Key Engineering Materials Vol. 583

Abstract: The heart functions normally when the impulses are produced at a rate of 80 bpm. When less than 60 bpm are triggered, pacemakers may be necessary to sustain the electrical activity of the heart. Pacemaker systems used in cardiac resynchronization therapy are made of an implantable pulse generator, leads, and unipolar or bipolar electrodes. They are aimed to simulate the cardiac depolarization, to sense intrinsic cardiac functions, to provide information stored by the system for deeper diagnosis. This paper presents a mathematical model and numerical simulation results on the ionic current distributed by the electrodes, in the absence of concentration gradients, in the cardiac tissue. The external electrical resistance variation with the anode to cathode spacing obtained by this approach may be used in the design phase of the device.

Abstract: The general purpose of this study was to assess the accuracy of geometric characteristics of electronic footprints acquired with Zebris FDM force platform based on comparison with corresponding characteristics of conventional ink footprints. The paper presents a comparative analysis of contact areas and plantar arch index calculated from simultaneously acquired ink and electronic footprints. The areas of the three main regions of the footprints have been determined using common image processing software. The plantar arch index was calculated based on Cavanagh method. The comparative analysis evidences the differences between the geometric characteristics. The total contact area is slightly overestimated in case of the electronic footprints. The electronic footprints overestimate fore-foot and rear-foot areas and underestimate mid-foot area. The mean values of AI in case of ink footprints generally have greater values than in case of electronic footprints.

Abstract: Among others, biomedical research is conducted for the systematic collection and analysis of data from which general conclusions can be drawn and which can increase the life quality of the patients. Given these issues, the aim of the research presented in this paper is to analyze the concentration of heavy elements from the human body, using complementary analysis methods, based on the energy dispersion spectrometry (EDS) technique.

Abstract: A 55-year-old female who undergone mitral valve replacement eight years ago with a mechanical graft, presented accusing sudden decrease of effort tolerance and two episodes of pulmonary edema in the last month. Anamnesis, physical examination, electrocardiogram (ECG), transthoracic echocardiography and coronarography were performed. The mechanical valve leaflets and the tissue surrounding the prosthetic ring were evaluated by: optical microscopy (hematoxylin eosin stain and immunohistochemistry), scanning electron microscopy (SEM) and EDAX analysis (Energy Dispersive X-ray spectroscopy). Anamnesis: inferior myocardial infarction in 2006, congestive cardiac insufficiency, pulmonary hypertension, and arterial hypertension. Clinical examination and ECG: minimal perimaleolar edema bilateral, sinus rhythm on admission. Transthoracic echocardiography: 55% ejection fraction, a pression gradient across the mitral valve (Gmax/Gmed= 24/11 mmHg), tricuspid regurgitation, and pulmonary hypertension. A mitral prosthetic valve’s leaflet was found immobile. No thrombus was evidenced. Coronarography: an immobile graft’s leaflet, stenoses on the right coronary artery, stenosis on left anterior descending artery and occlusion at the circumflex artery emergence. The prosthesis was replaced, and two coronary artery bypasses were performed. Macroscopic examination: a fibroconjunctive tissue expansion in close contact with the leaflet. Histopathological evaluation: muscle cells with altered phenotypes, fibroblasts along with fibrous connective tissue and calcium depots areas. SEM evaluation: tissue depots on the immobile leaflet, suggesting that the connective tissue expansion was blocking the leaflet’s movements. EDAX analysis: the metallic leaflets surface was made of tantalum; sodium, calcium and chloride deposits were also detected. Graft failure was caused by the tissue proliferation affecting leaflet’s mobility. SEM is a viable method for failed cardiovascular grafts investigation.

Abstract: Intra-articular treatments offer the advantage of achieving high active substance concentrations at the site of cartilage lesion. One problem with these drugs is that of low remanence. A method to prolong the survival time of substance inside the joint may improve the cartilage repair and patient symptoms. Targeted therapy aims to optimize the delivery of these drugs set in a solution of magnetic nanoparticles, by injection into the knee joint, in order to increase the residence time of active substances through the application of high magnetic field gradients in the joint area by using extracorporeal magnets. Synthesized magnetic nanoparticles, which were covered by layer-by-layer method in consecutive layers of protection, are stable and retain their character and magnetic-polymer composites features required to be used for their intended purpose. FTIR analysis demonstrated the presence of iron salts in the synthesized ferrofluid, and of the characteristic groups of polymer coating which demonstrated that the technique of embedding in polymer layers by layer-by-layer method is viable.

Abstract: Many researchers perform different research in the area of ostheosznthesis metallic implants used in orthopedic surgery. The main goal of internal fixation is to achieve full operation until patient recovery. Although implants are intended to withstand until bone consolidation in some cases problems occur due to accelerate wear and corrosion processes. The aim of the present study was to determine the causes leading to adverse reactions of the surrounding tissues in case of three implants for osteosynthesis type plate-screw.

Abstract: In the case of renoureteral lithiasis, shockwave lithotripsy (ESWL) proved to be an effective and safe method with a low risk of significant clinical consequences for long term The therapeutic effect is the result of the pulse amplitude, high pressure and shock wave energy content focused on striking stones or urethral calculi. The negative pressure specific shock wave is responsible for the phenomenon of cavitation. Cavitation plays an important role in the fragmentation of calculus as the technical components accelerates wear mechanism for generating shock waves in special electrode (the electrohydraulic generator). The main objective of this study is to find technical solutions in terms of improving energy transfer shock waves from the generator to the target and reliability/optimization of the shock wave generator (the electrohydraulic lithotriptor EHL vulnerable point).

Abstract: This paper aims to characterize two dental bridges made from Co-Cr alloy, the first one obtained by the conventional method (casting) and the second one by Selective Laser Sintering technique (SLS). The elemental composition, microstructure, hardness and corrosion behavior in artificial saliva were investigated, allowing a parallel analysis of this two samples obtained with the two methods mentioned above.

Abstract: Numerous clinical observations performed on patients who have achieved dental restorations on implants drew attention to the risk of immediate or late complications. The most common late complications are lost of implant components and fracture of implant. While loss of screw only produce patient discomfort, implant fracture lead to more serious complications and subsequent treatment is extremely difficult. The causes of these complications are static mechanical failure of the implant system and overloading of the assembly [1]. The main function of dental implants is to transfer the load to the surrounding biological tissues. Therefore, the first objective of functional design is to dissipate and distribute biomechanical loads, in order to optimize function on prosthesis built on implants.

Abstract: The present paper put in evidence the mechanical behaviour of some commercial dental cobalt alloys, after own classification. The experimental cobalt alloys were classified in according either with molybdenum content, or with Cr+Mo content. A hierarcy of the alloys was finally made. The fractographic surfaces were investigate both by stereomacroscopy and scanning electron microscopy, putting in evidence the main structural features.