and cost efficiency. In addition, local delivery has broad applications in combating infection-related diseases. Polymeric coatings may present some... 

    Size tuning of Ag‐decorated TiO2 nanotube arrays for improved bactericidal capacity of orthopedic implants [electronic resource]

    , Article Journal of Biomedical Materials Research Part A ; Auguest 2014, Vol. 102, Issue 8, P.2625-35 Esfandiari, N ; Simchi, A. (Abdolreza) ; Bagheri, R ; Sharif University of Technology
    Abstract
    Surface modification of orthopedic implants using titanium dioxide nanotubes and silver nanoparticles (SNs) is a promising approach to prevent bacteria adhesion, biofilm formation, and implant infection. Herein, we utilized a straightforward and all-solution process to prepare silver-decorated TiO2 nanotube arrays with surface density of 10(3) to 10(4) per µm(2). With controlling the synthesis conditions, hexagonal closed-packed nanotubes with opening diameter of 30-100 nm that are decorated with SNs with varying sizes (12-40 nm) were prepared. Various analytical techniques were utilized to characterize the size, morphology, distribution, valance state, surface roughness, and composition of... 

    The effect of microthread design on magnitude and distribution of stresses in bone: a three-dimensional finite element analysis

    , Article Dental Research Journal ; Volume 15, Issue 5 , 2018 , Pages 347-353 ; 17353327 (ISSN) Golmohammadi, S ; Eskandari, A ; Movahhedy, M. R ; Shirmohammadi, A ; Amid, R ; Sharif University of Technology
    Abstract
    Background: The researches regarding the influence of microthread design variables on the stress distribution in bone and a biomechanically optimal design for implant neck are limited. The aim of the present study is to compare the effect of different microthread designs on crestal bone stress. Materials and Methods: Six implant models were constructed for three-dimensional finite element analysis including two thread profile (coarse and fine) with three different lengths of microthreaded neck (1 mm, 2 mm, and 3 mm). A load of 200 N was applied in two angulations (0° and 30°) relative to the long axis of the implant and the resultant maximum von Mises equivalent (EQV), compressive, tensile,... 

    Nitinol spinal vertebrae: A favorable new substitute

    , Article International Journal of Engineering, Transactions B: Applications ; Volume 32, Issue 6 , 2019 , Pages 842-851 ; 1728144X (ISSN) Sadrnezhaad, S. K ; Parsafar, M ; Rashtiani, Y ; Jadidi, M ; Sharif University of Technology
    Materials and Energy Research Center  2019
    Abstract
    Scoliosis, kyphosis, and bone fracture are health problems, especially of the elderly throughout the world. The vertebra protects the spinal cord. Any impairment to the vertebra can lead to pain and nervousness. NiTi alloy (Nitinol) helps to resolve the problem by fulfilling such requirements as for strength, durability, resistance to wear, and shockwave damping which is due to the shape memory effect. Nitinol medical applications have so far been restricted to surgical devices and orthopaedics. Little has been said about Nitinol use for medication of the spinal vertebra disorder. This article appraises the potential features of Nitinol for vertebral implantation and therapeutic prescription... 

    Comparison of periodontally compromised splinted teeth and implant supported fixed partial denture: a three-dimensional finite element analysis on bone response

    , Article Journal of long-term effects of medical implants ; Volume 31, Issue 2 , 2021 , Pages 1-8 ; 19404379 (ISSN) Amid, R ; Kadkhodazadeh, M ; Talebi Ardakani, M. R ; Movahhedy, M. R ; Mirakhori, M ; Hakimi, A ; Broukhim, M ; Sharif University of Technology
    NLM (Medline)  2021
    Abstract
    Introduction - This study aimed to compare the amount and pattern of stress and strain distributed around periodontally compromised splinted teeth and the two-implant abutments supported six-unit fixed partial denture (FPD) using finite element analysis (FEA). Methods and Materials - Six mandibular anterior teeth of a dental model were scanned and the scans were transferred to 3D CAD design and finite element software. Jaw bone was also designed and the teeth were splinted by fiber-reinforced composite (FRC) band. In another model, two implants were placed at the site of canine teeth and a six-unit FPD was designed over them. Models were transferred to finite element software and after... 

    The nonlinear finite element analysis of a novel dental implant with an interposed internal layer imitating periodontal ligament's function

    , Article ASME 2011 International Mechanical Engineering Congress and Exposition, IMECE 2011, 11 November 2011 through 17 November 2011 ; Volume 2 , November , 2011 , Pages 543-548 ; 9780791854884 (ISBN) Ahmadian, M. T ; Ghanati, G ; Firoozbakhsh, K ; Ghanati, P ; Sharif University of Technology
    2011
    Abstract
    Osseointegrated dental implants are deficient in natural periodontal ligaments. It may therefore, disrupts the natural function of implant and leads to excessive stress and strain in jaw bone. Our new proposed implant has the nonlinear internal component which imitates periodontal ligaments function. A nonlinear finite element analysis developed to investigate the efficiency of utilizing this nonlinear internal layer for three conditions of bone implant interface conditions under vertical and horizontal loading conditions. Our results so far indicate that the use of a class of material exhibiting incompressible hyperelastic behaviour as a internal layer can reduce the peak stress deduced... 

    Design of Customized Cemented Stems for Hip Joint Arthroplasty Surgery in Patients with Severe Femoral Deformity

    , M.Sc. Thesis Sharif University of Technology Ebadi, Yashar (Author) ; Farahmand, Farzam (Supervisor)
    Abstract
    Hip replacement surgery is performed with the aim of relieving pain and restoring the normal function of the joint for patients who are in the final stages of arthritis. Standard prostheses offered by implant manufacturers come in a wide variety of models and sizes to meet the needs of patients. However, these commercial prostheses may not be suitable for patients with significant bony abnormalities, leading to implant instability and loosening. In such cases, a suitable solution is to use customized implants that are specifically designed to match the patient's unique anatomy. The purpose of this research was to design a customized cement stem for hip joint replacement surgery in patients... 

    Design, Simulation, Prototyping and Analysis of a Lengthening Femoral Implant

    , M.Sc. Thesis Sharif University of Technology Mahdavifar, Mohsen (Author) ; Farahmand, Farzam (Supervisor) ; Durali, Mohammad (Supervisor)
    Abstract
    Motorized intramedullary nails are a viable solution to treat patients with limb-length inequality. These fully implanted devices use external magnetic actuation to extend. This research examines the conceptual design of this type of nails by investigating various ideas and previous designs. The implant mechanism, body and controller are designed in detail. It was then simulated in standard tests to evaluate it. In addition, the implanted nail undergoes a biomechanical analysis and its stiffness is assessed. Finally, the controller design is carried out using dipole magnetic theory and verified by finite element simulations. As a proof of concept, we made a prototype that is twice the size... 

    Effect of Fluorine Addition on Properties of Electrodeposited Fluorine-doped Hydroxyapatite Coating on AZ31 alloy

    , M.Sc. Thesis Sharif University of Technology Amirloo, Hossein (Author) ; Afshar, Abdollah (Supervisor)
    Abstract
    Magnesium and its alloys are potentialy biodegradable implant materials due to their attractive biological properties. But their poor corrosion resistance may result in sudden failure of the implants. Recently, many researchers have focused on applications of fluorine-doped hydroxyapatiteCa10(PO4)6(OH)2−xFx (FHA, x is the degree of fluoridation) as a bioactive coating to provide early stability and long-term performance. In comparison with pure HA coating,FHA coating could provide significant dissolution-resistant property, better apatite-like layer deposition, better protein adsorption, better cell attachment and improved alkaline phosphatase activity in cell culture. In this... 

    Preparation and Characterization of Polyurethane/Carbon Nanoparticles Nanocomposite for Biomedical Applications (Orthopedic)

    , Ph.D. Dissertation Sharif University of Technology Alishiri, Maryam (Author) ; Shojaei, Akbar (Supervisor) ; Abd Khodaei, Mohammad Jafar (Supervisor)
    Abstract
    Present study demonstrated carbon nanoparticles/acrylate-terminated polyurethane composites as promising materials for bone implants applications. Neat polymer and composites containing nanoparticles at different loadings up to 2 wt % were prepared by in situ polymerization method. Morphological analysis exhibited that nanoparticles caused considerable phase separation between soft and hard domains as well as increased crystallinity. Mechanical analysis showed a significant improvement in mechanical properties. Maximum improvement in tensile properties of APUA was observed at 1 wt% loading of ND-HEAMs, namely 175% improvement in modulus. In vitro biocompatibility evaluation via culturing... 

    Electrical properties of nanocontacts on silicon nanoparticles embedded in thin SiO2 synthesized by ultralow energy ion implantation

    , Article Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures ; Volume 23, Issue 6 , 2005 , Pages 2821-2824 ; 10711023 (ISSN) Ben Assayag, G ; Shalchian, M ; Coffin, H ; Claverie, A ; Grisolia, J ; Dumas, C ; Atarodi, S. M ; Sharif University of Technology
    2005
    Abstract
    In this paper, we present the room temperature current-voltage characteristics of large (100×100 μ m2) and a nanoscale (100×100 nm2) metal-oxide-semiconductor (MOS) capacitor containing few silicon nanocrystals. The layer of silicon crystals is synthesized within the oxide of this capacitor by ultralow energy ion implantation and annealing. Current fluctuations in the form of discrete current steps and sharp peaks are apparent in the static and dynamic I (V) characteristics of the capacitor. These features have been associated to quantized charging and discharging of the nanoparticles and the resulting Coulomb interaction to the tunneling current. © 2005 American Vacuum Society  

    Antibacterial Ti–Cu implants: A critical review on mechanisms of action

    , Article Materials Today Bio ; Volume 17 , 2022 ; 25900064 (ISSN) Mahmoudi, P ; Akbarpour, M. R ; Lakeh, H. B ; Jing, F ; Hadidi, M. R ; Akhavan, B ; Sharif University of Technology
    Elsevier B.V  2022
    Abstract
    Titanium (Ti) has been widely used for manufacturing of bone implants because of its mechanical properties, biological compatibility, and favorable corrosion resistance in biological environments. However, Ti implants are prone to infection (peri-implantitis) by bacteria which in extreme cases necessitate painful and costly revision surgeries. An emerging, viable solution for this problem is to use copper (Cu) as an antibacterial agent in the alloying system of Ti. The addition of copper provides excellent antibacterial activities, but the underpinning mechanisms are still obscure. This review sheds light on such mechanisms and reviews how incorporation of Cu can render Ti–Cu implants with... 

    The Effect of Using a Viscoelastic Layer on a Dental Implant on the Stress/Strain Distribution at the Interface of Implant and Jaw Bone

    , M.Sc. Thesis Sharif University of Technology Ghanati, Golsa (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    Abstract
    Natural teeth are connected to alveolar bone by periodontal ligaments ( PDL). PDL in addition to supporting tooth have the damping effect on transferring load from tooth to the surrounding bone. The most common replacement for a complete tooth loss is the use of Osseointegrated dental implants. The healthy bone remodeling and full bonding between bone and titanium surface of the implant is subjected to a successful osseointegration. The lack of PDLs in the structure of implant-bone system could lead to the failure of implant’s components due to overloading or to the impact loads. The aim of this study is to use viscoelastic material in the structure of dental implants to compensate for the... 

    Design and Implement of the Ion Implanter’s Ion Gun Power Supplies by Using the Resonant Converters

    , Ph.D. Dissertation Sharif University of Technology Beiranvand, Reza (Author) ; Rashidian, Bizhan (Supervisor) ; Zolghadri, Mohammad Reza (Supervisor) ; Alavi, Mohammad Hossein (Co-Advisor)
    Abstract
    In the Ion Implanter system a controled current through a tungesten filament, supplies the heat which causes the thermoionic emmition to ionize the gas molecules. Then the negativly charged electrones that are boiled off the filament, and also the ones that are removed from the outer ring of the gas molecules during the ionization process, are attracted by an adjustable voltage source. In this thesis, two resonant converter topologies are proposed to designe and to implement the adjustable current and voltage sources for ion implantation system. Unlike the PWM converters soft switching techniques, used auxiliary circuits to reduce the switching losses and EMI noises, in the proposed resonant... 

    Design of a Non-Bianry Analog to Digital Converterfor Impantable Neural Recording Microsystem

    , M.Sc. Thesis Sharif University of Technology Eslampanah Sendi, Mohammad Sadegh (Author) ; Sharifkhani, Mohammad (Supervisor) ; Sodagar, Amir Masoud (Supervisor)
    Abstract
    A new structure of implantable neural recording microsystem base on multiple valued logic (MVL) has been proposed. MVL is a new idea for reduction of occupied area and the power consumption of microelectronic. In another side, in implantable microsystems , occupied area and power consumption by this type of micro systems is a challenging problem in this field. Therefore, the problem of power consumption and occupied area can introduce as a prime stage of suggested microsystem completed design of convertor of analog to digital in usage of multiple level in this micro system worked. Design of convertor of analog to digital is a convertor of quaternary successive approximation. And also,... 

    Comparison of the effects of different implant apical designs on the magnitude and distribution of stress and strain in bone: A finite element analysis study

    , Article Journal of Long-Term Effects of Medical Implants ; Vol. 24, issue. 2-3 , 2014 , p. 109-120 Kadkhodazadeh, M ; Lafzi, A ; Raoofi, S ; Khademi, M ; Amid, R ; Movahhedy, M. R ; Torabi, H ; Sharif University of Technology
    Abstract
    Objectives: The aim of this study was to investigate the effects of implant design on the apex area and on stress and stress patterns within surrounding bone. Methods: Three commercially available implants with the same diameter (3.5 mm), same length (10-11 mm), and same complement abutment were selected for modeling as follows: (1) flat apical design with light tapering degree, (2) dome-shaped apical design with light tapering, and (3) flat apical design with intense tapering in one-third of the apical area. According to human cone-beam computed tomography (CBCT), the bone was modeled using a cortical thickness of 2 mm and cancellous bone. Forces of 100 N and 300 N in the vertical and 15°... 

    In vitro biological outcome of laser application for modification or processing of titanium dental implants

    , Article Lasers in Medical Science ; Volume 32, Issue 5 , 2017 , Pages 1197-1206 ; 02688921 (ISSN) Hindy, A ; Farahmand, F ; Tabatabaei, F. S ; Sharif University of Technology
    Abstract
    There are numerous functions for laser in modern implant dentistry including surface treatment, surface coating, and implant manufacturing. As laser application may potentially improve osseointegration of dental implants, we systematically reviewed the literature for in vitro biological responses to laser-modified or processed titanium dental implants. The literature was searched in PubMed, ISI Web, and Scopus, using keywords “titanium dental implants,” “laser,” “biocompatibility,” and their synonyms. After screening the 136 references obtained, 28 articles met the inclusion criteria. We found that Nd:YAG laser was the most commonly used lasers in the treatment or processing of titanium... 

    Electrophoretic deposition of nano-zirconia coating on AZ91D magnesium alloy for bio-corrosion control purposes

    , Article Surface and Coatings Technology ; Volume 311 , 2017 , Pages 182-190 ; 02578972 (ISSN) Amiri, H ; Mohammadi, I ; Afshar, A ; Sharif University of Technology
    Elsevier B.V  2017
    Abstract
    Magnesium alloys are considered as potential biodegradable biomaterials in hard tissue implants. However, the fast degradation rate of these alloys in the biological environment causes failure of the implant just prior to the desirable time. In the present work, in order to decrease and curb the bio-corrosion rate of AZ91D Magnesium alloy, zirconia, which is classified as a biocompatible ceramic, was coated on the alloy surface through electrophoretic deposition (EPD) technique. The effects of alterations in the EPD parameters such as current density, duration time and ZrO2 particles concentration on coating properties including thickness, morphology and adhesion were then characterized.... 

    Effect of oxidizing atmosphere on the surface of titanium dental implant material

    , Article Journal of Bionic Engineering ; Volume 16, Issue 6 , 2019 , Pages 1052-1060 ; 16726529 (ISSN) Khodaei, M ; Alizadeh, A ; Madaah Hosseini, H. R ; Sharif University of Technology
    Springer  2019
    Abstract
    Direct oxidation is a simple and effective method for titanium surface treatment. In this research, a titanium sample was directly oxidized at the high temperature in two different atmospheres, air and pure oxygen, to obtain better atmosphere for titanium surface treatment. The results of the Raman spectroscopy indicated that in both atmospheres, the rutile bioactive phase (TiO2) has been formed on the titanium surface. The results of X-ray diffraction (XRD) also revealed that the surface of oxygen-treated sample was composed of the rutile phase and titanium monoxide (TiO), while at the surface of the air-treated sample, the rutile phase and titanium dioxide had been formed. Further, the... 

    Low power receiver with merged N-path LNA and mixer for MICS applications

    , Article AEU - International Journal of Electronics and Communications ; Volume 117 , 2020 Beigi, A ; Safarian, A ; Sharif University of Technology
    Elsevier GmbH  2020
    Abstract
    In this paper, a low power receiver for medical implant communication service (MICS) is presented. Low power design is vital in the MICS applications since the implanted chip has to work for a long time without the need to change its battery. As a result, a merged N-path low noise amplifier (LNA) and mixer block is proposed. In this structure, the LNA and down-conversion mixer share a transconductance to lower the overall power consumption. An N-path feedback is utilized around the shared transconductance not only to improve the LNA selectivity and relax the linearity requirements but also to downconvert the radio frequency (RF) component and create the intermediate frequency (IF) signal. In...